Parameter optimization and exergy efficiency analysis of petroleum coke-to-hydrogen by chemical looping water splitting process with CO2 capture and self-heating

Abstract

The petroleum coke-to-hydrogen process is promising since the output of high-sulfur petroleum coke is increasing year by year, the pollution emissions of its combustion for power generation are serious, and the refinery needs a lot of hydrogen. Therefore, this study establishes the process model and conduct the parameter optimization of the petroleum coke direct chemical looping hydrogen production process. The optimized mass ratios of oxygen carrier (Fe2O3), steam, and air to petroleum coke are 12.71, 2.98, and 2.18; however, that are 12.71, 1.79–2.08, and 4.53–5.32 when the proportion of the reduced oxygen carrier entering steam reactor is reduced from 100% to 60–70%, which can be operated in a self-heating mode with air preheating temperature of 278.54–816.80 ℃. When the proportion is increased from 60% to 65.32% and 70%, the product exergy of hydrogen is increased from 454.58 MW to 494.92–530.36 MW with about 100% CO2 capture and the exergy efficiency is therefore increased from 59.56 to 60.75% to 62.32–63.59% and 62.65–63.91%. This paper also studies the sulfur distribution and existing forms of sulfides. Finally, this study found that the exergy efficiency of the chemical looping hydrogen process with the proportion of 65–70% is significantly higher than that of the hydrogen production process by petroleum coke gasification.