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In all rare metals, the importance and scarcity of chrome ore and scarce are most obvious, which is at the top of "strategic metals". The chrome ore is mainly used in the production of stainless steel and various kinds of alloy steel in the form of ferroalloy (such as ferrochrome), which has the advantages of strong hardness, wear-resisting, heat-resisting and corrosion resistance.
At present, the common chrome extraction processes mainly include gravity separation, magnetic separation, electric separation, flotation, gravity-magnetic separation process. Below, let's take you to learn about each chromite ore processing process.
Use the table of contents below to navigate through the guide:
From the point of production practice, the gravity separation is still the main chrome extraction method in the world method now, which uses the loose stratification in the water medium. At present, the gravity separator used in the chromite ore processing includes the shaker table, jig, spiral chute and centrifugal separator.
It is worth noting that stage grinding and gravity separator, or the combination of various gravity separators can be used according to the chrome ore properties, thus further improving the grade and recovery of chrome concentrate.
Because the chromite has a weak magnetism, we can use the strong magnetic separator for chrome extraction. There are mainly the following two cases: one is in the weak magnetic field, remove the ore in the strong magnetic separation of minerals (main magnetite), improve the ratio of ferrochrome. Another is to separate the gangue minerals and recover chrome ore (weakly magnetic mineral) under the strong magnetic field. If necessary, the weak magnetic - strong magnetic separation process can also be used to effectively separate the ore and achieve the chrome extraction.
The electric concentration process is mainly used to separate chromium ore from silicate gangue by using the difference of electrical properties of minerals, such as conductivity, dielectric constant, etc. For the chrome ore, a few chrome can be used directly by the electrical concentration, most of them only use the electrical concentration process in the concentration process. The concentration process has a special effect on removing silicate minerals (such as quartz, etc.) from chrome. Therefore, after the separation of chrome, another stage of the electric concentration process can be added for cleaning, which not only further improves the grade of chrome concentrate, but also greatly reduces the content of silicon dioxide.
At present, we can use the flotation process to recover the chromite with fine grain size (-100um) after the gravity separation. The results show that Mg2+ and Ca2+ can inhibit the chromium ore, and the inhibition of Mg2+ is influenced by the type of anions in the slurry. Therefore, after knowing the cationic behavior in the pulp, we can choose the appropriate pulp PH value, reagents concentration, add the order of inhibitors and activators, achieve the separation of chromite and pyrite.
Sometimes, the single gravity separation method cannot recover the chrome concentrate effectively. At this time, the concentrate obtained by the gravity separation can be separated by weak magnetic separation or strong magnetic separation, further improving the grade of chrome concentrate and chromic oxide-ferrous oxide ratio.
For example, the 100-10mm grade of raw ore adopts two-stage dense media separation. The medium ore of the dense media separator is crushed to 10-0mm and then merged with the 10-0mm grade of raw ore for separation. The grades of 10-3mm and 3-0mm are sent to the jigging process. After the middling of the jigging process is ground to 0.5-0mm, the spiral concentrator is used for separation, and the shaker table is used for the separation of mineral mud (0.5-0mm). Then, the high-field magnetic separator is used to recover 0.25mm slime separated from the tailings of the shaker table and spiral separator, ensuring the content of chromium oxide in the concentrate and reduce the loss of valuable components in the tailings.
Here are the common five chrome extraction processes. For the rich ore with high chromium oxide content, single gravity separation or magnetic separation process can be adopted. For the chrome with low chromium oxide content, the combined process of gravity separation and magnetic separation usually gets a better index than the single process. Of course, the specific chrome extraction process should be determined comprehensively according to the nature of the chrome ore, the actual situation of the chromite ore processing plant, the investment budget, so as to ensure the ideal beneficiation benefits and economic benefits.