General Method A diffuse out of the conventional method of wet leaching process by leaching zinc refining economic indicators and subsequent leaching steps are normally performed can play a decisive role. Therefore, people attach great importance to the leaching process. The zinc smelting plants at home and abroad have created a variety of different processes according to their different conditions. According to the number of leaching segments:
a leaching method - only one neutral leaching section;
Two-stage leaching method—a neutral leaching section and an acidic leaching section, or both of which are neutral leaching sections;
Three-stage leaching method - one neutral leaching section and two acidic leaching sections, or two neutral leaching sections and one acidic leaching section;
Neutral leaching means that the acidity of the leaching solution is close to neutral at the end of the leaching process. The general pH value is 5.2~5.4. 0 Acid leaching means that the leaching solution is low in acidity at the end of the leaching process, usually containing about 1~5g/L of sulfuric acid. Due to the large number of leaching defects, the leaching rate of zinc is very low, and it is rarely used without special reasons. The three-stage leaching is likely to cause too much equipment, and the solution volume is too large, so generally two-stage leaching is taken. According to the operation process: continuous leaching and intermittent leaching. Continuous leaching means that the material and solution are continuously passed through the leaching equipment (usually several leaching tanks in series) in a certain ratio to complete the leaching operation. Intermittent leaching means that the calcined ore is periodically leached in batches in a leaching tank. The advantages of continuous leaching are: (1) high equipment utilization; (2) labor saving and high labor productivity; (3) easy process automation; (4) stable slurry composition; (5) lower leaching acid, thereby reducing The harmful impurities enter the leachate; (6) hot roasting can be used to save the calcine cooling equipment, and the physical heat of the hot calcined sand is used to save energy. The advantages of intermittent leaching are: (1) strict control of technical conditions, accurate control of the leaching end point, good neutral supernatant; (2) roasting of a wide variety, complex composition, poor quality (such as high silicon) ), can achieve better leaching effect.
The following figure shows the process flow of two successive sections of Zhuzhou Smelter and continuous wet leaching.
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The process is two-stage countercurrent leaching (only a small amount of acid leaching is added to the small amount of large-sized raw materials after classification), that is, one section of immersion and one section of acid leaching. The supernatant is immersed in the supernatant for purification, the bottom of the immersion is acid leached, and the supernatant after acid leaching is returned to the immersion. The utility model is characterized in that: a chute is arranged under the roasting ore outlet of the roaster, and the hot material is directly discharged into the chute, and a sulfuric acid solution (factory called oxidizing solution) containing 30~50g/L of acid is arranged in the chute, and the continuous row is arranged. The hot ore in the inflow trough is continuously conveyed by hydraulic force to the mechanical agitation tank and sent to the leaching process. The main advantages are: the cooling equipment of the hot baking sand is omitted; at the same time, the leaching solution can be heated by the residual heat of the hot baking sand to reduce the load of the leaching tank.
The following picture shows the two-stage countercurrent continuous leaching of Hikoshima, Japan. The difference between it and the Zhuzhou smelter process is that no blasting is used. The calcined ore is cooled and sieved, and the large particles are directly returned to the roast without acid leaching. The advantage of the process is that the leaching material can better ensure the granule size after two grading, and the zinc in the large granules is mainly in the form of unoxidized zinc sulfide, and the ZnS which is not easily dissolved during leaching. Returning to roasting is beneficial to increase the leaching rate.
The following picture shows a neutral continuous leaching process for the American smelting company's electric zinc plant. The utility model is characterized in that the neutral leaching concentrated bottom stream is filtered by countercurrent washing, and the filter residue is dried and sent to the lead plant. The advantage of this process is that the process is simple, the equipment is small, and the operation is simple. It is also an optional process in the case where the raw materials are suitable, such as less zinc ferrite and high zinc solubility.
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