Improving GTC production capacity after reaching operating emission limits

THE OBJECTIVE

SOLAFT was approached by an Australian Aluminium smelter to find a way to cost effectively increase production in the GTC after upgrading their anodes, anode bake, and busbars whilst enabling compliance to emission standards.

THE ISSUE

Aluminium smelters often seek to increase production outputs through upgrading the busbars/anodes/potroom to enable increased line current.

In this case, the GTC design limited the ability to achieve these production increases.  With amperage creep, the GTC inlet temperature increases and the efficiency of HF gas adsorption on alumina decreases. The reduced scrubbing efficiency resulted in higher HF gas and particulate fluoride emissions. Therefore, without upgrading the GTC, emission limits would be breached with any increase in production.

WHAT WE DID AND THE SOLUTION

SOLAFT supplied StarBags™, which were installed into the existing cell plate, and cleaned with the existing cleaning system. The increased surface of the StarBags™ lowered the air-to-cloth ratio (or filter velocity in m/s) by 45%. This distributed the alumina dust cake over a much larger area, reducing filter differential pressure and pulse cleaning frequency, which dramatically lowered emissions. Following the successful deployment of StarBags™, the customer concluded that a capital upgrade of the GTC was no longer required.

OUTCOME

After a successful trial, the benefits to the Aluminium smelter were:

  • 45% reduction in Particulate Emissions
  • 45% reduction in Gaseous HF Emissions from the GTC
  • 35% reduction in Differential Pressure
  • 50%-70% drop in Pulse Frequency
  • 20% reduction in Fan Electricity ($260K p.a. savings)
  • Debottlenecked the GTC (enabled capacity creep all year round)
  • Debottlenecked the process, allowing increased Metal Production without capital equipment upgrade