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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28 E&MJ; • JANUARY 2016 www.e-mj.com M O D U L A R P L A N T S "Modular structures are designed to accept a range of machine sizes," he explained. "For example, screen modules are de- signed to accept 6-, 7- and 8-in. screen sizes and are interchangeable. Cone mod- ules can accept 300-, 400-, 500- and 600-hp cone sizes, and are interchange- able with an adapter plate. "And, of course, modular plants can be taken down and relocated, while you can both build complete modular plants and add other 'snap-on' components," he added. ...and Constraints E&MJ; next asked whether the respondents see limits—in terms of geography, logis- tics, transport and so on—that might actu- ally restrict the use of modular construc- tion and favor "traditional" on-site plant assembly. Cobbett summed up the situa- tion thus: "The limits are determined by what can be safely, legally and economi- cally built and transported to the job site. It is therefore dependent on available infra- structure to accommodate moving the modules, whether by ship, barge, rail or truck. Other factors include handling equipment and job-site access in remote locations, as well as severe weather condi- tions," he said. Kossl noted that functionality remains constant as modular structures are rarely modified, but are versatile in design to allow for mechanical upgrades, as are improved chute liners or special customer requests. "More importantly, the modular design allows for easy upgrades to varying safety standards ranging across the globe. "Logistics is no more of an issue for a modular plant than any other heavy piece of industrial equipment," he said. "Whether an entire plant or specific modu- lar structures, there will be a combination of permitted and legal loads within the United States, and if shipping off shore there will be both containerized and break-bulk loads." Grigg's view was that really there are no limits in terms of geography, logistics and transport. "In operation, the biggest limit is the tonnage modular plants are designed to handle. Gekko often limits throughputs to 50–100 mt/h as this is often ideal for gold projects, so this might be a limitation in bulk-commodity projects such as iron ore or coal. "Multiple 50-mt/h parallel circuits have been used in the past, allowing easy expand- ability," he went on, before giving the exam- ple of Gekko's recent project in the Canadian Arctic for TMAC Resources, which is designed to have one 50-mt/h modular Python plant that will be expanded to 100 mt/h one year after the initial installation. Grigg pointed out that other limitations include POX, BIOX, ultra-fine grind and specialized metallurgical processes, which are not suitable for Gekko's current modu- lar plant design. "However, at Gekko, we believe that these could be incorporated into a modular design in the future by other companies," he said. Cost Considerations Next, E&MJ; asked how capital costs com- pare between specifying modular or on-site construction for plant items and assem- blies. According to Cobbett, Fluor would anticipate that the total installed cost of a modular project would be less than a stick- built execution, up to 20% in some cases, when using Fluor's 3 rd Gen Modular Execution approach. "Modular construc- tion can offer improved productivity, short- er schedules, better quality control at a lower cost, and greater opportunities for completing the project on time. Typical mining-industry modules include process facilities, crusher and conveyor modules and pipe racks," he stated. "Given the completion of full factory commissioning, the costs of on-site con- struction and installation are often signifi- cantly reduced for modular plants," Grigg agreed. "Also, considering the standard design of the modules developed by Gekko, capex is also reduced considerably, while we have modularized the gold room, MCCs, laboratories and so on, making them less capital-intensive than traditional plants." Kossl sounded a slightly more cautious note, however. "The initial thought is that structurally modular plants tend to have a higher price tag, but what is commonly over- looked is the benefits of a modular struc- Gekko's Python modular mineral processing plant, designed for installation either on surface or underground.