Budgetary quotations were obtained for a dual 2 ½ ton per hour (TPH) detention slaker and a 3 TPH Verti-mill slaker. There is no hard data on how much the lime consumption would increase compared to using slaked lime, but a chemist with on the project estimates lime consumption would increase 5 – 10%.Īn economic comparison of the three lime addition systems was done. Lime particles will continue to react under non-optimum conditions until a coating forms on the particle surface. The lime to water ratio and temperature in a SAG mill environment are not optimal to produce fine calcium hydroxide particles. The pebble lime addition and hydrated lime systems were considered to be cleaner and easier to operate.Ĭalcium hydroxide particle size, and the resulting surface area, is dependent on the lime slaking temperature. Test work has indicated that adding reagents to the grinding mill increases recovery. A smaller supplemental system would then be required for final pH control of the rougher and cleaner flotation circuits.
For a copper concentrator which will have one primary grinding line, so the primary pH control could be accomplished with pebble lime addition to the SAG mill feed belt. The revived cost estimate carried extra cost for a milk of lime tank and showed the verti-mill and 500 ton silo at zero cost. This test work indicates improved copper and molybdenum recovery and concentrate grade at a rougher pH of 10.8.Īn earlier proposed lime addition system was changed from a verti-mill slaker to the currently proposed pebble lime / hydrated lime system. Initial flotation test work conducted included a box statistical study that compared grind size, reagent schemes, and pH. Due to the increased reagent usage and cost of hydrated lime to achieve the same pH impact, the proposed lime addition system will have the highest operating costs of the three possible systems. The operating costs are dependent on the slaker efficiency, hydrated lime consumption, proportion of pebble lime used, and slaker grit loss. The proposed system is the lowest capital cost option available. Other lime delivery options are detention slakers and Verti-mill slakers. A pebble lime silo will dose dry lime to the SAG mill feed belt a hydrated lime make down system will provide slurry lime to multiple addition points in the flotation circuit. A lime slaking and addition system can consists of two systems to control the pH in the rougher and cleaner flotation circuits.
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