Category Archives: Pyrolysis

Biochemical Reactions

Acetic acid (CH3COOH) and ethanol (C2H5OH) are the two major products from syngas fermentation. Equations (1)-(4) show the four basic reactions producing acetic acid and ethanol. In this case, the gaseous substrates CO and H2 follow the acetyl-CoA pathway to produce acetic acid and ethanol under strict anaerobic conditions.

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Pyrolysis

Pyrolysis is the fundamental chemical reaction process that is the precursor of both the gasification and combustion of solid fuels, and is simply defined as the chemical changes occurring when heat is applied to a material in the absence of oxygen. The products of biomass pyrolysis include water, charcoal (carbonaceous solid), pyrolysis oils or tars, and permanent gases including methane, […]

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Mass Transfer

In microbial syngas fermentation, the gaseous substrates, such as CO and H2, require trans­port from gas phase to the cell surface (Vega et al., 1990). In that case, the gaseous substrate is first absorbed at the gas-liquid interface and then diffused through the culture media to the cells. Microbes consume the diffused substrates as their carbon and energy sources and […]

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Liquefaction

Hydrothermal liquefaction is the conversion of solid biomass into gaseous and/or liquid products in the presence of water. Liquefaction consists of the catalytic thermal decomposi­tion of large molecules to unstable shorter species that polymerize again into a bio-oil.

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MICROBIOLOGY OF SYNGAS FERMENTATION

Microorganisms can be categorized into two major types depending on their optimum growth temperature, namely, mesophilic and thermophilic. In general, optimum growth tem­perature for mesophilic microorganisms varies from 37 to 40 °C, whereas for thermophiles, the temperature range varies from 55 to 80 °C (Munasinghe and Khanal, 2010 (a)). Mesophilic microorganisms, for example, Clostridium aceticum, Acetobacterium woodii, C. carboxydivorans,

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Slow Pyrolysis

Heating of the lignocellulosic biomass in inert atmosphere for hours to a maximum temperature of 400-500 °C is called slow pyrolysis. The charcoal yield is 35-40% by weight. In general, the yield of liquid products would be less than the fast pyrolysis of biomass. Several types of catalysts can be employed for the pyrolysis of biomass and/or upgradation of the […]

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Reactor Configuration

Bioreactor configuration is closely related to the effective gas-liquid mass transfer. Thus, reactor design plays an important role in syngas fermentation. High mass transfer rates, high cell densities, low operation and maintenance costs, and easy scale-up are some of the key parameters for designing an efficient bioreactor system. Similarly, the bioreactor size greatly depends on the rate of mass transfer […]

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Direct and Indirect Liquefaction

Currently, more research is being done on direct and indirect thermal liquefaction methods for biomass and wastes than on the other methods. Direct liquefaction is either reaction of bio­mass components with smaller molecules such as H2 and CO (e. g., Pittsburg Energy Research Centre (PERC) and Lawrence Berkeley Laboratory, Berkeley, USA (LBL) processes) or short­term pyrolytic treatment, sometimes in the […]

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SYNGAS CHARACTERISTICS

4.1 Syngas Composition Gasification of biomass produces a gas mixture consisting of CO, CO2, H2, N2, CH4, trace amounts of NOx and SOx, tar, char, particulate matter, and higher hydrocarbons such as C2H2, C2H4, and C2H6. This gas mixture is sometimes referred to as a producer gas (Datar et al., 2004). The gas composition greatly depends on the type of […]

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ABLATIVE FAST PYROLYSIS

Ablative pyrolysis, in which much larger particle sizes can be employed than in other systems, as the heat is transferred from a hot surface to the biomass particle and the process, is limited by the rate of heat supply to the reactor rather than the rate of heat absorption by the pyrolyzing biomass. Ablative pyrolysis is fundamentally different from fluid […]

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