JP2013012381A - Fuel cell cogeneration system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a fuel cell cogeneration system which, without circulating hot water from a filled hot water tank in a hot water circulation passage, can recover water from the moisture vapor contained in exhaust gas from a fuel battery cell stack by making use of tap water.SOLUTION: A fuel cell cogeneration system 1 comprises a power generation unit 2 which generates electric power, a hot water storage unit 3 with a hot water tank 31 in which hot water after heat exchange is stored, and a hot water circulation passage 4 or the like in which hot water is circulated between the units 2 and 3. On the downstream side from a heat exchanger passage 11a of a heat exchanger 11 and the upstream side from the hot water tank 31 of the hot water circulation passage 4 is provided a branch passage 45 which branches off to the outside from the hot water circulation passage 4. When the hot water in the hot water tank 31 is at a prescribed temperature or higher and a water level in a reservoir tank 21 is at low level, hot water circulation to the hot water tank 31 is stopped and the branch passage 45 is opened, whereby hot water is discharged from the hot water circulation passage 4 and also low temperature tap water is introduced through a water entry passage 32 connected to the hot water circulation passage 4.

Description

  TECHNICAL FIELD The present invention relates to a fuel cell cogeneration system, and in a configuration for recovering reforming water from water vapor contained in exhaust gas generated from a fuel cell stack, particularly for reforming by circulating hot water in a hot water tank. The present invention relates to a fuel cell cogeneration system that collects water.

  Conventionally, a fuel cell cogeneration system that generates electric power by supplying air and reformed fuel gas (hydrogen-containing gas) to the fuel cell stack, and recovers the secondary heat generated during this power generation as hot water The system is in practical use. A conventional fuel cell cogeneration system has a power generation unit for generating power, a hot water storage unit having a hot water storage tank for storing hot water after heat exchange, and a hot water circulation passage for circulating hot water between the power generation unit and the hot water storage unit. And a hot water circulation passage provided with a radiator for cooling the hot water.

  Here, the power generation unit generally includes a fuel cell stack that generates power using air and reformed fuel gas, and the reformed fuel gas supplied to the fuel cell stack from water and a fuel gas such as natural gas. A reformer to be generated, a heat exchanger for exchanging heat between exhaust gas from the fuel cell stack and hot water in a hot water tank, a storage tank for storing water to be supplied to the reformer, and the like Yes.

  By the way, in the fuel cell cogeneration system, as means for supplying the reforming water supplied to the reformer, heat exchange is performed between the exhaust gas and the hot water in the hot water tank using a heat exchanger. A method has been adopted in which condensed water generated at the time is recovered and reused as reforming water. By adopting this method, a so-called water self-supporting system that does not need to supply water for reforming from the outside is established.

  However, the temperature of the hot water flowing from the hot water tank to the heat exchanger via the hot water circulation passage rises due to the heat storage condition of the hot water tank, and eventually the hot water tank becomes full, and the hot water circulating through the hot water circulation passage is heat exchanged. Reaches a temperature above the dew point in the vessel. As a result, the amount of condensed water generated in the heat exchanger decreases and a sufficient amount of condensed water cannot be recovered, and the supply of reforming water becomes insufficient.

In such a case, normally, by operating the radiator, the temperature of the hot water supplied to the heat exchanger is lowered to recover the condensed water.
In Patent Document 1, when the full storage state is reached, the temperature of the hot water in the hot water tank is determined by discharging a part of the hot water in the hot water storage tank and supplying low temperature clean water to the hot water tank. There is also disclosed a configuration in which the radiator can be omitted by circulating the reduced hot water in the hot water circulation passage and collecting the condensed water.

JP 2010-277773 A

  However, the technique of discharging a part of hot water in a hot water storage tank in the above-mentioned Patent Document 1 to the outside and supplying low temperature clean water to lower the temperature of the hot water, There is a possibility that it may not be possible to take out hot water suddenly. That is, when the temperature of hot water is insufficient at the time of hot water discharge, it is necessary to heat again with an auxiliary water heater or the like, resulting in useless costs.

  On the other hand, when the radiator is provided, the above problem does not occur. However, since a radiator is generally complicated and expensive, it is disadvantageous to provide a radiator in the hot water circulation passage in order to reduce manufacturing costs and downsize the apparatus.

  Furthermore, in the fuel cell cogeneration system, a circulation pump for circulating hot water in the hot water circulation passage is provided in the power generation unit (or hot water storage unit). Generally, the hot water circulation passage is configured in a closed circuit, so the circulation pump When priming water or filling with water at the start of operation, there is a problem in that it is necessary to manually open and close valves and the like according to the procedure, which is very troublesome at the start of operation.

  An object of the present invention is to recover water from water vapor contained in exhaust gas from a fuel cell stack by using tap water without circulating hot water in a hot water storage tank that has been fully stored in a hot water circulation passage. To provide a fuel cell cogeneration system that can perform the priming to the circulation pump of the hot water circulation passage and water filling at the start of operation, and to reduce the production cost and operation cost And so on.

  The fuel cell cogeneration system according to claim 1 removes impurities of the condensed water recovered by the water recovery means that condenses and recovers water vapor contained in the exhaust gas discharged from the fuel cell power generation unit. A water treatment means, a storage tank for storing the water treated by the water treatment means, a water supply means for supplying water in the storage tank to the fuel cell power generation unit, a hot water storage tank for storing hot water, and the water In a fuel cell cogeneration system comprising a hot water circulation passage for exhaust heat recovery including a heat exchange passage portion of a recovery means and circulating hot water in the hot water tank to condense the water vapor, A branch passage portion branched from the hot water circulation passage to the outside on the downstream side of the heat exchange passage portion of the water recovery means and the upstream side of the hot water storage tank in the hot water circulation passage. When the hot water temperature in the hot water storage tank is equal to or higher than a predetermined set temperature and the water in the storage tank drops to a predetermined set water level, the hot water circulation to the hot water tank is stopped and the branch passage portion is opened. Thus, hot water is drained from the hot water circulation passage, and low temperature clean water is introduced from an incoming passage connected to the hot water circulation passage.

  A fuel cell cogeneration system according to a second aspect is the invention according to the first aspect, wherein a three-way valve is provided at a branch portion where the branch passage portion branches from the hot water circulation passage, and the hot water in the hot water storage tank is supplied to the hot water circulation passage. When the circulation passage is closed, the branch passage portion is closed through the three-way valve to bring the hot water circulation passage into a circulation state, and when the branch passage portion is opened, the branch passage is passed through the three-way valve. And the circulation of hot water to the hot water tank is stopped.

  According to a third aspect of the present invention, there is provided the fuel cell cogeneration system according to the second aspect, wherein an opening / closing valve is provided in the branch passage portion, and the hot water is branched from the branch passage portion between the three-way valve and the opening / closing valve. A bypass passage connected upstream of the heat exchange passage portion of the circulation passage is provided, and when the branch passage portion is opened, the on-off valve is opened, and the hot water in the hot water circulation passage and the inlet are opened. It is characterized by mixing and draining the clean water from the water passage through the bypass passage.

  A fuel cell cogeneration system according to a fourth aspect of the present invention is the fuel cell cogeneration system according to the third aspect, wherein the on-off valve is closed when the hot water in the hot water circulation passage becomes a predetermined set temperature or less after the branch passage portion is opened. It is characterized by stopping the introduction of clean water from the water intake passage and circulating hot water to the heat exchange passage portion through the bypass passage.

  According to the first aspect of the present invention, a branch passage portion that branches from the hot water circulation passage to the outside is provided downstream of the heat exchange passage portion of the water recovery means in the hot water circulation passage and upstream of the hot water storage tank. When the hot water temperature in the tank is equal to or higher than a predetermined set temperature and the water in the storage tank is lowered to the predetermined set water level, the hot water circulation to the hot water tank is stopped and the branch passage section is opened to open the hot water circulation path. In addition to draining hot water from the hot water, low-temperature clean water is introduced from the water passage connected to the hot water circulation passage, so that the hot water in the hot water tank is maintained without draining even when the hot water tank is full. The heat exchange between the low temperature clean water and the exhaust gas in the heat exchanger makes it possible to easily recover the condensed water from the exhaust gas. Therefore, it is not necessary to provide an expensive radiator and it is not necessary to reheat the hot water in the hot water storage tank at the time of hot water, so that the fuel cell cogeneration system can be downsized, and the manufacturing cost and the operating cost can be reduced.

  According to the second aspect of the present invention, when the branch passage portion is opened via the three-way valve, the clean water introduced from the water supply flows upstream of the hot water circulation passage and passes through the heat exchange passage portion of the heat exchanger. Since it flows downstream from the circulation passage and is discharged to the outside from the branch passage portion, priming water to the circulation pump of the hot water circulation passage can be easily performed, and the operation at the initial stage of operation can be simplified. In addition, for the convenience of the user, water filling at the start of operation after draining in the absence of a long period of time can be easily performed by the user himself / herself even if there is no dedicated maintenance staff for system startup.

  According to the invention of claim 3, since hot water and clean water can be mixed and discharged through the bypass passage, high temperature hot water is prevented from being discharged directly from the hot water circulation passage to The danger associated with discharging hot water can be avoided. Moreover, since direct drainage of high-temperature hot water is prevented, a highly durable drain pipe is not required, and the manufacturing cost can be reduced.

  According to the invention of claim 4, when the hot water in the hot water circulation passage becomes a predetermined temperature or less after the branch passage portion is opened, the open / close valve is closed and the introduction of clean water from the water inlet passage is performed. Since the hot water is circulated to the heat exchange passage through the bypass passage, low temperature clean water can be effectively used to eliminate waste of the clean water and reduce the operating cost.

1 is a schematic configuration diagram of a power generation unit of a fuel cell cogeneration system according to Embodiment 1. FIG. It is a schematic block diagram of a water treatment apparatus. It is a schematic block diagram of a hot water storage unit. It is a chart which shows the control pattern of a three-way valve. It is a schematic block diagram of the hot water storage unit which concerns on Example 2. FIG. It is a graph which shows the control pattern of a 1st, 2nd on-off valve. 6 is a schematic configuration diagram of a hot water storage unit according to Embodiment 3. FIG. It is a chart which shows the control pattern of a three-way valve and an on-off valve.

  Hereinafter, modes for carrying out the present invention will be described based on examples.

First, the overall configuration of the fuel cell cogeneration system 1 will be described.
As shown in FIGS. 1 to 3, the fuel cell cogeneration system 1 includes a power generation unit 2 that generates power, a hot water storage unit 3 that has a hot water storage tank 31 that stores hot water after heat exchange, and these units 2 and 3. It consists of a hot water circulation pipe 4 for circulating hot water between them.

Next, the power generation unit 2 will be described.
As shown in FIG. 1, the power generation unit 2 includes a power generation module 5, a cathode air blower 6, a fuel gas booster blower 7, a fuel reforming air blower 8, an exhaust gas discharge passage 9, a heat exchanger 11, The water treatment device 12 and the inverter 13 are included. The DC power generated by the power generation module 5 is converted into AC power via the inverter 13 and output to the outside.

Next, the power generation module 5 will be described.
The power generation module 5 (corresponding to a fuel cell power generation unit) includes a fuel cell stack 14, an evaporator 15, a fuel reformer 16, an off-gas combustion chamber 17, and the like, and is reformed by the fuel reformer 16. The reformed fuel gas and air as an oxidant are chemically reacted in the fuel cell stack 14 to generate power.

  The evaporator 15 generates steam for mixing with fuel gas and supplies it to the fuel reformer 16. In the evaporator 15, fuel gas (natural gas, city gas, propane, etc.) taken in by the fuel gas booster blower 7 and pressurized and fuel reforming air taken in by the fuel reforming air blower 8 are contained. The water is supplied through the common supply passage 18a, and water is supplied from the water treatment device 12 through the water supply passage 28, and these are mixed and vaporized to generate fuel gas and water vapor.

  The fuel reformer 16 includes a reforming catalyst such as platinum therein, and mixes the fuel gas supplied from the evaporator 15 via the mixing supply passage 18b with water vapor to react (so-called steam reforming). Thus, a reformed fuel gas containing a hydrogen-containing gas is generated, and this reformed fuel gas is supplied to the fuel electrode side of the fuel cell stack 14 via the reformed fuel gas supply path 18c.

  The fuel cell stack 14 is configured by stacking a plurality of fuel cells in multiple layers. Each fuel cell is formed of a fixed electrolyte such as zirconia, a fuel electrode, and an oxygen electrode. The reformed fuel gas is supplied from the fuel reformer 16 to the fuel electrode side of the fuel cell stack 14, and the oxygen electrode side of the fuel cell stack 14 is supplied from the cathode air blower 6 through the air supply passage 18d. Air is supplied, and these are electrochemically reacted in a high temperature environment to generate DC power.

  The off-gas combustion chamber 17 is for processing the residual fuel gas generated with the power generation of the fuel cell stack 14 and is connected to the discharge side of the fuel cell stack 14 on the fuel electrode side and the oxygen electrode side. . The off-gas combustion chamber 17 is supplied with a reaction fuel gas containing residual fuel gas discharged from the fuel electrode side and air containing oxygen discharged from the oxygen electrode side, and these are used using a known combustion catalyst. High-temperature exhaust gas is generated by burning, and water vapor in the exhaust gas is condensed in the heat exchanger 11 and then discharged to the outside through the exhaust gas discharge passage 9.

Next, the heat exchanger 11 will be described.
As shown in FIG. 1, the heat exchanger 11 (corresponding to water recovery means) is provided inside the exhaust gas discharge passage 9, and includes a heat exchange passage portion 11 a that constitutes a part of the hot water circulation passage 4. Yes. In this heat exchanger 11, the exhaust gas discharged from the power generation module 5 is heat-exchanged with hot water flowing through the heat exchange passage portion 11a, and the water vapor contained in the exhaust gas is cooled and condensed to be condensed water. It becomes.

Next, the water treatment device 12 will be described.
As shown in FIG. 2, the water treatment device 12 includes a water treatment means 19, a storage tank 21, a water supply means 22, and the like, and condensate water condensed in the heat exchanger 11 is passed through a recovery passage 23. Then, the water from which impurities are removed by the water treatment means 19 is supplied to the evaporator 15 of the power generation module 5 through the water supply passage 28.

  The water treatment means 19 is for removing impurities of condensed water collected from the heat exchanger 11 and includes a treatment tank 24. The treatment tank 24 is provided with an ion exchange resin that removes impurities contained in the condensed water by ion exchange. A recovery passage 23 is connected to the lower portion of the processing tank 24.

  The storage tank 21 is for temporarily storing the water treated by the water treatment means 19. In the upper part of the storage tank 21, a tank connecting passage 25 connected to the upper part of the processing tank 24, and a discharge passage 26 for discharging to the external drain discharge part 27 when the storage tank 21 is filled with water, Is connected. In the storage tank 21, for example, a water level sensor 21 a that detects water that has dropped to a height position of about 1/5 in the storage tank 21 (corresponding to a predetermined set water level) is provided, and the water level sensor 21 a When the liquid level of the stored water is detected, the normal operation mode is switched to the clean water introduction operation mode. The normal operation mode is an operation state in which hot water in the hot water tank 31 is circulated through the hot water circulation passage 4 and heat exchange with the exhaust gas is performed by the heat exchanger 11, and the water supply operation mode is a low temperature water supply from a water source. And the heat exchanger 11 exchanges heat with the exhaust gas.

  The water supply means 22 is for supplying the purified water in the storage tank 21 to the evaporator 15 of the power generation module 5, the water supply passage 28 connected to the lower end of the storage tank 21, and this water The water supply pump 29 is provided in the middle of the supply passage 28, and the water in the storage tank 21 is supplied to the evaporator 15 through the water supply passage 28 by driving the water supply pump 29.

Next, the hot water storage unit 3 will be described.
As shown in FIG. 3, the hot water storage unit 3 includes a hot water storage tank 31 for storing heat of exhaust gas as hot water, a water inlet passage 32, a hot water passage 33, a hot water circulation passage 4, a three-way valve 35, a mixing valve 36, an auxiliary hot water supply. A container 37 and the like. The hot water storage tank 31 is a heat insulating sealed tank that can store hot water and is relatively long in the vertical direction, and the temperature of hot water in a plurality of reservoirs in the hot water storage tank 31 is detected by a plurality of tank hot water temperature sensors 38a to 38d. .

  Connected to the lower part of the hot water storage tank 31 is a lower passage portion 41 to which the downstream end of the incoming water passage 32 and the upstream end of the hot water circulation passage 4 are connected. Hot water is sent from the hot water storage tank 31 via the circulation pump 39 to the heat exchange passage 11 a of the heat exchanger 11 through the lower passage 41 and the forward passage 4 a of the hot water circulation passage 4. The hot water heated by the heat exchanger 11 flows to the upstream return passage portion 4b and the downstream return passage portion 4c. A downstream return passage 4 c and a hot water passage 33 are connected to the upper part of the hot water storage tank 31. Hot hot water (for example, 80 to 90 ° C.) stored in the hot water tank 31 can be supplied to the hot water passage 33.

  The water inlet passage 32 has a common passage portion 32a, an upper passage portion 32b, and a lower passage portion 32c. The downstream end of the upper passage portion 32 b is connected to the mixing valve 36, and the downstream end of the lower passage portion 32 c is connected to the lower passage portion 41. A water source (not shown) is connected to the upstream end of the common passage portion 32a. A pressure reducing valve 42 is provided in the common passage portion 32a. The temperature of clean water in the common passage portion 32 a near the inlet of the pressure reducing valve 42 is detected by the incoming water temperature sensor 43.

  The hot water circulation passage 4 is a passage through which hot water is exchanged with water vapor by the heat exchange passage portion 11a of the heat exchanger 11, and the forward passage portion 4a, the upstream return passage portion 4b, and the downstream return passage portion 4c. Have. The upstream end of the forward passage portion 4a is connected to the lower passage portion 41, and the downstream end of the forward passage portion 4a is connected to the heat exchange passage portion 11a. The upstream end of the upstream return passage portion 4 b is connected to the heat exchange passage portion 11 a and the downstream end is connected to the three-way valve 35. The upstream end of the downstream return passage portion 4 c is connected to the three-way valve 35, and the downstream end is connected to the upper part of the hot water storage tank 31.

  In the hot water circulation passage 4, a branch passage portion 45 that branches from the hot water circulation passage 4 to the outside is provided on the downstream side of the heat exchange passage portion 11 a of the heat exchanger 11 and the upstream side of the hot water storage tank 31. A three-way valve 35 is provided at a branch portion 46 where the branch passage portion 45 branches. A drain discharge portion 47 is provided at the downstream end of the branch passage portion 45.

  The downstream end of the upstream return passage 4b is connected to the three-way valve 35 (port A), the upstream end of the branch passage 45 is connected to the three-way valve 35 (port B), and the upstream end of the downstream return passage 4c is The three-way valve 35 (port C) is connected, and the three-way valve 35 selectively connects the upstream return passage portion 4b to either the downstream return passage portion 4c or the branch passage portion 45.

  In the normal operation mode, when the hot water in the hot water storage tank 31 is circulated through the hot water circulation passage 4, the branch passage portion 45 is closed via the three-way valve 35 so that the hot water circulation passage 4 is circulated. That is, the port A and the port C of the three-way valve 35 are opened, and the upstream return passage 4b and the downstream return passage 4c are connected. In the water supply operation mode, when the branch passage 45 is opened, the branch passage 45 is opened via the three-way valve 35 and the circulation of hot water to the hot water tank 31 is stopped. That is, the port A and the port B of the three-way valve 35 are opened, and the upstream return passage 4b and the branch passage 45 are connected.

  The circulation pump 39 is a pump for circulating hot water in the hot water circulation passage 4, and is provided on the power generation unit 2 side of the forward passage portion 4a (see FIG. 1). The circulation pump 39 may be disposed on the hot water storage unit 3 side.

  The temperature of hot water in the outgoing passage portion 4a near the outlet of the hot water storage unit 3 (near the inlet of the power generation unit 2) is detected by the inlet hot water temperature sensor 49a, and is near the inlet of the hot water storage unit 3 (near the outlet of the power generation unit 2). The temperature of the hot water in the upstream return passage portion 4b is detected by the outlet hot water temperature sensor 49b.

  The outlet hot water passage 33 has an upstream passage portion 33a through which high-temperature hot water flows and a downstream passage portion 33b through which mixed hot water mixed with water and high-temperature hot water flows. The upstream end of the upstream passage portion 33 a is connected to the upper part of the hot water storage tank 31, and the downstream end of the upstream passage portion 33 a is connected to the mixing valve 36. The upstream end of the downstream passage portion 33b is connected to the mixing valve 36, and the hot water tap 51 is connected to the downstream end of the downstream passage portion 33b. A discharge passage portion 52 that branches off from the middle portion of the upstream-side passage portion 33 a and is connected to the external drain discharge portion 47 is provided, and a pressure relief valve 53 is provided in the discharge passage portion 52.

  The mixing valve 36 controls the flow rate ratio of water to be mixed and hot hot water so that the tapping temperature becomes the command temperature. The flow rate and temperature of the hot water in the upstream passage portion 33a near the inlet of the mixing valve 36 are detected by the upstream flow rate sensor 54a and the upstream hot water temperature sensor 54b, respectively, and the downstream passage portion 33b near the outlet of the mixing valve 36 is detected. The flow rate and temperature of the inside hot water are detected by the downstream flow rate sensor 55a and the downstream hot water temperature sensor 55b, respectively.

  A common passage portion 32a of the water intake passage 32 and a downstream passage portion 33b of the hot water discharge passage 33 are connected by a bypass passage 57, and a safety valve 58 for avoiding high temperature hot water discharge is provided in the bypass passage 57. An auxiliary hot water heater 37 for heating the hot water when the amount of heat of the hot water is insufficient is provided in the middle of the downstream passage portion 33 b of the hot water passage 33.

  A plurality of tank hot water temperature sensors 38a to 38d, incoming water temperature sensor 43, inlet hot water temperature sensor 49a, outlet hot water temperature sensor 49b, upstream flow rate sensor 54a, downstream flow rate sensor 55a, upstream hot water temperature sensor 54b, downstream hot water temperature Signals from the sensor 55b and the water level sensor 21a are transmitted to a control device (not shown), and based on this signal, the three-way valve 35, the mixing valve 36, the circulation pump 39, etc. are controlled to perform various operations (normal exhaust heat recovery). Operation, water recovery operation, priming operation, hot water operation, hot water supply heating operation, etc.).

Next, the operation of the fuel cell cogeneration system 1 will be described.
As shown in FIG. 4, the fuel cell cogeneration system 1 supplies hot water in the hot water tank 31 to the hot water circulation passage 4 according to the storage state of the water in the storage tank 21 and the hot water storage state of the hot water tank 31. Normal operation mode (a) in which heat is exchanged with the exhaust gas in the heat exchanger 11 and low temperature clean water is introduced from the water source without using hot water in the hot water tank 31 and exhausted in the heat exchanger 11 There are three operation patterns: a clean water introduction operation mode (b) for exchanging heat with gas, and a priming operation mode (c) for executing priming water to the circulation pump 39.

  As shown in FIG. 4, in this normal operation mode (a), the three-way valve 35 is set to an open state in which the port A and the port C are connected. That is, the three-way valve 35 is controlled so that the branch passage portion 45 is closed and the hot water circulation passage 4 is circulated. The hot water flowing into the heat exchange passage portion 11a from the lower end portion of the hot water tank 31 through the lower passage portion 41 and the forward passage portion 4a of the hot water circulation passage 4 by driving the circulation pump 39 is exhausted from the off-gas combustion chamber 17. Heat is exchanged with gas to warm this hot water, and the heated hot water is stored in the hot water storage tank 31 through the upstream return passage portion 4b and the downstream return passage portion 4c. Hot water is stored.

  On the other hand, in the power generation unit 2, the water vapor contained in the exhaust gas is cooled by the heat exchanger 11 to generate condensed water, and this condensed water is sent to the treatment tank 24 of the water treatment means 19 via the recovery passage 23. Then, impurities in the condensed water are removed in the processing tank 24, and the purified water is sent to the storage tank 21 to be temporarily stored. Thereafter, the water stored in the storage tank 21 is sent to the evaporator 15 of the power generation module 5 by the water supply means 22 and reused as reforming water.

  However, the temperature of the hot water flowing from the hot water storage tank 31 to the heat exchanger 11 through the outgoing passage portion 4a rises due to the heat storage state of the hot water storage tank 31, and eventually the hot water storage tank 31 becomes fully stored, and the hot water circulation path 4 passes through. The circulating hot water reaches a temperature near the dew point in the heat exchanger 11. As a result, the temperature drop of the exhaust gas is reduced, the amount of condensed water generated in the heat exchanger 11 is reduced, and a sufficient amount of condensed water cannot be recovered, and the supply of reforming water is insufficient. In this case, when the plurality of tank hot water temperature sensors 38a to 38d of the hot water storage tank 31 detect the full storage state and the water level sensor 21a of the storage tank 21 detects the level of the lowered water, based on these detection signals. The operation mode is switched to a clean water introduction operation mode (b) described below. The full animal state is a state in which the inside of the hot water tank 31 is filled with high-temperature hot water of, for example, 90 ° C. (corresponding to a predetermined set temperature).

  As shown in FIG. 4, in this clean water introduction operation mode (b), the valve-opening state in which the port A and the port B of the three-way valve 35 of the hot water storage unit 3 are connected is set. As described above, when the temperature of the hot water in the hot water tank 31 is equal to or higher than the predetermined set temperature and the water in the storage tank 21 is lowered to the predetermined set water level, the circulation of the hot water to the hot water tank 31 is stopped via the three-way valve 35. Then, by opening the branch passage portion 45, hot water is drained from the hot water circulation passage 4, and low temperature clean water is introduced from the incoming passage 32 connected to the hot water circulation passage 4 into the forward passage portion 4a. The warm water drained at this time is a relatively small amount of warm water in the forward passage portion 4a, the heat exchange passage portion 11a, and the upstream return passage portion 4b.

  Next, the low temperature clean water that has flowed into the heat exchange passage portion 11 a through the incoming water passage 32 and the forward passage portion 4 a of the hot water circulation passage 4 exchanges heat with water vapor contained in the exhaust gas discharged from the off-gas combustion chamber 17. Then, the clean water is warmed, and the heated clean water is discharged to the outside (drain discharge portion 47) of the hot water storage unit 3 through the upstream return passage portion 4b and the branch passage portion 45.

  On the other hand, in the power generation unit 2, since the cooling capacity of the heat exchanger 11 is increased by introducing low temperature clean water, a larger amount of condensed water is generated than in the normal operation mode (a). This condensed water is sent to the treatment tank 24 of the water treatment means 19 through the recovery passage 23, processed in the treatment tank 24, and then stored in the storage tank 21.

  Thus, instead of hot water in the hot water storage tank 31 that has become fully charged, low-temperature clean water is used for heat exchange, thereby promoting heat exchange with steam and supplying a sufficient amount of condensed water. It can be recovered, and abnormal operation due to lack of water for reforming can be avoided. After that, when the water level of the storage tank 21 is restored to the set water level or higher, or when the temperature of the hot water in the hot water storage tank 31 is lower than the predetermined set temperature, the introduction of the clean water from the clean water source is stopped and the normal operation is performed. You may switch to mode (a).

  By the way, although the circulation pump 39 which circulates the hot water in the hot water circulation passage 4 in the power generation unit 2 is provided, the priming water to the circulation pump 39 in the initial operation after the construction of the fuel cell cogeneration system 1 is performed. When water filling is performed at the start of operation, control is performed in a priming operation mode (c) described below.

  As shown in FIG. 4, in this priming operation mode (c), the valve-opening state in which the port A and the port B of the three-way valve 35 of the hot water storage unit 3 are connected is set. That is, the three-way valve 35 is controlled to close the downstream return passage portion 4c and open the branch passage portion 45. In this state, when low temperature clean water is supplied from the clean water source to the incoming water passage 32, it flows into the heat exchange passage portion 11 a via the forward passage portion 4 a of the hot water circulation passage 4, and is connected to the upstream return passage portion 4 b, the branch passage. Since it is discharged to the outside of the hot water storage tank 31 through the section 45, it is possible to perform priming water to the circulation pump 39 at the initial stage of operation and water filling at the start of operation.

Next, the effect of the fuel cell cogeneration system 1 of the present invention will be described.
According to the above configuration, the hot water circulation passage 4 branches outside from the hot water circulation passage 4 on the downstream side of the heat exchange passage portion 11 a of the heat exchanger 11 (water recovery means) and the upstream side of the hot water storage tank 31 in the hot water circulation passage 4. A branch passage portion 45 is provided. When the hot water temperature in the hot water storage tank 31 is equal to or higher than a predetermined set temperature and the water in the storage tank 21 is lowered to the set water level, the circulation of the hot water to the hot water storage tank 31 is stopped and the branch passage portion 45 is provided. Since the hot water is drained from the hot water circulation passage 4 and low temperature clean water is introduced from the incoming water passage 32 connected to the hot water circulation passage 4, even when the hot water storage tank 31 becomes full. Condensed water can be easily recovered from the exhaust gas by exchanging heat between the low temperature clean water and the exhaust gas in the heat exchanger 11 while maintaining the hot water in the hot water storage tank 31 without draining. .

  Therefore, it is not necessary to provide an expensive radiator and it is not necessary to reheat the hot water in the hot water tank 31, so that the fuel cell cogeneration system 1 can be downsized, and the manufacturing cost and the operating cost can be reduced.

When the branch passage portion 45 is opened via the three-way valve 35, the clean water introduced from the water supply flows upstream of the hot water circulation passage 4 and passes through the heat exchange passage portion 11a of the heat exchanger 11 to pass the hot water circulation passage. 4, and is discharged to the outside from the branch passage portion 45, so that the priming water to the circulation pump 39 of the hot water circulation passage 4 can be easily performed, and the operation at the initial stage of operation can be simplified.
Further, for the convenience of the user, water filling at the start of operation after draining in the absence of a long period of time can be easily performed by the user himself / herself even if there is no dedicated maintenance staff to start the system.

  Next, a second embodiment in which the hot water storage unit 3 of the first embodiment is partially changed will be described. However, the same components as those in the first embodiment are denoted by the same reference numerals, the description thereof is omitted, and different configurations are described. Only the elements are described. As shown in FIG. 5, the hot water storage unit 3 </ b> A is provided with first and second on-off valves 61 and 62 instead of the three-way valve 35 of the first embodiment.

  As shown in FIG. 5, in the hot water storage unit 3 </ b> A, in the hot water circulation passage 4, on the downstream side of the heat exchange passage portion 11 a of the heat exchanger 11 and on the upstream side of the hot water storage tank 31, A branch passage portion 45 that branches to the outside is provided, and a first on-off valve 61 is provided in the branch passage portion 45. A second on-off valve 62 is provided in the downstream return passage portion 4c. The upstream return passage portion 4 b is alternatively connected to either the downstream return passage portion 4 c or the branch passage portion 45 by the first and second on-off valves 61 and 62.

  In the normal operation mode, when the hot water in the hot water tank 31 is circulated through the hot water circulation passage 4, the first opening / closing valve 61 is closed, the branch passage portion 45 is closed, and the second opening / closing valve 62 is opened. The upstream return passage 4b and the downstream return passage 4c are connected in a valve state to bring the hot water circulation passage 4 into a circulation state. In the water supply operation mode, when the branch passage portion 45 is opened, the first on-off valve 61 is opened, the branch passage portion 45 is opened, the second on-off valve 62 is closed, and the upstream side The return passage portion 4b and the branch passage portion 45 are connected to stop the circulation of hot water to the hot water tank 31.

Next, the operation of the fuel cell cogeneration system 1A will be described.
As shown in FIG. 6, the fuel cell cogeneration system 1 </ b> A includes a normal operation mode (a), a clean water introduction operation mode (b) similar to the first embodiment, and a priming water that performs priming water to the circulation pump 39. It has three operation patterns with the operation mode (c).

  As shown in FIG. 6, in the normal operation mode (a), the first on-off valve 61 of the hot water storage unit 3A is set to the closed state, and the second on-off valve 62 is set to the open state. That is, the first and second on-off valves 61 and 62 are controlled so that the branch passage portion 45 is closed and the hot water circulation passage 4 is circulated. Since the operation of the heat exchanger 11 in the normal operation mode (a) is the same as that of the first embodiment on both the hot water storage unit 3A side and the power generation unit 2 side, detailed description thereof is omitted.

  As shown in FIG. 6, in the clean water introduction operation mode (b), the first on-off valve 61 of the hot water storage unit 3A is set to the open state, and the second on-off valve 62 is set to the close state. When the hot water temperature in the hot water storage tank 31 is equal to or higher than a predetermined set temperature and the water in the storage tank 21 is lowered to a predetermined set water level, the circulation of the hot water to the hot water storage tank 31 is stopped and the branch passage portion 45 is opened. Then, hot water is drained from the hot water circulation passage 4, and low temperature clean water is introduced from the incoming water passage 32 connected to the hot water circulation passage 4. The warm water drained at this time is a relatively small amount of warm water in the forward passage portion 4a, the heat exchange passage portion 11a, and the upstream return passage portion 4b. Since the operation of the heat exchanger 11 in the water supply operation mode (b) is the same as that of the first embodiment on both the hot water storage unit 3A side and the power generation unit 2 side, detailed description thereof is omitted.

As shown in FIG. 6, in the priming operation mode (c), the first on-off valve 61 of the hot water storage unit 3A is set to the valve open state, and the second on-off valve 62 is set to the valve close state. That is, the first and second on-off valves 61 and 62 are controlled to close the downstream return passage portion 4c and open the branch passage portion 45. In this state, when low temperature clean water is supplied from the clean water source to the incoming water passage 32, it flows into the heat exchange passage portion 11 a via the forward passage portion 4 a of the hot water circulation passage 4, and is connected to the upstream return passage portion 4 b, the branch passage. Since it is discharged to the outside of the hot water storage tank 31 through the section 45, it is possible to perform priming water to the circulation pump 39 at the initial stage of operation and water filling at the start of operation.
Since other configurations and operations are the same as those of the first embodiment, description thereof is omitted.

  Next, a third embodiment in which the hot water storage unit 3 of the first embodiment is partially changed will be described. However, the same components as those in the first embodiment are denoted by the same reference numerals, the description thereof is omitted, and different configurations are described. Only the elements are described. As shown in FIG. 7, in addition to the main configuration of the first embodiment, the hot water storage unit 3B includes a bypass passage 65 branched from the branch passage portion 45B and an on-off valve 66 provided in the branch passage portion 45B. Yes.

  As shown in FIG. 7, in the hot water storage unit 3B, in the hot water circulation passage 4B, on the downstream side of the heat exchange passage portion 11a of the heat exchanger 11 and on the upstream side of the hot water storage tank 31, from the hot water circulation passage 4B to the branch portion 46B. A branch passage portion 45B branching to the outside is provided, and a three-way valve 35B is provided at a branch portion 46B where the branch passage portion 45B branches.

  The downstream end of the upstream return passage 4b is connected to the three-way valve 35B (port A), the upstream end of the branch passage 45B is connected to the three-way valve 35B (port B), and the upstream end of the downstream return passage 4c is The three-way valve 35B (port C) is connected, and the three-way valve 35B selectively connects the upstream return passage portion 4b to either the downstream return passage portion 4c or the branch passage portion 45B.

  Further, an opening / closing valve 66 is provided in the branch passage portion 45B. The forward passage portion branches from the branch passage portion 45B between the three-way valve 35B and the opening / closing valve 66 and is upstream of the heat exchange passage portion 11a of the hot water circulation passage 4B. A bypass passage 65 connected to 4a is provided.

  In the normal operation mode, when the hot water in the hot water storage tank 31 is circulated to the hot water circulation passage 4B, the port A-port C of the three-way valve 35B is opened, the on-off valve 66 is closed, and the upstream By connecting the side return passage portion 4b and the downstream side return passage portion 4c, the hot water circulation passage 4B is brought into a circulation state. In the water supply operation mode, when the branch passage 45B is opened, the port A-port B of the three-way valve 35B is opened, the on-off valve 66 is opened, and the upstream return passage 4b is opened. And the branch passage portion 45B are connected, the branch passage portion 45B is opened via the three-way valve 35B, and the circulation of hot water to the hot water storage tank 31 is stopped.

Next, the operation of the fuel cell cogeneration system 1B will be described.
As shown in FIG. 8, the fuel cell cogeneration system 1B includes a normal operation mode (a), a clean water introduction operation mode (b), and a priming water operation mode for executing priming water to the circulation pump 39 as in the first embodiment. In addition to (c), there are four operation patterns of a water supply introduction circulation operation mode (b ′) in which low temperature clean water is circulated in the hot water circulation passage 4B.

  As shown in FIG. 8, in the normal operation mode (a), the three-way valve 35B of the hot water storage unit 3B is set to an open state that connects between the ports A and C, and the on-off valve 66 is set to a closed state. . That is, the three-way valve 35B and the on-off valve 66 are controlled so that the branch passage portion 45B is closed and the hot water circulation passage 4B is circulated. Since the operation of the heat exchanger 11 in the normal operation mode (a) is the same as that of the first embodiment on both the hot water storage unit 3B side and the power generation unit 2 side, detailed description thereof is omitted.

  As shown in FIG. 8, in the water supply operation mode (b), the three-way valve 35B of the hot water storage unit 3B is set to an open state that connects between the ports A and B, and the on-off valve 66 is set to an open state. Set. When the hot water temperature in the hot water storage tank 31 is equal to or higher than the predetermined set temperature and the water in the storage tank 21 is lowered to the predetermined set water level, the circulation of the hot water to the hot water storage tank 31 is stopped and the branch passage portion 45B is opened. Then, hot water is drained from the hot water circulation passage 4B, and low temperature clean water is introduced from the incoming water passage 32 connected to the hot water circulation passage 4B. The warm water drained at this time is a comparatively small amount of warm water in the forward passage portion 4a, the heat exchange passage portion 11a, and the upstream return passage portion 4b. Can be mixed and drained. Since the operation of the heat exchanger 11 in the water supply operation mode (b) is the same as that of the first embodiment on both the hot water storage unit 3B side and the power generation unit 2 side, detailed description thereof is omitted.

  Here, after the circulation of the hot water to the hot water tank 31 is stopped and the branch passage 45B is opened, the hot water in the hot water circulation passage 4B is set at a predetermined set temperature by the inlet hot water temperature sensor 49a (or the outlet hot water temperature sensor 49b). When it is detected that the temperature is below (for example, 50 degrees or less), the operation mode is switched to a clean water introduction circulation operation mode (b ′) described below based on the detection signal from the inlet hot water temperature sensor 49a.

  As shown in FIG. 8, in the clean water introduction / circulation operation mode (b ′), the open / close valve 66 is switched to the closed state from the set state of the clean water introduction operation mode (b), and the low temperature from the incoming water passage 32 is reduced. Stop the introduction of clean water. Then, the hot water in the hot water circulation passage 4B, which has decreased due to the supply of low temperature clean water, bypasses the vicinity of the branch portion 46B of the branch passage portion 45B from the upstream return passage portion 4b by driving the circulation pump 39. It flows to the going passage part 4a via the passage 65, and hot water is circulated through the heat exchange passage part 11a to exchange heat with the exhaust gas.

  Thereafter, when it is detected by the inlet hot water temperature sensor 49a (or the outlet hot water temperature sensor 49b) that the hot water in the hot water circulation passage 4B is equal to or higher than a predetermined set temperature (for example, 90 degrees or higher), the water supply operation mode ( Switching to b), the on-off valve 66 is switched to the open state, hot water in the hot water circulation passage 4B is discharged through the branch passage portion 45B, and low temperature clean water is introduced from the water supply source. Also at this time, the hot water in the hot water circulation passage 4B and the clean water from the incoming water passage 32 can be mixed through the bypass passage 65 and drained from the branch passage portion 45B. On the other hand, as in the first embodiment, when the water level of the storage tank 21 of the power generation unit 2 recovers to a set water level or higher, or when the temperature of the hot water in the hot water storage tank 31 falls below a predetermined set temperature, the water source The introduction of clean water may be stopped and switched to the normal operation mode (a).

  As shown in FIG. 8, in the priming operation mode (c), the valve opening state is set to connect between the ports A and B of the three-way valve 35B of the hot water storage unit 3B, and the on-off valve 66 is set to the valve opening state. . That is, the three-way valve 35B and the on-off valve 66 are controlled so as to close the downstream return passage portion 4c and open the branch passage portion 45B. In this state, when low temperature clean water is supplied from the clean water source through the water intake passage 32, a part of the clean water is discharged to the outside of the hot water storage unit 3B through the bypass passage portion 45B via the bypass passage 65. The remainder of the clean water flows into the heat exchange passage portion 11a through the forward passage portion 4a of the hot water circulation passage 4B, and is discharged outside the hot water storage unit 3B through the upstream return passage portion 4b and the branch passage portion 45B. Therefore, priming water to the circulation pump 39 in the initial stage of operation and water filling at the start of operation can be performed.

Next, the effect of the fuel cell cogeneration system 1B of the present invention will be described.
According to said structure, since hot water and clean water can be mixed and discharged | emitted via the bypass channel 65, it is prevented that high temperature hot water is discharged | emitted directly from the inside of the hot water circulation channel | path 4B to high temperature. The danger associated with discharging hot water can be avoided. Moreover, since direct drainage of high-temperature hot water is prevented, a highly durable drain pipe is not required, and the manufacturing cost can be reduced.

Furthermore, when the hot water in the hot water circulation passage 4B becomes a predetermined temperature or less after the branch passage portion 45B is opened, the on-off valve 66 is closed and the introduction of clean water from the incoming water passage 32 is stopped. Since hot water is circulated through the bypass passage 65 to the heat exchange passage portion 11a, it is possible to effectively use low temperature clean water to eliminate waste water and to reduce operating costs.
Since other configurations and operations are the same as those of the first embodiment, description thereof is omitted.

Next, a mode in which the above embodiment is partially changed will be described.
[1] In the first to third embodiments, the three-way valves 35, 35B and the on-off valves 61, 62, 66 are provided with a flow rate adjusting function so that the amount of hot water discharged from the hot water circulation passages 4, 4B can be adjusted. May be. According to this configuration, it is possible to adjust the flow rate of clean water flowing through the heat exchange passage portion 11a, and efficiently exchange heat between clean water and water vapor, thereby eliminating waste of clean water.

[2] In the first to third embodiments, the predetermined set water level detected by the water level sensor 21a is set to a height position of about 1/5 of the storage tank 21, but it is particularly necessary to limit to this position. Alternatively, other height positions may be set. Further, the water level sensor 21a does not need to be limited to the liquid level of the stored water, but may be in the vicinity of the liquid level.

[3] In addition, those skilled in the art can implement the present invention in various forms added with various modifications without departing from the spirit of the present invention, and the present invention includes such modifications. is there.

1, 1A, 1B Fuel cell cogeneration system 2 Power generation unit 3, 3A, 3B Hot water storage unit 4, 4B Hot water circulation passage 5 Power generation module (fuel cell power generation section)
11 Heat exchanger (water recovery means)
11a Heat exchange passage portion 19 Water treatment means 21 Storage tank 22 Water supply means 31 Hot water storage tank 32 Water entry passages 35, 35B Three-way valves 45, 45B Branch passage portions 46, 46B Branch portions 61, 62 First and second on-off valves 65 Bypass Passage 66 on-off valve

Claims (4)

Water recovery means for condensing and recovering water vapor contained in the exhaust gas discharged from the fuel cell power generation unit, water treatment means for removing impurities of condensed water recovered by the water recovery means, and processing by the water treatment means A storage tank for storing the generated water, water supply means for supplying the water in the storage tank to the fuel cell power generation section, a hot water storage tank for storing hot water, and a heat exchange passage section for the water recovery means In a fuel cell cogeneration system comprising a hot water circulation passage for recovery and circulating hot water in the hot water storage tank to condense the water vapor,
In the hot water circulation passage, on the downstream side of the heat exchange passage portion of the water recovery means and the upstream side of the hot water storage tank, a branch passage portion branching from the hot water circulation passage to the outside is provided,
When the hot water temperature in the hot water tank is equal to or higher than a predetermined set temperature and the water in the storage tank is lowered to a predetermined set water level, the circulation of the hot water to the hot water tank is stopped and the branch passage portion is opened. A fuel cell cogeneration system characterized in that hot water is drained from the hot water circulation passage and low temperature clean water is introduced from a water inlet passage connected to the hot water circulation passage. A three-way valve is provided at a branching portion where the branching passage portion branches from the hot water circulation passage,
When circulating the hot water in the hot water tank to the hot water circulation passage, the branch passage portion is closed via the three-way valve to bring the hot water circulation passage into a circulation state,
2. The fuel cell core according to claim 1, wherein when the branch passage portion is opened, the branch passage portion is opened via the three-way valve and the circulation of hot water to the hot water storage tank is stopped. Generation system. An opening / closing valve is provided in the branch passage portion,
A bypass passage is provided between the three-way valve and the on-off valve that is branched from the branch passage portion and connected to the upstream side of the heat exchange passage portion of the hot water circulation passage,
When opening the branch passage portion, the open / close valve is opened,
3. The fuel cell cogeneration system according to claim 2, wherein hot water in the hot water circulation passage and clean water from the incoming passage are mixed and drained through the bypass passage.   When the hot water in the hot water circulation passage becomes a predetermined set temperature or less after the branch passage portion is opened, the on-off valve is closed and the introduction of clean water from the water inlet passage is stopped. The fuel cell cogeneration system according to claim 3, wherein hot water is circulated to the heat exchange passage through the bypass passage.