– H2Stopper 7106
Heavy oil from the refinery fluid catalytic cracking unit is normally hydrotreated to remove sulfur compounds and to upgrade the oil to reduce unsaturated molecules for additional downstream treatment and recovery. During the bi-yearly catalyst change out in the hydrotreating unit, the heavy oil is diverted to storage for sale as a low value bunker fuel oil.
During this period of several weeks, the oil must be treated by a H2S scavenger to avoid poisonous hydrogen sulfide gas from concentrating in the head space of the storage tank. Low levels of hydrogen sulfide will be released from the oil in storage as the oil stagnates and cools. It is very common for oil with only 10 ppm of H2S to have over 100 times this amount in the vapor space of the storage tank. The H2S concentration is the vapor space will vary with tank level, tank throughput and temperature but past experiences gave measurements of 300-1000 ppm, all dangerous levels. Personnel exposed to 500 ppm of H2S can loose consciousness and exposure levels from 700 to 1000 ppm can lead to death.