Hydrogen production feedstock for the hydrorefining unit
Thread Content
Can catalytic dry gas and coking dry gas be mixed to use as a raw material for hydrogen production? Will this cause any difficulties in operation?
Yes, it goes through hydrogenation and desulfurization before entering the conversion, medium-pressure shift, low-pressure shift, and PSA systems for hydrogen production.
Refinery gas (catalytic dry gas, coking dry gas) is a cheap raw material for hydrogen production (ammonia synthesis). Its gas composition mainly consists of C1–C4 alkanes, with significant amounts of olefins and organic sulfur as well; the olefin content is generally between 6% and 20%, while the organic sulfide content is around 200 μg/g. The form of sulfur present is also quite complex. Therefore, for the olefins and organic sulfur present in such feedstocks, hydrogenation conversion catalysts must be used to convert the olefins into alkanes and the organic sulfur into H2S; thereafter, a zinc oxide desulfurization agent is employed to reduce the mass fraction of total sulfur in the feedstock to 0.1×10-6.
The water vapor light hydrocarbon conversion process technology offers advantages such as low investment costs, low energy consumption, as well as high operational reliability and flexibility. The feedstocks suitable for hydrogen production via water vapor light hydrocarbon conversion can be divided into gaseous hydrocarbons and liquid hydrocarbons. Gaseous hydrocarbons mainly include natural gas, various hydrogenated dry gases, reformed dry gases, or treated coker dry gases, catalytic dry gases, etc ； Liquid hydrocarbons mainly include straight-run naphtha, hydrogenated light naphtha, reformation residue oil, and tail oil. When selecting raw materials for hydrogen production, gas materials with a high H/C ratio, low sulfur content, and low cost should be given priority, such as hydroprocessed dry gas, refinery gas, and natural gas. The gaseous feedstocks need to undergo pretreatment, such as desulfurization and pre-conversion, to convert organic sulfur into inorganic sulfur and to convert olefins into alkanes through hydrogenation. Currently, newly built hydrogen production facilities in China generally use gaseous feedstocks, allowing for stable operation with no issues.
Absolutely! However, desulfurization is not required, especially for hydrogen-rich dry gas, which has a high hydrogen sulfide content.
Generally, for hydrogen production from dry gas, natural gas and hydrogenated dry gas are the preferred choices; the worst options are coking dry gas and catalytic dry gas, as these contain high levels of impurities, abundant light hydrocarbons, and high sulfur content. Nowadays, many facilities use coking dry gas or catalytic dry gas for hydrogen production, and the hydrogen production equipment can be designed accordingly based on the demand for hydrogen.
It’s completely possible; all that’s needed is to install pre-hydrogenation and desulfurization/dechlorination reactors before entering the conversion furnace.