(422c) Design Integration and Performance of Syngas Coolers and Steam System at the Kemper IGCC Power Plant

Authors: 
Keb, P. J. - Presenter, Southern Company
Vimalchand, P., Southern Company
Peng, W., Southern Company
Hewitt, A., Southern Company
Nelson, M., Southern Company
Liu, G., Southern Company
Guan, X., Southern Company
Pinkston, T., Southern Company
Madden, D. R., U. S. Department of Energy, National Energy Technology Laboratory
The Kemper County Project has demonstrated air-blown Transport Integrated Gasification (TRIG™) technology at a 2-on-1 combined cycle facility located in Kemper County, Mississippi. Kemper is the largest Integrated Gasification Combined Cycle (IGCC) project in the world, the first to use lignite as fuel, the first to capture and sell CO2, and the first to produce multiple byproducts from initial startup. The TRIG™ technology centers around the Transport Gasifier—a pressurized, circulating fluidized bed unit that features high riser densities and solids circulation rates.

Syngas generated in two Transport Gasifiers at Kemper first flows through specially designed syngas coolers that cool the syngas from 1740°F to around 600°F while generating large quantities of superheated steam from boiler feed water. The cooled syngas then proceeds through a gas cleanup process before flowing to combustion turbines for power generation. Exhaust from the turbines flows through triple-pressure-level heat recovery steam generators (HRSGs) to produce additional steam. The high pressure superheated steam from the HRSGs is combined with superheated steam from the gasifier island syngas coolers and passed to the steam turbine. Supplemental firing in the HRSGs was also available to produce an additional 60 MW of power. Due to the high mass flow generated from the air-blown gasifiers, the gasifier syngas coolers are capable of generating up to 45% of the steam to the steam turbine, a unique feature among IGCC plants that allows Kemper to recover up to 25% of the input coal energy.

Another unique aspect to the Kemper IGCC is the high degree of integration of the plant steam system between the gasification island and the combined cycle. Not only did Kemper produce a larger amount of steam in the gasification island than typical of IGCC plants, but multiple systems within the gasifier island, coal preparation area, and gas cleanup system consumed steam during startup and/or normal operation. The Kemper plant also features a Wet gas Sulfuric Acid plant (WSA), where sulfur removed from the syngas is converted into sulfuric acid. The WSA process releases heat, which produces additional steam. By highly integrating the plant steam system, the plant was able to meet its steam demand while maintaining efficiency. This paper discusses the design, commissioning, and operation of the Kemper steam system, with particular detail on the syngas cooler operation and performance. The paper also reviews the performance highlights and challenges of the system and suggests ways to further improve the integrated design.