Process input sequences, desired

Separations are an important phase in almost all chemical engineering processes. Separations are needed because the chemical species from a single source stream must be sent to multiple destinations with specified concentrations. The sources usually are raw material inputs and reactor effluents the destinations are reactor inputs and product and waste streams. To achieve a desired species allocation you must determine the best types and sequence of separators to be used, evaluate the physical or chemical property differences to be exploited at each separator, fix the phases at each separator, and prescribe operating conditions for the entire process. Optimization is involved both in the design of the equipment and in the determination of the optimal operating conditions for the equipment. 

Process planning There are many operations involved in factory planning for transforming the inputs into some desired end product. In process planning these operations are located and the sequence of these operations in the production process is determined. Plans are also made for the layout of work centers in each process. 

From a control standpoint, the most important variables are those which ultimately affect the end-use properties. These will be referred to as controlled variables affecting product quality. The most important of these are MW, MWD, monomer conversion, copolymer composition distribution, copolymer sequence distribution, and degree of branching. Most of these variables are not measurable on-line. The common approach is to control those variables which are measurable, to estimate those which are estimable and control based on the estimates, and to fix those which cannot be estimated by controlling the inputs to the process. Closed-loop control involves the adjustment of some manipulated variable(s) in response to a deviation of the associated control variable from its desired value. The purpose of closed-loop control is to bring the controlled variable to its desired value and maintain it at that point. Those variables which are not controllable in a closed-loop sense are maintained at their desired values (as measured by laboratory or other off-line measurement) by controlling all the identifiable input in order to maintain an unmeasured output at a constant value. 

Programmable logic controllers PLCs) are widely used in batch process control to execute the desired binary logic operations and to implement the desired sequencing. The inputs to the PLC are a set of relay contacts representing various device states (for example, limit... 

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