The conceptual design of a process that identifies the best process flowsheet structure, such as the conversion of raw materials into a product. This requires the consideration of many alternative designs. Due to the complexity of most processes, the flowsheet is divided into smaller parts and each considered in turn, then choices and decisions made. Various techniques are used to arrive at the best flowsheet such as those based on total cost, which needs to be minimized, the use of graphical methods, the use of heuristics, and various other forms of minimization such as the use of process integration.