Chrome ore beneficiation process optimisation and industrialisation practice

As an important raw material for refractories and special alloys, the core of chromite ore beneficiation process lies in the high-efficiency extraction of high-grade concentrate through classification, re-election and process improvement. Taking the process innovation of Tonkin River Mining and Processing Joint Enterprise as an example, after rough crushing of the raw ore to 300mm, the ore is divided into 300-50mm, 50-10mm and 10-0mm grains through multi-stage screening, in which 300-50mm grains are removed from the waste rock through manual hand-selection, initially improving the quality of the ore. However, as the demand for the development of poor ore resources grows, the traditional process is difficult to meet the cost and efficiency requirements. 1973, the new beneficiation plant adopted an innovative process, the raw ore crushed to 80mm and screened into 80-10mm, 10-3mm and 3-0mm three grades, of which the 80-10mm grades through the heavy suspension separation (density 2.8-3.2g/cm³) directly output concentrate and tailings, significantly simplifying the traditional multi-stage hopping process. The process is significantly simplified from the traditional multi-stage jigging process.

In heavy suspension separation, loose ferrosilicon is used as an aggravating agent, with electromagnetic separator to achieve suspension recycling, and the recovery rate of magnetic components reaches 99.9%. For 10-3mm and 3-0.5mm fine grains, MOI-2 jigger is used for sorting, and the concentrate and middle ore go into the subsequent processing, while the tailings are directly discarded. For 0.5-0.07mm ultra-fine grains, the original design used shaking table sorting, but in actual production found that the proportion of intermediate grains (density 2.6-3.6g/cm³) is low and the chromium distribution is not uniform, and finally cancelled the shaking table operation to further simplify the process. The key improvement in the jigging process is equipment upgrading, such as replacing MOJI-3 with OMTK-4 jigger to increase the processing capacity to 100 tonnes/hour, and optimising the sorting effect by desliming the sludge with hydroclassifier.

In order to reduce the loss of valuable components in the fine mud, the plant returns the sieve product of the heavy suspension wash screen to the jigging process, which increases the concentrate yield by 1.5%. In addition, the processing capacity of the plant was increased to 575,000 tonnes/year in 1978, and the Cr₂O₃ content of the concentrate reached 50.8% through the modification of the feeding system of the crushed ore storage silo, which avoided the problem of arching of the pulverised ore, and ensured the stable delivery of the raw ore. For chrome-rich ores (300-50mm grain size), radiation picking was adopted to replace manual hand picking, and the vein rejection rate was increased to 5-6%, with a 2-2.5% increase in Cr₂O₃ grade in concentrate. In the filtration process, KCH-15 dewatering screen and spiral classifier are introduced to effectively reduce the moisture of the concentrate and improve the stability of the product.

The future direction of chrome ore beneficiation will focus on the integration of high-efficiency sorting technologies at the full grain level, such as the introduction of intelligent sorting equipment to replace traditional radiation picking, and the development of environmentally friendly suspension systems to reduce ferrosilicon consumption. Through continuous optimisation of the process and equipment configuration, chrome ore beneficiation is expected to achieve greater breakthroughs in resource utilisation and economic benefits.