The heart of the bluegas™ technology is catalytic hydromethanation, an elegant process by which carbon-rich feedstocks – such as coal, petcoke, and biomass – are converted through a combination of catalytic reactions in the presence of water into a methane-rich gas stream. Figure below illustrates the basic process to produce Substitute Natural Gas (SNG).
The first step in the hydromethantion process is to disperse the catalyst throughout the matrix of a carbon-rich feedstock under specific conditions so as to ensure 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 particles. 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 (shown below) is thermally neutral, requiring no addition or removal of energy, making it highly efficient.
The proprietary sulfur-tolerant 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 methanation reactions concurrently take place. The catalyst is continuously recycled and reused within the process.
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, nearly all of the CO2 produced in the process is captured as a pure stream suitable for sequestration or enhanced oil recovery.
Clear Advantages
Traditionally, producing natural gas from carbon-rich feedstocks has been an inefficient and capital intensive process. Conventional gasification technologies produce synthesis gas (or syngas), a combination of hydrogen and carbon monoxide which has a significantly lower energy value than natural gas. Syngas also cannot be transported in natural gas pipelines, and is not compatible with existing power facilities, industrial plants, and commercial/residential heating systems. Although syngas can be further upgraded into methane, this can currently only be done through the addition of multiple complex, high cost and low efficiency processing plants. The result is a far more expensive end product.
In contrast, GreatPoint Energy has developed a proprietary process for directly producing substitute natural gas utilizing a catalyst and a reactor design which together enable multiple chemical reactions to occur in a single vessel at relatively low temperatures.
Hydromethanation has several key advantages over conventional gasification technologies that have fundamentally shifted the economics of SNG production:
- Higher efficiency — Efficiency is significantly higher than conventional processes due to the direct capture and utilization of the heat generated inside the bluegas™ reactor. Competing reactors cannot operate in heat balance without injecting large amounts of expensive and parasitic oxygen. The bluegas™ process uses roughly 75% less oxygen than traditional gasification.
- Water Efficiency — Hydromethanayion is very water efficient. It uses one-third of the water required by other coal gasification processes. As a result, it is possible to locate bluegas™ plants in a wide variety of water constrained locations, such as the Middle East and other arid regions.
- Lower Temperature — Hydromethanation occurs at much lower temperatures and milder conditions than conventional non-catalytic processes, eliminating the need for spare reactors and resulting in lower cost construction materials and reduced maintenance costs in the reactor, gas cooling and heat recovery systems.
- Smaller Equipment — The methane produced in the bluegas™ process is far more energy dense than syngas, significantly reducing the amount of gasses that need to be cooled and cleaned, and reducing the size of downstream gas processing equipment by up to 50%.
- Better For The Environment — The bluegas™ process uses less coal per mmbtu of gas than conventional gasification technologies because of its efficiency advantage. Furthermore, unlike conventional gasification, for which carbon capture adds significant additional cost, energy loss, and complexity, hydromethanation intrinsically captures nearly all of the CO2 and other impurities produced in the process. GreatPoint Energy plans to market CO2 for enhanced oil recovery ("EOR") or provide for geological sequestration. Sulfur, nitrogen, char and mineral matter, nickel, vanadium, mercury and trace metals are all converted into valuable products or disposed of in a safe manner.
Unlike many conventional processes, hydromethanation is well suited for some of the lowest cost feedstocks such as sub-bituminous and lignite coals, as well as petroleum coke. Biomass also represents an attractive feedstock, either as a co-feed or on its own. The result is a technology which GreatPoint Energy believes will provide dramatically improved economics and an environmentally sound alternative to the use of coal and drilled or imported natural gas.
Source: GreatPoint Energy
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