A feasibility study of adaptive Plasma‐Assisted incineration, Part 1: Demonstration on a laboratory model system

Abstract

ncineration is a widely applicable method of hazardous. waste treatment. It is relatively simple, inexpensive, and is firmly I established in the field of waste management. Yet recent scientific evidence has brought into question the safety of conventional thermal treatment operations (Eduljee, 1995). A major point of contentioii is the toxicological hazard of organic pollutants released by incinerators, including compounds of the polychlorinated dibenzo dioxin and furan classes (Harrison, 1996). The public has shown growing concern over the impacts of incineration facilities on human health and the enviroinment.These factors, combined with increasingly strict environmental regulations, have prompted interest in the development of alternative waste treatment methods.The limitations of conventional incineration relate to the properties of fuel combustion environments. Thermodynamic and stoichicimetric constraints on the temperature and oxygen concentration around a flame limit the rate of oxidation reactions. Incomplete combustion of persistent organic contaminants (e.g ., halogenated aromatic hydrocarbons, PCBs, etc.) is largely responsible for the formation of toxic by-products such as dioxins and furans (Harrad, 1996;Williams, 1995).Variability in the waste composition also contributes to the problem. Incinerators have a high thermal inertia and cannot respond rapidly to changes in feed composition. The cost-eff iciency of incineration processes is notably low when a small fraction of contaminant i s nonhomogeneously dispersed in a large matrix, such as in contaminated soil.A typical incineration system comprises two thermal treatment stages.The primary stag.e is usually a rotary kiln through which solids and sludge travel over several minutes. The temperature is adjusted to allow complete volatilization and/or combustion of the organic fraction of the waste. An ashy solid residue is collected at the exit while the gas stream proceeds to a high-temperature secondary chamber (afterburner). The purpose of the afterburner is to promote complete combustion by providing supplemental fuel and air. Heat transfer rates are crucial in the operation of this unit, where the residence time is of the order of seconds. Liquid organic waste may be introduced at this stage (Brunner, 1996). Thermal plasmas are a potential alternative to combustion heat sources. The characteristic properties of atmospheric-pressure plasmasintense power dissipation, molecular dissociation and ionization -createThe use of a thermal plasma afterburner in hazardous waste incineration could prevent the formation of toxic organochlorine pollutants. The present work demonstrated cost-optimal adaptive operation of a laboratory model system composed of an induction plasma jet with optical emission diagnostic tools. Input settings (plasma power and oxygen content) were continually adjusted in response to on-line spectroscopic analysis of the product gas. This adaptive strategy allowed cost-effective destruction of organic contaminants under a variable fee...

Design and Techno‐Economic Analysis of a Process for Transforming Pig Manure into a Value‐Added Product

“…The methodology employed in this design study is somewhat similar to those described by Filion et al (2001) and Khataniar et al (2002), who used a techno-economic analysis to evaluate the design of processes for the incineration of hazardous wastes with a plasma burner and the production of gas from hydrates. The design methodology described in this paper is more systematic and it employs design tools to evaluate the critical controllable and uncontrollable risks.…”

Molecular Emission Spectroscopy as a Potential Diagnostic Tool in Plasma-Assisted Incineration

“…In the feedback process, the C 2 signal was driven down to undetectable levels by corrective changes in power and/or oxygen input, leading to a costeffective route traced by the optimization algorithm. 14,17…”