Environmental Engineering Reference
In-Depth Information
military w
astes, fuel reforming, waste water, ash vitrification, engines (such as sta-
tionary gas turbine and micro gas turbine, internal combustion), and compact-size
combustion systems such as micro-combustors; see
Figure 6.2
.
The chemical wastes
include wastes generated by the petrochemical industries, paints, oils, and residues.
The technology is particularly attractive in systems that require fuel lean combustion.
It is expected that many new applications and innovations will evolve with further
research and development focused on this innovative combustion technology.
We describe below the application of high temperature air combustion technol-
ogy for the thermal destruction and energy utilization of negative-costs waste fuels.
6.2
COMBUSTION OF WASTES AND SOLID FUELS
Comb
ustion of any moisture-containing organic materials occurs in the following
four stages: drying, pyrolysis, gasification, and oxidation of volatiles. In the tradi-
tional case the combustion air used for solid waste fuels (municipal and industrial
wastes and low grade coals) is characteristically preheated to about 300˚C. The
combustion reaction essentially involves two components: fuel waste and oxygen.
A simplified combustion reaction can be represented as:
Hydrocarbon fuel (waste) + Oxidizer
Products + Heat + Pollution
All industrialized countries worldwide have been actively engaged in discussing
the growing environmental problems, such as global warming, acid rain, and destruc-
tion of the ozone layer. Many of the pollutants are also known to cause adverse
effects on human health. Indeed, some of the combustion-generated pollutants are
carcinogenic and mutagenic. Attention must be given to environmental pollution in
addition to conservation of natural resources. Recently, much attention has been
given to recycling, and secondary or tertiary use of wastes and energy recovery from
wastes. Emission of dioxins and furans from the thermal destruction of wastes is
also an important issue from plastic-containing wastes. Principles of high tempera-
ture air combustion technology are also potentially attractive for use in the thermal
destruction of plastic-containing wastes. The energy resource recovery technology
applied to waste materials is one such constituent of the high temperature air
technology. Technology used for transforming the organic portion of the materials
present in wastes to attractive fuels also includes refuse-derived fuel (RDF).
The United States produces about 4 pounds per person per day of solid waste.
In the United Kingdom the waste generated is about 1.5 kg per person per day. In
Japan the amount of general waste disposed per person per day is approximately 1
kg. Wastes produced in Japan today are divided into two categories of industrial and
general wastes in accordance with the Waste Disposal and Public Cleansing Act.
General disposal of such large quantities of wastes is processed according to the
following: 74.3% incineration, 11.3% conversion to resources, and 14.4% buried in
landfills. The landfill option of the past for the disposal of wastes is becoming
increasingly small everywhere in the world since it is difficult to secure land for the
disposal of wastes. The future trend for solid waste disposal seems to be further
reduction in the amount of waste produced, recycling, and cascade use of resources.
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