Page 18 - Chemical process engineering design and economics

Processes and Process Engineering 5

CHEMICAL ENGINEERING ACTIVITIES

It is usefiil to delineate the various activities of a chemical engineer, from the con-
ception of a project to its final implementation. Companies will assign a variety of
job titles to these activities. In some companies, these activities will be subdi-
vided, but in other companies many activities may be included under one job title,
according to company policy. In this discussion, the engineering activity is of
more concern than any particular job title assigned by a company. We will use the
most frequently employed job title, keeping in mind that any particular company
must be consulted for its definition of the job.
A project is initiated by determining if there is a market for a product, which
may be a chemical, a processed food, a metal, a polymer or one of the many other
products produced by the process industries. For example, a chemist first synthe-
sizes a new drug in the laboratory, which after many tests is approved by the Food
and Drug Administration (PDA) of the federal government. Then, chemical engi-
neers develop and design the process for producing the drug in large quantities.
The steps required to accomplish this task are outlined in Table 1.2. Under some
circumstances, where knowledge of the process is highly developed and sufficient
data exists, the research or pilot phase of the process, or both, may be omitted. In
order to cover all aspects of a project, we will assume that a new chemical, which
is marketable, has just been synthesized in the laboratory by a chemist.
Next, the technical, economic, and financial feasibility of proposed proc-
esses must be demonstrated. Unless the project shows considerable promise when
matched against other potential projects, it may be abandoned. Any particular
company will have several projects to invest in but limited financial resources so
that only the most promising projects will be continued. The research engineer
should estimate the capital investment required and the production cost of the
product. No matter how crude or incomplete the process data may be, the research
engineer must estimate the profitability of the process to determine if further proc-
ess development is economically worth the effort. This analysis will also uncover
those areas requiring further research to obtain more information for a more accu-
rate economic evaluation.
If the project analysis shows sufficient uncertainty or the need for design
data, the research engineer will plan experiments, design an experimental setup
and correlate the resulting data. After completing the experiments, the research
engineer, or more likely a cost engineer, revises the flow diagram and reevaluates
the project. Again, he must show that the project is still economically feasible.
After completion of the research phase, it is usually found that further dem-
onstration of the viability of the process and more design data is needed, but under
conditions that will more closely resemble the final plant. It may also be required
to obtain some product for market research. In this case, the development engi-
neer will plan the development program and design the pilot plant. Whenever pos-
sible the equipment selected will be smaller versions of the plant size equipment,
using the same materials of construction selected for the plant.

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