Zhenghe Group has successfully carried out hydrogen desulfurization recycling for its gasoline and diesel hydrogenation unit during unit overhauls.
There was a large quantity of hydrogen sulfide in the recycled hydrogen from the hydrogenation unit, which brought down hydrogen purity and pressure and made it harder for raw material desulfurization. At the same time, it sped up coking of catalysis. The lack of desulfurization in the original design required the use of torches to control hydrogen sulfide concentration, which not only had an economic impact, but also created environmental pollution.
To upgrade diesel quality, protect the environment and reduce hydrogen loss, Zhenghe decided to renovate its hydrogen desulfurization recycling project. The recycled hydrogen went through a high-pressure separator, entered a liquid separation tank and then a desulfurization tank. Then the desulfurized hydrogen was pressurized in a compressor after going through the liquid separating tank again. The pregnant solution at the bottom of the desulfurization tank went into a flash tank, and acid gas and low grade gas came out of the top of the unit. The hydrocarbon-free solution containing hydrogen sulfide came directly out of the unit.
The project has increased hydrogen concentration and pressure, making it easier to desulfurize raw oil. It could produce 48,000 standard cubic meters per hour of recycled gas, with hydrogen sulfide less than 100 parts per million in the recycled hydrogen, laying a solid foundation for diesel quality upgrade. It could save 4.8 million yuan ($790,210) per year in costs, another growth point for Zhenghe.