Wood continued waste

A survey of commercial thermal gasification in the United States shows that few gasifiers have been installed since 1984 (115). Most units in use are retrofitted to small boilers, dryers, and kilns. The majority of existing units operate at 0.14 to 1.0 t/h of wood wastes on updraft moving grates. The results of this survey are summarized in Table 36. Assuming all 35 of these units are operated continuously, extremely unlikely, the maximum amount of LHV gas that can be produced is about 0.003 to 0.006 EJ/yr (222—445 td /d). 

More recently, interest has developed in the use of enzymes to catalyze the hydrolysis of cellulose to glucose (25—27). Domestic or forest product wastes can be used to produce the fermentation substrate. Whereas there has been much research on alcohol fermentation, whether from cereal grains, molasses, or wood hydrolysis, the commercial practice of this technology is primarily for the industrial alcohol and beverage alcohol industries. About 100 plants have been built for fuel ethanol from com, but only a few continue to operate (28). 

Wood waste Particulates, smoke, and combustion Continuous-feed systems operation at... 

In the growing of food yeast on wood sugar, one of the most difficult problems is that of foaming. This difficulty has been largely overcome by a fermenter designed for use in the production of yeast from sulfite waste liquor in the Waldhof plant at Mannheim. A modification of the fermenter was used for the continuous production of yeast on wood sugars in America. Fermentation periods of 2.6 to 3 hours were obtained with a strain of Torula utilis. Yields were 38 to 49% of the total sugar. 

Combustion of waste wood presents special problems from a regulatory standpoint, and research should continue on reducing pollutant emissions. There is some potential for blending with clean wood without substantially altering emission control systems in existing units. Better fuel characterization is needed for waste materials. 

This research and development work on wood wastes has led to the design and construction of two large industrial fluid bed combustors. In one of these, a fluid bed is used for the generation of steam with a fuel that was previously suited only for landfill. Rocks and inerts are continuously removed from... 

The smooth flow of wood is an essential prerequisite of an efficient mill. For this reason mills are elevated with space beneath so that waste material from each saw can be collected and conveyed away at a lower level than the timber that moves from saw to saw. The headrig is elevated relative to the other saws and the timber moves through the mill on powered (live) roll conveyors, or continuous belts or chain conveyors with cleats. 

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