Pressurized, pyrolytic steam process

In liquefaction systems wood and wood wastes are the most common fuelstocks. They are reacted with steam or hydrogen and carbon monoxide to produce liquids and chemicals. The chemical reactions that take place are similar to gasification but lower temperatures and higher pressure are used. Liquefaction processes can be direct or indirect. The product from liquefaction is pyrolytic oil which has a high oxygen content. It can be converted to diesel fuel, gasoline or methanol. 

Pyrolytic carbon is formed mainly by three different reactions, namely, the reversible decomposition of methane (Reaction 2.5), the irreversible cracking of higher hydrocarbons (Reaction 2.6), and/or coke formation (Reaction 2.7). The formation of these carbon deposits leads to the breakdown of the catalyst and hot spots in the reactor. Pyrolytic carbon is usually found as dense shales on the reformer wall or encapsulating the catalyst particles. The process leads to the deactivation of the catalyst and increase of pressure drop across the reformer tubes. The thermal cracking of hydrocarbon occurs at high temperatures and at low steam to hydrocarbon ratios. 

Research described in this paper focuses on the second step of the gasification process, and details the effects of temperature and residence time on product gas formation. Cellulose is used as a feedstock for pyrolytic volatiles formation. Earlier papers (JS.M) have discussed the effect of steam on cellulose pyrolysis kinetics. Two recent papers (1, 1 6) presented early results on pelletized red alder wood pyrolysis/gasification in steam. Future papers will discuss results using other woody materials, crop residues, and manures (17,1 ). Research to date indicates that all biomass materials produce qualitatively similar results in the gasification reactor described in the following section of this paper. Effects of pressure on the heat of pyrolysis of cellulose are also discussed as a prelude to future papers detailing the more general effects of pressure on reaction rates and product slates. 

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