Engineering & Mining Journal

JUN 2013

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

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COMPANY PROFILE-PAID ADVERTISEMENT Comparing the Cost of Dust Collector Bags vs. Cartridge Filters Which type of dust collection system will save money over time, a traditional baghouse or cartridge-style collector? A detailed filter cost analysis of bags vs. cartridges can provide revealing answers. (See article in May 2013 issue of E&MJ.) There are many factors beyond initial price that must be considered in formulating a true cost comparison between bags and cartridges. By understanding how to make that evaluation, mining professionals looking to upgrade their dust collection equipment will be better able to make informed decisions. Cost Comparison Example A large mining company was looking at upgrading the dust collector used to serve a fine ore crushing and screening plant. The existing equipment was a 47,000 cfm baghouse. The following analysis compares the change-out costs for the existing filter bags with projected costs for the same application substituting high efficiency cartridge filters. The dust collector used 544 bags, while a cartridge collector serving the same process would only require 72 cartridges. At the time of the evaluation, the cost per bag was $32, compared to an individual cartridge cost of $234. The total cost of filtration using bags is therefore $17,408 (544 x $32), in comparison to total cartridge cost of $16,848 (72 x $234). That amounts to a savings of $560 in initial filter cost—while achieving significantly higher filtration efficiency with the cartridges as an added bonus. The analysis also compared the energy requirements of the existing baghouse with a cartridge collector sized for the same cfm. Annual energy cost for the baghouse was $89,663.23 per year. Electrical cost to operate the cartridge collector was projected to be $67,247.42—a $22,415.81 per year savings. The Importance of Production Downtime Even more important in this evaluation is that mine maintenance personnel had to schedule two 10-hour "down" days to replace the 544 bags inside the unit, or 20 hours of lost production. With a cartridge dust collector sized for the same cfm, change-out of the 72 cartridges would only take an estimated four hours, recouping 80% of the lost production time. Figure 1 summarizes the costs of one hour of lost production. If the potential production run rate is 3,500 dry tons per hour (dtph), the average head grade of the ore is 0.45%/ton, and the ultimate recovery of the product is 80%, the mine would lose 25,200 lb of copper. If copper is selling on the market for $3.65/lb. and the production cost to produce 1 lb of copper is $2.50, the lost revenue due to that shutdown would be $28,980. As mentioned above, change-out of the baghouse filters required two 10-hour down days or 20 hours of lost production. As shown in Figure 2, applying the hourly cost parameters from Figure 1, over 20 hours the mine would lose 504,000 lb of copper, equaling $579,600 in lost revenue during bag filter change-out compared to only 4 hours of downtime with cartridge filters, totaling a loss of 100,800 lb of copper for $115,920 in lost revenue. There is a difference of $463,680 between changing out bags and cartridges when factoring in the costs of lost production. The total annual savings (downtime plus electrical) achieved by using cartridges in place of bags amount to $486,096—a significant difference. Adding in the initial filter cost differential of $560, the grand total comes to $486,656 saved with cartridge filters. As this exercise demonstrates, it is not the cost of one bag vs. one cartridge that matters when evaluating dust collector filter costs: It is all of the other factors that come into play during dust collector operation and change-out. A detailed white paper on this topic is available from Camfil APC at the following web page: Camfil Air Pollution Control Phone: 800-479-6801 or 870-933-8048 Email: Web: JUNE 2013 • E&MJ 165

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