BASIC SEPARATION THEORY
In the Badger stage, about 50% of the process gas entering a converter diffuses through the
tubing and flows to the stage above. This fraction is called the "cut." A cut of 50% has been
found to yield the best separation. As mentioned previously, the "cut" in a Badger Cluster stage
may be more or less than 50% depending upon its position in the cluster.
It is necessary to have a higher pressure inside the barrier tubes than outside in order to have
a flow through the walls of the tubes. This inside pressure is called the fore pressure or high
side pressure (H.S.P.), and is measured at an arbitrary point inside the tubes near the middle of
the second pass. The pressure outside the tubes is the back pressure or low side pressure
(L.S.P.), and is measured at an arbitrary point outside the tubes near the middle of the second
The fore pressure is regulated by a control valve in the "B" stream, or down flow, from the
converter. Actually, the control valve regulates the pressure immediately above it. This is
called the control pressure and is the pressure which is indicated at the cell panel. It is slightly
lower than the fore pressure due to the pressure drops in the converter and piping.
The rate of diffusion through the tubing walls for any given pressure drop across the barrier is
determined by the permeability of the barrier. Mathematically, this is a dimensionless quantity
which is the ratio of the rate of gas flow through the barrier to the rate of gas flow through the
same area which would take place if the barrier were not there. The term, usually called
permeability, is used to relate the actual permeability to the design permeability. For example,
if the flow through the barrier has decreased 10% due to plugging of the barrier holes, the
permeability would be 90%.