Rotary air preheater system and working method thereof

Abstract

The present invention discloses a rotary air preheater system and a working method thereof that can reduce air leakage rate and prevent blockage. In the rotary air preheater system, the smoke side bin of the air preheater is divided into mutually independent conventional smoke bins and clearing smoke bins. According to the rotation direction of the air preheater rotor, the clearing smoke bin is arranged at the end of the turning direction of the smoke side. The cold end flue and the hot end flue of the conventional smoke bin and the clearing smoke bin are respectively connected with a first connecting flue and a second connecting flue. The first connecting flue is provided with a first control valve, and the outlet flue is also connected to the cold end flue of the clearing smoke bin through an exhaust flue provided with a booster fan. The system includes two working modes, a "conventional operation mode" and an "online clearing mode". In the "online clearing mode", the smoke in the clearing smoke bin flows in the opposite direction to the smoke in the conventional smoke bin. The present invention can effectively extend the blockage period of the air preheater and increase economic benefits.

Description

Technical Field

[0001] The present invention relates to a rotary air preheater, and in particular to a design for preventing ammonium bisulfate from clogging. Background Art

[0002] The rotary air preheater is an important heat exchange equipment for power station boilers. It usually adopts the rotation of the rotor (including the heat storage element) to exchange heat between high-temperature flue gas and cold air in countercurrent. When the flue gas flows through the rotor, the flue gas releases heat to the heat storage element, the flue gas temperature decreases, and the heat of the flue gas is utilized. When the heat storage element rotates to the air side, it releases heat to the air again, and the air temperature increases. Hot air entering the furnace can improve the combustion efficiency of the fuel. For pulverized coal furnaces, part of the hot air is used for pulverized coal preparation and powder delivery.

[0003] The rotary air preheater has two compartments, three compartments, four compartments and other types according to the number of compartments in the flue and air duct. Currently, there are about 20,000 units in service worldwide. The equipment composition of the air preheater system includes the central spindle, modular compartments, heat storage elements, flue, air duct, upper support beam, lower support beam, shell, expansion support, support bearing assembly, guide bearing assembly, insulation and outer guard plate, electric drive device, bearing lubrication system, fire alarm system, fire protection system, water flushing system, soot blowing system, etc.

[0004] The performance indicators of rotary air preheater include heat exchange efficiency, flue gas side resistance, air side resistance, air leakage rate, anti-clogging ability, etc.

[0005] Air leakage in the air preheater will increase the heat loss of the flue gas and increase the power consumption of the forced and induced draft fans. Excessive leakage will cause the output of the forced and induced draft fans to reach their limits. When the leakage is more serious, it will cause the fan to surge and the boiler will not be able to operate at full load.

[0006] The air leakage control technology of air preheater mainly takes measures from two aspects: reducing the pressure difference at both ends of the sealing piece and reducing the area of ​​the air leakage zone. The current mainstream applied technologies include contact type multi-flexible seal, air leakage automatic control system, four-compartment air preheater, etc.

[0007] According to GB13223-2011 "Emission Standards for Air Pollutants from Thermal Power Plants", since 2014, the nitrogen oxide emissions from coal-fired boilers in thermal power plants have been 100 mg / Nm 3 The emission limit is 50mg / Nm 3 In order to meet the above indicators, SCR / SNCR denitrification devices are widely used to reduce NO xThe emission will inevitably cause ammonia escape, which will react with water vapor and sulfur trioxide to form ammonium bisulfate after entering the air preheater. The catalyst of the denitrification device increases the conversion rate of sulfur dioxide to sulfur trioxide, which has a more adverse effect on downstream equipment.

[0008] When the metal wall temperature of the air preheater's heat exchange element is in the liquid phase temperature range of ammonium bisulfate, ammonium bisulfate is easy to condense and deposit on the surface of the air preheater's heat exchange element, and adhere to the fly ash particles in the flue gas, blocking the heat exchange element channel. When the ammonium bisulfate deposition temperature range covers the metal wall temperature of two layers of heat exchange elements, the ammonium bisulfate at the layering of the heat exchange element adsorbs fly ash and forms scale, forming a serious blockage that is difficult to clean even with soot blowing steam and high-pressure water. Dust accumulation or blockage on the surface of the air preheater's heat exchange element will cause the differential pressure to rise, increase the energy consumption of the forced draft fan, and also reduce the heat exchange efficiency of the heat exchange element.

[0009] The blockage of air preheaters caused by ammonium bisulfate is a global problem, which has seriously affected the safety and economy of boiler unit operation. The air preheater has to be cleaned by water due to serious blockage, resulting in unplanned shutdown. The cost of water flushing is often hundreds of thousands of yuan. In addition to the cost of starting the unit and the loss of life of the boiler pressure-bearing parts due to the start-up and shutdown of the unit, the estimated economic loss will reach millions of yuan.

[0010] At present, the main measures to solve the problem of ammonium bisulfate clogging the air preheater include: ① Select the plate type of the cold section heat exchange element of the air preheater with large corrugations and independent closed channels according to the fuel characteristics; ② Calculate the metal wall temperature of the heat exchange element under various load conditions, select a sufficient height of the cold section heat exchange element and consider a moderate height margin, and arrange the deposition temperature range of ammonium bisulfate in the cold section heat exchange element; ③ Remove or alleviate the dust accumulation in the cold section heat exchange element by steam soot blowing or online high-pressure water flushing; ④ Control the escape rate of ammonia in the denitrification device; ⑤ Calculate the flow field of the air preheater inlet flue and set a flow equalizer to ensure that the dust concentration entering the air preheater flow surface is uniform and avoid local dust concentration; ⑥ Ensure that the superheat of the soot blowing steam is not less than 130℃ and the pressure is not higher than 1.6MPa; ⑦ Forced ventilation should be carried out for 12 to 36 hours after the air preheater is shut down and flushed with water to thoroughly dry the surface of the heat exchange element. ⑧ Every time the furnace is shut down for maintenance, the internal flushing water pipes and fire water pipes of the air preheater should be checked for leaks, and the heater should be checked for leaks.

[0011] There are also technologies that use heat medium water medium heater-smoke cooler system, smoke cooler system, etc. to increase the air temperature at the inlet of the air preheater to increase the metal wall temperature of the heat exchange element as a whole, thereby lowering the temperature range of ammonium bisulfate deposition. For example, the "A system for utilizing waste heat from flue gas at the tail of a thermal power plant based on deep coupling of the machine and boiler" with the announcement number CN206320726U published on July 11, 2017 can effectively alleviate the blockage caused by ammonium bisulfate, but the exhaust gas temperature will also rise by 20 to 60°C at the same time, and then the heat will be recovered through the smoke cooler. The metal consumption of the smoke cooler of these two systems is very huge, and the corrosion and blockage problems of the smoke cooler due to being in a low temperature environment are also unavoidable.

[0012] There are also many applications for the scheme of preventing ammonium bisulfate from clogging by increasing the cold section comprehensive temperature of the air preheater. For example, the "System and process for preventing hot air countercurrent blocking and corrosion of air preheater in coal-fired power plants" with publication number CN105972632A published on September 28, 2016, and the "rotary air preheater for preventing ammonium bisulfate from clogging" with publication number CN207094650U published on March 13, 2018. The above patents all extract high-temperature flue gas or primary hot air or secondary hot air into the air side (primary air or secondary air) inlet of the air preheater. This method has a good effect on preventing low-temperature corrosion, but has limited effect on alleviating corrosion and clogging of ammonium bisulfate, and consumes a lot of energy for the booster fan of the flue gas extraction system.

[0013] The "rotary air preheater and its method for reducing air leakage and preventing blockage" with publication number CN107842872A, published on March 27, 2018, isolates a "heating chamber" at the location near the flue gas on the primary and secondary air sides. The system needs to be equipped with a high-temperature and high-pressure fan, and the outlet pressure of the fan needs to be higher than the pressure of the primary and secondary air at the outlet of the air preheater. The energy consumption of the fan is relatively large when the system is put into operation.

[0014] In the "Five-compartment rotary air preheater for preventing ammonium bisulfate deposition and its working method" published on August 13, 2019 with the publication number CN110118361A, the air side of the air preheater is divided into four compartments, plus one compartment on the flue gas side, a total of five compartments, to achieve control of the ammonium bisulfate deposition area. The implementation of the method requires a complex set of fans, pipes, and sonic soot blowers, and the structure is relatively complex. Summary of the invention

[0015] In order to improve the reliability of a two-compartment, three-compartment or four-compartment rotary air preheater, the technical problem to be solved by the present invention is to provide a rotary air preheater system and a working method thereof with a lower air leakage rate and the function of online removal of low-temperature sulfuric acid corrosion ash blockage and ammonium bisulfate blockage by dividing the smoke compartment of the air preheater and assisted by corresponding pipelines equipped with booster fans.

[0016] The technical solution adopted by the present invention to solve its technical problems is: a rotary air preheater system, including an outlet flue and an air preheater connected to the outlet flue, an air preheater rotor is arranged in the air preheater, and a heat exchange element is arranged on the air preheater rotor; the air preheater includes a smoke side compartment and an air side compartment, and the smoke side compartment is divided into two independent adjacent compartments, namely a conventional smoke compartment and a clearing smoke compartment. According to the rotation direction of the air preheater rotor, the clearing smoke compartment is arranged at the turning end of the smoke side, and the cold end flue and the hot end flue of the conventional smoke compartment and the clearing smoke compartment are respectively connected with a first connecting flue and a second connecting flue, and a first control valve is arranged on the first connecting flue, and the outlet flue is also connected to the cold end flue of the clearing smoke compartment through an exhaust flue provided with a booster fan.

[0017] By arranging small beams, fan-shaped plates, inlet and outlet flues and other components, the smoke bin can be divided into two completely independent bins, a conventional smoke bin and a clearing smoke bin, using technical means similar to dividing the air bin into compartments. Due to the presence of the booster fan, the high-temperature flue gas from the outlet flue can be sent to the cold end flue of the clearing smoke bin of the air preheater after being pressurized. The clearing smoke bin has a higher pressure head than the conventional smoke bin, which can reduce the pressure difference on the adjacent air side (primary air or secondary air), forming a pressure relief zone between the conventional smoke bin and the air bin. This is a technology that reduces air leakage rate by reducing the pressure difference. At the same time, compared with the air preheater with conventional structure, in the air preheater with the above structure, the flue gas of the cleaning smoke chamber and the conventional smoke chamber can flow in a controllable reverse direction, and the flue gas temperature of the cleaning smoke chamber can reach 380-420℃. The high-temperature flue gas can increase the metal wall temperature of the cold end heat storage element at the lowest temperature by 16-35℃, while the metal wall temperature of the hot end heat exchange element at the highest temperature can be reduced by 4-8℃. In the cleaning smoke chamber, the reverse flushing of the high-temperature flue gas can remove the sulfuric acid condensation ash and ammonium bisulfate blockage on the surface of the air preheater low temperature section heat storage element online, and the rotor continues to rotate to achieve the cleaning of the surface of all heat storage elements; at the same time, the temperature field distribution of the rotor is also adjusted, the temperature difference between the cold and hot ends of the air preheater rotor is reduced, and the mushroom-shaped deformation of the hot operation is reduced, which is beneficial to reducing the air leakage rate. In view of the above analysis, the cleaning smoke chamber is suitable for being arranged at the end of the turning direction on the flue gas side according to the rotation direction, that is, in the area where the rotor metal wall temperature is high.

[0018] The smoke bin for clearing blockage of the present invention can be regarded as a conventional smoke bin in the "normal operation mode", and the sum of the smoke bin angle and the air bin angle is 180°. The operating performance indicators of this double smoke bin air preheater are not significantly different from those of the conventional air preheater, and the economic indicators of the long-term operation of the unit can be maintained.

[0019] In the online clearing mode, the clearing smoke bin of the present invention has the same flow direction as the air bin and is opposite to the conventional smoke bin. The clearing smoke bin is arranged at the end of the smoke turning, the area with the highest metal temperature. The smoke extracted by the booster fan performs countercurrent heat exchange to heat the metal wall surface at the inlet end of the air preheater. The extracted high-temperature smoke has the function of heating and purging the ammonium bisulfate droplets. The present invention has a significant effect on increasing the metal wall temperature at the cold end of the air preheater and has a strong clearing ability.

[0020] The exhaust flue is connected in series with a stop valve and a second control valve, wherein the stop valve is located between the outlet flue and the booster fan, and the second control valve is located between the booster fan and the cold end flue of the smoke clearing bin. When the stop valve is closed, the smoke clearing bin works in the normal operation mode; when the stop valve is opened, the smoke clearing bin works in the online clearing mode, and the second control valve is used to adjust the smoke flow entering the smoke clearing bin and the normal smoke bin respectively, so as to control the temperature and flushing intensity in the bin.

[0021] A temperature measuring point and a pressure measuring point are arranged between the booster fan and the cold end flue of the smoke clearing bin, and a flow meter is arranged between the middle stop valve and the booster fan. It is convenient to judge the operation effect of the clearing work and whether it is necessary to exit the online clearing mode according to the feedback of temperature and pressure.

[0022] The second control valve is a stop valve.

[0023] The first control valve is a normally closed valve, and the stop valve is a normally open valve.

[0024] The exhaust flue is provided with a heating device.

[0025] The height of the cold section heat exchange element of the air preheater is 900-1300 mm.

[0026] The air side compartment is one compartment; or two compartments, namely a primary air compartment and a secondary air compartment; or three compartments, namely a secondary air compartment, a primary air compartment, and a secondary air compartment.

[0027] The center angles of the bins of the cigarette bin are 15°, 20°, 22.5°, 30° or 37.5° respectively.

[0028] The central angles of the fan-shaped plates for clearing the cigarette bin are 7.5°, 10°, 15° or 20° respectively.

[0029] The working method of the above-mentioned rotary air preheater system, the system includes two working modes, one is the normal operation mode, and the other is the online clearing mode. In the "normal operation mode", the booster fan is stopped, the exhaust flue is kept in a closed state, and the flue gas from the outlet flue is divided into two parts, which flow in the same direction through the clearing flue bin and the conventional flue bin to enter the air preheater for heat exchange; in the "online clearing mode", the booster fan is put into operation, the exhaust flue is kept in a connected state, and the flue gas from the outlet flue is divided into two parts, which flow in the countercurrent direction through the clearing flue bin and the conventional flue bin to enter the air preheater for heat exchange - part of the flue gas from the outlet flue is sent to the cold end flue of the clearing flue bin through the exhaust flue, and then passes through the clearing flue bin and its hot end flue and then enters the conventional flue through the second connecting flue, and the rest of the flue gas is sent to the hot end flue of the conventional flue bin.

[0030] In the "online clearing mode", the amount of smoke entering the cold end flue of the clearing smoke bin accounts for 10-20% of the total amount of smoke in the outlet flue.

[0031] The air preheater is equipped with a steam soot blower, and the steam soot blower runs continuously in the "online plugging removal mode" until the work of the "online plugging removal mode" is completed, so as to further improve the flushing effect.

[0032] The beneficial effects of the present invention are as follows: in the "conventional operation mode", its operation economic index is the same as that of the conventional air preheater, but after entering the "online clearing mode", the smoke in the clearing cigarette bin flows in the opposite direction to the smoke in the conventional cigarette bin, which can adjust the temperature field distribution of the rotor, and can utilize the reverse flushing function of the high-temperature smoke to clear the sulfuric acid condensation ash and ammonium sulfate blockage on the surface of the low-temperature section heat exchange element of the air preheater online; on the other hand, because the clearing cigarette bin has a higher pressure head than the conventional cigarette bin, it can reduce the pressure difference of the adjacent air side (primary air or secondary air), form a pressure relief zone between the conventional cigarette bin and the air bin, and reduce the air leakage rate by reducing the pressure difference. At the same time, due to the reverse flow of smoke in the clearing cigarette bin of the double cigarette bin air preheater and the conventional cigarette bin, the temperature difference between the cold and hot ends of the air preheater rotor is reduced, and the mushroom-shaped deformation of the hot operation is reduced, which is also conducive to reducing the air leakage rate. Therefore, the present invention can effectively extend the blockage period of the air preheater, reduce the number of unplanned shutdowns of the air preheater due to blockage problems, and increase economic benefits. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 It is a schematic diagram after the present invention is applied to a conventional two-compartment air preheater.

[0034] Figure 2 It is a schematic diagram of the present invention applied to a conventional three-compartment air preheater (forward rotation arrangement).

[0035] Figure 3It is a schematic diagram after the present invention is applied to a conventional three-compartment air preheater (inverted arrangement).

[0036] Figure 4 It is a schematic diagram after the present invention is applied to a conventional four-compartment air preheater.

[0037] Figure 5 It is a schematic diagram of the working method in the normal operation mode of an embodiment of the present invention.

[0038] Figure 6 It is a schematic diagram of a working method in an online blockage clearing mode according to an embodiment of the present invention.

[0039] Figure 7 It is a diagram of the metal wall temperature distribution of the flue gas side heat exchange element in the normal operation mode of an embodiment of the present invention.

[0040] Figure 8 This is a diagram of the metal wall temperature distribution of the flue gas side heat exchange element in the online clearing mode of an embodiment of the present invention.

[0041] Fig. 9 It is a schematic diagram comparing the change in metal wall temperature of a flue gas side heat exchange element in an online clearing mode and a conventional operation mode according to an embodiment of the present invention.

[0042] Fig.10 is a pressure distribution diagram of the air preheater system of the present invention.

[0043] Fig.11 It is a pressure distribution diagram of the existing patented air preheater system.

[0044] Fig.10 and Fig.11 The “~” in Chinese means “approximately equal to”.

[0045] Marked in the figure: 1-air preheater, 2-hot end flue of conventional smoke bin, 3-cold end flue of conventional smoke bin, 4-cold end flue of clear and blocked smoke bin, 5-hot end flue of clear and blocked smoke bin, 6-first control valve, 7-first connecting flue, 8-second control valve, 9-boosting fan, 10-stop valve, 11-exhaust flue, 12-denitrification device, 13-export flue, 14-second connecting flue, 15-clear and blocked smoke bin, 16-conventional smoke bin, 17-primary air bin, 18-primary air bin inlet duct, 19-primary air bin outlet duct, 20-secondary air bin outlet duct, 21-secondary air bin inlet duct, 22-secondary air bin, 23-flow meter, 24-temperature measuring point, 25-pressure measuring point, 26-heating device, 27-steam soot blower, 28-air bin. DETAILED DESCRIPTION

[0046] The present invention is further described below in conjunction with the accompanying drawings and embodiments.

[0047] like Figure 1 , Figure 2 , Figure 3 , Figure 4 , Figure 5 and Figure 6 As shown, the rotary air preheater system of the present invention comprises an outlet flue 13 and an air preheater 1 connected to the outlet flue 13, wherein an air preheater rotor is arranged in the air preheater 1, and a heat exchange element is arranged on the air preheater rotor; the air preheater 1 comprises a smoke side bin and an air side bin, wherein the smoke side bin is divided into two adjacent bins independent of each other, namely a conventional smoke bin 16 and a clear smoke bin 15, wherein the clear smoke bin 15 is arranged at the end of the turning direction of the smoke side according to the rotation direction of the air preheater rotor, and the conventional smoke bin The first communication flue 7 and the second communication flue 14 are respectively connected between the cold end flue 16 and the hot end flue of the smoke clearing bin 15, and the first communication flue 7 is provided with a first control valve 6. The outlet flue 13 is also connected to the cold end flue 4 of the smoke clearing bin through an exhaust flue 11 provided with a booster fan 9, and a stop valve 10 and a second control valve 8 are connected in series on the exhaust flue 11, wherein the stop valve 10 is located between the outlet flue 13 and the booster fan 9, and the second control valve 8 is located between the booster fan 9 and the cold end flue 4 of the smoke clearing bin.

[0048] like Figure 5 and Figure 6 As shown, a temperature measuring point 24 and a pressure measuring point 25 are provided between the booster fan 9 and the cold end flue 4 of the smoke bin for clearing blockage, and a flow meter 23 is also provided between the stop valve 10 and the booster fan 9.

[0049] like Figure 5 and Figure 6 As shown, the first control valve 6 is a normally closed valve, and the stop valve 10 is a normally open valve. When working in the normal operation mode, the first control valve 6 is opened, the second control valve 8 is closed, and the stop valve 10 is manually closed, and the exhaust pipe and the equipment connected in series in the pipeline can be repaired. If the air preheater system chooses to operate in the online clearing mode all the time, the first control valve 6 can also be set as a normally closed valve, the stop valve 10 can be set as a normally open valve, the second control valve 8 can be set as a normally open valve, or the first connecting flue 7 and the first control valve 6 can be cancelled. The outlet flow of the booster fan 9 can be controlled and adjusted by instruments such as flowmeter 23, temperature measuring point 24, pressure measuring point 25 and electrical control system. Based on the statement of the principle of the present invention, the scheme that only has "online clearing mode" or only runs in "online clearing mode" should be regarded as an equivalent technical scheme of the scheme described in the present invention. In this case, the equipment installed in the exhaust flue 11 and its pipeline will run for a long time, so the second control valve 8 is preferably a stop valve to facilitate the maintenance of the booster fan 9.

[0050] As a backup plan under certain special working conditions, a heating device 26 is preferably provided on the exhaust flue 11 to further increase the temperature of the flue gas entering the smoke clearing bin. Depending on different engineering design conditions, the heating device 26 can be an electric heater or an air-to-air heat exchanger.

[0051] according to Figure 7 , Figure 8 and Fig. 9 According to the analysis results, the height of the cold section heat exchange element of the air preheater 1 is recommended to be 900-1300mm, and the better choice is 1200-1300mm. In the two working modes, the metal wall temperature of the cold section heat exchange element of the flue gas bin can be kept below 250℃, and the temperature difference between the two working modes can be kept below 5℃, which is conducive to its long-term stable operation. The metal wall temperature of the hot section heat exchange element of the flue gas bin is above 250℃, and the ammonium bisulfate is kept in liquid state, and ammonium bisulfate will not be deposited at the stratification of the heat exchange element, which is convenient for cleaning by steam soot blowing, thereby reducing the energy consumption of the forced draft fan and maintaining the heat exchange efficiency of the heat exchange element.

[0052] like Figure 1 , Figure 2 , Figure 3 and Figure 4 As shown, based on the above principle analysis, no matter the air side compartment is one compartment; or two compartments, namely a primary air compartment and a secondary air compartment; or three compartments, namely a secondary air compartment, a primary air compartment, and a secondary air compartment, the present invention can be applied, that is, the traditional two-compartment, three-compartment or four-compartment air preheater can be modified by applying the present invention.

[0053] like Figure 1 , Figure 2 , Figure 3 and Figure 4 As shown, if the rotary air preheater adopts 48 compartments or 36 compartments, the number of compartments of the clearing cigarette bin 15 generally occupies 2 to 5 compartments, and the angle of a single compartment corresponds to 7.5 or 10°. The possible values ​​of the central angle θ1 corresponding to the clearing cigarette bin 15 are 15°, 20°, 22.5°, 30° or 37.5°. Correspondingly, if the fan-shaped plate of the clearing cigarette bin 15 adopts a single seal, the corresponding central angle θ2 is 7.5° and 10° respectively. If the fan-shaped plate of the clearing cigarette bin 15 adopts a double seal, the corresponding central angle θ2 is 15° or 20° respectively.

[0054] Example:

[0055] like Figure 2 (Forward mode), Figure 5 , Figure 6 and Figure 7 to Figure 9As shown, a 600MW unit, the original design of the air preheater is a three-compartment rotary air preheater with a rotating heating surface (hereinafter referred to as the traditional three-compartment), adopts a modular compartment structure, and a heat exchange element is arranged on the air preheater rotor. All heat storage elements are installed in 48 compartments, and the degree of the center angle of each compartment is 7.5°. After the application of the present invention for transformation, its air preheater is a double smoke compartment four-compartment structure, that is, the 24 compartments on the flue gas side are divided into two parts, one part is the clearing smoke compartment 15, which is composed of three modular compartments (smoke compartments numbered 22 to 24) at the end of the rotation direction of the smoke side, and the degree of the center angle θ1 corresponding to it is 22.5°, and the rest is the conventional smoke compartment 16, which is composed of the remaining 21 compartments on the smoke side (smoke compartments numbered 1 to 21); the air side compartments are respectively the primary air compartment 17 and the secondary air compartment 18.

[0056] The modified rotary air preheater system includes an outlet flue 13 and an air preheater 1 connected to the outlet flue 13, the upstream of the outlet flue 13 is connected to the denitrification device 12, a first connecting flue 7 is connected between the cold end flue 3 of the conventional smoke bin and the cold end flue 4 of the smoke bin for clearing blockage, a second connecting flue 14 is connected between the hot end flue 2 of the conventional smoke bin and the hot end flue 5 of the smoke bin for clearing blockage, a first control valve 6 is arranged on the first connecting flue 7, the outlet flue 13 is also connected to the cold end flue 4 of the smoke bin for clearing blockage through an exhaust flue 11, a heating device 26, a stop valve 10, a flow meter 23, a booster fan 9, a second control valve 8, a temperature measuring point 24, and a pressure measuring point 25 are connected in series in sequence from the outlet flue 13 to the cold end flue 4 of the smoke bin for clearing blockage, wherein the first control valve 6 is a normally closed valve, and the stop valve 10 is a normally open valve.

[0057] The working method of the rotary air preheater system is as follows.

[0058] The system includes two working modes, one is the normal operation mode, and the other is the online clearing mode. In the "normal operation mode", the stop valve 10 is kept in a normally open state, the first control valve 6 is opened, the booster fan 9 and the second control valve 8 are closed, the exhaust flue 11 is closed, and the flue gas from the outlet flue 13 is divided into two parts, which flow in the same direction through the hot end flues 5 and 2 of the clearing smoke bin 15 and the conventional smoke bin 16 respectively into the air preheater 1 for heat exchange. After the heat exchange, the flue gas is collected into the outlet flue 3 of the conventional smoke bin of the air preheater, and then enters the downstream equipment of the air preheater; in the "online clearing mode", the first control valve 6 is closed, the stop valve 10 is kept in a normally open state, the booster fan 9 and the second control valve 8 are opened, and the flue gas from the outlet flue 13 is divided into two parts, one part flows through the exhaust flue 11 The flue gas flows to the cold end flue 4 of the unblocked tobacco barn, and the rest flows to the hot end flue 2 of the conventional tobacco barn, after heat exchange with the air preheater, it is collected in the outlet flue 3 of the conventional tobacco barn, and then enters the downstream equipment of the air preheater; the flue gas of the cold end flue 4 of the unblocked tobacco barn enters the unblocked tobacco barn 15, flushes the heat storage elements in the barn, removes the condensed sulfuric acid dew thereon, and vaporizes its liquid ammonium bisulfate by heating, and with the help of a steam blower, the accumulated dust on the surface of the heat storage element is blown away, so that the blockage on the surface of the heat storage element is alleviated or removed, and then the flue gas enters the hot end flue 5 of the unblocked tobacco barn and enters the conventional tobacco barn 16 through the second connecting flue 14, after heat exchange with the air preheater, it is collected in the outlet flue 3 of the conventional tobacco barn of the air preheater, and then enters the downstream equipment of the air preheater, such as a dust collector.

[0059] In the "normal operation mode", the smoke in the clearing smoke bin 15 and the regular smoke bin 16 flows in the same direction; in the "online clearing mode", the smoke in the clearing smoke bin 15 and the regular smoke bin 16 flows in the opposite direction.

[0060] like Figure 7 , Figure 8 and Fig. 9 As shown in the figure, when working in the "online clearing mode", the metal wall temperature of the cold section heat exchange element of the clearing smoke bin 15 is 0-35°C higher than that in the "normal operation mode", while the metal wall temperature of the hot section heat exchange element is reduced by 0-7°C. The metal wall temperature of the cold section heat exchange element increases, and the ammonium bisulfate deposition temperature range moves toward the cold end in the height direction, which will not cause cross-layer condensation blockage.

[0061] The corresponding design parameter comparison is shown in Table 1 below.

[0062] Table 1 Comparison of technical design parameters between this embodiment and the traditional three-compartment

[0063]

[0064] It can be seen that by applying the present invention and operating in the "online clearing mode", the air leakage rate can be further reduced by about 1.36 percentage points.

[0065] The selection of the booster fan 9 in the system is designed according to the amount of smoke extraction. The fan pressure head of the booster fan 9 set in the present invention only needs to overcome the resistance of the air preheater (about 1500Pa), and the operating energy consumption is extremely low. In other related existing patent documents, the booster fan set needs to increase the pressure head to about 14000Pa because the smoke needs to be sent into the primary air of the air preheater, and the operating energy consumption is very large.

[0066] In this embodiment, the designed flue gas extraction volume accounts for 10-20% of the total flue gas volume at the outlet of the denitrification device 12, and the selection of the booster fan 9 is designed based on 20% of the total flue gas volume at the outlet of the denitrification device 12. The flue gas extraction volume can be adjusted by controlling and adjusting the corresponding control valves through instruments such as the flow meter 23, the temperature measuring point 24, the pressure measuring point 25, and the electrical control system.

[0067] The invention can be used for new construction projects or renovation projects and has good operating economic benefits.

[0068] After applying the present invention, the air preheater system can choose to run intermittently in the "online clearing mode" or continuously in the "online clearing mode" as needed. If it is run intermittently, it is usually recommended to switch to the "online clearing mode" when the operating pressure difference of the air preheater 1 is detected to rise by 100pa. In the "online clearing mode", the steam soot blowing of the air preheater is also carried out simultaneously. When the operating pressure difference of the air preheater 1 returns to normal, it can be switched to the "normal operation mode" again to continuously maintain the stable operation state of the air preheater 1.

[0069] The economic benefit analysis of the operation of the 600MW unit of this embodiment after transformation according to the present invention is as follows: the equipment cost increases by about 3 million yuan, and the number of unplanned shutdowns caused by the blockage of the air preheater is reduced, which can save about 8 million yuan in startup and maintenance costs per year. The fan energy loss (three major fans, namely, the blower, the induced draft fan and the primary fan) caused by the blockage of the air preheater can be reduced by about 3.5 million yuan each year, and the damage to the heat exchange element caused by the blockage of the air preheater can be reduced by about 2 million yuan each year.

[0070] Taking the 300MW unit as an example, it is estimated that the equipment cost will increase by about 2 million yuan. Reducing the number of unplanned shutdowns caused by air preheater blockage problems can save about 5 million yuan in startup and maintenance costs once a year. The fan energy consumption loss (three major fans) caused by air preheater blockage can be reduced by about 1.8 million yuan each year, and the heat exchange component damage caused by air preheater blockage can be reduced by about 1 million yuan each year.

[0071] Comparison of fan energy consumption.

[0072] like Fig.10 , Fig.11As shown, for the same boiler system, the traditional three-compartment scheme, or the technical scheme of "rotary air preheater and method for reducing air leakage and preventing blockage" with publication number CN107842872A (hereinafter referred to as the existing patent), or the technical scheme of this embodiment, the corresponding theoretical calculation of fan energy consumption comparison is shown in Table 2 below.

[0073] The booster fan set in the existing patent needs to consider the primary air for sending the flue gas into the air preheater, so the pressure head of the booster fan needs to be increased to about 14000Pa, and the operating energy consumption is very large. In comparison, all fans in the air preheater system of Example 1 increase the energy consumption by about 258KW compared with the conventional solution, but can save about 3393KW of energy compared with the existing patent.

[0074] The fan energy consumption comparison is shown in Table 2 below.

[0075] Table 2 Fan energy consumption comparison

[0076]

Claims

1. A rotary air preheater system, comprising an outlet flue (13) and an air preheater (1) connected to the outlet flue (13), wherein an air preheater rotor is arranged in the air preheater (1), and a heat exchange element is arranged on the air preheater rotor; the air preheater (1) comprises a flue gas side compartment and an air side compartment, and is characterized in that: The smoke side bin is divided into two mutually independent adjacent bins, namely a conventional smoke bin (16) and a clear smoke bin (15). According to the rotation direction of the air preheater rotor, the clear smoke bin (15) is arranged at the end of the turning direction of the smoke side. The cold end flue and the hot end flue of the conventional smoke bin (16) and the clear smoke bin (15) are respectively connected to a first connecting flue (7) and a second connecting flue (14). The first connecting flue (7) is provided with a first control valve (6). The outlet flue (13) is also connected to the cold end flue (4) of the clear smoke bin via an exhaust flue (11) provided with a booster fan (9).

2. The rotary air preheater system according to claim 1, characterized in that: The exhaust flue (11) is connected in series with a stop valve (10) and a second control valve (8), wherein the stop valve (10) is located between the outlet flue (13) and the booster fan (9), and the second control valve (8) is located between the booster fan (9) and the cold end flue (4) of the smoke bin.

3. The rotary air preheater system according to claim 2, characterized in that: A temperature measuring point (24) and a pressure measuring point (25) are provided between the booster fan (9) and the cold end flue (4) of the smoke bin for clearing blockage, and a flow meter (23) is also provided between the stop valve (10) and the booster fan (9).

4. The rotary air preheater system according to claim 3, characterized in that: The second control valve (8) is a stop valve.

5. The rotary air preheater system of claim 2, wherein: The first control valve (6) is a normally closed valve, and the stop valve (10) is a normally open valve.

6. The rotary air preheater system of claim 1, wherein: The exhaust flue (11) is provided with a heating device (26).

7. The rotary air preheater system according to any one of claims 1 to 6, characterized in that: The height of the cold section heat exchange element of the air preheater (1) is 900 to 1300 mm.

8. The operating method of the rotary air preheater system according to any one of claims 1 to 7, characterized in that: The system includes two working modes, one is a normal operation mode, and the other is an online clearing mode. In the "normal operation mode", the booster fan (9) is stopped, the exhaust flue (11) remains in a closed state, and the flue gas from the outlet flue (13) is divided into two parts and flows in the same direction through the clearing flue bin (15) and the normal flue bin (16) to enter the air preheater (1) for heat exchange; in the "online clearing mode", the booster fan (9) is put into operation, the exhaust flue (11) remains in a connected state, and the flue gas from the outlet flue (13) is divided into two parts and flows in the same direction through the clearing flue bin (15) and the normal flue bin (16) to enter the air preheater (1) for heat exchange. The flue gas from the outlet flue (13) is divided into two parts and respectively passes through the clean smoke bin (15) and the conventional smoke bin (16) in countercurrent directions to enter the air preheater (1) for heat exchange. Part of the flue gas from the outlet flue (13) is sent to the cold end flue (4) of the clean smoke bin through the exhaust flue (11), then passes through the clean smoke bin (15) and the hot end flue (5) of the clean smoke bin, and then enters the conventional smoke bin (16) through the second connecting flue (14). The remaining flue gas is sent to the hot end flue (2) of the conventional smoke bin.

9. The operating method of the rotary air preheater system according to claim 8, characterized in that: In the "online clearing mode", the amount of smoke entering the cold end flue (4) of the clearing smoke bin accounts for 10 to 20% of the total amount of smoke in the outlet flue (13).

10. The operating method of the rotary air preheater system according to claim 8, characterized in that: The air preheater (1) is equipped with a steam soot blower (27). In the "online plugging removal mode", the steam soot blower (27) operates continuously until the operation of the "online plugging removal mode" is completed.

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