Glass manufacturing – Processes – With measuring – sensing – inspecting – indicating – or testing
Reexamination Certificate
2000-03-14
2003-03-18
Vincent, Sean (Department: 1731)
Glass manufacturing
Processes
With measuring, sensing, inspecting, indicating, or testing
C065S029170, C065S029210, C065S134300, C065S134600, C065S134800, C065S136300, C065S162000, C065S335000, C110S185000, C110S186000, C588S011000, C588S253000, C588S252000
Reexamination Certificate
active
06532768
ABSTRACT:
The present invention has been developed by the Europlasma corporation with funding provided by the City Council of Bordeaux (France) under the aegis of the Socogest (France) corporation, with assistance and technical input provided by the Aerospatiale (France) corporation.
1. Field of the Invention
The present invention relates to a continuous vitrification process for a powdered material and an apparatus for implementing said process.
The process of the invention is designed to render inert by vitrification any type of solid waste or residue, in particular pulverulent (powdered) or particulate materials containing, for example, metals, in particular heavy metals such as mercury, cadmium, lead, etc. and their salts, and asbestos, and generally speaking to render inert by vitrification any pulverulent or particulate material containing heavy metals or other toxic substances that must be destroyed, transformed or trapped for recycling or storage under present or future legislation regarding the treatment and elimination of said toxic waste.
The pulverulent materials may, for example, result from the incineration of household, industrial or hospital waste. Therefore the invention will be described below in its application for rendering inert solid residues from the incineration of household waste, particularly residues composed of boiler dust, fly-ash and filter cake used to neutralize and treat the incineration fumes of such waste.
The process and the apparatus of the present invention also have the advantage of being suitable for integration as a kit into a standard existing incineration center, preferably comprising a system for treating the fumes and gases from waste incineration. The combination of the incineration center and the kit comprising the process and the apparatus of the invention thus constitute a “zero waste” incineration plant.
The incineration of household waste produces two types of effluent: solid waste and gaseous waste or incineration fumes.
The solid waste constitutes the mineral fraction of the waste and is alkaline in character due to the presence of certain metal oxides such as the oxides of alkaline metals, and alkaline earth. This solid waste is boiler dust and clinker. Certain types of clinker are considered non-toxic by the legislation in force and may be used without risk, for example in bitumen, after deferrization. Boiler dust, on the other hand, is a highly toxic pulverulent substance since it contains heavy metals and their salts and, once stabilized, needs careful storage on protected sites with a view to later retreatment.
The gaseous waste is more or less acid in character due to the presence of acidic gases such as Hcl and HF, together with gaseous acid anhydrides such as SO
2
and CO
2
. It also contains toxic ingredients such as heavy metals and their salts and solid incineration residues such fly-ash. This gaseous or fume effluent must be filtered and treated to neutralize its acidity, condense the metals and their salts and trap the fly-ash before it is released into the atmosphere. The wet neutralization of this effluent produces a pulverulent or particulate material that is more or less agglomerated and known as filter cake.
The combination of fly-ash and filter cake comprises the purification residues of household waste incineration fumes known as REFIOM.
This REFIOM and the boiler-dust described above constitute the materials currently considered the “final waste”. They contain vitrifiable ingredients such as silica and alumina, metallic salts that are volatile at high temperature and toxic substances such as the heavy metals and their salts mentioned above.
The metallic salts in this waste, the heavy metals and their salts are soluble in water and are easily carried by rainwater to be dispersed in the soil and groundwater tables. The same is true of other substances that are more or less stable over time and more or less soluble, making them subject to dispersal by rainwater.
These substances may thus constitute a major source of pollution, particularly by leaching. The nature and composition of the materials therefore justifies their being classified as solid, mineral, vitrifiable Special Industrial Waste (SIW) and therefore subject to legislation requiring them to be stabilized or stored in special waste storage centers.
At the present time, vitrification would seem the surest way of rendering these materials or final incineration waste inert with a view to storage or recycling.
These materials contain silica and alumina that liquefy to form a melt when subjected to temperatures above 1300° C. When this melt cools it forms a crystalline or solid amorphous vitreous material that acts as an effective trapping matrix for the heavy metals.
2. Prior art
Various processes and techniques have already been developed for vitrifying this type pulverulent material. The techniques mainly differ in the heating means used.
Pulverulent materials are usually vitrified by means of electricity using the Joule effect and an electric arc. Fossil fuel systems using gas or fuel oil have also been developed.
For example, document WO-A-92/15532 describes a vitrification apparatus for treating fly-ash from chemical waste and other materials. The heating mean described in this document are electrodes or a gas burner. The electrodes cause an electric current to pass directly through the ash and chemical waste, causing melting of the materials due to the Joule effect. The gas burner melts the ash by convection.
However, using the Joule effect to heat the material has a large number of drawbacks. It produces an uncontrollable fusion process in which the distribution of heat within the vitrifying material depends on the variable chemical composition of the materials and the temperatures reached are often too low to give a uniform melt. Moreover, this type of heating causes the formation of a non-vitrifiable slag that causes technical problems in the design of the furnace and lowers the quality of the final vitrified product. Additives are often required when using this type of heating in order to overcome these drawbacks; unfortunately, though, these additives have a negative effect on the thermal balance of the melt and increase the cost of the vitrification treatment.
Furthermore, some systems using the Joule effect require additional furnace start-up means when the materials to be vitrified do not conduct electricity when cold.
Document WO-A-95/17981 describes an apparatus for treating fly-ash by means of electric arc vitrification. In this apparatus, the ash is introduced into a furnace via a conduit that constitutes an electrode. Gravity causes the ash to move from the open end of the furnace to the bottom, passing through an electric arc created between the free end of the electrode and the base of the furnace. The ash is thus rapidly heated and melted. The electric arc causes melting due to a combination of the Joule effect, radiation and convection, resulting from the development of the arc, whose trajectory is partly within the ash and partly outside it.
Heating by means of electric arc also has a certain number of drawbacks such as the difficulty of controlling a highly uneven fusion process, technical problems in the design of the furnace due to radiation of the arc and the creation of highly toxic fumes resulting from the formation of carbon/oxygen/chlorine compounds.
Fossil-fuel powered furnaces have the drawback of requiring high combustion gas flow-rates, of often having inefficient rates of heat transmission and producing toxic fumes resulting from the formation of carbon/oxygen/chlorine compounds.
Using the energy sources described above has the drawback not only of having high energy consumption, giving poor thermal balances of vitrification to obtain the high temperatures required for vitrification, but some of them also causes significant emission of toxic gaseous effluents requiring treatment. Moreover, the vitrified material obtained is not uniform, has numerous structural defects and contains clusters of particles and unmelted pulveru
Beudin Vincent
Guihard Bruno
Labrot Maxime
Pineau Didier
Europlasma
Oblon & Spivak, McClelland, Maier & Neustadt P.C.
Vincent Sean
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