CN114109545B - Peak regulating system and peak regulating method for recovering cold end waste heat of thermal power plant - Google Patents

Abstract

The invention discloses a peak shaving system and a peak shaving method for recovering cold end waste heat of a thermal power plant, wherein the peak shaving system comprises a deaerator, a condenser, a low-pressure heater, a steam turbine exhaust pipeline, a steam turbine exhaust bypass regulating valve, a water/steam-carbon dioxide heat exchanger, a heat regenerator, a carbon dioxide-water heat exchanger, a condensate regulating valve, a condensate bypass regulating valve, a deaerator water supply bypass regulating valve, a cold tank and a hot tank.

Description

A peak-shaving system and a peak-shaving method for recovering waste heat at the cold end of a thermal power plant

technical field

The invention belongs to the technical field of thermal power generation, and relates to a peak-shaving system and a peak-shaving method for recovering waste heat at the cold end of a thermal power plant.

Background technique

In recent years, my country's wind power and solar power have developed rapidly. As of the end of July 2021, the total installed capacity of power generation in the country reached 2.27 billion kilowatts, of which the installed capacity of wind power was 290 million kilowatts, a year-on-year increase of 34.4%, and the installed capacity of solar power was 270 million kilowatts, a year-on-year increase of 23.6%. With the further growth of wind power and solar power installed capacity, my country's power industry will gradually transform into a new power system with clean energy power generation as the mainstay in the future.

Due to the volatility, intermittency, and geographical limitations of wind and solar energy, the grid-connection of wind power and photovoltaic power generation will pose a huge challenge to the safe and stable operation of the power grid. In order to stabilize the volatility of wind power and photovoltaic power generation and further absorb the large-scale and high proportion of new energy power generation, it is necessary to improve the operation and regulation capabilities of the power system, such as building pumped storage, natural gas power generation and other peak-shaving power stations, and carrying out flexible transformation of coal power. Or use compressed air energy storage, battery energy storage and other technologies. However, although battery energy storage is the most efficient, the cost is too high; compressed air energy storage and pumped storage power plants are difficult to promote on a large scale due to geological conditions; natural gas power generation costs are also high. The flexibility transformation of coal power has become one of the most effective technologies to improve the operation and regulation capabilities of the power system. Deeply tapping the peak-shaving potential of existing coal-fired units is one of the keys to ensuring the safety and stability of energy and power.

During the operation of the coal-fired unit, the exhaust steam of the steam turbine will release a large amount of low-temperature heat to the outside world, resulting in a huge energy loss, and the heat pump cycle can convert the low-temperature heat into high-temperature heat by consuming high-quality energy, so as to recycle it. High thermal economy. Hot water storage technology is one of the more mature heat storage technologies at present, with high safety and low investment and operation costs, and can be widely used in thermal power plants. Therefore, the heat pump cycle and hot water storage technology can be considered to realize the recovery and utilization of the waste heat at the cold end of the coal-fired unit, but there is no similar disclosure in the prior art.

Contents of the invention

The purpose of the present invention is to overcome the above-mentioned shortcomings of the prior art, and provide a peak regulation system and a peak regulation method for recovering waste heat at the cold end of a thermal power plant. The system and method can reduce the heat loss at the cold end of the unit.

In order to achieve the above-mentioned purpose, the peak-shaving system for recovering the waste heat at the cold end of the thermal power plant according to the present invention includes a deaerator, a condenser, a low-pressure heater, a steam turbine exhaust pipe, a steam turbine exhaust bypass regulating valve, a water/steam- Carbon dioxide heat exchanger, regenerator, carbon dioxide-water heat exchanger, condensate regulating valve, condensate bypass regulating valve, deaerator water supply regulating valve, deaerator supply water bypass regulating valve, cold tank and hot water Can;

The carbon dioxide side outlet of the water/steam-carbon dioxide heat exchanger is connected with the cold side inlet of the regenerator, and the cold side outlet of the regenerator is connected with the carbon dioxide side inlet of the carbon dioxide-water heat exchanger, and the carbon dioxide-water heat exchanger The carbon dioxide side outlet of the regenerator is connected with the hot side inlet of the regenerator, and the hot side outlet of the regenerator is connected with the carbon dioxide side inlet of the water/steam-carbon dioxide heat exchanger;

The outlet of the condenser is divided into two paths, one of which is connected to the inlet of the low-pressure heater through the condensate regulating valve, and the other is connected to the inlet of the cold tank through the condensate bypass regulating valve; the outlet of the low-pressure heater is divided into There are two paths, one of which is connected to the deaerator through the water supply regulating valve of the deaerator, and the other is connected to the inlet of the cold tank through the water supply bypass regulating valve of the deaerator; the outlet of the cold tank is connected to the carbon dioxide-water The water side inlet of the heat exchanger is connected, the water side outlet of the carbon dioxide-water heat exchanger is connected with the inlet of the heat tank, and the outlet of the heat tank is connected with the deaerator;

The outlet of the steam turbine exhaust pipe is divided into two paths, one of which is connected to the condenser, and the other is connected to the water/steam side inlet of the water/steam-carbon dioxide heat exchanger through the steam turbine exhaust bypass regulating valve. The water/steam side outlet of the /steam-carbon dioxide heat exchanger communicates with the condenser.

It also includes a compressor; the outlet of the cold side of the regenerator is connected with the inlet of the compressor; the outlet of the compressor is connected with the inlet of the carbon dioxide side of the carbon dioxide-water heat exchanger.

An electric motor is also included; the output shaft of the electric motor is connected to the drive shaft of the compressor.

The outlet of the cold tank communicates with the water-side inlet of the carbon dioxide-water heat exchanger through the first water pump and the first regulating valve in sequence.

The water side outlet of the carbon dioxide-water heat exchanger communicates with the inlet of the heat tank through the electric boiler.

The outlet of the hot tank communicates with the deaerator through the second water pump and the second regulating valve in sequence.

The hot side outlet of the regenerator communicates with the carbon dioxide side inlet of the water/steam-carbon dioxide heat exchanger through a throttling valve.

The outlet of the condenser is divided into two paths by the condensate pump.

The peak-shaving method of recovering the waste heat at the cold end of the thermal power plant according to the present invention comprises:

When the dispatching load of the power grid decreases, increase the opening of the condensate regulating valve or increase the speed of the condensate pump to increase the condensate flow into the low-pressure heater, simultaneously increase the steam extraction volume of the low-pressure cylinder, and reduce the power generation of the low-pressure cylinder; Open the water supply bypass regulating valve of the deaerator to divert part of the condensed water output from the low-pressure heater into the cold tank; after the power generation of the standby unit is reduced, open the condensed water bypass regulating valve to recover part of the condensed water to the cold tank; The condensed water in the cold tank is sent to the water side of the carbon dioxide-water heat exchanger to absorb the high-temperature heat of carbon dioxide in the heat pump cycle, and then enters the electric boiler to be heated and stored in the hot tank; at this time, the electric motor and the electric boiler use The electricity comes from the excess electricity generated by photovoltaic and wind power or the electricity generated by the unit itself;

When the dispatching load of the power grid increases, reduce the opening of the condensate regulating valve or reduce the speed of the condensate pump to reduce the flow of condensate entering the low-pressure heater, simultaneously reduce the steam extraction of the low-pressure cylinder, and increase the power generation of the low-pressure cylinder. In order to maintain the water level and feed water flow of the deaerator, the high-temperature hot water in the hot tank is sent into the deaerator; in order to maintain the water level of the condenser, the condensate bypass regulating valve is opened to divert part of the condensed water to the cold tank store.

The present invention has the following beneficial effects:

The peak-shaving system and peak-shaving method for recovering the waste heat at the cold end of the thermal power plant described in the present invention use heat pump circulation to improve the quality of a large amount of low-temperature heat released by the exhaust steam of the steam turbine in the thermal power plant and recover it, so as to reduce the heat loss at the cold end of the unit. ; At the same time, combined with hot water storage technology, a storage tank is set in the steam turbine heat recovery system to absorb and release the heat recovered from the cold end during the peak-shaving operation of the unit, thereby greatly improving the AGC response ability and ramp rate of the coal-fired unit, and the investment The cost is lower and the technology maturity is higher. In addition, compressors and electric boilers use excess electricity generated by photovoltaics and wind power or electricity generated by the unit itself, reducing the amount of electricity entering the grid, improving the ability of the unit to perform deep peak regulation, and effectively promoting the consumption of new energy.

Description of drawings

Fig. 1 is a structural schematic diagram of the present invention.

Among them, 1 is the steam turbine exhaust bypass regulating valve, 2 is the water/steam-carbon dioxide heat exchanger, 3 is the regenerator, 4 is the compressor, 5 is the electric motor, 6 is the carbon dioxide-water heat exchanger, and 7 is the economizer. flow valve, 8 is the condensate regulating valve, 9 is the condensate bypass regulating valve, 10 is the water supply regulating valve of the deaerator, 11 is the water supply bypass regulating valve of the deaerator, 12 is the cold tank, 13 is the first Water pump, 14 is the first regulating valve, 15 is the electric boiler, 16 is the heat tank, 17 is the second water pump, 18 is the second regulating valve.

Detailed ways

In order to enable those skilled in the art to better understand the solutions of the present invention, the following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only The embodiments are a part of the present invention, not all embodiments, and are not intended to limit the scope of the present invention. Also, in the following description, descriptions of well-known structures and techniques are omitted to avoid unnecessarily obscuring the concepts disclosed in the present invention. Based on the embodiments of the present invention, all other embodiments obtained by persons of ordinary skill in the art without making creative efforts shall fall within the protection scope of the present invention.

The schematic diagrams of the structures according to the disclosed embodiments of the present invention are shown in the accompanying drawings. The figures are not drawn to scale, with certain details exaggerated and possibly omitted for clarity of presentation. The shapes of various regions and layers shown in the figure and their relative sizes and positional relationships are only exemplary, and may deviate due to manufacturing tolerances or technical limitations in practice, and those skilled in the art may Regions/layers with different shapes, sizes, and relative positions can be additionally designed as needed.

Referring to Fig. 1, the peak shaving system for recovering waste heat at the cold end of a thermal power plant according to the present invention includes a steam turbine exhaust bypass regulating valve 1, a water/steam-carbon dioxide heat exchanger 2, a regenerator 3, a compressor 4, and an electric motor 5 , Carbon dioxide-water heat exchanger 6, throttle valve 7, condensate regulating valve 8, condensate bypass regulating valve 9, deaerator water supply regulating valve 10, deaerator supply water bypass regulating valve 11, cold tank 12. The first water pump 13, the first regulating valve 14, the electric boiler 15, the hot tank 16, the second water pump 17 and the second regulating valve 18;

The carbon dioxide side outlet of the water/steam-carbon dioxide heat exchanger 2 is connected to the cold side inlet of the regenerator 3, and the cold side outlet of the regenerator 3 is connected to the compressor 4 inlet; the output shaft of the motor 5 is connected to the compressor 4 The drive shaft is connected, the outlet of the compressor 4 is connected with the carbon dioxide side inlet of the carbon dioxide-water heat exchanger 6, the carbon dioxide side outlet of the carbon dioxide-water heat exchanger 6 is connected with the hot side inlet of the regenerator 3, and the return The hot side outlet of the heater 3 communicates with the carbon dioxide side inlet of the water/steam-carbon dioxide heat exchanger 2 through the throttle valve 7;

The outlet of the condenser is divided into two paths through the condensate pump, one of which is connected to the inlet of the low-pressure heater through the condensate regulating valve 8, and the other path is connected to the inlet of the cold tank 12 through the condensate bypass regulating valve 9; The outlet of the low-pressure heater is divided into two paths, one of which is connected to the deaerator through the deaerator water supply regulating valve 10, and the other is connected to the inlet of the cold tank 12 through the deaerator water supply bypass regulating valve 11 The outlet of the cold tank 12 is connected with the water side inlet of the carbon dioxide-water heat exchanger 6 through the first water pump 13 and the first regulating valve 14 successively, and the water side outlet of the carbon dioxide-water heat exchanger 6 is connected with the heat through the electric boiler 15 The inlet of the tank 16 is connected, and the outlet of the hot tank 16 is connected with the deaerator through the second water pump 17 and the second regulating valve 18 in sequence.

The outlet of the steam turbine exhaust pipe is divided into two paths, one of which is connected to the condenser, and the other is connected to the water/steam side inlet of the water/steam-carbon dioxide heat exchanger 2 through the steam turbine exhaust bypass regulating valve 1 , the water/steam side outlet of the water/steam-carbon dioxide heat exchanger 2 communicates with the condenser.

The circulating working medium of the heat pump adopts carbon dioxide.

The peak-shaving method of recovering the waste heat at the cold end of the thermal power plant described in the present invention comprises the following steps:

The operation process of the heat pump cycle system to recover the waste heat at the cold end of the unit is as follows:

The exhaust steam of the steam turbine is divided into two parts, of which, one part of the exhaust steam directly enters the condenser to release heat and condense; The heat is released in the steam side to cool down, and the exhaust steam after heat release and cooling is condensed into liquid and then enters the condenser; among them, the exhaust steam entering the water/steam-carbon dioxide heat exchanger 2 is controlled by the steam turbine exhaust bypass regulating valve 1 Steam flow, thereby controlling the recovered heat.

After the throttle valve 7 depressurizes and lowers the temperature, the carbon dioxide enters the two-phase area, and the two-phase carbon dioxide enters the carbon dioxide side of the water/steam-carbon dioxide heat exchanger 2 to absorb the low-grade heat of the exhaust steam of the steam turbine, and the carbon dioxide saturated gas after absorbing heat After the cold side of the regenerator 3 absorbs heat and heats up, it enters the compressor 4 to pressurize, then enters the carbon dioxide side of the carbon dioxide-water heat exchanger 6 to heat the condensed water, and finally passes through the hot side of the regenerator 3 to release heat and cool down again. Enter the throttle valve 7 to lower the pressure and lower the temperature, so as to complete the heat pump cycle and recover the waste heat at the cold end.

When the dispatching load of the power grid decreases, in order to quickly reduce the generating power of the unit, increase the opening of the condensate regulating valve 8 or increase the speed of the condensate pump to increase the flow of condensate entering the low-pressure heater and simultaneously increase the steam extraction volume of the low-pressure cylinder , to reduce the generating power of the low-pressure cylinder; in order to maintain the water level and feedwater flow of the deaerator, open the deaerator feed water bypass regulating valve 11, and divert the condensed water output from the low-pressure heater into the cold tank 12; After the power generation is reduced, the steam flow rate of the steam turbine is reduced, and the feedwater and condensed water flow rates of the recuperation system are correspondingly reduced. The condensed water bypass regulating valve 9 is opened to recover part of the condensed water to the cold tank 12; the condensed water in the cold tank 12 passes through the first The water pump 13 and the first regulating valve 14 are sent to the water side of the carbon dioxide-water heat exchanger 6 to absorb the high-temperature heat of carbon dioxide in the heat pump cycle, and then enter the electric boiler 15 to be heated and stored in the heat tank 16; at this time, the heat pump Circular operation recovers waste heat from the cold end. Electric motor 5 and electric boiler 15 use excess electricity generated by photovoltaic and wind power or electricity generated by the unit itself, so as to reduce the electricity entering the grid. closure.

When the dispatching load of the power grid increases, in order to quickly increase the generating power of the unit, reduce the opening of the condensate regulating valve 8 or reduce the speed of the condensate pump, reduce the flow of condensate entering the low-pressure heater, and simultaneously reduce the steam extraction volume of the low-pressure cylinder , improve the generating power of the low-pressure cylinder, in order to maintain the water level and feed water flow of the deaerator, the high-temperature hot water in the hot tank 16 is sent into the deaerator through the second water pump 17 and the second regulating valve 18; Water level, properly open the condensate bypass regulating valve 9, and divert part of the condensate to the cold tank 12 for storage; at this time, the heat pump cycle and the electric boiler 15 are not working, the first water pump 13 is out of service, and the first regulating valve 14 is closed.

But other layouts of the heat pump circulation system shown in Figure 1 do not affect the application of the present invention, and the content of the present invention is also applicable to other layouts of the heat pump circulation, so the heat pump circulation in the present invention is a heat pump circulation in a broad sense, rather than limitation in the diagram layout. For example, other heat pump cycles do not use the regenerator 3 , and the working medium may also be air or other refrigerants.

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

Claims (4)

1. A peak-shaving system for reclaiming cold end waste heat of a thermal power plant is characterized in that it comprises a deaerator, a condenser, a low-pressure heater, a steam turbine exhaust pipe, a steam turbine exhaust bypass control valve (1), water/ Steam-carbon dioxide heat exchanger (2), regenerator (3), carbon dioxide-water heat exchanger (6), condensate regulating valve (8), condensate bypass regulating valve (9), deaerator water supply Regulating valve (10), deaerator water supply bypass regulating valve (11), cold tank (12) and hot tank (16); The carbon dioxide side outlet of the water/steam-carbon dioxide heat exchanger (2) is connected with the cold side inlet of the regenerator (3), and the cold side outlet of the regenerator (3) is connected with the carbon dioxide-water heat exchanger (6) The carbon dioxide side inlet is connected, the carbon dioxide side outlet of the carbon dioxide-water heat exchanger (6) is connected with the hot side inlet of the regenerator (3), and the hot side outlet of the regenerator (3) is connected with the water/steam-carbon dioxide exchange The carbon dioxide side inlet of heater (2) is connected; The outlet of the condenser is divided into two paths, one of which is connected to the inlet of the low-pressure heater through the condensate regulating valve (8), and the other path is connected to the inlet of the cold tank (12) through the condensate bypass regulating valve (9) The outlet of the low-pressure heater is divided into two paths, one of which is connected to the deaerator through the deaerator water supply regulating valve (10), and the other is connected to the deaerator water supply bypass regulating valve (11) and The inlet of the cold tank (12) is connected; the outlet of the cold tank (12) is connected with the water side inlet of the carbon dioxide-water heat exchanger (6), and the water side outlet of the carbon dioxide-water heat exchanger (6) is connected with the hot tank The inlet of (16) is connected, and the outlet of hot tank (16) is connected with deaerator; The outlet of the steam turbine exhaust pipe is divided into two paths, one of which is connected to the condenser, and the other path passes through the steam turbine exhaust bypass regulating valve (1) and the water/steam of the water/steam-carbon dioxide heat exchanger (2). The side inlets are connected, and the water/steam side outlet of the water/steam-carbon dioxide heat exchanger (2) is connected with the condenser; The outlet of the cold tank (12) communicates with the water side inlet of the carbon dioxide-water heat exchanger (6) through the first water pump (13) and the first regulating valve (14) successively; The water side outlet of the carbon dioxide-water heat exchanger (6) is communicated with the inlet of the heat tank (16) through the electric boiler (15); The outlet of the hot tank (16) communicates with the deaerator through the second water pump (17) and the second regulating valve (18) successively; The hot side outlet of the regenerator (3) communicates with the carbon dioxide side inlet of the water/steam-carbon dioxide heat exchanger (2) through a throttle valve (7); Also includes a compressor (4); the cold side outlet of the regenerator (3) is connected with the inlet of the compressor (4); the outlet of the compressor (4) is connected with the carbon dioxide side inlet of the carbon dioxide-water heat exchanger (6) connected. 2. The peak shaving system for recovering waste heat at the cold end of a thermal power plant according to claim 1, further comprising a motor (5); the output shaft of the motor (5) is connected to the drive shaft of the compressor (4). 3. The peak shaving system for recovering waste heat at the cold end of a thermal power plant according to claim 1, wherein the outlet of the condenser is divided into two paths through a condensate pump. 4. A peak-shaving method for recovering cold-end waste heat of a thermal power plant, characterized in that, based on a kind of peak-shaving system for recovering cold-end waste heat of a thermal power plant according to claim 1, comprising: When the grid dispatching load decreases, increase the opening of the condensate regulating valve (8) or increase the speed of the condensate pump to increase the condensate flow into the low-pressure heater, simultaneously increase the steam extraction volume of the low-pressure cylinder, and reduce the pressure of the low-pressure cylinder. Generating power; open the water bypass regulating valve (11) of the deaerator, and divert the condensed water output from the low-pressure heater into the cold tank (12); after the power generation of the standby unit is reduced, open the condensed water bypass regulating valve (9), recovering part of the condensed water to the cold tank (12); the condensed water in the cold tank (12) is sent to the water side of the carbon dioxide-water heat exchanger (6) to absorb the high-temperature heat of carbon dioxide in the heat pump cycle, and then enters the electric The boiler (15) is heated and stored in the hot tank (16); at this time, the electricity for the motor (5) and the electric boiler (15) comes from the excess electricity generated by photovoltaics and wind power or the electricity generated by the unit itself; When the dispatching load of the power grid increases, reduce the opening of the condensate regulating valve (8) or reduce the speed of the condensate pump to reduce the flow of condensate entering the low-pressure heater, simultaneously reduce the steam extraction volume of the low-pressure cylinder, and increase the pressure of the low-pressure cylinder. Generating power, in order to maintain the water level and feed water flow of the deaerator, the high-temperature hot water in the hot tank (16) is sent into the deaerator; in order to maintain the water level of the condenser, open the condensate bypass regulating valve (9), Part of the condensed water is distributed to the cold tank (12) for storage.

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