A low-carbon coal-fired cogeneration system and operation method

Abstract

The present invention discloses a low-carbon coal-fired cogeneration system and operating method, belonging to the technical field of coal-fired cogeneration. This system preheats the gasification feed water step by step through heaters No. 1, No. 2, No. 3, and No. 4. The multi-stage heat exchange method can more fully utilize the heat in the system. Among them, heater No. 4 not only participates in the preheating process of the gasification feed water, but also provides additional heat for the gasification reaction by recovering part of the sensible heat of the high-temperature flue gas at the burner outlet, reducing the irreversibility of the supercritical water gasification reaction and reducing heat loss. The design of the diverter enables the gas outlet of the supercritical water gasification reactor to be connected to the first hot end of the waste heat boiler of the steam Rankine cycle system and the hot end of heater No. 2, respectively, increasing the flexibility of heat cascade utilization, enabling the system to adjust heat distribution according to actual needs and improving overall efficiency.

Description

Technical Field

[0001] The present invention relates to the technical field of coal-fired cogeneration, and in particular to a low-carbon coal-fired cogeneration system and an operation method thereof. Background Art

[0002] As an important form of traditional energy utilization, cogeneration technology is widely used in power generation and district heating, playing a vital role in ensuring energy supply and improving energy efficiency. Traditional cogeneration systems directly burn coal to produce high-temperature, high-pressure steam, but suffer from strong thermal-electric coupling and insufficient flexibility, making them difficult to adapt to the dynamic changes in modern power grids and heating demand. Furthermore, the large amount of pollutants generated during coal combustion, such as carbon dioxide, nitrogen oxides, and sulfur oxides, poses a serious threat to the environment. With the global energy transition and the introduction of carbon reduction targets, achieving efficient, clean, and low-carbon coal-fired cogeneration has become a current research priority.

[0003] Supercritical water gasification is a clean technology for efficiently converting coal into syngas. By leveraging the solubility and catalytic properties of supercritical water under high-temperature and high-pressure conditions, it achieves complete coal gasification, producing hydrogen-rich, high-calorific-value syngas. This technology not only significantly improves coal conversion efficiency but also reduces pollutant generation during the gasification process, particularly nitrogen and sulfur emissions. Compared to traditional direct combustion methods, supercritical water gasification provides a cleaner and lower-carbon path for coal-fired cogeneration. However, because the supercritical water gasification reaction requires a large amount of heat, improper heat supply can easily lead to increased system irreversibility, thus affecting power generation efficiency. For example, patent application "CN117266947A" discloses a coal supercritical water gasification power generation system and operating method coupled with a supercritical carbon dioxide cycle. By coupling the supercritical carbon dioxide cycle at the heat flow end, the system recovers gasified syngas and turbine exhaust waste heat, achieving efficient matching of the system's waste heat and improving power generation efficiency. However, the sensible heat of the high-temperature flue gas generated during the supercritical water gasification process is not fully recovered and utilized, resulting in low overall waste heat utilization efficiency.

[0004] Therefore, it is urgent to explore the technical route of combining supercritical water gasification technology with coal-fired cogeneration system, improve the efficiency of waste heat utilization, and realize the technical advantages of efficient, clean and low-carbon cogeneration of coal-fired system. Summary of the Invention

[0005] The object of the present invention is to provide a low-carbon coal-fired cogeneration system and an operation method thereof, so as to overcome the problem of low waste heat utilization efficiency of traditional coal-fired cogeneration systems.

[0006] The present invention solves the above technical problems through the following technical solutions:

[0007] A low-carbon coal-fired cogeneration system includes a steam Rankine cycle system and a supercritical water gasification system, wherein the supercritical water gasification system includes a coal-water slurry pump, a first feedwater pump, a first heater, a second heater, a third heater, a fourth heater, a supercritical water gasification reactor, a diverter, a gas-liquid separation system, a regenerator, and a burner;

[0008] The gasification feed water is connected to the cold end of heater No. 1, the cold end of heater No. 2, the cold end of heater No. 3 and the cold end of heater No. 4 in sequence through the first feed water pump, and the cold end outlet of heater No. 4 is connected to the supercritical water gasification reactor; the water-coal slurry is connected to the supercritical water gasification reactor through the water-coal slurry pump; the solid outlet of the supercritical water gasification reactor is used to discharge ash; the gas outlet of the supercritical water gasification reactor is connected to the inlet of the splitter through the hot end of heater No. 3, and the outlet of the splitter is respectively connected to the first hot end of the waste heat boiler of the steam Rankine cycle system and the hot end of heater No. 2, and the first hot end outlet of the waste heat boiler and the hot end outlet of heater No. 2 are merged and connected to the hot end of heater No. 1; the hot end outlet of heater No. 1 is connected to the gas-liquid separation system, and the liquid phase outlet of the gas-liquid separation system is used for drainage. The gas phase outlet of the gas-liquid separation system is connected to the cold end of the regenerator, the burner, the hot end of heater No. 4 to the second hot end of the waste heat boiler in sequence, and the second hot end outlet of the waste heat boiler is connected to the gas-liquid separation system through the hot end of the regenerator.

[0009] A further improvement of the present invention is that: the supercritical water gasification system also includes a throttle valve, a cooler and a carbon dioxide capture device, the gas-liquid separation system includes a No. 1 gas-liquid separator and a No. 2 gas-liquid separator, the hot end outlet of the No. 1 heater is connected to the No. 1 gas-liquid separator through the throttle valve, the liquid phase outlet of the No. 1 gas-liquid separator is used for drainage, the gas phase outlet of the No. 1 gas-liquid separator is connected in sequence to the cold end of the regenerator, the burner, the hot end of the No. 4 heater to the second hot end of the waste heat boiler, and the cold end inlet of the regenerator is connected to oxygen; the second hot end outlet of the waste heat boiler is connected in sequence to the hot end of the regenerator and the cooler to the No. 2 gas-liquid separator, the liquid phase outlet of the No. 2 gas-liquid separator is used for drainage, and the gas phase outlet of the No. 2 gas-liquid separator is connected to the carbon dioxide capture device.

[0010] A further improvement of the present invention is that the operating temperature range of the burner is 900°C - 1400°C.

[0011] A further improvement of the present invention is that: the steam Rankine cycle system also includes a steam turbine, a heating heater, a condenser, a condensate pump, a deaerator and a second feed water pump; the cold end outlet of the waste heat boiler is connected to the steam turbine, the first outlet of the steam turbine is connected to the deaerator via the hot end of the heating heater, the cold end of the heating heater is connected to the steam pipe network of the heating system, the second outlet of the steam turbine is connected to the condenser and the condensate pump to the deaerator in sequence, and the outlet of the deaerator is connected to the cold end inlet of the waste heat boiler via the second feed water pump, forming a steam Rankine cycle.

[0012] A further improvement of the present invention is that the steam turbine includes a multi-stage structure of high pressure, medium pressure and low pressure, wherein the high pressure structure is used for expansion and power generation, the medium pressure structure is used to assist the high pressure structure in expansion and power generation and to heat hot water for the heating system, and the low pressure structure is used to assist the high pressure structure in expansion and power generation. Adjusting the exhaust volume of the steam turbine can control the distribution ratio of the steam turbine's power generation power and heat supply. When the power grid load is at its peak, reducing the exhaust volume of the steam turbine and increasing the expansion ratio of steam in the steam turbine can increase the power generation; when the heat demand is at its peak, increasing the exhaust volume of the steam turbine and using more steam for heating in the heat network can increase the heat supply.

[0013] A further improvement of the present invention is that the temperature of the hydrophobic water at the hot end outlet of the heating heater can be dynamically adjusted according to the heating demand, with an adjustment range of 60°C to 150°C to adapt to the heating needs of different environmental conditions and regions.

[0014] A further improvement of the present invention is that the No. 1 heater, the No. 2 heater, the No. 3 heater, the No. 4 heater, the regenerator and the waste heat boiler are all partition-type heat exchangers, and the minimum heat exchange temperature difference range is 5°C to 20°C.

[0015] A further improvement of the present invention is that the operating temperature of the supercritical water gasification reactor is 600°C to 700°C, and the operating pressure is 25 MPa to 30 MPa.

[0016] The present invention also provides an operating method for a low-carbon coal-fired cogeneration system, using the low-carbon coal-fired cogeneration system as described above, wherein the gasification feed water is pressurized by a first feed water pump and then sequentially enters the cold ends of the first heater, the second heater, and the third heater for heating, the high-temperature and high-pressure gasification synthesis gas in the supercritical water gasification reactor exchanges heat with the heated gasification feed water, the gasification feed water after heat exchange enters the fourth heater, and the gasification synthesis gas after heat exchange flows into the diverter through the hot end of the third heater;

[0017] The gasified synthesis gas is divided into two paths through the splitter: the first path enters the hot end of the No. 2 heater for preheating the gasification feed water, and the second path enters the hot end of the waste heat boiler for heating the feed water of the steam Rankine cycle system to generate steam. The gasified synthesis gas after the two reactions is mixed and enters the hot end of the No. 1 heater for further preheating the gasification feed water; the gasified synthesis gas at the outlet of the hot end of the No. 1 heater enters the gas-liquid separation system for gas-liquid separation to obtain water and dry gasified synthesis gas. The water is discharged from the system through the liquid phase outlet of the gas-liquid separation system, and the dry gasified synthesis gas and oxygen enter the cold end of the regenerator for preheating, and then enter the burner. A complete oxidation reaction occurs to generate high-temperature flue gas; the high-temperature flue gas enters the No. 4 heater and releases heat to the gasification feed water after heat exchange to obtain the first flue gas; the water-coal slurry is pressurized by the water-coal slurry pump and enters the supercritical water gasification reactor. After the gasification feed water absorbs heat to the temperature required for the supercritical water gasification reaction, it enters the supercritical water gasification reactor and undergoes a supercritical water gasification reaction with the water-coal slurry to generate high-temperature and high-pressure gasification synthesis gas; the first flue gas enters the hot end of the waste heat boiler and releases heat to the feed water of the steam Rankine cycle system to generate steam to obtain the second flue gas. The second flue gas enters the hot end of the regenerator and releases heat to preheat the dry gasification synthesis gas and oxygen.

[0018] A further improvement of the present invention is that the gasified synthesis gas is divided into two paths through a splitter, and the mass flow ratio of the first path to the second path ranges from 0.4 to 0.6.

[0019] Compared with the prior art, the present invention has the following positive effects:

[0020] The low-carbon coal-fired cogeneration system provided by the present invention adopts a multi-stage heat exchange structure, and preheats the gasification feed water step by step through heater No. 1, heater No. 2, heater No. 3 and heater No. 4. The multi-stage heat exchange method can more fully utilize the heat in the system and improve energy utilization efficiency. Heater No. 4 not only participates in the preheating process of gasification feed water, but also provides additional heat for the gasification reaction by recovering part of the sensible heat of the high-temperature flue gas at the burner outlet, avoiding the use of partial oxidation supercritical water gasification reaction, thereby reducing the irreversibility of the supercritical water gasification reaction, reducing heat loss, and overcoming the problem of low waste heat utilization efficiency of traditional coal-fired cogeneration systems; the design of the diverter enables the gas outlet of the supercritical water gasification reactor to be connected to the first hot end of the waste heat boiler of the steam Rankine cycle system and the hot end of the No. 2 heater respectively, increasing the flexibility of heat cascade utilization, enabling the system to adjust heat distribution according to actual needs and improve overall efficiency.

[0021] Furthermore, the throttle valve enables the system to accurately control the pressure and flow of the gas-liquid mixture at the hot end outlet of heater No. 1, which helps to optimize the gas-liquid separation process and ensure that gas-liquid separator No. 1 can more effectively separate gas and liquid; the cooler helps to reduce the temperature of the gas flowing out of the second hot end outlet of the waste heat boiler, facilitating the subsequent carbon dioxide capture process; by capturing and separating carbon dioxide in the gas phase outlet of gas-liquid separator No. 2, greenhouse gas emissions can be reduced.

[0022] Furthermore, the supercritical water gasification system is highly coupled with the steam Rankine cycle system, which improves the heat utilization efficiency. The waste heat boiler can efficiently recover part of the sensible heat of the second part of the gasified synthesis gas and the first flue gas. At the same time, by adjusting the steam turbine extraction volume, the distribution ratio of the steam turbine power generation and heat supply is controlled to meet the grid load and heating needs.

[0023] Furthermore, the steam turbine includes a multi-stage structure of high pressure, medium pressure and low pressure, and the medium pressure steam is used for heating the heat network. By dynamically adjusting the extraction volume of the steam turbine and controlling the distribution ratio of the steam turbine's power generation and heat supply, the grid load and heating demand are met, and a flexible distribution of the power generation and heating ratio is achieved, so that the system can respond quickly according to real-time load demand and enhance the load regulation capability of cogeneration. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] The drawings in the specification are used to provide further understanding of the present invention and constitute a part of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute improper limitations on the present invention.

[0025] Figure 1 This is a structural schematic diagram of a low-carbon coal-fired cogeneration system of the present invention;

[0026] Among them, 1 is a water-coal slurry pump, 2 is the first water supply pump, 3 is the No. 1 heater, 4 is the No. 2 heater, 5 is the No. 3 heater, 6 is the No. 4 heater, 7 is a supercritical water gasification reactor, 8 is a diverter, 9 is a throttle valve, 10 is the No. 1 gas-liquid separator, 11 is a regenerator, 12 is a burner, 13 is a waste heat boiler, 14 is a steam turbine, 15 is a heating heater, 16 is a condenser, 17 is a condensate pump, 18 is a deaerator, 19 is the second water supply pump, 20 is a cooler, and 21 is the No. 2 gas-liquid separator. DETAILED DESCRIPTION

[0027] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments, which are intended to explain the present invention rather than to limit it.

[0028] A low-carbon coal-fired cogeneration system includes a steam Rankine cycle system and a supercritical water gasification system. The supercritical water gasification system includes a coal-water slurry pump 1, a first water feed pump 2, a first heater 3, a second heater 4, a third heater 5, a fourth heater 6, a supercritical water gasification reactor 7, a diverter 8, a gas-liquid separation system, a regenerator 11, and a burner 12.

[0029] The gasification feed water is connected to the cold end of the No. 1 heater 3, the cold end of the No. 2 heater 4, the cold end of the No. 3 heater 5 and the cold end of the No. 4 heater 6 in sequence through the first feed water pump 2, and the cold end outlet of the No. 4 heater 6 is connected to the supercritical water gasification reactor 7; the water-coal slurry is connected to the supercritical water gasification reactor 7 through the water-coal slurry pump 1; the solid outlet of the supercritical water gasification reactor 7 is used to discharge ash; the gas outlet of the supercritical water gasification reactor 7 is connected to the inlet of the splitter 8 through the hot end of the No. 3 heater 5, and the outlets of the splitter 8 are respectively connected to the steam Rankine cycle system The first hot end of the waste heat boiler 13 and the hot end of the No. 2 heater 4, the first hot end outlet of the waste heat boiler 13 and the hot end outlet of the No. 2 heater 4 are merged and connected to the hot end of the No. 1 heater 3; the hot end outlet of the No. 1 heater 3 is connected to the gas-liquid separation system, and the liquid phase outlet of the gas-liquid separation system is used for drainage. The gas phase outlet of the gas-liquid separation system is connected to the cold end of the regenerator 11, the burner 12, the hot end of the No. 4 heater 6 in sequence to the second hot end of the waste heat boiler 13, and the second hot end outlet of the waste heat boiler 13 is connected to the gas-liquid separation system through the hot end of the regenerator 11.

[0030] The low-carbon coal-fired cogeneration system provided by the present invention adopts a multi-stage heat exchange structure, and preheats the gasification feed water step by step through heater No. 1, heater No. 2, heater No. 3 and heater No. 4. The multi-stage heat exchange method can more fully utilize the heat in the system and improve energy utilization efficiency. Heater No. 4 not only participates in the preheating process of gasification feed water, but also provides additional heat for the gasification reaction by recovering part of the sensible heat of the high-temperature flue gas at the burner outlet, avoiding the use of partial oxidation supercritical water gasification reaction, thereby reducing the irreversibility of the supercritical water gasification reaction, reducing heat loss, and overcoming the problem of low waste heat utilization efficiency of traditional coal-fired cogeneration systems; the design of the diverter enables the gas outlet of the supercritical water gasification reactor to be connected to the first hot end of the waste heat boiler of the steam Rankine cycle system and the hot end of the No. 2 heater respectively, increasing the flexibility of heat cascade utilization, enabling the system to adjust heat distribution according to actual needs and improve overall efficiency.

[0031] Specifically, the supercritical water gasification system also includes a throttle valve 9, a cooler 20 and a carbon dioxide capture device. The gas-liquid separation system includes a No. 1 gas-liquid separator 10 and a No. 2 gas-liquid separator 21. The hot end outlet of the No. 1 heater 3 is connected to the No. 1 gas-liquid separator 10 through the throttle valve 9. The liquid phase outlet of the No. 1 gas-liquid separator 10 is used for drainage. The gas phase outlet of the No. 1 gas-liquid separator 10 is connected in sequence to the cold end of the regenerator 11, the burner 12, and the hot end of the No. 4 heater 6 to the second hot end of the waste heat boiler 13, and the cold end inlet of the regenerator 11 is connected to oxygen; the second hot end outlet of the waste heat boiler 13 is connected in sequence to the hot end of the regenerator 11 and the cooler 20 to the No. 2 gas-liquid separator 21. The liquid phase outlet of the No. 2 gas-liquid separator 21 is used for drainage, and the gas phase outlet of the No. 2 gas-liquid separator 21 is connected to the carbon dioxide capture device.

[0032] The throttle valve enables the system to precisely control the pressure and flow of the gas-liquid mixture at the hot end outlet of the No. 1 heater, helping to optimize the gas-liquid separation process and ensuring that the No. 1 gas-liquid separator can more effectively separate the gas and liquid; the cooler helps to lower the temperature of the gas flowing out of the second hot end outlet of the waste heat boiler, facilitating the subsequent carbon dioxide capture process; and by capturing and separating carbon dioxide from the gas phase outlet of the No. 2 gas-liquid separator, greenhouse gas emissions can be reduced.

[0033] Specifically, the operating temperature range of the burner 12 is 900°C - 1400°C.

[0034] Specifically, the steam Rankine cycle system also includes a steam turbine 14, a heating heater 15, a condenser 16, a condensate pump 17, a deaerator 18 and a second feedwater pump 19; the cold end outlet of the waste heat boiler 13 is connected to the steam turbine 14, the first outlet of the steam turbine 14 is connected to the deaerator 18 via the hot end of the heating heater 15, the cold end of the heating heater 15 is connected to the steam pipe network of the heating system, the second outlet of the steam turbine 14 is connected to the condenser 16 and the condensate pump 17 to the deaerator 18 in sequence, and the outlet of the deaerator 18 is connected to the cold end inlet of the waste heat boiler 13 via the second feedwater pump 19, forming a steam Rankine cycle.

[0035] The supercritical water gasification system is highly coupled with the steam Rankine cycle system, which improves heat utilization efficiency. The waste heat boiler can efficiently recover part of the sensible heat of the second part of the gasified synthesis gas and the first flue gas. At the same time, by adjusting the steam turbine extraction volume, the distribution ratio of the steam turbine's power generation and heat supply is controlled to meet the grid load and heating needs.

[0036] Specifically, the steam turbine 14 includes a high-pressure, medium-pressure and low-pressure multi-stage structure, wherein the high-pressure structure is used for expansion and power generation, the medium-pressure structure is used to assist the high-pressure structure in expansion and power generation and to heat hot water for the heating system, and the low-pressure structure is used to assist the high-pressure structure in expansion and power generation. Adjusting the extraction volume of the steam turbine 14 can control the distribution ratio of the power generation power and heat supply of the steam turbine 14. When the load of the power grid is at a peak, reducing the extraction volume of the steam turbine 14 and increasing the expansion ratio of steam in the steam turbine 14 can increase the power generation; when the heat demand is at a peak, increasing the extraction volume of the steam turbine 14 and using more steam for heating in the heat network can increase the heat supply.

[0037] The steam turbine includes a multi-stage structure of high pressure, medium pressure and low pressure. The medium pressure steam is used to supply heat to the heat network. By dynamically adjusting the extraction volume of the steam turbine and controlling the distribution ratio of the steam turbine's power generation and heat supply, the grid load and heating demand are met, and a flexible distribution of the power generation and heating ratio is achieved, enabling the system to respond quickly according to real-time load demand and enhance the load regulation capability of cogeneration.

[0038] Specifically, the temperature of the hydrophobic water at the hot end outlet of the heating heater 15 can be dynamically adjusted according to the heating demand, and the adjustment range is 60°C to 150°C to adapt to the heating demand of different environmental conditions and regions.

[0039] Specifically, the No. 1 heater 3, the No. 2 heater 4, the No. 3 heater 5, the No. 4 heater 6, the regenerator 11 and the waste heat boiler 13 are all partition-type heat exchangers, and the minimum heat exchange temperature difference range is 5°C to 20°C.

[0040] Specifically, the operating temperature of the supercritical water gasification reactor 7 is 600° C. to 700° C., and the operating pressure is 25 MPa to 30 MPa.

[0041] Based on the same inventive concept, the present invention also provides an operating method for a low-carbon coal-fired cogeneration system. Using a low-carbon coal-fired cogeneration system as described above, the gasified feed water is pressurized by the first feed water pump 2 and then enters the cold ends of the No. 1 heater 3, the No. 2 heater 4, and the No. 3 heater 5 in sequence for heating. The high-temperature and high-pressure gasified synthesis gas in the supercritical water gasification reactor 7 exchanges heat with the heated gasified feed water. The gasified feed water after heat exchange enters the No. 4 heater 6, and the gasified synthesis gas after heat exchange flows into the diverter 8 through the hot end of the No. 3 heater 5.

[0042] The gasified synthesis gas is divided into two paths by the splitter 8: the first path enters the hot end of the No. 2 heater 4 for preheating the gasification feed water, and the second path enters the hot end of the waste heat boiler 13 for heating the feed water of the steam Rankine cycle system to generate steam. The gasified synthesis gas after the two reactions is mixed and enters the hot end of the No. 1 heater 3 for further preheating the gasification feed water; the gasified synthesis gas at the hot end outlet of the No. 1 heater 3 enters the gas-liquid separation system for gas-liquid separation to obtain water and dry gasified synthesis gas. The water is discharged from the system through the liquid phase outlet of the gas-liquid separation system, and the dry gasified synthesis gas and oxygen enter the cold end of the regenerator 11 for preheating, and then enter the burner 12 A complete oxidation reaction occurs in the reactor to generate high-temperature flue gas; the high-temperature flue gas enters the No. 4 heater 6, releases heat to the gasification feed water after heat exchange, and obtains the first flue gas; the water-coal slurry is pressurized by the water-coal slurry pump 1 and enters the supercritical water gasification reactor 7. After the gasification feed water absorbs heat to the temperature required for the supercritical water gasification reaction, it enters the supercritical water gasification reactor 7 and undergoes a supercritical water gasification reaction with the water-coal slurry to generate a high-temperature and high-pressure gasification synthesis gas; the first flue gas enters the hot end of the waste heat boiler 13 to release heat to the feed water of the steam Rankine cycle system to generate steam, and obtains the second flue gas. The second flue gas enters the hot end of the regenerator 11 to release heat, which is used to preheat the dry gasification synthesis gas and oxygen.

[0043] Specifically, the gasified synthesis gas is divided into two paths through the splitter 8, and the mass flow ratio of the first path to the second path is in the range of 0.4 to 0.6.

[0044] Example 1

[0045] See also Figure 1 A low-carbon coal-fired cogeneration system includes a gasification water supply device, a coal-water slurry supply device, an oxygen supply device, a carbon dioxide capture device, a coal-water slurry pump 1, a first feedwater pump 2, a No. 1 heater 3, a No. 2 heater 4, a No. 3 heater 5, a No. 4 heater 6, a supercritical water gasification reactor 7, a diverter 8, a throttle valve 9, a No. 1 gas-liquid separator 10, a regenerator 11, a burner 12, a steam Rankine cycle system, a cooler 20, and a No. 2 gas-liquid separator 21; the steam Rankine cycle system includes a waste heat boiler 13, a steam turbine 14, a heating heater 15, a condenser 16, a condensate pump 17, a deaerator 18, and a second feedwater pump 19;

[0046] The gasification water supply device is connected to the cold end of the No. 1 heater 3, the cold end of the No. 2 heater 4, the cold end of the No. 3 heater 5 and the cold end of the No. 4 heater 6 in sequence through the first water supply pump 2, and the cold end outlet of the No. 4 heater 6 is connected to the supercritical water gasification reactor 7, and the water-coal slurry supply device is connected to the supercritical water gasification reactor 7 through the water-coal slurry pump 1; the solid outlet of the supercritical water gasification reactor 7 is used to discharge ash; the gas outlet of the supercritical water gasification reactor 7 is connected to the inlet of the diverter 8 through the hot end of the No. 3 heater 5, and the outlet of the diverter 8 is respectively connected to the first hot end of the waste heat boiler 13 and the hot end of the No. 2 heater 4, and the first hot end outlet of the waste heat boiler 13 and the hot end outlet of the No. 2 heater 4 After the ports are merged, they are connected to the hot end of the No. 1 heater 3; the hot end outlet of the No. 1 heater 3 is connected to the No. 1 gas-liquid separator 10 through the throttle valve 9, and the liquid phase outlet of the No. 1 gas-liquid separator 10 is used for drainage. The gas phase outlet of the No. 1 gas-liquid separator 10 is sequentially connected to the cold end of the regenerator 11, the burner 12, and the hot end of the No. 4 heater 6 to the second hot end of the waste heat boiler 13, and the cold end inlet of the regenerator 11 is connected to the oxygen supply device; the second hot end outlet of the waste heat boiler 13 is sequentially connected to the hot end of the regenerator 11 and the cooler 20 to the No. 2 gas-liquid separator 21, and the liquid phase outlet of the No. 2 gas-liquid separator 21 is used for drainage. The gas phase outlet of the No. 2 gas-liquid separator 21 is connected to the carbon dioxide capture device;

[0047] The cold end outlet of the waste heat boiler 13 is connected to the steam turbine 14. The first outlet of the steam turbine 14 is connected to the deaerator 18 via the hot end of the heating heater 15. The cold end of the heating heater 15 is connected to the steam pipe network of the heating system. The second outlet of the steam turbine 14 is connected to the condenser 16 and the condensate pump 17 to the deaerator 18 in sequence. The outlet of the deaerator 18 is connected to the cold end inlet of the waste heat boiler 13 via the second feed water pump 19, forming a steam Rankine cycle.

[0048] Example 2

[0049] A method for operating a low-carbon coal-fired cogeneration system, using the low-carbon coal-fired cogeneration system described in Example 1, wherein gasification feed water is pressurized by a first feed water pump 2 and then sequentially enters the cold ends of a first heater 3, a second heater 4, and a third heater 5 for heating. High-temperature and high-pressure gasification synthesis gas in a supercritical water gasification reactor 7 exchanges heat with the heated gasification feed water. The gasification feed water after heat exchange enters a fourth heater 6, and the gasification synthesis gas after heat exchange flows through the hot end of the third heater 5 into a diverter 8.

[0050] The gasified synthesis gas is divided into two paths by the splitter 8: the first path enters the hot end of the No. 2 heater 4 for preheating the gasification feed water, and the second path enters the hot end of the waste heat boiler 13 for heating the feed water of the steam Rankine cycle system to generate steam. The gasified synthesis gas after the two reactions is mixed and enters the hot end of the No. 1 heater 3 for further preheating the gasification feed water; the gasified synthesis gas at the hot end outlet of the No. 1 heater 3 enters the No. 1 gas-liquid separator 10 for gas-liquid separation to obtain water and dry gasified synthesis gas. The water is discharged from the system through the liquid phase outlet of the No. 1 gas-liquid separator 10. The dry gasified synthesis gas and oxygen enter the cold end of the regenerator 11 for preheating, and then enter the burner 12 for complete oxidation reaction to generate high-temperature flue gas.

[0051] The high-temperature flue gas enters the No. 4 heater 6, releases heat to the gasification feed water after heat exchange, and obtains the first flue gas; the water-coal slurry is pressurized by the water-coal slurry pump 1 and enters the supercritical water gasification reactor 7. After the gasification feed water absorbs heat to the temperature required for the supercritical water gasification reaction, it enters the supercritical water gasification reactor 7 and undergoes a supercritical water gasification reaction with the water-coal slurry to generate a high-temperature and high-pressure gasification synthesis gas;

[0052] The first flue gas enters the hot end of the waste heat boiler 13 and releases heat to the feed water of the steam Rankine cycle system to generate steam, thereby obtaining the second flue gas. The second flue gas enters the hot end of the regenerator 11 and releases heat to preheat the dried gasified synthesis gas and oxygen, thereby obtaining the third flue gas. The third flue gas is cooled by the cooler 20 to obtain low-temperature flue gas. The low-temperature flue gas enters the second gas-liquid separator 21 for gas-liquid separation to obtain water and carbon dioxide. The water is discharged from the system through the liquid phase outlet of the second gas-liquid separator 21, and the carbon dioxide is captured by the carbon dioxide capture device.

[0053] In the steam Rankine cycle system, the cold end of the waste heat boiler 13 serves as the steam Rankine cycle feed water. Steam is generated by utilizing the second portion of the gasified synthesis gas and part of the sensible heat of the first flue gas. The steam then enters the steam turbine 14 and expands to generate electricity. The exhaust gas at the outlet of the steam turbine 14 is sequentially cooled by the condenser 16, pressurized by the condensate pump 17, deoxygenated by the deaerator 18, and pressurized by the second feed water pump 19 to obtain the steam Rankine cycle feed water, thus forming a cycle. The exhaust gas at the outlet of the steam turbine 14 enters the heating heater 15, which heats the hot water of the heating system to obtain drainage water. The drainage water then enters the deaerator 18 through the hot end outlet of the heating heater 15.

[0054] Finally, it should be noted that the embodiments listed above are merely one or more specific manifestations of the technical solution of the present invention. Their purpose is to clearly illustrate the concept, principles, and application of the present invention through specific examples, and is in no way intended to limit the scope of protection of the present invention to these specific embodiments. In fact, the true value of this invention lies in its technical ideas and innovations, not in its form of expression or implementation.

[0055] For ordinary technicians in the relevant technical field, after thoroughly reading and understanding the technical solutions of the present invention, they are fully capable of making various forms of changes, modifications or equivalent replacements to the specific implementation methods of the invention based on their own professional knowledge and skills. These changes may include but are not limited to: adjusting the value range of technical parameters, optimizing algorithm processes to improve efficiency, replacing some technical components to achieve better compatibility or reduce costs, etc. As long as these modified technical solutions still substantially maintain the technical features claimed for protection by the original invention, that is, they can still achieve the core functions and effects of the present invention, then these changes should be deemed to fall within the scope of protection of the pending claims of the present invention.

[0056] Furthermore, with the continuous advancement and development of technology, new technical means and methods continue to emerge, providing ample room for further improvement and perfection of the present invention. Therefore, the scope of protection of the present invention should also include reasonably foreseeable improvements and extensions based on existing technologies. As long as these improvements and extensions do not deviate from the basic principles and core concepts of the present invention, they should be considered equivalent to the present invention and equally protected by patent rights.

Claims

1. A low-carbon coal-fired cogeneration system, characterized in that: The invention comprises a steam Rankine cycle system and a supercritical water gasification system, wherein the supercritical water gasification system comprises a water-coal slurry pump (1), a first water feed pump (2), a No. 1 heater (3), a No. 2 heater (4), a No. 3 heater (5), a No. 4 heater (6), a supercritical water gasification reactor (7), a diverter (8), a gas-liquid separation system, a regenerator (11) and a burner (12); The gasification feed water is connected to the cold end of the No. 1 heater (3), the cold end of the No. 2 heater (4), the cold end of the No. 3 heater (5) and the cold end of the No. 4 heater (6) in sequence through the first feed water pump (2), and the cold end outlet of the No. 4 heater (6) is connected to the supercritical water gasification reactor (7); the water-coal slurry is connected to the supercritical water gasification reactor (7) through the water-coal slurry pump (1); the solid outlet of the supercritical water gasification reactor (7) is used to discharge ash; the gas outlet of the supercritical water gasification reactor (7) is connected to the inlet of the splitter (8) through the hot end of the No. 3 heater (5), and the outlet of the splitter (8) is respectively connected to the steam Rankine cycle The first hot end of the waste heat boiler (13) of the system and the hot end of the No. 2 heater (4), the first hot end outlet of the waste heat boiler (13) and the hot end outlet of the No. 2 heater (4) are connected to the hot end of the No. 1 heater (3) after merging; the hot end outlet of the No. 1 heater (3) is connected to the gas-liquid separation system, the liquid phase outlet of the gas-liquid separation system is used for drainage, the gas phase outlet of the gas-liquid separation system is connected in sequence to the cold end of the regenerator (11), the burner (12), the hot end of the No. 4 heater (6) to the second hot end of the waste heat boiler (13), and the second hot end outlet of the waste heat boiler (13) is connected to the gas-liquid separation system through the hot end of the regenerator (11).

2. A low-carbon coal-fired cogeneration system according to claim 1, characterized in that: The supercritical water gasification system further comprises a throttle valve (9), a cooler (20) and a carbon dioxide capture device. The gas-liquid separation system comprises a No. 1 gas-liquid separator (10) and a No. 2 gas-liquid separator (21). The hot end outlet of the No. 1 heater (3) is connected to the No. 1 gas-liquid separator (10) via the throttle valve (9). The liquid phase outlet of the No. 1 gas-liquid separator (10) is used for drainage. The gas phase outlet of the No. 1 gas-liquid separator (10) is sequentially connected to the cold end of the regenerator (11), the burner (12), the hot end of the No. 4 heater (6) to the second hot end of the waste heat boiler (13). The cold end inlet of the regenerator (11) is connected to oxygen. The second hot end outlet of the waste heat boiler (13) is sequentially connected to the hot end of the regenerator (11), the cooler (20) to the No. 2 gas-liquid separator (21). The liquid phase outlet of the No. 2 gas-liquid separator (21) is used for drainage. The gas phase outlet of the No. 2 gas-liquid separator (21) is connected to the carbon dioxide capture device.

3. The low-carbon coal-fired cogeneration system according to claim 1, characterized in that: The operating temperature range of the burner (12) is 900°C – 1400°C.

4. A low-carbon coal-fired cogeneration system according to claim 1, characterized in that: The steam Rankine cycle system further includes a steam turbine (14), a heating heater (15), a condenser (16), a condensate pump (17), a deaerator (18) and a second feed water pump (19); the cold end outlet of the waste heat boiler (13) is connected to the steam turbine (14), the first outlet of the steam turbine (14) is connected to the deaerator (18) via the hot end of the heating heater (15), the cold end of the heating heater (15) is connected to the steam pipe network of the heating system, the second outlet of the steam turbine (14) is connected to the condenser (16), the condensate pump (17) and the deaerator (18) in sequence, and the outlet of the deaerator (18) is connected to the cold end inlet of the waste heat boiler (13) via the second feed water pump (19), thereby forming a steam Rankine cycle.

5. A low-carbon coal-fired cogeneration system according to claim 4, characterized in that: The steam turbine (14) includes a high-pressure, medium-pressure and low-pressure multi-stage structure, wherein the high-pressure structure is used for expansion power generation, the medium-pressure structure is used to assist the high-pressure structure in expansion power generation and heating hot water for the heating system, and the low-pressure structure is used to assist the high-pressure structure in expansion power generation. Adjusting the air extraction volume of the steam turbine (14) can control the distribution ratio of the steam turbine (14) power generation and heat supply. When the load of the power grid is at a peak, reducing the air extraction volume of the steam turbine (14) and increasing the expansion ratio of steam in the steam turbine (14) can increase the power generation; when the heat demand is at a peak, increasing the air extraction volume of the steam turbine (14) and using more steam for heat supply in the heat network can increase the heat supply.

6. The low-carbon coal-fired cogeneration system according to claim 4, characterized in that: The temperature of the hydrophobic water at the hot end outlet of the heating heater (15) can be dynamically adjusted according to the heating demand, and the adjustment range is 60℃ ~ 150℃ to adapt to the heating demand of different environmental conditions and regions.

7. The low-carbon coal-fired cogeneration system according to claim 1, characterized in that: Heater No. 1 (3), Heater No. 2 (4), Heater No. 3 (5), Heater No. 4 (6), Regenerator (11) and Waste Heat Boiler (13) are all wall-type heat exchangers, and the minimum range of heat exchange temperature difference is 5°C to 20°C.

8. The low-carbon coal-fired cogeneration system according to claim 1, characterized in that: The operating temperature of the supercritical water gasification reactor (7) is 600°C to 700°C, and the operating pressure is 25 MPa to 30 MPa.

9. A method for operating a low-carbon coal-fired cogeneration system, characterized in that: A low-carbon coal-fired cogeneration system according to any one of claims 1 to 8 is used, wherein the gasification feed water is pressurized by the first feed water pump (2) and then enters the cold ends of the No. 1 heater (3), the No. 2 heater (4) and the No. 3 heater (5) in sequence for heating, the high-temperature and high-pressure gasification synthesis gas in the supercritical water gasification reactor (7) exchanges heat with the heated gasification feed water, the gasification feed water after heat exchange enters the No. 4 heater (6), and the gasification synthesis gas after heat exchange flows into the diverter (8) through the hot end of the No. 3 heater (5); The gasified synthesis gas is divided into two paths through the splitter (8): the first path enters the hot end of the second heater (4) for preheating the gasification feed water, and the second path enters the hot end of the waste heat boiler (13) for heating the feed water of the steam Rankine cycle system to generate steam. The gasified synthesis gas after the two reactions is mixed and enters the hot end of the first heater (3) for further preheating the gasification feed water; the gasified synthesis gas at the hot end outlet of the first heater (3) enters the gas-liquid separation system for gas-liquid separation to obtain water and dry gasified synthesis gas. The water is discharged from the system through the liquid phase outlet of the gas-liquid separation system, and the dry gasified synthesis gas and oxygen enter the cold end of the regenerator (11) for preheating, and then enter the burner (12 ) undergoes a complete oxidation reaction to generate high-temperature flue gas; the high-temperature flue gas enters the fourth heater (6) and releases heat to the gasification feed water after heat exchange to obtain the first flue gas; the water-coal slurry is pressurized by the water-coal slurry pump (1) and enters the supercritical water gasification reactor (7), and the gasification feed water absorbs heat to the temperature required for the supercritical water gasification reaction, and then enters the supercritical water gasification reactor (7) to undergo a supercritical water gasification reaction with the water-coal slurry to generate high-temperature and high-pressure gasification synthesis gas; the first flue gas enters the hot end of the waste heat boiler (13) and releases heat to the feed water of the steam Rankine cycle system to generate steam to obtain the second flue gas, and the second flue gas enters the hot end of the regenerator (11) and releases heat to preheat the dried gasification synthesis gas and oxygen.

10. The method for operating a low-carbon coal-fired cogeneration system according to claim 9, characterized in that: The gasified synthesis gas is divided into two paths through a splitter (8), and the mass flow ratio of the first path to the second path ranges from 0.4 to 0.6.

Images