HybridICE^®HIF filter: principle and operation

Abstract

The HybridICE technology operates on the principle that growing ice crystals reject impurities during freezing and is a "zero liquid discharge" process, whereby the water is completely isolated from the dissolved waste species. The technology recovers water from waste waters for re uses for all purposes. The process allows the utilisation of both surplus process heat and cooling energy. The waste heat from the refrigeration cycle is, moreover, utilised for vacuum evaporation to recover a fraction of the water as condensate. The predominant water fraction is recovered by isolating the ice from a concentrated process brine stream. The process takes place in a static concentrator, known as the HybridICE Filter module (HIF) that separates the suspended ice crystals from the concentrated brine slurry to recover ice crystals as pure water. The recovered ice from the freeze crystallisation does not require rinsing with fresh water. Basic factors influence the quality and yield of recovered water. These include but are not limited to: TDS of the waste water stream; first ice point; ice content of the process waste water; mass-flow. The slurry ice feed stream was generated using the HybridICE freeze crystallisation plant. The objective was to establish the comparative behaviour of a low and high sodium chloride feed using 2% and 8% (m/m) NaCl feed brine streams.

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“…The project has benefited from various funding, thereby enabling researchers to develop a filter for separating ice from ice slurry formed from using freezing technology to clean mine waste water. The principle and the operation of the filter was published in Water Resources Management VII, 149 while the design of the filter was presented and published at the International Mine Water Association Conference in Colorado, United States of America (USA) in 2013. 150 Further work on the filter and technology was published in Water SA 151 and Environmental Chemistry Letters.…”