Biogas engine system

Abstract

To provide a biogas engine system which can control the amount of generation of air bubbles.SOLUTION: A biogas engine system 1 comprises: a biogas generation part 2 for generating a biogas; a biogas engine 3 for combusting the biogas; a waste heat collection device 4 for heating the biogas generation part 2 by the waste heat of the biogas engine 3, a temperature sensor 5 for detecting a temperature of the biogas generation part 2; a bubble amount sensor 6 for detecting a bubble amount of the biogas generation part 2, and a control unit 7 for controlling the waste heat collection device 4 according to the temperature and the bubble amount. When the temperature of the biogas generation part 2 is equal to or higher than a prescribed value and / or the bubble amount of the biogas generation part 2 is equal to or larger than a prescribed value, the control unit 7 can switch to a cooling mode for cooling the biogas generation part 2, and when the temperature of the biogas generation part 2 is lower than the prescribed value and the bubble amount of the biogas generation part 2 is smaller than the prescribed value, the control unit 7 can switch to a heating mode for heating the biogas generation part 2.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a biogas engine system. Background Art

[0002] In recent years, biogas engines have attracted attention. A biogas engine is an engine that uses biogas as fuel. Biogas is produced through methane fermentation of organic waste. Examples of the organic waste include garbage, sewage, livestock excrement and food waste.

[0003] Organic waste undergoes methane fermentation when heated, producing biogas. For example, it has been proposed to heat organic waste using waste heat from a biogas engine. More specifically, the following method has been proposed. This method utilizes heat generated from a gas engine that uses biogas as fuel. More specifically, heat generated from the gas engine is retained in hot water or steam, and a methane fermentation tank is heated by the hot water or steam. Thereby, biogas is generated. Biogas is transported through a biogas transport pipe and temporarily stored in a gas tank. Thereafter, the biogas is supplied to a biogas generator and combusted (see, for example, Patent Document 1). Prior Art Documents Patent Documents

[0004] Patent Document 1 Japanese Unexamined Patent Application Publication No. 2008-253963 Summary of the Invention Problem to be Solved by the Invention

[0005] On the other hand, when organic waste ferments, air bubbles may sometimes be generated together with biogas in the methane fermentation tank. Since the air bubbles are transported together with the biogas, they may block the biogas transport pipe.

[0006] Therefore, biogas engine systems are required to control the amount of bubbles generated.

[0007] This invention relates to a biogas engine system that can control the amount of bubbles generated. [Means for solving the problem]

[0008] The present invention [1] includes a biogas engine system comprising: a biogas generating unit that ferments organic waste to generate biogas; a biogas engine that burns the biogas; a waste heat recovery device that recovers waste heat from the biogas engine and heats the biogas generating unit with the waste heat; a temperature sensor that detects the temperature of the biogas generating unit; a foam volume sensor that detects the amount of foam in the biogas generating unit; and a control unit that controls the waste heat recovery device according to the temperature of the biogas generating unit and the amount of foam in the biogas generating unit, wherein the control unit can switch between a cooling mode that reduces the supply of waste heat to the biogas generating unit by the waste heat recovery device and cools the biogas generating unit when the temperature of the biogas generating unit is above a predetermined value and / or the amount of foam in the biogas generating unit is above a predetermined value; and a heating mode that heats the biogas generating unit with the waste heat recovery device when the temperature of the biogas generating unit is below a predetermined value and the amount of foam in the biogas generating unit is below a predetermined value. [Effects of the Invention]

[0009] In the biogas engine system of the present invention, the control unit switches between a cooling mode for cooling the biogas generation unit and a heating mode for heating the biogas generation unit.

[0010] The cooling mode is activated when the temperature of the biogas generation unit exceeds a predetermined value, and / or when the amount of foam in the biogas generation unit exceeds a predetermined value. In cooling mode, the supply of waste heat to the biogas generation unit by the waste heat recovery device is reduced, thereby cooling the biogas generation unit.

[0011] The heating mode is activated when the temperature of the biogas generation unit is below a predetermined value and the amount of bubbles in the biogas generation unit is also below a predetermined value. In heating mode, the biogas generation unit is heated by the waste heat recovery device.

[0012] According to the biogas engine system described above, the biogas generator is heated only when the temperature of the biogas generator is below a predetermined value and the amount of bubbles in the biogas generator is below a predetermined value. If the temperature of the biogas generator is above a predetermined value and the amount of bubbles in the biogas generator is above a predetermined value, the biogas generator is cooled.

[0013] Therefore, the biogas engine system described above allows for control over the amount of bubbles generated in the biogas generation section. As a result, blockage of the biogas transport pipe due to bubbles can be suppressed. [Brief explanation of the drawing]

[0014] [Figure 1] Figure 1 is a block diagram showing one embodiment of the biogas engine system of the present invention. [Figure 2] Figure 2 is a flowchart illustrating the operation of the biogas engine system shown in Figure 1. [Modes for carrying out the invention]

[0015] 1. Configuration of the biogas engine system (1) Overall structure Referring to Figure 1, one embodiment of the biogas engine system of the present invention will be described in detail. The biogas engine system 1 is a power source. The biogas engine system 1 generates power (kinetic energy) by burning biogas, as will be described in more detail later.

[0016] More specifically, the biogas engine system 1 comprises a biogas generation unit 2, a biogas engine 3, a waste heat recovery device 4, a temperature sensor 5, a foam volume sensor 6, and a control unit 7.

[0017] Incidentally, the biogas engine system 1 is connected to a power generator 100, for example. The power generator 100 is a device that converts power into electric power (electrical energy). An example of the power generator 100 is an inverter.

[0018] (2) Biogas generation unit The biogas generation unit 2 is provided for generating biogas and temporarily storing the biogas. More specifically, the biogas generation unit 2 includes, for example, a biogas generation tank 21, a biogas storage tank 22, and a biogas transport pipe 23.

[0019] The biogas generation tank 21 is a known fermentation tank. The biogas generation tank 21 is formed of, for example, a known heat-resistant and pressure-resistant container. The biogas generation tank 21 is supplied with organic waste (a liquid phase or a solid-liquid mixed phase) from, for example, a waste storage tank not shown. The organic waste generates methane gas (a gas phase) through methane fermentation. Examples of the organic waste include garbage, sewage, livestock excrement, and food waste.

[0020] The biogas generation tank 21 also contains microorganisms that contribute to the methane fermentation of organic waste. As a result, the biogas generation tank 21 causes methane fermentation of the organic waste inside the tank, as will be described later in detail. Accordingly, biogas is generated within the biogas generation tank 21.

[0021] A temperature adjustment unit 80 (described later) of the waste heat recovery device 4 is connected to the outside of the biogas generation tank 21. Then, the internal temperature of the biogas generation tank 21 is adjusted by the temperature adjustment unit 80 (described later).

[0022] The biogas storage tank 22 is a known gas tank. The biogas storage tank 22 is formed of, for example, a known heat-resistant and pressure-resistant container. For example, the biogas storage tank 22 is supplied with biogas from the biogas generation tank 21 via the biogas transport pipe 23. The biogas storage tank 22 temporarily stores the supplied biogas.

[0023] The biogas transport pipe 23 is a known pipe. The biogas transport pipe 23 communicates the inside of the biogas generation tank 21 with the inside of the biogas storage tank 22. Although not shown in the figure, the biogas transport pipe 23 is provided with a valve. Although not shown in the figure, the biogas transport pipe 23 may be provided with a pump as needed. For example, biogas is transported from the biogas generation tank 21 to the biogas storage tank 22 by driving the pump in the biogas transport pipe 23 and opening / closing the valve.

[0024] Furthermore, the biogas transport pipe 23 may be provided with a desulfurization device (not shown) and / or a siloxane removal device (not shown) in a midway portion along the flow direction of biogas as needed. Accordingly, biogas is subjected to desulfurization treatment and / or siloxane removal as needed.

[0025] (3) Biogas engine The biogas engine 3 includes an engine body 31, a biogas supply pipe 32, a combustion gas discharge pipe 33, and a radiator device 35.

[0026] The engine body 31 generates power (kinetic energy) through combustion of biogas. The engine body 31 has, for example, a known reciprocating engine structure. Although not shown in the figure, the engine body 31 includes, for example, a fuel intake port, an air intake port, a piston, a combustion chamber, an igniter, and an exhaust port. The fuel intake port takes in biogas. The air intake port takes in air. The piston compresses the air-fuel mixture of biogas and air. The igniter ignites the air-fuel mixture of biogas and air. The combustion chamber combusts the air-fuel mixture of biogas and air. The exhaust port discharges the combustion gas generated from biogas combustion. Accordingly, the engine body 31 generates power (kinetic energy).

[0027] Furthermore, the engine body 31 is equipped with a cooling water passage 34. The cooling water passage 34 is connected to a radiator device 35. When the radiator device 35 supplies water to the cooling water passage 34, the engine body 31 is cooled.

[0028] The biogas supply pipe 32 is a known pipe. The biogas supply pipe 32 connects the inside of the biogas storage tank 22 and the engine body 31. Although not shown, the biogas supply pipe 32 is equipped with a valve. Although not shown, the biogas supply pipe 32 may be equipped with a pump as needed. For example, biogas is transported from the biogas storage tank 22 to the engine body 31 by driving the pump in the biogas supply pipe 32 and opening and closing the valve.

[0029] The combustion gas exhaust pipe 33 is a known pipe. One end of the combustion gas exhaust pipe 33 is connected to the engine body 31. The other end of the combustion gas exhaust pipe 33 is open to the outside (outside air). As a result, the combustion gas produced by the combustion of biogas is released to the outside through the combustion gas exhaust pipe 33. As will be described in more detail later, a portion of the combustion gas exhaust pipe 33 is housed in the second heat exchanger 63 (described later). This recovers the thermal energy of the combustion gas.

[0030] The radiator unit 35 is a device that cools the engine body 31 with water. In other words, the radiator unit 35 supplies relatively cold water (coolant) to the engine body 31 to cool it. The water is heated by the heat of the engine body 31. Then, the heated, relatively hot water (thermal storage water) is collected in the radiator unit 35.

[0031] More specifically, the radiator device 35 comprises a radiator body 36, a radiator coolant transport pipe 37, and a radiator heat storage water transport pipe 38.

[0032] The radiator body 36 is a known engine radiator. The radiator body 36 stores coolant (heat transfer medium) for cooling the engine body 31. The radiator body 36 also includes, for example, a cooling fan. This allows the radiator body 36 to dissipate the stored water for cooling.

[0033] The radiator coolant transport pipe 37 is a known pipe. One end of the radiator coolant transport pipe 37 (upstream side in the direction of water transport) is connected to the radiator body 36. The other end of the radiator coolant transport pipe 37 (downstream side in the direction of water transport) is connected to the coolant passage 34 of the engine body 31. Although not shown, the radiator coolant transport pipe 37 is also equipped with an on / off valve and a pump as needed. In this way, the radiator coolant transport pipe 37 transports the relatively cold water (coolant) stored in the radiator body 36 toward the engine body 31 (coolant passage 34).

[0034] The radiator thermal storage water transport pipe 38 is a known pipe. One end of the radiator thermal storage water transport pipe 38 (upstream side in the direction of water transport) is connected to the cooling water passage 34 of the engine body 31. The other end of the radiator thermal storage water transport pipe 38 (downstream side in the direction of water transport) is connected to the radiator body 36. Although not shown, the radiator thermal storage water transport pipe 38 is also equipped with an on / off valve and a pump as needed. As a result, the radiator thermal storage water transport pipe 38 transports relatively hot water (thermal storage water) heated by the engine body 31 toward the radiator body 36.

[0035] As will be explained in more detail later, the radiator heat storage water transport pipe 38 is connected to the radiator bypass pipe 51 (described later) of the waste heat recovery device 4 via the third valve 93. This allows the heat storage water to be transported to the radiator bypass pipe 51 (described later) as needed. The heat storage water may be in liquid (hot water) or gas (steam) form (the same applies hereafter).

[0036] (4) Waste heat recovery system The waste heat recovery device 4 is a device that recovers waste heat from the biogas engine 3. The waste heat recovery device 4 comprises a main heat recovery unit 50, an exhaust gas heat recovery unit 60, a heat recovery water storage unit 70, and a temperature control unit 80.

[0037] The main heat recovery unit 50 is equipment that recovers waste heat from the engine body 31 of the biogas engine 3. The main heat recovery unit 50 is equipped with a radiator bypass pipe 51, a first water transport pipe 52, and a first heat exchanger 53.

[0038] The radiator bypass pipe 51 is a bypass pipe to the radiator system 35. One end of the radiator bypass pipe 51 (upstream side in the direction of water transport) is connected to a portion of the radiator's heat storage water transport pipe 38 in the direction of water flow. The other end of the radiator bypass pipe 51 (downstream side in the direction of water transport) is connected to the cooling water passage 34 of the engine body 31. Although not shown, the radiator bypass pipe 51 is also equipped with an on / off valve and a pump as needed. This allows heat storage water to be transported to the radiator bypass pipe 51 as needed. In other words, the radiator bypass pipe 51 bypasses the radiator system 35.

[0039] Furthermore, a third valve 93 (described later) is interposed at the connection point between the radiator bypass pipe 51 and the radiator heat storage water transport pipe 38. The third valve 93 (described later) adjusts the flow rate of water in the radiator heat storage water transport pipe 38 and the flow rate of water in the radiator bypass pipe 51.

[0040] The first water transport pipe 52 is a known pipe. The first water transport pipe 52 transports relatively cold water (cooling water) toward the first heat exchanger 53. The first water transport pipe 52 then causes the relatively cold water (cooling water) to undergo heat exchange in the first heat exchanger 53, obtaining relatively hot water (heat recovery water). The first water transport pipe 52 then transports the relatively hot water (heat recovery water) discharged from the first heat exchanger 53. In this way, the first water transport pipe 52 recovers the waste heat from the engine body 31 as heat recovery water (hot water or steam).

[0041] More specifically, the first water transport pipe 52 comprises a first cooling water transport section 54, a first heat exchange section 55, and a first heat recovery water transport section 56.

[0042] The first cooling water transport section 54 is part of the first water transport pipe 52. The first cooling water transport section 54 is the forward path for water to the first heat exchanger 53. The first cooling water transport section 54 transports cooling water to the first heat exchanger 53. More specifically, one end of the first cooling water transport section 54 (upstream side in the direction of water transport) is connected to the temperature control unit 80 (described later). The other end of the first cooling water transport section 54 (downstream side in the direction of water transport) is connected to one end of the first heat exchange section 55 (upstream side in the direction of water transport). Although not shown, the first cooling water transport section 54 is also equipped with an on / off valve and a pump as needed. As a result, the first cooling water transport section 54 transports water cooled by the temperature control unit 80 (described later) (cooling water) towards the first heat exchanger 53.

[0043] The first heat exchange section 55 is part of the first water transport pipe 52. The first heat exchange section 55 is the part in the first heat exchanger 53 where water recovers heat. The first heat exchange section 55 exchanges heat between the water in the first water transport pipe 52 and the water in the radiator bypass pipe 51. More specifically, the entire first heat exchange section 55 is housed in the first heat exchanger 53. One end of the first heat exchange section 55 (upstream side in the water transport direction) is connected to the other end of the first cooling water transport section 54 (downstream side in the water transport direction). The other end of the first heat exchange section 55 (downstream side in the water transport direction) is connected to one end of the first heat recovery water transport section 56 (upstream side in the water transport direction). As a result, the first heat exchange section 55 allows the water transported by the first cooling water transport section 54 to recover heat from the water in the radiator bypass pipe 51. The first heat exchange unit 55 then discharges the water from which heat has been recovered (heat-recovered water) to the first heat-recovered water transport unit 56.

[0044] The first heat-recovered water transport section 56 is part of the first water transport pipe 52. The first heat-recovered water transport section 56 is the return path for water to the first heat exchanger 53. The first heat-recovered water transport section 56 transports the heat-recovered water to the temperature control unit 80 (described later). More specifically, one end of the first heat-recovered water transport section 56 (upstream side in the water transport direction) is connected to the other end of the first heat exchange section 55 (downstream side in the water transport direction). The other end of the first heat-recovered water transport section 56 (downstream side in the water transport direction) is connected to the temperature control unit 80 (described later). Although not shown, the first heat-recovered water transport section 56 is also equipped with an on / off valve and a pump as needed. As a result, the first heat-recovered water transport section 56 transports the water heated in the first heat exchanger 53 (heat-recovered water) toward the temperature control unit 80 (described later).

[0045] The first heat exchanger 53 is a known heat exchanger. The first heat exchanger 53 houses a portion of the radiator bypass pipe 51 and a portion of the first water transport pipe 52. More specifically, the first heat exchanger 53 houses a portion of the radiator bypass pipe 51 in the direction of water flow. The first heat exchanger 53 also houses the entire first heat exchange section 55 of the first water transport pipe 52. As a result, the first heat exchanger 53 exchanges heat between the water in the radiator bypass pipe 51 and the water in the first water transport pipe 52.

[0046] The exhaust gas heat recovery unit 60 is equipment that recovers waste heat from the exhaust gas of the biogas engine 3. The exhaust gas heat recovery unit 60 is equipped with a second water transport pipe 62 and a second heat exchanger 63.

[0047] The second water transport pipe 62 is a known pipe. The second water transport pipe 62 transports relatively low-temperature water (cooling water) toward the second heat exchanger 63. The second water transport pipe 62 then causes the relatively low-temperature water (cooling water) to undergo heat exchange in the second heat exchanger 63, obtaining relatively high-temperature water (heat-recovered water). The second water transport pipe 62 then transports the relatively high-temperature water (heat-recovered water) discharged from the second heat exchanger 63. In this way, the second water transport pipe 62 recovers the waste heat from the combustion gas (exhaust gas) as heat-recovered water (hot water or steam).

[0048] More specifically, the second water transport pipe 62 comprises a second cooling water transport section 64, a second heat exchange section 65, and a second heat recovery water transport section 66.

[0049] The second cooling water transport section 64 is part of the second water transport pipe 62. The second cooling water transport section 64 is the forward path for water to the second heat exchanger 63 (described later). The second cooling water transport section 64 transports cooling water to the second heat exchanger 63. More specifically, one end of the second cooling water transport section 64 (upstream side in the direction of water transport) is connected to a portion of the first cooling water transport section 54 in the direction of water flow. The other end of the second cooling water transport section 64 (downstream side in the direction of water transport) is connected to one end of the second heat exchange section 65 (upstream side in the direction of water transport). Although not shown, the second cooling water transport section 64 is equipped with an on / off valve and a pump as needed. As a result, the second cooling water transport section 64 transports water cooled by the temperature control unit 80 (described later) (cooling water) toward the second heat exchanger 63.

[0050] The second heat exchange section 65 is part of the second water transport pipe 62. The second heat exchange section 65 is the part in the second heat exchanger 63 where water recovers heat. The second heat exchange section 65 exchanges heat between the water in the second water transport pipe 62 and the combustion gas (exhaust gas) in the combustion gas discharge pipe 33. More specifically, the entire second heat exchange section 65 is housed in the second heat exchanger 63. One end of the second heat exchange section 65 (upstream side in the direction of water transport) is connected to the other end of the second cooling water transport section 64 (downstream side in the direction of water transport). The other end of the second heat exchange section 65 (downstream side in the direction of water transport) is connected to one end of the second heat-recovered water transport section 66 (upstream side in the direction of water transport). As a result, the second heat exchange section 65 recovers heat from the exhaust gas into the water transported by the second cooling water transport section 64. The second heat exchange unit 65 then discharges the water from which heat has been recovered (heat-recovered water) to the second heat-recovered water transport unit 66.

[0051] The second heat-recovered water transport section 66 is part of the second water transport pipe 62. The second heat-recovered water transport section 66 is the return path for water to the second heat exchanger 63. The second heat-recovered water transport section 66 transports heat-recovered water to the first heat-recovered water transport section 56. More specifically, one end of the second heat-recovered water transport section 66 (upstream side in the water transport direction) is connected to the other end of the second heat exchanger 65 (downstream side in the water transport direction). The other end of the second heat-recovered water transport section 66 (downstream side in the water transport direction) is connected to a portion of the first heat-recovered water transport section 56 in the middle of the water flow direction (upstream side of the first valve 91). Although not shown, the second heat-recovered water transport section 66 is also equipped with an on / off valve and a pump as needed. As a result, the second heat-recovered water transport section 66 transports water heated in the second heat exchanger 63 (heat-recovered water) toward the first heat-recovered water transport section 56.

[0052] The second heat exchanger 63 is a known heat exchanger. The second heat exchanger 63 houses a portion of the combustion gas exhaust pipe 33 and a portion of the second water transport pipe 62. More specifically, the second heat exchanger 63 houses a portion of the combustion gas (exhaust gas) in the combustion gas exhaust pipe 33 in the direction of flow. The second heat exchanger 63 also houses the entire second heat exchange section 65 of the second water transport pipe 62. The second heat exchanger 63 then exchanges heat between the combustion gas (exhaust gas) in the combustion gas exhaust pipe 33 and the water in the second water transport pipe 62.

[0053] The heat recovery water storage unit 70 stores the waste heat from the biogas engine 3 as heat recovery water (hot water or steam). The heat recovery water storage unit 70 also supplies the waste heat from the biogas engine 3 as heat recovery water (hot water or steam) to the temperature control unit 80 as needed.

[0054] More specifically, the heat recovery water storage unit 70 comprises a heat recovery water tank 71, a heat recovery water storage pipe 72, and a heat recovery water supply pipe 73.

[0055] The heat recovery water tank 71 is a known tank. The heat recovery water tank 71 consists of, for example, a known heat-resistant and pressure-resistant vessel. The other end (downstream side in the water transport direction) of the heat recovery water storage pipe 72 (described later) is connected to it. As a result, the heat recovery water tank 71 is supplied with heat recovery water and stores the heat recovery water.

[0056] Furthermore, the heat recovery water tank 71 is equipped with a heater, for example (not shown). This allows the heat recovery water tank 71 to maintain a relatively high temperature while storing the heat recovery water. The temperature of the heat recovery water stored in the heat recovery water tank 71 is, for example, 35 to 100°C.

[0057] The heat recovery water storage pipe 72 is a known pipe. The heat recovery water storage pipe 72 transports the heat recovery water to the heat recovery water tank 71. More specifically, one end of the heat recovery water storage pipe 72 (upstream side in the direction of water transport) is connected to a portion of the first heat recovery water transport section 56 in the direction of water flow. The other end of the heat recovery water storage pipe 72 (downstream side in the direction of water transport) is connected to the heat recovery water tank 71. Although not shown, the heat recovery water storage pipe 72 is also equipped with an on / off valve and a pump as needed. As a result, the heat recovery water storage pipe 72 branches off the heat recovery water from the first heat recovery water transport section 56 and transports it to the heat recovery water tank 71.

[0058] Furthermore, a first valve 91 (described later) is interposed at the connection between the heat recovery water storage pipe 72 and the first heat recovery water transport unit 56. The first valve 91 (described later) switches between transporting water to the heat recovery water tank 71 and transporting water to the temperature control unit 80 (described later).

[0059] The heat recovery water supply pipe 73 is a known pipe. The heat recovery water supply pipe 73 transports heat recovery water from the heat recovery water tank 71 to the temperature control unit 80 (described later). More specifically, one end of the heat recovery water supply pipe 73 (upstream side in the direction of water transport) is connected to the heat recovery water tank 71. The other end of the heat recovery water supply pipe 73 (downstream side in the direction of water transport) is connected to the temperature control unit 80 (described later). Although not shown, the heat recovery water supply pipe 73 is also equipped with an on / off valve and a pump as needed. In this way, the heat recovery water supply pipe 73 transports heat recovery water from the heat recovery water tank 71 to the temperature control unit 80 (described later).

[0060] Furthermore, a second valve 92 (described later) is interposed in the middle of the water flow direction of the heat recovery water supply pipe 73. The flow rate of water in the heat recovery water supply pipe 73 is adjusted by the second valve 92 (described later).

[0061] The temperature control unit 80 is equipment that adjusts the temperature of the biogas generation tank 21 using waste heat. The temperature control unit 80 includes, for example, a heating jacket that covers the biogas generation tank 21. The temperature control unit 80 adjusts the internal temperature of the biogas generation tank 21 by, for example, supplying and stopping heat-recovered water to the heating jacket.

[0062] More specifically, the other end (downstream side in the water transport direction) of the first heat recovery water transport unit 56 is connected to the temperature control unit 80. In addition, one end (upstream side in the water transport direction) of the first cooling water transport unit 54 is connected to the temperature control unit 80.

[0063] As a result, the heat-recovered water is supplied to and held in the temperature control unit 80 as needed. When the heat-recovered water is supplied to and held in the temperature control unit 80, the biogas generation tank 21 is heated by the thermal energy of the heat-recovered water. Meanwhile, the heat-recovered water is cooled. When the heat-recovered water is cooled, the biogas generation tank 21 is cooled (releasing heat). The cooled heat-recovered water is then discharged from the temperature control unit 80 as cooling water. More specifically, the cooled heat-recovered water (cooling water) is discharged from the temperature control unit 80 via the first cooling water transport unit 54 and transported to the first heat exchanger 53 and / or the second heat exchanger 63.

[0064] Furthermore, the waste heat recovery device 4 includes a first valve 91, a second valve 92, a third valve 93, and a water temperature sensor 94.

[0065] The first valve 91 is a known three-way valve. The first valve 91 is a flow path switching valve. The first valve 91 is interposed at the connection between the first heat recovery water transport unit 56 and the heat recovery water storage pipe 72. As a result, the first valve 91 switches between transporting water to the heat recovery water tank 71 and transporting water to the temperature control unit 80 (described later).

[0066] The second valve 92 is a known on-off valve. The second valve 92 is interposed in the heat recovery water supply pipe 73. As a result, the second valve 92 controls the opening and closing of the heat recovery water supply pipe 73.

[0067] The third valve 93 is a known three-way valve. The third valve 93 is a flow control valve (opening control valve). The third valve 93 is interposed at the connection point between the radiator heat storage water transport pipe 38 and the radiator bypass pipe 51. As a result, the third valve 93 can adjust the flow rate of heat storage water in the radiator heat storage water transport pipe 38. The third valve 93 also adjusts the flow rate of heat storage water in the radiator bypass pipe 51.

[0068] The water temperature sensor 94 is a known temperature sensor. The water temperature sensor 94 is positioned, for example, in the middle of the water flow direction of the first heat recovery water transport unit 56. More specifically, the water temperature sensor 94 is positioned downstream of the first heat exchanger 53. The water temperature sensor 94 is also positioned upstream of the first valve 91. Furthermore, the water temperature sensor 94 is positioned downstream of the connection portion between the first heat recovery water transport unit 56 and the second heat recovery water transport unit 66. As a result, the water temperature sensor 94 detects the temperature of the water (heat recovery water) supplied from the first heat recovery water transport unit 56 to the temperature control unit 80.

[0069] (5) Temperature sensor The temperature sensor 5 is a known temperature sensor. The method for detecting temperature by the temperature sensor 5 is not particularly limited, and a known method can be used. The temperature sensor 5 is placed, for example, inside the biogas generator 21. In this way, the temperature sensor 5 detects the internal temperature of the biogas generator 21. Preferably, the temperature sensor 5 detects the temperature of the organic waste (liquid phase or solid-liquid mixed phase) inside the biogas generator 21.

[0070] (6) Foam volume sensor The foam volume sensor 6 is a known foam volume sensor. The method for detecting the amount of foam using the foam volume sensor 6 is not particularly limited, and a known method can be used. The foam volume sensor 6 is placed, for example, inside the biogas generator 21. In this way, the foam volume sensor 6 detects the amount of bubbles generated inside the biogas generator 21.

[0071] (7) Control Unit The control unit 7 is a control unit that performs electrical control of the biogas engine system 1. The control unit 7 is equipped with known memory and arithmetic processing units. The control unit 7 is electrically connected to the biogas engine 3 (not shown). This allows the control unit 7 to arbitrarily control the operation and stopping of the biogas engine 3.

[0072] Furthermore, the control unit 7 is electrically connected to the temperature sensor 5 (see dashed line). This allows the control unit 7 to receive the internal temperature of the biogas generator 21 as an electrical signal.

[0073] Furthermore, the control unit 7 is electrically connected to the bubble volume sensor 6 (see dashed line). This allows the control unit 7 to receive the amount of bubbles inside the biogas generator 21 as an electrical signal.

[0074] Furthermore, the control unit 7 is electrically connected to the first valve 91 (see dashed line). This allows the control unit 7 to arbitrarily adjust the opening and closing of the first valve 91. In other words, the control unit 7 uses the first valve 91 to switch between transporting water to the heat recovery water tank 71 and transporting water to the temperature control unit 80 (described later).

[0075] Furthermore, the control unit 7 is electrically connected to the second valve 92 (see dashed line). This allows the control unit 7 to arbitrarily adjust the opening and closing of the second valve 92. In other words, the control unit 7 controls whether or not heat recovery water is supplied by the heat recovery water supply pipe 73.

[0076] Furthermore, the control unit 7 is electrically connected to the third valve 93 (see dashed line). This allows the control unit 7 to arbitrarily adjust the opening and closing and degree of opening of the third valve 93. In other words, the control unit 7 adjusts the flow rate of the stored heat water in the radiator stored heat water transport pipe 38. The control unit 7 also adjusts the flow rate of the stored heat water in the radiator bypass pipe 51.

[0077] Furthermore, the control unit 7 is electrically connected to the water temperature sensor 94 (see dashed line). This allows the control unit 7 to receive the temperature of the water supplied from the first heat recovery water transport unit 56 to the temperature control unit 80 as an electrical signal.

[0078] The control unit 7 has a foam volume control program P. The foam volume control program P is a program for controlling the amount of foam (amount of foam generated) in the biogas generator 21. The foam volume control program P is designed using a known method and stored in the memory of the control unit 7. The foam volume control program P is executed by the arithmetic processing unit when the biogas engine system 1 is in operation. This allows the control unit 7 to control the amount of foam. The method of controlling the amount of foam using the foam volume control program P will be described later.

[0079] 2. Operation of the biogas engine system In the biogas engine system 1, first, hot water or steam is stored in the heat recovery water tank 71. Preferably, heat recovery water is stored in the heat recovery water tank 71. Then, the hot water or steam (heat recovery water) is supplied from the heat recovery water tank 71 to the temperature control unit 80 via the heat recovery water supply pipe 73. The hot water or steam (heat recovery water) heats the biogas generator 21, and the internal temperature of the biogas generator 21 is controlled to a predetermined temperature (steady-state temperature). For example, when organic waste is subjected to mesothermal fermentation, the internal temperature of the biogas generator 21 is, for example, 35°C. Also, for example, when organic waste is subjected to high-temperature fermentation, the internal temperature of the biogas generator 21 is, for example, 55°C.

[0080] The organic waste is then transported from an organic waste storage tank (not shown) to a biogas generation tank 21. Inside the biogas generation tank 21, the organic waste undergoes methane fermentation, resulting in the generation of biogas. The main component of the biogas is methane gas.

[0081] Next, the biogas is pre-treated (desulfurization and siloxane removal) as needed. The biogas is then transported from the biogas generation tank 21 to the biogas storage tank 22 via the biogas transport pipe 23. The biogas is temporarily stored in the biogas storage tank 22. Finally, the biogas is supplied to the engine body 31 via the biogas supply pipe 32.

[0082] In the engine body 31, biogas and air are mixed. Power (kinetic energy) is generated by the combustion of this biogas and air mixture. More specifically, the engine body 31 first draws the air and biogas mixture into the cylinder. Next, the engine body 31 compresses the mixture in the cylinder with a piston. Then, the engine body 31 ignites the mixture, causing an explosion. After that, the engine body 31 exhausts water vapor and combustion gases. By repeating this drive cycle, the engine body 31 generates power (kinetic energy).

[0083] The power (kinetic energy) generated by the engine body 31 is converted into electricity (electrical energy) in a known power generation device 100. For example, in the power generation device 100, the power (kinetic energy) generated by the engine body 31 rotates a magnet and / or coil. This causes the power generation device 100 to generate electricity (electrical energy).

[0084] 3. Utilization of waste heat (1) Waste heat from the engine itself In the engine body 31, waste heat (thermal energy) is generated along with the power (kinetic energy) mentioned above. More specifically, when the engine body 31 burns a mixture of biogas and air, the engine body 31 is heated to a relatively high temperature.

[0085] Meanwhile, the hot water or steam (heat-recovered water) supplied to the temperature control unit 80 is cooled by heating the biogas generation tank 21. As a result, the cooled water is discharged from the temperature control unit 80 as cooling water. The temperature of the cooling water is, for example, 35 to 60°C.

[0086] Therefore, in the biogas engine system 1, waste heat (thermal energy) from the engine body 31 is recovered by cooling water and then reused as heat recovery water.

[0087] More specifically, when the engine body 31 is heated to a relatively high temperature, the radiator device 35 activates first. When the radiator device 35 activates, water (coolant) in the radiator body 36 is supplied to the coolant passage 34 via the radiator coolant transport pipe 37. The coolant cools the engine body 31. At the same time, the coolant is heated by the engine body 31, that is, heat-retaining water is generated. The temperature of the heat-retaining water is, for example, 80 to 105°C.

[0088] Then, the coolant (i.e., heat storage water) of the radiator device 35, which has been heated in the engine body 31, is recovered into the radiator body 36 via the radiator heat storage water transport pipe 38.

[0089] In this biogas engine system 1, the cooling water in the temperature control unit 80 is discharged at any time and supplied to the first heat exchange unit 55 via the first cooling water transport unit 54.

[0090] Furthermore, in the biogas engine system 1 described above, the opening degree of the third valve 93 is controlled by the control unit 7.

[0091] As a result, the radiator body 36 is opened to a predetermined degree (steady-state opening of 50%). Also, the radiator bypass pipe 51 is opened to a predetermined degree (steady-state opening of 50%). As a result, a portion of the heat-retaining water recovered in the radiator body 36 is supplied to the radiator bypass pipe 51.

[0092] Then, in the first heat exchanger 53, the cooling water in the first heat exchange section 55 and the heat storage water in the radiator bypass pipe 51 exchange heat.

[0093] Through the heat exchange described above, the cooling water in the first heat exchange unit 55 is heated, and relatively high-temperature water (heat-recovered water) is obtained. The obtained heat-recovered water is supplied to the temperature control unit 80 via the first heat-recovered water transport unit 56. This heat-recovered water then heats the biogas generation tank 21.

[0094] Furthermore, the heat exchange described above cools the heat-storage water in the radiator bypass pipe 51, yielding coolant. This coolant is then supplied to the coolant passage 34 via the radiator bypass pipe 51. This coolant then cools the engine body 31.

[0095] As described above, in the biogas engine system 1, waste heat (thermal energy) from the engine body 31 is recovered and reused.

[0096] (2) Waste heat from combustion gases Furthermore, in the biogas engine system 1, in addition to the waste heat (thermal energy) from the engine body 31, the waste heat (thermal energy) from the combustion gas is also recovered and reused.

[0097] More specifically, when the engine body 31 burns the mixture of biogas and air, relatively high-temperature combustion gases are generated.

[0098] Therefore, in the biogas engine system 1, the waste heat (thermal energy) from the combustion gas is recovered using cooling water and then reused as heat recovery water.

[0099] More specifically, when relatively high-temperature combustion gases are generated in the engine body 31, the combustion gases are discharged through the combustion gas exhaust pipe 33 and supplied to the second heat exchanger 63.

[0100] In this biogas engine system 1, the cooling water in the temperature control unit 80 is discharged at any time and supplied to the second heat exchange unit 65 via the first cooling water transport unit 54.

[0101] Then, in the second heat exchanger 63, the cooling water in the second heat exchange section 65 and the combustion gas (exhaust gas) in the combustion gas exhaust pipe 33 exchange heat.

[0102] Through the heat exchange described above, the cooling water in the second heat exchange unit 65 is heated, and relatively high-temperature water (heat-recovered water) is obtained. The obtained heat-recovered water is supplied to the first heat-recovered water transport unit 56 via the second heat-recovered water transport unit 66, and then supplied to the temperature control unit 80. As a result, the heat-recovered water heats the biogas generation tank 21.

[0103] Furthermore, the combustion gas in the combustion gas exhaust pipe 33 is cooled by the heat exchange described above. The cooled combustion gas is then released into the atmosphere.

[0104] As described above, in the biogas engine system 1, the waste heat (thermal energy) from the combustion gas is recovered and reused.

[0105] 4. Adjusting the amount of foam In the biogas engine system 1, bubbles may be generated along with the biogas during the methane fermentation of organic waste. More specifically, a relatively large number of bubbles are generated when the temperature of the biogas generator 21 is relatively high and the methane fermentation of organic waste is accelerated.

[0106] In particular, as described above, when the waste heat from the biogas engine 3 is recovered and reused, the biogas generator 21 may be overheated, the temperature of the biogas generator 21 may become excessively high, the methane fermentation of organic waste may be excessively accelerated, and excessive bubbles may be generated.

[0107] These bubbles are usually transported along with the biogas through the biogas transport pipe 23. In such cases, if an excessive amount of bubbles are generated, the bubbles may clog the biogas transport pipe 23.

[0108] Therefore, in the biogas engine system 1 described above, the amount of foam in the biogas generator 21 is controlled by the following method.

[0109] The method for controlling the amount of biogas generated by the foam volume control program P will be described in detail below. Figure 2 is a flowchart showing the control flow performed in the biogas engine system shown in Figure 1.

[0110] The foam volume control program P is executed, for example, when the biogas engine system 1 starts operating (start S1).

[0111] When the foam volume control program P is executed, first the foam volume sensor 6 detects the amount of foam in the biogas generator 21. The amount of foam in the biogas generator 21 is input to the foam volume control program P as an electrical signal. The foam volume control program P then determines whether the amount of foam in the biogas generator 21 is above a predetermined value (S2).

[0112] The predetermined value for the foam volume is, for example, a threshold for determining if the foam volume is excessive. The predetermined value for the foam volume is set appropriately according to, for example, the size of the biogas generator 21 and the size of the biogas transport pipe 23. The predetermined value for the foam volume is indicated, for example, as the height of the foam surface (water level of the foam phase). In other words, if the height of the foam surface (water level of the foam phase) is equal to or greater than the predetermined value, it is determined that the foam volume is equal to or greater than the predetermined value. The predetermined value for the height of the foam surface (water level of the foam phase) is, for example, -100 mm relative to the connection point (biogas inlet) between the biogas transport pipe 23 and the biogas generator 21.

[0113] If the amount of foam in the biogas generator 21, as detected by the foam volume sensor 6, exceeds a predetermined value, it is determined that the amount of foam is excessive and that blockage of the biogas transport pipe 23 is likely to occur.

[0114] Therefore, if it is determined that the amount of foam is above a predetermined value (S2; YES), the control unit 7 operates the biogas engine system 1 in cooling mode (S3).

[0115] In cooling mode, the control unit 7 controls the first valve 91, the second valve 92, and the third valve 93 as follows (S4).

[0116] More specifically, in cooling mode, the control unit 7 adjusts the opening degree of the third valve 93 to increase the opening degree on the radiator body 36 side compared to the steady-state opening degree mentioned above. The control unit 7 also adjusts the opening degree of the third valve 93 to decrease the opening degree of the radiator bypass pipe 51 compared to the steady-state opening degree mentioned above.

[0117] For example, if the amount of foam in the biogas generator 21 is greater than or equal to a predetermined value, the opening degree on the radiator body 36 side can be set to 100%, and the opening degree on the radiator bypass pipe 51 side can be set to 0%.

[0118] Furthermore, if the amount of foam in the biogas generator 21 exceeds a predetermined value, the opening degree of the third valve 93 can be adjusted according to the amount of foam in the biogas generator 21. For example, the greater the amount of foam in the biogas generator 21, the larger the opening degree on the radiator body 36 side can be adjusted to be relatively larger, and the smaller the opening degree on the radiator bypass pipe 51 side can be adjusted to be relatively smaller.

[0119] As a result, the control unit 7 reduces the amount of heat-recovered water supplied to the radiator bypass pipe 51. In other words, the control unit 7 suppresses heat exchange (i.e., waste heat recovery) in the first heat exchanger 53 and reduces the amount of heat-recovered water produced.

[0120] In addition, in cooling mode, the control unit 7 controls the first valve 91 to open the flow path on the heat recovery water tank 71 side and close the flow path on the temperature control unit 80 side.

[0121] In addition, in cooling mode, the control unit 7 controls the second valve 92 to close the heat recovery water supply pipe 73.

[0122] In other words, in cooling mode, the control unit 7 stops the transport of heat recovery water to the temperature control unit 80. The control unit 7 also transports and stores the heat recovery water in the heat recovery water tank 71.

[0123] This suppresses the heating of the biogas generator 21 by the heat-recovered water. As a result, the amount of bubbles generated in the biogas generator 21 is reduced, and the amount of bubbles in the biogas generator 21 detected by the bubble amount sensor 6 decreases.

[0124] The foam volume control program P repeatedly executes the above cooling mode until the amount of foam in the biogas generator 21 falls below a predetermined value.

[0125] Then, if the foam volume control program P determines that the foam volume is below a predetermined value (S2; NO), the temperature sensor 5 then detects the internal temperature of the biogas generator 21. The internal temperature of the biogas generator 21 is input to the foam volume control program P as an electrical signal. The foam volume control program P then determines whether the internal temperature of the biogas generator 21 is above a predetermined value (S5).

[0126] The predetermined internal temperature of the biogas generator 21 is, for example, a threshold value used to determine whether the amount of biogas generated is above a predetermined value. The predetermined internal temperature of the biogas generator 21 is set appropriately according to, for example, the size of the biogas generator 21 and the size of the biogas transport pipe 23. For example, when organic waste is fermented at a moderate temperature, the predetermined internal temperature of the biogas generator 21 is, for example, a temperature exceeding 35°C (e.g., 36°C). Also, for example, when organic waste is fermented at a high temperature, the predetermined internal temperature of the biogas generator 21 is, for example, a temperature exceeding 55°C (e.g., 56°C).

[0127] If the internal temperature of the biogas generator 21, as detected by the temperature sensor 5, exceeds a predetermined value, methane fermentation in the biogas generator 21 will be excessively accelerated. As a result, an excessive amount of biogas may be generated.

[0128] Furthermore, if the internal temperature of the biogas generator 21, as detected by the temperature sensor 5, is above a predetermined value, the possibility of excessive bubble generation associated with biogas increases. In other words, even if the amount of bubbles detected by the bubble volume sensor 6 does not reach the predetermined value, if the internal temperature of the biogas generator 21 is above a predetermined value, the possibility of blockage of the biogas transport pipe 23 increases as operation continues.

[0129] Therefore, if it is determined that the internal temperature of the biogas generator 21 is above a predetermined value (S5; YES), the control unit 7 operates the biogas engine system 1 in cooling mode (S3).

[0130] In cooling mode, the control unit 7 controls the first valve 91, the second valve 92, and the third valve 93 as described above (S4).

[0131] More specifically, in cooling mode, the control unit 7 adjusts the opening degree of the third valve 93 to increase the opening degree on the radiator body 36 side compared to the steady-state opening degree mentioned above. The control unit 7 also adjusts the opening degree of the third valve 93 to decrease the opening degree of the radiator bypass pipe 51 compared to the steady-state opening degree mentioned above.

[0132] In cooling mode, the control unit 7 controls the first valve 91 to open the flow path on the heat recovery water tank 71 side and close the flow path on the temperature control unit 80 (described later) side. As a result, the control unit 7 transports the heat recovery water to the heat recovery water tank 71.

[0133] In cooling mode, the control unit 7 controls the second valve 92 to close the heat recovery water supply pipe 73. As a result, the control unit 7 stores the heat recovery water in the heat recovery water tank 71.

[0134] In other words, in cooling mode, the control unit 7 stops the transport of heat recovery water to the temperature control unit 80. The control unit 7 also transports and stores the heat recovery water in the heat recovery water tank 71.

[0135] This suppresses the heating of the biogas generation tank 21 by the heat-recovered water. As a result, the internal temperature of the biogas generation tank 21, as detected by the temperature sensor 5, decreases.

[0136] The foam volume control program P repeatedly executes the above cooling mode until the amount of foam in the biogas generator 21 falls below a predetermined value and the internal temperature of the biogas generator 21 falls below a predetermined value.

[0137] Furthermore, if the amount of bubbles in the biogas generator 21 is below a predetermined value, and the internal temperature of the biogas generator 21 is below a predetermined value, it is determined that excessive bubbles will not be generated, and blockage of the biogas transport pipe 23 is unlikely to occur.

[0138] Therefore, if it is determined that the amount of bubbles in the biogas generator 21 is below a predetermined value and the internal temperature of the biogas generator 21 is below a predetermined value (S5; NO), the control unit 7 operates the biogas engine system 1 in heating mode (S6).

[0139] In heating mode, the control unit 7 selects either the first heating mode or the second heating mode (S7).

[0140] In the first heating mode, the heat-recovered water (hereinafter referred to as unstored heat-recovered water) transported by the first water transport pipe 52 and the second water transport pipe 62 is directly supplied to the temperature control unit 80 to heat the biogas generation tank 21.

[0141] In the second heating mode, the heat-recovered water from the heat-recovered water tank 71 (hereinafter referred to as the stored heat-recovered water) is supplied to the temperature control unit 80 to heat the biogas generation tank 21.

[0142] These first and second heating modes are adopted alternately. More specifically, in selecting between the first and second heating modes, the water temperature sensor 94 first detects the temperature of the unstored heat-recovered water in the first heat-recovered water transport unit 56. The temperature of the unstored heat-recovered water is input as an electrical signal to the foam volume control program P. The foam volume control program P then determines whether the temperature of the unstored heat-recovered water is above a predetermined value (S7).

[0143] The predetermined temperature of the unstored heat-recovered water is a threshold value used to determine that the biogas generator 21 is sufficiently heated. The predetermined temperature of the unstored heat-recovered water is set appropriately according to, for example, the size of the biogas generator 21 and the size of the biogas transport pipe 23. For example, when organic waste is subjected to mesothermal fermentation, the predetermined temperature of the unstored heat-recovered water is, for example, 40°C. Also, for example, when organic waste is subjected to high-temperature fermentation, the predetermined temperature of the unstored heat-recovered water is, for example, 60°C.

[0144] If the temperature of the unstored heat-recovered water detected by the water temperature sensor 94 is above a predetermined value, it is determined that the biogas transport pipe 23 can be sufficiently heated by the unstored heat-recovered water.

[0145] Therefore, if it is determined that the temperature of the unstored heat-recovered water is above a predetermined value (S7; YES), the control unit 7 operates the biogas engine system 1 in the first heating mode (S8).

[0146] In the first heating mode, the control unit 7 controls the first valve 91, the second valve 92, and the third valve 93 as follows (S9).

[0147] More specifically, in the first heating mode, the control unit 7 adjusts the opening degree of the third valve 93 to adjust the opening degree on the radiator body 36 side to below the above-mentioned steady-state opening degree. The control unit 7 also adjusts the opening degree of the third valve 93 to adjust the opening degree of the radiator bypass pipe 51 to above the above-mentioned steady-state opening degree.

[0148] For example, if the temperature of the unstored heat recovery water is above a predetermined value, the opening degree on the radiator body 36 side can be set to 0%, and the opening degree on the radiator bypass pipe 51 side can be set to 100%.

[0149] Furthermore, if the temperature of the unstored heat-recovered water is above a predetermined value, the opening degree of the third valve 93 can be adjusted according to the temperature of the unstored heat-recovered water. For example, the greater the temperature of the unstored heat-recovered water is above a predetermined value, the smaller the opening degree on the radiator body 36 side can be adjusted, and the larger the opening degree on the radiator bypass pipe 51 side can be adjusted.

[0150] As a result, the control unit 7 increases the amount of heat-recovered water supplied to the radiator bypass pipe 51. In other words, the control unit 7 promotes heat exchange (i.e., waste heat recovery) in the first heat exchanger 53 and increases the amount of heat-recovered water produced.

[0151] In addition, in the first heating mode, the control unit 7 controls the first valve 91 to close the flow path on the heat recovery water tank 71 side and open the flow path on the temperature control unit 80 side.

[0152] In addition, in the first heating mode, the control unit 7 controls the second valve 92 to close the heat recovery water supply pipe 73.

[0153] In other words, in the first heating mode, the control unit 7 supplies unstored heat-recovered water to the temperature control unit 80. Furthermore, the control unit 7 does not supply stored heat-recovered water to the temperature control unit 80.

[0154] As a result, the biogas generator 21 is heated by the unstored heat-recovered water. This promotes methane fermentation in the biogas generator 21, increasing the amount of biogas produced.

[0155] On the other hand, if it is determined that the temperature of the unstored heat-recovered water is below a predetermined value (S7; NO), the control unit 7 operates the biogas engine system 1 in second heating mode (S10).

[0156] In the second heating mode, the control unit 7 controls the first valve 91, the second valve 92, and the third valve 93 as follows (S11).

[0157] More specifically, even in the second heating mode, the control unit 7 adjusts the opening degree of the third valve 93 to adjust the opening degree of the radiator body 36 to be below the above-mentioned steady-state opening degree. In addition, the control unit 7 adjusts the opening degree of the third valve 93 to adjust the opening degree of the radiator bypass pipe 51 to be above the above-mentioned steady-state opening degree.

[0158] For example, if the temperature of the unstored heat recovery water is above a predetermined value, the opening degree on the radiator body 36 side can be set to 0%, and the opening degree on the radiator bypass pipe 51 side can be set to 100%.

[0159] Furthermore, if the temperature of the unstored heat-recovered water is above a predetermined value, the opening degree of the third valve 93 can be adjusted according to the temperature of the unstored heat-recovered water. For example, the greater the temperature of the unstored heat-recovered water is above a predetermined value, the smaller the opening degree on the radiator body 36 side can be adjusted, and the larger the opening degree on the radiator bypass pipe 51 side can be adjusted.

[0160] As a result, the control unit 7 increases the amount of heat-recovered water supplied to the radiator bypass pipe 51. In other words, the control unit 7 promotes heat exchange (i.e., waste heat recovery) in the first heat exchanger 53 and increases the amount of heat-recovered water produced.

[0161] In the second heating mode, the control unit 7 controls the first valve 91 to open the flow path on the heat recovery water tank 71 side and close the flow path on the temperature control unit 80 side.

[0162] In the second heating mode, the control unit 7 controls the second valve 92 to open the heat recovery water supply pipe 73.

[0163] In other words, in the second heating mode, the control unit 7 does not supply the unstored heat-recovered water to the temperature control unit 80, but instead supplies it to the heat-recovered water tank 71. In the heat-recovered water tank 71, the heat-recovered water is temperature-controlled by a heater (not shown). Then, in the second heating mode, the control unit 7 supplies the heat-recovered water stored in the heat-recovered water tank 71 to the temperature control unit 80.

[0164] As a result, the biogas generator 21 is heated by the heat-recovered water stored in the heat-recovered water tank 71. This promotes methane fermentation in the biogas generator 21, increasing the amount of biogas produced.

[0165] In the first and second heating modes, heating the biogas generator 21 may increase the amount of bubbles generated in the biogas generator 21. Therefore, the amount of bubbles in the biogas generator 21 and the internal temperature of the biogas generator 21 are continuously monitored (return).

[0166] The control unit 7 then reduces the supply of waste heat to the biogas generator 21 by the waste heat recovery device 4 when the temperature of the biogas generator 21 is above a predetermined value and / or the amount of foam in the biogas generator 21 is above a predetermined value. As a result, the control unit cools the biogas generator 21 (cooling mode).

[0167] Furthermore, the control unit 7 heats the biogas generator 21 using the waste heat recovery device 4 when the temperature of the biogas generator 21 is above a predetermined value and the amount of foam in the biogas generator 21 is below a predetermined value (heating mode).

[0168] In addition, during heating mode, the temperature of the unstored heat-recovered water is continuously detected, and either the first heating mode or the second heating mode is selected as appropriate based on that temperature.

[0169] In other words, the control unit 7 continuously detects the temperature of the biogas generator 21, the amount of foam in the biogas generator 21, and the temperature of the unstored heat-recovered water, and switches between the cooling mode, the first heating mode, and the second heating mode as needed. Furthermore, the control unit 7 continues the above processing while the biogas engine system 1 is in operation.

[0170] In other words, the control unit 7 operates the biogas engine system 1 by appropriately switching between the cooling mode, the first heating mode, and the second heating mode.

[0171] 4. Effects In the biogas engine system 1 described above, the control unit 7 switches between a cooling mode for cooling the biogas generator 21 and a heating mode for heating the biogas generator 21.

[0172] The cooling mode is activated when the temperature of the biogas generator 21 is above a predetermined value, and / or when the amount of foam in the biogas generator 21 is above a predetermined value. In cooling mode, the supply of waste heat to the biogas generator 21 by the waste heat recovery device 4 is reduced, thereby cooling the biogas generator 21.

[0173] The heating mode is activated when the temperature of the biogas generator 21 is below a predetermined value and the amount of foam in the biogas generator 21 is below a predetermined value. In heating mode, the biogas generator 21 is heated by the waste heat recovery device 4.

[0174] According to the biogas engine system 1 described above, the biogas generator 21 is heated only when the temperature of the biogas generator 21 is below a predetermined value and the amount of bubbles in the biogas generator 21 is below a predetermined value. If the temperature of the biogas generator 21 is above a predetermined value and the amount of bubbles in the biogas generator 21 is above a predetermined value, the biogas generator 21 is cooled.

[0175] Therefore, the biogas engine system 1 described above allows for the control of the amount of bubbles generated in the biogas generator 21. As a result, blockage of the biogas transport pipe 23 due to bubbles can be suppressed.

[0176] 5. Variations In the biogas engine system 1 described above, the foam volume control program P has a first heating mode and a second heating mode. In the heating mode, either the first heating mode or the second heating mode is selected.

[0178] Preferably, the foam volume control program P has both a first heating mode and a second heating mode as heating modes. Then, either the first heating mode or the second heating mode is selected depending on the temperature of the unstored heat-recovered water. With this method, the biogas generator 21 can be heated by waste heat more efficiently.

[0179] Furthermore, in the above method, the waste heat recovery device 4 includes a main body heat recovery unit 50 that recovers heat from the engine body 31 and an exhaust gas heat recovery unit 60 that recovers heat from the exhaust gas. The biogas generation tank 21 is then heated by the waste heat from the engine body 31 and the waste heat from the exhaust gas. However, the waste heat recovery device 4 may be equipped with only one of either the main body heat recovery unit 50 or the exhaust gas heat recovery unit 60.

[0180] For example, if the waste heat recovery device 4 is equipped with a main unit heat recovery unit 50 but not with an exhaust gas heat recovery unit 60, the biogas generation tank 21 is heated by the waste heat from the engine body 31. Furthermore, the biogas generation tank 21 is not heated by the waste heat from the exhaust gas. Also, for example, if the waste heat recovery device 4 is equipped with an exhaust gas heat recovery unit 60 but not with a main unit heat recovery unit 50, the biogas generation tank 21 is heated by the waste heat from the exhaust gas. Furthermore, the biogas generation tank 21 is not heated by the waste heat from the engine body 31. The biogas generation tank 21 can also be heated by waste heat through these methods.

[0181] Preferably, the waste heat recovery device 4 includes both a main body heat recovery unit 50 that recovers heat from the engine body 31 and an exhaust gas heat recovery unit 60 that recovers heat from the exhaust gas. The biogas generation tank 21 is then heated by both the waste heat from the engine body 31 and the waste heat from the exhaust gas. This method allows the biogas generation tank 21 to be heated by waste heat more efficiently. [Explanation of Symbols]

[0182] 1. Biogas Engine System 2. Biogas generation unit 3. Biogas engine 4. Waste heat recovery system 5. Temperature sensor 6. Foam volume sensor 7 Control Unit

Claims

[Claim 1] A biogas generation unit that ferments organic waste to produce biogas, A biogas engine for burning the aforementioned biogas, A waste heat recovery device that recovers waste heat from the biogas engine and heats the biogas generation unit with the waste heat, A temperature sensor for detecting the temperature of the biogas generation unit, A foam volume sensor for detecting the amount of foam in the biogas generation unit, The system comprises a control unit that controls the waste heat recovery device according to the temperature detected by the temperature sensor and the amount of foam detected by the foam volume sensor, The aforementioned waste heat recovery device is From the biogas engine, waste heat is recovered and stored as heat recovery water. The biogas generation unit is heated by supplying heat-recovered water to the biogas generation unit. The control unit is When the temperature of the biogas generation unit is above a predetermined value and / or the amount of foam in the biogas generation unit is above a predetermined value, a cooling mode is provided which reduces the supply of waste heat to the biogas generation unit by the waste heat recovery device and cools the biogas generation unit. When the temperature of the biogas generation unit is below a predetermined value and the amount of foam in the biogas generation unit is below a predetermined value, the waste heat recovery device is used to heat the biogas generation unit in a heating mode. This can be switched, Furthermore, in the heating mode, After waste heat recovery, if the temperature of the unstored heat-recovered water is above a predetermined value, a first heating mode is performed in which the unstored heat-recovered water is used to heat the biogas generation unit. If, after waste heat recovery, the temperature of the unstored heat-recovered water is below a predetermined value, a second heating mode is activated in which the stored heat-recovered water is used to heat the biogas generation unit. A biogas engine system that allows for switching between different power sources.

Images