JP2017025732A - Power generation system and power generation method using compost fermentation heat - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a power generation system and a power generation method which can stably generate electricity using compost fermentation heat.SOLUTION: A power generation system comprises: evacuation collection means which can collect fermentation heat of compost raw materials as evacuation; heat recovery means which can recover heat in the evacuation collected by the evacuation collection means; power generation means which can generate electricity using the recovered heat recovered by the heat recovery means; and heat feeding means which is provided between the heat recovery means and the power generation means and can control the recovered heat and feed required heat to the power generation means.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a power generation system and a power generation method that enable effective use of compost fermentation heat.

  In recent years, there has been an increasing social demand for renewable energy against the backdrop of shrinking nuclear power generation and rising crude oil prices. In addition, biomass resources, which are one of renewable energies, are expected to be effectively used for the formation of a recycling-oriented society as clean and efficient energy with the emergence of global environmental problems. Specifically, in the composting process that recycles organic waste, effective use of the heat of fermentation that occurs along with the decomposition of organic matter is required, and technology for recovering and using fermentation heat generated in the composting process Various studies have been conducted.

  Conventionally, as a method for recovering fermentation heat, there are a direct recovery method for directly extracting heat from compost and a suction aeration method for recovering heat as exhaust. As heat utilization by the direct recovery method, heat generation is performed by burying a heat medium pipe inside the compost raw material, and the medium is vaporized by the extracted heat to drive the turbine (for example, Patent Document 1). There is a type in which a power generation device using a power generation element is embedded inside a compost raw material, and a low temperature heat source is sent from the outside into the compost raw material to perform temperature difference power generation (for example, Patent Document 2). In addition, as for heat utilization by the suction aeration method, air is sucked from the bottom of the fermenter where the compost raw material is deposited and heat is recovered as exhaust (exhaust heat), and the exhaust itself is led to a heat utilization room (greenhouse, etc.) (For example, Patent Document 3).

Japanese Patent No. 4280135 JP 2005-204442 A Patent No. 4418886

  However, heat recovery by the method of embedding a heat medium pipe inside the compost raw material can extract only the heat of the compost raw material around the pipe, and the fermentation heat recovery rate is low. In addition, heat recovery by the method of embedding power generation devices using power generation elements inside compost raw materials corrodes the power generation device under the influence of ammonia in compost, ammonia gas generated during composting, and hydrogen sulfide. Therefore, there is a problem that durability is lowered. And the heat recovery by the suction aeration method can solve the problems by the above-mentioned direct recovery method, but the heat utilization by the above-mentioned suction aeration method uses the exhaust gas after recovering ammonia as a direct heat source. Nevertheless, there remains concern about ammonia inflow into the heat utilization room. In addition, the conventional heat recovery / utilization technique described above does not have any technique for absorbing fluctuations in response to fluctuations in the amount of recovered heat caused by fermentation conditions such as changes in temperature and properties of compost raw materials. Therefore, fluctuations in the amount of recovered heat directly affect heat utilization efficiency (power generation capacity and heat utilization room temperature). Thus, it is difficult to say that efficient recovery / use technology has been established for the recovery / use technology of compost fermentation heat, and there is room for further study.

  The present invention has been made in view of the above circumstances, and an object thereof is to provide a power generation system and a power generation method capable of performing stable power generation using compost fermentation heat.

  The power generation system according to the present invention includes an exhaust recovery unit that can recover fermentation heat of compost raw material as exhaust, a heat recovery unit that can recover heat in the exhaust recovered by the exhaust recovery unit, and the heat recovery unit. Power generation means capable of generating power using the recovered heat collected, heat provided between the heat recovery means and the power generation means, and capable of supplying the predetermined power to the power generation means by adjusting the recovered heat Supply means.

  According to the present invention, it is possible to solve the above-described problems and perform stable power generation using compost fermentation heat.

It is a block block diagram which shows the electric power generation system of embodiment of this invention. It is a figure which shows the electric power generation data in the electric power generation system of embodiment of this invention. It is a block block diagram which shows the electric power generation system of the modification of embodiment of this invention.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  FIG. 1 is a block diagram showing a power generation system 100 according to an embodiment of the present invention. The power generation system 100 according to the embodiment of the present invention includes a compost fermenter 10, an exhaust recovery unit 20, a heat recovery unit 30, a buffer tank 40, a power generation unit 50, and a deodorization unit 60. Note that the power generation system 100 of the present invention is recommended to be applied to a suction ventilation type or closed type composting facility that can directly recover the exhaust gas H generated in the composting process of the compost raw material T without diluting it with outside air. Here, a suction ventilation type composting facility will be described as an example.

  The compost fermenter 10 of this Embodiment is provided in a suction ventilation type composting facility. The compost raw material T is deposited inside the compost fermenter 10, and composting is performed by turning back and forced ventilation by the exhaust gas recovery unit 20 described later. In the compost fermenter 10, fermentation heat is generated by composting the compost raw material T. In addition, the compost after heat recovery can be used as a material for fertilizer, soil improvement, etc. in the same manner as normal compost.

  The exhaust gas recovery unit 20 of the present embodiment supplies air from the surface of the compost raw material T to the inside by sucking air from the bottom surface (compost raw material T bottom portion) of the compost fermenter 10 by a ventilation device such as a blower. The fermentation heat generated in the composting process is recovered as exhaust H. The exhaust H recovered at this time has a high temperature (60 to 70 ° C.) and high humidity (about 100% RH), and the amount of latent heat of evaporation occupies most of the heat amount of the exhaust H.

  A latent heat recovery type heat exchanger is used for the heat recovery unit 30 of the present embodiment. For example, a plate fin type heat exchanger is used. The heat recovery unit 30 performs heat exchange between the exhaust H (60 to 70 ° C.) and the heat medium 31 (in this case, water), and the exhaust H converts the low-temperature heat medium 31L into the high-temperature heat medium 31H according to the amount of heat of the exhaust H. Change the temperature to. Here, since the exhaust H taken into the heat recovery unit 30 is not deodorized, the heat recovery unit 30 is made of a corrosion-resistant material that is resistant to ammonia corrosion contained in the exhaust H. Further, the heat recovery unit 30 is provided with a discharge port 32 through which the condensed water Ha generated in the heat exchange process can be discharged. In addition, since the exhaust gas Hb after heat exchange (after heat recovery) contains a malodor-causing substance such as ammonia, it is necessary to appropriately perform processing in the deodorizing unit 60 described later. Condensed water Ha does not contain a bad odor causing substance that normally requires treatment, but when it exceeds the specified standard, it is appropriately treated.

The buffer tank 40 of the present embodiment is a storage tank that is thermally insulated. The buffer tank 40 is set to a capacity that can cope with a change in the temperature of the exhaust H within a predetermined time (within about 1 hour), that is, a change in latent heat of vaporization (recovered heat). Specifically, the capacity of the buffer tank 40 is set to be larger than the flow rate of the heat medium 31 per hour. For example, when the flow rate is 30 to 50 L / min, the buffer tank 40 having a capacity of about 4 m ³ is desirable. And by always circulating the heat medium 31 between the heat recovery part 30 and the buffer tank 40, it becomes possible to cope with fluctuations in the amount of heat recovered from the exhaust H. Factors that cause fluctuations in the amount of recovered heat include climatic conditions such as the outside air temperature, an operating program for the ventilation device of the exhaust recovery unit 20, changes in the state of the compost raw material T, and the like. The buffer tank 40 absorbs fluctuations in the amount of recovered heat for about one hour (that is, temperature change of the heat medium 31H), and even if there is a sudden change in the temperature of the heat medium 31H, heat generated at a stable temperature in the power generation unit 50 at the subsequent stage An adjustment function is provided so that the medium 41H can be supplied.

  The power generation unit 50 according to the present embodiment changes the state of a medium having a low boiling point from a liquid to steam by a high-temperature heat medium 41H sent from the buffer tank 40, and uses the generated steam to drive a turbine with the generated steam (binary power generation). I do. A binary power generation system that can use a heat source of 100 ° C. or lower is applied to the power generation unit 50. The heat medium 41L used for binary power generation and having a lowered temperature is sent to the heat recovery unit 30 via the buffer tank 40.

  The deodorization part 60 of this Embodiment performs the deodorizing process of the exhaust Hb after the exhaust H passes the heat recovery part 30. FIG.

  Next, with reference to FIG. 2, the influence of the temperature change of the exhaust H in the power generation system on the power generation amount will be described. FIG. 2 is a diagram showing power generation data in the power generation system according to the embodiment of the present invention.

  The thin dotted line in the figure indicates the temperature of the exhaust H containing the fermentation heat of the compost raw material T. As shown in FIG. 2, the temperature of the exhaust gas H may fluctuate greatly at intervals of several minutes. Such a rapid decrease in the exhaust temperature is due to the blower operation program of the exhaust recovery unit 20 and is basically an inevitable factor. In addition, since it is also affected by climate change and the like as described above, a temperature change of about 10 ° C. occurs a plurality of times (about 10 times) even in an exhaust of 60 to 70 ° C. on average.

  The broken line in the figure indicates the temperature of the heat medium 41H supplied from the buffer tank 40 to the power generation unit 50. In addition, the solid line in the figure indicates the power generation amount of the power generation unit 50. As described above, in the present embodiment, a buffer tank 40 having a capacity larger than the flow rate per hour of the heat medium is interposed between the heat recovery unit 30 and the power generation unit 50, so that several minutes to several hours. Even if there is a temperature change of the exhaust H (fermentation heat) during the unit period, the heat utilization in the power generation unit 50 in the subsequent stage is not affected.

  Therefore, as shown by the broken line in FIG. 2, the temperature of the heat medium 41H sent out from the buffer tank 40 has a small influence (temperature decrease of the heat medium 41H) even if the temperature of the exhaust H is decreased. For this reason, as shown by the solid line in FIG. 2, the power generation amount in the power generation unit 50 can maintain a stable power generation amount even when the temperature of the exhaust H decreases.

  Thus, although the temperature of the exhaust gas H temporarily decreases in the composting process, it can be seen that the temperature of the heat medium 41H is less affected by the exhaust gas temperature decrease and has almost no effect on the power generation amount.

(Effect of embodiment)
According to the power generation system of the embodiment of the present invention, it is possible to efficiently recover and use compost fermentation heat corresponding to composting characteristics. Specifically, the influence of the fluctuation is minimized by interposing the buffer tank 40 with respect to the fluctuation of the recovered heat amount of the compost fermentation heat caused by the temperature change and property change of the compost raw material T unavoidable in actual composting. The generated heat source can be provided to the power generation unit 50. The buffer tank 40 has not only a quantitative compensation function for stabilizing the heat source flow rate, but also a qualitative compensation function such as the temperature and heat quantity of the heat source necessary for stable power generation, thereby unavoidable fluctuation characteristics in composting. Stable power generation can be provided even with the use of compost fermentation heat.

  Further, since the buffer tank 40 has a capacity larger than the flow rate of the heat medium 31 per predetermined time (1 hour), the influence of the temperature change of the exhaust H, that is, the fluctuation of the recovered heat amount can be reduced. Therefore, even if there is a sudden change in the temperature of the heat medium 31H supplied from the heat recovery unit 30 to the buffer tank 40, the heat medium 41H having a stable temperature can be supplied to the subsequent power generation unit 50.

  Moreover, since the compost fermentation heat | fever used as a heat source is collect | recovered without being diluted with the external air as the exhaust_gas | exhaustion H, heat recovery efficiency is good. Moreover, since the compost fermentation heat can be recovered by aeration essential for composting, it is not necessary to make significant changes to the composting facility itself. Therefore, this power generation system can be introduced by adding necessary equipment (the heat recovery unit 30, the buffer tank 40, and the power generation unit 50) without affecting the composting process and the quality of the compost. Moreover, since water can be utilized for the heat mediums 31 and 41 circulating in the power generation system, the running cost can be suppressed. Therefore, promotion of use can be expected.

  Further, since the heat of compost fermentation of the exhaust H is heat-exchanged by the heat recovery unit 30 and supplied to the power generation unit 50, the ammonia contained in the compost raw material T and the exhaust H and the power generation unit 50 are not in direct contact with each other. . Therefore, the risk of corrosion of the power generation unit 50 can be significantly reduced, and the adverse effects on facilities and workers can be greatly reduced as compared to the case of using exhaust directly in heat utilization.

  The power generation unit 50 uses a binary power generation device that can generate power with a low-temperature heat source (100 ° C. or less). In the composting process of livestock manure, the compost temperature rises to about 70 ° C due to the decomposition of microorganisms, and a large amount of fermentation exhaust H containing water vapor and ammonia is generated, but this is lower than industrial exhaust. Binary power generation using fermentation exhaust H (60 to 70 ° C.) as a heat source was difficult. Compared with the conventional method of driving livestock compost fermentation heat of about 60-70 ° C as a heat source for power generation by a binary power generator that can generate power with a low-temperature heat source developed in recent years, and burning the compost to drive the turbine Energy that can reduce the environmental load can be realized. Moreover, since the electric power obtained by the electric power generation part 50 can be used as normal electricity, it is versatile compared with the case where compost fermentation heat is directly used as heat.

  In this way, unlike other renewable energy such as photovoltaic power generation, power generation using fertilization heat of livestock waste is energy that can be used constantly and stably during the production of compost. Can be made.

  Since compost fermentation heat is used for power generation, as a result of maintaining the compost raw material T at a high temperature, a secondary composting process is achieved. It can contribute to reduced high quality compost production. Furthermore, since the moisture content of the compost is reduced through the high-temperature composting process, the compost can be expanded as a livestock litter or manure moisture adjusting material in place of sawdust and the like.

  In the power generation system according to the embodiment of the present invention, as a heat supply unit capable of supplying the power generation unit 50 with a heat source adjusted to minimize the influence of the fluctuation with respect to the fluctuation of the recovered heat amount of the compost fermentation heat, Although the buffer tank 40 is provided, it is not limited to this. It is a power generation that collects the fermentation heat of compost raw material as exhaust, recovers the heat in the recovered exhaust, and uses the recovered heat recovered, and supplies stable heat (predetermined heat) to the power generation Therefore, there is no problem if the recovered heat can be adjusted. For example, even if the heating medium 31H from the heat recovery unit 30 is heated and adjusted by a heater or a heat pump and the heating medium 41H having a stable temperature is supplied to the power generation unit 50, the compost fermentation heat that is the object of the present invention is maintained. The stable power generation used can be achieved. Since the buffer tank 40 can be achieved without the control of an additional heat source or sensor from the outside, the additional heat source is unnecessary, so that the entire system is energy efficient, the facilities and management can be simplified, and the cost can be reduced. It can be said that this is a more efficient and useful heat supply means.

(Modification of the embodiment)
Next, with reference to FIG. 3, a circulation pattern that enables more efficient recovery and use of fermentation heat will be described by paying attention to the circulation of the heat medium (water) of the power generation system 100 described above. FIG. 3 is a block diagram showing a power generation system according to a modification of the embodiment of the present invention, and shows (A) circulation pattern 1 and (B) circulation pattern 2.

  In the above-described embodiment, the buffer tank 40 supplies the low temperature water 31L to the heat recovery unit 30 and receives the high temperature water 31H (recovered heat) by heat exchange with the exhaust H. And while supplying the high temperature water 41H (predetermined heat) to the power generation part 50 of the back | latter stage, the low temperature water 41L (heat which was not used for electric power generation) from the power generation part 50 is received.

  On the other hand, in the modification, as shown in FIGS. 3A and 3B, a heat recovery unit 35 is additionally provided in series with the heat recovery unit 30 on the flow path of the exhaust H, and the buffer tank 40 is heated. High temperature water 41H (predetermined heat) is supplied to the power generation unit 50 via the recovery unit 35. The heat exchange between the exhaust H and the high temperature water 41H in the heat recovery unit 35 is hardly performed because the temperature of the heat medium is already high and the temperature difference between the two is small. In the heat recovery unit 35, the high temperature water 41H is slightly heated by heat exchange with the exhaust H to become high temperature water 41H +. Then, the high temperature water 41H + is supplied to the power generation unit 50. Therefore, the exhaust gas introduced into the heat recovery unit 30 is equivalent to the exhaust gas H recovered by the exhaust gas recovery unit 20.

  Further, in the circulation pattern 1 shown in FIG. 3A, the heat recovery unit 30 directly receives the low temperature water 31L (heat not used for power generation) from the power generation unit 50 without passing through the buffer tank 40. Therefore, in the circulation pattern 1, low-temperature water 31 </ b> L, which will be described later, is heated by heat exchange with the exhaust H in the heat recovery unit 30 to become high-temperature water 31 </ b> H (recovered heat).

  After the hot water 31H is stored in the buffer tank 40, it is sent out from the buffer tank as high-temperature water 41H (predetermined heat), further heated by the heat recovery unit 35, and supplied to the power generation unit 50 as high-temperature water 41H +. Is done. Here, when the temperature drop of the exhaust H occurs, the high temperature water 31H flows into the buffer tank 40 at a temperature lower than usual, so that the adjustment function of the buffer tank 40 is activated, and the high temperature water 31H is By mixing with a sufficient amount of high temperature stored water in the tank, it becomes high temperature water 41H within the temperature range necessary for power generation.

  Since the power generation unit 50 performs binary power generation using the temperature difference of the heat medium, the temperature of the hot water supplied from the power generation unit 50 to the heat recovery unit 30 decreases and becomes low-temperature water 31L. The low-temperature water 31L is heated by heat exchange with the exhaust H in the heat recovery unit 30 to become high-temperature water 31H and repeats circulation. The power generation unit 50 starts operation when the raw water introduced and circulated into the buffer tank 40 is heated by heat exchange with the exhaust H to become warm water of a predetermined temperature (about 63 ° C.).

  Further, in the circulation pattern 2 shown in FIG. 3B, the high temperature water 31H heated by the heat exchange with the exhaust gas H is supplied to the buffer tank 40, and then the buffer tank 40, the heat recovery unit 35 and the power generation unit 50 are circulated, and the heat recovery unit 30 is not circulated. Therefore, in the circulation pattern 2, the raw water is heated by heat exchange with the exhaust H in the heat recovery unit 30 to become high-temperature water 31 </ b> H (recovered heat).

  After the hot water 31H is stored in the buffer tank 40, it is sent out from the buffer tank as high-temperature water 41H (predetermined heat), further heated by the heat recovery unit 35, and supplied to the power generation unit 50 as high-temperature water 41H +. Is done. Here, when the temperature drop of the exhaust H occurs, the high temperature water 31H flows into the buffer tank 40 at a temperature lower than usual, so that the adjustment function of the buffer tank 40 is activated, and the high temperature water 31H is By mixing with a sufficient amount of high temperature stored water in the tank, it becomes high temperature water 41H within the temperature range necessary for power generation.

  Since the power generation unit 50 performs binary power generation using the temperature difference of the heat medium, the temperature of the hot water supplied from the power generation unit 50 to the buffer tank 40 is reduced to 41L. Then, the low temperature water 41L is supplied to the buffer tank 40. Here, the hot water in the buffer tank 40 circulates through the heat recovery unit 35 and the power generation unit 50. The power generation unit 50 starts operating when the raw water introduced and circulated into the heat recovery unit 30 is heated by heat exchange with the exhaust H to become hot water of a predetermined temperature (about 63 ° C.).

(Effect of modification of embodiment)
According to the power generation system of the modification of the embodiment, since the basic concept is the same as that of the above-described embodiment, the same effect can be obtained, and the heat recovery unit 35 is provided between the buffer tank 40 and the power generation unit 50. By providing it, it is possible to provide more efficient recovery and use of compost fermentation heat. Specifically, when a pipe leading from the buffer tank 40 to the power generation unit 50 is provided outdoors or is long, the temperature drops while the high-temperature water 41H (predetermined heat) necessary for the power generation unit 50 flows through the pipe. Although there is a concern that the heat recovery unit 35 is interposed, the heat recovery unit 35 can be heated before being supplied to the power generation unit 50, so that the concern can be eliminated and an appropriate amount of heat can be provided to the power generation unit 50. it can.

  Moreover, since the high temperature water 41 (predetermined heat) is slightly heated by the heat recovery unit 35 immediately before the supply to the power generation unit 50, if there is no concern as described above, the buffer tank 40 changes to the power generation unit 50. Hot water (high temperature water 41H +) that is higher in temperature than the direct supply (high temperature water 41H) can be supplied to the power generation unit 50. Therefore, the power generation in the power generation unit 50 can be further stabilized.

  In addition, since the circulation pattern 1 includes the heat recovery unit 30 and the heat recovery unit 35 in the circulation path, the temperature of the circulating hot water is more stable than when only the heat recovery unit 35 of the circulation pattern 2 is included in the circulation path. Therefore, more efficient recovery and use of compost fermentation heat can be provided.

  It should be noted that the present invention is not limited to the above-described embodiment, and it goes without saying that the present invention can be implemented in various modes as long as it belongs to the technical scope of the present invention.

  For example, in the above-described embodiment, composting processing of livestock waste such as livestock excreta is taken as an example, but it can also be applied to general waste processing and industrial waste.

100 Power generation system 10 Compost fermenter 20 Exhaust recovery unit 30 Heat recovery unit (heat exchanger)
31 Heat medium (water)
32 Discharge port 40 Buffer tank (heat supply part)
41 Heat medium (water)
50 Power generator (binary power generator)
60 Deodorizing part T Compost raw material H Exhaust Ha Condensed water Hb Exhaust after heat recovery

Claims (4)

Exhaust recovery means capable of recovering the fermentation heat of compost raw material as exhaust;
Heat recovery means capable of recovering heat in the exhaust recovered by the exhaust recovery means;
Power generation means capable of generating power using the recovered heat recovered by the heat recovery means;
A heat supply means provided between the heat recovery means and the power generation means, capable of adjusting the recovered heat and supplying predetermined heat to the power generation means;
A power generation system comprising:   2. The power generation according to claim 1, wherein the heat supply unit absorbs a fluctuation in the recovered heat accompanying a temperature change of the exhaust gas and stably supplies the predetermined heat necessary for power generation by the power generation unit. system. The heat recovery means exchanges heat with a heat medium using the exhaust as a heat source,
The power generation system according to claim 1, wherein the heat supply unit has a capacity larger than a total amount of the heat medium that can flow into the heat supply unit per predetermined time. An exhaust recovery process capable of recovering the fermentation heat of compost raw material as exhaust;
A heat recovery step capable of recovering heat in the exhaust recovered in the exhaust recovery step;
A power generation process capable of generating power using the recovered heat recovered in the heat recovery process;
A heat supply step that can be performed between the heat recovery step and the power generation step, adjusts the recovered heat, and can supply predetermined heat to the power generation step;
Including power generation method.

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