Electrolysis: processes – compositions used therein – and methods – Electrolytic synthesis – Preparing single metal
Patent
1999-05-13
2000-12-19
Bos, Steven
Electrolysis: processes, compositions used therein, and methods
Electrolytic synthesis
Preparing single metal
205606, 205607, 423109, 423110, C25C 116, C22B 1900
Patent
active
061623466
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The invention concerns a process for recovery of zinc from sphalerite containing ores or concentrates, whereby, in a first step, these ores or concentrates are submitted to a thermal treatment to convert sphalerite to a substance that is more readily attacked in hydrometallurgical media and, in a second step, said substance is leached.
BACKGROUND OF THE RELATED ART
According to the state of the art, sphalerite containing ores or concentrates are submitted to a roasting step wherein the ore or concentrate is oxidized at an elevated temperature. In this roasting step, zinc sulfide is converted to zinc oxide while liberating SO.sub.2 and heat. subsequently zinc oxide is leached to bring it into solution. This traditional flowsheet has several disadvantages: the S0.sub.2 has to be further processed and results in a high amount of sulfuric acid. Also, the leaching which is carried out in sulfuric acid, normally necessitates two steps, whereby in a first step the ore or concentrate is submitted to neutral leaching and, in a second step, the remaining zinc ferrites are conducted to strong acid leaching. The iron which has dissolved during the strong acid leaching is precipitated, depending upon the method, as jarosite, goethite or hematite.
SUMMARY OF THE INVENTION
The invention has as an aim, among others, to present a process which renders it possible to generate much less acid than in the process according to the state of the art and to carry out the leaching in a single step instead of two.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
For this purpose, according to the invention, said thermal treatment consists essentially of a heating cycle performed under non-oxidizing conditions and above the inversion temperature of sphalerite to wurtzite, i.e. above 900.degree. C., allowing sphalerite to be, at least partly, transformed to wurtzite, and of a rapid cooling cycle, e.g., quenching, performed in such conditions as to retain, at least partly, this wurtzite at low temperature.
It is presumed that the inversion temperature of sphalerite to wurtzite is function of the amount of impurities in the sphalerite, in such a way that, the larger the amount of iron dissolved in sphalerite, the lower said inversion temperature would be.
In a preferred embodiment of the invention, the heating cycle is performed at a temperature above 1020.degree. C.
According to another preferred embodiment of the invention, the said rapid cooling cycle is carried out by quenching in water or in said hydrometallurgical media.
Leaching in the second step can take place in all kinds of acid, neutral or basic hydrometallurgical media capable of leaching zinc out of wurtzite. Although, according to the state of the art, hydrometallurgical media used for leaching usually contain sulfuric acid, it is also possible to use solutions containing HCl, NaOH, NH.sub.4.sup.+ ions (e.g. NH.sub.4 Cl solutions) or others; HCl and/or H.sub.2 SO.sub.4 are used in a preferred embodiment of the invention.
Leaching can be performed under non-oxidizing conditions or under oxidizing conditions, for instance with O.sub.2 or Cl.sub.2 as oxidizing agent.
After leaching, the zinc containing solution is purified and subsequently zinc is recovered from this solution by electrolysis.
Other characteristics and advantages of the invention will result from the description of a specific embodiment of the process for treating ores or bulk concentrates according to the invention.
To be mentioned is EP-A-0195650 which discloses a process for the recovery of zinc from iron-bearing sulphidic zinc concentrates. The concentrates, which contain sphalerite, are hereby subjected to an oxidation roasting step in an oxygen deficient atmosphere at 700-1050.degree. C. In this step, iron is oxidised preferentially and the formation of zinc ferrites, which would require a separate and costly treatment, is retarded. The iron containing fraction and the unreacted zinc sulphide containing fraction are then separated and further processed. WO-A-9013679 als
REFERENCES:
patent: 4049770 (1977-09-01), Swinkels et al.
Database WPI, Week 37, 1983, Derwent Publications Ltd., London, GB; AN83-26972k, Su 926045 Abstract, May, 1982.
Brouwer Sybolt
Vanhoutte Dirk
Bos Steven
N.V. Union Miniere S.A.
LandOfFree
Process for recovery of zinc from sphalerite containing ores or does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Process for recovery of zinc from sphalerite containing ores or , we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Process for recovery of zinc from sphalerite containing ores or will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-268314