The use of horizontal bubble columns in gas-liquid chromatography
Claypool, David Donald
Deans, H. A. (Harry A.)
Master of Science
When a single long gas bubble flows with the surrounding liquid through a small capillary tube, its velocity exceeds the average velocity of the liquid. The phenomenon is due to the thin film of stagnant liquid surrounding the bubble. A succession of these bubbles closely spaced, greatly reduces the average liquid velocity even further by making the stagnant film an even greater fraction of the total liquid volume. With relatively long bubbles, very closely spaced together, a great deal of relative separation is possible between the gas and liquid phases at high velocity and therefore, such a system is worthy of consideration as a chromatographic device. The power of resolution attainable by a particular chromatographic system is a ratio of the separation distance between two components, or in this case, the gas and liquid phases, to the half width of the dispersed liquid peak. It is used as a final criteria in evaluating the column performance as bubble velocity, liquid fillet length, and bubble length vary. Behavior of the liquid film thickness, the relative separation, and the liquid phase dispersion coefficient were compared with hydrodynamic and dispersion theories in evaluating the behavior of the resolution. Liquid film thickness increased nearly according to theory at low velocities, but approached limiting values at high velocities. This upper limit of film thickness increased with decreasing fillet length. Increased bubble length appeared to decrease the film thickness only slightly. The net result was a large increase in relative separation with increased bubble length to fillet length, but a limited increase as bubble velocity approached high values. The overall dispersion coefficient increased with nearly the velocity squared, but decreased somewhat with increasing fillet length. The resulting power of resolution appeared to have maxima when plotted against velocity. The value of these maxima increased with an increase in bubble length to fillet length. Further investigations of this system were well justified.