MINERAL SEPARATION
Weir partnered to optimise the desliming stage at Vale ’ s Vargem Grande 2 Plant , in Minas Gerais , Brazil , using its Cavex 2.0 hydrocyclones
( VGR2 ), near the town of Nova Lima in the state of Minas Gerais , Brazil . The average iron ore
slimes losses at VGR2 corresponded to approximately 18 % by weight of the total iron ore mined , totalling 1.9 Mt lost every year .
To increase its mass recovery and enhance the VGR2 desliming separation performance , Vale and Weir conducted an industrial trial to compare the incumbent first-generation Cavex CVX hydrocyclones with the latest Cavex 2 CVD hydrocyclones . The effects of the apex and vortex were examined by combining static simulation and industrial tests .
The head-to-head trial confirmed the extra capacity of Cavex 2 hydrocyclones . The combination of the Cavex 2 CVD hydrocyclone ’ s LIG + ™ inlet and feed chamber design reduced pulp turbulence and promoted an increased volumetric capacity of approximately 30 %, which meant fewer operating CVD cyclones were required to achieve similar results ( five versus seven ), Weir says .
The new hydrocyclone also presented a finer granulometric cut for the same cyclone diameter and apex / vortex configurations when compared with CVX , in addition to the greater mass separation to the underflow and , consequently , a 9 percentage point gain in mass recovery .
To ensure a thorough comparison , Weir Minerals proposed to operate a cluster of six Cavex 500CVX hydrocyclones and a cluster of six Cavex 2 CVD 500 hydrocyclones under the same feed conditions in the VGR2 desliming stage .
Several comparative industrial tests , as well as the former hydrocyclone unit and sampling campaigns , were carried out to evaluate possible improvements . Samples were characterised using X-ray Fluorescence , as well as particle size distribution ( PSD ) through gravimetry and wet sieving ( 0.045 mm ) followed by laser diffraction , and percentage of solids analysis in feed , underflow and overflow .
Experimental industrial testing was carried out on CVX and CVD hydrocyclone clusters . During testing , three variables were manipulated : pressure ( kgf / cm ²), vortex and apex diameters ( mm ).
Tests were supported by static processing simulations . The mass flow rate , granulometry , percentage of solids and iron content constituted data input for USIM PAC , a software used for performing mass balancing , hydrocyclone model calibration and simulating operating conditions .