Page 144 - Analysis, Synthesis and Design of Chemical Processes, Third Edition

alkylbenzyldimethylammonium chloride (alkyl chains between 12 and 16 carbons) will kill existing
infestations, and dead mussels detach from the wall [10]. Also, assume that it has also been determined
that 0.3 wt % hydrogen peroxide will inhibit veliger attachment. Describe the manufacturing stage.

A delivery system is needed, both for the initial kill and for the hydrogen peroxide to prevent infestation.
One possible solution is to design and market a technology for delivery of these chemicals. For example,
suppose that a grating for the intake pipe containing flow channels with holes discharging into the intake
pipe were designed. A pumping system would be needed to deliver the chemicals through the holes in the
grating. If the fluid mechanics of the discharge into the intake pipe were studied to optimize hole
placement, the hole placement could be optimized to ensure that the chemicals covered the entire cross
section of the pipe at the desired concentration. This technology could then be marketed to water treatment
facilities and power plants to prevent zebra mussel infestation.

4.6 Batch Processing

In the manufacture of a chemical product that is actually a chemical, batch operations are often employed.
This is because specialty chemical products are usually produced in small batches. In the Douglas

hierarchy discussed in Chapter 2, the first decision to be made in designing a chemical process is batch
versus continuous. For production of a commodity chemical in the quantities reflected in the examples on
the CD-ROM accompanying this book, the choice will always be a continuous process. Similarly, for
production of a specialty chemical, the choice will almost always be a batch process.

The issues involved in batch processing were discussed in Chapter 3.

4.7 Economic Considerations

When a new process is constructed for a commodity chemical, the sale price for the chemical is largely
determined by the price competitors charge for the same chemical. However, the law of supply and
demand does affect the price. If new capacity exists without additional demand, the value of the chemical
may drop; if new capacity is created in response to a demand, the value of the chemical can probably be
estimated from its value before the demand increased. Either way, the value of the chemical can probably
be bracketed reasonably easily.

However, when a new product enters the market, the initial price usually reflects the value of its
uniqueness. We see this every day. When new electronic devices enter the market (CD players, DVD
players, projection TVs, HDTV), they usually carry a high price tag. In part, this is because they are not
being produced in large quantities, and in part it is because there are customers who will pay a huge
premium to be the first to have one. Eventually, prices decrease to attract new customers and then
decrease significantly if the product becomes a commodity. Pharmaceuticals, an example of a chemical
product, also carry a high price tag when they are new. Pharmaceutical companies must recover the

extremely high costs of product research and development and the regulatory process before their patents
expire and low-cost, generic alternatives become available, or before a competitor invents a superior
alternative.