【Ten Years of Rapid Development in Chemical Equipment】1837–2014: Successful reuse of exhaust gases from China’s first polyethylene cryogenic plant

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2024: Safety first, prevention foremost. Let’s give recognition and support to the achievements made in China’s chemical technology and equipment sector. **********************【Ten Years of Progress in Chemical Equipment】A continuously updated summary post – feel free to join the discussions: https://bbs.hcbbs.com/thread-3576046-1-1.html (Source: Haichuan Chemical Forum Website) ***************** In June 2014, the first domestic system for reusing exhaust gases from polyethylene deep-cold processing was successfully implemented at Zhongyuan Petrochemical; this system enables savings of 3.04 million Nm3/h of nitrogen gas per year, which is equivalent to 30% of the nitrogen gas consumed by traditional systems. It also generates annual savings of 1.42 million yuan, while reducing energy consumption by 1.096 kilograms of standard oil per ton. 　　The polyethylene cryogenic separation unit applies the power-free ammonia recovery technology to the recovery of polyethylene off-gases. The system utilizes a multi-channel cyclic expansion process, which provides sufficient cooling capacity; as a result, hydrocarbon components can be recovered effectively without the need for external power input. Compared with traditional PSA recovery processes, it features a simpler process flow and easier operation control; it can reduce both the land area required and the investment amount by half, with the investment being recovered within 3 months of operation. 　　At the end of November 2012, after the 1500 Nm3/h polyethylene unpowered mixed hydrocarbon recovery unit at Zhongyuan Petrochemical was put into operation for the first time, the polyethylene workshop carried out careful operations and strengthened management to ensure the safe, stable, and long-term operation of the unit. To continue to leverage the role of this facility as a model in the polyethylene industry, the workshop has actively pursued technical solutions, focusing on ways to utilize the approximately 500 m3/h of residual exhaust gases in order to extract as much of the heavy hydrocarbons with a molecular weight of C2 or higher from the flare gas, thereby achieving clean production and energy savings. After evaluating various options, the deep-cold emissions from this workshop are sent to the flare, while the tail gas rich in 95% N2 is fed into a degassing chamber after pressurization, to serve as a substitute for the nitrogen used under the original design conditions. 　　After a period of trial operation, the data showed that the entire system was safe and stable in operation, achieving the goal of saving nitrogen.