VANCOUVER, BRITISH COLUMBIA--(CCNMatthews - July 21, 2006) - Baja Mining Corp. (the "Company") (TX VENTURE:BAJ) is pleased to announce the successful completion of the Demonstration Phase 2 Pilot Plant campaign ("Pilot Plant") at SGS Lakefield Research Ltd. ("Lakefield") treating ore from the Company's Boleo property ("Boleo"), Baja California Sur, Mexico.
Summary:
A 6 week Pilot Plant campaign was conducted continuously from June 7 to July 14, 2006 treating a composite sample totaling 4.2 tonnes of ore that was obtained during the Test Mining campaign conducted in March at Boleo. The purpose of the demonstration campaign was to:
1) Finalize design criteria for recoveries of metals and consumption of key consumables to be used in the Definitive Feasibility Study ("DFS") being prepared by Bateman Engineering Canada Inc. ("Bateman");
2) Provide a design basis for Bateman to give process guarantees in the next phase of the project which is detail design and procurement;
3) Demonstrate that the high clay content of the Boleo ore does not present a problem for washing in the Counter Current Decantation ("CCD") circuit;
4) Produce sufficient quantities of copper cathode, cobalt cathode and zinc sulphate to enable off-take buyers to evaluate the quality of product(s);
5) Produce a saleable Manganese product (manganese carbonate);
6) Demonstrate that the limestone located at Boleo is suitable for use as the neutralizing agent;
7) Confirm that Commonwealth Scientific and Industrial Research Organization's ("CSIRO") Direct Solvent Extraction ("DSX") technology is capable of giving good separation and recovery of Cobalt and Zinc into saleable products; and
8) Provide an opportunity for equipment vendors to work with Bateman on equipment design.
Operation of the Pilot Plant was stable and reached a steady state condition within a few days of start-up. Operation continued smoothly 24 hours/day for the scheduled period. Test results met or exceeded the desired objectives in all aspects. The extractions of key metals in the leaching circuit under design conditions were: copper 91%; cobalt 82%; zinc 55%; manganese 97%. A number of specialist assays of final products are still pending but it is expected that the copper cathode grade meets LME Grade 'A' specifications (as was the case in the November 2004 pilot plant) and the cobalt metal is suitable for sale without requiring further refining.
The overflow of the metal bearing solution from the CCD circuit was very clear and leach residues settled quickly. The Company's locally available limestone was used for the entire test period. Several equipment vendors were on-site for the test period and the data collected is being used for design of several of the solid/liquid separation steps in the anticipated flowsheet. Good separation of zinc and cobalt was achieved and the zinc solution collected is suitable for production of zinc sulphate that can be sold in the fertilizer and animal feed markets.
President John Greenslade said, "The pilot plant was a technical success. The extraction and recovery of copper, cobalt, zinc and manganese was demonstrated from ore to saleable products. Copper metal cathode, cobalt metal cathode, zinc sulphate solution and precipitated manganese carbonate were all successfully recovered from Boleo ore."
The results of the pilot test are now being incorporated into the DFS report which will be released after receipt of the results of the infill drill campaign currently being conducted at Boleo.
Details:
The Pilot Plant was run over the period June 7 to July 14, 2006. It was performed to confirm the results of the "Proof of Principle" Pilot Plant performed in 2004 and to provide final engineering inputs to the DFS currently nearing completion with Bateman.
A representative sample of Boleo ore was delivered to Lakefield by truck from Mexico. The ore sample was blended by Lakefield to produce a sufficient quantity for the demonstration pilot plant run. Approximately 5 tonnes of ore was crushed, scrubbed and milled to produce a slurry feed to the leach circuit. Scrubbing and milling were performed in acidic raffinate from copper solvent extraction (the acid solution remaining after copper extraction). The final particle size of the ore was reported at 80% less than 38 microns.
A series of samples of the blended feed were obtained prior to milling. These were assayed by Lakefield as shown below.
--------------------------------------------------------------------- Chemical Analysis (%) --------------------------------------------------------------------- Sample Cu Co Zn Mn Fe Ca Mg Al Ni Si --------------------------------------------------------------------- 1 2.16 0.102 0.48 4.14 8.04 NA 2.75 5.29 0.014 18.7 2 2.25 0.123 0.47 5.58 8.15 NA 2.76 5.21 0.011 19.4 3 2.26 0.141 0.48 5.99 8.22 0.996 2.74 5.39 0.013 18.5 4 2.26 0.124 0.53 4.27 8.9 0.978 3.08 4.93 0.013 20.4 5 2.27 0.157 0.50 5.21 7.9 1.32 2.86 5.35 0.017 19.0 6 2.18 0.137 0.51 5.25 8.59 1.16 2.96 5.67 0.016 20.1 7 2.04 0.155 0.46 5.45 7.71 1.03 2.67 4.73 0.015 20.6 8 2.04 0.137 0.50 4.16 8.58 0.979 3.01 4.83 0.016 21.2 Average 2.18 0.135 0.49 5.01 8.26 1.08 2.85 5.18 0.014 19.7 ---------------------------------------------------------------------
The demonstration pilot plant flowsheet encompassed all of the unit processes of the expected full scale circuit and comprised the following steps:
- Acid oxidation leaching of the ore with sulfuric acid addition;
- Acid reduction leaching of the ore with sulfur dioxide and sulfuric acid;
- Partial neutralization with Boleo limestone (local, low-cost limestone, available on the Boleo mining lease);
- CCD washing of the leach residue in thickeners (to separate the metal rich aqueous solution from the clayey waste);
- Copper solvent extraction/electrowinning (SX/EW);
- Iron removal by pH adjustment, with Boleo limestone, and oxidation with oxygen (and polish with hydrogen peroxide);
- Thickening and filtration/washing of the iron residue;
- DSX technology for selective recovery of cobalt and zinc (and small amounts of residual copper); DSX technology is the property of CSIRO, Perth, Australia.
- Manganese carbonate precipitation from the raffinate (barren solution) emanating from the DSX solvent extraction circuit;
- Thickening, filtration and washing of the manganese carbonate by-product;
- Purification of the zinc and cobalt strip solutions from the DSX solvent extraction circuit using zinc dust cementation and ion exchange;
- Recovery of cobalt cathode from the DSX cobalt strip solution using a solvent extraction and electrowinning process.
The pilot plant was constructed by Lakefield technical staff to the specification of Bateman and the Company. It was operated by a team of approximately 60 Lakefield staff (working on 4 shifts), backed up by Lakefield's in-house analytical team. Bateman and the Company's staff were present at Lakefield to observe and help in overall supervision/control of the pilot plant operation. Additional technical specialists from the following organizations were present during the pilot plant to make measurements on key parts of the process flowsheet. Technical specialists present included:
- Pocock Industrial - performed specialist testwork on solid/liquid separation and rheology of slurries
- Mixtec - performed agitation studies
- RPA Process - performed filtration studies
- Outokumpu - performed specialist testwork on high rate thickener design and flocculant selection and dosage.
In addition to on-site specialists, the Saskatchewan Research Council (SRC) has received a sample of leach slurry and is testing the slurry pumping characteristics. GLV are performing "paste-thickening" studies on a sample of leach slurry. Separate reports from each of these technical groups will be received and incorporated in the final engineering design of the Boleo metallurgical facility.
A total of 4.2 tonnes of ore were leached during the pilot plant. The leach plant conditions were varied during the pilot plant to test the sensitivity of the process to acid and sulfur dioxide addition levels. The results were excellent as shown in the table below.
------------------------------------------------------------------------
Condition
-pH in Sulfur Boleo
oxidation Acid Dioxide Limestone Average Extraction (%)
leach Addition Addition Cons. (i)
------------------------------------------------------------------------
(kg H2SO4/ (kg SO2/
t ore) t ore) (kg/t) Cu Co Zn Mn
------------------------------------------------------------------------
pH equals 1.7 225 80 68 90.9 82.6 53.9 97.1
------------------------------------------------------------------------
pH equals 1.5 235 73 75 90.9 81.4 55.4 96.4
------------------------------------------------------------------------
pH equals 1.4 315 124 113 92.7 83.8 61.0 98.0
------------------------------------------------------------------------
(i) Average extraction is calculated from the final washed solid assay
compared to the ore feed assay.
The CCD circuit for washing of barren solids worked very well. The CCD was set up to simulate the use of the "high rate" type of thickeners with recirculation of overflow solution to dilute the feed slurry prior to flocculation. The leach residue settled quickly producing clear overflow solutions to advance to copper, cobalt, zinc and manganese recovery.
Copper was recovered from the clarified solution using conventional solvent extraction and electrowinning. An average extraction of 98.5% of the copper was achieved through solvent extraction (the remaining copper in the raffinate is partly recovered by recycle of the raffinate to the ore milling circuit). A total of 47 kg of copper metal was recovered by electrowinning at a current efficiency of greater than 97%. The samples of copper have been submitted for assay according to the Comex specification for purity and results are pending. Initial results obtained from Lakefield show iron levels typically less than 4 ppm and lead levels less than 3 ppm in selected copper cathode samples.
The copper solvent extraction raffinate was split with a portion of the raffinate recycled to leaching and a portion advanced to cobalt, zinc and manganese recovery.
The iron removal circuit was designed to remove iron, aluminum and other impurities from the solution prior to recovery of cobalt and zinc using DSX technology from CSIRO. The iron removal circuit consistently produced very low concentrations of key impurities in solution with negligible losses of cobalt and zinc. Boleo limestone was successfully used throughout the pilot plant for neutralization during iron removal thus confirming its suitability for use in the circuit at Boleo.
The CSIRO DSX circuit for cobalt and zinc recovery performed very well. The feed to the DSX circuit was the solution after iron removal. The average composition was 789 mg/L Zn, 219 mg/L Co, 44 mg/L Cu, 1.6 mg/L Fe, 10038 mg/L Mn, 600 mg/L Ca, 6612 mg/L Mg and 14900 mg/L Cl. The raffinate (barren solution) from DSX contained on average 4.2 mg/L of Zn and 0.95 mg/L of Co. These values confirm that over 99% of both Zn and Co were recovered through the DSX circuit.
The two products from the DSX circuit were a zinc strip solution and a cobalt strip solution. The selective stripping of zinc and cobalt were gradually optimized during the pilot plant with average compositions for the last four days of pilot plant operation are shown below.
Zinc strip solution composition (average of last four days of pilot plant operation) ----------------------------------------------------------------- Composition (mg/L) ----------------------------------------------------------------- Zn Co Fe Ni Mn Cd Ca Mg ----------------------------------------------------------------- 35969 764 17 1 98 6.2 6.7 43 -----------------------------------------------------------------
The zinc strip solution was generally very pure. The average Zn/Co ratio in the zinc strip solution was about 47:1. The small amount of cobalt impurity with the zinc strip solution would represent a loss of a small amount of cobalt from the circuit if allowed to go to final product (less than approximately 5% of the cobalt). A small bench scale test program is underway at SGS Lakefield to demonstrate that the cobalt in the zinc strip can be recovered and recycled in the process to eliminate this potential loss. The purified zinc strip solution (after zinc dust cementation to remove cadmium) will be crystallized to form zinc sulfate crystals using evaporative crystallization.
The cobalt strip solution from the DSX circuit was rich in cobalt but still contained large amounts of zinc and other minor impurities. The composition of the cobalt strip solution (average for last four days of pilot plant operation) is shown below.
Cobalt strip solution composition (average of last four days of pilot plant operation) ------------------------------------------------------------------- Composition (mg/L) ------------------------------------------------------------------- Cu Zn Co Fe Ni Mn Cd Ca Mg ------------------------------------------------------------------- 613 9717 5882 37 214 11 3 4 21 -------------------------------------------------------------------
The cobalt strip solution was accumulated during the main part of the leach pilot plant. The strip solution was then treated by zinc dust cementation to remove copper and cadium followed by an anion exchange purification process step. The strip solution was then sent to a zinc/cobalt solvent extraction circuit for separation and purification of the zinc and cobalt. The purified zinc solution will join the DSX zinc sulfate solution as feed to zinc sulfate crystallization. The purified cobalt solution was electrowon to produce cobalt metal.
The results of the cobalt/zinc solvent extraction and cobalt electrowinning processes were excellent. The Cyanex 272 solvent extractant was used to separate and purify these two elements. Over 99.5% of the zinc and cobalt was recovered through these solvent extraction circuits. The compositions of the purified zinc sulfate solution and the cobalt strip solution for cobalt electrowinning are shown below. In each case these are average values over the last four days of the pilot plant.
Zinc strip solution composition from the zinc SX circuit (average of
last 4 days of pilot plant operation)
----------------------------------------------------------------
Composition (mg/L)
----------------------------------------------------------------
Zn Co Fe Ni Mn Cd Ca Mg
----------------------------------------------------------------
68036 12 26 less less less 2 less
than than than than
0.6 0.2 0.1 0.3
----------------------------------------------------------------
Cobalt strip solution composition from the cobalt SX circuit (average
of last 4 days of pilot plant operation)
----------------------------------------------------------------
Composition (mg/L)
----------------------------------------------------------------
Zn Co Fe Ni Mn Cd Ca Mg
----------------------------------------------------------------
less 80647 less 44 77 2 61 298
than than
2 3
----------------------------------------------------------------
The cobalt strip solution was passed through two ion exchange columns for minor element purification prior to electrowinning to deposit cobalt metal. The cell design used a lead anode with anode bag opposite a stainless steel "blank" for cobalt deposition. A total of nearly 2 kg of cobalt was deposited during the pilot plant at a current efficiency of 89%. The cobalt cathode is currently undergoing specialist assay to confirm the purity of the final metal product.
A portion of the cobalt strip solution (after ion exchange for minor element control) was also withdrawn and precipitated with sodium carbonate to make cobalt carbonate as a potential alternative cobalt product.
The last product that was recovered from the demonstration pilot plant was manganese carbonate. Manganese carbonate was precipitated from the DSX raffinate solution using sodium carbonate. The manganese carbonate was thickened, filtered and washed. The barren solution after manganese precipitation was returned to the circuit as wash water for the CCD.
The manganese precipitation was very selective with an average (for all days except startup day) manganese content of 44.2%. Minor amounts of other elements precipitated with the manganese in the final product.
Average Manganese Carbonate Analysis --------------------------------------------------------------- Cu Co Zn Mn Fe Ca Mg Al Ni Si Cd --------------------------------------------------------------- g/t g/t g/t g/t g/t g/t g/t g/t g/t g/t g/t --------------------------------------------------------------- 6 27 201 442105 173 11205 1917 4163 364 443 5 ---------------------------------------------------------------
Approximately 160 kg of manganese carbonate was recovered during the demonstration pilot plant.
The results of the demonstration pilot plant will now be fully integrated into the DFS by Bateman.
ON BEHALF OF THE BOARD OF DIRECTORS OF BAJA MINING CORP.
JOHN W. GREENSLADE, PRESIDENT
The statements made in this News Release may contain certain forward-looking statements. Actual events or results may differ from the Company's expectations. Certain risk factors may also affect the actual results achieved by the Company.
FOR FURTHER INFORMATION PLEASE CONTACT:
Baja Mining Corp.
John Greenslade
President
(604) 685-2323
(604) 629-5228 (FAX)
www.bajamining.com
