 Coalition for
Responsible Waste Incineration
FURNACES, BOILERS AND INCINERATORS
Technical Issue
Hazardous materials and wastes are burned in different
processing units for different purposes. These include material
recovery in furnaces, energy recovery in boilers, and waste treatment
in incinerators. It is important to distinguish the primary purposes of
different units and the types of materials or wastes being burned to
encourage uses of most environmentally preferable management
alternatives.
Technical Background
The objective of hazardous waste management is to both
minimize waste generation and maximize waste control. Waste reduction,
including energy and material recoveries, is applied to materials
before they are discarded as wastes; waste control, including storage,
treatment and disposal, is applied after discard. Recovery and
treatment processes are applied immediately to minimize long-term
adverse effects of waste constituents and perpetual care required by
subsequent disposal. Thermal processes comprise both recovery and
treatment alternatives. Waste minimization is encouraged through
recovery of material and energy values before destruction of
combustible constituents by incineration. Thermal processes reduce
volume and/or hazard of both materials or wastes, but do not completely
eliminate ultimate disposal. Noncombustible residues of no value must
be disposed as treated solid residues and dispersed as treated gaseous
and liquid discharges.
All thermal processes involve application of controlled flame
or indirect heating at high temperature to enhance concentration,
separation, or chemical conversion of constituents. They are integral
to manufacture of basic products. Glass, cement, metals, pigments, and
medicinals are ancient examples of thermally produced materials. Modern
examples include chemical production, petroleum refining, metal
smelting, cement manufacture, and glass fabrication. Thermal processing
is used extensively for chemical production, energy and material
recovery, and waste treatment. Examples include production of carbon
black, carbon dioxide, and hydrochloric acid; combustion of fuels;
recoveries of brines, catalysts, and solvents; and destruction of
combustible organic constituents or conversion of inorganic
constituents of waste to more stable oxides through incineration.
Alternatives include several self contained, high-temperature
combustion processes conducted in thermal processing units:
- Waste reduction in chemical processing facilities,
- Energy recovery in industrial boilers,
- Material recovery in industrial furnaces, and
- Waste treatment in industrial incinerators.
Thermal processes in the chemical industry encompass a variety of
different process units, commercial purposes, and inputs and outputs:
Unit -- Processing
Purpose -- Chemical production
Input -- Raw materials, intermediates, by-products
Output -- Products, secondary materials, fuels, wastes
Unit -- Furnace
Purpose -- Material recovery
Input -- Undiscarded materials, spent solvents, spent
catalysts, other spent materials
Output -- Reclaimed materials, fuels, wastes
Unit -- Boiler
Purpose -- Energy recovery
Input -- Fossil fuels, refuse-derived fuels, ignitable
wastes
Output -- Recovered energy, wastes
Unit -- Incinerator
Purpose -- Waste treatment
Input -- Discarded materials, solid wastes, hazardous
wastes
Output -- Reduced waste volumes, reduce waste toxicity
Chemical processing facilities are designed for conversion of
raw materials into finished products. Furnaces are designed for
conversion of secondary materials into recoverable by-products. Boilers
are designed for combustion of fuels and recovery of energy.
Incinerators are designed for reduction of waste volume and hazard. All
processes are conducted within totally enclosed engineered devices.
A single combustible substance may be a raw material, a
process intermediate, a fuel, and/or a waste, and be any or all four at
any given time on the same site. For example, petroleum hydrocarbons
are naturally derived, refined as fuels, recombined as polymers and
other useful items, and ultimately discarded as wastes. Crude oil,
gasoline, benzene, and flammable solvent waste are each perceived
differently.
Incineration has multiple purposes: (i) reduction in volume of
solid wastes, (ii) conversion of hazardous constituents into
non-hazardous forms, (iii) selective removal of gaseous and
water-soluble products of combustion for further treatment, and (iv)
formation of stable noncombustible solid residues for ultimate
disposal. Treatment of combustible constituents is immediate thereby
minimizing perpetual care of land disposal. Incinerators are designed
and operated for specific functions. A medical waste incinerator (MWI)
burns hospital and medical wastes. A municipal waste combustor (MWC)
burns solid wastes from municipalities. A hazardous waste incinerator
(HWI) burns primarily hazardous wastes of industrial origin. All three
usually burn non-hazardous solid wastes (trash, garbage). The MWI may
be owned and operated by a large medical facility. The MWC is often
publicly owned and supported by tax funds and/or user fees. The HWI may
be owned and operated exclusively by a waste generator. All three types
may also be commercial incinerators, i.e., owned and operated by a
waste management firm in which wastes from second parties are burned
for a fee.
The primary functions of boilers, furnaces, and incinerators
are significantly different. The types of wastes burned by incinerators
are quite different. Emission control devices and the management of
gaseous emissions, wastewater, and solid residuals are different.
Consequently, environmental regulations that have evolved are
different. However, all three are stringently regulated under the
Resource Conservation and Recovery Act (RCRA). All combustion sources
are also subject to provisions of the Clean Air Act (CAA) and the Clean
Water Act (CWA).
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