Internal combustion engine-steam combined cycle power generation system for chemical waste gas recovery

Abstract

The invention provides an internal combustion engine-steam combined cycle power generation system for chemical waste gas recovery. The problems that in a traditional scheme, available energy is little, and energy quality is low are solved. Based on an internal combustion engine low-temperature combustion technology, heat transfer loss of a combustion chamber is reduced, waste heat energy taken away by cooling liquid is minimum, and the problem that waste heat available energy of an internal combustion engine is small is solved. Based on the ultra-lean combustion technology of the internal combustion engine, the exhaust oxygen content is increased, the exhaust temperature is reduced, and the input boundary of a downstream waste heat boiler is met. Based on the waste heat boiler graded afterburning technology, oxygen-enriched exhaust gas of an upstream internal combustion engine serves as combustion-supporting air and over-fire air of a boiler burner, graded afterburning is implemented, and the energy quality of waste heat of the internal combustion engine is greatly improved. Based on implementation of the three key technologies, the system heat efficiency of the internal combustion engine-steam combined cycle can be remarkably improved, and the energy efficiency level similar to that of the gas turbine-steam combined cycle is achieved.

Description

Technical Field

[0001] This invention belongs to the field of gas-fired power generation technology, and specifically provides an internal combustion engine-steam combined cycle power generation system for chemical waste gas recovery. Background Technology

[0002] Chemical production processes generate large amounts of waste gas, which often contains combustible substances such as hydrocarbons, carbon monoxide, hydrogen, and volatile organic compounds. Directly releasing these combustible substances into the atmosphere with the waste gas would result in resource waste and environmental pollution. Using chemical waste gas as fuel for internal combustion engines to generate electricity not only allows for efficient energy utilization but also contributes to achieving environmentally friendly production and sustainable development goals.

[0003] The proportion of chemical energy of fuel input into an internal combustion engine that is converted into mechanical energy output is generally no more than 45%, with the remaining energy entering the environment as waste heat through exhaust, coolant, and engine radiation. There are generally two main technical routes for recovering waste heat from internal combustion engines: combined heat and power (CHP) and combined cycle. CHP recovers waste heat from the internal combustion engine through the heating system, effectively improving the system's thermal efficiency. However, since the heating system itself does not output mechanical power, CHP does not improve the system's thermal efficiency. Combined cycle recovers waste heat from the internal combustion engine through the steam system and sends the superheated steam to the steam turbine to generate additional mechanical power output, further improving the system's thermal efficiency. This is currently the most advanced route for recovering waste heat from internal combustion engines.

[0004] Although the thermal efficiency of an internal combustion engine is significantly higher than that of a gas turbine, the system thermal efficiency of an internal combustion engine-steam combined cycle is relatively lower than that of a gas turbine-steam combined cycle. On the one hand, because the internal combustion engine coolant carries away about half of the waste heat, and this heat energy has almost no potential for doing work, the usable energy of the internal combustion engine's waste heat is relatively low. On the other hand, due to the limitations of the turbocharging system, the exhaust temperature of the internal combustion engine is not high, resulting in a relatively low energy quality of the waste heat.

[0005] This invention proposes an internal combustion engine-steam combined cycle power generation system for chemical waste gas recovery, solving the problems of low usable energy and low energy quality in traditional solutions. Based on low-temperature combustion technology of the internal combustion engine, heat transfer losses in the combustion chamber are reduced, minimizing the waste heat energy carried away by the coolant and improving the problem of low usable energy from the internal combustion engine's waste heat. Based on ultra-lean combustion technology of the internal combustion engine, the oxygen content of the exhaust gas is increased, and the exhaust temperature is reduced, meeting the input boundary of the downstream waste heat boiler. Based on staged supplementary combustion technology of the waste heat boiler, the oxygen-enriched exhaust gas from the upstream internal combustion engine is used as the combustion air and burnout air of the boiler burner, implementing staged supplementary combustion, which greatly improves the energy quality of the internal combustion engine's waste heat. Based on the implementation of these key technologies, the system thermal efficiency of the internal combustion engine-steam combined cycle can be significantly improved, reaching an energy efficiency level similar to that of a gas turbine-steam combined cycle. Summary of the Invention

[0006] The combined cycle power generation system includes an internal combustion engine 1, a waste heat boiler 2, a fuel valve 3, a steam turbine 4, a cooling tower 5, a deaerator 6, a coolant heat exchanger 7, a feedwater pump 8, a tail flue 9, an intake flue 10, and a feed pipe 11; the internal combustion engine 1 includes an internal combustion engine body 101, a coolant circulation loop 102, an intake port 103, and an exhaust port 104; the waste heat boiler 2 includes a furnace 201, a burner 202, a boiler heat exchange surface 203, a fuel inlet 204, and an exhaust outlet 205; the deaerator 6 includes a deaerator shell 601 and a condensate circulation pipe 602; the coolant heat exchanger 7 includes a heat exchanger shell 701, a cold end 702, and a hot end 703; The exhaust port 104 of the internal combustion engine 1 is connected to the waste heat boiler 2 through the intake flue 10, and the chemical waste gas enters from the intake port 103 of the internal combustion engine 1; the fuel inlet 204 of the waste heat boiler 2 is connected to the fuel valve 3 through the feed pipe 11; the exhaust outlet 205 of the waste heat boiler 2 is connected to the tail flue 9; the superheated steam of the waste heat boiler 2 enters the steam turbine 4; the steam turbine 4 is connected to the cooling tower 5; the cooling tower 5 is connected to the deaerator 6; the condensate circulation pipe 602 of the deaerator 6 is connected to the cold end 702 of the coolant heat exchanger 7; the coolant circulation loop 102 of the internal combustion engine 1 is connected to the hot end 703 of the coolant heat exchanger 7; the deaerator 6 is connected to the feed water pump 8; the feed water pump 8 is connected to the waste heat boiler 2.

[0007] The burner 202 and boiler heat exchange surface 203 of the waste heat boiler 2 are installed inside the furnace 201; the burner 202 is connected to the fuel valve 3; the boiler heat exchange surface 203 is connected to the feed water pump 8; the superheated steam of the boiler heat exchange surface 203 enters the steam turbine 4.

[0008] The internal combustion engine 1 uses chemical waste gas as fuel.

[0009] The internal combustion engine 1 is in an ultra-lean combustion state under rated operating conditions, the fuel valve 3 is opened, and the waste heat boiler 2 performs supplementary combustion.

[0010] Under low-load conditions, the internal combustion engine 1 has its fuel valve 3 closed and the waste heat boiler 2 stops supplementary combustion. Attached Figure Description

[0011] Figure 1 This is a schematic diagram of an internal combustion engine-steam combined cycle power generation system for chemical waste gas recovery according to the present invention.

[0012] Figure 2 This is a schematic diagram of an internal combustion engine in a combined cycle power generation system for chemical waste gas recovery according to the present invention.

[0013] Figure 3This is a schematic diagram of a waste heat boiler for an internal combustion engine-steam combined cycle power generation system for recovering chemical waste gas, according to the present invention.

[0014] Figure 4 This is a schematic diagram of a deaerator for an internal combustion engine-steam combined cycle power generation system for chemical waste gas recovery according to the present invention.

[0015] Figure 5 This is a schematic diagram of a coolant heat exchanger for an internal combustion engine-steam combined cycle power generation system for chemical waste gas recovery, according to the present invention. Specific implementation methods

[0016] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments, so that the advantages and features of the present invention can be more easily understood by those skilled in the art, thereby making a clearer and more explicit definition of the scope of protection of the present invention.

[0017] like Figure 1 , 2As shown, when the internal combustion engine-steam combined cycle power generation system for chemical waste gas recovery described in this invention operates under rated conditions, the excess air coefficient of the internal combustion engine 1 is controlled between 1.5 and 2.5, at which point the internal combustion engine 1 is in an ultra-lean combustion state; the exhaust temperature of the internal combustion engine 1 is around 300℃, meeting the design requirements of the burner expansion joint; the exhaust oxygen concentration of the internal combustion engine 1 is around 10%, approximately half the oxygen concentration of air, meeting the design requirements of the combustion air and burnout air; the low-temperature oxygen-rich exhaust gas generated by the internal combustion engine 1 is introduced into the waste heat boiler 2 through the intake flue 10 as the combustion air for the waste heat boiler 2; the fuel valve 3 is open. Fuel is injected into the waste heat boiler 2 via the feed pipe 11 and burner 202, where it mixes with the low-temperature oxygen-enriched exhaust gas from the internal combustion engine 1 for supplementary combustion and generates high-temperature flue gas, significantly improving the energy quality of the exhaust waste heat from the internal combustion engine 1. The high-temperature flue gas passes through the boiler heat exchange surface 203 of the waste heat boiler 2, heating the boiler feedwater and generating superheated steam. The inlet header of the boiler heat exchange surface 203 is connected to the feedwater pump 8 to supply water to the waste heat boiler 2, and the superheated steam from the outlet header of the boiler heat exchange surface 203 enters the steam inlet of the steam turbine 4 to supply steam to the steam turbine 4. The low-temperature flue gas, after heat exchange with the boiler feedwater, enters the waste heat boiler 2 through the exhaust outlet 205. The superheated steam enters the tail flue duct 9, passes through modules such as SCR and economizer, and deeply recovers the waste heat of the flue gas to meet emission standards; the superheated steam enters the steam turbine 4, expands and does work inside the steam turbine 4; the exhaust steam after doing work enters the cooling tower 5 and condenses into saturated water; the superheated steam from the outlet header of the boiler heat exchange surface 203 enters the steam inlet of the steam turbine 4, and the exhaust steam from the steam turbine 4 enters the cooling tower 5, which is the conventional operation mode and will not be described in detail here; the saturated water flows into the deaerator 6 and merges with the boiler makeup water; the condensate circulation pipeline 602 of the deaerator 6 is connected to the cold end 702 of the coolant heat exchanger 7; the coolant circulation loop 102 of the internal combustion engine 1 exchanges heat with the coolant. The hot end 703 of the deaerator 7 is connected; since the evaporation rate of the waste heat boiler 2 is large at this time, the operating power of the internal combustion engine 1 is large, and the heat generation of the engine body is high, the low-temperature waste heat of the internal combustion engine 1 is transferred to the cooling water of the deaerator 6 through the coolant heat exchanger 7, which can completely recover the low-temperature waste heat of the internal combustion engine 1, and achieve the purpose of thermal deaeration and heating boiler makeup water while protecting the internal combustion engine body; after this, the feed water flows out from the deaerator 6, is pressurized by the feed water pump 8 to form subcooled water, and re-enters the boiler heat exchange surface 203 of the waste heat boiler 2 to complete one cycle, fully recover the exhaust waste heat of the internal combustion engine 1, and effectively improve the thermal efficiency of the internal combustion engine-steam combined cycle.

[0018] When the internal combustion engine-steam combined cycle power generation system for chemical waste gas recovery described in this invention operates under low load conditions, the internal combustion engine 1 struggles to maintain an ultra-lean combustion state, resulting in increased exhaust temperature and decreased oxygen content, failing to meet the design requirements of the burner 202; the fuel valve 3 closes, stopping fuel injection into the waste heat boiler 2, and the waste heat boiler 2 stops combustion; the medium-temperature exhaust gas from the internal combustion engine 1 heats the boiler feedwater through the boiler heat exchange surface 203 and generates superheated steam; the low-temperature flue gas after heat exchange with the boiler feedwater enters the tail flue through the top flue of the waste heat boiler 2. The waste heat from the flue gas is deeply recovered through modules such as SCR and economizer to meet emission standards. Superheated steam enters the turbine 4 and expands to do work. The exhaust steam after doing work enters the cooling tower 5 and condenses into saturated water, which flows into the deaerator 6. Since the evaporation rate of the waste heat boiler 2 is small at this time, it is difficult to recover the low-temperature waste heat of the internal combustion engine 1. The coolant heat exchanger 7 is closed, and the feedwater flows directly out through the deaerator 6. The feedwater pump 8 pressurizes the water to form subcooled water, which re-enters the boiler heat exchange surface 203 of the waste heat boiler 2, completing one cycle according to the traditional combined cycle scheme.

[0019] In summary, this invention proposes an internal combustion engine-steam combined cycle power generation system for chemical waste gas recovery, solving the problems of low usable energy and low energy quality in traditional solutions. Based on low-temperature combustion technology of the internal combustion engine, heat transfer losses in the combustion chamber are reduced, minimizing the waste heat energy carried away by the coolant and improving the problem of low usable energy from the internal combustion engine's waste heat. Based on ultra-lean combustion technology of the internal combustion engine, the oxygen content of the exhaust gas is increased, and the exhaust temperature is reduced, meeting the input boundary of the downstream waste heat boiler. Based on staged supplementary combustion technology of the waste heat boiler, the oxygen-enriched exhaust gas from the upstream internal combustion engine is used as the combustion air and burnout air of the boiler burner, implementing staged supplementary combustion, which greatly improves the energy quality of the internal combustion engine's waste heat. Based on the implementation of these three key technologies, the system thermal efficiency of the internal combustion engine-steam combined cycle can be significantly improved, reaching an energy efficiency level similar to that of a gas turbine-steam combined cycle.

Claims

1. An internal combustion engine-steam combined cycle power generation system for recovering chemical waste gas, characterized in that: The combined cycle power generation system includes an internal combustion engine (1), a waste heat boiler (2), a fuel valve (3), a steam turbine (4), a cooling tower (5), a deaerator (6), a coolant heat exchanger (7), a feed water pump (8), a tail flue (9), an intake flue (10), and a feed pipe (11); the internal combustion engine (1) includes an internal combustion engine body (101), a coolant circulation loop (102), an intake port (103), and an exhaust port (104); the waste heat boiler (2) includes a furnace (201), a burner (202), a boiler heat exchange surface (203), a fuel inlet (204), and an exhaust outlet (205); the deaerator (6) includes a deaerator shell (601) and a condensate circulation pipe (602); the coolant heat exchanger (7) includes a heat exchanger shell (701), a cold end (702), and a hot end (703); the internal combustion engine (1) includes an internal combustion engine body (101), a coolant circulation loop (102), a coolant heat exchanger (703), a steam turbine (4), a cooling tower (5), a deaerator (6), a coolant heat exchanger (703), a feed water pump (8), a tail flue (9), an intake flue (10), and a feed pipe (11); the internal combustion engine (1) includes an internal combustion engine body (101), a coolant circulation loop (102), a coolant heat exchanger (703), a coolant heat exchanger (701), a coolant heat exchanger (702), and a coolant heat exchanger (703); the combined cycle power generation system includes an internal combustion engine body (101), a coolant circulation loop (202), a coolant heat exchanger (703), a coolant heat exchanger (701), a coolant heat exchanger (702), and a coolant heat exchanger (703); the internal combustion engine (102) includes an internal combustion engine body (101 The exhaust port (104) of the engine (1) is connected to the waste heat boiler (2) through the intake flue (10), and the chemical waste gas enters from the intake port (103) of the internal combustion engine (1); the fuel inlet (204) of the waste heat boiler (2) is connected to the fuel valve (3) through the feed pipe (11); the exhaust outlet (205) of the waste heat boiler (2) is connected to the tail flue (9); the superheated steam from the waste heat boiler (2) enters the steam turbine (4); The turbine (4) is connected to the cooling tower (5); the cooling tower (5) is connected to the deaerator (6); the condensate circulation pipeline (602) of the deaerator (6) is connected to the cold end (702) of the coolant heat exchanger (7); the coolant circulation loop (102) of the internal combustion engine (1) is connected to the hot end (703) of the coolant heat exchanger (7); the deaerator (6) is connected to the feed water pump (8); the feed water pump (8) is connected to the waste heat boiler (2).

2. The internal combustion engine-steam combined cycle power generation system for chemical waste gas recovery according to claim 1, characterized in that: The burner (202) and boiler heat exchange surface (203) of the waste heat boiler (2) are installed in the furnace (201); the burner (202) is connected to the fuel valve (3); the boiler heat exchange surface (203) is connected to the feed water pump (8); the superheated steam from the boiler heat exchange surface (203) enters the steam turbine (4).

3. The internal combustion engine-steam combined cycle power generation system for chemical waste gas recovery according to claim 1, characterized in that: The internal combustion engine (1) uses chemical waste gas as fuel.

4. The internal combustion engine-steam combined cycle power generation system for chemical waste gas recovery according to claim 1, characterized in that: The internal combustion engine (1) is in an ultra-lean combustion state under rated operating conditions, the fuel valve (3) is opened, and the waste heat boiler (2) performs supplementary combustion.

5. The internal combustion engine-steam combined cycle power generation system for chemical waste gas recovery according to claim 1, characterized in that: When the internal combustion engine (1) is under low load, the fuel valve (3) is closed and the waste heat boiler (2) stops supplementary combustion.

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