Leaching backmixing

Burovoi, I. A., Dracheva, T. V, and Ibraev, A. Kh., Semi-Industrial Testing of the Fluidized-Bed Acid Leaching of Zinc Calcine, Tsvet, Metal. 44(10), 16(1971) Chem. Abs. 76,36,301 (1972). Cankurt, N. T., and Yerushalmi, J., Gas Backmixing in High Velocity Fluidized Beds, Second Intern. Conf. Fluidization. Cambridge, pp. 387-393 (1978). 

Bader et al. (1988) used common salt as a solid tracer, which was injected into a flowing catalyst bed. Solids samples, withdrawn downstream of tracer injection, were leached with water and the salt concentration determined by electrical conductivity of the solution. Their results indicated substantial solids backmixing. Li et al. (1991) observed solids mixing in a fast fluidized bed combustor by using raw coal as a tracer, which was injected into the ash bed. Their results also showed that near-perfect mixing prevailed. Similar experiments was also conducted by Chesonis et al. (1991) in a cold model. 

Marked axial dispersion in both the liquid and solid phases has been observed in continuous countercurrent leaching systems. The solid-phase dispersion is probably caused by nonuniform conveying and by backmixing caused by the baffles which are used to prevent solid beds from turning en masse. VnliD n values of 16.1 m and 20 m, respectively, have b n repotted for sugar beet extraction in tower and slope extractors. Local fiow nonuniformity and larger-scale flow maldistribution are the primary factors that cause axial dispersion in the extract. 

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