Online shutdown, heating, and purging achieved for the air separation expander in Hubei Fertilizer Plant

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Hubei Fertilizer’s air separation expansion machine underwent online shutdown, heating, and purging – Author/Source: China Chemical Industry News, Date: 2019-02-12, Clicks: 89. Sinopec Hubei Fertilizer Company recently carried out online shutdown, heating, and purging of its air separation expansion machine for the first time; this measure eliminated the bottleneck associated with increased load on the facility, laying a foundation for improving its performance and efficiency as well as for enhancing the production system. 　　The cooling capacity provided by the booster turbine expansion mechanism can compensate for the cooling loss in the air separation system, and it is essential for the stable operation of the plant. Over the past few days, the expander of this company has experienced ice blockage, resulting in insufficient cooling capacity in the system. This has affected the oxygen production volume of the air separation unit as well as the loads downstream, and has also led to issues such as reduced rotational speed and surge, thereby impacting the operation of the unit. It is urgent to carry out equipment heating and degassing procedures. 　　The company’s 48,000 standard cubic meter domestic air separation unit operates in a single series configuration, without any backup systems for oxygen or nitrogen; moreover, the heating and purging technique involved is complex and difficult to implement. The company’s technical staff conducted research, communicated with industry experts, systematically calculated the heat load and material balance, evaluated the technical measures necessary to achieve system equilibrium, and repeatedly discussed the possibility of shutting down the expander online. 　　Subsequently, the company’s technical staff further refined the process plan for stopping the machine and heating it, carried out joint tabletop simulations with upstream and downstream parties, added liquid nitrogen to maintain thermal balance in the system, and coordinated with various departments to closely monitor changes in the load on the upstream and downstream sections of the equipment as well as product quality. As a result, the water content in the gas exiting the expander after heating met the specified standards, allowing the online shutdown, heating, and purging process for the air separation expander to be completed ahead of schedule.