A nitrogen-containing and coal-dust-containing gas emission recovery and utilization system and method

Abstract

The present invention belongs to the technical field of waste gas recovery and utilization, and particularly relates to a nitrogen-containing and coal-dust-containing purge gas recovery and utilization system and method. The nitrogen-containing and coal-dust-containing purge gas recovery and utilization system provided by the present invention includes a nitrogen buffer tank; a plurality of pulverized coal lock hoppers communicated with the nitrogen inlet of the nitrogen buffer tank, and a gas filter is arranged on the pipeline where the pulverized coal lock hopper is communicated with the nitrogen buffer tank; a heat exchanger communicated with the nitrogen outlet of the nitrogen buffer tank. The system provided by the present invention and the method for recovering and utilizing nitrogen-containing and coal-dust-containing purge gas using the system can realize the separation of pulverized coal and nitrogen in the nitrogen-containing and coal-dust-containing purge gas, the storage and heating of nitrogen, and the obtained heated nitrogen can be recycled, effectively solving the problem that nitrogen in the nitrogen-containing and coal-dust-containing purge gas cannot be recovered and utilized and is wasted by venting. The present invention turns the nitrogen-containing and coal-dust-containing purge gas into a useful resource, improves the utilization rate of nitrogen and pulverized coal, reduces the production cost, and improves the surrounding environment.

Description

Technical Field

[0001] The invention belongs to the technical field of waste gas recovery and utilization, and specifically relates to a system and method for recovering and utilizing nitrogen- and coal dust-containing purge gas. Background Art

[0002] In the pulverized coal pressurized conveying production line, the pulverized coal from the coal grinding and drying system enters the pulverized coal storage bin V1201A, and the pulverized coal is fed into the pulverized coal lock hopper V1204A by gravity through the double coal discharge valve from the pulverized coal storage bin V1201A. When the pulverized coal storage bin V1201A discharges coal to the pulverized coal lock hopper V1204A to the set weight (the discharge amount is adjusted between 30 and 60 tons each time according to the system operation), the pulverized coal lock hopper V1204A is isolated from the pulverized coal storage bin V1201A, and then the pulverized coal lock hopper V1204A is pressurized to 4.7MPa with nitrogen, which is the same as the pressure of the high-pressure pulverized coal feeding tank V1205A. When the low material level switch of the high-pressure pulverized coal feeding tank V1205A is activated, the pulverized coal lock hopper V1204A discharges the material to the high-pressure pulverized coal feeding tank V1205A by gravity under the control of the discharge sequence control. After the pulverized coal lock hopper V1204A is unloaded, the discharge valve and the balance valve are closed to isolate it from the high-pressure pulverized coal feeding tank V1205A, and then the pulverized coal lock hopper V1204A begins to depressurize. Depressurization is divided into two steps. First, the pressure is released through the primary pressure relief valve to reduce the pressure of the pulverized coal lock hopper V1204A to 2.00MPa. The second step is to close the primary pressure relief valve and open the secondary pressure relief valve to release the pressure. When the pressure of the pulverized coal lock hopper V1204A is released to 0.15MPa, and the pressure difference between the pulverized coal lock hopper V1204A and the vent filter S1201A on the pulverized coal lock hopper V1204A pressure relief main pipe is less than 0.10MPa, the secondary pressure relief valve is closed and the balance valve between the pulverized coal lock hopper V1204A and the vent filter S1201A is opened. Among them, during the primary pressure relief process of V1204A, the nitrogen enters the vent filter S1201A to separate the coal powder and is then directly discharged into the atmosphere, wasting nitrogen resources. At the same time, the nitrogen separated by the vent filter S1201A is still dusty gas, and direct discharge will cause environmental pollution. Summary of the invention

[0003] The object of the present invention is to provide a system and method for recycling nitrogen-containing coal dust-containing purge gas. The system provided by the present invention can not only recycle nitrogen, but also solve the problem that nitrogen-containing coal dust-containing purge gas cannot be recycled, resulting in nitrogen waste. At the same time, the present invention further recovers coal powder in the nitrogen-containing coal dust-containing purge gas, thereby improving the utilization rate of coal powder, reducing the emission of coal dust-containing gas, and improving the surrounding environment.

[0004] In order to achieve the above object, the present invention provides the following technical solutions:

[0005] The present invention provides a system for recycling nitrogen-containing and coal-dust-containing flue gas, including a nitrogen buffer tank V1208, which is provided with a nitrogen inlet, a nitrogen outlet and a pulverized coal outlet;

[0006] A plurality of pulverized coal lock hoppers V1204 communicated with the nitrogen inlet of the nitrogen buffer tank V1208, and a gas filter S1204 is arranged on the pipeline where the pulverized coal lock hopper V1204 is communicated with the nitrogen buffer tank V1208;

[0007] A heat exchanger E1201 communicated with the nitrogen outlet of the nitrogen buffer tank V1208.

[0008] Preferably, the pulverized coal lock hopper V1204 is provided with an exhaust port, and a second blind plate 2 is arranged at one end of the pipeline where the pulverized coal lock hopper V1204 is communicated with the gas filter S1204 close to the exhaust port.

[0009] Preferably, the gas filter S1204 is provided with a gas outlet, and an anti-blowing gas inlet is arranged at one end of the pipeline where the gas outlet is communicated with the nitrogen buffer tank V1208 close to the gas outlet.

[0010] Preferably, a regulating valve 3 and a switching valve 4 are arranged on the pipeline where the gas filter S1204 is communicated with the nitrogen buffer tank V1208, and the regulating valve 3 is close to the gas filter S1204 on the pipeline.

[0011] Preferably, a pressure regulating valve 5 is arranged on the pipeline where the nitrogen buffer tank V1208 is communicated with the heat exchanger E1201.

[0012] The present invention provides a method for recycling nitrogen-containing and coal-dust-containing flue gas by using the system adopting the above technical scheme, including the following steps:

[0013] Dust-removing the nitrogen-containing and coal-dust-containing flue gas in the pulverized coal lock hopper V1204 through the gas filter S1204, and discharging the dust-removed flue gas into the nitrogen buffer tank V1208;

[0014] Heating the dust-removed flue gas in the nitrogen buffer tank V1208 through the heat exchanger E1201, and recycling the heated flue gas; the recycling includes: using the heated flue gas for one or more of the transportation of limestone in the coal grinding process, boiler ash transportation, fly ash treatment process ash transportation and fire fighting gas.

[0015] Preferably, in the pulverized coal lock hopper V1204: the initial pressure of the nitrogen-containing and coal-dust-containing flue gas is 4.5-4.8 MPa, and the pressure after pressure relief is 2.0-2.2 MPa.

[0016] Preferably, the pressure of the dust removal purge gas when entering the heat exchanger E1201 for heating is 0.6 - 0.7 MPa.

[0017] Preferably, the temperature of the heated purge gas is 80 - 85 °C.

[0018] Preferably, when the gas filter S1204 removes dust from the nitrogen - containing and coal - dust - containing purge gas, it also includes using pressurized nitrogen to back - blow the gas filter S1204, and the pressure of the pressurized nitrogen is 4.7 - 5.3 MPa.

[0019] The present invention provides a system for recycling nitrogen - containing and coal - dust - containing purge gas, including a nitrogen buffer tank V1208, which is provided with a nitrogen inlet, a nitrogen outlet, and a pulverized coal outlet; several pulverized coal lock hoppers V1204 connected to the nitrogen inlet of the nitrogen buffer tank V1208, and a gas filter S1204 is arranged on the pipeline where the pulverized coal lock hopper V1204 is connected to the nitrogen buffer tank V1208; a heat exchanger E1201 connected to the nitrogen outlet of the nitrogen buffer tank V1208. The system provided by the present invention can separate pulverized coal from nitrogen in the nitrogen - containing and coal - dust - containing purge gas, store and heat the nitrogen, and the heated nitrogen obtained can be recycled, effectively solving the problem that nitrogen in the nitrogen - containing and coal - dust - containing purge gas cannot be recycled and is wasted by discharging to the atmosphere. The system provided by the present invention can turn the nitrogen - containing and coal - dust - containing purge gas into a valuable resource, improve the utilization rate of nitrogen and pulverized coal, and reduce production costs; reduce the emission of coal - dust - containing gas and improve the surrounding environment.

[0020] The present invention provides a method for recycling nitrogen-containing and coal-dust-containing purge gas by using the system described in the above technical solution, including the following steps: dust-removing the nitrogen-containing and coal-dust-containing purge gas in the coal powder lock hopper V1204 through the gas filter S1204, and discharging the dust-removed purge gas into the nitrogen buffer tank V1208; heating the dust-removed purge gas in the nitrogen buffer tank V1208 through the heat exchanger E1201, and recycling the heated purge gas; the recycling includes: using the heated purge gas for one or more of the transportation of limestone in the coal grinding process, the ash transportation of the boiler, the ash transportation in the fly ash treatment process, and the fire extinguishing gas. The method provided by the present invention uses the gas filter S1204 to separate the coal powder and nitrogen from the nitrogen-containing and coal-dust-containing purge gas, and recycles the stored nitrogen after heating, which can avoid the increase of the dew point of the purge gas after dust removal and the condensation of moisture in the purge gas, causing blockage of the pipeline during the recycling process. Therefore, the method provided by the present invention neither affects the normal operation of the existing coal powder production device, nor can recycle nitrogen, and uses the clean nitrogen to transport powder media such as coal ash and limestone, or uses the non-combustible property of nitrogen as the fire extinguishing gas, maximizing the use of the residual pressure in the purge gas, reducing the production cost, and improving the safety of the easily explosive dust system; at the same time, reducing the tail gas emission. The results of the examples show that the method provided by the present invention can effectively recycle nitrogen, and the recycling amount is 3000-4000 Nm 3 / h. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 is a schematic diagram of a system for recycling nitrogen-containing and coal-dust-containing purge gas provided by the present invention;

[0022] Figure 1 In the figure: V1204 is a coal powder lock hopper, S1204 is a gas filter, V1208 is a nitrogen buffer tank, E1201 is a heat exchanger, 1 is a first blind plate, 2 is a second blind plate, 3 is a regulating valve, 4 is a switching valve, 5 is a pressure regulating valve, 6 is a safety valve, 7 is a water sample observation tank, and 8 is a dust analyzer. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0023] The present invention provides a system for recycling nitrogen-containing and coal-dust-containing purge gas, including a nitrogen buffer tank V1208, and the nitrogen buffer tank V1208 is provided with a nitrogen inlet, a nitrogen outlet, and a coal powder outlet;

[0024] A plurality of coal powder lock hoppers V1204 communicated with the nitrogen inlet of the nitrogen buffer tank V1208, and a gas filter S1204 is arranged on the pipeline connecting the coal powder lock hopper V1204 and the nitrogen buffer tank V1208;

[0025] A heat exchanger E1201 communicated with the nitrogen outlet of the nitrogen buffer tank V1208.

[0026] In the present invention, unless otherwise specified, all raw materials / components are commercially available products well-known to those skilled in the art.

[0027] Figure 1 It is a schematic diagram of a nitrogen-containing and coal-dust-containing blow-by gas recovery and utilization system provided by the present invention. The following will be combined with Figure 1 A nitrogen-containing and coal-dust-containing blow-by gas recovery and utilization system provided by the present invention will be described in detail.

[0028] The nitrogen-containing and coal-dust-containing blow-by gas recovery and utilization system provided by the present invention includes a nitrogen buffer tank V1208, and the nitrogen buffer tank V1208 is provided with a nitrogen inlet, a nitrogen outlet, and a coal powder outlet. In the present invention, the nitrogen buffer tank V1208 is used to temporarily store nitrogen filtered by the gas filter S1204. The nitrogen inlet of the nitrogen buffer tank V1208 is used to convey nitrogen into the nitrogen buffer tank V1208. The nitrogen outlet of the nitrogen buffer tank V1208 is used to convey the nitrogen in the nitrogen buffer tank V1208 to the heat exchanger E1201 for heating. The coal powder outlet of the nitrogen buffer tank V1208 is used to discharge a small amount of coal powder sedimented from the nitrogen in the nitrogen buffer tank V1208 to prevent the accumulation of coal powder at the bottom of the nitrogen buffer tank V1208.

[0029] As one or more embodiments of the present invention, the volume of the nitrogen buffer tank V1208 is 100 m 3 .

[0030] As one or more embodiments of the present invention, there are 2 nitrogen inlets of the nitrogen buffer tank V1208, which are respectively arranged on the side wall of the nitrogen buffer tank V1208 and are symmetrically distributed.

[0031] As one or more embodiments of the present invention, the coal powder outlet of the nitrogen buffer tank V1208 is located at the bottom of the nitrogen buffer tank V1208. The present invention preferably discharges the coal powder sedimented in the nitrogen buffer tank V1208 to the coal powder silo bag filter through a small-flow exhaust.

[0032] The nitrogen and coal dust-containing gas emission recovery and utilization system provided by the present invention includes a plurality of pulverized coal lock hoppers V1204 connected to the nitrogen inlet of the nitrogen buffer tank V1208, and a gas filter S1204 is provided on the pipeline where the pulverized coal lock hopper V1204 is connected to the nitrogen buffer tank V1208. In the present invention, the pulverized coal lock hopper V1204 is used to store and receive low-pressure pulverized coal transported from the pulverized coal storage bin. After the pulverized coal is pressurized by pressurized nitrogen, it is fed into the high-pressure pulverized coal feed bin. The gas filter S1204 is used to perform dust removal and filtration on the nitrogen and coal dust-containing gas emissions discharged from the pulverized coal lock hopper V1204, and separate the pulverized coal and nitrogen in the nitrogen and coal dust-containing gas emissions. In the present invention, most of the pulverized coal filtered by the gas filter S1204 falls back into the pulverized coal lock hopper V1204, and a small amount of pulverized coal is carried into the nitrogen buffer tank V1208 by the gas and discharged from the pulverized coal outlet provided at the bottom of the nitrogen buffer tank V1208.

[0033] As one or more embodiments of the present invention, the gas filter S1204 is a high-pressure filter.

[0034] As one or more embodiments of the present invention, the number of the pulverized coal lock hoppers V1204 is 2. Each pulverized coal lock hopper V1204 is connected to the nitrogen buffer tank V1208 through one nitrogen inlet (interface).

[0035] As one or more embodiments of the present invention, the number of the gas filters S1204 is 2, and one gas filter S1204 is provided on the pipeline where each pulverized coal lock hopper V1204 is connected to the nitrogen buffer tank V1208.

[0036] As one or more embodiments of the present invention, the pulverized coal lock hopper V1204 is provided with an exhaust port, and a second blind plate 2 is provided at one end of the pipeline where the pulverized coal lock hopper V1204 is connected to the gas filter S1204 and close to the exhaust port. In the present invention, the second blind plate 2 is used to isolate the gas filter S1204 and the pulverized coal lock hopper V1204.

[0037] As one or more embodiments of the present invention, the volume of the pulverized coal lock hopper V1204 is 91m 3 。

[0038] As one or more embodiments of the present invention, a π-shaped bend is further provided on the pipeline where the pulverized coal lock hopper V1204 is connected to the gas filter S1204. The elbow material of the π-shaped bend is a casting to prevent wear, and flanges are provided at both ends for easy disassembly and maintenance.

[0039] In the present invention, the second blind plate 2 and the π-shaped bend are used to isolate the pulverized coal lock hopper V1204 and the gas filter S1204. When the filter element of the gas filter S1204 is damaged or broken, the broken object enters the pulverized coal lock hopper V1204 and the downstream equipment of the pulverized coal lock hopper V1204, which will cause the blockage of the downstream material pipe of the subsequent system. In severe cases, the corresponding coal burner will be forced to stop operating, resulting in a decrease in the synthetic ammonia production and an increase in the extra workload of the workers. The present invention isolates the pulverized coal lock hopper V1204 and the gas filter S1204 through the second blind plate 2 and the π-shaped bend, so as to prevent the broken object from entering the pulverized coal lock hopper V1204 when the filter element of the gas filter S1204 is damaged or broken.

[0040] As one or more embodiments of the present invention, the pulverized coal lock hopper V1204 still retains the original purge gas outlet. The original purge gas outlet is used for secondary pressure relief of the purge gas with a pressure less than 2.2 MPa after the first pressure relief of the pulverized coal lock hopper V1204. A first blind plate 1 is arranged on the pipeline connected to the original purge gas outlet.

[0041] As one or more embodiments of the present invention, the gas filter S1204 is provided with a gas outlet, and an anti-blowing gas inlet is arranged at one end of the pipeline connecting the gas outlet to the nitrogen buffer tank V1208 close to the gas outlet. In the present invention, the anti-blowing gas inlet is used to supply pressurized nitrogen to the working gas filter S1204 for back blowing, reduce the attachment of pulverized coal on the filter element of the gas filter S1204, and settle the pulverized coal to the pulverized coal lock hopper V1204 by gravity.

[0042] As one or more embodiments of the present invention, a regulating valve 3 and a switch valve 4 are arranged on the pipeline connecting the gas filter S1204 to the nitrogen buffer tank V1208, and the regulating valve 3 is located close to the gas filter S1204 on the pipeline. In the present invention, the regulating valve 3 is used to regulate the pressure relief rate of the nitrogen filtered by the gas filter S1204. The switch valve 4 is used to disconnect or connect the passage between the gas filter S1204 and the nitrogen buffer tank V1208.

[0043] The nitrogen-containing and coal-dust-containing purge gas recovery and utilization system provided by the present invention includes a heat exchanger E1201 connected to the nitrogen outlet of the nitrogen buffer tank V1208. In the present invention, the heat exchanger E1201 is used to heat the nitrogen in the nitrogen buffer tank V1208 before reuse.

[0044] As one or more embodiments of the present invention, a pressure regulating valve 5 is arranged on the pipeline connecting the nitrogen buffer tank V1208 to the heat exchanger E1201. The pressure regulating valve 5 is used to control the pressure of the nitrogen entering the heat exchanger E1201 from the nitrogen buffer tank V1208.

[0045] As one or more embodiments of the present invention, the heating medium used in the heat exchanger E1201 is 0.7 MPa low-pressure steam.

[0046] As one or more embodiments of the present invention, the heat exchanger E1201 is provided with a heating gas outlet, and a safety valve 6 is provided on the pipeline connected to the heating gas outlet. The safety valve 6 is used to control the maximum pressure of the heated nitrogen gas, avoid excessive pressure of the heated nitrogen gas, and prevent overpressure of the subsequent system.

[0047] As one or more embodiments of the present invention, a sampling conduit is further provided on the pipeline connected to the heating gas outlet. The sampling conduit is connected to a dust analyzer 8 and a water sample observation tank 7.

[0048] In the present invention, although the nitrogen gas recycled in the nitrogen buffer tank V1208 has been dust-removed by the gas filter S1204, it still contains a small amount of dust. Especially when the gas filter S1204 is damaged, it will lead to greater risks. The increase in the dust content in the recycled nitrogen gas will cause the valve core of the subsequent pressure relief valve to wear more severely. In order to prevent special situations such as the increase in the dust content of the recycled nitrogen gas and the damage of the gas filter S1204, the present invention uses the dust analyzer 8 to detect the change of dust in real time, and sets an interlock to close the recycling system when the dust content in the recycled nitrogen gas reaches a certain limit value. The present invention also connects the gas phase to the water sample observation tank 7 through the sampling conduit for on-line observation, regularly observes the water quality, and assists in judging the change of gas-phase dust. In the present invention, if the dust content in the recycled nitrogen gas increases, secondary treatment can be carried out by means of the ash bin of the subsequent system and the bag filter of the coal grinding system.

[0049] The present invention provides a method for recycling nitrogen-containing and coal-dust-containing flue gas by using the system described in the above technical solution, including the following steps:

[0050] Dust-remove the nitrogen-containing and coal-dust-containing flue gas in the coal powder lock hopper V1204 through the gas filter S1204, and discharge the dust-removed flue gas into the nitrogen buffer tank V1208;

[0051] Heat the dust-removed flue gas in the nitrogen buffer tank V1208 through the heat exchanger E1201, and recycle the heated flue gas; the recycling includes: using the heated flue gas for one or more of the transportation of limestone in the coal grinding process, boiler ash transportation, ash transportation in the fly ash treatment process, and fire fighting gas.

[0052] The present invention dust-removes the nitrogen-containing and coal-dust-containing flue gas in the coal powder lock hopper V1204 through the gas filter S1204, and discharges the dust-removed flue gas into the nitrogen buffer tank V1208.

[0053] In the present invention, in the pulverized coal lock hopper V1204: the initial pressure of the nitrogen-containing and coal dust-containing purge gas is preferably 4.5 - 4.8 MPa, more preferably 4.8 MPa. The pressure after pressure relief is preferably 2.0 - 2.2 MPa, more preferably 2 MPa. In the present invention, after the pressure of the pulverized coal lock hopper V1204 is less than 2.2 MPa after pressure relief, secondary pressure relief is carried out using the original purge gas outlet.

[0054] In the present invention, when the gas filter S1204 removes dust from the nitrogen-containing and coal dust-containing purge gas, the present invention preferably further includes using pressurized nitrogen to backflush the gas filter S1204, and the pressure of the pressurized nitrogen is preferably 4.7 - 5.3 MPa, more preferably 5.1 MPa.

[0055] After the dust-removed purge gas obtained is discharged into the nitrogen buffer tank V1208, the present invention heats the dust-removed purge gas in the nitrogen buffer tank V1208 through the heat exchanger E1201, and the heated purge gas obtained is recycled; the recycling includes: using the heated purge gas for one or more of the conveying of limestone in the coal grinding process, boiler ash conveying, fly ash treatment process ash conveying, and fire fighting gas.

[0056] In the present invention, the pressure relief rate of the dust-removed purge gas filtered by the gas filter S1204 entering the nitrogen buffer tank V1208 is preferably 0.120 - 0.125 MPa / min. The present invention preferably adjusts the pressure relief rate of the dust-removed purge gas entering the nitrogen buffer tank V1208 through the regulating valve 3.

[0057] In the present invention, the pressure of the dust-removed purge gas when entering the heat exchanger E1201 for heating is preferably 0.6 - 0.7 MPa.

[0058] In the present invention, the temperature of the heated purge gas is preferably 80 - 85 °C, more preferably 80 °C.

[0059] The above nitrogen-containing and coal dust-containing purge gas recovery and utilization method provided by the present invention separates pulverized coal from nitrogen, which neither affects the normal operation of the existing production device nor can recover and utilize nitrogen, uses the clean nitrogen to convey powder media such as coal ash and limestone, maximizes the residual pressure in the purge gas, reduces production costs; and at the same time reduces tail gas emissions. In addition, the non-combustible property of nitrogen can be utilized, and nitrogen is used as fire fighting gas to improve the safety of the easily explosive dust system.

[0060] In order to further illustrate the present invention, the technical solutions provided by the present invention will be described in detail below in conjunction with embodiments, but they cannot be understood as limiting the protection scope of the present invention.

[0061] Example 1

[0062] This embodiment adopts Figure 1 The nitrogen-containing coal dust-containing exhaust gas recovery and utilization system shown is used to recover and utilize the nitrogen-containing coal dust-containing exhaust gas in the coal powder lock bucket V1204.

[0063] Coal powder lock bucket V1204 (equipment volume 91m 3 ) contains nitrogen and coal dust. The gas pressure is about 4.8MPa, and is discharged to the high-pressure filter S1204 through the pipeline. After the gas is dusted by the high-pressure filter S1204, it enters the nitrogen buffer tank V1208 (100m 3 ), the pulverized coal lock hopper V1204 connected to another gas inlet of the nitrogen buffer tank V1208 and the high-pressure filter S1204 are connected to the nitrogen buffer tank V1208 through the same setting.

[0064] The recovered clean nitrogen is reduced in pressure from the nitrogen buffer tank V1208 to 0.7MPa through the pressure regulating valve 5 (at the same time, a safety valve 6 is provided to avoid system overpressure), enters the heat exchanger E1201, is heated to 80°C with 0.7MPa low-pressure steam, and is then transported to the coal gasification and boiler unit through a pipeline to replace the fly ash transport gas of the coal gasification fly ash treatment unit, the limestone transport nitrogen of the coal grinding unit, and the boiler ash transport air.

[0065] In this embodiment: the high-pressure filter S1204 uses 5.1MPa nitrogen gas for back-blowing to reduce the adhesion of coal powder on the filter element, and gravity settles it to the coal powder lock bucket V1204. In order to prevent a small amount of coal powder from accumulating at the bottom of the nitrogen buffer tank V1208, a discharge pipe is set to discharge it to the powder coal bin bag filter with a small flow rate.

[0066] Control measures to avoid the dew point increase of recycled nitrogen in this embodiment: the material in the coal powder lock hopper V1204 is coal powder dried by the coal grinding system, and the water content of the coal powder is 0.5-2.0%. After the nitrogen is depressurized by the coal powder lock hopper V1204, the dew point of the discharged purge gas will increase. The recycled nitrogen is used for limestone transportation in the coal grinding system. The pipeline is short and the limestone particle size is large, so the blockage problem is controllable. The recycled nitrogen is used for coal gasification and boiler ash transportation. Because the pipeline from the starting point of the ash transportation pipeline to the end of the ash storage is long, there may be a risk of blockage of the fly ash pipeline. In order to avoid the dew point of the purge gas rising and the condensation of water in the purge gas causing the ash transportation pipeline to be blocked, the system of this embodiment is additionally equipped with a heat exchanger E1201. The heat exchanger E1201 uses 0.7MPa low-pressure steam to heat the purge gas to a temperature of 80°C, and the steam condensate of the heat exchanger E1201 is recovered to the condensate pipeline network.

[0067] Control measures in this embodiment to prevent the increase in the dust content of recycled nitrogen: After the recycled nitrogen is dust-removed by the high-pressure filter S1204, there is still a small amount of dust. Especially when the high-pressure filter S1204 is damaged, it will lead to greater risks. If the dust content in the recycled nitrogen increases, the ash silo in the subsequent system and the bag filter in the coal grinding system can be used for secondary treatment, and the overall risk is controllable. Moreover, due to the increase in the dust content, the wear of the subsequent pressure relief valve spool will be aggravated. In response to the above risks, in this embodiment, to prevent special situations such as the increase in the dust content of recycled nitrogen and the damage of the filter, a sampling conduit is introduced by opening a hole in the recycled gas pipeline. A dust analyzer 8 is set on the sampling conduit to detect the change of dust in real time. When the dust content reaches a certain limit, the recycled system is set to be interlocked and closed. A sampling conduit is introduced by opening a hole in the pipeline, and the gas phase is connected to the water sample observation tank 7. The daily observation is carried out by means of direct observation through the water sample observation tank 7, and the water quality is observed regularly to assist in judging the change of gas-phase dust. In addition, the pressure relief time is timed and analyzed in the DCS to judge the wear degree of the pressure relief valve.

[0068] Control measures in this embodiment to avoid the increase in the primary pressure relief time of the coal powder lock hopper V1204: After the flue gas is recycled and utilized, due to the back pressure (nitrogen buffer tank V1208) in the primary pressure relief and the pressure relief rate limit (the pressure relief rate is controlled at 0.120 - 0.125 MPa / min through the regulating valve), the primary pressure relief increases by about 5 minutes on the basis of the original pressure relief time. From the actual operation experience data, under the condition of full-load operation of the system, before the flue gas is recycled and utilized, the idle time for single coal feeding is about 10 minutes. Therefore, after the flue gas is recycled and utilized, the increase in the pressure relief time will not affect the overall coal feeding time.

[0069] Control measures in this embodiment to avoid blockage of downstream equipment caused by damage to the filter element of the newly added high-pressure filter S1204: If the filter element of the newly added high-pressure filter S1204 is damaged or broken, and the broken object enters the downstream equipment, it will cause blockage of the downstream material pipe. In severe cases, the corresponding coal burner will be forced to stop operating, resulting in a decrease in the synthetic ammonia output and an increase in the extra workload of workers. In response to this situation, a π-shaped bend is set between the pressure relief pipe of the coal powder lock hopper V1204 and the high-pressure filter S1204. The elbow material is a casting to prevent wear, and flanges are set at both ends for easy disassembly and maintenance. A blind plate is set at the root of the pressure relief pipe at the top of the coal powder lock hopper V1204 for isolation, and at the same time, the original pressure relief pipe function is retained at the top of the coal powder lock hopper V1204.

[0070] In this embodiment, nitrogen is recycled, and the recycling amount is about 3000 - 4000 Nm 3 / h. When the pressure of the coal powder lock hopper V1204A drops to 2.0 MPa, the regulating valve 3 and the switching valve 4 are closed, and the coal powder lock hopper V1204A switches back to the original process for secondary pressure relief.

[0071] The nitrogen- and coal-dust-containing blow-by gas recovery and utilization method provided by the present invention has the following advantages: 1) Recycling nitrogen solves the problem that nitrogen- and coal-dust-containing blow-by gas cannot be recovered and utilized, resulting in wasteful venting, turning waste into treasure; improving the utilization rates of nitrogen and pulverized coal and reducing production costs; 2) Recycling pulverized coal improves the utilization rate of pulverized coal, reduces the emission of coal-dust-containing gas, and improves the surrounding environment; 3) Recycling the residual pressure of blow-by gas for transporting powder media such as coal ash and limestone; 4) According to the characteristics of production devices, broadening the utilization ways of nitrogen: Using the non-flammable property of nitrogen as fire protection gas to improve the safety of the easily explosive dust system; 5) After process optimization, the wear rate of blow-by gas pipelines can be reduced, the risk of pipe explosion can be reduced at the same time, and the maintenance cost of production devices can be reduced.

[0072] Although the above embodiments have made a detailed description of the present invention, they are only a part of the embodiments of the present invention, rather than all embodiments. Other embodiments can be obtained based on these embodiments without creative efforts, and these embodiments all fall within the protection scope of the present invention.

Claims

1. A method for recycling nitrogen-containing and coal-dust-containing gas emission, characterized in that, It is carried out by using a nitrogen-containing and coal-dust-containing bleed gas recovery and utilization system. The nitrogen-containing and coal-dust-containing bleed gas recovery and utilization system includes a nitrogen buffer tank (V1208), and the nitrogen buffer tank (V1208) is provided with a nitrogen inlet, a nitrogen outlet and a pulverized coal outlet; several pulverized coal lock hoppers (V1204) communicated with the nitrogen inlet of the nitrogen buffer tank (V1208), a gas filter (S1204) is arranged on the pipeline where the pulverized coal lock hopper (V1204) is communicated with the nitrogen buffer tank (V1208), the pulverized coal lock hopper (V1204) is provided with an exhaust port, and a second blind plate (2) is arranged at one end of the pipeline where the pulverized coal lock hopper (V1204) is communicated with the gas filter (S1204) near the exhaust port. The gas filter (S1204) is provided with a gas outlet, and an anti-blowing gas inlet is arranged at one end of the pipeline where the gas outlet is communicated with the nitrogen buffer tank (V1208) near the gas outlet. A regulating valve (3) and a switching valve (4) are arranged on the pipeline where the gas filter (S1204) is communicated with the nitrogen buffer tank (V1208), and the regulating valve (3) is positioned on the pipeline close to the gas filter (S1204); a heat exchanger (E1201) communicated with the nitrogen outlet of the nitrogen buffer tank (V1208). It includes the following steps: Dust-remove the nitrogen-containing and coal-dust-containing bleed gas in the pulverized coal lock hopper (V1204) through the gas filter (S1204), and discharge the dust-removed bleed gas into the nitrogen buffer tank (V1208). Heat the dust-removed bleed gas in the nitrogen buffer tank (V1208) through the heat exchanger (E1201), and the heated bleed gas obtained is recycled. The recycling includes: using the heated bleed gas for one or more of the conveying of limestone in the coal grinding process, the ash conveying of the boiler, the ash conveying in the fly ash treatment process and the fire fighting gas.

2. The method according to claim 1, characterized in that, A pressure regulating valve (5) is arranged on the pipeline where the nitrogen buffer tank (V1208) is communicated with the heat exchanger (E1201).

3. The method according to claim 1, wherein In the pulverized coal lock hopper (V1204): the initial pressure of the nitrogen-containing and coal-dust-containing bleed gas is 4.5 - 4.8 MPa, and the pressure after pressure relief is 2.0 - 2.2 MPa.

4. The method according to claim 1, wherein The pressure of the dust-removed bleed gas when entering the heat exchanger (E1201) for heating is 0.6 - 0.7 MPa.

5. The method according to claim 1 or 4, characterized in that The temperature of the heated bleed gas is 80 - 85 °C.

6. The method according to claim 1, characterized in that, When the gas filter (S1204) dust-removes the nitrogen-containing and coal-dust-containing bleed gas, it also includes using pressurized nitrogen to backflush the gas filter (S1204), and the pressure of the pressurized nitrogen is 4.7 - 5.3 MPa.

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