The achievement and performance of SINOPEC’s ethylene production in 2023 are introduced and analyzed briefly from the aspects of safety and environmental protection, feedstock and operation optimization, energy saving and consumption reduction, technology research, long-term operation and maintenance, and the objectives and focus of SINOPEC’s ethylene production in 2024 are put forward.

This paper summarizes the development of PetroChina's ethylene business in 2023, including the ethylene production, ethylene yield, yields of ethylene and propylene, processing loss ratio and energy consumption of its subordinate petrochemical enterprises, as well as the feedstock optimization, long-term operation, maintenance, technical modification and technical measures. The focus of work concerning long-term optimum operation of ethylene plants in 2024 is put forward.

 In recent years, affected by the diversification of raw material to ethylene plant, the emulsification of quench water occurred. More and more benzene series remain in the system, leading to serious polymerization in process water system. The polymerization of process water not only leads to the blockage of multiple heat exchangers in the quench unit, but also may lead to the shutdown of the quench unit in severe cases, which becomes one of the main bottlenecks for the long-term operation of ethylene plant. A new reagent is used in the quench water system to improve the water quality and alleviate the emulsification and fouling problems of the water system, thus effectively prolonging the operation period of the ethylene plant.

With the increase in the load of propylene rectification tower in a 220 kt/a ethylene plant, the propylene loss in the circulating propane at the bottom of tower reached 10％. In order to reduce the propylene loss at the bottom of propylene rectification tower, Aspen Plus was used to establish a propylene rectification tower model with the operation data of propylene rectification tower, and the current operation of the propylene rectification tower was analyzed and studied. By identifying the deviation points between the simulation data and the actual operating parameters, the operation of propylene rectification tower was adjusted and optimized, so as to reduce propylene loss at the bottom of tower, increase propylene production and achieve the purpose of improving quality and efficiency.

To solve the vibration problem of the silencer and pipeline at the outlet of screw compressor in a chemical company, the gas pulsation and pipeline vibration of the existing exhaust pipe was analyzed, the main causes of the pipeline vibration were identified combined with the measured data of pipeline vibration on site, and some corresponding modification measures were put forward. Some reasonable vibration elimination measures were taken such as replacing the silencer with three-chamber impedance compound silencer, revamping the exhaust pipe, installing pipe supports and reinforcing the thermocouple branches. After modification，the pressure unevenness at each point inside the exhaust pipe can meet the requirements of API 619, and the gas pulsation decreased by 72% on average. The first-order natural frequency of the exhaust pipe system increased from 4.572 Hz to 8.862 Hz, and the high-order natural frequency was ±10% away from the compressor excitation frequency. The maximum vibration of the silencer decreased by 64% to 32 mm/s and the maximum vibration of the outlet pipe decreased by 87.5% to 10 mm/s compared with those before the modification, proving the effectiveness of the modification measures.

To solve the leakage of steam-water corrugated-tube heat exchanger in hydrogen plant, the causes of the leakage of heat exchanger tube bundle were analyzed combined with the specific operating conditions, the analysis results were obtained combined with the actual inspection report based on the corrosion mechanism of corrugated tubes in the environment of chlorine-containing medium, and some specific preventive measures were developed correspondingly based on the cause analysis. The corrosion hazards were completely eliminated through heat exchange tube modification, the operating cycle of the heat exchanger was extended, and the long-term operation of the heat exchanger was ensured.

 In 2019, the capacity of a megaton ethylene plant was expanded in the overhaul window period, including the installation of an ethane cracking furnace, a viscosity reducing tower system and a toluene extraction system as well as the transformation of related supporting equipment and facilities, so that the capacity reached 1.15 million tons per year. This paper analyzes and summarizes the operation of the ethylene plant after two overhauls in 2015 and 2019 respectively, in order to find out the operation bottleneck of quench system and formulate targeted optimization plans.

Recycling decoking effluent to firebox of cracking furnace is one of the effective measures to reduce pollutant emissions from the cracking furnace, and the piping layout for recycling decoking effluent to firebox has a significant impact on the decoking effect. This article uses CFD technology to numerically simulate the piping layout for recycling decoking effluent to firebox. RNG k- ε turbulence model is used for the simulation, and the wall function Standard Wall Fn is used to correct the near wall flow. The calculation results indicate that a reasonable piping layout can ensure the even entry of decoking effluent into the firebox without affecting the normal operation. The simulation calculation based on CFD technology can accurately predict the flow of decoking effluent in pipelines, providing technical reference for the piping layout for recycling decoking effluent to firebox of large-scale cracking furnace.

In order to reduce the energy consumption of the 220 kt/a ethylene plant in Dushanzi, it was proposed to change the operating mode of cracking furnace from 6 for operation and 1 standby to 5 for operation, 1 stopped and 1 standby based on the energy consumption analysis of the ethylene plant and the current working conditions of cracking furnace and cracking gas compressor. In order to select the optimal operating mode of 5 for operation, 1 stopped and 1 standby, the working conditions were tested in 5 stages. By comparing the design parameters of the No.2 gasoline fractionator (C-103), the relationship between the cracking gas load of the tower and the middle pumparound and gasoline reflux was optimized and adjusted, ensuring the stable and controlled quench oil viscosity and quench water quality. Through optimizing the operating mode of cracking furnace, the goal of energy saving and consumption reduction of the ethylene plant was quickly achieved.

The condenser of cracking gas compressor in ethylene plant is the accessory equipment of cracking gas compressor, and its leakage will affect the long-term operation of the ethylene plant. The causes of tube bundle leakage in the heat exchanger are analyzed, and some corresponding preventive measures are developed to extend the operation cycle of heat exchanger and reduce the probability of heat exchanger leakage during operation, thus ensuring the long-term operation of critical equipment in the ethylene plant.

 This paper introduces the abnormal phenomenon of liquid entrainment in the suction line of cracked gas compressor in the 1100 kt/a ethylene plant at PetroChina Dushanzi Petrochemical Company, analyzes the causes of the problem from various aspects, and puts forward some specific measures for alleviating the liquid entrainment in the suction line of cracked gas compressor. The analysis results show that the root cause of the liquid entrainment in suction line of cracked gas compressor and the abnormal formation of grease in caustic wash tower is the serious blockage of demisters for the interstage tank of cracked gas compressor and the knockout drum at inlet of caustic wash tower, which resulted in a decrease in demisting efficiency and then the liquid entrainment in suction line of compressor. Therefore, the demister for the interstage tank of cracked gas compressor was replaced as a whole, fundamentally solving such problems as the liquid entrainment in suction line of compressor and the abnormal phenomenon in caustic wash.

This paper briefly describes the revamping content and purposes of the control system for three key compressors in ethylene plant, and introduces the operating conditions and steps of the new system after revamping. The new system focuses on unit protection and anti-surge, and over-speed protection, unit status monitoring and unit interlock protection (emergency shutdown system) are combined into one set of ITCC system, providing a safe and reliable operation platform for production. The performance of the control system for three key compressors has been improved, the functions have been further improved, the operating load has been reduced, the comprehensive control and operation of the unit has been realized on the integrated operation interface, and the operating efficiency has been improved.

 As an important part of the cryogenic separation of ethylene plant, expander-recompressor is used to purify the exhaust gas in cryogenic zone and provide cooling capacity for the cold box in process system. It is the core equipment of the cryogenic separation system, and its long period and stable operation plays a vital role in reducing the ethylene loss of ethylene plant. This paper introduces the process flow and operational problems of expander-recompressor in ethylene plant, and puts forward some optimization and improvement measures based on the analysis of the operational problems, so as to ensure the stable operation of the expander-recompressor system.

In recent years, the capacity of ethylene plant has been continuously expanded, and cracking gas compressor unit is developing towards large scale. At the same time, the requirements for the design and performance of compressor unit are higher. Based on the problems in the operation of cracking gas compressor unit of a 200 kt/a ethylene plant, this paper introduces the equipment, facilities and related technologies for the cracking gas compressor and driving steam turbine of the 1200 kt/a ethylene plant of SINOPEC Tianjin Company. The innovative application of a number of advanced technologies has solved some of the key problems in the ethylene plant, providing a strong guarantee for the design and construction of subsequent larger-scale ethylene plants.

 After the shutdown of the ethylene plant at PetroChina Dushanzi Petrochemical Company for maintenance, the radial bearing bush temperature at the turbine side of propylene refrigeration compressor kept rising during operation. The causes of the rise of bearing bush temperature were investigated, and API Group V base oil was injected into the propylene refrigeration compressor in advance to solve the problem of radial bearing bush temperature rise at the turbine side according to the previous experience, thus ensuring the long-term operation of compressor unit.