JPH05299107A - System for utilizing exhaust heat of fuel battery and control method therefor - Google Patents

Abstract

PURPOSE:To avoid the redundant installation of cooling equipment and at the same time improve controllability of a refrigeration capacity in a system for utilizing the exhaust heat of a fuel battery in a single and double utility combined absorption type refrigerator. CONSTITUTION:A coolant guided into an evaporator 11 from the condenser 9 of an absorption type refrigerator 101 is controlled by bypassing to an absorber 10 on the basis of the temperature of water returned from a load to the evaporator 11. Thereby, when the load is smaller than the refrigeration ability, the refrigeration ability is controlled on quick response without controlling the heat of a driving heat source which is collected from a steam separator 2 in the cooling water system of a fuel battery body 1 and then brought into a high-temperature regenerator 7. The collection of condensed water required by a fuel battery 100 is performed by a low-temperature side exhaust heat collection heat exchanger 6 for collecting the low- temperature side exhaust heat from the fuel battery exhaust gas system to drive a low- temperature regenerator 8 and at the same time a condensed water collection heat exchanger 5 is provided in the exhaust gas system so as to obtain the necessary and sufficient amount of condensed water, and the cooling water to flow therethrough branches from the absorption type refrigerator cooling water circuit, so that the redundant installation of cooling equipment can be avoided.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fuel cell exhaust heat utilization system and its control method for recovering exhaust heat emitted from a fuel cell to drive an absorption refrigerator to obtain cold heat. is there.

[0002]

2. Description of the Related Art Generally, in order to obtain cold heat by utilizing exhaust heat emitted from a fuel cell, heat recovered from a cooling water system cooling the cell body of the fuel cell (exhaust heat on the high temperature side) is used. It drives a double-effect absorption refrigerator. FIG. 4 is a configuration diagram of a first conventional example showing a fuel cell exhaust heat utilization system using such a double-effect absorption refrigerator.

A fuel cell 100 'has a fuel cell body 1, a water vapor separator 2 and a fuel reformer 3, and city gas or the like is reformed by the fuel reformer 3 and supplied to the fuel cell body 1. Electricity is generated by electrochemically reacting hydrogen with oxygen in the air. Since this power generation generates heat, a fuel cell cooling water system is provided, and a steam separator 2 is connected to this for extracting exhaust heat as steam. This steam is supplied to the absorption refrigerating machine 101 'and also to the fuel reforming device 3 for reforming city gas and the like. Further, a heat exchanger 5 for collecting condensed water is provided in the exhaust gas system of the fuel cell 100 ′, and the condensed water is recovered from the exhaust gas and supplied to the steam separator 2 via the condensed water tank 4. An outdoor heat exchanger 26 is provided to pass cooling water through the condensed water recovery heat exchanger 5.

The absorption type refrigerator 101 'includes a high temperature regenerator 7,
It has a low temperature regenerator 8, a condenser 9, an absorber 10, an evaporator 11, and solution heat exchangers 12 and 13, and the cooling water cooled by the outdoor heat exchanger 20 is circulated to the condenser 9 and the absorber 10. Cold heat is obtained through the evaporator 11 by an absorption refrigeration cycle in which heat is exchanged. This cold heat is conveyed as cold water to an indoor unit (not shown). The high temperature side exhaust heat from the fuel cell 100 ', which is recovered as water vapor from the water vapor separator 2 of the fuel cell, is used as the high temperature regenerator 7 of the absorption refrigerator 101'.
Is being supplied to.

5, the low temperature side exhaust heat recovered from the exhaust gas system of the fuel cell 100 'is also supplied to the absorption refrigerator 101' by using the low temperature side exhaust heat recovery circuit as compared with the conventional system of FIG. It is the second prior art example which shows the fuel cell exhaust heat utilization system which performs single and double effect combined operation. In this conventional example, in addition to the configuration of the first conventional example, in the fuel cell exhaust gas system, a low temperature side exhaust heat recovery heat exchanger 6 that constitutes a low temperature side exhaust heat recovery circuit is provided and included in the exhaust gas. By cooling the condensed steam, condensing it and supplying it to the steam separator 2 of the fuel cell cooling water system, the steam required for the fuel reformer 3 is replenished, and the exhaust gas system exhaust collected at this time is exhausted. The heat is supplied to the low temperature regenerator 8 of the absorption refrigerator 101 '. With this configuration, the single-effect absorption cycle is driven simultaneously.

In any of the conventional systems shown in FIGS. 4 and 5,
When the load of the absorption chiller 101 ′ is changed, the refrigerating capacity is controlled by dividing the steam supplied to the high temperature regenerator 7 by the flow rate control three-way valve 24 and exchanging the outdoor heat through the heat recovery heat exchanger 21. The heat quantity radiated from the device 23 is recovered from the fuel cell 100 'by controlling the flow rate adjusting three-way valve 24 based on the return temperature of the cold water to the evaporator 11 detected by the driving steam control device 36 by the temperature sensor 33. Absorption refrigerator 10
This is performed by controlling the amount of heat supplied to 1 '(heat input control).

[0007]

As described above, in the conventional fuel cell exhaust heat utilization system according to the prior art, the load condition of the indoor unit to which the cold heat is supplied, that is, the load condition of the absorption chiller 101 'is changed. The capacity control of the absorption chiller 101 'is performed by heat input control that adjusts the steam consumption in the high temperature regenerator 7 or the heat input to the low temperature regenerator 8 to partially operate the absorption chiller 101'. The operation is performed under load.

On the other hand, since the operation of the fuel cell 100 'is controlled by the power demand regardless of the operation of the absorption refrigerator 101', what is the heat consumption amount as a heat source for driving the absorption refrigerator 101 '? Regardless, it is necessary to release the exhaust heat generated from the fuel cell 100 'to the outside according to the operating state of the fuel cell 100'. For this reason, when all of the exhaust heat released from the fuel cell main body 1 cannot be completely consumed by the absorption chiller 101 ', excess waste heat that cannot be recovered is processed.
In addition to the exhaust heat recovery circuit guided to the regenerator of the absorption refrigerator 101 ', a cooling circuit for discharging exhaust heat to the outside is required.
In the high temperature side exhaust heat recovery circuit for recovering exhaust heat from the fuel cell cooling water system, the cooling water of the fuel cell body 1 is pure water,
A closed circulation circuit is configured to avoid mixing of impurities, and it is necessary to install a heat radiation circuit by the outdoor heat exchanger 23 via the exhaust heat recovery heat exchanger 21 in order to radiate heat to the outside.

Further, in a low temperature side exhaust heat recovery circuit for recovering exhaust heat from the fuel cell exhaust gas system, water vapor contained in the exhaust gas is cooled, condensed and recovered, and then used as fuel cell cooling water to be used as a fuel cell main body. After cooling 1, the steam is supplied again to the fuel reformer 3 as steam, so that a condensed water recovery heat exchanger 5 is provided so that a necessary and sufficient amount of condensed water can be recovered, and the cooling water is passed through to perform outdoor heat exchange. It was necessary to radiate heat from the container 26 to the outside. As described above, the conventional system has a problem that the cooling equipment such as the outdoor heat exchanger is redundantly installed.

Further, by controlling the capacity of the absorption refrigerator according to load fluctuations, the high-temperature regenerator 7 and the low-temperature regenerator 8 having a large heat capacity are adjusted by adjusting the amount of heat for driving supplied to the high-temperature regenerator 7 and the low-temperature regenerator 8. Since it is performed by controlling the refrigerant regeneration capacity in the above, there is a problem that the capacity control of the evaporator 11 on the cold heat generation side becomes very slow.

The present invention has been made to solve the above problems, and an object thereof is to recover all the exhaust heat released in the cooling water system of the fuel cell regardless of the operating state of the absorption refrigerator. , When the load is smaller than the refrigerating capacity corresponding to the obtained amount of recovered heat, the system should be such that the refrigerating capacity is controlled without limiting the heat input of the driving exhaust heat, and the absorption type for the fuel cell exhaust gas system After recovering the exhaust heat that can be used in the refrigerator, by operating the condensed water recovery heat exchanger as necessary and sharing it with the outdoor heat exchanger of the absorption refrigerator, It is an object of the present invention to provide a fuel cell exhaust heat utilization system and a control method thereof which can avoid redundant installation and can be expected to improve the capability controllability of an absorption refrigerator.

[0012]

To achieve the above object, in the fuel cell exhaust heat utilization system of the present invention, the high temperature side generated in the fuel cell main body from the steam separator provided in the cooling water system of the fuel cell main body. The exhaust heat is recovered as water vapor and supplied to the high temperature regenerator of the absorption refrigerator, and the low temperature side exhaust heat is recovered from the exhaust gas by the low temperature side exhaust heat recovery heat exchanger provided in the exhaust gas system of the fuel cell. The high temperature regenerator, the low temperature regenerator, the condenser, the evaporator, the absorber and the condenser, the absorber are supplied to the low temperature regenerator of the absorption refrigerator by the high temperature side exhaust heat and the low temperature side exhaust heat. In a fuel cell exhaust fuel utilization system for driving an absorption refrigeration cycle of the absorption refrigerating machine configured to be an absorption refrigerating machine cooling circuit for cooling to obtain cold heat,
A refrigerant bypass circuit that bypasses a part of the refrigerant condensed in the condenser and sent to the evaporator to either the absorber, the high temperature regenerator, or the low temperature regenerator, and the refrigerant bypass circuit that divides the refrigerant bypass circuit. Refrigerant flow rate adjusting means for adjusting the refrigerant flow rate, a temperature sensor for measuring the inlet temperature of the heat carrier medium guided to the evaporator, and a refrigerating capacity for the refrigerant flow rate adjusting means based on the temperature detected by this temperature sensor. A condensate water recovery heat exchanger for condensing water vapor contained in the exhaust gas of the fuel cell, and a cooling device for controlling the condensate water recovery heat exchanger, the control device transmitting an operation signal for control. Cooling medium flow rate adjusting means for branching the medium from the absorption refrigerating machine cooling circuit and adjusting the amount of the cooling medium, condensed water of the low temperature side exhaust heat recovery heat exchanger and the condensed water recovery A condensed water tank for storing condensed water of an exchanger and supplying it to a necessary place, a liquid level sensor for detecting a liquid level height in the condensed water tank, and a cooling medium which receives a detection signal from the liquid level sensor A control device for transmitting an operation signal for maintaining the condensed water flow rate to a predetermined amount is provided to the flow rate control means.

Also, in the method of controlling the fuel cell exhaust heat utilization system of the present invention, the high temperature side exhaust heat generated in the fuel cell main body is recovered as steam from the steam separator provided in the cooling water system of the fuel cell main body. Is supplied to the high temperature regenerator of the absorption chiller, and the low temperature side exhaust heat is recovered from the exhaust gas by the heat exchanger for low temperature side exhaust heat recovery provided in the exhaust gas system of the fuel cell, and the low temperature regeneration of the absorption chiller is performed. And a high temperature side exhaust heat and a low temperature side exhaust heat to cool the high temperature regenerator, the low temperature regenerator, the condenser, the evaporator, the absorber and the condenser, and the absorption refrigerator. In a fuel cell exhaust fuel utilization system for obtaining cold heat by driving an absorption refrigeration cycle of the absorption refrigerating machine configured by a cooling circuit, first, regarding the refrigerating capacity control of the absorption refrigerating machine, first, between the load and the evaporator. About heat carrier medium Detecting a return temperature that changes according to the load, and then comparing the return temperature with a set value to determine whether the refrigerating capacity of the absorption chiller has become excessive with respect to the load. In the case where the refrigerating capacity of the absorption refrigerator is excessive, a part of the refrigerant sent from the condenser to the evaporator is bypassed to either the absorber, the high temperature regenerator or the low temperature regenerator. The control of the amount of exhaust heat on the high temperature side recovered from the cooling water system of the fuel cell is performed by first detecting the saturated steam pressure in the steam separator of the cooling water that has cooled the fuel cell, and then detecting the absorption. In order to maintain the temperature of the fuel cell at a value suitable for the power generation reaction, the saturated steam pressure in the steam separator is set to be constant independently of the refrigeration capacity control of the automatic refrigerator. Supply to the absorption chiller to maintain The exhaust gas amount of the water vapor is controlled to control the exhaust heat treatment of the exhaust gas system of the fuel cell.First, in the condensed water from the low temperature side exhaust heat recovery heat exchanger and the exhaust gas system of the fuel cell. It is detected whether the liquid level of the condensed water tank that collects the condensed water from the provided condensed water recovery heat exchanger and supplies it to the required place reaches a predetermined height, and then the liquid level reaches the predetermined height. If the condensed water amount is not sufficient, then it is branched from the absorption refrigerating machine cooling circuit so that the condensed water recovery heat exchanger operates only when the condensed water amount is insufficient. It is characterized in that the amount of the cooling medium to be flown is controlled so that the amount of the condensed water in the condensed water tank is maintained at a certain value or more.

[0014]

In the fuel cell exhaust heat utilization system and the control method thereof according to the present invention, the capacity control of the absorption refrigerator is performed by the bypass control of the refrigerant so that the drive is performed when the load is smaller than the refrigeration capacity of the absorption refrigerator. It is possible to reduce the refrigerating capacity without performing heat input control for limiting the steam consumption as a heat source, and to prevent the refrigerant in the evaporator from freezing.

Regarding the high temperature side exhaust heat amount of the cooling water system of the fuel cell, in order to keep the temperature of the cooling water for cooling the fuel cell main body constant and maintain the temperature suitable for the power generation reaction in the battery cell, the absorption refrigerator Regardless of the operation, the steam pressure in the steam separator of the fuel cell cooling water system is controlled to always be kept constant. Therefore, as the exhaust heat utilization form in the fuel cell exhaust heat utilization system of the present invention, the operation control of the fuel cell according to the power demand is given the highest priority, and the exhaust heat released there is taken into the absorption refrigerator and recovered. It is possible to control the capacity of the absorption chiller within a range that can be driven with a large amount of heat.

In the case of recovering low temperature side exhaust heat from the fuel cell exhaust gas system, the exhaust heat is recovered from the exhaust gas within the range in which the single-dual effect combined operation of the absorption refrigerator is possible. At the same time, it collects the cooling water for the fuel cell cooling water system and the condensed water necessary for steam generation in the fuel reformer. The exhaust gas system is equipped with a heat exchanger for recovering condensed water so that a necessary and sufficient amount of condensed water can be obtained from the exhaust gas in preparation for this fluctuation in the amount of condensed water, but the cooling medium passing through it is diverted from the absorption refrigerator cooling water circuit. To do. As a result, the present invention includes an exhaust heat recovery heat exchanger and an outdoor heat exchanger in the high temperature side exhaust heat recovery circuit, which were required to be redundantly installed in the conventional system in order to process the exhaust heat of the fuel cell. It is possible to omit the cooling equipment such as the heat radiation circuit and the outdoor heat exchanger that supplies the cooling water to the condensed water recovery heat exchanger.

Further, in the absorption refrigerator, by controlling the capacity thereof by bypass control of the refrigerant, the responsiveness of the refrigerating capacity control in the evaporator is higher than that in the conventional heat input control method of adjusting the input heat amount for driving. To improve controllability.

[0018]

Embodiments of the present invention will now be described in detail with reference to the drawings.

FIG. 1 shows a first embodiment of the present invention. In the figure, 1 is a fuel cell main body, 2 is a fuel cell cooling water vapor separator, 3 is a fuel reformer, 4 is a condensed water tank, 5 is a condensed water recovery heat exchanger, and 6 is a low temperature from the exhaust gas system. Side exhaust heat recovery heat exchanger, 27 is a pressure sensor, 28
Is a flow rate control two-way valve, 29 is an exhaust steam flow rate control device, 30 is a liquid level sensor, 37 is a fuel cell cooling water circulation pump, and the above devices are the main elements constituting the fuel cell 100. Further, 7 is a high temperature regenerator, 8 is a low temperature regenerator, 9 is a condenser, 10 is an absorber, 11 is an evaporator, 12 is a high temperature side solution heat exchanger, 13 is a low temperature side solution heat exchanger, and 14 is a solution. A pump, 15 is a refrigerant pump, 33 is a temperature sensor, 34 is a refrigerant flow rate adjusting three-way valve, 35 is a refrigerant flow rate control device, and the above-mentioned devices constitute the absorption refrigerator 101. Furthermore, 1
6 is a high temperature side exhaust heat recovery pump, 17 is a steam separator, 18 is a low temperature side exhaust heat recovery pump, 19 is a cooling water pump, 20 is an outdoor heat exchanger, 31 is a cooling water flow rate control three-way valve, and 32 is cooling. 1 shows a water flow controller. This embodiment will be described with reference to this figure.

First, in the structure of the fuel cell 100 side,
The fuel cell main body 1 generates electric power by inputting hydrogen and oxygen as fuel, and generates heat at the same time. The fuel reformer 3 produces hydrogen by reforming city gas and supplies it to the fuel cell body 1. The fuel cell body 1 is provided with a cooling water system pipe for cooling generated heat, and in the middle of the pipe,
A fuel cell cooling water circulation pump 37 and a water vapor separator 2 provided to supply liquid to the fuel cell cooling water circulation pump 37 are arranged. The water vapor separator 2 recovers heat generated in the fuel cell body as water vapor and absorbs the heat.
The high temperature side exhaust heat recovery circuit for supplying to the high temperature regenerator 7 of No. 01 is connected. The high temperature side exhaust heat recovery circuit is provided with a flow rate adjusting two-way valve 28 for controlling the steam pressure sent from the steam separator 2 to the fuel reformer 3, and the exhaust steam flow rate controller 29 controls the steam separator. Upon receiving a signal from the pressure sensor 27 for measuring the pressure inside 2, the operation signal is transmitted to the flow rate control two-way valve 28, and the steam pressure is controlled to be constant. The exhaust gas system from the fuel cell main body 1 and the fuel reformer 3 comprises a low temperature side exhaust heat recovery circuit for recovering exhaust heat from the exhaust gas and supplying it to the low temperature regenerator 8 of the absorption refrigerator 101. A low temperature side exhaust heat recovery heat exchanger 6 and a condensed water recovery heat exchanger 5 are provided. Condensed water collected in these heat exchangers 5 and 6 is supplied to the steam separator 2 via the condensed water tank 4.

The absorption refrigerating machine 101 drives the absorption refrigeration cycle for single and double effect use by the heat supplied from the high temperature side exhaust heat recovery circuit and the low temperature side exhaust heat recovery circuit connected to the fuel cell 100 to cool water. To make. This absorption refrigerator 101
In the above configuration, an absorption refrigerating machine cooling circuit is provided for cooling the condenser 9 and the absorber 10, and in order to release the heat received by the cooling to the atmosphere, the absorption refrigerating machine cooling circuit has outdoor heat. The exchanger 20 is connected via the cooling water pump 19. The structure of the absorption chiller 101 itself of this embodiment is basically the same as that of the conventional example of FIG. 5, but in this embodiment, a circuit for sending the refrigerant condensed in the condenser 9 to the evaporator 11 is used. A difference is that a refrigerant bypass circuit that bypasses a part of the refrigerant to the absorber 10 is provided on the way. A refrigerant flow rate control three-way valve 34 for adjusting the refrigerant flow rate branched to the refrigerant bypass circuit is used for connection of this refrigerant bypass circuit, and a refrigerant flow rate control device 35 is used to guide the evaporator 11 from an indoor unit (not shown). Based on the temperature detected by the temperature sensor 33 that measures the inlet temperature of the cold water, an operation signal for controlling the refrigerating capacity is transmitted to the refrigerant flow rate control three-way valve 34 to prevent the evaporator 11 from freezing due to the load state. ..

In the high temperature side exhaust heat recovery circuit, a high temperature side exhaust heat recovery pump 16 for returning the driving steam drain from the high temperature regenerator 7 of the absorption chiller 101 to the steam separator 2 of the fuel cell cooling water system, and this pump A steam separator 17 is provided in front of 16. In the low temperature side exhaust heat recovery circuit, the low temperature side exhaust heat recovered by the low temperature side exhaust heat recovery heat exchanger 6 provided for recovering the exhaust heat from the fuel cell exhaust gas system is subjected to low temperature regeneration of the absorption refrigerator 101. A low temperature side exhaust heat recovery pump 18 for circulating hot water supplied to the vessel 8 as hot water is provided. The cooling water flow to the condensed water recovery heat exchanger 5 for condensing the water contained in the fuel cell exhaust gas is divided by adjusting the cooling water flow rate by providing the cooling water flow rate three-way valve 31 in the absorption refrigerator cooling circuit. To do. The cooling water flow control device 32 receives the detection signal from the liquid level sensor 30 which detects the liquid level in the condensed water tank 4 which stores the condensed water, and adjusts the cooling water control three-way valve 31. Is transmitted to the cooling water flow rate control three-way valve 31 to maintain a predetermined amount.

A method of utilizing the exhaust heat recovered from the fuel cell 100 in the present embodiment having the above configuration will be described. The high temperature side exhaust heat recovered from the fuel cell cooling water system is sent through the steam separator 2 to the high temperature regenerator 7 as a heat source for driving the absorption refrigerator 101 in a vapor state. To the high temperature regenerator 7, the LiBr diluted solution having a low concentration due to the absorption of the refrigerant in the absorber 10 is sent by the solution pump 14, heated by the vapor recovered from the fuel cell 100, and the refrigerant evaporates. .. The generated refrigerant vapor gives heat to the diluted LiBr solution sent from the absorber 10 in the low temperature regenerator 8 similarly to the high temperature regenerator 7, and is condensed and then guided to the condenser 9. Further, to the low temperature regenerator 8, hot water as low temperature side exhaust heat recovered by the low temperature side exhaust heat recovery heat exchanger 6 from the fuel cell exhaust gas system is introduced together with the refrigerant vapor sent from the high temperature regenerator 7. The refrigerant is evaporated by heat exchange between these and the diluted LiBr solution sent from the absorber 10. The evaporated refrigerant is sent to the condenser 9, cooled by the cooling water of the absorption refrigerator cooling circuit, and condensed. The refrigerant condensed in the condenser 9 is sent to the evaporator 11, where it is sprayed on the surface of the heat transfer tube and takes heat from the water flowing in the tube to evaporate again. The water that has been deprived of heat and cooled is transported as cold water from the evaporator 11 to an indoor unit or the like.

On the other hand, the concentrated LiBr solution heated and concentrated in the high-temperature regenerator 7 and the low-temperature regenerator 8 is diluted with the LiBr solution delivered from the absorber 10 and the solution heat exchangers 12, 1.
After exchanging heat in 3, the refrigerant introduced into the absorber 10 and evaporated again in the evaporator 11 is absorbed there, and the absorbed heat is released to the absorption refrigerator cooling water circuit. The diluted LiBr solution that has absorbed the refrigerant and becomes low in concentration is used as the solution heat exchanger 1.
After heat exchange with the concentrated LiBr solution at 2 and 13, it is again distributed and sent to the high temperature regenerator 7 and the low temperature regenerator 8.

By repeating the above cycle, the exhaust heat of the fuel cell 100 is recovered from the cooling water system as steam which is exhaust heat on the high temperature side and from the exhaust gas system as hot water which is exhaust heat on the low temperature side, and these are collected as the heat source. The absorption refrigeration cycle is driven to supply cold heat.

Next, the capacity control of the absorption refrigerator 101 will be described. When the load on the absorption refrigerator 101 becomes smaller than the refrigerating capacity of the absorption refrigerator 101, the temperature of cold water returning to the evaporator 11 becomes lower than that of the indoor unit. Along with this, the refrigerant evaporation temperature in the evaporator 11 also gradually decreases.
It is necessary to prevent the freezing of the refrigerant in the evaporator 11 by controlling the capacity of the evaporator. With this lower limit value, the return temperature of cold water is detected by the temperature sensor 33, and the refrigerant flow rate adjusting three-way valve 34 is operated to bypass a part of the refrigerant supplied from the condenser 9 to the evaporator 11 to, for example, the absorber 10. To do. As a result, only the amount of the refrigerant is supplied to the evaporator 11 according to the external load, and as a result, the cooling capacity is controlled, and the operation can be continued without abnormally lowering the evaporation temperature. On the other hand, the refrigerant bypassed by the refrigerant flow rate control three-way valve 34 is mixed with the LiBr solution in the absorber 10 and then distributed by the solution pump 14 to the high temperature regenerator 7 and the low temperature regenerator 8 via the solution heat exchangers 12 and 13. To be done. Therefore,
The concentration of the diluted LiBr solution, the refrigerant circulation amount, etc. in the high temperature regenerator 7 and the low temperature regenerator 8 are the same as those in the rated operation, and the steam consumption and hot water consumption required for the refrigerant regeneration are the same. , The rated value is maintained.

In the fuel cell cooling water system, the fuel cell 1
When the operation of No. 00 is a partial load operation, the calorific value from the fuel cell body 1 fluctuates, but the cooling water temperature is kept constant so as to maintain the battery cells at a temperature suitable for the power generation reaction. The amount of vapor discharged to the outside of the fuel cell is controlled by the flow rate control two-way valve 28 so that the pressure in the water vapor separator 2 is kept constant during operation.

In the fuel cell exhaust gas system as well, the fuel cell 1
The required heat radiation amount for securing the necessary condensed water amount varies with the operating state of 00. Further, the exhaust heat uptake temperature for causing the low temperature regenerator 8 of the absorption refrigerator 101 to function as a regenerator in a single-effect cycle cools the absorber 10 and the condenser 9 of the absorption refrigerator 101. It changes under the influence of the temperature of the cooling water, that is, the outside air temperature. Therefore, the heat exchanger 6 for recovering exhaust heat on the low temperature side, which recovers the exhaust heat from the exhaust gas system of the fuel cell and supplies the recovered heat as hot water to the absorption refrigerator 101.
At, the temperature of the cooling water of the absorption refrigerator 101 rises,
When the temperature of the hot water supplied to the low temperature regenerator 8 rises, it becomes impossible to secure necessary and sufficient cooling water. In this case, the amount of condensed water is detected by the liquid level sensor 30 installed in the condensed water tank 4, and the cooling water amount adjusting three-way valve 31 is adjusted so that the condensed water amount in the condensed water recovery heat exchanger 5 is insufficient. Control to secure.

By carrying out the above-described absorption refrigeration functional force control by refrigerant bypass, fuel cell cooling water system radiating steam amount control, and cooling water amount control for condensate water recovery, power generation is performed with top priority given to the operation of the fuel cell. At the same time, all the exhaust heat that needs to be radiated is taken into the absorption refrigerator, and the capacity is controlled within the range of the capacity of the absorption refrigerator that can be driven by the obtained heat amount, and it is recovered from the fuel cell. The excess exhaust heat can be released to the atmosphere by using the absorption refrigerator cooling circuit, and the redundant installation of the outdoor heat exchanger for external heat dissipation and the exhaust heat recovery heat exchanger is unnecessary.

Further, by controlling the refrigerating capacity of the absorption refrigerating machine by the refrigerant bypass control, the responsiveness of the evaporator capacity to the load variation is better than that of the conventional heat input control to the regenerator, and the conventional It is possible to construct a system having higher controllability than that of the absorption refrigerator.

FIG. 2 shows a second embodiment of the present invention. In the present embodiment, instead of the refrigerant bypass circuit in the first embodiment, the refrigerant that evaporates in the high temperature regenerator 7 and further gives heat to the LiBr dilute solution in the low temperature regenerator 8 to be condensed and then returns to the condenser 9. By providing a refrigerant bypass circuit that bypasses a part of the refrigerant and returns it to the high temperature regenerator 7,
The capacity of the absorption refrigerator 101 is controlled by controlling the amount of refrigerant sent to. It is the absorber 10 that bypasses the refrigerant.
However, it is different from the first embodiment in that it is a high temperature regenerator 7, and the other configurations and operations of the system are common to the first embodiment.

FIG. 3 shows a third embodiment of the present invention. In the present embodiment, instead of the refrigerant bypass circuit in the first embodiment, by providing a refrigerant bypass circuit that bypasses a part of the refrigerant guided from the condenser 9 to the evaporator 11 to the low temperature regenerator 8, the evaporator is provided. The amount of the refrigerant sent to 11 is controlled to control the capacity of the absorption refrigerator 101. The refrigerant is bypassed not by the absorber 10 but by the low temperature regenerator 8, which is a difference from the first embodiment, and the other configurations and operations of the system are the same as those of the first embodiment.

[0033]

As is apparent from the above description, according to the fuel cell exhaust heat utilization system and the control method thereof of the present invention, the fuel cell operation according to the power demand is given the highest priority, and the fuel cell is generated together with the power generation. In the exhaust heat, the absorption refrigerating machine is controlled so that the total amount of heat released required for the amount of steam in the cooling water system is taken into the absorption refrigerating machine. By controlling to use a dedicated heat exchanger for collecting condensed water only when it is necessary to collect more condensed water, the heat exchanger for radiating heat in the cooling water system and exhaust gas system of the fuel cell becomes unnecessary, and the entire system is eliminated. It is possible to avoid the redundant installation of the outdoor heat exchanger that releases the exhaust heat of the outside, and can also serve as the outdoor heat exchanger of the absorption chiller.

By controlling the refrigerating capacity of the absorption chiller by the refrigerant bypass control, the responsiveness to the load is better than that of the heat input control which controls the amount of driving heat input to the regenerator. It is possible to build a system with high controllability.

[Brief description of drawings]

FIG. 1 is a configuration diagram showing a first embodiment of the present invention.

FIG. 2 is a configuration diagram showing a second embodiment of the present invention.

FIG. 3 is a configuration diagram showing a third embodiment of the present invention.

FIG. 4 is a configuration diagram showing a first conventional example.

FIG. 5 is a configuration diagram showing a second conventional example.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Fuel cell main body, 2 ... Steam separator, 3 ... Fuel reformer, 4 ... Condensed water tank, 5 ... Condensed water recovery heat exchanger, 6
... Heat exchanger for low temperature side exhaust heat recovery, 7 ... High temperature regenerator, 8 ... Low temperature regenerator, 9 ... Condenser, 10 ... Absorber, 11 ... Evaporator,
12 ... High temperature side solution heat exchanger, 13 ... Low temperature side solution heat exchanger, 14 ... Solution pump, 15 ... Refrigerant pump, 16 ... High temperature side exhaust heat recovery pump, 17 ... Steam separator, 18 ... Low temperature side exhaust heat Recovery pump, 19 ... Cooling water pump, 20 ... Outdoor heat exchanger, 27 ... Pressure sensor, 28 ... Flow control two-way valve, 29
... Exhaust steam flow rate control device, 30 ... Liquid level sensor, 31 ... Cooling water flow rate control three-way valve, 32 ... Cooling water flow rate control device, 33
... Temperature sensor, 34 ... Refrigerant flow rate adjusting three-way valve, 35 ... Refrigerant flow rate control device, 37 ... Fuel cell cooling water circulation pump.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Kazuo Oshima 1-1-6 Uchisaiwaicho, Chiyoda-ku, Tokyo Nihon Telegraph and Telephone Corporation (72) Inoue Tsuneo Uekusa 1-1-6 Uchiyuki-cho, Chiyoda-ku, Tokyo Nihonhon Telegraph and Telephone Co., Ltd. (72) Kenji Machizawa, Inventor Kenjicho, Tsuchiura-shi, Ibaraki Prefecture, 603 Kuchitate Factory, Hitachi Co., Ltd. Inside the Tsuchiura Plant of the Works (72) Inventor Kyoji Kono 4-6, Surugadai Kanda, Chiyoda-ku, Tokyo Inside Hitachi, Ltd.

Claims (2)

[Claims] 1. A high temperature side exhaust heat generated in the fuel cell main body is recovered as steam from a steam separator provided in a cooling water system of the fuel cell main body and supplied to a high temperature regenerator of an absorption refrigerator.
Further, the low temperature side exhaust heat recovery heat exchanger provided in the exhaust gas system of the fuel cell recovers the low temperature side exhaust heat from the exhaust gas and supplies it to the low temperature regenerator of the absorption refrigerating machine. Absorption of the absorption chiller constituted by the high temperature regenerator, the low temperature regenerator, the condenser, the evaporator, the absorber and the absorption chiller cooling circuit for cooling the absorber by the side exhaust heat. In a fuel cell exhaust heat utilization system for driving a refrigeration cycle to obtain cold heat, a part of the refrigerant condensed in the condenser and sent to the evaporator is either the absorber, the high temperature regenerator or the low temperature regenerator. A refrigerant bypass circuit for bypassing the refrigerant, a refrigerant flow rate adjusting means for adjusting the flow rate of the refrigerant branched to the refrigerant bypass circuit, a temperature sensor for measuring an inlet temperature of a heat carrier medium guided to the evaporator, and this temperature sensor. Inspected And a control device for transmitting an operation signal for controlling the refrigerating capacity to the refrigerant flow rate control means based on the temperature output, and for collecting condensed water for condensing water vapor contained in the exhaust gas of the fuel cell. A heat exchanger, cooling medium flow rate adjusting means for branching the cooling medium to the condensed water recovery heat exchanger from the absorption refrigerating machine cooling circuit to adjust the amount of the cooling medium, and the low temperature side exhaust heat recovery heat A condensed water tank that stores condensed water of an exchanger and condensed water of the condensed water recovery heat exchanger and supplies the condensed water to a necessary place, a liquid level sensor that detects a liquid level in the condensed water tank, and this liquid A fuel cell exhaust heat utilization system comprising: a control device that receives a detection signal from a surface sensor and transmits an operation signal for maintaining the amount of condensed water at a predetermined amount to the cooling medium flow rate adjusting means. 2. A high temperature side exhaust heat generated in the fuel cell main body is recovered as steam from a steam separator provided in a cooling water system of the fuel cell main body and supplied to a high temperature regenerator of an absorption refrigerator.
Further, the low temperature side exhaust heat recovery heat exchanger provided in the exhaust gas system of the fuel cell recovers the low temperature side exhaust heat from the exhaust gas and supplies it to the low temperature regenerator of the absorption refrigerating machine. Absorption of the absorption chiller constituted by the high temperature regenerator, the low temperature regenerator, the condenser, the evaporator, the absorber and the absorption chiller cooling circuit for cooling the absorber by the side exhaust heat. In a fuel cell exhaust heat utilization system that drives a refrigeration cycle to obtain cold heat, the refrigerating capacity control of the absorption refrigerating machine first changes according to the load of a heat carrier medium between the load and the evaporator. The return temperature is detected, and then the return temperature is compared with a set value to determine whether the refrigeration capacity of the absorption refrigerator is excessive with respect to the load. If the refrigeration capacity becomes excessive, the steam is removed from the condenser. By controlling a part of the refrigerant sent to the generator by bypassing the absorber, the high temperature regenerator or the low temperature regenerator, and controlling the amount of high temperature side exhaust heat recovered from the cooling water system of the fuel cell. First, the saturated water vapor pressure in the water vapor separator of the cooling water that has cooled the fuel cell is detected, and then the temperature of the fuel cell is used for power generation reaction independently of the refrigerating capacity control of the absorption refrigerator. The amount of exhaust steam of the steam supplied to the absorption refrigerator is controlled so as to maintain the saturated steam pressure in the steam separator so that the temperature of the cooling water becomes constant in order to maintain a suitable value. For exhaust heat treatment control of the exhaust gas system of the fuel cell, first, from the condensed water from the low temperature side exhaust heat recovery heat exchanger and the condensed water recovery heat exchanger provided in the exhaust gas system of the fuel cell Collect the condensed water of It is detected whether the liquid level of the condensed water tank to be supplied to has reached a predetermined height, then if the liquid level has not reached the predetermined height, it is determined that the amount of condensed water is insufficient, and then The amount of the condensed water in the condensed water tank is controlled to a constant value by controlling the amount of the cooling medium branched from the absorption refrigerating machine cooling circuit so that the condensed water recovery heat exchanger operates only when the amount of the condensed water is insufficient. A method for controlling a fuel cell exhaust heat utilization system, characterized in that the above method is performed.