Boilers solid-waste fuels burned

TABLE 27-19 Solid-Waste Fuels Burned in Industrial Boilers... 

It is useful to examine the combustion process applied to solid wastes as fuels and sources of energy. All solid wastes are quite variable in composition, moisture content, and heating value. Consequently, they typically are burned in systems such as grate-fired furnaces or fluidized-bed boilers where significant fuel variability can be tolerated. 

Formation of Airborne Fmissions. Airborne emissions are formed from combustion of waste fuels as a function of certain physical and chemical reactions and mechanisms. In grate-fired systems, particulate emissions result from particles being swept through the furnace and boiler in the gaseous combustion products, and from incomplete oxidation of the solid particles, with consequent char carryover. If pile burning is used, eg, the mass bum units employed for unprocessed MSW, typically only 20—25% of the unbumed solids and inerts exit the combustion system as flyash. If spreader-stoker technologies are employed, between 75 and 90% of the unbumed solids and inerts may exit the combustion system in the form of flyash. 

Certain oilseed processors use byproducts of production as alternative fuels, which is particularly true in sunflower and peanut processing where hulls are burned as boiler fuel. This creates additional combustion challenges, but reduces solid waste. 

Allocated costs, Cgnoo nre included to provide or upgrade off-site utility plants (steam, electricity, cooling water, process water, boiler feed water, leMgeration, inert gas, fuels, etc.) and related facilities for liquid waste disposal, solids waste disposal, off-gas treatment, and wastewater treatment. Some typical capital investment costs for utility plants, estimated by Busche (1995), are shown in Table 16.12. Cogeneration plants can provide both steam and electricity by burning a fuel. When utilities, such as electricity, are purchased firom vendors at so many cents per kilowatt-hour, that cost includes the vendor investment cost. Thus, a capital cost for the plant is then not included in the capital cost estimate. 

Palm oil industry is one of the biggest industries in Malaysia which contribute to a large amount of solid waste as an output. The palm ash is produced after burning the palm oil shells and fibres as boiler fuel for palm oil consumption. 

The Identification of Non-Hazardous Secondary Materials That Are Solid Waste rule published by the US Environmental Protection Agency (EPA) in 2012 determines whether non-hazardous secondary materials are considered fuels or wastes when burnt. Combustion units that burn non-hazardous secondary materials that are classified as fuels are regulated as boilers under Section 112 of the Clean Air Act, while units that burn materials that are classified as wastes are regulated as incinerators under Section 129 of the Clean Air Act. In the rule, the EPA identified two secondary materials (resinated wood and scrap tyres managed under the oversight of the established tyre collection programmes) as non-wastes when used as fuel, and also identified off-specification tyres managed under the contractual relationship as non-waste fuels. However, scrap tyres that are discarded in stockpiles, landfills or monofills will be considered wastes unless these tyres are processed as specified in the rule. 

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