Method and equipment for purifying an extraction solution from aqueous entrainment and impurities

Settling equipment for use in hydrometallurgical liquid-liquid extraction for scrubbing an organic extraction solution that contains drops of aqueous solution and a valuable metal or substance separated into it during extraction, and where said equipment comprises:

• a substantially rectangular settling tank having a feed end, a rear end, two opposite sides and a bottom and defining a generally horizontal direction of flow from the feed end to the rear end, the rear end of the settling tank having a well in the bottom of the tank for collection of aqueous solution,
• at least one organic solution feed unit,
• at least one outlet unit,
• at least one feed pipe at the feed end of the settling tank, the feed pipe being connected at one end to the organic solution feed unit and the feed pipe being equipped with several separate discharge elements evenly spaced across the entire width of the tank,
• several picket fences positioned in the settling tank and spaced apart in the generally horizontal direction of flow and inclined upwards towards the rear end of the tank, wherein each picket fence extends from one side of the tank to the other side of the tank and comprises several slotted elements, whereby at each picket fence the direction of flow of the organic extraction solution flowing generally horizontally from the feed end is diverted vertically and/or sideways,
• at least one organic solution outlet pipe at the rear end of the settling tank, the outlet pipe being connected at one end to the outlet unit and said outlet pipe being equipped with several separate suction elements for removing the scrubbed organic solution evenly across the entire width of the tank,
• at least one aqueous solution outlet pipe in the well at the rear end of the tank, the aqueous solution outlet pipe being equipped with separate several suction elements for removing the aqueous solution evenly across the entire width of the tank, and
• a scrubbing solution feed pipe located for feeding scrubbing solution into the tank near or at the most upstream picket fence.

A method of carrying out liquid-liquid extraction to separate metal contained in an aqueous solution from impurities in the aqueous solution, said method comprising:

• mixing the aqueous solution with an organic extraction reagent such that metal in the aqueous solution reacts selectively with the organic extraction reagent and is separated from the aqueous solution,
• separating the mixture of aqueous solution and extraction reagent to provide an aqueous solution containing impurities and an extraction reagent loaded with metal and containing droplets of aqueous solution,
• supplying the extraction reagent to a feed end of a settling tank in several separate sub-streams, the settling tank also having a discharge end and defining a generally horizontal direction of flow from the feed end to the discharge, the sub-streams being distributed evenly across the entire width of the tank at the feed end thereof, whereby the extraction reagent flows in a generally horizontal direction towards the discharge end of the settling tank,
• at several locations spaced apart along the generally horizontal direction of flow, diverting the direction of flow of the extraction reagent flowing generally horizontally from the feed end to the discharge end obliquely to the vertical,
• feeding an aqueous scrubbing solution into the settling tank near or at a location at which the direction of flow of the extraction reagent is diverted obliquely to the vertical,
• at several locations spaced apart along the generally horizontal direction of flow, momentarily decreasing the cross-sectional area of the flow,
• deflecting the direction of flow laterally by means of picket fences,
• removing extraction reagent from the rear end of the settling tank in several separate sub-streams, and
• removing aqueous solution from the rear end of the settling tank in several separate sub-stream.