Abstract

Coking dry gas from delayed coking processes is rich in light hydrocarbons, making it a comparative ideal feedstock for hydrogen production. Current steam reforming processes have the disadvantages of high energy consumption and carbon emissions, whereas chemical looping hydrogen generation produces high-purity hydrogen with inherent carbon capture and a low energy penalty. Therefore, this study proposes a coking dry gas chemical looping process for hydrogen production, considering two schemes (external-heating and self-heating) and optimizes key parameters of the systems in detail. The optimal molar ratios of the oxygen carrier, steam, and air to coking dry gas for the externally heated and self-heated schemes were 8.62, 4.90, 2.27 and 8.62, 3.78, 4.07, respectively. The energy efficiencies of the two systems can reach 76.55% and 77.93% with carbon capture rates of 76.29% and 100%, 3.26% and 5.13% higher than efficiency of the steam reforming system. The self-heated system had the highest hydrogen production of 2.67 kmol/kmol coking dry gas. Based on a self-heated hydrogen system, a chemical looping hydrogen generation system was coupled with a solid oxide fuel cell. This integrated system achieved the better power generation performance with an anode recycling ratio of about 0.7. The net electrical efficiency of the system was 58.79%, which is 3.34% higher than that of a steam reforming system coupled with a solid oxide fuel cell. The results reveal that the chemical looping systems are suitable for the clean utilization of dry gas and provide a strategy for efficient hydrogen production and power generation.

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