A method and device for controlling the water level in the storage tank of a boiler circulating pump.

Abstract

This invention relates to the field of boiler circulating pump water tank level regulation, and particularly to a method and system for controlling the water level of a boiler circulating pump water tank. The method includes: boiler water intake; starting the boiler circulating pump to establish circulation flow; the boiler entering wet operation; detecting the water level in the boiler's wet water tank and determining whether to activate the automatic regulation system based on the detection result; the automatic regulation system automatically adjusting the water level in the water tank according to the feedwater flow; when the boiler load reaches its maximum load, the boiler switches from wet to dry operation; when the boiler water intake flow is greater than 33% of the BMCR flow and the water tank overflow valve opening is less than 10%, the automatic regulation system is activated; when the boiler is in a wet state, the boiler feedwater main valve is closed, and water is supplied to the boiler by the first bypass electric regulating valve and the second bypass electric regulating valve. By using the parallel-arranged second electric regulating valve to divert the feedwater from the first electric regulating valve, the accuracy of boiler feedwater regulation is improved, ensuring the stability of the water level in the water tank during boiler start-up and shutdown.

Description

Technical Field

[0001] This invention relates to the field of water level regulation in boiler circulating pump water tanks, and particularly to a method and apparatus for controlling the water level in boiler circulating pump water tanks. Background Technology

[0002] This invention relates to the field of boiler circulating pump water tank level regulation. During boiler start-up and shutdown, water level regulation in the boiler circulating pump water tank is typically done manually, requiring a high level of skill. This invention adds a boiler feedwater regulating valve to the existing equipment, which, in conjunction with automatic adjustment of the steam pump outlet pressure, ensures stable water tank levels during wet operation of a once-through boiler. Furthermore, the automatic control method enables precise water level regulation in the water tank under special conditions such as working fluid expansion, steam pressure changes, and feedwater flow rate variations during wet boiler operation. This significantly reduces manual operation, avoids operational risks, ensures unit safety, and lays the foundation for fully automatic feedwater regulation during once-through boiler start-up and shutdown. Summary of the Invention

[0003] The purpose of this invention is to enable precise adjustment of the water level in the storage tank under various operating conditions during boiler wet operation, thereby reducing a large amount of manual operation, avoiding operational risks, and ensuring unit safety.

[0004] To achieve the above objectives, some embodiments of this application provide a method for controlling the water level in a boiler circulating pump storage tank, including:

[0005] Step 1: Fill the boiler with water and start the boiler circulation pump to establish circulation flow;

[0006] Step 2: Boiler wet operation, check the water level in the boiler wet water storage tank and determine whether to start the automatic adjustment system based on the detection results;

[0007] Step 3: The automatic adjustment system automatically adjusts the water level in the storage tank according to the water supply flow rate;

[0008] Step 4: When the boiler load reaches its native load, the boiler switches from wet operation to dry operation;

[0009] Specifically, step 2 involves activating the automatic adjustment system when the boiler feedwater flow rate is greater than 33% of the BMCR flow rate and the overflow valve opening of the water storage tank is less than 10%.

[0010] When the boiler is in a wet state, the main boiler feedwater valve is closed, and water is supplied to the boiler by the first bypass electric regulating valve and the second bypass electric regulating valve.

[0011] In some embodiments of this application, step 3 specifically includes:

[0012] Preset the opening percentage matrix A of the second bypass electric control valve, (A1, A2, A3, A4, A5, A6), where A1 is the first preset percentage of the opening of the second bypass electric control valve; A2 is the second preset percentage of the opening of the second bypass electric control valve; A3 is the third preset percentage of the opening of the second bypass electric control valve; A4 is the fourth preset percentage of the opening of the second bypass electric control valve; A5 is the fifth preset percentage of the opening of the second bypass electric control valve; A6 is the sixth preset percentage of the opening of the second bypass electric control valve; and A1 < A2 < A3 < 20%; 80% < A4 < A5 < A6;

[0013] Preset the switching rate matrix B of the first bypass electric control valve, (B1, B2, B3, B4), where B1 is the first preset value of the switching rate of the first bypass electric control valve, B2 is the second preset value of the switching rate of the first bypass electric control valve, B3 is the third preset value of the switching rate of the first bypass electric control valve, B4 is the fourth preset value of the switching rate of the first bypass electric control valve, and B1 < B2 < B3 < B4;

[0014] Preset the feed water flow of the second bypass electric control valve to be 30% of the real-time flow of the first bypass electric control valve. When the opening percentage of the second bypass electric control valve is greater than 80%, the first bypass electric control valve increases the opening at a set rate to increase the real-time feed water flow by 15%. Determine the real-time switching rate b of the first bypass electric control valve based on the relationship between the opening percentage matrix A of the second bypass electric control valve and the switching rate matrix B of the first bypass electric control valve, that is:

[0015] When the opening percentage a of the second bypass electric control valve is 80% < a < A4, the real-time switching rate b of the first bypass electric control valve is between the first preset value B1 of the switching rate of the first bypass electric control valve and the second preset value, that is B1 < b < B2;

[0016] When the opening percentage a of the second bypass electric control valve is A4 < a < A5, the real-time switching rate b of the first bypass electric control valve is between the second preset value B2 of the switching rate of the first bypass electric control valve and the third preset value, that is B2 < b < B3;

[0017] When the opening percentage a of the second bypass electric control valve is A5 < a < A6, the real-time switching rate b of the first bypass electric control valve is between the third preset value B3 of the switching rate of the first bypass electric control valve and the fourth preset value, that is B3 < b < B4;

[0018] When the opening percentage a of the second bypass electric control valve is A6 < a, the real-time switching rate b of the first bypass electric control valve is greater than the fourth preset value B4 of the switching rate of the first bypass electric control valve, that is B4 < b.

[0019] In some embodiments of the present application, step 3 further includes:

[0020] When the opening percentage of the second bypass electric control valve is less than 20%, the first bypass electric control valve reduces its opening at a set rate to reduce the real-time feed water flow by 15%. The real-time opening and closing rate b of the first bypass electric control valve is determined based on the relationship between the opening percentage matrix A of the second bypass electric control valve and the opening and closing rate matrix B of the first bypass electric control valve, that is:

[0021] When the opening percentage a of the second bypass electric control valve satisfies A3 < a < 20%, the real-time opening and closing rate b of the first bypass electric control valve is between the first preset value B1 and the second preset value of the opening and closing rate of the first bypass electric control valve, that is, B1 < b < B2;

[0022] When the opening percentage a of the second bypass electric control valve satisfies A2 < a < A3, the real-time opening and closing rate b of the first bypass electric control valve is between the second preset value B2 and the third preset value of the opening and closing rate of the first bypass electric control valve, that is, B2 < b < B3;

[0023] When the opening percentage a of the second bypass electric control valve satisfies A1 < a < A2, the real-time opening and closing rate b of the first bypass electric control valve is between the third preset value B3 and the fourth preset value of the opening and closing rate of the first bypass electric control valve, that is, B3 < b < B4;

[0024] When the opening percentage a of the second bypass electric control valve satisfies A1 > a, the real-time opening and closing rate b of the first bypass electric control valve is greater than the fourth preset value B4 of the opening and closing rate of the first bypass electric control valve, that is, B4 < b.

[0025] In some embodiments of the present application, it further includes:

[0026] When the first bypass electric control valve increases its opening, the second bypass electric control valve reduces its opening according to a preset rate;

[0027] When the first bypass electric control valve reduces its opening, the second bypass electric control valve increases its opening according to a preset rate.

[0028] In some embodiments of the present application, the process of regulating the water level in the storage tank in step 3 is specifically as follows:

[0029] A first water level and a second water level are preset. When the water level in the storage tank is higher than the first water level of the storage tank, the overflow valve is automatically opened to reduce the water level. When the water level in the storage tank is lower than the second water level of the storage tank, the overflow valve is automatically closed;

[0030] When the water level in the storage tank fluctuates within the normal range, the water flow controller obtains the feedforward signal and the water level signal, and adjusts the flow rate of the water flow controller based on the feedforward signal and the water level signal.

[0031] In some embodiments of this application, the water level adjustment process in step 3 of the water storage tank further includes:

[0032] When the pressure difference across the feedwater bypass electric regulating valve is less than the first differential pressure value, the first steam pump will increase the feedwater main pipe pressure according to the preset increase rate; when the pressure difference across the feedwater bypass electric regulating valve is greater than the second differential pressure value, the first steam pump will maintain its real-time speed; when the pressure difference across the feedwater bypass electric regulating valve is greater than the third differential pressure value, the first steam pump will decrease the feedwater main pipe pressure according to the preset increase rate; when the pressure difference across the feedwater bypass electric regulating valve is less than the fourth differential pressure value, the first steam pump will maintain its real-time speed.

[0033] In some embodiments of this application, step 4 specifically includes:

[0034] When the boiler load reaches its native load and the differential pressure across the boiler feedwater bypass valve is less than 1 MPa, the second bypass electric valve and the first bypass electric valve are fully opened, the boiler switches from wet to dry operation, and the automatic water level regulation and control system of the boiler wet water storage tank is deactivated.

[0035] In some embodiments of this application, a boiler circulating pump water tank level control device is provided, comprising:

[0036] An overflow valve, connected to the water storage tank, is used to regulate the water level in the tank.

[0037] The first bypass unit is used to supply water to the boiler when the boiler is in a wet state.

[0038] The second bypass unit is used to supply water to the boiler when the boiler is in a wet state.

[0039] The first bypass unit includes:

[0040] The first bypass electric regulating valve is used to control the water supply flow of the first bypass.

[0041] The first flow meter is installed on the pipeline after the first bypass electric regulating valve and is used to measure the water flow rate through the first bypass electric regulating valve.

[0042] The second bypass unit includes:

[0043] The second bypass electric regulating valve is used to control the water supply flow of the second bypass.

[0044] The second flow meter is installed on the pipeline after the second bypass electric regulating valve and is used to measure the water flow rate passing through the second bypass electric regulating valve.

[0045] Some embodiments of this application also include:

[0046] The main water supply switch is connected in parallel with the front and rear pipes of the first bypass electric regulating valve and the front and rear pipes of the second bypass electric regulating valve. The main water supply switch is used to supply water to the boiler.

[0047] Some embodiments of this application also include:

[0048] A steam pump unit is used to control the pressure difference between the front and rear water supply of the first bypass electric regulating valve and the pressure difference between the front and rear water supply of the second bypass electric regulating valve.

[0049] Compared with the prior art, the water level control method and device for a boiler circulating pump storage tank according to an embodiment of the present invention has the following advantages:

[0050] This application improves the accuracy of boiler feedwater regulation by diverting the feedwater from the first electric control valve through a parallel arrangement of the second electric control valve, ensuring the stability of the water level in the storage tank, and assisting the boiler in completing the dry-wet state transition after startup.

[0051] This application comprehensively considers the factors affecting feedwater flow rate, and can cope with changes in feedwater flow rate caused by steam pressure changes and desuperheating water consumption due to oil gun operation, start-up and shutdown, etc. It stabilizes the water level in the storage tank, has strong anti-interference ability, and uses the speed of the operating steam pump to adjust the feedwater pressure. By setting a rate limit, it ensures the stability of feedwater flow rate regulation, reduces a lot of manual operation, avoids operational risks, and ensures the safety of the unit.

[0052] This application can ensure the stability of the water level in the boiler circulating pump storage tank during boiler startup and shutdown, and has strong anti-interference ability. It reduces a lot of manual operation, avoids operational risks, and ensures unit safety. It is applicable to the adjustment of the water level in the boiler circulating pump storage tank of similar units and has a wide range of application prospects. Attached Figure Description

[0053] Figure 1 This is a schematic flowchart of a boiler circulating pump water tank level control method according to an embodiment of this application;

[0054] Figure 2 This is a schematic diagram of a boiler circulating pump water tank level control device according to an embodiment of this application.

[0055] 1 - First bypass electric regulating valve; 2 - Second bypass electric regulating valve; 3 - First flow meter; 4 - Second flow meter; 5 - First steam pump; 6 - Second steam pump; 7 - Steam-water separator; 8 - Water storage tank; 9 - Overflow valve; 10 - Boiler circulating pump. Detailed Implementation

[0056] The specific embodiments of the present invention will be described in further detail below with reference to the accompanying drawings and examples. The following examples are for illustrative purposes only and are not intended to limit the scope of the invention.

[0057] In the description of this application, it should be understood that the terms "center", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", etc., indicating the orientation or position relationship, are based on the orientation or position relationship shown in the accompanying drawings, and are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on this application.

[0058] The terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of the technical features being referred to. Thus, a feature specified as "first" or "second" may explicitly or implicitly include one or more of such features. Throughout this application, unless otherwise specified, "plurality" means two or more.

[0059] In the description of this application, it should be noted that, unless otherwise expressly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection between two components. Those skilled in the art can understand the specific meaning of the above terms in this application based on the specific circumstances.

[0060] like Figure 2 As shown, a preferred embodiment of this application provides a boiler circulating pump 10 and a water storage tank 8 water level control system, including:

[0061] Overflow valve 9 is connected to water storage tank 8 and is used to regulate the water level in water storage tank 8;

[0062] The first bypass unit is used to supply water to the boiler when the boiler is in a wet state.

[0063] The second bypass unit is used to supply water to the boiler when the boiler is in a wet state.

[0064] The first bypass unit includes:

[0065] The first bypass electric regulating valve 1 is used to control the water supply flow of the first bypass.

[0066] The first flow meter 3 is installed on the pipeline after the first bypass electric regulating valve 1 and is used to measure the water flow rate through the first bypass electric regulating valve 1.

[0067] The second bypass unit includes:

[0068] The second bypass electric regulating valve 2 is used to control the water supply flow of the second bypass.

[0069] The second flow meter 4 is installed on the pipeline after the second bypass electric regulating valve 2 and is used to measure the water flow rate through the second bypass electric regulating valve 2.

[0070] Specifically, since a 5% change in the opening of the boiler feedwater regulating valve during feedwater regulation results in a significant change in feedwater flow, greatly affecting the water level in the boiler circulating pump 10 and the water storage tank 8, a second bypass electric regulating valve 2 is installed in parallel with the main boiler feedwater valve, connecting the pipes before and after the first bypass electric regulating valve 1. Flow meters are installed on the pipes after the first bypass electric regulating valve 1 and the second bypass electric regulating valve 2 to measure the feedwater flow through the valves. The sum of the two flow meters is the feedwater flow rate under wet boiler conditions. In wet boiler conditions, the main boiler feedwater valve remains closed, and the boiler is fed water by the first bypass electric regulating valve 1 and the second bypass electric regulating valve 2. The boiler feedwater flow rate is equal to the circulating flow rate at the outlet of the boiler circulating pump 10 and the flow rate from the boiler feedwater pipe. The feedwater flow rate is mainly used to control the water level in the water storage tank 8. The opening of the boiler circulating pump outlet regulating valve is maintained at a certain degree to ensure the minimum circulating flow rate of the boiler, thus guaranteeing the boiler's own flow rate. The circulating flow rate and the water level in the water storage tank 8 should conform to the requirements of a function curve to prevent the circulating pump from sucking in steam. Meanwhile, the opening of the boiler water circulation pump outlet regulating valve is a function of the boiler load; the higher the boiler load, the smaller the opening of the boiler water circulation pump outlet regulating valve.

[0071] Some embodiments of this application also include:

[0072] The steam pump unit is used to control the pressure difference between the front and rear water supply of the first bypass electric regulating valve 1 and the pressure difference between the front and rear water supply of the second bypass electric regulating valve.

[0073] Specifically, during the wet operation of the boiler, the feedwater head is determined by the speed of the operating feedwater pump. Generally, the boiler is equipped with two steam pumps and feedwater pumps. The first steam pump 5 is put into operation, and the second steam pump 6 is rotated and on standby.

[0074] like Figure 1 As shown, a preferred embodiment based on the above examples provides a method for controlling the water level in the storage tank of a boiler circulating pump, which is implemented through the following steps:

[0075] Step 1: Fill the boiler with water and start the boiler circulation pump to establish circulation flow;

[0076] Step 2: Boiler wet operation, check the water level in the boiler wet water storage tank and determine whether to start the automatic adjustment system based on the detection results;

[0077] Step 3: The automatic adjustment system automatically adjusts the water level in the storage tank according to the water supply flow rate;

[0078] Step 4: When the boiler load reaches its native load, the boiler switches from wet operation to dry operation;

[0079] Specifically, step 2 is as follows: when the boiler water flow rate is greater than 33% of the BMCR flow rate and the opening degree of the overflow valve 9 of the water storage tank is less than 10%, the automatic adjustment system is activated.

[0080] When the boiler is in a wet state, the main boiler feedwater valve is closed, and water is supplied to the boiler by the first bypass electric regulating valve 1 and the second bypass electric regulating valve.

[0081] Specifically, after the boiler is filled with water and the boiler circulation pump is started to establish circulation flow, or after the boiler reaches its native load and transitions to a wet state, check that the automatic water level regulation system of the boiler wet storage tank meets the following conditions: the boiler water flow rate is greater than 33% of the BMCR flow rate; the selected steam pump is running and its speed is greater than the specified value; the differential pressure before and after the boiler feedwater bypass electric valve is appropriate; the water level in the storage tank is appropriate; there are no boiler circulation pump tripping conditions; and the opening degree of the storage tank overflow valve 9 is less than 10%.

[0082] Specifically, an automatic water level regulation system for the boiler's wet water storage tank is activated. This system can be switched to manual control at any time; it can be activated to regulate the water level in the storage tank once the automatic activation conditions are met.

[0083] In some embodiments of this application, step 3 specifically includes:

[0084] A preset matrix A, (A1, A2, A3, A4, A5, A6) represents the opening percentage of the second bypass electric regulating door, where A1 is the first preset percentage of the second bypass electric regulating door opening; A2 is the second preset percentage of the second bypass electric regulating door opening; A3 is the third preset percentage of the second bypass electric regulating door opening; A4 is the fourth preset percentage of the second bypass electric regulating door opening; A5 is the fifth preset percentage of the second bypass electric regulating door opening; and A6 is the sixth preset percentage of the second bypass electric regulating door opening; and A1 <A2<A3<20%;80%<A4<A5<A6;

[0085] A preset first bypass electric regulating door opening and closing rate matrix B, (B1, B2, B3, B4), is defined, where B1 is the first preset value for the first bypass electric regulating door opening and closing rate, B2 is the second preset value, B3 is the third preset value, and B4 is the fourth preset value. Furthermore, B1... <B2<B3<B4;

[0086] The preset feedwater flow rate of the second bypass electric control valve is 30% of the real-time flow rate of the first bypass electric control valve. When the opening percentage of the second bypass electric control valve is greater than 80%, the first bypass electric control valve increases its opening degree at a set rate to increase the real-time feedwater flow rate by 15%. The real-time opening and closing rate b of the first bypass electric control valve is determined based on the relationship between the opening percentage matrix A of the second bypass electric control valve and the opening and closing rate matrix B of the first bypass electric control valve, that is:

[0087] When the opening percentage a of the second bypass electric control valve is 80% < a < A4, the real-time opening and closing rate b of the first bypass electric control valve is between the first preset value B1 and the second preset value of the opening and closing rate of the first bypass electric control valve, that is, B1 < b < B2;

[0088] When the opening percentage a of the second bypass electric control valve is A4 < a < A5, the real-time opening and closing rate b of the first bypass electric control valve is between the second preset value B2 and the third preset value of the opening and closing rate of the first bypass electric control valve, that is, B2 < b < B3;

[0089] When the opening percentage a of the second bypass electric control valve is A5 < a < A6, the real-time opening and closing rate b of the first bypass electric control valve is between the third preset value B3 and the fourth preset value of the opening and closing rate of the first bypass electric control valve, that is, B3 < b < B4;

[0090] When the opening percentage a of the second bypass electric control valve is A6 < a, the real-time opening and closing rate b of the first bypass electric control valve is greater than the fourth preset value B4 of the opening and closing rate of the first bypass electric control valve, that is, B4 < b.

[0091] Specifically, the feedwater flow rate of the second bypass electric control valve is designed to be 30% of the current flow rate of the first bypass electric control valve. When the opening of the second bypass electric control valve is greater than 80%, the first bypass electric control valve gradually opens a certain opening degree at a set rate to increase the current feedwater flow rate by 15%. During the opening process of the first bypass electric control valve, the second bypass electric control valve gradually closes to ensure the stability of the water level in the storage tank. When the flow opening of the second bypass electric control valve is less than 20%, the first bypass electric control valve gradually closes a certain opening degree at a set rate to reduce the current feedwater flow rate by 15%. During the closing process of the first bypass electric control valve, the second bypass electric control valve gradually opens to ensure the stability of the water level in the storage tank.

[0092] In some embodiments of the present application, step 3 further includes:

[0093] When the opening percentage of the second bypass electric control valve is less than 20%, the first bypass electric control valve reduces its opening at a set rate to decrease the real-time feed water flow by 15%. The real-time opening and closing rate b of the first bypass electric control valve is determined based on the relationship between the opening percentage matrix A of the second bypass electric control valve and the opening and closing rate matrix B of the first bypass electric control valve, that is:

[0094] When the opening percentage a of the second bypass electric control valve satisfies A3 < a < 20%, the real-time opening and closing rate b of the first bypass electric control valve is between the first preset value B1 and the second preset value of the opening and closing rate of the first bypass electric control valve, that is, B1 < b < B2;

[0095] When the opening percentage a of the second bypass electric control valve satisfies A2 < a < A3, the real-time opening and closing rate b of the first bypass electric control valve is between the second preset value B2 and the third preset value of the opening and closing rate of the first bypass electric control valve, that is, B2 < b < B3;

[0096] When the opening percentage a of the second bypass electric control valve satisfies A1 < a < A2, the real-time opening and closing rate b of the first bypass electric control valve is between the third preset value B3 and the fourth preset value of the opening and closing rate of the first bypass electric control valve, that is, B3 < b < B4;

[0097] When the opening percentage a of the second bypass electric control valve satisfies A1 > a, the real-time opening and closing rate b of the first bypass electric control valve is greater than the fourth preset value B4 of the opening and closing rate of the first bypass electric control valve, that is, B4 < b.

[0098] Specifically,

[0099] In some embodiments of the present application, it further includes:

[0100] When the first bypass electric control valve increases its opening, the second bypass electric control valve reduces its opening according to a preset rate;

[0101] When the first bypass electric control valve reduces its opening, the second bypass electric control valve increases its opening according to a preset rate.

[0102] Specifically, after the boiler is started, as the steam volume increases, the boiler feed water flow also becomes larger. The opening trend of the second bypass regulating valve of the boiler feed water is a cyclic switching process of opening first and then closing, and the opening trend of the first bypass regulating valve of the boiler feed water remains steadily increasing. After the boiler load is reduced and it changes from the dry state to the wet state, as the steam volume decreases, the boiler feed water flow also becomes smaller. The opening trend of the second bypass regulating valve of the boiler feed water is a cyclic switching process of closing first and then opening, and the opening trend of the first bypass regulating valve of the boiler feed water remains steadily decreasing.

[0103] In some embodiments of the present application, the process of regulating the water level in the storage tank in step 3 is specifically as follows:

[0104] The system presets a first water level and a second water level. When the water level in the storage tank is higher than the first water level, the overflow valve 9 is automatically opened to lower the water level. When the water level in the storage tank is lower than the second water level, the overflow valve 9 is automatically closed.

[0105] When the water level in the storage tank fluctuates within the normal range, the flow controller acquires the feedforward signal and the water level signal, and adjusts the flow rate of the flow controller based on the feedforward signal and the water level signal.

[0106] Specifically, the feedforward signals include the steam-water separator outlet pressure, steam-water separator water level changes, boiler fuel (oil and coal) changes, and boiler desuperheating water flow rate changes.

[0107] Specifically, when the steam-water separator outlet pressure rise rate is higher than the first rise rate, the steam-water separator water level drop rate is higher than the first drop rate of the separator, the boiler fuel increase is greater than the first fuel change, the boiler desuperheating water flow increase is greater than the first desuperheating water change, and the water tank level drop rate is higher than the first drop rate of the water tank, all feedforward signals and water level signals act on the feedwater flow controller to increase the flow rate and raise the water tank level. When the steam-water separator outlet pressure drop rate is higher than the first drop rate, the steam-water separator water level rise rate is higher than the first rise rate of the separator, the boiler fuel decrease is greater than the second fuel change, the boiler desuperheating water flow decrease is greater than the second desuperheating water change, and the water tank level rise rate is higher than the first rise rate of the water tank, all feedforward signals and water level signals act on the feedwater flow controller to reduce the flow rate and lower the water tank level.

[0108] Specifically, when the rate of change of the steam-water separator outlet pressure, steam-water separator water level, boiler fuel (oil and coal quantity), and boiler desuperheating water quantity are too large, causing the water level in the storage tank to exceed the limit, the rate of change of each variable serves as a feedforward signal for the regulator. The opening of the first bypass electric regulating valve and the second bypass electric regulating valve are automatically adjusted according to different regulation rates. The second bypass regulating valve is quickly opened to 80% or closed to 20% and then remains stationary. The first bypass electric regulating valve performs coarse adjustment of the water level in the storage tank based on the rapid change in the water level. When the rate of change of the steam-water separator outlet pressure, steam-water separator water level, boiler fuel (oil and coal quantity), and boiler desuperheating water quantity are lower than a certain value, the second bypass electric regulating valve and the first bypass electric regulating valve participate in the fine regulation of the water level in the storage tank according to the normal regulation procedure to ensure the stability of the water level in the storage tank.

[0109] In some embodiments of this application, the water level adjustment process in step 3 of the water storage tank further includes:

[0110] When the pressure difference across the feedwater bypass electric regulating valve is less than the first differential pressure value, the first steam pump will increase the feedwater main pipe pressure according to the preset increase rate; when the pressure difference across the feedwater bypass electric regulating valve is greater than the second differential pressure value, the first steam pump will maintain its real-time speed; when the pressure difference across the feedwater bypass electric regulating valve is greater than the third differential pressure value, the first steam pump will decrease the feedwater main pipe pressure according to the preset increase rate; when the pressure difference across the feedwater bypass electric regulating valve is less than the fourth differential pressure value, the first steam pump will maintain its real-time speed.

[0111] Specifically, during wet operation of the boiler, the feedwater head is determined by the operating speed of the feedwater pump. Generally, the boiler is equipped with two steam pumps and feedwater pumps. The first steam pump is in operation, and the second steam pump is rotating and on standby. Since the boiler feedwater is throttled and reduced to the boiler circulating pump outlet pressure through the feedwater bypass electric regulating valve, it is necessary to ensure that the feedwater pressure difference before and after the feedwater bypass electric regulating valve is greater than the first differential pressure value during operation. When the feedwater pressure difference before and after the feedwater bypass electric regulating valve is less than the first differential pressure value and after a certain delay, the first steam pump will automatically increase the feedwater header pressure at a certain rate. When the feedwater pressure difference before and after the feedwater bypass electric regulating valve is greater than the second differential pressure value, the first steam pump will remain at its current speed to ensure that the boiler has sufficient feedwater margin. When the pressure difference between the feedwater bypass electric regulating valve and the feedwater supply is greater than the third differential pressure value and after a certain delay, the first steam pump will automatically reduce the pressure of the feedwater main pipe at a certain rate. When the pressure difference between the feedwater bypass electric regulating valve and the feedwater supply is less than the fourth differential pressure value, the first steam pump will remain at its current speed to prevent the feedwater bypass regulating valve from becoming unstable due to excessively small throttling opening, and also to reduce the power consumption of the steam pump.

[0112] In some embodiments of this application, step 4 specifically includes;

[0113] During the startup process of a DC boiler, when the boiler load reaches its native load and the differential pressure before and after the boiler feedwater bypass valve is less than 1 MPa, the second bypass electric valve and the first bypass electric valve are fully opened, the boiler switches from wet to dry operation, and the automatic water level regulation and control system of the boiler wet water storage tank is deactivated.

[0114] During the shutdown process of a DC boiler, after the boiler load is reduced from dry to wet state, the automatic water level regulation and control system of the boiler wet water tank is activated to control the water level of the water tank to be reasonable. After the boiler trips, the steam pump trips, the first bypass electric regulating valve of the boiler feedwater, the first bypass electric regulating valve and the main power valve of the boiler feedwater automatically close, and the automatic water level regulation and control system of the boiler wet water tank automatically deactivates.

[0115] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and substitutions can be made without departing from the technical principles of the present invention, and these improvements and substitutions should also be considered within the scope of protection of the present invention.

Claims

1. A method for controlling the water level in the storage tank of a boiler circulating pump, characterized in that, Including: Step 1: Fill water into the boiler and start the boiler circulation pump to establish a circulation flow rate. Step 2: Operate the boiler in the wet state, detect the water level in the wet-state storage tank of the boiler, and determine whether to start the automatic regulation system according to the detection result. Step 3: The automatic regulation system automatically regulates the water level in the storage tank according to the feed water flow rate. Step 4: When the boiler load reaches the Benson load, the boiler changes from wet-state operation to dry-state operation. Among them, Step 2 is specifically: when the feed water flow rate of the boiler is greater than 33% of the BMCR flow rate and the opening degree of the overflow valve of the storage tank is less than 10%, start the automatic regulation system. When the boiler is in the wet state, the main electric valve of the boiler feed water is closed, and the boiler is filled with water by the first bypass electric regulating valve and the second bypass electric regulating valve. The main electric valve of the feed water is connected in parallel with the front and rear pipelines of the first bypass electric regulating valve and the front and rear pipelines of the second bypass electric regulating valve, and the main electric valve of the feed water is used to fill water into the boiler. The specific content of Step 3 is as follows: Preset the opening percentage matrix A of the second bypass electric regulating valve, (A1, A2, A3, A4, A5, A6), where A1 is the first preset percentage of the opening degree of the second bypass electric regulating valve; A2 is the second preset percentage of the opening degree of the second bypass electric regulating valve; A3 is the third preset percentage of the opening degree of the second bypass electric regulating valve; A4 is the fourth preset percentage of the opening degree of the second bypass electric regulating valve; A5 is the fifth preset percentage of the opening degree of the second bypass electric regulating valve; A6 is the sixth preset percentage of the opening degree of the second bypass electric regulating valve; and A1 < A2 < A3 < 20%; 80% < A4 < A5 < A6. Preset the switching rate matrix B of the first bypass electric regulating valve, (B1, B2, B3, B4), where B1 is the first preset value of the switching rate of the first bypass electric regulating valve, B2 is the second preset value of the switching rate of the first bypass electric regulating valve, B3 is the third preset value of the switching rate of the first bypass electric regulating valve, B4 is the fourth preset value of the switching rate of the first bypass electric regulating valve, and B1 < B2 < B3 < B4. Preset that the feed water flow rate of the second bypass electric regulating valve is 30% of the real-time flow rate of the first bypass electric regulating valve. When the opening percentage of the second bypass electric regulating valve is greater than 80%, the first bypass electric regulating valve increases the opening degree at a set rate to increase the real-time feed water flow rate by 15%. Determine the real-time switching rate b of the first bypass electric regulating valve based on the relationship between the opening percentage matrix A of the second bypass electric regulating valve and the switching rate matrix B of the first bypass electric regulating valve, that is: When the opening percentage a of the second bypass electric regulating valve is 80% < a < A4, the real-time switching rate b of the first bypass electric regulating valve is between the first preset value B1 of the switching rate of the first bypass electric regulating valve and the second preset value, that is, B1 < b < B2. When the opening percentage a of the second bypass electric regulating valve is A4 < a < A5, the real-time switching rate b of the first bypass electric regulating valve is between the second preset value B2 of the switching rate of the first bypass electric regulating valve and the third preset value, that is, B2 < b < B3. When the opening percentage a of the second bypass electric control valve satisfies A5 < a < A6, the real-time opening and closing rate b of the first bypass electric control valve is between the third preset value B3 and the fourth preset value of the opening and closing rate of the first bypass electric control valve, that is, B3 < b < B4; When the opening percentage a of the second bypass electric control valve satisfies A6 < a, the real-time opening and closing rate b of the first bypass electric control valve is greater than the fourth preset value B4 of the opening and closing rate of the first bypass electric control valve, that is, B4 < b; Step 3 further includes: When the opening percentage of the second bypass electric control valve is less than 20%, the first bypass electric control valve reduces its opening at a set rate to reduce the real-time feed water flow by 15%. The real-time opening and closing rate b of the first bypass electric control valve is determined based on the relationship between the opening percentage matrix A of the second bypass electric control valve and the opening and closing rate matrix B of the first bypass electric control valve, that is: When the opening percentage a of the second bypass electric control valve satisfies A3 < a < 20%, the real-time opening and closing rate b of the first bypass electric control valve is between the first preset value B1 and the second preset value of the opening and closing rate of the first bypass electric control valve, that is, B1 < b < B2; When the opening percentage a of the second bypass electric control valve satisfies A2 < a < A3, the real-time opening and closing rate b of the first bypass electric control valve is between the second preset value B2 and the third preset value of the opening and closing rate of the first bypass electric control valve, that is, B2 < b < B3; When the opening percentage a of the second bypass electric control valve satisfies A1 < a < A2, the real-time opening and closing rate b of the first bypass electric control valve is between the third preset value B3 and the fourth preset value of the opening and closing rate of the first bypass electric control valve, that is, B3 < b < B4; When the opening percentage a of the second bypass electric control valve satisfies A1 > a, the real-time opening and closing rate b of the first bypass electric control valve is greater than the fourth preset value B4 of the opening and closing rate of the first bypass electric control valve, that is, B4 < b; It further includes: When the first bypass electric control valve increases its opening, the second bypass electric control valve reduces its opening at a preset rate; When the first bypass electric control valve reduces its opening, the second bypass electric control valve increases its opening at a preset rate; After the boiler is started, as the steam flow increases, the boiler feed water flow also increases. The opening trend of the second bypass control valve of the boiler feed water is a cyclic switching process of opening first and then closing. The opening of the first bypass control valve of the boiler feed water maintains a stable increasing trend. After the boiler load is reduced from the dry state to the wet state, as the steam flow decreases, the boiler feed water flow also decreases. The opening trend of the second bypass control valve of the boiler feed water is a cyclic switching process of closing first and then opening. The opening of the first bypass control valve of the boiler feed water maintains a stable decreasing trend.

2. The boiler circulating pump water tank level control method as described in claim 1, characterized in that, The specific process of regulating the water level in the storage tank in Step 3 is as follows: Preset the first water level and the second water level. When the water level in the storage tank is higher than the first water level of the storage tank, the overflow valve is automatically opened to lower the water level. When the water level in the storage tank is lower than the second water level of the storage tank, the overflow valve is automatically closed; When the water level in the storage tank fluctuates within the normal range, the water flow controller obtains the feedforward signal and the water level signal, and adjusts the flow rate of the water flow controller based on the feedforward signal and the water level signal.

3. The boiler circulating pump water tank level control method as described in claim 1, characterized in that, Step 4 specifically includes: When the boiler load reaches its native load and the differential pressure across the boiler feedwater bypass valve is less than 1 MPa, the second bypass electric valve and the first bypass electric valve are fully opened, the boiler switches from wet to dry operation, and the automatic water level regulation and control system of the boiler wet water storage tank is deactivated.

4. A boiler circulating pump water tank level control device, employing the boiler circulating pump water tank level control method according to any one of claims 1-3, characterized in that, include: An overflow valve, connected to the water storage tank, is used to regulate the water level in the tank. The first bypass unit is used to supply water to the boiler when the boiler is in a wet state. The second bypass unit is used to supply water to the boiler when the boiler is in a wet state. The first bypass unit includes: The first bypass electric regulating valve is used to control the water supply flow of the first bypass. The first flow meter is installed on the pipeline after the first bypass electric regulating valve and is used to measure the water flow rate through the first bypass electric regulating valve. The second bypass unit includes: The second bypass electric regulating valve is used to control the water supply flow of the second bypass. The second flow meter is installed on the pipeline after the second bypass electric regulating valve and is used to measure the water flow rate through the second bypass electric regulating valve. The main water supply switch is connected in parallel with the front and rear pipes of the first bypass electric regulating valve and the front and rear pipes of the second bypass electric regulating valve. The main water supply switch is used to supply water to the boiler.

5. The boiler circulating pump water tank level control device as described in claim 4, characterized in that, Also includes: A steam pump unit is used to control the pressure difference between the front and rear water supply of the first bypass electric regulating valve and the pressure difference between the front and rear water supply of the second bypass electric regulating valve.

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