Increase capacity and recovery of existing Claus sulfur recovery/tail gas cleanup units, provide redundant sulfur processing capacity, and improve combustion performance of units processing lean acid gas through oxygen (O2) enrichment.
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 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 about 2,700–2,800°F. 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 increased by 0.5% to 1%. A single proprietary COPE burner handles acid gas, recycle gas, air and oxygen.
Operating conditions: Combustion pressure from 6 psig to 12 psig; combustion temperature up to 2,800°F. Oxygen concentration from 21% to 100%. SRU sulfur recovery is 95% to 98%.
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., and Air Products and Chemicals, Inc.
