Method for processing waste containing metal contaminants using

Details Method for processing waste containing metal contaminants using Method for processing waste containing metal contaminants using

1998-04-22

2000-06-27

Willis, Prince

Specialized metallurgical processes, compositions for use therei

Processes

Producing or treating free metal

75416, 75961, 423 5, 588 11, C22B 100

Patent

active

060802243

DESCRIPTION:

BRIEF SUMMARY
BACKGROUND OF THE INVENTION

1. Field of the Invention
The invention relates to a method for processing waste containing metal contaminants. It further relates to applications of this method, in particular in the iron and steel or car industry or in the field of the recovery of household garbage.
2. Background Information
The metal contaminants in question within the context of the present invention are, in particular, metals modified by carbon, oxygen, phosphorus or sulfur, with a view to their inerting and to their recovery for the purpose of reclaiming the same.
Methods are already known which are intended for processing waste containing metal contaminants.
By way of example, it is possible to cite the pyrometallurgical processing methods based on a reduction of the metal contaminants by carbon at high temperature, such as the IMS--Tetronics or Waelz methods.
However, these methods are not entirely satisfactory to the extent that they are essentially costly, difficult to implement and do not always enable the recovery of all the reclaimable metals.
Accordingly, there is a need to provide a method for processing such waste which is more economical, easier to exploit and more profitable than those which are already in existence, this method further guaranteeing in a reliable manner the inerting of the metal contaminants.


SUMMARY OF THE INVENTION

The object of the invention is to provide a method for processing waste containing metal contaminants, which combines the aforementioned advantages and by which it is further possible to recover the majority of the reclaimable metals.
This is achieved, according to the invention, by carrying out the following operations: reducing agent in an inert liquid medium, in particular molten glass, the reducing agent being less electronegative than oxygen and, where appropriate, a supplementary mineral vitrification charge based on silica (SiO.sub.2) and/or alumina (Al.sub.2 O.sub.3), metal phase, and disposal or temporary storage of the first phase and the recycling of the second phase.


BRIEF DESCRIPTION OF THE DRAWINGS

No Figures are supplied with this patent.


DETAILED DESCRIPTION OF THE INVENTION

According to the invention, the use of aluminum nitride as reducing agent is excluded.
Preferably, the waste is mixed, in the pulverulent condition, with a reducing agent having a percentage of ionic character within the range between 20 and 50%.
According to the invention, the percentage of ionic character of the reducing agent is calculated in accordance with the Pauling method. In fact, Pauling proposed an evaluation of the percentage of ionic character in compounds on the basis of the difference of electronegativity between the elements. Thus, for example in the case of boron nitride BN, the difference of electronegativity between nitrogen and boron is: electro-negativities of nitrogen and of boron.
In the present case of BN,
A result of this is a percentage of ionic character of 22%, and, consequently, a percentage of covalent character of 78%.
Table I hereinbelow gives the difference of electronegativity of various compounds and the percentage of ionic character:


TABLE I ______________________________________ Chemical Percentage Reducing-agent formula of the of ionic family reducing agent .DELTA. character ______________________________________ Saline hydrides Li H 1.22 31 Ca H.sub.2 1.20 30 LiAlH.sub.4 0.90 19 Saline carbides Al.sub.4 C.sub.3 0.94 20 Ca C.sub.2 1.55 45 Saline sulfides Na.sub.2 S 1.65 49 Ca S 1.58 46 Fe S 0.75 14 Zn S 0.93 20 Saline nitrides Li.sub.3 N 2.06 65 Ca.sub.3 N.sub.2 2.04 65 Mg.sub.3 N.sub.2 1.73 52 Be.sub.3 N.sub.2 1.47 42 LaN 1.94 61 Si.sub.3 N.sub.4 1.14 28 BN 1.00 22 ______________________________________
Table II hereinbelow gives the electro-negativities .chi. of various elements.


TABLE II ______________________________________ Elements .chi. ______________________________________ Hydrogen [sic] 2.20 Sulfur 2.58

REFERENCES:
patent: 4094809 (1978-06-01), Ross
patent: 4395367 (1983-07-01), Rohrmann et al.
patent: 5104494 (1992-04-01), Tench et al.
patent: 5662579 (1997-09-01), Bickford

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