For example, pyrite is generally contained in polymetallic sulfide ore. In the presence of water and oxygen, pyrite is slowly oxidized and FeSO4 and H2SO4 are formed. The reaction formula is:
Chemical action: 2FeS2+7O2+2H2O ————→2FeSO4+2H2SO4
In the presence of aerobic and sulfuric acid, ferric bacteria oxidize FeSO4 to Fe2(SO4)3 at a very fast rate. The reaction formula is:
Bacterial action: 2FeSO4+H2S04+1/2O2————→Fe2(SO4)3+H2O
Fe2 (SO4) 3 can minerals dissolved out of the metal, for example, when the luminance copper ORE, can generate CuSO4, FeSO4, and S, the reaction is:
Cu2S+3Fe2(SO4)3—→2CuSO4+4FeSO4+S
The FeSO4 formed by the above reaction can be reoxidized by the iron oxidizing bacteria to form Fe2(SO4)3, and the reaction is repeatedly circulated in the solution, and the leaching action is continuously performed. If there is sulfur oxidizing bacteria in the solution, the S formed by the reaction will be oxidized by sulfur oxidizing bacteria to form H2SO4, which is more effective for the leaching of ore. The reaction formula is:
Bacterial action: 2S+3O2+2H2O ————→2H2SO4
Advantages of bacterial leaching: (1) Simple equipment and convenient operation, (2) Suitable for treating poor ore, waste ore, tailings and slag, etc. (3) Comprehensive leaching and comprehensive recovery of various metals, (4) Currently The bacterial leaching process of copper and uranium is relatively mature, and the copper leaching solution can recover copper by extraction-electrowinning method or iron displacement-flotation method.
The main disadvantage of bacterial leaching is that the cultivation of bacteria is troublesome and the leaching period is relatively long.
There are many examples of application of bacterial beneficiation in China, such as a copper mine in Guangdong, bacterial leaching in an old mining area in a copper mine in Anhui, and a copper mine in Hunan. This paper introduces the application of bacterial leaching to treat copper-bearing tailings in a copper mine in Hunan.
A large number of flotation tailings and re-election tailings exist in a copper mine in Hunan. The flotation tailings contain 0.11%~0.20% copper; the re-election tailings contain 2.25%~1.50% copper, and both tailings contain Rare metal.
The process of bacterial leaching of tailings is shown in Figure 7-7. Since the tailings have a fine particle size, the leaching tank is used for leaching. The acid, acidified water and alkaline gangue in the ore are first added. When the pH reaches about 2.0, the leaching solution containing the high-iron (Fe3+) is added for cyclic leaching until the concentration of copper and rare metals in the immersion liquid is low. Then add a copper, rare metal bacteria infusion, when the concentration of the leachate is lower, and then wash for 2 to 3 days to discharge.
The tailings leaching time is 20 days, and the leaching results are listed in Table 7-2. After the rare metal in the leachate is adsorbed, the tail liquid contains about 1.5~2.0 g/L of copper, and the copper is precipitated into sponge copper by the iron replacement method. The chemical reaction formula is:
Fe+CuSO4—→FeSO4+Cu↓
(1) The higher the copper content of the replacement liquid, the better, the iron content should be as low as possible, pH = 1.8%~2.0;
Table 7-2, Results of tailings bacterial leaching
Leaching pool number | Feeding amount (tons) | Sulfuric acid consumption (kg/ton) | Temperature (°C) | Leaching cycle | copper(%) | Rare metal leaching rate (%) | ||
| Raw ore | Leaching | Leach rate | ||||||
| 1 2 3 | 100 100 100 | 34 32 30 | 25~35 25~35 25~35 | 27 18 28 | 0.81 1.25 1.51 | 0.17 0.48 0.44 | 79.02 61.60 70.86 | 86.4 51.85 80.37 |
(2) When the pH value of the solution is about 1.5, the copper concentration is 2~4g/L, the iron consumption ratio is 2.0~2.5 times of copper; when the pH value is about 2, when the copper concentration is high, the iron consumption ratio is 1.5 times that of copper;
(3) Iron replacement time, which is related to temperature, quality and quantity of scrap iron, acidity of solution and replacement method. Generally, when the temperature is greater than 20 ° C, in the case of ventilation, the replacement can be completed in six hours;
(4) Discharge the tail liquid immediately after the replacement, adjust the Fe2+ concentration and acidity in the tail liquid, and return to the bacterial culture solution for use.
The main technical and economic indicators:
(1) The total recovery of copper is 70%~75%; the total recovery of rare metals is 75~80%;
(2) Sponge copper grade 60%~650%;
(3) 40%~45 kg of sulfuric acid per ton of mine; 2.5 tons of iron per ton of copper;
(4) The cost of converting pure metal copper per ton is 2,000 yuan.
The hollow paddle dryer is a horizontal structure drying equipment with heat conduction.
The drying of the equipment relies on indirect heating by heat conduction. so the drying process requires no or only a small of gass to remove moisture. It greatly reduce the heat loss taken away by the airflow, inproves the heat utilization rate, and is an energy-saving drying equipment. The paddle dryer is widely used in the drying of powder, granular, filter cake and slurry materials in petrochemical, chemical, metallurgy, food, medicine, pesticine and other industries.Indirect heating or cooling of paste, granular, powder and slurry materials can complete unit operations such as drying, cooling, heating, sterilization, and reaction. The special wedge-shaped stirring heat transfer blade in the equipment has high heat transfer efficiency and self-cleaning function of the heat transfer surface.
Principle:
The heat transfer surface of the hollow paddel dryer has several parts such as blades, stirring shafts, and a large heat transfer area per unit volme. In addition, stirring and mixing make the materials violently turn, so as to obtain a high heat transfer coefficient, so the floor space and space are very small, saving the cost of plant infrastructure. In the drying process, the gas consumption is small. the flow rate is low. and the amount of dust carried away by the gas is small, so the gas dust recovery after drying is comvenient, and the recovery equipment in small in size, which can save equipment investment. For drying processes that require solvent recovery, the solvent concentration can be greatly increased. Due to the special stracture of the paddle, the material is alternately squeezed and relaxed during the drying process, which strengthens the drying process. The filling rate of the material in the drying room is very high, which can reach 80%-90%. The residence time of the material can be adjusted by adjusting the parameters such as the feeding speed, the rotating speed of the stirring shaft, and the filling degree of the material, and can be adjusted arbitrarily from a few minutes to a few hours. In addition, the movement of the material from the feeding port to the discharging port in the dryer is basically a piston motion, and the residence time distribution is narrow, so the moisture content of the product is uniform. The paddle has a certain axial angle on the stirring shaft, so it can continuously dry the material.
Features:
The equipment has a compact structure, a small footprint, and a large effective heat transfer area: a large heat transfer surface per unit of eccective volume.
The balde shafts can be meshed with each other, which has a self-cleaning effect and can prevent materials from sticking to the wall.
Low energy consumption per unit evaporation, low operating cost, indirect heating, closed heating, heating the material partition, high energy efficiency and utilizaion.
The low speed of the blade shaft does not damage the shape and properties of the product.
The operation of the equipment is flexible, the operation is stable and reliable, it can be operated continously or intermittently, and it can be applied in many fields.
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Jiangyin Jirui Machinery Manufacturing Co,LTD , https://www.jyjiruimachine.com