Flue gas waste heat gradient total recovery system for central heating

Abstract

The utility model provides a flue gas waste heat gradient total recovery system for central heating, which comprises a controller, a first-stage heat exchanger, a dust remover, a second-stage heat exchanger, a spray tower, a third-stage heat exchanger, a first-stage plate heat exchanger, a second-stage plate heat exchanger, a centrifugal heat pump unit and a screw type heat pump unit, a first-stage heat exchange circulation pipeline is arranged between the first-stage heat exchanger and the first-stage plate heat exchanger, a second-stage heat exchange circulation pipeline is arranged between the second-stage heat exchanger and the second-stage plate heat exchanger, and a third-stage heat exchange circulation pipeline is arranged between the spray tower and the third-stage heat exchanger. A heating return water circulation heating pipeline is arranged among the first-stage plate heat exchanger, the second-stage plate heat exchanger, the centrifugal heat pump unit and the screw type heat pump unit, and a fourth-stage heat exchange circulation pipeline is arranged among the third-stage heat exchanger, the centrifugal heat pump unit and the screw type heat pump unit. The system can achieve effective recovery of flue gas waste heat, meanwhile, the waste heat recovery cost is low, and system operation is safe and reliable.

Description

Technical Field

[0001] The utility model relates to the technical field of flue gas waste heat recovery, in particular to a flue gas waste heat gradient full recovery system for central heating and an operation control method. Background Art

[0002] The technology of waste heat recovery from flue gas of coal-fired boilers is developed on the basis of the importance of utilizing waste heat from flue gas of coal-fired boilers. Waste heat from flue gas is the heat generated by coal-fired boilers during the combustion process, and most of it is usually directly discharged into the atmosphere, causing energy waste and thermal pollution to the environment. Therefore, recycling this part of heat can not only improve energy utilization, but also reduce the impact on the environment.

[0003] In thermal power generating units, boiler efficiency is an important indicator of economical operation of the unit. Among all types of boiler heat losses, exhaust heat loss accounts for more than half of the total heat loss of the boiler. Research results show that for every 10°C increase in exhaust temperature, boiler efficiency decreases by 0.6-1.0%, and the unit standard coal consumption increases by 1.2-2.4g / (kW·h). The exhaust temperature design value of the current units is about 130°C, but due to coal-fired conditions and power plant operation levels, the actual exhaust temperature is generally around 150°C. Higher exhaust temperatures will lead to lower boiler efficiency and increased energy consumption.

[0004] The common problems in the existing flue gas waste heat recovery technology are: the system composition is relatively complex, resulting in high cost of waste heat recovery technology; the traditional absorption heat pump adopts high-temperature steam drive, and the system heating efficiency is high, but the investment cost is high and the flexibility is poor; the traditional single electric heat pump method cannot achieve high-temperature water heating, and the system efficiency is low. Utility Model Content

[0005] The purpose of the utility model is to provide a flue gas waste heat gradient full recovery system and an operation control method for central heating. By using this system and the operation method, the recovery and utilization of flue gas waste heat can be effectively realized, thereby reducing energy efficiency.

[0006] The technical solution adopted by the utility model to solve the technical problem is: a flue gas waste heat gradient full recovery system for centralized heating, including a controller, a primary heat exchanger, a dust collector, a secondary heat exchanger, a spray tower, a tertiary heat exchanger, a primary plate heat exchanger, a secondary plate heat exchanger, a centrifugal heat pump unit, and a screw heat pump unit. The primary heat exchanger, the dust collector, the secondary heat exchanger and the spray tower are connected in sequence through a flue gas pipeline. A primary heat exchange circulation pipeline is arranged between the primary heat exchanger and the primary plate heat exchanger. The secondary heat exchanger and the secondary plate heat exchanger are connected to each other through a flue gas pipeline. A secondary heat exchange circulation pipeline is arranged between the plate heat exchangers, a tertiary heat exchange circulation pipeline is arranged between the spray tower and the tertiary heat exchanger, a heating return water circulation heating pipeline is arranged between the primary plate heat exchanger, the secondary plate heat exchanger, the centrifugal heat pump unit and the screw heat pump unit, a quaternary heat exchange circulation pipeline is arranged between the tertiary heat exchanger, the centrifugal heat pump unit and the screw heat pump unit, and the controller can control the operation of the primary heat exchange circulation pipeline, the secondary heat exchange circulation pipeline, the tertiary heat exchange circulation pipeline, the quaternary heat exchange circulation pipeline and the heating return water circulation heating pipeline.

[0007] Preferably, the primary heat exchanger is an enameled glass flue gas heat exchanger, the secondary heat exchanger is a titanium alloy plate heat exchanger, the tertiary heat exchanger is a combined titanium alloy spiral plate heat exchanger, and the primary plate heat exchanger and the secondary plate heat exchanger are both heating plate heat exchangers.

[0008] Furthermore, the primary heat exchange circulation pipeline includes a first pipeline and a second pipeline, and the first pipeline and the second pipeline realize the circulation between the heat release side of the primary heat exchanger and the heat absorption side of the primary plate heat exchanger. A first variable frequency water pump is arranged on the first pipeline, and the controller is electrically connected to the first variable frequency water pump.

[0009] Furthermore, the secondary heat exchange circulation pipeline includes a third pipeline and a fourth pipeline, and the third pipeline and the fourth pipeline realize the circulation between the heat release side of the secondary heat exchanger and the heat absorption side of the secondary plate heat exchanger. A second variable frequency water pump is arranged on the third pipeline, and the controller is electrically connected to the second variable frequency water pump.

[0010] Furthermore, the three-stage heat exchange circulation pipeline includes a fifth pipeline and a sixth pipeline, and the fifth pipeline and the sixth pipeline realize the circulation between the spray slurry inlet and outlet of the spray tower and the heat absorption side of the three-stage heat exchanger. A third variable frequency water pump is arranged on the fifth pipeline, and the controller is electrically connected to the third variable frequency water pump.

[0011] Furthermore, the four-stage heat exchange circulation pipeline includes a seventh pipeline, an eighth pipeline, and a ninth pipeline. The seventh pipeline realizes the connection between the heat release side outlet of the three-stage heat exchanger and the inlet of the evaporator of the screw heat pump unit, the eighth pipeline realizes the connection between the outlet of the evaporator of the screw heat pump unit and the inlet of the evaporator of the centrifugal heat pump unit, and the ninth pipeline realizes the connection between the outlet of the evaporator of the centrifugal heat pump unit and the inlet of the heat release side of the three-stage heat exchanger. A fourth variable frequency water pump is connected in series to the ninth pipeline, and the controller is electrically connected to the fourth variable frequency water pump.

[0012] Furthermore, the heating return water circulation heating pipeline includes a tenth pipeline, an eleventh pipeline, a twelfth pipeline, a thirteenth pipeline, and a fourteenth pipeline. One end of the tenth pipeline is connected to the return water pipe of the hot end, and the other end is connected to the inlet of the condenser of the centrifugal heat pump unit. A first control valve is arranged on the tenth pipeline. The eleventh pipeline realizes the connection between the outlet of the condenser of the centrifugal heat pump unit and the inlet of the condenser of the screw heat pump unit. The twelfth pipeline realizes the connection between the outlet of the condenser of the centrifugal heat pump unit and the inlet of the condenser of the screw heat pump unit. The outlet is connected with the inlet of the heat release side of the secondary plate heat exchanger, a second control valve is arranged on the twelfth pipeline, the thirteenth pipeline realizes the connection between the outlet of the heat release side of the secondary plate heat exchanger and the inlet of the heat release side of the primary plate heat exchanger, a third control valve is arranged on the thirteenth pipeline, one end of the fourteenth pipeline is connected with the outlet of the heat release side of the primary plate heat exchanger, and the other end is connected with the water supply pipe of the heat-using end, and the fourth control valve and the fifth variable frequency water pump are connected in series on the fourteenth pipeline.

[0013] Furthermore, a steam purge pipeline is arranged on one side of the primary heat exchanger, the steam purge pipeline includes a steam channel and a steam drum, the steam pipeline realizes the connection between the steam drum and the steam gas source, the steam drum realizes the connection with the primary heat exchanger through a fifteenth pipeline, a fifth control valve is arranged on the fifteenth pipeline, a high-pressure water flushing pipeline is arranged on one side of the secondary heat exchanger, the high-pressure water flushing pipeline includes a sixteenth pipeline, the sixteenth pipeline realizes the connection between the twelfth pipeline and the secondary heat exchanger, a sixth variable frequency water pump and a sixth control valve are connected in series to the sixteenth pipeline, an expandable decontaminant is connected in series to the fifth pipeline, a seventh control valve and an eighth control valve are arranged on the fifth pipeline, which are located upstream and downstream of the expandable decontaminant, a first bypass pipeline is arranged between the upstream of the seventh control valve and the downstream of the eighth control valve, a ninth control valve is connected in series to the first bypass pipeline, and a ninth control valve is connected in series to the first bypass pipeline. A cyclone-type dirt remover is connected in series to the tenth pipeline, and a tenth control valve and an eleventh control valve are arranged on the tenth pipeline, which are located upstream and downstream of the cyclone-type dirt remover, respectively; a second bypass pipeline is arranged between the upstream of the tenth control valve and the downstream of the eleventh control valve, and a twelfth control valve is connected in series to the second bypass pipeline; a third bypass pipeline is arranged between the tenth pipeline and the eleventh pipeline, and a thirteenth control valve is arranged on the third bypass pipeline; a fourth bypass pipeline is arranged between the eleventh pipeline and the twelfth pipeline, and a fourteenth control valve is arranged on the fourth bypass pipeline; a fifth bypass pipeline is arranged between the thirteenth pipeline and the fourteenth pipeline, and a fifteenth control valve is arranged on the fifth bypass pipeline; a sixth bypass pipeline is arranged between the twelfth pipeline and the fourteenth pipeline, and a sixteenth control valve is arranged on the sixth bypass pipeline.

[0014] Furthermore, pressure sensors and temperature sensors are provided on the flue gas duct, the fifth duct, the seventh duct, the ninth duct, the tenth duct and the twelfth duct; and temperature sensors are provided on the first duct, the second duct, the third duct, the fourth duct and the eighth duct.

[0015] The beneficial effects of the utility model are:

[0016] (1) The flue gas waste heat recovery rate is high, and both the sensible heat and latent heat of high-temperature flue gas are recovered, with the lowest flue gas temperature reaching 35°C; when the exhaust temperature of the spray tower reaches below 35°C, the white smoke elimination function can be effectively realized, thereby improving the environmental quality.

[0017] (2) Heat recovery in stages: waste heat recovery units are configured according to different flue gas temperatures, effectively solving problems such as easy blockage and corrosion of flue gas heat exchangers;

[0018] (3) The system has a high heating efficiency. The first two stages use heat exchangers, and the third stage uses a combination of centrifugal heat pumps and screw heat pumps. The total system efficiency can reach more than 10.

[0019] (4) The system has a high heating temperature and can be directly integrated into the heating network, thereby effectively saving heating energy.

[0020] (5) The system can run fully automatically under the program set inside the controller, thereby greatly reducing the operating and maintenance costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] In order to more clearly illustrate the embodiments of the utility model 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 utility model. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0022] Figure 1 It is a schematic diagram of the composition framework of the utility model;

[0023] In the figure: 1 primary heat exchanger, 2 dust collector, 3 secondary heat exchanger, 4 spray tower, 5 tertiary heat exchanger, 6 primary plate heat exchanger, 7 secondary plate heat exchanger, 8 centrifugal heat pump unit, 9 screw heat pump unit, 10 expansion type dirt remover, 11 cyclone dirt remover, 101 flue gas channel, 102 steam channel 103 drum, 201 first pipeline, 202 second pipeline, 203 third pipeline, 204 fourth pipeline, 205 fifth pipeline, 206 sixth pipeline, 207 seventh pipeline, 208 eighth pipeline, 209 ninth pipeline, 210 tenth pipeline, 211 eleventh pipeline, 212 twelfth pipeline, 213 thirteenth pipeline, 214 fourteenth pipeline, 215 fifteenth pipeline, 216 sixteenth pipeline, 301 first bypass pipeline, 302 second bypass pipeline, 30 3 the third bypass pipeline, 304 the fourth bypass pipeline, 305 the fifth bypass pipeline, 306 the sixth bypass pipeline, 401 the first variable frequency water pump, 402 the second variable frequency water pump, 403 the third variable frequency water pump, 404 the fourth variable frequency water pump, 405 the fifth variable frequency water pump, 406 the sixth variable frequency water pump, 501 the first control valve, 502 the second control valve, 503 the third control valve, 504 the fourth control valve, 505 the fifth control valve, 506 the sixth control valve, 507 the seventh control valve, 508 the eighth control valve, 509 the ninth control valve, 510 the tenth control valve, 511 the eleventh control valve, 512 the twelfth control valve, 513 the thirteenth control valve, 514 the fourteenth control valve, 515 the fifteenth control valve, 516 the sixteenth control valve, 601 the temperature sensor, 701 the pressure sensor. DETAILED DESCRIPTION

[0024] The following will be combined with specific embodiments and attached Figure 1 , the technical solutions in the embodiments of the utility model are clearly and completely described. Obviously, the described embodiments are only part of the preferred embodiments of the utility model, not all of the embodiments. Those skilled in the art can make similar modifications without violating the connotation of the utility model, so the utility model is not limited by the specific embodiments disclosed below.

[0025] A flue gas waste heat gradient full recovery system for central heating (such as Figure 1As shown), it includes a controller, a primary heat exchanger 1, a dust collector 2, a secondary heat exchanger 3, a spray tower 4, a tertiary heat exchanger 5, a primary plate heat exchanger 6, a secondary plate heat exchanger 7, a centrifugal heat pump unit 8, and a screw heat pump unit 9. In the field of flue gas waste heat recovery technology, the heat exchanger is a commonly used technical product, so the detailed working principle of the heat exchanger is not introduced in detail. The dust collector 2 and the centrifugal heat pump unit 8 and the screw heat pump unit 9 are also commonly used technical products in the field of flue gas waste heat technology, so the working principle of the dust collector 2 and the heat pump unit is not introduced in detail. In actual application, the dust collector 2 can be cloth Bag dust collector, the primary heat exchanger 1, the dust collector 2, the secondary heat exchanger 3 and the spray tower 4 are connected in sequence through the flue gas pipeline 101, that is, the high-temperature flue gas discharged from the boiler passes through the primary heat exchanger 1, the dust collector 2, the secondary heat exchanger 3 and the spray tower 4 in sequence through the diversion effect of the flue gas pipeline 101, and a primary heat exchange circulation pipeline is arranged between the primary heat exchanger 1 and the primary plate heat exchanger 6, and the first gradient heat exchange of the waste heat of the high-temperature flue gas is realized by the primary heat circulation pipeline, and a secondary heat exchange circulation pipeline is arranged between the secondary heat exchanger 2 and the secondary plate heat exchanger 7, and the ... The pipeline realizes the second gradient heat exchange of the high-temperature flue gas waste heat. A three-stage heat exchange circulation pipeline is arranged between the spray tower 4 and the three-stage heat exchanger 5. The three-stage heat exchange circulation pipeline is used to realize the third gradient heat exchange of the high-temperature flue gas waste heat. Through the three-gradient heat exchange of the high-temperature flue gas waste heat, it is beneficial to realize the effective absorption of the high-temperature flue gas waste heat. The absorbed heat energy is finally used to supply heat to the heat-using end through subsequent heat transfer, thereby achieving the purpose of energy saving; a heating return water circulation heating pipeline is arranged between the first-stage plate heat exchanger 6, the second-stage plate heat exchanger 7, the centrifugal heat pump unit 8 and the screw heat pump unit 9, and the heating return water circulation heating pipeline is used to realize the third gradient heat exchange of the high-temperature flue gas waste heat. The heat pipe can transfer the heat absorbed by the high-temperature flue gas directly to the return water at the heat-using end, so as to realize the final utilization of the flue gas waste heat; a four-stage heat exchange circulation pipeline is arranged between the three-stage heat exchanger 5, the centrifugal heat pump unit 8 and the screw heat pump unit 9. The four-stage heat exchange circulation pipeline can facilitate the centrifugal heat pump unit 8 and the screw heat pump unit 9 to further absorb and utilize the low-temperature waste heat, and then realize the large temperature difference cooling of the flue gas. The controller can control the operation of the first-stage heat exchange circulation pipeline, the second-stage heat exchange circulation pipeline, the third-stage heat exchange circulation pipeline, the fourth-stage heat exchange circulation pipeline and the heating return water circulation heating pipeline. The flue gas waste heat recovery system of this system has a relatively simple composition structure, so it is conducive to reducing the cost of recovering flue gas waste heat.

[0026] Taking into account the problems of corrosion of heat exchangers and heat exchange stability of high-temperature flue gas during the gradient cooling process, the first-stage heat exchanger 1 is an enameled glass flue gas heat exchanger, which has a small flow resistance coefficient and corrosion resistance. The second-stage heat exchanger 2 is a titanium alloy plate heat exchanger, and the third-stage heat exchanger 3 is a combined titanium alloy spiral plate heat exchanger. Both the titanium alloy plate heat exchanger and the titanium alloy spiral plate heat exchanger have good mechanical properties and high corrosion resistance. The first-stage plate heat exchanger and the second-stage plate heat exchanger are heating plate heat exchangers. The heating plate heat exchanger has good heat exchange performance. At the same time, its structure is simple and its operation is reliable.

[0027] On the basis of the above embodiment, the specific implementation method of the primary heat exchange circulation pipeline is as follows: the primary heat exchange circulation pipeline includes a first pipeline 201 and a second pipeline 202, the first pipeline 201 and the second pipeline 202 realize the circulation connection between the heat release side of the primary heat exchanger 1 and the heat absorption side of the primary plate heat exchanger 6, a first variable frequency water pump 401 is arranged on the first pipeline 201, the controller is electrically connected to the first variable frequency water pump 401, when the first variable frequency water pump 401 is operated under the control of the controller, the heat exchange medium is realized to circulate between the primary heat exchanger and the primary plate heat exchanger 6, thereby realizing the heat of the high-temperature flue gas to the primary plate heat exchanger 6, and the high-temperature flue gas temperature can generally be reduced by about 35°C after passing through the primary heat exchanger.

[0028] On the basis of the above embodiment, the specific implementation method of the secondary heat exchange circulation pipeline is as follows: the secondary heat exchange circulation pipeline includes a third pipeline 203 and a fourth pipeline 204, and the third pipeline 203 and the fourth pipeline 204 realize the circulation connection between the heat release side of the secondary heat exchanger 3 and the heat absorption side of the secondary plate heat exchanger 7. A second variable frequency water pump 402 is arranged on the third pipeline 203, and the controller is electrically connected to the second variable frequency water pump 402. When the second variable frequency water pump 402 is operated under the control of the controller, the heat exchange medium is realized to circulate between the secondary heat exchanger 3 and the secondary plate heat exchanger 6, thereby realizing the heat of the high-temperature flue gas to the secondary plate heat exchanger 7. After the high-temperature flue gas passes through the secondary heat exchanger, the flue gas temperature can generally be reduced by about 35°C. In actual application, when the high-temperature flue gas is heat exchanged in the secondary heat exchanger 3, a large amount of condensed water will be sucked out. At the same time, the pH of the condensed water is extremely low. The titanium alloy plate heat exchanger has high corrosion resistance, which can effectively ensure its long-term and effective operation.

[0029] On the basis of the above embodiment, the specific implementation method of the three-stage heat exchange circulation pipeline is as follows: the three-stage heat exchange circulation pipeline includes a fifth pipeline 205 and a sixth pipeline 206, and the fifth pipeline 205 and the sixth pipeline 206 realize the circulation of the spray slurry inlet and outlet of the spray tower 4 and the heat absorption side of the three-stage heat exchanger 5. A third variable frequency water pump 403 is arranged on the fifth pipeline 205, and the controller is electrically connected to the third variable frequency water pump 403. During the continuous movement of the third variable frequency water pump 403, it continuously transports the spray slurry from the bottom of the spray tower 4 to the upper part of the spray tower, thereby realizing continuous heat exchange between the spray slurry and the flue gas in the spray tower 4.

[0030] The use of the primary plate heat exchanger 6, the secondary plate heat exchanger 7 and the tertiary heat exchanger 5 in the above embodiment realizes the three-gradient absorption and utilization of the high-temperature flue gas waste heat, thereby greatly improving the recovery effect of the high-temperature flue gas waste heat.

[0031] On the basis of the above embodiment, the specific implementation of the four-stage heat exchange circulation pipeline is as follows: the four-stage heat exchange circulation pipeline includes a seventh pipeline 207, an eighth pipeline 208, and a ninth pipeline 209, wherein the seventh pipeline 207 realizes the connection between the heat release side outlet of the three-stage heat exchanger 7 and the inlet of the evaporator of the screw heat pump unit 9, the eighth pipeline 208 realizes the connection between the outlet of the evaporator of the screw heat pump unit 9 and the inlet of the evaporator of the centrifugal heat pump unit 8, and the ninth pipeline 209 realizes the heat release side outlet of the evaporator of the centrifugal heat pump unit 8 and the three-stage heat exchanger 5. The side inlet is connected, and a fourth variable frequency water pump 404 is connected in series on the ninth pipeline 209. The controller is electrically connected to the fourth variable frequency water pump 404. The screw heat pump unit 9 and the centrifugal heat pump unit 8 have low-temperature absorption capabilities. When the fourth variable frequency water pump 404 is continuously running, the heat exchange medium circulates in the three-stage heat exchanger 5, the screw heat pump unit 9 and the centrifugal heat pump unit 8 in sequence, so that the heat of the low-temperature flue gas in the spray tower 4 absorbed by the three-stage heat exchanger 5 is continuously transported to the screw heat pump unit 9 and the centrifugal heat pump unit 8, thereby realizing the effective absorption of the waste heat of the low-temperature flue gas.

[0032] On the basis of the above embodiment, the specific implementation method of the heating return water circulation heating pipeline is as follows: the heating return water circulation heating pipeline includes the tenth pipeline 210, the eleventh pipeline 211, the twelfth pipeline 212, the thirteenth pipeline 213, and the fourteenth pipeline 214. One end of the tenth pipeline 210 is connected with the return pipe of the hot end, and the other end is connected with the inlet of the condenser of the centrifugal heat pump unit 8. A first control valve 501 is arranged on the tenth pipeline 210. The eleventh pipeline 211 realizes the connection between the outlet of the condenser of the centrifugal heat pump unit 8 and the screw heat pump The inlet of the condenser of the unit 9 is connected. When the first control valve 501 is in the connected state, the return water enters the condenser of the centrifugal heat pump unit 8 from the tenth pipeline 210 and flows into the eleventh pipeline 211. When the condenser of the centrifugal heat pump unit 8 is working, condensation and heat release are performed, thereby realizing the first gradient heating of the return water. The twelfth pipeline 212 realizes the connection between the outlet of the condenser of the screw heat pump unit 9 and the inlet of the heat release side of the secondary plate heat exchanger 7. A second control valve is arranged on the twelfth pipeline. When the second control valve 501 is in the connected state, the return water enters the condenser of the centrifugal heat pump unit 8 from the tenth pipeline 210 and flows into the eleventh pipeline 211. When the condenser of the centrifugal heat pump unit 8 is working, condensation and heat release are performed, thereby realizing the first gradient heating of the return water. The twelfth pipeline 212 realizes the connection between the outlet of the condenser of the screw heat pump unit 9 and the inlet of the heat release side of the secondary plate heat exchanger 7. The pipe 211 enters the condenser of the screw heat pump unit 9 and flows into the twelfth pipe 211. When the condenser of the screw heat pump unit 9 is working, condensation releases heat, thereby realizing the second gradient heating of the return water. The thirteenth pipe 213 realizes the connection between the outlet of the heat release side of the secondary plate heat exchanger 7 and the inlet of the heat release side of the primary plate heat exchanger 6. During the flow of the return water from the secondary plate heat exchanger 7, the third gradient heating is realized. A third control valve 503 is set on the thirteenth pipe 213. One end of the fourteenth pipe 214 is connected to the primary plate heat exchanger 6. The outlet of the heat release side is through-connected, and the other end is through-connected with the water supply pipe of the heat-using end. When the third control valve 503 is in the through state, the return water is heated by the primary plate heat exchanger 6, and the fourth gradient heating of the return water is realized. After the return water is heated by the four gradients, the temperature can reach about 100 degrees, and then it can directly flow into the heat-using end for heating. The fourth control valve 504 and the fifth variable frequency water pump 405 are connected in series on the fourteenth pipeline 214. During the heating process, the fourth control valve 504 is in the through state, and the fifth variable frequency water pump 405 operates in real time under the operation of the controller.

[0033] In practical applications, in order to facilitate the effective cleaning of the primary heat exchanger 1, a steam purge pipeline is arranged on one side of the primary heat exchanger 1. The steam purge pipeline includes a steam channel 102 and a steam drum 103. The steam pipeline 102 realizes the connection between the steam drum 103 and the steam source. The steam drum 103 realizes the connection with the primary heat exchanger 1 through the fifteenth pipeline 215. A fifth control valve 505 is arranged on the fifteenth pipeline 215. The controller intermittently realizes the opening and closing of the fifth control valve 505, and then realizes the regular cleaning of the primary heat exchanger 1, thereby effectively maintaining the heat exchanger 1. To ensure the cleanliness of the primary heat exchanger, the high-temperature flue gas can flow smoothly in the primary heat exchanger 1; to facilitate the effective and timely flushing of the condensed water in the secondary heat exchanger 3, a high-pressure water flushing pipeline is arranged on one side of the secondary heat exchanger 3, and the high-pressure water flushing pipeline includes a sixteenth pipeline 216, and the sixteenth pipeline 216 realizes the connection between the twelfth pipeline 212 and the secondary heat exchanger 3. The sixth variable frequency water pump 406 and the sixth control valve 506 are connected in series to the sixteenth pipeline 216. The sixth control valve 506 is an electric regulating valve, and its opening degree can be realized by using a controller. The controller can also realize the timing opening and closing of the sixth variable frequency water pump 406 and the sixth control valve 506, so as to realize the timing flushing of the secondary heat exchanger; in order to ensure the cleanliness of the spray slurry and realize the lasting and effective circulation of the spray slurry, an expansion type dirt remover 10 is connected in series to the fifth pipeline 205, and a seventh control valve 507 and an eighth control valve 508 are arranged on the fifth pipeline 205, which are located upstream and downstream of the expansion type dirt remover 10. A first bypass pipeline 301 is arranged between the downstream of the expansion type decontaminant 10 and the expansion type decontaminant 10, and a ninth control valve 509 is connected in series to the first bypass pipeline 301. Under the condition of normal circulation of the spray slurry, the seventh control valve 507 and the eighth control valve 508 are in a through state, so that the spray slurry flows through the expansion type decontaminant 10 to achieve impurity filtration. When the expansion type decontaminant 10 is discharged or needs to be repaired, the seventh control valve 507 and the eighth control valve 508 are closed, and at the same time, the ninth control valve 509 is opened, so that the spray slurry does not flow into the expansion type decontaminant 10;In order to achieve effective filtration of the return water from the hot end so as to ensure the cleanliness of the return water from the hot end, a cyclone type dirt remover 11 is connected in series to the tenth pipeline 210, and a tenth control valve 501 and an eleventh control valve 511 are arranged on the tenth pipeline 210, which are located upstream and downstream of the cyclone type dirt remover 11. A second bypass pipeline 302 is arranged between the upstream of the tenth control valve 510 and the downstream of the eleventh control valve 511, and a twelfth control valve 512 is connected in series to the second bypass pipeline 302. In normal operation, the twelfth control valve 512 is in a closed state, and the tenth control valve 510 and the tenth control valve 511 are in a closed state. The first control valve 511 is in an open state, so the return water can be directly placed in the cyclone type dirt separator 11, so as to achieve the filtration of the return water. When the cyclone type dirt separator 11 needs to be discharged or repaired, at this time, the tenth control valve 510 and the eleventh control valve 511 are closed, and the twelfth control valve 512 is opened, so that the return water can directly bypass the cyclone type dirt separator 11 through the second bypass pipeline 302; in actual application, the return water heating process can be adjusted according to the heat load of the heat-using end. In order to facilitate the regulation of the heating participation process of the centrifugal heat pump unit 8 and the screw heat pump unit 9, here, the tenth pipeline 210 and the eleventh pipeline are connected. A third bypass pipeline 303 is provided between the eleventh pipeline 211 and the twelfth pipeline 212, and a thirteenth control valve 513 is provided on the third bypass pipeline 303. When the centrifugal heat pump unit 8 is required to participate in the return water heating process, the thirteenth control valve 513 is in a closed state, and when the centrifugal heat pump unit 8 is not required to participate in the return water heating process, the thirteenth control valve 513 is in an open state; a fourth bypass pipeline 304 is provided between the eleventh pipeline 211 and the twelfth pipeline 212, and a fourteenth control valve 514 is provided on the fourth bypass pipeline 304. When the screw heat pump unit 9 is required to participate in the return water heating process, the fourteenth control valve 51 4 is in a closed state, and when the screw heat pump unit 9 is not required to participate in the return water heating process, the fourteenth control valve 514 is in an open state; in order to facilitate the heating control of the return water by the primary plate heat exchanger, a fifth bypass pipeline 305 is arranged between the thirteenth pipeline 213 and the fourteenth pipeline 214, and a fifteenth control valve 515 is arranged on the fifth bypass pipeline 305. The fifteenth control valve 515 and the third control valve 503 are both electric regulating valves. Through the joint action of the fifteenth control valve 515 and the third control valve 503, the return water flow rate of the primary plate heat exchanger is controlled, and then the return water heating regulation is realized;In order to facilitate the stable delivery of the heated return water, a sixth bypass pipeline 506 is provided between the twelfth pipeline 12 and the fourteenth pipeline 14, and a sixteenth control valve 516 is provided on the sixth bypass pipeline 506. The sixteenth control valve 516 is an electric regulating valve. In actual application, the controller can adjust the opening degree of the sixteenth control valve 516 according to actual needs, so as to achieve the stable delivery of the heated return water. ;

[0034] During the operation of the entire system, in order to facilitate the staff to understand the operating conditions of the more important components of the system in real time, pressure sensors 701 and temperature sensors 601 are provided on the flue gas duct 101, the fifth duct 205, the seventh duct 207, the ninth duct 209, the tenth duct 210 and the twelfth duct 212, and temperature sensors 601 are provided on the first duct 201, the second duct 202, the third duct 203, the fourth duct 204 and the eighth duct 208. The pressure sensor 601 can transmit the monitored temperature signal to the controller in real time, and the controller can process the monitoring signal and display the corresponding temperature value on the monitoring screen. At the same time, the controller can use the relevant temperature monitoring information according to the set program to realize the regulation of the operating logic of the system, so as to realize the reasonable and effective operation of the system; the pressure sensor 701 can transmit the monitored temperature signal to the controller in real time, and the controller can process the monitoring signal and display the corresponding pressure value on the monitoring screen. The staff can predict the system operation status based on work experience through the displayed temperature value and pressure value.

[0035] In actual application, all control valves in the system are electrically connected to the controller, wherein the sixth control valve 506, the third control valve 503, the fifteenth control valve 515 and the sixteenth control valve 516 are electric regulating valves, and the remaining control valves are electric switch valves, which can adjust the opening size according to demand, and the electric switch valves have only two operating states: closed and open. In actual operation, the controller controls the operation of each variable frequency water pump, each control valve, centrifugal heat pump unit 8 and screw heat pump unit 9 in the system, thereby realizing the control of various operating states of the system, and then realizing the automatic operation of the system, which greatly reduces the workload of manual assistance.

[0036] The operation control steps of an embodiment of the utility model are as follows:

[0037] S1. Start the controller, which performs power-on fault detection on each electronically controlled operating component. If a fault is found, the controller will issue a fault alarm message to notify the staff to troubleshoot the fault;

[0038] S2. When there is no fault in each electronically controlled operating component or the fault is eliminated, the staff sets the comparison threshold value T11 of the smoke inlet temperature T1 of the dust collector 2, the comparison threshold value T21 of the smoke inlet temperature T2 of the spray tower, the comparison threshold value T31 of the slurry outlet temperature T3 of the spray tower, and the comparison threshold values ​​T41, T42, T43, and T44 of the return water temperature T4 of the hot end in the control program of the controller, T41<T42<T43<T44. After setting the above comparison thresholds, the controller starts the relevant components accordingly, so that the system enters the heating operation state; by effectively controlling the smoke inlet temperature T1 of the dust collector 2, it can be avoided that the smoke inlet temperature T1 is too low to enter When the smoke temperature in the dust collector 2 is too low, steam condensation is likely to occur. Smoke condensation will cause the dust collector 2 to be easily blocked, which will greatly affect the flow of smoke in the dust collector 2, and then affect the subsequent flue gas waste heat recovery process; under full load operation, by effectively controlling the smoke inlet temperature T2 and the slurry outlet temperature T3 of the spray tower, the final smoke outlet temperature of the spray tower 4 can be controlled at about 35 degrees, so that white smoke control can be achieved, which is beneficial to improve the environmental quality; by monitoring the return water temperature T4 of the heat-using end, the heat supply logic control of the heat-using end can be achieved, which is convenient for realizing the effective utilization of flue gas waste heat and at the same time, realizing energy conservation. In the actual operation process, the specific values ​​of T11, T21 and T31 can be determined according to the smoke emission characteristics and work experience; T41, T42, T43 and T44 can be set according to the heat characteristics and work experience of the heat-using end.

[0039] S3. During the whole process of heating operation, the controller always compares T1 with T11 in real time. When T1≤T11, the controller adjusts the working frequency of the first variable frequency water pump 401 according to the set program until T1>T11, then stops adjusting the first variable frequency water pump 401. T11 is the minimum operating value of the smoke inlet temperature T2 of the dust collector 2. Only when T2 is kept above T11, it can ensure that the high-temperature smoke will not condense in the dust collector 2. The change of the working frequency of the first variable frequency water pump 401 realizes the change of the heat exchange medium flow rate, thereby realizing the regulation and control of the smoke inlet temperature T2.

[0040] During the entire heating operation process, the controller always compares T4 with T41, T42, T43, and T44 in real time:

[0041] When T4≤T41, it means that the heat load at the heat-using end is large and a large amount of heat source is required, so the system automatically enters the full-load operation state. At this time, the first-stage plate heat exchanger 6, the second-stage plate heat exchanger 7, the third-stage heat exchanger 5, the centrifugal heat pump unit 8 and the screw heat pump unit 9 are all performing heat exchange work, the sixteenth control valve 516 is in a partially open state to ensure the stability of heating, the ninth control valve 509, the fifteenth control valve 515, the twelfth control valve 512, the thirteenth control valve 513 and the fourteenth control valve 514 are in a closed state, and the remaining control valves are in an open state. During the full-load operation state, the controller real-time Compare T2 with T21, and compare T3 with T31. When T2≥T21, the controller adjusts the working frequency of the second variable frequency water pump 402 and the fifth variable frequency water pump 405 according to the set program, until T2<T21, then stop adjusting the second variable frequency water pump 402 and the fifth variable frequency water pump 405. When T3≥T31, the controller adjusts the working frequency of the third variable frequency water pump 403 and the fourth variable frequency water pump 404 according to the set program, until T3<T31, then stop adjusting the third variable frequency water pump 403 and the fourth variable frequency water pump 404. The purpose of the above two control logics is to adjust the exhaust temperature of the flue gas at the end so as to The white smoke elimination function is realized; when T41<T4, it indicates that the heat load of the heat-using end is reduced and the required heat is reduced, so the system can enter the partial load operation state at this time; in the partial load operation state, when T41<T4≤T42, at this time, the controller stops the operation of the centrifugal heat pump unit 8, and the heat demand decreases. The operation of the centrifugal heat pump unit 8 is stopped first, thereby reducing the power consumption and realizing the saving of waste heat recovery energy. After the centrifugal heat pump unit 8 stops working, the thirteenth control valve 513 is opened synchronously, so that the return water directly enters the screw heat pump unit 9, and the system only uses the primary plate heat exchanger 6 and the secondary plate heat exchanger 6. The operation of the heat exchanger 7 and the screw heat pump unit 9 can meet the demand for heat load at the heat-using end; when T42<T4≤T43, it means that the heat load at the heat-using end is reduced, and the required heat is further reduced, so the controller stops the operation of the screw heat pump unit 9 at this time. When the screw heat pump unit 9 stops running, the fourteenth control valve 514 is opened synchronously, and the return water does not pass through the screw heat pump unit 9 but directly enters the secondary plate heat exchanger 7 to be heated again. When the screw heat pump unit 9 stops running, the heating cost is further reduced. At this time, the system only needs to use the primary plate heat exchanger 6 and the secondary plate heat exchanger 7 for heating;When T43<T4≤T44, it means that the heat load of the heat-using end is reduced, and the required heat is further reduced. Therefore, the controller stops the heat exchange operation of the primary plate heat exchanger 6 at this time, and opens the fifteenth control valve 515 at the same time. The stopping of the primary plate heat exchanger 6 is achieved by closing the third control valve 503 and the first variable frequency water pump 401. At this time, the system only realizes heating through the secondary plate heat exchanger 7. When only the secondary plate heat exchanger 7 is in operation, the controller appropriately adjusts the opening degree of the fifteenth control valve 515 according to the setting program based on the value of T4 to meet the heating load demand of the heat-using end; when T44<T4, it means that the heat-using end no longer needs to be heated. At this time, the heating of the heat-using end can be stopped, so the controller stops the heat exchange operation of the secondary plate heat exchanger 7. The stopping of the secondary plate heat exchanger 7 is achieved by closing the second control valve 502 and the second variable frequency water pump 402. When the secondary plate heat exchanger 7 is closed, the return water is no longer heated. ;

[0042] During partial load operation, the system adopts a control logic sequence of shutting down the centrifugal heat pump unit, the screw heat pump unit, the primary plate heat exchanger and the secondary plate heat exchanger in sequence, thereby saving heating energy. At the same time, the primary plate heat exchanger is shut down before the secondary plate heat exchanger, which can effectively ensure that the inlet temperature of the dust collector 2 is within a relatively high range when entering the dust collector 2, thereby ensuring that the high-temperature flue gas will not condense in the dust collector 2, effectively ensuring the safe operation of the dust collector 2.

[0043] In the present utility model, "upper", "lower", "front", "back", "left" and "right" are relative positions used to conveniently describe positional relationships, and therefore cannot be understood as absolute positions to limit the scope of protection.

[0044] Except for the technical features described in the specification, all other technical features are known technologies to those skilled in the art.

[0045] The above description in combination with the accompanying drawings has detailed the preferred implementation modes and embodiments of the utility model, but the utility model 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 utility model, and these improvements and modifications should also be regarded as the protection scope of the utility model.

Claims

1. A flue gas waste heat gradient full recovery system for central heating, characterized in that: The utility model comprises a controller, a primary heat exchanger, a dust collector, a secondary heat exchanger, a spray tower, a tertiary heat exchanger, a primary plate heat exchanger, a secondary plate heat exchanger, a centrifugal heat pump unit, and a screw heat pump unit. The primary heat exchanger, the dust collector, the secondary heat exchanger and the spray tower are connected in sequence through a flue gas pipeline. A primary heat exchange circulation pipeline is arranged between the primary heat exchanger and the primary plate heat exchanger, a secondary heat exchange circulation pipeline is arranged between the secondary heat exchanger and the secondary plate heat exchanger, and the spray A three-stage heat exchange circulation pipeline is arranged between the tower and the three-stage heat exchanger, a heating return water circulation heating pipeline is arranged between the first-stage plate heat exchanger, the second-stage plate heat exchanger, the centrifugal heat pump unit and the screw heat pump unit, a fourth-stage heat exchange circulation pipeline is arranged between the third-stage heat exchanger, the centrifugal heat pump unit and the screw heat pump unit, and the controller can control the operation of the first-stage heat exchange circulation pipeline, the second-stage heat exchange circulation pipeline, the third-stage heat exchange circulation pipeline, the fourth-stage heat exchange circulation pipeline and the heating return water circulation heating pipeline.

2. The flue gas waste heat gradient full recovery system for central heating according to claim 1 is characterized in that: The first-stage heat exchanger is an enameled glass flue gas heat exchanger, the second-stage heat exchanger is a titanium alloy plate heat exchanger, the third-stage heat exchanger is a combined titanium alloy spiral plate heat exchanger, and the first-stage plate heat exchanger and the second-stage plate heat exchanger are both heating plate heat exchangers.

3. The flue gas waste heat gradient full recovery system for central heating according to claim 2 is characterized in that: The primary heat exchange circulation pipeline includes a first pipeline and a second pipeline. The first pipeline and the second pipeline realize the circulation connection between the heat release side of the primary heat exchanger and the heat absorption side of the primary plate heat exchanger. A first variable frequency water pump is arranged on the first pipeline, and the controller is electrically connected to the first variable frequency water pump.

4. The flue gas waste heat gradient full recovery system for central heating according to claim 3 is characterized in that: The secondary heat exchange circulation pipeline includes a third pipeline and a fourth pipeline. The third pipeline and the fourth pipeline realize the circulation connection between the heat release side of the secondary heat exchanger and the heat absorption side of the secondary plate heat exchanger. A second variable frequency water pump is arranged on the third pipeline, and the controller is electrically connected to the second variable frequency water pump.

5. The flue gas waste heat gradient full recovery system for central heating according to claim 4 is characterized in that: The three-stage heat exchange circulation pipeline includes a fifth pipeline and a sixth pipeline. The fifth pipeline and the sixth pipeline realize the circulation of the spray slurry inlet and outlet of the spray tower and the heat absorption side of the three-stage heat exchanger. A third variable frequency water pump is arranged on the fifth pipeline, and the controller is electrically connected to the third variable frequency water pump.

6. The flue gas waste heat gradient full recovery system for central heating according to claim 5 is characterized in that: The four-stage heat exchange circulation pipeline includes a seventh pipeline, an eighth pipeline, and a ninth pipeline. The seventh pipeline realizes the connection between the heat release side outlet of the three-stage heat exchanger and the inlet of the evaporator of the screw heat pump unit. The eighth pipeline realizes the connection between the outlet of the evaporator of the screw heat pump unit and the inlet of the evaporator of the centrifugal heat pump unit. The ninth pipeline realizes the connection between the outlet of the evaporator of the centrifugal heat pump unit and the inlet of the heat release side of the three-stage heat exchanger. A fourth variable frequency water pump is connected in series to the ninth pipeline, and the controller is electrically connected to the fourth variable frequency water pump.

7. The flue gas waste heat gradient full recovery system for central heating according to claim 6 is characterized in that: The heating return water circulation heating pipeline includes a tenth pipeline, an eleventh pipeline, a twelfth pipeline, a thirteenth pipeline, and a fourteenth pipeline. One end of the tenth pipeline is connected with the return pipe of the heat-using end, and the other end is connected with the inlet of the condenser of the centrifugal heat pump unit. A first control valve is arranged on the tenth pipeline. The eleventh pipeline realizes the connection between the outlet of the condenser of the centrifugal heat pump unit and the inlet of the condenser of the screw heat pump unit. The twelfth pipeline realizes the connection between the outlet of the condenser of the screw heat pump unit and the inlet of the heat release side of the secondary plate heat exchanger. A second control valve is arranged on the twelfth pipeline. The thirteenth pipeline realizes the connection between the outlet of the heat release side of the secondary plate heat exchanger and the inlet of the heat release side of the primary plate heat exchanger. A third control valve is arranged on the thirteenth pipeline. One end of the fourteenth pipeline is connected with the outlet of the heat release side of the primary plate heat exchanger, and the other end is connected with the water supply pipe of the heat-using end. A fourth control valve and a fifth variable frequency water pump are connected in series to the fourteenth pipeline.

8. The flue gas waste heat gradient full recovery system for central heating according to claim 7 is characterized in that: A steam purge pipeline is arranged on one side of the primary heat exchanger, the steam purge pipeline includes a steam channel and a steam drum, the steam pipeline realizes the connection between the steam drum and the steam gas source, the steam drum realizes the connection with the primary heat exchanger through the fifteenth pipeline, a fifth control valve is arranged on the fifteenth pipeline, a high-pressure water flushing pipeline is arranged on one side of the secondary heat exchanger, the high-pressure water flushing pipeline includes a sixteenth pipeline, the sixteenth pipeline realizes the connection between the twelfth pipeline and the secondary heat exchanger, a sixth variable frequency water pump and a sixth control valve are connected in series to the sixteenth pipeline, an expansion type decontaminant is connected in series to the fifth pipeline, a seventh control valve and an eighth control valve are arranged on the fifth pipeline, which are located upstream and downstream of the expansion type decontaminant, a first bypass pipeline is arranged between the upstream of the seventh control valve and the downstream of the eighth control valve, a ninth control valve is connected in series to the first bypass pipeline, and a ninth control valve is connected in series to the tenth A cyclone-type dirt remover is connected in series on the pipeline, a tenth control valve and an eleventh control valve are arranged on the tenth pipeline, which are located upstream and downstream of the cyclone-type dirt remover, a second bypass pipeline is arranged between the upstream of the tenth control valve and the downstream of the eleventh control valve, and a twelfth control valve is connected in series on the second bypass pipeline; a third bypass pipeline is arranged between the tenth pipeline and the eleventh pipeline, a thirteenth control valve is arranged on the third bypass pipeline, a fourth bypass pipeline is arranged between the eleventh pipeline and the twelfth pipeline, a fourteenth control valve is arranged on the fourth bypass pipeline, a fifth bypass pipeline is arranged between the thirteenth pipeline and the fourteenth pipeline, a fifteenth control valve is arranged on the fifth bypass pipeline, a sixth bypass pipeline is arranged between the twelfth pipeline and the fourteenth pipeline, and a sixteenth control valve is arranged on the sixth bypass pipeline.

9. The flue gas waste heat gradient full recovery system for central heating according to claim 8 is characterized in that The flue gas duct, the fifth duct, the seventh duct, the ninth duct, the tenth duct and the twelfth duct are all provided with pressure sensors and temperature sensors; the first duct, the second duct, the third duct, the fourth duct and the eighth duct are all provided with temperature sensors.

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