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Gasification-Catalytic Synthesis Process
Biomass gasification offers an attractive alternative system for producing cellulosic ethanol. Although gasification reactions can take many forms, these processes are defined by cranking up the temperature to between 650 and 1,400oC.
There are two approaches to achieving these elevated temperatures: direct heating and indirect heating. In direct heating, a relatively small amount of oxygen is added to the reactor. If this gas is made up of more than 90 percent oxygen, the resulting syngas will be rich in carbon monoxide and hydrogen. The contrasting approach uses various means of indirect heat transfer to achieve high operating temperatures, including hot sand circulation and exotic alloy heat exchangers.
Gasification methods have the advantage of being fast and relatively less sensitive to feedstock type, but the disadvantage of destroying useful structure like the glucose molecule. Enzymatic methods are slower, but produce glucose, which is the metabolic substrate of choice for producing ethanol, butanol, and a wide variety of useful organic acids as industrial feedstocks for plastics and bio-based chemicals and solvents
The gasification process has the following steps:
- Feed Handling and Preparation
- Gasification
- Gas Cleanup and Conditioning
- Catalytic Synthesis to Alcohol
- Alcohol Separation
Syngas can be chemically treated using catalysts (referred to as the catalytic synthesis process) to produce ethanol.
Catalytic Synthesis is a process which involves the catalytic conversion of cellulose materials including prairie grass, switch grass, bagasse, wood fiber, wood sawdust, news paper, cotton, waste cellulose products and starch materials in an acid digestion solvent to ethanol. The catalysts possess a high degree of symmetry in their lower valence states for conversion of cellulose and natural plant materials to ethanol. Lignin and lignin compounds may also be recovered as byproducts. Advantageously, the low valent catalysts produce high yields of ethanol from cellulose.
The catalytic conversion method appears at present to be more advanced than enzymatic conversion, but the enzymatic process may ultimately prove more efficient based on carbon emission rates and other factors.
Related Links:
- Ethanol as Biofuels
- What are feedstocks?
- Properties of Feedstocks for ethanol production
- Yield of Biomass for Various Feedstocks
- Feedstocks used by Various Companies
- Why Cellulosic Ethanol?
- Cellulosic Ethanol Production
- Cellulosic Ethanol Production Value Chain
- Ethanol production methods
- Latest Discoveries and Breakthroughs
- R & D Roadmap in Cellulosic Ethanol
- Future projections
- Companies Involved in Producing Cellulosic Ethanol
- Investments & Funding
- Challenges & Barriers in the commercialization process
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