Starting method of pyrolysis system of pulverized coal rotary kiln

Abstract

The invention relates to the field and particularly discloses a starting method of a pyrolysis system of a pulverized coal rotary kiln, which is characterized in that a nitrogen pipe is communicated with a screw feeder, a nitrogen control valve is mounted on the nitrogen pipe, a diffusing pipe is communicated with the top of a high-temperature filter element dust remover, and a diffusing control valve is mounted on the diffusing pipe. The method has the advantages that the system is replaced by nitrogen, and the oxygen content of the system is reduced; in the process, a vertical furnace discharging valve, a primary cyclone dust collector discharging valve, a secondary cyclone dust collector discharging valve, a high-temperature filter element dust collector discharging valve and a diffusion control valve are all in an open state, and hot nitrogen can be discharged out of the system through the valves, so that all devices and pipelines of the system are preheated in all directions; in the initial stage of feeding production, the phenomenon that tar is condensed and separated out due to local low temperature of the pipeline or equipment is avoided, and the problems that the pipeline is blocked, the inner surface of the equipment is coked, and long-period operation cannot be achieved are solved.

Description

Technical field: The invention relates to the technical field of a pulverized coal rotary kiln pyrolysis system, and in particular to a method for starting a pulverized coal rotary kiln pyrolysis system. Background technology: The pulverized coal rotary kiln pyrolysis system mainly includes a rotary kiln, a hot air furnace, a vertical furnace, a two-stage cyclone dust collector, a high-temperature filter dust collector and other equipment. The pyrolysis process is as follows: Pulverized coal is fed into the rotary kiln through a screw feeder. A certain number of parallel heat dissipation radiation tubes are arranged inside the rotary kiln. The hot flue gas generated by the hot blast furnace first passes through the upper part of the vertical furnace and then enters the hot air hood. From the hot air hood, it is guided into the radiation tubes, exchanging heat with the pulverized coal inside the rotary kiln and outside the radiation tubes, thereby achieving the purpose of pyrolysis and quality improvement of the pulverized coal. After the hot air in the radiation tube exchanges heat with the coal and cools it down, it is discharged from the kiln hood and discharged into the subsequent processing steps. The pulverized coal after pyrolysis and upgrading in the rotary kiln falls into the vertical furnace from the kiln tail hood, and is heated to about 600℃-700℃ in the volatilization section of the vertical furnace for secondary pyrolysis, reducing the volatile matter in the coal to 8%-12%. The upgraded coal flows down to the solid transducer section at the bottom of the cooling boiler to cool down to below 60℃, and is discharged from the discharge valve of the vertical furnace. It is sent to the upgraded coal conveyor belt conveyor by a screw conveyor and then transferred to the top of the upgraded coal silo for humidification; the coal gas generated by pyrolysis is discharged from the side of the vertical furnace to the dust removal section (including the first-level cyclone dust collector, the second-level cyclone dust collector, and the high-temperature filter element dust collector). Specifically, the high-temperature dusty and oily raw coal gas from the pulverized coal pyrolysis rotary kiln and the vertical furnace passes through the first-level cyclone dust collector, the second-level cyclone dust collector, and the high-temperature filter element dust collector to remove most of the upgraded coal powder in the gas. The coal gas after dust removal is sent to oil recovery.

[0001] In order to prevent the tar condensation and dust produced by pyrolysis of pulverized coal from clogging pipes and equipment in the early stage of production, thereby causing system production interruption and forced shutdown, the pulverized coal rotary kiln pyrolysis system needs to be preheated before each production. At present, the preheating of the system is carried out in a segmented and equipment-by-equipment manner, that is, after the system gas replacement is completed, the first and second cyclone dust collectors are preheated using the heating device installed inside the first and second cyclone dust collectors; the high-temperature filter dust collector is heated using the regenerative hot air furnace set up in the high-temperature filter dust removal system; after the cyclone dust collector and the high-temperature filter dust collector meet the temperature standards, the hot air furnace is started, a small amount of material is added for production, the kiln body is heated, and the initial unqualified coal gas is discharged from the vent pipe to the torch for combustion. After the temperature gradually rises, the vent system is slowly closed to enter formal production. However, because the pipes connecting the equipment couldn't be preheated in advance, they created a preheating blind spot. During the initial production phase, dusty and oily raw gas could easily cool down within the pipes, leading to tar precipitation and blockage, which in turn caused production interruptions. The system operated continuously for approximately 100 days before requiring shutdown for maintenance. Furthermore, even with oxygen-depleted combustion, even after preheating the high-temperature filter dust collector using a regenerative hot air furnace to the required temperature, it was difficult to quickly control the oxygen content below 1%, posing a significant risk to system safety. Summary of the invention: The object of the present invention is to provide a method for starting up a pulverized coal rotary kiln pyrolysis system to solve the problems existing in the prior art.

[0002] The present invention is implemented by the following technical solution: a method for starting a pulverized coal rotary kiln pyrolysis system, which includes connecting a nitrogen pipe to a screw feeder, installing a nitrogen control valve on the nitrogen pipe, and connecting a bleed pipe to the top of a high-temperature filter dust collector, installing a bleed control valve on the bleed pipe; the method includes the following steps: S1: Open the nitrogen control valve, vertical furnace discharge valve, first-stage cyclone dust collector ash discharge valve, second-stage cyclone dust collector ash discharge valve, vent control valve, and high-temperature filter dust collector ash discharge valve to the fully open state, close the high-temperature filter dust collector exhaust port valve, introduce nitrogen into the system through the nitrogen pipe to replace the pulverized coal rotary kiln pyrolysis system, and monitor the oxygen content of the gas discharged from the vent control valve in real time; S2: When it is detected that the oxygen content of the gas discharged from the vent control valve is less than 0.5%, the vertical furnace discharge valve, the first-stage cyclone dust collector ash discharge valve, the second-stage cyclone dust collector ash discharge valve, the high-temperature filter element dust collector ash discharge valve, and the vent control valve are all adjusted to slightly open; S3: Start the rotary kiln and hot blast furnace, and keep the rotary kiln's drive motor rotating at a frequency of 5-10 Hz; the hot flue gas output by the hot blast furnace enters the radiant tube of the rotary kiln and heats the nitrogen in the rotary kiln. During the heating process, the internal environment of the pulverized coal rotary kiln pyrolysis system is maintained at a slightly positive pressure; S4: When the internal temperature of the high-temperature filter element dust collector reaches 400-600℃, close the nitrogen control valve, vertical furnace discharge valve, first-stage cyclone dust collector ash discharge valve, second-stage cyclone dust collector ash discharge valve, high-temperature filter element dust collector ash discharge valve, and vent control valve; S5: After S4 is completed, the exhaust valve of the high-temperature filter element dust collector is opened, the frequency of the rotary kiln drive motor is increased to 50Hz, the screw feeder is started, and the pulverized coal rotary kiln pyrolysis system is put into operation.

[0003] Furthermore, in S3, the operating method for maintaining a slightly positive pressure environment inside the pulverized coal rotary kiln pyrolysis system is: keeping the opening of the nitrogen control valve unchanged, and controlling it by adjusting the opening of the vertical furnace discharge valve, the first-stage cyclone dust collector ash discharge valve, the second-stage cyclone dust collector ash discharge valve or the high-temperature filter element dust collector ash discharge valve.

[0004] Furthermore, the outlet of the vertical furnace discharge valve is connected to the nitrogen pipe on the outlet side of the nitrogen control valve through a recovery pipe, and a recovery valve is installed on the recovery pipe. The recovery valve remains closed during the S1-S2 process; during the S3 process, the recovery valve is opened, and the gas discharged through the vertical furnace discharge valve is sent into the rotary kiln together with the incoming nitrogen; during the S4 process, the recovery valve is closed when the internal temperature of the high-temperature filter element dust collector rises to 400-600°C.

[0005] Furthermore, in S3, the nitrogen in the rotary kiln is heated at a heating rate of 50-60°C per hour.

[0006] Furthermore, in S5, the specific process of feeding and operating the pulverized coal rotary kiln pyrolysis system is: first, feeding and operating at 20-30% of the rated output of the rotary kiln for 1 hour, then feeding and operating at 30-40% of the rated output of the rotary kiln for 1 hour, then feeding and operating at 50-60% of the rated output of the rotary kiln for 1 hour, then feeding and operating at 70-80% of the rated output of the rotary kiln for 1 hour, and finally feeding and operating at 100% of the rated output of the rotary kiln.

[0007] Furthermore, in S2, the slightly open degree is 1 / 4 open degree.

[0008] Furthermore, in S3, the pressure of the micro-positive pressure environment is 1-2 kPa.

[0009] The advantages of the present invention are as follows: nitrogen is first used to displace the system to reduce the oxygen content in the system; then heated nitrogen is used to preheat the system. During this process, the vertical furnace discharge valve, the first-stage cyclone dust collector ash discharge valve, the second-stage cyclone dust collector ash discharge valve, the high-temperature filter element dust collector ash discharge valve, and the vent control valve are all in an open state. The hot nitrogen can be discharged from the system through these valves, achieving all-round preheating of all equipment and pipelines in the system without blind spots or dead angles. In the early stage of production, tar condensation and precipitation will not occur due to local low temperatures in the pipelines or equipment, thus solving the problems of pipeline blockage and coking on the inner surface of the equipment, which prevent long-term operation. In addition, from the end of preheating to the 100% production operation of the rotary kiln, a step-by-step increase in the feed rate is used to achieve gradual production. This can solve the problems of system cooling caused by the rotary kiln directly running at 100% feed after preheating and the tar condensation and precipitation system pipeline blockage, thereby extending the system operation cycle. Description of the drawings: Figure 1 This is a diagram of the pulverized coal rotary kiln pyrolysis system of Example 1.

[0010] Figure 2 This is a diagram of the pulverized coal rotary kiln pyrolysis system of Example 2.

[0011] 1. Material silo; 2. Screw feeder; 3. Nitrogen control valve; 4. Nitrogen pipe; 5. Vent pipe; 6. Rotary kiln; 7. Drive motor; 9. Dust discharge valve for first-stage cyclone dust collector; 10. Kiln tail hood; 11. Vertical furnace; 12. Dust discharge valve for vertical furnace; 13. Hot blast furnace; 14. First-stage cyclone dust collector; 15. Second-stage cyclone dust collector; 16. Dust discharge valve for second-stage cyclone dust collector; 17. High-temperature filter dust collector; 18. Vent control valve; 19. Dust discharge valve for high-temperature filter dust collector; 20. Recovery pipe; 21. Recovery valve; 22. Exhaust port for high-temperature filter dust collector. Specific implementation method: The following will provide a clear and complete description of the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. All other embodiments obtained by ordinary technicians in this field based on the embodiments of the present invention without making any creative efforts shall fall within the scope of protection of the present invention.

[0012] Example 1: Figure 1As shown, a method for starting a pulverized coal rotary kiln 6 pyrolysis system, wherein the pulverized coal rotary kiln 6 pyrolysis system includes a feed bin 1, a screw feeder 2, a rotary kiln 6, a vertical furnace 11, a hot blast furnace 13, a primary cyclone dust collector 14, a secondary cyclone dust collector 15, and a high-temperature filter element dust collector 17. The feed bin 1, the screw feeder 2, and the rotary kiln 6 are connected in sequence. The exhaust port of the kiln tail hood 10 of the rotary kiln 6 is connected to the inlet of the primary cyclone dust collector 14, the outlet of the primary cyclone dust collector 14 is connected to the inlet of the secondary cyclone dust collector 15, and the secondary cyclone dust collector 17 is connected. The outlet of the secondary cyclone dust collector 15 is connected to the inlet of the high-temperature cyclone dust collector, the discharge port of the kiln tail cover 10 of the rotary kiln 6 is connected to the top inlet of the vertical furnace 11, the hot air outlet of the hot air furnace 13 is connected to the hot air inlet of the vertical furnace 11, and the hot air outlet of the vertical furnace 11 is connected to the hot air inlet of the rotary kiln 6; the nitrogen pipe 4 is connected to the screw feeder, and a nitrogen control valve 3 is installed on the nitrogen pipe 4; the top of the high-temperature filter element dust collector 17 is connected to the vent pipe 5, and a vent control valve 18 is installed on the vent pipe 5; the process includes the following steps: S1: Open the nitrogen control valve 3, the vertical furnace discharge valve 12, the first-stage cyclone dust collector ash discharge valve 9, the second-stage cyclone dust collector ash discharge valve 16, the bleed control valve 18, and the high-temperature filter dust collector ash discharge valve 19 to the full open state, close the exhaust valve of the high-temperature filter dust collector 17, introduce nitrogen into the system through the nitrogen pipe 4 to replace the pyrolysis system of the pulverized coal rotary kiln 6, and monitor the oxygen content of the gas discharged from the bleed control valve 18 in real time; S2: When it is detected that the oxygen content of the gas discharged from the vent control valve 18 is less than 0.5%, indicating that the gas replacement in the system is basically completed, the vertical furnace discharge valve 12, the first-stage cyclone dust collector ash discharge valve 9, the second-stage cyclone dust collector ash discharge valve 16, the high-temperature filter element dust collector ash discharge valve 19, and the vent control valve 18 are all adjusted to a slightly open position, in this embodiment, to 1 / 4 opening; at this time, the nitrogen control valve 3 remains fully open, and nitrogen is continuously introduced into the system through the nitrogen pipe 4; S3: Start the rotary kiln 6 and the hot blast furnace 13, and keep the drive motor 7 of the rotary kiln 6 rotating at a frequency of 5-10 Hz; the hot flue gas output by the hot blast furnace 13 enters the radiation tube of the rotary kiln 6 and heats the nitrogen in the rotary kiln 6. During the heating process, the rotary kiln 6 keeps rotating at a low speed, so that all parts of the rotary kiln 6 can be preheated evenly; the nitrogen in the rotary kiln 6 is heated at a heating rate of 50-60°C per hour; during the heating process, the interior of the pyrolysis system of the pulverized coal rotary kiln 6 is maintained at a slightly positive pressure environment, which in this embodiment is 1-2 kPa, to prevent external air from entering the interior of the rotary kiln 6 and maintain a low oxygen environment inside the rotary kiln 6; Specifically: Keep the opening of the nitrogen control valve 3 unchanged, and control it by adjusting the opening of the vertical furnace discharge valve 12, the first-stage cyclone dust collector ash discharge valve 9, the second-stage cyclone dust collector ash discharge valve 16 or the high-temperature filter element dust collector ash discharge valve 19. If the internal pressure of the system exceeds 2KPa, the opening of the vertical furnace discharge valve 12, the first-stage cyclone dust collector ash discharge valve 9, the second-stage cyclone dust collector ash discharge valve 16 or the high-temperature filter element dust collector ash discharge valve 19 can be increased; if the pressure in the system is lower than 1KPa, the opening of the vertical furnace discharge valve 12, the first-stage cyclone dust collector ash discharge valve 9, the second-stage cyclone dust collector ash discharge valve 16 or the high-temperature filter element dust collector ash discharge valve 19 can be reduced. During the process of heating nitrogen, the vertical furnace discharge valve 12, the first-stage cyclone dust collector ash discharge valve 9, the second-stage cyclone dust collector ash discharge valve 16, the high-temperature filter element dust collector ash discharge valve 19, and the vent control valve 18 are all in the open state. The hot nitrogen can be discharged from the system through these valves, realizing all-round preheating of all equipment and pipelines in the system without blind spots or dead angles. In the initial stage of feeding production, tar condensation and precipitation will not occur due to local low temperature in the pipeline or equipment, thus solving the problems of pipeline blockage and coking on the inner surface of the equipment, which make it impossible to operate for a long period of time.

[0013] S4: The high-temperature filter dust collector 17 is the terminal equipment of the system. When the internal temperature of the high-temperature filter dust collector 17 is 400-600℃, the temperature of other equipment or pipelines in the system is higher than this temperature, indicating that the preheating is completed. The nitrogen control valve 3, the vertical furnace discharge valve 12, the first-stage cyclone dust collector ash discharge valve 9, the second-stage cyclone dust collector ash discharge valve 16, the high-temperature filter dust collector ash discharge valve 19, and the bleed control valve 18 can be closed; stop the nitrogen supply.

[0014] S5: After S4 is completed, the valve of the high-temperature filter dust collector exhaust port 22 is opened, and the frequency of the drive motor of the pulverized coal rotary kiln is increased to 50Hz. Specifically, the frequency of the drive motor can be increased by 5Hz every half an hour, and the frequency of the drive motor is gradually increased from 5-10Hz in S3 to 50Hz; the screw feeder 2 is started, and the screw feeder 2 sends the pulverized coal stored in the silo 1 to the rotary kiln. The pulverized coal rotary kiln pyrolysis system is fed and operated, and the hot blast furnace 13 continues to send hot air into the rotary kiln 6, entering the production operation stage. The specific process is: first, feed and operate at 20-30% of the rated output of the rotary kiln 6 for 1 hour, then feed and operate at 30-40% of the rated output of the rotary kiln 6 for 1 hour, then feed and operate at 50-60% of the rated output of the rotary kiln 6 for 1 hour, then feed and operate at 70-80% of the rated output of the rotary kiln 6 for 1 hour, and finally feed and operate at 100% of the rated output of the rotary kiln 6. During the transition period from the end of preheating to the 100% feeding operation of the rotary kiln, a step-by-step method of increasing the feeding amount is adopted to achieve gradual production. This can solve the problems of instantaneous low temperature of the system caused by the direct 100% feeding operation of the rotary kiln 6 after the end of preheating, as well as tar condensation and precipitation, and system pipeline blockage, thereby extending the system operation cycle.

[0015] In this embodiment, the total start-up preheating time is 12-13 hours. After the equipment is 100% put into production, the continuous operation time is about 300 days.

[0016] Example 2: The whole is the same as Example 1, except that Figure 2 As shown, the outlet of the vertical furnace discharge valve 12 is connected to the nitrogen pipe 4 on the outlet side of the nitrogen control valve 3 through the recovery pipe 20, and a recovery valve 21 is installed on the recovery pipe 20. The recovery valve 21 remains closed during the S1-S2 process to ensure gas replacement efficiency. During the S3 process, the recovery valve 21 is opened, and the gas discharged through the vertical furnace discharge valve 12 is sent into the rotary kiln 6 together with the nitrogen sent. During the S3 process, the nitrogen discharged through the vertical furnace discharge valve 12 is high-temperature nitrogen (compared with the nitrogen sent to the screw feeder through the nitrogen pipe 4). It is mixed with the nitrogen newly sent into the system and then enters the rotary kiln 6 through the screw feeder, which can increase the temperature of the nitrogen entering the kiln, thereby improving the nitrogen heating efficiency, reducing the energy consumption of the hot blast furnace 13, and improving the start-up efficiency. At the same time, it can solve the problems of high temperature at the outlet of the vertical furnace discharge valve 12 and poor production environment during the start-up process. During S4, when the internal temperature of the high-temperature filter element dust collector 17 rises to 400-600° C., the recovery valve 21 is closed to prepare for system commissioning. Compared with Example 1, the commissioning time of this embodiment is shortened to 8-9 hours.

[0017] In the description of the present invention, it should be noted that the terms "center", "up", "down", "front", "back", "top", "bottom", "left", "right", "vertical", "horizontal", "inside", "outside", etc., indicating the orientation or position relationship, are based on the orientation or position relationship shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as limiting the present invention.

Claims

1. A method for starting up a pulverized coal rotary kiln pyrolysis system, characterized in that: Connect a nitrogen pipe to the screw feeder, install a nitrogen control valve on the nitrogen pipe, connect a vent pipe to the top of the high-temperature filter element dust collector, and install a vent control valve on the vent pipe; the process includes the following steps: S1: Open the nitrogen control valve, vertical furnace discharge valve, first-stage cyclone dust collector ash discharge valve, second-stage cyclone dust collector ash discharge valve, vent control valve, and high-temperature filter dust collector ash discharge valve to the fully open state, close the high-temperature filter dust collector exhaust port valve, introduce nitrogen into the system through the nitrogen pipe to replace the pulverized coal rotary kiln pyrolysis system, and monitor the oxygen content of the gas discharged from the vent control valve in real time; S2: When it is detected that the oxygen content of the gas discharged from the vent control valve is less than 0.5%, the vertical furnace discharge valve, the first-stage cyclone dust collector ash discharge valve, the second-stage cyclone dust collector ash discharge valve, the high-temperature filter element dust collector ash discharge valve, and the vent control valve are all adjusted to slightly open; S3: Start the rotary kiln and hot blast furnace, and keep the rotary kiln's drive motor rotating at a frequency of 5-10 Hz; the hot flue gas output by the hot blast furnace enters the radiant tube of the rotary kiln and heats the nitrogen in the rotary kiln. During the heating process, the internal environment of the pulverized coal rotary kiln pyrolysis system is maintained at a slightly positive pressure; S4: When the internal temperature of the high-temperature filter element dust collector reaches 400-600℃, close the nitrogen control valve, vertical furnace discharge valve, first-stage cyclone dust collector ash discharge valve, second-stage cyclone dust collector ash discharge valve, high-temperature filter element dust collector ash discharge valve, and vent control valve; S5: After S4 is completed, the exhaust valve of the high-temperature filter element dust collector is opened, the frequency of the rotary kiln drive motor is increased to 50Hz, the screw feeder is started, and the pulverized coal rotary kiln pyrolysis system is put into operation.

2. The method for starting up a pulverized coal rotary kiln pyrolysis system according to claim 1, characterized in that: In S3, the operating method for maintaining a slightly positive pressure environment inside the pulverized coal rotary kiln pyrolysis system is: keep the opening of the nitrogen control valve unchanged, and control it by adjusting the opening of the vertical furnace discharge valve, the first-stage cyclone dust collector ash discharge valve, the second-stage cyclone dust collector ash discharge valve or the high-temperature filter element dust collector ash discharge valve.

3. The method for starting up a pulverized coal rotary kiln pyrolysis system according to claim 1, characterized in that: The outlet of the vertical furnace discharge valve is connected to the nitrogen pipe on the outlet side of the nitrogen control valve through a recovery pipe. A recovery valve is installed on the recovery pipe. During the S1-S2 process, the recovery valve remains closed. During the S3 process, the recovery valve is opened, and the gas discharged through the vertical furnace discharge valve is sent into the rotary kiln together with the incoming nitrogen. During the S4 process, the recovery valve is closed when the internal temperature of the high-temperature filter element dust collector rises to 400-600℃.

4. The method for starting up a pulverized coal rotary kiln pyrolysis system according to claim 1, characterized in that: In S3, the nitrogen in the rotary kiln is heated at a heating rate of 50-60°C per hour.

5. The method for starting up a pulverized coal rotary kiln pyrolysis system according to claim 1, characterized in that: In S5, the specific process of feeding and operating the pulverized coal rotary kiln pyrolysis system is as follows: first, feed and operate at 20-30% of the rated output of the rotary kiln for 1 hour, then feed and operate at 30-40% of the rated output of the rotary kiln for 1 hour, then feed and operate at 50-60% of the rated output of the rotary kiln for 1 hour, then feed and operate at 70-80% of the rated output of the rotary kiln for 1 hour, and finally feed and operate at 100% of the rated output of the rotary kiln.

6. The method for starting up a pulverized coal rotary kiln pyrolysis system according to claim 1, characterized in that: In S2, the slightly opened degree is 1 / 4.

7. The method for starting up a pulverized coal rotary kiln pyrolysis system according to claim 1, characterized in that: In S3, the pressure of the slightly positive pressure environment is 1-2 kPa.

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