DE1184088B - Process for the extraction of non-ferrous heavy metals - Google Patents

Description

Process for the recovery of non-ferrous heavy metals The invention relates to a process for the extraction of non-ferrous heavy metals from halogen, in particular chlorine-containing dusts from metallurgical furnaces, in particular blast furnace gas dusts. In the thermal reduction of z. B. Iron fall in the gas cleaning system Dusts, e.g. B. blast furnace dust, which is volatilized or dusty Put together discharged substances. These materials are beneficial after the method according to German Patent 1019 666 in melting chambers or funnels or processed by the levitation melting process (see chemical engineering technology, 35 [1963], No. 5, p. 402).

According to these methods, ores or other fine-grained and Dust-like raw materials are recycled to reduce their metal content by volatilization to win. Here, the material can either be mixed with the fuel or blow it into the combustion chamber separately. This becomes a molten one Component obtained and the heat content of the exhaust gases used to generate steam; In addition, secondary dust (secondary fly ash) is generated. The advantage of these processes lies in the design of the heat balance and in the fact that complicated reactions run very quickly due to the high specific surface area. The secondary dusts contain above all the volatile elements and their compounds; this includes z. B. CI2, Zn, Pb, Cd, Sn, TI, Se, Ge, Re, Sb, Bi, As.

The recovery of such metal-rich dusts according to the usual procedures is shaped as a result of their high Cl. -Content difficult. First of all, the C12 Content to be removed. This enforces the wet metallurgical route of separation Alkalis and precipitates, the chlorine-bound metals remaining in the residue - Converts metal oxides, while bound C12 goes into the filtrate. Usually leave However, satisfactory results can only be achieved by repeating it several times of the processes achieve what is appropriate to the technical facilities and affects the cost.

This wet metallurgical processing of chlorine-containing volatilization products can be circumvented according to the invention in that one is already in the combustion process ensures that the Cl. - Quantitative content of free alkali oxide, such as Na20 and / or K20, is bound.

The invention therefore consists in one as mentioned at the beginning Method in that one in the processing of the dusts, in particular in melting chambers or funnels or by the levitation melting process, for the supply of alkali oxide, like Na20 and / or K20, in one of the halogen content of the dust at least stoichiometrically appropriate amount. This is e.g. B. can be achieved by having alkali rich Fuels used and / or corresponding additives rich in alkali, for example Alkali hydroxides or carbonates.

So was z. B. found that the levitation melting process and when The alkali chlorides are used to lump fine-grained iron ores in melting chambers or funnels even at temperatures above 800 ° C., preferably around 1000 ° C., exist as such stay, d. H. do not have a chlorinating effect despite the high temperature and the volatile metals are not converted into chlorides, but are preserved as oxides stay. Surprisingly, the conditions are accordingly at such temperatures unlike the known chlorination processes in which heavy metals pass through Addition of NaCl and KCl can be converted into chlorides during roasting. At temperatures about z. B. 1000 ° C there is no chlorination of metals by alkali chlorides. This state can be maintained by deterrence (hypothermia). The privilege Such a way of working consists primarily in saving the wet metallurgy Cleaning.

An economic advantage of the process can be seen in the fact that the hot exhaust gases and / or dusts and exhaust gases from the heat exchangers in a downstream wet gas scrubber, e.g. B. a Venturi system can be treated. The alkali chlorides are dissolved and removed without any additional effort. The residue consists of chlorine-free oxides and can be processed into the metals using known smelting processes. Example 1 a) (old method) The smelting of normal gout dust with low-alkali or alkali-free fuels according to German patent 1019 666 resulted in secondary dust of the following composition: Zn. . . . . . . . . . . . . . . . . 2511 / o Pb ................. 10% C12 ................ 17% Fe ................. 7% Alkaline earth ........... 2% 5102 ............... 2% Alkali. . . . . . . . . . . . . . 5 0/0 Oxide oxygen ...... rest Leaching this secondary dust with hot water results in 500/0 soluble heavy metal chlorides. The solution must therefore continue to be treated with Ca (OH) 2; the oxides precipitated in the process are filtered off.

Example 1 b) (new process) If the same gas dust is smelted with lignite containing Na20 at a temperature of more than 800 ° C or NaOH is injected during combustion, a secondary dust is produced which has the following composition: Zn ............... 18.0o / 0 Pb. . . . . . . . . . . . . . . 8.01 / 0 C12 ... »» - «- - 17.0o / 0 Fe ............... 2.50 / 0 Alkaline earth ......... 2.0% Si02 "'***" *** - *** 2.00 / 9 Alkali. . . . . . . . . . . . 20.00 / 0 Oxide oxygen .... remainder After separation in a wet wash, a residue forms. This contains the heavy metals as insoluble, chlorine-free oxides.

Claims (4)

Claims: 1. Process for the extraction of non-ferrous heavy metals from halogen, especially chlorine-containing dusts from metallurgical furnaces, especially Blast furnace gas dusts, d u r c h g e n n n -z e i c h n e t, that one with the Processing of the dust, especially in melting chambers or funnels. or after the levitation melting process, for the supply of alkali oxide, such as Na20 and / or K20, in a stoichiometrically at least equivalent to the halogen content of the dust Crowd cares. 2. The method according to claim 1, characterized in that rich alkali Fuels are used. 3. The method according to claims 1 and 2, characterized characterized that the material to be smelted before or during its processing Alkali-rich additives, for example alkali hydroxides or carbonates, are added. 4. Process according to Claims 1 to 3, characterized in that at temperatures above z. B. works about 1000 ° C.