Reactor models for a series of continuous stirred tank reactors with a gas-liquid-solid leaching system: Part III. Model
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I.
INTRODUCTION
IN Part I m and Part II, ~21model equations suitable for the calculation of the conversion of multisize feeds subjected to leaching in a series of continuous stirred tank reactors (CSTRs) under isothermal or nonisothermal conditions were developed. In Part I, the equations describing the reactor operation under surface reaction control kinetics were described, while in Part II, the corresponding equations for the case of gas-transfer control kinetics were developed. These equations were used to construct a computer algorithm to simulate the autothermal steady-state performance of a multistage g-l-s reactor operating under either surface reaction or gastransfer control. It is the object of this article to demonstrate how this computer algorithm can aid in describing and predicting the performance of a continuous reactor on the basis of the intrinsic kinetics of the particle dissolution reactions, the gas-transfer kinetics of the reactor, and the heat balance of the reaction system. The system chosen for the application of the model is the autogenous pressure oxidation of auriferous pyritic concentrates under high-temperature and oxygen pressure conditions, c31
A. The Feed The feed material makeup chosen for this application resembles that of the Olympias gold concentrate.t4'5] The selection of this particular concentrate was made because it consists primarily of pyrite and arsenopyrite, for which appropriate rate equations had been developed. 16"71The composition, ~4~size distribution, and density data of the concentrate are given in Table I. As seen in this table, the weight fractions of pyrite (WFes2) and arsenopyrite (WFeAsS) are 0.665 and 0.261, respectively. The particle size distribution parameters that were used in Eq. [1] (from Reference 8 and Part I m)
2 ~ exp
ado - do + 15
2
f(d~163
~ adoad~d - d2~+
[11
[3exp [ - ( q 2 - ~ )
correspond to 98 pct-44/zm material.* The parameters *Equation [1] is used as a mass-PSD function, fro(d).
II.
THE CHEMICAL REACTION SYSTEM
In this article, a concentrate composed of pyrite and arsenopyrite is considered as being the feed to a continuous multistage pressure reactor. V.G. PAPANGELAKIS, Assistant Professor, is with the Department of Chemical Engineering and Applied Chemistry, University of Toronto, Toronto, ON M5S 1A4, Canada. G.P. DEMOPOULOS, Associate Professor, is with the Department of Metallurgical Engineering, McGill University, Montreal, PQ H3A 2A7, Canada. Manuscript submitted August 2, 1991. METALLURGICAL TRANSACTIONS B
/~ and c were calculated from discrete size distribution data of the Olympias concentrate? 9J Details on this calculation are given in Appendix A. It is tacitly assumed that the pyrite/arsenopyrite particles are completely liberated and that both minerals follow the same distribution function (i.e., ~ = /*FeS2 = /~FeAsS, and c = CFes~ = CFCass)- Constant density values are assumed for each component of the feed. tml The density of SiO2 (an average value over several polymorphic forms of silica Ira) is taken as that
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