阅读说明：本技术 一种回收利用汽轮机乏蒸汽的供热发电联产系统 (Heat supply and power generation cogeneration system for recycling exhausted steam of steam turbine ) 是由 刘学 李国栋 杨晓巳 单小勇 金红伟 林伟宁 于 2020-07-13 设计创作，主要内容包括：本申请公开了一种回收利用汽轮机乏蒸汽的供热发电联产系统,包括：热网管路；设置在热网管路上以对热网回水加热的第一加热器和对回水再次加热的第二加热器；汽轮机；通过第一抽汽管路与汽轮机连通的蒸汽喷射器,蒸汽喷射器的喷汽出口与第二加热器连通；空冷凝汽器；用于排出汽轮机乏蒸汽的排汽管路,排汽管路包括与汽轮机连通的排汽主管路以及与排汽主管路的末端连通的第一排汽支管路、第二排汽支管路和第三排汽支管路；第一排汽支管路与所述空冷凝汽器连通,第二排汽支管路与第一加热器连通,第三排汽支管路与蒸汽喷射器连通。上述系统不仅能有效降低机组的运行背压,提高发电能力,而且还能减少汽轮机的冷端损失,提高机组的热经济性和发电量。(The application discloses heating power generation cogeneration system of recycle steam turbine exhaust steam includes: a heat supply network pipeline; the first heater is arranged on the heat supply network pipeline to heat return water of the heat supply network, and the second heater is used for reheating the return water; a steam turbine; the steam ejector is communicated with the steam turbine through a first steam extraction pipeline, and a steam injection outlet of the steam ejector is communicated with the second heater; an air-cooled condenser; the system comprises a steam exhaust pipeline, a steam turbine and a control system, wherein the steam exhaust pipeline is used for exhausting exhausted steam of the steam turbine and comprises a main steam exhaust pipeline communicated with the steam turbine, and a first branch steam exhaust pipeline, a second branch steam exhaust pipeline and a third branch steam exhaust pipeline which are communicated with the tail end of the main steam exhaust pipeline; the first exhaust branch pipeline is communicated with the air-cooling condenser, the second exhaust branch pipeline is communicated with the first heater, and the third exhaust branch pipeline is communicated with the steam ejector. The system not only can effectively reduce the running back pressure of the unit and improve the power generation capacity, but also can reduce the cold end loss of the steam turbine and improve the heat economy and the power generation capacity of the unit.)

1. A heating and power generation cogeneration system for recycling spent steam of a steam turbine is characterized by comprising:

a heat supply network pipeline;

the first heater is arranged on the heat supply network pipeline and used for heating the return water of the heat supply network;

the second heater is arranged on the heat supply network pipeline and used for heating the return water of the heat supply network again;

a steam turbine;

the steam ejector is communicated with the intermediate pressure cylinder and the low pressure cylinder of the steam turbine through a first steam extraction pipeline, and a steam injection outlet of the steam ejector is communicated with the second heater;

an air-cooled condenser;

the steam exhaust pipeline comprises a main steam exhaust pipeline communicated with a steam exhaust outlet of the steam turbine, and a first branch steam exhaust pipeline, a second branch steam exhaust pipeline and a third branch steam exhaust pipeline which are communicated with the tail end of the main steam exhaust pipeline;

wherein the content of the first and second substances,

the first exhaust branch pipeline is communicated with the air-cooling condenser, the second exhaust branch pipeline is communicated with the first heater, and the third exhaust branch pipeline is communicated with the steam ejector.

2. A cogeneration system for recycling steam turbine spent steam according to claim 1, further comprising a third heater provided on the heat network pipeline to heat return water of the heat network, wherein the third heater is communicated with the intermediate pressure cylinder and the low pressure cylinder of the steam turbine through a second steam extraction pipeline.

3. A cogeneration system for recycling steam turbine spent steam according to claim 1, wherein an absorption heat pump system is disposed on the heat network pipeline, and the absorption heat pump system is located at a user side of the heat network pipeline.

4. A cogeneration system for recycling steam turbine spent steam according to claim 3, wherein said absorption heat pump system comprises an absorption heat exchanger and a water-water heat exchanger.

5. A cogeneration system for recycling steam turbine spent steam according to claim 1, further comprising a ventilation cooling tower disposed on said heat supply network pipeline, said ventilation cooling tower being disposed in parallel with said first heater.

6. A cogeneration system for recycling steam turbine spent steam according to claim 1, wherein said air-cooled condensers are provided in plurality in parallel.

Technical Field

The invention relates to the technical field of cogeneration, in particular to a heat supply and power generation cogeneration system for recycling exhausted steam of a steam turbine.

Background

Currently, in order to save energy better, most areas in the north generally adopt a centralized heating mode. In a 300 MW-level power plant, most generator sets run in a heat supply mode, and compared with a pure condensing unit, the heat supply unit utilizes high-grade heat energy to generate electricity and utilizes lower-grade heat energy which is subjected to partial work in a steam turbine to supply heat to the outside.

Generally, a thermal power plant is used as a heat source end for heat supply, generally, return water heating of a heat supply network is completed in the thermal power plant, as shown in fig. 1, a traditional heat supply mode is that a steam turbine is used for extracting steam to heat return water of the heat supply network, a unit generally adopts the steam extraction (steam pressure is about 0.4MPa) on a communicating pipe of a medium-pressure cylinder and a low-pressure cylinder during heat supply as a heating source for primary heat supply, the temperature of water supply/return water of the primary heat supply network is generally about 130 ℃/70 ℃, the extracted high-quality steam directly enters a primary heat supply network heater to be heated, so that the problems of partial high-grade energy loss, high unit power supply coal consumption and the like can be caused, and along with the continuous increase of heat supply requirements, the heat supply area is increased, and if the high-quality steam is still directly.

In addition, at present, a high back pressure heat supply technology exists, the exhaust back pressure of a steam turbine is increased, high back pressure steam is used for primarily heating return water of a heat supply network, so that partial or whole utilization of exhausted steam of the steam turbine can be realized, and cold end loss is reduced.

Disclosure of Invention

In view of this, the invention provides a heating and power generation cogeneration system for recycling exhaust steam of a steam turbine, which not only can effectively reduce the running back pressure of a unit and improve the power generation capacity, but also can reduce the cold end loss of the steam turbine and improve the heat economy and the power generation capacity of the unit.

In order to achieve the purpose, the invention provides the following technical scheme:

a heating and power generation cogeneration system for recycling spent steam of a steam turbine comprises:

a heat supply network pipeline;

the first heater is arranged on the heat supply network pipeline and used for heating the return water of the heat supply network;

the second heater is arranged on the heat supply network pipeline and used for heating the return water of the heat supply network again;

a steam turbine;

the steam ejector is communicated with the intermediate pressure cylinder and the low pressure cylinder of the steam turbine through a first steam extraction pipeline, and a steam injection outlet of the steam ejector is communicated with the second heater;

an air-cooled condenser;

the steam exhaust pipeline comprises a main steam exhaust pipeline communicated with a steam exhaust outlet of the steam turbine, and a first branch steam exhaust pipeline, a second branch steam exhaust pipeline and a third branch steam exhaust pipeline which are communicated with the tail end of the main steam exhaust pipeline;

wherein the content of the first and second substances,

the first exhaust branch pipeline is communicated with the air-cooling condenser, the second exhaust branch pipeline is communicated with the first heater, and the third exhaust branch pipeline is communicated with the steam ejector.

Preferably, the heat supply and power generation cogeneration system for recycling the exhaust steam of the steam turbine further comprises a third heater arranged on the heat supply network pipeline to heat return water of the heat supply network, and the third heater is communicated with the intermediate pressure cylinder and the low pressure cylinder of the steam turbine through a second steam extraction pipeline.

Preferably, in the heat supply and power generation cogeneration system for recycling the steam exhausted from the steam turbine, the heat pipe network is provided with an absorption heat pump system, and the absorption heat pump system is located at a user side of the heat pipe network.

Preferably, in the heat supply and power generation cogeneration system for recycling the steam exhausted from the steam turbine, the absorption heat pump system includes an absorption heat exchanger and a water-water heat exchanger.

Preferably, the heating and power generation cogeneration system for recycling the steam exhausted by the steam turbine further comprises a ventilation cooling tower arranged on the heat supply network pipeline, and the ventilation cooling tower and the first heater are arranged in parallel.

Preferably, in the cogeneration system for heating and generating power by recycling the exhaust steam of the steam turbine, the air-cooled condensers are arranged in parallel.

The heat supply and power generation cogeneration system for recycling the steam exhausted by the steam turbine heats the first-stage heat supply network backwater by using the waste heat of part or all of the exhausted steam exhausted by the steam turbine, can reduce the cold end loss of the unit and improve the heat efficiency of the unit, and compared with the existing system which directly adopts the steam extracted from the steam extraction pipes of the medium and low pressure cylinders as a heat supply source, the system can only extract a small amount of high-grade steam from the medium and low pressure cylinders as the power steam of the steam ejector, and the steam ejector mainly absorbs the exhausted steam which is used for completing the work of the steam turbine to heat the first-stage heat supply network backwater, thereby not only effectively reducing the running backpressure of the unit, but also being capable of enabling more high-quality steam to be used for power generation along with the reduction of the extraction amount of the high-quality steam, thereby improving the heat economy.

Drawings

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, it is obvious that the drawings in the following description are only embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to the provided drawings without creative efforts.

FIG. 1 is a schematic diagram of a cogeneration system for heating and power generation in the prior art;

fig. 2 is a schematic diagram of a heat supply and power generation cogeneration system for recycling steam turbine exhaust steam according to an embodiment of the present invention.

Detailed Description

The invention provides a heating and power generation cogeneration system for recycling exhausted steam of a steam turbine, which not only can effectively reduce the running back pressure of a unit and improve the power generation capacity, but also can reduce the cold end loss of the steam turbine and improve the heat economy and the power generation capacity of the unit.

The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

As shown in fig. 2, an embodiment of the present invention provides a heating and power generation cogeneration system for recycling steam exhausted from a steam turbine, which can heat return water of a primary heat supply network by recycling the steam exhausted from the steam turbine on the basis that the exhaust back pressure of the steam turbine is in a lower range, and the system mainly includes: heat supply network pipeline, first heater, second heater, steam turbine, steam ejector, air cooling condenser and exhaust pipe (of course, this system still includes boiler, generator, heat supply network circulating pump etc. and guarantees the part that heat supply power generation coproduction normally realized, but because these parts are not the improvement parts that this application is directed to, so this application does not carry out special explanation to it), wherein: the heat supply network pipeline is a pipeline for forming a primary heat supply network; the first heater is arranged on the heat supply network pipeline, and particularly is arranged at a heating end of the heat supply network pipeline close to the generator set (when the first heater, the second heater and a third heater which is described later are arranged in a power plant in actual arrangement), and is used for heating return water which flows back in the heat supply network pipeline; the second heater is also arranged at the heating end and used for heating the return water which flows back in the heat supply network pipeline, and in the flowing direction of the return water, the second heater is positioned at the downstream of the first heater, the return water heated by the second heater is the return water heated by the first heater, namely the return water flows through the second heater after being heated by the first heater and then is heated again; the steam turbine comprises a high-pressure cylinder, an intermediate-pressure cylinder and a low-pressure cylinder which are sequentially connected, and the intermediate-pressure cylinder and the low-pressure cylinder are connected with a first steam extraction pipeline which extracts high-quality steam in the intermediate-pressure cylinder and the low-pressure cylinder; the air-cooled condenser is communicated with a low pressure cylinder of the steam turbine through an exhaust pipeline, the exhaust pipeline comprises an exhaust main pipeline communicated with an exhaust steam outlet of the low pressure cylinder, and a first exhaust branch pipeline, a second exhaust branch pipeline and a third exhaust branch pipeline which are communicated with the tail end of the exhaust main pipeline (the tail end refers to the end of the exhaust main pipeline far away from the steam turbine), the three exhaust branch pipelines divide exhausted steam led out from the exhaust main pipeline and respectively convey the divided exhausted steam to different parts, wherein the first exhaust branch pipeline is communicated with the air-cooled condenser so that the air-cooled condenser can partially or completely cut off the exhaust steam loss at the cold end of the unit, the second exhaust branch pipeline is communicated with a first heater so as to directly utilize the heat of the exhausted steam to carry out primary heating on backwater, and the third exhaust branch pipeline is communicated with a steam ejector so that part of the exhausted steam flowing through the third exhaust branch pipeline can enter the steam ejector, and the steam is pressurized and injected into a second heater by the steam injector under the action of the power steam entering the steam injector through the first steam extraction pipe (the second heater can also be regarded as a condenser of the steam injector), and the temperature of the bled steam after heating and injection is increased, so that the return water can be reheated by the bled steam with higher temperature in the second heater. Thus, the return water can be fully heated under the condition that the exhaust back pressure of the steam turbine is not too high. In addition, the number of the steam ejectors in the above structure may be one or more, and the specific value of the number is determined according to the change of the heat load, and when a plurality of steam ejectors are provided, as shown in fig. 2, the plurality of steam ejectors are arranged in parallel.

In order to further optimize the technical solution, in this embodiment, it is preferable that the heat supply and power generation co-generation system for recycling the steam exhausted from the steam turbine further includes a third heater disposed on the heat pipe network to heat the return water, and the third heater is communicated with the intermediate pressure cylinder and the low pressure cylinder of the steam turbine through a second steam extraction pipeline, as shown in fig. 2. Preferably, the third heater may be an original heater in the primary heat supply network, and the heating mode of the third heater to the return water is as follows: and a second steam extraction pipeline is led out from the intermediate pressure cylinder and the low pressure cylinder of the steam turbine, and high-quality steam with higher temperature in the intermediate pressure cylinder and the low pressure cylinder is extracted and conveyed to a third heater through the second steam extraction pipeline, so that the return water flowing through the third heater is directly heated by the high-quality steam. This is so because the third heater can be used as a spike heater, for example, in cold seasons using raw extraction steam (i.e., high quality steam) and the heater can provide a spike regulation function for the primary heat network.

When the system is in operation, the operating back pressure of the steam turbine can be changed within the range of about 7kPa to 34kPa, and the loss of a cold source of the unit can be reduced and the heat efficiency of the unit can be improved by utilizing the residual heat of part or all of the exhausted steam; compared with the existing system which directly adopts the medium-pressure cylinder and the low-pressure cylinder to extract steam as a heat supply source, the system in the embodiment only extracts a small amount of high-grade extracted steam from the medium-pressure cylinder and the low-pressure cylinder to serve as power steam of the steam ejector and absorbs exhausted steam which is used by the steam turbine to do work, so that heat required by initial and final heat supply can be realized, and in severe cold weather, the second extracted steam pipeline and the third heater can be continuously adopted as peak heater heat sources of the first-grade heat supply network, so that the existing heating mode can be adopted to heat the return water of the first-grade heat supply network. Therefore, the system of the embodiment can not only effectively reduce the running back pressure of the unit and improve the power generation capacity, but also reduce the cold source loss of the existing system, fully utilize the heat of the exhausted steam for heat supply, reduce the cold end loss of the steam turbine and improve the heat economy and the power generation capacity of the unit.

Further, as shown in fig. 2, it is preferable that an absorption heat pump system is disposed on the heat supply network pipeline, and the absorption heat pump system is located at a user side of the heat supply network pipeline. Specifically, the absorption heat pump system comprises an absorption heat exchanger and a water-water heat exchanger. Although the system can realize energy conservation and consumption reduction, the energy utilization rate is also restricted by the return water temperature of the primary heat supply network, if the return water temperature of the primary heat supply network can be effectively reduced, the utilization rate of the heat energy of the power plant can be greatly improved, and the heat supply heat load of a heat supply area can be effectively increased, for example, the return water temperature is reduced to 30 ℃, and the water supply temperature is kept at 130 ℃, namely, the heat supply temperature difference is increased from 60 ℃ to 100 ℃, so that the original heat supply capacity can be increased by 67 percent without additionally increasing heat supply sources. Based on this, in order to realize effectively reducing the return water temperature of the first-level heat supply network, the return water temperature of the first-level heat supply network can be effectively reduced by adopting the heat pump technology at the user side, namely, the absorption heat pump system is arranged at the user side to reduce the return water temperature of the first-level heat supply network, and the heat absorption capacity of the return water of the first-level heat supply network in the power plant is improved. And after the arrangement, the regulating valve of the steam turbine participates in regulation and control according to the influence factors such as heat supply load change, steam turbine power generation load, steam turbine exhaust back pressure and the like, so that the whole unit can keep higher efficiency.

By reducing the return water temperature of the primary heat supply network, the effective utilization rate of the spent steam can be increased, and further the steam extraction amount of the high-quality steam is reduced, so that more high-quality steam can continue to expand in the steam turbine to do work, and the generating capacity of the unit is increased; at the initial stage and the final stage of heat supply, a steam ejector is used for absorbing the first-stage heat supply network backwater heated by the steam turbine exhausted steam (namely heated by a second heater) and primarily heated by the steam turbine exhausted steam (namely heated by a first heater), so that the basic heat supply load required by the unit can be ensured; in a severe cold period, the third heater is used for peak heating, the primary heat supply network backwater sequentially passes through the first heater, the second heater and the third heater, the heat supply requirement can be completely met, and the reduction of the steam inlet quantity of the original air cooling island or zero steam inlet is realized, so that the cold source loss of the air cooling unit is effectively reduced, the energy utilization rate is improved, and the power generation coal consumption is reduced.

As shown in fig. 2, the present embodiment preferably further includes a ventilation cooling tower disposed on the heat supply network line, the ventilation cooling tower being disposed in parallel with the first heater. So set up, can make the heat supply power generation cogeneration system of the exhausted steam of recycle steam turbine that this embodiment provided have more functions, specifically are: the system that this embodiment provided except being used for winter heat supply, can also utilize first heater as the condenser in summer, act as the effect of peak cooler, mainly utilize first heater promptly, and have peak cooling function through increasing the ventilation cooling tower when making air cooling unit summer high load, can realize that unit summer peak load is full and guarantee safe summer of ferrying, this has not only improved the utilization ratio of equipment, but also can effectively reduce unit electricity generation coal consumption, can also make the system have the operation nimble simultaneously, load regulation can the reinforce, it is convenient to overhaul, the advantage that the reliability is high.

As shown in fig. 2, in the present embodiment, it is also preferable that the air-cooling condenser is provided in plurality in parallel. With such an arrangement, the exhaust steam loss at the cold end of the unit can be reduced as much as possible, so that the exhaust steam loss is taken as a preferable arrangement mode of the embodiment.

The heat supply and power generation cogeneration system for recycling the exhaust steam of the steam turbine can reduce the steam consumption of high-quality steam, and recycle and utilize the low-quality exhaust steam as much as possible for heat supply, thereby reducing the cold source loss of the steam turbine, increasing the heat supply capacity of a unit, improving the heat economy, realizing the gradient utilization of temperature and energy, improving the energy utilization rate and realizing the reasonable utilization of energy.

Specifically, the following description is made by taking a certain 300 MW-class heating power plant as an example, comparing the heating and power generation cogeneration system for recycling the steam turbine spent steam provided by the application with the existing system:

determining the rated steam extraction amount of a unit to be 330t/h according to the unit heat balance data under the rated steam extraction heat supply working condition of a certain 300 MW-level thermal power plant; the steam extraction parameters are as follows: the pressure is 400kPa, the temperature is 249.7 ℃, and the enthalpy is 2963.9 kJ/kg; the steam turbine exhaust parameters are as follows: the pressure is 13.8kPa, the temperature is 52.3 ℃, and the enthalpy is 2509.6 kJ/kg; preliminarily determining the structural size of the steam ejector, and calculating to obtain 185t/h of power steam and 40t/h of injection steam under the condition;

the basic parameters of the first-level heat supply network circulating water in the traditional steam extraction and heat supply mode are as follows:

traditional heat supply network circulating water flow	t/h	3141
			Water inlet temperature of conventional heat supply network	℃	45
Water outlet temperature of conventional heat supply network	℃	105
			Traditional extraction mass flow	t/h	330
Conventional heating thermal load	GJ/h	789.9

A steam ejector (changing exhaust back pressure) and a peak heater are adopted for supplying heat, and the main parameters are as follows:

heat supply network circulating water mass flow	t/h	3141	3141	3141	3141	3141
							Inlet temperature of circulating water of heat supply network	℃	45	45	45	45	45
Outlet temperature of circulating water of heat supply network	℃	105	105	105	105	105
							Heating thermal load	GJ/h	789.9	789.9	789.9	789.9	789.9
Exhaust steam flow of steam turbine	t/h	0.0	0.0	0.0	0.0	0.0
							Dynamic steam flow	t/h	185.0	185.0	185.0	185.0	185.0
Exhaust steam flow injection	t/h	40.0	46.7	74.3	102.2	115.9
							Exhaust back pressure of steam turbine	kPa	13.8	15.0	20.0	25.0	34.0
Peak extraction mass flow	t/h	136.2	129.3	100.9	71.8	58.2
							Coal consumption gain	g/(kWh)	1.315	2.039	5.131	8.169	8.392

The method comprises the following steps of adopting high back pressure (adopting a first heater to primarily heat first-level heat supply network backwater), an ejector (changing exhaust back pressure) and a peak heater to supply heat:

heating in a severe cold period: the high back pressure (adopting the first heater preliminary heating one-level heat supply network return water) mode is restricted by unit operating conditions, and only can adopt ejector (change exhaust back pressure) + peak heater heat supply:

heat supply network circulating water mass flow	t/h	3141
			Inlet temperature of circulating water of heat supply network	℃	70
Outlet temperature of circulating water of heat supply network	℃	130
			Heating thermal load	GJ/h	789.9
Exhaust steam flow of steam turbine	t/h	0.0
			Dynamic steam flow	t/h	185.0
Exhaust steam flow injection	t/h	115.9
			Exhaust back pressure of steam turbine	kPa	34.0
Peak extraction mass flow	t/h	60.2
			Coal consumption gain	g/(kW.h)	8.143

The method adopts high back pressure (the first heater is adopted to primarily heat the return water of the first-level heat supply network), an ejector (the steam exhaust back pressure is changed), and a peak heater to supply heat, and the yield during the annual heating period is as follows:

saving coal consumption and income	g/(kW.h)	1.315	2.039	5.131	8.169	8.392
							Increase of power generation	kW.h	1105.3	1713.3	4311.4	6864.4	7051.4
Temporary on-line electricity price	yuan/kW.h	0.25	0.25	0.25	0.25	0.25
							Length of operation in heating period	h	4000	4000	4000	4000	4000
Revenue of electricity generation	Ten thousand yuan	110.5	171.3	431.1	686.4	705.1

The parameters do not consider that the system is added with an absorption heat pump system and has summer peak cooling function, such as the absorption heat pump system and the system has summer peak cooling function, and the benefits are more.

The overall structure and the partial structure of the heating and power generation cogeneration system for recycling the exhaust steam of the steam turbine can be obtained by combining the structures of the parts.

The previous description of the disclosed embodiments is provided to enable any person skilled in the art to make or use the present invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other embodiments without departing from the spirit or scope of the invention. Thus, the present invention is not intended to be limited to the embodiments shown herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.