Page 112 - Packed bed columns for absorption, desorption, rectification and direct heat transfer

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2,1.1.3.5. Sampling device for the liquid phase under the packing.
Nevertheless that the column is constructed to ensure uniform
distribution of both phases over the cross-section of the apparatus, some
deviation of the liquid phase concentration from the average value is possible.
To reduce the influence of this deviation and to ensure that always a fresh
sample is taken for analysis, the device presented in Figs. 8 and 9 is offered.
The condition for the fresh sample is especially important when the process in
the column, for some reason, is not exactly steady state.
The liquid phase is collected in the triangular channel (1), the tap of
which reaches the vertical axis of the column. The distance R is the radius of the
column. The channel is placed in box B welded to the body of the column. The
section A-A of the channel is represented in Fig. 9. The sample liquid exits the
channel through pipe A. The rest of the collected liquid passes through the
channel slits C and flows downwards to the bottom of the column providing
always a fresh sample.

A-A

TLout
A L 2 TLout

Fig. 8. Construction of the sampling device. Fig. 9. A-A section from Fig. 8.
1- triangular channel; B- box; A^- pipe for taking
samples of the liquid phase; Ttm- thermometer; C-
channel slitfThe dimensions are in mm,)

The thermometer T Lou t measures the outlet temperature of the liquid.
To avoid difficulties in entering of the gas in the packing over the
sampling device, the distance between the supporting grid and the triangular
channel should not be very small. It should not be very big either, to avoid
significant change in the sample concentration because of mass transfer between