Scope and Hierarchy of Optimization

Optimization can take place at many levels in a company, ranging from a complex combination of plants and distribution facilities down through individual plants, combinations of units, individual pieces of equipment, subsystems in a piece of 

more specific decisions are made in process design, including the actual choice of equipment (e.g., more than ten different types of heat exchangers are available) and the selection of construction materials of various process units. 

Plant operations deal with the allocation of raw materials on a daily or weekly basis. One classical optimization problem, which is discussed later in this text, is the allocation of raw materials in a refinery. Typical day-to-day optimization in a plant minimizes steam consumption or cooling water consumption. 

Plant operations are also concerned with the overall picture of shipping, transportation, and distribution of products to engender minimal costs. For example, the frequency of ordering, the method of scheduling production, and scheduling delivery are critical to maintaining a low-cost operation. 

The following attributes of processes affecting costs or profits make them attractive for the application of optimization  

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