Extraction of dissolved matter from precipitate moisture in a continuous counterflow regime

Abstract

Results are presented for investigation of the continuous counterflow wash-out of solid phase (precipitate after breakdown of a chemical uranium concentrate) in an experimental-industrial plant with a pulsed column 400 mm in diameter and 8 m high.Rare, trace, and radioactive elements are usually extracted from raw material by the hydrometallurgical method; here, a slurry, whose liquid phase (LP) contains the dissolved element, is obtained [1]. In separating the phases, the dissolved target components should be removed from the solid phase (SP) -insoluble precipitate.The dissolved substance is separated from the moisture of the precipitate (wash-out or flushing) by replacement of the mother liquor with fresh flushing fluid. Usually the SP is the product produced, and the flushing solution the waste product during flushing, while the strengthened solution is the product that product produced, and the SP is the waste product during wash-out [2].During counterflow in the replacement mode, the existence of a difference in the deposition rates of the SP and the ascending flow of flushing fluid exists during counterflow wash-out of the SP of a suspension. After the breakdown of a chemical uranium concentrate by nitric acid, however, the deposition rate of the SP is negligible; preliminary flocculation of the suspension obtained is therefore required for its wash-out in a counterflow replacement regime in a pulsed vessel.The deposition rate of the SP was determined from the accumulation of sediment Q at the bottom of a calibrated cylinder, and rate of clarification (deposition of floccules) v, i.e., the travel speed of the phase interface [1-5].Polyacrylamide (PAA) was used as the flocculating agent, and the deposition rate of the floccules was determined as the PAA was added to the suspension:• v = 0.2 m/h after completion of breakdown of the chemical concentrate (t ≤ 100°C);• v = 0.34 m/h after the slurry had been heated to 90°C, and agitated for 30 min (breakdown when t ≤ 45°C); and• v = 0.28 m/h after breakdown had been completed at t ≤ 45°C, and the slurry heated to t = 90°C and agitated for 30 min. In all cases, the average deposition rate of the flocculated SP was found to be low, and, as a result, wash-out productivity was low in the pulsating column vessels. As practice indicates, the difference between the deposition rare of the SP and the ascending flow of flushing fluid should be 1-4 m/h to ensure counterflow wash-out.Mixing of the slurry produced after breakdown of the chemical concentrate with the reclaimed product of uraniumore sorption reduction increases the deposition rate of the SP to 0.6 m/h. The addition of a flocculent leads to a pronounced increase in the deposition rate of the SP, whereupon it is established that flocculation is improved after dilution, since the floccules that have formed here are partially disintegrated.After treatment with the flocculating agent, the deposition rate of the finely disperse SP was determined as a function of its concentration. It is apparent from Fig. 1 that this...