Separation of chemical beneficiation - flotation
Segregation-flotation is a combination of pyrochemical treatment and flotation. E.g. refractory segregation of copper oxide ores - flotation ore is crushed to a particle size after mixing to a small amount of salt (0.1-1.0%) and coal dust (0.5-2.0%), the oxygen barrier heated to about 900 degrees, ore to metallic copper will be deposited on the surface state of the carbon particles, calcine the flotation after cooling the grinding an oxygen barrier, i.e., to obtain copper concentrate.
The biggest advantage of the segregation-flotation method is that it can solve the ore that cannot be treated by conventional beneficiation methods, and it can comprehensively recover useful metals in the ore. For example, in copper ore, when the ore contains a large amount of cyanite, azurite and bound copper, or contains a large amount of slime, the flotation method of such ore often has a low index, and the segregation rule is More effective. The segregation method can also process mixed ore of copper oxide ore and copper sulfide ore, and can comprehensively recover useful metals such as gold, silver and iron . In addition, the compounds of several metals gold, silver, nickel, aluminum, cobalt, antimony, palladium, bismuth, tin and the like are readily reduced and easily form volatile chlorides, also adapted to the processing method segregation.
The disadvantage of the segregation method is that the cost is high, the capital construction investment is large, and the production cost is also high. It is estimated that the infrastructure investment of the segregation method is about twice that of the same capacity flotation plant, and the production cost is also 2-3 times higher. Therefore, when the oxidized copper ore is difficult to be treated by the separation method, it is considered that the copper grade in the ore should be greater than 2% to obtain a better economic effect. So the separation method is only used to solve ore that cannot be treated by other methods. Therefore, before using this method, a comprehensive study should be conducted on the treated ore. If it can be treated by other methods, it is not appropriate to use the segregation method.
Three stages of copper segregation
The segregation process is more complicated. Although many experimental work has been done on the segregation of copper, there are still some different opinions on some issues. Most believe that the segregation process of copper oxide ore is roughly divided into three stages.
(1) In the decomposition stage of salt, during the separation process, first, the crystal water in the salt and the ore forms hydrogen chloride at a temperature of 700 °C. Its reaction formula is as follows:
4NaCl+Al2O3·2SiO2+2H2O=Na4Al2·2SiO3+4HC1↑
(2) During the volatilization stage of cuprous chloride, hydrogen chloride reacts with copper oxide minerals to produce volatile cuprous chloride. There are many types of copper oxide minerals. For the sake of simplicity, simple Cu2O is used as a representative. The formula is:
4HC1+3Cu2O=2Cu3C13↑+3H2O
(3) In the reduction and isolation stage, the copper chloride vapor is reduced by hydrogen (hydrogen adsorbed by the carbon particles) to form isolated copper and covers the carbon particles. Its reaction formula is:
2Cu3C13↑+3H2=6Cu+6HC1↑
The copper (Cu) is efficiently recovered by flotation, and the hydrogen chloride (regenerated HC1) produced by the reduction of cuprous chloride can continue to react with the copper oxide mineral to form cuprous chloride, which causes the above reaction cycle to occur cyclically.
There are many factors affecting the segregation process, among which the following are the main factors.
(1) Ore properties The ore particle size and the material composition of the ore should affect the segregation process, especially when dealing with calcareous gangue, especially calcite , limestone, etc., the formation of calcium oxide will hinder the segregation of copper.
(2) Temperature influence The temperature directly affects the chlorination reaction rate, and accurate temperature control is an important condition for the separation process. The upper limit of the separation temperature depends on both the ore properties and the heat exchange conditions, as well as the economic factors. If the separation temperature is high, not only fuel is wasted, but also the sintering of the material occurs, and the kiln skin phenomenon occurs. If the temperature is below the separation temperature, the segregation effect is deteriorated.
(3) Residence time The residence time of the material in the separation kiln depends on the volume of the kiln, the relative density of the material, and the passing speed of the material. In general, the residence time of the material in the kiln should be sufficient to achieve a high recovery rate.
(4) Reducing conditions The reducing conditions have a great influence on the segregation process, and moderate reducing conditions are beneficial to the progress of the chlorination reaction.
(5) The amount of chlorinating agent The salt itself has no effect on the chlorination reaction, and the initiating reaction of the segregation is hydrogen chloride produced by the hydrolysis of the salt, and the chlorination reaction rate is proportional to the hydrogen chloride pressure. If the amount of salt added is too small, the supply of hydrogen chloride cannot meet the needs of the initial chlorination reaction rate. Excessive use of salt is also harmful, it will dissolve cuprous chloride, reducing the recovery of segregation.
(6) Water vapor steam plays an important role in the decomposition of chlorinating agent and the formation of hydrogen chloride. Experiments have shown that if the ore loses crystal water, the segregation process cannot proceed.
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