Estimating maximum removal efficiency in Venturi scrubbers

Abstract

A simplified 2-D model to predict liquid flux distribution and collection efficiency in a Venturi scrubber was tested successfully with experimental data from pilot- and industrial-scale units. Establishing nonuniformity of flux distribution is the key to estimating collection efficiencies accurately. Liquid jet penetration and liquid injection velocity are critical in defining flux distribution for the entire range of conditions simulated. Increase in gas velocity makes flux distribution more uniform and enhances collection efficiencies. This effect becomes insignificant beyond a gas velocity as finer droplets get accelerated quickly to the throat gas velocity giving the collector very little interaction time. Increase or decrease in the liquid to gas (L/G) ratio beyond an optimum value made flux distribution more nonuniform and decreases collection efficiencies. Design parameters of the Venturi scrubber (aspect ratio and nozzle diameter) have an optimum that offers the most uniform flux distribution and the maximum collection efficiency. A new dimensionless group, the Venturi number, derived from the jet penetration correlation, could define both nonuniformity in flux distribution and collection efficiency for changes in the L/G ratio, aspect ratio, nozzle diameter, and number of nozzles. Simulation results indicate that a maximum efficiency exists for the Venturi number between 1.0 and 1.5 x 10 -3. The useful length of the scrubber throat could be determined from the L/G ratio defined by the Venturi number concept and appropriate throat gas velocity.