Hydromethanation is an elegant and highly efficient process by which natural gas is produced through the reaction of steam and carbonaceous solids in the presence of a catalyst. The process enables the conversion of low-cost feedstock such as coal, petroleum coke and biomass (wood waste, municipal solid waste, and energy crops such as poplar and switchgrass) into clean, high-purity methane.
The chemistry of catalytic hydromethanation involves reacting steam (2H2O) and carbon (2C) to produce methane (CH4) and carbon dioxide (CO2) according to the following reaction:
The first step in the hydromethantion process is to combine the catalyst with the feedstock in such a way as to ensure that the catalyst disperses throughout the matrix of the feedstock for effective reactivity. The catalyst/feedstock material is then loaded into the hydromethanation reactor. Inside the reactor, pressurized steam is injected to “fluidize” the mixture and ensure constant contact between the catalyst and the carbon particles. In this environment, the catalyst facilitates multiple chemical reactions between the carbon and the steam on the surface of the coal or biomass. These reactions (shown below) catalyzed in a single reactor and at the same low temperature, generate a mixture predominately composed of methane and CO2.
The overall combination of reactions is thermally neutral, requiring no addition or removal of energy, making it highly efficient.
The proprietary catalyst formulation is made up of abundantly available, low-cost metal materials specifically designed to promote gasification at the low temperatures where water gas shift and reactions concurrently take place. The catalyst is continuously recycled and reused within the process shown below.
By adding this catalyst to the system, GreatPoint Energy is able to reduce the operating temperature in the gasifier while directly promoting the reactions that yield methane. Under these mild “catalytic” conditions, less expensive reactor components can be utilized, pipeline grade methane is produced, and very low-cost carbon sources (such as lignites, sub-bituminous coals, petroleum coke and biomass) can be used as feedstock.
As part of the overall process, the bluegas™ technology enables the recovery of contaminants in coal, petroleum coke and biomass as useful byproducts. In addition, roughly half the carbon in the feedstock is removed and captured as a pure CO2 stream suitable for sequestration.
Hydromethanation yields dramatically improved economics for the production of natural gas and an environmental footprint equivalent to that of the most environmentally-friendly commercial fuel.
