SulfaTreat process is similar to the iron sponge process. It uses a patented proprietary mixture of ferric oxide and triferric oxide to react with H2O to sweeten gas streams. In SulfaTreat process the iron oxides are supported on the surface of an inert, inorganic substrate forming a granular material, while in the iron sponge process the ferric oxide is impregnated on wood chips. The SulfaTreat starting material and the spent product are safe and stable. The spent product can be recycled or disposed in a landfill.
Two vessels arranged in series, a lead/lag arrangement, will allow the SulfaTreat material to be used more efficiently with no interruption in unit service and greater process reliability. The first vessel, the “lead” unit, acts as the “working” unit to remove all the H2S at the beginning of a treatment period with its outlet H2S increasing over time. The exit gas from the first vessel can go to the second vessel, the “lag” unit, for further polishing or bypass the second vessel as though the first vessel is operating in a single vessel arrangement. The second vessel is to be placed in operation as the lag unit to polish the H2S remaining in the gas when the lead unit outlet H2S starts to approach the specification.
Once the lead unit inlet and outlet concentrations are equal, the SulfaTreat material is considered spent or exhausted. Then, the gas flow is directed to the second vessel, which becomes the lead unit. The spent material is removed from the first vessel and the fresh SulfaTreat material reloaded to be placed into operation as the lag unit without gas flow interruption. Removal of the spent SulfaTreat material and the reload of the fresh material could be conveniently scheduled using the change-out “window” available without exceeding maximum outlet H2S concentrations when operating in this lead/lag mode.