Ethylene Production

Pygas Hydrotreating (DPG™ I & II)

DPG™ I & II are pyrolysis gasoline hydrogenation technologies. The pyrolysis gasoline is a major by-product produced in an ethylene plant. DPG I is utilized to saturate the diolefins and acetylenes contained in the pyrolysis gasoline stream. The saturation of the diolefins and acetylene is required prior to using the pyrolysis gasoline as a gasoline blending stock. DPG II is used to saturate the olefins and to remove the sulfur in the pyrolysis gasoline stream. Saturation of the olefins and sulfur removal are required prior to sending the pyrolysis gasoline stream to an aromatics extraction. Both DPG I and DPG II are catalytic hydrogenation processes that occur in separate fixed bed reactors. Fractionation is provided to fit the ultimate configuration required by the desired by-product slate. DPG I and DPG II are the most widely-used pyrolysis gasoline hydrogenation technologies, with more than 50 units in operation or under design.


DPG™ I & II are highly energy efficient. Heat interchange with the reactor systems ensures minimum energy input. No fired heater is required due to this heat interchange. DPG I & II operate at low pressure and low recycle rates around the reactor. Feed hydrogen compression is not required. These all lead to minimum capital costs. Unit reliability is high. The average on-stream factor of the operating units is nearly 99%. Much of this reliability is due to design steps taken to minimize equipment fouling. These steps include the elimination of feed preheating equipment which can readily foul and the ability to operate at turndowns as low as 25% of nominal design capacity as the amount of pyrolysis gasoline produced in the adjoining ethylene plant changes with changes in feed and cracking conditions. When licensed with Lummus Technology's ethylene technology, single source design services and single source guarantees for the cracker and pyrolysis gasoline hydrotreater helps to ensure seamless execution of the project.