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RECOVERY OF METALS FROM RESIDUES USING A PYROMETALLURGICAL PLASMA SYSTEM.

Objective

- EVALUATION OF PRETREATMENT AND AGGLOMERATION OF DUSTS AND MODIFICATION OF EXISTING PLANTS
- DETERMINATION OF SLAGS SUITABLE FOR DUMPING AS NON-TOXIC WASTES IN THE EEC
- MAXIMISING THE RECOVERY OF ZINC FROM STEEL DUSTS
- RECOVERY PROCESS FOR CO, MO, V AND NI FROM SPENT CATALYSTS CURRENTLY DUMPED.
The use of the Tetronics plasma furnace in the carbothermic smelting of steel plant dust materials and spent petroleum catalysts has been investigated. The technique is suitable for treating a wide range of materials, producing a nontoxic slag which may be dumped directly, and recovering the valuable metals to offset the cost of treatment.

By treating steel dust at 1000 C, under an oxidising atmosphere, it was possible to drive off all the halides, although this would introduce additional cost. Trials were conducted on a stainless steel dust containing significant levels of zinc in addition to chromium and nickel.

The recovery of molybdenum, cobalt and nickel deposited on alumina, from catalysers used in the petroleum refining industry, was also evaluated.
THIS PROJECT AIMS AT TWO TREATMENT METHODS:

A) THE TREATMENT OF EAF AND AOD FURNACE DUSTS.
ELECTRIC ARC FURNACE (EAF) DUSTS TYPICALLY CONTAIN 10 - 40 % ZNO, 2 - 15 % PBO, 20 - 50 % FEO AND 5 - 20 % CAO.
ARGON OXYGEN DECARBURISATION (AOD) DUSTS CONTAIN 15 - 20 % CR2O3, 5- 10 % NIO AND 2 - 3 % MOO3.
THE DUST TREATMENT PROCESS WILL UTILISE A TRANSFERRED-ARC PLASMA FURNACE FOR THE CARBOTHERMIC REDUCTION OF THE OXIDES IN THE DUST.
THE MAIN WORKING STEPS CONCERN WITH:
- CHARACTERISATION AND PRIOR TREATMENT OF STEELPLANT DUSTS
- DEGREE OF CARBOTHERMIC REDUCTION OF EAF DUSTS
- SLAG COMPOSITION AND TOXICITY (GROUND WATER LEACHABILITY OF PB, CD, CR6X)
- CONDENSATION OF MOLTEN ZINC (OPERATING PARAMETERS)
A COMMERCIALLY AVAILABLE, FULLY DEVELOPED ZINC SPLASH CONDENSER WILL BE INSTALLED IN THE EXHAUST SYSTEM OF THE TETRONICS PLASMA FURNACE TO RECOVER THE ZINC AS A METAL. THE OPERATING PARAMETERS TO MAXIMISE THE RECOVERY OF ZINC AND THE AVAILABILITY OF THE CONDENSER WILL BE EVALUATED, INCLUDING GAS TEMPERATURE AND ANALYSES, PARTICULATE MATTER LOADING AND HALOGEN CONTENT.

B) THE TREATMENT OF PETROLEUS REFINERY CATALYST
SPENT PETROLEUM CATALYSTS CONTAIN 0 - 5 % COO, 8 - 12 % MOO3, 3 - 15 % NIO, 2 - 15 % V AND VARIABLE AMOUNTS OF S AND C ON AN SIO2 OR AL2O3 SUBSTRATE.
THE PLASMA BASED PROCESS INVOLVES DRYING THE CATALYST, CALCINING TO REMOVE THE MAJORITY OF THE RESIDUAL OIL, CARBON AND SULPHUR AND BLENDING WITH A SUITABLE FLUX TO FORM A LOW MELTING SLAG WITH THE CERAMIC SUBSTRATE. THE FEED BLEND WILL BE FED CONTINUOUSLY TO THE PLASMA FURNACE, A NON-TOXIC SLAG WILL BE CONTINUOUSLY DISCHARGED AND A FERROALLOY CONTAINING THE CO, NI AND MO WILL BE INTERMITTENTLY TAPPED.

Funding Scheme

CSC - Cost-sharing contracts

Coordinator

CONSEJO SUPERIOR DE INVESTIGACIONES CIENTIFICAS
Address
Calle Serrano 117
Madrid
Spain

Participants (1)

Tetronics Research and Development Company Ltd
United Kingdom
Address
5B Lechlade Road
SN7 9AJ Faringdon