CN212252568U - Subcritical parent pipe feedwater system boiler recirculation heat exchange start-up system - Google Patents

Abstract

The utility model discloses a boiler recirculation heat exchange start-up system of a subcritical parent pipe water supply system. The system comprises a water-water heat exchanger, a feedwater pressure and a water-water heat exchanger, which are sequentially installed between the boiler drum water level regulating valve and the No. 1 and No. 2 boilers. Transmitter and feed water temperature sensor, regulating valve installed on the refrigerant return pipe of the water-water heat exchanger, feed water recirculation pressure regulating valve installed on the recirculation pipe from the feed water pipe to the deaerator, and the corresponding boiler water heat The feedwater temperature PID controller connected with the refrigerant flow control valve of the exchanger and the feedwater temperature sensor, the feedwater pressure PID controller connected with the corresponding boiler feedwater recirculation pressure regulating valve and the feedwater pressure transmitter; the feedwater pressure PID controller controls the feedwater recirculation The pressure regulating valve is slowly closed, and the feedwater temperature PID controller controls the opening of the water-water heat exchanger refrigerant flow regulating valve to control the feedwater pressure and temperature within the allowable pressure and temperature range of the boiler metal tube wall.

Description

Subcritical parent pipe feedwater system boiler recirculation heat exchange start-up system

technical field

The utility model relates to the technical field of automatic control of thermal power plants, in particular to a boiler recirculation heat exchange start-up system of a subcritical parent control water supply system.

Background technique

In the existing subcritical parent-controlled water supply system with two boilers and one unit, two boilers share one water supply system, which has become the first choice for thermal power companies to reduce initial investment. First of all, in a conventional thermal power generating unit, a set of water supply system includes a water supply pump set, a high-pressure heater system, a high-pressure steam extraction system and a high-pressure drainage system, while two boilers share a set of water supply system, which can greatly increase the initial investment of the enterprise. Second, there is one less water supply system, and the maintenance and maintenance costs of the water supply system equipment will also be significantly reduced. However, the starting method of the main control feedwater boiler, or the two boilers are started at the same time; or the first boiler is started to drive the steam turbine to run, connect to the grid for power generation, and bring the initial load, and then wait for the second boiler to pass through the steam turbine bypass system. When the quality is close to that of the first boiler, the steam of the two boilers will be merged into the same steam main pipe through the steam merging equipment, and the synchronous steam turbines of the last two boilers will reach full load operation of the unit.

The main pipe feed water system imposes some restrictions on the flexible operation of the unit. For example, while the second boiler is under maintenance, the first is running at full load with the steam turbine. When the second boiler completes the maintenance task, it needs to be put into operation. The first boiler and steam turbine need to reduce the load, reduce the output of each auxiliary machine, stop the coal feeder in sequence, put in oil to support combustion, put into bypass, disconnect the generator, The steam turbine is tripped, the boiler is finally turned off and the furnace is stopped, and the two boilers are started synchronously to bring the unit to full output; or the first boiler goes through a series of operations such as load reduction, reduction of feeding system, and oil injection to stabilize combustion from the state of full output. It may take several hours or even a whole day to drop to the initial load state of the steam turbine and wait for the temperature of the feed water to drop to a temperature suitable for the maintenance of the boiler metal. The second boiler is filled with water from the boiler, flushed in a cold state, ignited and heated up, flushed in a hot state until the steam quality meets the steam conditions. This process may take several hours or even a whole day. Then synchronize the steam turbine with the first boiler to full output. In the process of merging into the second boiler, it is assumed that a layer of oil burners is put into operation, and a layer of 4 oil guns, each with 500 kg of fuel oil per hour, and considering that the first boiler is not fully loaded , business losses on the grid. In the process of starting and incorporating the second boiler in this way, the economic loss caused to the enterprise is obvious.

There are several problems with this startup method:

First of all, when two boilers are started at the same time, the equipment that operators need to monitor will increase exponentially. It is inevitable that mistakes will occur in the process of starting the boilers, which will bring unnecessary losses to enterprises and employees. Also because of the inconsistency of the equipment materials of the two boilers, the requirements for the water supply system during the start-up process are also different, which is also a big test for the professional quality of the operators and the reliability of the equipment and materials.

Second, the first boiler with initial load waiting for the second boiler to start is a waste in itself, and the long-term operation of the unit below the stable combustion load is a kind of damage to the equipment and reduces the service life of the equipment.

Third, the greater the temperature difference between the boiler metal tube wall and the feed water, the greater the possibility of brittle failure of the boiler metal tube wall. When the second boiler that has been repaired needs to be put into use, it must wait for the first boiler to be in the same state as it. The economic loss to the enterprise in this process is obvious, and the damage to the unit equipment cannot be ignored.

SUMMARY OF THE INVENTION

In order to solve the problems existing in the above-mentioned prior art, the purpose of the present utility model is to provide a boiler recirculation heat exchange start-up system of a subcritical parent-control water supply system, which is effective in improving the thermal power plant of a two-boiler one-machine or a multi-boiler and multi-machine parent-control water supply system for thermal power plants. It is of great significance to improve the operation reliability of the boiler, prolong the life of the key equipment of the boiler, reduce the probability of damage to the metal tube wall or even the occurrence of tube burst accidents, reduce the maintenance and repair costs, and reduce the start-up cost of the unit.

In order to achieve the above purpose, the utility model adopts the following technical solutions:

A boiler recirculation heat exchange start-up system for a subcritical parent pipe feedwater system, comprising: No. 1 boiler water-water heat exchangers 1, 1, and 1, which are sequentially installed on the pipeline between the No. No. 1 boiler feed water pressure transmitter 5 and No. 1 boiler feed water temperature sensor 4, installed on the No. 1 boiler water-water heat exchanger 1 refrigerant water return pipe No. 1 boiler water-water heat exchanger refrigerant flow control valve 2, The No. 1 boiler feed water recirculation pressure regulating valve 3 installed on the No. 1 boiler feed water pipeline to the deaerator recirculation pipeline is connected to the No. 1 boiler water-water heat exchanger refrigerant flow regulating valve 2 and No. 1 boiler feed water temperature sensor 4 The No. 1 boiler feed water temperature PID controller 6, the No. 1 boiler feed water pressure PID controller 7 connected to the No. 1 boiler feed water recirculation pressure regulating valve 3 and the No. 1 boiler feed water pressure transmitter 5.

It also includes the No. 2 boiler water-water heat exchanger 11, the No. 2 boiler feed water pressure transmitter 15 and the No. 2 boiler feed water temperature installed in sequence on the pipeline between the No. 2 boiler drum water level control valve 18 and the No. 2 boiler 20 Sensor 14, No. 2 boiler water-water heat exchanger refrigerant flow control valve 12 installed on the No. 2 boiler water-water heat exchanger 11 refrigerant water return pipe, installed on the No. 2 boiler feed water pipe to the deaerator recirculation pipe The No. 2 boiler feed water recirculation pressure regulating valve 13, the No. 2 boiler feed water temperature PID controller 16 connected to the No. 2 boiler water-water heat exchanger refrigerant flow control valve 12 and the No. 2 boiler feed water temperature sensor 14, and the No. 2 boiler feed water temperature PID controller 16. The No. 2 boiler feed water pressure PID controller 17 is connected to the feed water recirculation pressure regulating valve 13 and the No. 2 boiler feed water pressure transmitter 15 .

The water inlets of the No. 1 boiler water-water heat exchanger 1 and the No. 2 boiler water-water heat exchanger 11 are connected to the condensate water pipeline between the condensate pump 21 and the low-pressure heater 22; the No. 1 boiler water-water heat exchange The water outlets of boiler 1 and No. 2 boiler water-water heat exchanger 11 communicate with the condensed water pipeline between the low-pressure heater 22 and the deaerator 23 .

The water inlet of the No. 1 boiler feed water recirculation pressure regulating valve 3 is communicated with the No. 1 boiler feed water pipeline between the No. 1 boiler drum water level regulating valve 8 and the No. 1 boiler water-water heat exchanger 1, and the No. 1 boiler The water outlet of the feed water recirculation pressure regulating valve 3 communicates with the deaerator 23 . The water inlet of the No. 2 boiler feed water recirculation pressure regulating valve 13 is communicated with the No. 2 boiler feed water pipeline between the No. 2 boiler drum water level regulating valve 18 and the No. 2 boiler water-water heat exchanger 11, and the No. 2 boiler The water outlet of the feed water recirculation pressure regulating valve 13 communicates with the deaerator 23 .

The working method of the boiler recirculation heat exchange start-up system of the subcritical parent pipe feedwater system, if the No. 2 boiler 20 is used as the start-up boiler, during the start-up process from the ignition of the No. 2 boiler 20 to the combination with the main steam of the No. 1 boiler 19 , the temperature of the metal material on the tube wall of the No. 2 boiler 20 changes, and the temperature and pressure of the feed water entering the No. 2 boiler 20 should also change accordingly. In order to reduce the mismatch between the metal temperature of the No. 2 boiler 20 and the temperature and pressure of the feed water, the 20 The possibility of brittle failure of the metal tube wall, the No. 2 boiler feed water pressure PID controller 17 controls the No. 2 boiler feed water recirculation pressure regulating valve 13 to slowly close at a preset rate, so that the No. 2 boiler feed water pressure transmitter 15 During the rising process, the feed water pressure of the No. 2 boiler is always within the allowable feed water pressure range of the metal material of the No. 2 boiler 20; the No. 2 boiler feed water temperature PID controller 16 reduces the refrigerant flow rate of the No. Adjust the opening of the valve 12 to reduce the flow of condensed water entering the No. 2 boiler water-water heat exchanger 11, so as to control the feed water temperature measured by the No. 2 boiler feed water temperature sensor 14 in the process of heating up the metal of the No. 2 boiler 20. Within the allowable temperature range of the tube wall; as the load of the No. 2 boiler 20 continues to increase, the temperature of the metal tube wall of the No. 2 boiler 20 also continues to rise, and the required feed water pressure and temperature are also under control. The allowable rising speed of the wall continues to increase until the main steam of the No. 2 boiler 20 is successfully merged into the No. 1 boiler 19; at this moment, the No. 2 boiler feed water recirculation pressure regulating valve 13 of the No. 2 boiler 20 has been fully closed, and the No. 2 boiler No. 2 boiler water-water heat exchanger refrigerant flow control valve 12 of 20 has been in a fully closed state, indicating that the utility model No. 2 boiler 20 has completed the start-up process; The start-up process of the main steam integration of the No. 2 boiler 20 is the same as the start-up process of the No. 2 boiler 20 from the ignition to the main steam integration of the No. 1 boiler 19 .

Compared with the prior art, the utility model has the following advantages:

(1) The utility model enriches the starting mode of two boilers (including multiple boilers) and one machine unit of the main pipe water supply system. The No. 1 boiler 19 that runs first does not have to be below the steady combustion load, waiting for the other No. 2 boiler 20 to complete the start-up process, and the two boilers can wait for the other boiler to be merged in any state. It reduces the economic cost of the power generation enterprise during the start-up process of the unit; it protects the metal tube wall of the boiler to the greatest extent; it also reduces the labor intensity of the operators; boiler, and cause unnecessary misoperation.

(2) The existing technology cannot accurately control the boiler feed water pressure. The utility model can realize the real-time control of the feed water pressure in front of the boiler, and on the premise of ensuring that the feed water pressure meets the requirements of the metal materials of the boiler at the present stage, the excess process feed water is recovered into the deaerator. This process solves the problem that the water supply pressure cannot be adjusted, and coincides with the enterprise's concept of saving and environmental protection.

(3) The existing technology cannot precisely control the feed water temperature of the boiler water wall. When it is judged that the feed water is over-temperature, the utility model can not only achieve the purpose of cooling the high temperature feed water with the help of the low temperature condensate water in a short period of time through the water-water heat exchanger; The amount of steam required in a disguised form increases the amount of steam in the steam turbine to do work, thereby increasing the power output of the unit and meeting the purpose of energy conservation and environmental protection of the enterprise; further enriching the safe start-up method of multiple boilers in the main control water supply system.

Description of drawings

Figure 1 is a schematic diagram of the system structure of the present invention.

1-No.1 boiler water-water heat exchanger; 2-No.1 boiler water-water heat exchanger refrigerant flow control valve; 3-No.1 boiler feed water recirculation pressure regulating valve; 4-No.1 boiler feedwater temperature sensor; 5-One No. 1 boiler feed water pressure transmitter; 6 - No. 1 boiler feed water temperature PID controller; 7 - No. 1 boiler feed water pressure PID controller; 8 - No. 1 boiler drum water level regulating valve; 9 - Feed water pump; 10 - High pressure Heater; 11 - No. 2 boiler water-water heat exchanger; 12 - No. 2 boiler water-water heat exchanger refrigerant flow control valve; 13 - No. 2 boiler feed water recirculation pressure regulating valve; 14 - No. 2 boiler feed water temperature sensor; 15—No. 2 boiler feed water pressure transmitter; 16—No. 2 boiler feed water temperature PID controller; 17—No. 2 boiler feed water pressure PID controller; 18—No. 2 boiler drum water level regulating valve; 19—No. 1 boiler; 20—No. 2 boiler; 21—condensate pump; 22—low pressure heater; 23—deaerator.

Detailed ways

The present utility model will be further described in detail below with reference to the accompanying drawings and specific embodiments.

As shown in Figure 1, a subcritical main pipe water supply system boiler recirculation heat exchange start-up system of the present invention includes a boiler drum water level regulating valve 8 of the No. 1 boiler to the pipeline between the No. 1 boiler 19. No. 1 boiler water-water heat exchanger 1, No. 1 boiler feed water pressure transmitter 5 and No. 1 boiler feed water temperature sensor 4, No. 1 boiler water installed on the No. 1 boiler water-water heat exchanger 1 refrigerant water return pipe Heat exchanger refrigerant flow regulating valve 2, No. 1 boiler feed water recirculation pressure regulating valve 3 installed on the No. 1 boiler feed water pipeline to the deaerator recirculation pipeline, and No. 1 boiler water-water heat exchanger refrigerant flow regulating valve 2 The No. 1 boiler feed water temperature PID controller 6 connected to the No. 1 boiler feed water temperature sensor 4, the No. 1 boiler feed water pressure PID controller connected to the No. 1 boiler feed water recirculation pressure regulating valve 3 and the No. 1 boiler feed water pressure transmitter 5 device 7.

It also includes the No. 2 boiler water-water heat exchanger 11, the No. 2 boiler feed water pressure transmitter 15 and the No. 2 boiler feed water temperature installed in sequence on the pipeline between the No. 2 boiler drum water level control valve 18 and the No. 2 boiler 20 Sensor 14, No. 2 boiler water-water heat exchanger refrigerant flow control valve 12 installed on the No. 2 boiler water-water heat exchanger 11 refrigerant water return pipe, installed on the No. 2 boiler feed water pipe to the deaerator recirculation pipe The No. 2 boiler feed water recirculation pressure regulating valve 13, the No. 2 boiler feed water temperature PID controller 16 connected to the No. 2 boiler water-water heat exchanger refrigerant flow control valve 12 and the No. 2 boiler feed water temperature sensor 14, and the No. 2 boiler feed water temperature PID controller 16. The No. 2 boiler feed water pressure PID controller 17 is connected to the feed water recirculation pressure regulating valve 13 and the No. 2 boiler feed water pressure transmitter 15 .

The water inlets of the No. 1 boiler water-water heat exchanger 1 and the No. 2 boiler water-water heat exchanger 11 are connected to the condensate water pipeline between the condensate pump 21 and the low-pressure heater 22; the No. 1 boiler water-water heat exchange The water outlets of boiler 1 and No. 2 boiler water-water heat exchanger 11 communicate with the condensed water pipeline between the low-pressure heater 22 and the deaerator 23 .

The water inlet of the No. 1 boiler feed water recirculation pressure regulating valve 3 is communicated with the No. 1 boiler feed water pipeline between the No. 1 boiler drum water level regulating valve 8 and the No. 1 boiler water-water heat exchanger 1; the No. 1 boiler The water outlet of the feed water recirculation pressure regulating valve 3 communicates with the deaerator 23 . The water inlet of the No. 2 boiler feed water recirculation pressure regulating valve 13 is communicated with the No. 2 boiler feed water pipeline between the No. 2 boiler drum water level regulating valve 18 and the No. 2 boiler water-water heat exchanger 11; the No. 2 boiler The water outlet of the feed water recirculation pressure regulating valve 13 communicates with the deaerator 23 .

The boiler drum water level regulating valve is located between the high-pressure heater 10 and the boiler, and is the main means of regulating water supply to the boiler, as well as the only way to supply water to the boiler. Before the boiler is started, process water with suitable pressure and temperature is provided to the boiler through the boiler drum water level control valve. The greater the temperature difference between the process water in the boiler metal tube wall and the tube wall metal, the greater the possibility of brittle failure of the boiler metal tube wall. Therefore, the pressure and temperature of the boiler process water supply cannot exceed the allowable temperature of the boiler metal tube wall. within the range. In a unit with two boilers (including multiple boilers) main pipe water supply system, during the start-up process, there is a possibility of brittle failure of the metal pipes of the second boiler that starts up. Under the existing technical conditions, when the second boiler needs to be started, in order to reduce the possibility of brittle failure of the metal tubes of the boiler, the first boiler must be stopped and started together; or the load of the first boiler should be reduced, Wait for proper feed water temperature and feed water pressure before putting into the second boiler. In this process, the labor intensity of operators will increase exponentially, and the possibility of misoperation at this stage will also increase greatly, and even more will bring unnecessary economic losses to the enterprise.

As shown in FIG. 1 , taking the No. 2 boiler 20 as the second start-up boiler as an example, the function of the present invention in the start-up process of the No. 2 boiler 20 is described in detail. During the start-up process from the ignition of the No. 2 boiler 20 to the combination with the main steam of the No. 1 boiler 19, the temperature of the metal material on the tube wall of the No. 2 boiler 20 changes, and the temperature and pressure of the feed water entering the No. 2 boiler 20 should also change accordingly. In order to Reduce the possibility of brittle failure of the metal tube wall of the No. 2 boiler 20 due to the mismatch between the metal temperature of the No. 2 boiler 20 and the temperature and pressure of the feed water, during the process of the No. 2 boiler 20 starting from ignition to merging with the main steam of the No. 1 boiler 19 In the middle, the No. 2 boiler feed water pressure PID controller 17 controls the No. 2 boiler feed water recirculation pressure regulating valve 13 in front of the No. 2 boiler 20 to slowly close to 0% at a rate of 5%/h, so that the No. 2 boiler feed water pressure changes. During the process of the feed water pressure measured by the feeder 15 gradually approaching the pressure of the feedwater main pipe from 0MPa, it is always within the allowable feedwater pressure range of the metal material of the No. 2 boiler 20 in the load-up stage; At a rate of 2%/h, gradually close the refrigerant flow control valve 12 of the small water-water heat exchanger to gradually reduce the flow of condensed water entering the water-water heat exchanger 11 of the No. 2 boiler to 0t/h, so as to control the measurement of the feed water temperature sensor 14 of the No. 2 boiler. In the process of heating up, the feed water temperature has been within the allowable temperature range of the metal tube wall of No. 2 boiler 20. With the continuous increase of the load of the No. 2 boiler 20, the temperature of the metal tube wall of the No. 2 boiler 20 also continues to rise, and the required feed water pressure and temperature are also under the control of the system of the present utility model. Within the range of 2 degrees/min, it will continue to increase until the main steam of the No. 2 boiler 20 is successfully merged into the No. 1 boiler 19.

Claims (3)

1. a subcritical parent tube water supply system boiler recirculation heat exchange start-up system, is characterized in that: comprise the pipeline between No. 1 boiler steam drum water level regulating valve (8) to No. 1 boiler (19) installed successively The No. 1 boiler water-water heat exchanger (1), the No. 1 boiler feed water pressure transmitter (5) and the No. 1 boiler feed water temperature sensor (4) are installed in the No. 1 boiler water-water heat exchanger (1). The refrigerant water returns The No. 1 boiler water-water heat exchanger refrigerant flow regulating valve (2) on the water pipeline, the No. 1 boiler feed water recirculation pressure regulating valve (3) installed on the No. 1 boiler feed water pipeline to the deaerator recirculation pipeline, and The No. 1 boiler feed water temperature PID controller (6), which is connected to the No. 1 boiler water-water heat exchanger refrigerant flow control valve (2) and the No. 1 boiler feed water temperature sensor (4), is connected to the No. 1 boiler feed water recirculation pressure regulating valve ( 3) The No. 1 boiler feed water pressure PID controller (7) connected to the No. 1 boiler feed water pressure transmitter (5); It also includes the No. 2 boiler water-water heat exchanger (11), the No. 2 boiler feed water pressure transmitter ( 15) and the No. 2 boiler feed water temperature sensor (14), the No. 2 boiler water-water heat exchanger refrigerant flow control valve (12) installed on the No. 2 boiler water-water heat exchanger (11) refrigerant water return pipe, installed The No. 2 boiler feed water recirculation pressure regulating valve (13) on the No. 2 boiler feed water pipeline to the deaerator recirculation pipeline, and the No. 2 boiler water-water heat exchanger refrigerant flow regulating valve (12) and the No. 2 boiler feed water temperature The No. 2 boiler feed water temperature PID controller (16) connected to the sensor (14), the No. 2 boiler feed water pressure connected to the No. 2 boiler feed water recirculation pressure regulating valve (13) and the No. 2 boiler feed water pressure transmitter (15) PID controller (17). 2. A subcritical parent pipe feedwater system boiler recirculation heat exchange start-up system according to claim 1, characterized in that: the No. 1 boiler water-water heat exchanger (1) and the No. 2 boiler water-water heat exchange The water inlet of the boiler (11) is communicated with the condensate pipeline between the condensate pump (21) and the low pressure heater (22); the No. 1 boiler water-water heat exchanger (1) and the No. 2 boiler water-water heat exchanger The water outlet of (11) is communicated with the condensed water pipeline between the low pressure heater (22) and the deaerator (23). 3. A kind of subcritical parent pipe feed water system boiler recirculation heat exchange start-up system according to claim 1, characterized in that: the water inlet of the No. 1 boiler feed water recirculation pressure regulating valve (3) and the No. 1 boiler The No. 1 boiler feed water pipeline between the steam drum water level regulating valve (8) and the No. 1 boiler water-water heat exchanger (1) is connected, and the water outlet of the No. 1 boiler feed water recirculation pressure regulating valve (3) is connected to the deaerator The water inlet of the No. 2 boiler feed water recirculation pressure regulating valve (13) and the water level regulating valve (18) of the No. 2 boiler drum to the No. 2 boiler water-water heat exchanger (11) are connected. The No. 2 boiler feed water pipeline is communicated, and the water outlet of the No. 2 boiler feed water recirculation pressure regulating valve (13) is communicated with the deaerator (23).

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