ALUMINA
 

Objective
An Australian alumina refinery approached SOLAFT to see if we could develop a solution to enable them to use a cost effective readily available low-quality bauxite, whilst not compromising Alumina quality.

Issue
The cheaper poor-quality bauxite contained less gibbsite and more impurities. This decreased the effectiveness of processing the ore, was detrimental to filtrate solids and therefore refined alumina quality.

Solution
SOLAFT’s highly qualified Technical Team worked tirelessly with the on-site engineer and maintenance manager.  After several years, multiple site visits and onsite pilot testing, SOLAFT custom engineered a multi-dimension high capture media. With this solution, the refinery was able to increase/maintain liquor flow whilst maintaining/improving filtrate clarity. The technical textile design addressed the complex issues resulting in changes to production with the poor raw material quality. The improved media allowed for greater uptime and reduced operational costs.

Outcome

After successful trials, the benefits to the Alumina refinery include:
• Maintained the previously low filtrate clarity.
• Greater filter throughput of 10% over the life of the filters.

Objective
An Australian alumina refinery approached SOLAFT to see if there was a way to improve Kelly Filter operation and bag handling, through reducing scale build up where the cuffs of the filter cloth is attached to the filter frame. The refinery was looking for increase equipment uptime and improve worker safety.

Issue
The alumina refinery increased green liquor alumina-to-caustic (A/C) ratio to improve production yield, this led to an increase in scale formation during clarification. The scale is formed in clarification through mechanisms including premature hydrate and DSP crystallisation seeded on un-extracted gibbsite in the bauxite mud, and through spontaneous hydrate and DSP crystallisation with a drop in liquor temperature in locations where green liquor is retained when cooled. The scale gradually builds with each filtration cycle and eventually the filter media permeability is reduced to a point where the set point liquor flow cannot be sufficiently maintained, or the filtration cycle time becomes uneconomically short (depending on the filtration control mechanism employed).

Solution
SOLAFT, developed for the top section of the Kelly Filter, a custom-engineered fabric, specifically to reduce the rate of scale formation under the lid of the filter vessel. This resulted in extending the safe operating life of the filter media, minimising filter leaf removal hazards and reducing filter vessel down time. With this unique solution, the use of pneumatic tools has been eliminated, considerably reducing the hazards posed to operators.
SOLAFT’S Technical Team then worked with the on-site engineer to trial the newly constructed Kelly Filter.

Outcome
After a successful trial, the new Kelly Filter was put into full production. The benefits to the Alumina refinery include:
• Filter life was extended by 10-20%.
• Uptime by up to 10%.
• Invaluable improvement in worker safety.