A distillation apparatus and method in which first and second compressed streams are formed from a compressed feed stream, for example, compressed air. The first compressed stream is fully cooled within a main heat exchanger so that it is substantially condensed. The second compressed stream is partly cooled within the main heat exchanger and then introduced into a turboexpander at a temperature such that the turboexpander exhaust stream is superheated. Part of the first compressed stream is mixed with the exhaust stream to produce a combined stream that is no more than 10° C. above saturation temperature at the pressure of the exhaust stream. The combined stream is introduced into a distillation column unit to produce one or more products that are enriched in components of the feed to be separated. In such manner the turboexpansion can occur at a higher temperature and with increased refrigerating effect.