A combinatorial optimization approach is proposed to derive flowsheets for systems that satisfy fixed demands of steam, electricity and mechanical power. This approach allows the selection of equipment available in standard capacities by handling discrete variables and discontinuous cost functions. Simulated annealing is a combinatorial optimization technique that has been efficiently applied to several areas, including process design. Two annealing schedules are compared by means of a numerical example that also demonstrates the importance of considering discrete equipment capacities.