The gas phase was treated as real rather than ideal throughout simulations to enable modelling of non-ideal vapour phase mixing, which can bring improvement in estimation accuracy at low computational cost. For unit operations where no vapour phase association was expected the Redlich-Kwong EOS was used, which is generally accurate for systems where the reduced pressure is less than half the reduced temperature (𝑃/𝑃𝑐 < 𝑇/2𝑇𝑐), as was the case for this study. For process steps with expected vapour phase association the Hayden-O'Connell EOS was employed.