Thermogravimetric study of lead sulfide chlorination between 783 and 953 K
- PDF / 808,658 Bytes
- 10 Pages / 614.28 x 794.28 pts Page_size
- 8 Downloads / 173 Views
I.
INTRODUCTION
II.
DUE to the growing concern of SO2 emission in conventional sulfide roasting processes, combined with the versatility of metal chlorides as intermediates in metal extraction and the high reactivity between chlorine and most sulfides, there has been a renewed interest in the chlorination of metal sulfides. A literature review of the chlorination processes, developed before 1977, of different sulfides was assessed by Parsons. t~l Recently, Mikhail and Webster studied the chlorination of many major sulfide minerals, e.g., sphalerite, pyrite, galena, and chalcopyrite, by differential thermal analysis.L2'3m Among the different minerals, galena was found to be the most reactive with chlorine. The reaction rate of lead sulfide with chlorine between 772 and 1193 K was measured ~reviously by Gerlach and Pawlek, [5] Landsberg et al., [ 1 and T i t i - M a n y a k a and Iwasaki. t71 However, most of these studies were carried out at constant chlorine pressure, and included few data on the extent of vaporization loss during chlorination. The reaction of lead sulfide and chlorine between the melting point and boiling point of PbC12 may be represented by Eq. [1]: PbS~) + C12r ) --~ PbC12fl ) + 1/2S2(g )
[1]
The replacement of sulfur by chlorine increases the weight of the sample, while the vaporization loss of PbCI2 decreases the sample weight. These weight changes can be used to study the reaction using a thermogravimetric (TG) technique. In the present investigation, the observed chlorination behavior as well as the vaporization rate of PbC12 from both pure PbC12 and PbCI~-PbS mixtures were studied. The mechanism of the chlorination process was deduced from these TG results and from micrographic and X-ray examinations. E C. CHEN is with the Department of Materials Science, Feng Chia University, Taiwan, Republic of China. J. M. TOGURI is INCO/NSERC Professor m Chemical Process Metallurgy, Department of Metallurgy and Materials Science, University of Toronto, Toronto, ON M5S 1A4, Canada. S. K. CHANG is Supervisor, Materials and Processes Engineering, Litton Systems Canada Ltd., Etobicoke M9W 5A7, Canada. Manuscript submitted March 16, 1988. METALLURGICAL TRANSACTIONS B
EXPERIMENTAL
A. Materials and Sample Preparation In the chlorination study, approximately 1 g of reagent grade PbS powder (99.45+ pct purity) from Matheson, Coleman and Bell Company was placed in a smaller cylindrical graphite crucible (approximately 0.76 cm I.D., 0.77 to 1.35 cm length) which in turn was inserted into a quartz retort. This assembly was placed in an induction furnace to melt the PbS sample. The resulting pellet of PbS was dense and compact. The vertical distance from the upper surface of the PbS pellet to the top edge of the crucible, which is referred to as free-board height (f.b.h.) of the sample, was measured with a micrometer. The tops of the graphite crucibles were carefully polished in order to prepare a group of samples with f.b.h, within ---0.2 mm of the average length. A quartz fiber hanger was attached to the cr
Data Loading...
