Matthew Bailey - Optimized Gas Treating, Inc.
The Claus Waste Heat Boiler (WHB) is a critical piece of equipment in the sulfur recovery unit (SRU). As refiners and gas producers have pushed towards higher sulfur feedstocks placing more load on the SRU, failures have become more common. These higher failure rates have come at a time when uptime metrics and environmental constraints have become concurrently stricter. In this work, a set of case studies were run using a newly developed rate-based heat transfer and chemical reaction rate model of the Waste Heat Boiler. The rate-based model provides quantitative insights into several aspects of the WHB that impact the sulfur plant performance:
Recombination reactions that occur at the front of the WHB.
- H2 + ½ S2= H2S
- CO + ½ S2=COS
- These reactions not only influence sulfur recovery, air demand, and hydrogen production in the SRU, they also impact the heat flux and performance of the WHB. These reactions occur towards the front (inlet) side of the WHB and are exothermic. The “hidden” heat associated with these reactions tends to increase heat flux near the critical tube-to-tubesheet joint.