Page 143 - Analysis, Synthesis and Design of Chemical Processes, Third Edition

Caution should be exercised before using this method. There are subtleties associated with it, which are
explained in more detail elsewhere [4].

4.5 Manufacture

This final step in the chemical product design structure is the most detailed. It includes determining
whether the product can be manufactured, developing detailed product specifications, determining how

the product is to be manufactured, and estimating the cost of manufacturing. It also includes sample or
prototype testing, which may result in changes in the selection process and undoubtedly will result in
modifications in every step of the manufacturing process until the optimal product and manufacturing
process is obtained.

These feedback loops in the manufacturing process exist for all the manufacture of any product, even a
commodity chemical. Before a multimillion-dollar plant is constructed, a pilot plant is usually
constructed. Before a new chemical product is manufactured, small quantities are made in the laboratory
to determine whether the product satisfies the need for which it was designed. Similarly, before a device
is manufactured, a prototype is built and tested.

One lesson is that device manufacture is likely to be a very interdisciplinary effort. In the magnetic
refrigerator example, Example 4.3, mechanical engineers would be needed for the pulley system, and
electrical engineers might be needed for the control systems. Industrial engineers may be needed to
determine the most efficient manufacturing procedure and to help determine the unit cost in mass
production, because the cost of a prototype always exceeds the unit cost in mass production. When
interdisciplinary efforts are needed, it is recommended that the interdisciplinary team be involved from
the beginning, if possible. Example 4.8 illustrates the type of product that might be manufactured.

Example 4.8

Suppose the following scenario has evolved for the zebra mussel problem discussed in Examples 4.1 and
4.5. It is not possible to use a filter to prevent zebra mussel infestation because in the veliger (infancy)
stage, zebra mussels are microscopic. They attach to the wall of the intake pipe, where they grow into
maturity. Once the walls are saturated, they stack on each other, eventually occluding the pipe. Therefore,
some type of chemical treatment is desirable. It has been determined from experimentation that