WO2016013966A1

WO2016013966A1 - Device and method for elimination of particles from gaseous media

Info

Publication number: WO2016013966A1
Application number: PCT/SE2015/000046
Authority: WO
Inventors: Ulf Johanson
Original assignee: Individual
Current assignee: Individual
Priority date: 2014-07-22
Filing date: 2015-07-15
Publication date: 2016-01-28
Anticipated expiration: 2017-01-22
Also published as: SE538662C2; SE1400364A1

Abstract

The present invention relates to a device for the elimination of particles present in gases, such as smoke and exhaust gases, in particular diesel engine exhaust gases and particles related to ventilation air by agglomerating said particle, whereby means for agglomeration of particles consists of a perforated conical structure (2) being arranged to let a gaseous media pass from the cone bottom (1) and inside the cone wall to the outside of the cone wall via said perforations (5) while any particulate matter is agglomerated inside the cone and collected at the apex (3) of the cone from where said matter is removed.

Description

TITLE

DEVICE AND METHOD FOR ELIMINATION OF PARTICLES FROM GASEOUS MEDIA.

DESCRIPTION

Technical field

The present invention relates to a device for the elimination of particles present in gases, such as smoke and exhaust gases, in particular diesel engine exhaust gases and particles related to ventilation air.

The object of the present invention is to obtain a device for elimination/reduction of the amount of particles in such gases in order to thereby reduce the environmental risks, in particular for those being present in the neighbourhood, i.e., are present close to a major road having a high traffic load.

Background of the invention

Soot, or particulate matter (PM), is produced in both gasoline and diesel-powered engines.

These engines create chemical and organic compounds from the combustion of hydrocarbon-based fuels (fossil fuels). These compounds then cluster together in particle form to create soot, which is released into the air as exhaust. Soot may also be produced as the indirect by product of nitrogen oxides (NOx) and sulphur dioxides (SOx) reacting in the atmosphere. Soot's composition often includes hundreds of different chemical elements, including sulphates, ammonium, nitrates, elemental carbon, condensed organic compounds, and even carcinogenic compounds and heavy metals such as arsenic, selenium, cadmium and zinc. One of reasons conventional diesel engines release more soot than their

conventional gasoline counterparts has to do with the way fuel is injected and ignited: on gas engines, fuel is injected during the intake stroke and ignited with a spark; on diesels, fuel is injected during the compression stroke, and the fuel ignites spontaneously from the pressure. As a result, gas engines have two emissions advantages: The ignition process is more carefully controlled and the air and fuel are more thoroughly mixed before ignition occurs, thereby reducing the amount of unburned fuel.

In a conventional diesel, fuel is injected late in the cycle and the air is not as well mixed as in a gasoline engine. As a result of this less homogeneously mixed fuel and air, there are fuel-dense pockets in the combustion chamber. The consequence is that diesel engine exhaust contains incompletely burned fuel (soot) known as particulate matter.

But new engine standards alone are not enough to protect the public from diesel pollution. New standards for diesel engines will be slowly phased in over the next 10 years. Plus, the durability of diesel engines means that older, high-polluting vehicles can continue to operate for decades. Diesel soot emissions are furthered by the fuel itself, as today's conventional diesel fuel contains significantly more sulfur than does gasoline.

The soot in your neighbourhood may be different than the soot in someone else's hometown, but no matter the source and type, soot can present a grave health threat. As previously mentioned, soot particles either come directly from the tailpipe, or can be formed when tailpipe emissions of NOx and SOx react with atmospheric agents. Once formed, soot comes in many sizes, though all just a fraction of the width of a human hair, from coarse PM (less than 10 microns in diameter) to fine PM (less than 2.5 microns) to ultra fine PM (less than 0.1 microns). Most soot is in the fine and ultra fine categories, with ultra fine particles making up 80-95% of soot. Ultra fine particles are the most dangerous, however, as they are small enough to penetrate the cells of the lungs. Soot particles can have an environmental lifetime of one to three weeks, and they can travel long distances, journeying to communities in far regions. Soot particles have even been found at the South Pole, where no major emission source exists for thousands of miles.

The diesel industry is constantly innovating new solutions to clean up existing diesel engines that run for millions of miles. Employing emissions control systems and devices, owners of diesel products are able to make the most out of their investment in diesel technology. In a white handkerchief test, a demonstration a white

handkerchief remains clean even when held in front of an exhaust pipe.

High Efficiency Diesel Particulate Filters (DPFs)

High efficiency diesel particulate filter (DPF) removes PM in diesel exhaust by filtering exhaust from the engine. The filter systems can reduce PM emissions by 80 to greater than 90 percent.

Wall-Flow Diesel Particulate Filter

High efficiency filters are effective in controlling the carbon fraction of the

particulate, the portion that some health experts believe may be the PM component of the greatest concern.

Since the volume of particulate matter generated by a diesel engine is sufficient to fill up and plug a reasonably sized filter over time, some means of disposing of this trapped particulate must be provided. The most promising means of disposal is to burn or oxidize the particulate in the filter, thus regenerating, or cleansing, the filter. This is accomplished through the use of a catalyst placed either in front of the filter or applied directly on the filter, a fuel-borne catalyst, or burners which are used to oxidize or combust the collected particulate. Flow-Through Filters

Flow-through filter technology is a relatively new method of reducing diesel PM emissions that unlike a high efficiency DPF, does not physically "trap" and accumulate PM. Instead, exhaust flows typically through a catalyzed wire mesh or a sintered metal sheet that includes a torturous flow path, giving rise to turbulent flow conditions. Any particles that are not oxidized within the flow-through filter flow out with the rest of the exhaust. So far, there have been limited commercial use of the flow-through filters but there is an increasing interest in this technology due to its ability to significantly reduce PM emissions from older, "dirtier" diesel engines.

Flow-through systems are capable of achieving PM reduction of about 30 to 70 percent.

Diesel Oxidation Catalysts (DOCs)

Like catalytic converters already used on all new gasoline vehicles, diesel oxidation catalysts (DOCs) cause chemical reactions to reduce emissions without being consumed and without any moving parts.

The exhausts of engines share similar physical and chemical characteristics with airborne materials from many sources. This makes it difficult to quantify the portion of an individual's exposure from the general environment that derives directly from engine exhausts and also complicates assessment of occupational exposures to engine exhausts.

A '"diesel particulate filter'", sometimes called a "DPF"', is device designed to remove diesel particulate matter or soot from the exhaust gas of a diesel engine, most of which are rated at 85% efficiency, but often attaining efficiencies of over 90%. A diesel-powered vehicle with a filter installed will emit no visible smoke from its exhaust pipe, as >99% have a particle size of less than 1 pm (visible particles have a size of more than 30 pm). In addition to collecting the particulate, a method must be designed to get rid of it. Some filters are single use (disposable), while others are designed to burn off the accumulated particulate, either through the use of a catalyst (passive), or through an active technology, such as a fuel burner which heats the filter to soot combustion temperatures, or through engine modifications (the engine is set to run a certain specific way when the filter load reaches a pre-determined level, either to heat the exhaust gasses, or to produce high amounts of nitrogen oxide, N02, which will oxidize the particulates at relatively low temperatures). This procedure is known as "filter regeneration." Fuel sulphur interferes with many "Regeneration" strategies, so almost all jurisdictions that are interested in the reduction of particulate emissions, are also passing regulations governing fuel sulphur levels. Particulate filters have been in use on non-road machines since 1980, and in automobiles since 1996. Diesel engines during combustion of the fuel/air mix produce a variety of particles generically classified as diesel particulate matter due to incomplete combustion. The composition of the particles varies widely dependent upon engine type, age, and the emissions specification that the engine was designed to meet, two-stroke diesel engines produce more particulate per horsepower output than do four-stroke diesel engines, as they less completely combust the fuel-air mix.

While no jurisdiction has made filters mandatory, the increasingly stringent emissions regulations that engine manufactures must meet mean that eventually all on-road diesel engines will be fitted with them. Neither the American 2007 heavy truck engine emissions regulations or the European Union 2007 automobile regulations can be met without filters. PSA Peugeot was the first company to make them standard fit on passenger cars, in anticipation of the future Euro V regulations. Unlike a catalytic converter which is a flow-through device, a DPF cleans exhaust gas by forcing the gas to flow through the filter. There are a variety of diesel particulate filter technologies on the market. Each is designed around similar requirements:

# Fine filtration

# Minimum pressure drop

# Low cost # Mass production suitability # Product durability Cordierite wall flow filters

The most common filter is made of cordierite (a ceramic material that is also used as catalytic converter supports (= cores)). Cordierite filters provide excellent filtration efficiency, are (relatively) inexpensive, and have thermal properties that make packaging them for installation in the vehicle simple. The major drawback is that cordierite has a relatively low melting point (about 1200°C) and cordierite substrates have been known to melt down during filter regeneration. This is mostly an issue if the filter has become loaded more heavily than usual, and is more of an issue with passive systems than with active systems, unless there is systems break down.

Cordierite filter cores look like catalytic converter cores that have had alternate channels plugged - the plugs force the exhaust gas flow through the wall and the particulate collects on the inlet face.

Silicon carbide wall flow filters

The second most popular filter material is silicon carbide, or SiC. It has a higher (1700°C) melting point than cordierite, however it is not as stable thermally, making packaging an issue. Small SiC cores are made of single pieces, while larger cores are made in segments, which are separated by special cement so that heat expansion of the core will be taken up by the cement, and not the package. SiC cores are usually more expensive than cordierite cores, however they are manufactured in similar sizes, and one can often be used to replace the other.

Silicon carbide filter cores also look like catalytic converter cores that have alternate channels plugged - again the plugs force the exhaust gas flow through the wall and the particulate collects on the inlet face. Metal fibre flow through filters

Some cores are made from metal fibres - generally the fibres are "woven" into a monolith. Such cores have the advantage that a current can be passed through the monolith to heat the core for regeneration purposes. Metal fibre cores tend to be more expensive than cordierite or silicon carbide cores, and generally not

interchangeable with them. Partial filters

There are a variety of devices that produce over 50% particulate matter filtration, but less than 85%. Partial filters come in a variety of materials. The only commonality between them is that they produce more back pressure than a catalytic converter, and less than a diesel particulate filter. Partial filter technology is popular for retrofit.

Filter usage

A properly designed filter will have little effect on fuel usage, however improper installation can be catastrophic, which is why automobile and truck engine

manufacturers have avoided the use of filter technology until now. It was first offered as standard by the French manufacturer PSA Peugeot Citroen in early 2000, and has been a huge success.

Maintenance

Filters require more maintenance than catalytic converters. Engine oil ash builds up on the surface of the inlet face of the filter, and will eventually clog the pores. This increases the pressure drop over the filter, which when it reaches 100 inches of water or higher is capable of causing engine damage. Regular filter maintenance is a necessity. Regeneration

Regeneration is the process of removing the accumulated soot from the filter. This is done either passively (by adding a catalyst to the filter) or actively. On-board active filter management can use a variety of strategies, such as engine management to increase exhaust temperature, fuel burner to increase the exhaust temperature, catalytic oxidizer to increase the exhaust temperature, resistive heating coils to increase the exhaust temperature, microwave energy to increase the exhaust temperature

All on-board active systems use extra fuel, whether through burning to heat the DPF, or providing extra power to the DPF's electrical system. Typically a computer monitors one or more sensors that measure back pressure and/or temperature, and based on preprogrammed set points the computer makes decisions on when to activate the regeneration cycle. The additional fuel can be supplied by a metering pump. Running the cycle too often while keeping the back pressure in the exhaust system low, will use extra fuel. The reverse runs risk of engine damage and/or uncontrolled regeneration and possible DPF failure. Quality regeneration software is a necessity for longevity of the active DPF system.

SE-C-513 391 discloses a device for complete combustion of solid fuels and comprises two combustion chambers joined together, of which one is a combustion chamber for drying and gasification of the fuel and the second one is a final combustion chamber for combustion of the gasified fuel and whereby a ceramic filter is arranged as a partition wall between the chambers, which filter allows the gasified fuel to pass through but blocks remaining solid substance to pass into the final combustion chamber and whereby the combustion gas is forced to pass the ceramic filter whereby the combustion temperature is raised to a suitable

combustion temperature. This device is meant to replace a conventional furnace.

NO-C-131 ,325 relates to a device for separating solid particles from a gas stream by direct the gas from a source to a mixing chamber where a mixture of steam and atomized liquid droplets are introduced under such conditions that the liquid droplets are accelerated to a speed of at least 60 m/s over the inlet speed, whereby solid particles are caught by the liquid droplets, whereby a subpressure is obtained in the mixing chamber. The invention is thereby related to a ration between steam and atomized droplets. US-A-6,019,819 relates to a device catching a condensate, which condensate contains oil and other hydrocarbons from food processing, such as French frying potatoes. WO 99/56854 relates to a process for separating particles from a flow of hot gas whereby the relative humidity is primarily increased to almost saturation, then gas and particles are cooled adiabatically so that water condenses upon the particles whereupon the particle containing water is separated off. EP-A-O 1 10 438 relates to a process and a device for purification of particle containing gas by means of condensation of water onto the particles in the gas and a separation of water droplets comprising particles.

WO 2009/051547 relates to a device for the elimination of particles from gaseous media, characterized by comprising a first pass-way having a first inlet for gaseous medium comprising minute particulate material, a means compressing the said gaseous medium bringing the fraction containing said particulate material to a return pass-way bringing said particles contained in the fraction of particulate material into agglomeration, a collecting means for collecting said agglomerated particles, a particle withdrawing means to eliminate said collected agglomerated particles, as well as those already being large, and a particulate purified gas outlet. In a preferred embodiment of WO 2009/051547 the means comprises a series of congruent open truncated cones of subsequently smaller diameters ending in a return pass-way bringing said particles contained in the fraction of particulate material into

agglomeration.

US 6,056,798 relates to a separator for eliminating particles from a gas flow comprising a series of cylindrical tubes having decreasing diameter, each tube part having a truncated cone part overlapping a distance between the tube parts, whereby the truncated cones having a decreasing angle to the longitudinal direction of the cylindrical tubes. The interspaces between the tube parts are arranged for letting gaseous medium out.

The distribution of particles derived from a diesel engine is quite wide. Thus they range all the way from nuclei mode (10 nm) to coarse mode 10000 nm), whereby the large mass of particles is concentrated around 100 nm.

However, there is a great demand for a completion of existing particles removing systems to reduce emissions of toxic particulates from in particular diesel engines, either mobile or stationary, as well as a complete cleansing of ventilation air. In particular particles having a size of less than 50 nm, more specifically less than 10 nm, still more specifically down to 1 nm or less, are of interest to be removed.

Nothing in the prior art discussed above can provide this. Summary of the present invention

The present invention relates to a device for the elimination of particles from gaseous media, characterized in that the means for agglomeration of particles consists of a perforated conical structure being arranged to let a gaseous media pass from the cone bottom and inside the cone wall to the outside of the cone wall via said perforations while any particulate matter is agglomerated inside the cone and collected at the apex of the cone from where said matter is removed.

The term conical structure means any solid or woven cone in accordance with the parameters given below. Thus a conical structure can be a cone of solid metal or a cone made of metal threads, a so called screen sheet. Screen sheets may have a mesh size in the range of 5.0 - 0.008 mm, and an open area of 25 % - 78 %.

The device of the invention it is arranged for agglomeration and collection of particles having a particle size less than 1 μηη, preferably less than 0.5 μιτι, more preferably less than 0.3 Mm, further more preferably less than 0.2 pm, even down to 10 nm or less, which particles after agglomeration have a particle size of at least 15 μιη, preferably 10 μιτι, more preferably 6 μηι or less, whereby that the device further catches and makes the agglomerated particles subject to a removal.

The gas flow in the tube arranged to create agglomeration is 10 m³/s or more, preferably 20 m³/s, 30 m³/s, or 40 m³/s or more.

In a further aspect of the invention it relates to a method for the elimination of particles from gaseous media, characterized by passing said gaseous media into a means for agglomeration of particles consisting of perforated conical structure being arranged to let a gaseous media pass from the cone bottom and inside the cone wall to the outside of the cone wall via said perforations while any particulate matter is agglomerated inside the cone and collected at the apex of the cone from where said matter is removed, whereby the gas flow in the tube arranged to create agglomeration is 10 m³/s or more, preferably 20 m³/s, 30 m³/s, or 40 m³/s or more.

The term minute particle refers to particles having a size of less than 0.2 pm. Detailed description of the present invention

The present invention will now be described in more detail with reference to the accompanying drawing, however, without being restricted to this or the embodiment being related thereto, in which drawing

FIG. 1 shows a schematic longitudinal cross-sectional view of an embodiment of the invention for treating a particle containing gaseous medium consisting of a conical structure made of solid metal in general;

In the following in operation exhaust gases containing particles to be separated off are passed into an inlet 11 of a pass-way 1 placed in a tube 6 and the gases are represented by the open arrows marked with black dotes. Pass-way 1 is the open bottom of a perforated cone 2 where the point or apex 3 of the cone ends in a hollow tube 4 connected to a vacuum source. The cone 2 is perforated in such a way that 20 to 70 %, preferably 20 to 60% of the cone surface is perforated with holes 5, which from a production point of view are preferably circular. In an embodiment in a ventilation air channel the perforations have a diameter of 3 mm and are placed at a distance of 3 mm from each other. This gives a perforation area of 23%. The cone 2 is placed in a tube 6 leading to an outlet 7, from where a cleansed exhaust gas or ventilation air is further distributed.

The function of the device of the present invention is as follows: The exhaust gas or ventilation air is passed into the bottom of the cone 2 whereby the gas or air is ventilated out through the perforations, while any particles will collide with the inside of the wall of the cone 2 and pass into the apex 3 from where they are sucked into the tube 4 by means of the vacuum source. When particles of extremely small dimensions are pressed together in the conical space, they will agglomerate together to form larger particles which then are collected in the vacuum source.

The basis or bottom diameter of the cone relative to the length of the cone is preferably 1 :2, more preferably 1 :5 to 1 :10.

Tests made show that elimination of particles to a high extent will occur even at 40 and 50% perforation area of the cone wall.

A test made with a perforation of 39% using a perforated screen made by metal yarns show good results as to agglomerate and collect minute particles. The screen tested was a 80 mesh screen (80 threads per inch), and having a mesh opening diameter of 0.20 mm, and the thread having a diameter of 0.12 mm.

Further, tests made show that the pressure drop is only 30 Pa at an air flow of 40 liter per second when there is a perforation of 23% (3 mm circular holes disposed 3 mm from each other). The flow in the tube to create agglomeration is 10 m³/s or more, preferably 20 m³/s, 30 m³/s , or 40 m³/s or more.

During the compression of the cross section at the conical parts minute particles will become agglomerated into particles having a size of 10 microns or more. Solid arrows will indicate pass-ways of the particles separated off. Open arrows without any black dotes indicate cleaned air flows freed from particles.

The present invention will work within a large range of diameters of the ingoing tube, i.e., in exhaust pipes of gasoline and diesel engines to ventilation tubes in larger buildings.

The embodiments shown discloses conical parts, cones of truncated cones, but, however, the form of these deflecting parts is not of importance but they may be parts of tetrahedrons, pentahedrons, hexahedrons, etc.

The present invention is used for eliminating particles from gaseous media including smoke and exhaust gases as well as air, such as ventilation air, whereby in the latter case microscopic particles, such as allergens, bacteria and virus can be eliminated, and air of combustion comprising a lot of ground and soil derived particles. The agglomerated particles can be disposed as such or be analysed with regard to their contents of singe constituents.

Claims

1. A device for the elimination of particles present in gases, such as smoke and exhaust gases, in particular diesel engine exhaust gases and particles related to ventilation air by agglomerating said particles, characterized in that means for agglomeration of particles consists of a perforated conical structure (2) being arranged to let a gaseous media pass from the cone bottom (1) and inside the cone wall to the outside of the cone wall via said perforations (5) while any particulate matter is agglomerated inside the cone and collected at the apex (3) of the cone from where said matter is removed.

2. Device according to claim 1 , wherein 20 to 70 %, preferably 20 to 60% of the surface of the conical structure is perforated with holes (5).

3. Device according to claim 1 , wherein particles having a particle size less than 1 pm, preferably less than 0.5 pm, more preferably less than 0.3 μιτι, further more preferably less than 0.2 μητι, even down to 10 nm or less are

agglomerated and collected, which particles after agglomeration have a particle size of at least 15 μητι, preferably 10 μιτι, more preferably 6 μιη or less, whereby that the device further catches and makes the agglomerated particles subject to a removal.

4. Device according to claims 1-3, wherein the gas flow in the tube arranged to create agglomeration is 10 m³/s or more, preferably 20 m³/s, 30 m³/s, or 40 m³/s or more.

5. Method for the removal of particles from a gaseous medium, characterized in passing said gaseous media into a means for agglomeration of particles consisting of a perforated conical structure (2) being arranged to let a gaseous media pass from the bottom (1) of the conical structure (2) and inside the cone wall to the outside of the cone wall via said perforations (5) while any particulate matter is agglomerated inside the cone under deflection to its apex (3) and collected at the apex of the cone from where said matter is removed.

6. A method according to claim 5, wherein the flow in the tube to create

agglomeration is 10 m³/s or more, preferably 20 m³/s, 30 m³/s, or 40 m³/s or more.

7. A method according to claim 5, wherein the removed agglomerated particles are transferred into a collector (4) for the said agglomerated particles.

8. A method according to claim 5, wherein the removed agglomerated particles are sucked away for disposal and/or analysis.