Fundamental factors affecting the extraction efficiency in a pulse liquid-liquid extractor

Abstract

The purpose of this investigation was to redesign, construct, and operate a two-inch experimental pulse liquid-liquid extractor, and to determine the effects of the pulse amplitude, the number of plates, and the plate-free-area on the stage efficiency of the column. The optimum liquid flow rates were also determined.

An examination of the literature was conducted for a review of the available information on pulse extractors. Although a great deal of literature was available on the topic of liquid-liquid extraction, detailed information on only two pulse extractors could be found. The results obtained during this investigation compare favorably with those reported in the literature.

A two-inch experimental pulse-type extractor was constructed. The liquids were pulsed by means of a sylphon-type bellows operated by a push rod which was driven by an eccentric cam. For the satisfactory operation of the extractor various auxiliary apparatus was required; important among these were the supporting framework, the push-rod bearing, the reduction train for the can, the storage tanks, and the tubing and fittings.

Twenty-seven individual experimental tests were conducted, extracting acetone from carbon tetrachloride with water, to determine the effects of the various operating parameters on the stage efficiency of the pulse column. During the experimental tests the following variables were studied: pulse amplitude at one, two, and three inches of vertical liquid displacement; number of plates with four, eight, and twelve plates; and plate-free-area with eight, sixteen, and thirty-two per cent free area.

It was found that the pulse amplitude, the number of plates, and the plate-free-area each have an independent significant effect on the stage efficiency of the pulse column; the plate-free-area has the largest relative effect, while the pulse amplitude has the smallest relative effect. It was further proven by this investigation that the interactions between the pulse amplitude and number of plates, the pulse amplitude and plate-free-area, and the number of plates and plate-free-area have no significant effect on the stage efficiency of the pulse column. The flow rates for satisfactory column operation are 1807, 2211, 1478, and 2299 pounds per hour-square foot of column cross-section for the feed, solvent, raffinate, and extract, respectively.