DE3422959A1 - METHOD FOR BIOLOGICAL REDUCTION OF SULFUR OXIDES AND OXYDATON FROM ORGANIC SUBSTANCES - Google Patents

Description

The invention relates to a highly effective and economical process for anaerobic biological conversion a mixture of sulfur oxides and organic material to form hydrogen sulfide, carbon dioxide and water. According to the invention, the term "sulfur oxides" means an oxide of sulfur or a salt derived therefrom such as a sulfite or sulfate. The procedure is in an expanded bed, continuous flow or fixed bed reactor carried out.

There are significant amounts of sulfur oxides such as Gypsum or calcium sulphate formed as by-products in industrial processes. For example, fall In the phosphate fertilizer industry around 5 tons of gypsum per ton of fertilizer are used. Calcium sulphate waste sludge is also used formed in numerous processes for the treatment of air and wastewater. Be through power plants deposited large amounts of gypsum, which arise when washing the sulfur dioxide from the gases, which in the Combustion of sulphurous fuels can be formed.

On the other hand, it is hydrogen sulfide, elemental sulfur and sulfuric acid to produce products that are required by industry. The invention creates a process with the help of which industrial waste, the sulfur oxides and organic materials contain

th, biological in hydrogen sulfide, carbon dioxide and water can be converted. The hydrogen sulfide can then be converted into elemental by conventional methods Sulfur, sulfuric acid or sulfide salts are converted. Other useful by-products such as Sodium, calcium or magnesium carbonates can, depending on the chemical structure of the the molecules containing sulfur oxides are recovered. With the method according to the invention are accordingly both the amount of industrial waste to be disposed of and useful products for recovered further industrial applications.

It is known that certain bacteria anaerobically reduce sulfur oxides to sulfide. The well-known sulfur-reducing bacteria belong to the genera Desulfovibrio, Desulfotomaculum and Desulfobacter . Some of these genera, for example the Desulfotomaculum , are versatile and also capable of methane fermentation. Indeed, the reduction of sulfur oxides is an undesirable side reaction in methane fermentation because hydrogen sulfide that has accumulated in the reactor is toxic to the methane producing bacteria. Some attempts have been made to understand and use the ability of microorganisms to reduce sulfur oxides. For example, SG Burgess et al., "Pilot-Plant Studies in Production of Sulfur from Sulphate-Enriched Sewage Sludge", J. Sei. Food Agric, L2, 326-35 (1961) and JC Sadana et al., "Microbiological Production of Sulfide from Gypsum", J. Sci. Indus. Res., 2IC , 124-27 (1962) both batch processes and semi-continuous processes in which the fermentation reactors were charged daily with batches of gypsum and sewage, sludge or acetic acid. the

Reactors were purged with nitrogen or a combination of nitrogen and carbon dioxide in order to avoid the to eliminate hydrogen sulfide formed during fermentation. The Sadana reactor became mechanically continuous and the Burgess reactor stirred before and after charging. Furthermore, A.C. Middleton et al., "Kinetics of Microbial Sulfide Reduction," J. Water Pollution Contro / Fed. 4-9, 1659-70 (1977) continuous process in which the growth takes place in a completely mixed suspension and the Reactor gases are recycled to effect mixing in the biological reactor.

None of these previously described methods would be economical on the scale as they are for industrial use is needed. Internal gas cleaning would require a large amount of energy and would be the right one Disrupt fluidization and stratification of the biological reactor. In addition, it is just not possible using a semi-continuous process to achieve the volume and flow rates that are found in commercial Facilities are required.

The invention provides a method for the biological reduction of sulfur oxides and for the biodegradation of organic ones Materials related to hydrogen sulfide, carbon dioxide, and water. It becomes a mixed culture that leads to Degradation of organic molecules, oxidation of organic molecules and / or reduction of sulfur oxides capable of being introduced into an anaerobic reactor together with sulfur oxides and organic materials. During fermentation, the sulfur oxides are reduced and the organic materials are reduced and oxidized.

According to a preferred embodiment of the invention the reaction takes place in an expanded bed reactor with continuously increasing flow. The hydrogen sulfide concentration is kept just below the toxic limit by keeping the reactor blows through with small amounts of gas. The reactor effluent is directed into a gas cleaning chamber or compartment, where a gas stream is used to at least substantially remove the remaining hydrogen sulfide -) Eliminate 0. At least part of the process will follow returned to the reactor after the removal of hydrogen sulfide. This step-by-step gas purification becomes an economical method of eliminating the toxic Hydrogen sulfide is created from the reactor.

It is an object of the invention to provide a process for the recovery of commercially useful resources biological conversion of materials containing sulfur oxide in the presence of industrial or other organic

2o nical waste liquids to be created.

It is also an object of the invention to provide a method with the aid of which a significant reduction is achieved the volume of solid waste achieved at sea, in pits or other approved landfills need to be eliminated.

Another object of the invention is to provide a method for biological conversion of sulfur oxides to ₃ Q, the large volumes of industrial waste liquids reacted without loss of conversion efficiency.

In order to achieve these objects, the invention provides an expanded bed reactor with a continuous Flow through or a fixed bed reactor used.

The profitability of the method is also in accordance with the invention to reduce sulfur oxides increased by going for a continuous elimination of the accumulated toxic hydrogen sulfide from the reactor cares.

Furthermore, the profitability of the method according to the invention increased by a low input ratio of carbon to sulfur, reducing the for the Organic materials required in the reaction are considerably reduced.

Furthermore, according to the invention, as a by-product of the reaction the self-formation of the reactor medium is achieved.

According to the invention, a reaction system is also provided that is stable and resistant to interference is.

The ^{materials suitable for} carrying out the process according to the invention can be obtained primarily from industrial and municipal wastes. Although the invention is intended to recycle various sulfur oxide-containing wastes and wastes containing organic materials, the invention also extends to the use of other sources for the required materials than wastes.

According to the invention, industrial or municipal waste, containing sulfur oxides are used as a source of sulfur oxides. So far it was anaerobic Treatment (i.e. for methane production) of waste with a high concentration of sulfur oxides is not possible, because the hydrogen sulfide formed during fermentation was toxic to the microorganisms. That

The method according to the invention counteracts this limitation. It does the anaerobic treatment of even this waste for resource recovery and disposal of contaminants and creates a cost-effective anaerobic treatment technology for industry.

One of the largest industrial sources of waste containing sulfur oxide is the phosphate fertilizer industry, where about 5 tons of gypsum (CaSO.) are formed per ton of fertilizer. This gypsum is currently deposited in Eliminated pits.

A second major source of sulfur oxide contains

"The incineration plants in power plants are the most common types of waste and other processes in which fuel containing sulfur is burned. The burning of Fuel containing sulfur is responsible for more than 75% of sulfur dioxide emissions in the United States responsible. The main method of desulfurization of these exhaust gases includes washing with lime and / or a Limestone slurry. The washing wastewater contains a calcium sulphate-calcium sulphite mixture contained in the inventive method is useful. Similarly, the drain contains a sodium carbonate scrubbing system a sodium sulfate-sodium sulfite mixture, which can also be used in the method according to the invention is. In some cases, magnesium and calcium oxides or carbonates may be used. It it is therefore clear that the material containing sulfur oxides useful in the process of the invention may include a variety of soluble or insoluble sulfates or sulfites.

Other suitable industrial sulfur oxides are emitted as waste water from the pulp and paper industry, which contain sulphite and sulphate residues together with degradable organic materials. Furthermore, wastewater with high concentrations of organic substances and sulfur oxides is formed in a large number of processes in the chemical industry. Parts of the food industry generate waste with high concentrations of organic substances and sulfur oxides -10 ^and certain pharmaceutical processes produce waste containing sulfur oxide. In some places municipal waste can also have high concentrations of sulfur oxide.

For the material containing organic compounds, in turn, a large number of municipal, industrial and agricultural sources of organic waste be used. For example, municipal waste or sludge is a suitable source of organic materials As well as wastewater containing synthetic substances, it is composed of a large number of industrial wastewater organic chemicals. Manure can also be used, as can much of the waste from distillers, from Cotton bleaching, of citrus fruits, wine, yeast, molasses and meat packaging processes. Waste sources for mixtures of organic materials and sulfur oxides are described above.

According to the invention, the usability of waste in primarily limited by the fact that no wastes should be used, the soluble ones for the microorganisms contain toxic impurities. Non-toxic, non-degradable soluble contaminants will be simply flow through the reduction / oxidation process. If the sulfur oxides and organic compounds

materials containing fertilizers other than liquid they should be fed to the reactor as a slurry. The solids concentration of the slurry while can vary, a range of about 5 to about 10% is preferred.

A mixed culture of microorganisms is used to inoculate the reactor. There are numerous in the inoculum Microorganism types be present; those suitable for the process according to the invention (i.e. those capable of adapting to the conditions prevailing in the reactor) will thrive and multiply to form the reactor biomass. Among these suitable microorganisms will be those the larger organic molecules break down into smaller organic acids and those that are both the acids oxidize to carbon dioxide and water as well as reduce the sulfur oxides to hydrogen sulfide. the different microorganisms that actively promote the reactions of the method according to the invention referred to according to the invention as a "mixed culture of microorganisms" .

A suitable mixed culture of microorganisms can be obtained from various sources. The conversion of Sulfur oxides in sulfide by anaerobic microorganisms takes place spontaneously and is quite common in communal Sielen and other anaerobic reactors for waste treatment were observed. A starter culture can from any of these sources or from a combination of the sources.

Once the fermentation process has started, the desired mixed microorganism culture will be more than sufficient formed to keep the response going,

provided that the minimum times for the solids retention time are observed. Indeed, the excess of grown biomass should be removed from the reactor periodically.
5

The inventive method is performed in an anaerobic Reactor carried out, within which the biomass grows either in suspension or as a solid layer. It the supply of materials containing organic compounds and sulfur oxides is provided. The at Hydrogen sulphide resulting from the reaction is preferably driven out of the system by gas cleaning, the use of nitrogen, methane and / or carbon dioxide being expedient.

15th

In the preferred embodiment of the invention an expanded bed reactor used with continuously ascending flow. The size of the reactor changes from location to location, depending on the amount of sulfur oxides and / or organic waste, that arise at the respective location. The size of the unit is determined primarily by the required Solid residence time and the rate of conversion of the organic Materials determined. The solids retention time, i.e. the time during which the biomass is in the System withheld is the primary parameter of the facility which is the system's ability to breakdown specific organic materials and sulfur oxides and the stability against disturbances of the process

30 determined.

The solids retention time "SRT") can be determined by taking the increase in biological solids in the reactor as a function the amount of oxidized organic materials

calculates. For example, 10 kg of microorganisms can produce 0.05 to 0.15 kg of new bacterial mass per day. If 0.1 kg are formed, the following calculation applies:

10 kg of bacteria

SRT = = 100 days

0.1 kg bacteria / day

The SRT in this example is 100 days. Typical SRT values for anaerobic systems can be 30 to 130 days.

Because of the generally high rate of conversion in this process is the liquid residence time required low. A low liquid residence time also means a high flow rate. It shows 5

that the high flow rate of the invention Process allows a relatively small reactor volume. Accordingly, the conversion becomes more efficient with a higher microorganism concentration per m reactor volume carried out. The reactor volume can be from 3

2.5 to 3000 m or more.

The reactor size is also determined by the loading with sulfur oxides. The intended reactor loading (kg sulfur oxides / m reactor space / day) changes .

with the type of organic material used however, it is usually higher than with conventional aerobic or anaerobic processes.

The shape of the reactor is similar to that of conventional 30

Expanded bed reactors. Usually the reactor has a conical lower part and a cylindrical one upper part. A sludge-liquid separator or clarifier is located in the upper one

Part of the reactor to the amount of solid that comes out of the 35

Reactor passes into the gas separation chamber to control.

The lower part of the reactor is equipped with filling devices provided for introducing the required materials into the reactor. It is cheap to use the materials from a source such as a storage tank to pump into the reactor. The upper part is equipped with a device for transferring the reaction process from the reactor to a Gas separation chamber or compartment provided. The reactor is equipped with a device for introducing small amounts of gas provided in the lower part of the reactor. Means for removing accumulated hydrogen sulfide, preferably by gas cleaning, attached outside the reactor. This hydrogen sulfide elimination is described in more detail below. Furthermore, a suitable device for recycling is at least part of the low-hydrogen sulfide effluent the gas separation chamber provided in the reactor. It may be desirable in the method of the invention to use a solid layer reactor to treat wastewater. Anything can be used to form a lawn suitable medium for example plastic or ceramic can be used, the growth of a fine, fixed Bacterial lawn promotes. The growth medium can be arranged oriented (channel-shaped) or packed randomly be. The arrangement should be such that there are gutters or cavities for the waste liquid to pass through are.

The reactor is connected to a continuous source of sulfur oxides containing material and a continuous one Source of material containing organic compounds connected. These materials can be used before Introduction to the reactor to be combined or it

there may be two separate inlet devices for each material. In the preferred reactor with increasing flow, these materials become fed through the bottom of the reactor, but it would also be possible to have the inlet device (s) on the side of the reactor to be attached.

In the preferred embodiment, a reactor used with expanded bed. The increasing flow velocity in the reactor is enough to keep the biomass in an expanded bed without significant Flush quantities of biomass from the reactor. The term "expanded bed" is intended according to the invention include both particles that are maintained in a fluidized state and those particles that which are subject to less relative movement. The upward flow velocity increases

2 preferably carries 1.9 to 3.8 l / min / 0.09 m, it can

2, however, be from about 0.7 to 19 l / min / 0.09 m, if it is desirable in a particular embodiment.

The reactor contains a sludge bed from a mixed culture of microorganisms, as described above and a medium on which the microorganisms are grown. It Calcium carbonate or other conventional media can be used to grow bacteria. When the sulfur oxides Containing inflow contains gypsum, the conditions for the formation of the sludge bed and the retention considerably improved by the presence of Ca ions. Because insoluble calcium carbonate is a by-product the reduction reaction is formed when calcium is present, according to the invention, is for self-regeneration of the growth medium. It was found that 1 to 2 months after inoculating with the mixed culture

stable mud beds can be formed.

A reactor which, according to the method according to the invention is operated, has a higher inherent stability when overloaded against environmental disturbances as methane reactors. In a methane reactor the organic Waste broken down in two stages. In the first stage, the organic substances are converted into acids ("Acid Fermentation") and in the second step the acids are converted into methane ("methane fermentation"). In a well-balanced reactor these two find Stages take place simultaneously. If these two stages get out of balance, however, so occur in the reactor pH disturbances. The microorganisms responsible for methane fermentation are very sensitive to acids and do not tolerate fluctuations in pH.

In the method according to the invention, a Two-stage procedure applied. In this procedure however, a stable pH value can be maintained in the reactor because of methane fermentation about four times the alkalinity is developed. This has the consequence that the reaction systems according to the invention essentially insensitive to pH disturbances

25 are.

The pH in the reactor was found to remain unchanged in the range of 7.0 to 8.0 regardless on the pH of the inflow. The pH of the feed can be at least from about 2.5 to at least 6.5 vary without changing the pH inside the reactor. This of course makes that easier Use a variety of waste liquids without the additional step of pH adjustment. About that

In addition, the system allows a higher load.

In this respect, the two-stage process according to the invention is the same methane fermentation, when "acid fermentation" forms the first stage. That is, microorganisms build larger ones organic molecules down to smaller organic acids. In the second step, however, other microorganisms oxidize the organic acids to water and carbon dioxide and also reduce the sulfur oxides to hydrogen sulfide.

-IQ The overall reaction taking place in the reactor can can be represented by the following (unbalanced) equations:

₅ CaSO. + organic compounds - »CaCO ₃ + C0„ + H ₃ O + H ₃ S

or

Na ₃ SO ₄ + organic compounds -> NaHCO ₃ + CO ₂ + H ₂ O + H ₃ S
or

MgSO ₄ + organic compounds -> MgCO ₃ + CO ₂ + H ₃ O + H ₃ S.

The ratio of carbon (in the material containing organic compounds) to sulfur (in the Material containing sulfur oxides should generally be in the range of about 0.75 to 1 to about 3 to 1 in order to achieve optimal effectiveness. The rate of conversion of, for example, calcium sulfate or Sodium sulfate is from. about 0.2 to about 0.9 kg / 0.03 m reactor volume daily.

3Q The products of this reaction vary depending on the Waste liquid. For example, insoluble calcium carbonate is used produced when gypsum is used as a material containing sulfur oxides. Soluble sodium carbonate is formed when the waste liquid is out comes from a sodium carbonate scrubber. Magnesium car

bonat is produced when the process according to the invention is carried out with waste from exhaust gas scrubbers in which magnesium carbonate is used.

In the preferred embodiment of this method accumulated hydrogen sulfide is removed from the reactor contents and the draining liquid is eliminated by stepwise wiping off. When removing the hydrogen sulfide It is a critical measure, as the microorganisms through an accumulation of Hydrogen sulfide quickly poisoned in the reactor will. The best way to drive off the hydrogen sulfide is to clean it with a suitable one inert gas such as nitrogen, but other means can be used if necessary. The presence of a gas phase facilitates the release of the hydrogen sulfide from the solution. It can any gas inert to the reactants and reaction products can be used. nitrogen gives good results for this purpose, as does carbon dioxide or a combination of both gases. Will If the reactor is operated near or in connection with a methane digester, the methane can be used for the Gas cleaning step can be used.

Two-stage stripping is preferred. With this procedure the hydrogen sulfide concentration in the reactor becomes slightly below that for the microorganisms kept toxic level by blowing small amounts of gas through the reactor. The ratio of Gas to liquid in the reactor is preferably about 2: 1 to about 10: 1 (the term "liquid" in this context refers to the liquid draining from the reactor). With this relatively the flow pattern will be the low gas flow rate

Liquid in the reactor and the stratification of the expanded bed are not significantly disturbed.

The liquid with reduced hydrogen sulfide content draining from the reactor is preferably used for the second stage of the abortion process and for gas separation in a separate chamber, compartment or one directed to another suitable location. The chamber is blown with large amounts of the selected gas to remove the remove all or most of the hydrogen sulfide from the effluent. In this external Abortion chamber can have the ratio of gas to liquid from about 5: 1 to about 100: 1, preferably about 5: 1 to about 20: 1, depending on the amount of hydrogen sulfide that is to be driven off and the desired quality of the draining liquid. It is possible to have a high ratio i.e. high Gas flow rates, to be used in the abortion chamber, as the gas and the liquid are vigorously mixed outside of the reactor, the flow pattern or the residence time of the biomass in the reactor itself is not disadvantageous influenced.

From the standpoint of energy efficiency is the use a staged cleaning process is advantageous in that it offers the possibility of double cleaning Use low gas: liquid ratio for the elimination of hydrogen sulfide. Furthermore the entire volume of the gas required for the cleaning process is preserved by lowering the flow rates.

Alternatively, the hydrogen sulfide can be either only by stripping from the reactor itself or just by

Abortion in a chamber or outside the 35th

The area located in the reactor must be eliminated. In the case of large reactor volumes, however, this is the only one Use of internal gas cleaning is inefficient from both an energetic and a technical point of view. In order to remove sufficient hydrogen sulfide, large amounts of gas have to pass through the relatively violently Reactor are pumped, whereby the economics of the recovery process is lowered. About that In addition, an internal gas purification of this intensity would change the flow pattern of the liquid in the reactor and interfere with the stratification of the expanded bed. The removal of the hydrogen sulphide only by expelling it in an external chamber avoids the problems arising from the exclusive internal cleaning, however, as stated above, it is less desirable for reasons of energy efficiency than gradual abortion.

After driving off the hydrogen sulfide from the draining Liquid by expulsion with gas or by other suitable means is at least part of the Low-hydrogen sulfide drainage liquid for further reaction and to maintain the expanded Recirculated bed into the reactor. By continuously removing those contaminated with hydrogen sulfide Reactor materials and recycling of the same after driving off the hydrogen sulfide is the Reactor kept in a healthy, active digesting condition. It is possible that Waste liquid instead of recycling the hydrogen sulfide poor drainage with water or another liquid. Such an approach would be however, far less economical, since in this way large amounts of water would be added to the system, which for the

35 would have to be eliminated and derived in the end.

Regardless of the location of the hydrogen sulfide abortion the hydrogen sulfide is used for further processing into an economically viable substance from the Reactor derived. This processing is carried out according to conventional methods. For example, can the hydrogen sulfide is converted into elemental sulfur using the commercially available Claus process where the hydrogen sulfide is catalytically oxidized to sulfur and water.

10

Alternatively, commercial standard sulfuric acid can be prepared by converting sulfur over a suitable catalyst system are formed. As a further option, the hydrogen sulfide can be extracted from the gas stream with caustic soda washed, whereby sodium bisulphide is obtained, which is useful in the organic chemical industry is. The inert gas can be returned for further cleaning of the reactor and / or the external stripping chamber will.

20th

The overflowing liquid from the external chamber can be discharged as non-polluting waste, possibly after processing. The overflowing volume is equal to the volume of the reactor fed slurry. The overflowing volume is accordingly controlled by controlling the reactor feed. For example, causing a focused Feed that a larger proportion of the liquid draining from the reactor must be recycled.

A more dilute feed results in a higher excess volume.

Although the feed concentration can be varied, there are practical limits to be considered should be. The concentration shouldn't be that high

be that it affects the expanded character of the reactor. The maximum concentration of the feed slurry is about 10%. On the other hand, an extremely dilute feed will not become full Utilize the conversion capacities of the reactor. So at a concentration of 0.05 to 0.1% of the Slurry the full advantages of the process of the invention cannot be used. Becomes a fixed bed reactor used, this should only or essentially can only be loaded with soluble wastes or compounds.

Furthermore, the solids are removed from the system continuously or periodically. Will

- | 5, for example, the method according to the invention in context used with a power plant that operates a gas desulphurisation system based on calcium (cf. Application B below), it allows continuous removal of solids from the reactor draining liquid may be required. In this way a continuous recovery of Calcium carbonate obtained for reuse in the power plant's waste gas scrubbers.

For other forms of application, periodic clarification may be desirable, whereby the time intervals can be determined by the solids content in the reactor. This means that if the solids concentration in the reactor has reached a certain limit, some of the sludge should be withdrawn in order to to lower the solids concentration. The intended The limit is determined by the reactor conditions. It is desirable to keep the solids content as high as possible to hold without causing mechanical problems in the reactor. Accordingly, signs of a discontinuation

zening or agglomeration of the solids or failure of the bed to expand indicates that the limit of solids concentration has been reached. A typical solids concentration limit can be 20 to 50 g / l.
5

The solids are typically dewatered and sold, reused, or otherwise disposed of. the Solid formation rate depends on the type of organic substances used and the amount of calcium ions that are present in the supplied waste liquid. The volume of solids that must be removed forms part of the volume of solid waste used to feed the reactor. this applies especially when the alkali by-product is used in an appropriate manner, i.e. for neutralizing, washing, Etc.

The advantages of the method according to the invention are manifold. For the industry, the main benefit will be the reclamation of resources. The through the Process according to the invention recovered hydrogen sulfide, elemental sulfur or sulfuric acid can be reused. In addition, calcium carbonate, which is a growth medium, is formed in some applications for the microorganisms forms or that is removed and put in lime gravel for reuse when washing industrial waste gases or neutralizing acidic waste liquids can be converted. About that In addition, the process according to the invention increases the volume of the industrial and / or communal to be eliminated Waste is significantly reduced and thus the need for landfills is significantly reduced.

Some possible applications for the method according to the invention are described below.

A) The method according to the invention can be used in the vicinity of a fertilizer factory of the normally 5 tons of waste gypsum per ton of fertilizer produced. Currently these systems dispose of the gypsum in landfills. In addition, elemental sulfur must be purchased, that is used to make the fertilizer. Since the cost of gypsum disposal is generally insignificant will be the main incentive for adopting the process of the invention for this industry be the sulfur recovery. For the environment, however, there are advantages through reduced gypsum deposition .

-15 The recovery plant becomes a matter of course the anaerobic basic reactor with expanded bed, together with the external gas separation chamber and the Enclose abortion and return devices. The hydrogen sulfide formed in the process according to the invention is converted into elemental sulfur by conventional methods as indicated above.

It is believed that the reactor of the invention is capable of about 8 to about 32 kg of gypsum to convert per m reactor space. Most preferably the rate of conversion is from about 16 to about 32 kg / m / day. The plaster of paris is called a slurry pumped into the reactor, preferably with a solids content of about 5 to 10%.

A variety of suitable "organic" materials can be used conveniently. Depending on the location of the plant, municipal sludge will be added were not subjected to a putrefaction process, manure or to reduce industrial organic waste on site

gen costs or maybe for the price of transportation costs. The choice of Materials will be site specific and there may be other available sources of organic Waste containing substances is used. A combination of the sources also comes in Consideration. About 20% of the organic sludge will not be digestible and will require disposal make, possibly as a fertilizing soil conditioner.

The energy released during the conversion of hydrogen sulfide into elemental sulfur stands for use as steam in the system. The theoretical yield is about 3 kg Steam per kg of sulfur produced. A part of this is in the gas separation system of the sulfur conversion system used, with about 1 kg of steam per 1 kg of sulfur for the further energy requirements of the system

20 is available.

B) A second important industrial application for the process according to the invention is on Given locations where the combustion of sulfur-containing fuel takes place, for example in Power plants. Exhaust gas desulfurization processes generally include scrubbing with lime and / or limestone sludge including alkaline fly ash washing. This process creates a slurry

3Q of lime or limestone in water used to that Absorb sulfur dioxide from the exhaust gas in a gas / liquid scrubber. The slurry contains generally 5 to 15% solids. In other washing systems, sodium or magnesium car-

₃₅ bonat used.

The drain from a lime or limestone washing system contains a calcium sulfate-calcium sulfite mixture which, according to the invention, is suitable as a material containing sulfur oxides. The outlet from a sodium carbonate washing system contains a sodium sulfate-sodium sulfite mixture, which can also be used in the method according to the invention. Alternatively, some systems deliver magnesium oxides. As described above, a plurality organic substances ^ _0-containing materials are combined with the scrubber operations to feed to the reactor.

A significant problem associated with these scrubbing systems is the removal of large sulfuric

. _c sludge volumes. About half of the operating and maintenance costs of washing systems are due to sludge formation and disposal. The method according to the invention significantly reduces the volume of sludge and thus both the problems and the costs associated with disposal are reduced. 'Other significant costs in the operation of calcium-based flue gas desulphurisation systems are caused by the purchase of lime or limestone and the production of the slurry. For example, limestone must be crushed prior to making the slurry. In the process according to the invention, calcium carbonate is obtained, which can be reused in the washing system. Alternatively, the sludge mixture of calcium carbonate

_The natural and organic residues are transferred to a kiln, where the sludge is burned off and the lime is recovered for reuse in the washers.

According to the invention, the gas flowing out of the reactor and / or the chamber is used to drive off the gas Contain hydrogen sulfide. This gas can be fed into an additional recovery system. For example, elemental sulfur can be obtained by working up the gas in a Claus plant will. The Claus plant does not need its own device for air purification, since the exhaust gas in the Flue gas scrubber can be returned to the main system. Additionally, the excess energy can be taken out the Claus process (about 3 kg steam / kg sulfur) partly for heating the lime kiln described above be used. Alternatively, the outflowing gas can be converted into sulfuric acid.

C) The pulp and paper industry can by treating the processes and recovering raw materials draw considerable advantages from the method according to the invention. With one of the cheapest methods for pulp production it is sulphited with sulfur dioxide Lime used. This process produces waste liquids, the sulfur oxides and Contain soluble organic substances. The organic matter content makes this waste for the anaerobic fermentation attractive, but the presence of the sulfur oxides has so far been efforts with conventional methane fermentation. The toxicity of the hydrogen sulfide formed during fermentation made careful monitoring of the methane reactors necessary. Additionally stay Sulphate / sulphite sludges such as calcium sulphate-calcium sulphite back and must be eliminated.

The inventive method for reducing the sulfur oxides offers advantages over methane

fermentation. Both sulfur oxide and carbon removal are achieved, it is in itself more stable and can accommodate low pH values of the inflow without the addition of bases necessary is. In addition, the drains from this industry contain both sulfur oxides and organic substances, eliminating the need to create a separate source of organic substances not applicable. If all wastes that are used to feed the reactor are soluble, then so For example, the reactor may have either an expanded sludge bed or a fixed layer.

D) In order to achieve a more complete digestion of the organic substances, it is possible to use the reduction of sulfur oxides according to the invention and oxidation of organic substances to be combined with a methane-forming digester. The two systems should be arranged in series. The first reactor constructed in accordance with the invention serves primarily Line for the reduction of sulfur oxides with simultaneous partial oxidation of organic substances. The draining liquid from the first reactor is pumped into the second reactor, where there is is a conventional methane fermenter. The second reactor enables the methane-forming Bacteria convert the remaining organic matter into methane gas without going through the toxicity of the sulphides in the reactor being adversely affected.

The invention is illustrated below with the aid of examples.

Example 1 Comparative Example

In this example, a continuous flow reactor with no gas purification was used. The reactor was made of plastic and was conical in shape with the other part pointing upwards. The reactor volume was 1.3 1. The feed liquid residence time was approximately 1 day. The sulfur oxides and organic

- | 0 niche substances were used in pumped the reactor floor. The draining liquid from the top of the reactor was placed in a gas separation chamber passed and then partially returned to the reactor. The return rate was chosen so that a ratio of 5: 1 to 10: 1 between the inflow rate of the make-up liquid and the return rate duration.

The immediate source of the bacterial inoculate used was another farmer in the laboratory of the inventor. The original source was sludge from a municipal treatment plant. The system was with a mixture of pigsty waste and plaster of paris started. The stock food used was a solution containing a variety of organic substances and nutrients and was composed as follows:

lot ml 10 ml 25th G 110 G 45 ml 55 ml 35 ml 20th ml 35 ml 45 ml 60 G 160 G 20th G 20th G 6th G 50 G 2 ml 40

component

Formaldehyde (37% aqueous)

Methanol sodium acetate benzoic acid

Propionic acid

Butanol

Ethanol

Monoethanolamine -JO Butyl ac et at

Diethylene glycol

Ammonium carbonate

Sodium phosphate (1Ή-0)

Potassium phosphate (anhydrous) ~ \ 5 phenol

sugar

Iron (II) sulfate (7Ή.Ο)

Trace elements

²⁰ The "trace elements" were added as a solution of the following ingredients:

5 mg / 1 NiSO ₄ , 5 mg / 1 MnCl ₂ 4 H ₂ O, 1000 mg / 1 FeSO ₄
7 H ₂ O, 100 mg / 1 ZnSO ₄ · 7 Η _£ 0, 50 mg / 1 CoCl ₂ · 6 H ₃ O, ²⁵ 5 mg / 1 CuSO _x . · 5 H "0, 100 mg / 1 H" BO_, 50 mg / 1 Na _p Mo0 ·

O II / "\

The indicated ingredients were combined and diluted to 18 liters to form a stock nutrient solution.
30th

The reactor was operated for 4 3 days. In Table I

the data are shown that were formed and collected over the period including days 14 to 42. The reactor had a stable pH in the range of 7.3 to ₃₅ 7.84 even if the pH of the feed was in the range of 2.5 to 6.0.

A cyclic decrease in gas formation was observed. It is believed to be the cause of this was in the cyclic rise of the hydrogen sulfide concentration to levels above the inhibitory concentration. If the hydrogen sulfide concentration was lower, i.e. below the toxic level, more gas could be formed will. The increased gas formation increased the hydrogen sulfide concentration, which in turn led to a decrease caused gas formation.

pH Intake sequence gas Results SO Tabel II - SOC ⁺ Loading 5 1 water sulfide mg S in.
educated % so ₄ 6.0 7.75 production mg / 1 - volume in gas Gas / mg S Eliminate 6.0 7.62 ml / day of experiments with gas cleaning 680 sequence l / day mg / day eliminated supply 6.0 7.35 50 Intake mg / 1 745 Day 6.0 7.7 130 _ 370 - 0.70 0 0 - 14 * 6.0 7.4 30th - Drain inlet 200 - 0.85 - - - 15th 6.0 7.84 150 - 325 - 90 0.85 - - - 17th 6.0 7.7 100 - - 500 210 '0.65 24 - - 20th 6.0 7.84 220 - - 390 120 0.88 56 - - 21 ** 4.0 7.63 120 - - - 130 0.8 - - - 25th 3.5 7.38 0 - 175 400 - 0.95 - - 30th 27 2.5 7.72 20th 1070 388 415 95 0.9 - - - 28 4.2 7.3 125 - - 75 1.5 21 0.14 62 34 *** 4.2 7.8 160 1480 750 CaSO ₄ in 1, - 1.5 49 0.15 55 35 4.2 7.5 120 1220 - 90 1.25 28 0.32 28 37 * Loading: 170 760 560 85 - - - 30 I. 39 50 760 550 i 41 550 42 530 65 ml pigsty waste + 12.5 g

Charge: 150 ml pigsty waste + 12.0 g CaSO ₄ in 1.5 l water

*** Charging: 10 ml pigsty waste + 0.9 g acetic acid, 40 ml standard nutrient solution, 3.9 g CaSO- in 1.5 l water.
+ SOC = Soluble Organic Carbon

NJ) NJ CD

Example 2

The reactor according to Example 1 was used, with the difference that a gas cleaning system was also used consisting of a gas separation chamber arranged outside the reactor was present. Nitrogen was used to clean the draining liquid in the gas separation chamber. The resulting nitrogen-hydrogen sulfide -Mixture was placed in a hydrogen sulfide separator which consisted of a vessel containing 200 ml of zinc acetate solution in H "0 (2-5 g / L) and sufficient sodium hydroxide to adjust the pH to 10-11. In this way the amount of hydrogen sulfide could be reduced

-15 can be measured by titration of the zinc acetate. the was draining liquid low in hydrogen sulfide then partially returned from the gas cleaning chamber into the reactor and the excess into a discharge storage tank directed.

The reactor charge contained 25 ml of pigsty waste plus 1.3 g of acetic acid and 160 ml of stock nutrient solution (for the composition of the stock solution, see Example 1). The sulfate content of the feed (CaSO ₄ ) varied as indicated in column 5, table II. The concentration of the slurry used was about 10%. The reactor was operated with external nitrogen purge for 14 days. The data generated and collected in Example 2 are presented in Table II.

Hydrogen sulfide formation increased during the first 8 days dramatically. On days 9-10, about 150 ml of the reactor contents were accidentally spilled. After filling up with 150 ml of the contents of a dormant sulfur oxide fermenter, the system won immediately its full potential.

It was found that the pH of the reactor was stable in the range of 7.38 to 8.10 even when the Feed had a pH of 2.0 to 3.4.

Intake PH sequence gas Results of the SO Tabel II Loading sulfide mg S in 4th I. 7.42 production try volume in gas educated Eliminate 3 7.38 ml / day mg / 1 sequence with gas cleaning l / day mg / day Gas / mg S supply O 3 7.99 **** mg / 1 1.5 186 eliminated I. 3 - **** Intake - SO-CALLED 1.5 94 - Day 2.5 7.82 **** 960 Intake 1.8 208 - 30th 1 2.5 7.63 **** - 560 sequence 0 282 0.88 - 2 2.0 8.10 **** 1360 570 - 1.1 477 - 64 3 3.4 7.78 **** 1430 600 780 - 1.8 443 1.30 67 4 * 3.4 - **** 1580 370 - 70 1.8 576 0.63 81 5 2.5 7.52 **** 1790 335 780 - 1.0 275 0.60 78 6th 2.5 7.8 **** 1990 - - 44 0 100 0.72 - 7th 2.5 7.50 **** 1500 73 970 - 1.4 500 - 96 8th** 2.5 7.55 **** - 75 - 22nd 0.83 368 0.68 93 9 **** 1670 96 - 26th 1.1 416 1.31 95 10 *** **** 1100 84 - - 0.6 - 0.67 95 11th 1800 - - - 12th 1740 - - 13th - - -

* Feed pump stopped.

** Part of the contents of the reactor was accidentally spilled.
*** Refilled biomass with material from another reactor.
**** No correct measurement due to gas cleaning.

+ SOC = Soluble Organic Carbon

CO -P - K) hO CD

During the last 4 days of reactor operation, the average conversion rate was about 1000 mg S0 ₄ / l reactor volume / day. More than 90% of this was converted to hydrogen sulfide. The corresponding removal of soluble organic carbon (SOC) was about 720 mg SOC / 1 reactor volume / day and resulted in more than 95% SOC removal.

Example 3

The economics of single-stage stripping in a chamber outside the reactor versus the one above multi-step drift described can be calculated in the following way. It is assumed that the waste influx 10 000 mg / 1 COD (chemical oxygen demand) - calculated by determination the amount of oxygen required to oxidize all organic matter in the sample by chemical Means is required) and 4500 mg / 1 SO. contains. It is also assumed that the Treatment with the method according to the invention results in a 90% reduction in sulfate, which is 4050 mg / 1 SO. or 1350 mg / 1 S. 1434 mg / l hydrogen sulfide are formed from this.

The total COD elimination by the method according to the invention is estimated at about 80% or about 8000 mg / l. The amount of COD eliminated by sulfate reducing microorganisms is about 4000 mg / 1. Accordingly, about 4000 mg / 1 COD are converted to methane by methane-producing microorganisms at a rate of about 0.32 1 methane / g COD removed. The total production of methane is 4.0 g COD χ 0.32 1 CH ₄ = 1.3 1 methane / l waste. The methane formed in the reactor supports the expulsion of the hydrogen sulfide

thus reducing the amount of gas that must be introduced within the reactor for stripping.

One-step external abortion; A final hydrogen sulfide concentration of about 20 rag / l is selected in the draining liquid of the external abortion chamber. The hydrogen sulfide concentration in the stripping gas leaving the chamber is also about 20 mg / 1, since there is a liquid-gas equilibrium of about 1: 1. Accordingly, about 70 liters of gas are required in the external chamber to drive off about 1400 mg / 1 hydrogen sulfide.

Multi-stage stripping: a hydrogen sulfide concentration of 100 mg / l is maintained in the reactor in order to avoid toxicity. The gas leaving the reactor accordingly contains about 100 mg / l hydrogen sulfide. Accordingly, 13 l of gas are required to remove 1300 mg / l of hydrogen sulfide. In the external abortion chamber, the hydrogen sulfide concentration is reduced from 100 mg / 1 to 20 mg / 1. Since the hydrogen sulfide concentration in the gas is accordingly 20 mg / 1, 4 liters of gas are required for the external stripping stage. The total amount of gas that is required for the stepwise stripping in this example is accordingly 13 liters (inside the reactor) plus 4 liters (outside) or 17 liters of gas per liter of discharge.

Claims (1)

UEXKÜLL & STOLBERG PATENT LAWYERS BESELERSTRASSE 4 D-2000 HAMBURG 52 EUROPEAN PATENT ATTORNEYS DR. J.-D. FRHR. by UEXKÜLL DR. ULRICH GRAF STOLBERG DIPL-ING. JÜRGEN SUCHANTKE DIPL.-ING. ARNULF HUBER DR. ALLARD von KAMEKE Duncan, Lagnese and
Associates, Inc.
3185 Babcock Boulevard,
Pittsburgh, PA 15237 V.St.A. (Prio .: June 20, 1983 US 505 940 - May 10, 1984 US 607 960 0398 / UGS / VOE / wo) June 1984 Process for the biological reduction of sulfur oxides
and oxidation of organic substances Claims 1. A method for the reduction of sulfur oxides and oxidation of organic substances, characterized in that that he a) an anaerobic reactor with an expanded bed or a fixed-bed reactor with a mixed culture of microorganisms inoculated, b) the reactor is charged with sulfur-containing material, c) charging the reactor with material containing organic substances, d) equips the reactor with means for removing accumulated hydrogen sulfide and e) optionally at least part of the hydrogen sulfide poor effluent from process step d) returned to the reactor. 10 2. The method according to claim 1, characterized in that that the material containing sulfur oxides used is soluble or insoluble sulfates or sulfites contains. 15th 3. The method according to claim 1, characterized in that that the material containing sulfur oxides used contains calcium sulfate or sodium sulfate. 4. The method according to claim 3, characterized in that the conversion rate for calcium sulfate or sodium sulfate about 8 to 32 kg / m of reactor space / day. 5. The method according to claim 1, characterized in that the organic substances used containing Material municipal waste, manure, industrial organic chemicals, agricultural organic Contains waste or a combination thereof. 30th 6. The method according to claim 1, characterized in that the ratio of carbon in the used material containing organic substances to sulfur in the used sulfur oxides Material is about 0.75: 1 to about 3: 1. 7. The method according to claim 1, characterized in that soluble or insoluble carbonates in the reaction are formed. 8. The method according to claim 7, characterized in that the carbonates formed are calcium carbonate, sodium carbonate or include magnesium carbonate. 9. The method according to claim 1, characterized in that -10 that accumulated hydrogen sulfide by eliminating multistage abortion by a) blowing small amounts of a suitable gas through the reactor, b) the discharge from the reactor into a chamber or a compartment outside the reactor directs and c) equips the chamber or compartment with a gas cleaning system that is used to remove the accumulated hydrogen sulfide from the drain is capable. 10. The method according to claim 9, characterized in that the gas used in stages a) and b) Contains nitrogen, carbon dioxide or methane. 11. The method according to claim 9, characterized in that there is a ratio of gas to in the reactor Use a liquid of about 2: 1 to about 10: 1 det. 12. The method according to claim 9, characterized in that the gas cleaning system is operated by a gas is introduced into the drain, which emits nitrogen contains substance, methane or carbon dioxide, and the resulting gas is discharged from the chamber. 13. The method according to claim 12, characterized in that there is a ratio of gas in the chamber used to liquid from about 5: 1 to about 100: 1. 14. The method according to claim 12, characterized in that there is a ratio of gas in the chamber used to liquid from about 5: 1 to about 20: 1. 15. The method according to claim 1, characterized in -15 that one has a device for removing accumulated Hydrogen sulfide is used which includes an internal gas cleaning system in the reactor. 16. The method according to claim 1, characterized in that that one uses a device for the removal of accumulated hydrogen sulfide, which the Including passing the reactor effluent to a chamber or compartment outside the reactor, and to equip the chamber with a gas cleaning system that removes the accumulated Is capable of hydrogen sulfide from the drain. 17. The method according to claim 1, characterized in that the driven off hydrogen sulfide the reactor and / or the chamber and leads to elemental sulfur, sulfuric acid or in a Sulfide salt converts. 18. Process for the reduction of sulfur oxides and oxidation of organic substances by anaerobes Digestion with a mixed culture of microorganisms, characterized in that one a) a reactor with continuously increasing Liquid and expanded bed used, b) blows through the reactor contents with small amounts of a suitable gas to remove part of the remove accumulated hydrogen sulfide, c) the drain from the reactor into a chamber outside - | ₅ heads half of the reactor, d) the drain in the chamber is subjected to gas cleaning to remove accumulated hydrogen sulfide to eliminate and e) optionally at least part of the hydrogen sulfide poor effluent resulting from stage d) is returned to the reactor. pe 19- process for the recovery of sulfur from waste gypsum, characterized in that one a) an anaerobic reactor with an expanded bed with a mixed culture of reducing sulfur oxides Microorganisms inoculated, b) the reactor is charged with gypsum, c) the reactor is charged with organic substances containing _oc ^d ^ m material, d) equips the reactor with means for removing accumulated hydrogen sulfide and e) the accumulated hydrogen sulfide to elemental Processed sulfur, 20. The method according to claim 19, characterized in that the plaster of paris with a feed rate of about 8 to about
■ 10 feeds the reactor. from about 8 to about 32 kg / m of reactor space / day in 21. The method according to claim 19, characterized in that that the gypsum is fed into the reactor as a slurry. 22. A method for desulfurizing the effluent from exhaust gas scrubbers, characterized in that one a) an anaerobic reactor with an expanded bed is inoculated with a mixed culture of microorganisms, b) the reactor is charged with the discharge from waste gas scrubbers, c) the reactor is charged with material containing organic substances and d) providing the reactor with means for removing accumulated hydrogen sulfide. 23. The method according to claim 22, characterized in that the calcium carbonate formed in the reaction for reuse in an exhaust gas ₃₅ washing processes recovered, 24. The method according to claim 22, characterized in that the calcium carbonate formed in the reaction and subjecting the obtained sludge containing organic residues to a temperature, which is sufficient to burn off the sludge and lime for reuse in a waste gas scrubbing process to win. 25. Methods of treatment of waste liquids from pulp and / or paper manufacture, thereby marked that one a) an anaerobic reactor with an expanded bed or fixed layer with a mixed culture of microorganisms inoculated, b) the reactor is charged with waste from pulp and / or paper-making processes, the soluble Contain sulfur oxides and organic substances and c) equipping the reactor for the removal of hydrogen sulfide with reasonable ^f sammeltem means. 26. Process for the reduction of sulfur oxides and oxidation of organic substances, characterized in that one a) a first anaerobic reactor with an expanded bed or fixed layer with a mixed culture of microorganisms inoculated, b) the first reactor containing sulfur oxides Material loaded, c) charging the first reactor with material containing organic substances, d) the first reactor with means for removing and recovering accumulated hydrogen sulfide equips e) if necessary for the return of at least part of the reactor effluent to the first -ΙΟ reactor ensures, f) a second anaerobic reactor is inoculated with methane-forming microorganisms, g) at least part of the hydrogen sulfide poor effluent from the first reactor in the second reactor and h) recovering the methane formed in the second reactor.