Chemistry of inorganic compounds – Treating mixture to obtain metal containing compound – Group va metal or arsenic
Patent
1984-05-07
1984-12-18
Carter, Herbert T.
Chemistry of inorganic compounds
Treating mixture to obtain metal containing compound
Group va metal or arsenic
75 6, 75 8, 75 21, 75 23, C01G 2800
Patent
active
044890460
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to a method of converting arsenic-containing waste products, to a depositable, substantially arsenic-free form, optionally while, at the same time, recovering arsenic and, possibly, also other metal values. The method particularly pertains to the working-up of arsenic-containing waste products originating from metallurgical or chemical processes, while recovering the arsenic content of the material and converting the material to a depositable form. By "depositable" is meant here and in the following a state in which the material can be deposited or dumped without detriment to the environment. By arsenic-containing waste products is meant all arsenic-containing material and products, such as slag, dross, dust and sludge products originating from metallurgical, chemical and pharmaceutical processes, and which products because of their physical and chemical character are not suitable as raw material for the conventional production of arsenic and arsenic products.
Considerable quantities of waste products are often produced within the metallurgical and chemical industries, partly as a result of the various activities within these industries and partly as a result of those steps which said industries are obliged to take in order to limit the emission of contaminating substances. Such waste products include sludge from metallurgical processes, such as wet-process waste sludge from hydrometallurgical zinc-producing processes, and waste sludge from the gas purification systems of sulphuric-acid plants. The waste products may also be dust of mutually different composition and origin, such as dust obtained when roasting copper concentrates and pyrite concentrates, or when converting matte; or dust obtained when producing lead pyrometallurgically. These dusts, which are produced in extremely large quantities in said context, normally accompany the process gases and are separated in special filters, which may be of an electrical or mechanical type. The arsenic content of such waste products is often up to 20-40%, rendering it difficult to safely dump said waste products because of the enormous environmental problems created thereby, even though the prescribed safeguards per se have been taken. The arsenic content, however, is normally so low that if it is to be recovered industrially, the waste products must be subjected to some form of further treatment. A major part of the development work in this field has been done by applicant, i.e. Boliden AB, which is an industry of the aforementioned kind, and is active in a country in which extremely advanced legislation concerning the deposition of poisonous wastes has long been in force. Many proposals have been made for converting waste products of the aforementioned kind to a form in which they can be safely dumped, and many attempts have been made to convert said waste products to said safely dumpable form, although hitherto in no case has it been possible to obtain a sufficiently low arsenic content, without diluting or thinning the material in some way. In addition, the resultant end product is always liable to weather, and disintegrate to form dust. Such is the case, for example, when arsenic-containing waste products are treated thermally with a reductant in a rotary furnace at temperatures up to 500.degree. C. When thus treated, the material is constantly in solid phase and is thus not melted, and the lowest content of arsenic which can be achieved when using solid reactants, which are substantially the only reductants, active in the present context, is about 2%, which is far greater than the permitted arsenic content of material which is to be deposited. Furthermore, the treatment times involved in such methods are unreasonably long, which renders them economically unviable. Attempts have also been made to carry out the aforementioned method at temperatures higher than 500.degree. C. This has created problems, such as the sintering of the material being treated, however, causing the fuming-off of arsenic to practically cease. For examp
REFERENCES:
patent: 527312 (1894-10-01), Austin
patent: 894764 (1908-07-01), Wedge
patent: 900467 (1908-10-01), Baggaley
patent: 943752 (1909-12-01), Livingston
patent: 1713127 (1929-05-01), Hills
patent: 1782418 (1930-11-01), Garred
patent: 2295219 (1942-09-01), Kalling et al.
patent: 2650159 (1953-08-01), Tan et al.
patent: 3380819 (1968-04-01), Cavanaugh
Ullmans Encyklopadie der Technischen Chemie, vol. 2, Published 1974, Verlag Chemie, Weinheim/Bergstr., p. 53.
Eriksson Bengt S.
Petersson Stig A.
Boliden Aktiebolag
Carter Herbert T.
LandOfFree
Method for working-up arsenic-containing waste does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Method for working-up arsenic-containing waste, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Method for working-up arsenic-containing waste will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-1988009