Based on the configuration of plant-wide steam network of chemical enterprises, a program control response strategy is proposed for the fluctuation of steam network. Program control is used to replace human decision-making to avoid the secondary accident caused by untimely decision-making or insufficient emergency response capacity of personnel, reduce economic loss and ensure the safety of the plant. When the steam turbine of large compressor unit trips, in order to avoid the fluctuation of steam network, a program control scheme is proposed according to the characteristic parameters of the control valve of temperature and pressure reducer to stabilize the pressure of steam network in time and reduce the economic loss caused by process fluctuations.

During the engineering design of ethylene plantefinsIene Plant,fourteen key heat exchangers are identified based on the characteristics of quench system, cracking gas compressor system and hydrocarbon separation system, and some suggestions are put forward for optimizing the design of heat exchangers based on the characteristics of specific process fluid. According to the operation during three operation cycles, the problems in design and operation are analyzed and some improvement measures are proposed. Moreover, focusing on the failure of both exchanger tube and water cooler of the ethylene plant in Zhenhai, this paper proposes several possible solutions which combine exchanger type selection, operation and static equipment management.

This paper introduces the short-term shutdown and startup of the 220 kt/a ethylene plant with material at PetroChina Dushanzi Petrochemical Company due to the relocation of control room. By preparing management manuals, special plans and operation cards in advance, the professional departments and operation departments of the Company carried out energy isolation control, ensured the construction manpower and the preparation and delivery of project materials, and strengthened the training and defense of supervisors at all levels. Simulation verification was carried out jointly with the repair company, and practical testing and verification were carried out in local areas with necessary conditions, so as to ensure that the risks of DCS/SIS/ITCC system relocation and commissioning are controllable and to further ensure the scientific nature of the project scheme. Mainly focusing on the relocation of control room, the hidden dangers in the equipment, facilities and instrumentation of production units were eliminated. After nearly 15 days of efforts, the intended target was achieved.

The 1100 kt/a ethylene plant of Dushanzi Petrochemical Company was equipped with two cracking gas dryers, one for operation and one standby. A single dryer was designed to run online for 36h and then switched for regeneration. The online operation cycle of a single cracking gas dryer was extended to 72h, in order to reduce the influence of regeneration times on the adsorption performance attenuation of molecular sieve and to respond to the call of ethylene plant to improve quality and efficiency. After 11 months of optimized operation, the pressure difference of the dryer increased by 8kPa, leading to the increase of outlet pressure of cracking gas compressor and affecting the long-term and optimum operation of the plant at full load. In this paper, the factors causing the abnormal pressure difference rise are analyzed and discussed from the aspects of material composition, regeneration medium, residual adsorption capacity, feed temperature and regeneration process. Through the combination of theoretical calculation with practical production, some measures for optimizing the operation of the dryer in stages were proposed and adopted, solving the problem of abnormal pressure difference rise and realizing both stable operation and cost saving.

This paper introduces the first ethylene process in China based on LNG cold energy utilization, which uses methanol as an intermediate refrigerant for indirect heat exchange, thereby realizing the mutual supply of cold and heat between the cooling capacity in the LNG receiving station and the ethylene plant. The cascade utilization of refrigerant temperature replaces some users of the original propylene and ethylene compressor, greatly reducing the power consumption of refrigeration compressors. The energy consumption of separation system is reduced by about 11％, and the comprehensive energy consumption of ethylene plant is as low as 497 kgEO/t ethylene. The methanol refrigerant system will be the key to the smooth operation of ethylene plant. Through the analysis of refrigerant start-up and typical accident conditions, some ideas are provided for the operation of ethylene plant.

This paper introduces the problems in the operation of low-pressure depropanizer of the separation unit in the 220 kt/a ethylene plant of PetroChina Dushanzi Petrochemical Company. Through the analysis of the material composition in the tower, it is found that the components that easily polymerize are mainly butadiene and cyclopentadiene and a small amount of styrene, and the scaling will cause the blockage of the bottom level gauge, resulting in abnormal display. The fluctuations in the operation of the low-pressure depropanizer are analyzed and discussed, the hazards are identified, and some corresponding preventive measures are developed, so as to ensure the long-term stable operation of the low-pressure depropanizer.

The theoretical calculation methods for the noise source intensity of safety valves of ethylene cracking furnaces are introduced, including the API STD 521, the noise and vibration control engineering manual and the Engineering Noise Control：Theory and Practice. By selecting API STD 521 method for calculation and considering the pipeline distance reduction, free space distance reduction, directivity reduction and A sound level correction in the actual working situation, the simulation calculation analysis and research on noise limits in the working platform area of operators are carried out, so as to meet the requirements on noise limits in the operators’ working area of cracking furnaces.

The new gas phase cracking furnace in the ethylene plant of a petrochemical company adopts HQC’s large-scale gas phase cracking furnace technology, double furnaces are designed, and all the heat is supplied by bottom burner. After the gas phase cracking furnace was completed and put into use, there was an abnormal situation of uneven thermal field distribution in the radiation section, which was manifested by unstable flame shape, large COT deviation and easy fluctuation, and low ethylene yield. The thermal field distribution of the gas phase cracking furnace was observed and the causes were analyzed, the burner was modified twice, the thermal field distribution of the cracking furnace was optimized, and the ethylene yield of the gas phase cracking furnace was improved.

The accuracy of coil outlet temperature (COT) measurement of ethylene cracking furnace is closely related to the yield of product and the operation cycle of cracking furnace. This paper discusses the error causes of three traditional COT measuring methods currently used based on practical cases, and summarizes their advantages and disadvantages, providing suggestions for engineering design and actual production.

The temperature of thrust bearing bush TE-12811A/B of turbine DST-201 has continuously increased and reached 120℃, the alarm value. High bearing bush temperature will accelerate the oxidation of lubricating oil and form a hot paint film on the surface of bearing bush. To effectively prevent the formation of paint film and remove the soft pollutants in the system, solubility-enhancing oil DECON was injected into the lubricating oil. After injecting the enhancing oil, the temperature of thrust bearing bush TE-12811A/B decreased by 5℃. By replacing the thrust bearing bush and upgrading the material of bearing bush to copper-chromium alloy, the bearing capacity of bearing bush was improved, the thermal conductivity efficiency of bearing bush was increased, and the temperature of bearing bush was reduced, fundamentally solving the problems such as the temperature fluctuation and high temperature of bearing bush.

Cracking gas compressor, ethylene refrigeration compressor and propylene refrigeration compressor are the core equipment of ethylene plant, and their high-efficiency operation is extremely important to the safe, stable, long-term, full-load and optimum operation of ethylene plant. This article focuses on the problems that occurred during the maintenance of three key compressors in the 1000 kt/a Ethylene Plant of PetroChina Dushanzi Petrochemical Company, and analyzes the root causes of the impeller erosion, coking and gas seal corrosion in the high pressure cylinder of cracking gas compressor based on process operation data. At the same time, in view of the leakage of extraction flange of cracking gas compressor, the detached spool of high pressure valve of ethylene and propylene refrigeration turbines and the air leakage of valve stem packing, some maintenance control methods and countermeasures are proposed.

Using air cooling instead of water cooling for compressor turbine exhaust is a good choice for the chemical plants in areas lack of water, but there are some problems that cannot be ignored in the operation of air cooling system. By introducing the air cooling system of turbine exhaust of cracking gas compressor, ethylene refrigeration compressor and propylene refrigeration compressor in the ethylene plant of a petrochemical company, the problems in high temperature operation in summer are studied, and some feasible solutions are given to ensure their normal and smooth operation.

The cracking gas compressor of the 220 kt/a ethylene plant of PetroChina Dushanzi Petrochemical Company was put into operation in 2021 after overhaul. After 11 months of continuous operation, some problems emerged such as the high first-stage suction pressure, the increased M factor of compressor and the fouling of interstage cooler. By optimizing the wash oil medium of compressor and changing the polymerization retarder, the M factor growth was effectively prevented, and the coking trend of compressor impeller and flow path was delayed. In view of the rising pressure difference of interstage cooler of cracking gas compressor, the influence of interstage resistance drop on compressor power was effectively reduced by installing isolation valve, monitoring pressure difference trend in real time and switching off a single furnace for decoking.