Pygas hydrogenation unit and styrene extraction unit are mutually upstream and downstream, with raw materials and products supplied to each other and close operational connections. Based on the process optimization and system integration research on these two units, measures such as joint separation process, thermal coupling for distillation separation, joint hydrogenation reaction and joint utilities can be taken. After optimization, the joint design of pygas hydrogenation unit and styrene extraction unit is feasible in engineering and can achieve the goals of reducing the investment, saving the energy consumption, and improving the economic benefits and competitiveness of the units.

In recent years, a research institute of a petrochemical company and some production plants have adopted information-based means to establish a database system for evaluation of cracking raw materials, which integrates the evaluation data of cracking raw materials into the database system for scientific and effective management. By making the classification, filing, management, transfer and analysis of data normalized, systematic and professional and making efficient use of the evaluation data, the database system can play a full role in raw material procurement, mixing, processing and production scheme optimization.

The process water stripping tower for the 220 kt/a ethylene plant of PetroChina Dushanzi Petrochemical Company had problems such as clogged packing and poor packing at the end of its operation. The operation was optimized by adding level gauges to the process water stripping tower, increasing the scale removal frequency of the system and injecting dispersant, so as to solve or alleviate the blockage in the packing layer of the process water stripping tower. Through online isolation and repair of the process water stripping tower, the operation bottleneck of process water system was solved.

After the processing capacity of an ethylene plant in Sinopec was expanded to 1.1 million tons per year, the vacuum degree of its cracking gas compressor unit decreased. The real-time operation parameters related to the condenser in different time periods were exported from the real-time database, python programming language was used to classify, screen and clean the big data of chemical production, the correlation was analyzed through mathematical statistics, and a three-dimensional scatter diagram was made. A multiple linear regression model of exhaust pressure was constructed based on historical data, and its accuracy was verified.

The C₂ hydrogenation reactor (R-401C/D) in the 220 kt/a ethylene plant of PetroChina Dushanzi Petrochemical Company was put into operation on November 8, 2022, and the ethylene increment at the reactor outlet was unstable during production. Product yield analysis software was used to extract production data every 4 hours to optimize the cracking depth and control the acetylene content at the reactor inlet. The EVA process of polymer grade ethylene was used to ensure that the flow rate of polymer grade ethylene was maintained at 26 t/h, so as to balance the cooling capacity of the system and control the overhead temperature of the deethanizer. The green oil in the first stage of reactor was removed regularly, and the amount of green oil entering the second stage bed was reduced, thus improving the activity of catalysts and the ethylene increment at the reactor outlet. In 2023, the average ethylene increment at the reactor outlet was 301 kg/h, with an average increase of 165 kg/h compared with that in the technical agreement.

During the second overhaul of the 800 kt/a ethylene plant of a petrochemical company in Sichuan, some chemical cleaning methods were used to remove the ferrous sulfides, heavy oil components and hydrocarbon polymers in quench oil tower system as well as the waste alkali grease, rust and other scale deposits in alkaline washing tower, waste alkali collection tank and waste alkali tank. After the cleaning, the equipment met the requirements of maintenance/production, and the goal of clean surface was achieved.

In this paper, the ethylene products of an ethylene plant are studied. The large fluctuations in the CO content of cracking gas in a short period of time led to bed temperature runaways in C₂ hydrogenation reactor, and the pulverization and carbonization of catalysts led to a decrease in the activity of catalysts, resulting in high acetylene at the reactor outlet and low qualified rate of ethylene products. The temperature runaway in C₂ hydrogenation reactor caused by CO fluctuations under typical working conditions was analyzed, and strategies were formulated from two aspects of process adjustment and catalyst replacement, so as to effectively solve the problem.

To solve the wear and tear problem of the floating ring seal of propylene refrigeration compressor, analysis is made from the aspects of installation clearance check of floating ring seal, quality of unit seal assembly, oxidation resistance test of seal oil, cleaning conditions of high-level oil tank for seal oil, and pressure difference between oil and gas, and some solutions are put forward for the wear and tear of floating ring seal. 

During the factory acceptance test of cracking gas compressor for a 1,200 kt/a ethylene plant, the radial bearing pad temperatures of low-pressure and medium-pressure cylinders exceeded the performance assessment indicators. This could be caused by the abnormal friction between the bearing pads and the shaft or by insufficient supply of lubricating oils which leads to poor heat dissipation. Excessively high bearing pad temperatures can cause thermal degradation of lubricating oils, leading to the formation of soft contaminants that deposit on the surfaces of bearing pads and shaft, and resulting in carbonization, sludge or even varnish. This reduces the lubricating and cooling effects of lubricating oils, accelerates the wear of bearing pads, and severely affects the long-term operation of cracking gas compressor. Since cracking gas compressor is one of the key core equipment in ethylene plant, its stable operation time directly determines whether the ethylene plant can achieve a safe, stable, long-term, full-load and optimum operation. Therefore, a comprehensive and scientific analysis shall be made for the causes of high bearing pad temperature, and a treatment plan shall be developed to solve this problem, so as to meet the mechanical trial run acceptance standards for compressors.

The cracking gas compressor in the 220 kt/a ethylene plant of PetroChina Dushanzi Petrochemical Company was started in September 2019 after overhaul, the third-stage outlet flow rate was maintained at around 118 t/h, and the third-stage outlet pressure reached a maximum of 1720 kPa, which is close to the set pressure of safety valve of 1746 kPa, resulting in limited load adjustment of cracking gas compressor and weakened ability to resist fluctuations. In response to the abnormal third-stage outlet pressure of cracking gas compressor and the deviations from design conditions, the operating process parameters and mechanical structure of the compressor were analyzed, and some measures such as setting internal control indicators for compressor outlet pressure, replacing inter-stage gas seals and adding high-pressure nitrogen sealing pipelines were taken to ensure the long-term, full-load and optimal operation of the cracking gas compressor.

This paper studies in depth the carburization failure mechanism and detection principles for tubes of ethylene cracker, and introduces an innovative intelligent carburization detection system. This system enables rapid carburization detection and analysis across the entire tube, significantly improving equipment management and maintenance efficiency and enhancing the sustainability and safety of industrial production. During the application of this system in the ethylene cracker of a petrochemical company, the detection data clearly indicates that the extent of carburization is influenced by various factors including both the temperature field generated by burners and the turbulence of medium inside furnace tubes. The 3D carburization data for each tube provides precise guidance for tube replacement. This intelligent carburization detection system helps reduce operational risks, optimize process parameters, implement accurate tube replacement and improve the economic benefits of enterprises. 

The feed to cracking furnace of ethylene plant is generally the mixture of gaseous raw materials and diluted steam in a certain proportion. Because the feed contains a certain proportion of steam, the measuring medium easily condenses during the actual measurement, resulting in phase instability of the measuring medium which leads to large deviations or fluctuations in flow measurement. The inaccurate measurement of cracking furnace feed flow will lead to the failure to use automatic control for the feed to cracking furnace, so that the labor intensity of process operators in monitoring DCS operation screen greatly increased, which makes it impossible for them to balance the normal control of cracking furnace, thus resulting in a short operation cycle of cracking furnace and the frequent switching of cracking furnace and then affecting the production efficiency of enterprises. By optimizing and improving the installation mode for feed flow meter of cracking furnace, the stability and accuracy of measuring instrument can be effectively guaranteed, the problem of measurement distortion can be solved, and the monitoring and maintenance intensity of measuring instrument personnel and technical personnel can be reduced, so as to achieve the long period operation of cracking furnace.