In the leaching process of the material, the difference in the direction of movement of the leached material and the leaching reagent can be divided into three leaching processes.
(1) downstream leaching
The direction of flow of the immersed material and the leaching reagent is the same (Fig. 7-2). The leaching solution with higher content of the target component can be obtained by downstream leaching. The leaching reagent consumption is lower, but the leaching speed is slower, and the leaching time is longer. Higher leaching rate.
(2) cross-flow leaching
The immersed material is separately leached by several new leaching reagents. The leachate obtained by each leaching is uniformly sent to the subsequent operation (Fig. 7-3). The leaching rate of the cross-flow leaching is faster. The leaching time is shorter and the leaching string is higher. However, the volume of the leachate is large. The concentration of the remaining reagent in the leachate is high, so the reagent consumption is large, and the content of the target component in the leachate is low.
(3) Countercurrent leaching
The direction of movement of the immersion material and the leaching reagent is reversed, that is, the depleted material is contacted with the new leaching solution after several leaching, and the original immersed material is contacted with the leaching solution (Fig. 7-3). Countercurrent leaching can obtain a leachate with a higher content of the target component, and the remaining reagent in the leachate can be fully utilized. Therefore, the leaching agent consumes less, but the leaching speed is lower than the cross-flow rate, and more leaching stages are required to obtain a higher leaching rate.
The percolation tank can be immersed in a downstream, cross-flow or counter-current leaching process; the heap leaching and local leaching generally adopt a downstream circulation leaching process, and the continuous agitation leaching generally adopts a downstream leaching process. If cross-flow or countercurrent leaching is to be used, solid-liquid separation operations should be added between the stages. The agitation leaching of the intermittent operation is generally a downstream leaching, but a cross-flow or counter-current leaching process can also be used. It is only necessary to perform solid-liquid separation after each leaching, and the operation is complicated. There are fewer applications in production. The leaching leaching can directly obtain the clarified leachate, and the agitated leached pulp must be separated by solid-liquid separation to obtain a clarified leachate for subsequent processing or a thin ore slurry containing a small amount of ore.
Twisted Tube Heat Exchanger is to strengthen the turbulence of the flowing gas/fluid, so that the gas and the tube wall contact thoroughly. In addition to enhancing heat transfer, the twisted tube heat exchanger also has the advantages of reducing scaling, self-supporting between tube bundles, no baffle plate elements and so on.
With that being said, novel Twisted Tube Heat Exchanger is much more efficient than conventional tubular heat exchanger, or Shell And Tube Heat Exchanger. Twisted tube heat exchangers are also used in applications where the fluids are corrosive or contain particulates, as they are better able to handle these conditions than other types of shell and tube heat exchangers or Air Heat Exchanger.
Twisted tube heat exchangers are constructed from a series of twisted tubes arranged around a central tube. The tubes are twisted in such a way that the fluid will change direction multiple times as it passes through the exchanger. This increases the turbulence of the fluid and creates a larger surface area for the heat exchange, which increases the efficiency of the exchanger.
The shell is usually made from a thick metal such as carbon steel, which increases the durability of the exchanger.
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