Unit waste heat recovery heating and heat supply energy system and operation strategy

Abstract

The invention provides a unit waste heat recovery heating and heat supply energy system and an operation strategy. The system comprises a first-stage heater, a second-stage heater, a third-stage heater, a first heating water return pipe, a medium-pressure cylinder, a low-pressure cylinder and a heat storage water pool. The input end of the first-stage heater is connected with a first heating water return pipe, and the output end of the first-stage heater is connected with the first input end of the second-stage heater; the first output end of the second-stage heater is connected with the first input end of the third-stage heater; the first output end of the third-stage heater is connected with the heat storage water tank; the second input end of the second-stage heater is connected with an intermediate-pressure cylinder, the third input end of the second-stage heater is connected with a low-pressure cylinder, and the fourth input end of the second-stage heater is connected with the second output end of the third-stage heater. One technical effect of the invention is that not only the operation flexibility is high, but also the heat supply energy consumption is low.

Description

Technical Field

[0001] The present invention belongs to the technical field of energy utilization, and in particular relates to a unit waste heat recovery heating energy system and an operation strategy. Background Art

[0002] Existing heating technologies mainly include high back pressure heating, medium and low pressure cylinder interconnecting pipe heating and low pressure cylinder zero output heating technology. Among the above technologies, high back pressure heating technology has low energy consumption but weak operation flexibility, while medium and low pressure interconnecting pipe heating technology and low pressure cylinder zero output heating technology have greater operation flexibility but high heating energy consumption.

[0003] Therefore, there is an urgent need for a unit waste heat recovery heating energy system and operation strategy that has both high operating flexibility and low heating energy consumption, so that it can adapt to the requirements of the new power system and earn higher profits under the existing electricity spot trading. Summary of the invention

[0004] The present invention aims to solve at least one of the technical problems existing in the prior art and to provide a new technical solution for a unit waste heat recovery heating energy system and an operation strategy.

[0005] According to a first aspect of the present invention, there is provided a unit waste heat recovery heating energy system, comprising a first stage heater, a second stage heater, a third stage heater, a first heating return pipe, a medium pressure cylinder, a low pressure cylinder and a heat storage tank; wherein the condenser is used as the first stage heater;

[0006] The input end of the first stage heater is connected to the first heating return pipe, the output end of the first stage heater is connected to the first input end of the second stage heater; the first output end of the second stage heater is connected to the first input end of the third stage heater; the first output end of the third stage heater is connected to the hot water storage tank, and the hot water storage tank is used for heating water supply;

[0007] The second input end of the second stage heater is connected to the medium pressure cylinder, the third input end of the second stage heater is connected to the low pressure cylinder, the fourth input end of the second stage heater is connected to the second output end of the third stage heater; the second input end of the third stage heater is connected to the medium pressure cylinder; the second output end of the second stage heater, the third output end of the second stage heater, and the fourth output end of the second stage heater are all used to output drain water;

[0008] The first-stage heater is used to heat the heating return water to a first preset temperature; the second-stage heater is used to heat the heating return water from the first preset temperature to the second preset temperature; the third-stage heater is used to heat the heating return water from the second preset temperature to the third preset temperature; wherein the heat source of the third-stage heater is the exhaust steam of the intermediate pressure cylinder, the heat source of the second-stage heater is the exhaust steam of the intermediate pressure cylinder or the exhaust steam of the low pressure cylinder or the drain water discharged from the second output end of the third-stage heater, and the heat source of the first-stage heater is the exhaust steam of the low pressure cylinder.

[0009] Optionally, the waste heat recovery heating energy system of the unit also includes a second heating return pipe, and the second heating return pipe is connected to the first input end of the second-stage heater.

[0010] Optionally, the waste heat recovery heating energy system of the unit further includes a first main pipe, a first branch pipe and a second branch pipe;

[0011] The input end of the first main pipe is connected to the medium-pressure cylinder, the first output end of the first main pipe is connected to one end of the first branch pipe, and the second output end of the first main pipe is connected to one end of the second branch pipe;

[0012] The other end of the first branch pipe is connected to the second input end of the third-stage heater; the other end of the second branch pipe is connected to the second input end of the second-stage heater.

[0013] Optionally, the unit waste heat recovery heating energy system further includes a second main pipe;

[0014] One end of the second main pipe is connected to the low-pressure cylinder, and the other end is connected to the third input end of the second-stage heater.

[0015] Optionally, the waste heat recovery heating energy system of the unit further includes a first regulating component, which includes a first check valve, a first regulating valve and a first isolation valve arranged in sequence along the flow direction of the steam;

[0016] The first main pipe, the second main pipe, the first branch pipe, and the second branch pipe are all provided with the first regulating assembly.

[0017] Optionally, the unit waste heat recovery heating energy system also includes a heating return water main;

[0018] The first output end of the heating water return main pipe is connected to the first heating water return pipe, and the second output end is connected to the second heating water return pipe.

[0019] Optionally, the unit waste heat recovery heating energy system further includes a second regulating component;

[0020] The second regulating assembly includes a second regulating valve, a second check valve and a second isolation valve;

[0021] The first heating return pipe is provided with a second regulating valve and a second check valve in sequence along the water flow direction; the second heating return pipe is provided with a second regulating valve and a second isolation valve in sequence along the water flow direction.

[0022] Optionally, the waste heat recovery heating energy system of the unit further includes a third main pipe and a condensate pump;

[0023] The first input end of the third main pipe is connected to the fourth output end of the second stage heater, the second input end is connected to the second output end of the second stage heater, the third input end is connected to the third output end of the second stage heater, and the output end of the third main pipe is connected to the condensate pump.

[0024] According to a second aspect of the present invention, an operation strategy of a unit waste heat recovery heating energy system is provided, comprising the following steps:

[0025] Step S11, in the heating season, the unit operates in a high back pressure state;

[0026] Step S12, conducting tests based on unit characteristics to obtain the relationship between the maximum heating supply Qmax of the unit in combination with the second heater and the medium pressure cylinder exhaust steam unit in the high back pressure mode and the unit electrical load P;

[0027] Step S13, under the condition of unit electrical load P, if the real-time load of the heat user Q≤Qmax, the heating return water inputted from the first heating return pipe is heated by the condenser, then enters the second-stage heater, then enters the third-stage heater, and finally flows into the hot water storage tank; wherein the hot water storage tank is partially opened by the regulating valve to store some surplus hot water;

[0028] If the real-time load Q of the heat user is greater than Qmax, the heating return water input from the first heating return pipe is heated by the condenser, then enters the second-stage heater, then enters the third-stage heater, and finally flows into the inter-seasonal hot water storage tank; wherein, the hot water storage tank increases the opening amplitude of the regulating valve to release the stored hot water;

[0029] Step S14, according to the deep regulation requirement of the power grid, the steam extraction amount of the third-stage heater is controlled, and the heat load supply is regulated by using the hot water storage tank.

[0030] Optionally, the operation strategy of the waste heat recovery heating energy system of the unit also includes the following steps:

[0031] Step S21, in the non-heating season, the unit operates in a conventional back pressure state;

[0032] Step S22, the heating return water enters the second-stage heater through the second heating return pipe, then enters the third-stage heater, and finally flows into the hot water storage tank;

[0033] Step S23, when the spot electricity price is less than or equal to the unit's power generation cost price, the steam inlet of the second-stage heater and the third-stage heater is turned on, and the corresponding pipeline valves are opened; when the spot electricity price is greater than the unit's power generation cost price, the steam inlet of the second-stage heater and the third-stage heater is turned off, and the corresponding pipeline valves are closed;

[0034] A technical effect of the present invention is:

[0035] In the embodiment of the present application, the waste heat recovery heating energy system and operation strategy of the unit have high operating flexibility and low heating energy consumption (that is, better economy).

[0036] For higher operational flexibility, firstly, thermal-electric decoupling can be achieved for daily operating conditions. For example, when the electrical load is 290MW, the low-pressure cylinder exhaust steam is about 650 tons. For conventional high back-pressure units, the return water volume of the heat network is limited, and only 500 tons of low-pressure cylinder exhaust steam can be absorbed, so the unit cannot generate 290MW of electricity; in the present invention, the extra 150 tons of exhaust steam can be used in the second-stage heater, that is, the electrical load of 290MW can be achieved.

[0037] Secondly, for intraday heat storage, you can choose to supply more heat or more electricity according to the electricity price at each moment, and the heat supply can fluctuate within the range of 0 to 300%; when more heat is supplied, the heat is stored in the hot water storage tank, and when less heat is supplied, heat is taken from the hot water storage tank, which better ensures the stability of heat supply.

[0038] On the third aspect, corresponding to cross-seasonal heat storage, taking summer operating conditions as an example, conventional units can only operate in pure condensing mode, with a minimum electrical load of about 30% THA (THA, steam turbine under heat rate acceptance conditions); while in the present invention, cold water can also be heated and stored in a hot water storage tank in summer, that is, steam can be extracted on the unit side in summer to reduce electrical load, with the lowest electrical load being 20% ​​THA.

[0039] For better economy, for example, in the present invention, high-quality steam at about 200°C drives the drain at 80°C and the low-pressure cylinder exhaust at about 80°C to heat the heating water at about 70°C, which can not only improve the heat exchange efficiency of the second-stage heater, but also make full use of the heat of the medium-pressure cylinder exhaust and the low-pressure cylinder exhaust. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] Figure 1 This is a schematic structural diagram of a heating energy system for recovering waste heat from a unit according to an embodiment of the present invention;

[0041] Figure 2 It is a flow chart of an operation strategy of a unit waste heat recovery heating energy system according to another embodiment of the present invention.

[0042] In the figure: 1, first stage heater; 2, second stage heater; 3, third stage heater; 4, heating return water main; 41, first heating return water pipe; 42, second heating return water pipe; 5, medium pressure cylinder; 6, low pressure cylinder; 71, first check valve; 72, first regulating valve;

[0043] 73, first isolation valve; 81, first main pipe; 82, first branch pipe; 83, second branch pipe;

[0044] 84. Second main pipe; 85. Third main pipe; 86. Condensate pump; 91. Second check valve;

[0045] 92. Second regulating valve; 93. Second isolating valve; 10. Heat storage tank; 11. Third regulating valve; 12. Third isolating valve; 13. Fourth regulating valve. DETAILED DESCRIPTION

[0046] Various exemplary embodiments of the present application will now be described in detail with reference to the accompanying drawings. It should be noted that unless otherwise specifically stated, the relative arrangement of components and steps, numerical expressions and numerical values ​​set forth in these embodiments do not limit the scope of the present application.

[0047] The embodiments of the present application will be described in detail below, and examples of the embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present application, and should not be construed as limitations on the present application. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in the field without making creative work are within the scope of protection of the present application.

[0048] The term "first" or "second" in the specification and claims of this application may include one or more of the features explicitly or implicitly. In the description of this application, unless otherwise specified, "plurality" means two or more. In addition, "and / or" in the specification and claims means at least one of the connected objects, and the character " / " generally means that the objects connected before and after are in an "or" relationship.

[0049] In the description of the present application, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise", "axial", "radial", "circumferential" and the like indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present application and simplifying the description, and do not indicate or imply that the referred device or element must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as a limitation on the present application.

[0050] In the description of this application, it should be noted that, unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in this application can be understood according to specific circumstances.

[0051] According to a first aspect of the present invention, see Figure 1 , provides a unit waste heat recovery heating energy system, which can adapt to the electricity spot trading policy, allowing the cogeneration unit to obtain greater electricity sales revenue while ensuring the heating load demand of residents, and can realize the thermal power plant has a higher thermal and electric decoupling capacity in the heating season, and can realize the unit in the non-heating season. Further reduce the electricity load on the basis of the lowest pure condensing operating load.

[0052] Specifically, the waste heat recovery heating energy system of the unit includes a first-stage heater 1, a second-stage heater 2, a third-stage heater 3, a first heating return pipe 41, a medium-pressure cylinder 5, a low-pressure cylinder 6 and a hot water storage tank 10; wherein the condenser serves as the first-stage heater 1; the second-stage heater 2 is an absorption heat pump; wherein the hot water storage tank 10 has a cross-seasonal adjustment property; in the heating season, the hot water storage tank 10 achieves a stable output of the heating heat load of residents when the unit's electrical load fluctuates greatly by storing or releasing hot water; and in the non-heating season, the hot water storage tank 10 can be used to store heat to assist in reducing the external power supply load of the unit, and the heat stored in the non-heating season can be used for the heating needs of residents in the heating season;

[0053] The input end of the first stage heater 1 is connected to the first heating return pipe 41, and the output end of the first stage heater 1 is connected to the first input end of the second stage heater 2; the first output end of the second stage heater 2 is connected to the first input end of the third stage heater 3; the first output end of the third stage heater 3 is connected to the hot water storage tank 10, and the hot water storage tank 10 is used for heating water supply;

[0054] The second input end of the second stage heater 2 is connected to the medium pressure cylinder 5, the third input end of the second stage heater 2 is connected to the low pressure cylinder 6, the fourth input end of the second stage heater 2 is connected to the second output end of the third stage heater 3; the second input end of the third stage heater 3 is connected to the medium pressure cylinder 5; the second output end of the second stage heater 2, the third output end of the second stage heater 2, and the fourth output end of the second stage heater 2 are all used to output water discharge;

[0055] The first-stage heater 1 is used to heat the heating return water to a first preset temperature; the second-stage heater 2 is used to heat the heating return water from the first preset temperature to the second preset temperature; the third-stage heater 3 is used to heat the heating return water from the second preset temperature to the third preset temperature; wherein the heat source of the third-stage heater 3 is the exhaust steam of the intermediate pressure cylinder 5, the heat source of the second-stage heater 2 is the exhaust steam of the intermediate pressure cylinder 5 or the exhaust steam of the low-pressure cylinder 6 or the drain water discharged from the second output end of the third-stage heater 3, and the heat source of the first-stage heater 1 is the exhaust steam of the low-pressure cylinder 6.

[0056] It should be noted that, in this embodiment, the nth input end and the nth output end correspond to each other to realize the input and output of the fluid medium.

[0057] In the embodiment of the present application, the waste heat recovery heating energy system and operation strategy of the unit have high operating flexibility and low heating energy consumption (that is, better economy).

[0058] For higher operational flexibility, firstly, for daily operating conditions, thermal-electric decoupling can be achieved. For example, when the electrical load is 290MW, the exhaust steam of the low-pressure cylinder 6 is about 650 tons. For conventional high back-pressure units, the return water volume of the heat network is limited, and only 500 tons of exhaust steam of the low-pressure cylinder 6 can be absorbed, so the unit cannot generate 290MW of electricity; in the present invention, the excess 150 tons of exhaust steam can be used in the second-stage heater 2, that is, the electrical load of 290MW can be achieved.

[0059] Secondly, for intraday heat storage, you can choose to supply more heat or more electricity according to the electricity price at each moment, and the heat supply can fluctuate within the range of 0 to 300%; when more heat is supplied, the heat is stored in the hot water storage tank 10, and when less heat is supplied, heat is taken from the hot water storage tank 10, which better ensures the stability of heat supply.

[0060] On the third aspect, corresponding to cross-seasonal heat storage, taking summer operating conditions as an example, conventional units can only operate in pure condensing mode, with a minimum electrical load of about 30% THA (THA, steam turbine under heat rate acceptance conditions); while in the present invention, cold water can also be heated in summer and stored in the hot water storage tank 10, that is, steam can be extracted on the unit side in summer to reduce electrical load, with the lowest electrical load being 20% ​​THA.

[0061] For better economy, for example, in the present invention, high-quality steam at about 200°C drives the drain at 80°C and the exhaust steam of the low-pressure cylinder 6 at about 80°C to heat the heating water at about 70°C, which can not only improve the heat exchange efficiency of the second-stage heater 2, but also make full use of the heat of the exhaust of the medium-pressure cylinder 5 and the exhaust of the low-pressure cylinder 6.

[0062] In a specific implementation manner, the exhaust steam temperature of the medium-pressure cylinder 5 is about 200°C, the 200°C steam exhausted from the medium-pressure cylinder 5 enters the third-stage heater 3 from the second input end of the third-stage heater 3 and heats the heating return water flowing through the third-stage heater 3, and then forms 80°C drain at the second output end of the third-stage heater 3; the exhaust steam temperature of the low-pressure cylinder 6 is about 80°C, the 200°C steam exhausted from the medium-pressure cylinder 5, the 80°C steam exhausted from the low-pressure cylinder 6 and the 80°C drain heat the heating return water passing through the second-stage heater 2 and form 25°C drain.

[0063] Moreover, the heating return water at about 50°C passes through the first-stage heater 1 to form heating return water at about 70°C, the heating return water at about 70°C passes through the second-stage heater 2 to form heating return water at about 90°C, the heating return water at about 90°C passes through the third-stage heater 3 to form heating return water at about 100°C, and the heating return water at about 100°C enters the heat storage tank 10 to form heating supply water.

[0064] Exemplarily, the output end of the hot water storage tank 10 is connected to a heating pipe, on which a third regulating valve 11 and a third isolating valve 12 are sequentially arranged along the water flow direction. The heating water flow of the hot water storage tank 10 is adjusted by the third regulating valve 11. The third isolating valve 12 is used to isolate the fluid medium in the heating pipe.

[0065] In the embodiment of the present application, the exhaust steam of the medium-pressure cylinder 5 is used as a driving heat source to drive low-grade heat to heat medium-temperature hot water.

[0066] For example, high-quality steam at about 200°C drives the drain at 80°C and the exhaust steam of the low-pressure cylinder 6 at about 80°C to heat the heating water at about 70°C.

[0067] In the embodiment of the present application, the working principle of the waste heat recovery heating energy system of the unit is as follows:

[0068] During the heating period, the steam turbine operates in a high back pressure mode, the steam turbine exhaust pressure is about 50kPa, and the heating return water is heated to about 75℃ in the condenser (first stage heater 1); then it enters the absorption heat pump (second stage heater 2), which uses the exhaust steam of the medium pressure cylinder 5 as the driving steam source, recovers the heat in the exhaust steam of the steam turbine, and heats the hot network water (i.e., heating return water) from about 75℃ to about 90℃; during the extremely cold period, the hot network water can be heated from about 90℃ to about 100℃ through the third stage heater 3, and the heat source of the third stage heater 3 is the exhaust steam of the medium pressure cylinder 5. During the variable load operation of the unit, the main steam flow of the steam turbine is adjusted, and the exhaust flow of the steam turbine changes accordingly; the external power supply load and heating heat load of the unit are adjusted by adjusting the exhaust flow of the medium and low pressure cylinders 6 entering the first stage heater 1 and the second stage heater 2, and the exhaust flow of the medium pressure cylinder 5 of the second stage heater 2 and the third stage heater 3.

[0069] In the non-heating season, the steam turbine operates in a conventional back pressure mode, and the heating return water does not pass through the condenser. When the spot electricity price is lower than the cost electricity price or the unit deep adjustment requirements cannot be met, the second-stage heater 2 and the third-stage heater 3 are operated to extract the exhaust steam of the intermediate pressure cylinder 5 and reduce the steam intake of the low-pressure cylinder 6, thereby reducing the external power supply and heating the return water.

[0070] Optionally, the waste heat recovery heating energy system of the unit further includes a second heating return water pipe 42 , and the second heating return water pipe 42 is connected to the first input end of the second-stage heater 2 .

[0071] Optionally, the waste heat recovery heating energy system of the unit further includes a first main pipe 81, a first branch pipe 82 and a second branch pipe 83;

[0072] The input end of the first main pipe 81 is connected to the medium-pressure cylinder 5, the first output end of the first main pipe 81 is connected to one end of the first branch pipe 82, and the second output end of the first main pipe 81 is connected to one end of the second branch pipe 83;

[0073] The other end of the first branch pipe 82 is connected to the second input end of the third-stage heater 3 ; the other end of the second branch pipe 83 is connected to the second input end of the second-stage heater 2 .

[0074] In the above embodiment, the steam turbine is operated in a conventional back pressure mode, and the heating return water does not pass through the condenser. Therefore, when the spot electricity price is lower than the cost electricity price or the deep adjustment requirements of the unit cannot be met, the second-stage heater 2 and the third-stage heater 3 are operated to extract the exhaust steam from the intermediate pressure cylinder 5 and reduce the steam intake of the low-pressure cylinder 6, thereby achieving the effect of reducing the external power supply power and heating the return water.

[0075] Optionally, a fourth regulating valve 13 is provided on the main steam pipeline of the intermediate pressure cylinder 5. The fourth regulating valve 13 is used to control the steam flow entering the first main pipe 81 and the steam flow entering the low pressure cylinder 6, and the operation is very convenient.

[0076] Optionally, the unit waste heat recovery heating energy system further includes a second main pipe 84;

[0077] One end of the second main pipe 84 is connected to the low pressure cylinder 6, and the other end is connected to the third input end of the second stage heater 2. This helps to ensure that the low pressure cylinder 6 supplies steam to the second stage heater 2.

[0078] Optionally, the waste heat recovery heating energy system of the unit further includes a first regulating component, which includes a first check valve 71, a first regulating valve 72 and a first isolation valve 73 arranged in sequence along the flow direction of the steam;

[0079] The first main pipe 81 , the second main pipe 84 , the first branch pipe 82 , and the second branch pipe 83 are all provided with the first regulating assembly.

[0080] In the above embodiment, the first adjustment component is reasonably designed, which helps to adjust the first main pipe 81, the second main pipe 84, the first branch pipe 82, and the second branch pipe 83, and is easy to operate.

[0081] Optionally, the unit waste heat recovery heating energy system further includes a heating return water main 4;

[0082] The first output end of the heating water return main pipe 4 is connected to the first heating water return pipe 41 , and the second output end is connected to the second heating water return pipe 42 .

[0083] In this embodiment, the heating return water in the heating return water main pipe 4 has two flow paths, namely, it flows into the first-stage heater 1 through the first heating return water pipe 41 (i.e., path 1), and directly flows into the second-stage heater 2 through the second heating return water pipe 42 (i.e., path 2).

[0084] Optionally, the unit waste heat recovery heating energy system further includes a second regulating component;

[0085] The second regulating assembly includes a second regulating valve 92, a second check valve 91 and a second isolation valve 93;

[0086] The first heating water return pipe 41 is provided with a second regulating valve 92 and a second check valve 91 in sequence along the water flow direction; the second heating water return pipe 42 is provided with a second regulating valve 92 and a second isolation valve 93 in sequence along the water flow direction.

[0087] In the above embodiment, the first heating water return pipe 41 and the second heating water return pipe 42 can be controlled by the second regulating component, and the operation is simple.

[0088] Optionally, the waste heat recovery heating energy system of the unit further includes a third main pipe 85 and a condensate pump 86;

[0089] The first input end of the third main pipe 85 is connected to the fourth output end of the second stage heater 2 , the second input end is connected to the second output end of the second stage heater 2 , the third input end is connected to the third output end of the second stage heater 2 , and the output end of the third main pipe 85 is connected to the condensate pump 86 .

[0090] In the above embodiment, the condensate pump 86 can be used to collect the condensate.

[0091] According to the second aspect of the present invention, see Figure 2 , provides an operation strategy for a unit waste heat recovery heating energy system, including the following steps:

[0092] Step S11, in the heating season, the unit operates in a high back pressure state;

[0093] Step S12, conducting tests based on unit characteristics to obtain the relationship between the maximum heating supply Qmax of the unit in the high back pressure mode combined with the second heater and the medium pressure cylinder 5 exhaust steam and the unit electrical load P;

[0094] Step S13, under the condition of unit electrical load P, if the real-time load of the heat user Q≤Qmax, the heating return water inputted from the first heating return water pipe 41 is heated by the condenser, then enters the second-stage heater 2, then enters the third-stage heater, and finally flows into the hot water storage tank 10; wherein the hot water storage tank 10 is partially opened by the regulating valve to store some surplus hot water;

[0095] If the real-time load Q of the heat user is greater than Qmax, the heating return water input from the first heating return pipe 41 is heated by the condenser, then enters the second-stage heater 2, then enters the third-stage heater, and finally flows into the inter-seasonal hot water storage tank 10; wherein, the hot water storage tank 10 increases the opening amplitude of the regulating valve to release the stored hot water to meet the heating needs of the heating users;

[0096] Step S14, according to the deep regulation requirement of the power grid, the steam extraction amount of the third-stage heater 3 is controlled, and the heat storage tank 10 is used to adjust the heat load supply.

[0097] Optionally, the operation strategy of the waste heat recovery heating energy system of the unit also includes the following steps:

[0098] Step S21, in the non-heating season, the unit operates in a conventional back pressure state;

[0099] Step S22, the heating return water enters the second-stage heater 2 through the second heating return pipe 42, then enters the third-stage heater, and finally flows into the hot water storage tank 10;

[0100] Step S23, when the electricity spot transaction price is less than or equal to the power generation cost price of the unit, the steam inlet of the second-stage heater 2 and the third-stage heater 3 is turned on, and the corresponding pipeline valve is opened, that is, the corresponding first regulating component is opened; when the electricity spot transaction price is greater than the power generation cost price of the unit, the steam inlet of the second-stage heater 2 and the third-stage heater 3 is turned off, and the corresponding pipeline valve is closed, that is, the corresponding first regulating component is closed;

[0101] Step S24, storing heat in the non-heating season for heating in the heating season.

[0102] In this application, the waste heat recovery heating energy system and operation strategy of the unit have the following technical effects:

[0103] In conventional high back pressure units, when the electric load is determined, the fluctuation degree of heat load generally does not exceed 5%; while in the present application, when the electric load is determined, the external heating load of the unit can fluctuate between 0 and 300%.

[0104] Furthermore, in non-heating season conditions, the minimum external power supply load of a conventional pure condensing unit is generally 30% THA; while the minimum external power supply load of the pure condensing unit of the present application can be reduced to 20% THA.

[0105] In addition, this application can realize flexible power quotation and flexible operation adjustment of units under power spot trading, thereby achieving a substantial increase in power spot trading revenue.

[0106] It is to be understood that the above embodiments are merely exemplary embodiments used to illustrate the principles of the present invention, but the present invention is not limited thereto. For those of ordinary skill in the art, various modifications and improvements can be made without departing from the spirit and essence of the present invention, and these modifications and improvements are also considered to be within the scope of protection of the present invention.

Claims

1. A unit waste heat recovery heating energy system, characterized in that: It includes a first-stage heater, a second-stage heater, a third-stage heater, a first heating return pipe, a medium-pressure cylinder, a low-pressure cylinder and a hot water storage tank; wherein the condenser serves as the first-stage heater; The input end of the first stage heater is connected to the first heating return pipe, the output end of the first stage heater is connected to the first input end of the second stage heater; the first output end of the second stage heater is connected to the first input end of the third stage heater; the first output end of the third stage heater is connected to the hot water storage tank, and the hot water storage tank is used for heating water supply; The second input end of the second stage heater is connected to the medium pressure cylinder, the third input end of the second stage heater is connected to the low pressure cylinder, the fourth input end of the second stage heater is connected to the second output end of the third stage heater; the second input end of the third stage heater is connected to the medium pressure cylinder; the second output end of the second stage heater, the third output end of the second stage heater, and the fourth output end of the second stage heater are all used to output drain water; The first-stage heater is used to heat the heating return water to a first preset temperature; the second-stage heater is used to heat the heating return water from the first preset temperature to the second preset temperature; the third-stage heater is used to heat the heating return water from the second preset temperature to the third preset temperature; wherein the heat source of the third-stage heater is the exhaust steam of the intermediate pressure cylinder, the heat source of the second-stage heater is the exhaust steam of the intermediate pressure cylinder or the exhaust steam of the low pressure cylinder or the drain water discharged from the second output end of the third-stage heater, and the heat source of the first-stage heater is the exhaust steam of the low pressure cylinder.

2. The unit waste heat recovery heating energy system according to claim 1 is characterized in that: It also includes a second heating water return pipe, which is connected to the first input end of the second-stage heater.

3. The unit waste heat recovery heating energy system according to claim 1 is characterized in that: It includes a first main pipe, a first branch pipe and a second branch pipe; The input end of the first main pipe is connected to the medium-pressure cylinder, the first output end of the first main pipe is connected to one end of the first branch pipe, and the second output end of the first main pipe is connected to one end of the second branch pipe; The other end of the first branch pipe is connected to the second input end of the third-stage heater; the other end of the second branch pipe is connected to the second input end of the second-stage heater.

4. The unit waste heat recovery heating energy system according to claim 3 is characterized in that: It also includes the second supervisor; One end of the second main pipe is connected to the low-pressure cylinder, and the other end is connected to the third input end of the second-stage heater.

5. The unit waste heat recovery heating energy system according to claim 4 is characterized in that: It also includes a first regulating assembly, which includes a first check valve, a first regulating valve and a first isolation valve arranged in sequence along the flow direction of the steam; The first main pipe, the second main pipe, the first branch pipe, and the second branch pipe are all provided with the first regulating assembly.

6. The unit waste heat recovery heating energy system according to claim 2 is characterized in that: It also includes the heating return water main; The first output end of the heating water return main pipe is connected to the first heating water return pipe, and the second output end is connected to the second heating water return pipe.

7. The unit waste heat recovery heating energy system according to claim 6 is characterized in that: Also included is a second adjustment assembly; The second regulating assembly includes a second regulating valve, a second check valve and a second isolation valve; The first heating return pipe is provided with a second regulating valve and a second check valve in sequence along the water flow direction; the second heating return pipe is provided with a second regulating valve and a second isolation valve in sequence along the water flow direction.

8. The unit waste heat recovery heating energy system according to claim 1, characterized in that: Also includes a third main pipe and condensate pump; The first input end of the third main pipe is connected to the fourth output end of the second stage heater, the second input end is connected to the second output end of the second stage heater, the third input end is connected to the third output end of the second stage heater, and the output end of the third main pipe is connected to the condensate pump.

9. An operation strategy of a unit waste heat recovery heating energy system, characterized in that: The steps include: Step S11, in the heating season, the unit operates in a high back pressure state; Step S12, conducting tests based on unit characteristics to obtain the relationship between the maximum heating supply Qmax of the unit in combination with the second heater and the medium pressure cylinder exhaust steam unit in the high back pressure mode and the unit electrical load P; Step S13, under the condition of unit electrical load P, if the real-time load of the heat user Q≤Qmax, the heating return water inputted from the first heating return pipe is heated by the condenser, then enters the second-stage heater, then enters the third-stage heater, and finally flows into the hot water storage tank; wherein the hot water storage tank is partially opened by the regulating valve to store some surplus hot water; If the real-time load Q of the heat user is greater than Qmax, the heating return water input from the first heating return pipe is heated by the condenser, then enters the second-stage heater, then enters the third-stage heater, and finally flows into the inter-seasonal hot water storage tank; wherein, the hot water storage tank increases the opening amplitude of the regulating valve to release the stored hot water; Step S14, according to the deep regulation requirement of the power grid, the steam extraction amount of the third-stage heater is controlled, and the heat load supply is regulated by using the hot water storage tank.

10. The operation strategy of the unit waste heat recovery heating energy system according to claim 9 is characterized in that: The following steps are also included: Step S21, in the non-heating season, the unit operates in a conventional back pressure state; Step S22, the heating return water enters the second-stage heater through the second heating return pipe, then enters the third-stage heater, and finally flows into the hot water storage tank; Step S23, when the spot electricity price is less than or equal to the unit's power generation cost price, the steam inlet of the second-stage heater and the third-stage heater is turned on, and the corresponding pipeline valves are opened; when the spot electricity price is greater than the unit's power generation cost price, the steam inlet of the second-stage heater and the third-stage heater is turned off, and the corresponding pipeline valves are closed; Step S24, storing heat in the non-heating season for heating in the heating season.

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