Based on the investigation on the strategy, effect and experience in the purging of super high pressure steam pipelines, this paper takes the Ethylene Project Phase II in Zhenhai as an example to analyze from the economic point of view the huge differences in commissioning cost due to different treatment methods for the internal cleanliness of super high pressure steam pipelines while meeting the quality and environment protection requirements of the system. The results show that safety and environment protection can be improved and great achievements can be made in energy saving during the commissioning of the new plant by continuously using new technologies and new ideas and optimizing the commissioning plan.

In steam cracking for ethylene process, a large number of high value-added C₄/C₅ fractions are produced. Currently C₄/C₅ fractions are processed in butadiene extraction unit, MTBE/butene-1 unit and C₅ separation unit. The by-products from the above-mentioned units such as the alkyne-containing butadiene tail gas, butadiene heavy component and C₄ raffinate from butadiene unit, the residual C₄ from MTBE/butene-1 unit and the C₅ raffinate from C₅ separation unit are not fully utilized. After continuous exploration and development by domestic research institutes, the process technologies for processing the above-mentioned resources have been improved and industrialized, and the comprehensive benefits have been further improved.

An 800 kt/a ethylene plant adopts domestic cracking technology and environmentally-friendly low-energy-consumption ethylene separation technology. The separation process is introduced, and design optimization is carried out such as installing closed steaming in quench system, reducing the pressure in ethylene rectification tower, directly sending ethylene to downstream units, reducing the emission of ethylene spherical tank and recovering cold energy from low-temperature raw materials. These optimizations can effectively improve the flexibility and progressiveness of ethylene separation process, reduce the unnecessary emissions, reduce the operation cost, and achieve a more environmentally-friendly and energy-saving production of the plant.

Modern ethylene plant has the characteristics of large system, long process flow, severe process conditions and numerous critical equipment, which make it difficult to store materials during startup and shutdown of the plant, and a large amount of material discharged will cause environmental pollution. By analyzing the characteristics of technologies for low emission startup and shutdown of three kinds of unit layout including two ethylene plants, a single ethylene plant with recovery system and a single ethylene plant, this paper presents the optimal solution to achieve the low emission startup and shutdown of the plant, so as to reduce the material emission and minimize the adverse impact on the environment.

This paper mainly introduces the background, improvement process, operation and energy consumption analysis of the low-pressure methane hydrogen process improvement project of the ethylene plant of a petrochemical company in China, and analyzes and evaluates the effect after the improvement. One methane hydrogen compressor is to be installed during this process improvement to recover and utilize the low-pressure methane hydrogen from cold separation system. The new compressor is used to boost the low-pressure methane hydrogen and send it to fuel gas pipe network, so as to improve the operation flexibility of the ethylene plant. It provides support for the subsequent lighter feedstock and reduces the energy consumption of the ethylene plant.

The viscosity of quench oil was high during the early operation of the megaton ethylene plant in Dushanzi. During operation, the designed quench oil viscosity reduction process not only reduced the quench oil viscosity, but also increased the gas phase load of the gasoline fractionator, limiting the operation. Quench oil viscosity reducing tower technology was applied in the expansion in 2019, which effectively solved the long standing problem of high quench oil viscosity and ensured the long-term and stable operation of the ethylene plant. This paper introduces the method for controlling quench oil viscosity, the working principle of viscosity reducing tower and the operation optimization ideas, and analyzes and determines the operation adjustment mode of quench oil system after the viscosity reducing tower is put into operation, so as to solve the problems in the operation of viscosity reducing tower.

Propylene products from ethylene plant are used as raw materials for polypropylene plant. If the methanol in propylene products exceeds the standard, it will have a great impact on the production and operation of polypropylene plant. During the production of ethylene plant, there are many sources of methanol in the target product, including the methanol carried in raw materials, the alcohols produced from oxygenated compounds under high-temperature cracking conditions, and the methanol and propanol prepared by the plant for defrosting. These alcohols will eventually enter the propylene distillation system and affect the quality of propylene products. In this paper, the raw materials, quench water system and propylene distillation system are optimized and adjusted to improve the quality of propylene products and reduce its methanol content.

PetroChina Liaoyang Petrochemical Company completed the modification of its ethylene plant for lighter raw materials in 2019 and transformed two gas furnaces to process liquefied gas and aromatic tail gas. The operation of the gas furnaces improved the ethylene yield, but the amount of circulating ethane increased greatly, resulting in the decrease of ethane conversion rate of the cracking furnace and affecting the normal operation of the plant. The secondary distribution of circulating ethane through process optimization solves the problem of low conversion rate. By reducing the outlet pressure of ethane vaporizer, the problem of high-frequency emission of ethane to flare due to high liquid level is reduced, and the system operation is optimized.

The fast regeneration switching rate of pyrolysis gas dryer will affect the system stability. In severe cases, accidents of unqualified ethylene products may occur. Through the analysis of the regeneration process of the cracked gas dryer in the 800,000 tons/year steam cracker at ZhongKe (Guangdong) Refinery & Petrochemical Company Limited, this paper analyzes the problems including the COT temperature runaway caused by fast cold regeneration rate, the system fluctuations caused by parallel switching and the user shunt timeout of the regeneration system, and proposes some effective methods such as presetting the fuel gas system during regeneration and determining the priority of generation users to mitigate the system fluctuations caused by the regeneration switching of pyrolysis gas dryer, thus ensuring the stable production of the unit.

Alkaline corrosion often occurs under the conditions of evaporation and concentration or high temperature heat transfer. High concentration alkali solution at a temperature higher than 79 ℃ causes the uniform corrosion of carbon steel, and the corrosion rate is very fast when the temperature reaches 93 ℃. Erosion corrosion is due to fluid erosion. The corrosion products leave the surface, and the exposed fresh metal surface is damaged under the repeated action of erosion and corrosion. It is easy to form pits and grooves, with a certain direction. In this paper, the corrosion leakage of ethylene glycol discharge flash tower in the ethylene oxide/ethylene glycol unit of a petrochemical company is analyzed, the causes of corrosion leakage are studied, and the rectification scheme and preventive measures are put forward to eliminate the potential risk of leakage.

In this paper, the main process parameters affecting the cracking yield and their interrelationships are briefly described. Five chemical raw materials, including ethane, propane, butane, LPG and naphtha, are selected respectively as the cracking feed to ethylene cracking furnace. The ethylene yield with different furnace tube configurations are mainly explored, and the influence of different tube configurations, coil outlet temperatures (COT) and coil outlet pressures (COP) of cracking furnace are analyzed. The relationship between ethylene yield and the conversion rate of key components, the ratio of propylene to ethylene and other indicators characterizing the cracking depth are analyzed, providing reference for the selection of radiant tube and the optimization of cracking furnace operation conditions.

Researches show that the production of nitrogen oxides (NO_X) is inevitable during fuel combustion, and nitrogen oxides are the main pollutants that form acid rain and damage ozone layer, so industrial emissions of nitrogen oxides have been listed as the major pollutants to be controlled. At present, ethylene cracking furnaces mainly use low nitrogen burners to reduce the nitrogen oxide content of flue gas. However, with the further stringent environmental requirements, the nitrogen oxide content of flue gas from cracking furnace have to meet lower emission targets. This paper introduces the application of SCR denitrification technology in the cracking furnace of a new ethylene plant in China, and puts forward some suggestions for optimization and improvement.

The structure of coke burning gas and coke particle separator in the ethylene plant at PetroChina Dushanzi Petrochemical Company is cyclone separator. With simple structure, this separator can withstand high temperature and pressure and has good application effect in separating coke particles from coke burning gas of cracking furnace. However, the wear of the inner wall of the separator has become the primary problem seriously restricting its operation cycle. After disassembling the coke burning gas and coke particle separator, it was found that its inner wall was seriously worn and the scouring thinning was local. Aiming at the wear problem of the inner wall of separator, this paper uses the research methods of theoretical analysis and numerical simulation to analyze the wear of inner wall of separator caused by gas-solid two-phase flow, and puts forward some improvement measures.

Cracking gas compressor, propylene compressor and ethylene compressor are the core of ethylene plant, and their ability to maintain high-efficiency operation is extremely important to the safe, stable, long-term and optimal operation of the ethylene plant at full capacity. This article introduces the process of the single test run of steam turbines of the compressors in the megaton ethylene plant at PetroChina Dushanzi Petrochemical Company, including the test run of main and auxiliary oil pumps, condensate pump, emergency shut-off valve and dry gas sealing system, and discusses the reasons and treatment measures against the problems in single test run such as the crank failure, the speed probe detection failure, the high shaft temperature at the drive end of propylene compressor turbine, and the unsuccessful single test run of cracking gas compressor turbine.

Based on the investigation on the strategy, effect and experience in the purging of super high pressure steam pipelines, this paper takes According to the characteristics of C₅ diolefins，which are prone to self-polymerization and copolymerization, and combined with the actual production of C₅ separation unit，this paper analyzes the influence of factors such as unit consumption of polymerization inhibitor，hydrolysate of DMF，free oxygen content in system，temperature in tower and diolefin concentration on the polymerization inhibition effect of polymerization inhibitor, and reasonably optimizes these factors. After optimization，the production stability of the extraction and separation system is improved obviously, the cleaning frequency of pump inlet filter decreases, and the operation cycle of reboiler is extended. The results show that the polymerization coking rate of diolefin remarkably decreases, the yields of the target products of C₅ separation unit are improved，the operating cost is reduced，and the operation cycle of the extraction and separation system is extended.