JP2016010777A - Method and apparatus for performing anaerobic treatment - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method and an apparatus for performing anaerobic treatment, in each of which an increase in the concentration of a by-product such as acetic acid is suppressed, the amount of the water or nutriment to be replenished is made small and a load of aerobic treatment is reduced.SOLUTION: The method for performing anaerobic treatment comprises the steps of: dissolving anaerobic gas 3 containing carbon monoxide or the like in a liquid culture medium 4 of a fermentation tank 21 to anaerobically produce organic substances such as alcohol; separating the organic substance-produced liquid culture medium 4e into an extracted fluid 7a and an extraction residual fluid 7b in an extraction part 22; reducing the COD (chemical oxygen demand) of the extraction residual fluid 7b in an anaerobic treatment part 30; branching a part of the extraction residual fluid 7b, on which anaerobic treatment is performed; and returning the branched fluid to the fermentation tank 21 as a return fluid 7c.

Description

  The present invention relates to an anaerobic treatment method and apparatus for anaerobically treating a treatment fluid using anaerobic microorganisms, and in particular, an extraction residue after synthesizing and extracting an organic substance such as alcohol from anaerobic gas by anaerobic fermentation. The present invention relates to an anaerobic treatment method and apparatus for anaerobically treating a fluid.

  Patent Document 1 discloses a method for producing an organic substance such as ethanol from industrial waste using a certain type of anaerobic bacteria. Specifically, an anaerobic gas containing carbon monoxide, hydrogen, and the like is generated by burning a feedstock such as industrial waste in a gasifier. This anaerobic gas is led to the fermenter. A liquid medium in which certain anaerobic bacteria are cultured is placed in the fermenter. The anaerobic gas is dissolved in the liquid medium. Then, ethanol etc. are produced | generated by the fermenting action of anaerobic bacteria. This ethanol or the like is extracted by a distillation process or the like. The extraction residual liquid other than ethanol or the like is preferably returned to the fermenter ([0085]).

  In patent document 2, the effluent from a fermenter is introduce | transduced into a distillation tower, and ethanol is extracted. Extraction residual liquid (water) other than ethanol is directly returned to the fermentor via the reflux path (FIG. 1). Therefore, the water distribution line is a closed circulation system.

JP 2014-050406 A JP 2004-504058 A

In this type of anaerobic fermentation, by-products such as acetic acid are synthesized in addition to organic substances intended for production such as ethanol ([0066] of Patent Document 1). For this reason, in the case of a closed circulation system as in Patent Document 2, the concentration of the by-product in the system increases, which adversely affects the culture of anaerobic bacteria. In addition, macromolecular organic substances (biomass) such as anaerobic bacterial carcasses also increase.
On the other hand, when the extraction residual liquid after distillation is discarded by one-through, the discarded water must be newly supplied, and the required amount of water becomes large. In addition, the load of waste liquid treatment or purification treatment for reducing the degree of pollution to a level that can be released to the environment becomes excessive. Furthermore, the nutrient residue for the above-mentioned anaerobic bacteria is also contained in the extraction residue, and if this is discarded together with the extraction residue, a new nutrient must be replenished to the fermenter, which is wasteful.
In a closed circulation system such as Patent Document 2, it can be considered that the extraction residual liquid is purified and returned to the fermenter. However, purifying all of the extraction residual liquid is heavy and time consuming. Further, when the nutrient is decomposed by the purification treatment, a new nutrient must be replenished to the fermenter as in the one-through method.

In order to solve the above-mentioned problems, the method of the present invention comprises dissolving an anaerobic gas containing at least one of carbon monoxide and hydrogen in a liquid medium of a fermenter, and organic matter such as alcohol by fermentation of anaerobic microorganisms in the liquid medium. Anaerobic that produces a substance and separates the effluent medium from the fermenter into an extraction fluid having a high concentration of the organic substance and an extraction residual fluid having a low concentration of the organic substance, and then processing the extraction residual fluid In the sex treatment method,
An anaerobic treatment step for reducing COD (Chemical Oxygen Demand) of the extraction residual fluid by anaerobic treatment;
A partial reflux step in which a part of the extraction residual fluid in the middle of the anaerobic treatment step is diverted and returned to the fermenter as a reflux body;
It is provided with.
Even if a by-product such as acetic acid is generated in the fermenter, an increase in the concentration of the by-product can be suppressed by the anaerobic treatment process. About a recirculation | reflux body, the excessive process of a nutrient can be suppressed by taking out in the middle of an anaerobic treatment process so that COD may not become low too much. By returning this reflux body to the fermenter, it can be recycled as a liquid medium, and the replenishment flow rate of water can be reduced. Furthermore, the remaining extraction residual fluid can be sufficiently anaerobically treated even after the recirculation of the refluxing body to sufficiently reduce the COD, thereby reducing the post-treatment of the subsequent aerobic treatment or the like, and hence the disposal or purification treatment. Thus, the processing efficiency can be increased.

When the COD of the extraction residual fluid during the anaerobic treatment step is 0.5 to 0.99 times the COD of the extraction residual fluid before the anaerobic treatment step, a part of the extraction residual fluid is removed from the reflux body. It is preferable to divert as
When the COD of the extraction residual fluid during the anaerobic treatment step becomes 0.9 to 0.97 times the COD of the extraction residual fluid before the anaerobic treatment step, a part of the extraction residual fluid is removed from the reflux body. It is more preferable to divert as.
As a result, it is possible to reliably prevent anaerobic treatment of the reflux body and to reliably prevent waste of nutrients.

It is preferable that the flow rate of the reflux body is larger than the flow rate of the remaining extraction residual fluid after the reflux body is divided.
As a result, the reuse rate of the liquid medium can be increased and the replenishment flow rate of water can be reliably reduced.

The extraction residual fluid may be sequentially sent to a plurality of stages of anaerobic treatment tanks, and a part of the extraction residual fluid may be divided as the reflux body between two adjacent adjacent anaerobic treatment tanks.
As a result, the COD of the extraction residual fluid can be reduced stepwise. And a part of extraction residual fluid in the middle of anaerobic processing can be reliably taken out as a reflux body. The extraction residual fluid may be stirred in each anaerobic treatment tank.

The extraction residual fluid flows in one anaerobic treatment tank so as to flow in one direction from the inlet to the terminal outlet, and halfway between the inlet and the terminal outlet of the anaerobic tank. A part of the extraction residual fluid may be diverted as the reflux body from the outlet.
As a result, the COD of the extraction residual fluid can be gradually reduced as the extraction residual fluid flows from the inlet to the terminal outlet of the anaerobic treatment tank. And a part of extraction residual fluid in the middle of anaerobic processing can be taken out as a reflux body.

It is preferable that anaerobic treatment is performed after anaerobic treatment is further performed on the remaining extraction residual fluid after the reflux body is divided.
This makes it possible to perform the aerobic process after sufficiently reducing the COD of the remaining extraction residual fluid to a level suitable for the aerobic process, thereby reducing the load of the aerobic process. By the aerobic treatment, the BOD (Biochemical Oxygen Demand) of the extraction residual fluid can be released to a level that can be released to the environment.
As the aerobic treatment process, at least one of a BOD oxidation process, a nitrification process, a denitrification process, a dephosphorization process, and a desulfurization process may be performed.

Before the anaerobic treatment step, the extraction residual fluid is separated into a solid extraction residue in which a solid component is concentrated and a liquid extraction residual fluid in which a solid component is diluted. It is preferable to perform an anaerobic treatment process.
As a result, the efficiency of the anaerobic process can be increased, and the time required for the anaerobic process can be shortened. The solid extraction residue can be treated separately.

It is preferable to solubilize the solid extraction residue by acid fermentation.
Thereby, the solubilized product can be forwarded to the anaerobic treatment step and anaerobically treated with the residual extraction fluid, or can be discarded by performing a post-treatment step such as aerobic treatment.

The anaerobic treatment apparatus according to the present invention contains a liquid medium in which an anaerobic gas containing at least one of carbon monoxide and hydrogen is dissolved, and an organic substance such as alcohol is removed by fermentation of anaerobic microorganisms in the liquid medium. A fermenter to produce,
An extraction unit that separates the effluent medium from the fermenter into an extraction fluid in which the organic substance is concentrated and an extraction residual fluid in which the organic substance is diluted;
An anaerobic treatment unit that reduces COD (chemical oxygen demand) of the extraction residual fluid by anaerobic treatment;
The anaerobic treatment unit has a midstream outlet provided in the middle and a terminal outlet provided at the end, and the midstream outlet is connected to the fermenter via a reflux path And
The COD of the reflux body flowing out from the midstream outlet is larger than the COD when the remaining extraction residual fluid reaches the terminal outlet.
Even if a by-product such as acetic acid is produced in the fermenter, for example, decomposition in the anaerobic treatment part can suppress an increase in the concentration of the by-product part. Moreover, a part of extraction residual fluid can be taken out in the middle of an anaerobic process part, can be returned to a fermenter, and can be circulated and reused as a liquid culture medium. Thereby, the replenishment flow rate of water can be reduced. In addition, by returning from the middle of the anaerobic treatment unit, it is possible to prevent waste of nutrients so that the COD of the reflux body does not become too low. Furthermore, with respect to the remaining extraction residual fluid, COD can be sufficiently reduced by continuously performing anaerobic treatment even after the flow of the reflux body, and the post-processing load such as aerobic treatment can be reduced, thereby increasing the processing efficiency. be able to.

The anaerobic treatment part has a plurality of anaerobic treatment tanks connected in series, and the intermediate outlet is connected between two adjacent anaerobic treatment tanks in these anaerobic treatment tanks, and the anaerobic treatment tank of the final stage The terminal outlet may be connected to the terminal.
As a result, the COD can be lowered stepwise by performing anaerobic treatment while sequentially sending the extraction residual fluid to a plurality of stages of anaerobic treatment tanks. And a part of extraction residual fluid can be shunted as a reflux body from between adjacent two predetermined anaerobic processing tanks, and can be returned to a fermenter. The extraction residual fluid may be stirred in each anaerobic treatment tank.

The anaerobic treatment part is formed with a one-way flow from the inlet to the terminal outlet, and the intermediate outlet is provided between the inlet and the terminal outlet of the anaerobic part. May be.
As a result, the COD of the residual extraction fluid can be gradually reduced as the residual extraction fluid flows from the inlet to the terminal outlet of the anaerobic treatment unit. And a part of extraction residual fluid in the middle of anaerobic processing can be taken out as a reflux body.

It is preferable that an aerobic processing unit is connected to the terminal outlet.
Thus, in the anaerobic treatment unit, the remaining extraction residual fluid after the flow of the reflux body is further anaerobically treated, so that the COD is sufficiently lowered to a level suitable for the aerobic treatment, and then the terminal outlet Can be aerobic processed out of. Therefore, the load of aerobic processing can be reduced. By the aerobic treatment, the BOD of the residual extraction fluid can be released to a level at which environmental release is possible.

It is preferable that the COD of the reflux body is 0.5 to 0.99 times the COD of the residual extraction fluid before the anaerobic treatment.
More preferably, the COD of the refluxing body is 0.9 to 0.97 times the COD of the extraction residual fluid before the anaerobic treatment.
As a result, it is possible to reliably prevent anaerobic treatment of the reflux body and to reliably prevent waste of nutrients.

The flow rate of the reflux body is preferably larger than the flow rate of the remaining extraction residual fluid.
As a result, the reuse rate of the liquid medium can be increased and the replenishment flow rate of water can be reliably reduced.

A solid-liquid separation unit that separates the extraction residual fluid into a solid extraction residue in which the solid component is concentrated and a liquid extraction residual fluid in which the solid component is diluted between the extraction unit and the anaerobic processing unit. It is preferable that the liquid extraction residual fluid is introduced into the anaerobic treatment section.
As a result, the efficiency of the anaerobic treatment can be increased and the required time can be shortened. The solid extraction residue can be treated separately.

It is preferable that an acid fermentation part for solubilizing the solid extraction residue by acid fermentation is provided.
As a result, the solubilized product can be sent to the anaerobic treatment unit to be anaerobically treated with the residual extraction fluid, or subjected to post-treatment such as aerobic treatment and discarded.

  According to the present invention, even if a by-product such as acetic acid is generated in the fermenter, an increase in the concentration can be suppressed. Moreover, it is possible to prevent the reflux body from being anaerobically treated, to suppress waste of nutrients, and to reduce the replenishment flow rate of water. Furthermore, the processing efficiency can be increased by reducing the load of subsequent processing (discarding or purification processing) such as aerobic processing.

FIG. 1 is a circuit diagram of a waste treatment system including an anaerobic treatment apparatus according to the first embodiment of the present invention. FIG. 2 is a circuit diagram of a waste treatment system including an anaerobic treatment apparatus according to the second embodiment of the present invention. FIG. 3 is a circuit diagram of a waste treatment system including an anaerobic treatment apparatus according to the third embodiment of the present invention. FIG. 4 is a circuit diagram of a waste treatment system including an anaerobic treatment apparatus according to the fourth embodiment of the present invention.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 shows a first embodiment of the present invention. The anaerobic treatment apparatus 1 is incorporated in a waste 2 treatment system. In the waste treatment system, the waste 2 is burned in the melting furnace 11 and decomposed to a low molecular level to generate an anaerobic gas 3 containing carbon monoxide (CO). In the anaerobic treatment apparatus 1, the anaerobic gas 3 is dissolved in the liquid medium 4, and ethanol (C ₂ H ₅ OH) and other organic substances are produced by the anaerobic fermentation action of the organic substance-producing anaerobic microorganisms 5. Extract this.
Details will be described below.

  The anaerobic treatment apparatus 1 includes a gas line 10 and a liquid material line 20. A gas line 10 extends from the melting furnace 11. The melting furnace 11 serves as a supply unit for the anaerobic gas 3. On the gas line 10, the deoxidation part 12 and the pressure pump 13 are provided in order. The deoxygenation unit 12 is provided with a catalyst 12a made of a transition metal such as Fe, Ni, Cr, Co, or Cu.

On the liquid material line 20, the fermenter 21, the extraction part 22, the anaerobic process part 30, and the aerobic process part 50 are provided in order. The downstream end of the gas line 10 is connected to the bottom of the fermenter 21. The fermenter 21 accommodates the liquid medium 4. Most of the liquid medium 4 is water (H ₂ O), and nutrients such as vitamins and phosphoric acid are dispersed or dissolved therein. An organic substance-producing anaerobic microorganism 5 is cultured in the liquid medium 4. As an organic substance production | generation anaerobic microorganism 5, the anaerobic bacterium disclosed by patent document 1, 2, etc. can be used, for example. This organic substance-producing anaerobic microorganism 5 synthesizes ethanol from CO, H _{2 and the} like by anaerobic fermentation. Other alcohols such as butanol and other organic substances may be synthesized (see Patent Documents 1 and 2).

An extraction unit 22 is connected to the liquid outlet 21 b of the fermenter 21. The extraction part 22 is comprised by the distillation tower, for example, and is extended up and down. The extraction unit 22 is provided with a top outlet 22a and a bottom outlet 22b. The top outlet 22a serves as an outlet for the extraction fluid 7a. The extraction fluid 7a contains alcohol such as ethanol produced in the fermenter 21 at a high concentration. Although illustration of the extraction unit 22 is omitted, a dehydration processing unit and the like are provided at the top outlet 22a. The concentration of alcohol such as ethanol in the extraction fluid 7a that has undergone extraction and dehydration is, for example, about 92 wt% to 99.9 wt%.
The extraction unit 22 may include a plurality of distillation columns. These plurality of distillation columns may be connected directly or in parallel. The extraction unit 22 may include a mash tower, a simple distillation unit, a rectification unit, and the like.

  The bottom outlet 22b serves as an outlet for the extraction residual fluid 7b. The extraction residual fluid 7b is mostly water, and the above-mentioned nutrients, high-molecular organic matter (biomass) such as the living body or skeleton of the organic substance-producing anaerobic microorganism 5, and low concentrations or traces that could not be extracted. Concentrations of ethanol and by-product acetic acid are included. An anaerobic treatment unit 30 is connected to the bottom outlet 22b.

  The extraction residual fluid 7b is introduced from the extraction unit 22 and stored in the anaerobic processing unit 30. The anaerobic microorganism 6 for residual extraction treatment is cultured in the residual extraction fluid 7b. Examples of the anaerobic microorganism 6 include acid-fermenting bacteria and methane-fermenting bacteria. The organic matter in the extraction residual fluid 7b is decomposed by the fermentation action of these bacteria, and the COD (chemical oxygen requirement) of the extraction residual fluid 7b is reduced.

  The anaerobic treatment unit 30 is provided with two outlets 35 and 36. The midway outlet 35 is provided in the middle of the process progress direction of the anaerobic processing unit 30. A part of the extraction residual fluid 7b flows out from the midstream outlet 35 as the reflux body 7c. The terminal outlet 36 is provided at the terminal of the anaerobic processing unit 30 in the processing progress direction. The remaining portion 7d of the extraction residual fluid 7b flows out from the terminal outlet 36 and becomes the discharged fluid 7e.

  Specifically, in the first embodiment, the anaerobic treatment unit 30 includes a plurality of (here, two) anaerobic treatment tanks 31 and 32. These anaerobic treatment tanks 31 and 32 are connected in series via a communication path 33. The extraction residual fluid 7b is sequentially introduced into the anaerobic treatment tanks 31 and 32. The anaerobic microorganism 6 is cultured in the extraction residual fluid 7b of each anaerobic treatment tank 31, 32, and anaerobic fermentation is performed. The sizes of the anaerobic treatment tanks 31 and 32 are substantially equal, but may be different from each other.

  The anaerobic treatment tanks 31 and 32 are provided with stirring mechanisms 31f and 32f. The residual extraction fluid 7b in the preceding anaerobic treatment tank 31 is stirred by the stirring mechanism 31f. Therefore, the COD distribution in the anaerobic treatment tank 31 and the dispersion concentration of the anaerobic microorganisms 6 are substantially uniform over the entire area of the anaerobic treatment tank 31. Similarly, the extraction residual fluid 7b in the subsequent anaerobic treatment tank 32 is agitated by the stirring mechanism 32f, so that the COD distribution in the anaerobic treatment tank 32 and the dispersion concentration of the anaerobic microorganisms 6 are spread over the entire area of the anaerobic treatment tank 32. It is almost uniform. The stirring mechanisms 31f and 32f may be stirring screws or stirring pumps.

A reflux path 40 is branched from the communication path 33. A reflux pump 37 is provided in the reflux path 40.
A flow pump 38 is provided in a portion of the communication path 33 closer to the anaerobic treatment tank 32 than the branch of the reflux path 40.

  A midway outlet 35 is provided on the reflux path 40. The midway outlet 35 is connected between two adjacent anaerobic treatment tanks 31 and 32 via a reflux path 40 on the communication path 33 side. The midstream outlet 35 may be disposed at a branch portion between the communication path 33 and the reflux path 40.

The reflux path 40 extends to the fermenter 21. As a result, the midway outlet 35 is connected to the fermenter 21 via the reflux path 40. A replenishment unit 41 is connected to the middle of the reflux path 40. The replenishing unit 41 replenishes (supplies) water (H ₂ O) to the fermenter 21 via the reflux path 40. Further, the replenishing unit 41 replenishes (supplies) the fermenter 21 with the nutrients (vitamin, phosphoric acid, etc.) for the organic substance-producing anaerobic microorganisms 5 through the reflux path 40 together with the water.

A deoxygenation unit 42 is provided between the replenishment unit 41 and the reflux path 40. The deoxidation part 42 has an aeration part of nitrogen (N ₂ ).

The outlet of the rear stage (final stage) anaerobic treatment tank 32 constitutes a terminal outlet 36. That is, the terminal outlet 36 is connected to the anaerobic treatment tank 32. An aerobic treatment unit 50 is connected to the terminal outlet 36. The aerobic treatment unit 50 includes an aerobic treatment tank 51 and an aeration mechanism 52. In the aerobic treatment tank 51, aerobic bacteria are cultured. The aeration mechanism 52 aerates air or oxygen (O ₂ ) into the aerobic treatment tank 51.

An anaerobic treatment method by the waste treatment system and the anaerobic treatment apparatus 1 will be described.
<Waste combustion to gas production process>
The waste 2 is put into the melting furnace 11. The waste 2 is, for example, an organic industrial waste. Preferably, almost 100% oxygen is supplied to the melting furnace 11. Then, the waste 2 is heated to, for example, about 2000 ° C. and burned. As a result, most of the constituent molecules of the waste 2 are gasified and an anaerobic gas 3 is generated. The anaerobic gas 3 contains H ₂ , CO _{2 and the} like in addition to CO.
Solid components (slag) generated by combustion of the waste 2 are separately discharged from the melting furnace 11.

<Gas deoxygenation process>
Anaerobic gas 3 is passed through deoxidation section 12. At this time, when O ₂ is contained in the anaerobic gas 3, CO or H ₂ in the anaerobic gas 3 reacts with O _{2 using} a transition metal such as Fe, Ni, Cr, Co, or Cu as a catalyst. Thus, CO ₂ and H ₂ O are generated. As a result, O ₂ is removed from the anaerobic gas 3.

<Gas supply process>
The anaerobic gas 3 after deoxygenation is compressed by the pressure pump 13 and is pumped to the fermenter 21. This anaerobic gas 3 is bubbled vigorously into the liquid medium 4 of the fermenter 21 and melts.

<Fermentation process>
Thereby, alcohol (organic substance) such as ethanol is generated from CO and H ₂ of the anaerobic gas 3 by the fermentation action of the organic substance-producing anaerobic microorganism 5 in the liquid medium 4. By-products such as CO ₂ and acetic acid (CH ₃ COOH) are also produced.
By removing O ₂ in the anaerobic gas by the above-described gas deoxygenation step, it is possible to prevent the anaerobic microorganism 5 from being damaged.

The gas components such as CO ₂ , unused CO, and H ₂ are discharged from the gas outlet of the fermenter 21. These gaseous components may be returned to the melting furnace 11 or may be burned together with air and used as a heat source such as distillation.

  From the liquid outlet 21b of the fermenter 21, a part 4e of the liquid medium 4 is continuously discharged at a constant flow rate. This effluent medium 4 e is sent to the extraction unit 22.

<Extraction (distillation) process>
In the extraction unit 22, the effluent medium 4e is distilled to extract ethanol. That is, the outflow medium 4e is separated into an extraction fluid 7a containing ethanol at a high concentration and an extraction residual fluid 7b having a low ethanol concentration. The extraction fluid 7a flows out from the top outlet 22a, and can be used for various uses such as a solvent, a chemical raw material, and a fuel through a purification process such as a low boiling point substance removal and a dehydration process.
The residual extraction fluid 7b is guided from the bottom outlet 22b to the anaerobic processing unit 30.

<Anaerobic treatment process>
In the anaerobic processing unit 30, the extraction residual fluid 7 b is subjected to anaerobic processing by anaerobic fermentation of the extraction residual processing anaerobic microorganism 6. Anaerobic fermentation includes acid fermentation and methane fermentation. By acid fermentation by acid-fermenting bacteria, a high-molecular organic substance (biomass) such as a skeleton of anaerobic microorganisms 5 in the extraction residual fluid 7b can be decomposed or solubilized into a low-molecular acidic organic substance such as acetic acid. Furthermore, low-molecular acidic organic substances such as acetic acid (including acetic acid as a by-product in the fermentation process) can be decomposed into methane (CH ₄ ) and carbon dioxide (CO ₂ ) by methane fermentation using methane-fermenting bacteria. Thereby, as the anaerobic process proceeds, the COD (Chemical Oxygen Demand) of the residual extraction fluid 7b can be gradually reduced.
Gas components (CH ₄ , CO _2, etc.) generated in the anaerobic treatment process are discharged from the gas outlets of the anaerobic treatment tanks 31 and 32.

<Diversion process (partial reflux process)>
The extraction residual fluid 7b is sequentially anaerobically treated by the plural stages of anaerobic treatment tanks 31 and 32, and a part of the extraction residual fluid 7b is returned when it is transferred from the anaerobic treatment tank 31 in the middle of the anaerobic treatment process. The fluid 7c is diverted.
Specifically, the extraction residual fluid 7 b is first introduced into the anaerobic treatment tank 31 of the previous stage (first stage), and after being anaerobically treated while being stirred in the anaerobic treatment tank 31, it is led out to the communication path 33. Then, in the communication path 33, the flow is divided into the reflux body 7c and the remaining extraction residual fluid 7d. The reflux body 7 c flows to the reflux path 40 and is sent to the fermenter 21. The remaining extraction residual fluid 7d flows to the anaerobic treatment tank 32 in the subsequent stage, and is further anaerobically treated while being stirred in the anaerobic treatment tank 32, and then is discharged from the terminal outlet 36 to become the discharged fluid 7e.

The COD of the reflux body 7c is smaller than the COD of the extraction residual fluid 7b before the anaerobic processing by the anaerobic processing unit 30, and the COD (aerobic processing unit 50) when the remaining extraction residual fluid 7d reaches the terminal outlet 36. Is larger than the COD of the discharged fluid 7e before the treatment. In addition, the flow rate of the reflux body 7c is smaller than the overall flow rate of the residual extraction fluid 7b (the flow rate of introduction to the anaerobic treatment unit 30) and larger than the flow rate of the remaining residual extraction fluid 7d.
The COD of the residual extraction fluid 7b before the anaerobic treatment is substantially equal to the COD obtained by subtracting the alcohol content in the effluent medium 4e.

Preferably, when the COD of the extraction residual fluid 7b during the anaerobic treatment becomes slightly smaller than the extraction residual fluid 7b before the anaerobic treatment, a part of the extraction residual fluid 7b is diverted to form the reflux body 7c. In other words, when the COD of the extraction residual fluid 7b during the anaerobic treatment is sufficiently larger than the COD of the discharged fluid 7e at the terminal outlet 36, a part of the extraction residual fluid 7b is diverted as the reflux body 7c.
Preferably, when the COD of the extraction residual fluid 7b during the anaerobic treatment becomes 0.5 to 0.99 times the COD of the extraction residual fluid 7b before the anaerobic treatment, the reflux body 7c is diverted.
More preferably, when the COD of the extraction residual fluid 7b during the anaerobic treatment becomes 0.9 to 0.97 times the COD of the extraction residual fluid 7b before the anaerobic treatment, the reflux body 7c is divided.
Thereby, it is possible to prevent the extraction residual fluid 7b from being excessively anaerobically treated in the anaerobic treatment tank 31, and to leave the nutrients for the organic substance-producing anaerobic microorganisms 5 in the reflux body 7c undecomposed.

  Preferably, the flow rate of the reflux body 7c is set to be slightly smaller than the entire flow rate of the remaining extraction fluid 7b and sufficiently larger than the flow rate of the remaining remaining extraction fluid 7d. Thereby, while being able to ensure the return flow rate to the fermenter 21, the flow rate of the exhaust fluid 7e can be reduced and the load of post-processing (aerobic treatment) can be reduced.

  Preferably, the residence time of the extraction residual fluid 7b in the anaerobic treatment tank 31 is shortened, and the residence time of the remaining extraction residual fluid 7d in the anaerobic treatment tank 32 is lengthened. As a result, the reflux body 7c can be reliably prevented from being anaerobically treated, and the remaining extraction residual fluid 7d is sufficiently anaerobically treated to sufficiently reduce the COD of the extraction residual fluid 7d. The load of post-processing (aerobic processing) can be surely reduced.

For example, if the COD of the extraction residual fluid 7b before anaerobic treatment (before introduction into the anaerobic treatment unit 30) is about 30000 mg / L, the COD of the reflux body 7c is set to about 27000 mg / L to 29000 mg / L. Thereby, it is possible to avoid the anaerobic treatment of the reflux body 7c, and it is possible to leave the nutrients almost undegraded.
Further, the COD of the remaining extraction residual fluid 7d is finally set to about 3000 mg / L. As a result, the COD of the discharged fluid 7e can be lowered to a level suitable for an aerobic process described later.
In addition, this invention is not limited to said numerical range.

Each flow rate of the reflux body 7c and the residual extraction fluid 7d and thus a flow rate ratio (a flow ratio from the communication path 33 to the reflux path 40) can be adjusted by outputs of the reflux pump 37 and the feed pump 38. Furthermore, the residence time of the extraction residual fluid 7b in the preceding anaerobic treatment tank 31 and the residence time of the remaining extraction residual fluid 7d in the subsequent anaerobic treatment tank 32, the final COD of the reflux body 7c and the remaining extraction residual fluid 7d. The typical COD can also be adjusted by the outputs of the reflux pump 37 and the feed pump 38.
Note that the above flow rate adjustment may be performed by a flow rate control valve.

<Replenishment process>
The reflux body 7 c is sent to the fermenter 21 through the reflux path 40.
In the middle of this, water and nutrients (vitamin, phosphoric acid, etc.) are supplied from the replenishing unit 41 to the reflux body 7 c via the deoxygenating unit 42. Thereby, water can be replenished to the liquid body line 20 and nutrients (vitamin, phosphoric acid, etc.) for the organic substance-producing anaerobic microorganisms 5 can be replenished. In the deoxygenation unit 42, nitrogen is aerated in the water containing the nutrients, so that dissolved oxygen in the water moves to the nitrogen and is exhausted together with the nitrogen.

  The replenishment flow rate of water from the replenishment unit 41 substantially corresponds to the flow rate of the residual extraction fluid 7d and thus the discharged fluid 7e. Thereby, even if the discharged fluid 7e is discharged to the outside, the water amount of the entire liquid material line 20 can be kept constant. Since the extraction residual fluid 7d is sufficiently small as compared with the reflux body 7c, the replenishment flow rate of water in the replenishment unit 41 can be sufficiently reduced. Further, since the reflux body 7c is taken out from the anaerobic treatment unit 30 when the nutrients are not decomposed so much, the replenishment amount of nutrients in the replenishment unit 41 can be small.

<Reflux process>
Thereafter, the reflux body 7 c is returned to the fermenter 21 to become the liquid medium 4. As a result, the liquid medium 4 can be circulated and reused.
As described above, anaerobic treatment in the anaerobic treatment tank 31 can prevent an increase in by-products such as acetic acid, so that the synthesis efficiency of alcohol such as ethanol in the fermentation tank 21 can be maintained. Further, by removing oxygen from the replenishing water in the deoxygenation unit 42, damage to the organic substance-producing anaerobic microorganisms 5 in the liquid medium 4 can be reduced.

<Aerobic treatment process (post-treatment process)>
The discharged fluid 7 e that has exited from the terminal outlet 36 is sent to the aerobic processing unit 50. In the aerobic treatment part 50, the exhaust fluid 7e is introduced into the aerobic treatment tank 51, and aerobic fermentation is caused by aeration of air or oxygen by the aeration mechanism 52. By this aerobic treatment, the organic matter in the exhaust fluid 7e can be oxidatively decomposed, and the BOD (Biochemical Oxygen Demand) of the exhaust fluid 7e can be reduced. Further, if necessary, a nitrification step, a denitrification step, a dephosphorization step, a desulfurization step, and the like of the discharged fluid 7e may be performed by a known method. Nitrifying bacteria may be used in the nitrification step. In the denitrification step, denitrifying bacteria may be used. In the dephosphorization step, dephosphorization bacteria may be used. In the desulfurization step, desulfurization bacteria may be used. As described above, by reducing the COD and thus BOD of the discharged fluid 7e to an aerobic treatment size by the anaerobic treatment in the anaerobic treatment tank 32, the load of the aerobic treatment and thus the disposal or purification treatment can be reduced. Processing efficiency can be increased.

<Discharge process>
As a result, the BOD of the discharged fluid 7e can be sufficiently lowered to the regulation level, and the discharged fluid 7e can be purified and released into an environment such as a river or sewage to be discarded.

Next, another embodiment of the present invention will be described. In the following embodiments, the same reference numerals are attached to the drawings for the same contents as those of the above-described embodiments, and the description thereof is omitted.
FIG. 2 shows a second embodiment of the present invention. In the second embodiment, the return path 20 b is branched from a line 20 a that connects the bottom outlet 22 b of the extraction unit 22 and the anaerobic processing unit 30. The return path 20 b is continuous with the fermenter 21.

Therefore, a part of the extraction residual fluid 7b from the extraction unit 22 is returned directly to the fermenter 21 from the return path 20b. The remaining portion of the extraction residual fluid 7b is sent to the anaerobic processing unit 30 for anaerobic processing. Thereby, when ethanol (an organic substance to be generated) remains in the extraction residual fluid 7b, a part of the ethanol can be returned to the extraction unit 22 via the fermenter 21 and can be subjected to the extraction process again. Therefore, the flow rate of ethanol that is decomposed or discarded through the anaerobic processing unit 30 and the aerobic processing unit 50 can be reduced. In other words, even if the ethanol extraction efficiency in the extraction unit 22 is not high, the amount of ethanol that is wasted can be reduced.
Moreover, since the flow rate of the extraction residual fluid 7b sent to the anaerobic processing unit 30 is reduced, the burden on the anaerobic processing unit 30 can be reduced.

  FIG. 3 shows a third embodiment of the present invention. In 3rd Embodiment, the anaerobic process part 30X is comprised by the upward flow type anaerobic sludge bed (USAB: Upflow Anaerobic Sludge Blanket). The anaerobic treatment unit 30X is filled with granules 6X in which the anaerobic microorganisms 6 for residual extraction processing have been aggregated from the bottom to the top.

An inflow port 34 is provided at the bottom of the anaerobic treatment unit 30X. A terminal outlet 36 is provided at the top of the anaerobic treatment unit 30X. A midway outlet 35 is provided in the middle of the anaerobic treatment unit 30X in the height direction (between the inlet 34 and the terminal outlet 36). A reflux path 40 extends from the midway outlet 35.
The anaerobic treatment unit 30X is not provided with a stirring mechanism.

  The extraction residual fluid 7b from the extraction unit 22 is introduced from the inlet 34 to the bottom of the anaerobic processing unit 30X and comes into contact with the anaerobic microorganism 6 for extraction residual processing of the granules 6X. As a result, the organic matter in the extraction residual fluid 7b is decomposed anaerobically. The residual extraction fluid 7b rises in the granule 6X from the inlet 34 toward the terminal outlet 36. Therefore, an upward unidirectional flow is formed in the granule 6X. Anaerobic fermentation progresses while flowing. Therefore, the higher the position in the anaerobic processing unit 30X, the smaller the COD of the extraction residual fluid 7b.

  A part of the extraction residual fluid 7b flows out from the midstream outlet 35 in the middle of ascending, and becomes the reflux body 7c. The point that this reflux body 7c is returned to the fermenter 21 via the reflux path 40 is the same as in the first embodiment. Further, preferably, similarly to the first embodiment, the flow rate of the reflux body 7c is set larger than the flow rate of the remaining extraction residual fluid 7d. Therefore, the flow rate of the extraction residual fluid 7b from the inlet 34 to the midstream outlet 35 in the anaerobic treatment unit 30X is large, and the flow rate of the extraction residual fluid 7d above the midstream outlet 35 is small.

  The remaining extraction residual fluid 7d rises to the top of the anaerobic treatment unit 30X while being further anaerobically treated. Then, it flows out from the terminal outlet 36 and becomes the discharged fluid 7e. Therefore, after the COD of the discharged fluid 7e is made sufficiently small, it can be introduced into the aerobic processing unit 50 and efficiently aerobic processed.

  FIG. 4 shows a fourth embodiment of the present invention. The anaerobic treatment apparatus 1 according to the fourth embodiment further includes a solid-liquid separation unit 60 and an acid fermentation unit 63 (solubilization unit). The solid-liquid separation unit 60 and the acid fermentation unit 63 are interposed between the extraction unit 22 and the anaerobic processing unit 30 in the liquid body line 20. Therefore, the extraction residual fluid 7 b that has come out of the extraction unit 22 is introduced into the solid-liquid separation unit 60.

  The solid-liquid separation unit 60 has a precipitation tank and a filter. In the solid-liquid separator 60, the extraction residual fluid 7b is separated into a solid extraction residue 7f and a liquid extraction residual fluid 7g. The solid extraction residue 7f is obtained by concentrating the solid components of the extraction residual fluid 7b (eg, the body of the organic substance-producing anaerobic microorganism 5). The liquid extraction residual fluid 7g is in a liquid state by diluting the solid component of the extraction residual fluid 7b.

  An outlet on the liquid extraction residual fluid 7 g side of the solid-liquid separation unit 60 is connected to the anaerobic processing unit 30. As a result, the liquid extraction residual fluid 7g is introduced into the anaerobic processing unit 30 and subjected to anaerobic processing. Since the liquid extraction residual fluid 7g contains almost no solid component, the time required for the anaerobic treatment can be shortened. In particular, it is possible to shorten the processing time of the remaining extraction residual fluid 7d after diverting the reflux body 7c, and to reduce the load of the anaerobic processing.

The outlet of the solid-liquid separation unit 60 on the solid extraction residue 7 f side is connected to the acid fermentation unit 63. In the acid fermentation part 63, acid fermentation bacteria 8 are cultured. The acid-fermenting bacteria 8 anaerobically decomposes and solubilizes the solid extraction residue 7f by acid fermentation. Accordingly, the carcass (biomass) of the organic substance-producing anaerobic microorganism 5 can be made liquid.
The solubilized product may be introduced into the anaerobic treatment unit 30 together with 7 g of the liquid extraction residual fluid. Or you may discard after performing an aerobic process.

The present invention is not limited to the above embodiment, and various modifications can be made without departing from the spirit of the present invention.
For example, anaerobic gas 3 may include at least one of CO and H _2. However, when the anaerobic gas 3 contains H ₂ and does not contain CO, another carbon source such as CO ₂ is required.
The organic substance to be generated is not limited to alcohols such as ethanol and butanol, and may be other organic compounds such as acetic acid.
The fluids 4, 7 a to 7 e, and 7 g may be flowable and may contain a solid content.
As a modification of the first embodiment, three or more anaerobic treatment tanks may be cascade-connected. Among these three or more anaerobic treatment tanks, the intermediate outlet 35 and the reflux path 40 are provided between two adjacent predetermined anaerobic treatment tanks, so that the predetermined two anaerobic treatment tanks are returned to each other. The fluid 7c may be diverted.
In the first embodiment (FIG. 1), the reflux path 40 may extend directly from the vicinity of the connection portion of the connection path 33 in the anaerobic treatment tank 31 instead of being branched from the connection path 33. The connection portion of the reflux path 40 with the anaerobic treatment tank 31 may constitute a midstream outlet 35.
A plurality of embodiments may be combined with each other. For example, in the third embodiment (FIG. 3) and the fourth embodiment (FIG. 4), the line connecting the bottom outlet 22b of the extraction unit 22 and the anaerobic processing unit 30 is the same as in the second embodiment (FIG. 2). The return path 20b may be branched from 20a, and the return path 20b may be connected to the fermenter 21.
In addition, the anaerobic treatment unit 30 of the fourth embodiment (FIG. 4) is a stirring type multi-stage anaerobic treatment tank 31 and 32 as in the first embodiment (FIG. 1), but the third embodiment (FIG. 4). You may comprise in the unidirectional flow anaerobic treatment tank 30X like 3).

  The present invention can be applied to a water treatment apparatus of an ethanol generation system that synthesizes ethanol from carbon monoxide generated by, for example, incineration of industrial waste.

DESCRIPTION OF SYMBOLS 1 Anaerobic processing apparatus 3 Anaerobic gas 4 Liquid culture medium 4e Outflow medium 5 Organic substance production | generation anaerobic microorganism 6 Anaerobic microorganism 7a for extraction residual processing Extraction fluid 7b Extraction residual fluid 7c Recirculation | reflux 7d Remaining extraction residual fluid 21 Fermenter 22 Extraction Unit 30 anaerobic processing unit 30X anaerobic processing unit 31, 32 anaerobic processing tank 34 inlet 35 intermediate outlet 36 terminal outlet 40 reflux path 41 replenishing unit 42 deoxygenating unit 50 aerobic processing unit 60 solid-liquid separation unit 63 acid fermentation unit

Claims (20)

Anaerobic gas containing at least one of carbon monoxide and hydrogen is dissolved in the liquid medium of the fermentor, and an organic substance is generated by the fermenting action of the anaerobic microorganisms in the liquid medium. In the anaerobic treatment method of treating the extraction residual fluid after separating the extraction fluid with a high concentration of the organic substance and the extraction residual fluid with a low concentration of the organic substance,
Anaerobic treatment step of reducing COD (chemical oxygen demand) of the extraction residual fluid by anaerobic treatment;
A partial reflux step in which a part of the extraction residual fluid in the middle of the anaerobic treatment step is diverted and returned to the fermenter as a reflux body;
An anaerobic treatment method characterized by comprising:   When the COD of the extraction residual fluid during the anaerobic treatment step is 0.5 to 0.99 times the COD of the extraction residual fluid before the anaerobic treatment step, a part of the extraction residual fluid is removed from the reflux body. The anaerobic treatment method according to claim 1, wherein the anaerobic treatment method is performed.   When the COD of the extraction residual fluid during the anaerobic treatment step becomes 0.9 to 0.97 times the COD of the extraction residual fluid before the anaerobic treatment step, a part of the extraction residual fluid is removed from the reflux body. The anaerobic treatment method according to claim 1, wherein the anaerobic treatment method is performed.   The anaerobic treatment method according to any one of claims 1 to 3, wherein the flow rate of the reflux body is made larger than the flow rate of the remaining extraction residual fluid after the reflux body is divided.   The extraction residual fluid is sequentially sent to a plurality of stages of anaerobic treatment tanks, and a part of the extraction residual fluid is diverted as the reflux body between two adjacent adjacent anaerobic treatment tanks. The anaerobic treatment method according to any one of 1 to 4.   The extraction residual fluid flows in one anaerobic treatment tank so as to flow in one direction from the inlet to the terminal outlet, and halfway between the inlet and the terminal outlet of the anaerobic tank. The anaerobic treatment method according to any one of claims 1 to 5, wherein a part of the extraction residual fluid is diverted from the outlet as the reflux body.   The exhaustive treatment method according to any one of claims 1 to 6, further comprising anaerobic treatment after the remaining extraction residual fluid after the flow of the reflux body is further anaerobically treated.   Before the anaerobic treatment step, the extraction residual fluid is separated into a solid extraction residue in which a solid component is concentrated and a liquid extraction residual fluid in which a solid component is diluted. The anaerobic treatment method according to any one of claims 1 to 7, wherein an anaerobic treatment step is performed.   The anaerobic treatment method according to claim 8, wherein the solid extraction residue is solubilized by acid fermentation.   The anaerobic treatment method according to claim 1, wherein the organic substance is alcohol. A fermenter in which a liquid medium in which an anaerobic gas containing at least one of carbon monoxide and hydrogen is dissolved is contained, and an organic substance is generated by a fermenting action of anaerobic microorganisms in the liquid medium;
An extraction unit that separates the effluent medium from the fermenter into an extraction fluid having a high concentration of the organic substance and an extraction residual fluid having a low concentration of the organic substance;
An anaerobic treatment unit that reduces COD (chemical oxygen demand) of the extraction residual fluid by anaerobic treatment;
The anaerobic treatment unit has a midstream outlet provided in the middle and a terminal outlet provided at the end, and the midstream outlet is connected to the fermenter via a reflux path And
An anaerobic treatment apparatus, wherein the COD of the reflux body flowing out from the midstream outlet is larger than the COD when the remaining extraction residual fluid reaches the terminal outlet.   The anaerobic treatment part has a plurality of anaerobic treatment tanks connected in series, and the intermediate outlet is connected between two adjacent anaerobic treatment tanks in these anaerobic treatment tanks, and the anaerobic treatment tank of the final stage The anaerobic treatment device according to claim 11, wherein the terminal outlet is connected to the anaerobic treatment device.   The anaerobic treatment part is formed with a unidirectional flow from the inlet to the terminal outlet, and the intermediate outlet is provided between the inlet and the terminal outlet of the anaerobic part. The anaerobic treatment apparatus according to claim 11.   The anaerobic treatment apparatus according to claim 11, wherein an aerobic treatment unit is connected to the terminal outlet.   The anaerobic treatment according to any one of claims 11 to 14, wherein the COD of the refluxing body is 0.5 to 0.99 times the COD of the extraction residual fluid before the anaerobic treatment. apparatus.   The anaerobic treatment according to any one of claims 11 to 15, wherein the COD of the reflux body is 0.9 to 0.97 times the COD of the extraction residual fluid before the anaerobic treatment. apparatus.   The anaerobic treatment apparatus according to any one of claims 11 to 16, wherein a flow rate of the reflux body is larger than a flow rate of the remaining extraction residual fluid.   A solid-liquid separation unit that separates the extraction residual fluid into a solid extraction residue in which the solid component is concentrated and a liquid extraction residual fluid in which the solid component is diluted between the extraction unit and the anaerobic processing unit. The anaerobic treatment device according to claim 11, wherein the liquid extraction residual fluid is introduced into the anaerobic treatment unit.   19. An anaerobic treatment apparatus according to claim 18, further comprising an acid fermentation unit that solubilizes the solid extraction residue by acid fermentation.   The anaerobic treatment apparatus according to claim 11, wherein the organic substance is alcohol.

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