CN1246921C - Two stage cyclic preheating high temperature fuel battery power generating system - Google Patents

Abstract

The present invention relates to an electricity generation system of a two-stage circulating preheating high-temperature fuel cell, which comprises high temperature fuel cells and an auxiliary power generation system. The present invention is characterized in that cathode reaction gas and anode reaction gas of the fuel cell are independently preheated, and the preheated reaction gas is simultaneously provided for the two fuel cells. Fuel gas is heated by a waste heat boiler after being heated and desulfurized and is respectively sent to anodes of the primary fuel cell and the secondary fuel cell for generating power; gas exhausted from the anode of the two fuel cells is respectively cooled by a heat exchanger and makes hot water by a water heater; the cooled gas exhausted from the anodes of the fuel cells and partial initial fuel are jointly sent to the waste heat boiler for combustion, and generated high-temperature high-pressure steam pushes a steam turbine to run to drive an electric generator to generate electric energy. The present invention can directly use underground gas or waste gas exhausted by chemical plants, effectively enhance energy utilization rate and reduce the exhaust of greenhouse gas.

Description

Two-stage cycle preheating high temperature fuel cell power generation system

Technical field:

The invention relates to a power generation system, in particular to a two-stage cycle preheating high-temperature fuel cell power generation system using underground gas as fuel, and belongs to the technical field of energy utilization.

Background technique:

In order to protect the environment and improve energy efficiency, countries around the world urgently need to develop new power generation technologies. Fuel cell technology is most likely to enter the electricity market in the form of centralized and decentralized power sources. It converts the chemical energy of the fuel directly into electrical energy without being limited by the Carnot cycle. Among them, molten carbonate fuel cell (Molten Carbonate Fuel Cell; MCFC) and solid oxide fuel cell (Solid Oxidant Fuel Cell, SOFC) have the advantages of high efficiency and low pollution, and have attracted great attention.

At present, China's coal is mainly used for power generation, and the efficiency of thermal power generation is only 40%, and it pollutes the environment. Large-scale thermal power generation also has problems such as resource transportation and war damage. With the extensive application of new energy, distributed power generation will develop rapidly, and MW-level distributed power generation systems will be widely used. On the one hand, it can meet the electricity demand of small businesses, and on the other hand, it can reduce the impact of disasters such as earthquakes and wars on society.

Some fuel cell power generation systems have been announced abroad, most of which use natural gas as fuel and use fuel cells and gas turbines to form combined cycle power generation (Wei He. 69-76.). But on the one hand, gas turbines are expensive, and developing countries do not have this technology, so it is difficult to promote; on the other hand, because this cycle power generation method requires the system to reach a certain pressure, it has higher requirements on the performance of fuel cells .

Invention content:

The purpose of the present invention is to address the deficiencies of the prior art, to provide a two-stage cycle preheating high-temperature fuel cell power generation system using underground gas as fuel, to further improve the feasibility of fuel cell combined cycle power generation technology, and to reduce the technical difficulty of the system. It can be used as a small power station in areas with underground gas fields or help chemical plants and other units improve energy efficiency.

In order to achieve such a purpose, in the technical solution of the present invention, the two-stage cycle preheating high-temperature fuel cell power generation system consists of a two-stage high-temperature fuel cell, a cathode-anode cycle preheating system, a waste heat boiler, a steam turbine, a generator, a heat exchanger, etc. The equipment is composed of electric energy provided by fuel cells and generators. In addition to power generation, the system can also provide a certain amount of hot water for the outside world.

The power generation system of the present invention is mainly divided into two parts: a high-temperature fuel cell and an auxiliary power generation system. The fuel cell uses hydrogen, carbon monoxide and an oxidant to undergo an electrochemical reaction to generate electric energy, and the auxiliary power generation system uses a waste heat boiler and a steam turbine to generate electric energy.

The fuel is divided into two supply systems, one is sent to the inlet of the fuel cell anode after passing through the back of the fuel cell anode and the waste heat of the waste heat boiler, and the other is mixed with the exhaust gas of the fuel cell anode and then sent to the waste heat boiler for combustion. A desulfurization device is connected to the outlet end of the anode exhaust heat exchanger of the secondary fuel cell, and the other end of the desulfurization device is connected to the waste heat boiler. The preheated fuel is divided into two paths and sent to the anode inlets of the two-stage fuel cells respectively. The anode outlet of the secondary fuel cell is sequentially connected to a heat exchanger and a water heater for producing hot water, and the outlet end of the gas working medium side of the water heater is connected to the furnace of the waste heat boiler to further improve fuel utilization. One end of the steam turbine coaxially connected with the generator is connected to the steam heating pipe of the furnace, the other end is connected to the condenser, and then connected to the steam heating pipe in the waste heat boiler through the condensate pump.

The oxidant required by the fuel cell is also preheated by the two cathode exhaust heat exchangers and the waste heat boiler, and the preheated oxidant is divided into two paths and sent to the cathode inlet of the bipolar fuel cell, and an electrochemical reaction occurs inside the fuel cell. , and generate electricity and heat. The cathode outlet of the primary fuel cell is connected to a heat exchanger, which is used to recover the heat in the cathode exhaust gas of the primary fuel cell, and the exhaust gas is mixed with the exhaust gas of the cathode exhaust heat exchanger of the secondary fuel cell to heat hot water Heat exchanger for recovering heat energy and producing hot water.

When the system is working, the fuel gas is first sent to the heat exchanger to raise the temperature, and then to the desulfurization device for desulfurization. The desulfurized fuel is heated by the waste heat boiler and then sent to the anode of the fuel cell for power generation. The anode exhaust is cooled by the two-stage heat exchanger. Then a water heater is used to produce hot water. The cooled fuel cell anode exhaust gas and part of the original fuel are sent to the waste heat boiler for combustion. The heat of combustion is used to heat the water to generate high-temperature and high-pressure steam. The steam generated by the boiler drives the steam turbine to run. A generator produces electricity.

In addition, after a certain amount of air and _CO2 are compressed by the air compressor, they are sent to the heat exchanger at the cathode outlet of the fuel cell to be heated, and the heated cathode mixed gas is sent to the cathode inlet of the bipolar fuel cell respectively. After the gas is cooled by a heat exchanger, it is sent to the decarburizer, and the cathode exhaust gas after _CO2 removal is directly discharged into the atmosphere.

Finally, the electricity generated by the fuel cell and generator is sent to the user.

Compared with the prior art, the present invention has obvious progress and beneficial effects. The present invention adopts two MW level fuel cells, and preheats the fuel and oxidant through two-stage heat exchangers, realizing cascade utilization of energy; part of the fuel not used by the fuel cells is mixed with part of the original fuel to increase the calorific value After that, it is sent to the waste heat boiler for combustion, and the energy conversion efficiency is further improved through auxiliary power generation equipment.

The invention adopts the method of combined cycle power generation of molten carbonate fuel cell and steam turbine, can directly utilize underground coal gas or waste gas discharged from chemical plants, effectively improves energy utilization rate, and reduces emission of greenhouse gases.

Description of drawings:

Fig. 1 is a schematic diagram of the system structure of the present invention.

In Figure 1, 1 is the AC/DC converter, 2 is the primary fuel cell, 3 is the fuel compressor, 4 is the anode heat exchanger of the primary fuel cell, 5 is the cathode heat exchanger of the primary fuel cell, and 6 is the secondary 7 is the anode heat exchanger of the secondary fuel cell, 8 is the hot water heat exchanger, 9 is the desulfurization device, 10 is the waste heat boiler, 11 is the chimney, 12 is the condensate pump, 13 is the condenser, 14 is Steam turbine, 15 is a generator, 16 is a decarburizer, 17 is a hot water heat exchanger, 18 is a secondary fuel cell cathode heat exchanger, 19 is a feed water pump, and 20 is an air compressor.

Detailed ways:

In order to better understand the technical solution of the present invention, further description will be made below in conjunction with the accompanying drawings.

The system structure of the present invention is shown in Figure 1. The anode outlet of the primary fuel cell 2 is connected to the inlet of the anode heat exchanger 4 of the primary fuel cell, the anode outlet of the secondary fuel cell 6 is connected to the inlet of the anode heat exchanger 7 of the secondary fuel cell, and the outlets of the heat exchangers 4 and 7 are connected together To the inlet end of the hot water heat exchanger 8 , the outlet end of the hot water heat exchanger 8 is connected to the waste heat boiler 10 . The cathode outlet of the primary fuel cell 2 is connected to the inlet of the cathode heat exchanger 5 of the primary fuel cell, the cathode outlet of the secondary fuel cell 6 is connected to the inlet of the cathode heat exchanger 18 of the secondary fuel cell, and the outlets of the heat exchangers 5 and 18 are connected together To the inlet end of the decarburizer 16. The fuel compressor 3 is respectively connected to the waste heat boiler 10 and the inlet of the heat exchanger 4, the outlet of the heat exchanger 4 is connected to the inlet of the anode heat exchanger 7 of the secondary fuel cell, and the outlet of the heat exchanger 7 is connected to the desulfurization device 9 , the outlet of the desulfurization device 9 is connected to the preheating device of the waste heat boiler, and is respectively connected to the anode inlet ports of the primary and secondary fuel cells through its outlet. The outlet of the air compressor 20 is connected to the cathode heat exchanger 5 of the primary fuel cell, the outlet of the heat exchanger 5 is connected to the inlet of the cathode heat exchanger 18 of the secondary fuel cell, and the outlet of the heat exchanger 18 is connected to the preheater in the waste heat boiler 10. The heat device is connected to the cathode inlet port of the primary and secondary fuel cells respectively through its outlet. The outlets of the feed water pump 19 are connected to hot water users through the hot water heat exchangers 8 and 17 respectively. One end of the steam turbine 14 coaxially connected with the generator 15 is connected to the steam heating pipe of the waste heat boiler 10 , the other end is connected to the condenser 13 , and then connected to the steam heating pipe in the waste heat boiler 10 through the condensate pump 12 .

When working, the fuel gas is heated up through the two-stage heat exchanger, and after being purified by the desulfurization device 9, it enters the waste heat boiler 10 to continue heating. The heated fuel is sent to the anode of the primary and secondary fuel cells for power generation. Cool down through heat exchangers 4 and 7 to recover heat. The fuel that does not participate in the electrochemical reaction and part of the original fuel are sent to the waste heat boiler for combustion, and the heat generated is further utilized to generate electricity. The hot water produced in the hot water heat exchangers 8, 17 can provide hot water for users.

The advantage of the two-stage cycle preheating high-temperature fuel cell power generation system is that the high-temperature exhaust gas of each stage can be fully utilized, reducing the heat absorption of fuel and oxidant in the waste heat boiler, which is conducive to improving the energy utilization efficiency of the entire system. Since the fuel enters the two-stage fuel cells separately, the flow rate of the gas working fluid of each stage of the fuel cell is reduced, so the volume of the fuel cell stack can be reduced. In addition, since the power generation system is composed of two-stage fuel cells, the system has a strong variable load capability.

Claims (1)

1. A two-stage cycle preheating high-temperature fuel cell power generation system, characterized in that the anode outlet of the primary fuel cell (2) is connected to the inlet of the anode heat exchanger (4) of the primary fuel cell, and the anode of the secondary fuel cell (6) The outlet end is connected to the inlet of the secondary fuel cell anode heat exchanger (7), and the outlets of the primary fuel cell anode heat exchanger (4) and the secondary fuel cell anode heat exchanger (7) are jointly connected to the hot water heat exchanger ( 8), the outlet end of the hot water heat exchanger (8) is connected to the waste heat boiler (10), the cathode outlet end of the primary fuel cell (2) is connected to the inlet of the primary fuel cell cathode heat exchanger (5), and the secondary The cathode outlet port of the first-stage fuel cell (6) is connected to the inlet of the cathode heat exchanger (18) of the second-stage fuel cell, and the outlet of the cathode heat exchanger (5) of the first-stage fuel cell and the cathode heat exchanger (18) of the second-stage fuel cell are connected together To the inlet port of the decarburizer (16), the fuel compressor (3) is respectively connected to the inlet port of the waste heat boiler (10) and the primary fuel cell anode heat exchanger (4), and the primary fuel cell anode heat exchanger (4 ) is connected to the inlet of the secondary fuel cell anode heat exchanger (7), the outlet of the secondary fuel cell anode heat exchanger (7) is connected to the desulfurization device (9), and the outlet of the desulfurization device (9) is connected to The preheating device of the waste heat boiler is connected to the anode inlet port of the primary fuel cell and the secondary fuel cell respectively through its outlet, the outlet of the air compressor (20) is connected to the cathode heat exchanger (5) of the primary fuel cell, and the primary fuel cell The outlet of the cathode heat exchanger (5) is connected to the inlet of the secondary fuel cell cathode heat exchanger (18), and the outlet of the secondary fuel cell cathode heat exchanger (18) is connected to the preheating device in the waste heat boiler (10), and The outlets are respectively connected to the cathode inlet ports of the primary and secondary fuel cells, and the outlets of the feed water pump (19) are respectively connected to hot water users through the hot water heat exchangers (8, 17), and coaxially connected with the generator (15) One end of the steam turbine (14) is connected to the steam heating pipe of the waste heat boiler (10), the other end is connected to the condenser (13), and then connected to the steam heating pipe in the waste heat boiler (10) through the condensate pump (12).