Studies On Optimization Of Hydrogen Network In ZRCC

Environmental policies and legislation are increasing the pressure for change in refining industry. Refinery must reduce sulfur and nitrogen in their products. Hence, hydrogen demand increases to remove them. Simultaneously, to meet the aromatics limits, refineries are reducing the operation load of naphtha reforming, with the result that less hydrogen is being generated. To rebalance supply with demand of hydrogen in refineries, mass integration was introduced to hydrogen networks, marginal profit pinch method, hydrogen purity pinch method and superstructure optimization method are studied by previous researchers, in this thesis hydrogen networks is investigated extensively, and it consists of four parts of contents as follows:1. The situation of hydrogen supply and demand in refinery is introduced first, and the corresponding methods refinery used to solve it, which include producing more hydrogen and purification method. Then the art-of-state of mass integration was completely reviewed covering through the research scheme to application of integration technology. Finally, the process of hydrogen integration is summarized, which provided solid base for future work.2. The units which constitute the hydrogen networks in ZRCC are introduced, including the processes, models and operating data of hydrotreater, hydrocracker, reforming, hydrogen plant and pressure swing adsorption, et al. More attention was paid to hydrotreater processes, for example, the influence of operating condition on reaction; the demand of make-up hydrogen, recycle hydrogen; the purity and usage of high pressure purge, low pressure purge, HaS removed gas and fuel gas produced by hydrotreaters.3. The optimum supply of hydrogen in refinery is studied by pinch technology, which forms the basis of a systematic approach to solving the complex problem of hydrogen system management. Pinch technology is established on the concept of hydrogen sinks and hydrogen sources. Using the data of sinks and sources, hydrogen composite curves and hydrogen surplus curve are plotted. The pinch point means the minimum utility target. In a case study of Zhenhai company, it was shown that the whole costcan be reduced by 6.68 million per year. The curve can also help to select the flow streams which should be purified. In our example, if the feed streams of PSA is changed, 27.23million can be saved further.4. Pressure ranking is introduced to synthesize the refinery hydrogen networks. Pressure ranking is used in many aspects in industry, and it can also be used in hydrogen networks because of its simpleness and economics. The hydrogen networks with pressure ranks are modeled and optimized by the superstructure method. The optimization problem was solved by SQP algorithm. In our example, three kinds of pressure ranks are optimum, which are SOMpa, lOOMpa and 200Mpa. Comparing with the designed hydrogen networks, optimized networks with these three pressure ranks can save ?2.23 million per year, and if the compressors are reorganized, ?30 million electric fee can be saved per year further.