Pressure as a further parameter of composite curves in energy process integration

An attempt has been made in this paper to classify in more detail, when pressure plays an important role in energy process integration. Rather than individual process streams available for heat recovery the whole tracks are considered. In addition to heat capacities and temperatures also pressures in stream ends are to be specified. If supply temperature and pressure in state 1 are T1 and P1 and final values in point 2 are T2 and P2, then four combinations among conditions T1T2, P1P2 are possible. If both temperature and pressure are to be changed along the path, both heat and work have to be exchanged with ambient. While an enthalpy change is always constant for any path from 1 to 2 the same holds true for a sum of heat and work Q+W. However, many other things depend on this path (heat transfer area, work target values etc.). Some illustrative examples are outlined and in conclusion some heuristical rules are formulated.