【Haichuan’s Best Practices】Increasing the proportion of feedstocks used in vapor-phase cracking to reduce the costs associated with ethylene cracking

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Since July, Unit 1 of Gulei Petrochemical has innovated its operating mode by adopting a system in which \"3 cracking furnaces are used to process naphtha + 3 cracking furnaces are used to process propylene and butane.\" As a result, the proportion of gas-phase cracking feedstock increased from 28% to 42%, and the ethylene yield also rose by about 0.3%, thereby helping the company to reduce costs and improve efficiency. 　　Since the beginning of this year, in order to thoroughly implement the 2023 \"Improving Quality and Efficiency\" action plan, the company’s Chemical Division, together with the Technology and Planning Department, Production and Operations Department, and Business Department, has worked closely together to predict in advance the price trends of the raw materials used in the ethylene production plants, thereby adjusting the composition of these raw materials dynamically. 　　During the summer, prices of propylene and butane dropped significantly. Seizing this opportunity, the company promptly adjusted the operation mode of its ethylene plants, reducing the amount of naphtha processed, and changed the setup from \"3.5 cracking units for processing naphtha + 2.5 cracking units for processing propylene and butane\" to \"3 cracking units for processing naphtha + 3 cracking units for processing propylene and butane\". 　　“This adjustment to the ratio of gaseous and liquid feedstocks used in the ethylene plant represents a new breakthrough; there is no existing experience to draw upon, so we have to figure things out on our own. ”Zhang Shengkui, manager of the First Chemical Engineering Department, said that it was not an easy task to change the processing ratio of naphtha and propylene-butane, which served as raw materials for the ethylene plant, from \"4:2\" to \"3.5:2.5\", and further adjust it to \"3:3\" at present. Due to the significant deviation between the gas-liquid phase processing ratios in this adjustment and those of the original design, with the gas-phase feed ratio exceeding the designed range, various problems will arise, such as reduced reliability of the gas-phase feed pump operation, imbalance in the produced fuel gas, and an excessive amount of propane circulating in the propylene distillation tower. 　　The First Chemical Engineering Department faced the challenges head-on by conducting risk assessments and preparing emergency response plans in advance, detailing the precautions for operations, providing training to the teams on multiple occasions, and making timely management adjustments. After a series of optimization adjustments, the pyrolysis furnace operates safely and stably under the new mode. 　　Next, Department 1 for Chemical Engineering will collect and analyze the operating parameters of various systems, and monitor changes in the yield of dienes and energy consumption in the plant, in order to provide baseline data for further optimization of the plant. At the same time, Gulei Petrochemical plans to add a gas-phase feed gasification system and carry out technical upgrades to cracking units 4 and 5 of the ethylene plant, in order to further enhance the flexibility of ethylene feedstock supply.