Engineering and Mining Journal - Whether the market is copper, gold, nickel, iron ore, lead/zinc, PGM, diamonds or other commodities, E&MJ takes the lead in projecting trends, following development and reporting on the most efficient operating pr
Issue link: https://emj.epubxp.com/i/271090
MARCH 2014 • E&MJ; 47 www.e-mj.com F I LT E R S A N D T H I C K E N E R S recovery and reduce the amount of water lost during tailings disposal. Paste thicken- ers increase the underflow solids concen- tration and reduce the final water content of material sent to the tailings pond. The company stated that its EIMCO deep cone paste thickeners accommodate up to 20 times the solids mass flow and 10 times the hydraulic loading of conventional thick- eners, which is achieved by optimizing the solids concentration for feed dilution, chemical addition and floc formation while minimizing floc degradation. FLSmidth told E&MJ; that it recently designed a new feed system, incorporating its E-duc feed-dilution technology and Evolute feedwell. This has been designed to maximize the critical parameters of "best practice" feedwell performance, the company said, and incorporates all of the benefits of both closed- and open-bottom feedwells without any of their drawbacks. The new feedwell has been designed for easy installation, with an upgrade available for retrofitting onto existing thickening equipment structures. E-Duc feed dilution and flocculation ahead of the feedwell allows for excellent mixing conditions for contact of flocculant, the company added. Followed by the low turbulence and further flocculation in the Evolute feedwell, this provides the optimal environment for flocculation and aggregate growth, minimizing flocculant usage and increasing settling rates. For more effective tailings management, pressure filters installed after the tailings thickeners increase the efficiency of mois- ture removal to create a filter cake general- ly containing less than 15% moisture. Cake stacking in multiple lifts can take up less than half of the area of a comparable tail- ings pond, with dry stacking proven to be safer and more sustainable for both a mine and its neighboring communities. With FLSmidth's AFPIV minerals pres- sure filters used for process-water recovery, the company's newly designed Colossal fil- ter press has been engineered to be twice as wide as previous models to give even better performance. The Colossal includes a patent-pending filter plate design, while 2-m-wide cloths are used on each side of each plate, making the cloth easy to han- dle. These filters not only provide high throughput and efficient solids capture, but they also operate continuously, auto- matically, in harsh environments, and can handle abrasive or corrosive slurries, the company stated. New Orders for Tenova Delkor Earlier this year, Tenova Delkor reported on three recently awarded contracts for its thickener technology from operations in Madagascar, Liberia and Sierra Leone. The order from an existing client, Dynatec Madagascar SA (DMSA), was for an addi- tional 80-m-diameter ore thickener mech- anism for the Ambatovy joint venture, and follows initial orders for thickener equip- ment dating back to 2007. Tenova Delkor said the thickener offers a number of advantages specific to the con- ditions at Ambatovy, such as a feed dilution system that enhances the thickening of the feed, using a forced dilution technology. The order was signed last November with the thickener mechanism due for delivery in the middle of this year. Tenova Delkor's scope of work covers design, supply and delivery, together with supervision of the installation and commissioning. Meanwhile the company received its first order from an operation in Liberia in December last year, with delivery due in the third quarter of 2014. Placed by BEA Mountain Mining Corp., part of Aureus Mining Inc., the order covers one 21-m- diameter high-rate thickener, two belt lin- ear screens (9 m 2 and 6 m 2 ) and a floccu- lant plant with auto dilution for increased steady-state conditions. The equipment is destined for the New Liberty gold mine, where the first gold pour is expected at the end of the first quarter in 2015. Lastly, Tenova Delkor reported that it recently delivered a 22-m-diameter ore tailings thickener to London Mining's Marampa iron-ore project in Sierra Leone. The company noted that this was its third order for Marampa, with the two previous contracts covering the design, supply and delivery of 85-m 2 belt filters. The first of these was installed in 2011, and the sec- ond last year. All three machines were designed by Tenova Delkor in Australia, with the first belt filter being manufactured in Australia, and the other equipment pro- duced in South Africa. Fully Automated Filter Presses The Japanese company, Ishigaki Co. Ltd., is the developer and worldwide supplier of the Lasta MC filter press for dewatering mineral concentrates and tailings. The company claimed that the Lasta MC has the largest capacity of any comparable fil- ter press, the fastest cycle time and has the best reliability, while allowing highly effective cake wash and achieving low cake moisture contents that can reduce or elim- inate drying requirements. Typical target performance includes tailings dewatering to 14% moisture and concentrates to 8%. The company noted that many of the more than 100 Lasta MC machines now in use have been operating efficiently for upward of 20 years. Ishigaki offers three models, with plate sizes of 1.5 m x 2 m, 2.1 m x 2.1 m and 2.1 m x 2.9 m. In 2011, the company's U.S. distribu- tor, Micronics Inc., received a $14 million order from a domestic gold producer for Lasta MC presses. With an initial through- put of 10,000 tons per day (t/d), and the capability of increasing this three-fold, the presses are being used for dewatering, with the removal of cyanide and 99% recovery of McLanahan Corp. is actively promoting the concept of combining thickener and filter-press technology; as shown in the inset, the resulting cake is much easier to handle. EMJ_pg46-58_EMJ_pg46-58 2/28/14 3:11 PM Page 47