CN111396156A - Multi-unit heating system of nuclear power plant with steam side unit system and water side combined system - Google Patents

Abstract

The invention discloses a multi-unit heating system for a nuclear power plant with a steam-side unit system and a water-side combined system. The nuclear power plant includes more than one unit with the same structure, and each unit is provided with a primary circuit and a secondary circuit, and is characterized in that: Each of the units includes a feed pump for delivering water in the secondary circuit to the steam generator, and the outlet of the steam generator is connected to the high-pressure cylinder, the low-pressure cylinder, the condenser, and the feed water pump to form a closed cycle. The output end of the low-pressure cylinder is connected to the generator, and the low-pressure cylinder is connected in parallel with the steam-side heat exchange pipeline in the steam-water heat exchanger; the water-side heat-exchange pipelines in the steam-water heat exchanger in all units are connected in parallel and circulate with the heat network The heat network circulating pumps in the pump station are connected to form a loop. The invention solves the problem of the reliability of the heat supply heat source side by using two units, one for standby, or multiple units for multiple use, one standby and the steam side unit system operation mode, and at the same time solves the problem that the heat supply is interrupted due to the long operation time of the standby heat source. problem, clean, stable and efficient.

Description

A multi-unit heating system of a nuclear power plant with a steam side unit system and a water side combined system

technical field

The invention relates to a multi-unit heating system of a nuclear power plant with a steam-side unit system and a water-side combined system, belonging to the technical field of nuclear power equipment.

Background technique

The principle of external heating of nuclear power plants is basically the same as that of conventional thermal power plants. They both extract part of the heat from the heat-to-electricity conversion of the power plant, and realize heating to local areas in winter while generating conventional power. However, due to the particularity of nuclear power units (for example, the unit maintenance cycle is relatively fixed, which leads to a conflict between the heating season and the unit refueling overhaul window; the division of physical protection areas leads to limited area of critical areas, and the facilities in the site are compactly arranged, and large-scale heat exchange is not available. There is still a certain difference between the heating of nuclear power units and the heating of conventional thermal power units.

After the cogeneration of conventional thermal power units, in order to effectively ensure the heating load of the unit in winter, it is usually necessary to adjust the shutdown and maintenance window of the thermal power unit to avoid the heating season, so as to effectively ensure the reliability of the heat source in the heating season.

The AP1000 nuclear power plant unit refueling maintenance cycle is 18 months. Adjusting the refueling maintenance cycle will bring about a profound change in the fuel burnup of the reactor, which will adversely affect the operating cost of the unit and the arrangement of fuel components after refueling.

The nuclear power plant area is divided into three physical protection areas: critical area, protection area and control area. The nuclear island workshop and conventional island workshop of AP1000 nuclear power plant are arranged in the key area. The conventional power plant heating scheme uses the extraction steam of the unit as the heating heat source, and heats the circulating water of the heating network to achieve external heat supply. Therefore, it is necessary to set up a heat exchange station around the unit, and arrange a steam-water heat exchanger, a heating network circulating pump, and a heating network make-up pump, etc. equipment. Due to the compact layout of workshops and equipment in the critical area of the nuclear power plant, large-scale heat exchange stations cannot be arranged, and arranging the heat exchange stations outside the critical area will lead to long steam pipelines, which will lead to large steam storage in the steam pipeline after the turbine trips. Safety risks, a series of problems such as the long flushing and heating time in the initial stage of the system operation, the inability to put it into standby in time, and the long-term unqualified water quality during the system operation stage.

SUMMARY OF THE INVENTION

The technical problem to be solved by the present invention is: the existing large-scale nuclear power unit directly adopts the conventional power plant cogeneration heating mode to supply external heat, which has the problems of low safety, reliability and economy.

In order to solve the above technical problems, the present invention provides a multi-unit heating system for a nuclear power plant with a steam-side unit system and a water-side combined system. The nuclear power plant includes more than one unit with the same structure, system and parameters. There is one loop and two loops, and it is characterized in that, each of the units includes a feed pump for conveying the water in the second loop to the steam generator, and the outlet of the steam generator is connected to the high-pressure cylinder, the low-pressure cylinder, the condensate The steam generator and the feed water pump form a closed cycle, the output end of the low pressure cylinder is connected to the generator, and the low pressure cylinder is connected in parallel with the steam side heat exchange pipeline in the steam water heat exchanger; the water side in the steam water heat exchanger in all units The heat exchange pipelines are connected in parallel with the heat network circulating pump in the heat network circulating pump station to form a loop.

Preferably, it is characterized in that the heat network circulating pump is connected in series with a constant pressure pump and a decontamination device in sequence, and the constant pressure pump is connected with the deaerator.

Preferably, it is characterized in that the three loops and other downstream loops are respectively communicated with the two heat exchange pipelines of the water-water heat exchanger (13) for heat exchange.

Preferably, it is characterized in that the water in the secondary circuit of the nuclear power plant is boosted by the feed water pump and then transported to the steam generator, where it absorbs heat and becomes saturated steam, and the saturated steam enters the high-pressure cylinder and the low-pressure cylinder in turn for operation. The steam turbine drives the generator to generate electricity. The steam after the work enters the condenser, exchanges the heat to the seawater in the three circuits, and condenses into water. After heating step by step, the steam is transported to the steam by the feed pump. The generator completes the closed cycle of the entire secondary circuit; the return water of the heat network circulating water in the water-side heat exchange pipeline in the steam-water heat exchanger first enters the heat network circulating pump, and is boosted by the heat network circulating pump and transported to the Two units meet the heating demand of the two groups of units.

Preferably, it is characterized in that, during normal operation, the steam-to-water heat exchanger in any unit of the nuclear power plant operates, and other steam-to-water heat exchangers are not in operation and are on standby.

Preferably, it is characterized in that valve a is provided on the steam side heat exchange pipeline of the steam-water heat exchanger in the unit, valve b and valve c are respectively provided on the water side heat exchange pipeline, and valves a and c are respectively provided in the unit in normal operation. Valve b and valve c are in the open state, and valve a, valve b and valve c in the standby unit are in the closed state.

More preferably, it is characterized in that valve d and valve e are respectively provided on both sides of the three-circuit water-to-water heat exchanger. During normal operation, valve d and valve e are in the open state, and under abnormal conditions, valve d , Valve e is closed, for example, when an accident occurs and isolation is required, it is used to cut off the communication state between the three-circuit and the downstream circuit.

The nuclear power unit supplies heat to the outside, because the refueling cycle is relatively fixed and the heat supply load is relatively large, so the reliability of the heat supply needs to be ensured from the heat source measurement, so the present invention adopts the operation mode of one use and one standby.

The use of the steam side unit system scheme can effectively ensure the water balance of the secondary circuits of each unit, and prevent the problems of water and steam between the units caused by the main control. Under the condition of one unit in use and one standby, if the heating system of the standby unit is in a cold standby state, since the steam extraction point brought by the main pipe is far away from the steam main pipe, the switching process of the heating unit will bring about flushing of the steam pipe, The problem that the heating time of the pipe is too long and cannot be put into normal operation in time; if the heating system of the standby unit is in a hot standby state, because the steam extraction point brought by the main pipe is far away from the steam main pipe, the steam drainage belt of the standby heating unit pipeline The heat loss is serious and the economy is poor. Therefore, the present invention proposes a steam side unit system scheme. Each unit is equipped with an adjacent house in the steam turbine workshop, and the heat network heater is arranged around the steam extraction point of the steam turbine and the drain point of the condenser, which can effectively solve the heat generated by the main pipe. At the same time, it can effectively shorten the length of steam pipelines in the plant area, reduce pipeline investment, and improve operational reliability. Due to the short length of steam and drainage pipelines, it can further ensure that the drainage water quality can meet the requirements of condensate recovery. Requirements; Since the heating network heater is arranged around the condenser, the drainage recovery can be directly realized through the pressure difference, which reduces the investment of the drainage pump equipment and further improves the economy.

The water-side joint system scheme can effectively solve the problem that the heating network circulating pump, make-up pump, deaerator, heating network heater and other equipment cannot be all arranged in the critical area due to the limited layout space of the critical area. Arrange the heating network heater in the key area to reduce the heat loss of the pipeline and improve the heating economy; arrange the heating network circulating pump, the heating network make-up pump, and the heating network deaerator outside the key area, and make reasonable use of the layout space of the plant area. The water-side combined system scheme can effectively improve the heating reliability. The two units share the heating network circulating pump and other equipment to improve the heating economy.

The invention solves the problem of the reliability of the heating source side by using two units, one for standby, or multiple units, one for standby, and the steam side unit system operation mode, and at the same time solves the heating interruption caused by the long switching time of the standby heat source. The problem. The multi-unit heating system of the nuclear power plant provided by the steam side unit system and the water side combined system ensures the safety and reliability, and has the advantages of cleanliness, stability and high efficiency.

Compared with the prior art, the beneficial effects of the present invention are:

1. The steam side unit system, the heater is arranged in the key area, and the length of the steam pipeline is shortened

The unit system is adopted on the steam side to ensure the effective isolation of the secondary circuits between the heating units and improve the reliability and safety. The heaters are arranged in the critical area, close to the steam extraction point of the steam turbine and the drain point of the condenser to reduce pipeline investment and steam heat loss , to ensure the water quality of heating steam drainage, shorten the standby switching time, and effectively ensure the corresponding speed of the accident.

2. Cancel the heat network drain pump to improve the economy

The heat network heater is arranged in the key area, close to the steam extraction point of the steam turbine and the drain point of the condenser. The pressure difference between the steam side of the heat network heater and the condenser can be used to achieve hydrophobic self-flow, which effectively improves the economy.

3. The water-side joint system, the circulating pump, deaerator and make-up pump are arranged outside the critical area

The water-side joint system, the two units share the heat network circulating pump, the heat network deaerator, the heat network make-up pump and other equipment, which reduces the equipment investment and at the same time, the water side interconnection can achieve rapid switching and improve the heating reliability. Arranging the heat network circulating pump, heat network deaerator, and heat network make-up pump outside the critical area can effectively solve the problem of tight arrangement of the critical area and the inability to arrange many large-scale equipment, and rationally utilize the space to solve the layout problem.

4. One use and one backup plan for heating units considered in the nuclear power maintenance cycle

The AP1000 nuclear power plant unit refueling maintenance period is 18 months, and the overhaul period is about 1 month. Adjusting the refueling maintenance period will bring about a profound change in the fuel burnup of the reactor, which will affect the operating cost of the unit and the arrangement of fuel components after the refueling. influences. When multiple units are combined for heating, it is inevitable that the unit will be overhauled during the heating season. Since nuclear power units can usually provide a large heating load, it may be a large heat source in the region, and the heating network usually needs to pay a lot of costs. The nuclear power unit provides a backup heat source. In order to effectively ensure the reliability of heat supply on the heat source side, a plan for one unit in use and one backup is adopted, and a spare unit is reserved for maintenance during the heating season to ensure the reliability of heat supply from the heat source side.

Description of drawings

FIG. 1 is a connection diagram of a multi-unit heating system of a nuclear power plant of a steam-side unit system and a water-side combined system provided in an embodiment.

Detailed ways

In order to make the present invention more obvious and comprehensible, preferred embodiments are described in detail below with reference to the accompanying drawings.

Example

As shown in FIG. 1 , a multi-unit heating system for a nuclear power plant with a steam-side unit system and a water-side combined system provided in this embodiment, the nuclear power plant includes more than two units with the same structure, and each unit is provided with a circuit , secondary circuits, each described unit includes a feed water pump 1 for delivering water in the secondary circuit to the steam generator 2, and the outlet end of the steam generator 2 is connected to the high-pressure cylinder 3, the low-pressure cylinder 4, the condensing steam in turn The output end of the low-pressure cylinder 4 is connected to the generator 6, and the low-pressure cylinder 4 is connected in parallel with the steam-side heat exchange pipeline in the steam-water heat exchanger 7; the steam-water heat exchange in all units The water-side heat exchange pipelines in the heat exchanger 7 are connected in parallel with the heat network circulating pump 8 in the heat network circulating pump station C to form a three-loop. , the constant pressure pump 10 is connected to the deaerator 9 . The three loops and other downstream loops are respectively communicated with the two heat exchange pipes of the water-water heat exchanger 13 for heat exchange.

The steam side heat exchange pipeline of the steam-water heat exchanger 7 in the unit is provided with valve a, and the water side heat exchange pipeline is provided with valve b and valve c respectively. In the normal running unit, valve a, valve b and valve c are: In the open state, valve a, valve b, and valve c in the standby unit are closed. Valves d and e are provided on both sides of the three-circuit upper water-to-water heat exchanger 13 respectively. During normal operation, valves d and e are open, and under abnormal conditions, valves d and e are closed.

The water in the secondary circuit of the nuclear power plant is boosted by the feed pump 1 and then sent to the steam generator 2, where it absorbs heat and becomes saturated steam. After rotating, the steam turbine drives the generator 6 to generate electricity, and the steam after the work enters the condenser 5, exchanges the heat to the seawater in the three circuits, and condenses into water. Device 2 completes the closed loop of the entire secondary loop. In the present invention, steam is extracted from the exhaust pipe of the high pressure cylinder 3 for heating the circulating water of the heating network, and the extracted steam is condensed and recovered to the condenser 5 to realize the water balance of the secondary circuit. Each unit is equipped with an independent heating network heater and a steam extraction and drainage circuit to ensure that the steam side is independent of each other and operates as a unit. Each unit operates independently to meet the heating demand. Unit maintenance or backup. Since the heater is arranged around the unit, the heater can be switched quickly, which can effectively shorten the heating and withdrawal time, shorten the length of the drainage pipe, and directly use the pressure difference to drain the water. Save investment while ensuring heating reliability.

The return water of the heat network circulating water in the water side heat exchange pipeline in the steam-water heat exchanger 7 first enters the heat network circulating pump station C. 8 to boost the pressure and send it to two units respectively. After being heated in the steam-water heat exchanger 7 of the unit, high-temperature circulating water is supplied to the outside.

During normal operation, the steam-water heat exchanger 7 of any one group of the two groups of units in the secondary circuit of the nuclear power plant is in operation, and the steam-water heat exchanger 7 of the other group is not in operation for standby. The other unit can isolate the heat exchanger of this unit by closing the isolation valves on the steam side and the water side, and put it into standby.

The present invention connects the water sides of the steam-water heat exchangers, and the water sides of the steam-water heat exchangers 7 of the two units are operated in parallel, which can effectively realize the standby fast switching operation, and save the investment of equipment such as steam pipelines and heat network circulating pumps. /2, the water-side joint plan effectively saves the layout space in the key area, and arranges the heat network circulating pump, deaerator, constant pressure pump and other equipment outside the key area, which improves reliability and saves investment.

Claims (7)

1. A multi-unit heating system for a nuclear power plant of a steam-side unit system and a water-side combined system, the nuclear power plant comprises more than one unit with the same structure, and each unit is provided with a primary circuit, a secondary circuit, and is characterized in that each unit The units all include a feed water pump (1) for delivering water in the secondary circuit to the steam generator (2), and the outlet end of the steam generator (2) is connected to the high-pressure cylinder (3) and the low-pressure cylinder (4) in sequence. ), the condenser (5), and the feed water pump (1) form a closed cycle, the output end of the low-pressure cylinder (4) is connected to the generator (6), and the low-pressure cylinder (4) is connected to the steam-water heat exchanger (7). The steam-side heat exchange pipelines are connected in parallel; the water-side heat exchange pipelines in the steam-water heat exchangers (7) in all units are connected in parallel with the heat network circulation pump (8) in the heat network circulation pump station (C) to form loop. 2. The multi-unit heating system of a nuclear power plant with a steam side unit system and a water side combined system according to claim 1, characterized in that the heat network circulating pump (8) is connected in series with a constant pressure pump (10), a decontamination pump The constant pressure pump (10) is connected to the deaerator (9). 3. The multi-unit heating system of a nuclear power plant of a steam-side unit system and a water-side combined system according to claim 1, characterized in that, the three circuits and other downstream circuits are respectively connected to the heating system of the water-water heat exchanger (13). The two heat exchange pipes are connected. 4. The multi-unit heating system of a nuclear power plant with a steam-side unit system and a water-side combined system according to claim 1, wherein the water in the secondary circuit of the nuclear power plant is boosted by the feed pump (1) and then transported to the The steam generator (2) absorbs heat in the steam generator (2) to become saturated steam, and the saturated steam enters the high-pressure cylinder (3) and the low-pressure cylinder (4) in turn to perform work, driving the steam turbine to rotate, and the steam turbine drives the generator ( 6) To achieve power generation, the steam after the work enters the condenser (5), exchanges the heat to the seawater of the three circuits, and condenses into water, and after being heated step by step, is transported to the steam generator (1) by the feed pump (1). 2), to complete the closed cycle of the entire secondary circuit; the heat network circulating water return water in the water-side heat exchange pipeline in the steam-water heat exchanger (7) first enters the heat network circulating pump (8), and passes through the heat network circulating pump. (8) Boost the pressure and deliver it to two units respectively to meet the heating demand of the two units. 5. The multi-unit heating system of a nuclear power plant of a steam-side unit system and a water-side combined system as claimed in claim 1, characterized in that, during normal operation, the steam-water heat exchanger ( 7) Running, other steam-water heat exchangers (7) are not running and stand by. 6. The multi-unit heating system of a nuclear power plant with a steam-side unit system and a water-side combined system according to claim 1, wherein the steam-side heat exchange pipeline of the steam-water heat exchanger (7) in the unit is provided with Valve a, valve b and valve c are respectively set on the water side heat exchange pipeline. Valve a, valve b, and valve c are open in the normal operation unit, and valve a, valve b, and valve c in the standby unit are closed. 7. The multi-unit heating system of a nuclear power plant with a steam-side unit system and a water-side combined system according to claim 3, characterized in that, valves are respectively provided on both sides of the three-circuit water-to-water heat exchanger (13) d. Valve e. During normal operation, valve d and valve e are open, and under abnormal conditions, valve d and valve e are closed.

Images