CLOSURE PROBLEM FOR PARALLEL CHEMICAL-REACTIONS

The effect of micromixing on parallel reactions was studied experimentally and interpreted theoretically using closure models. A solution of sodium hydroxide was contacted with a pre-mixture of hydrochloric acid and ethyl chloroacetate solutions in a tubular reactor equipped with an impingement mix-head. Two different impingement mix-heads were applied: the first was T shaped with two feeding nozzles; the second was equipped with six feeding nozzles. The selectivity of the parallel reactions was then dependent upon the mix-head used, the Reynolds number, the concentration of reactants and the volume ratio of reagent solutions. The effect of the volume ratio of the reagent solutions on the selectivity was used as the test effect for closure models. It is shown that simple closures based on moments are not able to describe properly the behaviour of parallel reactions. A closure method based on the probability density functions of the concentrations of chemically inert species and on the interpolation of the local concentrations of reactants between the asymptotes of infinitely slow and infinitely fast chemical reactions is verified experimentally.