However especially if the contaminant has little or no value if concentrated

However especially if the contaminant has little or

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However, especially if the contaminant has little or no value if concentrated, there will be relatively dilute waste streams generated and sent to the environmental control section.
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Major Process Control Loops During the initial synthesis of the PFD, the major control loops are developed. These control loops affect more than just one unit of a process. Significant design improvements can be made through the early development of major control loops. E.g. In the high-temperature exothermic reactor, for example, failure to consider the control loop might lead one to propose an integrated heat-exchanger network that is difficult or impossible to control. Major process control loops provide early clues to the flexibility of the process operation. E.g if the feed to is cut in half, less heat needs to be removed. Therefore, there must be an increase in the temperature of the cooling medium, which occurs when the coolant flowrate is reduced. Process control can be both very difficult and extremely important in biological processes, as demonstrated in Example 12.5.
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Flow Summary Table Each of the conditions (T, P, flowrate, composition, and phase) should be estimated early in the flowsheet development. All are needed to get preliminary costs. Even estimates based on perfect separations can provide sufficient data to estimate the cost of a recycle versus the value of burning the impure, unreacted feed material as a fuel. Completeness of the estimates, not their accuracy, is important at this stage. E.g., an early determination of phase is needed to help choose a separation scheme or reaction type.
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Major Equipment Summary Table In the context of initial PFD development, the process of creating the table forces the process design engineer to question the size (and cost) of various units of operation. The early consideration of materials of construction provides the clue that normal temperatures and pressures usually result in less expensive materials.
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  • Fall '08
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