Device for removing phase-change substances in blast furnace

Abstract

The utility model discloses a device for removing phase-change substances in a blast furnace, and belongs to the field of metallurgy. The device comprises a blast furnace, branch gas pipes, an annular pipeline, a stop valve I, a gravity dust collector, a stop valve II, a regulating valve, a stop valve III, a nitrogen backflushing pipe and a valve, a nitrogen cleaning pipe and a valve, a nitrogen cleaning gas diffusing pipe and a valve, a phase change material recovery tank, and a phase change material discharge hole and a valve. According to the characteristics of phase-change substances in the furnace, a furnace section with large vapor pressure is selected, holes are formed in the furnace wall, part of coal gas is led out, the coal gas is conveyed to the position from the top of the blast furnace to the front portion of a dust remover, meanwhile, the phase-change substances are discharged out of the furnace along with the coal gas, and the temperature of the coal gas is controlled to be lower than the bearable temperature of a dust removal filter material through natural cooling or forced cooling measures. The temperature of the mixed coal gas is lower than the freezing point temperature of the phase-change substance, and the phase-change substance can be captured in the dust remover. By adopting the scheme, the blast furnace gas utilization rate can be obviously improved, the comprehensive coke ratio is reduced, and the blast furnace air permeability is obviously improved.

Description

Technical Field

[0001] The utility model belongs to the field of metallurgy, and in particular relates to a device for removing phase-change substances in a blast furnace. Background Art

[0002] Blast furnace ironmaking is still the most important ironmaking process. It is generally believed that it is a high-energy-consuming ironmaking process. How to reduce the energy consumption of this process has always been an important issue in the steel industry.

[0003] A blast furnace is a very special smelting equipment. The maximum temperature in the tuyere area of ​​the furnace can reach about 2400℃, the molten pool temperature is about 1500℃, and the furnace top is only about 200℃. Since the furnace is full of charge, the temperature field distribution changes relatively evenly. Many substances in the blast furnace exist in the three states of gas, liquid and solid. These substances are gasified in the high-temperature zone. As the gas rises and the temperature decreases, the saturated vapor pressure of these substances decreases. They will precipitate condensation or solidify on the surface of the charge, and then descend with the charge. After the temperature rises, they will gasify again and ascend again, circulating and enriching in the furnace. Condensation prevents metallurgical reactions between the charge and the coal gas, reducing smelting efficiency and increasing overall energy consumption. Condensation on the charge surface binds dust, worsening charge permeability, increasing blast kinetic energy consumption, and also reducing smelting efficiency. Some substances solidify within the coke crevices. Due to the large difference in expansion coefficients, this can reduce coke strength and cause pulverization, increasing coke consumption and worsening charge permeability. These substances can also condense on the furnace walls, where dust builds up and causes nodules, preventing the charge from flowing smoothly and, in severe cases, preventing smelting. This phenomenon occurs in nearly all blast furnaces, varying in severity, and has severely restricted the advantages of blast furnace smelting.

[0004] Currently, the common method for removing these substances is to overdevelop the central airflow, causing the central airflow temperature to exceed the solidification temperature of the phase change material, and then remove the phase change material in a gaseous state. The disadvantage of this removal method is high energy consumption. Overdeveloping the central airflow weakens the edge airflow, lowering the edge charge temperature, increasing condensation of the phase change material, and reducing air permeability. This weakens the edge iron flow and reduces the temperature of the molten iron at the edge of the furnace hearth, leading to the precipitation and scaling of titanium carbide and titanium nitride in the furnace hearth, which not only swells the furnace bottom but also thickens the furnace walls. These changes in the furnace structural parameters can lead to a series of problems in blast furnace operation. Therefore, it is very important to develop suitable equipment for removing phase change materials from blast furnaces. Utility Model Content

[0005] In view of the problems existing in the prior art, the present invention aims to provide a device for removing phase change materials in a blast furnace.

[0006] Based on the characteristics of the phase-change materials (PCMs) within the furnace, furnace sections with higher vapor pressures are selected. Openings are made in the furnace walls to divert some of the gas, directing it to the top of the blast furnace and the front of the dust collector. The PCMs are simultaneously discharged from the furnace along with the gas. Natural or forced cooling is used to keep the gas temperature below the temperature that the dust collector filter media can withstand. After mixing, the gas temperature remains below the freezing point of the PCMs, allowing them to be captured in the dust collector. Through drainage and removal, the PCM vapor pressure within the furnace gradually decreases, mitigating the side effects of the PCMs. When the PCM vapor pressure within the furnace has dropped to a level that no longer impacts blast furnace operation, meaning normal smelting conditions have been restored, gas drainage is stopped. Drainage is resumed when the furnace resistance increases. During gas transmission through the pipeline, some PCMs may condense on the dust collector bags due to the temperature they can withstand. Therefore, the pipeline design incorporates the collection and removal of these substances to prevent blockage.

[0007] The phase change material of the present invention refers to a material including zinc, potassium sodium alkali, cadmium, antimony and the like, which can form a gas-liquid-solid three-state cyclic change in a blast furnace.

[0008] A device for removing phase-change material from a blast furnace comprises a blast furnace, a bronchial pipe, a ring pipe, a stop valve I, a gravity dust collector, a stop valve II, a regulating valve, a stop valve III, a nitrogen recoil pipe and valve, a nitrogen purge pipe and valve, a nitrogen purge gas release pipe and valve, a phase-change material recovery tank, and a phase-change material discharge hole and valve.

[0009] Multiple air intake holes are provided at selected, uniform heights on the blast furnace shaft and connected to one end of multiple bronchial pipes. The other ends of the bronchial pipes are connected to a pre-installed annular duct. The annular duct delivers the extracted gas to a gravity dust collector via a pipeline. A stop valve II is provided between the annular duct and the gravity dust collector. After dust removal by the gravity dust collector, the gas is delivered via a pipeline from the furnace top to any location in front of the gravity dust collector, ultimately entering the gas recovery system. A stop valve I is provided on each bronchial pipe, and a nitrogen backflush pipe and valve are added before the stop valve I to clear blocked materials. The corresponding stop valve I is closed when nitrogen backflush is activated. A nitrogen purge pipe and valve are provided on the annular duct. A regulating valve is provided between the gravity dust collector and the gas recovery system, and a stop valve III is provided between the regulating valve and the gas recovery system. A nitrogen purge gas vent pipe and valve are provided between the regulating valve and the stop valve III. At the lowest point of the pipe connecting the gravity dust collector to the gas recovery system, a phase change material recovery tank should be installed, along with a phase change material discharge port and valve. The gravity dust collector and the pipes and valves preceding it should be insulated. The phase change material recovery tank requires insulation, while the pipe connecting the gravity dust collector to the gas recovery system is not insulated. Natural cooling or enhanced cooling is required, such as increasing the heat dissipation area to reduce gas flow rate, adding fins to the pipe wall to increase heat dissipation area, or implementing spray cooling measures. Material selection for the entire system should prioritize gas temperature tolerance.

[0010] The location of the air duct must be selected in an area above the boiling point of the phase change material to be removed, and in an area with a high vapor pressure of the pre-excluded phase change material. The high vapor pressure of the phase change material in the drawn-out coal gas can increase the speed of removing the phase change material, and can also reduce the amount of air ducted, reducing the heat loss of the drawn-out coal gas. Therefore, when specifically selecting the location of the air duct, first, it is necessary to determine the area with a high vapor pressure of the phase change material to be removed based on the saturated vapor pressure curve of the phase change material to be removed; second, the location of the air duct must be higher than the fluctuation area of ​​the blast furnace soft melting zone to avoid the soft melting material from clogging the air duct; third, when selecting the air duct area, the heat resistance of the air duct material must also be considered to ensure the safety of the air duct process. Based on the above three factors, the location of the air duct is finally determined.

[0011] The rate at which phase change material is produced in the furnace is determined by the rate at which the precursor of the phase change material is brought into the furnace by the incoming charge. Therefore, the rate at which the precursor is brought into the furnace by the incoming charge can be calculated based on the composition of the incoming charge, and the rate at which the phase change material is produced can be predicted through the precursor.

[0012] The design of the air intake volume and air intake holes is calculated based on the predicted maximum rate of phase change material generation within the furnace. The rate at which the phase change material is removed by the extracted gas must be greater than or equal to the maximum rate of phase change material generation within the furnace. Based on the vapor pressure of the phase change material at the determined air intake hole locations, the concentration of the phase change material in the extracted gas per cubic meter of operating conditions is calculated, and the extracted gas volume (referred to as the air intake rate) is thus calculated. If a continuous removal method is used, the rate of phase change material removal can be slightly greater than the rate of material generation. If a staged removal method is used, a large amount of gas can be extracted to rapidly remove the phase change material. Once the furnace conditions return to normal, gas extraction can be stopped, concluding the phase change material removal operation. If phase change material accumulation reoccurs and affects normal smelting operations, the phase change material removal operation can be resumed. The main manifestations of phase change material accumulation are decreased charge permeability, increased blast resistance, and decreased furnace top pressure. In order to reduce the impact of increased air intake on smelting, it is recommended that the air intake should not exceed 20% of the total blast furnace gas volume, and preferably be controlled at less than 10% of the total blast furnace gas volume. After determining the air intake, determine the flow rate of the drawn gas. It is recommended that the flow rate of the drawn gas be less than 15 meters per second, preferably less than 10 meters per second, to avoid excessive flow rate, which may cause the air flow to carry out the charge. After determining the air intake and the flow rate of the drawn gas, the total drawn gas flow cross-sectional area can be calculated. In order to reduce the impact of the drawn gas on the blast furnace gas flow distribution, a multi-point air intake method is adopted, in which multiple holes are opened in the blast furnace wall. The more holes are opened, the smaller the impact on the blast furnace gas flow distribution. However, the more holes are opened, the more control points there are, the greater the construction workload and the more investment. However, opening small holes does not require changing the water-cooled wall, and holes can be opened in the gaps between the water-cooled tubes. If large holes are opened, the construction workload is small, there are fewer control points, and the investment is small, but the water-cooled wall design needs to be changed and remade. According to the actual situation of each blast furnace, the number of air intake holes is determined. The total gas extraction flow cross-sectional area calculated above is divided by the number of holes to obtain the cross-sectional area of ​​each air intake hole. The hole diameter is calculated based on the cross-sectional area.

[0013] The design principle of the air duct is: the sum of the internal flow areas of all air ducts and bronchi ≥ the calculated total gas flow cross-sectional area.

[0014] In order to ensure that the drawn-out coal gas will not cause high-temperature damage to the gas recovery system when it enters the gas recovery system, cooling measures need to be taken on the gas pipeline at the rear of the gravity dust collector, or heat dissipation fins need to be installed on the pipeline to rely on natural wind to cool the drawn-out coal gas naturally, or by reducing the flow rate and increasing the heat dissipation area, or by taking water spraying to enhance cooling.

[0015] Insulation measures are taken for the front pipeline and annular pipeline of the gravity dust collector to prevent the phase change material from condensing and precipitating in the front of the gravity dust collector, causing dust to agglomerate inside the gravity dust collector or stick to the dust collector wall.

[0016] Advantages and effects of this utility model:

[0017] 1. Compared with the prior art, the present invention does not remove the phase change material from the blast furnace by developing the central airflow, which has low energy consumption. It not only overcomes the problems of increased condensation of phase change material at the edge and poor air permeability in the prior art, but also overcomes the problems of precipitation and scaling of titanium carbide and titanium nitride in the furnace hearth due to weakening of the edge iron flow and lowering of the molten iron temperature at the edge of the furnace hearth, which leads to bulging of the furnace bottom and thickening of the furnace wall.

[0018] 2. After adopting the technical solution of the utility model, the utilization rate of blast furnace gas is significantly improved, the comprehensive coke ratio is reduced, the permeability of the blast furnace is significantly improved, the resistance of the blast furnace charge is significantly reduced, and the blast furnace utilization coefficient is improved.

[0019] 3. By solving the problem of cyclic enrichment of phase-change materials in blast furnaces, the control of phase-change elements in blast furnace charging can be relaxed. Various zinc-containing materials and alkali metal-containing materials that were previously unusable in blast furnaces can now be used for smelting in blast furnaces using the technology of this utility model, which can greatly reduce the procurement cost of blast furnace charging. Various solid wastes that were previously unusable can now be turned into valuable raw materials, which can be said to be turning waste into treasure. It not only processes solid waste but also increases social resources.

[0020] 4. Compared with the traditional process elimination method, this device is more flexible in operation, more thorough in elimination, has less impact on the smelting process and is less costly. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 This is a schematic diagram of the overall structure of a device for removing phase change materials in a blast furnace;

[0022] Figure 2 A schematic diagram of the structure of a blast furnace portion of a device for removing phase change materials in a blast furnace;

[0023] Figure 3 This is a partial structural diagram of a device for removing phase-change materials in a blast furnace, from a gravity dust collector to a gas recovery system;

[0024] Figure 4 This is a schematic diagram of the structure between the regulating valve and the stop valve III of a device for removing phase change materials in a blast furnace;

[0025] In the figure, 1-blast furnace, 2-branch pipe, 3-annular pipe, 4-stop valve I, 5-gravity dust collector, 6-stop valve II, 7-regulating valve, 8-stop valve III, 9-nitrogen recoil pipe and valve, 10-nitrogen purge pipe and valve, 11-nitrogen purge gas release pipe and valve, 12-phase change material recovery tank, 13-phase change material discharge hole and valve. DETAILED DESCRIPTION

[0026] like Figure 1-4As shown, a device for removing phase change material in a blast furnace comprises a blast furnace 1, a bronchial pipe 2, an annular pipe 3, a stop valve I4, a gravity dust collector 5, a stop valve II6, a regulating valve 7, a stop valve III8, a nitrogen recoil pipe and a valve 9, a nitrogen purge pipe and a valve 10, a nitrogen purge gas release pipe and a valve 11, a phase change material recovery tank 12, a phase change material discharge hole and a valve 13; a plurality of air intake holes are provided on the body of the blast furnace 1, and are connected to one end of a plurality of bronchial pipes 2, the other end of the bronchial pipe 2 is connected to the annular pipe 3, the annular pipe 3 sends the drawn-out gas to the gravity dust collector 5 through a pipeline, and a gas discharge port is provided between the annular pipe 3 and the gravity dust collector 5. A stop valve II6 is installed, and the coal gas finally enters the coal gas recovery system after dust removal by the gravity dust collector 5; a regulating valve 7 is installed between the gravity dust collector 5 and the coal gas recovery system, and a stop valve III8 is installed between the regulating valve 7 and the coal gas recovery system; a nitrogen purge gas release pipe and a valve 11 are installed between the regulating valve 7 and the stop valve III8; a stop valve I4 is installed on each bronchus 2, and a nitrogen backflush pipe and a valve 9 are added in front of the stop valve I4; a nitrogen purge pipe and a valve 10 are installed on the annular pipe 3; a phase change material recovery tank 12 is installed at the lowest point of the pipeline connecting the gravity dust collector 5 and the coal gas recovery system, and a phase change material discharge hole and a valve 13 are also installed.

[0027] Example 1

[0028] A 1080m2 steel plant 3 Blast furnaces, due to the inclusion of some converter dust in the incoming charge, have excessively high zinc loading, poor furnace permeability, reduced gas utilization, increased overall coke ratio, decreased utilization coefficient, and observed furnace wall nodules. Using excessively developed central airflow for zinc removal has led to a bulging furnace floor and poor furnace performance. To completely resolve the zinc enrichment issue, this new device has been adopted for zinc removal.

[0029] On the furnace wall of blast furnace 1 in the temperature range of 850℃-900℃, 12 air intake holes with a diameter of 380mm are evenly opened at the same height. One end of 12 bronchial pipes 2 are respectively connected to the air intake holes, and the other ends of the 12 bronchial pipes 2 are connected through pipes to form an annular pipe 3 with a diameter of 1300mm. A stop valve I4 is provided on each bronchial pipe 2, a nitrogen recoil pipe and a valve 9 are added in front of the stop valve I4, a nitrogen purge pipe and a valve 10 are provided on the annular pipe 3, the annular pipe 3 sends the drawn-out coal gas to the gravity dust collector 5 through a pipeline, and a stop valve II6 is provided on the pipeline between the annular pipe 3 and the gravity dust collector 5, a regulating valve 7 and a stop valve III8 are provided on the pipeline from the gravity dust collector 5 to the coal gas recovery system before entering the coal gas recovery system, a nitrogen purge gas release pipe and a valve 11 are provided between the regulating valve 7 and the stop valve III8, an external cooling pipeline system is provided between the gravity dust collector 5 and the regulating valve 7, and heat dissipation fins are provided on the gas transmission pipeline to cool the coal gas by natural wind. A phase-change material recovery tank 12 (for zinc recovery) is installed at the lower end of the external cooling piping system, along with a phase-change material discharge port and valve 13 at its base. A shut-off valve is installed between the phase-change material recovery tank 12 and the external cooling piping system. The cooling system aims to: first, prevent excessive coal gas temperatures from damaging the dust collector filter media; second, reduce piping and valve material costs; and third, recover some zinc. In this solution, insulation measures are implemented in the front-end piping of the gravity dust collector 5 and the annular duct 3 to prevent zinc from precipitating and clogging the piping and dust, thereby reducing zinc waste.

[0030] The method for removing phase change material (zinc) in a blast furnace by using the above device is as follows:

[0031] 1. System Purge and Pressurization: Close shutoff valves I4 and III8, the phase change material discharge port and valve 13, and the dust collector discharge system. Open shutoff valve II6 and regulating valve 7, open the nitrogen purge pipe and valve 10, and open the nitrogen purge gas release pipe and valve 11. Purge the system with nitrogen for 12 minutes to remove air. Close the nitrogen purge gas release pipe and valve 11, pressurize the system to 250 kPa, and close the nitrogen purge pipe, valve 10, and regulating valve 7 to complete the system purge and pressurization.

[0032] 2. Open stop valve I4 and stop valve III8 in sequence, then gradually open regulating valve 7 to put the zinc removal system into operation. The intake air volume is controlled to be less than 10% of the total blast furnace gas volume, and the flow rate of the intake gas is controlled to be less than 10 m / s.

[0033] 3. Regularly discharge dust ash: The dust discharge system uses a two-stage valve. When discharging dust, first close the upper valve and then open the lower ash discharge valve.

[0034] 4. To prevent high-temperature coal gas from damaging the dust removal system, the connection pipe between gravity dust collector 5 and the coal gas recovery system adopts an enhanced cooling mode. Zinc condenses and precipitates as the coal gas cools. To prevent pipe blockage, a zinc recovery tank is installed at the lowest point of this section of the pipeline. The recovery tank is equipped with a liquid level gauge. When the precipitated zinc liquid level reaches the design upper limit, the phase-change material discharge hole and valve 13 are opened to discharge the liquid metallic zinc. When the discharge reaches the lower limit, the phase-change material discharge hole and valve 13 are closed.

[0035] In the first week after the equipment was started up, more than 3 tons of metallic zinc were recovered every day. In the next two weeks, the amount of metallic zinc recovered was about 2 tons per day, and then gradually decreased. In the fifth week, the amount of zinc recovered was about 1 ton per day. The utilization rate of blast furnace gas was significantly improved, the comprehensive coke ratio was reduced, the permeability of blast furnace was significantly improved, and the utilization coefficient of blast furnace increased by 0.3 tons / m 3 ·day.

[0036] Having solved the zinc enrichment problem, the steel mill is now injecting previously discarded blast furnace dust into the blast furnace through a coal injection system. The blast furnace dust now contains approximately 30% carbon, 40% iron, and 8% zinc. The daily injection volume is around 100 tons, recovering over 10 tons of zinc and approximately 35 tons of iron daily. The economic benefits are significant. The blast furnace dust has been transformed from waste into valuable resources.

[0037] Thanks to the injection of blast furnace dust removal ash, the zinc removal equipment has been kept running smoothly to maintain the blast furnace's operating conditions, with good results and no abnormalities. Preparations are underway to carry out this technical retrofit on other blast furnaces.

[0038] Example 2

[0039] A 1280m2 steel plant 3The blast furnace has excessive sodium load due to the addition of red mud from the alumina industry into the charge, resulting in poor air permeability and nodules on the furnace wall. To solve this problem, the utility model device is used. Twelve air intake holes with a diameter of 400 mm are evenly opened on the ninth layer of the furnace wall. One end of each of the twelve bronchial pipes 2 is connected to the air intake holes, and the other end of the twelve bronchial pipes 2 is connected to a ring pipe 3 with a diameter of 1500 mm. The coal gas from the twelve air intake holes is centrally fed into the set ring pipe 3. Each bronchial pipe is provided with a stop valve I4, and a nitrogen recoil pipe and valve 9 are provided before each stop valve I4. A nitrogen purge pipe and valve 10 are provided on the ring pipe 3. A gravity dust collector 5 is provided after the ring pipe 3. A stop valve II6 is provided on the pipe between the ring pipe 3 and the gravity dust collector 5. The gravity dust collector 5 and its front-end pipeline valves are all insulated. After dust removal, the drawn gas is piped into the gas recovery system. A regulating valve 7 and a shutoff valve III8 are installed at the ends of this pipe. A nitrogen purge gas release pipe and valve 11 are located between the regulating valve 7 and the shutoff valve III8. To accelerate gas cooling, a water spray system has been added to the exterior of this pipe. A phase-change material recovery tank 12 (for recovering alkali metals) is located at the lowest point of this pipe to prevent condensation and clogging of the pipe caused by the vapor of phase-change materials such as alkali metals that form during gas cooling. The bottom of this tank (for recovering alkali metals) is equipped with a phase-change material discharge port and valve 13, as well as a liquid level gauge.

[0040] All gas pipelines and valves are made of high-temperature heat-resistant stainless steel.

[0041] The method for removing phase change substances (alkali metals) in a blast furnace by using the above-mentioned device is as follows:

[0042] 1. System Purge and Pressurization: Close shutoff valves I4 and III8, the phase change material discharge port and valve 13, and the dust collector discharge system. Open shutoff valve II6 and regulating valve 7, open the nitrogen purge pipe and valve 10, and open the nitrogen purge gas release pipe and valve 11. Purge the system with nitrogen for 12 minutes to remove air. Close the nitrogen purge gas release pipe and valve 11, pressurize the system to 280 kPa, and close the nitrogen purge pipe, valve 10, and regulating valve 7 to complete the system purge and pressurization.

[0043] 2. Open stop valves I4 and III8 in sequence, then gradually open regulating valve 7 to put the alkali metal removal system into operation. Control the intake air volume to less than 10% of the total blast furnace gas volume, and the intake gas flow rate to less than 10 m / s.

[0044] 3. Regularly discharge dust: When discharging dust from the dust discharge system, close stop valve II6 and stop valve III8 to prevent pressure relief and splashing.

[0045] 4. To prevent high-temperature coal gas from damaging the dust removal system, the connection pipe between gravity dust collector 5 and the coal gas recovery system adopts a spray-enhanced cooling mode. After the coal gas cools, phase-change material condenses and precipitates. To prevent pipe blockage, a phase-change material recovery tank 12 is installed at the lowest point of this section of the pipeline. Phase-change material recovery tank 12 is equipped with a liquid level gauge. When the precipitated liquid level reaches the design upper limit, the phase-change material discharge hole and valve 13 are opened to discharge the liquid phase-change condensate. When the discharge reaches the lower limit, the phase-change material discharge hole and valve 13 are closed.

[0046] After one week of operation, the blast furnace charge resistance was significantly reduced and the blast furnace utilization factor increased by 0.35 tons / m 3 The comprehensive coke ratio decreased by 5 kg / ton of iron per day. Initially, 2.5 tons of alkali metal compounds were recovered daily, and later, approximately 2.2 tons were recovered daily. A small amount of zinc was also recovered during the alkali metal recovery process. The operation has been normal for eight months.

Claims

1. A device for removing phase change materials in a blast furnace, characterized in that: The invention comprises a blast furnace (1), a bronchial pipe (2), an annular pipe (3), a stop valve I (4), a gravity dust collector (5), a stop valve II (6), a regulating valve (7), a stop valve III (8), a nitrogen recoil pipe and valve (9), a nitrogen purge pipe and valve (10), a nitrogen purge gas release pipe and valve (11), a phase change material recovery tank (12), and a phase change material discharge hole and valve (13); a plurality of air intake holes are provided on the body of the blast furnace (1), and are connected to one end of the plurality of bronchial pipes (2); the other end of the bronchial pipe (2) is connected to the annular pipe (3); the annular pipe (3) sends the drawn-out coal gas to the gravity dust collector (5) through a pipeline; a stop valve II is provided between the annular pipe (3) and the gravity dust collector (5). (6), the coal gas finally enters the coal gas recovery system after being dusted by the gravity dust collector (5); a regulating valve (7) is provided between the gravity dust collector (5) and the coal gas recovery system, and a stop valve III (8) is provided between the regulating valve (7) and the coal gas recovery system; a nitrogen purge gas release pipe and a valve (11) are provided between the regulating valve (7) and the stop valve III (8); a stop valve I (4) is provided on each branch pipe (2), and a nitrogen backwash pipe and a valve (9) are provided in front of the stop valve I (4); a nitrogen purge pipe and a valve (10) are provided on the annular pipe (3); a phase change material recovery tank (12) is provided at the lowest point of the pipe connecting the gravity dust collector (5) and the coal gas recovery system, and a phase change material discharge hole and a valve (13) are provided.

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