1992-06-10_REVISION - M1988112 (3)

Home Browse Search

-HNULL6IE~ INC. TEL~303-7.+2-5533 Jun 09 92 ~0~07 No.OG2 P.03 • o There ie no indication that the processing of the pond with pero a will require continued processing of ore through the plant (as was pu ported with the CY4'OX process) and thus I would again raise the su estlon that the processing of ore be stopped while the cyanide levels in the pond ere reduced to the target 4 ppm total cyanide by peroxide alone. In introducing this approach at the May public hearing, BMG indicated that the delay in putting peroxide treatment in place would mitigate against Its use as an alternative to CY1Y)X, but this delay seems to not be an Issue of substance at this point. o The introduction of peroxide into the pond w(thout some means of mixing certainly raises the probability that uneven treatment will occur ana that cyanides w;ll escape destruction. Gravity Induced mixing and diflY;sion of the reagent are not reliable techniques. Dr. E.A Devuyst, in the paper entitled "Cyanide Pollution Control .The Inco Process" distributed at the (SMG sponsored) meeting we reoently attended to hear details of the process notes that; "Hydrogen cyanide is selective for cyanide in solutions, but i an extremely expensive reagent which, In many cases decomposes rapit~ly in the presence of solids. This may lead to high reagent consumption anld/or incomplete cyanide destruction" (italics, mine). If peroxide Is used in the San Luis ponds, then it would seem prudeht to assure mitdng to at least have a chance oP maximizing cyadldes decomposition. I~ection of the peroxide at the spigot might move toward accomplishing this but probably at the cost of signiflcanlly hiklter peroxide demand. o As in much of the work and proposed work which has preceded this i test revision, there to precious little laboratory data with real solutfons under conditions that accurately redact practice at San Luis (for exa le, simultaneous use of peroxide and CYTOX) to demonstrate the abilit to reach 4 ppm cyanide levels. The AVR system was supposed to work (based on design estimates) anki it apparently did not. The decomposition of cyanide in the ponds did hot proceed as MODELED and inadequate testwork was performed'. to determine whether it should have. Ore characterizations were not all t~ey should have been, and hence the copper "problem" which complicates the cyanide destruct[on chemistry. CYTOX was supposed to reduce cyanl~lea (total cyanides as we were given to understand at the hearing) to 4 ppm but there la no evidence that this is going to be achieved. All in all, then seems to 6e too much emphasis to jump on the latest "maybe" technical fix and not to test it first in a thorough manner. A 1A60992DEH1