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CN-121972106-A - Four-step-in-one negative pressure oil-carrying shutdown method of styrene dehydrogenation reaction system

CN121972106ACN 121972106 ACN121972106 ACN 121972106ACN-121972106-A

Abstract

The invention discloses a four-step-in-one negative pressure oil-carrying shutdown method of a styrene dehydrogenation reaction system, and relates to the technical field of styrene dehydrogenation. The method adopts a negative pressure steam oil-carrying mode for the first time, maintains the operation of the tail gas compressor after the feeding of the dehydrogenation reaction system is cut off, maintains the normal negative pressure working condition of the reaction system, carries out negative pressure working condition steam oil carrying, maintains the operation of the tail gas compressor after oil carrying is finished, gradually rises to micro positive pressure to burn the catalyst, maintains the operation of the tail gas compressor in the steam cooling and nitrogen cooling processes after the burning is finished until the nitrogen cooling is finished, and simultaneously realizes that the tail gas compressor is started and stopped for multiple times in the stages of steam oil carrying, catalyst burning, steam cooling and nitrogen circulating cooling to be optimized into one-time stop operation. The negative pressure shutdown of the invention realizes the operation of one-time shutdown of the tail gas compressor, greatly simplifies the shutdown operation steps of the reaction system and reduces the shutdown treatment difficulty of the dehydrogenation reaction system.

Inventors

  • CAI DEBIN
  • ZHANG YOUCHAO
  • Ding Nanpeng
  • WANG HUQING
  • DI XIAOLEI
  • LI JUNHAO
  • MA SHIDA
  • DU JIANAN
  • ZHANG WEI
  • WANG XIUFAN

Assignees

  • 中国石油化工股份有限公司
  • 中国石化青岛炼油化工有限责任公司

Dates

Publication Date
20260505
Application Date
20260105

Claims (10)

  1. 1. A four-step-in-one negative pressure oil-carrying shutdown method of a styrene dehydrogenation reaction system is characterized by comprising the following steps of: S1, reducing the load of the reaction to the feeding and cutting of ethylbenzene, namely reducing the feeding load of ethylbenzene to the feeding and cutting of ethylbenzene, wherein a tail gas compressor (17) operates normally in the process, maintaining the negative pressure of a reaction system stable, and reducing the temperature of a dehydrogenation reactor bed to 545-555 ℃; S2, carrying out negative pressure oil carrying on the reaction system, namely introducing steam into an ethylbenzene feed pipeline (101) of the reaction system, jacking residual materials in the ethylbenzene feed pipeline (101) into an ethylbenzene evaporator (1) and finally into a dehydrogenation reactor bed, maintaining the temperature of the dehydrogenation reactor bed and the inlet temperature to be 545-555 ℃, and maintaining a tail gas compressor (17) to operate so as to maintain the reaction system in a normal negative pressure working condition, carrying out negative pressure working condition steam oil carrying, and continuously cooling the dehydrogenation reactor bed to 450-500 ℃ after the negative pressure working condition steam oil carrying is finished, wherein the reaction system enters a scorching process; S3, burning the bed layer of the dehydrogenation reactor, namely, maintaining the temperature of the bed layer of the dehydrogenation reactor at 450-500 ℃, reducing the rotating speed of a tail gas compressor (17), adjusting the opening of an inlet circulation valve (2104) of the tail gas compressor (17), boosting the pressure of the reaction system until the pressure of the reaction system reaches 105-115kPaA, and then cutting the tail gas compressor (17) out of the reaction system under the condition of continuous operation; And S4, cooling nitrogen of the reaction system, namely continuously cooling the bed layer of the dehydrogenation reactor to 245-255 ℃ after the scorching is finished, introducing nitrogen into the reaction system, cutting into a tail gas compressor (17) again, establishing nitrogen circulation, blowing off water vapor of the bed layer of the dehydrogenation reactor and continuously cooling, and stopping the tail gas compressor (17) when the temperature of the reaction system is reduced to below 100 ℃ and the temperature of a hearth of a steam superheating furnace (4) is lower than 200 ℃, so that shutdown operation of the styrene dehydrogenation reaction system is completed.
  2. 2. The four-step-in-one negative pressure oil-carrying shutdown method of the styrene dehydrogenation reaction system according to claim 1, wherein in the step S1, the primary steam amount fed into the ethylbenzene evaporator (1) is increased along with the reduction of the feeding load of ethylbenzene, or the emergency steam of the ethylbenzene evaporator (1) is simultaneously fed, so that the tube side outlet temperature of the superheater (2) is ensured to be less than or equal to 380 ℃.
  3. 3. The four-step-in-one negative pressure oil-carrying shutdown method of the styrene dehydrogenation reaction system according to claim 1 is characterized in that in the step S2, when negative pressure working condition steam carries oil, nitrogen is purged into the reaction system or nitrogen is introduced into an inlet of a tail gas compressor (17), so that the air quantity of a suction inlet of the tail gas compressor (17) is ensured, and the normal operation of the tail gas compressor is ensured.
  4. 4. The method for stopping the styrene dehydrogenation reaction system by using the negative pressure with oil in a four-step manner according to claim 1, wherein in the step S2, after the steam with oil under the negative pressure working condition of the reaction system is carried out for 3-5 hours, if the liquid level of the oil phase chamber of the oil-water separator (15) is observed not to rise any more, the end of the oil carrying of the bed layer can be judged.
  5. 5. The method for stopping the styrene dehydrogenation reaction system by using the negative pressure with oil and in a four-step mode according to claim 1, wherein in the step S3, when the reaction system is pressurized, the pressurizing rate is controlled to be less than or equal to 0.01MPaG/h.
  6. 6. The four-step-in-one negative pressure oil-carrying shutdown method of the styrene dehydrogenation reaction system according to claim 1 is characterized in that in the step S3, the tail gas compressor (17) is cut out of the reaction system by closing an inlet butterfly valve of the tail gas compressor (17), meanwhile, nitrogen is supplemented through an inlet of the tail gas compressor (17) to maintain self circulation of the tail gas compressor (17), and a torch pipeline hand valve I (1803) of a water seal tank (18) connected with an inlet tank (16) of the compressor and a torch pipeline hand valve II (2204) of an absorption tower (22) are closed to prevent burnt gas from channeling into the torch system.
  7. 7. The method for stopping the styrene dehydrogenation reaction system by using the negative pressure oil with four steps as set forth in claim 1, wherein in the step S3, the industrial wind is injected into the dehydrogenation reactor by introducing the industrial wind into the inlet of the steam superheating furnace (4).
  8. 8. The method for stopping the styrene dehydrogenation reaction system by using the negative pressure oil in four steps as set forth in claim 7, wherein in the step S3, the industrial wind is injected into the dehydrogenation reactor by introducing the industrial wind into the inlet of the dehydrogenation reactor and the inlet of the ethylbenzene evaporator (1).
  9. 9. The "four-step-in-one" negative pressure oiled shutdown method of a styrene dehydrogenation reaction system according to claim 7 or 8, characterized in that in step S3, the gas generated during the scorching is discharged through the compressor inlet tank (16).
  10. 10. The method for stopping the four-step-in-one negative pressure oil-carrying shutdown of the styrene dehydrogenation reaction system according to claim 1, wherein in the step S3, when the bed layer of the dehydrogenation reactor is not heated any more, sampling is carried out at an outlet pipeline of the bed layer, and when the oxygen content in the sample is more than 21%, the injection of industrial air into the reaction system is stopped, and the scorching is finished.

Description

Four-step-in-one negative pressure oil-carrying shutdown method of styrene dehydrogenation reaction system Technical Field The invention relates to the technical field of styrene dehydrogenation, in particular to a four-step-in-one negative pressure oil-carrying shutdown method of a styrene dehydrogenation reaction system. Background The styrene dehydrogenation reaction system has long flow and large system, is operated under the condition of negative pressure, and normally has the shutdown steps of stopping the tail gas compressor after the ethylbenzene feed amount is reduced to 60 percent of load, converting the dehydrogenation reaction system into positive pressure production, and then continuously reducing the ethylbenzene feed until the ethylbenzene feed is cut off, wherein the water ratio of the system is controlled to be more than 2. The shutdown operation has the following defects that firstly, the positive pressure shutdown is used for controlling the high water ratio, the load of the heating furnace is increased, the operation of the steam superheating furnace is required to be adjusted repeatedly by on-site coordination, the risk of shutdown is increased, and meanwhile, the main body of the steam superheating furnace is also greatly influenced. Secondly, the positive pressure shutdown needs high water ratio control, so that the scouring of catalyst beds of the dehydrogenation reactor can be increased, the loss of potassium ions and other components in the catalyst can seriously affect the service life of the catalyst (the catalyst effective component potassium slowly runs off or migrates under the scouring of high-temperature steam for a long time, so that the catalyst is irreversibly deactivated, if the shutdown occurs in the middle section of the operation period, the long-period operation of the device is not facilitated), simultaneously, the potassium ions are lost, and the parts of the low-pressure waste heat boiler, the low-pressure waste heat boiler and the like stay for crystallization, contact with liquid styrene at the bottom layer of the equipment, and are mixed to form a relatively hard green solid polymer, so that the catalyst is extremely difficult to clean. Thirdly, in the positive pressure shutdown process, the excessive vapor quantity can increase the load of a condensing system, a chiller is deactivated, the inlet temperature of an air cooler is rapidly increased, various forms of polymerization including styrene, divinylbenzene and the like are extremely easy to occur in air cooling fin tube bundles under the working conditions of positive pressure and high temperature, polymers similar to popcorn are generated, the polymers are accumulated at the air cooling main tube and the inlet liquid package, the air cooling tube bundles are blocked, the polymer quantity of an oil-water separator is increased, and serious influence is brought to subsequent treatment. Disclosure of Invention The invention aims to solve the technical problems of overcoming the defects of the prior art and providing a four-step-in-one negative pressure oil-carrying shutdown method of a styrene dehydrogenation reaction system, wherein the negative pressure shutdown realizes one-time shutdown operation of a tail gas compressor, thereby greatly simplifying the shutdown operation steps of the reaction system and reducing the shutdown disposal difficulty of the dehydrogenation reaction system. The technical scheme of the invention is as follows: A four-step-in-one negative pressure oil-carrying shutdown method of a styrene dehydrogenation reaction system comprises the following steps: S1, reducing the load of the reaction to the feeding and cutting of ethylbenzene, namely reducing the feeding load of ethylbenzene to the feeding and cutting of ethylbenzene, wherein a tail gas compressor normally operates in the process, maintaining the negative pressure of a reaction system stable, and reducing the temperature of a dehydrogenation reactor bed to 545-555 ℃; S2, carrying out negative pressure oil carrying on the reaction system, namely introducing steam into an ethylbenzene feed pipeline of the reaction system, jacking residual materials in the ethylbenzene feed pipeline into an ethylbenzene evaporator and finally entering a dehydrogenation reactor bed layer, maintaining the temperature of the dehydrogenation reactor bed layer and the inlet temperature to be 545-555 ℃, and maintaining the operation of a tail gas compressor to ensure that the reaction system keeps a normal negative pressure working condition for carrying out negative pressure working condition steam oil carrying; S3, burning the bed layer of the dehydrogenation reactor, namely, maintaining the temperature of the bed layer of the dehydrogenation reactor at 450-500 ℃, reducing the rotating speed of a tail gas compressor, adjusting the opening of an inlet circulation valve of the tail gas compressor, boosting the pressure of a reaction system until the