OCR Text |
Show including pulp and paper manufacturing, lumber and plywood mills, agribusinesses and food products manufacturers, cement kilns, and those fums supporting PURPA cogeneration facilities. They are used because they are locally available, low in cost, and their combustion often solves twin problems of energy generation and waste disposal. The usage of low grade fuels and wastes is extensive, if insufficiently documented. Lignite consumption data are largely integrated into coal consumption data [61], for example. Lignite and coal waste utilization in industry could well exceed 2 quadrillion Btu (quad), annually however. Wood fuel consumption in industry, is estimated at close to 2 quads annually [61]. Utilization is largely confmed to the forest products industry, including pulp and paper, although several PURPA facilities have been constructed supplying electricity to the grid and process steam to industry. The use of agriCUltural wastes has expanded dramatically, particularly within the agribusiness sector. MSW incineration has also grown. Over 120 million tons of MSW, containing some 1.1 quads of energy, are incinerated annually [51] with dramatic expansions in capacity now under construction. Industrial firms such as Hooker Chemical have played a major role in the development of this low grade fuel use. Further, industrial utilization of low grade fuels is commonly encouraged. States such as California have had long standing programs encouraging the use of low grade biomass fuels. The state of Washington encourages the use of municipal waste based fuels in industrial boilers. Recently the "SMART Bum" legislation provided explicit encouragement for industry to utilize MSW and RDF fuels in existing facilities. Industrial utilization of low grade energy resources, then, is continually expanding. Low grade fuels tend to be highly oxygenated and contain significant quantities of moisture and/or ash [41]. The dominant technology used for low grade solid fuels in industrial boilers involves combustion on stationary or moving grates [25, 38, 50, 53]. Fluidized beds are rapidly emerging frring. Suspension frring is appropriate in specific cases such as finely divided dry biomass fuels or firing of industrial process kilns (Le. cement kilns), but is a specialized technology which may not be appropriate for most industrial settings associated with low grade fuels. Grate fuing dominance is particularly apparent in the combustion of MSW and RDF [45, 51] however it exists throughout low grade fuels utilization. 1.1. Issues Associated with Low Grade Utilization Both technical/economic and environmental issues exist with the use of low grade fuels. TechnicaVeconomic issues include system efficiency, and the quantity of useful heat generated. Some evaluations also require attention to the quality of that useful heat TechnicaVeconomic issues also include the volume of gaseous and solid products of combustion produced, particularly as they impact the capital cost and projected operating cost of systems to be installed. Environmental issues relate to the design considerations of post-combustion control system configuration. Further they include the pennittability of a project, with particular emphasis on the Environmental Impact Statement (EIS) and associated Risk Assessment (RA). Both must be addressed if the project is to be sited, permitted, constructed, and 2 |