JP2012254426A - Apparatus for methane fermentation of biomass - Google Patents

Abstract

PROBLEM TO BE SOLVED: To efficiently raise a digested sludge solid concentration and enhance the sludge treatment capability in a digestion step by mixing a fluid biomass and a non-fluid biomass basically in a pump and piping and charging the mixture in a digestion tank.SOLUTION: This apparatus includes: a fluid biomass feeder pump 4 which supplies a fluid biomass, a screw conveyance part 11 which makes a non-fluid biomass 2 to be dropped from the lower part of a temporary reservoir to be confluent with the fluid biomass, and conveys the confluent fluid in one direction, a confluent loading pump 10 including a conveyance pump part 12 which is connected with the screw conveyance part 11 and quantitatively conveys and sends out the confluent fluid, a digested sludge circulation path 20 for circulating back the digested sludge pulled out of a digestive tank 30, and a mixing and loading means 23 which sends the confluent fluid into a circulation channel including the circulation path and the digestive tank from the confluent loading pump 10.

Description

  The present invention relates to a methane fermentation apparatus for processing a plurality of biomasses.

  Biomass such as sewage sludge (primary sludge, surplus sludge), factory wastewater treatment sludge, human waste, septic tank sludge, food waste (garbage, okara, etc.), livestock manure, etc. is input to the digestion tank and anaerobically digested It is known that the organic matter is finally converted into digestion gas mainly composed of methane and carbon dioxide.

  In this case, the rate of hydrolysis of the solid matter is changed to a form susceptible to microbial action, and the growth rate of the methanogen (converting the organic acid produced by acid fermentation of the hydrolyzate to methane) is the rate-limiting step of the digestion process. (When a dynamic process such as a chemical reaction is composed of several processes, the process having the greatest influence on the progress speed of all the processes among them).

  In the case of intermediate temperature digestion (35 to 38 ° C.), in order to obtain a digestion rate of 50% (a state in which 50% of the organic substances put into the digestion tank is converted into digestion gas) in sewage sludge having a relatively slow hydrolysis rate. It is known that the digestion days (time spent in the space of the input sludge) is 20 to 30 days, and in the case of food waste with a relatively fast hydrolysis rate, 5 to 10 days are required.

  However, since the digestion tank to be processed has a predetermined volume, in order to satisfy the required digestion days and increase the processing amount, the solids concentration of the input slurry is improved (solids are concentrated). Is effective.

  In order to stably process biomass, the solid content concentration of digested sludge is monitored and the amount of water in the input slurry is controlled (Patent Document 1: Japanese Patent Laid-Open No. 2006-150253). A method is known in which solid organic waste having a solid concentration of 15% or more and digested sludge having a solid concentration of 15% or less are mixed and introduced into a digestion tank (Patent Document 2: Japanese Patent Laid-Open No. 2007-98228). .

  However, in the method of adding water to the garbage described in Patent Document 1 (Japanese Patent Laid-Open No. 2006-150253) and then throwing it into the digestion tank, the pH of the garbage and water and digested sludge is controlled in the mixing tank before the digestion tank is charged. It is necessary to produce a slurry by mixing the alkali for the purpose. Moreover, when throwing away garbage with a high proportion of readily degradable organic matter, it is necessary to throw in a large amount of garbage in order to maintain the solid matter concentration in the digested sludge. Therefore, a large amount of slurry having fluidity that can be supplied in the mixing tank has to be manufactured, and there is a problem that the required volume of the garbage storage facility required for the mixing tank and the preceding stage is increased.

  By the way, it is known that the high-concentration slurry of organic matter such as sludge loses its fluidity when the solid concentration exceeds the region of about 4 to 6% (however, depending on the properties). Further, in the digestion process, since the contact frequency with the methanogen or the like influences the processing capability, it is desirable that the concentration of solids is such that fluidity can be obtained even for digested sludge in the digestion tank.

  In conventional sewage treatment facilities, there are many cases where the primary sludge is concentrated by gravity and surplus sludge is mechanically concentrated (centrifugation, belt concentration, etc.) to obtain concentrated sludge, which is then put into the digestion tank. When the product concentration exceeds about 4 to 6%, the concentrated sludge loses fluidity and it is difficult to put it into the digestion tank. Since the required capacity of the digestion tank is determined by the number of days of digestion and the amount of sludge input, the upper limit of concentration on the input sludge side determined the upper limit of digestion tank treatment capacity. In addition, as the amount of readily degradable organic matter in the input sludge increases, the amount of solid matter in the digested sludge decreases. Was naturally fluctuating. In addition, moisture that does not contribute to the generation of digestion gas is introduced instead of solids, and heat energy is consumed to heat this moisture.

JP 2006-150253 A JP2007-98228

  Therefore, the main problem to be solved by the present invention is to increase the concentration of digested sludge solids in the digestion tank. More specifically, non-fluid biomass and fluid biomass are basically mixed in the pump and piping to digest. It is to increase the digested sludge solids concentration efficiently and increase the sludge treatment capacity in the digestion process by introducing into the tank without having excessive facilities.

The present invention that has solved this problem is as follows.
[Invention of Claim 1]
A fluid biomass supply pump for supplying fluid biomass;
A screw transfer unit that joins fluid biomass and non-fluid biomass supplied from a fluid biomass supply pump inside and transfers the merged liquid in one direction, and is connected to the screw transfer unit to quantitatively analyze the merged liquid. A confluence injection pump having a transfer pump section for transferring and delivering;
A digested sludge circulation path for circulating and returning digested sludge drawn from the digestion tank;
A biomass methane fermentation apparatus, comprising: a mixing input unit that sends out the combined liquid from the combined input pump in a circulation path including the circulation path and the digestion tank.

(Function and effect)
In the screw transfer part of the merging charge pump, fluid biomass and non-fluid biomass are merged. In this case, the mass of the non-fluid biomass is in a wet state due to the fluid biomass, and this is smoothly fed to the transfer pump unit connected to the screw transfer unit by the transfer force of the screw transfer unit. The transfer pump unit quantitatively transfers the combined liquid and sends it out into the circulation path including the circulation path and the digestion tank.
As a result, for example, in a adjustment tank provided separately from the digestion tank, a large amount of fluid biomass is added to non-fluid biomass, and compared with a case where a low-concentration slurry is introduced into the digestion tank, Since a high-concentration combined liquid can be introduced into the circulation path, the concentration of digested sludge solids can be increased, and the sludge treatment capacity in the digestion process can be maximized.
Of course, it is not impossible to pump non-fluid biomass, but usually the pressure loss is excessive, the pump discharge pressure and power consumption become very large, and the transportation speed in the pipe is sufficiently reduced. The pipe diameter needs to be very large. On the other hand, according to the present invention, as described above, the fluidized biomass enters the contact surface between the mass of non-fluidized biomass and each device or pipe, so that it becomes wet, and this is transferred by the screw transfer unit. Since the force is smoothly sent to the transfer pump unit connected to the screw transfer unit, the pressure loss is extremely small, smooth transportation can be performed, and power consumption and cost reduction of piping materials can be achieved.
On the other hand, for example, in a regulating tank, it is possible to mix non-fluid biomass and fluid biomass, transfer to a metering pump, and put it into a circulation path, but blockage at the regulating tank outlet, metering pump inlet, etc. In order to prevent this, it is necessary to provide a stirrer or the like and perform sufficient mixing to reduce the particle size of the solid matter in the mixed solution and uniformly diffuse it. On the other hand, in the form of the present invention, while the fluid biomass enters the contact surface between the mass of non-fluid biomass and each device and piping, it is in a wet state, so that it is sequentially transferred by the screw transfer unit. Even if a stirrer is not provided, blockage at the screw transfer section or the like can be prevented, and installation of an adjustment tank is basically unnecessary.

[Invention of Claim 2]
A fluid biomass supply pump for supplying fluid biomass;
A screw transfer unit that joins fluid biomass and non-fluid biomass supplied from a fluid biomass supply pump inside and transfers the merged liquid in one direction, and is connected to the screw transfer unit to quantitatively analyze the merged liquid. A confluence injection pump having a transfer pump section for transferring and delivering;
A digested sludge circulation path for circulating and returning digested sludge drawn from the digestion tank;
Temperature control means of digested sludge provided in the circulation path;
In the circulation path including the circulation path and the digestion tank, mixing and charging means for sending the combined liquid from the combined charging pump;
And a sludge crusher provided in the circulation path for crushing the input liquid circulating in the circulation path. A biomass methane fermentation apparatus, comprising:

(Function and effect)
In the present invention, it is preferable that the flowable biomass has a flow rate of three times or more that of the non-flowable biomass, and that no special crushing treatment is performed in the combined charging pump. Therefore, the combined liquid thrown into the circulation path is transported into the circulation path in a state where a large number of non-flowable biomasses are floating in the flowable biomass.
When the combined liquid joins the digested sludge, it flows in the circulation path in a state where the mass of non-fluid biomass and the fluid biomass digested sludge are mixed.
In the present invention, digestion sludge temperature control means is provided in the circulation path. In this way, the temperature of the digested sludge (generally, the temperature of the combined fluid is lower than the digested sludge temperature) can be reduced by preheating the input fluid mixed with the combined fluid and digested sludge and then introducing it into the digestion tank. Capability reduction can be prevented.
In addition, by installing a sludge crusher in the circulation path, non-fluid biomass lump and digested sludge are finely crushed, and at the same time, non-fluid biomass, fluid biomass and digested sludge are effectively removed in the circulation path. Can be mixed. Furthermore, because the combined liquid is supplied to the crusher in a state diluted with digested sludge, the crushing mechanism such as the crushing blade is worn or clogged compared to the case where the combined liquid or non-fluid biomass is directly fed into the sludge crusher. Can be reduced.

[Invention of Claim 3]
A confluence storage tank that combines fluid biomass and non-fluid biomass, a screw transfer section that communicates with the lower opening of the confluence storage tank, receives the merge liquid, and transfers the merge liquid in one direction, and the screw transfer section. A merging input pump having a transfer pump unit for quantitatively transferring and delivering the merging liquid;
A digested sludge circulation path for circulating and returning digested sludge drawn from the digestion tank;
A biomass methane fermentation apparatus, comprising: a mixing input unit that sends out the combined liquid from the combined input pump in a circulation path including the circulation path and the digestion tank.

(Function and effect)
According to the present invention, the fluid biomass and the non-fluid biomass are merged in the screw transfer unit of the merge input pump, and the fluid biomass and the non-flow are provided at the front stage of the screw transfer unit. It is also possible to provide a merging storage tank that merges with the biomass, and the lower opening of the merging storage tank directly communicates with the screw transfer section. According to this embodiment, since the combined liquid is continuously transferred by the screw transfer unit, when the fluid biomass and the non-flowable biomass are combined in the combined storage tank, the mixed liquid is generated without causing a bridge or the like in the storage tank. Can be transported.

[Invention of Claim 4]
The biomass methane fermentation apparatus according to any one of claims 1 to 3, wherein the circulation path has an indirect heat exchanger that heats the input liquid using a heat medium.

[Invention of Claim 5]
Based on the solids concentration measurement value of the digested sludge in the circulation path including the circulation path and the digestion tank, the solids of the merged liquid from the merge input pump so that the solids concentration is maintained within a predetermined range. The biomass methane fermentation apparatus according to any one of claims 1 to 4, further comprising means for adjusting the concentration.

[Invention of Claim 6]
6. The biomass methane fermentation apparatus according to claim 5, wherein the means for adjusting the solid concentration of the combined liquid is performed by adjusting a flow rate of the fluid biomass.

[Invention of Claim 7]
3. The biomass methane fermentation apparatus according to claim 1, wherein the fluid biomass supply pump is a metering pump and is capable of rotating speed control. 4.

(Function and effect)
The density control will be described in relation to claims 5 to 7.
As a form of the present invention, the flow rate of the merging charge pump and the circulation pump provided in the circulation path can be fixed. When the flow rate of the fluid biomass supply pump is increased with the flow rate of the merging charge pump and the circulation pump provided in the circulation path fixed, the amount of fluid biomass passing through the merging charge pump increases and is dropped from the hopper. For example, the amount of non-fluid biomass supplied from the merging input pump is reduced. Conversely, if the flow rate of the fluid biomass supply pump is lowered, the flow rate of the non-fluid biomass increases. The solids concentration of the input liquid rises and falls as the amount of non-fluid biomass delivered increases and decreases.
The flow rate of the fluid biomass supply pump is determined from the measurement result of the solid matter concentration of the digested sludge. In this way, it is possible to easily and practically control the solid matter concentration of the combined liquid by fixing the flow rate of the combined pump and the circulating pump provided in the circulation path and operating only the flow rate of the fluid biomass supply pump It becomes.
Even if the solids concentration in the digested sludge varies and the solids concentration in the input liquid is adjusted, the flow rate of the combined input pump is fixed, so the number of methane producing bacteria in the digestion tank is kept constant. Is maintained.
Here, the decrease in the digested sludge solids concentration is due to a low organic matter load on the digestion tank, and conversely, an increase in the digested sludge solids concentration means a high organic matter load.
Therefore, by controlling the digested sludge solids concentration to a predetermined level, it is possible to always create a situation of operating with the maximum processing capacity adapted to the organic load of the input liquid.

[Invention of Claim 8]
The structure of the merge input pump is as follows:
An upper part of the casing is opened, accepts falling non-fluid biomass, has a feeding port of the fluid biomass in a part of the casing, and a screw transfer unit having a screw rotating shaft inside,
The biomass methane fermentation according to claim 1 or 2, further comprising: a transfer pump portion that is a uniaxial screw pump in which a rotor that is a single-thread male screw is rotatably inserted in a stator having a double-thread female screw space. apparatus.

  According to the present invention, the concentration of digested sludge solids in the digestion tank is increased, and more specifically, non-fluid biomass and fluid biomass are basically mixed in a pump and piping and put into the digestion tank. Without providing any facilities, it is possible to efficiently increase the concentration of digested sludge solids and increase the sludge treatment capacity of the digestion process.

  Next, an embodiment of the present invention will be described. Note that the following description of the embodiment is merely an exemplification, and is not intended to limit the present invention, its application, or its use.

FIG. 1 shows a first embodiment, in which a fluid biomass 1 and a non-fluid biomass 2 are merged by a merge input pump 10, and the merged liquid is quantitatively transferred and sent to a circulation path 20. To do.
Here, the flowable biomass 1 includes, for example, raw garbage slurry obtained by processing gravity-concentrated sludge or raw garbage into a slurry form by crushing or solubilizing with a crusher or the like, and the solid matter concentration is about 4% or less. Say things. The non-fluid biomass 2 is, for example, ultra-high concentration concentrated sludge, dehydrated sludge, solid food residue, or the like, and refers to a solid matter concentration of about 20% or less. The lower limit is preferably 10%, more preferably 8%.
The fluid biomass 1 is pumped from the storage tank 3 by the fluid biomass supply pump 4 to the screw transfer unit 11 of the merging input pump 10 and input.
Here, it is desirable that the fluid biomass supply pump 4 is a metering pump, particularly a single screw screw pump that can easily obtain a quantitative property.
Moreover, when fluid biomass is the concentrated sludge in a sewage treatment plant, the gravity concentration tank can be used as the storage tank 3.
On the other hand, the non-fluid biomass 2 is gravity dropped from, for example, the hopper 5 and charged into the screw transfer unit 11.
In addition, as the hopper 5, it can serve as receiving hoppers, such as an off-site dewatering sludge which carries in a vehicle. In order to smoothly drop non-flowable biomass into the merging and charging pump 10, it is desirable to incorporate a discharging screw at the bottom of the hopper.

As the confluence injection pump 10, it is desirable to use a metering pump, particularly a uniaxial screw type pump that can easily obtain a quantitative property. The combined injection pump 10 receives, for example, non-fluid biomass from the top surface of the pump unit, and simultaneously receives fluid biomass from the side surface of the pump unit, and sends it out as a combined liquid without special crushing and mixing, and inputs it into the digested sludge system. . When the flowable biomass supply pump 4 stops, it is desirable to make it interlock | cooperate so that the joining injection pump 10 must be stopped. Examples of the structure of the confluence injection pump 10 are shown in FIGS. The merging input pump 10 includes a screw transfer unit 11 that is driven and rotated by a drive motor 13, and a transfer pump unit 12 that is connected to the screw transfer unit 11 to quantitatively transfer and send out the merging liquid.
More specifically, the screw transfer unit 11 has an opening at the top of the casing 11A, receives the falling non-fluid biomass 2 and has an inlet 11B for the fluid biomass 2 in a part of the casing 11A. It has a screw rotating shaft 11C.
The transfer pump unit 12 has a single-shaft eccentric pump structure in which a single male screw 12C as a rotor is provided in a double female screw space 12B formed in the stator 12A.
The joining ratio of the fluid biomass and the non-fluid biomass in the joining pump is preferably about 3: 1 to 10: 1, and the solid concentration after joining is preferably about 4 to 6%.

On the other hand, a digested sludge circulation path 20 that circulates and returns the digested sludge drawn from the digestion tank 30 is provided, and this circulation path 20 receives an external heat medium as temperature control means 21 for the digested sludge and inputs liquid. An indirect heat exchanger is provided for heating. In addition, although hot water, a vapor | steam, etc. can be employ | adopted as an external heat medium, Preferably, it is good to use the heat source obtained from the utilization equipment of the digestion gas generated from the digestion tank. For example, hot water can be obtained by recovering heat from exhaust gas generated from a micro gas turbine or a gas engine. It is expected that the efficiency of methane fermentation in the digestion tank will be improved by heating the input liquid containing the combined liquid and having a high solid concentration.
In this embodiment, the temperature control means is provided in the circulation path, but it can also be provided in the digestion tank.

  In the circulation path 20, digested sludge having a solid concentration of, for example, about 3.5% is circulated by the circulation pump 22, and the merged liquid is sent from the merged injection pump 10 into the circulation path, and is supplied to the digestion tank as the input liquid. It comes to be thrown in. In the present embodiment, the merge point between the transfer pump unit 12 and the circulation path 20 is the mixing and charging means 23.

  The circulation path 20 preferably has a rotary blade that is rotationally driven by a drive motor, and a disk-shaped fixed screen concentrically with the rotary blade, and the rotary blade can rotate while contacting the fixed screen. There is provided a sludge crusher 24 that crushes solids when the input liquid circulating in the circulation path 20 passes through the fixed screen. As the sludge crusher 24, for example, “Rota Cut” manufactured by Hugo Vogelsang Machinechinbau GmbH can be used. By providing the sludge crusher 24 in the circulation path 20, the mass of the non-flowable biomass is finely crushed, and at the same time, the non-flowable biomass, the flowable biomass, and the digested sludge can be effectively mixed in the circulation path. A biaxial crusher or the like can also be employed.

As the circulation pump 22, it is desirable to employ a metering pump, particularly a single screw screw type pump that can easily obtain a quantitative property. It is used for charging the mixed liquid into a digestion tank, circulating and heating digested sludge, and can be used for sending digested sludge out of the system by switching the piping.
A concentration meter 25 for measuring the solid concentration of the input liquid is provided in the preceding stage of the mixing input means 23.
The solid concentration measured by this densitometer is transmitted to a control means (not shown) and compared with a solid concentration setting value set by the control means. Based on the difference between the target value and the measured value, for example, the number of rotations of the fluid biomass supply pump is controlled to control the amount of fluid biomass supplied. As a result, the solid concentration of the input liquid is adjusted by changing the solid concentration of the combined liquid.
The digestion tank 30 preferably has a volume of 20 days or more. It is desirable to adjust the solid concentration of the digested sludge in the digestion tank to about 3.5%.
A well-known apparatus is employable after a digestion tank. For example, digestion gas can also be supplied to utilization facilities, such as a micro gas turbine and a gas engine, or can be supplied to a city gas line after desulfurization.

  In the present invention, in addition to the embodiment in which the joining of the fluid biomass and the non-fluid biomass is carried out for the first time in the screw transfer section 11 of the confluence injection pump 10, as shown in FIG. It is also possible to provide a confluence storage tank 40 that joins the functional biomass and the non-fluid biomass, and the lower opening of the confluence storage tank 40 communicates directly with the screw transfer section 11. The merging storage tank 40 can be provided with a mixing blade 41 for rotational mixing.

It is a schematic diagram showing an example of the present invention. It is a schematic diagram of a confluence injection pump. It is a detailed longitudinal cross-sectional view of a merging input pump. It is a detailed plane sectional view of a confluence injection pump. It is a schematic diagram of another example.

  DESCRIPTION OF SYMBOLS 1 ... Fluid biomass, 2 ... Non-fluid biomass, 10 ... Confluence injection pump, 11 ... Screw transfer part, 12 ... Transfer pump part 12, 20 ... Circulation path, 21 ... Temperature control means, 23 ... Mixing injection means, 24 ... sludge crusher, 30 ... digestion tank.

Claims (8)

A fluid biomass supply pump for supplying fluid biomass;
A screw transfer unit that joins fluid biomass and non-fluid biomass supplied from a fluid biomass supply pump inside and transfers the merged liquid in one direction, and is connected to the screw transfer unit to quantitatively analyze the merged liquid. A confluence injection pump having a transfer pump section for transferring and delivering;
A digested sludge circulation path for circulating and returning digested sludge drawn from the digestion tank;
A biomass methane fermentation apparatus, comprising: a mixing input unit that sends out the combined liquid from the combined input pump in a circulation path including the circulation path and the digestion tank. A fluid biomass supply pump for supplying fluid biomass;
A screw transfer unit that joins fluid biomass and non-fluid biomass supplied from a fluid biomass supply pump inside and transfers the merged liquid in one direction, and is connected to the screw transfer unit to quantitatively analyze the merged liquid. A confluence injection pump having a transfer pump section for transferring and delivering;
A digested sludge circulation path for circulating and returning digested sludge drawn from the digestion tank;
Temperature control means of digested sludge provided in the circulation path;
In the circulation path including the circulation path and the digestion tank, mixing and charging means for sending the combined liquid from the combined charging pump;
And a sludge crusher provided in the circulation path for crushing the input liquid circulating in the circulation path. A biomass methane fermentation apparatus, comprising: A confluence storage tank that combines fluid biomass and non-fluid biomass, a screw transfer section that communicates with the lower opening of the confluence storage tank, receives the merge liquid, and transfers the merge liquid in one direction, and the screw transfer section. A merging input pump having a transfer pump unit for quantitatively transferring and delivering the merging liquid;
A digested sludge circulation path for circulating and returning digested sludge drawn from the digestion tank;
A biomass methane fermentation apparatus, comprising: a mixing input unit that sends out the combined liquid from the combined input pump in a circulation path including the circulation path and the digestion tank.   The biomass methane fermentation apparatus according to any one of claims 1 to 3, wherein the circulation path has an indirect heat exchanger that heats the input liquid using a heat medium.   Based on the solids concentration measurement value of the digested sludge in the circulation path including the circulation path and the digestion tank, the solids of the merged liquid from the merge input pump so that the solids concentration is maintained within a predetermined range. The biomass methane fermentation apparatus according to any one of claims 1 to 4, further comprising means for adjusting the concentration.   6. The biomass methane fermentation apparatus according to claim 5, wherein the means for adjusting the solid concentration of the combined liquid is performed by adjusting a flow rate of the fluid biomass.   3. The biomass methane fermentation apparatus according to claim 1, wherein the fluid biomass supply pump is a metering pump and is capable of rotating speed control. 4. The structure of the merge input pump is as follows:
An upper part of the casing is opened, accepts falling non-fluid biomass, has a feeding port of the fluid biomass in a part of the casing, and a screw transfer unit having a screw rotating shaft inside,
The biomass methane fermentation according to claim 1 or 2, further comprising: a transfer pump portion that is a uniaxial screw pump in which a rotor that is a single-thread male screw is rotatably inserted in a stator having a double-thread female screw space. apparatus.

Images