The nature of chromium is hard, wear-resistant, corrosion resistant and high temperature resistant. Therefore, chromium metal is used as an important raw material of stainless steel, with a demand comparable to that of steel. As an important source of chromium metal, chromite has become a hot investment in mining industry in recent years. What are the beneficiation processes and equipment for chromite?
The beneficiation process flow of chromite: the fine chromite ore that has been broken and ground to a reasonable fineness is cleaned and classified by the spiral classifier with the help of the different specific gravity of solid particles and the different settling speed in the liquid. Then use jigs and shakers to wash the materials, transport them to spiral chutes for separation of fine mineral powder, and send them to magnetic separators for magnetic separation after screening. The separated chromium concentrates are dehydrated by thickeners, and then continue to be sent to dryers for drying to obtain usable dry concentrates.
The embedded particle size of chromium ore in the ore is generally coarse, and there is a large specific gravity difference between ferrochrome and waste rock, which meets the two major indicators of gravity concentration. Therefore, gravity concentration is the main method of chromium ore dressing. The main chrome ore dressing equipment used are jigs, shakers, etc. The jig has large processing capacity, good beneficiation effect, small floor area, energy saving and high efficiency; In contrast, the shaking table covers a large area and has a small processing capacity for a single equipment. It is often used as an auxiliary equipment for the work of jigs and cannot complete the chrome ore dressing operation alone.
Chromite gravity concentration case
A chromium ore in the Philippines contains 23.47% chromium oxide and a small amount of pyrite and pentlandite. Gangue minerals are mainly serpentine and a small amount of carbonate. In the beneficiation test, magnetic separation, shaking table and spiral chute were respectively used for rough separation and tailing test. The test results show that the shaking table and spiral chute tailing effect is good, but the mineral rate of spiral chute tailing is low, so the shaking table was used for separation, After expanding the scale of the test, the test is carried out on the variable of grinding. The final adopted chromium ore dressing process is one-stage shaking table roughing, direct re concentration of the middle ore in the shaking table, coarse concentration of the middle ore in the concentrate, and combination of the re concentration concentrates. With this process, the concentrate yield is 57.19%, the chromium oxide grade is 37.46%, and the recovery rate is 88.78%.
In addition to the selection of shaking table and jig gravity separation, the chrome ore is also subject to weak magnetic separation or strong magnetic separation for re separation to further improve the grade of chrome concentrate. The magnetic separation process of chromium ore is relatively simple, and it can enter the separation process after simple crushing and grinding. The selection of crusher can be determined according to the customer's own situation. The grinding equipment is usually a rod mill, so as to avoid the reduction of beneficiation index caused by over grinding. Therefore, the main equipment for chrome ore dressing by magnetic separation method is jaw crusher, rod mill, grader, high strength magnetic separator, thickener, dryer and other main equipment, which is combined with feeder, bucket elevator and belt conveyor to form a complete set of chrome ore dressing equipment.
Chromite magnetic separation case
A chromite raw ore contains 35.28% chromium oxide and 8.55% ferrous oxide. It has simple structure, coarse particles and high dissociation degree. Its main gangue minerals include olivine, serpentine, chlorite, etc. After comparing the shaking table gravity separation, shaking table high intensity magnetic separation, and high intensity magnetic separation processes, good indicators are obtained in the wet high intensity magnetic separation process. The final process is the wet high intensity magnetic separation coarse scavenging process, The grade of chrome oxide concentrate is 47.61% and the recovery rate is 96.26%.
The chromite is enriched by high intensity magnetic separation, and then further cleaned by gravity separation; Single re selection and multiple selection are adopted; The impurities such as magnesium, aluminum and silicon are removed by flotation, or the combined treatment process of the above methods is adopted. The magnetic gravity combined beneficiation process uses many equipment, so it is necessary to integrate all the equipment of the above two beneficiation methods, or determine the required beneficiation equipment after beneficiation test according to the different properties of different ores.
Ferrochrome magnetite heavy combination case
A low-grade chromite in Yunnan has only 8.51% chromium oxide, 16.81% chromite and 0.65% magnetite. Gangue minerals mainly include serpentine, quartz, etc., with complex composition. First of all, the classification desliming test was carried out, and a cyclone with a diameter of 6mm was used for desliming, so that the raw ore was effectively enriched, and the chromium oxide grade reached 18.52%. The following single shaking table test and single high gradient magnetic separation test concluded that the shaking table only achieved good enrichment, with the chromium oxide grade of 40.56%, while the chromium oxide grade after the high gradient magnetic separation treatment could only reach 38.93%. Then, the magnetic gravity combined separation test was carried out, and the chromium oxide grade was 45.29%. Therefore, the mineral processing flow that can be used in the mine is classified desliming and magnetic gravity combined separation process flow.
The above is about the three beneficiation processes and equipment of chromite, as well as the case sharing corresponding to each process. Through the above cases, we can draw the following conclusions:
1. For rich ores with high chromium oxide content, a single gravity separation or magnetic separation process can be adopted.
2. For chromium ores with low chromium oxide content, the magnetic gravity combined process often obtains better indicators than the single process.
3. The specific process flow shall be determined according to the nature of the ore itself.
The above conclusions are based on the different associated minerals of the vast majority of chromite. The specific process to be selected needs to be determined through beneficiation test to achieve better separation effect and create greater value.
