Detox t to gold 2 short version
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Transcript of Detox t to gold 2 short version
Gold Recovery During Cyanide Detox
In Heap Leach Pads
Pintail Systems Inc.
Presentation Authors
Caren Caldwell
Leslie Thompson
Cyanide is used in heap leach pads to complex gold and silver in the mining industry
Cyanide detoxification is required for mine closure.
PSI’s bio-detoxification process, which uses native bacteria, has proven to be more efficient than conventional chemical processes
Bacteria culture used in cyanide detox
Pintail Systems, Inc. was founded in 1987 by Leslie Thompson
Primary focus was on cyanide detoxification in gold and silver heap leach pads using native bacteria cultures.
In 1991,The Hecla Mining Company contracted with PSI to develop a treatment process for the Yellow Pine Mine using native bacteria cultures.
Located Near Yellow Pine, Idaho
Alpine Climate
1.2 Million Ton Spent Ore Heap
Environmentally sensitive area
Detox Goals
To degrade WAD cyanide to 0.2 mg/L or less in heap leachate solutions in one operating season
Prior to contracting with PSI, Hecla investigated chemical methods and was quoted 2 to 4 operating seasons.
Heap Bio-Detox
WAD Cyanide in Heap Effluent Solutions
0
10
20
30
40
50
1
29
25
50
59
71
85
94
10
7
11
4
12
1
12
8
13
6
14
6
15
5
Time, Days
WA
D C
ya
nid
e
Detox goal of 0.2 mg/l WAD cyanide was achieved in one operating season, (155) days
During the detox process, there was a significant increase in gold production
Increased gold production was unexpected and more than paid for the detox process
Increased gold recovery paid for mine operations through the end of detox
Mine closure was signed off by the Idaho Department of Environmental Quality
The Hecla Mining Company won the 1992 Pacific Northwest Pollution Control Association’s Idaho Award for the Innovative use of Bacteria in Improving Water Quality
1.3 million ton heap
Located near Parker, AZ
Detox goal was 0.2 mg/L total cyanide in heap leachate solution
Total cyanide closure goal of <0.2 mg/L TCN met in 111 days
Significant Gold Recovery Improvement.
>3000 oz.
Mine closure signed off by the State of Arizona DEQ
Located near Victor, Colorado
5 million ton cyanide-leached spent ore heap
Heap was water-rinsed for 4 years prior to bio-detox
Average detox solution temperature = 35 deg F
Altitude 10,000 ft above sea level.
Detox Goals
Detox WAD cyanide to 0.2 mg/L in heap leachate solution
Decrease the bond requirement for closure by the state of Colorado
l
Cripple Creek WAD Cyanide
0
0.5
1
1.5
2
2.5
3
1 24 47 70 93 116 139 162 185 208 231 254 277 300 323 346
time, days
leach
ate
WA
D C
N,
mg
/L
Cripple Creek Gold Recovery
0.00
1000.00
2000.00
3000.00
4000.00
5000.00
6000.00
1 26 51 76 101 126 151 176 201 226 251 276 301 326 351
time, days
cu
mu
lati
ve o
un
ces g
old
Increased gold recovery duringcyanide detox
Met the goal of 0.2 mg/L WAD cyanide in heap leachate solution in 346 days
CC&V water rinse and peroxide treatment (30 pore volumes) did not detoxify cyanide to regulatory limits
Pintail bio-detox achieved cyanide limits with application of less than 3 pore volumes of treatment solution
Bond requirement for mine closure was reduced
Increased gold recovery paid for the detox process. The detox process actually became a profit center for the mine.
Yellow Pine1.2 million tons
CyprusCopperstone
1.3 million tons
Cripple CreekVictor
5 million tons
CyanideConcentration at start of detox
50 mg/L WAD CN in heap leachate solution
20 mg/L TCN in heap leachate solution
Just over 3 mg/L WAD CN in heap leachate solution
Cyanide concentration at end of detox
< 0.2 mg/L WAD CN heap leachate solution
< 0.2 mg/L TCN in heap leachate solution
< 0.2 mg/L WAD CN in heap leachate solution
Gold Recovery > 2700 >3000 oz >6700 oz
Treatment Days 155 days 111 days 350 days
Regulatory Goals Met
Yes Yes Yes
1Technical advances have produced more gold over the
last 160 years than the previous 6000.
2Majority of gold produced in the U.S. is from the Heap
Leaching Process
3Heap Leaching leaves 25 – 40% of the original gold in
the ore at mine closure
Pintail Bio-Processes are the solution to economically recover heap gold4
Cyanide typically recovers 55% to 75% of the gold in a heap leach pad. 25% to 45% residual gold is left in the heap.
Using PSI’s microbial treatment system has been shown to get significant recovery of residual gold during cyanide detoxification.
Ore Tonnage Ore Grade
(oz/ton)
Estimated
Total
remaining
gold (oz)
Estimated
PSI gold
recovery
Mine A 71,000,000 0.009 642,550 417,657
Mine B 81,000,000 0.008 648,000 421,200
Mine C 68,000,000 0.007 465,000 302,250
Mine D 23,000,000 0.008 174,000 113,100
Mine E 36,000,000 0.009 324,000 210,000
Mine F 150,000,000 0.010 1,500,000 975,000
Mine G 170,000,000 0.005 850,000 552,500
Totals 650,000,000 4,603,550 2,992,307
$1100/ oz gross $1300/ oz gross $1500/ oz gross
EstimatedPSI Gold Recovery
$900/ oz net $1100/ oz net $1300/ oz net
Mine A 417,657 $375,891,300 $459,422,700 $542,954,100
Mine D 113,100 $101,790,000 $124,410,000 $147,030,000
Mine F 975,000 $877,500,000 $!,072,500,000 $1,267,500,000
Potential profits based on $200/ oz production cost using PSI Bio Processes