Effect of mesh characteristics of mesh degasifier on the upper limit of steady operation and liquid reserve of bubble tray

Abstract

In this work we studied the hydraulic mechanisms of operation of trays with overflow devices having mesh degasifiers. The effect of equivalent diameter of a mesh hole d h (at effective mesh cross section ~m =26%) and effective mesh cross section of 26-53% (at d h = 0.00037 m) on the upper limit of steady operation of the tray was studied. The requisite value of ~m was ensured by closing a part of the mesh degasifier with vertical strips placed all over the degasifier. The overflow device (Fig. i) was placed at the center of the sieve tray with a diameter of 0.215 m and a free cross section mt =4.75%. The investigations were carried out in the water--air system at irrigation densities L = 20-70 m3/m2.h and effective gas velocities in the free column cross section Wc = 0.3-1.2 m/sec. The upper limit of steady operation was determined from the effective gas velocity through the holes of the tray sieve Wh which corresponds to the beginnin$ of the rapid rise of liquid reserve hst on the tray at definite weight loads due to liquid L and to gas G. In the study of the effect of mesh characteristics of mesh degasifier on the liquid reserve hst on the bubble tray we used air as the gas phase and liquids whose characteristics are given in Table 1 as the liquid phase. The effect of viscosity of the liquid phase ~L on hst was studied making use of aqueous glycerin solutions because their surface tension changes negligibly within wide limits of viscosity of these solutions. Water and water mixed with the surface-active agent SV-102 and a microquantity of a defoaming agent, viz., tributyl sulfate, were used in the study of the effect of surface tension of the liquid phase OL on hst. Meshes with m m =48.6-62% and d h = 0.00037-0.00159 m were used in the experiments. The effective gas velocity in the column Wc. ef f referred to the bubbling zone was calculated by the equation