CHAPTER 4 Understanding Process Conditions Don Scott ENCH 430 1/24/06

The ability to make an economic analysis of a chemical process based on a PFD is not proof that the process will actually work.

It is usually easier to adjust temperature and/or pressure than it is to change composition.

HOWEVER

A decision to operate outside the pressure range of 1 to 10 bar must be justified $$$$$$$$$$$$

A decision to operate above 400º C must be justified Microstructure of steel pipe after 28 years service at 773K, shows several creep pores (dark) and carbides(white).

A decision to operate outside the range of 40°C to 260°C, thus requiring special heating/cooling media, must be justified.

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Conditions outside the favored temperature and pressure ranges are identified as “conditions of special concern.”

Items for justification Favorable equilibrium conversion Increase reaction rates Maintain a gas phase Improve selectivity Also, consider tables 4.1,2,3 on pages

Changes in process conditions for a stream passing through a single piece of equipment Table 4.4 on page 124 Table 4.5 on page 128 process conditions matrix.