PROJECT: Hydrogen Sulfide Incinerator Replacement for Geothermal Generation

A large number of generating units were installed in the Geysers area around Clear Lake, CA, while PG&E owned these facilities. A by-product of using the steam out of the ground is the off gassing of hydrogen sulfide (H2S) gas which has a strong odor of rotten eggs. While PG&E owned these units, the local air pollution control district implement regulations to control release of H2S gas. PG&E had their Department of Engineering Research build a pilot incinerator at one of the generating site's location. In the year 2000, this pilot incinerator was at least 5 years old and was failing. An independent power producer (IPP) purchased the majority of PG&E's geysers units and also bought a used incinerator of much larger capacity to replace the pilot incinerator. The used incinerator system consisted of a simple antiquated hardwired analog control system using basic control theory to maintain combustion and quenching water flow rates.

The IPP requested that the control system be upgraded to an Allen-Bradley ControlLogix PLC including building the burner management system in a stand-alone ControlLogix PLC. The IPP specified that process safety and stability were a premium due to past challenges from the original prototype incinerator. Therefore, process and control engineering design, testing, construction, and startup services were provided for a completely new and upgraded control system. Included in these services was the development and finalization of the functional process organization for H2S abatement.