Cyclotetrasulfide content after etherification
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Recently, the sulfur content in the tetrahydrocarbon product obtained after etherification in the etherification unit has increased from the normal level of 3 mg/m3 to around 13 mg/m3. I would like to ask the experts: what factors could cause an increase in the sulfur content in this tetrahydrocarbon product?
The catalyst also contains sulfur; could the reaction temperature and pressure be fluctuating as well? Is the increase in volume too large or too rapid? Has the reactor’s temperature spiked?
There is no over-temperature or over-pressure condition; it is operating under normal processing load
It should be H2S that enters the C4 fraction; let’s check whether the carbon tetra-sulfur compound obtained after refining the pyrolysis liquefied gas upstream is of acceptable quality
There is an alkali washing step before MTBE, so the probability of hydrogen sulfide forming is low. Moreover, the boiling point of H2S is similar to that of propylene and propane; with a gas separation unit in place beforehand, it is likely that the gas will end up in the propylene and propane streams, rather than reaching the MTBE unit
Most of the sulfur that can enter MTBE is dimethyl disulfide, which is the disulfide produced during the alkaline washing and regeneration of desulfurized alcohols.