Up-to-date handling technologies for alumina are a major concern in many ports, not only to achieve low operational costs for the vessel unloading, but also for the protection of the environment.
Alumina is a white powder with a density generally between 0.85 to 1.05, very free flowing and quite abrasive: its particle characteristics make its handling rather complex in order to achieve optimum performances, in terms of quantity that can be conveyed, and the amount of dust and spillage must also be taken into consideration during unloading operations.
Most frequently, alumina is unloaded from sea vessels via a special conveying system to the storage facilities or into a hopper from which it is loaded into trucks (special or normal bulk ones). However, it can also be directly packed on the quays, into one- or two-tonne big bags for instance. These bags are then loaded onto trucks and/or railcars and transported to the smelting plants. Eventually, they are stored in stockpiles nearby the quays before being transported onwards.
The traditional unloading method is done by grabs and simple hoppers on the quay.
The hoppers can be integrated with weighing scales and filling equipment for large-size bags. Usually one grab crane is able to feed up two of these hoppers, each one with one or two weighing-filling lines.
Pneumatic unloading is a very convenient way for conveying alumina. Its free-flowing characteristics make suctioning easy, and because the product is handled in a totally enclosed system, pollution and spillage are almost totally eliminated.
After the alumina is ‘vacuumed’ from the ship hold, it is separated from the conveying air thanks to a special large-size air filter before passing through a special designed valve (see picture on p105), down to a chain conveyor which transports the alumina to the top of the quay hopper, for instance. The end of this conveyor has one or two loading telescopic chute(s) with a cover to provide a seal around the alumina’s entrance into the hopper (see picture above).
When entering into the receiving hopper, the alumina flows down gently in such a way that it will be easily conveyed downwards.
This means handling must be controlled very carefully from the negative to normal pressure area, in order to be continuously conveyed at a determined rate.
VIGAN technology achieves this control thanks to its engineering and equipment design to precisely monitor the amount of alumina in the receiving tank and its flow down to the conveyor through a specially designed valve.
This technology allows for the elimination of all the maintenance costs of an airlock for instance, which often suffers significant wear due to the abrasive nature of alumina.
Special sealing features ensure that no dust will escape out of the mechanical conveyor and the dust at transfer points is continuously collected thanks to a suction fan with self-cleaning filter.
Moreover, as they are self-propelled on rails or tyres, the unloaders are able to move easily along the ship and no
additional equipment (such as hoppers) must be displaced to ensure quick and reliable unloading operations and eventual packing (see picture, left). VIGAN is also able to design and manufacture the entire bagging system.
In all equipment, a frequency converter — also called a speed variator, or an inverter — allows for the continuous and precise control of the suction pattern, as well as significant energy consumption savings.
With equipment for alumina unloading already commissioned in several countries such as Finland, France, Poland, China and Iran, VIGAN has gained a large amount of experience regarding this raw material handling in bulk. This cost- effective technology for alumina unloading is a most promising alternative for many ports and the alumina processing industry.
E-Cranes unloading 5mt of bauxite each year for Sherwin Alumina
E-Crane Worldwide is a modern, state-of-the-art engineering and heavy equipment construction company, based in Adegem, Belgium and with subsidiary companies for sales management, technical support
and service in The Netherlands (E-Crane International Europe) and Ohio, USA (E-Crane International USA). E-Crane Worldwide develops turnkey material handling solutions with engineering services, equipment manufacturing, erection, operator/maintenance training and custom tailored ongoing service programmes for its clients.
The standard E-Crane product line consists of five series of balanced hydraulic cranes (E-Cranes): 700 Series, 1000 Series, 1500 Series, 2000 Series, and 3000 Series. The E-Crane is a truly revolutionary material handling machine as its main design feature is a parallelogram style boom configuration which allows the machine to be in near- perfect balance throughout the duty cycle. Compared to conventional cranes that require as much as 80% of their available energy just to move the boom, stick, and grab, the E-Crane makes gravity work for you instead of against
you, reducing horsepower requirements and power consumption by up to 50% and significantly reducing maintenance andoperating costs.
E-CRANE IN BAUXITE AND ALUMINA: THE SHERWIN ALUMINA COMPANY
Two 2000 Series E-Cranes were put into service at The Sherwin Alumina Company LLC in Gregory,Texas in 2010. Both E-Cranes are high gantry rail mounted and have an outreach of up to 147’ and a duty cycle capacity of 27 US tonnes. Together, these cranes unload up to 5mt (million tonnes) of bauxite from Handymax and Panamax size ships annually.
Sherwin Alumina has been producing alumina (aluminium oxide) near Gregory Texas for more than 50 years. Before 2010, Sherwin Alumina was using continuous ship unloaders (CSUs) purchased in the 1980s. These were complicated machines that required lots of maintenance,
generated high amounts of dust, and could not unload ships on time. While these CSUs have an impressive mechanical design, the constant and high cost of maintenance, along with poor reliability, was causing major unloading delays resulting in huge demurrage costs. Sherwin needed to find a replacement for these unloaders that would reliably unload the incoming bauxite ships.
Research showed E-Crane to be the perfect and reliable solution, and E-Crane was contacted in late 2008. After a detailed analysis of all possible ship unloading solutions, it was decided that two 2000 Series E-Cranes would be the solution. These E-Cranes were purchased fully assembled and ready for pick-up at an offsite location for less than half the cost of one CSU, new in the 1980s. The new E-Cranes were built in the E-Crane
Worldwide facility in Adegem, Belgium and were transported to Sherwin Alumina exactly one year after the initial down payment. A special heavy lifting shipping method was used to minimize downtime at the customer’s dock.
E-Crane also provided one week of classroom training for the 32 operators. After a written test, the operators experienced ‘simulator’ training. After passing a test in
the cab simulator, the operators moved on to ‘in-the-seat’ training, and E-Crane technicians were there monitoring the operators 24/7 for a further two weeks until management was satisfied that the operators could function on their own.
The E-Cranes immediately proved themselves to be reliable and cost-effective ship unloaders by minimizing demurrage costs due to lower maintenance, minimal downtime, and high reliability. Bally Kissoon, former port manager, often says, “I wish all our equipment was working like the E-Cranes!” Since the installation, both E-Cranes have been in 24/7 continuous operation at the docks with average cycle times of 60 seconds.