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Title: Chlorination for the removal of zinc from Basic Oxygen Steelmaking (BOS) by-product
Author: Jaafar, Izan
ISNI:       0000 0004 5358 7503
Awarding Body: Cardiff University
Current Institution: Cardiff University
Date of Award: 2014
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A study on the chlorination of Basic Oxygen Steelmaking (BOS) by-product dusts followed by water leaching was conducted. The samples used for the studies sourced from the earth works and beneficiation of BOS byproduct from the stockpile. Comprehensive reports resulted from the excavation, beneficiation, physical and chemical analysis are reported. Zinc and iron removal studies from BOS by-product were investigated by means of chlorination roasting. Chlorination roasting of the BOS material by means of pyrometallurgical extraction was undertaking, assessing parameters such as roasting temperature, roasting time and chemical stoichiometry. A preliminary study was carried out using a solid chlorination agent, Ammonium Chloride (NH4Cl) in a muffle furnace for a 3 stage roasting conducted for 15 minutes to 180 minutes at 450C to 750C. Selected studies were carried out with 1-stage roasting. Further experimental studies then took place for chlorination using gaseous Cl2/N2 mixture gas in the tube furnace with 5 times chemical stoichiometry for a roasting time from 5 minutes to 90 minutes, with various temperatures from 150C to 750C. A 1 times and 2 times stoichiometry were added in selected procedure to foresee the effects of starvation agent. Additional surface area affects were also added to the chlorination with Cl2/N2 gas using bigger sample boat. Water leaching for 1 hour and 24 hours were conducted on the sample roasted with Cl2/N2 to investigate the leachability of Zn to assist further removal. The chemical and mineralogical composition of the BOS stockpile varied widely. The pH value were highly alkaline ranging from 10.2 – 13.5, while the moisture content showed a very wide range from 6 – 43%. The particle size analysis of the earth works excavation on the study site established five stockpile particle size fraction, ranging from as fine as <0.8mm to >38.22 mm. The composition of zinc ranging from 2.78% - 5.96%, while the iron content ranging from 41.36 to 62.18% respectively. This amount of iron has the potential for recovery and reused within a steel making process. It is possible to recover 97% of Zn and 30% Fe by roasting at 750C for a period of 135 minutes with NH4Cl salt. Roasting with 3 stages of NH4Cl addition proved to be more appropriate to increase the percentage of zinc removal. 97% Zn are removed Cl2/N2 gas for a period of 30 minutes roasting. The water leaching was conducted More than 90% Zn are recovered using bigger surface area sample boat with only 2.5 times stoichiometry. The extraction of Zn was greatly enhanced by the water leaching following the chlorination roasting using Cl2/N2 gas. 95% of Zn was leached while only 7% Fe was extracted after chlorination at 650C for 20 minutes roasting. It is possible to leach up to 98% Zinc after the chlorination roasting at 450C at 20 mins. The research has demonstrated that chlorination extraction has potential application in the steel sector for removal of Zn from steelmaking BOS dusts. In conducting the chlorination roasting, operational parameters such as temperature, roasting, chlorine agent stoichiometry, and surface area are important in determining the best operational condition. Hybrid process of chlorination roasting with leaching could highly assist in the further removal of Zn from BOS dust.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available
Keywords: TN Mining engineering. Metallurgy