What is M2M-Technology?

M2M-Technology™, developed by Alcor and Alfa Laval, is a novel, patented combination of well known re-digestion and spiral heater technology. Implementation of M2M-Technology™ requires the installation of an M2M-Unit™ in the pipeline which connects decanter (thickener) underflow with first washer feed for a second digestion of bauxite residue. The additional digest typically increases alumina production by 4% and reduces specific residue generation by 8%.

The technology is particularly applicable to refineries using atmospheric digestion, low temperature digestion or sweetening digestion for the first, main digest. M2M-Technology™ can easily be implemented in existing refineries or incorporated into greenfield projects, substantially boosting project economics whilst reducing environmental impact.

The process

The demos below simulate the process flow of bauxite residue slurry between digestion discharge and the second washer.

Click here for process flow simulation of M2M-Technology™ with pressure digestion.

Click here for process flow simulation of M2M-Technology™ with atmospheric digestion.

By clicking the buttons in the flash simulations the liquor A/C ratio increase before and after installation of an M2M-Unit™ is displayed by the color intensity of the green liquor.

M2M-Units

The main equipment of an M2M-Unit™ comprises M2M-Heaters, i.e. spiral heat exchangers designed by Alfa Laval to handle the dense decanter underflow slurry, and M2M-Digester vessels in which remaining gibbsite, auto-precipitated or not yet extracted, is recovered from the bauxite residue. The 3D-graphic to the right depicts a single M2M-Unit™, in full size after clicking on it.

Publications

Patent Cooperation Treaty publication number WO2006/031098 A1:

Method and apparatus for the extraction of gibbsite from bauxite

Chemical Engineering, August 2007: