In the last three posts we talked about reflux ratio or reboiler ratio (depending on column's section). We know that this parameter has a big influence on cost and quality of the product. There are however several factors or parameters that are just as important as reflux ratio for distillation fields. They tell us whether the column will run smoothly or not. In other words they affect the efficiency of the column.
Those factors are :
1) Liquid load, L
2) Gas load, G
If we plot G/A against L/A in a diagram, we will obtain this kind of diagram:
If gas load is too low, it will lead to weeping. Weeping means liquid starts to fall through the perforations as gas flow is not sufficient to hold it up.
If gas load is too high, then we will have a situation called flooding. It is the opposite of weeping. Instead of leaking through, liquid gets carried upwards together with the vapour/gas.
If liquid load is too low, there will be no homogeneous distribution of liquid on each tray or plate. Hence the mass transfer quality becomes poor.
If liquid load is too high, we will have a similar situation with weeping.
The shaded area is the region where distillation should be operated or run. This guarantees a good separation efficiency.
No comments:
Post a Comment