A drum level regulation system equipped with a water storage device and a control method

Abstract

The present application relates to the technical field of boiler, disclose a kind of equipped with water storage device's drum liquid level regulating system and control method, the system, including steam drum, water-cooled wall, superheater system, water inlet control valve, water outlet control valve, water storage device, shut-off valve;The water-cooled wall import and export are connected with steam drum respectively, form loop;Steam drum steam space is connected with superheater system, steam drum water space is connected with the water space of water storage device by shut-off valve, the water space of water storage device is connected with steam drum steam space by water outlet control valve, the water space of water storage device is connected with superheater system by water inlet control valve.This application solves the problem that steam drum water level is difficult to maintain stable in the process of existing technology steam drum rapid load change, while improve steam drum heat storage capacity, increase steam drum load change rate promotion space.

Description

Technical Field

[0001] This invention relates to the field of boiler technology, specifically to a steam drum liquid level regulation system and control method equipped with a water storage device. Background Technology

[0002] Due to the temporal and spatial differences between wind and solar power resources and residential electricity consumption, the rapid development of wind and solar power has led to increasingly prominent issues of wind and solar curtailment in areas rich in these resources. As coal-fired power units are the main force for peak shaving in the power system, improving their peak shaving capacity is one of the most direct and effective means to solve the problem of wind and solar curtailment.

[0003] Most coal-fired power units below 300,000 kilowatts are drum boilers. A conventional drum is a horizontally placed cylindrical pressure vessel. The drum water level is generally controlled between the midpoint and 100 mm below the midpoint of the drum's elevation. Therefore, the effective water storage volume of the drum is approximately half of its total volume. During rapid load changes in the boiler, the drum water level may fluctuate due to differences in the response speed of the furnace heat load and feedwater flow. Excessive or rapid changes in the drum water level may trigger a water level alarm or even a minimum power failure (MFT).

[0004] Conventional subcritical boilers require the drum water level to be maintained between 0 and -100 mm, resulting in limited room for variation in drum water volume. This makes it difficult to adapt to rapid load changes in the boiler. The usable drum heat storage capacity during rapid load changes is limited to the total enthalpy of the water stored in the drum between the 0 and -100 mm water levels. This small volume is insufficient to meet the load change requirements.

[0005] Rapid load change regulation methods for steam drum boilers include the utilization of the unit's thermal storage, of which the utilization of the steam drum is one. Specific implementation methods include reducing the steam drum pressure to enable rapid steam generation and reducing feedwater flow to decrease steam extraction from the blast furnace. Both of these methods will lead to a decrease in the steam drum water level. Therefore, the safety margin of the steam drum water level is also one of the factors that limit the rapid load change of the steam drum boiler. Summary of the Invention

[0006] To overcome the shortcomings of the prior art, the present invention provides a steam drum liquid level regulation system and control method equipped with a water storage device, which solves the problem that the steam drum water level is difficult to maintain during the rapid load change process of the steam drum boiler in the prior art, while improving the heat storage capacity of the steam drum and increasing the space for improving the load change rate of the steam drum boiler.

[0007] The technical solution adopted by the present invention to solve the above problems is:

[0008] A steam drum liquid level regulation system equipped with a water storage device includes a steam drum, a water-cooled wall, a superheater system, an inlet water control valve, an outlet water control valve, a water storage device, and a shut-off valve;

[0009] The inlet and outlet of the water-cooled wall are respectively connected to the steam drum to form a loop;

[0010] The steam drum steam space is connected to the superheater system, the steam drum water space is connected to the water storage device water space through a shut-off valve, the water storage device steam space is connected to the steam drum steam space through an outlet control valve, and the water storage device steam space is connected to the superheater system through an inlet control valve.

[0011] As a preferred technical solution, the superheater system includes a ceiling-mounted wall superheater, a low-temperature superheater, a screen-type superheater, and a high-temperature superheater connected in sequence.

[0012] As a preferred technical solution, the connection point between the inlet control valve and the superheater system is selectively located after any of the following superheaters: ceiling-mounted superheater, low-temperature superheater, screen-type superheater, and high-temperature superheater, depending on the required differential pressure value.

[0013] As a preferred technical solution, the water storage device is a cylindrical pressure vessel.

[0014] As a preferred technical solution, the water storage device is placed vertically.

[0015] As a preferred technical solution, the bottom of the water storage device is located 100mm below the water level of the steam drum.

[0016] A method for controlling the liquid level of a steam drum equipped with a water storage device, wherein a steam drum liquid level regulating system equipped with a water storage device is used, and when the regulating system does not participate in the regulation of the steam drum water level, both the inlet control valve and the outlet control valve are in the closed state.

[0017] A method for controlling the liquid level of a steam drum equipped with a water storage device, wherein a steam drum liquid level regulating system equipped with a water storage device is used, and when it is necessary to lower the water level of the steam drum, the inlet control valve is opened and the outlet control valve is closed.

[0018] A method for controlling the liquid level of a steam drum equipped with a water storage device, wherein a steam drum liquid level regulating system equipped with a water storage device is used, wherein when it is necessary to raise the water level of the steam drum, the inlet control valve is closed and the outlet control valve is opened.

[0019] Compared with the prior art, the present invention has the following advantages:

[0020] (1) Compared with controlling the steam drum liquid level by the water flow rate, the present invention has a faster adjustment response speed for the steam drum liquid level;

[0021] (2) The present invention improves the available water volume and heat storage capacity of the steam drum during rapid load change, which can increase the potential for increasing the load change rate of the steam drum boiler.

[0022] (3) The present invention utilizes the boiler’s own pressure difference, and the water inlet and outlet of the water storage tank do not require additional power. Attached Figure Description

[0023] Figure 1 This is a schematic diagram of the structure of a steam drum liquid level regulating system equipped with a water storage device according to the present invention.

[0024] The labels and their corresponding names in the attached diagram are as follows: 1. Steam drum, 2. Water-cooled wall, 3. Roof and wall superheater, 4. Low-temperature superheater, 5. Screen-type superheater, 6. High-temperature superheater, 7. Inlet control valve, 8. Outlet control valve, 9. Water storage device, 10. Shut-off valve. Detailed Implementation

[0025] The present invention will be further described in detail below with reference to the embodiments and accompanying drawings, but the embodiments of the present invention are not limited thereto.

[0026] Example 1

[0027] like Figure 1 As shown, the present invention proposes a steam drum liquid level regulation system equipped with a water storage device to address the above-mentioned problems, which can maintain a stable steam drum liquid level during rapid load changes in the boiler.

[0028] This invention addresses the problems of existing technologies by installing an additional water storage tank outside the steam drum. By increasing the additional water volume of the storage tank, the amount of heat stored in the steam drum that can be utilized during rapid load changes of the unit is increased. At the same time, by setting inlet and outlet water control valves as a means of controlling the water level in the steam drum, the response speed is faster than that of feedwater flow control.

[0029] The steam drum water circulation system and superheater system of the present invention are consistent with those of conventional subcritical boilers: the working fluid in the steam drum 1 comes from the economizer, and the working fluid enters the water-cooled wall 2 through the downcomer to absorb heat and then returns to the steam drum. The steam generated in the steam drum 1 passes through the steam-water separator and then enters the roof wall superheater 3, the low-temperature superheater 4, the screen superheater 5 and the high-temperature superheater 6 in sequence to absorb heat, and then enters the steam turbine to do work.

[0030] The steam drum liquid level regulation system of this invention is equipped with a water storage device 9 (water tank). This water tank is a vertically placed cylindrical pressure vessel. The bottom elevation can be set below the steam drum -100mm water level, and the top elevation can be selected according to the water storage requirements and the space of the boiler steel frame. The bottom of the water storage device 9 is connected to the water space of the steam drum 1 through a connecting pipe, which serves as the inlet and outlet channel for the water storage device 9. A shut-off valve 10 is installed on the horizontal section of the connecting pipe. The shut-off valve is normally kept fully open and is only used for isolation in case of an emergency. Two parallel pressure balancing pipelines are set at the steam space outlet of the water storage device 9. One pipeline is connected to the outlet steam pipeline of the low-temperature superheater, with the connection point located between the low-temperature superheater outlet header and the first-stage desuperheater, and is equipped with an electric regulating valve as the inlet control valve 7. The other pipeline is connected to the steam space of the steam drum and is equipped with an electric regulating valve as the outlet control valve 8.

[0031] The water storage device 9 should have good insulation. The working fluid temperature is mainly maintained through heat conduction of the working fluid in the water space. Since the working fluid temperature of the water storage device 9 is slightly lower than that of the steam drum, the evaporation during the water intake process can be reduced.

[0032] Preferably, a steam-water separation device can be installed at the outlet of the water storage device 9 to prevent water from being carried into the steam pipeline entering the outlet of the low-temperature superheater.

[0033] Control methods:

[0034] When the control system is not involved in the steam drum water level regulation, both the inlet control valve 7 and the outlet control valve 8 are in the closed state.

[0035] When it is necessary to lower the steam drum water level, open the inlet control valve 7 and close the outlet control valve 8. At this time, the steam space of the water storage tank is connected to the superheater system, and the pressure in the steam space of the water storage device 9 is lower than that of the steam drum 1. Under the action of the pressure difference, the working fluid in the steam drum enters the water storage tank through the connecting pipe, the steam drum liquid level decreases, and the water level in the water storage tank rises. By adjusting the opening of the inlet control valve 7, the rate at which the steam drum liquid level decreases can be controlled. Opening the inlet control valve 7 more will accelerate the rate at which the steam drum liquid level decreases, and vice versa.

[0036] When it is necessary to raise the steam drum water level, close the inlet control valve 7 and open the outlet control valve 8. At this time, the steam space of the water storage tank is connected to the steam space of the steam drum, and the pressure in the steam space of the water storage device 9 is equal to that of the steam drum 1. Under the action of gravity difference, the working fluid in the water storage tank enters the steam drum through the connecting pipe, the water level in the water storage tank decreases, and the steam drum liquid level rises. By adjusting the opening of the outlet control valve 8, the rate at which the steam drum liquid level rises can be controlled. Opening the outlet control valve 8 more will accelerate the rate at which the steam drum liquid level rises, and vice versa.

[0037] In this invention, the low-temperature superheater 4 refers to the low-temperature stage convection heat exchanger, the screen-type superheater 5 refers to the radiation heat exchanger, and the high-temperature superheater 6 refers to the high-temperature stage convection heat exchanger.

[0038] This invention increases the amount of heat storage that can be utilized in the steam drum by setting an external water storage tank;

[0039] This invention enables the water storage tank to obtain an inlet pressure differential by setting a steam connection pipe with the superheater system;

[0040] This invention enables the water storage tank to obtain an outlet pressure difference by setting a steam connection pipe with the steam space of the steam drum.

[0041] The present invention has the following technical effects:

[0042] (1) Compared with controlling the steam drum liquid level by the water flow rate, the present invention has a faster adjustment response speed for the steam drum liquid level;

[0043] (2) This invention improves the available water volume and heat storage capacity of the steam drum during rapid load change, thereby increasing the potential for increasing the boiler load change rate.

[0044] (3) The present invention utilizes the boiler’s own pressure difference, and the water inlet and outlet of the water storage tank do not require additional power.

[0045] Example 2

[0046] like Figure 1 As shown, as a further optimization of Embodiment 1, this embodiment also includes the following technical features based on Embodiment 1:

[0047] Taking a 300MW subcritical boiler as an example, the subcritical boiler is equipped with a steam drum 1, which has a diameter of 1800mm and a length of approximately 22250mm. The water level control range is 0 to -100mm, and the usable water volume under varying loads is approximately 4m³. 3 The working fluid in the steam drum 1 comes from the economizer. The working fluid enters the water-cooled wall 2 through the downcomer to absorb heat and then returns to the steam drum. The steam generated in the steam drum 1 passes through the steam-water separator and then enters the roof wall superheater 3, low-temperature superheater 4, screen superheater 5 and high-temperature superheater 6 in sequence to absorb heat, and then enters the steam turbine to do work.

[0048] A water storage device 9 is installed. This water tank is placed vertically, with its bottom elevation set at the steam drum - 100mm water level. It has an inner diameter of 1 meter, a height of 6 meters, and a water storage volume of approximately 4.7m³. 3 This is equivalent to doubling the usable water volume of the steam drum during variable load processes.

[0049] The bottom of the water storage device 9 is connected to the water space of the steam drum 1 via a connecting pipe, which serves as the inlet and outlet channel for the water storage device 9. A shut-off valve 10 is installed on the horizontal section of the connecting pipe. The steam space outlet of the water storage device 9 is equipped with two parallel steam channels. One channel is connected to the outlet steam pipe of the low-temperature superheater, with the connection point located between the low-temperature superheater outlet header and the first-stage desuperheater, and is equipped with an electric regulating valve as the inlet control valve 7. The other channel is connected to the steam space of the steam drum, and is equipped with an electric regulating valve as the outlet control valve 8.

[0050] A steam-water separation device can be installed at the outlet of the water storage device 9 to prevent water from being carried into the steam pipeline of the low-temperature superheater.

[0051] When the control system is not involved in the steam drum water level regulation, both the inlet control valve 7 and the outlet control valve 8 are in the closed state.

[0052] When it is necessary to lower the steam drum water level, open the inlet control valve 7 and close the outlet control valve 8. At this time, the steam space of the water storage tank is connected to the superheater system. The pressure of the steam space of the water storage device 9 is lower than that of the steam drum 1. Under the action of the pressure difference, the working fluid in the steam drum enters the water storage tank through the connecting pipe, the steam drum liquid level decreases, and the water level in the water storage tank rises.

[0053] When it is necessary to raise the steam drum water level, close the inlet control valve 7 and open the outlet control valve 8. At this time, the steam space of the water storage tank is connected to the steam space of the steam drum. The pressure of the steam space of the water storage device 9 is equal to that of the steam drum 1. The water level of the water storage tank is higher than that of the steam drum. There is a gravity difference between the two. Under the action of the gravity difference, the working fluid in the water storage tank enters the steam drum through the connecting pipe. The water level of the water storage tank decreases and the steam drum water level rises.

[0054] As described above, the present invention can be implemented well.

[0055] All features disclosed in all embodiments of this specification, or steps in all methods or processes implied in the disclosure, may be combined and / or extended or replaced in any way, except for mutually exclusive features and / or steps.

[0056] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Based on the technical essence of the present invention, any simple modifications, equivalent substitutions, and improvements made to the above embodiments within the spirit and principles of the present invention shall still fall within the protection scope of the present invention.

Claims

1. A steam drum liquid level regulating system equipped with a water storage device, characterized in that, Includes steam drum (1), water-cooled wall (2), superheater system, inlet water control valve (7), outlet water control valve (8), water storage device (9), and shut-off valve (10); The inlet and outlet of the water-cooled wall (2) are respectively connected to the steam drum (1) to form a loop; The steam space of the steam drum (1) is connected to the superheater system. The water space of the steam drum (1) is connected to the water space of the water storage device (9) through the shut-off valve (10). The steam space of the water storage device (9) is connected to the steam space of the steam drum (1) through the outlet control valve (8). The steam space of the water storage device (9) is connected to the superheater system through the inlet control valve (7). The shut-off valve (10) is normally kept fully open and is only closed in case of an accident to isolate the water storage device (9) from the steam drum (1); The water storage device (9) is placed vertically, and the bottom of the water storage device (9) is located below the -100mm water level of the steam drum (1). When it is necessary to raise the water level of the steam drum, the inlet control valve (7) is closed and the outlet control valve (8) is opened. At this time, the steam space of the water storage tank is connected to the steam space of the steam drum. The pressure of the steam space of the water storage device (9) is equal to that of the steam drum (1). The water level of the water storage tank is higher than that of the steam drum. There is a gravity difference between the two. Under the action of the gravity difference, the working fluid in the water storage tank enters the steam drum through the connecting pipe. The water level of the water storage tank decreases and the steam drum level rises. The connection point between the water inlet control valve (7) and the superheater system is set at the outlet of any stage of superheater. When it is necessary to lower the water level in the steam drum, the water inlet control valve (7) is opened and the water outlet control valve (8) is closed. At this time, the steam space of the water storage tank is connected to the superheater system. The pressure of the steam space of the water storage device (9) is lower than that of the steam drum (1). Under the action of the pressure difference, the working fluid in the steam drum enters the water storage tank through the connecting pipe, the liquid level in the steam drum decreases, and the water level in the water storage tank rises.

2. The steam drum liquid level regulating system equipped with a water storage device according to claim 1, characterized in that, The superheater system includes a ceiling-mounted wall superheater (3), a low-temperature superheater (4), a screen-type superheater (5), and a high-temperature superheater (6) connected in sequence.

3. A steam drum liquid level regulating system equipped with a water storage device according to claim 2, characterized in that, The connection point between the inlet control valve (7) and the superheater system is selectively located after any of the following superheaters: ceiling-mounted wall superheater (3), low-temperature superheater (4), screen-type superheater (5), and high-temperature superheater (6), depending on the required differential pressure value.

4. A steam drum liquid level regulating system equipped with a water storage device according to claim 1, characterized in that, The water storage device (9) is a cylindrical pressure vessel.

5. A method for controlling the liquid level of a steam drum equipped with a water storage device, characterized in that, The steam drum liquid level regulating system equipped with a water storage device as described in any one of claims 1 to 4: When the regulating system does not participate in the steam drum water level regulation, the inlet control valve (7) and the outlet control valve (8) are both in the closed state; When it is necessary to lower the water level of the steam drum (1), open the inlet control valve (7) and close the outlet control valve (8). When it is necessary to raise the water level of the steam drum (1), close the inlet control valve (7) and open the outlet control valve (8).

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