ENV-97-03 USING THERMAL OXIDATION TO CONTROL COMPLEX VOC VAPOR STREAMS

Description:

In 1996-97 the Bechtel Corporation undertook the engineering task to replace a large three-bed carbon adsorption unit in a 175,000 BbVday refinery. Replacement was necessary because the carbon unit was experiencing occasional shutdowns when the VOC load would exceed its capacity. The unit, which handled 20,000 SCFM of hydrocarbon vapors, was replaced with a regenerative thermal oxidizer (RTO). Installation of the RTO provided an opportunity not only to improve the reliability of the control device but also to route vapors from several additional VOC sources to a single oxidizer. Adding these other sources increased the degree of complexity because of the variability in their individual flow rates and compositions. Engineering, procurement, and installation were scheduled over about a 13-month period. During the engineering design phase, it was necessary to analyze each of the diverse streams being sequentially merged together so a safe operation could be ensured. Changing from a relatively benign carbon adsorption technology to an oxidation technology required a complete review of the safety and operability issues involved.