Abstract The simplified micromixing model, derived in Part I (J. Baldyga and J.R. Bourne, Chem. Eng. J., 42 (1989) 83) and valid when Sc « 4000 and F « 1, was applied to calculate the influence of partial segregation on the product distribution of competitive, consecutive and parallel reactions. Six problems, two of which refer to four reactions and four to two reactions, were easy to model and much faster to compute than when modelling with partial differential equations. Various operating modes (plug flow, semibatch, continuously stirred tank reactor, etc.) as well as different operating variables (volume ratio of reagents, Damköhler number, i.e. ratio of mixing and reaction times, etc.) were readily evaluated. The phenomenon of self-engulfment, whereby ineffective engulfments occur between elements of the same fluid, is important when analysing plug flow regions. Expressions were worked out to describe useful engulfments between chemically different fluids and were applied to plug flow reactors.