The ‘iodide–iodate’ reaction scheme has been used to ascertain the effectiveness of micromixing in a semi-batch reactor when feeding with pipes rotating and discharging continuously into the region of highest local specific energy dissipation rate, ε T . The results are compared with those obtained using a fixed pipe at the equivalent position and at other positions including near the top surface, the most convenient position industrially. The results show significant intensification, i.e., a seven-fold reduction in ‘waste product’, between the most convenient fixed feed pipe position and the rotating pipes, even at the modest specific power input of ∼ 1.0 W / kg . This mode of addition also ensures that feeding is always into a constant value of ε T , whereas with a static pipe close to the impeller the reactants are being fed in a region where ε T varies cyclically. This difference in the ε T values experienced by the two modes of addition poses problems for previous models of micromixing in the literature linking selectivity to local specific energy dissipation rates.