Oxygen Enrichment Technology
As environmental legislation mandates stricter sulfur dioxide emission standards and products with lower sulfur contents, sulfur recovery plant loadings are increasing. To address this need, Air Products offers a range of oxygen-based technologies engineered to increase sulfur recovery unit (SRU) capacities by 10-150%, thereby often eliminating the need for building expensive new sulfur plants.
Benefits of SRU Oxygen Enrichment
Increased Acid Gas Capacity. When an SRU is faced with either hydraulic or velocity limitations, its capacity can be increased via oxygen enrichment of the combustion air.
Capital Expenditure Savings. SRU oxygen enrichment is implemented at only 5-25% of the new cost to build a new SRU, depending on the enrichment technology deployed.
Flexible Capacity Expansion. Oxygen enrichment provides a flexible method for SRU capacity expansion. Unlike physical expansion, no penalty is incurred for operating at lower-than-maximum capacity, since the costs of oxygen enrichment are essentially variable.
Quick Implementation. For low-level enrichment (21-28% oxygen), the oxygen supply can be "hot-tapped" into the combustion air main while the SRU is in operation.
Improved Conversion and Reduced Emissions. The reduction of nitrogen diluent leads to higher conversions in the Claus process and significantly reduced flow in the Tail Gas Unit (TGU).
Air Products SRU Oxygen Enrichment Technologies
SRU capacity is normally limited by hydraulic pressure drop through the unit. As combustion air is replaced with oxygen, inert nitrogen contained in the air is reduced, decreasing the SRU pressure drop and allowing more acid gas or sour water stripper gas feed to be processed. Air Products offers three distinct oxygen enrichment technologies for the SRU.
The figure illustrates the potential SRU capacity increase and technologies for various acid gas stream concentrations and oxygen enrichment levels.
Low-level oxygen enrichment technology (LLE). This entails injection of oxygen into the combustion air main through a custom designed oxygen diffuser. Oxygen compatibility, affected by the air piping metallurgy and cleanliness, generally limits this technology to about 28% oxygen. LLE yields about a 10-30% SRU capacity increase with minimal plant modification and investment cost and can be implemented with zero downtime
COPE™ technologies The COPE (Claus Oxygen-based Process Expansion) Process is a technology developed and jointly patented by Air Products and Chemicals, Inc. and Goar, Allison & Associates Engineered Systems, Inc. The process is a modification to the conventional Claus SRU that allows operation at oxygen enrichment levels beyond 28% and thus provides SRU capacity increases beyond those achievable via LLE. This requires overcoming two hurdles: oxygen compatibility and secondly, in most instances, excessive reaction furnace temperatures. The COPE technology comprises COPE Phase I which tackles the problem of oxygen compatibility via the use of a proprietary burner and COPE Phase II which adds gas recycle to moderate furnace temperature. These technologies can be implemented in two phases, depending on the timing of the required capacity increase.
Air Products and Chemicals, Inc., 7201 Hamilton Boulevard, Allentown, PA 18195-1501. Tel: 610-481-4911; Fax: 800-880-5204.