A gas-steam boiler tail gas waste heat recycling regulation system

Abstract

The application discloses a kind of gas steam boiler tail gas waste heat recycling regulation and control system, it includes: low-pressure steam pocket;Water supply pump is used to water supplement in low-pressure steam pocket;Flue gas temperature monitor is used to monitor the flue gas temperature value of the tail of boiler in real time;Water level monitor is used to monitor the water level value in low-pressure steam pocket in real time;Hot water heater is connected between water supply pump and low-pressure steam pocket, for using the flue gas waste heat of the tail of boiler to preheat water body before entering low-pressure steam pocket;Water temperature monitor is used to monitor the water body temperature value at hot water heater outlet in real time;Control unit is used to comprehensively regulate and control the water body flow that is preheated by hot water heater according to the data collected by instrument.The water supplement of low-pressure steam pocket is heated by hot water heater before being sent into low-pressure steam pocket to continue to carry out steam-water circulation, which can reduce the flue gas temperature of boiler, improve the thermal efficiency of boiler, and the water body flow that needs to be preheated can also be accurately regulated and controlled by control unit using relevant data.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of boiler equipment, in particular to a gas-steam boiler tail gas waste heat recycling regulation system. BACKGROUND

[0002] In the actual operation process of the gas turbine power plant, since the fuel burned is natural gas, the fuel is relatively clean and pure, almost no sulfur, and the combustion temperature in the operation is reasonably controlled, the NOX emission of the gas turbine is relatively low, and the possibility of low-temperature acid mist corrosion caused by exhaust smoke is relatively small. Since the last stage heat exchange module of the boiler of the gas-steam combined cycle back pressure unit is a hot water heater, the hot water heater is designed to heat the boiler tail flue gas waste heat to supply hot water outside. At present, there is no hot water supply demand, and the hot water heater has been in idle standby state.

[0003] After the gas-steam combined cycle back pressure unit is started, the boiler exhaust smoke temperature reaches 150 DEG C, compared with the boiler design exhaust smoke temperature of 90 DEG C, the boiler exhaust smoke temperature is relatively high, the exhaust smoke heat loss is relatively large, and the boiler thermal efficiency is reduced, therefore, the exhaust smoke temperature has a large enough reduction space. If this part of heat is not reasonably utilized, it will cause large gas consumption and energy waste. SUMMARY

[0004] The technical problem to be solved by the present application is that the prior art cannot reasonably utilize the heat of the boiler exhaust smoke, causing large energy loss.

[0005] In order to solve the above technical problems, the present application provides a gas-steam boiler tail gas waste heat recycling regulation system, comprising:

[0006] A low-pressure steam drum;

[0007] A feed water pump arranged at the water inlet end of the low-pressure steam drum, the feed water pump being used to supplement water into the low-pressure steam drum;

[0008] A flue gas temperature monitor arranged at the tail of the boiler, the temperature detection device being used to monitor the flue gas temperature value of the tail of the boiler in real time;

[0009] A water level monitor arranged in the low-pressure steam drum, the water level monitor being used to monitor the water level value in the low-pressure steam drum in real time;

[0010] A hot water heater connected between the feed water pump and the low-pressure steam drum, the hot water heater being used to preheat the water body before entering the low-pressure steam drum by using the flue gas waste heat of the tail of the boiler;

[0011] A water body temperature monitor arranged at the water outlet of the hot water heater, the water body temperature monitor being used to monitor the water body temperature value at the water outlet of the hot water heater in real time;

[0012] A control unit is electrically connected with the flue gas temperature monitor, the water body temperature monitor, the water level monitor, and the water supply pump, and is configured to comprehensively regulate the water flow preheated by the hot water heater according to the data collected by the flue gas temperature monitor, the water body temperature monitor, and the water level monitor.

[0013] Further, the control unit comprises:

[0014] An acquisition module is connected with the flue gas temperature monitor, the water body temperature monitor, and the water level monitor, and is configured to acquire the data parameters of the flue gas temperature monitor, the water body temperature monitor, and the water level monitor, and transmit the data parameters to a processing module;

[0015] The processing module is connected with the acquisition module, and is configured to set the working state instruction of the water supply pump according to the data parameters;

[0016] A control module is connected with the processing module, and is configured to adjust the output flow of the water supply pump according to the working state instruction.

[0017] Further, the acquisition module is configured to acquire the flue gas temperature value △g of the tail part of the boiler, and the control module is configured to control the water supply pump;

[0018] The processing module is configured to set a preset flue gas temperature value g0, and is further configured to set a first preset flue gas temperature difference g1, a second preset flue gas temperature difference g2, a third preset flue gas temperature difference g3, and a fourth preset flue gas temperature difference g4, and g1

[0019] The processing module is further configured to select a preset output flow ai as the output flow of the water supply pump according to the difference between the acquired flue gas temperature value △g and the preset flue gas temperature value g0;

[0020] When △g-g0≤g1, the first preset output flow a1 is selected as the output flow of the water supply pump;

[0021] When g1<△g-g0≤g2, the second preset output flow a2 is selected as the output flow of the water supply pump;

[0022] When g2<△g-g0≤g3, the third preset output flow a3 is selected as the output flow of the water supply pump;

[0023] when g3 < Δg - g0≤ g4, the fourth preset output flow a4 is selected as the output flow of the feed water pump;

[0024] wherein, when the ith preset output flow ai is selected as the output flow of the feed water pump, the control module controls the feed water pump to work at the ith preset output flow, i = 1, 2, 3, 4.

[0025] Further, the acquisition module is configured to acquire a water temperature value ΔB at the outlet of the hot water heater, and the processing module is configured to determine whether the acquired water temperature value ΔB at the outlet of the hot water heater exceeds a preset water temperature value.

[0026] If the water temperature value ΔB at the outlet of the hot water heater exceeds the preset water temperature value, it indicates that the output flow of the water preheated by the hot water heater is appropriate, and the output flow of the feed water pump does not need to be corrected.

[0027] If the water temperature value ΔB at the outlet of the hot water heater does not exceed the preset water temperature value, it indicates that the output flow of the water preheated by the hot water heater is not appropriate, and the output flow of the feed water pump needs to be corrected.

[0028] Further, if the water temperature value ΔB at the outlet of the hot water heater exceeds the preset water temperature value, it indicates that the output flow of the water preheated by the hot water heater is not appropriate, and the output flow of the feed water pump needs to be corrected, including:

[0029] The acquisition module is configured to acquire a water temperature value ΔB at the outlet of the hot water heater, and the processing module is configured to pre-set a first preset water temperature value B1, a second preset water temperature value B2, a third preset water temperature value B3 and a fourth preset water temperature value B4, and B1 > B2 > B3 > B4; pre-set a first preset first correction coefficient x1, a second preset first correction coefficient x2, a third preset first correction coefficient x3 and a fourth preset first correction coefficient x4, and 1 > x1 > x2 > x3 > x4 > 0.7.

[0030] The processing module is further configured to correct the output flow of the feed water pump according to the relationship between the acquired water temperature value ΔB at the outlet of the hot water heater and each preset water temperature value Bi.

[0031] When B1 ≥ ΔB > B2, the first preset first correction coefficient x1 is selected to correct the output flow of the feed water pump, and the corrected output flow of the feed water pump is ai * x1.

[0032] When B2≥△B>B3, the second preset first correction coefficient x2 is selected to correct the output flow of the feed water pump, and the corrected output flow of the feed water pump is ai*x2;

[0033] When B3≥△B>B4, the third preset first correction coefficient x3 is selected to correct the output flow of the feed water pump, and the corrected output flow of the feed water pump is ai*x3;

[0034] When B4≥△B, the fourth preset first correction coefficient x4 is selected to correct the output flow of the feed water pump, and the corrected output flow of the feed water pump is ai*x4.

[0035] Further, the processing module is configured to correct the output flow ai of the feed water pump by selecting the i-th preset first correction coefficient xi, and the acquisition module is configured to acquire the corrected output flow ai*xi of the feed water pump, i=1, 2, 3, 4;

[0036] The acquisition module is configured to acquire the water level value △A in the low-pressure steam pocket, and the processing module is configured to pre-set a first preset water level value A1 in the low-pressure steam pocket, a second preset water level value A2 in the low-pressure steam pocket, a third preset water level value A3 in the low-pressure steam pocket, and a fourth preset water level value A4 in the low-pressure steam pocket, and A1

[0037] The processing module is further configured to correct the corrected output flow ai*xi of the feed water pump again according to the relationship between the acquired water level value △A in the low-pressure steam pocket and each preset water level value Ai in the low-pressure steam pocket:

[0038] When A1<△A≤A2, the first preset pressure correction coefficient y1 is selected to correct the output flow ai*xi of the feed water pump again, and the corrected output flow of the feed water pump is ai*xi*y1;

[0039] When A2<△A≤A3, the second preset pressure correction coefficient y2 is selected to correct the output flow ai*xi of the feed water pump again, and the corrected output flow of the feed water pump is ai*xi*y2;

[0040] When A3<△A≤A4, the third preset pressure correction coefficient y3 is selected to correct the output flow ai*xi of the feed water pump again, and the corrected output flow of the feed water pump is ai*xi*y3;

[0041] When A4 < delta A, the fourth preset pressure correction coefficient y4 is selected to correct the output flow ai*xi of the feed water pump again, and the output flow of the feed water pump after the second correction is ai*xi*y4.

[0042] Further, the hot water heater is connected between the feed water pump and the low-pressure steam drum through an external water supply pipe.

[0043] Further, the acquisition module is connected with the flue gas temperature monitor, the water temperature monitor and the water level monitor in a wireless manner.

[0044] Compared with the prior art, the gas-steam boiler tail gas waste heat recycling regulation system has the beneficial effects that:

[0045] In the application, the water supplement of the low-pressure steam drum is heated by the hot water heater and then sent to the low-pressure steam drum to continue the steam-water circulation, so that the exhaust gas temperature of the boiler is reduced, the waste heat of the boiler tail gas is recycled twice, the thermal efficiency of the boiler is improved, and the water flow to be preheated can be accurately regulated by the control unit according to the related data and the water flow to be preheated can be adjusted in real time according to the changing flue gas temperature, so that the waste heat of the flue gas can be accurately utilized by the water flow, and the energy waste is reduced. BRIEF DESCRIPTION OF DRAWINGS

[0046] Figure 1 is a composition schematic diagram of the gas-steam boiler tail gas waste heat recycling regulation system in the embodiment of the application;

[0047] Figure 2 is a composition schematic diagram of the control unit of the gas-steam boiler tail gas waste heat recycling regulation system in the embodiment of the application;

[0048] Figure 3 is a connection schematic diagram of the control unit of the gas-steam boiler tail gas waste heat recycling regulation system in the embodiment of the application. DETAILED DESCRIPTION

[0049] The specific embodiments of the application will be further described in detail below with reference to the drawings and examples. The following examples are used to illustrate the application, but not to limit the scope of the application.

[0050] In the description of the present application, it needs to be understood that the terms "center", "upper", "lower", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer" and the like indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings, and are only for the convenience of describing the present application and simplifying the description, and do not indicate or imply that the device or element referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as a limitation on the present application.

[0051] The terms "first", "second" are only for descriptive purpose, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of the technical features indicated. Therefore, the features defined with "first", "second" can explicitly or implicitly include one or more of the features. In the description of the present application, unless otherwise specified and limited, the meaning of "a plurality of" is two or more.

[0052] In the description of the present application, it needs to be explained that, unless otherwise explicitly specified and limited, the terms "mounting", "connecting", "connection" should be understood broadly, for example, it can be fixed connection, or detachable connection, or integral connection; it can be mechanical connection, or electrical connection; it can be direct connection, or indirect connection through intermediate medium, or internal communication of two elements. For those skilled in the art, the specific meaning of the above terms in the present application can be understood according to the specific circumstances.

[0053] In the production process of large power plants at home and abroad, it is generally adopted to reduce the boiler exhaust gas temperature as much as possible, reduce the boiler exhaust loss, which is one of the important means to improve the thermal efficiency of the unit. Controlling the reasonable exhaust gas temperature can not only make full use of the waste heat of boiler tail smoke, but also effectively prevent acid mist corrosion, which has very important practical significance for the economy and safety of the unit.

[0054] As Figure 1As shown in the embodiments of this application, a waste heat recovery and control system for gas-fired steam boiler exhaust gas is provided, comprising: a low-pressure steam drum; a feedwater pump disposed at the water inlet of the low-pressure steam drum, the feedwater pump being used to replenish water into the low-pressure steam drum; a flue gas temperature monitor disposed at the tail end of the boiler, the temperature detection device being used to monitor the flue gas temperature value at the tail end of the boiler in real time; a water level monitor disposed inside the low-pressure steam drum, the water level monitor being used to monitor the water level value inside the low-pressure steam drum in real time; and a hot water heater connected between the feedwater pump and the low-pressure steam drum, the hot water heater being used to... The heater is used to preheat the water before it enters the low-pressure steam drum using the waste heat of the flue gas at the tail end of the boiler; a water temperature monitor is installed at the outlet of the hot water heater, and the water temperature monitor is used to monitor the water temperature at the outlet of the hot water heater in real time; a control unit is electrically connected to the flue gas temperature monitor, the water temperature monitor, the water level monitor, and the feed water pump, and the control unit is used to comprehensively regulate the flow rate of the water preheated by the hot water heater based on the data collected by the flue gas temperature monitor, the water temperature monitor, and the water level monitor.

[0055] Furthermore, by first heating the makeup water from the low-pressure steam drum in the hot water heater before sending it back into the low-pressure steam drum to continue the steam-water circulation, the boiler's flue gas temperature can be reduced, enabling the secondary utilization of waste heat from the boiler's tail flue gas. This also improves the boiler's thermal efficiency. Moreover, the control unit can use relevant data to precisely regulate the flow rate of the water to be preheated, adjusting the flow rate of the water to be preheated in real time based on the changing flue gas temperature. This ensures that the waste heat energy of the flue gas is precisely utilized by the makeup water flow, reducing energy waste.

[0056] like Figure 2 As shown in Figure 3, in an embodiment of this application, a waste heat recovery and control system for gas-fired steam boiler exhaust gas is provided. The control unit includes: a data acquisition module connected to the flue gas temperature monitor, water temperature monitor, and water level monitor, respectively, the data acquisition module being used to acquire data parameters from the flue gas temperature monitor, water temperature monitor, and water level monitor, and transmit the data parameters to the processing module; a processing module connected to the data acquisition module, the processing module being used to set the operating state command of the feedwater pump according to the data parameters; and a control module connected to the processing module, the control module being used to adjust the output flow rate of the feedwater pump according to the operating state command.

[0057] In an embodiment of this application, a waste heat recovery and control system for flue gas from a gas-fired steam boiler is provided. The acquisition module is used to acquire the flue gas temperature value Δg at the tail end of the boiler, and the control module is used to control the feedwater pump.

[0058] The processing module is configured to set a preset flue gas temperature value g0, and set a first preset flue gas temperature difference g1, a second preset flue gas temperature difference g2, a third preset flue gas temperature difference g3, and a fourth preset flue gas temperature difference g4, and g1 < g2 < g3 < g4; the processing module is further configured to set a first preset feed water pump output flow a1, a second preset feed water pump output flow a2, a third preset feed water pump output flow a3, and a fourth preset feed water pump output flow a4, wherein a1 < a2 < a3 < a4.

[0059] The processing module is further configured to select a preset output flow ai as the output flow of the feed water pump according to the difference between the collected flue gas temperature value and the preset flue gas temperature value g0.

[0060] When Δg-g0≤g1, the first preset output flow a1 is selected as the output flow of the feed water pump.

[0061] When g1 < Δg-g0≤g2, the second preset output flow a2 is selected as the output flow of the feed water pump.

[0062] When g2 < Δg-g0≤g3, the third preset output flow a3 is selected as the output flow of the feed water pump.

[0063] When g3 < Δg-g0≤g4, the fourth preset output flow a4 is selected as the output flow of the feed water pump.

[0064] When the i-th preset output flow ai is selected as the output flow of the feed water pump, the control module controls the feed water pump to work at the i-th preset output flow, i = 1, 2, 3, 4.

[0065] Specifically, since the flue gas temperature value changes constantly each time, and is not fixed, the output flow of the feed water pump is selected according to the difference between the collected flue gas temperature value and the preset flue gas temperature value, so that the waste heat of the flue gas can be accurately utilized in the hot water heater, and the hot water heater is preheated by selecting an appropriate output flow of the feed water pump, thereby improving the utilization efficiency of heat. By using this method, the boiler exhaust loss can be reduced to about 90℃ of the design value, and the boiler thermal efficiency can be improved from the current 78% to 87%.

[0066] In the embodiment of the present application, a gas steam boiler tail gas waste heat recycling regulation system is provided. The collection module is used to acquire the water temperature value △B at the outlet of the hot water heater. The processing module is used to determine whether the water temperature value △B at the outlet of the hot water heater exceeds the preset water temperature value. If the water temperature value △B at the outlet of the hot water heater exceeds the preset water temperature value, it indicates that the output flow of the water preheated by the hot water heater is appropriate, and the output flow of the feed water pump does not need to be corrected. If the water temperature value △B at the outlet of the hot water heater does not exceed the preset water temperature value, it indicates that the output flow of the water preheated by the hot water heater is not appropriate, and the output flow of the feed water pump needs to be corrected.

[0067] Specifically, in the process of preheating the water flow by the hot water heater, if the water temperature value at the outlet of the hot water heater does not reach the preset water temperature value, the output flow of the feed water pump needs to be corrected, so that the water temperature value heated by the hot water heater can reach a certain temperature, thereby reducing the exhaust gas temperature of the boiler and improving the secondary utilization efficiency of the flue gas waste heat.

[0068] In the embodiment of the present application, a gas steam boiler tail gas waste heat recycling regulation system is provided. If the water temperature value △B at the outlet of the hot water heater exceeds the preset water temperature value, it indicates that the output flow of the water preheated by the hot water heater is not appropriate, and the output flow of the feed water pump needs to be corrected, including:

[0069] The collection module is used to acquire the water temperature value △B at the outlet of the hot water heater. The processing module is used to pre-set a first preset water temperature value B1, a second preset water temperature value B2, a third preset water temperature value B3, and a fourth preset water temperature value B4, and B1>B2>B3>B4. A first preset correction coefficient x1, a second preset correction coefficient x2, a third preset correction coefficient x3, and a fourth preset correction coefficient x4 are pre-set, and 1>x1>x2>x3>x4>0.7.

[0070] The processing module is further used to correct the output flow of the feed water pump according to the relationship between the water temperature value △B at the outlet of the hot water heater and each preset water temperature value Bi.

[0071] When B1≥△B>B2, the first preset correction coefficient x1 is selected to correct the output flow of the feed water pump, and the corrected output flow of the feed water pump is ai*x1.

[0072] When B2≥△B>B3, a second preset first correction coefficient x2 is selected to correct the output flow of the feed water pump, and the corrected output flow of the feed water pump is ai*x2;

[0073] When B3≥△B>B4, a third preset first correction coefficient x3 is selected to correct the output flow of the feed water pump, and the corrected output flow of the feed water pump is ai*x3;

[0074] When B4≥△B, a fourth preset first correction coefficient x4 is selected to correct the output flow of the feed water pump, and the corrected output flow of the feed water pump is ai*x4.

[0075] Specifically, by correcting the output flow of the feed water pump according to the relationship between the water temperature value at the outlet of the hot water heater and each preset water temperature value, the accuracy of the output flow of the feed water pump can be improved.

[0076] In the embodiment of the present application, a gas-steam boiler tail gas waste heat recycling control system is provided, the processing module is used to correct the output flow ai of the feed water pump by selecting the i-th preset first correction coefficient xi, and the acquisition module is used to obtain the corrected output flow ai*xi of the feed water pump, i=1, 2, 3, 4;

[0077] The acquisition module is used to obtain the water level value △A in the low-pressure steam drum, the processing module is used to pre-set the first preset water level value A1 in the low-pressure steam drum, the second preset water level value A2 in the low-pressure steam drum, the third preset water level value A3 in the low-pressure steam drum, and the fourth preset water level value A4 in the low-pressure steam drum, and A1

[0078] The processing module is further used to correct the corrected output flow ai*xi of the feed water pump again according to the relationship between the obtained water level value △A in the low-pressure steam drum and each preset water level value Ai in the low-pressure steam drum:

[0079] When A1<△A≤A2, the first preset pressure correction coefficient y1 is selected to correct the output flow ai*xi of the feed water pump again, and the corrected output flow of the feed water pump is ai*xi*y1;

[0080] When A2<△A≤A3, the second preset pressure correction coefficient y2 is selected to correct the output flow ai*xi of the feed water pump again, and the output flow of the feed water pump after the second correction is ai*xi*y2;

[0081] When A3<△A≤A4, the third preset pressure correction coefficient y3 is selected to correct the output flow ai*xi of the feed water pump again, and the output flow of the feed water pump after the second correction is ai*xi*y3;

[0082] When A4<△A, the fourth preset pressure correction coefficient y4 is selected to correct the output flow ai*xi of the feed water pump again, and the output flow of the feed water pump after the second correction is ai*xi*y4.

[0083] Specifically, the output flow of the feed water pump after the correction is corrected again through the relationship between the water level value in the low-pressure steam drum and each preset water level value in the low-pressure steam drum, which can further improve the accuracy of the output flow of the feed water pump.

[0084] In the embodiment of the present application, a gas-steam boiler tail gas waste heat recycling control system is provided, and the hot water heater is connected between the feed water pump and the low-pressure steam drum through an external water supply pipe.

[0085] In the embodiment of the present application, a gas-steam boiler tail gas waste heat recycling control system is provided, and the acquisition module is connected with the flue gas temperature monitor, the water body temperature monitor, and the water level monitor in a wireless manner.

[0086] In summary, the embodiment of the present application provides a gas-steam boiler tail gas waste heat recycling control system, which comprises a low-pressure steam drum, a feed water pump for supplying water to the low-pressure steam drum, a flue gas temperature monitor for monitoring the flue gas temperature value of the tail of the boiler in real time, a water level monitor for monitoring the water level value in the low-pressure steam drum in real time, a hot water heater connected between the feed water pump and the low-pressure steam drum, for preheating the water body before entering the low-pressure steam drum by using the flue gas waste heat of the tail of the boiler, a water body temperature monitor for monitoring the water body temperature value at the outlet of the hot water heater in real time, and a control unit for comprehensively controlling the water body flow preheated by the hot water heater according to the data collected by the instruments. The water supplied to the low-pressure steam drum is heated by the hot water heater before being sent to the low-pressure steam drum for further steam-water circulation, which can reduce the flue gas temperature of the boiler, improve the thermal efficiency of the boiler, and accurately control the water body flow to be preheated by the control unit.

[0087] Finally, it should be noted that obvious modifications and variations to the present application can be derived from the teachings of the present application without departing from the spirit and scope of the present application. Thus, it is intended that the present application cover the modifications and variations of this application provided they come within the scope of the appended claims and their equivalents.

[0088] The above description is only one embodiment of the present application, but cannot limit the scope of the present application. Any structural changes made according to the present application, as long as the essence of the present application is not lost, should be considered to fall within the scope of the present application. For the convenience and brevity of the description, the specific working process of the system and the related description described above can refer to the corresponding process in the foregoing method embodiment, which will not be described here.

[0089] The term "comprising" or any other similar word is intended to encompass a non-exclusive inclusion, so that a process, method, article or equipment / device including a series of elements not only includes those elements, but also includes other elements not explicitly listed, or includes elements inherent to the process, method, article or equipment / device.

[0090] So far, the technical solutions of the present application have been described in combination with the further embodiments shown in the drawings, but those skilled in the art can easily understand that the protection scope of the present application is obviously not limited to these specific embodiments. Those skilled in the art can make equivalent changes or replacements to the related technical features without departing from the principles of the present application, and the technical solutions after the changes or replacements will fall within the protection scope of the present application.

[0091] The above description is only a preferred embodiment of the present application, and is not intended to limit the protection scope of the present application.

Claims

1. A waste heat recovery and control system for gas-fired steam boiler tail gas, characterized in that, include: Low-pressure steam drum; A feedwater pump is installed at the water inlet end of the low-pressure steam drum, and the feedwater pump is used to replenish water into the low-pressure steam drum; A flue gas temperature monitor is installed at the tail end of the boiler, and the flue gas temperature monitor is used to monitor the flue gas temperature at the tail end of the boiler in real time. A water level monitor is installed inside the low-pressure steam drum, and the water level monitor is used to monitor the water level value inside the low-pressure steam drum in real time. A hot water heater is connected between the feedwater pump and the low-pressure steam drum. The hot water heater is used to preheat the water before it enters the low-pressure steam drum using the waste heat of the flue gas at the tail end of the boiler. A water temperature monitoring instrument is installed at the outlet of the hot water heater, and the water temperature monitoring instrument is used to monitor the water temperature at the outlet of the hot water heater in real time. The control unit is electrically connected to the flue gas temperature monitor, water temperature monitor, water level monitor, and water supply pump, respectively. The control unit is used to comprehensively regulate the flow rate of the water preheated by the hot water heater based on the data collected by the flue gas temperature monitor, water temperature monitor, and water level monitor. The control unit includes: The data acquisition module is connected to the flue gas temperature monitor, the water temperature monitor, and the water level monitor respectively. The data acquisition module is used to acquire the data parameters of the flue gas temperature monitor, the water temperature monitor, and the water level monitor, and transmit the data parameters to the processing module. The processing module is connected to the acquisition module, and the processing module is used to set the working status command of the water supply pump according to the data parameters; A control module is connected to the processing module, and the control module is used to adjust the output flow rate of the water supply pump according to the working status command; The acquisition module is used to acquire the flue gas temperature value Δg at the tail end of the boiler, and the control module is used to control the feedwater pump. The processing module is used to set a preset value g0 for the flue gas temperature. The processing module is also used to set a first preset flue gas temperature difference g1, a second preset flue gas temperature difference g2, a third preset flue gas temperature difference g3, and a fourth preset flue gas temperature difference g4, where g1 < g2 < g3 < g4. The processing module is also used to set a first preset water pump output flow rate a1, a second preset water pump output flow rate a2, a third preset water pump output flow rate a3, and a fourth preset water pump output flow rate a4, where a1 < a2 < a3 < a4. The processing module is also used to select a preset output flow rate ai as the output flow rate of the water supply pump based on the difference between the collected flue gas temperature value Δg and the preset flue gas temperature value g0. When △g-g0≤g1, the first preset output flow rate a1 is selected as the output flow rate of the water supply pump; When g1 < Δg - g0 ≤ g2, the second preset output flow rate a2 is selected as the output flow rate of the water supply pump; When g2 < Δg - g0 ≤ g3, the third preset output flow rate a3 is selected as the output flow rate of the water supply pump; When g3 < Δg - g0 ≤ g4, the fourth preset output flow rate a4 is selected as the output flow rate of the water supply pump; When the output flow rate ai of the preset water supply pump is selected as the output flow rate of the water supply pump, the control module controls the water supply pump to work at the i-th preset output flow rate, i=1, 2, 3, 4; The acquisition module is used to obtain the water temperature value △B at the outlet of the hot water heater, and the processing module is used to determine whether the acquired water temperature value △B at the outlet of the hot water heater exceeds the preset water temperature value. If the water temperature value ΔB at the outlet of the hot water heater exceeds the preset water temperature value, it means that the output flow rate of the water preheated by the hot water heater is appropriate and there is no need to correct the output flow rate of the water supply pump. If the water temperature value ΔB at the outlet of the hot water heater does not exceed the preset water temperature value, it indicates that the output flow rate of the water preheated by the hot water heater is not appropriate, and the output flow rate of the water supply pump needs to be corrected. If the water temperature ΔB at the outlet of the hot water heater exceeds the preset water temperature value, it indicates that the output flow rate of the preheating process by the hot water heater is inappropriate, and the output flow rate of the water supply pump needs to be corrected, including: The acquisition module is used to obtain the water temperature value ΔB at the outlet of the hot water heater. The processing module is used to preset a first preset water temperature value B1, a second preset water temperature value B2, a third preset water temperature value B3, and a fourth preset water temperature value B4, where B1 > B2 > B3 > B4; and to preset a first preset first correction coefficient x1, a second preset first correction coefficient x2, a third preset first correction coefficient x3, and a fourth preset first correction coefficient x4, where 1 > x1 > x2 > x3 > x4 > 0.

7. The processing module is also used to adjust the output flow rate of the water supply pump based on the relationship between the water temperature value ΔB at the outlet of the hot water heater and each preset water temperature value Bi. When B1≥△B>B2, the first preset first correction coefficient x1 is selected to correct the output flow rate of the water supply pump, and the corrected output flow rate of the water supply pump is ai*x1; When B2≥△B>B3, the second preset first correction coefficient x2 is selected to correct the output flow rate of the water supply pump, and the corrected output flow rate of the water supply pump is ai*x2; When B3≥△B>B4, the third preset first correction coefficient x3 is selected to correct the output flow rate of the water pump, and the corrected output flow rate of the water pump is ai*x3; When B4≥△B, the fourth preset first correction coefficient x4 is selected to correct the output flow rate of the water supply pump, and the corrected output flow rate of the water supply pump is ai*x4; The processing module is used to correct the output flow rate ai of the water supply pump by selecting the i-th preset first correction coefficient xi, and the acquisition module is used to obtain the corrected output flow rate of the water supply pump as ai*xi, i=1,2,3,4. The acquisition module is used to acquire the water level value ΔA in the low-pressure steam drum. The processing module is used to preset a first preset water level value A1, a second preset water level value A2, a third preset water level value A3, and a fourth preset water level value A4 in the low-pressure steam drum, where A1 < A2 < A3 < A4. The processing module is also used to preset a first preset pressure correction coefficient y1, a second preset pressure correction coefficient y2, a third preset pressure correction coefficient y3, and a fourth preset pressure correction coefficient y4, where 1 > y1 > y2 > y3 > y4 > 0.

5. The processing module is further configured to further correct the output flow rate ai*xi of the feedwater pump based on the relationship between the obtained water level value △A in the low-pressure steam drum and the preset water level values ​​Ai in each low-pressure steam drum: When A1<△A≤A2, the first preset pressure correction coefficient y1 is selected to correct the output flow rate ai*xi of the water supply pump again. The output flow rate of the water supply pump after the second correction is ai*xi*y1. When A2<△A≤A3, the second preset pressure correction coefficient y2 is selected to correct the output flow rate ai*xi of the water supply pump again. The output flow rate of the water supply pump after the second correction is ai*xi*y2. When A3<△A≤A4, the third preset pressure correction coefficient y3 is selected to correct the output flow rate ai*xi of the water supply pump again. The output flow rate of the water supply pump after the second correction is ai*xi*y3. When A4 < △A, the fourth preset pressure correction coefficient y4 is selected to correct the output flow rate ai*xi of the water supply pump again. The output flow rate of the water supply pump after the second correction is ai*xi*y4.

2. The waste heat recovery and control system for gas-fired steam boiler tail gas according to claim 1, characterized in that, The hot water heater is connected between the water supply pump and the low-pressure steam drum via an external water supply pipe.

3. The waste heat recovery and control system for gas-fired steam boiler tail gas according to claim 1, characterized in that, The data acquisition module is wirelessly connected to the flue gas temperature monitor, water temperature monitor, and water level monitor.

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