Procedure:
Step 1. Draw a block diagram of the process.
Show each significant step as a block, linked by lines and arrows to show the
stream connections and flow direction.
Step 2. List all the available data.
Show on the block diagram the known flows (or quantities) and stream compositions.
Step 3. List all the information required from the balance.
Step 4. Decide the system boundaries (see Section 2.6).
Step 5. Write out all the chemical reactions involved for the main products and byproducts.
Step 6. Note any other constraints,
such as: specified stream compositions, azeotropes, phase equilibria, tie substances.
The use of phase equilibrium relationships and other constraints in determining stream compositions and flows is discussed.
Step 7. Note any stream compositions and flows that can be approximated.
Step 8. Check the number of conservation (and other) equations that can be written, and compare with the number of unknowns. Decide which variables are to be design variables.
This step would be used only for complex problems.
Step 9. Decide the basis of the calculation;
The order in which the steps are taken may be varied to suit the problem.
The best way to tackle a problem will depend on the information given; the information required from the balance; and the constraints that arise from the nature of the problem. No all embracing, best method of solution can be given to cover all possible problems. The following step-by-step procedure is given as an aid to the efficient solution of material balance problems. The same general approach can be usefully employed to organise the solution of energy balance, and other design problem
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