This paper reviews SINOPEC’s ethylene business in 2022, briefly summarizes its ethylene production from the aspects of safety and environmental protection, feedstock optimization, energy saving and consumption reduction, technology research, long-term operation and maintenance, and puts forward its objectives and important tasks in 2023.

This paper reviews PetroChina's ethylene business in 2022, including its subordinate petrochemical enterprises' ethylene production, ethylene yield, yields of ethylene and propylene, processing loss ratio, energy consumption as well as feedstock optimization, long-term operation, technical modification and technical measures. Its objectives and important tasks concerning ethylene business in 2023 is put forward.

This paper reviews the removal of coke particles from quench oil in the quench zone of ethylene plant and the changes in the design schemes in China over the past 30 years, and analyzes the advantages and disadvantages of the design schemes at each stage. The current design scheme of decoking system, which combines automatic scraper filtration system with cyclone separation filtration system, is emphatically described. It can efficiently separate coke particles from quench oil and has remarkable advantages. Its system composition, structural characteristics and design ideas are expounded in detail, and its working principle and technical characteristics are analyzed.

This paper analyzes the reasons for the poor separation effect of grease and spent caustic in caustic wash tower, and optimizes the operation of caustic wash tower, solving the problem of grease separation and creating conditions for the long-term operation of the unit.

 During the production of ethylene plant, the operation of ethylene rectification tower directly influences the quality and output of ethylene product. In this paper, the reasons for tray blockage in ethylene rectification tower are comprehensively analyzed. It is determined that the green oil generated during C₂ hydrogenation reaction is the main reason for tray blockage. The normal operation of ethylene rectification system can be restored by injecting methanol to eliminate the tray blockage, and some corresponding improvement measures are proposed to ensure the long-term and stable operation of ethylene rectification tower.

This paper introduces the abnormal operation of the caustic wash tower and spent caustic oxidation system in the megaton ethylene plant at PetroChina Dushanzi Petrochemical Company, and analyzes the causes of the problems. In view of the main reasons, some specific measures were put forward and implemented. The cracking gas compressor was briefly stopped to open the interstage tanks. During the inspection, it was found that the root cause of the polymer produced in caustic wash tower was the serious blockage of the demister in separation tank at the entrance of caustic wash tower, which resulted in lower demister efficiency and eventually led to the entrainment of heavy components into the caustic wash tower to produce polymer. The replacement of demister of interstage tank fundamentally solved the problems such as the abnormal operation of caustic wash tower and the off-spec saline wastewater.

The traceability analysis of the cracking of quench pipeline in second-stage reactor of pyrolysis gasoline hydrogenation caused by chemical corrosion and stress corrosion was carried out. Through the macroscopic and low-magnification metallographic examination of the 1# outer tube, the chemical composition analysis of the sample tube, the microstructure analysis of the sample tube, the electron microscope observation and the energy spectrum analysis, the reasons for the cracking of quench pipeline were comprehensively analyzed. It was determined that chloride ion stress corrosion cracking played a leading role, and the sensitization of welds and heat-affected zone accelerated the cracking process. Corresponding countermeasures were taken to effectively prevent the cracking of pipelines, which provides a guarantee for the long-term, safe and stable operation of pyrolysis gasoline hydrogenation unit.

Preheating is required for the first startup of EO reactor after the overhaul of EO/EG unit. The oxygen flow rate should not be too high, just slightly higher than the minimum flow limit. Over high oxygen flow rate may trigger the high oxygen concentration interlock at reactor outlet. The inlet and outlet oxygen concentration increases first and then decreases. The outlet oxygen concentration decreases obviously, and the oxygen balance gradually rises and finally tends to a stable value. The limiting factor of critical ethylene flow is catalyst selectivity. Higher catalyst selectivity leads to higher ethylene flow and more difficult oxidation reaction.

The pressure difference in the debutanizer of the steam cracker of a company frequently increased during normal operation due to the gradual accumulation of coke in the distillation column, resulting in off-spec products and bringing great potential hazard to the stable operation of the unit. The analysis results showed that the accumulation of coke was caused by multiple factors including the water entrained in the feed to condensate stripper, the trace oxygen brought in during equipment maintenance, the rust of distillation tower tray and the heavier cracking feedstock. By optimizing the operation, strengthening process monitoring and adding inhibitor injection process flow, the pressure difference in debutanizer returned to normal and stable operation was achieved.

 This paper discusses the process flow of quench oil system in ethylene plant and the pressure for achieving long period operation at full load, analyzes the influence of key points of process control, and expounds the difficulties in process control for long period operation at full load and the measures to be taken.

This paper describes the reducer weld cracking in ultra-high pressure steam pipeline in the 220 kt/a ethylene plant at PetroChina Dushanzi Petrochemical Company, finds out the causes of reducer weld cracking by carrying out appearance inspection, alloy analysis, in-situ metallographic coating and hardness test of the reducer weld, and develops maintenance measures for the ultra-high pressure steam pipeline to prolong its service life, thus guaranteeing the safety and economic benefit of ethylene plant.