Concentrates, Tailings and Middling and Grade

Concentrates, Tailings and Middling and Grade

Concentrates are the enriched mineral products of ores after beneficiation to remove most of the gangue and impurities. Concentrates are the final product in the processing plant, sometimes called final concentrates. Concentrates can be qualified only if when both the main components and impurities reach the national standard.

For example: K-feldspar (potassium feldspar) for ceramics, in accordance with the general industrial standards, K2O + Na2O content must be greater than or equal to 11%, and the Fe2O3 content is less than 0.2%.

Tailings are the materials left over after beneficiation to extract the useful minerals from the uneconomic fraction (gangue) by beneficiation, also called  residue, waste, slimes, mine dumps, culm dumps, tails, refuse or slickens,

Limited by the current level of technology, it is difficult utilize tailings, but in the future it is likely to be reused.

For example: large amounts of tailings, commonly known as red mud or red sludge are produced every day from aluminum factories. For the huge quantity, tens of thousands of tons of red mud accumulation in the reservoirs with the risk of leakage at any time, taking up a lot of land, polluting groundwater. On October 4, 2010, a million cubic meters of red mud was leaked from Ajkai alumina Factory in Hungary. Four people were killed and 3 people missing. Although the reusing has been researched for years, there is no better plan. To lower the content of Fe in red mud is the key.

In recent years, with the development of technology, magnetic material and non-magnetic material are separated by high gradient magnetic separator. After separation, Fe content of 20% of the mud can be increased more than 56% for reuse; extracted non-magnetic substances are available to produce cement, brick, road filler material.

Middling is the middle product in beneficiation process. Content of economic components in middling is generally between the concentrate and tailings. Middling is usually returned to early stage for processing in beneficiation flow, or separately treated.

Grade: refers to the ratio of mass of the metal or useful components to the mass product, commonly expressed as a percentage.

For example: Total Fe% of hematite (feebly magnetic) run-of-mine is 46%, a = 46%. After high intensity magnetic separation, in concentrate the iron content increased to 60%, β= 60%. Fe% in tailings is reduced to 20%,θ= 20%.