® ¨ MOLLER TECHNOLOGY: ADVANCED SOLUTION FOR DIRECT FEEDING OF ELECTROLYTIC CELLS
Introduction
Figure 1: Fluorinated alumina silo, MÖLLER FLUIDFLOW® pipe air slide to the pot room wall, main bins and MÖLLER FLUIDFLOW® pipe air slide along the pot.
General Description The secondary oxide (fluorinated alumina), produced in the gas treatment centres (GTC) will be stored in silos, near by the GTC. This fluorinated alumina will be taken from the so-called fluorinated alumina silos and will be transported directly by the direct pot feeding system to each of the electrolytic cells. This pneumatic transport ensures a continuous fluorinated alumina feeding to each of the electrolytic cells. The MÖLLER® Direct Pot Feeding System works independently from the pot room cranes, fully automatically and completely dust free. Because of the design, maintenance work as well as the amount of spare parts are minimised. Furthermore, the MÖLLER® Direct Pot Feeding System has been designed to work with highest possible reliability under strongest winter summer and tropical conditions.
Functional Description One of the main requirements for the direct pot feeding is the smooth bulk material transport to the electrolytic cells. Bulk characteristics as grain size distribution are unchanged. Generation of fines (attrition), scaling as well as segregation is prevented by lowest possible conveying velocities (< 0.1 m/s) and minimised fluidising air amount. The fluorinated alumina will be taken from the fluorinated alumina silo at the gas treatment centre and will be transported to the so-called main bins, normally one main bin for each half of a pot room. The pneumatic transport to the main bins (near by the pot room walls) as well as the transport along the two pot room walls will be realised by the MÖLLER FLUIDFLOW pipe air slide system. According to client requirements, different kinds of feeding systems to the electrolytic cells are available. The so-called 'Single-
It is a long way to the aluminium, beginning with mining of the clay-like ore called “bauxite”, and finalised with the electrolysis of alumina in the electrolytic cells. However the goal to realise the final step inside the electrolytic cell of this 24 hr smelting process in an environmentally friendly way with the highest level of reliability is extremely dependent on the method chosen for the feeding of electrolyte cells. Self-regulating and continuous feeding of the ore bunkers of the electrolytic cells, absolute dust free operation, no generation of fine particles, no segregation, no scaling, minimised energy consumption as well as minimised maintenance work, these are the indispensable characteristics of an advanced solution of a MÖLLER® Direct Pot Feeding System. Feed', the 'Double-Feed' or even 'Multi-Feed' systems can be foreseen.
'Single Feed System' The main MÖLLER FLUIDFLOW pipe air slide along the pot room feeds directly each of the MÖLLER FLUIDFLOW pipe air slides on top of the superstructure of the electrolytic cell.
'Double Feed System' or 'Multi Feed System' The main MÖLLER FLUIDFLOW pipe air slide along the pot room feeds distribution bins. Each of those distribution bins are connected with two or more electrolytic cells via MÖLLER FLUIDFLOW pipe air slides on top of the superstructure of the electrolytic cells. All necessary venting is realized via venting domes which are connected to the gas duct of the GTC. The MÖLLER Direct Pot Feeding
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System is working fully automatically and is more or less 100% filled with Alumina all the time. The different customer requirements in view of free access to crust breakers, dosing devices and the possibility for removing the ore bunkers during operation, influences the final design of the MÖLLER FLUIDFLOW pipe air slide on top of the superstructure of the electrolytic cell. When the bunker of an electrolytic cell is full and the bulk material cone level has reached the filling spout discharge opening of the MÖLLER FLUIDFLOW pipe air slide, the mass flow of alumina is blocked automatically. When fluorinated alumina oxide is removed from the ore bunker of the electrolytic cell, the pneumatic transport starts again automatically and a constant and reliable mass feed rate to the pots is ensured. The fluidising of the fluorinated alumina inside the MÖLLER FLUIDFLOW pipe air slide works permanently to ensure a constant bulk density. Due to the material cone level in the ore bunker of an electrolytic cell, the self-closing filling spout allows a self-regulating and continuous re-filling of the ore bunkers during operation of the smelting plant. The self-closed filling spout and the filling process of the ore bunker are shown in figure 2/3. Furthermore, no pressure tight sealing of the electrolytic cell is necessary, because of the low (over) pressure in the MÖLLER FLUIDFLOW pipe air slide. The fluidisation air for the MÖLLER FLUIDFLOW pipe air slide along the pot room will be supplied by rotary piston blowers or fans. The fluidisation air for the MÖLLER FLUIDFLOW pipe air slide on top of the superstructure of the electrolytic cells will be supplied by
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fans in order to reduce the energy consumption during operation to the necessary minimum amount.
Conclusion The direct feed of the electrolytic cells is a fully integrated part of the electrolysis of Alumina. Highest possible quality of the aluminium as well as reliability of the smelting process cannot be achieved with any equivalent direct pot feeding system. The MÖLLER Direct Pot Feeding System satisfies highest possible requirements in view of reliability, smooth materials transport with unchanged bulk characteristics, dust emission and energy consumption. Variable design on top of the cell combined with single-, double- or multi-feed solutions meets all possible site requirements. Furthermore, this system is working fully self regulating and maintenance free. Figure 2/3: Self-closed filling spout and filling process of the ore bunker of the electrolytic cell.
Figure 4: MÖLLER FLUIDFLOW® pipe air slide on top of the superstructure of the electrolytic cell.
PRIMARY SMELTING AND PROCESSES
About FLSmidth FLSmidth® is a market-leading supplier of equipment and services to the global minerals and cement industries. FLSmidth® supplies everything from single machine units to complete minerals and cement flow sheets including associated services. With more than 13,000 employees, FLSmidth® is a global company with headquarters in Denmark and local presence in more than 50 countries including project and technology centres in Denmark, India, USA and Germany. FLSmidth® has over the past 130 years developed a business culture based on three fundamental values: competence, responsibility and cooperation. The Group’s in-house resources are primarily engineers who develop, plan, design, install and service equipment, with most of the manufacturing being outsourced to a global network of subcontractors. This has proved to be both a robust and sustainable business model. FLSmidth®, therefore, has relatively few tangible assets and fixed costs leading to a flexible cost structure, which makes it possible to plan and adjust resources. FLSmidth® is a learning organization, and our employees are our most valuable asset. As we continue to evolve, we will place even greater emphasis on performance and on attracting, developing and retaining people who can enhance our highperformance culture. FLSmidth® carries out a focused effort in the area of research and development aiming at fulfilling customers’ future needs in terms of innovative technical solutions, high reliability and availability, minimum environmental impact and the lowest possible product lifecycle costs.
FLSmidth® in the alumina business FLSmidth® first entered the alumina industry more than 100 years ago. Today FLSmidth® has an experienced team of engineers and support staff with extensive alumina experience located in offices around the world – and offers the latest equipment for most areas of an alumina plant.
Red side, white side and alumina handling Based on the Bayer process, invented by the Austrian chemist Josef Bayer, the alumina production process can be split into a ‘red side’ and a ‘white side’. Red side solutions FLSmidth® offers equipment for the complete bauxite handling, storage, crushing and grinding flowsheet, complementing the digestion or dissolution of bauxite in hot caustic liquor. This is followed by the complete SettlerWasher train flowsheet for Red Mud using the leading technology acquired from Dorr-Oliver Eimco. White side solutions FLSmidth® offers white side equipment, covering the complete flowsheet after the hydrate precipitation process, including MÖLLER® equipment technology for alumina handling and load-out. Overall, FLSmidth® equipment covers more than 50 percent of the equipment needs of a complete alumina plant, from the bauxite mine to the above refinery equipment. In addition, FLSmidth® also offers all equipment for alumina handling in the smelters. MÖLLER® Technology Through MÖLLER® technology, FLSmidth® specialises in design, engineering, procurement, erection and commissioning of pneumatic material handling systems for turnkey projects and components for the alumina industry. Our capabilities of handling primary alumina, secondary alumina, crushed bath and aluminium
fluoride comprise • Large capacity storage silo (up to 85.000 t realized) including antisegregation filling and discharge • MÖLLER airlift conveying systems (up to 6oo t/h realized) • Pressure vessel dense phase conveying either with MÖLLER Turbuflow® our standard conveying pipe • MÖLLER screw pump conveying systems • Truck/wagon loading and unloading stations • Dosage systems • MÖLLER Fluidflow® pipe air slide and rectangular air slide conveying systems • MÖLLER direct pot feeding systems either with 100 % MÖLLER Fluidflow® pipe air slide conveying technology or as a hybrid of MÖLLER Turbuflow conveying pipe and MÖLLER Fluidflow pipe air slide • PTM filling stations • Modular designed systems – plug and play For more than 75 years the MÖLLER® brand has stood for high quality standard systems with more than 5.000 references worldwide. Actual contracts under execution for Emirates Aluminium Smelter (secondary alumina silos, MÖLLER direct pot feeding system, PTM filling stations, primary alumina truck unloading stations and pressure vessel dense phase conveying systems for a mix of crushed bath/alumina oxide), for UC RUSAL/RusHydro’s Boguchansky Aluminium Smelter (MÖLLER direct pot feeding system) and C.V.G. ALCASA (MÖLLER direct pot feeding system) prove the strong position of FLSmidth® in the global aluminium smelter industry. MÖLLER Alumina Handling Systems - High performance, high efficiency. FLSmidth Hamburg GmbH Haderslebener Strasse 7 25421 Pinneberg, Germany hamburg@flsmidth.com
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