STUDY OF THE KINETICS OF ROASTING OF ZINC AND COPPER CONCENTRATES IN A FLUIDIZED BED

Abstract

The roasting of sphalerite and chalcopyrite concentrates is an important step in the production technology of zinc and copper. The recent development in the roasting is the use of fluidized bed technige in which the fine solids are transferred into a fluid like state through the contact of gas. This technique was first developed in 1920' $ and the first large scale use of. flvldized bed was made by Fritz and Winkler for the gassifieation of powderedcoal. The patent for this process was awarded in 1922 and the first gas producer started its operation in 1926. A number of similar units were constructed in Germany and Japan to supply raw gas for the synthetic chemical industries• This type of gas . producer was very inefficient therefore numerous developments were made by many individuals and organizations. This technique was first developed by Chemical Engineers and _ later on its use was made in metallurgical field. In 1944 Dorr-Oliver Company acquired rights to use this technique in the roasting of sulphide ores. They soon developed the fluo-'solid system and first such unit was constructed in 1947 in Ontario y Canada to roast arsenopyrite and to obtain a cinder suitable for gold production by cyanidation. In 1942 at Berlin$ New Hampshire' Dorr-Oliver introduced this type of roaster for producing SO2 from sulphide ores. As early as 1945 Badische Anilin and Soda-Fabrik (BASF) in Germany and Sumitomo Chemical Manufacturing Company in Japan independently developed a roaster similar to..fluosolid system. Dorr.»olitrer engineers pioneered two additional important uses of fluidized bed in the area of drying .powdery materials and the calcination of lime stone. Another application .of fluidized bed in metallurgy is the reduction of Iron ore. This technique has been extensively used in the previous years particularly in the United States. The purpose of these studies is to develop a process for producing iron and steel from fines of high grade ores* Hydrocarbon Research Corporation and Bethlehem steel company jointly developed a process for direct reduction of iron ore called H-Iron process and the United States company developed its Nu.Iron process for reduction with hydrogen of less than 10 mesh size ore. Further, development made by ESSO Research engineers is the use of multi stage recorders. In the present investigation an attempt has been made to study the effects of temperature and particle size on the rate of roasting of zinc sulphide and copper sulphide concentrates in fluidized bed by using chemical analysis method for sulphur determination. This thesis has been d0iided into four chapters. Chapter4 deals with the general introduction.to the subject, advantages and disadvantages and industrial applications of fluidized bed. Literature review is included in Chapter II anddeals with fundamentals of fluidization, theory of oxidation of sulphide concentrates$ and a brief review of the previous work done on the roasting of zinc and copper concentrates. Chapter-iII gives the description of the experimental set-up and procedure followed in the present investigation. Pellets of three various sizes (0.1435 am, 0#184 cm, 0.213 cm.) of spherical shapes were made with the help of pelletizer$ they were then dried and roasted at various temperatures. The zinc concentrates were treated at temperature 700' , 7500 and 800°C and copper concentrates were treated at temperatures 500°,560°,600°,650° and 700'C. The kinetic data were obtained by chemical analysis of roasted samples.