The objective of filtration tests is to determine the filtration characteristics of thickened slurry and to provide data for the sizing of full-scale filters (e.g. belt, drum, disc filters). Basically, most continuous filters use vacuum to provide the driving force for filtration. Laboratory tests can be employed to size and predict performance of full scale filters using a filter leaf assembly. Usually, the circular leaf has an area of 0.1 ft2. The filter cloth is supported by a number of grooves which simulate the drainage passages of a full scale filter. The cloth and slurry containing ring are clamped into position. The concentrate filter removes water from concentrate slurry by two systems, vacuum or pressing the slurry in a series of filter compartments. The first one has been employed in the gold mining industry for a long time. The second one is highly efficient.
The main requirement is that the concentrate sample be as representative as possible, including particle size distribution, mineralogy, pH and reagent content (if supplied in slurry form). The basic equipment to perform filtration tests comprises vacuum pump and gauge, test leaf filter with slurry containing ring, variety of filter clothes, filtrate vacuum flask of 1L and rubber vacuum hose, graduated cylinder, slurry pail with variable speed mixer, 500 mL beakers, sample pans, scale, spatula, thermometer, pH meter, timer, retort stand with clamp and drying oven.
There are two basic filtration test methods, Pour-on and Pick-up. They must be accomplished as part of the evaluation of the filtration properties of different materials (concentrates, tailings, sub-products, etc). Filtration testing programs need 10 to 60 kg dry weight equivalent of solids in slurry suspension of each sample tested based on the test work program. Additional processes water needed for simulation testing would be required in special cases. Additional information pertaining to the process stream must be provided to the lab, including specific gravity of the solids, pH, process temperature, cake percent solids, turbidity and mineralogy. It is important to mention that the presence of clays or excessive amounts of fine particles affect filtration efficiency.