CN105820842B - A kind of coal gasification supercritical CO2Cycle generating system - Google Patents

Abstract

A coal gasification supercritical _CO cycle power generation system, comprising a coal gasification unit, an air separation unit and an internal combustion type supercritical _CO cycle unit, wherein the air separation unit inputs air to generate oxygen, and outputs the oxygen in two ways, One of them is input into the gasifier, and the other is input into the combustion chamber of the internal combustion type supercritical _CO circulation unit. The internal combustion type supercritical _CO circulation unit also includes a turbine that converts thermal energy into mechanical energy and a recuperation unit for heat exchange, wherein the outlet from the turbine interstage, the turbine outlet, or the hot end outlet on the cold side of the recuperation unit A part of the gas is extracted and input as a gasification agent to be used as the gasification furnace in the coal gasification unit. A coal gasification supercritical CO ₂ cycle power generation system proposed by the present invention can achieve high system efficiency while realizing zero CO ₂ emissions, which is 8-8-8% higher than the net efficiency of the integrated coal gasification combined cycle power generation system based on pre-combustion capture 14 percent.

Description

A coal gasification supercritical CO2 cycle power generation system

technical field

The invention belongs to the field of energy power and coal chemical industry, and in particular relates to a coal gasification supercritical _CO2 cycle power generation system.

Background technique

Under the coal-dominated energy structure in China, how to reduce _CO2 emissions from coal-based power plants efficiently and at low cost is an important issue in the energy field. The technical routes for reducing CO ₂ emissions in conventional coal-based power plants include pre-combustion capture, post-combustion capture, and oxygen-enriched combustion.

Post-combustion capture refers to the separation and capture of CO ₂ from flue gas after combustion, and its main application is conventional pulverized coal power plants. Its main advantages are mature technology, simple principle and good inheritance to existing power stations. The disadvantages are that due to the large volume flow rate of flue gas after combustion, the partial pressure of _CO2 is small, the energy consumption of the decarbonization process is large, the investment and operation costs of equipment are high, and the cost of capture is high. Post-combustion _CO2 capture will reduce system efficiency by 8-15 percentage points.

Pre-combustion capture refers to the separation and capture of carbon-containing components in the fuel before combustion, and is mainly used in integrated coal gasification combined cycle IGCC power plants. The capture process is as follows: the coal-based gas produced by the gasifier enters the water-gas shift unit after purification, and the CO and water vapor in it undergo a water-gas shift reaction to generate CO ₂ and H ₂ , increasing the content of CO ₂ in the gas, and then reducing the CO 2 in the gas. CO ₂ for separation. Compared with post-combustion capture, pre-combustion capture requires significantly less volume of gas to be treated and significantly higher _CO2 concentration. Capturing _CO2 prior to combustion will reduce system efficiency by 6-15 percentage points.

Oxygen-enriched combustion refers to the use of O ₂ /CO ₂ mixture instead of air as the oxidant, which is burned together with pulverized coal in a pure oxygen combustion furnace. The concentration of _CO2 in the combustion product reaches more than 90%, which can be directly separated, which significantly reduces the energy consumption of the capture process. Due to changes in the combustion-supporting medium, the combustion characteristics, flue gas radiation heat transfer characteristics, desulfurization and desulfurization characteristics of this technology will all change. Based on this combustion technology, it is necessary to develop a corresponding pure oxygen combustion furnace. In addition, the oxygen required for oxyfuel combustion needs to be supplied by the air separation system. Although the energy consumption of the CO ₂ separation process is reduced, the application of the air separation process increases the energy consumption of the system and will greatly increase the investment of the system. The energy consumed by air separation in oxyfuel combustion will reduce the system efficiency by about 10 percentage points.

Under the above three technical routes, the efficiency of coal-based CO ₂ near-zero emission power plants is about 30%-38%, which is 6-15% lower than that without capture. On the one hand, it is necessary to vigorously develop related key technologies to further enhance the technical economy of the system; on the other hand, it is necessary to develop more efficient and low-cost zero-emission coal-based power generation technologies through circular innovation.

The proposal of the internal combustion supercritical CO ₂ cycle provides a new cycle innovation idea for CO ₂ emission reduction in coal-based power plants. The currently proposed internal combustion supercritical CO ₂ cycle includes COOPERATE cycle, Matiant cycle (including CO ₂ condenser and excluding CO ₂ condenser), E-Matiant cycle, OCDOPUS and Allam cycle, etc. These cycles are all proposed with natural gas as fuel, but coal-to-synthesis gas can be used as fuel at the same time. The above internal combustion supercritical _CO2 cycle has the advantages of high cycle efficiency and simple system flow. When natural gas is used as fuel, the system efficiency is about 45%-58.9%, and the Allam cycle has the highest efficiency. However, due to the physical properties of the supercritical CO ₂ working medium, the above two types of cycles face two problems: 1) The specific heat of CO ₂ under high pressure will first increase and then decrease with the decrease of temperature, which is prone to heat transfer mismatch in the low temperature section problems, resulting in greater 2) Under the working parameters of the turbine, the specific heat ratio of CO ₂ is lower than that of air or water vapor. Under the same drop pressure ratio, the temperature ratio of the inlet and outlet of the turbine is small, and the exhaust gas temperature of the turbine is high. Due to restrictions, the inlet temperature of the turbine cannot be increased, and it is difficult to improve the efficiency.

When combined with coal gasification, coal gasification is combined with internal combustion supercritical CO ₂ cycle. The current combination method is simple sharing of air separation, and synthetic gas is used instead of natural gas. The efficiency advantage of internal combustion supercritical CO ₂ cycle disappears. do. As we all know, coal gasification itself is a process that significantly reduces the available energy. The energy consumed by the coke gasification reaction, gasification agent, oxygen and solid temperature rise in the gasifier must be provided by the combustion of a part of the coke. The larger the proportion of coke combustion, The greater the loss of available energy. At present, the cold gas efficiency of common gasifiers is only about 82% at best. Considering the energy consumption of air separation, the energy conversion and utilization efficiency of coal will be lower. Although the heat of syngas cooling from high temperature to 40°C in the process of dust removal and purification can be recovered by producing steam from waste boilers and heating water from waste boilers, the energy loss of water vapor condensation in syngas is large and the heat utilization rate is low. In addition, in addition to meeting the needs of gasification and purification processes, the steam produced by waste boilers in the gas cooling process needs to be equipped with multi-stage steam turbines and condensing systems for consumption. Due to the difference in working medium between the steam cycle and the _CO2 cycle, it is impossible to share the equipment, so two sets of independent power generation systems need to be set up, resulting in complex systems, high investment costs, and difficult control. Its internal efficiency is about 6-8% lower than that of a large steam turbine, and the efficiency is further reduced.

In summary, the three technical routes currently applied to _CO2 emission reduction in coal-based power plants have the problems of low system efficiency and high power generation costs. It is urgent to develop near-zero-emission coal-based power plant technologies through circular innovation. The proposal of the internal combustion supercritical CO ₂ cycle provides a new option for the coal-fueled CO ₂ zero emission system, but there are still some technical problems in the internal combustion supercritical CO ₂ cycle, and when it is combined with coal gasification , if only the sharing of air separation and the combination of fuel are considered, the system will be complicated and the system efficiency will be low.

Contents of the invention

Aiming at the above-mentioned shortcomings and deficiencies of the prior art, the object of the present invention is to propose a coal gasification supercritical _CO2 cycle power generation system.

To achieve the above object, the present invention provides a coal gasification supercritical _CO cycle power generation system, comprising a coal gasification unit, an air separation unit and an internal combustion type supercritical _CO cycle unit, wherein,

The coal gasification unit includes a gasifier, and the internal combustion supercritical _CO circulation unit includes a combustion chamber;

The air separation unit inputs air to generate oxygen, and outputs the oxygen in two ways, one of which is input into the gasifier and the other into the combustion chamber.

Preferably, the internal combustion supercritical _CO circulation unit also includes a turbine for converting thermal energy into mechanical energy and a heat recovery unit for heat exchange, wherein the turbine interstage, the turbine outlet or the cold side of the heat recovery unit A part of the gas is extracted from the outlet of the hot end, and is input as a gasification agent to be used as a gasifier in the coal gasification unit.

Preferably, the gasifier is a high-temperature gasifier with an operating temperature ≥ 1300°C; or the gasifier is a medium-low temperature catalytic gasifier with an operating temperature of 700-900°C.

Preferably, it is characterized in that: the coal gasification unit includes a waste heat boiler, and the waste heat boiler produces supercritical steam with a pressure ≥ 22MPa, or medium-high pressure superheated steam with a pressure greater than or equal to 3MPa and less than 22MPa, which is directly injected into the internal combustion supercritical steam Combustion chamber for critical _CO2 cycle.

Preferably, the coal gasification unit includes a dedusting unit, wherein part of the heat of the syngas cooling process after dedusting by the dedusting unit is input for heating the waste boiler feed water, and part of the heat is input for preheating the internal combustion supercritical _CO2 circulation unit Cycle CO ₂ .

Preferably, the internal combustion type supercritical _CO Circulation unit is provided with N-stage combustors and turbines, and N is a natural number from 1 to 5;

Preferably, the heat source required by the heat recovery unit is exhaust heat from the turbine; preferably, the heat source required by the heat recovery unit also includes: the heat of the syngas cooling process, the heat of the air compression process, and the heat of the oxygen compression process and/or _CO2 compression process heat.

Preferably, the sources of heat required by the heat recovery unit include: syngas cooling process heat, air compression process heat, oxygen compression process heat and/or CO ₂ compression process heat.

Preferably, the heat recovery unit is composed of a plurality of heat regenerators, and the arrangement of the heat regenerators is set according to the principle of "energy matching and cascade utilization".

Preferably, the internal combustion supercritical CO ₂ circulation unit adopts Allam circulation process, Matiant circulation process or E-Matiant circulation process.

Through the above technical scheme, the beneficial effects of the present invention are:

(1) said a kind of coal gasification supercritical _CO cycle that the present invention provides, the high-temperature rich _CO in the internal-combustion supercritical _CO cycle is drawn back as the gasifying agent of the gasifier, which can bring the following Effects in several aspects: a. Injection of high-temperature rich CO ₂ into the gasifier can reduce the proportion of coke used for combustion and heating in the gasification process, and improve the efficiency of the gasifier. efficiency and cold gas efficiency, and at the same time reduce the oxygen consumption and air separation power consumption of the gasifier; b. The reflux working medium is mainly CO ₂ . Less heat loss due to water vapor condensation;

(2) said a kind of coal gasification supercritical _CO cycle provided by the present invention directly injects the steam produced by the waste pot into the internal combustion type supercritical _CO cycle combustion chamber, which can bring the following effects: a . Simplify the power output unit; b. Water vapor can replace a part of CO ₂ as a diluent, reduce the flow of circulating CO ₂ working fluid, and reduce the power consumption of CO ₂ compression process; c. The injection of water vapor will change the thermal properties of the turbine inlet working fluid , to increase the specific heat ratio of the working fluid, the inlet temperature of the turbine can be increased under the same temperature limit of the hot end of the regenerator; d. The injection of water vapor can increase the flow rate of the working fluid on the hot side of the regenerator unit, and increase the total heat transfer on the hot side The amount can improve the problem of heat mismatch at the low temperature end of the heat exchanger to a certain extent.

(3) A coal gasification supercritical CO ₂ cycle proposed by the present invention, through two methods of steam injection and high-temperature CO ₂ -enriched working fluid reflux, combined with the utilization of medium and low temperature heat in gas cooling, on the one hand can solve the problem of internal combustion supercritical CO 2 The heat mismatch of the regenerator in the critical cycle itself makes it difficult to improve performance. On the other hand, high net efficiency of the system can be obtained;

(4) A coal gasification supercritical _CO cycle power generation system proposed by the present invention achieves high system efficiency while achieving zero _CO emissions, which is higher than the net efficiency of the integrated coal gasification combined cycle power generation system based on pre-combustion capture 8-14 percentage points.

Description of drawings

Fig. 1 is a kind of coal gasification supercritical _CO cyclic power generation system proposed by the present invention

In the above drawings, the components and corresponding marks are: 1-gasifier; 2-waste heat boiler; 3-dust removal unit; 4-synthesis gas cooling unit; 5-desulfurization and sulfur recovery unit; 6-fuel compressor; 7-combustor; 8-turbine; 9-regeneration unit; 10-cooler; 11-flash tank; 12-CO ₂ compressor; 13-CO ₂ cooler; 14-CO ₂ pump; 15-empty points; 16-oxygen compressor; 17-oxygen booster;

101-coal, 102-high temperature crude synthesis gas, 103-medium temperature crude synthesis gas, 104-dust-removed synthesis gas, 105-normal temperature synthesis gas; 106-net synthesis gas, 107-compressed clean synthesis gas, 108-high temperature flue gas , 109- high temperature turbine exhaust, 110- flue gas to regenerator, 111- flue gas from regenerator, 112- flue gas after cooling, 113- CO ₂ gas, 114- compressed CO ₂ gas, 115- liquid CO ₂ , 116-pressurized CO ₂ , 117-de-storage CO ₂ , 118-cycle CO ₂ , 119-high temperature cycle CO ₂ , 120-high temperature turbine exhaust for degasification furnace, 121-air, 122-oxygen , 123-Oxygen after compression, 124-Oxygen to gasifier, 125-Oxygen to combustor, 126-Oxygen after pressurization.

Detailed ways

In order to make the object, technical solution and advantages of the present invention clearer, the present invention will be further described in detail below with reference to the accompanying drawings and examples. The following description of the embodiments of the present invention with reference to the accompanying drawings is intended to explain the general inventive concept of the present invention, but should not be construed as a limitation of the present invention.

Referring to Fig. 1, a kind of coal gasification supercritical _CO2 circulation power generation system proposed by the present invention, coal 101 enters gasifier 1, under the action of high-temperature _CO2 -enriched working medium 120 and oxygen 124, reacts to generate high-temperature crude synthesis gas 102, high-temperature The crude synthesis gas is cooled to about 350°C by the waste heat boiler 2 to become a medium-temperature crude synthesis gas 103, and then enters the dust removal unit 3 to remove most of the solid impurities. The steam 129 generated by the waste heat boiler 2 is directly injected into the combustion chamber 7 of the internal combustion supercritical CO ₂ circulation unit. The dedusted synthesis gas 104 is further cooled (to become room temperature synthesis gas 105 ) and enters the desulfurization and sulfur recovery unit 5 to remove sulfur components (H ₂ S, COS, etc.) and produce elemental sulfur products. The desulfurized net syngas 106 is compressed by the fuel compressor 6 (to become the compressed syngas 107 ) and enters the internal combustion type supercritical CO ₂ circulating combustor 7 for pure oxygen combustion as fuel. The high-temperature gas 108 after combustion is expanded through the high-temperature and high-pressure turbine 8 to perform work. According to the operating pressure of the coal gasification process, a part of the high-temperature turbine exhaust gas 120 is extracted between the 8 stages of the turbine or at the outlet of the turbine 8 and circulated to the gasifier 1 as a gasification agent in the gasification process. Another part of the expanded high-temperature turbine exhaust gas 110 enters the hot side of the heat recovery unit 9 for cooling, and the gas 111 exiting the heat recovery unit 9 is further cooled by the cooler 10 (becoming cooling gas 112 ) and separated by the flash tank 11 The H ₂ O becomes CO ₂ gas 113 with higher purity. _CO2 gas 113 is compressed to 8MPa by multi-stage _CO2 compressor 12 (to become compressed _CO2 gas 114), then cooled by _CO2 cooler 13 to become liquid _CO2 115, and then pressurized to 15-30MPa by _CO2 pump , become supercharged CO ₂ 116, a part of the supercharged CO ₂ 117 is exported to be sealed, and the rest is passed through the regenerating unit 9 as circulating CO ₂ 118 (becomes high-temperature circulating CO ₂ 119) and enters the combustion chamber 7 to continue to participate in the cycle.

In the present invention, "supercritical" in the coal gasification supercritical _CO2 cycle power generation system and the internal combustion type supercritical _CO2 cycle unit refers to the temperature of carbon dioxide gas in the regenerator of the internal combustion type supercritical _CO2 cycle unit greater than 30.98°C and the gas pressure is greater than 73.8MPa.

Preferably, the temperature of the gasifying agent in the gasifier 1 can reach about 750-1000°C, and the gasification agent is mainly CO ₂ (CO ₂ volume fraction > 90%), which is different from the current conventional gasification agent using water/steam and O ₂ Compared with the gasifier, the coke used for burning heat is less, and the cold gas efficiency of the gasification process is higher.

Preferably, the gasification agent required by the gasifier 1 can come from the 8th stage of the internal combustion supercritical CO ₂ cycle turbine, the outlet of the turbine 8 or the outlet of the hot end on the cold side of the heat recovery unit 9 .

Preferably, the gasifier 1 can be a high-temperature gasifier with an operating temperature ≥ 1300°C.

Preferably, the gasifier 1 can be a medium-low temperature catalytic gasifier with an operating temperature of 700-900°C and an alkali metal as a catalyst. Compared with conventional gasifiers, it can realize autothermal reaction without supplying oxygen.

Preferably, the water vapor generated by the waste heat boiler 2 may be supercritical water vapor (pressure ≥ 22 MPa).

Preferably, the steam generated by the waste heat boiler 2 may be medium-high pressure superheated steam (3MPa≤pressure<22MPa).

Preferably, the water vapor produced by the waste heat boiler 2 is directly injected into the combustion chamber 7 of the internal-combustion supercritical _CO circulation unit, which can save devices such as a small steam turbine generating set and a condensate pump separately, and the injection of water vapor can change the supercritical Critical CO ₂ physical properties, lower turbine exhaust gas temperature, reduce heat recovery unit heat recovery difference, alleviate the heat recovery unit cold end energy mismatch problem.

Preferably, part of the heat in the syngas cooling process after dedusting (350°C-60°C exothermic heat) is used to heat the waste heat boiler 2 feed water, and part is used to preheat the internal combustion supercritical CO ₂ cycle and partly circulate CO ₂ to solve the heat recovery unit 9 Cold end energy mismatch problem.

Preferably, the internal combustion supercritical CO ₂ circulation unit can be provided with N-stage (1≤N≤5) combustors and turbines.

Preferably, the operating pressure range of the first-stage combustion chamber of the internal combustion supercritical CO ₂ circulation unit is 3-40 MPa.

Preferably, the heat required by the internal combustion type supercritical _CO2 cycle heat recovery unit 9 is mainly the exhaust heat of the turbine, which can be combined with the heat of the syngas cooling process, the heat of the air compression process, the heat of the oxygen compression process, the _CO2 heat of compression process;

Preferably, the internal combustion supercritical CO ₂ circulation heat recovery unit is composed of a series of heat regenerators, and the heat regenerators are set according to the principle of "energy matching and cascade utilization".

Preferably, the internal-combustion supercritical CO ₂ circulation unit can adopt Allam circulation flow configuration, Matiant circulation flow configuration, E-Matiant circulation flow configuration.

Preferably, the air separation unit comprises an air separation unit, an oxygen compressor and an oxygen booster, the air separation unit inputs air 121, produces oxygen 122 (also discharges nitrogen 127), and the oxygen is exported after being compressed by the oxygen compressor Oxygen, a part of the compressed oxygen 124 is sent to the coal gasification unit, and another part of the compressed oxygen 125 is continuously pressurized by the oxygen booster (forming the pressurized oxygen 126) and then output to the internal combustion supercritical _CO2 cycle unit.

The coal gasification supercritical _CO2 cycle provided by the present invention extracts the high-temperature _CO2 -enriched working fluid from the internal combustion supercritical _CO2 cycle as the gasification agent of the gasifier, which can bring the following aspects Beneficial effects: 1) Injection of high-temperature rich CO ₂ into the gasifier can reduce the proportion of coke used for burning heat in the gasification process, and improve the efficiency of the gasifier. efficiency and cold gas efficiency, and at the same time reduce the oxygen consumption and air separation power consumption of the gasifier; 2) The reflux working medium is mainly CO ₂ . Less heat loss due to condensation of water vapor.

Said a kind of coal gasification supercritical _CO circulation that the present invention provides, the steam that waste pot produces is directly injected in the internal combustion type supercritical _CO circulation combustion chamber, and it can bring the beneficial effect of following aspects: 1) Simplify Power output unit; 2) Water vapor can replace a part of CO ₂ as a diluent, reduce the flow of circulating CO ₂ working fluid, and reduce the power consumption of CO ₂ compression process; 3) The injection of water vapor will change the thermal properties of the turbine inlet working fluid, improving The specific heat ratio of the working fluid can increase the inlet temperature of the turbine under the same temperature limit of the hot end of the regenerator; 4) The injection of water vapor can increase the flow rate of the working fluid on the hot side of the regenerator unit, increasing the total heat transfer capacity of the hot side, The problem of heat mismatch at the low temperature end of the heat exchanger can be improved to a certain extent.

Performance Comparison and Analysis

According to the flow chart of a coal gasification supercritical _CO2 cycle power generation system shown in Figure 1, the operating pressure of the gasifier 1 is 3 MPa, the operating temperature is 1400 °C, the outlet temperature of the waste heat boiler 2 is 350 °C, and the dust removal unit 3 removes solids. The removal rate is 99.5%, the desulfurization rate of desulfurization and sulfur recovery unit 5 is 99.8%, the internal combustion supercritical _CO2 circulation unit adopts the first-stage combustion chamber and the first-stage turbine, the pressure of combustion chamber 7 is 30MPa, and the temperature of combustion chamber 8 is 1150℃ , turbine 8 outlet pressure 3MPa, heat recovery unit 9 hot side outlet temperature 86°C, cooler 10 outlet temperature 30°C, multi-stage _CO2 compressor 12 outlet pressure 8MPa, _CO2 compressor pump outlet pressure 30MPa, heat recovery unit cold The outlet temperature of the side hot end is 750°C. The waste heat boiler 2 produces 30MPa, 600°C supercritical steam, which is directly injected into the combustion chamber 7 of the internal combustion supercritical CO ₂ circulation unit.

The gasification coal used in this example is Datong bituminous coal, and its composition and calorific value are shown in Table 1.

Table 1

See Table 2 for the comparison between the performance of the gasifier in a coal gasification supercritical CO ₂ cycle power generation system described in the examples and the performance of the conventional Shell gasifier.

It can be seen that the cold gas efficiency of the gasifier in the present invention reaches 84.36%. Compared with the conventional Shell gasifier (82.12%), the cold gas efficiency has increased by about 2.24 percentage points, which means more coke energy conversion is the calorific value of the syngas.

Table 2

The present invention proposes a coal gasification supercritical _CO2 circulation power generation system. The performance of capture rate) is shown in Table 4. It can be seen that the present invention proposes a coal gasification supercritical _CO2 circulation power generation system with a net efficiency of 47.02%, and can realize _CO2 zero emission, which is better than the IGCC carbon capture power generation system based on the Shell gasifier (90% carbon capture set) is about 10.9 percentage points higher in net efficiency.

table 3

name unit The system of this embodiment Gasifier coal consumption t/h 125.00 Turbine output work MW 667.57 power consumption of fuel compressor MW 15.86 Air compressor power consumption MW 69.52 Oxygen compressor power consumption MW 29.48 Oxygen booster power consumption MW 13.11 Multi-stage _CO2 compressor power consumption MW 62.66 _CO2 compressor pump power consumption MW 43.42 Other auxiliary power consumption MW 11.12 System power supply MW 422.4 System power supply efficiency % 47.02

Table 4

So far, the present embodiment has been described in detail with reference to the drawings. Based on the above description, those skilled in the art should have a clear understanding of the coal gasification supercritical CO ₂ cycle power generation system of the present invention.

In addition, the above definitions of each element and method are not limited to the various specific structures, shapes or methods mentioned in the embodiments, and those of ordinary skill in the art can easily modify or replace them, for example:

(1) Although in the above-mentioned embodiment supercritical _CO Circulation unit flow process setting adopts the same configuration as Allam cycle, the present invention is not limited to this, internal combustion type supercritical _CO Circulation unit flow process setting can also be respectively Matian cycle, E-Matiant cycle form;

(2) Although the gasification furnace in the above-mentioned embodiment adopts a high-temperature gasification furnace without adding catalyst, the present invention is not limited thereto. chemical reaction catalyst;

(3) Although in the above-mentioned embodiment, the refluxing high-temperature _CO2 -rich working fluid is extracted from the end of the turbine, the present invention is not limited thereto, and the refluxing high-temperature _CO2 -rich working fluid can also be heated from the cold side of the recuperation unit. port exit extraction;

(4) Although internal combustion type supercritical _CO in the above-mentioned embodiment Circulation part adopts one-stage combustor and one-stage turbine to arrange, but the present invention is not limited to this, the number of stages of combustor and turbine can be according to The maximum cycle pressure varies with the principle that the exhaust gas temperature of the last stage turbine is greater than 760°C, generally 1≤N≤5;

(5) Although the heat recovery unit in the above-mentioned embodiment adopts a regenerator, the present invention is not limited thereto. The number and arrangement of the regenerators are determined according to the heat and temperature requirements of the circulating _CO2 , and can be used The heat of the gas cooling unit, the heat of the air compression process, the heat of the oxygen compression process, the heat of the _CO2 compression process, and the regenerator are set according to the principle of "energy matching, cascade utilization";

(6) Although the waste heat boiler in the above-mentioned embodiment produces supercritical steam, the present invention is not limited thereto, and the steam production parameters can be adjusted and adjusted according to the combustion chamber stages and parameter settings of the internal-combustion supercritical _CO cycle part match;

In summary, a coal gasification supercritical _CO cycle proposed by the present invention is based on coal gasification as a source and an internal combustion supercritical _CO cycle as a power output unit. According to the respective characteristics of the two, steam injection and The two methods of high-temperature _CO2 -rich working fluid reflux can solve the problem of heat mismatch in the regenerator and difficulty in performance improvement in the internal combustion supercritical cycle itself, and on the other hand, can obtain high system net efficiency. A coal gasification supercritical _CO2 cycle power generation system proposed by the present invention can achieve high system efficiency while realizing zero emission of _CO2 , which is 8-8% higher than the net efficiency of the integrated coal gasification combined cycle power generation system based on pre-combustion capture 14 percent.

The specific embodiments described above have further described the purpose, technical solutions and beneficial effects of the present invention in detail. It should be understood that the above descriptions are only specific embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention shall be included within the protection scope of the present invention.

Claims (9)

1. a coal gasification supercritical _CO cyclic power generation system is characterized in that comprising a coal gasification unit, an air separation unit and an internal combustion type supercritical _CO cyclic unit, wherein, The coal gasification unit includes a gasifier, and the internal combustion supercritical _CO circulation unit includes a combustion chamber; The air separation unit inputs air to generate oxygen, and outputs the oxygen in two ways, one of which is input into the gasifier, and the other is input into the combustion chamber; The internal combustion type supercritical _CO circulation unit also includes a turbine that converts thermal energy into mechanical energy and a recuperation unit for heat exchange, wherein the outlet from the turbine interstage, the turbine outlet, or the hot end outlet on the cold side of the recuperation unit A part of the gas is extracted and input into the gasifier in the coal gasification unit as a gasification agent. 2. The coal gasification supercritical _CO2 cycle power generation system according to claim 1, characterized in that, the gasifier is a high-temperature gasifier with an operating temperature ≥ 1300°C; or the gasifier is a medium-low temperature catalytic Gasifier, the operating temperature is 700-900°C. 3. The coal gasification supercritical _CO cycle power generation system according to claim 1, characterized in that: the coal gasification unit includes a waste heat boiler, and the waste heat boiler produces supercritical steam with a pressure ≥ 22 MPa, or a pressure greater than or equal to The medium-high pressure superheated steam of 3MPa and less than 22MPa is directly injected into the combustion chamber of the internal combustion supercritical _CO2 circulation unit. 4. The coal gasification supercritical _CO cycle power generation system according to claim 1, characterized in that: the coal gasification unit includes a dedusting unit, wherein a part of the heat in the syngas cooling process is input for heating after dedusting by the dedusting unit Waste boiler feed water, and a part of input is used to preheat the internal combustion supercritical CO ₂ circulation unit to circulate CO ₂ . 5. The coal gasification supercritical CO ₂ cycle power generation system according to claim 1, characterized in that: the internal combustion type supercritical CO ₂ cycle unit is equipped with N-stage combustion chambers and turbines, and N is a natural number from 1 to 5. 6. The coal gasification supercritical CO ₂ cycle power generation system according to claim 1, characterized in that: the source of heat required by the heat recovery unit is the exhaust heat of the turbine. 7. The coal gasification supercritical _CO2 cycle power generation system according to claim 6, characterized in that: the heat source required by the heat recovery unit also includes: the heat of the syngas cooling process, the heat of the air compression process, and the heat of the oxygen compression process and/or _CO2 compression process heat. 8. The coal gasification supercritical _CO2 cycle power generation system according to claim 1, characterized in that: the heat recovery unit is composed of a plurality of heat regenerators, and the heat regenerators are set according to the principle of "energy matching, cascade utilization" Principle setting. 9. The coal gasification supercritical CO ₂ cycle power generation system according to claim 1, characterized in that: the internal combustion supercritical CO ₂ cycle unit adopts Allam cycle flow, Matiant cycle flow or E-Matiant cycle flow configuration.