Automatic control method for a hierarchically arranged flue gas waste heat recovery system

Abstract

The present invention provides an automatic control method for a hierarchically arranged flue gas waste heat recovery system, including a boiler, a dust collector, an induced draft fan, a desulfurization tower, a chimney, a first-stage heat pipe type low-temperature economizer, a second-stage heat pipe type low-temperature economizer, a controller, and a flue gas temperature monitoring module. The flue gas temperature monitoring module is used to monitor the inlet and outlet flue gas temperatures of the first-stage heat pipe type low-temperature economizer, the inlet flue gas temperature of the dust collector, and the inlet and outlet flue gas temperatures of the second-stage heat pipe type low-temperature economizer in real time. The controller implements the operation control of the first-stage heat pipe type low-temperature economizer and the second-stage heat pipe type low-temperature economizer based on the temperature data fed back by the flue gas temperature monitoring module. The system can realize the precise control of the flue gas outlet temperature of the two-stage heat pipe type low-temperature economizer. At the same time, when the heat pipe type low-temperature economizer is shut down, it is not necessary to open the exhaust valve. By automatically controlling the inlet and outlet water flow of the heat pipe type low-temperature economizer, the operation safety of the equipment is realized and the workload of the operating personnel is reduced.

Description

Technical Field

[0001] The invention relates to an automatic control method for a hierarchically arranged flue gas waste heat recovery system. Background Art

[0002] In coal-fired power plants, the design exhaust temperature of power station boilers is usually 120~150℃, accounting for 60%~70% of the entire boiler design heat loss. Especially for coal-fired industrial boilers, due to the small unit capacity and low boiler efficiency, the exhaust temperature is higher, which can reach 150~240℃. At present, coal-fired industrial boilers are still widely used in various fields of national production and life, such as steel, chemical industry, and residential heating. The direct emission of a large amount of high-temperature flue gas has caused a large waste of energy. With the gradual increase in the country's requirements for energy conservation and emission reduction in recent years, flue gas waste heat recovery equipment, mainly represented by low-temperature economizers, has been widely used.

[0003] In coal-fired power plants, most use heat pipe type low temperature economizer for waste heat recovery. When using heat pipe type low temperature economizer for waste heat recovery, an exhaust valve is usually set at the highest point of the water inlet and outlet pipes of the hot water chamber of the heat pipe type low temperature economizer. The functions of the exhaust valve are: 1. Completely exhaust the air in the pipeline during the water supply stage of the equipment; 2. During the normal operation of the boiler, if the equipment needs to be suspended due to low flue gas temperature or equipment failure, the steam generated in the hot water chamber is discharged by opening the exhaust valve in time to prevent the large amount of hot water remaining in the hot water chamber from being continuously heated by high-temperature flue gas and causing pipe burst or explosion accidents. In order to ensure the safety of the equipment, the exhaust valve generally adopts manual mode, and a dedicated person is responsible for operation before the equipment is started and stopped. In the normal waste heat recovery process, when the boiler flue gas temperature is low and the single-stage or two-stage heat pipe type low temperature economizer cannot be put into operation at the same time, it is necessary to manually frequently exhaust and release steam from the heat pipe type low temperature economizer. The above operation not only greatly increases the operating burden and heat waste of the operating personnel, but also the continuous high-temperature exhaust steam to the outside also has the disadvantages of hidden dangers of scalding. Summary of the invention

[0004] The object of the present invention is to provide an automatic control method for a flue gas waste heat recovery system with a hierarchical arrangement. The system can realize the precise control of the flue gas outlet temperature of a two-stage heat pipe type low-temperature economizer. At the same time, when the heat pipe type low-temperature economizer is shut down, there is no need to open the exhaust valve. By automatically controlling the inlet and outlet water flow of the heat pipe type low-temperature economizer, the operation safety of the equipment can be achieved and the workload of the operating personnel can be reduced.

[0005] The technical solution adopted by the present invention to solve its technical problem is: a hierarchically arranged flue gas waste heat recovery system and its automatic control method, including a boiler, a dust collector, an induced draft fan, a desulfurization tower, a chimney, a first-level heat pipe type low-temperature economizer, a second-level heat pipe type low-temperature economizer, a controller, and a flue gas temperature monitoring module. The air preheater, the first-level heat pipe type low-temperature economizer, the dust collector, the second-level heat pipe type low-temperature economizer, the induced draft fan, the desulfurization tower and the chimney of the boiler are connected in sequence through a flue gas conveying pipeline, a boiler water supply main pipe is used to convey water to the boiler, and a circulation pipeline is used to The boiler water supply main pipe is used to transport part of the water flow in the first-level heat pipe type low-temperature economizer and the second-level heat pipe type low-temperature economizer, and the water flow flowing out of the first-level heat pipe type low-temperature economizer and the second-level heat pipe type low-temperature economizer is transported to the boiler water supply main pipe again. The smoke temperature monitoring module is used to monitor the inlet smoke temperature and outlet smoke temperature of the first-level heat pipe type low-temperature economizer, the inlet smoke temperature of the dust collector, and the inlet smoke temperature and outlet smoke temperature of the second-level heat pipe type low-temperature economizer in real time. The controller realizes the operation control of the circulation pipeline according to the temperature data fed back by the smoke temperature monitoring module.

[0006] Preferably, the circulation pipeline includes a water supply branch, a return water branch, a first water inlet pipe, a first water outlet pipe, a second water inlet pipe, and a second water outlet pipe. The water supply branch and the return water branch are both connected to the boiler water supply main pipe, and the return water branch is located downstream of the water supply branch. The water inlet and water outlet of the first-level heat pipe type low-temperature economizer are respectively connected to the first water inlet pipe and the first water outlet pipe, and the water inlet and water outlet of the second-level heat pipe type low-temperature economizer are respectively connected to the second water inlet pipe and the second water outlet pipe, and a first manual exhaust valve and a second manual exhaust valve are respectively arranged on the first-level heat pipe type low-temperature economizer and the second-level heat pipe type low-temperature economizer.

[0007] Furthermore, the water outlet end of the return water branch pipe is located in the boiler water supply main pipe, and the water flow direction of the water outlet end of the return water branch pipe is the same as the water flow direction in the boiler water supply main pipe.

[0008] Furthermore, a first electric regulating valve and a first check valve are sequentially arranged on the boiler water supply main pipe located between the water supply branch and the return branch, a first electric switch valve and a second electric regulating valve are arranged on the first water inlet pipe, a second electric switch valve is arranged on the first water outlet pipe, a fourth electric switch valve and a third electric regulating valve are arranged on the second water inlet pipe, and a fifth electric switch valve is arranged on the second water outlet pipe.

[0009] Furthermore, the circulation pipeline includes a first circulation booster pump and a second circulation booster pump, the first circulation booster pump is arranged on the first water inlet pipe, the second circulation booster pump is arranged on the second water inlet pipe, the first water inlet pipe and the second water inlet pipe are connected with the water supply branch in parallel, the first water outlet pipe and the second water outlet pipe are connected with the return water branch in parallel, and a second check valve and a third electric switch valve are arranged on the return water branch.

[0010] Furthermore, the circulation pipeline includes a third circulation booster pump and a branch pipe, the third circulation booster pump is arranged on the water supply branch pipe, the water inlet end of the branch pipe and the water inlet end of the second water inlet pipe are connected in parallel with the water outlet end of the water supply branch pipe in a parallel manner, the water outlet end of the branch pipe and the water outlet end of the first water outlet pipe are connected in parallel with the water inlet end of the return branch pipe in a parallel manner, the first water inlet pipe and the second water outlet pipe are respectively connected with the branch pipe, and the connection between the first water inlet pipe and the branch pipe is located downstream of the connection between the second water outlet pipe and the branch pipe, a sixth electric switch valve and a fourth check valve are arranged on the branch pipe upstream of the connection between the second water outlet pipe and the branch pipe, and a seventh electric switch valve and a third check valve are arranged on the branch pipe downstream of the connection between the first water inlet pipe and the branch pipe.

[0011] The present invention also provides two automatic control methods for the hierarchically arranged flue gas waste heat recovery system, wherein one automatic control method comprises the following steps:

[0012] S1. During the operation of the boiler, the temperature sensor is used to monitor the smoke temperature T1 at the inlet of the dust collector, the smoke temperature T2 at the inlet of the secondary heat pipe low-temperature economizer, the smoke temperature T3 at the outlet of the secondary heat pipe low-temperature economizer, the smoke temperature T7 at the inlet of the primary heat pipe low-temperature economizer, and the smoke temperature T8 at the outlet of the secondary heat pipe low-temperature economizer in real time; the controller receives the data information of T1, T2, T3, T7, and T8 in real time, and at this time, the first electric regulating valve is in operation;

[0013] S2, the controller receives the instruction of not putting into operation in real time, and at the same time, the controller compares T1 with the set temperature T4, T2 with the set temperature T5, and T3 with the set temperature T6 in real time, where T4>T5>T6;

[0014] S2.1 When T1>T4 and T2>T5, the two-stage operation mode is entered; the controller first puts the first-stage heat pipe type low-temperature economizer into operation, and realizes a stable operation state where T1 and T4 are equal by controlling the operation process of the first-stage heat pipe type low-temperature economizer. Specifically, the controller controls the operation of the first circulation booster pump and the second electric regulating valve, and adjusts the speed of the first circulation booster pump and the opening degree of the second electric regulating valve in real time according to the change of T1 until T1 and T4 are equal. When T1 and T4 are equal, the controller maintains the speed of the first circulation booster pump and the opening degree of the second electric regulating valve. The opening degree of the regulating valve remains unchanged; when the stable operating state in which T1 and T4 are equal is reached, the controller starts the operation of the two-stage heat pipe type low-temperature economizer, and finally achieves the stable operating state in which T3 and T6 are equal by controlling the operation process of the two-stage heat pipe type low-temperature economizer. Specifically, the controller controls the operation of the second circulation booster pump and the third electric regulating valve, and adjusts the speed of the second circulation booster pump and the opening degree of the third electric regulating valve in real time according to the change of T3, until T3 and T6 are equal, the controller keeps the speed of the second circulation booster pump and the opening degree of the third electric regulating valve unchanged;

[0015] S2.2 When T1≤T4 and T2>T6, enter the single-stage operation control mode; the controller puts the first-stage heat pipe low-temperature economizer in the insulation working mode. Specifically, the controller stops the operation of the first circulation booster pump, and monitors the flue gas inlet temperature T7 and the flue gas outlet temperature T8 of the first-stage heat pipe low-temperature economizer in real time. The controller adjusts the opening of the second electric regulating valve in real time according to the changes of T7 and T8, until the difference between T7 and T8 is maintained at about 1°C. When the difference between T7 and T8 is maintained at about 1°C, the controller keeps the opening of the second electric regulating valve unchanged; when the first-stage heat pipe low-temperature economizer is in the insulation working mode, the controller controls the operation of the second circulation booster pump and the third electric regulating valve, and adjusts the speed of the second circulation booster pump and the opening of the third electric regulating valve in real time according to the changes of T3, until T3 is equal to T6, the controller keeps the speed of the second circulation booster pump and the opening of the third electric regulating valve unchanged;

[0016] S2.3 When T1≤T4 and T2≤T6 or the controller receives an instruction not to put into operation, the controller makes the first-stage heat pipe type low-temperature economizer and the second-stage heat pipe type economizer enter the insulation working mode. Specifically, the controller stops the operation of the first circulation booster pump, and monitors the smoke inlet temperature T7 and the smoke outlet temperature T8 of the first-stage heat pipe type low-temperature economizer in real time. The controller adjusts the opening degree of the second electric regulating valve in real time according to the changes of T7 and T8, until the difference between T7 and T8 is maintained at about 1°C. When the difference between T7 and T8 is maintained at about 1°C, the controller makes the opening degree of the second electric regulating valve remain unchanged; then, the controller stops the operation of the second circulation booster pump, and monitors the smoke inlet temperature T2 and the smoke outlet temperature T3 of the second-stage heat pipe type low-temperature economizer in real time. The controller adjusts the opening degree of the third electric switch valve in real time according to the changes of T2 and T3, until the difference between T2 and T3 is maintained at about 1°C. When the difference between T2 and T3 is maintained at about 1°C, the controller makes the opening degree of the third electric regulating valve remain unchanged.

[0017] Another automatic control method includes the following steps:

[0018] S3. During the operation of the boiler, the temperature sensor is used to monitor the smoke temperature T10 at the inlet of the dust collector, the smoke temperature T20 at the inlet of the secondary heat pipe low-temperature economizer, the smoke temperature T30 at the outlet of the secondary heat pipe low-temperature economizer, the smoke temperature T70 at the inlet of the primary heat pipe low-temperature economizer, and the smoke temperature T80 at the outlet of the secondary heat pipe low-temperature economizer in real time; the controller receives the data information of T10, T20, T30, T70, and T80 in real time, and at this time, the first electric regulating valve is in operation;

[0019] S4, the controller receives the instruction of not putting into operation in real time, and at the same time, the controller compares T10 with the set temperature T40, T20 with the set temperature T50, and T30 with the set temperature T60 in real time, where T40>T50>T60;

[0020] S4.1 When T10>T40 and T20>T50, enter the two-stage operation mode; the controller makes the first-stage heat pipe type low-temperature economizer and the second-stage heat pipe type low-temperature economizer synchronously put into operation, and realizes a stable operation state in which T10 is equal to T40, T30 is equal to T60 by controlling the operation process of the first-stage heat pipe type low-temperature economizer and the second-stage heat pipe type low-temperature economizer. Specifically, the controller closes the sixth electric switch valve and the seventh electric switch valve, and controls the third circulation booster pump and the second electric regulating valve. , and the operation of the third electric regulating valve, and adjust the speed of the third circulation booster pump and the opening degrees of the second electric regulating valve and the third electric regulating valve in real time according to the changes of T10 and T30, until T10 is equal to T40, T30 is equal to T60. When T10 is equal to T40, T30 is equal to T60, the controller keeps the speed of the third circulation booster pump and the opening degrees of the second electric regulating valve and the third electric regulating valve unchanged, thereby realizing the stable operation of the first-stage heat pipe type low-temperature economizer and the second-stage heat pipe type low-temperature economizer;

[0021] S4.2 When T10≤T4 and T20>T60, enter the single-stage operation control mode; the controller puts the first-stage heat pipe low-temperature economizer in the insulation working mode, and puts the second-stage heat pipe low-temperature economizer in the stable operation state. Specifically, the controller opens the seventh electric switch valve to close the sixth electric switch valve. The controller monitors the changes of T70, T80 and T30 in real time. The controller adjusts the speed of the third circulation booster pump and the opening degree of the second electric regulating valve and the third electric regulating valve in real time according to the changes of T70, T80 and T30 until the difference between T70 and T80 is maintained at about 1°C and T30 is equal to T60. When the difference between T70 and T80 is maintained at about 1°C and T30 is equal to T60, the controller keeps the speed of the third circulation booster pump and the opening degree of the second electric regulating valve and the third electric regulating valve unchanged, thereby realizing that the first-stage heat pipe low-temperature economizer is in the insulation working mode and the second-stage heat pipe low-temperature economizer is in the stable operation state;

[0022] S4.3 When T10≤T40 and T20≤T6 or the controller receives an instruction not to put into operation, the controller makes the first-stage heat pipe type low-temperature economizer and the second-stage heat pipe type economizer enter the insulation working mode. Specifically, the controller opens the sixth electric switch valve and the seventh electric switch valve, and monitors T20, T30, T70 and T80 in real time. The controller adjusts the speed of the third circulation booster pump and the opening degree of the second electric regulating valve and the third electric regulating valve in real time according to the changes of T20, T30, T70 and T80, until the difference between T70 and T80 and the difference between T20 and T30 are both maintained at about 1°C; when the difference between T70 and T80 and the difference between T20 and T30 are both maintained at about 1°C, the controller makes the speed of the third circulation booster pump and the opening degree of the second electric regulating valve and the third electric regulating valve remain unchanged, thereby achieving that the first-stage heat pipe type low-temperature economizer and the second-stage heat pipe type economizer enter the insulation working mode.

[0023] The beneficial effects of the present invention are as follows: during operation, the controller controls the rotation speed of the corresponding circulating boost pump and the opening degree of each corresponding electric regulating valve in real time according to the relevant temperature signals monitored in real time and according to the temperature change process, so as to realize the precise control of the flue gas outlet temperature of each heat pipe type low-temperature economizer, thereby realizing the maximum waste heat recovery and ensuring the effective and safe operation of the waste heat system; further, when the flue gas temperature is too low or the heat pipe type low-temperature economizer is not needed to be put into operation, the system does not need to open the exhaust valve, and can realize the equipment operation safety and reduce the workload of the operating personnel by automatically controlling the inlet and outlet water flow of the heat pipe type low-temperature economizer. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some preferred embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0025] Figure 1 It is a composition framework diagram of the first embodiment of the present invention;

[0026] Figure 2 It is a composition framework diagram of a second embodiment of the present invention;

[0027] Figure 3 It is a cross-sectional view of the distribution of the outlet end of the return branch pipe in the boiler water supply main pipe;

[0028] In the figure: 1 boiler, 2 first-stage heat pipe type low-temperature economizer, 3 dust collector, 4 second-stage heat pipe type low-temperature economizer, 5 induced draft fan, 6 desulfurization tower, 7 chimney, 8 flue gas conveying pipeline, 101 boiler water supply main pipe, 1011 water supply branch pipe, 1012 return water branch pipe, 102 first water inlet pipe, 103 first water outlet pipe, 104 second water inlet pipe, 105 second water outlet pipe, 106 branch pipe, 201 first electric switch valve, 202 second electric switch valve, 203 third electric switch valve, 204 The fourth electric switch valve, 205 the fifth electric switch valve, 206 the sixth electric switch valve, 207 the seventh electric switch valve, 301 the first electric regulating valve, 302 the second electric regulating valve, 303 the third electric regulating valve, 401 the first check valve, 402 the second check valve, 403 the third check valve, 404 the fourth check valve, 501 the first circulation boost pump, 502 the second circulation boost pump, 503 the third circulation boost pump, 601 the first manual exhaust valve, 602 the second manual exhaust valve. DETAILED DESCRIPTION

[0029] The following will be combined with specific embodiments and attached Figure 1-3 , the technical solutions in the embodiments of the present invention are clearly and completely described. Obviously, the described embodiments are only part of the preferred embodiments of the present invention, rather than all the embodiments. Those skilled in the art can make similar modifications without violating the connotation of the present invention, so the present invention is not limited by the specific embodiments disclosed below.

[0030] The present invention provides a flue gas waste heat recovery system (such as Figure 1As shown), it includes a boiler 1, a first-level heat pipe type low-temperature economizer 2, a dust collector 3, a second-level heat pipe type low-temperature economizer 4, an induced draft fan 5, a desulfurization tower 6, a chimney 7, a controller, and a flue gas temperature monitoring module. The above-mentioned boiler 1, the first-level heat pipe type low-temperature economizer 2, the dust collector 3, the second-level heat pipe type low-temperature economizer 4, the induced draft fan 5, the desulfurization tower 6, the chimney 7, and the controller equipment are all commonly used technical equipment in this field. Therefore, the structure and operation principle of the above-mentioned equipment are no longer described in detail here. The flue gas temperature monitoring module includes a plurality of temperature sensors, which are used to realize real-time monitoring of the inlet and outlet flue gas temperatures of the first-level heat pipe type low-temperature economizer, the inlet and outlet flue gas temperatures of the dust collector, and the inlet and outlet flue gas temperatures of the second-level heat pipe type low-temperature economizer. The air preheater, the first-level heat pipe type low-temperature economizer 2, the dust collector 3, the second-level heat pipe type low-temperature economizer 4, the induced draft fan 5, the desulfurization tower 6 and the chimney 7 of the boiler 1 are connected in sequence through flue gas conveying pipelines. A boiler supplies The water supply pipe 101 is used to transport water into the boiler 1, and a circulation pipeline is used to transport part of the water flow in the boiler water supply pipe 101 to the first-level heat pipe type low-temperature economizer 2 and the second-level heat pipe type low-temperature economizer 4, and transport the water flow out of the first-level heat pipe type low-temperature economizer 2 and the second-level heat pipe type low-temperature economizer 4 to the boiler water supply pipe 101 again. The controller realizes the operation control of the circulation pipeline according to the temperature data fed back by the flue gas temperature monitoring module, and can realize the effective operation of the first-level heat pipe type low-temperature economizer 2 and the second-level heat pipe type low-temperature economizer 4, so as to ensure the normal and safe operation of the waste heat recovery system while realizing the heat recovery of high-temperature flue gas. The hot water absorbed by the first-level heat pipe type low-temperature economizer 2 and the second-level heat pipe type low-temperature economizer 4 is transported to the boiler water supply pipe 101 again through the circulation pipeline, thereby reducing the heat demand of hot water in the boiler 1, thereby effectively reducing the coal burning amount of the boiler 1, thereby achieving the effect of saving coal.

[0031] In the above embodiment, the specific implementation of the circulation pipeline is as follows: the circulation pipeline includes a water supply branch pipe 1011, a return water branch pipe 1012, a first water inlet pipe 102, a first water outlet pipe 103, a second water inlet pipe 104, and a second water outlet pipe 105. The water supply branch pipe 1011 and the return water branch pipe 101 are both connected to the boiler water supply main pipe 101, and the return water branch pipe 1012 is located downstream of the water supply branch pipe 1011. The water supply branch pipe 1011 is used to realize the boiler water supply main pipe. The water in 101 is divided into the primary heat pipe type low temperature economizer 2 and the secondary heat pipe type low temperature economizer 4. The return water branch 1012 is used to transport the hot water in the primary heat pipe type low temperature economizer 2 and the secondary heat pipe type low temperature economizer 4 to the boiler water supply main pipe 101 again. When the return water branch 1012 transports the hot water to the boiler water supply main pipe 101, in order to prevent the backflow phenomenon, the water outlet end of the return water branch 1012 is located in the boiler water supply main pipe 101. , and the water flow direction of the water outlet end of the return water branch pipe 1012 is the same as the water flow direction in the boiler water supply main pipe 101. The same direction makes the hot water in the water outlet end of the return water branch pipe 1012 have a small obstruction pressure when it flows out, thereby preventing the occurrence of backflow; the water inlet and outlet of the first-level heat pipe type low-temperature economizer 2 are respectively connected to the first water inlet pipe 102 and the first water outlet pipe 103, and the water inlet and outlet of the second-level heat pipe type low-temperature economizer 4 are respectively connected to the second water inlet pipe 104 and the second water outlet pipe 105. A first manual exhaust valve 601 and a second manual exhaust valve 602 are respectively arranged on the first-level heat pipe type low-temperature economizer 2 and the second-level heat pipe type low-temperature economizer 4. When the equipment is running and exhausting, the first manual exhaust valve 601 and the second manual exhaust valve 602 can be manually opened to exhaust the circulation pipeline. After the exhaust is completed, the first manual exhaust valve 601 and the second manual exhaust valve 602 are manually closed again;Furthermore, in order to facilitate the circulation pipeline to realize the convenience of automatic regulation of water flow, a first electric regulating valve 301 and a first check valve 401 are sequentially arranged on the boiler water supply main pipe 101 located between the water supply branch pipe 1011 and the return water branch pipe 1012. The first electric regulating valve 301 is used to realize the water volume regulation in the boiler water supply main pipe 101. A first electric switch valve 201 and a second electric regulating valve 302 are arranged on the first water inlet pipe 102, and a second electric switch valve 201 and a second electric regulating valve 302 are arranged on the first water outlet pipe 103. 2. A fourth electric switch valve 204 and a third electric regulating valve 303 are provided on the second water inlet pipe 104, and a fifth electric switch valve 205 is provided on the second water outlet pipe 105. The second electric regulating valve 302 can be used to adjust the flow rate in the first-stage heat pipe type low-temperature economizer 2, and the third electric regulating valve 303 can be used to adjust the flow rate in the second-stage heat pipe type low-temperature economizer 4. The flow rates in the first-stage heat pipe type low-temperature economizer 2 and the second-stage heat pipe type low-temperature economizer 4 can be effectively controlled, and then the corresponding flue gas temperature can be effectively controlled. ;

[0032] Based on the above-mentioned circulation pipeline embodiment, two booster pumps can be used to supply water to the first-level heat pipe type low-temperature economizer 2 and the second-level heat pipe type low-temperature economizer 4 separately; or one booster pump can be used to supply water to the first-level heat pipe type low-temperature economizer 2 and the second-level heat pipe type low-temperature economizer 4.

[0033] When two booster pumps are used to supply water to the first-stage heat pipe low-temperature economizer 2 and the second-stage heat pipe low-temperature economizer 4 separately, the circulation pipeline includes a first circulation booster pump 501 and a second circulation booster pump 502. The first circulation booster pump 501 is arranged on the first water inlet pipe 102, and the second circulation booster pump 502 is arranged on the second water inlet pipe 104. The first water inlet pipe 102 and the second water inlet pipe 104 are connected in parallel with the water supply branch pipe 1011, and the first water outlet pipe 103 and the second water outlet pipe 105 are connected in parallel with the return water branch pipe 1012. The return water branch pipe 1012 is provided with a second check valve 402 and a third electric switch valve 203.

[0034] When a booster pump is used to supply water to the primary heat pipe type low-temperature economizer 2 and the secondary heat pipe type low-temperature economizer 4, the circulation pipeline includes a third circulation booster pump 503 and a branch pipe 106. The third circulation booster pump 503 is arranged on the water supply branch pipe 1011. The water inlet end of the branch pipe 106 and the water inlet end of the second water inlet pipe 104 are connected in parallel with the water outlet end of the water supply branch pipe 1011. The water outlet end of the branch pipe 106 and the water outlet end of the first water outlet pipe 103 are connected in parallel with the water outlet end of the return water branch pipe 1012. The water inlet ends are connected in parallel, the first water inlet pipe 102 and the second water outlet pipe 105 are respectively connected to the branch pipe 106, and the connection between the first water inlet pipe 102 and the branch pipe 106 is located downstream of the connection between the second water outlet pipe 105 and the branch pipe 106, and the sixth electric switch valve 206 and the fourth check valve 404 are arranged on the branch pipe 106 upstream of the connection between the second water outlet pipe 105 and the branch pipe 106, and the seventh electric switch valve 207 and the third check valve 403 are arranged on the branch pipe 106 downstream of the connection between the first water inlet pipe 102 and the branch pipe 106.

[0035] In actual application, the controller implements real-time regulation of the above-mentioned booster pumps, electric switch valves and electric regulating valves based on the real-time monitoring data of the inlet and outlet flue gas temperatures of the first-stage heat pipe low-temperature economizer, the inlet and outlet flue gas temperatures of the dust collector, and the inlet and outlet flue gas temperatures of the second-stage heat pipe low-temperature economizer, thereby realizing the operation control of the first-stage heat pipe low-temperature economizer 2 and the second-stage heat pipe low-temperature economizer 4.

[0036] When the system uses two booster pumps to supply water to the primary heat pipe type low temperature economizer 2 and the secondary heat pipe type low temperature economizer 4 separately, the automatic control operation method of the system includes the following steps:

[0037] S1. During the operation of the boiler, the temperature sensor is used to monitor the smoke temperature T1 at the inlet of the dust collector, the smoke temperature T2 at the inlet of the secondary heat pipe low-temperature economizer, the smoke temperature T3 at the outlet of the secondary heat pipe low-temperature economizer, the smoke temperature T7 at the inlet of the primary heat pipe low-temperature economizer, and the smoke temperature T8 at the outlet of the secondary heat pipe low-temperature economizer in real time; the controller receives the data information of T1, T2, T3, T7, and T8 in real time, at which time, the first electric regulating valve 301 is in operation;

[0038] S2, the controller receives the instruction of not putting into operation in real time, and at the same time, the controller compares T1 with the set temperature T4, T2 with the set temperature T5, and T3 with the set temperature T6 in real time, where T4>T5>T6;

[0039] S2.1 When T1>T4 and T2>T5, enter the two-stage operation mode; the controller first puts the first-stage heat pipe type low-temperature economizer 2 into operation, and realizes a stable operation state in which T1 and T4 are equal by controlling the operation process of the first-stage heat pipe type low-temperature economizer 2. Specifically, the controller controls the operation of the first circulation booster pump 501 and the second electric regulating valve 302. At this time, the controller synchronously opens the first electric switch valve 201, the second electric switch valve 202 and the third electric switch valve 203. The controller adjusts the speed of the first circulation booster pump 501 and the opening degree of the second electric regulating valve 302 in real time according to the change of T1 until T1 and T4 are equal. When T1 and T4 are equal, the controller keeps the speed of the first circulation booster pump 501 and the opening degree of the second electric regulating valve 302 unchanged, thereby realizing the first-stage heat pipe. The controller realizes the stable and effective operation of the two-stage heat pipe type low-temperature economizer 2; when the stable operation state in which T1 and T4 are equal is reached, the controller starts the operation of the two-stage heat pipe type low-temperature economizer 4, and finally realizes the stable operation state in which T3 and T6 are equal by controlling the operation process of the two-stage heat pipe type low-temperature economizer 4. Specifically, the controller controls the operation of the second circulation boosting pump 502 and the third electric regulating valve 303. At this time, the controller continues to open the fourth electric switch valve 204 and the fifth electric switch valve 205. The controller adjusts the speed of the second circulation boosting pump 502 and the opening degree of the third electric regulating valve 303 in real time according to the change of T3, until T3 and T6 are equal, the controller keeps the speed of the second circulation boosting pump 502 and the opening degree of the third electric regulating valve 303 unchanged, thereby realizing the stable operation of the two-stage heat pipe type low-temperature economizer 4;

[0040] S2.2 When T1≤T4 and T2>T6, enter the single-stage operation control mode; the controller puts the first-stage heat pipe type low-temperature economizer 2 in the insulation working mode. Specifically, the controller stops the operation of the first circulation booster pump 501. At this time, the first electric switch valve 201, the second electric switch valve 202 and the third electric switch valve 203 are still in the open state. The controller monitors the flue gas inlet temperature T7 and the flue gas outlet temperature T8 of the first-stage heat pipe type low-temperature economizer 2 in real time. The controller adjusts the opening degree of the second electric regulating valve 302 in real time according to the changes of T7 and T8 until the difference between T7 and T8 is maintained at about 1°C, and the difference between T7 and T8 is always maintained at about 1°C, so that the first-stage heat pipe type low-temperature economizer 2 absorbs very little heat. The first-stage heat pipe type low-temperature economizer 2 absorbs little heat and basically has no cooling effect, so that the flue gas temperature at its outlet meets the inlet flue gas temperature requirement of the dust collector 3. , there is still a certain amount of water flowing continuously in the first-stage heat pipe type low-temperature economizer 2, so that the first-stage heat pipe type low-temperature economizer 2 will not have a pressurization problem. When the difference between T7 and T8 is maintained at about 1°C, the controller keeps the opening degree of the second electric regulating valve 302 unchanged; when the first-stage heat pipe type low-temperature economizer 2 is in the insulation working mode, the controller controls the operation of the second circulation boosting pump 502 and the third electric regulating valve 303. At this time, the controller continues to open the fourth electric switch valve 204 and the fifth electric switch valve 205. The controller adjusts the speed of the second circulation boosting pump 502 and the opening degree of the third electric regulating valve 303 in real time according to the change of T3, until T3 is equal to T6, the controller keeps the speed of the second circulation boosting pump 502 and the opening degree of the third electric regulating valve 303 unchanged, thereby realizing the effective and stable operation of the second-stage heat pipe type low-temperature economizer 4;

[0041] S2.3 When T1≤T4 and T2≤T6 or the controller receives an instruction not to put into operation, the controller makes the first-stage heat pipe low-temperature economizer 2 and the second-stage heat pipe economizer 4 enter the insulation working mode. Specifically, the controller stops the operation of the first circulation booster pump 501, and the first electric switch valve 201, the second electric switch valve 202 and the third electric switch valve 203 are still in the open state. The controller monitors the smoke inlet temperature T7 and the smoke outlet temperature T8 of the first-stage heat pipe low-temperature economizer 2 in real time. The controller adjusts the opening degree of the second electric regulating valve 302 in real time according to the changes of T7 and T8 until the difference between T7 and T8 remains at about 1°C. When the difference between T7 and T8 remains at about 1°C, the controller makes the opening degree of the second electric regulating valve 302 remain unchanged; then, the controller stops the operation of the second circulation booster pump 502. At this time, the fourth electric switch valve 204 and the fifth electric switch valve 205 are in the open state, and the controller monitors the flue gas inlet temperature T2 and the flue gas outlet temperature T3 of the secondary heat pipe type low-temperature economizer 4 in real time. The controller adjusts the opening degree of the third electric switch valve 303 in real time according to the changes of T2 and T3, until the difference between T2 and T3 is maintained at about 1°C. When the difference between T2 and T3 is maintained at about 1°C, the controller keeps the opening degree of the third electric regulating valve 303 unchanged, and the difference between T2 and T3 is always maintained at about 1°C, so that the heat absorption of the secondary heat pipe type low-temperature economizer 4 is very small. The heat absorption of the secondary heat pipe type low-temperature economizer 4 is small and basically has no cooling effect, so that the flue gas temperature at its outlet meets the inlet flue gas temperature requirement of the desulfurization tower 6. At the same time, there is still a certain amount of water flowing continuously in the secondary heat pipe type low-temperature economizer 4, so that the secondary heat pipe type low-temperature economizer 4 will not have a pressurization problem.

[0042] When a booster pump is used to supply water to the primary heat pipe type low temperature economizer 2 and the secondary heat pipe type low temperature economizer 4, the automatic control operation method of the system includes the following steps:

[0043] S3. During the operation of the boiler, the temperature sensor is used to monitor the smoke temperature T10 at the inlet of the dust collector, the smoke temperature T20 at the inlet of the secondary heat pipe low-temperature economizer, the smoke temperature T30 at the outlet of the secondary heat pipe low-temperature economizer, the smoke temperature T70 at the inlet of the primary heat pipe low-temperature economizer, and the smoke temperature T80 at the outlet of the secondary heat pipe low-temperature economizer in real time; the controller receives the data information of T10, T20, T30, T70, and T80 in real time, at which time, the first electric regulating valve 301 is in operation;

[0044] S4, the controller receives the instruction of not putting into operation in real time, and at the same time, the controller compares T10 with the set temperature T40, T20 with the set temperature T50, and T30 with the set temperature T60 in real time, where T40>T50>T60;

[0045] S4.1 When T10>T40 and T20>T50, enter the two-stage operation mode; the controller makes the first-stage heat pipe type low-temperature economizer 2 and the second-stage heat pipe type low-temperature economizer 4 put into operation synchronously, and realizes the stable operation state in which T10 is equal to T40, T30 is equal to T60 by controlling the operation process of the first-stage heat pipe type low-temperature economizer 2 and the second-stage heat pipe type low-temperature economizer 4. Specifically, the controller closes the sixth electric switch valve 206 and the seventh electric switch valve 207, and controls the operation of the third circulation booster pump 503, the second electric regulating valve 302, and the third electric regulating valve 303. At this time, the first electric switch valve 201, the second electric switch valve 202, and the third electric regulating valve 303 are closed. The electric switch valve 202, the fourth electric switch valve 204 and the fifth electric switch valve 205 are all in the open state. The controller adjusts the speed of the third circulation boost pump 503 and the opening degree of the second electric regulating valve 302 and the third electric regulating valve 303 in real time according to the changes of T10 and T30 until T10 is equal to T40, T30 is equal to T60. When T10 is equal to T40, T30 is equal to T60, the controller keeps the speed of the third circulation boost pump 503 and the opening degree of the second electric regulating valve 302 and the third electric regulating valve 303 unchanged, thereby realizing the stable operation of the first-stage heat pipe type low-temperature economizer 2 and the second-stage heat pipe type low-temperature economizer 4;

[0046] S4.2 When T10≤T4 and T20>T60, enter the single-stage operation control mode; the controller puts the first-stage heat pipe low-temperature economizer 2 in the insulation working mode, and puts the second-stage heat pipe low-temperature economizer 4 in a stable operating state. Specifically, the controller opens the seventh electric switch valve 207, so that the sixth electric switch valve 206 is in a closed state. At this time, the first electric switch valve 201, the second electric switch valve 202, the fourth electric switch valve 204 and the fifth electric switch valve 205 are all in an open state. The controller monitors the changes of T70, T80 and T30 in real time. The controller adjusts the speed of the third circulation booster pump 503 and the opening degree of the second electric regulating valve 302 and the third electric regulating valve 303 in real time according to the changes of T70, T80 and T30 until the difference between T70 and T80 is maintained at about 1°C and T30 is equal to T60, and the difference between T70 and T80 is always maintained at about 1°C, so that the heat absorption of the first-stage heat pipe type low-temperature economizer 2 is very small. The heat absorption of the first-stage heat pipe type low-temperature economizer 2 is small, and basically has no cooling effect, so that the flue gas temperature at its outlet meets the inlet flue gas temperature requirement of the dust collector 3. At the same time, there is still a certain amount of water flowing continuously in the first-stage heat pipe type low-temperature economizer 2, so that the first-stage heat pipe type low-temperature economizer 2 will not have a pressurization problem; when the difference between T70 and T80 is maintained at about 1°C and T30 is equal to T60, the controller keeps the speed of the third circulation booster pump 503 and the opening degrees of the second electric regulating valve 302 and the third electric regulating valve 303 unchanged, thereby realizing that the first-stage heat pipe type low-temperature economizer is in a heat preservation working mode and the second-stage heat pipe type low-temperature economizer is in a stable operating state;

[0047] S4.3 When T10≤T40 and T20≤T6 or the controller receives an instruction not to put into operation, the controller makes the first-stage heat pipe low-temperature economizer 2 and the second-stage heat pipe economizer 4 enter the insulation working mode. Specifically, the controller opens the sixth electric switch valve 206 and the seventh electric switch valve 207. At this time, the first electric switch valve 201, the second electric switch valve 202, the fourth electric switch valve 204 and the fifth electric switch valve 205 are all in the open state. The controller monitors T20, T30, T70 and T80 in real time. The controller adjusts the speed of the third circulation boost pump 503 and the opening degree of the second electric regulating valve 302 and the third electric regulating valve 303 in real time according to the changes of T20, T30, T70 and T80, until the difference between T70 and T80 and the difference between T20 and T30 are both Maintained at about 1°C; when the difference between T70 and T80 and the difference between T20 and T30 are both maintained at about 1°C, the controller makes the rotation speed of the third circulating boost pump 503 and the opening degrees of the second electric regulating valve 302 and the third electric regulating valve 303 remain unchanged, thereby achieving that the first-stage heat pipe type low-temperature economizer 2 and the second-stage heat pipe type economizer 4 both enter the insulation working mode, and the difference between T20 and T30 is always maintained at about 1°C, so that the heat absorption of the second-stage heat pipe type low-temperature economizer 4 is very small, the heat absorption of the second-stage heat pipe type low-temperature economizer 4 is small, and basically has no cooling effect, so that the flue gas temperature at its outlet meets the inlet flue gas temperature requirement of the desulfurization tower 6, and at the same time, there is still a certain amount of water flowing continuously in the second-stage heat pipe type low-temperature economizer 4, so that the second-stage heat pipe type low-temperature economizer 4 will not have a pressurization problem.

[0048] In the above two automatic control methods, T4 is equal to T40, which is the minimum flue gas operating temperature of the dust collector 3; T6 is equal to T60, which is the minimum flue gas operating temperature of the desulfurization tower. When the controller controls the operation mode of the first-stage heat pipe low-temperature economizer 2 and the second-stage heat pipe low-temperature economizer 4 to achieve the equal operation state of T1 or T10 and T4, T3 or T30 and T6, then the effective recovery of flue gas waste heat and the stable operation of the system are achieved while ensuring the normal operation of the dust collector and the desulfurization tower.

[0049] In the above two automatic control methods, the operation design parameters of boiler 1, primary heat pipe type low temperature economizer 2, secondary heat pipe type low temperature economizer 4, dust collector 3 and desulfurization tower 6 can be carried out according to the following requirements: the design exhaust gas temperature of boiler 1 is ≤160℃, the design flue gas inlet and outlet temperature drop ranges of primary heat pipe type low temperature economizer 2 and secondary heat pipe type low temperature economizer 4 are 50℃ and 20℃ respectively; the inlet flue gas temperature of dust collector 3 is required to be not less than 105℃, and the inlet flue gas temperature of desulfurization tower is not less than 80℃. Therefore, in the above two automatic control methods, T4 and T40 can be set to 105℃, and T6 and T60 can be set to 80℃.

[0050] Except for the technical features described in the specification, all other technical features are known technologies to those skilled in the art.

[0051] The above description in combination with the accompanying drawings has detailed the preferred implementation modes and embodiments of the present invention, but the present invention is not limited to the above implementation modes and embodiments. For ordinary technicians in this technical field, several improvements and modifications can be made without departing from the concept of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. An automatic control method for a hierarchically arranged flue gas waste heat recovery system, characterized in that: The invention comprises a flue gas waste heat recovery system arranged in a hierarchical manner, which comprises a boiler, a dust collector, an induced draft fan, a desulfurization tower and a chimney, and is characterized in that the waste heat recovery system also comprises a primary heat pipe type low-temperature economizer, a secondary heat pipe type low-temperature economizer, a controller and a flue gas temperature monitoring module, and the air preheater, the primary heat pipe type low-temperature economizer, the dust collector, the secondary heat pipe type low-temperature economizer, the induced draft fan, the desulfurization tower and the chimney of the boiler are interconnected in sequence through a flue gas conveying pipeline, a boiler water supply main pipe is used to convey water into the boiler, a circulation pipeline is used to convey part of the water in the boiler water supply main pipe to the primary heat pipe type low-temperature economizer and the secondary heat pipe type low-temperature economizer, and the flue gas conveying ... The water flowing out of the primary heat pipe type low-temperature economizer and the secondary heat pipe type low-temperature economizer is transported to the boiler water supply main pipe again. The smoke temperature monitoring module is used to monitor the inlet and outlet smoke temperatures of the primary heat pipe type low-temperature economizer, the inlet smoke temperature of the dust collector, and the inlet and outlet smoke temperatures of the secondary heat pipe type low-temperature economizer in real time. The controller realizes the operation control of the circulation pipeline according to the temperature data fed back by the smoke temperature monitoring module; the circulation pipeline includes a water supply branch, a return branch, a first water inlet pipe, a first water outlet pipe, a second water inlet pipe, and a second water outlet pipe. The water supply branch and the return branch are both connected to the boiler water supply main pipe, and the return branch is located downstream of the water supply branch. The water inlet and outlet of the high-temperature economizer are connected to the first water inlet pipe and the first water outlet pipe respectively, the water inlet and outlet of the secondary heat pipe low-temperature economizer are connected to the second water inlet pipe and the second water outlet pipe respectively, and a first manual exhaust valve and a second manual exhaust valve are respectively arranged on the first-level heat pipe low-temperature economizer and the secondary heat pipe low-temperature economizer; the water outlet end of the return water branch pipe is located in the boiler water supply main pipe, and the water flow direction of the water outlet end of the return water branch pipe is the same as the water flow direction in the boiler water supply main pipe; the first electric regulating valve and the first check valve are sequentially arranged on the boiler water supply main pipe located between the water supply branch pipe and the return water branch pipe, and the first an electric switch valve and a second electric regulating valve, the second electric switch valve is arranged on the first water outlet pipe, the fourth electric switch valve and the third electric regulating valve are arranged on the second water inlet pipe, and the fifth electric switch valve is arranged on the second water outlet pipe; the circulation pipeline comprises a first circulation booster pump and a second circulation booster pump, the first circulation booster pump is arranged on the first water inlet pipe, the second circulation booster pump is arranged on the second water inlet pipe, the first water inlet pipe and the second water inlet pipe are connected in parallel with the water supply branch pipe, the first water outlet pipe and the second water outlet pipe are connected in parallel with the return branch pipe, and the second check valve and the third electric switch valve are arranged on the return branch pipe;The circulation pipeline comprises a third circulation booster pump and a branch pipe, wherein the third circulation booster pump is arranged on the water supply branch pipe, the water inlet end of the branch pipe and the water inlet end of the second water inlet pipe are connected in parallel with the water outlet end of the water supply branch pipe in a parallel manner, the water outlet end of the branch pipe and the water outlet end of the first water outlet pipe are connected in parallel with the water inlet end of the return water branch pipe in a parallel manner, the first water inlet pipe and the second water outlet pipe are respectively connected with the branch pipe, and the connection between the first water inlet pipe and the branch pipe is located downstream of the connection between the second water outlet pipe and the branch pipe, a sixth electric switch valve and a fourth check valve are arranged on the branch pipe located upstream of the connection between the second water outlet pipe and the branch pipe, and a seventh electric switch valve and a third check valve are arranged on the branch pipe located downstream of the connection between the first water inlet pipe and the branch pipe; the automatic control method also comprises the following steps:; S1. During the operation of the boiler, the temperature sensor is used to monitor the smoke temperature T1 at the inlet of the dust collector, the smoke temperature T2 at the inlet of the secondary heat pipe low-temperature economizer, the smoke temperature T3 at the outlet of the secondary heat pipe low-temperature economizer, the smoke temperature T7 at the inlet of the primary heat pipe low-temperature economizer, and the smoke temperature T8 at the outlet of the secondary heat pipe low-temperature economizer in real time; the controller receives the data information of T1, T2, T3, T7, and T8 in real time, and at this time, the first electric regulating valve is in operation; S2, the controller receives the instruction of not putting into operation in real time, and at the same time, the controller compares T1 with the set temperature T4, T2 with the set temperature T5, and T3 with the set temperature T6 in real time, where T4>T5>T6; S2.1 When T1>T4 and T2>T5, enter the two-stage operation mode; the controller first puts the first-stage heat pipe type low-temperature economizer into operation, and realizes the stable operation state of T1 and T4 equal by controlling the operation process of the first-stage heat pipe type low-temperature economizer. When the stable operation state of T1 and T4 equal is reached, the controller starts the operation of the second-stage heat pipe type low-temperature economizer, and finally realizes the stable operation state of T3 and T6 equal by controlling the operation process of the second-stage heat pipe type low-temperature economizer; S2.2 When T1≤T4 and T2>T6, the single-stage operation control mode is entered; the controller puts the first-stage heat pipe type low-temperature economizer in the insulation working mode. When the first-stage heat pipe type low-temperature economizer is in the insulation working mode, the controller starts the operation of the second-stage heat pipe type low-temperature economizer, and finally achieves a stable operating state where T3 and T6 are equal by controlling the operation process of the second-stage heat pipe type low-temperature economizer; S2.3 When T1≤T4 and T2≤T6 or the controller receives an instruction not to put into operation, the controller causes both the first-stage heat pipe type low-temperature economizer and the second-stage heat pipe type economizer to enter the insulation working mode.

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