Optimization of refinery hydrogen distribution systems considering the number of compressors
Growing hydrogen demands in oil refining are forcing many refiners to optimize their hydrogen distribution networks in order to address the demands without incurring excessive energy consumption, capital investment and operating costs. In addition to the use of hydrogen utility, the foremost consumption of energy is the compression power. In order to express hydrogen consumption and compression power on a common basis, this study uses the convention of "exergy standard" in the optimization of hydrogen distribution networks. Besides, the optimization of hydrogen networks should also minimize the number of hydrogen compressors, which are among the most expensive devices in a refinery. Consequently, two mathematical models are proposed for hydrogen distribution network synthesis. A sequential optimization strategy is utilized to determine the targets of total exergy consumption and number of compressors. In addition, several practical strategies for compressor combination are introduced which can further reduce the number of compressors. The proposed methodology can be applied to hydrogen networks with either the flowrate constraint or the pure hydrogen load constraint imposed on sink streams. The applicability and effectiveness of the proposed methodology are illustrated by two case studies.