I. Overview
Flotation is the most widely used beneficiation method, and the problems and influencing factors need to be studied the most. Many of the influencing factors are objective factors that are not subjectively controlled by researchers, such as ore characteristics, water composition and ambient temperature; others are operational factors that researchers can adjust to control, such as grinding fineness, pulp Concentration, pulp pH value, pharmaceutical system, pulping time and strength, flotation machine stirring intensity and aeration amount, and flotation time, etc., the selection effect is sensitive to changes in these factors. Therefore, many ore bodies must continue to carry out flotation test research work not only before the development, but also after the production, until the ore body is completely finished. Of course, most of these research work belongs to the application and process changes of the new drug, and rarely Replace the equipment. The development of flotation science is rapid, and sufficient knowledge and experience have been accumulated for reference by flotation testers in the preparation of the test plan, but it is rare to directly select the process and conditions directly from the literature. System testing is indispensable, and the test plan must be constantly revised during the test.
Second, test equipment and technology
Laboratory flotation tests are usually composed of a series of batch-unit test tests, so they are often referred to as "batch-floating tests" to distinguish them from continuity tests conducted on intermediate tests and industrial test equipment.
1. Preparation of samples
Considering the representativeness of the sample and the efficiency of the laboratory small mill, the particle size of the flotation test is generally less than 1 to 3 mm. Original samples may be selected jaw crusher to about 6 millimeters or less according to the desired crushing score segment or segments, then the shaker closed circuit mill feed size of the roll mill to break. The crushing process should try to avoid the loss of dust flying, especially when the grade of dust is high.
If the ore containing sulfide minerals, especially those containing large pyrrhotite, oxidation may have a significant impact on the flotation test results, samples should be phased so as crushing, so that a large number of samples in the coarse-grained Store under. During the preparation of the sample, the sample should also be protected from contamination, and the incorporation of a small amount of oil will hinder the normal operation of the flotation. Sealed samples should be placed in a dry, cool, ventilated place that is not easily contaminated, but even then, ore that is easily oxidized should not be placed for long periods of time.
2. Grinding
The laboratory flotation test generally has a sample volume of 500, 1000 or 2000 g. Correspondingly, the inner wall of the grinder has a size of Ф200 mm. It is suitable to prepare a smaller grinding machine for re-grinding the intermediate product. use. The shape of the body is better in the shape of a cylinder, which can be either a ball or a rod, and the length is the same as or slightly longer. Domestically, a large number of cone mills of 240 × 90 and 150 × 50 mm are used in large quantities. The advantage is not in the shape of the body, but because the entire structure is designed to be easier to operate and saves energy. The amount of ball loading is preferably about 40% of the volume of the grinding machine. Depending on the size of the ore and the size of the product and the size of the barrel, 2 to 3 different sizes of balls are used, the smallest being 12.5 to 15 mm and the largest being 25 to 32 mm. When rough grinding, the number of large, medium and small balls can be equal. When fine grinding, the weight of the large, medium and small balls can be equal, and generally it can be between them. Grinding concentration is often 50~67% solids in many literatures, which is equivalent to a liquid-solid weight ratio equal to 1:1 to 1:2, but the author tends to use a concentration similar to that of the current production, for example, in general The hard ore is 75% (solid (liquid-solid ratio 1:3). In this case, the product has a uniform particle size and less coarse particles; on the other hand, if the ore contains more mud and the product has a fine particle size or low density, it must be Use a lower concentration. When the sample density is very large or very small, the volume of the grinding water can be calculated by changing the volume concentration (the solid volume to the total volume of the slurry) to 40~50%. In short, the consistency of the slurry should be moderate.
The laboratory uses batch open grinding, which has inconsistent particle size characteristics compared with industrial closed-circuit grinding. Generally, the fine fraction is high. Therefore, some people prefer to use rod grinding, and experimental data prove that the particle size distribution of laboratory open rod grinding products is closer to the closed-circuit ball milling than the laboratory open ball milling. However, this does not take into account that in the grinding circuit with a classifier closed circuit, heavy mineral particles are usually finer than other mineral particles. Laboratory rod mill rods are typically 12.5 to 25 mm in size.
Sometimes the flotation machine can be made smaller than the mill. In this case, the primary grinding product can be used for several flotation tests, and the ground slurry can be reduced to a representative number by wet sampler (currently, Tianjin Mining Instrument Factory can produce such wet sampler). ). Since the flotation test is performed sequentially, the placement time of each sample will be different, and the researcher must pay attention to the effect of the shelving time on the flotation. There are similar problems in the study of pulp samples taken from the factory.
3. Scrub
Scrubbing sometimes before flotation can significantly improve the floatability of useful minerals and improve flotation selectivity. Scrubbing can be carried out after grinding, or it can be scrubbed without grinding. Scrubbing can be done using a special laboratory scrubber, or by using a flotation machine at high concentrations (eg 70% solids), or using a laboratory grinder to scrub at low speeds (eg 10 rpm) It can contain some materials that are light in weight and therefore only scratched without pulverizing.
Scrub with quartz sand, iron ore, phosphate rock, potash and other vulnerable sludge influence of ore flotation has special importance for the manufacture of glass. Acids, bases, and surfactants improve scrubbing performance, but their impact on subsequent flotation operations must be considered.
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