What is a decontamination process all about?
Decontamination process is the first stage of plant shut down activities upon draining of petrochemical products or feedstock from the process lines, vessels or columns back to the storage tanks. The process is primarily to evacuate facilities and equipments from toxic and combustible gasses or vapor in order for maintenance personnel to perform maintenance task without safety hazards. An outstanding decon assignment is to ensure the facilities achieve zero LEL and toxic gas-free in the shortest time in order to achieve the shortest turnaround time for the facilities to resume production way ahead of schedule.
Virtually every single equipments and facilities of any refineries that require human intervention for mechanical works during plant maintenance has the economical values to perform decon job. Such important facilities are identified to be: Crude Distillation Unit, Deethanizer Unit, Crude Fractioning Distillation Unit, Hydro Cracker, Coker, Aromatic Plant, etc, with their associated columns, heat exchangers, vessels, discharge line, overhead, etc.
The target of decon task is to eliminate toxic gasses such as Hydrogen Sulfide (H2S) and Benzene, combustible gasses such as traces of hydrocarbon and pyrophoric materials to achieve zero LEL. Normally such contaminants are dealt with conventional method by purging the facilities with steam continuously, the resultant exhaust will be discharged to the flaring tower and residual contaminants will be vented to atmosphere upon achieveing the permissible level. SUch method is not known as decon task, it is non-economical for refinery operator as the whole process can take as long as 7 days or more for a sour crude system and it does not guarantee to be environmental friendly.
Decontamination chemicals are designed to replace the conventional methods during turnaround. The chemicals are injected at appropriately sized inlet point employing steam injection or circulation method. The objective is to ensure the facilities achieve a safe condition that is free from hazardous gases to allow personnel to enter to perform maintenance activities as soon as possible. The next step is to ensure that the by-product is environmental friendly (according to world HSE standards) and can be discharged safely into effluent treatment systems or the environment without further treatment.