Abstract: Based on the practices and characteristics of energy consumption in refining and chemical enterprises, with the help of process simulation, benchmarking and big data analysis etc., CNOOC Ningbo Daxie Petrochemical Co., Ltd. conducted a study on optimizing the energy utilization of the entire plant. Improvement measures and optimization plans were proposed in terms of process analysis, heat exchange network, reasonable utilization of low-temperature heat, and energy utilization of steam cascade. In addition, the optimization of direct feed ratio of DCC unit raw materials and the circulation heat exchange integration at fractionating column overhead, including recovery and utilization of low-temperature waste heat in the ethylbenzene unit, and the optimization of the feed heat exchange network in the toluene column, and the application of steam jet pump technology in the extractive distillation units were carried out. The economic benefit is about 57.27 million yuan per year, and the energy saving of 36 ktCE/a (1 tCE=29.3 GJ) is realized by energy-saving optimization transformation. The carbon dioxide emission is reduced by 103 kt/a, and the low-temperature heat utilization ratio of the whole refinery is increased by 16.3%.

Key words: refinery, energy conservation, low carbon, energy utilization, optimization, cascade utilization, heat pump