Emptying hot inert gas recovery method

Abstract

The invention discloses an emptying hot inert gas recovery method, and belongs to the technical field of energy conservation and environmental protection. The gas-steam heat exchanger is used for carrying out heat exchange on the emptying hot inert gas from the coal mill and the compressed air from the compressed air buffer tank, the heat of the emptying hot inert gas is recovered, and the compressed air heated by the gas-steam heat exchanger is conveyed to the filter press to dry the coal slime filter cake. According to the emptying hot inert gas recycling method, by recycling emptying hot inert gas, resource reutilization is achieved, energy consumption and production cost are remarkably reduced, meanwhile, the field environment is improved, and remarkable economic and social benefits are achieved.

Description

Technical Field

[0001] The present invention relates to the field of energy conservation and environmental protection, and in particular to a method for recovering discharged hot inert gas. Background Art

[0002] The coal grinding system is designed to raise the temperature of pulverized coal to about 100°C and reduce the moisture content to 200g / m 3 The system is heated using a hot blast furnace to maintain an appropriate mill outlet temperature. A circulating fan circulates the heat, with a circulating air volume of approximately 100,000 standard cubic meters per hour. A circulating gas venting control valve controls system pressure and moisture content, ensuring the pulverized coal meets the gasification requirements. The vented gas temperature is approximately 95°C, primarily composed of nitrogen and water vapor, with an oxygen content of approximately 2% and a water content of 135 grams per cubic meter. A large amount of hot inert gas is vented on-site, cannot be recycled, and poses an environmental risk.

[0003] The black mud slurry from the slag water section is pumped to the filter press plate through the sedimentation tank underflow pump. After entering the filter press, it goes through the feeding step, the pressing step, the angle blowing step, and the back blowing step. The coal slurry is pressed into filter cakes and then discharged to the coal slurry storage for transportation out of the factory.

[0004] The moisture content of the finished filter cake of the filter press is 35%-42%, which is too high to be transported or used for other purposes. The filter press mud is transformed into filter cake mainly through the pressing process and the angle blowing process. The pressing process mainly allows 0.8mpa desalted water to enter the template. After the template is filled with the slurry, the matching plate storing the mud is squeezed to squeeze out the moisture to form the coal slime filter cake. At this time, the moisture content is about 75%. The remaining moisture needs to be dried for the second time through the angle blowing process. Compressed air is used as the angle blowing medium. The angle blowing time is controlled at 800-900 seconds. The long time and the instantaneous air consumption are large, which can easily cause pressure fluctuations in the pipeline network. The daily consumption is about 15,000 standard cubic meters. Summary of the Invention

[0005] The object of the present invention is to provide a method for recovering vented hot inert gas, which recovers the vented hot inert gas from a coal mill and exchanges heat with the compressed air from a filter press to increase the temperature of the compressed air, reduce the amount of compressed air used, and lower the temperature of the vented hot inert gas. Part of the water vapor in the vented hot inert gas is condensed and recovered and sent to a condensate pipe network, thereby reducing system water consumption. The hot inert gas after dehydration replaces the coal mill seal gas, thereby reducing production costs.

[0006] To achieve the above-mentioned objectives, the present invention provides a method for recovering vented hot inert gas, which utilizes a gas-steam heat exchanger to exchange heat between the vented hot inert gas from the coal mill and the compressed air from the compressed air buffer tank, thereby recovering the heat of the vented hot inert gas. The compressed air heated by the gas-steam heat exchanger is then sent to a filter press to dry the coal slime filter cake.

[0007] Preferably, a first induced draft fan is provided on one piping path of the pulverized coal circulating air venting main pipe to communicate with the gas-steam heat exchanger, and the intake flow rate of the vented hot inert gas entering the gas-steam heat exchanger is controlled by adjusting the frequency conversion of the first induced draft fan.

[0008] Preferably, a temperature sensor and a pressure sensor are provided on the pipeline between the first induced draft fan and the gas-steam heat exchanger, and are interlocked with the pressure setting of the coal grinding system.

[0009] Preferably, a first valve is provided at one end of the vent main pipe communicating with the distribution pipe, and a second valve is provided between the distribution pipe and the vent gas inlet of the first induced draft fan; When the coal grinding system pressure is too low, the interlock closes the second valve of the first induced draft fan inlet valve, and the frequency conversion of the first induced draft fan is reduced to zero. The system pressure is automatically adjusted through the first valve on the circulating fan vent main pipe to maintain system pressure stability.

[0010] Preferably, the discharged hot inert gas after heat exchange in the gas-steam heat exchanger is cooled in a condenser and then sent to a vapor-liquid separator, which outputs inert gas and condensate; The condensate is transported to the squeeze water tank and condensate pipe network through pipelines; The inert gas is sent to the coal mill for use as sealing gas.

[0011] Preferably, valves are provided on the pipelines between the vapor-liquid separator and the squeeze water tank, and on the pipelines between the vapor-liquid separator and the condensate pipe network.

[0012] Preferably, the inert gas output from the vapor-liquid separator is pressurized by the second fan and sent to the outlet of the third fan to be used as sealing gas for the coal mill.

[0013] Therefore, the method for recovering vented hot inert gas of the present invention has the following beneficial effects: (1) Add an induced draft fan in front of the pulverized coal circulating air vent main valve to transport the vented hot inert gas to the gas-steam heat exchanger for heat exchange with compressed air, recover the heat energy of the vented hot inert gas, and output compressed air at 65°C; (2) The compressed air after heat exchange is transported to the filter press to perform angle blowing and drying of the coal slime filter cake, which can reduce the angle blowing time to 100 seconds, which is 700-800 seconds shorter than the traditional angle blowing time. The moisture content of the finished coal slime filter cake is 20%-25%, which is 10%-15% lower than the traditional method, saving 10,000 standard cubic meters of compressed air per day; (3) The condensate is transported to the squeeze water tank and condensate network through pipelines, reducing the amount of desalted water added and reducing water consumption; (4) Inert gas is sent to the coal mill as sealing gas, replacing the atmospheric pressure nitrogen in the coal mill system, reducing nitrogen consumption and lowering production costs; (5) Reduce vent gas emissions, improve on-site environment, and reduce environmental risks.

[0014] The technical solution of the present invention is further described in detail below through the accompanying drawings and embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following briefly introduces the drawings required for use in the description of the embodiments of the present invention. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative labor.

[0016] Figure 1 The figure is a flow chart of a method for recovering vented hot inert gas according to an embodiment of the present invention.

[0017] Reference numerals: 1. Vent main; 2. First induced draft fan; 3. First valve; 4. Second valve; 5. Gas-steam heat exchanger; 6. Compressed air buffer tank; 7. Third valve; 8. Filter press; 9. Condenser; 10. Gas-liquid separator; 11. Squeeze water tank; 12. Condensate pipe network; 13. Second induced draft fan; 14. Third induced draft fan; 15. Coal mill. DETAILED DESCRIPTION

[0018] The technical solution of the present invention is further described below with reference to the accompanying drawings and embodiments.

[0019] In order to make the purpose, technical solutions and advantages of the present application clearer, more thorough and more complete, the technical solutions of the present invention are clearly and completely described below through the accompanying drawings and Examples. The following detailed description is an explanation of the embodiments and is intended to provide further details of the present invention. Unless otherwise specified, all technical terms used in the present invention have the same meaning as those generally understood by those skilled in the art to which the application belongs.

[0020] The instruments, equipment, reagents and materials used in the examples were obtained from commercial sources.

[0021] Example A method for recovering hot inert gas discharged from a coal grinding system can realize resource reuse, energy saving and consumption reduction. The overall process is as follows: Figure 1 As shown, specifically including: A first induced draft fan 2 is installed on one of the piping lines of the pulverized coal circulating air vent main pipe 1. A first valve 3 is installed on the end of the vent main pipe 1 that connects to the piping line. A second valve 4 is installed on the piping line between the vent gas inlet of the first induced draft fan 2. The first valve 3 controls the opening and closing of the vent main pipe 1, while the second valve 4 controls the opening and closing of the piping line. The piping line is connected to a gas-steam heat exchanger 5 through the first induced draft fan 2, introducing the hot inert gas from the vent into the gas-steam heat exchanger 5 for heat exchange.

[0022] The gas-steam heat exchanger 5 carries compressed air in the tube side and vented hot inert gas in the shell side. The compressed air temperature after heat exchange can be raised to approximately 65°C. The compressed air comes from the filter press's compressed air buffer tank 6. A third valve 7 is installed between the outlet manifold of the compressed air buffer tank 6 and the compressed air inlet of the gas-steam heat exchanger 5.

[0023] The flow rate of the vented hot inert gas entering the gas-steam heat exchanger 5 is controlled by adjusting the frequency of the first induced draft fan 2, thereby affecting the temperature of the compressed air after heat exchange in the gas-steam heat exchanger 5. The pipeline between the first induced draft fan 2 and the gas-steam heat exchanger 5 is equipped with temperature and pressure sensors, which are interlocked with the coal grinding system pressure setting. When the coal grinding system pressure is too low, the interlock closes the second valve 4 at the inlet of the first induced draft fan 2, and the frequency of the first induced draft fan 2 is reduced to zero. At this time, the system pressure is automatically adjusted by the first valve 3 on the circulating fan vent main pipe 1 to maintain system pressure stability.

[0024] The compressed air after heat exchange is delivered to the filter press 8, and the filter cake is dried by corner blowing. The thermal efficiency of drying after compressed air heat exchange is about 10 times higher than that of drying with cool air, and the corner blowing time is minimized while ensuring the moisture content of the filter cake is qualified.

[0025] When the temperature of the compressed air output by the gas-steam heat exchanger 5 is 65°C, the angle blowing time can be reduced to 100 seconds, and the moisture content of the finished filter cake can be reduced to 20%-25%.

[0026] After heat exchange, the inert gas is cooled in condenser 9 and sent to vapor-liquid separator 10. The condensate can be used to replenish the squeeze water tank 11 or sent to the condensate pipeline 12. The uncondensed inert gas is pressurized by the second fan 13 and sent to the outlet of the third fan 14 for use as sealing gas in the coal mill 15.

[0027] Therefore, the present invention provides a method for recovering hot inert gas from venting, which recovers the hot inert gas from the circulating gas venting and exchanges heat with the compressed air from the filter press, thereby increasing the temperature of the compressed air, reducing the corner blowing time, and reducing the water content of the filter cake. The compressed air consumption can be saved by 10,000 standard cubic meters per day. After the temperature of the hot inert venting gas is reduced, part of the water vapor in the venting gas is condensed and recovered. After the condensate is cooled and recovered, the pressure is increased by a pump and used as water to replenish the squeeze water tank or to be sent to the condensate pipeline network, thereby reducing water consumption. The uncondensed inert gas replaces the atmospheric pressure nitrogen in the coal grinding system, thereby reducing production costs.

[0028] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit the same. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that they can still modify or replace the technical solutions of the present invention with equivalents, and these modifications or equivalent replacements cannot cause the modified technical solutions to deviate from the spirit and scope of the technical solutions of the present invention.

Claims

1. A method for recovering vented hot inert gas, characterized in that: The gas-steam heat exchanger is used to exchange heat between the discharged hot inert gas from the coal mill and the compressed air from the compressed air buffer tank, and the heat of the discharged hot inert gas is recovered. The compressed air heated by the gas-steam heat exchanger is sent to the filter press to dry the coal slime filter cake.

2. A method for recovering vented hot inert gas according to claim 1, characterized in that: A first induced draft fan is arranged on the piping line of the coal grinding circulating air venting main pipe to be connected with the gas-steam heat exchanger, and the intake flow rate of the venting hot inert gas entering the gas-steam heat exchanger is controlled by adjusting the frequency conversion of the first induced draft fan.

3. A method for recovering vented hot inert gas according to claim 2, characterized in that: A temperature sensor and a pressure sensor are provided on the pipeline between the first induced draft fan and the gas-steam heat exchanger, and are interlocked with the pressure setting of the coal grinding system.

4. A method for recovering vented hot inert gas according to claim 3, characterized in that: A first valve is provided at one end of the vent main pipe connected to the distribution pipe, and a second valve is provided between the distribution pipe and the vent gas inlet of the first induced draft fan; When the coal grinding system pressure is too low, the second valve of the first induced draft fan inlet valve is interlocked to close, and the frequency conversion of the first induced draft fan is reduced to zero. The system pressure is automatically adjusted through the first valve on the circulating fan vent main pipe to maintain the system pressure stable.

5. A method for recovering vented hot inert gas according to claim 1, characterized in that: The discharged hot inert gas after heat exchange in the gas-steam heat exchanger is cooled by the condenser and then sent to the vapor-liquid separator, which outputs the inert gas and condensate; The condensate is transported to the squeeze water tank and condensate pipe network through pipelines; The inert gas is sent to the coal mill for use as sealing gas.

6. A method for recovering vented hot inert gas according to claim 5, characterized in that: Valves are provided on the pipelines between the vapor-liquid separator and the squeeze water tank, and between the vapor-liquid separator and the condensate pipe network.

7. A method for recovering vented hot inert gas according to claim 5, characterized in that: The inert gas output from the vapor-liquid separator is pressurized by the second fan and sent to the outlet of the third fan for use as sealing gas for the coal mill.

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