SO2 REMOVAL FROM AIR ABSORPTION IN A VENTURI SCRUBBER

Abstract

Venturi scrubber has gained enormous importance because of its role in curbing the menace of air pollution by re-moving the sub-micron range particles and aerosols and obnoxious gaseous pollutants. These scrubbers are, however, inhibited because of larger energy los's incurred as compared to other types of wet scrubbers. By properly designing the venturi so that the maximum pressure recovery is possible (by properly adjusting the, angle of divergence and the length of the divergent section for minimal friction losses) and using optimum liquid to gas ratio, for a given throat gas velocity, the extent of absorption of the gaseous pol-lutant and the collection of dust particles per unit of scrubber energy loss may be maximized. Sulfur dioxide is known to affect adversely the human beings, flora, fauna and materials. In consanance with the U.N,. Declaration on the Human Environment, I.S.I. has for-mulated TLV's for SO2 concentration in ambient air. Many workers has reported their results on the pressure drop and absorption of SO2 in venturi scrubbers using dif-ferent liquids. However, these works are restricted to higher range of throat gas velocities, lower values of liquid to gas ratio and lower ratios of throat length to diameter. Thus, not much information is available to satisfactorily correlate data for pressure drop for lower range of throat to gas velocity, for higher divergence angle and for larger throat length to diameter ratio. Similarly not much is available on absorption of SO2 in venturi scrubbers having above characteristics. The aim of the present investigation was to obtain data on pres-sure drop and absorption of SO2 in water for a large range of throat gas velocity and liquid to gas flow ratio, on a venturi scrubber having angle of divergence as 16° and throat length to diameter ratio of 3.0. The data were obtained for pressure drop for two modes of operation - Node-1 where the liquid is introduced at the top of the convergent section by a nozzleless tube and Node-2 where the liquid is introduced at just the top of the throat. The data are correlated for both the modes for throat gas velocity, Ut ;48 m/s and Ut >48 m/s for 0.5 <q <4.5 where q is expressed in litres of liquid/m3 of gas. It is found that the angle of divergence and length to diameter ratio of the throat has significant effect on the pressure drop, and the pressure drop obtained is much larger than those predicted by correlations of various workers. Same data for Ut = 89.2 rap; and 60 m/s were taken for absorption of SO2 in water. It was found that the percent absorption of SO2 in water shows increasing trend with increase in q and then stabilizes. This is perhaps because of the fact that increase in q ca uses the formation of a large number circulation. in q reduces droplets are the droplets of smaller droplets with intense internal However, after a certain q, further increase the no of smaller droplets (more larger size formed) and thus reduces the specific area of resulting in almost stagnant absorption rate.