CYTEC SOLUTIONS. for Solvent Extraction, Mineral Processing and Alumina Processing. Volume 17 DELIVERING TECHNOLOGY BEYOND OUR CUSTOMERS IMAGINATION

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1 DELIVERING TECHNOLOGY BEYOND OUR CUSTOMERS IMAGINATION IN PROCESS SEPARATION Volume 17 CYTEC SOLUTIONS for Solvent Extraction, Mineral Processing and Alumina Processing

2 Letter from the Vice President To our Valued Customers, Advancements in our new product development effort as well as mergers and acquisitions over the past several years has transformed Cytec s business portfolio. These changes have created a leading high growth specialty chemical business. What does this mean for our mining customers? We continue to collaborate with you to address challenges and meet them with our technology and products. With economic challenges, changes in ore grades, and the demand for natural resources, Cytec is committed to finding sustainable, quality solutions to help you keep up with these challenges. To help meet the growing demand from our customers, Cytec has made significant investments in our manufacturing assets to improve reliability and increase capacity. One of the most significant investments includes a several hundred million dollar investment to expand our site in Niagara Falls, Canada. This site produces both mining products and phosphine derivates. We are also investing in assets to increase R&D capabilities at other global sites. We at Cytec want to help bring about solutions to your current and future operation s success and we have a well balanced portfolio of products and expertise that are unmatched. The major benefits of our products include increasing revenue through improved production, reducing operating costs, and reducing capital expenditure to build new plants. We have a significant focus on technology development and you can rely on Cytec to bring you the latest technology with our steady stream of new products that ensures you always have the best option by partnering with Cytec. In this edition, we highlight some of these new product advances. These include a scale controlling solution for phosphoric acid product plants with our innovative PHOSFLOW technology, an alternative to traditional hazardous modifiers with our AERO 7260 HFP, and nitration residence with our ACORGA NR series reagents. We are also pleased to share that our MAX HT Bayer sodalite scale inhibitor was awarded the 2012 EPA Presidential Green Chemistry Challenge Award. I have been with Cytec for over 18 years and in many roles that have helped prepare me for my new role to lead the In Process Separation business. Now, I am excited to lead a business that is focused on our valued customers and partners in the mining industry. I am dedicated along with my team to provide you with the service and solutions you are looking for now and in the future. Thank you for your interest and business, Michael Radossich Vice President, In Process Separation

3 Solvent Extraction, Mineral Processing and Alumina Processing Table of Contents: Solvent Extractions Crud Processing Improvements Using ACORGA CB 1000 Crud Busting Reagent...4 Use of ACORGA NR Reagents in the Presence of Nitrate Ions in SX: The State of the Art... 9 Mineral Processing AERO 7260 HFP Depressant: Novel, Safe and Sustainable Alternative to Traditional Hazardous Modifiers NaSH, Nokes, Na 2 S, and Cyanide Rejection of Pyrite: Challenges and Sustainable Chemical Solutions...23 Alumina Processing MAX HT Bayer Sodalite Scale Inhibitor: A Green Solution to Energy Consumption...30 Performance Evaluation of CYFLOC ULTRA HX-5300 A New HXPAM Red Mud Flocculant Applied in CBA (Companhia Brasileira de Aluminio)...35 Industrial Minerals Scale Controlling Chemical Additives for Phosphoric Acid Production Plants...42 IN PROCESS SEPARATION 03

4 Crud Processing Improvements Using Acorga Cb 1000 Crud Busting Reagent Tyler McCallum, Troy Bednarski, and Matthew Soderstrom Cytec has developed a unique crud treatment process utilizing both chemical and mechanical means to enhance the solid/liquid separation, improve recovered organic quality, and reduce operational costs. Crud (a complex solid stabilized emulsion of aqueous and organic) is a common concern in most solvent extraction processes [1,3]. If crud is allowed to build up in the circuit, aqueous and organic velocities within the settlers will increase, resulting in higher entrainments and operational costs. Crud movement between stages can cause continuities to flip and may require a significant reduction in plant flows or a plant shutdown to stabilize the operation [2]. To prevent these events, interfacial pumping is typically carried out to remove crud from the circuit and process it for organic recovery [4]. Crud processing can be very time consuming, and the recovered organic quality is often lower than desired with current processing methods. Cytec has developed a unique crud treatment process utilizing both chemical and mechanical means to enhance the solid/liquid separation, improve recovered organic quality, and reduce operational costs. The use of ACORGA CB 1000 crud busting reagent allows a rapid separation of solids from the organic phase. ACORGA CB 1000 is an SX qualified chemical additive, which aids in the recovery of organic from crud. The process involves breaking the stabilized crud emulsion, freeing the associated organic, and settling the solids very rapidly. This process allows operations to return clean organic back to the plant more efficiently and may enable operations to process more crud. In addition to the improvement in processing time, the crud buster process enables more efficient clay treatment and therefore can improve the quality of organic that is returned to the SX circuit. The crud buster process involves mixing the crud with organic (under organic continuity) then breaking the crud emulsion through the addition of hydrophilic solids (clay). Once the emulsion has been temporarily broken, the addition of ACORGA CB 1000 will bind to the solids causing them to settle and preventing the emulsion from re-forming. Following the clay and ACORGA CB 1000 addition, the agitator may be stopped, allowing the phases to separate and quickly recover the majority of the organic freed from the crud emulsion. This organic can then be more efficiently clay treated and returned to the process quickly without the typical issues associated with filtration of an emulsion. The solids remaining after the primary separation (containing some residual organic and aqueous, which was freed from the crud emulsion) can then be processed using typical methods for a secondary solid/liquid separation and further organic recovery. The volume of the secondary separation is substantially less; therefore limited time is required for processing. Any organic recovered from the secondary separation should also be subjected to clay treatment. The laboratory test shown in Figure 2 illustrates the effect of ACORGA CB 1000 in breaking the crud emulsion and freeing the associated organic. For this test, crud was dispersed in an organic continuous mix of diluent. The picture on the left is the organic continuous mix before clay addition; the middle picture is after addition of clay and ACORGA CB 1000; and the picture on the right is the immediate result after agitation was ended. As shown, a very clear organic phase is evident using the process and recovery of this organic can be quickly achieved. 04

5 Solvent Extraction, Mineral Processing and Alumina Processing Crud Processing Improvements Using ACORGA CB 1000 Crud Busting Reagent FIGURE 2: ACORGA CB 1000 Mixing and Settling Crud Buster Benefits Crud processing using ACORGA CB 1000 can offer significant time savings due to the rapid chemical separation of organic from crud without requiring the initial step of using a press or centrifuge to break the crud emulsion. The organic that is quickly recovered is a very clean stream largely free of suspended solids. This clean organic stream can then be clay treated more efficiently producing a high quality recovered organic. The small amount of ACORGA CB 1000 remaining in the organic after the solid/liquid separation is removed by the clay during clay treatment. Time Savings Eliminating the need of a press or centrifuge for the initial rupturing of the crud emulsion to free organic allows significant time savings. The crud emulsion can blind filter cloths when using a plate and frame filter press (requiring additional time to drop and recharge the press). Centrifuges are limited by the flow rate and crud volume to be processed. The crud buster process allows a rapid solid/liquid separation without the additional steps/equipment. Total Suspended Solids (TSS) Current crud treatment methods (regardless if using a centrifuge or filter press) are often inefficient and frequently allow suspended solids to be left in the recovered organic. The return of organic with these now finely dispersed solids can be the cause of additional operational difficulties. The amount of solids remaining in the organic following mechanical processing can vary greatly and is dependent on the equipment being utilized. High TSS in recovered organic is common. Figure 3 shows solids removed from the organic during each step of processing. The top row of pictures gives an indication of the TSS present in the organic phase after each step using a traditional filter press process without ACORGA CB The bottom row of pictures represents the crud buster process after each step. IN PROCESS SEPARATION 05

6 Crud Processing Improvements Using ACORGA CB 1000 Crud Busting Reagent FIGURE 3: TSS of Standard Filter Press and CRUD BUSTER Process Visually it is easy to see that the final organic product returned to the circuit post clay treatment was much cleaner using the crud buster process than the process using only mechanical separation. Interfacial Tension (IFT) Mechanical rupturing of crud often results in surface active species associated with crud being transferred to the organic, lowering the IFT and organic quality. This is in addition to the problem of solids often being redistributed. Figure 4 shows the interfacial tension of various organic samples from operating plants. Traditional mechanical rupturing processes return organic with a lower IFT than the circuit organic. This reduction in organic IFT is true for operations using plate and frame filter presses or centrifuges. The figure also shows that both the plant organic and crud processed organic have the potential to be of higher quality with efficient clay treatment. Without clay treatment of the recovered organic, the associated surface active species from the crud are often returned to the circuit. Interfacial Tension (dynes/cm) Sample 1 Sample 2 Sample 3 Sample 4 Plant Organic Recovered Organic from Crud Clay Treated Organic FIGURE 4: IFT of Circuit Organic, Recovered Organic, and Clay Treated Organic 06

7 Solvent Extraction, Mineral Processing and Alumina Processing Crud Processing Improvements Using ACORGA CB 1000 Crud Busting Reagent Operations that practice clay treatment of recovered organic typically only utilize wt% clay due to plugging concerns. This is rarely sufficient to remove all surfactants from the organic, and the clay is often deactivated by aqueous remaining with the organic. As shown in Figure 5, an excess of 2% clay is required to restore the organic IFT (of this specific plant organic) to its maximum value. 39 Recovery Organic Clay Treatment Curve Interfacial Tension Time (dynes/cm) Clay Concentration (wt%) FIGURE 5: Clay Treatment vs. Interfacial Tension The use of ACORGA CB 1000 efficiently separates the organic from the solids/aqueous emulsion, enabling the organic to be treated with the appropriate clay dosage without deactivation of the clay. Benefits of Higher Organic Quality Pilot plant testing was completed to compare organic recovered by crud buster to organic recovered by typical mechanical crud processing means. This work was completed using a 2E + 1S configuration at 6 lpm feed flow and results are shown in Table 1. Table 1. Pilot Plant Comparison CB Processed Organic Typical Processed Organic IFT (dynes/cm) Extract PDT Org Cont. (seconds) Extract PDT Aq Cont. (seconds) Strip PDT Org Cont. (seconds) Dispersion Band Org Cont. (% of org depth) 0% 61.2% Organic Entertainment 34% decrease Aqueous Entertainment 18% decrease Cu:Fe Transfer Ration IN PROCESS SEPARATION 07

8 Crud Processing Improvements Using ACORGA CB 1000 Crud Busting Reagent The crud buster process (enabling efficient clay treatment) produced an organic with a higher IFT and better overall organic quality. This resulted in a significant improvement in phase disengagement times, dispersion band depth, organic and aqueous entrainments, and Cu:Fe selectivity. Note: Lower Fe transfer (along with reduced aqueous entrainment) would be expected to result in a significant reduction in operating costs through electrolyte bleed reduction. Conclusion Current crud treatment and organic recovery practices are often not efficient in producing a high quality organic product. Use of mechanical equipment to break the crud emulsion is effective, but often leaves suspended solids and surfactants in the organic. It is critical to clay treat recovered organic (although not always practiced). When clay treatment is performed, the clay concentration used is often lower than optimal because of concerns related to plugging of the filtration equipment. The resulting organic returned to the circuit leads to redistribution of solids, poor phase disengagement, and higher entrainments. Metallurgical performance can also be negatively impacted. The crud buster process enables efficient clay treatment and results in a high quality recovered organic in a timely manner. Crud buster is expected to produce an organic with a lower TSS and a higher IFT than current processes. These improvements in organic quality have been shown to result in improved SX performance (break times, entrainments, kinetics, stage efficiency, Cu/Fe selectivity) and are expected to bring operational cost savings. References 1. R.F. Dalton, C.J. Maes, and K.J. Severs, Aspects of Crud Formation in Solvent Extraction Systems, Arizona Conference of the AIME, Tucson, AZ., Cytec Industries Inc., Crud: How It Forms and Techniques for Controlling It, Marketing Publication, T. Burniston, J.N. Greenshields, and P.E. Tetlow, Crud control in Copper SX Plants, E&MJ, 1992, (Jan) pp M. Cox, Liquid-Liquid Extraction and Liquid Membranes in the Perspective of the Twenty-First Century, Solvent Extraction and Liquid Membranes, 2008, pp For more information on this subject and other Cytec technologies, please visit our website at TRADEMARK NOTICE: The indicates a Registered Trademark in the United States and the indicates a trademark in the United States. The mark may also be registered, subject of an application for registration, or a trademark in other countries. 08

9 Use of ACORGA NR Reagents in the Presence of Nitrate Ions in SX: The State of the Art Rodrigo Zambra*, Alejandro Quilodran, Gonzalo Rivera, and Osvaldo Castro Given the relevance of the nitration threat in Chile due to high nitrate containing ores in some plants and the lack of an available practical solution for the industry, Cytec developed a superior line of modified aldoxime extractants. This work presents the results of studies of different solvent extraction operations in the north of Chile where nitration concerns are the greatest. While all copper solvent extraction operations have some nitrates present, this paper is focused on the four copper SX plants that have the potential for appreciable levels of nitrate ions in their leach solutions. Nitration is a phenomenon that initially attracted the interest of the copper mining industry in the late 90 s due to the experience at Lomas Bayas where they experienced significant nitration of the organic inventory. Since then the industry developed the position that ketoxime-based extractants were the best solution for operations with nitration risk. Nitrated oximes (ketoximes and aldoximes) form stable Cu complexes that prevent the stripping of copper. Once the oxime is nitrated, the oxime no longer works as an extractant because that portion of the organic no longer transfers copper. Nitration is certainly a function of the nitrate concentration in aqueous solutions, but it is also a function of the acidity, temperature, redox potential, interfacial tension and the reactivity of the aqueous and organic phases. Nitration of oxime compounds leads not only to reduced copper transference capacity, but also increased phase disengagement times, reduced interfacial tension, increased entrainment and hydrolytic degradation. Given the relevance of the nitration threat in Chile due to high nitrate containing ores in some plants and the lack of an available practical solution for the industry, Cytec developed a superior line of modified aldoxime extractants. These products, known commercially as the ACORGA NR series, provide nitration protection without reducing copper production capacity. Examples of the relative performance of ACORGA NR series extractants and ketoxime-based extractants are discussed next. The nitration mechanism is shown below: NO H 2 SO 4 HNO 3 + HSO 4 - (1) HNO 3 + H 2 SO 4 NO H 2 O + HSO 4 - (2) OH OH N OH OH OH N OH N O R 2 N O 2 N NO 2 R 1 R H + 1 R 2 R 2 R 2 R1 H or CH3 (aldoxime or ketoxime) R2 C9H19 or C12H25 (nonylaldoxime or dodecylaldoxime) 09

10 Use of ACORGA NR Reagents in the Presence of Nitrate Ions in SX: The State of the Art Case 1, Plant A The conditions at Plant A prior to substitution of the ketoxime extractant LIX 84I with the modified aldoxime ACORGA NR10 are listed below: Table 1: Characterization of the Solutions at Plant A Element Units PLS Spent Cu g/l ph/h2so4 -/g/l NO3- ppm 1, ORP mv Simulations In order to compare the extraction efficiency of the reagents LIX 84I and ACORGA NR10, the extraction and stripping isotherms were created in the laboratory using real plant solutions. McCabe Thiele analysis was then used to calculate the expected recovery for the configuration. The results are presented in Table 2. Table 2: Results of Simulations with Plant Solutions (23% extractant). Extractant Efficiency [%] Train A Efficiency [%] Train B Lix 84I NR The better extraction kinetics under high copper tenor and low ph conditions of ACORGA NR10 results in a 6% higher copper recovery than LIX 84I extractant, which was used in the plant. Accelerated Nitration Tests Several tests were then carried out in order to evaluate the behavior of the extractant in a possible nitration scenario. The properties of the evaluated PLS feed (which had adjusted values of ph and nitrate to make the solution more aggressive) are shown in Table 3. This PLS was mixed continuously in a 1:1 ratio at 40 C with three separate reagents prepared at 25 vol %: LIX 84I (ketoxime), LIX 860 (pure aldoxime), ACORGA NR10 (modified aldoxime) and Plant Organic (a blend of the regents appointed previously). Table 3: PLS Conditions for the Accelerated Nitration Tests. Value Units Cu 2.50 g/l NO g/l FeT 4.70 g/l Cl g/l P. Redox 752 mv T 40 C ph

11 Solvent Extraction, Mineral Processing and Alumina Processing Use of ACORGA NR Reagents in the Presence of Nitrate Ions in SX: The State of the Art The results presented in Figure 1 show that there was a strongest resistance to nitration when using the ACORGA NR10 reagent (approx. 50%) compared to LIX 84I, LIX 860 and Plant Organic. Nitration (%) Ketoxime Unmodified Aldoxime Plant Organic NR Residual Copper, gpl Cu FIGURE 1: Results of the accelerated nitration tests based on residual copper and nitroxime IN PROCESS SEPARATION 11

12 Use of ACORGA NR Reagents in the Presence of Nitrate Ions in SX: The State of the Art Case 2, Plant B The second case shows the laboratory and piloting test to compare the behavior of the ACORGA NR 20 extractant and the reagent currently in use at the plant LIX 84I. This plant has a complex SX configuration, with two different PLS feeds: the heap leaching solution at 1.8 gpl Cu and ph 2.0 and the ROM leaching solution at 1.6 gpl Cu and ph 1.6. The stage efficiency was measured to compare the performance of LIX 84I and ACORGA NR 20, with both feeds FIGURE 2: 40 Acorga NR 20 HEAP LIX 84 IC HEAP Acorga NR 20 ROM LIX 84 IC ROM Stage efficiencies for PLS HEAP and ROM As shown in the graph above higher stage efficiencies were achieved with the ACORGA NR reagent. Accelerated Nitration Tests The following products were tested, LIX 84I, ACORGA NR20 and a traditional aldoxime that is not nitration resistant, unprotected reagent under aggressive nitrating conditions. The evaluation took place over a period of 150 days. The PLS used in this study was modified to be highly nitrating. Impurities were added to a real PLS (chloride, iron, and nitrate) with a ph of 1.0, as shown in Table 5. The extractants were mixed in a 1:1 ratio, and the solution was submerged in a thermostatic bath at a temperature of 40 C with constant agitation. Table 4: Characterization of the PLS COMPOSITION MODIFIED PLS Acidity g/l 5.7 NO3- g/l 58.8 FeT g/l 3.08 Cl- g/l It can be clearly seen in Figure 2 that both the ACORGA NR20 and LIX 84I extractants had an appropriate resistance to nitration but the unprotected extractant had significant nitration before 80 days of mixing. 12

13 Solvent Extraction, Mineral Processing and Alumina Processing Use of ACORGA NR Reagents in the Presence of Nitrate Ions in SX: The State of the Art Nitration (%) Sample Acorga NR 20 Unprotected Reagent LIX 84IC FIGURE 3: Results of accelerated nitration tests based on residual copper and nitroxime Pilot Plant Evaluation The ACORGA NR20 extractant was then evaluated in a 100 cm 3 /min pilot plant utilizing two PLS solutions (Heap and ROM). The initial conditions for the pilot study are presented in Table 5. The configuration of the pilot plant corresponded to that of an industrial plant, and the extractant was added at % for LIX 84I and 24.94% for ACORGA NR 20. The results of the tests are shown in Table 6. Table 5: Pilot Plant Test Initial Conditions HEAP ROM Spent Cu PLS g/l ph / H 2 SO 4 - / g/l O/A E O/A S The extraction efficiency results clearly show a better metallurgical performance for the ACORGA NR20 extractant, resulting in a 5.8% increase in copper recovery for the Heap and 8.8% increase for the ROM. Both extraction efficiencies are enhanced using the ACORGA NR20 extractant, which is based on a modified aldoxime that has favourable kinetics for mass transfer as compared to those for extractants based on ketoxime chemistry. As a result, a better mixing efficiency near the equilibrium point is achieved. In addition, the ACORGA extractant tolerates a wider ph range, maintaining good chemical and metallurgical performance from ph 1.0 to 2.5. Table 6: Extraction Efficiency, Pilot Plant Results Extractant HEAP Extraction Efficiency (%) ROM Extraction Efficiency (%) Ketoxime ACORGA NR In addition, the results for the selectivity of the ACORGA NR20 extractant conclusively confirm that the new reagent improves the plant selectivity by approximately 50%. The organic Fe loading for both the Heap and the ROM PLS streams are shown in Figure 4. IN PROCESS SEPARATION 13

14 Use of ACORGA NR Reagents in the Presence of Nitrate Ions in SX: The State of the Art Heap-Ketoxime Heap-NR20 20 Fe+3, ppm Loaded Organic, % ROM-Ketoxime ROM-NR20 20 Fe+3, ppm Loaded Organic, % FIGURE 4: Organic Fe Co-extraction as a function of copper loading for Heap and ROM solutions CONCLUSION Based on the results of the studies in the laboratory, and in the pilot plant, the following conclusions can be made: There is a great increase in the extraction efficiency and transfer of copper when using the ACORGA NR extractant, mainly because it provides better performance at low ph and enhanced extraction kinetics, which help improve the stage efficiency. In all of the cases studied, the ACORGA NR reagent performed better in terms of copper recovery by at least two percentage points with a maximum difference of 8 percentage points. Cu/Fe selectivity is also increased significantly (50%) by use of ACORGA NR extractants rather than ketoxime. The ACORGA NR extractant offers protection for the plant organic inventory under nitration conditions, ensuring a similar or better response than the LIX 84I extractant. For more information on this subject and other Cytec technologies, please visit our website at TRADEMARK NOTICE: The indicates a Registered Trademark in the United States and the indicates a trademark in the United States. The mark may also be registered, subject of an application for registration, or a trademark in other countries. 14

15 AERO 7260 HFP Depressant : Novel, Safe and Sustainable Alternative to Traditional Hazardous Modifiers NaSH, Nokes, Na 2 S, and Cyanide Mukund Vasudevan and D.R. Nagaraj Cytec has developed AERO 7260 HFP Depressant, a highly efficient and versatile sulfide mineral depressant with wide applicability. Introduction NaSH/Nokes are commonly used modifiers in Cu-Mo separation systems. However, these materials present a significant safety and health hazard to humans and a potential environment risk. After listening to the industry s need for safer alternatives, Cytec s innovation laboratory in Stamford, CT USA, focused its resources on finding a solution which is described in this article. Cu-Mo operations typically process ores rich in Cu sulfides (head grade 0.1-2%) and molybdenite (MoS 2, head grade %) via an operation consisting of a) the bulk flotation circuit, followed by b) Mo circuit as seen in Figure 1. Cu-Mo ore Cu ~ 0.5% Mo ~ 0.05% Roasting Steam Cl 2, O 3, H 2 O 2,etc Bulk Circuit Flotation Cu-Mo Bulk Concentrate (28% Cu, 1% Mo) Pre-Treatment (Optional) Mo Circuit Cu Depressants Conditioning with Cu Depressant Mo Rougher Conc Mo Ro Conc Tails Cu Conc Mo Cleaner Circuit FIGURE 1: A generic flow sheet for a Cu-Mo circuit The bulk flotation circuit is intended to produce a high grade Cu concentrate containing molybdenite values along with minor amounts of pyrite and some non-sulfide gangue. This concentrate is then processed in the Mo circuit to selectively float MoS 2 while depressing Cu sulfides and pyrite. This selective Cu-Mo separation is accomplished with the use of depressants such NaSH, Nokes, and Na 2 S (and cyanide, in some instances) with NaSH as the most widely used. 15

16 AERO 7260 HFP: Novel, Safe and Sustainable Alternative to Traditional Hazardous Modifiers NaSH, Nokes, Na 2 S, and Cyanide NaSH, Nokes and Na 2 S depressants generate significant amounts of a toxic, lethal, and flammable gas, H 2 S. Cyanide, which is also used as a depressant is both poisonous and has the potential to generate HCN, a toxic and flammable gas. In order to insure the safety of workers, the surrounding communities and the environment, Cu-Mo plants require several safety measures including H 2 S alarms and exhaust hoods over flotation cells and other exposed areas. In addition, H 2 S monitors are required on all personnel entering these plants and workers must adhere to strict safety protocols which involve rigorous training and evacuation procedures. In spite of these measures, hazards still persist and the industry is waiting for a safer, economically viable depressant which will provide the same metallurgical benefits. In response, Cytec has developed AERO 7260 HFP Depressant, a highly efficient and versatile sulfide mineral depressant with wide applicability as a selective depressant for Cu sulfides and pyrite and a safer alternative to NaSH, Na 2 S, and Nokes reagent. The following sections discuss in greater detail the issues with conventional depressants and benefits and application guidelines for AERO 7260 HFP in Cu-Mo separation. Problems with Current/Conventional Depressant Technology NaSH has been the main Cu sulfide depressant used in Cu-Mo separations for many decades. However, due to the danger of generation of high concentrations of toxic, flammable, hazardous, and lethal H 2 S gas, NaSH poses significant issues in plant operations and poses a threat to the local environment. Transportation of 20 to 40 tons per day of 40% solution of NaSH present shipping and logistics issues both in urban and remote areas. Metallurgical performance with NaSH is also not robust, for instance, plants can observe large performance swings with changes in ore mineralogy, and often pyrite depression with NaSH is inadequate even at very large dosages, creating a significant challenge in flotation operations. In the absence of a robust and economically viable alternative, NaSH (Na 2 S and Nokes in some plants) continues to be used extensively in Cu-Mo operations globally despite the hazards and all the safety concerns associated with it. AERO 7260 HFP is Cytec s innovative solution to this challenging issue. Advantages of AERO 7260 HFP Depression Efficiency AERO 7260 HFP is a highly efficient depressant for Cu sulfides and pyrite which effectively replaces 50 to 90% of NaSH depending on the process conditions. Dosage-Performance AERO 7260 HFP requires only 10% to 20% of the dosage of NaSH, providing similar metallurgical performance. Stability and Ease of Handling Stable and chemically inert reagent in storage, transportation, and under process conditions Does not release H 2 S or other toxic gases, and is non-hazardous Classified as non-hazardous to the environment No downstream or upstream effects to mineral processing Easy-to-handle aqueous solution Completely miscible in water ph AERO 7260 HFP is effective in a wide ph range (6 to 12). Staged Addition AERO 7260 HFP is long lasting reagent eliminating the necessity of staged addition down the bank in scavengers and cleaner cells as with NaSH. Bulk Concentrate Pretreatment Eliminates pretreatment of bulk Cu-Mo concentrate with steam, acid and CO 2 conditioning, attrition conditioning, etc. 16

17 Solvent Extraction, Mineral Processing and Alumina Processing AERO 7260 HFP: Novel, Safe and Sustainable Alternative to Traditional Hazardous Modifiers NaSH, Nokes, Na 2 S, and Cyanide Applicability and Other Advantages Eliminates the need for N2 or covered cells. Does not require extended conditioning time. Does not contain any phosphorous or arsenic, so is suitable in many MoS 2 operations. Clearly, with such advantages, AERO 7260 HFP offers a significant technological step forward in minimizing human and environmental hazards in Cu-Mo separations. Proven Performance of AERO 7260 HFP Lab and Plant Data The cumulative Cu and Mo recoveries from the concentrate from a North American mine are shown in Figure 2. For this concentrate sample, 7.5 kg/t of NaSH was required to provide efficient Cu depression (Cu recovery ~ 10%) and Mo recovery of greater than 95%. AERO 7260 HFP at 0.5 kg/t replaced approximately 65% of the NaSH dosage and provided comparable Cu depression. 100 Cu Mo 80 Recovery (%) NaSH 7.5 kg/t NaSH 7.5 kg/t kg/t FIGURE 2: Cumulative Cu and Mo recovery from a Cu-Mo North American concentrate IN PROCESS SEPARATION 17

18 AERO 7260 HFP: Novel, Safe and Sustainable Alternative to Traditional Hazardous Modifiers NaSH, Nokes, Na 2 S, and Cyanide In Figure 3, the Cu and Mo recoveries for a Cu-Mo concentrate from an Asian mine are shown. Efficient Cu depression was achieved only when 44 kg/t of Na 2 S was used. Under these conditions, Cu recovery was about 20% and Mo recovery was about 80%. The effect of 1.2 kg/t AERO 7260 HFP helped achieve even better Cu depression and Mo selectivity with only half the dosage of Na 2 S Mo Cu Recovery (%) Na 2 S 44 kg/t 11.8 Na 2 S 22 kg/t, AERO 7260 HFP 1.2 kg/t FIGURE 3: Cumulative Cu and Mo recovery from a Cu-Mo Asian concentrate 18

19 Solvent Extraction, Mineral Processing and Alumina Processing AERO 7260 HFP: Novel, Safe and Sustainable Alternative to Traditional Hazardous Modifiers NaSH, Nokes, Na 2 S, and Cyanide Figures 4A and B show Cu, Mo, and Fe recoveries and grades for lab data using AERO 7260 HFP on another North American mine Cu-Mo cleaner concentrate. In terms of Cu depression, this concentrate required about 11 kg/t of NaSH; however the Fe depression was not efficient at this dosage. For efficient Cu and Fe depression, a higher dosage of 55 kg/t NaSH was required. The addition of 0.25 kg/t of AERO 7260 HFP plus 11 kg/t of NaSH significantly enhanced both Cu and Fe depression and Mo selectivity. This suggests that AERO 7260 HFP is highly effective in the depression of both Cu and Fe and enables mine operations to significantly reduce NaSH consumption, in this case by over 80%. a) NaSH 55 kg/t NaSH 11 kg/t 80 NaSH 11 kg/t kg/t Recovery (%) Cu Mo Fe Mo Concentrate B) Grade (%) FIGURE 4: nd Cleaner Circuit Lab data of Cu, Mo and Fe a) recovery and b) grade Cu Mo Fe Mo Concentrate Clearly, the benefits of adding AERO 7260 HFP are observed by the improved metallurgical performance and substantially reduced dosage of NaSH. IN PROCESS SEPARATION 19

20 AERO 7260 HFP: Novel, Safe and Sustainable Alternative to Traditional Hazardous Modifiers NaSH, Nokes, Na 2 S, and Cyanide Figure 5 provides the average Mo assay in the scavenger tails from another Cu-Mo plant. The overall objective in this plant was to significantly reduce or eliminate Nokes (1400 g/t) usage in its Mo circuit, while maintaining Mo recovery (Mo < 0.2% in scavenger tails). With only about 100 to 200 g/t of AERO 7260 HFP, a significant volume of Nokes was replaced, while the key specifications were maintained Average Mo in Scav Tail (%) Nokes Standard 50% Reduction 75% Reduction 100% Reduction FIGURE 5: Plant data for Mo in scavenger tails as a function of Nokes dosages used Figure 6 shows the plant data when using AERO 7260 HFP in an on/off cycle on 3 consecutive days. The plot shows the percentage difference in Cu, Mo and Fe grades in the cleaner circuit with and without AERO 7260 HFP on any given day. In the off-cycle, only NaSH was being used to control the respective grades in order to meet production specifications. With NaSH only, both Mo and Cu specifications were achieved while Fe was above the specifications, i.e. sufficient pyrite depression was not achieved. With the addition of AERO 7260 HFP (on-cycle), all the specifications were achieved in addition to reducing the NaSH consumption by over 60%. Further, it was observed that Mo grades were significantly better in the on-cycle. This clearly suggests the benefits of AERO 7260 HFP in such operations. Moreover, through optimization, the NaSH dosage could be reduced by 80%, by adding only about 2 kg/t of AERO 7260 HFP. 20

21 Solvent Extraction, Mineral Processing and Alumina Processing AERO 7260 HFP: Novel, Safe and Sustainable Alternative to Traditional Hazardous Modifiers NaSH, Nokes, Na 2 S, and Cyanide % Difference between control and with AERO 7260 HFP (%) Day 1 Day 2 Day 3 Fe Cu Mo FIGURE 6: Three consecutive days of plant data using AERO 7260 HFP in an on/off cycle in the cleaner circuit. The % difference in Fe, Cu, and Mo grades between control (off cycle) and with AERO 7260 HFP (on cycle) is shown General Guidelines for Application The typical dosages to test AERO 7260 HFP is around g/t, and needs to be adjusted depending on the ore mineralogy and other process conditions. Higher dosages may be evaluated as needed. Optimization should be based upon Cu and pyrite depression, Mo selectivity, and economics. The performance of AERO 7260 HFP is best when air is used. Note: N 2 can be used, however the performance advantages and benefits of AERO 7260 HFP may not be fully realized. Pretreatments are not required with AERO 7260 HFP. AERO 7260 HFP should be added along with NaSH (or Nokes/Na 2 S). Recommended conditioning times are 5 to 15 minutes. Longer conditioning times, e.g. 30 min or longer are not required. AERO 7260 HFP can be added in the roughers, scavenger or cleaner stage, as needed. Usually, if the dosages are optimized, stage addition is not required. AERO 7260 HFP can be added as-is, or may be diluted as needed. Other Applications for AERO 7260 HFP AERO 7260 HFP is an excellent depressant for a variety of sulfide minerals, selectivity being dictated by dosage of AERO 7260 HFP and process conditions. Products based on AERO 7260 HFP have a wide range of applications including: a) Rejection of gangue from sulfide concentrates: Depression of all sulfide minerals while floating Non Sulfide Gangue E.g. Ni-talc separation. IN PROCESS SEPARATION b) Depression of penalty/toxic elements in Cu and complex sulfide ores. c) Enhancement of selectivity in Cu-Pb, Pb-Zn, Cu-Zn separations. d) Depression of iron sulfides in Cu-pyrite and Zn-pyrite separations. e) Depression of Cu sulfides and pyrite in Cu-Mo, Cu-graphite, Cu-F, Cu-Talc separations. 21

22 AERO 7260 HFP: Novel, Safe and Sustainable Alternative to Traditional Hazardous Modifiers NaSH, Nokes, Na 2 S, and Cyanide Conclusion AERO 7260 HFP is a novel, safer, versatile and highly effective Cu sulfide and pyrite depressant with broad applicability. This paper focuses on the application and benefits of using AERO 7260 HFP in Cu-Mo separations. The examples discussed in the paper include both lab and plant data which highlight the effectiveness of AERO 7260 HFP in depressing Cu sulfides and pyrite and improving the selectivity with respect to Mo. In addition to enhanced selectively, dosages of hazardous reagents such as NaSH, Nokes, and Na 2 S could be reduced by 60%-80% with relatively small dosage of AERO 7260 HFP (0.5 to 2 kg/t). References D. R. Nagaraj, S. S. Wang, P. V. Avotins and E. Dowling, Structureactivity relationships for copper depressants, Trans. IMM, Sect C: Vol 95, 1986, pp D.R. Nagaraj, C.I. Basilio, R.-H. Yoon and C. Torres, The Mechanism of Sulfide Depression with Functionalized Synthetic Polymers, Proc. Symp. Electrochemistry in Mineral and Metals Processing, The Electrochemical Society, Princeton, Proceedings Vol 92-17, 1992, pp Chander, S Inorganic depressants for sulfide minerals. Chapter 14 in Reagents in Mineral Technology. Edited by P. Somasundaran and B.M. Moudgil. New York: Marcel Dekker. For more information on this subject and other Cytec technologies, please visit our website at TRADEMARK NOTICE: The indicates a Registered Trademark in the United States and the indicates a trademark in the United States. The mark may also be registered, subject of an application for registration, or a trademark in other countries. 22

23 Rejection of Pyrite: Challenges and Sustainable Chemical Solutions Mario Palominos* and Carmina Quintanar In recognition of the growing interest in meeting sustainability challenges, Cytec has been focused on the creation of greener products (collectors, modifiers and frothers) and processes using the FLOTATİON MATRİX 100 approach. Abstract The mining industry is currently facing significant sustainability challenges in terms of dealing with difficultto-process low-grade resources. These ores are typically characterized by complex mineralogy and the presence of significant amounts of penalty gangue sulfide minerals and toxic elements. Among them, pyrite is a common challenge in many operations. Three chemical strategies for dealing with gangue sulfides and penalty elements include: a) selective flotation of value minerals while rejecting penalty minerals throughout the entire circuit; b) rejecting penalty minerals in an appropriate part of the circuit using selective depressants; and c) using a combination of selective collectors and depressants in appropriate parts of the circuit. New products and application technologies have been developed in recent years for implementing these strategies as dictated by the particular needs of a given plant. However, in recognition of the growing interest in meeting sustainability challenges, Cytec has been focused on the creation of greener products (collectors, modifiers and frothers) and processes using the FLOTATİON MATRİX 100 approach. Chemicals today play a critical role, not just in flotation, but in almost all areas of mineral processing. They will play an even greater role in tackling the challenges and achieving the goals of sustainable mineral processing, particularly in the areas of water efficiency and water resource management; waste reduction and remediation; minimizing environmental impact, safety and health risks (meeting and exceeding the requirements of regulations); energy efficiency; and dealing with difficult-to-process, low-grade mineral resources and reserves. Together, these challenges are often termed greener processing. There is also a growing desire to develop greener chemicals, a major challenge in itself. Different strategies for dealing with difficult-to-process low-grade resources in a sustainable manner are evaluated in order to determine the most efficient alternatives. The discussion includes an overview of recent developments at Cytec using case studies in which the application of selective collectors and polymeric modifiers, including the newer, greener chemistries, are demonstrated. 23

24 Rejection of Pyrite: Challenges and Sustainable Chemical Solutions Introduction In earlier years, pyrite content and other sulphide gangues were less of a problem in the mineral processing of copper, lead, zinc and other elements, mainly due to the lower content of this mineralogical species, the high content of the valuable minerals and the lower ecological sensitivity to gas emissions (principally SO 2 ) coming from the smelter. The first goal was to achieve higher selectivity, which was achieved through the development of dithiophosphate alternatives to the well-known xanthates (introduced to the market in 1923). Subsequently, it was found that thionocarbamates (and most commonly the isopropyl ethyl derivative, IPETC), generally have a higher selectivity than the above-mentioned chemistries. A third stage in the development of selective collectors focused on xanthate esters and dithiocarbamates 1. In parallel, the use of high ph 2 to depress pyrite was implemented (particularly as a cleaning step). Lime (CaO) was the depressant agent, and was used as a slurry (Ca(OH) 2 in preference to caustic soda (NaOH) or soda ash (Na 2 CO 3 ). Hence, the solution used was based on flotation at high ph (10-11) using a selective collector in the rougher stage and a very high ph (> 11) in the cleaning step. The solution was acceptable for the processing conditions at that time. However, the use of lime negatively affected the recovery of valuable secondary elements (e.g., molybdenum and gold). Currently, use of seawater is an additional limiting factor for the application of lime. A second alternative, employed now for several years, is based on the use of depressants for iron sulphides (mainly pyrite and pyrrhotite). Sodium cyanide yields some good results; however, secure handling and environmental issues make its use unattractive. Thus, sulphoxy depressants have been increasingly applied in recent years. A factor not always considered is the degree of activation of the pyrite, mainly by copper ions from altered or oxidized minerals. When pyrite is unactivated, it is possible to obtain good results using lime, sodium cyanide or sulphoxy species (such as sodium or ammonium sulphite or metabisulphite 3 ). When pyrite is activated, however, lime is much less effective, cyanide has its safety, health and environmental (SHE) issues and the sulphoxy species have to be used at high dosages. Furthermore, the degree of association of pyrite, particularly in conjunction with valuable species (copper, molybdenum, gold, lead, zinc etc.) must be considered. Selectivity should be for liberated pyrite in order to prevent the loss of any valuable species associated with the pyrite. Alternatives to inorganic depressants have also been utilized, including organic products from natural sources 4,5,6 (including quebracho, tannins and their derivatives) and ethylene diamine tetraacetic acid. In recent years, polymeric depressants have been developed that work effectively for both active and non-activated pyrites. These products are actually hydrophilic copolymers containing chemical functionality that is able to adhere selectively to iron sulphide species and lead to their depression. Importantly, polymeric depressants do not have the toxicity problems associated with the inorganic depressants, and they may be used at significantly lower doses. The need to process ores with higher iron sulphide content, the generally lower grades of valuable elements and the growing importance of secondary elements (molybdenum, gold, etc.), are driving greater interest in the use of selective collectors. In recent years, more selective reagents have been developed for the rougher stage in order to achieve selective flotation with high efficiency at this point, and thus minimise the use of depressants in the cleaning step. The compounds of interest have included structurally modified dithiocarbamates and thionocarbamates. These collectors have the advantage of being selective against liberated pyrite, but effective for the valuable elements associated with pyrite, such as copper, molybdenum, and others, thereby avoiding the loss of these valuable species related to the non-flotation of associated particles (middlings). 24

25 Solvent Extraction, Mineral Processing and Alumina Processing Rejection of Pyrite: Challenges and Sustainable Chemical Solutions Methodology Mineral ore samples from South America were used to evaluate the application of selective collectors and polymeric depressants. The feed grades of the ores are listed in Table 1. Table 1: Feed Grades of the Mineral Ores Used in the Evaluation of Selective Collectors. Ore Copper content, % Iron content, % Molybdenum content, ppm Ore Ore Ore Experimental Procedure Laboratory flotation tests were conducted to simulate 1) just the Rougher stage and 2) the different stages of the plant (open cycle test). The flotation products were collected and analysed for copper, iron and molybdenum using atomic absorption analysis. These mass balance results allowed the calculation of the metallurgical balance, and therefore the metallurgical recoveries, for each test. The conditions for the laboratory tests with the different mineral ores are described in Table 2. Table 2: Laboratory Test Conditions for Each of the Ores Conditions Ore-1 Ore-2 Ore-3 Machine Agitair L500 Denver Wemco ph % Solids Flotation time (min) Grinding 30% + 100#Ty 20% #Ty 20% +65#Ty Note that with Ore-3, when the standard collector was used, typical conditions for the cleaning stage were used (lime was added) and the ph was However, lime was not added in the cleaning stage for the other collectors tested with Ore-3 (final ph=8.7). Results and Discussion The study with Ore-1 demonstrated the difference in the selectivity for iron for the different types of selective collectors: dithiophosphate (DTP), isopropyl ethylthionocarbamate (IPETC) and a structurally modified thionocarbamate (SMTC). IN PROCESS SEPARATION 25

26 Rejection of Pyrite: Challenges and Sustainable Chemical Solutions DT IPET SMTC 90 Cu Recovery Fe Recovery FIGURE 1: Selectivity comparison for copper minerals vs. pyrite for 3 collector types The difference in the performance of DTP and IPETC, as described above in the Introduction, can be readily seen in Figure 1. IPETC, one of the first selective collectors to replace the xanthates, provides good recoveries and better selectivity. Importantly, though, it can also be seen in Figure 1 that the structurally modified thionocarbamate AERO XD-5002 promoter, which represents a new family of collectors developed by Cytec, is clearly advantageous in terms of its selectivity for copper minerals against pyrite (as represented by the Fe assay). A complementary study was then conducted with a second ore (Ore-2) with different mineralogical characteristics. Again, a series of selective collectors was evaluated, including the structurally modified thionocarbamate AERO 9950 promoter, which provided the highest selectivity against iron and also the best copper recovery among the tested chemicals. The results of this study are presented in Figure 2, while the different collectors and their dosage levels used in the test are listed in Table 3. Collector-1 refers to the main collector that was added to the grind. Collector-2, when used, refers to a secondary collector added in the conditioning stage prior to initiation of flotation Cu Rec (%) Fe Rec (%) Mass Pull (weight %) std Test FIGURE 2: Evaluation of selective versus non-selective collectors using Ore 2 26

27 Solvent Extraction, Mineral Processing and Alumina Processing Rejection of Pyrite: Challenges and Sustainable Chemical Solutions Table 3: Reagent Scheme for the Study Using Ore-2. N Collector-1[M] Collector-2 [C] 1 AP-9950; 20 g/t 2 XD-5002; 10 g/t 3 AP-9950; 15 g/t MX-945; 5 g/t 4 MX-8522; 15 g/t MX-945; 5 g/t 5 MX-7017; 15 g/t MX-945; 5 g/t STD PAX; 20 g/t [M]: Grind mill; [C]: Conditioning The third study included a cleaning stage (evaluated in an open cycle test). As indicated in the Experimental section, for the standard collector, the cleaning stage was conducted at ph 11.5, the regular condition for depression when lime is used. For the evaluated alternatives, however, lime was not added in the cleaning stage, so that comparisons could be made with results obtained for the subsequent study using depressants (see below). The selective collectors evaluated with Ore-3 included AERO 9950 promoter (structurally modified thionocarbamate) and AERO 9955 promoter (a mix of thionocarbamate and dithiocarbamate). Their performance was compared to that of the non-selective collector SIPX (sodium isopropyl xanthate), for which the standard conditions were used. The following figure (Figure 3) shows both the rougher and global recoveries (considering an open cycle test with two cleaning stages and a scavenger stage) conducted on Ore Cu-FC Grade = Cu Fe Mo Recovery (%) Rougher Final Rougher Final Rougher Final ST AP- AP- FIGURE 3: Comparative study between a non-selective collector (SIPX) and two selective collectors It can be seen in the figure that similar copper rougher recoveries were obtained for all three of the collectors, while in the rougher stage, the xanthate and AERO 9950 promoter had similar molybdenum recoveries and the AERO 9955 promoter provided a greater recovery. The iron recoveries in the rougher stage were significantly different, however. The xanthate had a high recovery (approximately 80%), followed by the AERO 9955 promoter (with a value near 65%), but the AERO 9950 promoter was the most selective (rougher Fe recovery of approximately 40%). The overall recovery of iron for the xanthate was calculated to be 30% based on analysis of the final concentrate after the two cleaning steps and considering the classical cleaning at high ph. AERO 9955 promoter, meanwhile, had an overall iron recovery of close to 20%, while that of AERO 9950 promoter (the most efficient in the rougher stage) was approximately 15%. With these values, the grades obtained for the final concentrate in terms of the copper content were determined and are indicated in Figure 3. With both AERO 9950 promoter and AERO 9955 promoter, IN PROCESS SEPARATION 27

28 Rejection of Pyrite: Challenges and Sustainable Chemical Solutions the final copper concentrates reached or exceeded the requirements for commercial grade material. In addition, due to the lower ph, there was limited loss during recovery of the by-product molybdenum (Mo) in the cleaning stage as compared to the reduction in the Mo recovery using the standard collector (SIPX). Comparative Study with Different Pyrite Depressants Figure 4 shows the results using different depressants, such as lime (for the standard condition), sodium metabisulphite (MBS), which is currently used, particularly when seawater is used for the processing, and new polymeric organic depressants. The ore used in this work was the same as that used to evaluate the selective collectors (Ore-3). In this study, the standard collector (xanthate) was used in all of the tests so that the effect of the different depressants could be evaluated in the cleaning stage Cu-FC Grade = Cu Fe Mo Recovery (%) Rougher Final Rougher Final Rougher Final Rougher Final ST Coll-STD / A-7260; 50 Coll-STD / A-7260; 100 Coll-STD / MBS-Na; 300 FIGURE 4: Inorganic and organic depressants for pyrite using Ore-3 MBS and the polymeric depressant developed by Cytec, AERO 7260 HFP depressant, were evaluated under similar conditions (ph = 8.5). The standard test used only lime as the depressant and was conducted at ph = All three depressants were added at the regrind mill stage. Importantly, as can be seen in Figure 4, neither the standard or the alternative depressants reached the values necessary for commercial concentrate grades (Cu > 25%). The addition of the depressant in the rougher stage to simulate the effect of the selective collector was also evaluated. However, low depression of iron was observed. The most significant effect was that copper and molybdenum species were depressed at high levels. 28

29 Solvent Extraction, Mineral Processing and Alumina Processing Rejection of Pyrite: Challenges and Sustainable Chemical Solutions Conclusion The results presented above demonstrate that there are new alternatives available on the market that are even more selective than the classic collectors commonly used for pyrite and other sulphide mineral gangue and can address the increasing levels of these contaminants that are present in today s mineral deposits. In addition, it was also shown that it is more efficient to use highly selective collectors in the roughing stage, rather than to use collectors with low or medium selectivity in conjunction with depressants. In the latter case, high doses are typically required, particularly when using organic depressants, which were found to be inefficient and have the potential to negatively affect the recovery of both the main sulphide product and secondary products, such as molybdenum and gold. References 1. Klimpel R. Richard, A discussion of traditional and new reagent Chemistries for a Flotation of Sulphide Minerals. Chapter 7, Reagents for Better Metallurgy, Society for Mining Metallurgy and Exploration Inc., Littleton, Colorado USA, Yuqiong Li, Jianhua Chen, Duan Kang, Jin Guo, Depression of Pyrite in alkaline medium and subsequent activation by copper, Minerals Engineering 26 (2012) G.I. Dávila-Pulido, A. Uribe-salas, R. Espinosaa-Gomez, International Journal of Mineral Processing, 101 (2011) Pedro E. Sarquis, Adriana Moyano, Mercedes Gonzalez, Vanesa Bazán, Organic Depressant Reagent Effect on pyrite in Copper Minerals Flotation, 8th International Mineral Processing Seminar (Procemin 2011), Maximiliano Zanin, Saeed Farrokhpay, Depression of Pyrite in Porphyry Copper Flotation, 8th International Mineral Processing Seminar (Procemin 2011), Jianhua Chen, Yuqiong Li,Ye Chen, Cu-S Flotation Separation via the combination of Sodium Humate and Lime in a low ph Medium, Minerals Engineering, 24 (2011), For more information on this subject and other Cytec technologies, please visit our website at TRADEMARK NOTICE: The indicates a Registered Trademark in the United States and the indicates a trademark in the United States. The mark may also be registered, subject of an application for registration, or a trademark in other countries. IN PROCESS SEPARATION 29

30 MAX HT Bayer Sodalite Scale Inhibitor: A Green Solution to Energy Consumption Morris Lewellyn, Alan Rothenberg, Calvin Franz, Frank Ballentine, Frank Kula, Luis Soliz, Qi Dai, and Scott Moffatt As the premier advanced chemicals partner for the Alumina industry, Cytec specializes in producing products with the breadth and depth to advance all stages in the Bayer Process. Our product innovations have transformed the industry s expectations regarding their technology suppliers and our strategy is to continue to develop solutions that will provide step changes in the industry. Our MAX HT scale inhibitor, a revolutionary product that eliminates sodalite scale from heat exchangers, recently received the 2012 Environmental Protection Agency s Presidential Green Chemistry award. The award recognizes companies that have pioneered sustainable technologies that incorporate the principles of green chemistry. MAX HT was developed to reduce or eliminate scaling from the evaporator and digester heaters in the Bayer process. This product has been successfully applied in 20 Bayer process plants worldwide, resulting in the significant benefits of increased heat transfer, reduced energy consumption and reduced acid waste from reduced heater cleanings. Based on trial data from a number of plants, the estimated annual savings per ton of alumina produced are Gj energy, resulting in kg reduction in CO 2 emissions, and kg reduction in acid waste.* When these savings are applied to the total alumina production from the 20 plants, this leads to an estimated realized annual savings of million Gj energy, billion kg CO 2 emissions, and million kg of acid waste reduction. * The range reflects the wide variety in the operation of Bayer plants around the world. Introduction Cytec has developed a line of polymers for use as scale inhibitors in evaporator and digester heaters used in the Bayer process [1-8]. These products provide benefits by reducing or eliminating the scale formation in the heaters resulting in significantly higher heat transfer, reducing energy consumption and waste. These products have been successfully applied in a number of plants utilizing the Bayer process throughout the world [9-11]. This technology is also being assessed for sodalite scale elimination in the evaporation process for the treatment of other types of substrate [12]. The scale deposited in these heaters is sodium aluminosilicate sodalite or DSP (desilication product). This is a result of the silica that is present in bauxite ores as silicates, primarily clay minerals, that dissolves quickly under typical Bayer alumina digestion conditions. The Bayer liquor remains supersaturated in silica and this supersaturation is greatest after the alumina precipitation step, i.e. in the spent liquor. As the alumina-depleted liquor is reheated, the rate of silica precipitation in the form of sodalite increases markedly with increasing temperature due to faster kinetics [13]. This precipitation occurs as scaling on the inside of the heat exchange tubes and a significant loss of heat transfer occurs, leading to increased energy consumption, increased caustic losses, reduced liquor flows, reduced throughput, reduced evaporation, and reduced production. 30

31 Solvent Extraction, Mineral Processing and Alumina Processing MAX HT Bayer Sodalite Scale Inhibitor: A Green Solution to Energy Consumption Without MAX HT, the method used to manage the sodalite scale problem is to clean out the system whenever the heat exchanger performance drops below a certain level, typically about half the original heat transfer rate. This cleaning is generally accomplished with the use of a 5-10% sulfuric acid solution to dissolve the scale. The used acid constitutes a waste stream requiring disposal. In addition to the acid cleaning, much of the inter-stage piping is cleaned using mechanical means, such as jackhammers, to remove the scale. The use of MAX HT is one way to make the Bayer process greener in terms of energy use and waste generation. MAX HT is commercial at twenty different plants across the globe, and under evaluation at a number of other plants. Many of these are double stream plants where the scale inhibitor can be used on both evaporator and digester heaters, but there are a number of single stream plants that find benefits from just treating the evaporator heaters. Cytec performed plant trials to research energy savings. See Figures 4 & 5. For detail on the results of the trials please go to The results of the trials show potential energy and waste savings which was the basis for the awarding Cytec the 2012 U.S. EPA (Environmental Protection Agency) Presidential Green Chemistry Challenge Award for MAX HT. Without Antiscalant With Antiscalant Dirty and clean heat exchangers from operating without and with MAX HT antiscalant after 160 hrs. of continuous operation, corresponding to the heat transfer curves in Figs. 4 and 5, respectively y = x Hours FIGURE 4: Typical heat transfer decay during 160 hrs. without MAX HT IN PROCESS SEPARATION 31