You work for Benson Mining Corporation in Arizona extracting gold ore from an open cast mining operation. A new leaching process needs to be developed on site to extract gold from gold ore. Determine the number of leachers required for each of the following 3. processes. (a) 625 kg/hour of an ore containing 12 wt. % gold is leached in a cascade series of agitators and thickeners using a 700 kg/hour solution of concentrated cyanide salt solution to extract the gold. It is assumed that all of the gold is extracted into solution, and perfect mixing is achieved. If 1 kg of solvent per 1.5 kg of solid ore is entrained in each thickener, calculate the number of agitators required to extract 99.00 % of the gold in the combined overflow solutions. [12] (b) 625 kg/hour of an ore containing 12 wt. % gold is leached in a counter- current series of agitators and thickeners using a 700 kg/hour solution of concentrated cyanide salt solution to extract the gold. It is assumed that all of the gold is extracted into solution, and perfect mixing is achieved. If 1 kg of solvent per 1.5 kg of solid ore is entrained in each thickener, calculate the number of agitators required to extract 99.00 % of the gold in the overflow solutions. It is strongly recommended that the calculation method (Figure 4) of determining agitator numbers be applied. For multiple stages cascade: solute in underflow of n stage When R, = R, : solute in feed of 1 stage (R+1)" solute in underflow of n stage When R,#R, : solute in feed of 1 stage (R, +1) (R+1)"-1 counter-current: When R, = R, : solute in underflow of n stage R-1 (R-1 -1) solute in feed of 1s stage solute in underflow of n stage R-1 When R,#Rn solute in feed of 1* stage (R,R" +R- R - 1) mass of solution in overflow R = mass of solution in underflow & R, refers to 1st stage Where : Figure 4: Multiple stage equation chart [12] You have determined the leachers required for the two processes in parts (a) and (b). Select which process would be the most appropriate to be applied on site and give a detailed explanation for the selection using direct reference to the previous calculations and potential benefits and drawbacks. (c) [6] [Total: 30]