Optimization of the Hydrogen Network in an Oil Refinery

The stricter environmental and product quality regulations are pushing oil refineries to increase hydrotreatment and hydrocracking capacities to lower the sulfur contents in the products, thus leading to a higher demand for hydrogen. The efficient use of hydrogen becomes a necessity. This project used two different approaches, which are Pinch Technology (PT) and mathematical modeling using mixed integer nolinear programming (MINLP), to obtain optimal Hydrogen network designs in a refinery. The hydrogen consuming and producing processes of an oil refinery were analyzed and identified. Computation of the missing information in the current scenario was conducted and then a reference case was established. With the focus on various purities, pressures and flowrates for the hydro-processing units, a pinch analysis was realized in order to set a target for the minimum hydrogen requirement of the system. A MINLP method was further created to optimize the hydrogen network with the objective functions to minimize the hydrogen consumption and the total annualized cost. A number of scenarios were analyzed considering different hydrogen production technologies and electricity suppliers. The results show that the scenario with the best economical performance is the one with hydrogen production from Steam Methane Reforming without Carbon and Capture and electricity supplied by a wind farm with a Total Annualized Cost of 142 [M CHF/year]. However, the one with hydrogen production from Steam Methane Reforming with Carbon Capture and electricity from a wind farm has the best overall performance with a total annualized Cost of 222 [M CHF/year]. The technologies using electrolysis for the production of hydrogen have the lowest CO2 emissions but are 98 [M CHF/year] more expensive than the previous scenario. However, with the evolution of green hydrogen technologies, this cost gap is expected to decrease.