Coke cleaning method for blocked furnace tube of radiation section of cracking furnace

Abstract

The invention discloses a decoking method after a furnace tube of a radiation section of a cracking furnace is blocked, and relates to the field of decoking of cracking furnaces. The decoking method can be used for solving the problem that the furnace tube of the radiation section is blocked due to complete blowing-out, local blowing-out or great fluctuation of operation conditions of the cracking furnace. According to the decoking method, the introduction amount of the dilution steam and the introduction amount of the air are intermittently and repeatedly increased under different temperature conditions, the flow of the dilution steam and the flow of the coke-burning air are strictly controlled, meanwhile, the different introduction amount and exchange frequency of the dilution steam are repeatedly and greatly adjusted, and the situation that the furnace tube is damaged due to local overheat points in the coke-burning process is prevented; and finally, the furnace tube blockage caused by different conditions can be effectively and thoroughly decoked, the decoking manpower and time cost is reduced, meanwhile, the online rate of the cracking furnace is increased, and the energy consumption of the device is reduced.

Description

Technical Field

[0001] The invention relates to the field of cracking furnace coke cleaning, in particular to a method for cleaning coke after a cracking furnace radiation section tube is blocked. Background Art

[0002] After the industrial cracking furnace runs to a certain condition, it is necessary to remove the material and clean the coke due to the reduced pressure difference of the furnace tube, the high surface temperature of the furnace tube and the high outlet temperature of the waste heat boiler. By introducing a mixture of air and water vapor into the cracking furnace tube, it reacts with the coke to generate carbon dioxide and carbon monoxide at a certain temperature, thereby achieving the purpose of cleaning the coke, and the cracking furnace is again ready for operation. The current coking method is to control the intensity of the coke reaction in the furnace tube by gradually increasing the proportion of air in the water vapor and the coking temperature, so as to prevent overheating during the coking process, thereby achieving the purpose of protecting the cracking furnace tube.

[0003] The existing coking method is based on the method of cleaning the cracking furnace tubes after they are operating normally to a certain condition. It is difficult to avoid abnormal operating conditions during the production of the cracking furnace. When the cracking furnace is stopped under abnormal conditions, it is easy for coke blocks in the cracking furnace radiation section to fall off and cause the furnace tubes to be blocked. It is difficult to remove the coke blocks in the furnace tubes through the normal coking procedure to meet the feeding operation state.

[0004] At present, the method adopted for the blockage of the radiation section tube of the cracking furnace is: cut the blocked tube, perform mechanical decoking, and then re-weld it to be able to feed the material. This method is complex and time-consuming, and consumes a lot of manpower and time costs. Summary of the invention

[0005] The present invention provides a method for clearing coke after a cracking furnace radiation section tube is clogged. The method can reduce unnecessary construction and construction risks of the cracking furnace tube after the clog, reduce the manpower and time costs of clearing coke, and at the same time improve the online rate of the cracking furnace and reduce the energy consumption of the device.

[0006] In order to solve the above technical problems, one of the purposes of the present invention is to provide a method for clearing coke after the radiation section furnace tube of a cracking furnace is blocked. The method comprises the following steps:

[0007] (1) Reignite the cracking furnace and heat it up. When the temperature of the cracking furnace reaches 220-250° C., start to introduce dilution steam, simultaneously raise the temperature of the cracking furnace, and gradually increase the amount of dilution steam to hot standby steam;

[0008] (2) When the average outlet temperature of the normal furnace tubes of the cracking furnace begins to rise to above 600°C, a small amount of 100-200 t / h of burning air is introduced for burning. When the average outlet temperature of the normal furnace tubes of the cracking furnace is 780-840°C, the burning air is increased to 1.5 t / h and maintained;

[0009] (3) Subsequently, the dilution steam is greatly increased to twice the original rate per hour, and the time is maintained at 1-2 minutes. Subsequently, the flow rate of the original dilution steam is restored to the original rate and maintained for 2-4 hours. During the coking process, the above operation of increasing and decreasing the dilution steam rate is repeated to maintain the average temperature of the cracking furnace tube outlet at 780-840°C. The coking time is extended to 5-7 days to complete the decoking of the cracking furnace radiation section tubes.

[0010] As a preferred solution, when the temperature of some furnace tube outlets is always less than 100°C during the heating process of the cracking furnace, and the inlet pressure of the furnace tube is consistent with the cross-section pressure, it indicates that the radiation section furnace tube of the current cracking furnace is blocked.

[0011] As a preferred embodiment, in steps (1) and (3), the pressure of the dilution steam introduced is 0.5-0.8 MPa and the temperature is 180-230°C.

[0012] As a preferred solution, in step (1), the heating rate of the cracking furnace is >50°C / h.

[0013] In order to solve the above technical problems, the second object of the present invention is to provide a method for clearing coke after the radiation section furnace tube of a cracking furnace is blocked. For the blockage of the radiation section furnace tube caused by the partial shutdown of the cracking furnace, the method for clearing coke comprises the following steps:

[0014] The average temperature at the outlet of the normal tubes of the cracking furnace is maintained at 800-840℃, the dilution steam is maintained at the amount of hot standby steam, the burning air is increased to 1.5t / h and maintained, and then the single group of dilution steam is greatly increased to twice the original / h, and the maintenance time is controlled at 1-2min, maintained for 2-4h, and then restored to the original single group of dilution steam input. The above single group of dilution steam increase and decrease operations are repeated during the burning process, and the average outlet temperature of the normal tubes of the cracking furnace is maintained at 800-860℃. The burning time is extended to 2-5 days, and the radiation section tubes of the cracking furnace are completely decoked.

[0015] As a preferred solution, due to partial shutdown of the cracking furnace, it is found that the outlet temperature of some furnace tubes drops to a difference of more than 100°C from other furnace tubes, and the inlet pressure of the furnace tube is consistent with the cross-section pressure, indicating that the radiation section furnace tube of the cracking furnace is blocked.

[0016] As a preferred solution, the pressure of the dilution steam introduced is 0.5-0.8 MPa and the temperature is 180-230°C.

[0017] In order to solve the above technical problems, the third object of the present invention is to provide a method for clearing coke after the radiation section furnace tube of a cracking furnace is blocked. The method comprises the following steps for the blockage of the radiation section furnace tube caused by the large fluctuation of the operating conditions of the cracking furnace:

[0018] The cracking furnace is discharged to a charred state. After the cracking furnace is purged, the average outlet temperature of the normal furnace tubes of the cracking furnace is maintained at 800-840°C, the dilution steam is maintained to the amount of hot standby steam, the charring air is gradually increased to 1.5t / h and maintained, and then the dilution steam input is greatly increased to 2 times / h of the original, and the maintenance time is controlled at 1-2min, and then restored to the original single-group dilution steam input, and maintained for 2-4h. The above single-group dilution steam lifting operation is repeated during the charring process to maintain the average outlet temperature of the normal furnace tubes of the cracking furnace at 800-860°C. The charring time is extended to 24-72h, and the radiation section furnace tubes of the cracking furnace are completely decoked.

[0019] As a preferred solution, due to the large fluctuations in the operating conditions of the cracking furnace, it is found that the outlet temperature of some furnace tubes drops to a difference of more than 100°C from other furnace tubes, and the furnace tube inlet pressure is consistent with the cross-section pressure, indicating that the radiation section furnace tube of the cracking furnace is blocked.

[0020] As a preferred solution, the pressure of the dilution steam introduced is 0.5-0.8 MPa and the temperature is 180-230°C.

[0021] As a preferred solution, the cracking furnace is a 28U1-1 type ethylene cracking furnace with an annual output of 35,000 tons, with two groups of feeds, and the hot standby steam for each group of feeds is 4.5t / h.

[0022] Compared with the prior art, the embodiments of the present invention have the following beneficial effects:

[0023] The charring method of the present application targets clogged furnace tubes by intermittently increasing the amount of dilution steam and air introduced under different temperature conditions for multiple times, strictly controlling the flow rates of dilution steam and charring air, and repeatedly and significantly adjusting the different amounts of dilution steam introduced and the exchange frequency. The charring process prevents the appearance of local hot spots in the furnace tubes, damage to the furnace tubes, and overpressure in the furnace tubes, and ultimately can effectively target the charring that causes clogged furnace tubes in different situations. DETAILED DESCRIPTION

[0024] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0025] Embodiment 1

[0026] A method for clearing coke after a cracking furnace radiation section tube is blocked. The method is for the following situations: due to the shutdown of all cracking furnaces, the temperature naturally drops to room temperature, resulting in the blockage of the radiation section tubes. Specifically, due to the failure of a fan, all cracking furnaces are shut down, resulting in blockage of up to 1 / 2 of the tubes. Taking a 28U1-1 ethylene cracking furnace with an annual output of 35,000 tons as an example, there are two groups of feeds, and the hot standby steam of each group of feeds is 4.5 t / h. The method comprises the following steps:

[0027] (1) The cracking furnace is re-ignited and heated at a heating rate of >50°C / h according to the heating curve. When the furnace temperature of the cracking furnace reaches 220-250°C, dilution steam is introduced. The pressure of the dilution steam is about 0.5-0.8MPa and the temperature is 180-230°C. Simultaneously, the furnace temperature is continued to be heated at a heating rate of >50°C / h according to the heating curve, and the amount of dilution steam is gradually increased to hot standby steam, i.e., 4.5t / h per group;

[0028] (2) in the cracking furnace temperature-raising process, it is found that the partial boiler tube outlet temperature is always <100 ℃, and the boiler tube inlet pressure is consistent with the cross section pressure, indicating that the current cracking furnace radiation section boiler tube is blocked. When the normal boiler tube average outlet temperature rises to more than 600 ℃, 100-200t / h of burning air is introduced in a small amount to burn. When the normal boiler tube outlet average temperature is at 780-840 ℃, the burning air is increased to 1.5t / h and maintained;

[0029] (3) Subsequently, the dilution steam pressure is greatly increased to about 0.5-0.8 MPa, and the temperature is 180-230°C. The single dilution steam is increased from 4.5 t / h to 9 t / h, and the maintenance time is controlled at 1-2 min. Then, it is restored to 4.5 t / h and maintained for 2-4 h. The above operation of raising and lowering the single dilution steam is repeated multiple times during the coking process, and the average outlet temperature of the furnace tube is maintained at 780-840°C. The coking time is extended to 5-7 days, and the radiation section furnace tube of the cracking furnace can be completely decoked.

[0030] For the corresponding cracking furnace blockage situation, if the cracking furnace tubes are cut and the coke is cleaned mechanically, it will take more than 14 days to complete the complete decoking.

[0031] Embodiment 2

[0032] A method for clearing coke after a cracking furnace radiation section tube is blocked. The method is for the following situations: due to partial shutdown of the cracking furnace, it is found that the outlet temperature of some tubes is lowered to a difference of more than 100°C from that of other tubes, and the inlet pressure of the tubes is consistent with the cross section pressure, indicating that the radiation section tubes of the cracking furnace are blocked. Specifically, due to the interruption of feed to the cracking furnace, the partial shutdown of the cracking furnace causes the blockage of 1 / 4 tubes. Taking a 28U1-1 type ethylene cracking furnace with an annual output of 35,000 tons as an example, there are two groups of feeds, and the hot standby steam of each group of feeds is 4.5 t / h. The method comprises the following steps:

[0033] When the normal average temperature of the furnace tube outlet is maintained at 800-840℃, the dilution steam is maintained at the amount of hot standby steam. After the burning air is increased to 1.5t / h and maintained, the dilution steam is greatly increased. The pressure of the dilution steam is about 0.5-0.8MPa, and its temperature is 180-230℃. It is increased from 4.5t / h to 9t / h per group, and the maintenance time is controlled at 1-2min. It is then restored to 4.5t / h and maintained for 2-4h. The above single group dilution steam lifting operation is repeated many times during the burning process to maintain the normal average furnace tube outlet temperature at 800-860℃. The burning time is extended to 2-5 days, and the furnace tubes of the radiation section of the cracking furnace can be completely decoked.

[0034] For the corresponding cracking furnace blockage situation, if the cracking furnace tubes are cut and the coke is cleaned mechanically, it will take more than 7 days to complete the complete decoking.

[0035] Embodiment 3

[0036] A method for clearing coke after a cracking furnace radiation section tube is blocked. The method is for cracking furnace tube blockage: due to large fluctuations in the operating conditions of the cracking furnace, it is found that the outlet temperature of some tubes is lowered to a difference of more than 100°C from that of other tubes, and the inlet pressure of the tube is consistent with the cross section pressure, indicating that the cracking furnace radiation section tube is blocked. Specifically, due to the switching of raw materials in the middle of the operation of the cracking furnace, the cracking furnace tube is de-coked, resulting in 1 / 14 of the tube being blocked. Taking a 28U1-1 type ethylene cracking furnace with an annual output of 35,000 tons as an example, there are two groups of feeds, and the hot standby steam of each group of feeds is 4.5 t / h. The method comprises the following steps:

[0037] The cracking furnace is discharged to a charred state. After the cracking furnace is purged, the average temperature at the normal furnace tube outlet is maintained at 800-840°C, the dilution steam is maintained at 4.5t / h, and the charring air is gradually increased to 1.5t / h and maintained. Subsequently, the dilution steam is greatly increased. The pressure of the dilution steam is about 0.5-0.8MPa, and its temperature is 180-230°C. It is increased from 4.5t / h to 9t / h per group, and the maintenance time is controlled at 1-2min. It is then restored to 4.5t / h and maintained for 2-4h. The above single group dilution steam lifting and lowering operations are repeated multiple times during the charring process to maintain the normal average furnace tube outlet temperature at 800-860°C. The charring time is extended to 24-72h, and the radiant section furnace tubes of the cracking furnace can be completely de-coked.

[0038] For the corresponding cracking furnace blockage situation, if the cracking furnace tubes are cut and the coke is cleaned mechanically, it will take more than 5 days to complete the complete decoking.

[0039] The specific embodiments described above further illustrate the purpose, technical solutions and beneficial effects of the present invention. It should be understood that the above description is only a specific embodiment of the present invention and is not intended to limit the scope of protection of the present invention. It is particularly pointed out that for those skilled in the art, any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention should be included in the scope of protection of the present invention.

Claims

1. A method for decoking after the radiation section tube of a cracking furnace is blocked, characterized in that: In view of the blockage of the radiation section furnace tubes caused by the shutdown of all cracking furnaces and the natural cooling to room temperature, the decoking method includes the following steps: (1) Reignite the cracking furnace and heat it up. When the temperature of the cracking furnace reaches 220-250° C., start to introduce dilution steam, simultaneously raise the temperature of the cracking furnace, and gradually increase the amount of dilution steam to hot standby steam; (2) When the average outlet temperature of the normal furnace tubes of the cracking furnace begins to rise to above 600°C, a small amount of 100-200 t / h of burning air is introduced for burning. When the average outlet temperature of the normal furnace tubes of the cracking furnace is 780-840°C, the burning air is increased to 1.5 t / h and maintained; (3) Subsequently, the dilution steam is greatly increased to twice the original rate per hour, and the time is maintained at 1-2 minutes. Subsequently, the flow rate of the original dilution steam is restored to the original rate and maintained for 2-4 hours. During the coking process, the above operation of increasing and decreasing the dilution steam rate is repeated to maintain the average temperature of the cracking furnace tube outlet at 780-840°C. The coking time is extended to 5-7 days to complete the decoking of the cracking furnace radiation section tubes.

2. A method for decoking after blockage of a cracking furnace radiation section tube as claimed in claim 1, characterized in that: During the heating process of the cracking furnace, if it is found that the outlet temperature of some furnace tubes is always less than 100° C., and the inlet pressure of the furnace tube is consistent with the cross-section pressure, it indicates that the radiation section furnace tube of the current cracking furnace is blocked.

3. A method for decoking after blockage of a cracking furnace radiation section tube as claimed in claim 1, characterized in that: In steps (1) and (3), the pressure of the dilution steam introduced is 0.5-0.8 MPa and the temperature is 180-230°C.

4. A method for decoking after blockage of a cracking furnace radiation section tube as claimed in claim 1, characterized in that: In step (1), the heating rate of the cracking furnace is >50°C / h.

5. A method for cleaning coke after the radiation section tube of a cracking furnace is blocked, characterized in that: In view of the blockage of the radiation section furnace tube caused by the partial shutdown of the cracking furnace, the coke cleaning method includes the following steps: The average temperature at the outlet of the normal tubes of the cracking furnace is maintained at 800-840℃, the dilution steam is maintained at the amount of hot standby steam, the burning air is increased to 1.5t / h and maintained, and then the single group of dilution steam is greatly increased to twice the original / h, and the maintenance time is controlled at 1-2min, maintained for 2-4h, and then restored to the original single group of dilution steam input. The above single group of dilution steam increase and decrease operations are repeated during the burning process, and the average outlet temperature of the normal tubes of the cracking furnace is maintained at 800-860℃. The burning time is extended to 2-5 days, and the radiation section tubes of the cracking furnace are completely decoked.

6. A method for decoking after blockage of a cracking furnace radiation section tube as claimed in claim 5, characterized in that: Due to the partial shutdown of the cracking furnace, it was found that the outlet temperature of some furnace tubes dropped to a level more than 100°C different from that of other furnace tubes, and the inlet pressure of the furnace tubes was consistent with the cross-section pressure, indicating that the radiation section furnace tubes of the cracking furnace were blocked.

7. A method for decoking after blockage of a cracking furnace radiation section tube as claimed in claim 5, characterized in that: The pressure of the dilution steam introduced is 0.5-0.8MPa and the temperature is 180-230℃.

8. A method for cleaning coke after the radiation section tube of a cracking furnace is blocked, characterized in that: In view of the blockage of the radiation section furnace tubes due to the large fluctuations in the operating conditions of the cracking furnace, the decoking method includes the following steps: The cracking furnace is discharged to a charred state. After the cracking furnace is purged, the average outlet temperature of the normal furnace tubes of the cracking furnace is maintained at 800-840°C, the dilution steam is maintained to the amount of hot standby steam, the charring air is gradually increased to 1.5t / h and maintained, and then the dilution steam input is greatly increased to 2 times / h of the original, and the maintenance time is controlled at 1-2min, and then restored to the original single-group dilution steam input, and maintained for 2-4h. The above single-group dilution steam lifting operation is repeated during the charring process to maintain the average outlet temperature of the normal furnace tubes of the cracking furnace at 800-860°C. The charring time is extended to 24-72h, and the radiation section furnace tubes of the cracking furnace are completely decoked.

9. A method for decoking after blockage of a cracking furnace radiation section tube as claimed in claim 8, characterized in that: Due to the large fluctuations in the operating conditions of the cracking furnace, it was found that the outlet temperature of some furnace tubes dropped to a level more than 100°C different from that of other furnace tubes, and the inlet pressure of the furnace tubes was consistent with the cross-section pressure, indicating that the radiation section furnace tubes of the cracking furnace were blocked.

10. A method for decoking after blockage of a cracking furnace radiation section tube as claimed in claim 8, characterized in that: The pressure of the dilution steam introduced is 0.5-0.8MPa and the temperature is 180-230℃.