【Haichuan’s Best Practices】Expand high-efficiency combined systems to reduce reliance on purchased steam

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Maoming Petrochemical: Expanding the heat integration system to reduce steam purchases 2019-02-18 Source: Sinopec News Network Print article Petrochemical news There are 3 CFB boilers in Maoming Petrochemical’s refining area, which are used to supply steam to the refining units. In January, Boiler No. 3 was taken out of service for maintenance, while Boilers No. 1 and No. 2 continued to operate. The maximum steam output of the two CFB boilers was 520 tons per hour, which was not sufficient to meet the steam demands of the refinery area; therefore, low-pressure steam from Maoming Thermal Power Plant was required. Purchasing steam from Maoming Thermal Power Plant means that, due to fluctuations in the power generation load of that plant, the steam supply volume varies greatly, which has a significant impact on the safety of steam supply to the refinery area and leads to disruptions in refinery operations. The leadership of Maoming Petrochemical Company attached great importance to this issue, and organized departments such as the Production Management Department, the Thermal Power Division, and the Refining Division to work together to find solutions. After extensive discussions and practical evaluations, they decided to expand the heat integration system by adding more cooling and heating sources, reducing the steam used for internal purposes by the boiler equipment, and increasing the amount of steam supplied by it. The technical experts from the thermoelectric division kept a close eye on the site and took proactive measures to optimize the operation of the deaerators. They redirected the steam leakage from the front steam seal of the turbine to Deaerator No. 1, and directed the return water from the boiler’s exhaust heat exchanger to Deaerator No. 2. This ensured that even with reduced inflow to Deaerator No. 2, the heating steam control valve could remain at a sufficiently large opening level, allowing for automatic control. As many desalinated waters as possible, along with all of the turbine condensate, will be directed to the combined heat and power low-temperature heat exchanger in order to increase the cold source. The thermoelectric division and the refining division strengthen communication by exchanging information daily through DingTalk groups to keep track of the load conditions of their respective units. The thermoelectric division focuses on optimizing the operation of the boiler units, while also coordinating with the refining division to redirect as many heat sources as possible to the low-temperature heat exchangers in order to maximize the use of heat sources. It also involves adding a low-temperature heat exchange system interface to the real-time database system, which facilitates monitoring by managers and dispatchers and enables timely coordination and handling by both parties. By enhancing heat integration, the return water temperature of the low-temperature heat exchange system can be increased from 82°C to over 120°C. The amount of low-pressure steam used internally by the CFB unit can be reduced by about 20 tons per hour, which helps to address the issue of insufficient steam supply for external use during maintenance of a CFB boiler, thereby reducing costs associated with purchasing steam from external sources. It is estimated that during the maintenance period, the cost of purchasing steam from external sources can be reduced by about 2.5 million yuan. Moreover, this attempt provides a valuable reference for increasing the steam supply capacity of CFB boilers and ensuring a stable and sufficient supply of steam. (Weng Qiaoshu, Qin Xiaoguang)