CS223181B1 - Process for processing iron-containing raw materials - Google Patents

Abstract

The invention relates to a method of processing raw materials which, in addition to metals from the group Zn, Cu, Co, Ni, Or, and Mn, contain iron. The technological procedure of hydrometallurgical separation of iron from other metals of interest is described, while simultaneously producing recoverable waste. The processing technology uses the processes of pressure precipitation of complex ferric salts, evaporation and crystallization of sulfates of metals of interest. Phase equilibria are given for the key nodes of the technology.

Description

The invention <relates to a method of processing raw materials which, in addition to metals from the group including Zn, Cu, Co, Ni, Cr and Mn, contain iron. The current technological processes for processing such raw materials by hydrometallurgical means consist mainly of acidic leaching of the raw material and partial neutralization of the leachate, which results in either hydrolytic exclusion of trivalent iron or its precipitation in the form of jarosite precipitates containing the appropriate cation of the neutralizing agent. At the same time, with the increasing iron content, the demands on the consumption of the neutralizing agent increase disproportionately and the production of ferric waste increases, which, due to contamination with other ions, cannot be further processed by conventional technologies.

At the same time, the demands on the consumption of leaching agent, which is degraded during neutralization, are also increasing. For these reasons, raw materials with an iron content comparable to the content of the metals of interest are not yet processed separately, but only in mixtures with selective concentrates.

The above-mentioned shortcomings are eliminated by the method of processing raw materials containing iron and at least the same amount of metals from the group including Zn, Cu, Co, Ni, Cd and Mn according to the invention, the essence of which is that after leaching the raw material with a sulfuric acid solution, the leachate is led to an evaporator, where crystals of divalent metal sulfates are precipitated, which are separated, the remaining solution is subjected to iron precipitation and, after separation, the ferric precipitate is returned back to the leaching stage.

The leaching with sulfuric acid solution preferably takes place at a temperature of 95 to 125°C and the precipitation of iron is preferably carried out at a temperature of 140 to 250°C.

The leachate fed to the evaporator contains all iron in trivalent form with a maximum content of 3.5% by weight, with the leaching being controlled so that the leachate contains the same amount of free sulfuric acid as iron.

The separated crystals of divalent metal sulfates are dissolved in the vapor condensate from the evaporator and the resulting solution is optionally neutralized with part of the raw material at a temperature of 60 to 115 °C,

The advantage of the method according to the invention is that by connecting the evaporator immediately after the leaching, it allows the separation of iron from the metals of interest in the first phase of the technological process. By concentrating the iron and unreacted sulfuric acid in a small volume of mother liquors, the energy requirement for the operation of the pressure precipitation unit is significantly reduced and the investment costs are also significantly reduced.

The intermediate product — a mixture of crystals of the metals of interest — can be easily converted back into a solution, which is further processed by classical ra.fiilation methods.

The produced basic ferric sulfate is a readily filterable crystalline precipitate that does not absorb metals of interest on its surface and can be easily converted into pure ferric oxide, a marketable product, by thermal decomposition.

The attached drawing shows a possible arrangement of a technological line for processing iron-containing raw materials in a method according to the invention.

Raw material 1, which is the oxidation roast of polymetallic concentrate, is dosed into the leaching node 2. A mixture of spent electrolyte 12, precipitated solution 16 and sulfuric acid 17 is used as the leaching solution. Leaching 2 is carried out in a cascade of at least two reactors at a temperature of 95 degrees Celsius with a residence time of at least 15 hours.

The leachate 4, after separation of the residue after leaching 3 and conversion of all iron into the trivalent form (by oxidation with air), is injected into a two-stage vacuum evaporator 5. Here, under the influence of steam 6, at a boiling point of 32 °C and a pressure of 50 to 60 kPa, hydrated zinc sulfate crystallizes together with sulfates of other accompanying divalent metals (Cu, Co, Ni, Cd and Mn), and the resulting crystals 7 are separated from the mother liquors 13. By dissolving the crystals 7 in the condensate of the evaporation 6, a solution 8 is obtained, from which copper, cobalt, nickel and cadmium are gradually separated in the refining unit 9 by cementation with zinc powder. The pure zinc sulfate solution 10 is led to electrolysis 11. The depleted electrolyte 12 is returned to the leaching unit 2.

The mother liquors 13 are fed into the autoclave for pressure precipitation 14. Here, at a temperature of 200 + 2 °C, a pressure of 1.5 to 1.7 MPa and a residence time of 1 h, iron is precipitated from the mother liquors 13 in the form of a precipitate 15 of basic ferric sulfate, the precipitate 15 is separated and the precipitated solution 16, enriched with the released sulfuric acid, is fed back to the leaching unit 2. The balance loss of sulfate ions in the precipitate 15 is covered by the addition of sulfuric acid 17 to the leaching unit

2.

The mass flow diagram of the described technological line, including the composition of individual streams, is shown in Table 1.

To determine the conditions for the crystallization of zinc sulfate from acidic leachates containing iron and to determine the conditions for the precipitation of iron, phase equilibria were measured. The results are summarized in Tables 2 and 3.

Table 1

Total Zn % Fe %/o H ₂ SO ₄ %/o weight weight weight weight (weight units)

oxidation roast (1) 1.66 29.2 ,22.5 leaching solution (X) 13.14 4.1 0.98 15.15 the rest after the puddle. (3) 0.592 1.0 8.99 leach (4) 14.03 7.26 3.2 3.2 evaporate — from leaching — 0.17 from evaporator (6) 3.36 crystals (7) 3,416 21.02 0.1 0.1 imitation solutions (13) 7,253 4.15 6.19 6.19 precipitate (15) 1.00 0.1 32 53.5 as SO ₄ precipitated solution (16) 6,253 4.79 2.06 11.67 electrolyte, zinc — 0.479 100 depleted electrolyte (12) 6,297 3.8 11.4 sulfuric acid (17) 0.59 92

(X) leaching solution is a mixture of — — spent electrolyte 12 — precipitated solution 16 — sulfuric acid 17

T a b l e 1 a n d 2

Solubility of ZnSO ₄ in the system Zn+ ² —Fe+ ³ —H ₂ O—(H ₂ SO ₄ ) temperature 32 °C, H ₂ SO ₄ content 3 to 6% by weight.

% Zn 12.5 9.5 ' 7.5 6.5 5.5 4.5 4.0 3.5 % Fe 1.56 3.18 4.28 4.83 5.39 5.95 6.25 6.58 Table 3 Phase equilibrium Fe+ ³ in sy stem Fe+3- —h ₂ sat ₄ — -H ₂ O_(Zn+2) temperature 200+ 2°C, Zn+ content ² 4 up to 8% by weight %, Fe+ ³ 0.34 1.07 1.07 1.38 1.62 1.70 1.82 1.91 1.95 _{% H2SO4} 5.25 4.67 5.01 4.47 4.17 4.18 5.25 6.92 11.7

SUBJECT

Claims (4)

SUBJECT Process for the treatment of iron-containing raw materials and at least the same amount of metals from the group comprising Zn, Cu, Co, Ni, Cd and Mn, characterized in that after extraction of the raw material with sulfuric acid solution the extract is fed to a evaporator where of the metals to be separated, the remaining solution is subjected to iron precipitation and after separation of the ferric precipitation is returned to the leaching stage. 2. The process according to claim 1, wherein the leaching with the sulfuric acid solution is carried out at a temperature of 95 to 125 [deg.] C. and the precipitation of the iron is carried out at a temperature of 140 to 250 [deg.] C. OF THE INVENTION 3. The process of claim 1 wherein the leachate to the evaporator comprises all trivalent iron at a maximum content of 3.5% by weight, wherein the leaching is controlled such that the leachate contains the same amount of free sulfuric acid as the iron. 4. The process according to claim 1, wherein the separated bivalent metal sulfate crystals are dissolved in the vapourous condensate from the evaporator and the resulting solution is optionally neutralized with a portion of the feedstock at a temperature of 60-115 [deg.] C.