JP2011251267A - Biodesulfurization apparatus and method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To achieve a biodesulfurization apparatus simple in the device constitution and excellent in the operability, and to provide a biodesulfurization method.SOLUTION: The biodesulfurization apparatus includes: an absorption tower 1 which brings a processed gas containing a hydrogen sulfide into contact with a circulation liquid of an acid aqueous solution containing a trivalent iron ion, so that the circulation liquid absorbs the hydrogen sulfide to be an absorption liquid; a biological reaction part 8 which subjects the absorption liquid to a regeneration treatment by iron-oxidizing bacteria and sulfur-oxidizing bacteria to make it a treatment liquid; and a circulation liquid supply means that recovers the treatment liquid and supplies it to the absorption tower 1 as the circulation liquid.

Description

  The present invention relates to a biological desulfurization apparatus and method.

  As is well known, dry desulfurization apparatuses, wet desulfurization apparatuses, and biological desulfurization apparatuses are known as desulfurization apparatuses. For example, in the following Patent Document 1 and Non-Patent Documents 1 and 2, as a technique related to the biological desulfurization apparatus, a technique of absorbing hydrogen sulfide into a circulating liquid containing an iron compound to form an absorbing liquid, and regenerating the absorbing liquid with microorganisms. Is disclosed. The biological desulfurization technique of Patent Document 1 uses a slurry containing iron oxide as a circulating liquid, and regenerates iron oxide reacted with hydrogen sulfide to a state before hydrogen sulfide absorption by sulfur-oxidizing bacteria (microorganisms). The biological desulfurization technology of Non-Patent Documents 1 and 2 uses an acidic aqueous solution of iron sulfate as a circulating liquid, separates sulfur generated in the absorption liquid, and converts iron sulfate reacted with hydrogen sulfide to iron-oxidizing bacteria (microorganisms). It is oxidized and regenerated.

Japanese Patent No. 3880468

C. Pagella et.al “H2S gas Treatment by iron bioprocess” Chemical Engineering Science 55 (2000) p2185-2194 M.M.Mesa et.al “Biological ion oxidation by Acidithiobacillus ferrooxidans in a packed bed bioreactor” Chem. Biochem. Eng, (2002) p69-73

  By the way, in the technique of the said patent document 1, since a circulating liquid is a slurry, the separation membrane and centrifuge which concentrate a slurry are required. Further, the techniques of Non-Patent Documents 1 and 2 require a separation device that separates solid sulfur in the absorbing liquid. That is, since the conventional biological desulfurization apparatus must handle slurry and solid sulfur, the apparatus configuration is complicated and the operability is poor.

  The present invention has been made in view of the above-described circumstances, and an object thereof is to provide a biodesulfurization apparatus and method having a simple apparatus configuration and good operability.

  In order to achieve the above object, in the present invention, as a first solution for a biological desulfurization apparatus, a gas to be treated containing hydrogen sulfide is brought into contact with a circulating liquid of an acidic aqueous solution containing trivalent iron ions. Absorbing means for absorbing the hydrogen sulfide into the circulating liquid to make an absorbing liquid, biological reaction means for regenerating the absorbing liquid with iron-oxidizing bacteria and sulfur-oxidizing bacteria to make a treating liquid, and collecting the treating liquid And a circulating fluid supply means for supplying the absorbing means as the circulating fluid.

  As a second solving means related to the biological desulfurization apparatus, a means is adopted in which, in the first solving means, the biological reaction means has a function of aeration of the absorbing solution.

  Further, in the present invention, as a first solving means related to the biological desulfurization method, a gas to be treated containing hydrogen sulfide is brought into contact with a circulating solution of an acidic aqueous solution containing trivalent iron ions to circulate the hydrogen sulfide. An absorption step of absorbing the solution into an absorption solution, a biological reaction step of regenerating the absorption solution with iron-oxidizing bacteria and sulfur-oxidizing bacteria to obtain a treatment solution, and collecting the treatment solution as the circulating solution A means of having a circulating fluid supply step for supplying to the absorption step is adopted.

  According to the present invention, by using an acidic aqueous solution containing trivalent iron ions as a circulating liquid, hydrogen sulfide is absorbed into the absorbing liquid, and the sulfur generated in the absorbing liquid is converted into sulfuric acid by sulfur-oxidizing bacteria and iron. Since trivalent iron ions are regenerated by oxidizing bacteria, solid sulfur does not deposit or slurries in the absorption liquid. Separation equipment for separating sulfur in the absorption liquid or separation for concentrating the slurry A membrane, a centrifuge, and the like are not required, and the apparatus configuration can be simplified and the operability can be improved.

It is a block diagram which shows the function structure of the biodesulfurization apparatus which concerns on one Embodiment of this invention.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
As shown in FIG. 1, the biological desulfurization apparatus according to this embodiment includes an absorption tower 1 (absorption means), an absorption liquid flow path 2, a regeneration tower 3 (biological reaction means), a circulation pump 4, a circulation liquid flow path 5, An air supply pipe 6, a purified gas pipe 7, a biological reaction unit 8, an air supply pipe 9, and an air exhaust pipe 10 are provided.

  The gas to be treated to which this biological desulfurization apparatus is applied is not particularly limited as long as it contains hydrogen sulfide. For example, biogas obtained by decomposing biomass such as organic waste, Coal gasification gas obtained by gasifying coal. This biological desulfurization apparatus removes (desulfurizes) hydrogen sulfide from such a gas to be treated by using microorganisms.

  In the absorption tower 1, one end of an air supply pipe 6 for introducing a gas to be treated is connected to the bottom, and one end of a circulating liquid flow path 5 is connected to the top. The absorption tower 1 makes a predetermined circulating liquid contact a gas to be processed supplied from the outside through an air supply pipe 6 and absorbs hydrogen sulfide in the gas to be processed into the absorbing liquid to obtain an absorbing liquid. Such an absorption tower 1 is, for example, a packed tower, a droplet tower, a bubble tower or the like. Since the circulating liquid supplied to the top of the absorption tower 1 by the circulating liquid flow path 5 is dropped downward in a sprayed manner, the gas to be treated supplied to the bottom of the absorption tower 1 via the air supply pipe 6 and Good gas-liquid contact.

The circulating fluid contains trivalent iron ions (Fe ³⁺ ), has a pH of, for example, 1 to 2, and an oxidation-reduction potential (an oxidation-reduction potential (E _H value) when the potential of the standard hydrogen electrode is “0”). ) Is an acidic aqueous solution of 600 mV or more, for example. Such a circulating liquid absorbs the hydrogen sulfide by contacting with the gas to be processed, and the trivalent iron ions (Fe ³⁺ ) react with the hydrogen sulfide contained in the gas to be processed. The above-mentioned pH and redox potential relating to the circulating fluid are conditions under which iron ions in the circulating fluid can exist as trivalent ions, and are known for iron ions. By maintaining the iron ions in the circulating fluid as trivalent ions instead of divalent ions, hydrogen sulfide and iron can react to remove hydrogen sulfide, and the pH and oxidation-reduction potential can be adjusted as described above. By maintaining it within the range, slurrying of the absorbent can be suppressed. Such a circulating liquid is, for example, an aqueous solution of iron (III) sulfate: Fe ₂ (SO ₄ ) ₃ .

  In addition, one end of the absorption liquid channel 2 is connected to the bottom of the absorption tower 1. The absorption liquid channel 2 is for discharging the absorption liquid from the absorption tower 1 and supplying it to the regeneration tower 3. One end of the purified gas pipe 7 is connected to the top of the absorption tower 1. This purified gas pipe 7 is for exhausting treated gas (purified gas) from which hydrogen sulfide has been removed from the gas to be treated to the outside.

  The regeneration tower 3 is connected to the other end of the absorbent flow path 2 at the top and includes a biological reaction section 8 that carries microorganisms. The other end of the circulating fluid flow path 5 is connected to the side of the regeneration tower 3, one end of the air exhaust pipe 10 is connected to the upper part of the regeneration tower 3, and the air supply pipe is connected to the bottom of the regeneration tower 3. One end of 9 is connected. A circulating pump 4 is provided in the middle of the circulating liquid flow path 5 to discharge the processing liquid from the regeneration tower 3 and supply it to the absorption tower 1.

  Such a regeneration tower 3 regenerates the absorbing solution introduced from the absorbing solution channel 2 by an aerobic decomposition reaction by microorganisms in the biological reaction section 8 and discharges it as a processing solution to the circulating solution channel 5. Further, in the regeneration tower 3, the absorption liquid in the biological reaction section 8 is aerated by the air supplied from the air supply pipe 9 to the bottom, so that the aerobic oxidative decomposition reaction of microorganisms is activated and the absorption liquid Let stir. Such air is exhausted to the outside from the upper air exhaust pipe 10.

  The carrier of the biological reaction unit 8 is not particularly limited, and examples thereof include sponges, activated carbon, packing materials used in the absorption tower, or combinations thereof, but can retain bacteria at high density, and can contain liquid and oxygen. A material that can be sufficiently passed and easily changed in shape is suitable. More specifically, a carrier that does not have an obstruction in the mesh, has a fine mesh, has a large specific surface area, and can be entangled with bacteria in the mesh and retained in a large amount, such as a slow-film sponge, is preferable.

Moreover, the microorganisms carried in the biological reaction unit 8 are sulfur-oxidizing bacteria capable of aerobically decomposing sulfur in the absorption liquid, and divalent iron ions (Fe ²⁺ ) and trivalent iron ions (Fe ³⁺ ). The iron-oxidizing bacteria that can be oxidized to each other, and the sulfur-oxidizing bacteria and the iron-oxidizing bacteria may be one kind or plural kinds respectively. These oxidizing bacteria are not particularly limited. Examples of sulfur oxidizing bacteria include Acidithiobacillus thiooxidans, and examples of iron oxidizing bacteria include Acidithiobacillus ferroxidans.

  The air is not particularly limited as long as it contains oxygen necessary for aerobic decomposition in the biological reaction section 8, and may be oxygen gas, air, or a combination thereof.

  Among the components of the present biological desulfurization apparatus, the absorbent liquid flow path 2, the regeneration tower 3, the circulation pump 4 and the circulating liquid flow path 5 are aerobic by microorganisms for absorbing liquid that has absorbed hydrogen sulfide. The circulating liquid supply means is configured to regenerate by an oxidative decomposition reaction and to supply the circulating liquid to the absorption tower 1 as a circulating liquid. The circulating liquid supply means recovers the absorption liquid that has absorbed hydrogen sulfide in the absorption tower 1 to the regeneration tower 3 via the absorption liquid flow path 2 and absorbs it through the circulation pump 4 and the circulating liquid flow path 5. It is resupplied to the tower 1 as a circulating liquid.

Next, a biodesulfurization method using the biodesulfurization apparatus configured as described above will be described.
The gas to be treated is introduced into the absorption tower 1 from the supply pipe 6 and comes into gas-liquid contact with the circulating liquid in the absorption tower 1. By this gas-liquid contact, hydrogen sulfide in the gas to be treated is absorbed into the circulating liquid and becomes an absorbing liquid. The treated gas from which hydrogen sulfide has been removed by gas-liquid contact with the circulating liquid in the absorption tower 1 is discharged to the outside as a purified gas from the purified gas pipe 7 and is used as fuel gas, synthesis gas, or the like. .

  Here, when the circulating fluid absorbs hydrogen sulfide, the trivalent iron ions in the circulating fluid become divalent iron ions, and the hydrogen sulfide becomes sulfur. At this time, if the circulating liquid has a pH of 1 to 2 and an oxidation-reduction potential of 600 mV or more, the absorbent does not become a slurry, and the handling of the absorbent in the apparatus is improved. Moreover, it is not necessary to concentrate the slurry.

  Such an absorption liquid is introduced from the absorption tower 1 to the regeneration tower 3 via the absorption liquid flow path 2 and is regenerated as a treatment liquid by an aerobic oxidative decomposition reaction by microorganisms in the biological reaction section 8. That is, divalent iron ions in the absorbing solution are oxidized by iron oxidizing bacteria and regenerated to trivalent iron ions. Moreover, since sulfur in the absorbing solution is converted into sulfuric acid by sulfur-oxidizing bacteria, it is not necessary to separate sulfur (solid matter) from the absorbing solution.

  The treatment liquid is acidic due to the sulfuric acid produced by the sulfur-oxidizing bacteria, but since this process proceeds under acidity, there is no problem, and it is convenient that the treatment liquid can be reused as a circulating liquid as it is. . If more precise pH adjustment of the circulating fluid is necessary, a pH adjusting agent may be added. Sodium hydroxide can be exemplified as a suitable alkali when raising the pH of the circulating liquid, and sulfuric acid can be exemplified as a suitable acid when lowering the pH of the circulating liquid. The processing liquid is supplied from the circulating liquid channel 5 to the absorption tower 1 and reused as the circulating liquid.

  The temperature of the circulating fluid is preferably maintained in the range of 25 to 35 ° C. for the purpose of maintaining the activity of microorganisms in the biological reaction section 8. This is because the activity of the microorganism is reduced outside this temperature range. The method of heating the circulating fluid is not particularly limited, and examples thereof include a method of spreading a heating device such as an electric heater over the entire circulating fluid flow path 5.

  As explained above, in the biological desulfurization apparatus and the biological desulfurization method according to this embodiment, slurrying of the absorbing liquid can be suppressed by using an acidic aqueous solution containing trivalent iron ions as a circulating liquid. Further, since sulfur in the absorbing solution is converted to sulfuric acid by sulfur-oxidizing bacteria and trivalent iron ions are regenerated by iron-oxidizing bacteria, the treatment liquid discharged from the regeneration unit 3 can be used as it is as a circulating solution. Therefore, according to this embodiment, the conventionally required slurry concentrating device, sulfur (solid matter) separating device, etc. are not required, the apparatus configuration and the process are not complicated, and the operability can be improved. it can.

  DESCRIPTION OF SYMBOLS 1 ... Absorption tower (absorption means), 2 ... Absorption liquid flow path, 3 ... Regeneration tower (biological reaction means), 4 ... Circulation pump, 5 ... Circulation liquid flow path, 6 ... Supply pipe, 7 ... Purified gas pipe, 8 ... Bioreaction unit, 9 ... Air supply pipe, 10 ... Air exhaust pipe

Claims (3)

An absorbing means for bringing the treated gas containing hydrogen sulfide into contact with the circulating solution of the acidic aqueous solution containing trivalent iron ions so that the circulating fluid absorbs the hydrogen sulfide to make the absorbing solution;
A biological reaction means for regenerating the absorption liquid with iron-oxidizing bacteria and sulfur-oxidizing bacteria to obtain a treatment liquid;
A biological desulfurization apparatus comprising: a circulating liquid supply unit that collects the processing liquid and supplies the treated liquid to the absorption unit as the circulating liquid.   The biological desulfurization apparatus according to claim 1, wherein the biological reaction means has a function of aeration of the absorbing solution. An absorption step in which a gas to be treated containing hydrogen sulfide is brought into contact with a circulating liquid of an acidic aqueous solution containing trivalent iron ions to absorb the hydrogen sulfide in the circulating liquid to obtain an absorbing liquid;
A biological reaction step in which the absorption liquid is regenerated by iron-oxidizing bacteria and sulfur-oxidizing bacteria to form a treatment liquid;
A biological fluid desulfurization method comprising: a circulating fluid supply step of collecting the treatment fluid and supplying the circulating fluid as the circulating fluid to the absorption step.

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