Application: The COPE Oxygen Enrichment Process allows existing Claus sulfur recovery/tail gas cleanup units to increase capacity and recovery, can provide redundant sulfur processing capacity, and can improve combustion performance of units processing lean acid gas.
Description: The sulfur processing capacity of typical Claus sulfur recovery units can be increased to more than 200% of the base capacity through partial to complete replacement of combustion air with pure oxygen (O2). SRU capacity is typically limited by hydraulic pressure drop. As O2 replaces combustion air, the quantity of inert nitrogen is reduced allowing additional acid gas to be processed.
The process can be implemented in two stages. As the O2 enrichment level increases, the combustion temperature (1) increases. COPE Phase I, which does not use a recycle stream, can often achieve 50% capacity increase through O2 enrichment to the maximum reaction furnace refractory temperature limit of 2,700ºF – 2,800ºF. Higher O2 enrichment levels are possible with COPE Phase II which uses an internal process recycle stream to moderate the combustion temperature allowing enrichment up to 100% O2.
Flow through the remainder of the SRU (2, 3, and 4) and the tail gas cleanup unit is greatly reduced. Ammonia and hydrocarbon acid gas impurity destruction and thermal stage conversion are improved at the higher O2 enriched combustion temperatures. Overall SRU sulfur recovery is typically increased by 0.5% to 1%. A single proprietary COPE burner handles acid gas, recycle gas, air and O2.
Operating conditions: Combustion pressure is from 6 psig to 12 psig; combustion temperature is up to 2,800ºF. Oxygen concentration is from 21% to 100%.
Economics: Expanded SRU and tail gas unit retrofit sulfur processing capacity at capital cost of 15% – 25% of new plant cost. New plant savings of up to 25%, and redundant capacity at 15% of base capital cost. Operating costs are a function of O2 cost, reduced incinerator fuel, and reduced operating and maintenance labor costs.
Licensor: Goar, Allison & Associates, Inc., an Air Products Company.
