Furnaces – Process – Treating fuel constituent or combustion product
Patent
1995-03-01
1997-05-20
Bennett, Henry A.
Furnaces
Process
Treating fuel constituent or combustion product
110259, F23J 300
Patent
active
056303696
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a reactor that is used for melting inorganic combustion residues, including those that may contain heavy metals and/or heavy metal compounds, in which the charge is heated and then acted upon with oxidation agents, in particular with gaseous oxygen or fuels, and oxidic slag is removed at temperatures of over 1400.degree. C., and to a procedure for melting combustion residues with a reactor of the type described heretofore.
2. Brief Description of the Prior Art
In procedures that are used to process the products of incinerating garbage that are largely inorganic and may contain heavy metals and/or heavy metal compounds so as to form environmentally benign products, it has already been proposed that the products of garbage incineration be melted and subjected to a thermal fusion process. The thermal fusion treatment serves, primarily, to separate off volatile metals and metal compounds which could be drawn off by way of the gas phase and, subsequently, to reduce the metallic elements, when at least all of those metals which under the particular process conditions are more noble than iron are meant to be transformed from the oxide form into metals. This sort of fractionated separation of noble metals from the melt subsequently leads to an iron bath or a copper alloy, when even iron soluble metals are contained, and to a slag melt that contains the elements and compounds that are not soluble in iron or copper. Cadmium, lead, and zinc can be carried off to the gas phase and separated off. The slag melt that is so formed can be used as an active additive in mixed cements after tempering. In order to permit this kind of fractionated reduction from the melt, in accordance with an older unpublished proposal, one proceeds such that prior to fractionated reduction the combustion residues that are to be processed are first subjected to oxidation during powerful turbulence caused by the injection of gas that contains oxygen or oxygen compounds. This is meant to ensure that all of the metals contained in the reactor are first converted to oxides, in order to permit the subsequent desired fractionated reduction.
In order to ensure the melting heat that is required to melt the combustion residues that are to be processed, up to now an electrically heated converter in which oxygen could be injected above the base has been proposed. The greater part of the melting heat had to be produced electrically. Because of the high iron oxide content and CaO content in the slag, it was possible to achieve a correspondingly low viscosity of the melt given an appropriately high melting temperature, when the viscosity of the melt became lower with increasing temperatures and increasing portions of iron oxide. However, during such melting processes, in which oxygen is injected to create turbulence, the melt displays structurally viscose flow behaviour and depending on the intensity of the gas insertion it begins to foam. In the case of the procedures formerly used efforts were made to prevent the melt from foaming, since this had a negative effect with respect to the settling properties of the reduced heavy metals. A further disadvantage of the melting procedures formerly used was that relatively large smelting aggregates had to be used in order to ensure the required high melting temperatures, since the introduction of heat was adversely affected and prevented by slag floating on the surface. In the case of liquid, quiescent smelt residual carbon floats to the top because of differences in density and burns only on the surface of the bath, where it has relatively little effect on the thermodynamic behaviour of the melt. The reduced metallic iron that is simultaneously formed sinks below the quiescent smelt because of differences in density and for this reason becomes relatively difficult to access for subsequent oxidation, so that up to now relatively large amounts of energy and relatively long oxidation times were required for the oxidative melting o
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"Holderbank" Financiere Glarus AG
Bennett Henry A.
Tinker Susanne C.
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