A METHOD FOR THE CHLORINATING REFINEMENT OF IRON RAW MATERIALS

Abstract: Method for the chlorinating treatment of oxidic materials containing chlorinateable metals, for example calcines, for the recovery of metals such as copper, lead, zinc, silver and cobalt. The material is treated in a suspended state at elevated temperatures, preferably at temperatures above 600`C, with chlorinating agent, to form metal chlorides which are separated out and from which said metals can be recovered. The chlorinating agent used is at least one chloride of metal selected from the group Mn, Zn, Ti, Pb, Fe and Ni which chloride is volatilized at the chlorinating temperature, preferably waterfree iron chloride. The chlorinating agent is recovered after separating the metals, by supplying the metal or metals present in the chlorinating agent to the residual aqueous solution in elementary form or as an oxide, hydroxide or carbonate, in a quantity such that the residual hydrogen chloride present in the aqueous solution is converted to chloride. The chloride is returned to the chlorinating stage as a chlorinating agent, together with a quantity of water equal at most to the amount of water required to achieve the desired selectivity during the chlorinating stage.

Description: A METHOD FOR THE CHLORINATING REFINEMENT OF IRON RAW MATERIALS The present invention relates to a novel method for chlorinating refining iron-oxide materials, comprising chlorinating chlorinateable non-ferrous metals with a chlorinating agent substantially consisting of solid metal chlorides, whereat chloride is recovered from vola¬ tilized chlorides and metal chloride or chlorides are re-formed and recycled together with a quantity of water equal at most to that required for the desired selectivity between different metals. A number of chlorinating refining methods are known to the art. The eldest of these methods include roasting the iron-oxide material while admixing a chlorinating agent, whereat one or more of the metals present is or are converted to chlorides, which can then be leached out and separated. A number of methods are known, in which different metal containing materials are chlorinated to form soluble chlorides, which then are leached out. From the leach solution the chlorinating agent may be recovered as disclosed in e.g. SE,C, 47171. A number of methods are also known in which an iron-oxide material . is chlorinated to form gaseous chlorides, which can be recovered from the waste gases generated during the chlorinating processes. For further information regarding these methods reference can be made to Ouisburger Kupferhϋtte. (DE,B,1068020), Metal!gesellschaft AG (DE,A,1758676, DE,B,1133560 and DE,C,1141793), Boliden (SE,B,319785 and US,A,3386815) and Mayor-Tord (FR,B,1508382 and 1525161 and FR,A, Application 123049 and 134647; i.e. the so-called V.I.P.-Method). Among the aforementioned chlorinating-volatilization methods there is disclosed in the cited French Patent Specifications and Applications a system in which sulphidic iron raw-materials are roasted and the hot cinders then chlorinated With a mixture of iron(II)chloride and hydrochloric acid. In this method it is necessary to supply heat during the chlorinating reaction stage in the chlorinating reactor vessel, for example by burning fuel, such as oil, supplied to said reactor vessel, since the water in the hydrochloric acid must be vapour zed. The chlorinating agent is recovered by washing out vola- tilized chlorides and by cementation, there being formed an iron- -chloride solution which is recycled to the chlorinating stage after adding hydrochloric acid, to replace chlorinating-agent losses. The presence of water in the system causes the equilibrium between metal oxide and chloride to be displaced, so that complete chlorina- tion cannot be achieved without a heavy surplus of chlorinating agent present. The lowest possible water content according to the afore¬ mentioned method is substantially above 50%, owing to the fact that hydrochloric acid must be added and that hydrochloric acid contains at least about 80% water. Assume that \% copper present in a roasted product is to be removed . by chlorinating the product with hydrochloric acid in accordance with the V.I.P. method. The presence of a large amount of water vapour will, in this case, counteract the chlorinating reaction. 3 Cu £ 0 + 6 HCl * • 2 Cu 3 Cl 3 ÷ 3 H 2 0 A large surplus of chlorinating agent will be required in order to achieve any appreciable quantitative chlorination. At least five times the stoichiometric amount must therewith be used. If the chlorinating agent is charged to the system in the form of 20%-solutioπ, then 200 kg of water must be vapourized per ton of oxide. If this vapouri∑ation is to be achieved by the physical heat content of the oxide, it will be necessary to heat the oxide to about 1500°C prior to the chlorinating stage. Thus, it is not poss¬ ible in practice to avoid combustion in the chlorinating stage, meaning that the handling of waste gases is considerably complicated, owing to the combustion gases present in said waste gases. With re- spect to suitable dilution of the chlorinating agent, there is re- quired a gas volume of about 120 m /ton of oxide calculated at 0 C 3 and 760 tons, designated normal cubic meter or N . 200 kg of water 3 vapour has a volume of 250 Nm , an addition gas from the combustion process. This water supply thus makes it necessary to greatly enlarge the process apparatus. Further, the presence of water makes it impossible to recover certain metals in chloride form, but that these metals are hydrolized in¬ stead. A large part of the volume of the waste gases from the chlo- rinating method will comprise water. These large quantities of water constitute an-extra load on the apparatus, and consequently the appa¬ ratus must be correspondingly dimensioned. These large quantities of water also create corrosion problems. There are known methods, in which the chlorinating agent is a solid compound, such as an iron chloride, but they are either low tempera¬ ture methods, such as the segregation process disclosed in DE,A, 2212360 (Hanna Mining) for recovery of nickel and the sea nodule benefication process for recovery of Mπ, Ni and Co disclosed in US,A, 4144056 (Cato Research). Such low-temperature processes result in formation of soluble metal chlorides. In the latter process alkali metal chloride used as a volatility depressant salt in the process may be recovered from the leach solution and reused. Further, ery specified processes for treating titanium or nickel oxide ore utilize solid metal chlorides, such as processes disclosed in SE,B, 407588 (Du Pont), N0,A, 124116 (Alcan) and US,A, 3875415 (INC0). None of aforementioned processes provides, however, any recovery possibility for the chlorinating agent. All prior processes utilizing solid metal chlorides have been limited to the treatment of specific materials or the recovery of specific elements and said processes have not included any recovery possibility for the chloricating agent, which must be considered as a severe limitation of its utility today, with regard to the economical and environmental aspects. It has now been found, however, that the aforementioned disadvan¬ tages can be substantially eliminated if the chlorinating stage, after the roasting stage, is carried out with a chlorinating agent in the form of a solid chloride of metal selected from the group Mn, Zn, Ti, Pb, Fe and Ni. By solid metal chloride is meant a water-free metal chloride, a metal chloride containing combined water or a moist metal chloride, but not a liquid aqueous slurry.. It will be understood that the lowest practically possible water content is striven for, with respect to the energy required to remove the water content. It has been found that an iron(II)chloride can be used to advantage with a combined water content of about 7%. All disclosed metal chlorides provides in practice chlorination of non-ferrous metals present in an iron-oxide material including copper, nickel and silver, but avoiding substantial iron chlorina- tion. Thus, there is charged to the chTorinating reactor vessel oxidic material, such as cinders obtained from a sulphide roasting process, or roasted products obtained in some other way, an inert gas for fluidizing the cinders or roasted products, and said metal chloride, for example iron(II)chloride or zinc chloride. The chlorinating re¬ action process, which is suitably effected at a temperature above 800°C, preferably above 900°C, results in the formation of a gas containing substantially inert gases, gaseous metal chlorides and entrained dust. The additional energy required to effect the chlo¬ rinating stage and to cover the heat lost during said stage is either obtained by heating the oxidic material to a temperature above the chlorinating temperature or by using an oxide material which has, at least to the extent necessary, a lower oxidation state, for example partially as magnetite, which can be oxidized during the chlorinating stage by supplying a limited quantity of air or oxygen to the reactor vessel. The gas is passed to a gas-purifying apppa- ratus, via a cyclone for separating dust accompanying said gas, in which apparatus the volatilized metal chlorides are washed from the gas with an aqueous liquid. The remaining, inert gases are returned to the chlorinating reactor vessel. The aqueous liquid, which now contains the volatilized metal chlorides, is passed to an apparatus in which the volatilized metal chlorides are subjected to a reduction treatment process for recovering the metals, for example by cementa¬ tion. It is not necessary to take out the whole of the metal content during the extraction stage, since the process system is closed and a given residual content of the metal or metals to be recovered can be permitted to circulate together with the chlorinating agent. Sub¬ sequent to having removed said valuable metals to the extent desired, the liquid is evaporated off to form a solid substance comprising chlorides of, for example, iron or zinc, this solid substance being returned to the chlorinating stage. An exemplary embodiment of the invention will now be described in more detail with reference to the accompanying drawing, the single figure of which illustrates a preferred apparatus for the chlorin¬ ating refinement of roasted products and pyrrhotite containing, inter alia, copper, zinc and noble metals, in accordance with the present invention. The figure illustrates a conditioning reactor vessel 1 provided with a feed means 2, by means of which pyrrhotite is charged to the reactor vessel 1 from a supply 3 and roasted products (hereinafter referred to as calcines) from a supply 4, via lines 5 and 6. The reactor vessel 1 is a fluidizing reactor vessel, to which air is passed from a fan 8 via a line 7. Pyrrhotite charged to the reactor vessel 1 is oxidized there, and constitutes the sole source of energy charged to the process. Gases departing from the system pass through a cyclone 9 and are charged to an optional gas-purifying apparatus (not shown) via a line 10. Hot calcines obtained from the reactor vessel i and the cyclone 9 are charged to the chlorinating reactor vessel 11, via lines 12 and 13. The chlorinating reactor vessel 11 is a fluidizing reactor vessel and is provided with an exhaust means through which exhaust gases are passed to a cyclone 15 via a line 14. A chlorinating agent is passed to the reactor vessel via a line 16, while gas is passed to said reactor vessel via a line 17. In the cyclone 15 dust accompanying the exhaust gases is separated therefrom, said gases containing volatilized chloride, and the gases are passed to a gas- purifying apparatus 19, via a line 18. Chlorinated material is passed from the chlorinating reactor vessel 11 and the cyclone 15 to a cooling reactor 22, via lines 20 and 21. Air from a fan 24 is passed to the cooling reactor vessel 22, via a line 23. Cooling gases are removed via line 25, and passed to a cyclone 26, from which the cooling gases are removed, via a line 27, and passed to an apparatus (not shown) for recovering the heat content of the gases. Purified oxide is removed from the cooling reactor 22 and the cyclone 26 via feed means 28 and lines 29, 30 and 31. The vola¬ tilized chlorides are purified in the gas-purifying apparatus 19, said gases being passed to ~ first washing tower or scrubber 32, via line 18, and from there to a second washing tower or scrubber 33, via a line 34. The gases are passed from the second cooling tower 33, via a line 35, to a Cottrell precipitator 36, and from there, via a line 37 and a fan 38, through a further cooling tower 39, from where said gases are passed, via line 40, to a fan 41 and the line 17 for intro¬ ducing said gases into the chlorinating reactor vessel 11. The line 40 is provided with an inlet 42 for charging additional gas to the system, for example air for effecting the oxidizing chlorinating step when magnetite is used as the further energy source,- and an outlet 43 passing to a chimney 44. Washing liquid is supplied to the scrubbers 32 and 33 from a supply 49, via lines 45 and 46 and pumps 47 and 48. In turn, washing liquid is charged to said supply 49 from the scrubbers 32 and 33, Cottrell precipitator 36 and the cooling tower 39, via lines 50, 51, ' 52 and 53. Washing liquid is also passed from the supply 49, via line 54, to a mixing vessel 55 provided with an agitating or stirring means 56. Iron oxide is also charged to the mixing vessel 55, through a line 57. A slurry of washing liquid and iron oxide is passed from the mixing vessel 55 to a decanter 58, via a line 59. The liquid is recycled to the mixing vessel 55 by means of a pump 60, through a line 61. Part of the liquid can be bled off via a line 62. The liquid is trans¬ ferred from the decanter 58, via line 63, to a cementing vessel 64 provided with an agitator or stirring means 65. Copper shavings or chips are charged to the cementation vessel via line 66. The liquid is passed, via a line 67, to a decanter 68, from which noble metals are taken out via a line 69, and the liquid passed to a liquid- extraction plant 71 via a line 70, the extraction plant being sche¬ matically illustrated by two stages 72 and 73, each of which is pro¬ vided with a respective agitator or stirring means 74 and 75. The extracted liquid, which contains mainly iron(II)chloride, is passed to an evaporation plant 77 via a line 76. The extract is passed from the first stage 72, via line 78, to the second stage 73, and from there is returned to the first stage, via line 79. Liquid from an electrolytic copper-precipitating apparatus 80 is also passed to the second stage 73, via pump 81 and line 82, and from the second stage 78 to the precipitating apparatus 80, via line 83. The arrow 84 indi¬ cates the removal of copper cathodes. In the evaporation plant 77 the liquid is heated in a heat exchanger 85, to which steam is charged via line 86. The liquid is evaporated in the evaporator 87, from which vapourized liquid is passed via a line 88 and a cooler 89 to the storage vessel 49. Evaporated iron chlorides are also removed from the evaporator 87, via line 90, and returned either to the closed system, via a line 91, or to the chlo¬ rinating reactor vessel 11, via line 92 and pump 93. EXAMPLE A copper concentrate comprising in per cent by weight Iron 12.2 Copper 10.4 Lead 11.0 Zinc - 18.2 Sulphur 24.3 Silver 0.75 and the remainder mainly gangue, was roasted twice in a fluidized bed, whereat the sulphur content was lowered to 4.8%, with 3.8% in the form of sulphate, with an unchanged ratio between the metals present. Solid, substantially divalent iron chloride, containing 1.3% by weight water, the rest being mainly combined water, was added to the calcines. The amount charged was about twice the stoichiometric quantity calculated on the amount of copper, lead and zinc present. The materials were charged together to the bed of a fluidizing re¬ actor vessel, to which nitrogen gas was also charged as a fluidizing agent. The bed temperature was maintained at 900-950°C. A material which had undergone chlorinating treatment was removed from the bed, said material containing in per cent by weight: Iron 43.9 • Copper 0.2 Lead 1.0 Zinc 13.4 Sulphur 0 Chlorine 0.2 Silica, Si0 2 12.0 Silver 0.008 The yield obtained in the departing exhaust gases was Copper 99% Lead 83% Zinc 39% Silver 99% which quantities could be quantitatively recovered from the gases. OMF

Claims: CLAIMS 1. A method for the chlorinating treatment of oxidic materials con¬ taining chlorinateable non-ferrous metals for recovering the metal content of said material, whereat the material in a substantially suspended state is first treated at an elevated temperature, prefer¬ ably a temperature above 600°C, with a chlorinating agent to form metal chlorides, whereafter the metal chlorides together with resid¬ ual chlorinating agent are separated from the material and absorbed in an aqueous solution from which metals are recovered to the extent desired, characterized in that the chlorinating agent is supplied to the chlorinating stage in the form of at least one chloride of metal selected from the group Mn, Zn, Ti, Pb, Fe and'Ni which chloride is volatilized at the chlorinating temperature, and in that at least the major part of said chloride is recovered from the aqueous solution subsequent to recovering said metal therefrom, by supplying the metal or metals present in the chlorinating agent in an elementary form or as an oxide, hydroxide or carbonate in a quantity such that hydrogen chloride present in the aqueous solution is converted to a chloride of the metal, said chloride being returned to the chlorinating stage as a chlorinating agent, in certain cases together with water in a quantity equal at most to the quantity required during the chlorin¬ ating stage to obtain the desired selectivity between different metals. 2. A method according to claim 1, characterized in that the chlo¬ rinating agent is iron chloride and that the chlorinateable metals are taken from the group copper, lead, zinc, silver, nickel, cobalt. 3. A method according to claim 2, characterized in that the iron chloride is substantially water free. 4. A method according to claim 1, characterized in that the oxidic material is a roasted product containing copper and zinc. - ΛT- E OMFI

Inventors: BAECK ERIK G, EKMAN DOUGLAS S
Applicants: BAECK ERIK G, BOLIDEN AB, EKMAN DOUGLAS S
Application year: 1981
Main classification: C22B1
IPC codes: C01G1, C22B1