Page 60 - Plant design and economics for chemical engineers

PROCESS DESlGN DEVELOPMENT 43
corrosive action of any chemicals that may contact the exposed surfaces.
Possible erosion caused by flowing fluids or other types of moving substances
must be considered, even though the materials of construction may have
adequate chemical resistance. Structural strength, resistance to physical or
thermal shock, cost, ease of fabrication, necessary maintenance, and general
type of service required, including operating temperatures and pressures, are
additional factors that influence the final choice of constructional materials.
If there is any doubt concerning suitable materials for construction of
equipment, reference should be made to the literature,? or laboratory tests
should be carried out under conditions similar to the final operating conditions.
The results from the laboratory tests indicate the corrosion resistance of the
material and also the effects on the product caused by contact with the
particular material. Further tests on a pilot-plant scale may be desirable in
order to determine the amount of erosion resistance or the effects of other
operational factors.

PROBLEMS
1. Using Chemical Abstracts as a basis, list the original source, title, author, and brief
abstract of three published articles dealing with three different processes for produc-
ing formaldehyde.
2. Prepare, in the form of a flow sheet, an outline showing the sequence of steps in the
complete development of a plant for producing formaldehyde. A detailed analysis of
the points to be considered at each step should be included. The outline should take
the project from the initial idea to the stage where the plant is in efficient operation.
3. A process for making a single product involves reacting two liquids in a continuously
agitated reactor and distilling the resulting mixture. Unused reactants are recovered
as overhead and are recycled. The product is obtained in sufficiently pure form as
bottoms from the distillation tower.
(a) Prepare a qualitative flow sheet for the process, showing all pieces of equipment.
(b) With cross reference to the qualitative flow sheet, list each piece of equipment
and tabulate for each the information needed concerning chemicals and the
process in order to design the equipment.
4. Figure 2-1 presents a qualitative flow diagram for the manufacture of nitric acid by
the ammonia-oxidation process. Figure 2-2 presents a quantitative flow diagram for
the same process. With the information from these two figures, prepare a quantita-
tive energy balance for the process and size the equipment in sufficient detail for a
preliminary cost estimate.
5. A search of the literature reveals many different processes for the production of
acetylene. Select four different processes, prepare qualitative flow sheets for each,
and discuss the essential differences between each process. When would one process
be more desirable than the others? What are the main design problems which would

TDetailed information on materials of construction is presented in Chap. 12.