Abstract
M.Tech. (Chemical Engineering)
The work presented here constitutes an account of the optimization of a chemical reaction process with special reference to the methodology of reagent addition in the
case of fast reactions. The chemical reaction process for manufacture of the
Formaldehyde Acetaldehyde condensation product Pentaerythritol (Penta) as it is conducted at the plant of National Chemical Products, a division of Sentrachem, was
studied in detail. The industrial scale reactor design was critically examined, 'with emphasis on the evaluation of mixing and reagent dispersion efficacy and its effect on
chemical reactor performance. Batches of Pentaerythritol products were prepared in a
laboratory bench scale reactor. Reagent concentrations and proportions were controlled at various values and the reaction temperature profiles were controlled so as to be
similar for all the tests. Moreover the mode and intensity of liquid agitation and reagent admixture was varied in a controlled manner between the various tests. The reaction liquors from the various batches were sampled and the samples subjected to chemical analysis. The results were then compared in order to show the effect of agitation and reagent dispersion intensity on the reaction process and products. The results indicate conclusively that liquid flow or agitation intensity and reagent admixture or sparging
variation has an effect on the type and relative amounts of chemical species produced in the laboratory apparatus. This effect is especially significant with respect to the
side products Di-pentaerythritol and Bis Penta Mono-formal (B.P.M.F.). The effect is also demonstrated for the gamut of various side products collectively and arbitrarily
designated as the so-called "unknowns". Furthermore the formation of coloured products in the reaction is distinctly influenced by the same variation. High intensity agitation and reagent sparging enhances Dipenta formation and inhibits formation of the Formal B.P.M.F, "unknowns" and colour. At very low agitation and sparging intensity Di-penta production is diminished while B.P.M.F., "unknowns" and colour formation is favoured. The work includes a proposal for the manufacture and installation of improved reagent sparging systems in the NCP Transvaal commercial scale Penta Reactor.A tentative method for the design of a continuous reactor for penta production using optimised Tee mixers for high velocity in-line reagent sparging is also developed.