Supercritical carbon dioxide coal-fired combined heat and power generation system with split-flow heat supply and low-temperature heat regeneration functions and operation method thereof

Abstract

The invention belongs to the field of supercritical carbon dioxide cycle combined heat and power generation, and relates to a split-flow heat supply and low-temperature backheating supercritical carbon dioxide coal-fired combined heat and power generation system and an operation method thereof. The system solves the problem of high-efficiency thermoelectric decoupling of a supercritical carbon dioxide coal-fired combined heat and power generation unit and comprises a coal-fired boiler system and a supercritical carbon dioxide circulating combined heat and power generation system. The supercritical carbon dioxide cycle combined heat and power generation system is mainly characterized in that on the basis that one part of a heat regenerator hot side outlet in the supercritical carbon dioxide cycle combined heat and power generation system supplies heat through a heat supply network heater, a low-temperature heat regenerator is additionally arranged on the other part to exchange heat with a carbon dioxide working medium at an outlet of a main compressor, and carbon dioxide exhaust heat in the cycle system is effectively utilized; the heat loss caused by directly entering the precooler is reduced, and the energy utilization efficiency of the system is improved. In addition, the invention further provides a scheme for thermoelectricity decoupling of the unit to realize flexible operation. And reference can be provided for future development of a supercritical carbon dioxide combined heat and power generation system.

Description

Technical Field

[0001] The invention belongs to the field of supercritical carbon dioxide cycle cogeneration, and relates to a split-flow heating and low-temperature heat recovery supercritical carbon dioxide coal-fired cogeneration system and an operation method thereof. Background Art

[0002] my country's resource endowment, which is mainly coal, determines that coal-fired power generation will still occupy an important position in my country's power generation industry for a long time. The "Notice on Carrying out the Renovation and Upgrading of Coal-fired Power Units Nationwide" proposes to implement "three-in-one transformation" including energy-saving transformation, heating transformation, and flexibility transformation for coal-fired power units. Among them, the heating transformation reflects the advantages of coal-fired combined heat and power (CHP) in energy saving, environmental protection, and high energy utilization efficiency.

[0003] Using supercritical carbon dioxide (SCO2) instead of traditional water vapor as the working medium can avoid the development difficulties of high-temperature nickel-based alloy materials and improve the efficiency of coal-fired power plants. It has the advantages of flexibility, compactness and low cost. The cogeneration of heat and power based on the supercritical carbon dioxide power cycle has broad development prospects.

[0004] Since the exhaust temperature of the low-pressure turbine in the supercritical carbon dioxide circulation system is high (above 530°C), the temperature is still above 200°C after heat release in the medium-temperature regenerator. On the one hand, it can meet the heating requirements of the heat network. On the other hand, if it directly enters the precooler, a large amount of heat loss will occur. Therefore, it is necessary to match the system with appropriate energy levels to make full use of the system heat.

[0005] The traditional cogeneration system has the problem of "determining electricity by heat", especially under the "dual carbon" goal, the scale of new energy installed capacity is growing rapidly, and the power generation of new energy is unstable. Its large-scale grid connection will require coal-fired power units to have deep peak-shaving capabilities. In this context, improving the flexible peak-shaving performance of coal-fired cogeneration systems is of great significance for promoting the consumption of new energy. Therefore, a split-flow heating and low-temperature heat recovery supercritical carbon dioxide coal-fired cogeneration system and its operation method are proposed, which improves the flexibility of the system by coupling heating and heat recovery, and realizes heat and electricity decoupling.

[0006] In the existing patent technology, there are also related reports on thermal-electric decoupling. For example, CN 208594975U discloses a gas-fired supercritical carbon dioxide cogeneration unit with a flexible and adjustable thermal-electric ratio. A heater and a shunt heater are arranged in sequence in the supercritical carbon dioxide waste heat boiler along the direction of flue gas flow. The outlet of the top gas turbine power generation system is connected to the inlet of the supercritical carbon dioxide waste heat boiler, the outlet of the compressor is connected to the cold side inlet of the regenerator and the inlet of the shunt heater, the cold side outlet of the regenerator and the outlet of the shunt heater are connected to the inlet of the heater through a pipeline, the outlet of the heater is connected to the inlet of the power turbine and the inlet of the drag turbine, the outlet of the power turbine and the outlet of the drag turbine are connected to the hot side inlet of the regenerator through a pipeline, and the hot side outlet of the regenerator is connected to the inlet of the compressor through a heat network heater and a precooler. The system can achieve complete thermal-electric decoupling, and the unit has high flexibility.

[0007] CN208380647U discloses a supercritical carbon dioxide cycle cogeneration unit with complete thermal and electrical decoupling. A high-temperature superheater, a low-temperature superheater, a shunt economizer and an SCR denitration device are arranged in the flue of the boiler. The outlet of the compressor is connected with the cold side inlet of the regenerator and the inlet of the shunt economizer. The cold side outlet of the regenerator and the outlet of the shunt economizer are connected through a pipeline and then connected in series through the gas-cooled wall of the boiler, the low-temperature superheater and the high-temperature superheater and connected with the inlet of the turbine. The outlet of the turbine is divided into two paths, one of which is connected with the hot side inlet of the regenerator, and the other is connected with the hot side outlet of the regenerator through a pipeline and then connected in series and divided into two paths, one of which is connected with the heat release side inlet of the heat network heater, and the other is connected with the heat release side inlet of the precooler. The outlet of the heat network heater and the heat release side outlet of the precooler are connected through a pipeline and then connected with the inlet of the compressor. The cogeneration system can achieve complete thermal and electrical decoupling. CN112554982B discloses a supercritical carbon dioxide cogeneration system and operation method, which uses supercritical carbon dioxide cycle as the cogeneration power cycle, coupled with the exhaust gas heating system, and provides users with both heat and electricity energy; through the coupling optimization of the hot end-heat recovery-heating process, the present invention can greatly improve the energy utilization rate of the supercritical carbon dioxide power system. The system of the present invention performs reasonable energy level matching for exhaust gas, couples the heating exhaust gas with the heat recovery system, reduces the irreversible loss of heat exchange in the system, and can meet different heating load requirements by adjusting the carbon dioxide diversion ratio of the heat recovery system, thereby improving the operating flexibility of the unit; it can also enable the system to increase the working fluid temperature entering the boiler while meeting the heating temperature, reduce the heat exchange temperature difference at the hot end, reduce irreversible losses, and improve the power generation efficiency of the unit.

[0008] Compared with the above patents, the main feature of the present invention is that, on the basis of diverting a part of the hot side outlet of the regenerator to heat through the heat network heater, the other part is added with a low-temperature regenerator to exchange heat with the carbon dioxide working medium at the outlet of the main compressor, effectively utilizing the heat of the carbon dioxide exhaust gas in the circulation system, reducing the heat loss caused by directly entering the precooler, and improving the energy utilization efficiency of the system. In addition, the present invention also provides a solution for thermal and electrical decoupling of the unit to achieve flexible operation. Summary of the invention

[0009] In order to solve the problem of high-efficiency heat and electricity decoupling of a supercritical carbon dioxide coal-fired heat and power cogeneration unit, the present invention adopts the following technical solution: a split-flow heating and low-temperature heat recovery supercritical carbon dioxide coal-fired heat and power cogeneration system and an operation method thereof, comprising a coal-fired boiler system and a supercritical carbon dioxide cycle heat and power cogeneration system.

[0010] The coal-fired boiler system is composed of a superheated gas-cooled wall, a reheated gas-cooled wall, a high-temperature superheater, a high-temperature reheater, a low-temperature superheater, a low-temperature reheater, and an economizer; the supercritical carbon dioxide cycle cogeneration system is composed of a high-pressure turbine, a low-pressure turbine, a high-temperature regenerator, a medium-temperature regenerator, a low-temperature regenerator, a heat network heater, a precooler, a main compressor, and a recompressor.

[0011] The superheated air-cooled wall is connected to the low-temperature superheater, the low-temperature superheater is connected to the high-temperature superheater, the high-temperature superheater is connected to the high-pressure turbine, the high-pressure turbine is connected to the reheated air-cooled wall, the reheated air-cooled wall is connected to the low-temperature reheater, the low-temperature reheater is connected to the high-temperature reheater, the high-temperature reheater is connected to the low-pressure turbine, and the low-pressure turbine is connected to the high-temperature regenerator; the hot side outlet of the high-temperature regenerator is connected to the medium-temperature regenerator, the hot side outlet of the medium-temperature regenerator is respectively connected to the heat network heater and the low-temperature regenerator, and the hot side outlet of the low-temperature regenerator is further connected to the outlet of the heat network heater, so that the outlet working fluid after heat release by the heat network heater and the low-temperature regenerator is mixed;

[0012] The mixed working fluid is connected to the precooler and the recompressor respectively, the precooler is connected to the main compressor, and the outlet of the main compressor is connected to the low-temperature regenerator and the medium-temperature regenerator in turn;

[0013] The outlet of the recompressor is connected to the cold test outlet of the medium-temperature regenerator, so that the working fluid at the outlet of the recompressor is connected and mixed with the working fluid at the cold test outlet of the medium-temperature regenerator;

[0014] After mixing, the working fluid channel forms two paths, which are respectively connected to the economizer and the high-temperature regenerator. Part of the working fluid after the economizer is mixed with the working fluid at the outlet of the high-temperature regenerator and then connected to the superheated gas cooling wall to complete the entire supercritical carbon dioxide heat transfer and cycle work.

[0015] Furthermore, a method for operating a supercritical carbon dioxide coal-fired cogeneration system with split-flow heating and low-temperature heat recovery is provided: the steps are: the carbon dioxide working medium in a supercritical state absorbs heat and is converted into a high-temperature and high-pressure state, and then passes through a high-pressure turbine to perform work once, and the working medium then returns to the reheat gas cold wall in the boiler, and then enters a low-temperature reheater and a high-temperature reheater in turn to absorb heat successively, and then enters a low-pressure turbine to perform work twice, and after the working medium passes through the low-pressure turbine to perform work, it enters a high-temperature reheater and a medium-temperature reheater in turn to release the remaining heat to the carbon dioxide working medium waiting to absorb heat on the cold side.

[0016] After the working fluid flows through the medium-temperature regenerator, the carbon dioxide working fluid is split into two parts for work. One part of the working fluid flows through the heat network heater to heat the heat network water; the other part flows through the low-temperature regenerator to heat the working fluid at the outlet of the main compressor. By adjusting the heat supply diversion ratio of the working fluid entering the heat network heater, the heating load demand can be met, the unit operation flexibility can be improved, and thermal-electric decoupling can be achieved.

[0017] The working fluid coming out of the heat network heater and the working fluid coming out of the low-temperature regenerator are mixed after releasing heat and then diverted. One part of the carbon dioxide working fluid is cooled to a near-critical state through the precooler, and then enters the main compressor for pressurization. The pressurized carbon dioxide working fluid enters the low-temperature regenerator and the medium-temperature regenerator in turn to absorb heat; the other part is directly sent to the re-compressor for compression processing, and the outlet working fluid is mixed with the cold outlet working fluid of the medium-temperature regenerator.

[0018] The two parts of the working fluid at the compressor outlet and the medium-temperature regenerator outlet are mixed and then divided into two parts. One part enters the high-temperature regenerator to absorb heat and further increase the temperature; the other part of the working fluid flows to the economizer in the tail flue of the boiler, so that the working fluid absorbs the heat of the flue gas and fully utilizes the waste heat of the boiler flue gas. After this series of heat absorption and temperature increase processes, the carbon dioxide working fluid is finally mixed and passes through the superheated gas cooling wall, low-temperature superheater and high-temperature superheater in the boiler again to complete a cycle.

[0019] In summary, the system and operation process of the present invention have the following advantages compared with the prior art: 1) Based on the single reheat split recompression supercritical carbon dioxide coal-fired power generation system, the present invention adds a heat network heater and a low-temperature regenerator to effectively utilize the heat of carbon dioxide exhaust gas in the cycle, reducing the heat loss caused by directly entering the precooler. This method improves the energy utilization efficiency of the system;

[0020] 2) The present invention can meet the heating load demand by adjusting the heat diversion ratio of carbon dioxide entering the heating network heater, and the rated heating load can be achieved under the condition of power supply load changes.

[0021] The operational flexibility of the system is improved and thermal and electrical decoupling is achieved.

[0022] Taking a supercritical carbon dioxide coal-fired heat and power cogeneration unit with a power supply load of 350MW and a heating load of 300MW as an example, under rated conditions, a split-flow heating and low-temperature heat recovery supercritical carbon dioxide coal-fired heat and power cogeneration system proposed in the present invention The efficiency is 44.48%, which is comparable to the common non-divided heating supercritical carbon dioxide coal-fired cogeneration system ( Figure 6 ), an increase of 7.01 percentage points, and the proposed new system can achieve thermal and electrical decoupling. The proposed split-flow heating and low-temperature heat recovery supercritical carbon dioxide coal-fired heat and power cogeneration system has better coupling performance for heating and heat recovery, which can provide a reference for the future development of supercritical carbon dioxide cogeneration systems. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 The split-flow heating and low-temperature heat recovery supercritical carbon dioxide coal-fired heat and power cogeneration system of the present invention;

[0024] Figure 2 Schematic diagram of key operating parameters of the system proposed by the present invention under 100% electrical load;

[0025] Figure 3 Schematic diagram of key operating parameters of the system proposed by the present invention under 75% electrical load;

[0026] Figure 4 Schematic diagram of key operating parameters of the system proposed by the present invention under 50% electrical load;

[0027] Figure 5 Schematic diagram of key operating parameters of the system proposed by the present invention under 30% electrical load;

[0028] Figure 6 Common non-divided heat supply supercritical carbon dioxide coal-fired cogeneration system;

[0029] Figure 7 The simulation process of the split-flow heating and low-temperature heat recovery supercritical carbon dioxide coal-fired heat and power cogeneration system proposed in the present invention;

[0030] Figure 8 Simulation process of supercritical carbon dioxide coal-fired cogeneration system with no-diversion heating;

[0031] Fig. 9 The simulation results are compared with literature data.

[0032] In the figure: 1-superheated air-cooled wall, 2-reheated air-cooled wall, 3-high-temperature superheater, 4-high-temperature reheater, 5-low-temperature superheater, 6-low-temperature reheater, 7-economizer, 8-high-pressure turbine, 9-low-pressure turbine, 10-high-temperature regenerator, 11-medium-temperature regenerator, 12-low-temperature regenerator, 13-heating network heater, 14-precooler, 15-main compressor, 16-recompressor. DETAILED DESCRIPTION

[0033] like Figure 1 As shown, a split-flow heating and low-temperature heat recovery supercritical carbon dioxide coal-fired heat and power cogeneration system and its operation method include a coal-fired boiler system and a supercritical carbon dioxide cycle cogeneration system.

[0034] The coal-fired boiler system is composed of a superheated gas-cooled wall 1, a reheated gas-cooled wall 2, a high-temperature superheater 3, a high-temperature reheater 4, a low-temperature superheater 5, a low-temperature reheater 6, and an economizer 7; the supercritical carbon dioxide cycle cogeneration system is composed of a high-pressure turbine 8, a low-pressure turbine 9, a high-temperature regenerator 10, a medium-temperature regenerator 11, a low-temperature regenerator 12, a heat network heater 13, a precooler 14, a main compressor 15, and a recompressor 16.

[0035] The superheated air-cooled wall 1 is connected to the low-temperature superheater 5, the low-temperature superheater 5 is connected to the high-temperature superheater 3, the high-temperature superheater 3 is connected to the high-pressure turbine 8, the high-pressure turbine 8 is connected to the reheated air-cooled wall 2, the reheated air-cooled wall 2 is connected to the low-temperature reheater 6, the low-temperature reheater 6 is connected to the high-temperature reheater 4, the high-temperature reheater 4 is connected to the low-pressure turbine 9, and the low-pressure turbine 9 is connected to the high-temperature regenerator 10; the hot side outlet of the high-temperature regenerator 10 is connected to the medium-temperature regenerator 11, the hot side outlet of the medium-temperature regenerator 11 is respectively connected to the heat network heater 13 and the low-temperature regenerator 12, and the hot side outlet of the low-temperature regenerator 12 is further connected to the outlet of the heat network heater 13, so that the outlet working fluid after heat release through the heat network heater 13 and the low-temperature regenerator 12 is mixed;

[0036] The mixed working fluid is connected to the precooler 14 and the recompressor 16 respectively, the precooler 14 is connected to the main compressor 15, and the outlet of the main compressor 15 is connected to the low-temperature regenerator 12 and the medium-temperature regenerator 11 in sequence;

[0037] The outlet of the re-compressor 16 is connected to the cold outlet of the medium-temperature regenerator 11, so that the working fluid at the outlet of the re-compressor 16 is connected and mixed with the working fluid at the cold outlet of the medium-temperature regenerator 11;

[0038] After mixing, the working medium channel forms two paths, which are respectively connected to the economizer 7 and the high-temperature regenerator 10. Part of the working medium after the economizer 7 is mixed with the working medium at the outlet of the high-temperature regenerator 10 and then connected to the superheated gas cooling wall 1, completing the entire supercritical carbon dioxide heat transfer and cycle work.

[0039] Refer to Figure 1A method for operating a split-flow heating and low-temperature heat recovery supercritical carbon dioxide coal-fired cogeneration system: the steps are: the carbon dioxide working medium in a supercritical state absorbs heat and is converted into a high-temperature and high-pressure state, and then passes through a high-pressure turbine 8 to perform work once, and the working medium then returns to the reheat gas cold wall 2 in the boiler, and then enters the low-temperature reheater 6 and the high-temperature reheater 4 in turn to absorb heat successively, and then enters the low-pressure turbine 9 to perform work twice, and after the working medium passes through the low-pressure turbine 9 to perform work, it enters the high-temperature reheater 10 and the medium-temperature reheater 11 in turn to release the remaining heat to the carbon dioxide working medium waiting to absorb heat on the cold side.

[0040] After the working medium flows through the medium-temperature regenerator 11, the carbon dioxide working medium is split into two parts for operation. One part of the working medium flows through the heat network heater 13 to heat the heat network water; the other part flows through the low-temperature regenerator 12 to heat the working medium at the outlet of the main compressor 15. By adjusting the heat supply split ratio of the working medium entering the heat network heater 13, the heating load demand is met, the operation flexibility of the unit is improved, and thermal-electric decoupling is achieved.

[0041] The working fluid coming out of the heat network heater 13 and the working fluid coming out of the low-temperature regenerator 12 are mixed after releasing heat and then diverted. A part of the carbon dioxide working fluid is cooled to a near-critical state by the precooler 14, and then enters the main compressor 15 for pressurization. The pressurized carbon dioxide working fluid enters the low-temperature regenerator 12 and the medium-temperature regenerator 11 in turn to absorb heat; the other part is directly sent to the re-compressor 16 for compression processing, and the outlet working fluid is mixed with the cold outlet working fluid of the medium-temperature regenerator 11.

[0042] The two parts of the working fluid at the outlet of the compressor 16 and the outlet of the medium-temperature regenerator 11 are mixed and then divided into two parts. One part enters the high-temperature regenerator 10 to absorb heat and further increase the temperature; the other part of the working fluid flows to the economizer 7 in the tail flue of the boiler, so that the working fluid absorbs the heat of the flue gas and fully utilizes the waste heat of the boiler flue gas. After this series of heat absorption and temperature increase processes, the carbon dioxide working fluid is finally mixed and passes through the superheated gas wall 1, low-temperature superheater 5 and high-temperature superheater 3 in the boiler again to complete a cycle.

[0043] like Figure 2 , 3 , 4, and 5 are respectively the key operating parameters of the system proposed by the present invention under 100%, 75%, 50%, and 30% electrical load.

[0044] Combination Figure 1 and Figure 6In comparison, compared with the common supercritical carbon dioxide coal-fired cogeneration system, the present invention adds a low-temperature regenerator to divert the working fluid at the hot side outlet of the medium-temperature regenerator. One part flows through the heat network heater to exchange heat with the heat network water; the other part flows through the low-temperature regenerator to heat the working fluid at the outlet of the main compressor; the two parts of the working fluid are mixed after heat release and then diverted to enter the re-compressor and the main compressor through the pre-cooler respectively. The heating load demand can be met by adjusting the heat diversion ratio entering the heat network heater, and the rated heating load can be reached under the condition of changes in the power supply load of the unit. The present invention effectively utilizes the heat of carbon dioxide exhaust gas in the circulation system, reduces the cold source loss of the pre-cooler and the key components involved in the present invention (medium-temperature regenerator, heat network heater, pre-cooler, main compressor, re-compressor) loss, thus improving the energy utilization efficiency of the system.

[0045] According to the comparison of the above system performance parameters, it is estimated according to the following data: the national installed capacity is 3 billion kW, of which 1% is supercritical carbon dioxide coal-fired cogeneration system, the annual system operating hours are 3500h, the on-grid electricity price is 0.5RMB / kWh, and the annual income of the bypass heating and low-temperature heat recovery supercritical carbon dioxide coal-fired cogeneration unit proposed in the present invention is about 3.623 billion yuan higher than the common non-shunt heating supercritical carbon dioxide coal-fired cogeneration system.

[0046] The following is the simulation verification process of the present invention:

[0047] Aspen Plus software was used to establish the simulation process of the above-mentioned split-flow heating and low-temperature heat recovery supercritical carbon dioxide coal-fired cogeneration system. The key parameters are shown in Table 1. PR-BM was selected for the physical properties of the coal-fired flue gas side, and the physical properties of CO2 were derived from the REFPROP database.

[0048] Table 1 Key system parameters

[0049]

[0050]

[0051] At present, since the SCO2 coal-fired cogeneration system has not yet been industrialized, it is difficult to obtain its actual operating parameters. In order to verify the accuracy of the constructed system model, the simulation results are compared with the SCO2 reheat recompression coal-fired power generation system parameters in the literature [Sun Enhui, Zheng Yawen, Wang Ge, et al. Supercritical CO2 recompression / reheating coal-fired power generation system thermal cycle [J]. Science Bulletin, 2019, 64(02): 234-244.] The comparison results are as follows: Fig. 9 shown.

[0053] The results show that the simulation errors of the boiler heat exchange, precooler heat release, main compressor power consumption, recompressor power consumption, high-temperature regenerator heat exchange, and low-temperature regenerator heat exchange obtained in this simulation are all less than 2.0%, indicating that the established model is accurate and reliable.

[0054] System performance analysis of the solution of the present invention:

[0055] 1 System performance analysis model

[0056] 1.1 System Efficiency calculation model

[0057]

[0058] Where: P e is the power generation, kW; R er is the comprehensive power consumption rate of the plant, which is 5%; Q h is the heat supply, kJ / h; T0 is the ambient temperature, K; T is the working medium heating temperature, K; B is the actual coal consumption, t / h; e coal For coal chemistry kJ / kg.

[0059] The chemistry of coal Computational model:

[0060]

[0061] Where: ΔH μ，l is the low calorific value of raw coal, kJ / kg; C, H, O, N are the mass fractions of C, H, O, N as received in coal, respectively, %.

[0062] 1.2 Components Loss calculation model

[0063] 1.2.11 Compressor Loss calculation model

[0064] ΔE W =W in +W C ―W out

[0065] Where: W in For input working fluid Value, MW; W C is the power consumption of the compressor, MW; W out For output working fluid Value, MW.

[0066] 1.2.2 Heat exchanger Loss calculation model

[0067]

[0068] In the formula: ΔQ is the heat transfer capacity, MW; T0 is the ambient temperature, K; T is the working fluid temperature, K.

[0069] 1.3 Split ratio calculation model

[0070] 1.3.1 Heating split ratio X1

[0071]

[0072] Where: m HNH is the flow rate of the working fluid entering the heating network heater, kg / s; m total is the total working fluid flow rate, kg / s.

[0073] 1.3.2 Recompression split ratio X2

[0074]

[0075] Where: m RC is the flow rate of the working fluid entering the re-compressor, kg / s; m total is the total working fluid flow rate, kg / s.

[0076] 1.3.3 Economizer split ratio X3

[0077]

[0078] Where: m ECO is the flow rate of the working fluid entering the economizer, kg / s; m total is the total working fluid flow rate, kg / s.

[0079] 2 System Performance Comparative Analysis

[0080] The comparison results of the split-flow heating and low-temperature heat recovery supercritical carbon dioxide coal-fired heat and power cogeneration system proposed in the present invention (referred to as system A of the present invention) and the non-split-flow heating supercritical carbon dioxide coal-fired heat and power cogeneration system (referred to as non-split-flow system B) are shown in Table 2-4.

[0081] (1) As can be seen from Table 2, under the conditions of rated thermal load 300MW and 30%-100% electrical load, the system of the present invention The efficiency of the two systems is higher than that of the control system; and as the electrical load decreases, The efficiency is reduced; the system of the present invention Efficiency compared to control system The efficiency improvement rate decreases, such as when the electric load is 100%, the efficiency of the system of the present invention is The efficiency is 44.48%, which is 7.01% higher than that of the control system; The efficiency is 32.62%, which is 0.11% higher than the control system.

[0082] Table 2 System performance comparison under rated conditions

[0083]

[0084] (2) The reasons why the efficiency of the system of the present invention is higher than that of the control system are as follows: ① Using the heat method analysis, the cold source loss of the precooler in the system of the present invention is lower than that of the control system under different load conditions, see Table 3. ② Using Method analysis shows that among the main components involved in the system of the present invention, except for the added low-temperature heat regenerator, the other components The damage of other components is less than or equal to that of the control system. The sum of the losses reduced is higher than that produced by the low temperature regenerator. Loss, see Table 4.

[0085] Table 3 Comparison of precooler cooling source loss

[0086]

[0087] Table 4 Components of the two types of systems damage

[0088]

[0089]

Claims

1. A split-flow heating and low-temperature heat recovery supercritical carbon dioxide coal-fired heat and power cogeneration system, characterized in that: It consists of two parts: coal-fired boiler system and supercritical carbon dioxide cycle cogeneration system. The coal-fired boiler system is composed of a superheated gas-cooled wall (1), a reheated gas-cooled wall (2), a high-temperature superheater (3), a high-temperature reheater (4), a low-temperature superheater (5), a low-temperature reheater (6), and an economizer (7); the supercritical carbon dioxide cycle cogeneration system is composed of a high-pressure turbine (8), a low-pressure turbine (9), a high-temperature regenerator (10), a medium-temperature regenerator (11), a low-temperature regenerator (12), a heat network heater (13), a precooler (14), a main compressor (15), and a recompressor (16).

2. A split-flow heating and low-temperature heat recovery supercritical carbon dioxide coal-fired heat and power cogeneration system according to claim 1, characterized in that: The superheated air-cooled wall (1) is connected to a low-temperature superheater (5), the low-temperature superheater (5) is connected to a high-temperature superheater (3), the high-temperature superheater (3) is connected to a high-pressure turbine (8), the high-pressure turbine (8) is connected to a reheated air-cooled wall (2), the reheated air-cooled wall (2) is connected to a low-temperature reheater (6), the low-temperature reheater (6) is connected to a high-temperature reheater (4), the high-temperature reheater (4) is connected to a low-pressure turbine (9), and the low-pressure turbine (9) is connected to a high-temperature reheater (10); the hot side outlet of the high-temperature reheater (10) is connected to a medium-temperature reheater (11), the hot side outlet of the medium-temperature reheater (11) is respectively connected to a heat network heater (13) and a low-temperature reheater (12), and the hot side outlet of the low-temperature reheater (12) is further connected to the outlet of the heat network heater (13), so that the outlet working fluid after heat release through the heat network heater (13) and the low-temperature reheater (12) is mixed.

3. A split-flow heating and low-temperature heat recovery supercritical carbon dioxide coal-fired heat and power cogeneration system according to claim 2, characterized in that: The mixed working fluid is connected to a precooler (14) and a recompressor (16) respectively, the precooler (14) is connected to a main compressor (15), and the outlet of the main compressor (15) is connected to a low-temperature regenerator (12) and a medium-temperature regenerator (11) in sequence.

4. A split-flow heating and low-temperature heat recovery supercritical carbon dioxide coal-fired heat and power cogeneration system according to claim 3, characterized in that: The outlet of the recompressor (16) is connected to the cold outlet of the medium-temperature reheater (11), so that the working fluid at the outlet of the recompressor (16) is connected and mixed with the working fluid at the cold outlet of the medium-temperature reheater (11).

5. A split-flow heating and low-temperature heat recovery supercritical carbon dioxide coal-fired heat and power cogeneration system according to claim 4, characterized in that: After mixing, the working medium channel forms two paths, which are respectively connected to the economizer (7) and the high-temperature regenerator (10). After part of the working medium is mixed with the working medium at the outlet of the high-temperature regenerator (10), it is connected to the superheated gas cooling wall (1), thereby completing the heat transfer and cycle work of the entire supercritical carbon dioxide.

6. A method for operating a split-flow heating and low-temperature heat recovery supercritical carbon dioxide coal-fired heat and power cogeneration system: characterized in that: The steps are as follows: the carbon dioxide working medium in a supercritical state absorbs heat and is converted into a high-temperature and high-pressure state, and then passes through a high-pressure turbine (8) to perform work once, and the working medium then returns to the reheating gas cold wall (2) in the boiler, and then enters a low-temperature reheater (6) and a high-temperature reheater (4) in sequence to successively absorb heat, and then enters a low-pressure turbine (9) to perform work twice, and after the working medium passes through the low-pressure turbine (9) to perform work, it enters a high-temperature reheater (10) and a medium-temperature reheater (11) in sequence to release the remaining heat to the carbon dioxide working medium waiting to absorb heat on the cold side.

7. The method for operating a split-flow heating and low-temperature heat recovery supercritical carbon dioxide coal-fired heat and power cogeneration system according to claim 6 is characterized in that: After the working medium flows through the medium-temperature regenerator (11), the carbon dioxide working medium is split into two parts for operation, one part of the working medium flows through the heat network heater (13) to heat the heat network water; the other part flows through the low-temperature regenerator (12) to heat the working medium at the outlet of the main compressor (15). By adjusting the heat supply split ratio of the working medium entering the heat network heater (13), the heating load demand is met, the operation flexibility of the unit is improved, and thermal-electric decoupling is achieved.

8. The method for operating a split-flow heating and low-temperature heat recovery supercritical carbon dioxide coal-fired heat and power cogeneration system according to claim 7 is characterized in that: The working fluid from the heating network heater (13) and the working fluid from the low-temperature regenerator (12) are mixed after releasing heat and then divided. A portion of the carbon dioxide working fluid is cooled to a near-critical state by the precooler (14) and then enters the main compressor (15) for pressure increase. The pressurized carbon dioxide working fluid enters the low-temperature regenerator (12) and the medium-temperature regenerator (11) in turn to absorb heat. The other portion is directly sent to the recompressor (16) for compression processing, and the outlet working fluid is mixed with the cold outlet working fluid of the medium-temperature regenerator (11).

9. The method for operating a split-flow heating and low-temperature heat recovery supercritical carbon dioxide coal-fired heat and power cogeneration system according to claim 8 is characterized by: The two parts of the working fluid at the outlet of the recompressor (16) and the outlet of the medium-temperature reheater (11) are mixed and then divided into two parts. One part enters the high-temperature reheater (10) to absorb heat and further increase the temperature; the other part of the working fluid flows to the economizer (7) in the tail flue of the boiler, so that the working fluid absorbs the heat of the flue gas and fully utilizes the waste heat of the boiler flue gas. After this series of heat absorption and temperature increase processes, the carbon dioxide working fluid is finally mixed and passes through the superheated gas cooling wall (1), the low-temperature superheater (5) and the high-temperature superheater (3) in the boiler again to complete a cycle.

Images