CN102628402A - Fuel cell and organic Rankine cycle combined power generating system based on LNG (Liquefied Natural Gas) cold energy utilization - Google Patents

Abstract

The invention discloses a fuel cell and organic Rankine cycle combined power generation system based on LNG cold energy utilization, including: a combined cycle system of a solid oxide fuel cell and a gas turbine, an organic Rankine cycle system, and LNG cold energy; The reacted fuel and air continue to burn in the post-combustion chamber to produce high-temperature and high-pressure gas, which enters the gas turbine to do work and output electric energy. The high-temperature exhaust gas from the gas turbine preheats air, fuel and water in sequence; , fuel and water, the waste heat of the medium and low temperature flue gas is recycled and converted into electric energy output to realize the cascade utilization of energy; The back pressure of the high-quality turbine is significantly reduced, the power output of the organic Rankine cycle is increased, and the cold energy of the LNG is recycled. The system of the invention can significantly improve energy conversion efficiency, reduce pollutant discharge and improve system performance.

Description

Combined power generation system of fuel cell and organic Rankine cycle based on cold energy utilization of LNG

technical field

The invention belongs to the field of high-temperature and medium-low temperature heat energy recovery and power engineering, and relates to a fuel cell and organic Rankine cycle combined power generation system based on cold energy utilization.

Background technique

Traditional fossil fuels, including coal, oil, and natural gas, have limited reserves, and most of them are used in the form of combustion, which not only makes energy utilization efficiency limited and leads to energy waste, but also inevitably produces a large amount of pollutant emissions. The solid oxide fuel cell is a power generation device that efficiently and environmentally friendly converts the chemical energy present in the fuel and the oxidant into electrical energy. The hydrogen in the fuel is directly converted into electrical energy by means of the electrolyte and oxygen in the air. It is a new power generation method that can well solve the contradiction between fossil fuel power generation efficiency and environmental pollution. In addition, the reaction temperature of the solid oxide fuel cell is relatively high, usually around 1000°C, and the waste heat discharged by it has a high grade, and there is a large space for recycling. Therefore, a solid oxide fuel cell and organic Rankine cycle combined power generation system based on LNG (liquefied natural gas, liquefied natural gas, liquefied natural gas) cold energy utilization is used to systematically combine fuel cell gas turbine combined cycle, organic Rankine cycle and LNG cold energy utilization. Integration can realize cascade utilization of energy and improve energy utilization efficiency.

Fig. 1 shows a schematic diagram of a combined cycle system of a solid oxide fuel cell and a gas turbine in the prior art. The air is sequentially pressurized by the air compressor 1', heated by the gas heater 4', and sent to the cathode of the solid oxide fuel cell 8'. At the same time, the fuel is boosted by the fuel compressor 2' and preheated by the gas heater 5'; the water is pressurized in the water pump 3', heated by the heater 6', and fully mixed with the preheated fuel in the mixer 7' After that, it is sent to the anode of the solid oxide fuel cell 8'. The fuel and oxygen undergo an electrochemical reaction in the solid oxide fuel cell 8' to output direct current, which is converted into alternating current output through the inverter 12'. On the other hand, the unreacted oxygen discharged from the fuel cell 8' and the unreacted combustible gas from the anode are sent to the combustion chamber 9' for combustion to generate high-temperature and high-pressure gas, which then enters the gas turbine 10' to do work and drive power generation Machine 11 ' generates electricity. Finally, the high-temperature exhaust gas from the gas turbine 10' is sequentially sent to the heater 4', heater 5', and heater 6' to complete the preheating of air, fuel and water respectively, and finally exit the system.

The above-mentioned system uses the high-temperature exhaust gas of the solid oxide fuel cell to generate electricity through the gas turbine, and uses the exhaust gas of the gas turbine to preheat fuel, air and water, recovers the heat energy of the high-temperature exhaust gas, and improves the efficiency of the system. However, due to the high exhaust temperature of the gas turbine, even after passing through the heat exchanger, there is still a large space for the utilization of medium and low temperature waste heat.

Medium and low temperature heat source power generation can adopt organic Rankine cycle technology. The organic Rankine cycle uses low-boiling organic working fluids, such as R123, R113, R245fa, isopentane, etc. The organic working medium is heated by the medium and low temperature waste heat in the waste heat boiler 1" to become saturated or superheated steam, which enters the organic working medium turbine 2" to do work, drives the generator 3" to output power generation, and the exhaust gas of the turbine 2" enters the condensation It is cooled to a liquid state in the tank 4", and then re-enters the waste heat boiler after being boosted by the booster pump 5", forming a complete cycle. The system is shown in Figure 2.

Contents of the invention

Aiming at the defects or deficiencies in the above-mentioned prior art, the purpose of the present invention is to provide a fuel cell and organic Rankine cycle combined power generation system based on LNG cold energy utilization, which utilizes the low-temperature waste heat of gas turbines and simultaneously utilizes the cold energy of liquefied natural gas. It can greatly increase the power generation capacity of the system, realize the cascade utilization of energy, improve the energy utilization rate, reduce atmospheric environmental pollution, and meet the needs of the country for energy conservation and emission reduction.

To achieve the above object, the present invention adopts the following technical solutions:

A fuel cell and organic Rankine cycle combined power generation system based on LNG cold energy utilization, including:

The combined cycle system of solid oxide fuel cells and gas turbines, in which the air is boosted by the primary air compressor, then enters the intercooler for cooling and cooling, then enters the secondary air compressor, and then is preheated by the first heater Enter the cathode electrode plate of the solid oxide fuel cell; after the fuel is heated up by the intercooler, it passes through the compressor and the second heater in turn; after the water is pressurized by the water pump, it is heated by the third heater, and then the preheated fuel Fully mixed in the mixer, and finally enter the anode electrode plate of the solid oxide fuel cell together; the unreacted oxygen discharged from the cathode of the solid oxide fuel cell and the unreacted combustible gas of the anode enter the after-combustion chamber connected to it Carry out complete combustion to produce high-temperature and high-pressure gas; the gas turbine is connected to the after-combustion chamber, and the high-temperature exhaust gas from the gas turbine is sent to the first heater, the second heater, and the third heater in sequence to preheat air, fuel and water in sequence;

The organic Rankine cycle system includes a waste heat boiler, an organic working fluid turbine, a condenser, and a booster pump connected in sequence, wherein one end of the booster pump is connected to the condenser, and the other end is connected to the waste heat boiler, and the waste heat The waste heat of the boiler comes from the high-temperature exhaust gas of the gas turbine and the medium-low temperature gas discharged after preheating air, fuel and water in sequence;

LNG cold energy, which is stored in the LNG storage tank, is connected to the condenser of the organic Rankine cycle system to condense the exhaust gas of the organic working fluid turbine, and then releases the cold energy through the cold storage heat exchanger, and finally, a part of it enters the room The cooler is used as fuel to supply the fuel cell, and the excess part is supplied to the gas pipeline network.

Preferably, the high-temperature and high-pressure gas generated by the afterburner enters the gas turbine to perform work, and drives the first generator connected to the gas turbine to generate electricity.

Preferably, the high-temperature exhaust gas from the gas turbine preheats air, fuel and water in sequence, and the discharged medium-low temperature gas enters the waste heat boiler, transfers energy to the organic working medium, and makes the organic working medium reach a saturated state or a superheated state, and then the working medium enters the organic working medium. Working in the working medium turbine to drive the second generator coaxially connected with the organic working medium turbine to generate electricity.

Preferably, the fuel and oxygen undergo an electrochemical reaction in the solid oxide fuel cell to output direct current, which is converted into alternating current output by an inverter connected to the solid oxide fuel cell.

Preferably, the organic Rankine cycle system can operate under subcritical conditions, using R123, R245fa, R600, R134a, isopentane, n-pentane, R113, R11, R152a, R236fa, R236ea or R141b refrigerant as the system operation working medium.

Preferably, the organic Rankine cycle system can operate under supercritical conditions, using carbon dioxide, R125 or R227ea as the working fluid for system operation.

Compared with the prior art, the fuel cell and organic Rankine cycle combined power generation system based on cold energy utilization of the present invention has at least the following advantages:

1) Significantly improved energy conversion efficiency and reduced pollutant emissions. After preheating fuel, air and water, the high-temperature exhaust of solid oxide fuel cells and gas turbines still has a high temperature level, which belongs to medium and low temperature waste heat. The organic Rankine cycle is used to recycle the medium and low temperature waste heat and convert it into The output of electric energy can greatly improve the energy conversion efficiency and reduce the discharge of pollutants into the environment. The working medium of the organic Rankine cycle is an organic working medium with a low boiling point. Compared with the conventional Rankine cycle, it has the advantages of small structure size, high efficiency, high cycle pressure, and the working medium will not enter the two-phase region during the turbine expansion process. It is suitable for Utilize waste heat at medium and low temperature.

2) Utilization of LNG cold energy and improvement of the performance of the entire combined power generation system. LNG is firstly used as a cold source of the power cycle to condense the exhaust gas of the organic working fluid turbine, which can significantly reduce the back pressure of the organic working fluid turbine and increase the power output of the organic Rankine cycle. The LNG coming out of the condenser still has a lot of cold energy. After the cold storage heat exchanger releases the cold energy, it enters the intercooler of the air compressor to cool the exhaust of the first-stage air compressor, thereby reducing the power consumption of the air compressor. .

Description of drawings

Fig. 1 is the structural block diagram of the combined cycle system of traditional solid oxide fuel cell and gas turbine;

Fig. 2 is a structural block diagram of a traditional organic Rankine cycle system;

Fig. 3 is a structural block diagram of the fuel cell and organic Rankine cycle combined power generation system based on cold energy utilization in the present invention.

Among them, the corresponding relationship between the labels and components in the figure is:

1 1st stage air compressor 2 Intercooler 3 Secondary air compressor 4 Compressor 5 water pump 6 1st heater 7 Second heater 8 The third heater 9 Mixer 10 Solid Oxide Fuel Cell 11 combustion chamber 12 gas turbine 13 The first generator 14 Inverter 15 Waste heat boiler 16 Organic working fluid turbine 17 Second generator 18 Condenser 19 booster pump 20 Cold storage heat exchanger 1' Air compressor 2' fuel compressor 3' water pump 4' 1st heater 5' Second heater 6' The third heater 7' Mixer 8' Solid Oxide Fuel Cell 9' combustion chamber 10' gas turbine 11' dynamo 12' Inverter 1" Waste heat boiler 2" Organic working fluid turbine 3” dynamo 4" Condenser 5" booster pump twenty one Gas pipeline network twenty two LNG storage tank

Detailed ways

A kind of embodiment of the system of the present invention is described in detail below in conjunction with accompanying drawing:

The invention relates to a solid oxide fuel cell and organic Rankine cycle combined power generation system based on LNG cold energy utilization, using hydrogen-rich fuel natural gas as the fuel of the solid oxide fuel cell, and organic working fluid as the working medium of the Rankine cycle power generation system A medium that can output electrical energy to the outside world. The invention consists of a solid oxide fuel cell, an afterburner, a gas turbine, a heat exchanger, a turbine, a condenser, a booster pump, a compressor, and the like. The unreacted combustible gas and air in the solid oxide fuel cell continue to burn in the afterburner to generate high-temperature and high-pressure gas, which enters the gas turbine to do work and output electric energy. The high-temperature exhaust of the gas turbine preheats air, fuel and water in sequence to realize gas Waste heat utilization: After preheating, the gas exhaust gas still has a high temperature level, which belongs to the medium and low temperature waste heat. The organic Rankine cycle is used to recycle the medium and low temperature waste heat and convert it into electric energy output to realize the cascade utilization of energy; for LNG Condensing the exhaust gas of the organic working fluid turbine as the cold source of the organic Rankine cycle can significantly reduce the back pressure of the organic working fluid turbine, increase the power output of the organic Rankine cycle, and utilize the cold energy of LNG at the same time. The LNG coming out of the condenser still has a lot of cold energy. After the cold storage heat exchanger releases the cold energy, part of it enters the intercooler of the air compressor to cool the exhaust of the first-stage air compressor, thereby reducing the consumption of the air compressor. work, and the excess is supplied to the gas pipeline network. The invented system can significantly improve energy conversion efficiency, reduce pollutant discharge and improve system performance.

Fig. 3 is a structural block diagram of a solid oxide fuel cell and organic Rankine cycle combined power generation system based on LNG cold energy utilization in the present invention, the system includes a primary air compressor 1, an intercooler 2, and a secondary air compressor 3. Fuel compressor 4, water pump 5, first heater 6, second heater 7, third heater 8, mixer 9, solid oxide fuel cell 10, afterburner 11, gas turbine 12, generator 1 13. Inverter 14, waste heat boiler 15, organic working medium turbine 16, generator II 17, condenser 18, booster pump 19, cold storage heat exchanger 20, gas pipeline network 21 and LNG storage tank 22.

The implementation plan is: after the air is boosted by the primary air compressor 1, it is cooled and cooled by the intercooler 2, enters the secondary air compressor 3, and then is preheated by the high-temperature exhaust of the gas turbine through the heater 16. Sent into the cathode electrode plate of the solid oxide fuel cell 10; the fuel (natural gas) after the temperature rise from the intercooler 2 passes through the fuel compressor 4 and the second heater 7 respectively; after the water is pressurized in the water pump 5, it passes through the first The third heater 8 heats, fully mixes with the preheated fuel in the mixer 9, and sends it to the anode electrode of the solid oxide fuel cell 10 together. The fuel and oxygen undergo an electrochemical reaction in the solid oxide fuel cell 10 to output direct current, which is converted into alternating current by the inverter 14 for output. Afterwards, the unreacted oxygen discharged from the cathode and the unreacted combustible gas from the anode enter the connected post-combustion chamber 11 for complete combustion to generate high-temperature and high-pressure gas, and the gas turbine 12 is connected to the post-combustion chamber 11 . The high-temperature and high-pressure gas enters the gas turbine 12 to perform work, and drives the first generator 13 connected to it to generate electricity. The high-temperature exhaust gas from the gas turbine 12 is sequentially sent to the first heater 6, the second heater 7, and the third heater 8 to preheat the air, fuel and water in sequence, and finally the discharged medium-low temperature gas enters the waste heat boiler 15 to convert the energy Transfer to the organic working medium, so that the organic working medium reaches a saturated state or a superheated state, and then the working medium enters the organic working medium turbine 16 to do work, driving the second generator 17 coaxially connected with it to generate electricity, and the organic working medium turbine 16 The exhaust gas is condensed into a liquid state by LNG in the condenser 18, and after being pressurized by the booster pump 19, it is sent to the waste heat boiler 15 to be heated by the exhaust gas of the gas turbine. Liquefied natural gas (LNG) enters the exhaust gas of the condensed organic working medium turbine 16 in the condenser 18 from the LNG storage tank 22 as a cold source, then enters the cold storage heat exchanger 20, releases cold energy, and then a part enters the air compressor The intercooler 2 cools the exhaust gas of the primary air compressor 1, and then sends it to the fuel compressor 4 as fuel for the solid oxide fuel cell 10; the excess natural gas discharged from the cold storage heat exchanger 20 is passed into the gas pipeline network .

The system of the present invention can not only improve the energy conversion efficiency, realize energy cascade utilization, but also utilize a large amount of cold energy rich in LNG to realize energy cascade utilization.

The above is only one embodiment of the present invention, not all or the only embodiment. Any equivalent transformation of the technical solution of the present invention adopted by those of ordinary skill in the art by reading the description of the present invention is the right of the present invention. covered by the requirements.

Claims (6)

1. A fuel cell and organic Rankine cycle combined power generation system based on LNG cold energy utilization, characterized in that: comprising a combined cycle system of a solid oxide fuel cell and a gas turbine, an organic Rankine cycle system and LNG cold energy; A combined cycle system of a solid oxide fuel cell and a gas turbine, wherein, after the air is boosted by the primary air compressor (1), it enters the intercooler (2) for cooling and cooling, and then enters the secondary air compressor (3), Then enter the cathode electrode plate of the solid oxide fuel cell (10) after being preheated by the first heater (6); after the fuel is heated up through the intercooler (2), it passes through the compressor (4) and the second heater ( 7); the water is pressurized by the water pump (5), heated by the third heater (8), fully mixed with the preheated fuel in the mixer (9), and finally enters the solid oxide fuel cell (10 ) of the anode electrode plate; the unreacted oxygen discharged from the cathode of the solid oxide fuel cell (10) and the unreacted combustible gas of the anode enter the afterburner (11) connected thereto for complete combustion, producing high-temperature and high-pressure gas, The gas turbine (12) is connected with the afterburner (11); the high-temperature exhaust gas from the gas turbine (12) is sent into the first heater (6), the second heater (7), and the third heater (8) in sequence, Preheating air, fuel and water in sequence; The organic Rankine cycle system includes a waste heat boiler (15), an organic working medium turbine (16), a condenser (18), and a booster pump (19) connected in sequence, wherein one end of the booster pump (19) It is connected to the condenser (18), and the other end is connected to the waste heat boiler (15). The waste heat of the waste heat boiler (15) comes from the high-temperature exhaust of the gas turbine (12) and the medium-low temperature gas discharged after preheating air, fuel and water in sequence ; LNG cold energy, which is stored in the LNG storage tank (22), is connected with the condenser (18) of the organic Rankine cycle system, and is used to condense the exhaust gas of the organic working fluid turbine (16), and then passes through the cold storage heat exchanger (20) release cold energy, and finally, a part enters the intercooler (2) to supply the fuel cell as fuel, and the excess part supplies the gas pipeline network (21). 2. The fuel cell and organic Rankine cycle combined power generation system based on LNG cold energy utilization according to claim 1 is characterized in that: the afterburner (11) produces high-temperature and high-pressure gas and enters the gas turbine (12) to do work, and drives and The first generator (13) connected to the gas turbine (12) generates electricity. 3. The fuel cell and organic Rankine cycle combined power generation system based on LNG cold energy utilization according to claim 1, characterized in that: the high-temperature exhaust of the gas turbine (12) is discharged after preheating air, fuel and water in sequence The low-temperature gas enters the waste heat boiler (15), transfers energy to the organic working medium, makes the organic working medium reach a saturated state or a superheated state, and then enters the organic working medium turbine (16) to do work, driving the organic working medium turbine (16 ) coaxially connected second generator (7) to generate electricity. 4. The fuel cell and organic Rankine cycle combined power generation system based on LNG cold energy utilization according to claim 1, characterized in that: the fuel and oxygen are chemically reacted in the solid oxide fuel cell (10) to output direct current externally , converted into AC output through an inverter (14) connected to the solid oxide fuel cell (10). 5. The fuel cell and organic Rankine cycle combined power generation system based on LNG cold energy utilization according to claim 1, characterized in that: the organic Rankine cycle system can operate under subcritical conditions, using R123, R245fa, R600 , R134a, isopentane, n-pentane, R113, R11, R152a, R236fa, R236ea or R141b refrigerant as the working fluid of the system. 6. The fuel cell and organic Rankine cycle combined power generation system based on LNG cold energy utilization according to claim 1, characterized in that: the organic Rankine cycle system can operate under supercritical conditions, using carbon dioxide, R125 or R227ea As the working fluid of the system operation.

Images