Range Fuels, Inc., formerly Kergy, a company that uses biomass gasification to produce ethanol, will build its first wood cellulosic ethanol plant in Treutlen County, Georgia. The company, founded by Khosla Ventures, estimates that this plant—combined with others to follow—will have the capacity to produce more than 1 billion gallons of ethanol per year.
Wood waste from Georgia’s millions of acres of indigenous Georgia Pine will be the main source of biomass for the ethanol production.
The Range system, which it calls K2, uses a two-step thermochemical conversion process. It first gasifies biomass waste such as wood chips, agricultural wastes, grasses, cornstalks, hog manure, municipal garbage, sawdust and paper pulp to create a syngas that it then converts catalytically to ethanol.
In addition to supporting a broad range of biomass for feedstock, the K2 system is also modular. Depending upon the quantity and availability of feedstock, the K2 system can scale from entry level systems to large configurations. This range of system performance will allow the K2 to be placed near the biomass location reducing transportation costs, and will allow the most economical size system to be deployed.
The Range system is based on a gasifier and ethanol reactor developed by Robert (Bud) Klepper, originally called the Klepper Pyrolytic Steam Reforming Gasifier (PSRG) with a Staged Temperature Reaction Process (STRP) and the Klepper Ethanol Reactor. Klepper had run his own company, called BioConversion technology, and targeted the gasification technology at coal as well as biomass feedstocks. (Earlier post.) He is now an advisor to Range.
In earlier evaluations, the Klepper PSRG with STRP system was found to generate syngas from coal, coal slurry, coal fines and other biomass feedstocks with energy content in the range of 400–600 BTU/ft3 at an average thermal energy conversion efficiency of 75%.
The Klepper system has the highest energy efficiency of any system and the highest syngas energy content of any thermochemical biomass conversion system that has been developed for biomass inputs of less than 1,000 tons/day, according to a comparative evaluation of such systems performed for the East Bay Municipal Utility District in Oakland, California.
The Klepper PSRG with STRP employs an entrained flow principle (using a gas to propel the pulverized feedstock through the direct fired reaction zone) but features two separate reactors: a devolitization reactor and a reforming reactor.
The devolitization reactor slowly raises the temperature of the feed material through 450°F (the temperature at which combustion will occur) until a substantial portion of the oxygen has reacted with more reactive material in the feed.
Once the available oxygen has been reacted at below combustion temperature, the feed material temperature is raised to a higher temperature, for example 650°F, prior to combination with super heated steam (1,500°F) and a subsequent rise in temperature to react with the carbonaceous feed material and produce the CO- and H2-rich syngas.
The Klepper system uses the produced syngas and process steam to propel the feedstock through the segregated steam reforming reactor. Among other things, this technique raises the calorific value of the syngas by not diluting the product syngas with nitrogen or carbon dioxide as is the case with an air-blown gasifier. Nor does it require a costly separate supply of oxygen or the elevated temperatures and “run-away” pyrolysis issues associated with the use of an oxygen-blown gasifier.
This multi-stage approach results in a very high conversion efficiency, while at the same time, keeping the tar content in the produced gas extremely low. Another unique feature specific to the Klepper system is that the cyclones and water condenser are integrated and contained within the biomass gasification chamber. This design conserves space and reduces the loss of heat energy.