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significant. Acid and water are used in the second step. The acid is catalytic
and therefore not of large cost significance. Water is relatively inexpensive.
6.7 SCALE-UP CONSIDERATIONS
Industrial chemicals are made on a large scale, often thousands of tons per
day. Laboratory chemists typically work on gram scale, sometimes running
reactions at the milligram level. The laboratory chemist usually uses glass
flasks, often in very dilute solutions and with a lot of surface area. The
laboratory reactions are usually run one at a time, also known as batch-wise.
A reaction can perform well under these conditions but can have serious
issues upon scale-up. There are many factors that go into a successful
scale-up and the sooner the chemist thinks about them, the more effective
they will be. My first boss [11] in industry was a chemical engineer and
fond of telling the story of the lab chemist who accidentally broke a test
tube containing a liquid on the bench and crystals formed in the puddle. The
chemist then turned to the chemical engineer and stated, “My job is done;
now you scale it up.” The story is an overstatement and a way to jab at naïve
chemists, but it is difficult not to be naïve as a recent graduate.
If you have several years' experience in scale-up, you will see a lot and
will learn from what goes right and from mistakes. Chances are that many of
you do not have decades of scale-up experience. If you are faced with scaling
from the laboratory, my best advice is to seek counsel from those that are
experienced.
Dependent upon the amount of material needed, the availability of
equipment, and the confidence in the ability of the process to be run on
a large scale, often an intermediate size operation is done. This can be a
large-scale laboratory reaction, perhaps moving from 100 mL to a 22 L flask.
Or it can be at a scale of several hundred gallons. Often these intermediate
size processes are done in a facility expressly built for the purpose of trialing
or piloting processes before eventual manufacturing scale. These facilities
are called pilot plants. They often have more versatility in equipment than a
manufacturing facility. However, sometimes they are built to exactly mimic
the existing manufacturing plant.
One of my first scale-ups involved isolating a solid from slurry. In the lab,
this was trivial; I just filtered with a Buchner funnel. I didn't care how long it
took because I could do other things while it was filtering. In the plant and at
a scale of thousands of gallons, it was important to be able to do an efficient
separation. The available equipment was a centrifuge. Think about a large
washing machine where after the wash the water and clothes are spun. The
water passes though the washing machine basket, leaving the clothes behind.
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