Originally owned by Global Energy, Destec and Dow, later by ConocoPhillips, and currently owned by CB&I, E-Gas™ coal gasifier technology was first demonstrated at the Louisiana Gasification Technology Inc. (LGTI) integrated gasification combined cycle (IGCC) plant (also known as the Dow Syngas Project), which operated from 1987 to 1995. The technology is currently incorporated in the Wabash River Coal Gasification Repowering Project, funded under the DOE Clean Coal Demonstration Program in the 1990s. The Wabash IGCC plant has been in operation since 1995.
The E-Gas™ coal gasifier is a pressurized, upflow, entrained slagging design with a unique two-stage operation. Like the GE gasifier, E-Gas™ is a slurry-feed gasifier. Wet crushers produce slurries from the raw feed coal. Coal slurry concentrations typically range from 50 to 70% depending on the inherent moisture and quality of the feed coal. About 75% of the total slurry feed is fed to the first (or bottom) stage of the gasifier through mixer nozzles, along with 95% pure oxygen. This stage involves highly exothermic oxidation reactions and operates at typically 2,600°F and 400 psig. These conditions do not allow the formation of hydrocarbon gases and liquids. Ash in the coal melts and exits through a tap hole at the bottom of the gasifier into a water quench, forming an inert vitreous slag product.
Hot synthesis gas (syngas) from the first stage then enters the oxygen-free second (top) stage where the remaining slurry feed is injected. Endothermic gasification and devolatization reactions take place at 1,900°F, resulting in the formation of some hydrocarbons in the product gas and the production of char, which are both recycled to the first stage where they are readily gasified. The second stage can be operated with some flexibility, facilitating fine tuning of the syngas composition in terms of hydrogen/carbon monoxide (H2/CO) ratio and methane content. This can reduce costs of downstream processes that otherwise might be required to adjust syngas composition.
The product gas exits the gasifier at 1,900°F and is cooled in a fire-tube cooler to 1,100°F, generating saturated steam. The E-Gas process utilizes a dry solids-gas separation system to remove particulates from the raw syngas stream. This system is reliable and more efficient than wet solids scrubbing systems and has none of the grey or black water treatment and disposal issues associated with wet solids removal. Downstream of the particulate dry scrubber, chlorides are removed from the cooled syngas in a wet scrubber. The syngas is then treated for removal of carbonyl sulfide and hydrogen sulfide before being used for energy conversion or other applications.
Demonstration and Early Commercialization
The Wabash River IGCC Power Plant is a 260-MW facility located in West Terre Haute, Illinois which uses E-Gas™ gasification technology. It is owned and operated by SG Solution (previously by PSI Energy, Inc.) The project was selected by the DOE as one of the three Clean Coal Demonstration Projects, beginning operation in 1995.