The chemistry is simple, the hydraulogy (sp?) is different.
With heap leaching, the ore is ground up to some degree, placed on a giant rubber pad, and very dilute cyanide solution is sprinkled over the ore, percolates down, extracting gold, is collect at he bottom of the pad and pumped away. Physically simple and simple chemistry.
In Situ is hydraulically more complex. The output wells are surrounded by a large number of input well, and possibly barrier wells to stop the input solution from migrating away into ground water. Enough input has to be pumped in to change the environment where the ore is from reducing to oxidizing. In an oxidizing environment, the Uranium dissolves, goes out the output well, and is recovered, and the solution then treated for re-use.
All the water pressures and flow rates need to be monitored.
The chemistry is also simple, expect in situ you may not know how much more reducing material there is near the ore, which means it will take MUCH longer to get the Uranium out.
The physical hydraulics is like a pollution mediation operation - lots of wells, pumps, and monitoring. |
