This blog is about, the diameter calculations of a sieve tray column. Software's can give diameter for each stage but to verify on our own,the below Sinnot Procedure will help you in comparing the results. We may not get the exact match becasue software equations might be much more detailed. The below procedure help a student on how text book methods are used for comparing the results and where exactly the basic knowledge will help in sizing a distillation column. |
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In a similar way, diameter is calculated for each stage and the
largest diameter will be selected.
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If you calculate for other stages the diameters will be different because properties will be different.
Constructing a column with single diameter is cheaper. But how
we accommodate the lesser diameter stages, is by simply blocking perforations
of a tray so that total openings will reduce which is equivalent to lesser
diameter.
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Columns with different diameters also in use, but only thing is
cost is higher.
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In my next blog I will write a blog on pressure drop
calculations.
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Approximate Column height is calculated as (Number of stages*Tray Spacing) + (15% of Number of stages*Tray Spacing).
Questions:
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How maximum vapor rate is decided?
This is an initial guess which we need to mention for a coloumn to converge. What i have done is i have taken a vapor fraction of feed stream and multiplied with feed flow. Simulator will give slightly different answer. But for hand calculations this value is required so guess value using above procedure. |
Topics you may like and will be covered in my future blogs:
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Column Height/Number of stages is decided by relative
volataility,lesser the value difficult will be separation and higher will be
the stages/Height.
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Example: C3 splitter, Separation of Xylenes.
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Poynting correction factor can be ignored for low or medium
pressure situations. This topic will be understood if you know gama-Phi
Formulation.
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References:
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Guidance by Prof KV Rao
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Introduction to chemical Engineering Thermodynamics by Smith,
Vannes and Abbot.
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Mass Transfer operations by Treybal.
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