CN114198802B - Heating system and method of low-pressure cylinder zero-output coupling absorption heat pump - Google Patents

Abstract

The invention discloses a heating system and a heating method of a low-pressure cylinder zero-output coupling absorption heat pump.A return water of a heat supply network and a water supply of the heat supply network are firstly preliminarily heated in the absorption heat pump and then divided into two parts, one part of the return water of the heat supply network and the water supply of the heat supply network are heated by a steam exhaust heater of a small steam turbine, the other part of the return water of the heat supply network and the water supply of the heat supply network are heated by a heat supply network heater and then converged to supply heat to the outside; a condensation water tank is arranged in front of a deaerator of the extraction condensing unit, condensation water is provided for the extraction condensing unit and the low-pressure cylinder zero-output unit, and the condensation water of the extraction condensing unit and the low-pressure cylinder zero-output unit is heated by a low-pressure heater of the extraction condensing unit. The invention utilizes the low-pressure heater of the extraction condensing unit to heat the condensed water of the low-pressure cylinder zero-output unit, solves the heating problem of the condensed water of the low-pressure cylinder zero-output unit, reasonably utilizes the waste heat of the system by reasonably distributing heating heat sources in different stages through a heat supply network, has higher energy utilization rate of the unit, meets the water supply temperature of the heat supply network required in different heat supply periods by adjusting the heat load of the absorption heat pump and the steam extraction quantity of the heat supply network heater, and has operation flexibility.

Description

A heating system and method for a low-pressure cylinder zero-output coupled absorption heat pump

technical field

The invention belongs to the field of cogeneration of heat and power, and relates to a heat supply system and method for a low-pressure cylinder zero-output coupled absorption heat pump.

Background technique

At present, cogeneration units mostly use extraction condensing turbines, backpressure turbines, or condenser turbines to increase backpressure operation under heating conditions. The characteristics are generally applicable, and the electrothermal load operating domain of other units will also have similar characteristics. The thermal and electrical load characteristics of a 300MW extraction condensing unit and a 300MW high back pressure unit are shown in Figure 1. The electrical load adjustment range of the high back pressure unit is very small, and the electrical load adjustment range of the extraction condensing unit is gradually reduced when the heat load is high; Finally, the thermal load adjustment range of the unit increases, and the electrical load adjustment range also increases accordingly, which can meet the flexible peak regulation requirements of the unit; in order to meet the heat supply of the unit and have flexible peak regulation capabilities, it also solves the problem of low-pressure cylinder zero output unit condensation To solve the problem of water heating, a heating system and method for low-pressure cylinder zero output coupling absorption heat pump are proposed.

Contents of the invention

The purpose of the present invention is to solve the problems in the prior art, and provide a heat supply system and method for a low-pressure cylinder zero output coupling absorption heat pump.

In order to achieve the above object, the present invention adopts the following technical solutions to achieve:

A low-pressure cylinder zero output coupled absorption heat pump heating system, comprising:

The first heat and power cogeneration unit, the first heat and power cogeneration unit includes a first boiler and a first steam turbine unit; the first steam turbine unit includes a first high-pressure steam turbine, a first medium-pressure steam turbine and a first steam turbine connected to the first boiler in sequence low pressure steam turbine;

The exhaust end of the first medium-pressure steam turbine is respectively connected with the inlet of the first low-pressure steam turbine and the first inlet of the first deaerator;

The exhaust end of the first low-pressure steam turbine is connected to the hot-side working medium inlet of the first condenser, and the hot-side working medium outlet of the first condenser is connected to the first inlet of the condensate tank through the first low-pressure heater, and the condensate tank The first outlet of the first deaerator is connected to the second inlet of the first deaerator; the outlet of the first deaerator is connected to the first boiler through the first high-pressure heater;

The second heat and power cogeneration unit, the second heat and power cogeneration unit includes a second boiler and a second steam turbine unit; the second steam turbine unit includes a second high-pressure steam turbine, a second medium-pressure steam turbine and a second steam turbine connected to the second boiler in sequence low pressure steam turbine;

The exhaust end of the second medium-pressure steam turbine is connected to the inlet of the second low-pressure steam turbine, the first inlet of the second deaerator, the heat source working medium inlet of the absorption heat pump, the inlet of the small steam turbine of the heat network circulating water pump, and the heat network heater The working fluid inlet on the hot side is connected;

The exhaust end of the second low-pressure steam turbine is connected with the hot-side working medium inlet of the second condenser, and the hot-side working medium outlet of the second condenser is connected with the hot well of the first condenser; the second deaerator The second inlet is connected with the second outlet of the condensate tank; the outlet of the second deaerator is connected with the second boiler through the second high pressure heater;

Absorption heat pump, the heat source working medium outlet of the absorption heat pump is connected to the second inlet of the condensate tank; the heated working medium inlet of the absorption heat pump is input into the heat network return water and the heat network replenishment water, and the heated working medium outlet is all the way It is connected to the cold side working medium inlet of the exhaust steam heater of the small steam turbine, and the other is connected to the cold side working medium inlet of the heat network heater;

The hot-side working medium outlets of the heating network heater and the exhaust steam heater of the small steam turbine are connected to the hot well of the first condenser, and the cold-side working medium outlets output the heating network water supply;

The hot side working medium outlet of the small steam turbine of the heat network circulating water pump is connected with the hot side working medium inlet of the exhaust steam heater of the small steam turbine.

The further improvement of the present invention is:

The first boiler includes a first boiler heater and a first boiler reheater, the outlet of the first boiler heater is connected to the inlet of the first high-pressure steam turbine, and the outlet of the first high-pressure steam turbine is connected to the inlet of the first boiler reheater, The outlet of the first boiler reheater is connected to the inlet of the first intermediate pressure steam turbine.

The steam extraction end of the first high-pressure steam turbine is connected with the hot-side working medium inlet of the first high-pressure heater; the steam extraction end of the first low-pressure steam turbine is connected with the hot-side working medium inlet of the first low-pressure heater.

A first condensate pump is arranged between the first condenser and the first low-pressure heater; a first feedwater pump is arranged between the first deaerator and the first high-pressure heater.

The second boiler includes a second boiler heater and a second boiler reheater, the outlet of the second boiler heater is connected to the inlet of the second high-pressure steam turbine, and the outlet of the second high-pressure steam turbine is connected to the inlet of the second boiler reheater, The outlet of the second boiler reheater is connected to the inlet of the second intermediate pressure steam turbine.

The steam extraction end of the second high-pressure steam turbine is connected to the hot-side working fluid inlet of the second high-pressure heater.

A second condensate pump is arranged between the second condenser and the plate heat exchanger; a second feedwater pump is arranged between the second deaerator and the second high-pressure heater.

The heating network return water and heating network make-up water sink are input to the inlet of the heating network circulating water pump, and the heating network circulating water pump is connected to the heated working medium inlet of the absorption heat pump; the small steam turbine of the heating network circulating water pump drives the heating network circulating water pump to pressurize the heating network water .

The first high-pressure steam turbine, the first medium-pressure steam turbine and the first low-pressure steam turbine jointly drive the first generator to rotate and output electric energy to the outside; the second high-pressure steam turbine, the second medium-pressure steam turbine and the second low-pressure steam turbine jointly drive the second generator Rotate to output electric energy to the outside.

A heat supply method for a low-pressure cylinder zero-output coupled absorption heat pump, comprising the following steps:

The working fluid at the outlet of the second medium-pressure steam turbine is divided, and the first channel of working fluid enters the second low-pressure steam turbine to prevent the blades of the second low-pressure steam turbine from overheating. 1-3% of the mass flow rate enters the second condenser after passing through the second low-pressure steam turbine;

The second working medium is used as driving steam to enter the small steam turbine of the heating network circulating water pump, and the heating network circulating water pump is driven by the small steam turbine of the heating network circulating water pump to pressurize the heating network water, and the exhaust steam of the small steam turbine of the heating network circulating water pump enters the exhaust steam heating of the small steam turbine The condenser continues to release heat, and finally enters the first condenser;

The third working medium enters the hot side working medium inlet of the absorption heat pump, and serves as the driving heat source of the absorption heat pump, drives the absorption heat pump to recover the loss of the cold source, and is used for preliminary heating of the return water of the heating network and replenishment of the heating network;

The fourth working medium enters the heating network heater, which is used to heat the circulating water of the heating network, and after releasing heat, it is collected into the hot well of the first condenser;

The working medium on the hot side of the heat network heater and the working medium on the hot side of the exhaust steam heater of the small steam turbine will both flow to the hot well of the first condenser after exothermic heat, join with the condensed water produced by the first condenser, and be fed by the second The extraction steam of a low-pressure steam turbine is heated, and in the condensed water tank, it is divided into the first deaerator and the second deaerator according to demand.

Compared with the prior art, the present invention has the following beneficial effects:

The first combined heat and power unit of the present invention is a condensing extraction unit, and the second combined heat and power unit is a low-pressure cylinder zero-output unit, which uses the middle exhaust steam extraction of the low-pressure cylinder zero-output unit to drive the absorption heat pump and the heat network circulating water pump. The principle of energy cascade utilization, and the low-pressure cylinder zero-output unit has a wide range of electric heating load adjustment, which can meet the needs of flexible peak regulation; the invention adopts the absorption heat pump to recover the waste heat at the cold end of the pure condensing unit, and the energy utilization rate is high. The water heating of the heating network is divided into The two processes conform to temperature matching and energy level matching, using heat at a lower temperature to meet the heating demand and significantly reducing the energy consumption of the unit; the condensate water of the low-pressure cylinder zero-output unit and the outlet of the working medium on the hot side of the heating network heater and the small steam turbine The working medium outlet on the hot side of the exhaust steam heater is connected to the hot well of the condenser of the extraction condensing unit, and the low-pressure heater of the extraction condensing unit is used to heat the condensate of the zero-output unit of the low-pressure cylinder, which solves the problem of heating the condensate of the zero-output unit of the low-pressure cylinder.

The invention couples the low-pressure cylinder zero-output unit and the absorption heat pump, and simultaneously provides users with two energy sources of heat and electricity. Through the coupling optimization of the cold end of the condensing unit-the low-pressure cylinder zero-output unit-absorption heat pump process, the invention can greatly improve the energy utilization rate of the coal-fired unit. The invention divides the heating process of the heating network return water into two stages: firstly, it conducts preliminary heating in the absorption heat pump, and then divides the flow into two parts, and one part enters the exhaust steam of the small steam turbine. , the other part enters the heat network heater and uses the mid-row exhaust steam of the low-pressure cylinder zero-output unit for heating, and then converges to supply heat to the outside to meet the heating demand of the heat network; set up a condensate tank before the deaerator of the condensing unit to The condensing unit and low-pressure cylinder zero-output unit provide condensed water, and the condensed water of the low-pressure cylinder zero-output unit merges into the hot well of the condenser of the condensing unit, is heated by the low-pressure heater of the condensing unit, and then flows into the condensate tank. The low-pressure cylinder zero-output unit has a strong electrical load adjustment capability, which can meet the needs of flexible peak regulation. The system uses the low-pressure heater of the condensing unit to heat the condensate of the low-pressure cylinder zero-output unit, which solves the problem of heating the condensate of the low-pressure cylinder zero-output unit. The heat pump recovers the waste heat at the cold end of the condensing unit and initially heats the water in the heating network. By distributing the water in the heating network reasonably in different stages to heat the heat source, the waste heat in the system is rationally utilized, and the energy utilization rate of the unit is high. By adjusting the heat load of the absorption heat pump and the heating network The steam extraction capacity of the heater can meet the water supply temperature of the heating network required in different heating periods, and it has operational flexibility.

Description of drawings

In order to illustrate the technical solutions of the embodiments of the present invention more clearly, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention, and thus It should be regarded as a limitation on the scope, and those skilled in the art can also obtain other related drawings based on these drawings without creative work.

Figure 1 is a comparison diagram of the electrothermal load characteristics of a conventional condensing unit and a high back pressure unit, in which (a) is a characteristic diagram of the electrothermal load of a 300MW condensing unit, and (b) is a characteristic diagram of the electrothermal load of a 300MW high backpressure unit.

Figure 2 is the thermoelectric load characteristic diagram of the low-pressure cylinder zero output unit.

Fig. 3 is a schematic diagram of a heat supply system of a low-pressure cylinder coupled with an absorption heat pump according to the present invention.

Among them: 1 is the first boiler, 1-1 is the first boiler heater, 1-2 is the first boiler reheater, 2 is the first high-pressure steam turbine, 3 is the first medium-pressure steam turbine, 4 is the first low-pressure steam turbine , 5 is the first condenser, 6 is the first condensate pump, 7 is the first low pressure heater, 8 is the first deaerator, 9 is the first feed water pump, 10 is the first high pressure heater, 11 is the first A generator, 12 is the second boiler, 12-1 is the second boiler heater, 12-2 is the second boiler reheater, 13 is the second high pressure steam turbine, 14 is the second medium pressure steam turbine, 15 is the second 16 is the second condenser, 17 is the second condensate pump, 18 is the second deaerator, 19 is the second feed water pump, 20 is the second high pressure heater, 21 is the second generator, 22 is Heat network heater, 23 is condensed water tank, 24 is absorption heat pump, 25 is heat network circulation water pump small steam turbine, 26 is heat network circulation water pump, 27 is exhaust steam heater of small steam turbine.

detailed description

In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments It is a part of embodiments of the present invention, but not all embodiments. The components of the embodiments of the invention generally described and illustrated in the figures herein may be arranged and designed in a variety of different configurations.

Accordingly, the following detailed description of the embodiments of the invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely represents selected embodiments of the invention. Based on the embodiments of the present invention, all other embodiments obtained by persons of ordinary skill in the art without creative efforts fall within the protection scope of the present invention.

It should be noted that like numerals and letters denote similar items in the following figures, therefore, once an item is defined in one figure, it does not require further definition and explanation in subsequent figures.

In the description of the embodiments of the present invention, it should be noted that the orientation or positional relationship indicated by the terms "upper", "lower", "horizontal", "inside" etc. is based on the orientation or positional relationship shown in the drawings , or the orientation or positional relationship that the product of the invention is usually placed in use is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation or be constructed in a specific orientation and operation, and therefore should not be construed as limiting the invention. In addition, the terms "first", "second", etc. are only used for distinguishing descriptions, and should not be construed as indicating or implying relative importance.

In addition, when the term "horizontal" appears, it does not mean that the part is required to be absolutely horizontal, but may be slightly inclined. For example, "horizontal" only means that its direction is more horizontal than "vertical", and it does not mean that the structure must be completely horizontal, but can be slightly inclined.

In the description of the embodiments of the present invention, it should also be noted that, unless otherwise specified and limited, the terms "setting", "installation", "connection" and "connection" should be interpreted 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 an indirect connection through an intermediary, and it can be the internal communication of two components. Those of ordinary skill in the art can understand the specific meanings of the above terms in the present invention according to specific situations.

The present invention is described in further detail below in conjunction with accompanying drawing:

Referring to Fig. 3, the embodiment of the present invention discloses a low-pressure cylinder zero output coupled absorption heat pump heating system, including a first combined heat and power unit and a second combined heat and power unit;

The first combined heat and power unit includes a condensed water tank 23, a first deaerator 8, a first feed water pump 9, a first high-pressure heater 10, a first boiler heater 1-1, a first high-pressure steam turbine 2, a first A boiler reheater 1-2, the first medium-pressure steam turbine 3, the first low-pressure steam turbine 4; the first condenser 5, the first condensate pump 6 and the first low-pressure heater 7; the first high-pressure steam turbine 2, the first The medium-pressure steam turbine 3 and the first low-pressure steam turbine 4 jointly drive the first generator 11 to rotate and output electric energy to the outside.

The inlet of the first high-pressure steam turbine 2 is connected with the outlet of the first boiler heater 1-1, the outlet of the first high-pressure steam turbine 2 is connected with the inlet of the first boiler reheater 1-2, and the steam extraction of the first high-pressure steam turbine 2 is connected with the first high-pressure The hot side working medium inlet of the heater 10 is connected; the inlet of the first medium-pressure steam turbine 3 is connected with the outlet of the first boiler reheater 1-2, the outlet of the first medium-pressure steam turbine 3 is connected with the inlet of the first low-pressure steam turbine 4 and the first dehumidifier The inlet of the oxygenator 8 is connected; the outlet of the first low-pressure steam turbine 4 is connected with the hot-side working medium inlet of the first condenser 5 , and the steam extraction of the first low-pressure steam turbine 4 is connected with the hot-side working medium inlet of the first low-pressure heater 7 .

The cold side working medium inlet of the first condenser 5 is connected with the cold source working medium outlet of the absorption heat pump 24, the cold side working medium outlet of the first condenser 5 is connected with the absorption heat pump 24 cold source working medium inlet, and the first Condenser 5 hot well and first low-pressure heater 7 hot-side working medium outlet, first condenser 5 hot-side working medium outlet, first condensate pump 6 inlet, second condensate pump 17 outlet, small turbine exhaust steam heating The working medium outlet on the hot side of the device 27 is connected with the working medium outlet on the hot side of the heating network heater 22;

The working medium inlet on the cold side of the first low-pressure heater 7 is connected with the outlet of the first condensate pump 6, and the working medium outlet on the cold side of the first low-pressure heater 7 is connected with the condensate tank 23; the first deaerator inlet 8 is connected with the condensate tank 23 connected; the inlet of the first feedwater pump 9 is connected with the outlet of the first deaerator 8, and the outlet of the first feedwater pump 9 is connected with the inlet of the working medium on the cold side of the first high pressure heater 10; the hot side of the first high pressure heater 10 is connected The gas outlet is connected to the inlet of the first deaerator 8, and the outlet of the working fluid on the cold side of the first high pressure heater 10 is connected to the inlet of the first boiler heater 1-1;

The second cogeneration unit includes a second deaerator 18, a second feed water pump 19, a second high-pressure heater 20, a second boiler heater 12-1, a second high-pressure steam turbine 13, and a second boiler that are connected in sequence. Heater 12-2, second medium-pressure steam turbine 14 and second low-pressure steam turbine 15, second condenser 16, second condensed water pump 17, heat network heater 22, first generator 11, second generator 21. Absorption heat pump 24, heating network circulating water pump and small steam turbine 25, heating network circulating water pump 26 and small steam turbine exhaust steam heater 27; The high-pressure steam turbine 13 and the second medium-pressure steam turbine 14 jointly drive the first generator 21 to rotate and output electric energy to the outside;

After the return water of the heating network and the supplementary water of the heating network are collected, it is firstly pressurized by the heating network circulating water pump 26, and then initially heated by the absorption heat pump 24, and then divided into two streams, and one part enters the exhaust steam heater 27 of the small steam turbine to utilize the heating network circulation The water pump small steam turbine 25 exhausts steam for heating, and the other part enters the heat network heater 22 to use the exhaust steam of the second medium-pressure steam turbine 14 for heating, and then converges for external heating to meet the heating demand;

The inlet of the second high-pressure steam turbine 13 is connected with the outlet of the second boiler heater 12-1, the outlet of the second high-pressure steam turbine 13 is connected with the inlet of the second boiler reheater 12-2, and the steam extraction of the second high-pressure steam turbine 13 is connected with the second high-pressure The hot side working medium inlet of the heater 20 is connected; the inlet of the second medium-pressure steam turbine 14 is connected with the outlet of the second boiler reheater 12-2, the outlet of the second medium-pressure steam turbine 14 is connected with the inlet of the second low-pressure steam turbine 15, the second Oxygenator 18 inlet, absorption heat pump 24 heat source working medium inlet, heat network circulating water pump small steam turbine 25 inlet and heat network heater 22 heat side working medium inlet are connected; second low-pressure steam turbine 15 outlet and second condenser 16 heat The side working medium inlet is connected;

The hot well of the second condenser 16 communicates with the outlet of the hot side working medium of the second condenser 16 and the inlet of the second condensed water pump 17; the inlet of the second deaerator 18 is connected with the outlet of the condensed water tank 23, the second medium-pressure steam turbine 14, and The outlet of the working medium on the hot side of the second high pressure heater 20 is connected; the inlet of the second feedwater pump 19 is connected to the outlet of the second deaerator 18, and the outlet of the second feedwater pump 19 is connected to the inlet of the working medium on the cold side of the second high pressure heater 20 Pass; the cold side working medium outlet of the second high pressure heater 20 is connected with the inlet of the second boiler heater 12-1;

The heat source working medium outlet of the absorption heat pump 24 is collected to the condensate tank 24, the heated working medium inlet of the absorption heat pump 24 is connected with the heat network circulating water pump 26 outlet, and the heated working medium outlet of the absorption heat pump 24 is connected with the small turbine exhaust steam heater 27 The cold-side working medium inlet is connected to the cold-side working medium inlet of the heating network heater 22;

The hot side working medium outlet of the small steam turbine 25 of the heat network circulation pump is connected with the hot side working medium inlet of the small steam turbine exhaust heater 27, and the small steam turbine 25 of the heat network circulation pump drives the heat network circulation water pump 26 to pressurize the heat network water, and the heat network The inlet of the circulating water pump 26 is connected with the heating return water and the heating supplementary water, and the outlet of the heating network circulating water pump 26 is connected with the inlet of the heated working medium of the absorption heat pump 24;

The working medium outlet on the hot side of the heating network heater 22 is connected with the hot well of the first condenser 5 and the hot side working medium outlet of the exhaust steam heater 27 of the small turbine, and the working medium outlet on the cold side of the heating network heater 22 is connected with the exhaust steam of the small turbine The outlet of the working medium on the cold side of the heater 27 is connected to the water supply of the heating network;

The embodiment of the present invention discloses a heat supply method of a low-pressure cylinder zero output coupled absorption heat pump, which includes the following steps:

The first is a pure condensing unit, the second is a pure condensing unit that undergoes low-pressure cylinder zero-output transformation, and the second medium-pressure steam turbine 14 outlet working fluid is divided into four parts,

The first part enters the second low-pressure steam turbine 15 to prevent the blades of the second low-pressure steam turbine 15 from overheating. The mass flow rate of this part of the working medium accounts for 1-3% of the mass flow rate of the working medium under the maximum output working condition of the boiler. After passing through the second low-pressure steam turbine 15, it enters the first part Second condenser 16;

The second part is used as driving steam to enter the small turbine 25 of the heating network circulating water pump, and the heating network circulating water pump 25 drives the heating network circulating water pump 26 to pressurize the heating network water, and the exhausted steam of the heating network circulating water pump small turbine 25 enters the exhausted steam of the small turbine The heater 27 continues to release heat, and finally flows into the first condenser 5;

The third part enters the inlet of the working medium on the hot side of the absorption heat pump 24, and serves as the driving heat source of the absorption heat pump 24, drives the absorption heat pump 24 to recover the loss of the first cold source, and is used for preliminary heating of the return water of the heating network and replenishment of the heating network;

The fourth part of the working medium enters the heating network heater 22 to heat the circulating water of the heating network, and collects it into the first condenser 5 hot well after releasing heat;

The working medium on the hot side of the heating network heater 22 and the exhaust steam heater 27 of the small steam turbine are all discharged to the first condenser 5 after the hot side working fluid is discharged, and the hot well is merged with the first condensed water, and is pumped by the first low-pressure steam turbine 4 The steam is heated and diverted into the first deaerator 8 and the second deaerator 18 in the condensed water tank 23 according to the demand, so as to realize cascade utilization of energy, reduce the loss of the first cold source, and solve the problem of the second process. The problem of condensate heating after zero-efficiency transformation of the low-pressure cylinder reduces the energy consumption of the unit.

The above are only preferred embodiments of the present invention, and are not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and changes. 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 (10)

1. A low-pressure cylinder zero output coupled absorption heat pump heating system, characterized in that it comprises: A first heat and power cogeneration unit, the first heat and power cogeneration unit includes a first boiler (1) and a first steam turbine unit; the first steam turbine unit includes a first high-pressure steam turbine (2) sequentially connected to the first boiler (1) , the first medium-pressure steam turbine (3) and the first low-pressure steam turbine (4); The exhaust end of the first medium-pressure steam turbine (3) is respectively connected with the inlet of the first low-pressure steam turbine (4) and the first inlet of the first deaerator (8); The exhaust end of the first low-pressure steam turbine (4) is connected to the hot-side working medium inlet of the first condenser (5), and the hot-side working medium outlet of the first condenser (5) passes through the first low-pressure heater (7) ) is connected to the first inlet of the condensed water tank (23), and the first outlet of the condensed water tank (23) is connected to the second inlet of the first deaerator (8); the outlet of the first deaerator (8) passes through the first high pressure The heater (10) is connected to the first boiler (1); The second heat and power cogeneration unit, the second heat and power cogeneration unit includes a second boiler (12) and a second steam turbine unit; the second steam turbine unit includes a second high-pressure steam turbine (13) connected to the second boiler (12) in sequence , the second medium-pressure steam turbine (14) and the second low-pressure steam turbine (15); The exhaust end of the second medium-pressure steam turbine (14) is respectively connected with the inlet of the second low-pressure steam turbine (15), the first inlet of the second deaerator (18), the heat source working fluid inlet of the absorption heat pump (24), the heat The inlet of the small turbine (25) of the network circulating water pump is connected with the hot side working medium inlet of the heating network heater (22); The exhaust end of the second low-pressure steam turbine (15) is connected to the hot side working medium inlet of the second condenser (16), and the hot side working medium outlet of the second condenser (16) is connected to the first condenser (5 ) of the hot well; the second inlet of the second deaerator (18) is connected with the second outlet of the condensate tank (23); the outlet of the second deaerator (18) is connected with the second high pressure heater (20) The second boiler (12) is connected; Absorption heat pump (24), the heat source working fluid outlet of the absorption heat pump (24) is connected to the second inlet of the condensate tank (23); the heated working fluid inlet of the absorption heat pump (24) is input into the heat network back Water and heating network replenishment, the outlet of the heated working medium is connected to the cold side working medium inlet of the exhaust steam heater (27) of the small steam turbine, and the other is connected to the cold side working medium inlet of the heating network heater (22); The hot-side working medium outlets of the heating network heater (22) and the exhaust steam heater (27) of the small steam turbine are connected to the hot well of the first condenser (5), and the cold-side working medium outlets output the heating network water supply; The hot side working medium outlet of the small steam turbine (25) of the heat network circulating water pump is connected with the hot side working medium inlet of the exhaust steam heater (27) of the small steam turbine. 2. The heat supply system of low-pressure cylinder zero output coupling absorption heat pump according to claim 1, characterized in that, the first boiler (1) includes a first boiler heater (1-1) and a first boiler reheating system Heater (1-2), the outlet of the first boiler heater (1-1) is connected to the inlet of the first high-pressure steam turbine (2), and the outlet of the first high-pressure steam turbine (2) is connected to the first boiler reheater (1- 2), the outlet of the first boiler reheater (1-2) is connected to the inlet of the first medium-pressure steam turbine (3). 3. The heat supply system of low-pressure cylinder zero-output coupled absorption heat pump according to claim 2, characterized in that the heat between the extraction end of the first high-pressure steam turbine (2) and the first high-pressure heater (10) The side working medium inlet is connected; the steam extraction end of the first low-pressure steam turbine (4) is connected with the hot side working medium inlet of the first low-pressure heater (7). 4. The heat supply system of the low-pressure cylinder zero output coupling absorption heat pump according to claim 1 or 2 or 3, characterized in that, the first condenser (5) and the first low-pressure heater (7) A first condensate pump (6) is arranged between them; a first feedwater pump (9) is arranged between the first deaerator (8) and the first high-pressure heater (10). 5. The heat supply system of low-pressure cylinder zero output coupling absorption heat pump according to claim 1, characterized in that, the second boiler (12) comprises a second boiler heater (12-1) and a second boiler reheating system Heater (12-2), the outlet of the second boiler heater (12-1) is connected to the inlet of the second high-pressure steam turbine (13), and the outlet of the second high-pressure steam turbine (13) is connected to the second boiler reheater (12- 2), the outlet of the second boiler reheater (12-2) is connected to the inlet of the second medium-pressure steam turbine (14). 6. The heat supply system of low-pressure cylinder zero-output coupling absorption heat pump according to claim 5, characterized in that, the heat between the extraction end of the second high-pressure steam turbine (13) and the second high-pressure heater (20) The side working medium inlet is connected. 7. The heat supply system of low-pressure cylinder zero output coupled absorption heat pump according to claim 1 or 5 or 6, characterized in that, between the second condenser (16) and the plate heat exchanger (24) A second condensate pump (17) is provided; a second feedwater pump (19) is provided between the second deaerator (18) and the second high-pressure heater (20). 8. The heat supply system of low-pressure cylinder zero output coupling absorption heat pump according to claim 7, characterized in that the return water of the heating network and the replenishment water of the heating network are input to the inlet of the circulating water pump (26) of the heating network, and the heating network circulates The water pump (26) is connected to the heated working medium inlet of the absorption heat pump (24); the heat network circulating water pump small turbine (25) drives the heat network circulating water pump (26) to pressurize the heat network water. 9. The heat supply system of low-pressure cylinder zero output coupling absorption heat pump according to claim 1, characterized in that, the first high-pressure steam turbine (2), the first medium-pressure steam turbine (3) and the first low-pressure steam turbine ( 4) jointly drive the first generator (11) to rotate, and output electric energy to the outside; the second high-pressure steam turbine (13), the second medium-pressure steam turbine (14) and the second low-pressure steam turbine (15) jointly drive the second generator (21) Rotate to output electric energy to the outside. 10. A heat supply method using the low-pressure cylinder zero output coupled absorption heat pump of the system according to any one of claims 1-9, characterized in that it comprises the following steps: The working fluid at the outlet of the second medium-pressure steam turbine (14) is divided, and the first-way working fluid enters the second low-pressure steam turbine (15) to prevent the blades of the second low-pressure steam turbine (15) from overheating and enter the second low-pressure steam turbine (15). The mass flow rate of the working medium accounts for 1-3% of the mass flow rate of the working medium under the maximum output condition of the boiler, and enters the second condenser (16) after passing through the second low-pressure steam turbine (15); The second working medium enters the small steam turbine (25) of the heating network circulating water pump as driving steam, and the heating network circulating water pump (26) is driven by the small steam turbine (25) of the heating network circulating water pump to pressurize the heating network water, and the small steam turbine of the heating network circulating water pump The exhausted steam of (25) enters the exhausted steam heater (27) of the small turbine to continue releasing heat, and finally imports into the first condenser (5); The third working medium enters the hot side working medium inlet of the absorption heat pump (24), and serves as the driving heat source of the absorption heat pump (24), drives the absorption heat pump (24) to recover the loss of the cold source, and is used to initially heat the return water of the heating network and heating network replenishment; The fourth working medium enters the heating network heater (22) for heating the circulating water of the heating network, and collects it into the hot well of the first condenser (5) after releasing heat; The working fluid on the hot side of the heat network heater (22) and the working fluid on the hot side of the exhaust steam heater (27) of the small steam turbine are both released to the hot well of the first condenser (5) and the first condenser (5) The condensed water produced merges, and is heated by the steam extraction of the first low-pressure steam turbine (4), and enters the first deaerator (8) and the second deaerator ( 18).

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