KR20200063894A - Apparatus for Circulating Heat Transfer Medium Using Exhaust Gas of Fuel Cell and Power Generation System Including That Apparatus - Google Patents

Abstract

According to one embodiment of the present invention, a power generation system capable of preventing pipes from being damaged by an increase and a decrease in volume due to a temperature change of a heat transfer medium includes: a fuel cell stack producing electric power with an electrochemical reaction; a heat collection unit increasing the temperature of a heat transfer medium by exchanging heat between the heat transfer medium and exhaust gas produced when electric power is generated from the fuel cell stack; a power generation cycle evaporating a working fluid by exchanging heat between the working fluid and the heat transfer medium with the increased temperature, and producing electric energy by using the evaporated working fluid; and a heat transfer medium circulating apparatus supplying the heat transfer medium with the increased temperature from the heat collection unit to the power generation cycle, and collecting the heat transfer medium with the lowered temperature from the power generation cycle to supply the heat transfer medium to the heat collection unit. The heat transfer medium circulating apparatus includes a flow rate control part changing the flow rate of the heat transfer medium so that the pressure of the heat transfer medium circulating apparatus is maintained at a reference pressure level when the volume of the heat transfer medium is changed by a temperature change of the heat transfer medium in the heat transfer medium circulating apparatus.

Description

{Apparatus for Circulating Heat Transfer Medium Using Exhaust Gas of Fuel Cell and Power Generation System Including That Apparatus}

The present invention relates to a power generation system, and more particularly, to a heat transfer medium that transfers heat to the working fluid of the power generation system.

An organic Rankine Cycle (ORC) power generation system (hereinafter referred to as an'ORC power generation system') generates power by evaporating a working fluid through heat energy generated from an external heat source or supplying heat energy to expand through a turbine. System.

In general, the ORC power generation system generates energy by recovering a heat source having a relatively low temperature range (60 to 200°C) using an organic medium as a working fluid. Recently, an ORC power generation system for exchanging working fluid using waste heat of a fuel cell has been proposed. The ORC power generation system will be described with reference to FIG. 1.

1 is a view showing the configuration of the ORC power generation system 100. 1, the ORC power generation system 100 includes a fuel cell stack 10, a heat recovery unit 14, and an organic Rankine cycle 20, the organic Rankine cycle 20 is an evaporator 22, It includes a turbine generator 24, a condenser 26, a transfer pump 28.

The fuel cell stack 10 generates electrical energy. Thermal energy is generated in the process of generating electrical energy by the fuel cell stack 210.

The heat recovery unit 14 recovers the heat of the exhaust gas discharged when generating electric energy from the fuel cell stack 10, and heats the heat transfer medium with the recovered heat. At this time, the heat transfer medium is supplied from the organic Rankine cycle 20 to the heat recovery unit 14 by the transfer pump 32.

The evaporator (Vaporizer) 22 of the organic Rankine cycle 20 vaporizes the working fluid supplied to the evaporator 22 into a gas using a heat transfer medium heated in the heat recovery unit 14. The turbine generator 24 is rotated by the working fluid supplied through the evaporator 22, and the shaft of the generator connected to the steam turbine shaft rotates together to generate electricity in the generator. The condenser 26 circulates the working fluid by rotating the turbine and condensing the working fluid out of the liquid into a liquid state and then supplying it back to the evaporator 14 through the transfer pump 28.

However, when the oil is used as a heat transfer medium in the ORC power generation system 100 as shown in FIG. 1, the volume of the oil changes depending on the temperature change. In particular, when the volume of the heat transfer medium expands, the heat transfer medium circulates. As the pressure inside the pipe increases, it not only damages the pipe, but also has a problem that operation control becomes unstable.

Korean Patent Publication No. 10-2013-0009268 (Invention name: Organic Rankine cycle power generation system using fuel cells, Publication date: January 23, 2013)

The present invention is to solve the above-mentioned problems, to provide a heat transfer medium circulating device using a fuel cell exhaust gas and a power generation system including the same that can prevent piping damage due to volume increase or decrease due to temperature change of the heat transfer medium The technical task.

In addition, another object of the present invention is to provide a heat transfer medium circulator using a fuel cell exhaust gas that can actively control the temperature of the heat transfer medium and a power generation system including the same.

In addition, another object of the present invention is to provide a heat transfer medium circulating device using a fuel cell exhaust gas in which a plurality of heat recovery units operating as heat sources are connected in parallel, and a power generation system including the same.

A power generation system according to an aspect of the present invention for achieving the above object, a fuel cell stack for producing electric power by an electrochemical reaction; A heat recovery unit that increases the temperature of the heat transfer medium by heat-exchanging the heat transfer medium with the exhaust gas generated during power generation in the fuel cell stack; A power generation cycle in which a working fluid is exchanged with a heat transfer medium having an increased temperature to vaporize the working fluid, and generate electric energy using the vaporized working fluid; And a heat transfer medium circulating device for supplying the heat transfer medium with the increased temperature from the heat recovery unit to the power generation cycle, and recovering the heat transfer medium with reduced temperature from the power generation cycle and supplying the heat transfer medium to the heat recovery unit, and the heat transfer medium. The circulating device controls the flow rate of changing the flow rate of the heat transfer medium so that the pressure of the heat transfer medium circulating device is maintained at a reference pressure when the volume of the heat transfer medium is changed according to the temperature change of the heat transfer medium in the heat transfer medium circulating device. It is characterized by including wealth.

The heat transfer medium circulating device using the fuel cell exhaust gas according to an aspect of the present invention for achieving the above object is heat-exchanged with the exhaust gas of the fuel cell stack to supply a heat transfer medium with an increased temperature from the heat recovery unit to the power generation cycle, and the power generation A heat transfer medium circulating unit for supplying a heat transfer medium whose temperature is reduced by heat exchange with the working fluid of the cycle from the power generation cycle to the heat recovery unit; And a flow rate control unit for changing the flow rate of the heat transfer medium so that the pressure of the heat transfer medium circulating portion is maintained at a reference pressure when the volume of the heat transfer medium is changed in accordance with the temperature change of the heat transfer medium in the heat transfer medium circulation part. It is characterized by.

According to the present invention, when the volume of the heat transfer medium expands as the temperature of the heat transfer medium increases, at least a portion of the heat transfer medium is extracted into the expansion tank, and when the volume of the heat transfer medium shrinks according to the temperature decrease of the heat transfer medium, the heat transfer medium in the expansion tank is removed. By supplementing it with a heat transfer medium circulating device, the effect of volume change of the heat transfer medium on the heat transfer medium circulating device is mitigated to protect the equipment and to stably control the power generation system.

In addition, according to the present invention, the heat transfer medium supplied from the heat recovery unit to the power generation cycle is bypassed through the first bypass pipe and supplied to the heat recovery unit to actively increase the temperature of the heat transfer medium within a short period of time, thereby rapidly increasing the temperature of the working fluid of the power generation cycle. It has the effect that can be increased quickly.

In addition, according to the present invention, when the heat transfer medium is supplied to the heat recovery unit through the recovery unit, at least a portion of the heat transfer medium is branched to the supply unit through the second bypass pipe, thereby actively reducing the temperature of the heat transfer medium within a short period of time to generate electricity. It has the effect of reducing the temperature of the working fluid in a short time.

In addition, according to the present invention, by connecting a plurality of heat recovery units connected 1:1 to a plurality of fuel cell stacks in parallel to a heat transfer medium circulator, the resistance to the exhaust gas flow, as well as the effect of the fuel cell stack due to the exhaust gas, are affected. It has the effect that it can be minimized.

1 is a view showing the configuration of a general ORC power system.
2 is a block diagram schematically showing a configuration of a power generation system including a heat transfer medium circulator using a fuel cell exhaust gas according to an embodiment of the present invention.
3 is a block diagram showing the configuration of the flow control unit shown in FIG. 2.
4 is a view showing an example of the implementation of the power generation system shown in FIG. 2.
5A to 5E are views showing the flow of the heat transfer medium according to the valve opening and closing state of the heat transfer medium circulating device.
6 is a view showing a configuration of a power generation system including a plurality of fuel cell stacks and a plurality of heat recovery units.

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

The meaning of the terms described in this specification should be understood as follows.

It should be understood that a singular expression includes a plurality of expressions unless the context clearly defines otherwise, and the terms "first", "second", etc. are intended to distinguish one component from another component, The scope of rights should not be limited by these terms.

It should be understood that terms such as “include” or “have” do not preclude the existence or addition possibility of one or more other features or numbers, steps, actions, components, parts or combinations thereof.

It should be understood that the term “at least one” includes all possible combinations from one or more related items. For example, the meaning of “at least one of the first item, the second item, and the third item” means 2 of the first item, the second item, and the third item, as well as each of the first item, the second item, and the third item. Any combination of items that can be presented from more than one dog.

2 is a block diagram schematically showing the configuration of a power generation system including a heat transfer medium circulator using a fuel cell exhaust gas according to an embodiment of the present invention.

As shown in FIG. 2, a power generation system (hereinafter referred to as a “power generation system” 200) including a heat transfer medium circulating device using fuel cell exhaust gas includes a fuel cell stack 210, a heat recovery unit 220, and heat transfer. It includes a medium circulating device 230, and a power generation cycle 240.

The fuel cell stack 210 produces electric power through an electrochemical reaction. Specifically, the fuel cell stack 210 generates electric power by the movement of electrons generated due to oxidation and reduction reactions of gases such as hydrogen and oxygen. In the process of generating electricity by the fuel cell stack 210, high-temperature exhaust gas corresponding to about 350 to 400°C is generated.

The heat recovery unit 220 increases the temperature of the heat transfer medium by heat-exchanging the high-temperature exhaust gas generated in the fuel cell stack 210 with the heat transfer medium. Specifically, the heat recovery unit 220 transfers the heat of the high-temperature exhaust gas corresponding to about 350 to 400°C discharged from the fuel cell stack 210 to the heat transfer medium flowing at a temperature of about 60 to 150°C so that the heat transfer medium is The temperature should be about 210~320℃ and the pressure of 4~7bar. The heat recovery unit 220 transfers heat to the heat transfer medium and discharges exhaust gas having a temperature of about 100 to 180°C.

In one embodiment, the heat recovery unit 220 may be installed in an exhaust duct (not shown) in communication with the outlet of the fuel cell stack 210. Accordingly, the heat recovery unit 220 recovers the high-temperature exhaust gas of the fuel cell stack 220 discharged through the exhaust duct, and heats the heat transfer medium with the heat of the recovered exhaust gas.

The heat transfer medium circulating device 230 transfers the heat transfer medium supplied from the heat recovery unit 220 at a temperature of about 210 to 320° C. and a pressure of 4 to 7 bar to the power generation cycle 240. In addition, the heat transfer medium circulating device 230 recovers the heat transfer medium having a reduced temperature through heat exchange with the working fluid in the power generation cycle 240 and supplies it to the heat recovery unit 220. The heat transfer medium circulates through the heat transfer medium circulating device 230.

In particular, the heat transfer medium circulating device 230 according to the present invention absorbs the volume change of the heat transfer medium when the temperature change and the volume change of the heat transfer medium occur due to absorption or release of heat.

To this end, the heat transfer medium circulating device 230 according to the present invention includes a heat transfer medium circulating unit 212 and a flow rate adjusting unit 214 as shown in FIG. 2. In addition, the heat transfer medium circulating device 230 according to the present invention may further include a first bypass unit 216 and a second bypass unit 218, as shown in FIG. 2.

First, the heat transfer medium circulation unit 212 includes a supply unit 310 and a recovery unit 320. The supply unit 310 connects between the heat recovery unit 220 and the power generation cycle 240, and receives heat from the heat recovery unit 220 to the exhaust gas of the fuel cell stack 210 to receive a heat transfer medium having an increased temperature to generate power generation cycles. (240).

The recovery unit 320 connects between the power generation cycle 240 and the heat recovery unit 220, and heat exchanges with the working fluid of the power generation cycle 240 to recover the heat transfer medium whose temperature has been reduced from the power generation cycle 240 to recover the heat. By supplying it to 220, the heat transfer medium is circulated.

In one embodiment, the supply unit 310 and the recovery unit 320 may be formed in a pipe shape as shown in FIG. 4.

In particular, as shown in FIG. 4, the recovery unit 320 includes a first pump P1, a first circulation valve 322, and a second circulation valve 324 for circulating the heat transfer medium. The first pump P1 pumps the heat transfer medium flowing through the recovery unit 320 and supplies it to the heat recovery unit 220 so that the heat transfer medium can be circulated. The first circulation valve 322 and the second circulation valve 324 are opened during normal operation of the system 200 so that the heat transfer medium can be circulated in the heat transfer medium circulation device 230.

Referring to FIG. 2 again, when the volume of the heat transfer medium is changed according to the temperature change of the heat transfer medium in the heat transfer medium circulation unit 212, the flow control unit 214 changes the pressure of the heat transfer medium circulation unit 212 to a reference pressure. Change the flow rate of the heat transfer medium to maintain it.

The reason for including the flow rate control unit 214 in the present invention is that when the heat transfer medium is made of oil, the oil is changed in volume according to the temperature change. This is because the volume expands or contracts, and as a result, the pipe pressure of the heat transfer medium circulating portion 212 through which the oil circulates is changed, which may damage the facility and may cause unstable operation control.

Therefore, the heat transfer medium circulating device 230 according to the present invention absorbs the volume change according to the temperature change of the heat transfer medium through the flow rate control unit 214. Hereinafter, the configuration of the flow control unit 214 according to the present invention will be described in more detail with reference to FIG. 3.

Figure 3 is a block diagram schematically showing the configuration of the flow control unit according to an embodiment of the present invention. As shown in Figure 3, the flow control unit 214 according to the present invention includes an expansion tank 330, a first flow control unit 340, a second flow control unit 350. In addition, the flow control unit 214 according to the present invention may further include a nitrogen injection unit 360, a storage tank 370, and a water level control unit 380.

The expansion tank 330 stores the heat transfer medium to be extracted from the heat transfer medium circulation unit 212 or supplied to the heat transfer medium circulation unit 212 when the volume of the heat transfer medium changes. That is, in the present invention, when the volume of the heat transfer medium increases due to an increase in the temperature of the heat transfer medium, at least a portion of the heat transfer medium is extracted from the heat transfer medium circulation unit 212 and stored in the expansion tank 330.

Conversely, in the present invention, when the volume of the heat transfer medium decreases due to a decrease in the temperature of the heat transfer medium, at least a portion of the heat transfer medium stored in the expansion tank 330 is supplemented with the heat transfer medium circulation part 212.

In one embodiment, the expansion tank 330 may be located at the front end of the first pump P1 to provide back pressure to the first pump P1, as shown in FIG. 4.

When the volume of the heat transfer medium increases, the first flow rate control unit 340 extracts at least a portion of the heat transfer medium from the heat transfer medium circulation unit 212 and supplies it to the expansion tank 330, and when the volume of the heat transfer medium decreases, the expansion tank 330 ) To supply the heat transfer medium stored in the heat transfer medium circulation unit 212. To this end, the first `flow control unit 340 includes a first connection pipe 410 and a first flow control valve 420 as shown in FIG. 4.

4, the first connection pipe 410 is branched at the first point T1 of the recovery part 320 and is connected to the expansion tank 330. When the volume of the heat transfer medium increases, the heat transfer medium extracted from the recovery unit 320 is supplied to the expansion tank 330 through the first connection pipe 410, and when the volume of the heat transfer medium decreases, the heat transfer medium stored in the expansion tank 330 A is supplied to the heat transfer medium circulation unit 212 through the first connection pipe 410.

When the volume of the heat transfer medium increases, the first flow rate control valve 420 allows the heat transfer medium to be supplied from the recovery unit 320 to the expansion tank 330 through the first connection pipe 410 and decreases the volume of the heat transfer medium. The heat transfer medium is supplied from the full tank 330 to the recovery unit 320 through the connection pipe 410. Specifically, before the volume increase or volume decrease of the heat transfer medium, the pressure of the recovery unit 320 and the expansion tank 330 is equilibrated to the reference pressure, but when the volume of the heat transfer medium increases or decreases, the recovery unit 320 ) And the pressure of the expansion tank 330 is different, so the heat transfer medium moves from the recovery unit 320 to the expansion tank 330 through the first flow control valve 420 or the recovery unit from the expansion tank 330 320).

Then, when the pressure of the recovery unit 320 and the expansion tank 330 is again in the equilibrium state through the movement of the heat transfer medium between the recovery unit 320 and the expansion tank 330, the recovery unit 320 and the expansion The movement of the heat transfer medium between the tanks 330 is stopped.

For example, when the power generation system 200 is initially started, the heat transfer medium is at 25° C., which is room temperature, but finally, the temperature rises to 210 to 320° C. through a preheating process. Accordingly, the heat transfer medium in the front end of the first pump (P1) undergoes a temperature change from approximately 25 ℃ to 320 ℃ density decreases and the volume expands. Accordingly, an unstable pressure is applied to the front end of the first pump P1, and thus the flow rate and pressure control of the heat transfer medium become unstable, and more pressure is applied to the heat transfer medium circulation device 230 to damage the facility. It becomes possible. In this case, the present invention supplies the heat transfer medium of the recovery unit 320 to the expansion tank 330 through the first flow control valve 420 so that the expansion tank 330 absorbs the volume change according to the temperature increase of the heat transfer medium. Do it.

As another example, the temperature of the heat transfer medium is reduced by reducing the amount of exhaust gas supplied from the fuel cell stack 210 when the system 200 is shut down, in which case the first pump ( At the front end of P1), the temperature of the heat transfer medium can be changed from 320°C to 25°C, thereby increasing the density and reducing the volume of the heat transfer medium, resulting in shrinkage in the heat transfer medium circulating device 230, and heat transfer. Similar to the case in which the volume of the medium expands, the control of the first pump P1 becomes unstable, so that a pressure shortage or bubbles may be generated in the front end of the first pump P1. In this case, the present invention supplements the heat transfer medium stored in the expansion tank 330 through the first flow control valve 420 with the recovery unit 320 so that the expansion tank 330 shrinks the volume according to the temperature reduction of the heat transfer medium. Try to absorb.

Meanwhile, the first flow control valve 420 is closed during maintenance of the system 200 so that the heat transfer medium stored in the expansion tank 330 is supplied to the recovery unit 320 through the first connection pipe 410. To be blocked. When the system 200 is restarted after the maintenance of the system 200 is completed, the first flow control valve 420 is opened again to allow the heat transfer medium to move between the recovery unit 320 and the expansion tank 330. The volume increase or volume reduction according to the temperature change can be alleviated.

The second flow control unit 350 moves the heat transfer medium in the heat transfer medium circulation unit 212 to the expansion tank 330 during maintenance of the system 200. To this end, the second `flow control unit 350 includes a second connection pipe 430 and a second flow control valve 440 as shown in FIG. 4.

4, the second connection pipe 430 is branched at the second point T2 of the recovery part 320 and is connected to the expansion tank 330. When the system 200 is maintained, the heat transfer medium in the heat transfer medium circulation part 212 is moved to the expansion tank 330 through the second connection pipe 430.

The second flow control valve 440 is maintained in a closed state when the system 200 is started, and is opened during maintenance of the system 200 so that the heat transfer medium in the heat transfer medium circulation part 212 is connected to the second connection pipe 430. Through it to be moved to the expansion tank 330. When the maintenance of the system 200 is completed, the second flow control valve 440 is closed again so that the heat transfer medium in the heat transfer medium circulation part 212 does not move to the expansion tank 330.

Meanwhile, the flow control unit 214 according to the present invention may further include a nitrogen injection unit 360. The nitrogen injection unit 360 injects nitrogen into the space except for the space in which the heat transfer medium is filled in the expansion tank 330 so that the pressure in the expansion tank 330 can be maintained at a reference pressure that is an equilibrium pressure. In addition, the nitrogen injection unit 360 may discharge nitrogen from the expansion tank 330 so that the expansion tank 330 can be maintained at a reference pressure that is a pressure in an equilibrium state when a heat transfer medium is supplied to the expansion tank 330. have.

As described above, in the present invention, by injecting nitrogen into the expansion tank 330 through the nitrogen injection unit 360, the expansion tank 330 can be maintained at a reference pressure (eg, positive pressure) state. It is possible to provide a constant back pressure at the front end of the first pump P1. In addition, the heat transfer medium stored in the expansion tank 330 is separated from the atmosphere through the nitrogen injected into the expansion tank 330 through the nitrogen injection unit 360, and the heat transfer medium is oxidized due to the contact of oxygen and heat transfer medium. By preventing this, it is possible to extend the service life of the heat transfer medium.

Meanwhile, the flow control unit 214 may further include a storage tank 370. The storage tank 370 is connected to the expansion tank 330 through a pipe (450 in FIG. 4) to store the heat transfer medium extracted from the expansion tank 330 or supplement the heat transfer medium in the expansion tank 330.

In one embodiment, the storage tank 370 removes some of the heat transfer medium from the expansion tank 330 so that the water level of the expansion tank 330 is equal to or less than the upper limit when the level of the expansion tank 330 exceeds a predetermined upper limit. Can be extracted and saved. In another embodiment, the storage tank 370 supplements the heat transfer medium with the expansion tank 330 so that the water level of the expansion tank 330 is higher than or equal to the lower limit when the water level of the expansion tank 330 becomes equal to or less than a predetermined lower limit. It might be.

In the above-described embodiment, the storage tank 370 extracts and stores a portion of the heat transfer medium from the expansion tank 330 to store the water level in the expansion tank 330 within the lower limit and the upper limit, or the expansion tank 330 It was described as supplementing the heat transfer medium. However, in a modified embodiment, the storage tank 370 may extract and store all heat transfer media present in the heat transfer media circulating apparatus 230 for maintenance of the heat transfer media circulating apparatus 230.

Meanwhile, the flow rate control unit 214 according to the present invention may further include a water level control unit 380. The water level control unit 380 monitors the water level of the expansion tank 330, and when the water level of the expansion tank 330 exceeds the upper limit, the second pump P2 is operated to move the heat transfer medium stored in the expansion tank 330. It moves to the storage tank 370, and when the heat transfer medium stored in the expansion tank 330 is below a lower limit, the heat transfer medium stored in the storage tank 330 is supplemented to the expansion tank 330.

Referring to FIG. 2 again, the heat transfer medium circulating device 230 according to the present invention may further include a first bypass unit 216.

When the temperature increase of the heat transfer medium is required, the first bypass unit 216 transfers at least a portion of the heat transfer medium supplied from the heat recovery unit 220 to the power generation cycle 240 through the supply unit 310 to the recovery unit 320. Bypass. The heat transfer medium bypassed through the first bypass unit 216 is re-supplied to the heat recovery unit 220 without passing through the power generation cycle 240, thereby raising the temperature.

To this end, the first bypass unit 216 may include a first bypass pipe 460 and a first bypass valve 470 as shown in FIG. 4.

The first bypass pipe 460 is branched from the first point P1 of the supply unit 310 and connected to the third point T3 of the recovery unit 320. The heat transfer medium supplied from the first bypass pipe 460 to the power generation cycle 240 through the supply unit 310 is directly supplied to the heat recovery unit 220 through the recovery unit 320.

The first bypass valve 470 is opened when the temperature increase of the heat transfer medium is required, so that at least a portion of the heat transfer medium supplied from the supply unit 310 to the power generation cycle 240 is recovered through the first bypass pipe 460 (320).

For example, when the temperature of the heat transfer medium is increased, the temperature of the heat transfer medium is preheated when the system 200 is initially operated. Specifically, the initial temperature of the heat transfer medium is about 25° C., which is the normal temperature. Since the temperature of the heat transfer medium required for heat exchange with the working fluid in the power generation cycle 240 is about 210 to 320° C., the temperature of the heat transfer medium is 210. The first bypass valve 470 is opened until it reaches ~320°C to raise the temperature of the heat transfer medium, and when the temperature of the heat transfer medium becomes 210 to 320°C, the first bypass valve 470 is closed to recover heat. All of the heat transfer media supplied from the unit 220 are supplied to the power generation cycle 240.

Meanwhile, the heat transfer medium circulating device 230 according to the present invention may further include a second bypass unit 218. The second bypass unit 2180 bypasses at least a portion of the heat transfer medium supplied to the heat recovery unit 220 through the recovery unit 320 to the supply unit 310 when a temperature reduction of the heat transfer medium is required. Since the heat transfer medium bypassed through the second bypass unit 218 does not pass through the heat recovery unit 220, the temperature does not rise, and thus the overall temperature of the heat transfer medium is reduced.

To this end, the second bypass unit 218 may include a second bypass pipe 480 and a second bypass valve 490 as shown in FIG. 4.

The second bypass pipe 480 is branched from the fourth point T4 of the recovery part 320 and connected to the second point P2 of the supply part 310. The heat transfer medium supplied to the heat recovery unit 220 through the recovery unit 320 is bypassed to the supply unit 310 by the second bypass pipe 480.

The second bypass valve 490 is opened when the temperature reduction of the heat transfer medium is required, so that at least a portion of the heat transfer medium supplied from the recovery unit 320 to the heat recovery unit 220 is supplied through the second bypass pipe 480. (310).

An example in which the temperature reduction of the heat transfer medium is required is a case in which the temperature reduction of the working fluid of the power generation cycle 240 is required during operation stoppage or maintenance. In this way, the temperature of the heat transfer medium can be appropriately reduced through the second bypass unit 218, thereby preventing carbonization due to excessive temperature increase of the heat transfer medium.

Referring back to FIG. 2, the power generation cycle 240 heats the high temperature heat transfer medium supplied from the heat transfer medium circulator 230 with the working fluid to vaporize the working fluid, and uses the vaporized working fluid to produce electrical energy. do. The power generation cycle 240 is used for heat exchange with the working fluid to supply the heat transfer medium that has become low temperature back to the heat recovery unit 220 through the heat transfer medium circulation device 230.

In one embodiment, the power generation cycle 240 shown in FIG. 2 may be an organic Rankine cycle using organic materials as a working fluid. For example, the organic working fluid may be cyclopentane or siloxane (Siloxane).

In accordance with this embodiment, the power generation cycle 240 is a compression unit 241, a preheating unit 242, an evaporation unit 243, an overheating unit 244, a power generation unit 245, as shown in FIG. And a condensing unit 246.

The power generation cycle 240 according to an embodiment of the present invention includes a compression unit 241, a preheating unit 242, an evaporation unit 243, an overheating unit 244, a power generation unit 245, and a condensation unit 246. It consists of a closed circuit connected sequentially, and the working fluid circulates through the closed circuit to produce energy through the power generation unit 245.

The compression unit 241 presses the working fluid. The compression unit 241 compresses the low-temperature working fluid supplied from the condensing unit 246, thereby increasing the pressure of the low-temperature working fluid. The compression unit 241 supplies the pressurized low-temperature working fluid to the preheating unit 242. In one embodiment, the compression unit 241 may be implemented as a pump (Pump, P) as shown in FIG.

The preheating unit 242 preheats the low-temperature working fluid supplied from the compression unit 241 through heat exchange. In one embodiment, the preheating unit 242 may preheat the low-temperature working fluid by exchanging heat between the high-temperature working fluid discharged from the power generation unit 245 and the low-temperature working fluid supplied from the compression unit 241. have.

The evaporation unit 243 changes the working fluid into a high temperature and high pressure gas by evaporating the working fluid by exchanging the working fluid preheated through the preheating unit 242 with a heat transfer medium discharged from the superheating unit 244. That is, the evaporation unit 243 changes the phase to a vapor state by exchanging the working fluid in the liquid phase having a temperature of 50 to 100° C. for heat exchange in the superheating unit 244 and then discharging it. The evaporation unit 243 discharges the heat transfer medium that has become low temperature after being used for heat exchange of the working fluid to the heat transfer medium circulation device 230.

The superheating unit 244 converts the saturated vapor phase-changed in the evaporation unit 243 into superheated steam by heating it using the heat transfer medium supplied from the heat transfer medium circulator 230 and supplies it to the power generation unit 255. That is, the working fluid that has been vaporized by the evaporation unit 243 absorbs heat from the heat transfer medium to become a superheated vapor having a temperature of approximately 180 to 240°C and a pressure of 18 to 27 bar.

The power generation unit 245 includes a turbine 245a and a generator 245b connected to the turbine 245a, as shown in FIG. 4. The turbine 224a is rotated by superheated steam supplied from the superheating unit 244 to convert chemical energy into mechanical energy. The generator 245b connected to the turbine 245a converts mechanical energy converted by the turbine 245a into electrical energy. The working fluid discharged from the power generation unit 245 is used for heat exchange in the preheating unit 242 and then provided to the condensation unit 246.

The condensing unit 246 condenses the working fluid provided from the preheating unit 242 using a cooling fluid supplied from a cooling tower (not shown). The condensing unit 246 supplies the condensed working fluid to the pressurizing unit 241.

Hereinafter, the flow of the heat transfer medium in the power generation system according to the present invention will be described with reference to FIG. 5.

5A is a view showing the flow of a heat transfer medium during preheating of the heat transfer medium during initial operation. At this time, as shown in FIG. 5A, the first circulation valve 322, the second circulation valve 324, the first flow control valve 420, and the first bypass valve 470 are opened and second during initial operation. The flow control valve 440 and the second bypass valve 490 are closed. Accordingly, during the initial operation, the heat transfer medium circulates in the order of heat recovery unit 220-supply unit 310-first bypass pipe 460-recovery unit 320-heat recovery unit 220. At this time, the flow rate of the heat transfer medium branched through the first bypass pipe 460 may be controlled by adjusting the opening degree of the first bypass valve 470 according to the temperature rise of the heat transfer medium.

In addition, since the first flow control valve 420 is maintained in an open state, when the heat transfer medium expands due to the temperature rise of the heat transfer medium, the heat transfer medium is recovered from the recovery unit 320 through the first flow control valve 420. It is supplied to the expansion tank 330.

5B is a view showing the flow of the heat transfer medium during normal operation of the power generation system 200. At this time, as shown in Figure 5b, the first circulation valve 322, the second circulation valve 324, and the first flow control valve 420 is opened and the second flow control valve 440, the first bi The pass valve 470 and the second bypass valve 490 are closed. Accordingly, during normal operation, the heat transfer medium is a heat recovery unit 220-a supply unit 310-an overheating unit 244 of the power generation cycle 240-an evaporation unit 243 of the power generation cycle 240-a recovery part 320- The heat recovery unit 220 is circulated in order.

5C is a view showing the flow of the heat transfer medium when the temperature reduction of the heat transfer medium is required when the power generation system 200 is stopped. At this time, as shown in Figure 5c, the first circulation valve 322, the second circulation valve 324, the first flow control valve 420, and the second bypass valve 490 is opened and the second flow rate The control valve 440 and the first bypass valve 470 are closed. Accordingly, the heat transfer medium is a supply unit 310-an overheating unit 244 of the power generation cycle 240-an evaporation unit 243 of the power generation cycle 240-a recovery part 320-a second bypass pipe 480- The supply unit 310 is circulated in order to decrease the temperature. At this time, since the first flow control valve 420 is maintained in an open state, when the heat transfer medium contracts due to a decrease in temperature of the heat transfer medium, the heat transfer medium is transferred from the expansion tank 330 through the first flow control valve 420. It is further supplied from the recovery unit 320.

5D is a view showing the flow of a heat transfer medium during maintenance of the power generation system 200. At this time, as shown in Figure 5d, the first circulation valve 322 and the second flow control valve 440 is opened, the second circulation valve 324, the first flow control valve 420, the first bi The pass valve 470 and the second bypass valve 490 are closed. Accordingly, the heat transfer medium is a heat recovery unit 220-a supply unit 310-an overheating unit 244 of the power generation cycle 240-an evaporation unit 243 of the power generation cycle 240-a recovery part 320-a second flow rate Control pipe 440-expansion tank 330 will be circulated in order. At this time, since the first flow control valve 420 is closed, movement of the heat transfer medium from the expansion tank 330 to the recovery unit 320 through the first flow control pipe 430 is stopped.

5E is a diagram showing the flow of the heat transfer medium when the power generation system 200 is restarted. At this time, as shown in Figure 5e, the second circulation valve 324 and the first flow control valve 420 is opened, the first circulation valve 322, the second flow control valve 440, the first bi The pass valve 470 and the second bypass valve 490 are closed. Accordingly, the heat transfer medium is a full tank 330-a first flow control pipe 430-a recovery unit 320-a heat recovery unit 220-a supply unit 310-an overheating unit 244 of the power generation cycle 240- The evaporation unit 243 of the power generation cycle 240 is moved.

6 is a block diagram schematically showing a configuration of a power generation system including a heat transfer medium circulator using fuel cell exhaust gas according to another embodiment of the present invention.

Unlike FIG. 2, the power generation system 600 according to FIG. 6 includes a plurality of fuel cell stacks 210a to 210n and a plurality of heat recovery units 220a to 220n. As described above, according to another embodiment of the present invention, a plurality of fuel cell stacks 210a to 210n and a plurality of heat recovery units 220a to 220n are connected to one heat transfer medium circulating device 230 and one power generation cycle 240. Since it is connected, the exhaust gas emitted from the plurality of fuel cell stacks 210a to 210n can be integrated and used as a heat source of the power generation cycle 240, so that each fuel cell stack 210a to 210n and the heat recovery units 220a to 220n ) It is possible to improve the power generation efficiency and economic efficiency than configuring the heat transfer medium circulating device 230 and one power generation cycle 240 for each.

In one embodiment, the plurality of fuel cell stacks 210a to 210n and the plurality of heat recovery units 220a to 220n may be connected 1:1, and the plurality of heat recovery units 220a to 220n circulate one heat transfer medium It may be connected to the device 230 in parallel.

Specifically, as illustrated in FIG. 6, heat transfer medium supply lines 222a to 222n connected to each heat recovery unit 220a to 220n are gathered in parallel and connected to the heat transfer medium circulating device 230. Accordingly, the heat transfer medium is supplied to the heat transfer medium circulating device 230 through the heat transfer medium supply lines 222a to 222n of each heat recovery unit 220a to 220n, then passed through the power generation cycle 240, and then circulated through the heat transfer medium again. After passing through the device 230 is supplied to each heat recovery unit (220a ~ 220n) through each heat transfer medium recovery line (224a ~ 224n).

As described above, in the present invention, a plurality of fuel cell stacks 210a to 210n and a plurality of heat recovery units 220a to 220n are connected 1:1, and a plurality of heat recovery units 220a to 220n are connected to a heat transfer medium circulating device 230 ) Is connected in parallel, the pressure drop when the exhaust gas discharged from each fuel cell stack (210a ~ 210n) passes through the heat recovery unit (220a ~ 220n) and the heat transfer medium supply line (222a ~ 222n), etc. This is because the fuel cell stacks 210a-210n may have an emergency stop because the fuel cell stacks 210a-210n are generated when they are greater than -70 mmAq.

Accordingly, in the present invention, the plurality of fuel cell stacks 210a to 210n and the plurality of heat recovery units 220a to 220n are connected 1:1, and the plurality of heat recovery units 220a to 220n heat transfer medium circulating device 230 ) In parallel to minimize the resistance of the exhaust gas flow and at the same time to minimize the effect of the fuel cell stack (210a ~ 210n) according to the flow of the exhaust gas.

On the other hand, as shown in Figure 6, the power generation system 600 according to another embodiment of the present invention is a heat transfer medium flow rate recovered by the heat recovery unit (220a ~ 220n) through each heat transfer medium recovery line (224a ~ 224n) In order to control the may further include a recovery valve (226a ~ 226n) installed on each heat transfer medium recovery line (224a ~ 224n). By adjusting the opening ratio of each of the recovery valves 226a to 226n, the temperature of the heat transfer medium supplied from each heat recovery unit 220a to 220n can be adjusted differently.

Those skilled in the art to which the present invention pertains will understand that the above-described present invention can be implemented in other specific forms without changing its technical spirit or essential features.

For example, in the above-described embodiment, the plurality of valves 322, 324, 420, 440, 470, and 490 included in the heat transfer medium circulating device 230 may have an opening degree adjusted through a separate controller (not shown). Can be. In addition, the water level control unit 380 may also be controlled through a controller.

Therefore, it should be understood that the embodiments described above are illustrative in all respects and not restrictive. The scope of the present invention is indicated by the following claims rather than the above detailed description, and it should be interpreted that all changes or modifications derived from the meaning and scope of the claims and equivalent concepts are included in the scope of the present invention. do.

200: waste heat power generation system 210: fuel cell stack
220: heat recovery unit 230: heat transfer medium circulator
240; Power Generation Cycle

Claims (18)

A fuel cell stack that produces electric power through an electrochemical reaction;
A heat recovery unit that increases the temperature of the heat transfer medium by heat-exchanging the heat transfer medium with the exhaust gas generated during power generation in the fuel cell stack;
A power generation cycle that heats the working fluid with the heat transfer medium having an increased temperature to vaporize the working fluid, and generates electrical energy using the vaporized working fluid; And
The heat recovery unit includes a heat transfer medium circulation ring device that supplies the heat transfer medium with the increased temperature to the power generation cycle, and recovers the heat transfer medium with reduced temperature from the power generation cycle and supplies it to the heat recovery unit.
The heat transfer medium circulating device,
When the volume of the heat transfer medium is changed in accordance with the temperature change of the heat transfer medium in the heat transfer medium circulating device comprising a flow control unit for changing the flow rate of the heat transfer medium so that the pressure of the heat transfer medium circulating device is maintained at a reference pressure Power generation system characterized by. According to claim 1,
The flow control unit,
An expansion tank in which a heat transfer medium to be extracted from the heat transfer medium circulating device or to be supplied to the heat transfer medium circulating device is stored; And
When the volume of the heat transfer medium increases, at least a portion of the heat transfer medium is extracted from the heat transfer medium circulating device and supplied to the expansion tank. When the volume of the heat transfer medium decreases, at least a portion of the heat transfer medium stored in the expansion tank is removed. Power generation system comprising a first flow control unit for supplying to the heat transfer medium circulating device. According to claim 2,
The flow control unit,
Further comprising a second flow control unit for extracting the heat transfer medium from the heat transfer medium circulator during maintenance and supplying it to the expansion tank,
The first flow control unit is a power generation system characterized in that when the restart after maintenance is completed, the heat transfer medium stored in the expansion tank is re-supplied to the heat transfer medium circulation device. According to claim 1,
The fuel cell stack and the heat recovery unit is a plurality,
The plurality of heat recovery units is a power generation system, characterized in that connected in parallel to the heat transfer medium circulating device. According to claim 1,
The heat transfer medium circulating device,
A supply unit supplying the heat transfer medium from the heat recovery unit to the power generation cycle;
A recovery unit that supplies the heat transfer medium discharged from the power generation cycle to the heat recovery unit; And
And further comprising a first bypass unit for bypassing at least a portion of the heat transfer medium supplied to the power generation cycle through the supply unit to the recovery unit so that the temperature of the heat transfer medium is increased. According to claim 1,
The heat transfer medium circulating device,
A supply unit supplying the heat transfer medium from the heat recovery unit to the power generation cycle;
A recovery unit that supplies the heat transfer medium discharged from the power generation cycle to the heat recovery unit; And
And a second bypass unit for bypassing at least a portion of the heat transfer medium supplied to the heat recovery unit through the recovery unit to the supply unit so that the temperature of the heat transfer medium is reduced. According to claim 1,
The power generation cycle is a power generation system, characterized in that the organic Rankine cycle to generate power using an organic working fluid. Supplying a heat transfer medium whose temperature is increased by heat exchange with the exhaust gas of the fuel cell stack to a power generation cycle, and supplying a heat transfer medium whose temperature is reduced by heat exchange with a working fluid of the power generation cycle from the power generation cycle to the heat recovery unit A heat transfer medium circulation unit; And
When the volume of the heat transfer medium is changed in accordance with the temperature change of the heat transfer medium in the heat transfer medium circulating portion, a flow control unit for changing the flow rate of the heat transfer medium so that the pressure of the heat transfer medium circulating portion is maintained at a reference pressure, Heat transfer medium circulator using fuel cell exhaust gas. The method of claim 8,
The flow control unit,
An expansion tank in which a heat transfer medium extracted from the heat transfer medium circulation part is stored;
When the volume of the heat transfer medium increases, at least a portion of the heat transfer medium is extracted from the heat transfer medium circulation portion and supplied to the expansion tank. When the volume of the heat transfer medium decreases, at least a portion of the heat transfer medium stored in the expansion tank is removed. A heat transfer medium circulating device using the fuel cell exhaust gas, characterized in that it comprises a first flow control unit for supplying to the heat transfer medium circulating device. The method of claim 9,
The heat transfer medium circulation unit includes a recovery unit for supplying the heat transfer medium from the power generation cycle to the heat recovery unit,
The first flow control unit,
A first connection pipe branched from the recovery part at a first point and connected to the expansion tank; And
When the volume of the heat transfer medium is increased, the heat transfer medium is supplied from the recovery unit to the expansion tank through the first connection pipe, and when the volume of the heat transfer medium is decreased, the expansion tank is connected to the recovery unit through the first connection pipe. It characterized in that it comprises a first flow control valve to supply a heat transfer medium circulating device using the fuel cell exhaust gas. The method of claim 8,
The flow control unit,
Further comprising a second flow control unit for supplying the heat transfer medium in the circulation section of the heat transfer medium to the expansion tank during maintenance,
The first flow control unit is a heat transfer medium circulating device using a fuel cell exhaust gas, characterized in that when the restart after maintenance is completed, the heat transfer medium stored in the expansion tank is re-supplied to the heat transfer medium circulation unit. The method of claim 11,
The second flow control unit,
A second connection pipe branched from the recovery part at a second point and connected to the expansion tank; And
And a second flow control valve that is opened during the maintenance to supply the heat transfer medium in the heat transfer medium circulation section to the expansion tank through the second connection pipe. Circulatory system. The method of claim 8,
The heat transfer medium circulation unit,
A supply unit supplying the heat transfer medium from the heat recovery unit to the power generation cycle; And
It includes a recovery unit for supplying the heat transfer medium to the power generation cycle,
The heat transfer medium circulating device further comprises a first bypass unit for bypassing at least a portion of the heat transfer medium supplied to the power generation cycle through the supply unit to the recovery unit so that the temperature of the heat transfer medium is increased. Circulation device for heat transfer medium using exhaust gas. The method of claim 13,
The first bypass unit,
A first bypass pipe branched from the first point of the supply part and connected to the third point of the recovery part; And
When the temperature increase of the heat transfer medium is required, characterized in that it comprises a first bypass valve that is opened to supply at least a portion of the heat transfer medium supplied from the supply unit to the power generation cycle through the first bypass pipe to the recovery unit. A heat transfer medium circulator using the fuel cell exhaust gas. The method of claim 8,
The heat transfer medium circulation unit,
A supply unit supplying the heat transfer medium from the heat recovery unit to the power generation cycle; And
It includes a recovery unit for supplying the heat transfer medium to the power generation cycle,
The heat transfer medium circulating device,
And a second bypass unit for bypassing at least a portion of the heat transfer medium supplied from the recovery unit to the heat recovery unit to the supply unit so that the temperature of the heat transfer medium decreases. Circulatory system. The method of claim 15,
The second bypass unit,
A second bypass pipe branched from the fourth point of the recovery part and connected to the second point of the supply part; And
When the temperature reduction of the heat transfer medium is required to include a second bypass valve that is opened to supply at least a portion of the heat transfer medium supplied from the recovery unit to the heat recovery unit through the second bypass pipe to the supply unit A heat transfer medium circulator using a fuel cell exhaust gas. The method of claim 8,
The flow control unit,
An expansion tank in which a heat transfer medium extracted from the heat transfer medium circulation part is stored; And
And a nitrogen injection unit for injecting nitrogen into a space other than the space filled with the heat transfer medium in the expansion tank so that the pressure of the expansion tank is maintained at the reference pressure. . The method of claim 8,
The flow control unit,
An expansion tank in which a heat transfer medium extracted from the heat transfer medium circulation part is stored;
A storage tank in which a heat transfer medium extracted from the expansion tank is stored or a heat transfer medium to be supplemented with the expansion tank is stored; And
When the amount of the heat transfer medium stored in the expansion tank exceeds a predetermined upper limit, it further comprises a water level control unit that stores the heat transfer medium stored in the expansion tank in the storage tank to adjust the level of the expansion tank. A heat transfer medium circulator using the fuel cell exhaust gas.

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