TransGas Development Systems to Build $3B CTL Plant in West Virginia; 6.5M Barrels of Gasoline Per Year
|Flow diagram of the PRENFLO gasification process with direct quench (PDQ) to be used in the TransGas plant. Click to enlarge.|
TransGas Development Systems LLC (TGDS) plans to build a $3B coal-to-liquids (CTL) plant in Mingo County, West Virginia, according to company announcement made during the West Virginia Energy Summit. Projected to be operational by 2013, the plant will be built in Mingo County’s new energy park near Gilbert. TGDS estimates the facility will use up to 3 million tons of locally mined coal a year to produce more than 6.5 million barrels of gasoline.
TGDS has signed a licensing agreement with Uhde Corporation of America for two 1,000 MWth PRENFLO (PRessurized ENtrained FLOw) gasifiers in the Direct Quench version (PDQ). The PRENFLO process, which operates at pressures of 40 bar and higher, is a further development of the Koppers-Totzek process developed in the 1940s, which operates at atmospheric pressure.
The PDQ version of the process is an optimized design of the basic PRENFLO process for chemical applications in which hydrogen-rich syngases are required. PDQ combines the dry feed system, multiple burners and membrane wall of the base PRENFLO system with a proprietary water quench system which saturates the raw syngas with water for subsequent gas treatment. The PDQ process also removes the requirement for capital-intensive systems such as the waste heat boiler system, the dry fly ash removal system and the quench gas compressor.
In the process, feedstock is prepared into a feed dust—about 80% of the dust is smaller than 0.1 mm and has a water content of approximately 1-2 wt% for hard coals and approximately 8-10 wt.% in the case of lignite. The feed dust is gasified in the PRENFLO gasifier using oxygen and steam as the agent. The gasification temperature is higher than the ash melting temperature, allowing the coal ash to be removed as slag.
The raw syngas, containing mainly CO and H2, is quenched with water and then cleaned in a scrubber. The filter cake from the slurry filtration system is recycled to the gasifier.
The PRENFLO technology handles all types of coal as well as petroleum coke, char and biomass. The gasification process produces economically valuable by-products such as slag and fly ash used in construction.
The syngas can be used in a number of applications. For synthetic gasoline production, Uhde uses ExxonMobil’s Methanol-to-Gasoline (MTG) catalytic process. (Earlier post.) Methanol is produced from the syngas, and then converted to gasoline. The conversion of methanol to hydrocarbons and water is virtually complete, Uhde says, and essentially stoichiometric in the process.
The reaction is exothermic with the reaction heat managed by splitting the process into two parts. In the first, the methanol is converted to an equilibrium mixture of methanol, DME (dimethyl ether) and water. In the second part, the equilibrium mixture is mixed with recycle gas and passed over a shape-selective catalyst to form hydrocarbons and water.
ExxonMobil and Uhde have been working together on MTG since the 1980s. In 2006, Shanxi Jincheng Anthracite Coal Mining Co. Ltd (JAM) awarded Uhde a contract to license and supply basic engineering, equipment and services for an MTG plant based on ExxonMobil’s fixed bed technology. Part of a demonstration project, the plant has a capacity of 2,600 barrels per day.
Separately, in July 2008, CONSOL Energy announced a joint venture—Northern Appalachia Fuel LLC (NAF)—in Marshall County to construct a CTL plant. NAF is currently negotiating with ExxonMobil Research and Engineering to license the MTG technology.
The joint venture formed by CONSOL to develop the plant will design a carbon-capture system in which waste carbon emissions from the plant will be sequestered in a deep saline aquifer. (Earlier post.)