Catalytic Hydrodesulfurization Process - continued.

In a typical catalytic hydrodesulfurization unit, the feedstock is deaerated and mixed with hydrogen, preheated in a fired heater (600-800 deg F or 315-425 deg C) and then charged under pressure (up to 1,000 psi) through a fixed-bed catalytic reactor.

In the reactor, the sulfur and nitrogen compounds in the feedstock are converted into hydrogen sulfide and ammonia (H2S and NH3.) The reaction products leave the reactor and after being cooled to a low temperature enter a liquid/gas separator.

The hydrogen-rich gas from the high-pressure separation is recycled to combine with the feedstock, and the low-pressure gas stream rich in H2S is sent to a gas treating unit where H2S is removed. The clean gas is then suitable as fuel for refinery furnaces.

The liquid stream is the product from the hydrotreating unit and is normally sent to a stripping column for removal of H2S and other undesirable components.