In most industrial processes, there is a significant need for electric power and for heating. Process cogeneration is aimed at the simultaneous provision of combined heat and power. The net result is usually a reduction in the overall cost and emissions of greenhouse gases. Therefore, there is a significant need for the optimal design of process cogeneration systems. This objective of this paper is to introduce an algorithmic approach to the optimal design of process cogeneration systems. Focus is given to the interaction of the power cycle with the process heat requirements. Because of the need for explicit thermodynamic expressions, a new set of thermodynamic correlations of steam properties is developed for proper inclusion within a mathematical-programming approach. An optimization formulation is developed to provide a generally applicable tool for integrating the process and the power cycle and for identifying the optimum equipment size, operating parameters (such as boiler pressure, superheat temperature and steam load). The objective can be chosen as minimizing the cost, satisfying the heat requirement of the process, or producing the maximum possible of power. A case study is solved to illustrate the applicability of the devised approach and associated thermodynamic correlations.