(34f) Advanced Control of Multiple Sulfur Recovery Units

Sulfur Recovery in a Refinery entails collecting sour vent gases (containing H2S) from a number of sources, including Hydrotreaters, Hydrocrackers, Crude Units, and others, then converting the H2S to a more useable form such as sulfuric acid or elemental sulfur. The feed rates and compositions to the Sulfur Recovery Units (SRUs) are not controllable at the SRU. In addition, most Refineries employ multiple SRUs operating in parallel. This gives rise to a number of process control challenges, including: 1)Load balancing among the various units 2)Response to changing loads (total feed load cannot be controlled) 3)Response to variable compositions (both geographic and dynamic variations) 4)Air/Oxygen load controls 5)Response to one SRU shutdown (rapid load increase for the remaining SRUs) This presentation will discuss the ramifications of these control problems along with the methodology used for successful implementation of the advanced control scheme for each.