Waste conversion, chemical

H. Alter and J. J. Duim, Jr., Solid Waste Conversion to Energy Current European and U.S. Practices, Marcel Dekker, Inc., New York, 1980, Chapt. 5 H. Alter andj. A. CampbeU, in J. L. Jones and S. B. Radding, eds.. The Preparation and Properties ofDensified Refuse-Derived Fuel, Thermal Conversion of Solid Wastes andBiomass, American Chemical Society, Washington, D.C., 1980, pp. 127—142. 

The function of pH adjustment is to neutralize acids and bases and to promote the formation of precipitates (especially of heavy metal precipitates) which can subsequently be removed by conventional settling techniques. These purposes are not mutually exclusive, precipitates can be formed as the result of neutralizing a waste. Conversely, neutralization of the waste stream can result when adjusting the pH to effect chemical precipitation. Typically, pH adjustment is effective in treating inorganic or... 

Boron compounds have low solubility relative to some cadmium, gadolinium, or europium compounds in nitric acid solutions, and would be more likely to precipitate from solution if high concentrations are required. Cadmium is a desirable poison however, it may be volatile at temperatures encountered in the waste conversion proqess and would therefore require an additional process for recovery. Additional requirements for, soluble poisons Include chemical stability in the solution and processing behavior similar to the fissile material. Each poison s neutron absorption rate is uniquely dependent on the neutron energy spectra of the system hence, the relative neutronic effectiveness of each poison varies from one system to another. Consequently, a mixture of poisons in a solution may be more effective than dither poison alone. ... 

Biofuels are liquid fuels that are derived from organic matter, either directly from plants or indirecdy from agricultural, domestic, or industrial wastes. They are made by conversion of biomass to convenient energy-containing substances in three different ways thermal conversion, chemical conversion, and biochemical conversion. An overview of biomass to biofuels conversion pathways is illustrated in Figure 10.388. 

The biomaterials available in the largest quantities on the Earth are cellulose and chitin, being easily isolated and processed into many articles and chemical forms. The manufacture of wood pulp is a worldwide business and the conversion of shellfish waste into chemical chitin is now an established industry. These materials are closely related polysaccharides and are found in nature as structural materials cellulose is found in the cell walls of plants and chitin is found in the shells of marine crustaceans. These structures are indicated in Fig. 12.1. 

J. L. Jones and S. B. Radding, eds.. Thermal Conversion of Solid Wastes and Biomass, ACS Symposium Series 130, American Chemical Society, Washington,... 

High density tungsten alloy machine chips are recovered by oxidation at about 850°C, foUowed by reduction in hydrogen at 700—900°C. Typically, the resultant powders are about 3-p.m grain size and resinter readily. There can be some pickup of refractory materials used in furnace constmction, which must be controUed. This process is important commercially. Eor materials that may be contaminated with other metals or impurities, the preferred recovery process is the wet chemical conversion process used for recovery of tungsten from ores and process wastes. Materials can always be considered for use as additions in alloy steel melting. 

In the United States the primary route for making calcium chloride is by the evaporation of underground brines (see Chemicals frombrines). Additional commercial material is available by the action of hydrochloric acid on limestone. Typically the hydrochloric acid is a by-product of some other commercial process and the conversion to calcium chloride is motivated by waste avoidance (see Hydrogen chloride). 

Technology Description Oxidation processes involve the conversion of organics to CO2, H2O, HCl, NO2 and SO3 or the conversion of inorganics to a more desirable form. For both organic and inorganic wastes, the function of chemical oxidation is to... 

Figure 11 -59. Representative expander refrigeration systems for temperature requirements and/or power recovery. (A) Expander coupled to a generator recovers pressure-loss energy for conversion to electric power. (B) System for power recovery from reactors in chemical processing plants. (C) Typical waste-heat recovery system using expansion turbines to generate electrical power. (Used by permission Bui. 2781005601. Atlas Copco Comptec, Inc.)...

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