The U-GAS® gasification process is based on a single-stage, fluidized-bed technology for the production of low-to-medium heating value syngas from a wide array of biomass feedstocks and coals using oxygen, oxygen enriched air, or air in the gasification reaction.
In the U-GAS® gasification process, the prepared feedstock is conveyed into the gasifier vessel. Within the fluidized bed, the feedstock reacts with steam, air and/or oxygen and the temperature is controlled to maintain high carbon conversion and non-slagging conditions for the ash. The U-GAS® process accomplishes four important functions in a single-stage, fluidized-bed gasifier: it decakes, devolatilizes and gasifies the feedstock, and if necessary, agglomerates and separates ash from the reacting coal. The operating pressure of the gasifier depends on the end use for the syngas and may vary from 3 to 40 bars (45 to 585 psia) or higher. After cleaning, the syngas can be used for many applications such as power, synthetic natural gas, methanol, di-methyl ether, glycol, ammonia, direct reduced iron, and gasoline. Other byproducts such as sulfur, carbon dioxide, steam and ash are viable commercial products.
During operation, the feedstock is gasified rapidly within the fluidized bed and produces a gaseous mixture of hydrogen, carbon monoxide, carbon dioxide, water vapor and methane, in addition to small amounts of ammonia, hydrogen sulfide and other trace impurities. Reactant gases, including steam, air, and/or oxygen are introduced into the gasifier and are used to fluidize the feedstock inside the reactor. Ash is removed by gravity from the fluidized bed and discharged into a system for depressurization and disposal. The gasifier maintains a low level of carbon in the bottom ash discharge stream and achieves overall carbon conversions up to 99%. Cold gas efficiencies of over 80% and carbon conversion of over up to 99% have been repeatedly demonstrated on a commercial scale.
Fines carried over from the fluidized bed are separated from the product syngas prior to heat recovery and syngas cleanup. The product syngas is essentially free of tars and oils due to the temperature and residence time of the gases in the fluidized bed, simplifying downstream heat recovery and gas cleaning operations.