cement copper evaluation w/email tls, w/o attchs a-b · summary report cement copper evaluation 4...

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Rodriguez, Dante

From: Seter, DavidSent: Thursday, September 25, 2014 2:50 PMTo: Rodriguez, Dante; Ball, Harold; Helmlinger, AndrewSubject: FW: SPS Cement Copper EvaluationAttachments: SPS Cement Cu Evaluation.pdf

Categories: A08 - Arimetco

David A. Seter, P.E. Remedial Project Manager USEPA Region 9 Superfund Division (SFD-8-2) 75 Hawthorne Street San Francisco, CA 94105 415-972-3250 From: Taurus Massey [mailto:[email protected]] Sent: Thursday, September 25, 2014 2:47 PM To: Jeryl Gardner Cc: Seter, David; Brian Johnson; Steve Dischler; Todd Bonsall; Carla Consoli Subject: SPS Cement Copper Evaluation Jeryl: Please find the attached Cement Copper Evaluation. Hard copies with appendices will be mailed to you, Dave Seter, and Brian Johnson.

Regards, Taurus

Taurus Massey

Singatse Peak Services LLC.

Office 775.463.9600 | Cell 775.722.3159

517 West Bridge St #A

Yerington Nevada 89447

[email protected]

SEMS-RM DOCID # 1162050

mailto:[email protected]

mailto:[email protected]

Yerington Anaconda Mine Cement Copper Evaluation September 25, 2014

517 West Bridge Street Ste. A Yerington, NV 89447 (775) 463-9600

Summary Report Cement Copper Evaluation

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Table of Contents 1 Introduction ................................................................................................................... 1

2 FMS Background ............................................................................................................. 2

3 Overview of Cement Copper ........................................................................................... 2

4 Technical Evaluation ....................................................................................................... 3

4.1 Initial Characterization and Laboratory Tests .................................................................. 3

4.2 Iron Consumption Test ..................................................................................................... 4

4.3 Phase 1 & 2 Pilot Tests ..................................................................................................... 5

4.3.1 Phase 1 ................................................................................... 5

4.3.2 Phase 2 Pilot Tests - Column Tests ........................................................................... 6

4.4 Spent Fluid Management ................................................................................................. 7

5 Conceptual Design .......................................................................................................... 8

5.1 Facilities Conceptual Design ............................................................................................. 8

5.2 Enhanced Evaporation Conceptual Design ...................................................................... 9

6 Conceptual Cost Estimates ............................................................................................ 10

6.1 Capital Cost Estimate ..................................................................................................... 10

6.2 Operating Cost Estimate ................................................................................................ 14

7 Cement Copper Market Evaluation ............................................................................... 16

8 Additional Work ........................................................................................................... 16

9 References ................................................................................................................... 17

Tables

1-1 Cement Copper Study Timeline ............................................................................................... 1

6-1 Conceptual Capital Cost Estimate ........................................................................................ 12


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Tables - Continued

6-2 Equipment List ..................................................................................................................... 13

6-3 Annual Operating Costs ....................................................................................................... 15

Figures

4-1 Phase 1 Pilot Test .................................................................................................................... 5

4-2 Phase 2 Column Test ............................................................................................................... 6

5-1 Kennecott Cone Schematic ..................................................................................................... 8

5-2 Conceptual Cement Copper Facility Layout ............................................................................ 9

5-3 Conceptual Spent Fluid Evaporation System Configuration ................................................. 10

Attachments (provided on CD given their large size)

A FMS Pond Characterization Report, Telesto, February 2013

B Cement Copper Pilot Studies, August 2013


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Introduction This report summarizes the evaluation of using cement copper to address the long term management of the Fluid Management System (FMS) at the Yerington (Anaconda) Mine site. The report describes the history of the cement copper process development, the assumptions and conclusions of the studies and provides preliminary capital and operating cost estimates. To date, ARC has co-funded the copper cement evaluation and has been provided with all of the test results. Table 1-1: Cement Copper Study Timeline June 2012 Telesto Samples FMS pond for characterization work July 2012 Data analysis of pond samples August 2012 Initial water balance calculations for FMS Sept 2012 Finalize FMS capacity study SOW October 2012 Start FMS capacity study and water balance per work plan Nov 2012 Site visit with SRK for capacity study Dec-Feb 2013 Capacity study alternatives evaluation and water balance April 2013 Capacity study completed May 2013 Tour of Montana Resources cement copper operation in Butte, MT. May 2013 Cement copper batch study to determine Fe/Cu ratio June 2013 Phase 1 bench testing to assess June 2013 Phase 2 bench tests, column tests to evaluate flow rate and reaction time July 2013 SPS contracts Dr. Joe Schlitt, Hydrometal Inc. regarding the Kennecott Cone August 2013 Additional testing of cement Cu samples Sept 2013 Cement copper work plan submitted to EPA, NDEP, ARC October 2013 Cement copper samples sent to prospective buyers October 2013 SPS responds to EPA and NDEP copper cementation process questions October 2013 samples not tested Nov 2013 Meeting to discuss cement copper (NDEP/ARC/SPS/EPA/BLM) Jan 2013 to Market assessment for sale of cement copper June 2014 Since June of 2012, SPS investigated various methods of treating the solutions (solids and liquids) to recover copper from the FMS. The primary objective of the cement copper evaluation was to generate additional capacity for the FMS with recovery of copper a secondary objective. Several technologies were screened out early in the study as being technically or economically not feasible, given the small scale and small amount of recoverable copper. For example, solvent extraction-electrowinning (SX/EW) is a technically viable option, but not economically feasible given the small scale and high capital cost of the FMS operation. Similarly, direct electrowinning using EMEW cells is also technically viable but is not economically feasible given the very high


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capital and operating costs. Hence, the copper cementation process was retained for further evaluation.

FMS Background

Arimetco operated several Heap Leach Pads (HLPs) on the Yerington mine site using various residuals, whereby they placed approximately 50 million tons of material on HLPs and introduced sulfuric acid to the HLPs. In 1998, Arimetco went into receivership and the property was abandoned. The HLPs were not properly closed and the NDEP and EPA subsequently made changes to the FMS to manage the drain down fluids. The FMS consists of a system of ponds, pumps and piping which control flow from the Phase I/II, Phase III South, Phase III 4X, Phase IV Slot and Phase IV VLT HLPs and deliver the fluids to the four-acre evaporation pond (4AP, now designated as evaporation pond A) that was constructed in 2006. In 2013, two additional ponds were constructed by NDEP, designated as Evaporation Ponds B and C (Broadbent, 2013). The 4AP was designed to evaporate water, but the resulting supersaturated solutions eventually generated excess solids in the pond. The 4AP is currently at capacity. The FMS has been the focus of several studies including the Feasibility Study for Arimetco Facilities Operable Unit 8 (CH2M HILL, 2012), the Arimetco FMS Water Balance and Short-Term Mitigation Alternatives (Brown and Caldwell, 2011), and the Yerington Mine Fluid Management System Study (SRK, 2013). Results from these previous studies on the FMS are not repeated in this document.

Overview of Cement Copper Cement copper using scrap iron to recover copper from oxide ores has been used for used for precipitating copper from oxide ore for many decades. Cement copper was historically used at the Anaconda-Yerington Mine from 1952-1979 to recover copper from oxide ores leached with dilute sulfuric acid in on-site concrete vats. The vat-leach tailings or VLT were the waste product following leaching. The acidic solutions would collect copper from the ore, and then would be piped to the iron launders where the copper was precipitated out using scrap iron into a consistency similar to cement. The cement copper was then washed, dried and shipped to the smelter in Anaconda, Montana. When solution bearing copper is placed into contact with iron, the iron goes into solution and the copper drops out of solution as copper metal. The iron is oxidized and the copper ions are reduced according to the following equation:

Cu2 + (aq) + Fe(s) Cu(s) + Fe2 + (aq)

This copper precipitate, known as cement copper, typically ranges from 60% to 90% copper with the balance being a variety of other metals and mineral salts.


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Technical Evaluation The evaluation of cement copper as part of the FMS progressed over an 18 month period with technical assistance provided by Telesto Nevada (now Welsh-Hagen), the University of Nevada, Reno (UNR) and Hydrometal Consulting, Inc. This work is summarized in the following sections.

4.1 Initial Characterization and Laboratory Tests

The initial work was completed during the summer of 2012 by Telesto Nevada. A copy of the report prepared by Telesto is provided in Attachment A. Additional details of the pilot tests are included in Attachment B. Samples of the 4AP were collected using a schedule 40 PVC-samples were taken to the UNR metallurgical laboratory where Dr. Carl Nesbitt performed quantitative and qualitative experiments to determine the copper content and recoverability of the 4AP solutions. These initial experiments were performed on existing solids from the pond and on solutions created when the solids were re-dissolved with water. Based on design drawings of the 4AP, preliminary estimates showed the 4AP contained approximately 10.6 million gallons of solid precipitates and fluids (solutions). Based on this information, preliminary estimates indicated that between 0.5 and 1 million pounds of copper may be present in the pond. In June 2012 samples were taken at six locations in the 4AP by Telesto Nevada and SPS personnel. The cores were sealed, logged and shipped to the University of Nevada and WET Labs in Sparks, Nevada. The assays and solubility test data are provided in Attachment A. Analytical testing of the cores showed a copper grade of approximately 0.5% Cu in the upper few feet of the solids in the 4AP. However, an accurate estimate could not be determined from these cores because of the limited sample depths caused by the inability to advance the PVC pipe to the full depth of the pond. Pond sampling was accompl PVC pipe into the 4AP solids. Using the approximate angle at which the pipe was pushed, the samples measured vertically approximately 30- down from the top of the 4AP. At the western end, the pond is approximately 4-ft deep. However, at the eastern end, the pond is nearly 8-ft deep, and the samples were not representative of the entire depth of the 4AP. However, the samples did provide suitable material for initial testing of the copper cementation potential, including recovery of copper, neutralization and re-solubilizing of the solids. The solution was tested at various depths at the sample locations to assess the best approach to solubilization, whether copper could be recovered efficiently, and how to manage the spent fluids. Experiments were performed to determine the amount of water that would be required to solubilize the solids from the 4AP. While measurements varied with depth and location in the pond, the overall finding was that approximately 4.4 lbs. of solids could be dissolved per 1 gallon of fresh makeup water. While the solids are water soluble, it is estimated that 30 to 35 million gallons of water would be required to dissolve all of the solids in the 4AP, which is over three times the working capacity of the 4AP.


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These initial tests also showed that over 90% of the copper could be recovered with the resulting cement copper having over 75% copper. The cement copper solids contained some unreacted iron which is not considered a detriment to copper smelters. The remaining solution after cementation was relatively free from copper but still high in total dissolved salts (TDS). The resulting solution contained over 47,000 mg/L TDS, containing the material that had precipitated in the 4AP minus much of the copper, including aluminum sulfate, copper sulfate, magnesium sulfate, chlorides, fluorides and other salts. At 47,000 mg/L TDS the solution would have limited capacity to further dissolve the solids. Therefore any attempt to recycle the spent solution to the pond would not result in significant dissolution and additional makeup water would need to be added to the solution to make the cement copper process work properly. This spent solution, including the additional makeup water, would need to be managed as part of the cement copper process by additional ponds and/or via enhanced evaporation.

4.2 Iron Consumption Test

A key factor in determining the operating cost for copper cementation is the amount of iron required since the amount of iron required to produce one pound of copper can vary significantly depending on the characteristics of the copper bearing solution. Telesto performed a series of tests to determine the iron consumption for the 4AP solutions (Attachment A). The kinetic rate of the exchange for copper by iron is primarily a function of the concentration of copper in the solution and the surface area of the iron. Shredded iron (such as cans, etc.) has less surface area than steel wool, wire or cable. The initial lab-scale tests were performed under

conditions using steel wool so that a maximum kinetic rate could be determined which would serve as the basis for the design of the cementation tanks for the plant. In these tests, fine steel wool was suspended in 5-gallon buckets of composite solutions of several cores that were dissolved in fresh water. Samples of the solution were taken periodically to show the rate of copper recovery (kinetics). Although steel wool is an impractical iron-source for a full-scale operation, it allowed the generation of a sample whose iron was known to be contaminant free. Therefore, the cement copper in these samples would be representative of the product with any possible contaminants only coming from the solution. The conclusion of this work showed that the solutions in the pond will produce approximately 1.0 pound of copper for every 1.2 pounds of iron dissolved (Attachment B). Stoichiometrically, the amount of iron consumed is 0.85 lbs per pound of copper produced, but other materials may be present that can dissolve the iron without producing copper. In addition, sulfuric acid can dissolve iron without producing copper or excess of ferric ions may be present. These materials directly - some commercial cement copper operations, as much as 3 lbs of iron can be consumed per pound of copper. However, the 4AP pond solutions may contain excess acid which may be the reason for the slightly higher than stoichiometric iron consumption.


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4.3 Phase 1 & 2 Pilot Tests

Following the initial laboratory characterization tests described above, pilot tests were then performed in two stages to refine the kinetic rate of reaction and to better estimate the recoverability of copper. In addition, the samples of cement copper were used to assess the marketability of the produced copper as discussed in Section 7. Welsh Hagen and SPS personnel conducted the pilot tests at the Yerington Site, as described below.

4.3.1 Phase 1 Tea Bag Pilot Test During the first set of pilot tests, several hundred gallons of solution from the 4AP were collected and transported in 55-gal plastic carboys to the warehouse facility on the site. A heavy plastic barrel was then plumbed so that a pump could circulate solution in the barrel (see Figure 4-1). Next, a woven geotextile sample bag was filled with representative scrap iron and the solution was re-circulated through the bag until the copper content in the fluids was reduced. Periodic sampling and testing was performed on the solution to assess the change in copper content of the solution. When the copper content of the solution had been asymptotically removed from the solution, the bag contents were rinsed with water and allowed to air dry. The analysis of the solutions showed that 87% of the copper was removed and the cement copper contained 53-77% copper (Attachment B). These tests confirmed the previous laboratory results of recovery using the cement copper.

Figure 4-1 Phase 1 Pilot Test

Scrap iron in core sample bag (14.2 lbs.)

Pump

PLS Flow

Ball valve used to control flow


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4.3.2 Phase 2 Pilot Tests - Column Tests For Phase 2 of the pilot tests, columns were built to test copper recovery at a larger scale (see Figure 4-2). For the column tests, air was injected into the columns as it was thought that injecting air (sparging) could be a method of removing the cement copper off of the scrap iron as it is being deposited. This is similar to how the Kennecott cones are designed, as discussed later. With this method, the cement copper settles to the bottom of the columns where it can then be removed.

Figure 4-2 Phase 2 Column Test - Major components of the cement Cu Column Study pilot test. The blue and light gray arrows show the PLS flow through each column, and color change from blue to gray shows the copper removal. Two columns were constructed to hold scrap iron and solution while allowing air to be injected at the bottom of the columns. Valves at the bottom of the columns were installed so that the cement copper could be collected as the process was operating. The flow of fluid progressed in series from column 1 into the bottom of column 2, making a large continuous process for recovering the copper by cementation.

Column # 1

Column # 2

PLS solution carboys

Spent fluid carboys

Cement copper collection barrels Pump

Air compressor


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Periodic sampling and testing was performed on the solution to assess the change in copper content as the test progressed. Copper removal was also visually discernible as the fluid color changed from blue/green to brown indicating copper removal and iron buildup in the spent solution. When the copper content of the solution had been asymptotically removed from the solution, the column contents were rinsed with water and the recovered cement copper was allowed to air dry. The column tests confirmed the kinetics and recoverability of copper. As with the previous tests, the concentration of copper in the spent solution was greatly reduced indicating a high recovery of copper. However, the final cement copper collected ranged from 15-35% copper. The significantly lower copper content in the cement copper was attributed to the possible oxidation of the cemented copper by the injected air.

4.4 Spent Fluid Management

A key aspect of using cement copper processing as a long term solution for the FMS is management of spent fluids. As part of the Settlement Agreement and Order on Consent (AOC) between SPS and the U.S. Environmental Protection Agency (EPA), SPS commissioned SRK to perform a capacity study of the FMS (SRK, 2013). In the Capacity Study, the recommended alternative was enhanced evaporation via drip/spray irrigation. This alternative was not selected by EPA as the solution for the FMS and two additional ponds were constructed adjacent to the 4AP later in 2013 (Broadbent, 2013). For the cement copper evaluation, it was assumed that enhanced evaporation would be used to manage the spent fluids from the cementation process. The enhanced evaporation system would use drip (or spray) irrigation panels installed on both the Slot HLP and VLT HLP (SRK, 2013). Drain-down solution from the HLPs would be pumped to these panels on a two week rotating basis at a low rate, estimated to be approximately 1 gallon/square foot/day. It was assumed that a combination of low rate fluid application and rotating the panels would allow the solution to evaporate during the peak evaporation period of May through October, although it could also be used selectively during March through December during certain days of relatively higher evaporation rates. The concept of the panels is to manage the fluids in the upper few feet of the HLPs (i.e., the evapotranspiration zone) with no incremental fluid reaching the HLP liners. The initial size and number of panels would be updated as operational data are collected during the first season of operation. An additional benefit of this system is that the all the precipitating sludge would be on top of the HLP and not creating solids in a pond that would require future closure and long term management. Additional testing of the enhanced evaporation details would need to be performed prior to construction and operation. The difference between the evaporation system designed by SRK and the system required for cement copper is the area required for the panels. The volume of spent fluids requiring evaporation following the cementation process is estimated to be significantly greater than the


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SRK conceptual design due to the addition of approximately 30 million gallons of fresh makeup water required to re-solubilize the solids.

Conceptual Design 5.1 Facilities Conceptual Design

In July 2013, SPS contracted Dr. Joe Schlitt of Hydrometal Inc. regarding the viability of producing cement copper through use of a Kennecott Cone (Figure 5-1). Kennecott Cones have been used with success since the 1960s to produce cement copper at a small scale. Dr. Schlitt was directly involved with development and operation of the Kennecott Cone (SME, 1966).

Figure 5-1: Kennecott Cone Schematic (SME, 1966) The Kennecott cone consists of a tank into which is mounted an inverted cone. The tank contains a sloped false-bottom floor from one side of the tank to a bottom side discharge at the opposite side. The annular space between the inner cone and the tank is covered by a heavy gage stainless steel screen. The cone contains a series of nozzles directed inward and upward. The nozzles are arranged in such a manner as to create a vortex when the copper-bearing solutions are pumped through the manifold into the cone. The inner cone and the area of the tank above the stainless steel screens are filled with shredded, de-tinned iron scrap. Copper-bearing solutions are pumped through the manifold with the nozzles injecting the copper-bearing solutions into the mass of iron. The injection of the solutions has the effect of not only rapidly precipitating copper, but also removing the metallic copper from the iron surface, thereby exposing clean, fresh iron. The pressure and velocity of the solutions in the lower conical section tend to move the copper precipitates in the same manner as an elutriation column, upward and out of the cone into the reduced velocity zone created by the larger diameter of the


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holding tank. The copper precipitates settle down through the stainless steel screen and accumulate on the sloped false-bottom of the tank. The copper can then be discharged into a thickener or holding basin. The copper precipitates produced in this manner are typically of substantially higher grade than the conventional cement copper produced in an iron launder-type plant. Figure 5-2 shows a conceptual layout of the cement copper facilities assuming a location at the northeast side of the 4AP.

Figure 5-2: Conceptual Cement Copper Facility Layout

5.2 Enhanced Evaporation Conceptual Design

Figure 5-3 shows a schematic of the proposed enhanced evaporation system (SRK, 2013). The original design completed during the FMS Capacity Study did not account for the addition of 30 million gallons as would be required for a cement copper operation. Therefore, this system would have to be scaled up to include several of the existing HLPs.


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Figure 5-3: Conceptual Spent Fluid Evaporation System Configuration (SRK, 2013) Conceptual Cost Estimates 6.1 Capital Cost Estimate

The Kennecott Cone process was used to estimate capital and operating costs for the cement copper approach. Hydrometal prepared a conceptual cost estimate, which does not include management of spent fluids. The capital cost estimate is provided in Table 6-1 and the equipment list is provided in Table 6-2. Equipment costs for the mechanical equipment and tankage are taken from a 2010 equipment guide for the same or a very similar item. T was then escalated to 2013 values. Finally, the 2013 equipment cost was factored to estimate the installed cost. Note that for some items, like the front end loader and buildings, the installed cost is the same as the base cost. Summing these costs gives the subtotal for the equipment and facilities. The costs for piping, electrical/instrumentation and civil works are then estimated by factoring the subtotal. Adding these three costs to the equipment subtotal gives the total direct field cost. The indirect costs are determined by factoring the total direct field cost. The indirect costs

construction management (EPCM).


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As shown in Table 6-1, the major cost items include the two large liquid storage tanks, the building to house the filter press and final product, and the front end loader. Although the various pumps are small, they are expensive and will require super duty alloys to avoid pump corrosion due to the very high chloride content of the feed solutions. Exclusive of the spent fluid management system (ponds and enhanced evaporation), the capital cost is estimated to be $820,000 +/- 30%. The enhanced evaporation system described in 2013 SRK study has an estimated capital cost of $70,000. This system would have to be scaled up to handle the spent fluids from a cement copper operation. A 2x multiple was arbitrarily used to arrive at a conceptual capital cost of $140,000. It is possible that the existing fluid ponds B and C constructed in 2013 (Broadbent, 2013) could be used for temporary storage of the spent fluids, but it is likely that additional pond capacity would need to be constructed. The cost of additional ponds is not included in the capital costs, but could add an additional $500,000. The total estimated capital cost is summarized below. Further work would be required to assess the spent fluid management system. The capital costs are summarized below by the three main process operations.

Process equipment $820,000 Evaporation system $140,000 Additional pond $500,000 Total $1,460,000


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Table 6-1: Conceptual Capital Cost Estimate (not including spent fluid management)

EQUIPMENT COST, $ INSTALLED COSTS, $

Cone Feed Tank (steel w/ PVC liner) 82,000 90,500

Process Water Tank (steel) 75,000 82,500

In-line Mixer (SS) 2,500 2,750

Cone Cementation Unit (SS) 9,700 10,700

Cone Overflow Clarifier (SS) 40,000 44,000

Cone Discharge Screen (SS) 1,500 1,650

Cone Discharge Thickener (SS) 40,000 44,000

Flocculant Addition System 2,500 x 2 5,500

Filter Press 19,500 21,500

Loadout Conveyor 26,000 28,600

Scrap Iron Storage 2,500 2,500

Inclined Conveyor 26,000 28,600

Front-end Loader 75,000 75,000

Loadout and Product Storage Building 120,000 120,00

Tail Water Pond Not included Not included

Barge-mounted Pump (500 gpm , 500-ft head, SS) 27,000 29,700

Solution Pump (200 gpm, 50-ft head, SS) 15,000 x 2 33,000

20 gpm ssSlurry Pump, 20 gpm,100ft head 12,000 x 2 26,400

Water Pump (20 gpm, 50-ft head) 500 x 2 1,100

Air Compressor (25 cfm) 5,800 6,300

Equipment & Facilities Subtotal 612,500 623,200

Piping 31,000

Electrical/Instrumentation 10,300

Civil Works 20,500

Total Plant Direct Field Cost Subtotal 685,000

Spare Parts & Maintenance Supplies 5,000

Owners Costs 35,000

Field Indirect Costs 27,000

EPCM 68,000

Total Plant (w/out spent fluid mgmt) 820,000


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Table 6-2: Equipment List EQUIPMENT

ITEM NO. CAPACITY SIZE DESCRIPTION

Cone Feed Tank 1 100,000

gal. 30 ft. dia. x 20 ft. H

Provide 8-hr. surge capacity @ 200 gpm cone feed; set at higher elevation than plant to provide gravity flow to cones. Must be corrosion resistant to hold pregnant solution.

Process Water Tank 1 110,000

gal. 30 ft. dia. x 20 ft. H

Provide 8-hr. surge capacity @ 225 gpm for cone feed dilution, copper washing and area wash down; set at higher elevation than plant to provide gravity flow to cones. Corrosion resistance not required. Could be enlarged to include fire protection water.

In-line Mixer 1 400 gpm 1.5 ft.

dia. x 4 ft. L

Required to blend dilution water into very dense, viscous pregnant solution. Must be corrosion resistant.

Cone Cementation

Unit 1 270 ft3

10 ft. top dia. x 10

ft. H

Conical semi-continuous upflow reactor based on design of the Kennecott cementation cones (patents have expired). Must be corrosion resistant. The 2 units operate in parallel. 10 min. retention time.

Cone Overflow Clarifier 1 4,000 gal. 10 ft. dia.

x 6 ft. H

Center-fed rake clarifier to recover suspended cement copper in cone overflow (10 min. retention time). Must be corrosion resistant. Includes 10 gpm underflow slurry pump to advance settled copper to cone discharge thickener. Overflow drains to tail water pond.

Cone Discharge

Screen 1 800 gpm 6 ft. L x 4

ft. W

Wedge-wire type screen to remove coarse material in cement product discharged periodically from each cone. Must be corrosion resistant.

Cone Discharge Thickener

1 2,500 gal. 10 ft. dia. x 5 ft. H

Center-fed rake thickener for cement copper discharged from cones. Overflow is pumped to Cone Overflow Clarifier; thickened underflow (~50% solids) is pumped to filter press. Includes 2 pumps.

Flocculant Addition System

(includes metering pump)

2 Approx. 1 gpm

4 ft. H x 4 ft. W x

4 ft. L

Self-contained flocculant mixing and addition systems to enhance settling of cement copper in thickener and clarifier.

Filter Press 1 TBD

Approx. 4 ft. H x 4 ft. W x 6 ft. L

Plate and frame type with provision for water wash and air blow. Washed and dried cement copper discharged to loadout conveyor beneath filter press. Filtrate advanced to cone overflow clarifier.


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Loadout Conveyor 1 TBD

3 ft. W x 40 ft. long

Standard conveyor system to move final cement copper product to stockpile or for direct loadout for shipment. Includes bin beneath filter press.

Scrap Iron Storage 1 50 ton

3-sided bunker, 10 ft. x 10 ft. x 10 ft.

Three sided structure with roof (15 ft. eve height); fourth side open for front-end loader (FEL) access.

Portable Inclined

Conveyor 1 TBD

3 ft. W belt, 40-ft

length with 15 ft. high

lift

Conveyor for charging scrap iron to top of cones. Equipped with loading bin at bottom. Iron added to bin with FEL.

Front-end loader 1 1-yard

bucket N/A Mainly used for moving scrap iron, but available for other duty.

Loadout and product storage building

1 N/A

60 ft. L x 40 ft. W x 20 ft. eve H

Steel frame building to house filter press and store final product for shipment. Needs high bay access.

Tail Water Pond 1 500,000

gal.

100 ft. L x 100 ft. W x 8 ft.

deep

Double lined pond to receive barren flow from cones (via clarifier). Also receives area wash downs and serves as storm catchment for plant area.

Barge-mounted Pump 1 500 gpm 500-ft

head Returns de-copperized solution to heap area for evaporation. (SS)

Process Solution Pumps

2 200 gpm 50-ft head

Cone feed pump and clarifier overflow pump. (SS)

Cement Copper Slurry

Pumps 2 20 gpm 100-ft

head Advances clarifier underflow to thickener and feeds slurry to filter press. (SS)

Process water pumps 2 20 gpm 100-ft

head Filter cake wash water and filtrate discharge pumps

Air Compressor 1 25 cfm N/A Provides air for cone discharge and air

blowing filter cake

6.2 Operating Cost Estimate

An important factor for the cement copper plant design is selecting the flow rate of the process operations. To estimate the flow rate, several factors were considered. The 4AP was estimated to have a working capacity of 10.6 million gallons of solution (solid, slush and liquid phases). The amount of each phase of solution in the pond is not known, but it is believed that most of the contents are in the solid or slush phase, depending on the time of the year. Studies conducted at


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UNR showed that approximately 4.4 lbs. of solids are re-solubilized for each 1 gallon of fresh makeup water. If this factor holds for the entire depth of the solids in the pond, then the ponds current content would be equivalent to approximately 30 million gallons of fluids to be managed and evaporated. This volume does not include the ongoing input of draindown solutions. It is estimated that the surrounding pads (Phase I and II, Phase III South, Phase III-4X, Phase IV- VLT and Slot) produce approximately 6.4 million gallons annually that are periodically pumped to FMS-pond for storage and evaporation. This annual estimate was extrapolated from information provided in the annual Operations and Maintenance Report for the FMS (Brown and Caldwell, 2013, pg. 28). Operating at 100 gpm, it would take approximately five years to treat all of the 4AP contents. Assuming 10-hour/day, 5 day/week schedule results in approximately 6,000,000 gallons/yr of processing. At this rate, the 30 million gallons of solution (after re-solubilizing the solids) would be processed in 500 operating days over a period of five years (100 operating days/yr). If the system were scaled to handle 200 gpm, using the same operating assumptions as above, the time to process the contents of the 4AP would be reduced to 2.5 yrs. The subsequent years would be processing the steady state inflow from the HLPs. Assuming approximately 6.4 million gallons of draindown annually, only a portion of the inflow would require processing due to natural evaporation. The amount of natural evaporation is not known with certainty, but it is possible that some amount of new makeup water would need to be added to keep the solids in solution for processing via cement copper. In any event, the first five years would have higher copper concentrations than in the subsequent years when only drain down and storm water run-off are treated. These factors were also considered in estimating the annual operating costs. Table 6-3: Annual Operating Costs (100 gpm operation)

Using a 30% contingency, the annual operating costs are estimated to be approximately $500,000 in the first five years and $275,000/yr in subsequent years. Note that the costs presented in Table 6-3 do not include the other O&M costs of the FMS (e.g., bird mitigation,

Description of Cost Annual

Operating Cost (Year 1-5)

Annual Operating Cost

(Years 5+) Plant maintenance $ 10,000 $ 10,000 Plant operation $ 139,600 $ 49,300

Labor Iron supply Electricity and water

$ 87,500 $ 46,400 $ 5,600

$ 74,200 $ 9,800 $ 2,400

Enhanced evaporation system $ 78,200 $ 39,100 Monitoring costs $ 25,000 $ 25,000

$ 392,300 $ 209,800


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balancing fluids between various ponds, etc.) The operating costs also do not include the cost of shipping cement copper to the buyer, which is discussed in Section 7.

Cement Copper Market Evaluation

From January 2013 to June 2014 SPS contacted numerous copper mines, smelters and refineries in the western U.S. and Mexico to evaluate the market for purchasing the final cement copper product that would be produced from the FMS. Mines that ship copper concentrate were thought to be a possible market as the addition of cement copper would raise their concentrate grades prior to shipping to a smelter. Contacts were made in Nevada, Utah, Arizona, Montana and Mexico. In general, there was little interest from potential buyers given the small amount of cement copper from the FMS and the amount of work that would be required on the receiving end to obtain approval/permitting of the addition of cement copper to their concentrates or smelter feed. One location in Mexico was a possibility, but shipping costs would be very expensive and this location was not pursued further.

With London Metals Exchange (LME) copper prices at approximately $3.25/lb., it is estimated that the price for cement copper, adjusted for various treatment and transportation surcharges would be approximately $2.00/lb. net payable copper. Net payable copper is directly dependent on the copper price and the transportation to the location of use.

The lack of a market for the sale of cement copper remains a barrier to the viability of using cement copper for management of the FMS.

Additional Work

questions regarding the viability of using cement copper to manage the FMS fluids Several key and solids need to be addressed in further detail, including the following:

The volume and grade of the 4AP and FMS copper content Detailed process engineering design and cost estimates Spent fluid management system Marketability of cement copper Regulatory and permitting issues Operational details


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References

CH2M HILL. May 2012. Feasibility Study for Arimetco Facilities Operable Unit 8 Heap Leach Pads and Drain-down Fluids. Broadbent, December 2013, Construction Quality Assurance Report plus Two Ponds, Yerington Mine 10-01-219. Brown and Caldwell. September 2011. Arimetco FMS Water Balance and Short-Term Mitigation Alternatives. Brown and Caldwell. September 2013. 2012 Annual Operations and Maintenance Report Arimetco Heap Leach Fluid Management System Yerington Mine Site. SRK. 2013. Yerington Mine Fluid Management System Study. Society of Mining Engineering (SME). 1966. Cone-Type Precipitators for Improved Copper Recovery.


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Attachment A (on CD)

FMS Pond Characterization Report

Prepared by Telesto Nevada January 2013


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Attachment B (on CD)

Cement Copper Pilot Studies

Prepared by SPS August 2013

cement copper evaluation w/email tls, w/o attchs a-b · summary report cement copper evaluation 4...

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