Coal-fired cogeneration units

Abstract

This invention discloses a coal-fired cogeneration unit, comprising: a boiler; a turbine unit comprising: a turbine and a generator, the turbine including a high-pressure cylinder, with the other end of a first steam pipe connected to the steam inlet of the high-pressure cylinder; the turbine connected to the generator; an air inlet pipe, one end of which is connected to the boiler, and the other end adapted to be connected to an external air source; a hot air heat exchanger having a first air duct and a first steam duct for mutual heat exchange, the first steam duct being connected in series to a second steam pipe, and the first air duct being connected in series to the air inlet pipe; and a first valve group, disposed on the first steam pipe and / or the second steam pipe, for controlling the superheated steam outlet to be switchably connected to the steam inlet of the hot air heat exchanger and / or the high-pressure cylinder. The carbon dioxide coal-fired cogeneration unit according to this invention is beneficial for improving the dynamic adaptability of the unit to grid load fluctuations and reducing the operating cost of the entire unit in long-term hot standby mode.

Description

Technical Field

[0001] This invention relates to the field of combined heat and power (CHP) technology, and in particular to a coal-fired CHP unit. Background Technology

[0002] With the rapid development of renewable energy in the power industry, coal-fired power units are taking on more peak-shaving tasks, and their flexibility is becoming increasingly prominent. Especially during midday, when photovoltaic power generation reaches its peak, coal-fired units need to perform deep peak shaving to balance the grid load. In some regions, renewable energy generation during midday has already fully met electricity demand, and coal-fired power grid prices have even reached zero or negative levels, resulting in significant economic losses. Against this backdrop, the demand for peak shaving through start-up and shutdown of coal-fired power units is becoming increasingly apparent. While shutdowns can reduce economic losses from power generation, the start-up and shutdown processes are complex and cannot quickly respond to changing load demands. Summary of the Invention

[0003] The present invention aims to at least solve one of the technical problems existing in the prior art. To this end, the present invention proposes a coal-fired cogeneration unit that can improve the dynamic adaptability of the unit to grid load fluctuations and reduce the operating cost of the entire unit in long-term hot standby mode.

[0004] According to the present invention, a coal-fired cogeneration unit includes: a boiler having a superheated steam outlet, a first steam pipe, and a second steam pipe, one end of which is connected to the superheated steam outlet; a turbine unit including a turbine and a generator, the turbine including a high-pressure cylinder, the other end of which is connected to the steam inlet of the high-pressure cylinder; the turbine being connected to the generator for driving the generator to rotate; an air inlet pipe, one end of which is connected to the boiler, and the other end of which is adapted to be connected to an external air source; a hot air heat exchanger having a first air duct and a first steam duct for mutual heat exchange, the first steam duct being connected in series with the second steam pipe, and the first air duct being connected in series with the air inlet pipe; and a first valve group disposed on the first steam pipe and / or the second steam pipe for controlling the superheated steam outlet to be switchably connected to the hot air heat exchanger and / or the steam inlet of the high-pressure cylinder.

[0005] According to the present invention, the coal-fired cogeneration unit, by setting a second steam pipe and a first valve group, can meet the needs of deep peak shaving and can quickly start the steam turbine in a short time when grid power generation is required, thereby improving the dynamic adaptability of the unit to grid load fluctuations. In addition, the hot air heat exchanger is used for heat exchange between superheated steam and secondary air circulation, which can also allow the heat generated by the boiler during low-load operation to circulate within the system. In this way, the unit can reduce the coal feed while maintaining stable boiler combustion and stable working fluid evaporation, thereby reducing the operating cost of the entire unit in long-term hot standby mode.

[0006] According to some embodiments of the present invention, the steam turbine further includes: an intermediate-pressure cylinder and a low-pressure cylinder; the coal-fired cogeneration unit further includes: a condenser, a low-pressure heater, a first deaerator, a high-pressure heater, a first branch pipe, and a first water pipe; one end of the first branch pipe is connected to the steam outlet of the high-pressure cylinder, and the other end is connected to the steam inlet of the condenser; the intermediate-pressure cylinder and the low-pressure cylinder are connected in series on the first branch pipe along the airflow direction; one end of the first water pipe is connected to the outlet of the condenser, and the other end is connected to the water inlet of the boiler; the low-pressure... The pressure heater, the first deaerator, and the high-pressure heater are connected in series on the first water pipe along the direction of water flow. The other end of the second steam pipe is connected to the high-pressure heater. A second branch pipe is connected at one end to the inlet of the boiler's reheater and at the other end to the steam outlet of the high-pressure cylinder. A condensate pump and a first feedwater pump are connected in series on the first water pipe and arranged between the condenser and the low-pressure heater. The first feedwater pump is connected in series between the first deaerator and the high-pressure heater.

[0007] According to some embodiments of the present invention, the boiler has a reheat steam outlet and a third steam pipe, and the coal-fired cogeneration unit further includes: a heating steam header, wherein the reheat steam outlet is connected to the heating steam header via the third steam pipe; a molten salt circulation pipeline, a low-temperature molten salt tank, a high-temperature molten salt tank, and a first heat exchanger, wherein the low-temperature molten salt tank and the high-temperature molten salt tank are connected in series on the molten salt circulation pipeline, and the first heat exchanger includes a first flow channel and a second flow channel that exchange heat with each other, wherein the first flow channel is connected in series on the molten salt circulation pipeline and is arranged between the outlet of the low-temperature molten salt tank and the inlet of the high-temperature molten salt tank, and the second flow channel is connected in series on the third steam pipe.

[0008] According to some embodiments of the present invention, the coal-fired cogeneration unit further includes: a second valve group, which is connected in series on the third steam pipe and / or the first branch pipe, for controlling the reheat steam outlet to be switchably connected to the intermediate pressure cylinder and / or connected to the heating steam header.

[0009] According to some embodiments of the present invention, the coal-fired cogeneration unit further includes: a molten salt circulation pipeline including a main pipeline, a first branch pipeline and a second branch pipeline, the low-temperature molten salt tank and the high-temperature molten salt tank being connected in series on the main pipeline, the two ends of the first branch pipeline and the second branch pipeline being respectively connected to the outlet of the low-temperature molten salt tank and the inlet of the high-temperature molten salt tank, the first heat exchanger being connected in series on the first branch pipeline, and the coal-fired cogeneration unit further includes: a fourth steam pipe and a second heat exchanger, one end of the fourth steam pipe being connected to the superheated steam outlet and the other end being connected to the inlet of the boiler's reheater, the second heat exchange pipe having a third flow channel and a fourth flow channel for mutual heat exchange, the third flow channel being connected in series on the second branch pipeline and the fourth flow channel being connected in series on the fourth steam pipe.

[0010] According to some embodiments of the present invention, the coal-fired cogeneration unit further includes: a third branch pipe, one end of which is connected to the outlet of the fourth flow channel and the other end of which is connected to the first deaerator; a condenser and a subcooler, the condenser having a first channel and a second channel for mutual heat exchange, the subcooler having a third channel and a fourth channel for mutual heat exchange, the first channel and the third channel being connected in series on the third branch pipe along the flow direction of the fluid in the third branch pipe, and the fourth channel and the second channel being connected in series on the second branch pipe along the flow direction of the molten salt.

[0011] According to some embodiments of the present invention, the coal-fired cogeneration unit further includes: a superheater and an evaporator, each having a first flow channel and a second flow channel, the first flow channels of the superheater and the evaporator being sequentially connected in series between the outlet of the high-temperature molten salt tank and the inlet of the low-temperature molten salt tank along the molten salt flow direction in the molten salt circulation pipeline; a fourth branch pipe, one end of which is connected to the outlet of the low-pressure heater and the other end of which is connected to the inlet of the second flow channel of the evaporator; and a fifth branch pipe, one end of which is connected to the outlet of the second flow channel of the evaporator and the other end of which is connected to the heating steam header, the second flow channel of the superheater being connected in series on the fifth branch pipe.

[0012] According to some embodiments of the present invention, the coal-fired cogeneration unit further includes: a second deaerator connected in series on the fourth branch pipe; a sixth branch pipe, one end of which is connected to the heating steam header and the other end of which is connected to the second deaerator; a second feedwater pump connected in series on the fifth branch pipe and arranged between the second deaerator and the evaporator; and / or a third valve group connected to the first water pipe and / or the fourth branch pipe for controlling the low-pressure heater to be switchably connected to the first deaerator and / or the second deaerator.

[0013] According to some embodiments of the present invention, the coal-fired cogeneration unit further includes: a low-temperature molten salt pump and a high-temperature molten salt pump, wherein the high-temperature molten salt pump is connected in series between the outlet of the high-temperature molten salt tank and the inlet of the superheater; and the low-temperature molten salt pump is connected in series between the outlet of the low-temperature molten salt tank and the subcooler.

[0014] According to some embodiments of the present invention, the coal-fired cogeneration unit further includes: a seventh branch pipe, one end of which is connected to the exhaust port of the high-pressure cylinder and the other end of which is connected to the high-pressure heater; an eighth branch pipe, one end of which is connected to the exhaust port of the intermediate-pressure cylinder and the other end of which is connected to the first deaerator; and a ninth branch pipe, one end of which is connected to the exhaust port of the low-pressure cylinder and the other end of which is connected to the low-pressure heater.

[0015] Additional aspects and advantages of the invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. Attached Figure Description

[0016] Figure 1 This is a schematic diagram of a carbon dioxide hydrogenation reactor according to an embodiment of the present invention.

[0017] Figure label: 100. Coal-fired combined heat and power units; 10. Boiler; 11. First steam pipe; 12. Second steam pipe; 13. Third steam pipe; 20. Heating steam header; 31. Steam turbine; 311. High-pressure cylinder; 312. Intermediate-pressure cylinder; 313. Low-pressure cylinder; 32. First generator; 40. Hot air heat exchanger; 51. Condenser; 52. Low-pressure heater; 53. First deaerator; 54. High-pressure heater; 55. First branch pipe; 56. First water pipe; 57. Condensate pump; 58. First feedwater pump; 61. Molten salt circulation pipeline; 611. Main pipeline; 612. First branch pipeline; 613. Second branch pipeline; 62. Low-temperature molten salt tank; 63. High-temperature molten salt tank; 64. First heat exchanger; 65. Fourth steam pipe; 66. Second heat exchanger; 67. Third branch pipeline; 681. Condenser; 682. Subcooler; 691. Low-temperature molten salt pump; 692. High-temperature molten salt pump; 71. Superheater; 72. Evaporator; 73. Fourth branch pipe; 74. Fifth branch pipe; 75. Second deaerator; 76. Sixth branch pipe; 77. Second feedwater pump; 81. First valve; 82. Second valve; 83. Third valve; 84. Fourth valve; 85. Fifth valve; 91. Second branch pipe; 92. Seventh branch pipe; 93. Eighth branch pipe; 94. Ninth branch pipe. Detailed Implementation

[0018] Embodiments of the present invention are described in detail below, examples of which are illustrated in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and intended to explain the present invention, and should not be construed as limiting the present invention.

[0019] The following is for reference. Figure 1 A carbon dioxide hydrogenation reactor apparatus according to an embodiment of the present invention is described.

[0020] like Figure 1 As shown, the coal-fired cogeneration unit 100 according to an embodiment of the present invention includes: a boiler 10, a steam turbine 31, an air inlet pipe, a hot air heat exchanger 40, and a first valve group.

[0021] The boiler 10 has a superheated steam outlet, a first steam pipe 11, and a second steam pipe 12, one end of which is connected to the superheated steam outlet. The superheated steam outlet is used to output superheated steam. The steam pipes, with one end of the first steam pipe 11 and the second steam pipe 12 connected to the superheated steam outlet, are mainly used to output superheated steam to a pre-set device.

[0022] The steam turbine 31 set includes a steam turbine 31 and a generator. The steam turbine 31 includes a high-pressure cylinder 311, and the other end of the first steam pipe 11 is connected to the steam inlet of the high-pressure cylinder 311. The steam turbine 31 is connected to the generator to drive the generator to rotate. Specifically, the superheated steam generated by the boiler 10 enters the high-pressure cylinder 311 in the steam turbine 31 through the first steam pipe 11 to do work. The steam turbine 31 converts the thermal energy of the superheated steam into mechanical energy to drive the first generator 32 to rotate and generate electrical energy, thereby realizing the input of electrical energy to the power grid.

[0023] One end of the air inlet pipe is connected to the boiler 10, and the other end is adapted to connect to an external air source. Specifically, the air inlet pipe is used to provide secondary air to the boiler 10 to ensure that the fuel in the furnace of the boiler 10 can obtain sufficient oxygen and achieve complete combustion.

[0024] The hot air heat exchanger 40 has a first air duct and a first steam duct for mutual heat exchange. The first steam duct is connected in series with the second steam pipe 12, and the first air duct is connected in series with the air inlet pipe. Specifically, the superheated steam generated by the boiler 10 enters the hot air heat exchanger 40 to heat the secondary air inlet, thereby increasing the temperature of the air inlet to the boiler 10. This can promote the combustion stability of the fuel, thereby improving the overall thermal efficiency of the boiler 10 and reducing incomplete combustion losses.

[0025] The first valve group is located on the first steam pipe 11 and / or the second steam pipe 12, and is used to control the superheated steam outlet to be switchably connected to the steam inlet of the hot air heat exchanger 40 and / or the high-pressure cylinder 311.

[0026] The phrase "the first valve assembly is provided on the first steam pipe 11 and / or the second steam pipe 12" indicates that the first valve assembly can be provided on the first steam pipe 11, or on the second steam pipe 12, or on both the first steam pipe 11 and the second steam pipe 12. For example, referring to the figure, the first valve assembly includes a first valve 81 and a second valve 82. The first valve 81 is provided on the first steam pipe 11 and is used to control the opening and closing of the first steam pipe 11 and the size of its passage. The second valve 82 is provided on the second steam pipe 12 and is used to control the opening and closing of the second steam pipe 12 and the size of its passage.

[0027] The phrase “for controlling the superheated steam outlet to be switchably connected to the steam inlet of the hot air heat exchanger 40 and / or the high-pressure cylinder 311” is intended to indicate that the superheated steam outlet can be controlled to be connected only to the hot air heat exchanger 40, or only to the steam inlet of the high-pressure cylinder 311, or connected to both the hot air heat exchanger 40 and the high-pressure cylinder 311 by controlling the switching of the first valve group.

[0028] When the first valve group controls the superheated steam outlet to be connected only to the steam inlet of the high-pressure cylinder 311, all the superheated steam enters the turbine 31 to do work, so that the generator can operate at full load and thus meet the system load requirements.

[0029] When the first valve group controls the superheated steam outlet to be connected only to the hot air heat exchanger 40, all the superheated steam enters the hot air heat exchanger 40. At this time, the steam turbine 31 no longer does work, that is, it does not output electrical energy to the grid. This allows the boiler 10 to operate at a lower load. Therefore, when the unit needs deep peak shaving, it is not necessary to shut down the boiler 10, thus achieving zero power output of the unit. This can effectively shorten the unit's peak shaving response time and improve its adaptability to grid load fluctuations. In addition, since the superheated steam entering the hot air heat exchanger 40 is mainly used to heat the secondary air intake, the temperature of the secondary air entering the boiler 10 can be increased, which can promote the combustion stability of the fuel, thereby improving the overall thermal efficiency of the boiler 10 and reducing incomplete combustion losses.

[0030] According to the coal-fired cogeneration unit 100 of the present invention, by setting a second steam pipe 12 and a first valve group, the coal-fired cogeneration unit 100 can meet the needs of deep peak shaving and can quickly start the steam turbine 31 in a short time when grid power generation is required, thereby improving the dynamic adaptability of the unit to grid load fluctuations. In addition, the hot air heat exchanger 40 is used for heat exchange between superheated steam and secondary air circulation, which can also enable the heat generated by the boiler 10 during low-load operation to circulate within the system. In this way, the unit can reduce the coal feed while maintaining stable combustion of the boiler 10 and stable evaporation of the working fluid, thereby reducing the operating cost of the entire unit in long-term hot standby mode.

[0031] According to some embodiments of the present invention, such as Figure 1 As shown, the steam turbine 31 also includes an intermediate-pressure cylinder 312 and a low-pressure cylinder 313. The coal-fired cogeneration unit 100 also includes a condenser 51, a low-pressure heater 52, a first deaerator 53, a high-pressure heater 54, a first branch pipe 55, and a first water pipe 56. One end of the first branch pipe 55 is connected to the steam outlet of the high-pressure cylinder 311, and the other end is connected to the steam inlet of the condenser 51. The intermediate-pressure cylinder 312 and the low-pressure cylinder 313 are connected in series on the first branch pipe 55 along the airflow direction. One end of the first water pipe 56 is connected to the outlet of the condenser 51, and the other end is connected to the water inlet of the boiler 10. The low-pressure heater 52, the first deaerator 53, and the high-pressure heater 54 are connected in series on the first water pipe 56 along the water flow direction. The other end of the second steam pipe 12 is connected to the high-pressure heater 54.

[0032] Understandably, when the coal-fired cogeneration unit 100 is in normal operation, the superheated steam generated by the boiler 10 enters the high-pressure cylinder 311 through the first steam pipe 11 to do work. The discharged steam enters the reheater for reheating and is then discharged from the reheated steam outlet. The discharged reheated steam is divided into two paths. One path enters the intermediate-pressure cylinder 312 and the low-pressure cylinder 313 in sequence to do work, and then is discharged through the exhaust port of the low-pressure cylinder 313 to the condenser 51 to condense into water. The condensate is then heated by the low-pressure heater 52, deaerated by the first deaerator 53, and heated by the high-pressure heater 54 through the first water pipe 56 before returning to the boiler 10. This reduces the use of external water sources and improves the overall economic efficiency of the unit. The other path enters the heating mixing header along the third steam pipe 13 for supplying heat to users.

[0033] The statement that "the other end of the second steam pipe 12 is connected to the high-pressure heater 54" is intended to indicate that when the unit is in hot standby mode, that is, when it is running at low load, the superheated steam output through the second steam pipe 12 exchanges heat with the secondary air through the hot air heat exchanger 40, and then enters the high-pressure heater 54 to exchange heat with the aqueous solution in the high-pressure heater 54. In other words, most of the heat generated by the unit in the hot standby mode in this embodiment can return to the system to achieve heat circulation, which can further reduce energy loss.

[0034] like Figure 1 As shown, the coal-fired cogeneration unit 100 also includes a second branch pipe 91. One end of the second branch pipe 91 is connected to the inlet of the reheater of the boiler 10, and the other end is connected to the steam outlet of the high-pressure cylinder 311. The second branch pipe 91 allows the steam from the high-pressure cylinder 311 to return to the reheater of the boiler 10 for secondary heating. This brings the steam temperature back close to the initial parameters, enabling the unit to extract more electricity from the same amount of fuel, thus significantly improving the overall thermal efficiency of the unit.

[0035] like Figure 1 As shown, the coal-fired cogeneration unit 100 also includes a condensate pump 57 and a first feedwater pump 58. The condensate pump 57 is connected in series on the first water pipe 56 and is arranged between the condenser 51 and the low-pressure heater 52. The first feedwater pump 58 is connected in series between the first deaerator 53 and the high-pressure heater 54. The condensate pump 57 and the first feedwater pump 58 are mainly used to provide driving force for the movement of the aqueous solution within the first water pipe 56.

[0036] According to some embodiments of the present invention, the boiler 10 has a reheat steam outlet and a third steam pipe 13. The coal-fired cogeneration unit 100 further includes a heating steam header 20, with the reheat steam outlet connected to the heating steam header 20 via the third steam pipe 13. Specifically, the reheat steam generated by the boiler 10 can be transmitted to the heating steam header 20 via the third steam pipe 13 for supplying heat to users. The heating steam header 20 can fully mix and collect steam with different temperatures and pressures, enabling high-temperature, high-pressure steam to be accurately and stably delivered to various heat-consuming equipment or external heating networks, thereby improving the precise control of flow rate under complex operating conditions.

[0037] like Figure 1 As shown, the coal-fired cogeneration unit 100 also includes: a molten salt circulation pipeline 61, a low-temperature molten salt tank 62, a high-temperature molten salt tank 63, and a first heat exchanger 64. The low-temperature molten salt tank 62 and the high-temperature molten salt tank 63 are connected in series on the molten salt circulation pipeline 61. The first heat exchanger 64 includes a first flow channel and a second flow channel that exchange heat with each other. The first flow channel is connected in series on the molten salt circulation pipeline 61 and is arranged between the outlet of the low-temperature molten salt tank 62 and the inlet of the high-temperature molten salt tank 63. The second flow channel is connected in series on the third steam pipe 13. Molten salt has high specific heat capacity, thermal stability, and thermal conductivity. Therefore, molten salt can be used to store heat. Thus, the arrangement of the first heat exchanger 64 can realize heat exchange between molten salt and reheat steam. Molten salt can absorb and store the heat of superheated steam, thereby improving energy utilization efficiency.

[0038] According to some embodiments of the present invention, such as Figure 1 As shown, the coal-fired cogeneration unit 100 also includes: a second valve group, which is connected in series on the third steam pipe 13 and / or the first branch pipe 55, for controlling the reheat steam outlet to be switchably connected to the intermediate pressure cylinder 312 and / or connected to the heating steam header 20.

[0039] The phrase "the second valve assembly is connected in series on the third steam pipe 13 and / or the first branch pipe 55" indicates that the second valve assembly can be provided only on the third steam pipe 13, only on the first branch pipe 55, or on both the third steam pipe 13 and the first branch pipe 55. For example, the second valve assembly includes a third valve 83 and a fourth valve 84. The third valve 83 is provided on the third steam pipe 13 for controlling the on / off state of the third steam pipe 13, and the fourth valve 84 is provided on the first branch pipe 55 and arranged before the steam inlet of the intermediate pressure cylinder 312 for controlling the on / off state of the first branch pipe 55.

[0040] The phrase "for controlling the reheat steam outlet to be switchably connected to the intermediate pressure cylinder 312 or to the heating steam header 20" is intended to indicate that the reheat steam outlet can be controlled to be connected only to the intermediate pressure cylinder 312, or only to the heating steam header 20, or connected to both the intermediate pressure cylinder 312 and the heating steam header 20, by controlling the switching of the second valve group.

[0041] When the second valve group controls the reheat steam outlet to be connected only to the intermediate pressure cylinder 312, the high-temperature and high-pressure reheat steam can all enter the turbine 31. Thus, when the unit switches from hot standby to normal operation, the passage between the reheat steam outlet and the heating steam header 20 can be cut off, allowing all the reheat steam and superheated steam generated by the boiler 10 to enter the turbine 31, thereby quickly starting the turbine 31 and enabling the turbine 31 speed to rise rapidly and smoothly to the rated speed, which is conducive to the unit quickly reaching a stable power generation state.

[0042] When the second valve group controls the reheat steam outlet to be connected only to the heating steam header 20, the high-temperature and high-pressure reheat steam can enter the heating steam header 20. At this time, the unit is in a low-load operation state, and the turbine 31 does not participate in the work. That is, by setting the second valve group in this embodiment, the cogeneration unit can meet the heating demand while outputting zero power.

[0043] When the second valve group controls the reheat steam outlet to be connected to the intermediate pressure cylinder 312 and the heating steam header 20, the unit can supply power normally and supply heat to the outside normally.

[0044] According to some embodiments of the present invention, such as Figure 1 As shown, the coal-fired cogeneration unit 100 also includes: a molten salt circulation pipeline 61 including a main pipeline 611, a first branch pipeline 612 and a second branch pipeline 613, a low-temperature molten salt tank 62 and a high-temperature molten salt tank 63 connected in series on the main pipeline 611, and the two ends of the first branch pipeline 612 and the second branch pipeline 613 are respectively connected to the outlet of the low-temperature molten salt tank 62 and the inlet of the high-temperature molten salt tank 63, and a first heat exchanger 64 connected in series on the first branch pipeline 612. The coal-fired cogeneration unit 100 also includes: a fourth steam pipe 65 and a second heat exchanger 66, one end of the fourth steam pipe 65 is connected to the superheated steam outlet and the other end is connected to the inlet of the reheater of the boiler 10, and the second heat exchanger has a third flow channel and a fourth flow channel for mutual heat exchange, the third flow channel is connected in series on the second branch pipeline 613 and the fourth flow channel is connected in series on the fourth steam pipe 65.

[0045] Specifically, during normal operation of the unit, the superheated steam discharged from the superheated steam outlet can be divided into two paths. One path enters the high-pressure cylinder 311 through the first steam pipe 11 to perform work and utilize thermal energy; the other path enters the second heat exchanger 66 through the fourth steam pipe 65 to exchange heat with the molten salt in the second branch pipe 613 to recover thermal energy. When the unit is in hot standby mode, the superheated steam discharged from the superheated steam outlet can also be divided into two paths. One path enters the back pressure turbine through the second steam pipe 12 to perform work and utilize thermal energy; the other path enters the second heat exchanger 66 through the fourth steam pipe 65 to exchange heat with the molten salt in the second branch pipe 613 to recover thermal energy.

[0046] Therefore, by setting up a fourth steam pipe 65 and a second heat exchanger 66 in this embodiment, it is beneficial for the redundant heat energy during low load and normal operation of the unit to be fully recovered and utilized.

[0047] According to some embodiments of the present invention, such as Figure 1 As shown, the coal-fired cogeneration unit 100 also includes: a third branch pipe 67, a condenser 681, and a subcooler 682. One end of the third branch pipe 67 is connected to the outlet of the fourth flow channel, and the other end is connected to the first deaerator 53. The condenser 681 has a first channel and a second channel for mutual heat exchange, and the subcooler 682 has a third channel and a fourth channel for mutual heat exchange. The first channel and the third channel are connected in series on the third branch pipe 67 along the flow direction of the fluid in the third branch pipe 67, and the fourth channel and the second channel are connected in series on the second branch pipe 613 along the flow direction of the molten salt. The condenser 681 and the subcooler 682 are mainly used to condense the steam after heat exchange with the second heat exchanger 66 into an aqueous solution. The condensed aqueous solution is transported to the first deaerator 53 through the third branch pipe 67 for deoxygenation, and then transported to the boiler 10 through the first water pipe 56. In this way, energy waste can be further reduced, the amount of external water used can be reduced, and the operating cost of the entire unit can be reduced.

[0048] Furthermore, this embodiment achieves condensation through heat exchange between low-temperature molten salt and high-temperature steam, which can further improve the heat recovery rate.

[0049] According to some embodiments of the present invention, such as Figure 1As shown, the coal-fired cogeneration unit 100 also includes: a superheater 71, an evaporator 72, a fourth branch pipe 73, and a fifth branch pipe 74. Both the superheater 71 and the evaporator 72 have a first flow channel and a second flow channel. The first flow channels of the superheater 71 and the evaporator 72 are connected in series between the outlet of the high-temperature molten salt tank 63 and the inlet of the low-temperature molten salt tank 62 along the molten salt flow direction in the molten salt circulation pipeline 61. One end of the fourth branch pipe 73 is connected to the outlet of the low-pressure heater 52, and the other end is connected to the inlet of the second flow channel of the evaporator 72. One end of the fifth branch pipe 74 is connected to the outlet of the second flow channel of the evaporator 72, and the other end is connected to the heating steam header 20. The second flow channel of the superheater 71 is connected in series on the fifth branch pipe 74.

[0050] Specifically, the fourth branch pipe 73 can transport the condensate heated at low temperature to the evaporator 72 and the superheater 71. During this process, the condensate can exchange heat with the flowing high-temperature molten salt in the first flow channel in stages. The condensate is converted into high-quality high-temperature superheated steam after absorbing heat. Subsequently, this part of the steam is connected to the heating steam header 20 through the fifth branch pipe 74 to serve as a supplementary heat source and be connected to the heating network to meet the unit's external heating needs.

[0051] Therefore, it can be understood that when the heating demand is large and the reheat steam generated by boiler 10 cannot meet the demand, this embodiment can use the high-temperature heat storage molten salt in the heat storage tank to heat the condensate or supplementary water to generate heating steam. In this way, the energy utilization rate of the coal-fired unit can be further improved and the economy of the entire system can be improved.

[0052] Optionally, the coal-fired cogeneration unit 100 also includes: a water inlet pipe, one end of which is connected to an external water source and the other end of which is connected to the inlet of a low-temperature heater, to supplement water to the boiler 10 so that the water intake meets the combustion requirements of the boiler 10.

[0053] According to some embodiments of the present invention, such as Figure 1 As shown, the coal-fired cogeneration unit 100 also includes a second deaerator 75, which is connected in series with the fourth branch pipe 73 and is used to remove oxygen from the aqueous solution entering the fourth branch pipe 73.

[0054] like Figure 1 As shown, the coal-fired cogeneration unit 100 also includes: a sixth branch pipe 76 and a second feedwater pump 77. One end of the sixth branch pipe 76 is connected to the heating steam header 20, and the other end is connected to the second deaerator 75. The second feedwater pump 77 is connected in series on the fifth branch pipe 74 and is arranged between the second deaerator 75 and the evaporator 72.

[0055] Specifically, the sixth branch pipe 76 can transport the steam in the heating steam header 20 to the second deaerator 75 to further preheat the aqueous solution in the fourth branch pipe 73, thereby increasing the initial temperature of the water entering the evaporator 72 and thus increasing the generation rate of high-temperature steam; the second feed water pump 77 can provide driving force for the flow of the aqueous solution in the fourth branch pipe 73.

[0056] According to some embodiments of the present invention, such as Figure 1 As shown, the coal-fired cogeneration unit 100 also includes a third valve group, which is connected to the first water pipe 56 and / or the fourth branch pipe 73, for controlling the low-pressure heater 52 to be switchably connected to the first deaerator 53 and / or the second deaerator 75.

[0057] The phrase "the third valve assembly is connected to the first water pipe 56 and / or the fourth branch pipe 73" is intended to illustrate that the third valve assembly can be located on the first water pipe 56, the fourth branch pipe 73, or both. For example, referring to the figure, the third valve assembly includes a fifth valve 85, which is located on the fourth branch pipe 73 and used to control the on / off state of the fourth branch pipe 73.

[0058] The phrase "for controlling the low-pressure heater 52 to be switchably connected to the first deaerator 53 and / or the second deaerator 75" is intended to illustrate that the low-pressure heater 52 can be controlled to be connected only to the first deaerator 53, or only to the second deaerator 75, or connected to both the first and second deaerators 53 and 75, via a third valve group. When the low-pressure heater 52 is connected only to the first deaerator 53, the aqueous solution heated by the low-pressure heater 52 is deoxygenated by the first deaerator 53 before entering the boiler 10. When the low-pressure heater 52 is connected only to the second deaerator 75, the aqueous solution heated by the low-pressure heater 52 is deoxygenated by the second deaerator 75 before entering the evaporator 72 and superheater 71 for heat treatment to generate high-temperature steam.

[0059] It should be noted that when the unit switches from hot standby mode to normal operation mode, all superheated steam will enter the turbine 31. At this time, reheated steam has not yet been generated. At this time, the external heating steam will be provided by superheated steam generated by heat exchange between high-temperature molten salt and condensate. Thus, it can be understood that this embodiment achieves the switching of the water circuit during the unit start-up transition phase (hot standby to normal operation phase) by setting a third valve group, so as to solve the heating gap problem when reheated steam has not yet been generated.

[0060] According to some embodiments of the present invention, such as Figure 1As shown, the coal-fired cogeneration unit 100 also includes: a cryogenic molten salt pump 691 and a high-temperature molten salt pump 692. The high-temperature molten salt pump 692 is connected in series between the outlet of the high-temperature molten salt tank 63 and the inlet of the superheater 71; the cryogenic molten salt pump 691 is connected in series between the outlet of the cryogenic molten salt tank 62 and the subcooler 682. The cryogenic molten salt pump 691 is mainly used to drive molten salt to flow from the cryogenic molten salt tank 62 towards the high-temperature molten salt tank 63; the high-temperature molten salt tank 63 is mainly used to drive molten salt to move from the high-temperature molten salt tank 63 towards the cryogenic molten salt tank 62.

[0061] According to some embodiments of the present invention, such as Figure 1 As shown, the coal-fired cogeneration unit 100 also includes: a seventh branch pipe 92, an eighth branch pipe 93, and a ninth branch pipe 94. One end of the seventh branch pipe 92 is connected to the exhaust port of the high-pressure cylinder 311, and the other end is connected to the high-pressure heater 54. One end of the eighth branch pipe 93 is connected to the exhaust port of the intermediate-pressure cylinder 312, and the other end is connected to the first deaerator 53. One end of the ninth branch pipe 94 is connected to the exhaust port of the low-pressure cylinder 313, and the other end is connected to the low-pressure heater 52. The installation of the seventh branch pipe 92, the eighth branch pipe 93, and the ninth branch pipe 94 can further improve the utilization of the unit's thermal energy. At the same time, since the steam transported in the seventh branch pipe 92 is the steam discharged from the high-pressure cylinder 311, its steam temperature is higher than that of the steam discharged from the eighth branch pipe 93 and the ninth branch pipe 94. Therefore, by connecting the seventh branch pipe 92 to the high-pressure heater 54, the eighth branch pipe 93 to the first deaerator 53, and the ninth branch pipe 94 to the low-pressure heater 52, the cascade utilization of energy can also be achieved.

[0062] The following will refer to Figure 1 This application describes a coal-fired cogeneration unit 100 according to a specific embodiment of the present application.

[0063] Reference Figure 1 The coal-fired cogeneration unit 100 includes: a boiler 10, a heating steam header 20, a steam turbine 31, a first valve 81, and a second valve 82.

[0064] The boiler 10 includes a superheated steam outlet, a first steam pipe 11, a second steam pipe 12, a reheated steam outlet, and a third steam pipe 13. The turbine 31 includes a high-pressure cylinder 311, an intermediate-pressure cylinder 312, and a low-pressure cylinder 313. The superheated steam outlet is connected to the steam inlet of the high-pressure cylinder 311 via the first steam pipe 11. The turbine 31 is connected to a first generator 32 to drive the first generator 32 to rotate. A first valve 81 is installed on the first steam pipe 11 to control the opening and closing of the first steam pipe 11 and the size of the passage. A second valve 82 is installed on the second steam pipe 12 to control the opening and closing of the second steam pipe 12 and the size of the passage. The reheated steam outlet is connected to the heating steam header 20 via the third steam pipe 13.

[0065] The coal-fired cogeneration unit 100 also includes: an air inlet pipe, a hot air heat exchanger 40, a condenser 51, a low-pressure heater 52, a first deaerator 53, a high-pressure heater 54, a first branch pipe 55, a first water pipe 56, a condensate pump 57, and a first feedwater pump 58.

[0066] One end of the air inlet pipe is connected to the boiler 10, and the other end is connected to the secondary air fan. The superheated steam outlet is connected to the high-pressure heater 54 through the second steam pipe 12. The hot air heat exchanger 40 is connected in series with the second steam pipe 12 and the air inlet pipe to heat the secondary air in the air inlet pipe. One end of the first branch pipe 55 is connected to the reheat steam outlet, and the other end is connected to the steam inlet of the condenser 51. The intermediate pressure cylinder 312 and the low pressure cylinder 313 are connected in series with the first branch pipe 55 along the airflow direction. One end of the first water pipe 56 is connected to the outlet of the condenser 51, and the other end is connected to the water inlet of the boiler 10. The low-pressure heater 52, the first deaerator 53, and the high-pressure heater 54 are connected in series with the first water pipe 56 along the water flow direction. The condensate pump 57 is connected in series with the first water pipe 56 and is arranged between the condenser 51 and the low-pressure heater 52. The first feedwater pump 58 is connected in series between the first deaerator 53 and the high-pressure heater 54.

[0067] The coal-fired cogeneration unit 100 also includes a third valve 83 and a fourth valve 84. The third valve 83 is located on the third steam pipe 13 and is used to control the opening and closing of the third steam pipe 13. The fourth valve 84 is located on the first branch pipe 55 and is arranged before the steam inlet of the intermediate pressure cylinder 312. It is used to control the opening and closing of the first branch pipe 55.

[0068] The coal-fired cogeneration unit 100 also includes: molten salt circulation pipeline 61, low-temperature molten salt tank 62, high-temperature molten salt tank 63, first heat exchanger 64, fourth steam pipe 65, and second heat exchanger 66.

[0069] The molten salt circulation pipeline 61 includes a main pipeline 611, a first branch pipeline 612, and a second branch pipeline 613. A low-temperature molten salt tank 62 and a high-temperature molten salt tank 63 are connected in series on the main pipeline 611. The two ends of the first branch pipeline 612 and the second branch pipeline 613 are respectively connected to the outlet of the low-temperature molten salt tank 62 and the inlet of the high-temperature molten salt tank 63. The first heat exchanger 64 includes a first flow channel and a second flow channel that exchange heat with each other. The first flow channel is connected in series on the first branch pipeline 612 and is arranged between the outlet of the low-temperature molten salt tank 62 and the inlet of the high-temperature molten salt tank 63. The second flow channel is connected in series on the third steam pipe 13. One end of the fourth steam pipe 65 is connected to the superheated steam outlet, and the other end is connected to the inlet of the reheater of the boiler 10. The second heat exchanger has a third flow channel and a fourth flow channel that exchange heat with each other. The third flow channel is connected in series on the second branch pipeline 613, and the fourth flow channel is connected in series on the fourth steam pipe 65.

[0070] The coal-fired cogeneration unit 100 also includes: a third branch pipe 67, a condenser 681, and a subcooler 682. One end of the third branch pipe 67 is connected to the outlet of the fourth flow channel, and the other end is connected to the first deaerator 53. The condenser 681 has a first channel and a second channel for mutual heat exchange, and the subcooler 682 has a third channel and a fourth channel for mutual heat exchange. The first channel and the third channel are connected in series on the third branch pipe 67 in the direction of fluid flow, and the fourth channel and the second channel are connected in series on the second branch pipe 613 in the direction of molten salt flow.

[0071] The coal-fired cogeneration unit 100 also includes: a low-temperature molten salt pump 691 and a high-temperature molten salt pump 692. The high-temperature molten salt pump 692 is connected in series between the outlet of the high-temperature molten salt tank 63 and the inlet of the superheater 71; the low-temperature molten salt pump 691 is connected in series between the outlet of the low-temperature molten salt tank 62 and the subcooler 682.

[0072] The coal-fired cogeneration unit 100 also includes: a superheater 71, an evaporator 72, a fourth branch pipe 73, and a fifth branch pipe 74. Both the superheater 71 and the evaporator 72 have a first flow channel and a second flow channel. The first flow channels of the superheater 71 and the evaporator 72 are connected in series between the outlet of the high-temperature molten salt tank 63 and the inlet of the low-temperature molten salt tank 62 along the molten salt flow direction in the molten salt circulation pipeline 61. One end of the fourth branch pipe 73 is connected to the outlet of the low-pressure heater 52, and the other end is connected to the inlet of the second flow channel of the evaporator 72. One end of the fifth branch pipe 74 is connected to the outlet of the second flow channel of the evaporator 72, and the other end is connected to the heating steam header 20. The second flow channel of the superheater 71 is connected in series on the fifth branch pipe 74.

[0073] The coal-fired cogeneration unit 100 also includes: a second deaerator 75, a sixth branch pipe 76, and a second feedwater pump 77. The second deaerator 75 is connected in series with the fourth branch pipe 73. One end of the sixth branch pipe 76 is connected to the heating steam header 20, and the other end is connected to the second deaerator 75. The second feedwater pump 77 is connected in series with the fifth branch pipe 74 and is arranged between the second deaerator 75 and the evaporator 72.

[0074] The coal-fired cogeneration unit 100 also includes: a fifth valve 85, which is located on the fourth branch pipe 73 and is used to control the opening and closing of the fourth branch pipe 73.

[0075] The coal-fired cogeneration unit 100 also includes: a second branch pipe 91, a seventh branch pipe 92, an eighth branch pipe 93, and a ninth branch pipe 94. Specifically, one end of the second branch pipe 91 is connected to the inlet of the reheater of the boiler 10, and the other end is connected to the steam outlet of the high-pressure cylinder 311; one end of the seventh branch pipe 92 is connected to the exhaust port of the high-pressure cylinder 311, and the other end is connected to the high-pressure heater 54; one end of the eighth branch pipe 93 is connected to the exhaust port of the intermediate-pressure cylinder 312, and the other end is connected to the first deaerator 53; one end of the ninth branch pipe 94 is connected to the exhaust port of the low-pressure cylinder 313, and the other end is connected to the low-pressure heater 52.

[0076] The following describes the two operating modes of the coal-fired cogeneration unit 100 based on the diagram.

[0077] In the first operating mode, the boiler 10 is connected to the steam turbine 31, the unit is in normal operation, and the unit generates electricity through the steam turbine 31.

[0078] Specifically, the superheated steam generated by boiler 10 is divided into two paths. One path enters the high-pressure cylinder 311 through the first steam pipe 11 to do work. After doing work, part of the steam enters the reheater of boiler 10 through the second branch pipe 91 for heating. The other path enters the second heat exchanger 66 through the fourth steam pipe 65 to exchange heat with molten salt before entering the reheater of boiler 10 for heating. The heated reheated steam is discharged through the reheated steam outlet and is divided into two paths. One path enters the intermediate-pressure cylinder 312 and low-pressure cylinder 313 of turbine 31 through the first branch pipe 55 to do work, thereby driving the first generator 32 to generate electricity. The other path enters the first heat exchanger 64 through the third steam pipe 13 to exchange heat with molten salt before entering the heating steam header 20 to supply heat to the outside. It should be noted that the steam that is discharged after doing work in the low-pressure cylinder 313 enters the condenser 51 and is cooled into condensate. The condensate is then pressurized by the condensate pump 57 and flows through the low-pressure heater 52. It then enters the first deaerator 53. After being deaerated by the first deaerator 53, the feedwater is pressurized by the first feedwater pump 58 and pumped to the high-pressure heater 54 for heating before flowing back into the boiler 10. In the second operating mode, boiler 10 is connected to the back pressure unit, the unit is in hot standby mode, boiler 10 is disconnected from steam turbine 31, the first generator 32 does not output power, and boiler 10 supplies steam to the second steam pipe 12.

[0079] Specifically, when the power generation of the new energy source reaches its peak, the unit's operating mode is adjusted to the second operating mode. The boiler 10 maintains a dry-state minimum load and continuously generates steam. The generated superheated steam is divided into three paths. The first path exchanges heat with molten salt in the fourth steam pipe 65. After heat exchange, part of the steam enters the reheater for reheating treatment. The reheated steam generated after reheating treatment passes through the reheated steam outlet, exchanges heat with the first heat exchanger 64 through the third steam pipe 13, and is then sent to the heating steam header 20 to supply heat to the outside. Part of it is condensed by the condenser 681 and the subcooler 682, and then the condensate is sent to the first deaerator 53 for deoxygenation through the third branch pipe 67 before being sent to the boiler 10 to achieve water circulation. The second path enters the hot air heat exchanger 40 through the second steam pipe 12 and exchanges heat with secondary air before entering the high-pressure heater 54 to heat the condensate and increase the feedwater temperature.

[0080] It should be noted that when the unit is in long-term hot standby operation, if the heat demand is less than the output of the boiler 10, the flow rate of the first main steam path can be increased and the flow rate of the second main steam path can be reduced to store the excess heat in the molten salt thermal storage system; when the heat demand is greater than the output of the boiler 10, the molten salt can be used to release heat to generate heating steam.

[0081] It should be noted that the power supply for all auxiliary equipment that maintains the operation of the entire unit relies on the power supply of neighboring units in the same plant, or on external power purchased from the power grid.

[0082] The following description uses a 350MW cogeneration unit as an example to illustrate the unit's operation in the second operating mode. The unit is a supercritical cogeneration unit; the maximum evaporation capacity of boiler 10 is 1067 t / h, the rated main steam temperature is 571℃, and the reheat steam temperature is 569℃; it is equipped with a 350MW primary reheat turbine 31, with rated inlet steam parameters of 24.2MPa / 566℃ / 566℃; the regenerative system includes 3 high-pressure heaters 54 + a deaerator + 4 low-pressure heaters 52; industrial steam is extracted from the intermediate-pressure cylinder 312, with a rated steam supply of 200 t / h and steam supply parameters of 305℃ / 1.25MPa.

[0083] In this embodiment, the unit enters the second operating mode, i.e., long-term hot standby state, when generating electricity at zero price. In hot standby state, boiler 10 maintains the minimum dry-state operating load, with the evaporation rate the same as under the 25% BRL condition, the main steam flow rate at 275 t / h, and the main steam parameters at 571℃ / 6MPa. At this time, the steam flow rate exceeds the rated steam supply. The system operating status is as follows: (1) The steam turbine 31 stops running, and the boiler 10 provides 5 t / h of steam for shaft seal for insulation to maintain the extremely hot state; the generator stops running and the power generation is zero. (2) When the first valve 81 at the steam inlet of the high-pressure cylinder 311 is closed, the superheated steam is divided into three paths. The first path flows through the fourth steam pipe 65, and then flows through the second heat exchanger 66, condenser 681, and subcooler 682 in sequence to exchange heat and condense into condensate. Then, it enters the first deaerator 53 through the third branch pipe 67. The steam flow rate of this path is 20 t / h. The second path of superheated steam enters the second heat exchanger through the fourth steam pipe 65 and returns to the reheater of the boiler 10 after heat exchange. The steam flow rate of this path is 200 t / h. The third path of superheated steam enters the hot air heat exchanger 40 through the second steam pipe 12 to exchange heat with the secondary air, raising the secondary air temperature by 70°C and enhancing the stable combustion effect. This allows the boiler 10 to maintain combustion stability even with a reduced coal feed rate. The steam after heat exchange enters the high-pressure heater 54 to replace the original steam extraction steam from the turbine 31 to heat the feedwater, raising the feedwater temperature and thus maintaining the dry operation of the boiler 10. The steam flow rate of this path is 50 t / h. (3) The fourth valve 84 of the steam inlet of the intermediate pressure cylinder 312 is closed. The reheat steam generated by the boiler 10 has a temperature of 569℃ / 1.5MPa. It enters the first heat exchanger 64 through the third valve 83 to exchange heat with molten salt. After heat exchange, the steam temperature is reduced to 305℃. Then it enters the heating steam header 20 for external heating to meet the rated steam supply of 200 t / h.

[0084] It should be noted that, based on the above data, to store the excess heat from superheated and reheated steam, the first heat exchanger 64, the second heat exchanger 66, the condenser 681, and the subcooler 682 in this embodiment have a total heat transfer capacity of approximately 100MW. This heat needs to be stored in a high-temperature molten salt tank. Therefore, when this embodiment is equipped with a 1000MWh molten salt thermal storage system, it can achieve 10 hours of long-term hot standby. During this long-term hot standby state, the unit does not generate electricity from the grid, operates at the lowest coal consumption level, and can quickly start the generator at any time, thereby achieving peak shaving and shutdown.

[0085] It should be further explained that the power supply for the auxiliary equipment in the above-mentioned units relies on the power supply of neighboring units in the same plant.

[0086] According to the coal-fired cogeneration unit 100 of the present invention, by setting a second steam pipe 12 and a first valve group, the coal-fired cogeneration unit 100 can meet the needs of deep peak shaving and can quickly start the steam turbine 31 in a short time when grid power generation is required, thereby improving the dynamic adaptability of the unit to grid load fluctuations. In addition, the hot air heat exchanger 40 is used for heat exchange between superheated steam and secondary air circulation, which can also enable the heat generated by the boiler 10 during low-load operation to circulate within the system. In this way, the unit can reduce the coal feed while maintaining stable combustion of the boiler 10 and stable evaporation of the working fluid, thereby reducing the operating cost of the entire unit in long-term hot standby mode.

[0087] In the description of this invention, it should be understood that the terms "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," "counterclockwise," "axial," "radial," and "circumferential" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0088] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this invention, "a plurality of" means two or more, unless otherwise explicitly specified.

[0089] In this invention, unless otherwise explicitly specified and limited, the terms "installation," "connection," "linking," and "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection, an electrical connection, or a communication connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0090] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the present invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0091] Although embodiments of the invention have been shown and described, those skilled in the art will understand that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the claims and their equivalents.

Claims

1. A coal-fired combined heat and power unit (100), characterized in that, include: A boiler (10) having a superheated steam outlet, a first steam pipe (11) and a second steam pipe (12), one end of the first steam pipe (11) and the second steam pipe (12) being connected to the superheated steam outlet; A steam turbine (31) unit includes a steam turbine (31) and a generator. The steam turbine (31) includes a high-pressure cylinder (311). The other end of the first steam pipe (11) is connected to the steam inlet of the high-pressure cylinder (311). The steam turbine (31) is connected to the generator and is used to drive the generator to rotate. An air inlet pipe, one end of which is connected to the boiler (10), and the other end of which is adapted to be connected to an external air source; Hot air heat exchanger (40) has a first air duct and a first steam duct that exchange heat with each other. The first steam duct is connected in series to the second steam pipe (12), and the first air duct is connected in series to the air inlet pipe. The first valve group, which is located on the first steam pipe (11) and / or the second steam pipe (12), is used to control the superheated steam outlet to be switchably connected to the steam inlet of the hot air heat exchanger (40) and / or the high-pressure cylinder (311).

2. The coal-fired cogeneration unit (100) according to claim 1, characterized in that, The steam turbine (31) further includes: an intermediate-pressure cylinder (312) and a low-pressure cylinder (313), and the coal-fired cogeneration unit (100) further includes: The boiler consists of a condenser (51), a low-pressure heater (52), a first deaerator (53), a high-pressure heater (54), a first branch pipe (55), and a first water pipe (56). One end of the first branch pipe (55) is connected to the steam outlet of the high-pressure cylinder (311), and the other end is connected to the steam inlet of the condenser (51). The intermediate-pressure cylinder (312) and the low-pressure cylinder (313) are connected in series on the first branch pipe (55) along the airflow direction. One end of the first water pipe (56) is connected to the outlet of the condenser (51), and the other end is connected to the water inlet of the boiler (10). The low-pressure heater (52), the first deaerator (53), and the high-pressure heater (54) are connected in series on the first water pipe (56) along the water flow direction. The other end of the second steam pipe (12) is connected to the high-pressure heater (54). The second branch pipe (91) has one end connected to the inlet of the reheater of the boiler (10) and the other end connected to the steam outlet of the high-pressure cylinder (311). A condensate pump (57) and a first feedwater pump (58) are provided. The condensate pump (57) is connected in series on the first water pipe (56) and is arranged between the condenser (51) and the low-pressure heater (52). The first feedwater pump (58) is connected in series between the first deaerator (53) and the high-pressure heater (54).

3. The coal-fired cogeneration unit (100) according to claim 2, characterized in that, The boiler (10) has a reheat steam outlet and a third steam pipe (13), and the coal-fired cogeneration unit (100) further includes: The heating steam header (20) is connected to the heating steam header (20) via the third steam pipe (13); The system includes a molten salt circulation pipeline (61), a low-temperature molten salt tank (62), a high-temperature molten salt tank (63), and a first heat exchanger (64). The low-temperature molten salt tank (62) and the high-temperature molten salt tank (63) are connected in series on the molten salt circulation pipeline (61). The first heat exchanger (64) includes a first flow channel and a second flow channel that exchange heat with each other. The first flow channel is connected in series on the molten salt circulation pipeline (61) and is arranged between the outlet of the low-temperature molten salt tank (62) and the inlet of the high-temperature molten salt tank (63). The second flow channel is connected in series on the third steam pipe (13).

4. The coal-fired cogeneration unit (100) according to claim 3, characterized in that, Also includes: The second valve assembly, connected in series on the third steam pipe (13) and / or the first branch pipe (55), is used to control the reheat steam outlet to be switchably connected to the intermediate pressure cylinder (312) and / or to the heating steam header (20).

5. The coal-fired cogeneration unit (100) according to claim 3, characterized in that, The molten salt circulation pipeline (61) includes a main pipeline (611), a first branch pipeline (612), and a second branch pipeline (613). The low-temperature molten salt tank (62) and the high-temperature molten salt tank (63) are connected in series on the main pipeline (611). The two ends of the first branch pipeline (612) and the second branch pipeline (613) are respectively connected to the outlet of the low-temperature molten salt tank (62) and the inlet of the high-temperature molten salt tank (63). The first heat exchanger (64) is connected in series on the first branch pipeline (612). The coal-fired cogeneration unit (100) also includes: The fourth steam pipe (65) and the second heat exchanger (66) are connected to the superheated steam outlet at one end and to the inlet of the reheater of the boiler (10) at the other end. The second heat exchanger has a third flow channel and a fourth flow channel that exchange heat with each other. The third flow channel is connected in series on the second branch pipe (613) and the fourth flow channel is connected in series on the fourth steam pipe (65).

6. The coal-fired cogeneration unit (100) according to claim 5, characterized in that, Also includes: The third branch pipe (67) has one end connected to the outlet of the fourth flow channel and the other end connected to the first deaerator (53). The condenser (681) and the subcooler (682) are provided. The condenser (681) has a first channel and a second channel for mutual heat exchange, and the subcooler (682) has a third channel and a fourth channel for mutual heat exchange. The first channel and the third channel are connected in series on the third branch pipe (67) in the direction of fluid flow. The fourth channel and the second channel are connected in series on the second branch pipe (613) in the direction of molten salt flow.

7. The coal-fired cogeneration unit (100) according to claim 6, characterized in that, Also includes: The superheater (71) and the evaporator (72) each have a first flow channel and a second flow channel. The first flow channel of the superheater (71) and the evaporator (72) are connected in series between the outlet of the high-temperature molten salt tank (63) and the inlet of the low-temperature molten salt tank (62) along the molten salt flow direction in the molten salt circulation pipeline (61). The fourth branch pipe (73) has one end connected to the outlet of the low-pressure heater (52) and the other end connected to the inlet of the second flow channel of the evaporator (72); The fifth branch pipe (74) has one end connected to the outlet of the second flow channel of the evaporator (72) and the other end connected to the heating steam header (20). The second flow channel of the superheater (71) is connected in series on the fifth branch pipe (74).

8. The coal-fired cogeneration unit (100) according to claim 7, characterized in that, Also includes: The second deaerator (75) is connected in series with the fourth branch pipe (73); The sixth branch pipe (76) has one end connected to the heating steam header (20) and the other end connected to the second deaerator (75); A second feedwater pump (77) is connected in series with the fifth branch pipe (74) and is arranged between the second deaerator (75) and the evaporator (72); and / or, A third valve assembly, connected to the first water pipe (56) and / or the fourth branch pipe (73), is used to control the low-pressure heater (52) to be switchably connected to the first deaerator (53) and / or the second deaerator (75).

9. The coal-fired cogeneration unit (100) according to claim 7, characterized in that, Also includes: A low-temperature molten salt pump (691) and a high-temperature molten salt pump (692) are connected in series between the outlet of the high-temperature molten salt tank (63) and the inlet of the superheater (71); the low-temperature molten salt pump (691) is connected in series between the outlet of the low-temperature molten salt tank (62) and the supercooler (682).

10. The coal-fired cogeneration unit (100) according to claim 2, characterized in that, Also includes: The seventh branch pipe (92) has one end connected to the exhaust port of the high-pressure cylinder (311) and the other end connected to the high-pressure heater (54); The eighth branch pipe (93) has one end connected to the exhaust port of the intermediate pressure cylinder (312) and the other end connected to the first deaerator (53). The ninth branch pipe (94) has one end connected to the exhaust port of the low-pressure cylinder (313) and the other end connected to the low-pressure heater (52).

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