Page 55 - Chemical engineering design

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4. As a first step, include any recycle streams within the system boundary (see
Section 2.14). CHEMICAL ENGINEERING
Example 2.4
Selection of system boundaries and organisation of the solution.
The diagram shows the main steps in a process for producing a polymer. From the
following data, calculate the stream flows for a production rate of 10,000 kg/h.
Reactor, yield on polymer 100 per cent
slurry polymerisation 20 per cent monomer/water
conversion 90 per cent
catalyst 1 kg/1000 kg monomer
short stopping agent 0.5 kg/1000 kg unreacted monomer
Filter, wash water approx. 1 kg/1 kg polymer
Recovery column, yield 98 per cent (percentage recovered)
Dryer, feed ¾5 per cent water, product specification 0.5 per cent H 2 O
Polymer losses in filter and dryer ¾1 per cent

Monomer Short stop
water
catalyst
Polymer
Filter Dryer
Reactor

Recycle Recovery
monomer column

Effluent

Solution

Only those flows necessary to illustrate the choice of system boundaries and method of
calculation are given in the Solution.

Basis: 1 hour
Take the first system boundary round the filter and dryer.

Filter Product
Input and 10,000 kg polymer
dryer 0.5% water
Water
+ monomer
Losses