Page 122 - Packed bed columns for absorption, desorption, rectification and direct heat transfer

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To eliminate the initial conductivity of the liquid, when operating with
tap water, the following equations for determination of the integrals in Eq. (13)
can be used [73]:

2
2
2
\T C(T)dt = JT [C(t) + C E Jdr - ]r C Bdt , (14)
0 0 0
]r C(t)dT = ]x[C( T) + C Jdr -fadt, (15)
s

T)dT = ][C(T) + C JdT - ]C dt , (16)
E
E
0 0
where Cg is the conductivity of the liquid without tracer. Because the liquid
velocity in the column is high, the integration time is short, usually about 1
minute. This time has to be found experimentally for each type and height of the
i
packing until C(t) changes no more with t , The integrals \x C Edx,
o

jrCgdr and \C Fdt are determined with the same time as the other
o o
integrals in Eq, (14), (15) and (16).
To ensure regular distribution of the tracer solution, it is offered [73] to
feed it in the form of many jets using identical syringe needles bound together.
For columns with diameters to 250 mm, it is better to use a shower liquid
distributor with a built-in distributor for the tracer, as shown in Fig. 13 taken
from [73].
The distributor is constructed of two chambers, one for the liquid phase
and another for the tracer. To ensure exact measuring of the time in the
integrals, the following must be taken into account:
1. Simultaneous switching on of the tracer valve and the conductivity
measurement device;
2. Placing the needles into coaxial short pipes, mounted to the
distributor to prevent the irrigation liquid to reach the needle, and in this way
small quantity of the tracer to flow after switching off the tracer valve;
3. Hard construction of the tracer distributor and the pipes for supplying
the tracer in it to avoid changing of their volume during the experiment