1. A pure condensing unit heat supply reconstruction system with energy gradient utilization comprises a boiler, a high-pressure cylinder, an intermediate-pressure cylinder and a boiler reheater arranged in the boiler, wherein main steam of the boiler is connected with an inlet of the high-pressure cylinder, cold reheat steam at an outlet of the high-pressure cylinder is connected with an inlet of the boiler reheater, and hot reheat steam at an outlet of the boiler reheater is connected with the intermediate-pressure cylinder; the method is characterized in that: the heat supply system comprises heat supply steam, a heat supply reheater, a temperature and pressure reducing device, a heat supply steam reheating bypass valve, a cold reheating steam stop valve and a cold reheating steam bypass valve; the high-pressure cylinder is provided with a heat supply steam extraction hole, the heat supply reheater is arranged in the boiler, the heat supply steam extracts steam from the heat supply steam extraction hole and is connected with an inlet of the heat supply reheater, and an outlet of the heat supply reheater is connected with the temperature and pressure reducing device; the outlet of the heat supply reheater is connected with the inlet of the boiler reheater through a pipeline, and the heat supply steam reheating bypass valve is arranged on the pipeline between the outlet of the heat supply reheater and the inlet of the boiler reheater; the cold reheat steam stop valve is arranged on a pipeline where the cold reheat steam is located; pass through the pipe connection between cold reheat steam and the heat supply steam, and the tie point is located before the cold reheat steam stop valve, cold reheat steam bypass valve sets up on the pipeline between cold reheat steam and the heat supply steam.

2. The energy cascade utilization straight condensing unit heat supply transformation system of claim 1, characterized in that: and a heat supply steam pressure reducing valve is arranged on the pipeline where the heat supply steam is located, and a connecting point between the cold reheat steam and the heat supply steam is positioned behind the heat supply steam pressure reducing valve.

3. The energy cascade utilization straight condensing unit heat supply transformation system of claim 2, characterized in that: the pipeline where the heat supply steam is located is sequentially arranged on the heat supply steam check valve, the heat supply regulating valve front stop valve and the heat supply regulating valve in the steam flowing direction in front of the heat supply steam pressure reducing valve.

4. The energy cascade utilization straight condensing unit heat supply transformation system of claim 3, characterized in that: and a heat supply valve adjusting rear stop valve is arranged on a pipeline between the outlet of the heat supply reheater and the temperature and pressure reducing device.

5. The energy cascade utilization straight condensing unit heat supply transformation system of claim 1, characterized in that: the temperature and pressure reducer is connected with a temperature reduction water pipeline.

6. The energy cascade utilization straight condensing unit heat supply transformation system of claim 5, characterized in that: and a temperature-reducing water control valve is arranged on the temperature-reducing water pipeline.

7. The energy cascade utilization straight condensing unit heat supply transformation system of claim 6, characterized in that: and the front stop valve of the temperature-reducing water control valve and the rear stop valve of the temperature-reducing water control valve are respectively arranged in front of and behind the temperature-reducing water control valve of the temperature-reducing water pipeline.

8. The energy cascade utilization straight condensing unit heat supply transformation system of claim 1, characterized in that: and a reheat steam inlet header and a reheat steam outlet header are respectively arranged at an inlet and an outlet of the boiler reheater.

9. The energy cascade utilization straight condensing unit heat supply transformation system of claim 8, characterized in that: and the inlet and the outlet of the heat supply reheater are respectively provided with a heat supply reheating inlet header and a heat supply reheating outlet header.

10. The energy cascade utilization straight condensing unit heat supply transformation system of claim 9, characterized in that: and two ends of a pipeline between the outlet of the heat supply reheater and the inlet of the boiler reheater are respectively connected with the heat supply reheating outlet header and the reheating steam inlet header.

Background

In order to realize carbon peak reaching and carbon neutralization, China needs to construct a clean, low-carbon, safe and efficient energy system, control the total amount of fossil energy and improve the energy utilization efficiency, and in the process, the survival and development of a coal-electricity unit face huge challenges. In order to improve the energy utilization efficiency, the coal-electricity unit needs to be upgraded and modified through technology, so that the purposes of energy conservation and emission reduction are realized, and the purposes of carbon peak reaching and carbon neutralization are achieved.

Heat supply can be divided into industrial heat supply and civil heat supply according to the nature of heat users. The civil heat supply is characterized by strong seasonality, generally only requiring temperature and having no special limitation on pressure, while the industrial heat supply is characterized by stable demand and no obvious seasonal wave band, the heat supply working medium is generally steam, and the requirements on heat supply parameters are limited by temperature and pressure. According to different requirements of industrial heating parameters, the heating can be divided into high-parameter heating, medium-parameter heating and low-parameter heating. High parameter heat supply means pressure 4.0MPa, temperature 400 deg.C and above, and steam is extracted from the outlet of the superheater of the thermal power plant; medium parameter heat supply means pressure of 1.0-2.5 MPa and temperature of 300-400 ℃, and steam is generally extracted from the first extraction, cold recycling or hot recycling section of a power plant; low-parameter heat supply means that steam is extracted from a low-parameter communicating pipe in a power plant at the pressure of 0.3-0.6 MPa and the temperature of below 350 ℃.

Under the target requirements of carbon peak reaching and carbon neutralization, the newly built cogeneration is difficult to concentrate, and the newly increased heat load is generally met by the transformation of a straight condensing unit. The heat supply reconstruction of the straight condensing unit has the following problems: the expansion curve of the steam turbine is determined, the steam extraction pressure and temperature of each steam extraction point are related parameters, the temperature and pressure required by industrial heat supply are determined according to the production process, and the pressure and temperature are not strongly related, so that the contradiction that the pressure and temperature of the steam extraction points cannot meet the process requirement exists in the unit, and the waste phenomenon that the energy level is unmatched is caused by adopting higher-parameter steam for temperature reduction and pressure reduction for heat supply users. In particular, the heat supply is realized by adopting main steam for temperature reduction and pressure reduction, so that serious energy level mismatch exists, and the whole cogeneration efficiency is reduced.

Disclosure of Invention

The invention aims to solve the problems in the prior art and provides a pure condensing unit heating system which can realize gradient utilization of steam energy and improve energy utilization efficiency.

In order to achieve the purpose, the technical scheme provided by the invention is as follows: a pure condensing unit heat supply reconstruction system with energy gradient utilization comprises a boiler, a high-pressure cylinder, an intermediate-pressure cylinder and a boiler reheater arranged in the boiler, wherein main steam of the boiler is connected with an inlet of the high-pressure cylinder, cold reheat steam at an outlet of the high-pressure cylinder is connected with an inlet of the boiler reheater, and hot reheat steam at an outlet of the boiler reheater is connected with the intermediate-pressure cylinder; the heat supply system comprises heat supply steam, a heat supply reheater, a temperature and pressure reducing device, a heat supply steam reheating bypass valve, a cold reheating steam stop valve and a cold reheating steam bypass valve; the high-pressure cylinder is provided with a heat supply steam extraction hole, the heat supply reheater is arranged in the boiler, the heat supply steam extracts steam from the heat supply steam extraction hole and is connected with an inlet of the heat supply reheater, and an outlet of the heat supply reheater is connected with the temperature and pressure reducing device; the outlet of the heat supply reheater is connected with the inlet of the boiler reheater through a pipeline, and the heat supply steam reheating bypass valve is arranged on the pipeline between the outlet of the heat supply reheater and the inlet of the boiler reheater; the cold reheat steam stop valve is arranged on a pipeline where the cold reheat steam is located; pass through the pipe connection between cold reheat steam and the heat supply steam, and the tie point is located before the cold reheat steam stop valve, cold reheat steam bypass valve sets up on the pipeline between cold reheat steam and the heat supply steam.

The technical scheme is further designed as follows: and a heat supply steam pressure reducing valve is arranged on the pipeline where the heat supply steam is located, and a connecting point between the cold reheat steam and the heat supply steam is positioned behind the heat supply steam pressure reducing valve.

The pipeline where the heat supply steam is located is sequentially arranged on the heat supply steam check valve, the heat supply regulating valve front stop valve and the heat supply regulating valve in the steam flowing direction in front of the heat supply steam pressure reducing valve.

And a heat supply valve adjusting rear stop valve is arranged on a pipeline between the outlet of the heat supply reheater and the temperature and pressure reducing device.

The temperature and pressure reducer is connected with a temperature reduction water pipeline.

And a temperature-reducing water control valve is arranged on the temperature-reducing water pipeline.

And the front stop valve of the temperature-reducing water control valve and the rear stop valve of the temperature-reducing water control valve are respectively arranged in front of and behind the temperature-reducing water control valve of the temperature-reducing water pipeline.

And a reheat steam inlet header and a reheat steam outlet header are respectively arranged at an inlet and an outlet of the boiler reheater.

And the inlet and the outlet of the heat supply reheater are respectively provided with a heat supply reheating inlet header and a heat supply reheating outlet header.

And two ends of a pipeline between the outlet of the heat supply reheater and the inlet of the boiler reheater are respectively connected with the heat supply reheating outlet header and the reheating steam inlet header.

In the technical scheme, the heating steam reheating bypass valve is a normally closed valve and is used for connecting part of heating steam into a boiler reheater and entering a main machine of the unit for circulation if the unit is opened when the high-parameter heating load is reduced.

The unit needs the pure operating mode operation of congealing, and when not supplying heat, closes cold reheat steam stop valve, and cold reheat steam bypass valve and heat supply steam reheat bypass governing valve are opened, and cold reheat steam resumes to the pure state operation of congealing.

Compared with the prior art, the technical scheme of the invention has the following beneficial effects:

according to the heat supply scheme, the heat supply steam reheating bypass is designed, so that the adaptability and the reliability of the system are improved; the invention designs two modes of flue gas heating and water spraying temperature reduction control, accurately controls the heat supply steam and ensures the quality of the heat supply steam. Therefore, the invention solves the problems of over-temperature of the reheater and under-temperature of the heat supply temperature in the high-parameter heat supply, realizes the cascade utilization of energy, improves the energy utilization efficiency and has good social benefit and economic benefit.

Drawings

FIG. 1 is a schematic diagram of a heating system according to an embodiment of the present invention;

fig. 2 is a schematic diagram of a temperature and pressure reducing heating system in the prior art.

In the figure: high pressure cylinder 1, heat supply check valve 2, heat supply damper valve front stop valve 3, heat supply damper valve 4, heat supply reheat outlet header 5, heat supply reheat inlet header 6, heat supply reheater 7, heat supply damper valve rear stop valve 8, heat supply steam 9, heat supply reheat bypass damper valve 10, cold reheat steam 11, reheat steam inlet header 12, boiler reheater 13, reheat steam outlet header 14, main steam 15, hot reheat steam 16, intermediate pressure cylinder 17, heat supply desuperheating water damper valve front stop valve 18, heat supply desuperheating water damper valve 19, heat supply desuperheating water damper rear stop valve 20, heat supply steam temperature controller 21, heat supply steam pressure regulator 22, cold reheat steam stop valve 23, cold reheat steam bypass valve 24, boiler 25.

Detailed Description

The invention is described in detail below with reference to the figures and the specific embodiments.

Examples

As shown in fig. 1, the condensing unit includes a boiler 25, a high-pressure cylinder 1, an intermediate-pressure cylinder 17, and a boiler reheater 13 provided in the boiler, and main steam 15 of the boiler 25 enters the high-pressure cylinder 1, and after performing work, enters the boiler reheater 13 as cold reheat steam 11, and after being reheated by the boiler reheater 13, enters the intermediate-pressure cylinder as hot reheat steam 16 to perform work. The boiler reheater 13 is provided at its inlet and outlet with a reheat steam inlet header 12 and a reheat steam outlet header 14, respectively, for collecting reheat steam.

The pure condensing unit heating system with energy gradient utilization comprises a heating steam extraction system, a heating steam reheating system and a heating temperature control system.

The heat supply steam extraction system is characterized in that an extraction hole is formed in a high-pressure cylinder 1 and heat supply steam 9 is extracted, a heat supply steam extraction check valve 2, a heat supply adjusting valve front stop valve 3 and a heat supply adjusting valve 4 are sequentially arranged on a pipeline where the heat supply steam 9 is located along the steam flowing direction, and a heat supply steam pressure reducing valve 22 is further arranged on the pipeline where the heat supply steam 9 is located in the steam extraction system to adjust the heat supply steam extraction pressure for protecting the safety of the system.

The heat supply steam reheating system comprises a heat supply reheater 7 arranged in a boiler, heat supply steam 9 enters the heat supply reheater 7 after being subjected to pressure regulation by a heat supply steam pressure reducing valve 22, the heat supply steam 9 is heated by smoke in the boiler, the temperature of the heat supply steam is increased, the heat supply requirement is met, and a heat supply reheating inlet header 6 and a heat supply reheating outlet header 5 are arranged at the inlet and the outlet of the heat supply reheater 7 respectively and used for collecting the heat supply steam.

The heating temperature control system comprises a heating steam temperature controller 21, which is used for accurately adjusting the temperature of the heating steam and ensuring the heating quality; the heating steam 9 heated by the heating reheater 7 enters the heating steam temperature controller 21, a heating water adjusting valve rear stop valve 8 is arranged on a pipeline between the heating reheater 7 and the heating steam temperature controller 21, the heating steam temperature controller 21 injects the temperature-reducing water to adjust the temperature and the pressure of the heating steam 9, and a temperature-reducing water control valve front stop valve 18, a temperature-reducing water adjusting valve 19 and a temperature-reducing water control valve rear stop valve 20 are arranged on the temperature-reducing water pipeline.

In the present embodiment, a bypass line is provided between the heating reheat outlet header 5 and the reheat steam inlet header 12, and a heating steam reheat bypass regulating valve 10, which is a normally closed bypass, is provided on the bypass line.

In the present embodiment, a cold reheat steam stop valve 23 is provided on a pipe where the cold reheat steam 11 is located, a bypass pipe is provided between the cold reheat steam 11 and the heating steam 9 for connection, and the connection point is located before the cold reheat steam stop valve 23, and a cold reheat steam bypass valve 24 is provided on the bypass pipe, and the bypass is a normally closed bypass.

Steam of the heat supply system is extracted by a high-pressure cylinder, the steam pressure is 6.07MPa, and the steam temperature is 386 ℃; the steam pressure required by the high-parameter heat user is 4.3MPa, the temperature is 430 ℃, and therefore, the heating steam extraction needs to be reheated.

The heating steam reheating adopts a flue gas reheating technology. Because steam is extracted by heat supply, the flow rate of an original boiler reheating system is reduced, and due to the reduction of cooling media, an overtemperature condition occurs in a reheater, so that the safe operation of a unit is influenced, therefore, the reheater needs to be modified, and the method for reducing the area of a reheating heating surface is adopted in the embodiment; on the other hand, because the temperature of the heating steam is low and needs to be reheated, the embodiment adopts a flue gas reheating technology, so that the embodiment modifies a part of an original boiler reheater 13 (as shown in fig. 2) into the heating reheater 7, and utilizes the heating surface of the original boiler reheating system to heat the heating steam, thereby solving the problems of the reheater over-temperature and the heating temperature under-temperature, achieving the purposes of reducing the reheater heat absorption and increasing the heating steam heat absorption, fully utilizing the original system equipment components, and achieving multiple purposes of reducing the modification range, saving the investment and improving the energy utilization efficiency.

When the heat load of the heat supply of the unit is unstable or part of the conditions exist, the unit needs to operate in a pure condensation working condition, namely the working condition that the high-parameter heat supply is completely stopped, the cold reheat steam stop valve 23 is closed, the cold reheat steam bypass valve 24 and the heat supply steam reheat bypass regulating valve 10 are opened, at the moment, the heating surface of the heat supply reheater 7 is recovered to be a part of the boiler reheater 13, and the cold reheat steam is recovered to operate in a pure condensation state.

Under partial working conditions, if the high-parameter heat supply amount of the unit is reduced, in order to protect the heating surface of the boiler heater 13, the heat supply steam reheating bypass valve 10 needs to be opened, and the heat supply steam used for connecting part of relatively cooled heat supply steam of the heat supply steam reheating system into a steam turbine main engine circulating system to form closed circulation.

The heating system of this embodiment supplies heat after the heat supply steam is done work, through the heat supply steam reheat system of design boiler side, has adjusted the temperature of heat supply steam, satisfies the user demand, retrieves heat supply steam acting capacity, has realized utilizing the heat supply steam energy step, improves energy utilization efficiency.

Comparative example

As shown in fig. 2, in the conventional temperature and pressure reducing and heating system in the prior art, main steam 15 is used for heating after temperature and pressure reduction, an air extraction point is arranged on the main steam 15 to extract heat supply extraction steam 9, and the heat supply extraction steam 9 is sprayed into temperature reducing water through a heat supply steam temperature controller 21 for temperature and pressure reduction and then heating for users.

In the comparative example, the steam pressure is 16.67MPa, the steam temperature is 538 ℃, the steam pressure of a hot user is 4.3MPa, and the steam temperature is 430 ℃; the pressure of the reduced water is 18MPa, the temperature is 150 ℃, and the heating scheme is shown in Table 1:

TABLE 1 temp. and pressure reducing heating plan

Item	Pressure (MPa)	Temperature (. degree.C.)	Enthalpy (kJ/kg)	Flow (t/h)
					Main steam heat supply steam extraction pressure	16.67	538	3397.26	95.78
Temperature reducing water	18	158	643.17	4.22
					Steam for heat supply	4.3	430	3280.90	100

As can be seen from the above table, the conventional heating scheme is adopted, the heating steam of 100t/h is met, 95.78t/h of heating steam and 4.22t/h of desuperheating water need to be extracted, and the heating is carried out after the heating steam and the desuperheating water are mixed. Strictly speaking, the heat supply belongs to the thermoelectric separate production, and the heat supply steam does not work, so the heat supply economical efficiency is poor, and the heat supply efficiency is not high.

According to the embodiment and the comparative example, the system can flexibly meet the heat supply requirement through modification, can improve the energy utilization efficiency, and has a good energy-saving effect.

The technical solutions of the present invention are not limited to the above embodiments, and all technical solutions obtained by using equivalent substitution modes fall within the scope of the present invention.