Optimized operations in Brazilian aluminium refinery with Metso conversion kit

Text: George Borges and Nelson Valêncio
Photos: George Borges & Shutterstock

Bauxite, a raw material used in metal production, is delivered in slurry form – a mixture of crushed ore and water – and needs to be filtered before processing. The ore moisture content must be 14 percent or lower and the continuity of operations must be maintained, since nearly 27 thousand tons of ore are moved daily.

Metso’s challenge was to improve pumping operations by ensuring the constant pressure necessary for the process. The upgrade was implemented on the wet end, with the conversion kit (as shown in the photo) installed in the filter lines to deliver slurry at a rate of 145 m3/ hour, or 100 tons of bauxite per hour. The replacement of the existing wet-end parts has optimized pumping operations, with constant pressure at the filters (which also last 6 months longer), enabling the product to perform to specification.

The situation prior to replacement

The inadequacies in previous filtering operations included an increase in the moisture content of the bauxite and level fluctuations in the filter pump feed tank. In addition, there was flow loss and the equipment was manually operated. Maintenance data were more critical, with high turnover of spare parts and frequent non-routine maintenance.

Combined with the increased power consumption, the process and maintenance history indicated that a change was needed.

From recommendations to results

Metso’s work focused on identifying opportunities for improvement. The pumps’ operating conditions could not be changed, including the required slurry flow rate of 145 m3/h and the head of 65 m. Also, the pump feed tank level of 80 percent and the size of the equipment (6/4 model) had to be maintained.

The recommended solution was to use Metso’s conversion kit, which would enable the client to meet all its requirements without needing to replace the equipment completely: it was necessary only to replace one wet end. The improvement has also reduced power consumption from 120HP to 106HP, with consequent savings in energy costs. The existing equipment had a rotor of diameter 365 mm, while Metso’s solution uses rotors of diameter 400 mm. This change has increased the internal working pressure from 5.8 bar to 6.1 bar. The discharge speed has increased too, from 5.65 m/s to 6.65 m/s. And pump efficiency has increased from 59.7 percent with the earlier equipment to 65 percent with Metso’s solution.

“Power consumption and maintenance and spare parts costs were also significantly reduced,” commented George Borgens, a senior technical sales representative at Metso. Regarding power consumption, Metso’s solution secured a 13.2 percent decrease. Maintenance costs have fallen too, with one annual stoppage instead of three previously. Spare parts costs fell by 67 percent.The figures presented are the result of a new setup in the ore slurry pumping process to supply the set of filters. The slurry level in the pump feed tank, previously subject to major fluctuations, is now stable. The bauxite moisture content is now maintained at the specified levels, ensuring the required production levels and eliminating unscheduled downtime. The equipment, previously operated manually, was automated, which helps achieve a constant flow rate. The internal pressure level of 6.1 bar is also maintained.

“With scheduled maintenance, there has been less replacement of pump wet end parts, maintenance costs overall have decreased, and the operation has reached the required consistent output levels,” Borges concludes.

Published in Results flow Control 1/2015 as 'Optimized operations in Brazilian refinery with Metso conversion kit' and previously published in Results minerals & aggregates 1/2015 as 'Metso conversion kit optimizes operations in Brazilian refinery'.