Beneficiation of low-grade silica sand for float glass production at Chu Lai, Vietnam
CFG-Chu Lai Float Glass Joint Stock Company, one of Vietnam's most significant glass manufacturers with a 900 tonnes per day float glass line, needed glass-grade silica sand from raw ore with elevated iron content. CFlo's Micrograder F70D modular wet processing plant, expanded to a 2x100 tph dual-line configuration, consistently delivers product exceeding 99.3% SiO2 with Fe2O3 below 0.05%, at approximately 71% yield and 95% water recovery.
The raw sand ore from CFG-Chu Lai's captive open-pit mines carried around 0.50% Fe2O3 against a float glass requirement of below 0.05%, a ten-fold reduction, alongside suboptimal silica purity (~98.5% SiO2), variable Al2O3 of 0.4-0.8% and a broad particle size distribution against a 150-600 micron target. Iron occurred both as surface-adhering contamination and as discrete heavy mineral grains, and the ore varied between mine faces in both chemical grade and granulometry, demanding a process circuit with inherent flexibility.
CFlo's DSIR-approved Material Testing Services laboratory in Kolkata ran an extensive bench-scale test programme, followed by pilot-scale trials on approximately one tonne of ore using Screenmax precision fine screening and Spiropure spiral concentrators. The validated flowsheet became a Micrograder F70D plant, factory-assembled in Kolkata, shipped in standard 40-foot containers and erected with minimal civil works, initially at 70 tph per line and expanded to 2x100 tph.
The eight-stage circuit combines Feedmax feeding, Atropure attrition scrubbing to dislodge surface-bound iron, Screenmax precision sizing at an accurate 600-micron cut, Centrimax hydrocyclone classification, Spiropure spiral gravity concentration to reject heavy iron minerals, and Vertimax upward-flow hydraulic classification for final polishing to the -600 +150 micron specification. Water recovery runs through the Hydromax Water Recycling System and Easysettle sludge management with Polydex polymer dosing, achieving approximately 95% overall recovery with polyelectrolyte consumption five to seven times lower than conventional thickening. The entirely gravity-based circuit uses no chemical reagents, and the +600 micron oversize is sold as a construction-grade by-product.
Despite operational feed deviating materially from test samples, with lower SiO2, higher Al2O3 and coarser sizing, the plant consistently met or exceeded specification.
The project validates CFlo's Micrograder platform for high-purity silica sand beneficiation and provides a replicable model for glass sand operations throughout Southeast Asia. It stands alongside CFlo's float glass sand installations for Saint-Gobain in India and Ghani Glass in Pakistan, and represents one of the largest and most technically demanding glass sand beneficiation plants in CFlo's portfolio of 500+ installations across 18 countries.
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