HK1201491B - Systems and methods for processing mixed solid waste - Google Patents

Description

System and method for processing mixed solid waste

Technical Field

The present invention relates to systems and methods adapted for waste recycling and conversion. More particularly, the present invention relates to the recycling and conversion of solid waste derived from, for example, commercial, industrial, or domestic waste.

Background

Commercial, industrial, and consumer life produce a large number of discarded and waste products (i.e., municipal solid waste) that need to be disposed of and disposed of in an environmentally satisfactory manner. Traditionally, municipal solid waste (hereinafter "MSW") is disposed of by landfilling or incineration. However, these waste product disposal methods contaminate soil, water, and air. Environmental constraints and land use requirements for housing reduce the number of sites available for landfill.

In response, governments and the public have demanded that recirculation systems should be used whenever possible to conserve material resources and reduce pollution problems. Efforts have been made to recover valuable resources such as glass, plastic, paper, aluminum, and ferrous and non-ferrous metals from waste materials. For example, many households in cities are required to sort their waste into recyclables (e.g., paper, plastic containers, metal containers, and glass containers) and non-recyclables. However, the rate of noncompliance and noncompliance is very high. Some people either classify recyclable materials as waste streams or contaminate recyclable streams with waste materials, who cannot classify their waste at all and others classify it incorrectly. Non-compliance and erroneous compliance reduce the efficiency and increase the cost associated with the operation of the recirculation system for the processed pre-sorted waste.

Some recycling systems attempt to avoid the problem of pre-separated waste by attempting to recover recyclable materials from mixed waste. However, many of these systems have a tendency to operate with a high degree of labor intensive effort while providing relatively low recyclables recovery.

The energy balance of many recirculation systems is low and in some cases negative. Some recycling systems are so inefficient that the process of recovering, transporting, and recycling the recyclable material consumes more energy than would be saved by simply landfilling the waste and manufacturing new products from the raw material. In other cases, so little recyclable material is recovered that the waste stream disposal problem is not substantially alleviated.

Disclosure of Invention

The present disclosure relates to methods and systems for processing waste comprising a mixture of wet and dry organic materials and optionally inorganic materials. The systems and methods mechanically separate the mixed solid waste to produce a wet organic stream rich in wet organics and a dry organic stream rich in dry organics. Each stream is separately processed to convert at least a portion of each stream into a renewable or recyclable product.

These separated and recovered wet and dry organic products constitute a highly efficient feedstock for energy conversion. The wet organic product may be digested in an anaerobic digester to produce biogas or composted for use as a soil amendment. Biogas produced in the anaerobic digester may be compressed or liquefied for use as transportation fuel and/or may be used to generate electricity or heat for use on site and/or for delivery to a power grid and/or conversion to liquid fuel. The dry organic material may be recycled and/or used or sold as an organic biomass fuel to produce heat and/or electricity. The inorganic material may be recycled and/or landfilled.

Separating the dry organic material, the wet organic material, and optionally the inorganic material maximizes the efficiency of the downstream conversion technology. For example, wet organics can be converted in an anaerobic digester with greater efficiency. Removing the non-digestible dry organics and inorganic materials prior to loading into the digester increases the volume available for microbial cultivation and biogas production. Similarly, removing wet organics and inorganic materials from dry organics increases the efficiency of the thermal conversion of the dry organics because less energy is consumed to evaporate the water and less ash is produced by the post-combustion materials. In cases where recyclables are recovered from dry organics, removing wet organics and inorganic materials reduces the burden depth in the sorting process, thereby allowing the sorting equipment to operate properly and more efficiently and reducing wear and tear on the machine. Furthermore, the non-recyclable inorganic fraction can be more easily landfilled, as the volume of the landfilled material will be smaller and more concentrated.

The need to efficiently extract multiple types of recyclable materials from different mixed waste streams is a long-felt but unmet need. The inability of the industry to extract significant proportions of different types of recyclable materials from different mixed waste streams has led to well-known political sports in many parts of the world, and it is their responsibility to educate laymen about manual sorting and then disposal of recyclable materials at the time and place of production. Due to natural human behavior, these efforts, while promising, have not resulted in the desired recirculation and corresponding diversion rates. The vast majority of recyclable waste material continues to be insufficiently recovered and/or used. The methods and systems described herein satisfy this long felt but unmet need by effectively recovering recyclables using mechanical devices arranged and configured to effectively treat different solid waste streams. Furthermore, traditional curbside residential recycling programs as well as commercial recycling programs require expensive and polluting separate collection paths and vehicles. Furthermore, when collected by separate vehicles, these materials still need to be separated and recyclables recovered in a conventional Material Recovery Facility (MRF). This is highly inefficient and expensive.

The systems and methods described herein can process a large number of highly diverse mixed waste materials. These systems and methods can effectively extract recyclables from unsorted mixed waste (e.g., black trash MSW), recyclable streams in which the error compliance with high household classification is high (e.g., blue trash MSW), and other types of MSW, such as different commercial waste streams from retail stores, light source manufacturing, warehouses, office buildings, etc., and industrial waste streams. The methods and systems described herein can recover a significantly greater proportion of different types of recyclable materials, as well as organic materials, from different waste streams for conversion to renewable fuels and energy than known systems. This capability is due in large part to the fact that mechanical separation separates wet organic material from dry organic material and optionally organic material using mechanical classifiers, such as crushers, size separators, density separators, and/or size classifiers, which produce a concentrated, uniform intermediate waste material stream from which renewable energy and recyclables can be mechanically extracted. Unlike conventional waste fuel plants, the methods and systems of the present invention sufficiently fractionate and spread the waste material to produce an intermediate stream for efficient conversion.

These and other features of the embodiments disclosed herein will become more fully apparent from the following description and appended claims.

Drawings

To further clarify the above and other advantages and features of the present invention, a more particular description of the invention will be rendered by reference to specific embodiments thereof which are illustrated in the appended drawings. It is appreciated that these drawings depict only typical embodiments of the invention and are therefore not to be considered limiting of its scope. The invention will be described and explained with additional specificity and detail through the use of the accompanying drawings in which:

FIG. 1 is a schematic diagram of a mechanical system for converting mixed dry organic and wet organic waste materials (and optionally inorganic materials) into higher value products;

FIG. 2 is a schematic diagram showing a conversion option for processing dry organic matter;

FIG. 3 is a schematic diagram showing a conversion option for processing wet organic matter;

FIG. 4 is a schematic diagram showing conversion options for processing inorganics;

FIG. 5 is a flow diagram illustrating a method for extracting recyclable materials from a mixed solid waste stream;

FIG. 6 shows a cross-sectional view of an air drum separator adapted for use in a system for separating solid waste by density, according to one embodiment of the present invention; and

fig. 7 shows a flow diagram of a system for separating solid waste, according to yet another embodiment of the present invention.

Detailed Description

I. Introduction to the design reside in

Fig. 1 is a schematic diagram of an integrated waste processing and recovery system 100 that generates renewable energy and/or products from mixed solid waste materials. The system 100 includes a source 110 of a mixed solid waste stream. The mixed solid waste stream includes at least 10% wet organic waste material and at least 10% dry organic material and optionally inorganic waste material.

The mixed waste material 110 is mechanically sorted to produce wet organic 114 and dry organic 116, and optionally inorganic 118. The waste material is processed in the mechanical separation system 112 to produce a plurality of separately sorted waste portions suitable for conversion into renewable energy and/or products. At least a portion of the dry and wet organics are independently processed using separate conversion processes 131 and 139, respectively. The optional inorganics 118 may be converted into renewable or recyclable products using inorganic conversion technology 135. Dry organic conversion 131 is particularly suitable for converting dry organic material to higher value products and wet organic conversion 139 is particularly suitable for converting wet organic material to higher value products. By concentrating the wet and dry organics into a single fraction, the efficiency of the dedicated conversion process is much higher than if the same conversion process were performed on mixed solid waste.

The separation system 112 may include components such as conveyors, grinders and/or crushers, screens, air classifiers, magnets, eddy current separators, classifiers, and plastic classifiers that together separate wet organic material from dry organic material. Mechanical classifiers for separating wet from dry organics can include grinding devices, size classification devices, and/or density separators.

Prior to loading the waste material 110 into the separation system 112, the waste material 110 may be manually sorted to remove heavy metals, concrete and rock items that may damage the separation system 112; an integral paperboard; electronic waste and/or obviously toxic waste/chemicals. Manual classification is usually minimal. For example, manual sorting may be performed by a loader operator of a ground sorter that simultaneously loads waste material into the sorting system 112 or by one or more line operators that pull apparently valuable items from the waste stream. In a preferred embodiment, less than 40%, 20%, 10% or even less than 1% (by weight) of the mixed waste stream is manually sorted to remove recyclables.

The use of automated systems allows for higher throughput and improved recovery of fuel and/or recyclables. In one embodiment, the throughput of the mechanical classifier of the separation system is at least 2, 5, 10, 20, 50, or 100 metric tons of mixed waste/hour/single line and/or less than 200, 150, 100, or 50 metric tons of mixed waste/hour/single line, or a range of upper and lower rates of throughput as previously described. The term "single line" is intended to refer to a single input line that produces a single partial stream of different materials.

The separation system 112 produces a dry organic material 116 having a low moisture content. In one embodiment, the separation produces dry organic material having a moisture content of less than 30%, a moisture content of less than 25%, a moisture content of less than 20%, or even a moisture content of less than 15%. Notably, these moisture contents can be achieved from the separation system without further drying with dry materials or dilution of the moisture content with mixing.

Referring to fig. 2, the dry organics 116 are converted to renewable materials with a first conversion technique 131. This dry organic conversion may be used to recover recyclables (step 124) and/or for fuel production 120. Recovering recyclables 124 can include sufficiently separating materials to produce a recycle commodity 107, which can be marketed and/or converted into a recycle product 133. Fuel production 120 may include conversion of dry organics to liquid fuel 119, generation of electricity 122, conversion to oil 121, or chemical conversion 109 or some other form of energy.

Such dry organic fuels may be advantageous even at moderately high moisture contents due to the evenly spread distribution of water. In one embodiment, the separation system 112 produces a dry organic material having less than 5% by mass of particles with a moisture content greater than 40% (more preferably greater than 30% or even greater than 25%). In one embodiment, the dry organic material has less than 3%, 2%, or even 1% by weight of particles with a moisture content of greater than 40%, 30%, or 25%.

While it is desirable to produce a dry organic fraction having a desired moisture content upon separation, the present invention also includes systems in which dry organic fuel can be dried. In a preferred embodiment, the drying is performed using waste heat, such as waste heat from the dry organic power generation system 122 and/or the biogas power generation system 145 (fig. 3). In a preferred embodiment, drying is performed using only waste heat (e.g., no combustion fuel is used for primary drying purposes).

In one embodiment, the present invention relates to maintaining a desired moisture content over time in the dry organic fraction. Maintaining the same moisture content over time may be important to operating a thermal conversion device that utilizes organic fuels. The separation system 112 may be operated so as to minimize variations in the moisture content of the dry organic material 116. In one embodiment, the density classifier can be adjusted up or down in density separation to capture more or less of the wet organic fraction to maintain a desired moisture content in the dry organic material. In one embodiment, the dry organic material output from the separation system 112 is measured over time and input to a computer configured to control one or more components of the separation system 112 to achieve a desired moisture content in the dry organic material 116.

Referring to fig. 3, the wet organic 114 is converted to renewable materials using a second conversion technique 139. The second conversion technique may include anaerobic digestion, which is typically performed by processing the wet organic 114 in a pre-processor 134 and digesting the wet material in an anaerobic digester 126. Alternatively, the wet organic 114 may be processed in an aerobic digester 130 or converted using compost 129. The products from the anaerobic digester 126 may include biogas 132 or biogas residue 128. The biogas 132 may be conditioned or purged using the conditioning 141 and subsequently converted to compressed natural gas 143. Alternatively, the biogas 132 may be used to generate electricity 145, converted to pipeline or industrial gas 147, or converted to liquid fuel (e.g., via fischer-tropsch synthesis).

The biogas residue from either the anaerobic digester 126 or the aerobic digester 130 may be further processed using solid/liquid separation to produce soil amendments and/or liquid fertilizer 137. Compost 129 may be used to further upgrade the solids from the biogas residue 128.

Inorganics 118 may also be processed to produce renewable products. The choice of processing minerals 118 tends to depend largely on the type of material and the proximity of the renewable market to the location of the system 100. The inorganic matter may be converted into a construction material 153, and the construction material 153 may be used in concrete or as a soil amendment. The glass product can be melted and reprocessed to produce recycled glass product 155. Metals tend to be of high value but may be difficult to extract using conventional systems. In contrast, the efficient separation system of the present invention can recover recycled metal products 157 from materials such as electronic equipment and other difficult to separate heterogeneous waste materials.

Separation of Dry organic waste from Wet organic waste

The components of the mixed waste stream are separated using mechanical separation to produce a wet organic stream rich in wet organics and a dry organic stream rich in dry organics. Fig. 5 depicts a flow diagram showing an example process 140 for extracting recyclables and recyclables from mixed waste. The step 152 of separating the dry organics from the wet organics comprises all or a portion of the following steps: (i) providing a solid waste stream 142, (ii) shredding the solid mixed waste, (iii) classifying 146 the waste stream by size, classifying 148 the waste stream by density, and mechanically sorting 150.

A. Providing a solid waste stream

The waste streams used in the methods and systems described herein include mixtures of different types of solid materials. The waste stream includes renewable and recyclable materials that can be used and therefore have value after separation from other types of renewable and recyclable waste. In one embodiment, the mixed solid waste may be municipal solid waste ("MSW") (i.e., waste or garbage). MSW is a type of waste material that primarily includes household waste, sometimes added to commercial and/or industrial waste collected by contractors employed by city authorities or by commercial and/or industrial enterprises within a given area. Commercial solid waste is waste of a type such as that typically collected from an enterprise (e.g., an office building or enterprise establishment). Industrial solid waste is commonly found in heavy-duty manufacturing. MSW and commercial waste do not typically include industrial hazardous waste. The mixed waste may be "black waste" in which the source of waste has performed little or no removal of renewable and recyclable materials, or alternatively, the mixed waste may be recyclable or "blue waste" comprising a mixture of renewable and recyclable waste materials (also referred to as "single-stream waste"). The single stream waste may be commercial or residential and may have low or high error compliance.

Mixed waste contains a variety of components that are only valuable as renewable and recyclable materials when separated from other components. These renewable and recyclable materials may include a range of plastics; fibrous materials, including paper and paperboard; metals, including ferrous metals as well as non-ferrous metals such as bronze and aluminum; glass; a fabric; rubber and wood. Preferably, the waste stream comprises 1, 2, 3, or more high value materials, including but not limited to one or more of paper, plastic, and non-ferrous metals.

Although even small proportions of these materials can be valuable, it is extremely challenging to separate the renewables and recyclables in the mixed solid waste stream from each other and from other components. This is particularly true when it is desired to separate two, three, four or more different types of renewables and recyclables.

The methods and systems described herein include providing a mixed solid waste stream that includes at least 10% of the blended wet organic material and at least 10% of the dry organic material. The mixed waste stream may also include inorganic materials that may be renewable or recyclable or non-renewable and non-recyclable.

The amount of renewable and recyclable materials in the stream, the proportion of renewable and recyclable materials recovered, and the value of the renewable and recyclable materials have a significant impact on the economic viability of extracting renewable and recyclable materials by mechanized classification (greater value is more desirable).

In one embodiment, the mixed waste stream comprises at least 10 wt% of dry organic waste selected from the group consisting of: 3-dimensional common rigid plastics, film plastics, paper, cardboard, textiles, rubber and wood. The mixed waste stream can include at least 15%, 20%, 25%, 30%, 40%, 50%, 70%, or 90% by weight dry organic material and less than 90%, 80%, 60%, 50%, 40%, 30%, 25%, 20%, or 15% by weight dry organic material or a range of any of the foregoing upper or lower endpoints.

In one embodiment, the mixed waste stream may comprise at least 10 wt% of wet organic material selected from the group consisting of: food waste (industrial, municipal, or domestic kitchen waste), animal waste (e.g., manure such as human or other animal manure waste), or green waste (e.g., industrial, municipal, or domestic lawn clippings or tree clippings). Such a mixed waste stream may include at least 15%, 20%, 25%, 30%, 40%, 50%, 70%, or 90% by weight dry organic material and less than 90%, 80%, 60%, 50%, 40%, 30%, 25%, 20%, or 15% by weight.

The ratio of wet to dry organics is generally dependent on the filler flow. In some cases, the wet organics may be more concentrated than the dry organics, or vice versa. However, in many cases, wet organic streams may be more prevalent due to food waste. In one embodiment, greater than at least 5%, 10%, 15%, 20%, 30%, 50%, or 70% by weight of the wet organic stream, and/or greater than 40%, 50%, 60%, or 80% by weight of the wet organic is food waste.

In certain embodiments, a substantial portion of this waste stream may be renewable or recyclable materials. At least a portion of the waste stream may include recyclable or renewable materials. The mixed waste stream may include at least 2.5%, 5%, 7.5%, or 10% recyclable plastic material or less than 60%, 40%, 20% (by weight) recyclable plastic material or any of the aforementioned upper and lower ranges of weight percentages.

The mixed waste stream can include at least 5%, 10%, 15%, 20%, 25%, or 30% recyclable or recyclable mixed paper material or less than 80%, 70%, 60%, 50%, or 40% (by weight) or upper and lower ranges of any of the foregoing weight percentages of mixed paper material.

The mixed waste stream can include at least 15%, 25%, 35% recyclable or renewable dry organic material and less than 80%, 70%, 60%, 50%, or 40% (by weight) or a range of any of the aforementioned upper and lower weight percentages of dry organic material. The mixed waste stream may include wet organic, dry organic and/or inorganic waste. In one embodiment, the weight percentages of wet organic waste, dry organic waste, and inorganic waste in the mixed waste stream are each (independently of each other) at least 5%, at least 10%, at least 20%, at least 50%, or at least 75% (the sum of the three weight percentages does not exceed 140%).

In one embodiment, the mixed waste stream can include at least 0.5%, 1%, 2%, 3%, 4%, 5% recyclable metal or less than 30%, 20%, 15%, 10%, or 5% (by weight) recyclable metal material or an upper and lower range of any of the foregoing weight percentages.

In one embodiment, the mixed solid municipal waste may be raw municipal waste. For example, the solid waste stream may be provided directly from a municipal waste collection process. Alternatively, the solid municipal waste may be partially pre-processed (e.g., by a homeowner or business) to remove a portion of the recyclable and/or recyclable materials. For example, solid municipal waste may be derived from a wide range of residential or commercial waste streams that include residual materials that exclude source separation materials collected by recycling projects in which a portion of certain recycles and/or recyclables (e.g., mixed paper, newspapers, cardboard, plastics, ferrous metals, and non-ferrous metal and/or glass containers) have been removed (i.e., the MSW may be recycled waste).

In either case (i.e., using either raw MSW or source-separated MSW methods), the mixed waste can be pre-sorted manually to recover and remove items that are difficult to break or grind, significantly harmful, and/or particularly large (i.e., easily sorted), and have high recovery value. This pre-sorting may be done on the ground (facility tip floor) at the lower end of the facility, prior to loading the waste into the system, or may be done by personnel on a dedicated pre-sorting line. For example, waste may be measured on a pre-sort conveyor where manual labor identifies pre-sorted items. Typically, pre-sorted articles will include articles that may damage or cause excessive wear on the crusher or grinder. Examples include automotive engine blocks, structural steel, tires, propane tanks, concrete blocks, large rocks, and the like. The hazardous waste is preferably removed prior to grinding to avoid contamination of other materials in the mixed waste. Examples of clearly hazardous waste include solvent and chemical containers, paint buckets, batteries, and the like.

Pre-sorting may also be used to remove particularly large and valuable items that are easily picked out of the mixed waste stream. Typically, recyclables recovered in pre-sorting will be several times more items than the depth of load of the process stream, making them easy to see and effectively removed manually. For example, large cardboard boxes (e.g., corrugated boxes), structural metal, and electronic waste (e.g., e-waste) may be recycled in a pre-sort. The percentage of material in the mixed waste stream described above refers to the percentage of the waste stream immediately before it is subjected to comminution and/or size adjustment (i.e., after pre-classification).

As mentioned, the methods described herein allow material to be mechanically sorted from municipal solid waste, even when the waste comprises a large proportion of non-recyclable material. In one embodiment, the solid waste stream comprises at least 20%, 25%, 35%, 50%, or 75% of one or more low value materials. Low value materials are materials that make separation of high value materials difficult and are not generally separation economical by themselves. In one embodiment, the low value material may be selected from the group consisting of: wet organics, garden waste, food waste, gravel, fines less than 1 inch, asphalt, concrete, fabric, wood, rubber, membrane plastic, PVC, foil, rock, used consumer products, low value glass (glass too far from the recycler), composite materials (e.g., tennis shoes), other materials commonly found in solid waste, and combinations of these. The methods described herein overcome a long felt but unmet need to economically recover (i.e., mechanically sort) all or a portion of the valuable recyclables and/or recyclables in these difficult to treat waste streams. Individual low value materials can be in the solid waste stream at a concentration of at least 5%, 10%, 15%, 20%, or more.

One of ordinary skill in the art will recognize that the composition of the solid waste stream substantially changes over a short period of time. Of all the variability found in MSW, there are three constant degrees or percentage features of variation: density, dimension (2 or 3 dimensions), and moisture content. The present invention uses, in part, various devices that separate by size, density, and dimension, and then directs the material to a device that separates or recovers by material type (e.g., resin type of plastic, ferrous metal, non-ferrous metal, glass, paper, etc.). For the purposes of this invention, the percentage of a particular type of material within a waste stream may be calculated according to acceptable industry standards, such as the 2011 waste disposal guide (also known as "CalRecycle" and previously known as the California Integrated waste management W Committee, published by the California resource recycle and recovery departmentate Management Board), which is incorporated herein by reference (in this document)www.calrecycle.ca.gov/wastechar/YourData.htm#SteplAnd the links associated therewith are available). The minimum sampling of the waste stream should include samples that are analyzed for at least 200lbs and sampled over a number of different days, weeks, and/or months.

B. Pulverizing

Separating the wet organics from the dry organics can optionally include grinding or shredding the mixed waste. Comminution (e.g., crushing or grinding) can improve the efficiency of other processes (e.g., size separation and density separation).

The crushed waste will have a range of particle size sizes. In one embodiment, the comminuted waste stream has an upper cut of 16 inches or less, 14 inches or less, 12 inches or less, 10 inches or less, or 8 inches or less, or a lower cut of greater than 1 inch, 2 inches, 4 inches, or 6 inches, or may have a distribution of upper and lower cuts with any of the aforementioned upper and lower cuts for comminuted waste. In one embodiment, the ratio of the upper cut to the lower cut may be less than 8, 6, or 4.

The size distribution of any particular fractured material is generally dependent on its material properties. For example, certain items such as transport pallets or tires will be ground or shredded to a relatively large particle size. In contrast, brittle materials that are prone to breakage, such as glass, and food waste that is prone to shredding, will be particularly small after being shredded.

The crusher or grinder used to comminute the mixed waste stream may include one or more shafts containing cutting heads that cut and/or crush the incoming waste material to a selected size. The waste material can be ground or crushed by a rotating rotor fitted with cutting blades or knives against a rigid blade housing, and then they fall through the grinder or crusher to a screen basket (circular perforated plate or screen of fin-like design). Material having an abrasive cut size less than the selected size falls through the screen and is moved to the next step in the process. Objects that are too large to pass through the screen are typically recirculated repeatedly through the grinder or crusher until they are ground to a size that can pass through the screen.

Many solid waste grinders or crushers available on the market may be or may be adapted for crushing the initial solid waste stream. For example, Vecoplan, LLC of High Point, N.C. manufactures a number of solid waste crushers that may be incorporated into the system and used in the methods described herein.

Preferably, the shredded waste from the shredding device is ground or shredded to a size of less than 18 inches, 16 inches, 12 inches, 10 inches, or 8 inches and greater than 2 inches, 4 inches, 6 inches, 8 inches, 10 inches, or a range from any of the foregoing upper and lower cutoff sizes. Crushing the mixed MSW prior to size separation and density separation will improve the separation efficiency of the density separator.

In the present disclosure, multiple comminution and/or size classification steps are described with respect to methods and systems for separation of solid waste. Typically, each of these steps has an associated size cutoff. Those skilled in the art will appreciate that graded materials typically exhibit a particle distribution. The distribution of any particular fraction will generally include a sub-optimal number of particles above or below the cut-off value. Unless otherwise specified, an upper cutoff number (e.g., an upper range of oversize of 16 "or less, 12" or less, 8 "to 2") generally means that about 90% of the particles in the particular fraction have a size less than the cutoff number, while about 10% of the particles in the particular fraction will be larger than the upper cutoff size. Unless otherwise specified, a lower cutoff number (e.g., a lower range of 8 "to 2" oversize) generally means that about 90% of the particles in the particular fraction have a size greater than the cutoff number, while about 10% of the particles in the particular fraction are smaller than the lower cutoff size. In certain embodiments, the cutoff value may be more effective than 90% and 10%. For example, the upper cut-off number of 95% or 99% of the particles in a particular fraction may be less than the upper cut-off number and/or less than 5% or less than 1% of the particles in the fraction may be less than the lower cut-off size. The particular cutoff number relates to a particular portion, not the entire distribution. Depending on the reject stream, a significant proportion of the feed reject stream may be less than the lower cut-off number and/or greater than the upper cut-off number, regardless of the efficiency of the separation device.

C. Size separation

The shredded waste may be transported to a size separator that fractionates the mixed waste by size to produce two or more sized waste streams (e.g., at least one oversized and at least one undersized).

Size separation can be performed to produce a size waste stream having a particularly desirable particle size distribution to facilitate density separation and produce an intermediate stream enriched in particular recyclable or renewable materials. One of ordinary skill in the art will recognize that the pulverized waste stream may be analyzed to determine size cut-offs in which portions of the stream separate different types of materials into different streams while concentrating similar types of waste streams into a slightly concentrated stream. Furthermore, the size waste stream can be optimized for density separation by producing a size waste stream with a narrow particle distribution.

In one embodiment, the size waste stream may have a size distribution with a ratio of small to large particles of less than about 10 (i.e., the ratio of the upper cut-off to the lower cut-off has a ratio of less than about 10), more preferably, less than about 8, 6, or 4. The undersized portion from the size separation may have an upper size cutoff of less than about 6 inches, 5 inches, 4 inches, 3 inches, or two inches and greater than 0.5 inches, 1 inch, 2 inches, or 3 inches, or a range within any of the aforementioned upper and lower limits of the upper size cut. The upper portion may have an upper dimension cutoff of less than 16 inches, 12 inches, 10 inches, 8 inches, or six inches, and a lower dimension cutoff of greater than 2 inches, 4 inches, 6 inches, or 8 inches, or any range therebetween.

Suitable examples of size separators that may be used in the present method include a tray screen separator having rubber or steel trays, a finger screen separator, a trommel separator, a shaker screen separator, a waterfall screen, a shaker screen, a flower tray screen, and/or other size separators known in the art.

Disc screens use a series of rolling shafts with a series of attached discs, where the space between the discs can allow objects to fall through. The rolling of the shaft creates a wave-like action that stirs the incoming material as it is conveyed forward. This agitation releases smaller material through the mesh and does not accompany shaking or plugging. The tray screen design greatly reduces the possibility of jamming or catching during operation. Trommel screens, vibrating or finger screens, waterfall screens, shaker screens, tray screens, and/or other size separators known in the art also accomplish the same type of size separation objective while using somewhat different engineering designs. The various size separators useful in the present invention are commercially available from many different manufacturers around the world. For example, tray screens, trommel screens, shaker screens, and waterfall screens are commercially available from Vecoplan, Inc. (LLC of HighPoint, NC) at North Carolina high.

D. Density separation

One or more size waste streams may be separated by density to produce an intermediate waste stream that is individually enriched in wet organics, dry organics, and/or specific renewable materials. Although not required, the density separation is preferably carried out in a separation device downstream of the size separator. Downstream density separation allows the use of separators of different densities for each size fraction, which allows each density separator to be configured for a particular material and flow. The density separator unit may be calibrated to provide separation between specific materials in the mixed waste stream. Density separation can be used to separate different types of materials, such as wet organics, dry organics, and inorganic materials, thereby enriching one or more particular intermediate streams in one or more different types of recyclable and/or renewable materials.

In mixed municipal waste streams, inorganic waste, wet organic, and dry organic often exhibit densities within specific ranges. For example, dry organics tend to have densities greater than 1.0 pounds per cubic foot and less than 12 or 15 pounds per cubic foot; the wet organics tend to have a density greater than 8, 10 or 12 pounds per cubic foot and less than 60, 80 or 140 pounds per cubic foot; inorganic materials tend to have densities greater than 80 or 140 pounds per cubic foot. Thus, by setting the density separator accordingly, the wet organic, dry organic and inorganic fractions can be separated on the basis of density. Similarly, particular types of recyclable and/or renewable materials, such as wood and textiles, will typically fall within a certain density range and can be selectively enriched in intermediate waste streams. While the foregoing densities are useful for many municipal waste streams, one of ordinary skill in the art will recognize that the techniques provided herein can be used to analyze any waste mixed solid waste stream and determine a density cutoff for producing an intermediate waste stream enriched in recyclable or renewable materials.

In certain embodiments, a series of density separators may be used to further fractionate the intermediate waste stream. In a downstream density separator, the density cutoff is selected to classify either the lower or upper limit portion received in the upstream density separator. Additional size separators may also be used on the density separated stream. Size and density separation is performed until the intermediate stream is sufficiently enriched in a particular recyclable or renewable material and uniform, allowing for efficient extraction of the recyclable or renewable material using mechanical sorting equipment.

Referring now to fig. 6, an example of a density separation unit adapted to separate municipal solid waste by density is shown. Fig. 6 shows an air drum separator 200. The air drum separator 200 includes an input conveyor 204, a blower 206, a drum 210, an output conveyor 222, a heavy fraction conveyor 218, and a light fraction conveyor 226. Mixed density waste 202 is input on an input conveyor 204. As the waste material 202 is added, it falls from the end of the conveyor 202 where the waste 202 encounters a moving air stream 208 from a blower 206.

The heavy portion 216 is separated from the mixed waste material 202 by being too heavy to be lifted by the air stream 208. The heavy fraction thus falls before drum 210 and onto heavy fraction conveyor 218. In contrast, lighter waste is lifted by air stream 208 and carried over drum 210 and carried forward by either air stream 220 or 222. The light portion 224 falls off the end of the conveyor 222 and onto a light portion conveyor 226. These machines are height adjustable to vary the gravimetric density separation factor, as desired.

The relative densities of the heavy fraction 216 and the light fraction 224 may be adjusted by controlling the air flow through the air drum separator 200. The velocity and volume of the air flow through the drum separator 200 can be adjusted by increasing or decreasing the speed of the fan 206 or by opening or closing the valve 212. In general, opening the valve 212 and/or increasing the speed of the fan 206 will carry heavier objects across the drum 210, resulting in a lighter weight part with a higher average mass. Similarly, closing the valve 212 or reducing the speed of the fan 206 will cause the heavy portion 216 to have a lower average mass and the light portion 224 to have a lower average mass, since only lighter objects are carried across the drum 210. Suitable density separators for use in the present invention include, but are not limited to, air separators (available from western fordetevone (ostbleren) Westeria fordertechnik gmbh, germany). Although the specific example illustrated in fig. 6 is preferred in certain embodiments, other separators may be used, including density separators that do not include a rotating drum (e.g., gravity/air separators, wind movers, air knives, etc.).

A density separator as illustrated in fig. 6 works best when the ratio of largest to smallest objects fed into the density separator is narrow. Thus, it is preferred that the ratio of largest to smallest objects fed into the density separator in the methods and systems described herein is about 12 to 1, about 10 to 1, about 8 to 1, 6 to 1, or about 4 to 1. More preferably, the ratio of maximum to minimum objects fed into the density separator in the methods and systems described herein is about 6 to 1 (i.e., wherein the ratio of the upper cutoff to the lower cutoff is within the aforementioned ratio). In one embodiment, the method and system of the present invention are designed to provide waste material having particle size ratios within these approximate ranges to the density separators.

E. Metering to control flow rate and depth of load

Optionally, the method further comprises metering the size separated waste stream and the intermediate waste stream throughout the system to achieve the desired mass flow and depth of loading. In one embodiment, the size separator, density separator, and/or mechanized classifier are separated by one or more conveyors with different speed controls. Different speed controls can be set to optimize flow optimization through the mass of the comminution apparatus, size separator, density separator, and/or mechanized classifier to optimize the quality, purity, and/or value of the recyclable or recyclable material recovered from the overall system by ensuring that metered and evenly distributed material is provided to each device. One or more sensors positioned upstream, downstream, or within one or more components of the system may be used to monitor the separation efficiency, effectiveness, separation purity, and/or recovery of the recyclable or renewable material. These values may then be used to optimize or maximize one or more parameters in the system, such as the recovery quality, purity, and/or value of the recycled recyclable or renewable materials. Examples of sensors that may be used to control the flow rate of the waste stream include level sensors, such as, but not limited to, optical sensors and/or ultrasonic sensors that measure the height of material accumulated on the conveyor and/or upstream of the metering device and/or measure open space on the conveyor belt. A conveyor belt, a metering device, or other kind of equipment may be accelerated or decelerated using sensor data to ensure that a flow rate or desired depth of load is achieved in the conveyor belt, or in or through a piece of processing equipment (e.g., a size separator) and/or any other portion of the system described herein. Other sensors include a mechanical switch that is physically actuated by the accumulation of waste stream above a desired level (e.g., height), which activates the mechanical switch to provide a signal that can then be used to adjust the flow or depth of the load. All metering devices, including walking floor, conveyors; a metering drum; crushers and grinders; an air drum separator; all types of sieves; a vibratory feeder; a cell-feeder barrel; a load leveler; and the speed of other such devices can be controlled and adjusted by the control system and other devices to properly meter the material through all parts of the invention. In certain embodiments, this metering may be critical to obtain the desired high recovery and purity of recyclable or renewable materials from mixed solid waste.

These systems and methods may include using a plurality of sensors and metering the flow rate and depth load of waste material transported to a plurality of sorting devices. Although not required, it is preferred that each sorting device has a sensor associated with it and that the sensor can be used to independently control the metering of the two or more sorting devices. For example, a level sensor or flow velocity sensor may be positioned adjacent to the inlet of any combination of 3-dimensional classifiers, optical classifiers, eddy current magnetic separators, and the like.

Conversion of renewable materials

The separated dry and wet organic streams are converted to renewable products using first and second conversion techniques, respectively. Any number of separated, enriched intermediate waste streams produced in separation system 112 (fig. 1) may be processed using any number of conversion techniques. The first and second conversion techniques are different techniques, which allow these techniques to be selected to be more suitable for converting wet or dry organic matter, respectively, than a single conversion technique. For example, dry organic matter can be converted to refuse derived fuels that consume less energy than materials that include wet organic matter, and wet organic matter can be converted more efficiently in an anaerobic digester without dry organic and inorganic matter.

A. Conversion of dry organic material

The dry organic fraction can be converted into a renewable product, such as Refuse Derived Fuel (RDF) or recyclable material, using any number of dry organic conversion techniques. Examples of suitable conversion techniques include plasma arc thermal conversion, evaporative fractionation, pyrolysis, biomass thermal conversion, plastic to oil, biogas to liquid fuel (e.g., fischer-tropsch synthesis), chemical conversion processes (e.g., plastic to chemicals).

In one embodiment, dry organic waste is converted into a refuse derived fuel by processing the dry organic waste to have a particularly desirable moisture content and BTU value. In one embodiment, the dry organic material has a BTU value in the range of from about 4000 to 15,000, more specifically about 5000-.

The Refuse Derived Fuel (RDF) may be compressed to allow its transport and/or proper combustion in a biomass boiler. Typically, the compressed dry organic material 116 has a density of about 0.5lb/ft³-50lb/ft³And more specifically about 1lb/ff³-30lb/ft³And even more specifically about 2lb/ff³-20lb/ft³And most specifically about 3lb/ft³-10lb/ft³。

The RDF fuel may be compressed to form chips or pellets and may be passed through any device to a location where the RDF fuel is used, such as, but not limited to, a cement plant that may use the dry organic material to heat a kiln that produces cement.

In a preferred embodiment, the dry organic material is not granulated and used on-site with one or more conversion techniques (e.g., thermal conversion or power generation). When generating electrical energy, the power may be used on site or linked to a local power grid. Because the power is generated locally, it is more valuable because very little power will be lost during transmission.

In one embodiment, the dry organic material 116 may be used as fuel in a biomass boiler to produce steam and drive a steam turbine to generate electricity. One example of a biomass boiler is described in U.S. patent application publication 2009/0183693 to Furman, which is incorporated by reference.

In one embodiment, the biomass boiler may be configured to be fired using fluidized feed (fluidized feed). The dry organic material can be relatively light and easily fluidized for good combustion in a fluidized biomass boiler. The use of this type of biomass boiler in conjunction with on-site power generation saves the cost of compression and/or granulation, produces efficient combustion within the boiler, allows for the use of electricity and waste heat locally, thereby maximizing the caloric value of the dry organic material and minimizing carbon emissions.

The dry organic material may be used in a gasification process. Gasification can be achieved by reacting the dry organic waste (without combustion) with controlled amounts of oxygen and/or steam at high temperatures (>700 ℃) to produce synthesis gas. The syngas can be further used to produce fuel. Several different gasification processes can be used with different dry organic wastes. Examples of suitable gasifiers include parallel flow fixed bed gasifiers, fluidized bed reactors, entrained flow gasifiers, and plasma gasifiers.

In one embodiment, the dry organic material can be converted to a high value compound (i.e., a non-hydrocarbon fuel). For example, plastic box rubbers can be converted to polystyrene by catalytic cracking using a two-step distillation process; polyolefin materials can be formed by catalytic cracking and polyethylene terephthalate can be produced from PETE by solvolysis. Transformation techniques for producing these high-value compounds are available from Gossler Envitec GmBH (germany).

In yet another embodiment, the isolated plastic, e.g., molding compound, may be converted to a liquid fuel by plastic to fuel conversion techniques known in the art (typically catalytic and/or pyrolysis). The components of the dry organic stream can also be converted to biogas by digestion. For example, paper products can be digested by pulping and then by anaerobic digestion to produce biogas, which can be burned or converted into a liquid fuel using a suitable process (fischer-tropsch process).

The wet organic matter may be converted, in part, using mechanical biological treatment, wherein the wet and dry organic matter is compressed and allowed to release moisture to reduce the moisture content. The dried organic waste may then be further processed using one or more other conversion techniques.

The methods described herein also include extracting a plurality of recyclable or recyclable materials from the intermediate waste stream using one or more mechanized classification devices. The particular mechanized sorting apparatus used depends on the particular recyclable or recyclable material to be extracted.

Referring again to fig. 2, the method 140 includes (i) in a first step 142, providing a mixed waste stream comprising recyclable materials, such as paper, plastic, and metals (particularly non-ferrous metals); (ii) in a second step 144, the mixed waste stream is comminuted; (iii) classifying the mixed waste stream by size in a third step 146 to produce a plurality of size separated waste streams; (iv) in a fourth step 148, at least a portion of the size separated waste streams are passed through density fractionation to produce a plurality of intermediate waste streams individually enriched in one or more recyclable materials; (v) in a fifth step 150, the plurality of intermediate waste streams are individually sorted using one or more sorting devices to produce a recyclable product such as, but not limited to, a recyclable paper product, a recyclable plastic product, and/or a recyclable metal product. Optionally, the method may include metering and/or distributing the size separated waste stream throughout any or all portions of the process 140 to control mass flow and/or depth of loading. In one embodiment, the sorting device may be a dimensional sorter, such as a 2-dimensional to 3-dimensional sorting device. Examples of 2D-3D sorters include an impact separator and/or a screen configured to separate two-dimensional articles from three-dimensional articles. Two or more impingement separators and/or screens may be used in series or in parallel. Dimensional separators may be used to recover one or more materials blended with each other having similar densities but substantially different dimensional characteristics (non-sizes). For example, in one embodiment, the 2D-3D separator may be used to separate rigid plastics (which tend to be three-dimensional) from plastic films and/or papers that are generally two-dimensional and flexible. Two-dimensional plastics, including films and rigid materials, typically have a thickness of less than 1/8 inches. Thus, 2-dimensional materials are considered to be 2-dimensional because their thickness is much smaller (e.g., 10 or 140 times smaller) than their length and width. Additionally or alternatively, 2D-3D separators may be used to separate wood (which tends to be more three-dimensional) from fabric (which tends to be more two-dimensional). The impact separator may also separate the material into hard and flexible species.

Another type of mechanized sorting apparatus that may be used is an optical sorting machine. The optical sorting machine may be configured to separate paper from film plastic or different types of plastic from each other. For example, the optical sorting machine may be configured to recover HDPE and/or PETE from the intermediate waste stream. The one or more optical sorters may also be configured to recycle #1-7 plastic and/or remove and/or recycle PVC plastic. Optical sorters may also be used to sort glass from the intermediate stream that is rich in small inorganic particles. There are many types of optical sorter technology including, but not limited to, Near Infrared (NIR), camera color sorter, X-ray, etc.

The optical sorting machine may scan the intermediate waste stream and determine whether the material being analyzed is a particular type of plastic, paper, or glass. The optical sorting machine uses air directed through nozzles to eject the target/identification material in detecting a particular material to produce one or more recyclable products, such as recyclable PETE, recyclable HDPE, recyclable film plastic, recyclable #3-7, and/or recyclable paper-like products.

Any optical sorting machine known in the art may be used. For example, in one embodiment, the optical sorting machine may operate by scanning a free-falling intermediate waste stream using a camera. The camera detects the material and then the air jet can rapidly eject the material as it falls freely. There are also optical sorters that utilize near infrared, X-ray and other scanning techniques to separate target materials from a mixed stream. Any number of optical sorters can be used in series or in parallel. Optical sorter manufacturers include TiTech pelletnc, MSS, NRT, and others.

B. Conversion of wet organic material

The wet organic fraction may be processed in one or more conversion techniques best suited for materials with high water content (e.g., greater than 25 wt% or 30 wt%) water. Suitable wet organic stream conversion techniques include wet or dry digestion, which includes anaerobic digestion, aerobic digestion, and composting.

Referring to fig. 1, the separation system 112 produces wet organic material 114 that is digested in anaerobic digestion 126. The separation system 112 may use any anaerobic digestion, including complete mixing, plug flow, and/or upflow anaerobic digestion. In a preferred embodiment, the anaerobic digestion system 126 comprises an upflow anaerobic digester, and most preferably, the upflow anaerobic digester system is a sensor blanket upflow anaerobic digester. The induced upflow anaerobic digester includes a horizontal membrane that increases the entrapment of solids and bacteria and reduces the hydraulic retention time required to digest the organic solids.

In one embodiment, the hydraulic retention time of the anaerobic digester is less than 20 days, more preferably less than 15 days, and most preferably less than about 10 days. Preferably, the anaerobic digestion system 126 includes a plurality of individual tanks that allow for maintenance without interrupting overall operation. Preferably, the anaerobic digester includes methanogenic and acidogenic bacteria in a single tank.

Suitable microbial digestion systems that can be used to digest the wet organic waste product produced in the present process can be found in: U.S. Pat. No. 7,615,155 entitled "Methods for removal of non-diagnostic from an upstream and diagnostic dicester"; U.S. patent 7,452,467 entitled "Induced slider bed and aerobic reagent"; U.S. patent 7,290,669 entitled "Upflow biorator having section and an anger and drive assembly" and U.S. patent 6,911,149 entitled "Induced slider and aerobic reactiver" and U.S. patent publication 2008/0169231 entitled "Upflow biorator with section and pressure assembly mechanism," which are hereby incorporated by reference in their entirety.

To provide optimal digestion in the digester system 126, a pre-processing digester feed system 134 as discussed above with respect to fig. 3 may be used. The digester feed system 1134 may include a mill or a crushing device for reducing the particle size of the wet organic material. In one embodiment, the particle size is reduced to less than about 1 inch, more preferably less than 3/4 inches, and even more preferably less than 1/2 inches. The digester feed system 134 may also include increasing the temperature of the wet organic material to achieve a temperature near or within 2-10 ℃ above the desired operating temperature of the digester. In addition, water may be added to the organic material to achieve the desired solids concentration. In one embodiment, the temperature may be a medium temperature or a high temperature. In one embodiment, the temperature is in the range of from about 110 ° F to about 180 ° F, more specifically about 120 ° F to about 150 ° F. These temperatures may be achieved using waste heat from the power generation site using on-site organic fuels and/or biogas and/or from operating the furnace. The heating may be to a component of the feed system 134 or directly to the anaerobic digester.

In one embodiment, the water added to the wet organic material is obtained from the effluent from the anaerobic digester system 126. The digester feed system 134 may produce a mixture of wet organic material having a solids content ranging from about 5% to about 40%, more specifically ranging from about 10% to about 35%, and about even more specifically about 15% to about 30%.

As mentioned above with respect to fig. 3, either the anaerobic digestion system 126 or the aerobic digestion system 130 may produce a compost-like product (i.e., biogas residue 128). Biogas residue 128 may be directly dehydrated or dried or further solidified and/or otherwise processed by aerobic composting 129 into a highly nutritious soil amendment 137. In a preferred embodiment, the biogas residue 128 has a reduced pathogenic bacteria and/or reduced bacterial content (seed content) and should be as free as possible of inorganic materials, such as glass and plastic. High temperature may be used in the anaerobic digester 126 in combination with the coarse separation process 112 and digester feed pre-processing 134 to remove undesirable inorganic materials to produce high quality biogas residue. The biogas residue 128 may be dewatered using a mechanical process 131 and dried using waste heat of the biogas power generation system 145 and/or the dry organic power generation system 122. In this embodiment, the exhaust gas from the combustion may directly heat the biogas residue or the exhaust gas may indirectly heat the biogas residue by using a heat exchanger. Alternative drying methods include anaerobic composting 129, solar drying, or air drying.

As mentioned above, the anaerobic digestion system 126 may produce a biogas 132 that may be conditioned using biogas conditioners to remove impurities and/or increase the concentration of hydrocarbons. Biogas conditioning 141 may include removal of hydrogen sulfide, carbon dioxide, water, and/or other components commonly found in biogas. The conditioning of the gas can be carried out by adsorbing the undesired components onto an adsorbent, for example a zeolite.

The conditioned biogas 132 may be processed into a liquid or concentrated fuel 131. Typically, the biogas 132 is compressed in a series of compressors to achieve the desired pressure for use in transportation fuels. The compressed and conditioned biogas 132 may be used on-site to power plants that traditionally use diesel fuel. Alternatively, the compressed and conditioned biogas 132 may be sold or transported for use in conventional compressed natural gas applications. In yet another embodiment, the conditioned biogas 132 may be liquefied using a compressor and/or refrigeration. The liquefied biogas can be sold or transported for use in conventional liquefied natural gas applications. The conditioned biogas 132 may also be converted to biodiesel using a fischer-tropsch synthesis.

The conditioned biogas 132 may also be combusted in a biogas power generation system 145 to produce heat and/or electrical energy. The biogas power generation system 145 may use a power generation system for burning methane to generate power as known in the art. The power generation system 145 may use a microturbine or a conventional internal combustion engine in combination with a generator and/or a thermal oxidizer in combination with a steam generator. Adjusting the biogas 132 may improve the combustion characteristics of the biogas 132 and the power generation system 145. However, when the power generation system 145 is designed to burn low BTU biogas and/or biogas containing gases such as hydrogen sulfide, the biogas 132 may be used in the power generation system 145 without gas conditioning.

Examples of other technologies for wet organic waste conversion include composting, where wet organic material is allowed to degrade in the presence of oxygen to produce compost with aerobic conditions. This technique is energy intensive and is not preferred when biogas is desired.

Wet organic matter may also be processed in dry digestion, where the wet organic matter may be placed in a digester, alone or in combination with other dry organic or inorganic materials, through which water is leached through the material under hypoxic conditions to produce anaerobic conditioning. The biogas produced by dry digestion can be collected and combusted for power generation or conversion to a liquid fuel.

C. Recovery of inorganic materials

In one embodiment, the intermediate waste stream may be enriched in metals, including ferrous metals and/or non-ferrous metals. For the extraction of non-ferrous metals, eddy current magnetic separators may be used. The eddy current magnetic separator can recover nonferrous metals such as aluminum, bronze, and copper. Alternatively or additionally, the metals may include ferrous metals and one or more magnetic separation devices may be positioned throughout the system and configured to collect the ferrous metals. Examples of magnetic separators include drum magnets, cross-belt magnets, head pulley magnets (head pulley magnets), and the like. Optical sorters, stainless steel sorters, infrared sorters, camera sorting machines, induction sorters, metal detection systems, X-ray sorters, and the like may be used to separate different types of materials from one another to produce a recyclable product. The recyclable metal product produced in the methods and systems described herein may be selected from the group consisting of: non-ferrous recyclable products such as aluminum, bronze, and copper and/or other metals such as iron and/or stainless steel.

The mechanical classification and sorting of the systems and methods described herein is particularly useful for extracting high value waste materials such as non-ferrous metals, as well as paper and plastics. In prior art systems, these items are particularly difficult (or practically impossible) to extract and/or sort from mixed solid waste. Conventional systems typically cannot extract a significant portion of paper or plastic and/or non-ferrous metals because these materials cannot be extracted using magnets. It is known to use magnets in conventional mixed waste processing systems. Magnets are very inexpensive and can be used at multiple locations within the system making their use economically viable even when the magnets only extract a small percentage of the ferrous metal. However, since many different materials are found in mixed solid waste, it is extremely difficult and inefficient to recover even iron metal from the mixed solid waste. The typical conditions of mixed solid waste, when it is swept from a collection vehicle and/or transport trailer, are such that a simple magnetic device would likely yield a very small percentage of the available ferrous metal contained in the mixed solid waste stream, less than 20% and any metal recovered in this way would be highly contaminated by other materials found in the mixed solid waste that would be trapped between the magnet surface and the attracted metal objects (e.g. cardboard, plastic, etc.). In contrast, materials like recyclable plastics, paper, and non-ferrous metals (e.g., bronze) often cannot be extracted from mixed waste because the sorting equipment for these particular materials cannot handle waste streams as configured in these systems. Despite the fact that nonferrous metals and many classes of recyclable plastics typically have values as high as 5-15 times that of ferrous metals, the industry generally uses only equipment for extracting ferrous metals from mixed waste. Furthermore, it is difficult to recover these higher value recyclables such as paper, plastic box nonferrous materials through the same common mixed solid waste conditions, as such recyclables are so completely mixed or concealed with the large amount of other unrecyclable items (e.g., organics, inert materials, wood, fabrics, fines, etc.) found in the mixed waste stream. In addition, most mixed solid waste, especially from urban collection routes and multi-family homes, is deposited in plastic bags and discarded. The manual opening of the trash bags picked from mixed solid waste in some way and the subsequent separation and recovery of any released recyclables is in fact cost prohibitive in most underdeveloped countries. Finally, the highest value recyclable goods/materials (e.g., PETE plastic, HDPE plastic, #3-7 plastic, aluminum boxes, stainless steel, copper, bronze, mixed non-ferrous metals) are commonly found in very small percentages, on an individual material basis, between.1% and 4%, relative to the total mixed solid waste stream. Without most or all of the components described herein (e.g., preparation, size separation, metering, homogenization, and sorting), separating these high value recyclable materials from materials having such low available percentages within mixed waste streams is not several times able to do so in an economically viable process. The methods described herein provide novel, efficient, and high-throughput solutions to the long-term challenges of this waste processing industry.

D. Recovery of recyclable and renewable materials.

The present invention is particularly advantageous for recovering a substantial portion of one or more recyclable and renewable materials present in mixed solid waste streams. These methods can be particularly useful when high value recyclables are present at very low concentrations. These systems and methods allow for processing of mixed waste streams, such as "lift-off pick-up needles from licorice piles". In one embodiment, the mixed solid waste stream may include at least one type of recyclable material having a concentration of less than 15%, less than 10%, less than 5%, or even less than 1%, wherein the systems and methods are configured to recover at least 50%, at least 70%, at least 80%, or even at least 90% of a particular recyclable material.

Further, the methods and systems described herein can recover at least 25%, 50%, 75%, or 90% (by weight) of the recyclable metal in the waste stream as a recyclable metal product having a purity suitable for sale to a recyclable metal wholesaler.

The method can recover at least 25%, 50%, 75%, or 90% by weight of recyclable plastic material in the mixed waste stream to produce a recyclable plastic product having a purity suitable for sale to a recyclable plastic product wholesaler.

The method can recover at least 25%, 50%, 75%, or 90% by weight of the recyclable mixed paper product in the mixed waste stream to produce a recyclable mixed paper product having a purity suitable for sale to a recyclable mixed paper wholesaler.

The process can recover at least 25%, 50%, 75%, or 90% of the recyclable dry organic material to produce one or more (e.g., 1, 2, 3, 4, or more) recyclable or renewable dry organic products. The dry organic product may be selected from the group of hybrid paper, 3-dimensional plastics, film plastics, textiles, and wood.

Comminution, size separation, and/or density separation can be used to produce uniform recyclable streams that are substantially free of recycled or used contaminants without further separation from other types of components present in the mixed waste and/or sold as recyclable goods.

Different renewable materials and products can be used on-site or off-site in the separation system to produce renewable products, such as plastic bottles, metal parts, energy, and/or for performing any manufacturing process known in the art to utilize the heat of the renewable energy and products.

System for separating mixed solid waste

Fig. 7 illustrates a system 300 that can be used to separate wet and dry organic materials from a mixed waste stream and recover renewable and recyclable products. In fig. 7, mixed solid waste, such as municipal solid waste, is metered into a pre-sorting conveyor 302. The metering may be performed using a metering drum 304 and a feed conveyor 306 that receives the mixed solid waste from a walk-plate bucket feeder 308. The mixed solid waste on the conveyor 302 is conveyed to a crusher or grinder 316. The mixed waste on the conveyor 302 may be sorted manually. For example, a manual worker may pick large pieces of cardboard that are easily identified and selected from a large volume of waste. Other materials may be manually picked prior to shredding, grinding, or size reduction, including large pieces of treated wood, electronic equipment waste (e.g., e-waste), or other apparently valuable items that may be efficiently hand picked or otherwise conveniently pulled from the conveyor 302. Household Hazardous Waste (HHW) may also be removed from the transporter 302 and appropriately packaged and removed to the appropriate facility. The picked sheets may be collected in a bin 310 and sorted or packaged and transported to a paper mill. Other recyclable materials, such as non-ferrous metals and/or other sources of renewable materials, may be collected and sorted in the drum 312 or conventional drums. In addition, hazardous waste may be collected and sorted in the bin 314 and then disposed of in an appropriate manner. Although pre-classification is not required, pre-classification can be particularly useful to avoid contamination of hazardous waste and potential damage to the crusher from heavy iron structural metals, cement, large stones and other items.

The unsorted material from the conveyor 302 is delivered to a crusher or grinder 316, which crushes or grinds the waste to the desired upper cut-off value described above. The broken material moves on a conveyor 318 under a levitation magnet 320 that collects ferrous metal exposed to the waste stream and delivers it to a ferrous metal storage point 322. Due to the depth of loading, magnet 320 is preferably a suspended drum magnet, however other magnets may be used alone or in combination with the suspended drum magnet. The drum magnet is advantageous because of the depth of the load prior to size sorting and its ability to capture the ferrous metal in flight discharged from the conveyor 318, thus minimizing most non-metallic cross contamination of the extracted ferrous metal. Other types of magnets (e.g., cross-belt magnets) can also be mounted in suspension above the conveyor belt drive shaft.

The shredded waste passing under the magnets 320 is delivered to a screen 324 that separates the shredded waste stream by size to produce a first oversized fraction and a first undersized fraction. The screen 324 may include one screen or a plurality of similar and/or different sized screens and types of screens to produce one or more undersized portions and one or more oversized portions. The oversized fraction may be enriched in dry organics and the undersized fraction may be enriched in wet organics.

Undersized portions (i.e., fines) from screen 324 are transported on a conveyor 326 to a second screen 328. The undersized fraction (i.e., fines) from the second screen 328 may include wet organics and/or heavy inorganic materials that may be processed using an eddy current magnetic separator 330 to remove non-ferrous metals. The conveyor 329 may be switchable to direct fines from the screen 328 directly to the conveyor 336 (if the inorganic fraction is predominant) or to the vortex separator 330 (if the wet organic fraction is predominant). The wet organics from the eddy current magnetic separator 330 can be collected and sorted in drum 332 and the non-ferrous metals collected in drum 333.

The oversize fraction (i.e., coarse material) from the fine screen 328 may be further processed in a density separator 334 to produce a light fraction having a small particle size and a heavy inorganic fraction. The heavy inorganic fraction may be transported to a conveyor 336 and the light fraction may optionally be loaded into a second density separator 338 for additional separation into a light dry organic fraction and a heavy wet organic fraction.

Referring now to the first oversized fraction (from screen 324), the oversized fraction is transported on a conveyor 340 to a third density separator 342. The third density separator 342 can be configured to produce a light intermediate stream and a heavy intermediate stream. For example, the third density separator 342 may be configured to intercept in the range of from 8-15 lbs. The light intermediate stream (i.e., less than 8-15lbs) may be rich in dry plastic, paper, light ferrous metal (e.g., tin cans and tin can lids and other light ferrous metal items), and light nonferrous metal (e.g., aluminum cans, and other light nonferrous items), which are conveyed to a conveyor 344.

The heavy intermediate waste stream (i.e., greater than 8-15lbs) from the third density separator 342 can be rich in inorganic and heavy wet organic materials as well as heavy dry organic materials (e.g., wood and textiles), which are delivered to the fourth density separator 346 for additional separation. The fourth density separator 346 can be truncated from the range of 60-120lbs to produce a light intermediate stream that is delivered to a fifth density separator 364. The fifth density separator 364 may intercept 40 to 60lbs of wet organic material from 10 to 15lbs of dry organic material consisting essentially of wood and fabric. The fifth density separator 346 may also produce a heavy intermediate stream (i.e., greater than 60-120lbs) rich in heavy inorganic waste, which is delivered to the conveyor 336. The intermediate stream on the conveyor 336 may be sorted using suspended drum magnets to collect ferrous metals and the rest of the stream loaded on the vibratory feeder 350 feeding the eddy current magnetic separator 352, which separates the non-ferrous metals from the rest of the inorganic waste. The nonferrous metals can be further separated in an infrared or other sorter 381 to extract copper and/or bronze (i.e., the mixed nonferrous products stored in barrel 396 and the copper products stored in barrel 398) from the other nonferrous metals. The nonferrous metal can be packaged and/or stored in bulk for transport to a mill.

The remainder of the waste stream exiting the eddy current magnetic separator 352 is loaded onto a conveyor 354 and further processed using a stainless steel sorter 356 and a glass optical sorter 358. The intermediate stream can be classified to extract stainless steel using a stainless steel classifier 356 and/or to extract glass using an optical classifier 358. This classification can produce a recyclable stainless steel product and a recyclable glass product, which are stored in barrels 362 and 360, respectively.

Referring again to the fifth density separator 364, the light intermediate stream from separator 346 may be fractionated at densities of up to 15lbs for wood and fabrics and up to 40lbs-60lbs for heavy wet organics to produce a light intermediate waste stream rich in wood and fabrics. The wood and fabric can be separated on a 2D-3D classifier such as, for example, an impact or angle-scale screen separator or other type of 2D-3D separator 366 to produce a three-dimensional recyclable or recycled wood product and a two-dimensional renewable or recyclable fabric product, which are collected in buckets 368 and 320, respectively. The heavy stream from separator 364 may be rich in heavy wet organics and may be delivered to eddy current separator 330 and/or combined with waste from screen 328 and density separator 338.

Referring again to conveyor 344, the intermediate light stream from density separator 342 may be processed through levitation magnets 372 to produce a recyclable ferrous metal product that is collected in drum 373. A portion of the intermediate stream passing under the magnet 372 to the vibratory feeder 374 is loaded onto a series of eddy current magnetic separators 376 and 378, which process the intermediate stream to collect the nonferrous metals. The nonferrous metals can be collected on a conveyor 377 and compressed into bales using a baler 379 and then stored for transport.

The dry organics recovered in the eddy current magnetic separators 376 and 378 provide an intermediate stream rich in paper and plastic. The intermediate stream rich in paper and plastic can be processed using a 2D-3D separator such as, for example, an impact or angled disk screen separator or other type of 2D-3D separator 380. An impact or angle disc screen separator or other type of 2D-3D separator 380 separates plastic films and/or paper (i.e., 2-dimensional particles) from three-dimensional particles (e.g., broken, hard plastic). The 2D-3D separator may be placed before or after the levitation magnet 372 and the eddy current separators 376 and 378.

Two-dimensional material from an impact or angle disc screen separator or other type of 2D-3D separator 380 may be delivered to a conveyor 400 and the three-dimensional material may be further processed using an optical sorter. The three-dimensional material can be processed in a first optical sorter 382 to produce HDPE plastic products or PETE plastic products or #3-7 plastic products, which are deposited on a quality control conveyor 383 and placed in a drum 384 or baled in a baler 385. The intermediate stream may then be processed in a second optical sorter 388 to produce PETE plastic product or HDPE plastic product or #3-7 plastic product, which is deposited on a quality control conveyor 389 and deposited into drum 386 or baled in a baler 387. Finally, the intermediate waste stream can be processed in a third optical sorter 390 to produce a #1-7 plastic product or a HDPE plastic product or a PETE plastic product, which is deposited on a quality control conveyor 391 and deposited into a drum 392 or baled in a baler 397. The remainder of the waste streams from optical sorters 382, 388, and 390 may be non-recyclable or renewable residual materials or improperly stored recyclable materials (e.g., PVC, stone, foam, e-waste, liquid-filled plastic bottles, scrap of aluminum cans, etc.) that may be recovered on conveyor 393 and/or stored in drum 395 or sent to a shipping tray prior to landfill disposal or further separation into potentially recyclable fractions of mixed inorganic materials and conversion into different building materials that may be potentially sold or used in building applications.

Reference is now made to the two-dimensional material received on the conveyor 400 from an impact or angle disc screen separator or other type of 2D-3D separator 380, which may be an intermediate stream of film-rich plastic box-mixed paper. The two-dimensional material may be loaded into a metering hopper or other type of metering storage and feeding device 402 and then metered into a plurality (e.g., 2-12) of optical sorters 404 configured to separate the film plastic magazine duroplastic from the paper. The optical sorter 404 produces recyclable highly concentrated plastic film products or fuels 406 and recyclable or recyclable hybrid paper products 408, any or all of which can be packaged and/or stored for sale or shipment.

The wet organics produced in system 300 (e.g., wet organics in drum 332) as well as any or all of the dry organics can be further processed using the conversion techniques described above. In one embodiment, plastic film products 406 or mixed plastics may be transported to a conveyor 430A and delivered to a material storage warehouse 432. From the material storage warehouse, the plastic product may be processed into a renewable fuel in a plastic conversion process 434. Alternatively, the plastic product may be shredded in shredder 436 and transported on conveyor 440 to gasifier 442. Gasifier 442 may generate heat to drive turbine 444 and produce electricity or produce mechanical power. In alternative embodiments, the mixed paper or mixed paper 408 or mixed paper and plastic may be transported to the conveyor 430 and delivered to the gasifier 442.

The wet organic matter produced in the system 300 (e.g., wet organic matter in the barrel 332) may be further processed, composted, provided to, or sold to processors as a highly concentrated mixed wet organic stream (e.g., food waste and yard waste and garden waste). Fig. 7 shows an embodiment for converting wet organic to a higher value product (e.g. biogas or electricity). The wet organics from the drum 332 are transported to a metering/storage drum 446 to be fed into a pre-processing apparatus 448. The pre-processing device 448 may be a separator, such as a scott turbine separator, having breaker bars that break up particles added to the anaerobic digester 450 and sprays flexible items, like rubber and fabric, which may be sprayed onto the conveyor 460 and sent to the residue tank 462 or delivered to the conveyor 440 for gasification (if appropriate).

The anaerobic digester 450 produces biogas and biogas residue. The biogas residue may be dewatered using dewatering device 452. The separated digestate can be stored in bulk storage 454 or delivered to a conveyor 440 for gasification in a gasifier 442. Solids from the digestate can be dried and/or composted to produce a soil amendment.

The biogas produced in the digester 450 may be conditioned to produce electricity prior to combustion in the internal combustion engine 458. The biogas conditioner 458 may include an absorbent that absorbs contaminants and/or carbon dioxide. The power generated from the internal combustion engine 458 may be used on-site to power components of the waste processing system and/or may be placed in a power grid for use by the consuming public. The biogas conditioner may be periodically regenerated to maintain its ability to absorb contaminants.

Dry organic dyes can replace coal and other carbon-based fuels in many industrial and power generation processes, for example, either alone or with another fuel. Dry organic fuels can also be used as fuels to produce syngas through a number of high temperature thermal conversion processes (e.g., gasification, plasma arc gasification, and pyrolysis). The dry organic material may also be stored on-site in bulk storage depots having mechanized filling and unloading systems or in storage silos having unloading devices.

One of ordinary skill in the art will recognize that the recyclable products produced using the methods described herein are highly enriched in a particular type of recyclable material, which makes one or more different products useful as feed materials in a recycling process. Nevertheless, the recyclable products are typically not 100% pure. Although the recycling industry cannot use the original raw waste, most recycling systems can operate properly with small amounts of impurities. The system and method of the present invention can be used to produce recycled products having a purity suitable for use in the recycling industry.

It is also desirable to convert recycled recyclables into new products using conventional manufacturing techniques (e.g., pulping for paper, producing aluminum ingots from aluminum cans, manufacturing PETE bottles to PETE bottles, PETE to insulation, HDPE to HDPE bottles or packaging, glass to building materials, etc.), directed to selling recycled materials to the conventional recycled materials market.

While it may be desirable to recover value from substantially all of the solid waste stream, the present invention includes the following examples in which all or a portion of the wet organic, dry organic or inorganic fractions are not completely separated into recovered product. For example, in one embodiment, all or a portion of the wet organic, dry organic, or inorganic fractions (whether mixed, separated appropriately, or not properly separated) may be merely landfilled, depending on the purity of the particular fraction and/or the market conditions for recycling the particular fraction (e.g., the membrane may be landfilled).

Although many of the methods and systems disclosed herein are described as including density separation, one of ordinary skill in the art will recognize that sufficient separation may be achieved without density separation in certain embodiments, so long as the waste stream is comminuted and size separated to produce an intermediate stream enriched in at least one recyclable material.

Additional embodiments of the invention include systems and methods incorporating one or more of the features described in the following applications: U.S. provisional patent application No. 61/298,208 filed on 25/1/2010, 61/308,243 filed on 25/2/2010, and 61/417,216 filed on 24/11/2010; and/or U.S. non-provisional patent application No. 12/897,996; all of which are incorporated herein by reference.

The present invention may be embodied in other forms without departing from its spirit or essential characteristics. The described embodiments are to be considered in all respects only as illustrative and not restrictive. The scope of the invention is, therefore, indicated by the appended claims rather than by the foregoing description. All changes which come within the meaning and range of equivalency of the claims are to be embraced within their scope.

Claims (20)

1. A method for processing mixed solid waste, comprising:

providing a mixed waste stream comprising at least 10 wt% of blended wet organic waste and at least 10 wt% of blended dry organic waste;

separating the wet organic waste from the dry organic waste using at least one mechanical separator to produce an intermediate wet organic stream and an intermediate dry organic stream, wherein the separating comprises sizing the mixed waste to produce a sized waste stream, the sized waste stream having a lower limit greater than 2 inches and an upper limit less than 18 inches, and the at least one mechanical separator comprises a density separator;

converting at least a portion of the intermediate wet organic stream into one or more renewable products using at least a first conversion technique; and

converting the intermediate dry organic stream into one or more renewable products using at least a second conversion technique, wherein the second conversion technique is different from the first conversion technique.

2. A method as in claim 1, wherein less than 40 wt% of the mixed waste stream is separated into recycled products using manual labor.

3. A method as in claim 1, wherein less than 1 wt% of the mixed waste stream is separated into recycled products using manual labor.

4. A method as in claim 1, wherein the mixed waste stream comprises at least 15% dry organic waste and at least 30% wet organic waste.

5. The method of claim 1, wherein at least 10 wt% of the mixed waste stream is dry organic waste selected from the group consisting of 3-dimensional plastics, film plastics, paper, cardboard, rubber, fabric, and wood.

6. A method as in claim 1, wherein at least 10 wt% of the mixed waste stream is wet organic waste selected from the group consisting of food waste, animal waste, yard waste, and garden waste.

7. The method of claim 1, wherein the mechanical separator comprises a crusher, a particle size separator, a density separator, or a combination thereof.

8. The method of claim 1, wherein the throughput of the mechanical separator has a throughput of at least 2 metric tons/hour/single line mixed solid waste.

9. The method of claim 1, wherein the first conversion technique is selected from wet digestion, dry digestion, anaerobic digestion, aerobic digestion, or composting.

10. The method of claim 9, wherein the first conversion technique produces biogas.

11. The method of claim 10, wherein the biogas is converted to liquid fuel or electricity.

12. A method as in claim 1, wherein the first conversion technique comprises digesting the organic waste in an induction blanket up-flow anaerobic digester.

13. The method of claim 1, wherein the dry organic material is further dried using aerobic composting, air drying, solar drying, waste heat from burning biogas and/or from burning dry organic material prior to conversion by the second conversion technique.

14. The method of claim 1, wherein the separation of the wet organic material from the dry organic material produces a dry organic material having a moisture content of less than 25% and the dry organic material is converted to a waste-derived fuel.

15. The method of claim 1, wherein the second conversion technique comprises compressing the dry organic material and/or thermally oxidizing the dry organic material to generate electricity and/or heat.

16. The method of claim 1, wherein the mixed waste stream comprises at least 20% by weight of low value materials selected from the group consisting of: wet organics, green waste, food waste, gravel, fines less than 1 inch, asphalt, concrete, fabric, wood, rubber, membrane plastic, PVC, foil, rock, used consumer products, low value glass, composites, and combinations of these.

17. The method of claim 1, wherein the dry organic waste is rich in plastics, the second conversion technique comprising sorting the dry organic material by separating 3-dimensional plastics from 2-dimensional plastics to produce a 3-dimensional recyclable plastic product.

18. The method of claim 17, wherein the 2-dimensional plastic is converted to fuel and the 3-dimensional plastic is recycled to form a plastic product.

19. The method of claim 1, wherein the mixed waste stream comprises inorganic waste, the method further comprising separating at least a portion of the inorganic waste from the wet organic waste material and the dry organic waste material to form an inorganic waste stream enriched in inorganic waste material.

20. The method of claim 1, wherein the mixed waste stream comprises inorganic waste, the method further comprising:

separating at least a portion of the inorganic waste from the wet organic waste material and the dry organic waste material to increase the purity of the wet organic waste stream and the dry organic waste stream; and

recovering at least a portion of the dry organic material as a recyclable product.