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%.

DLS Vertical Ring High Gradient Magnetic Separator

Reduce-Fe Type

Application of DLS High Gradient Magnetic Separator, Reduce Iron type:
Purify quartz, feldspar, silica sands, kaolin, clay, nepheline, fluorite, sillimanite, andalusite, kyanite, etc. Remove iron, biotite, managnese, hornblende, mica, tourmaline, garnet and other impurities 

1. Why use high gradient magnetic separator to purify feldspar?
Whiteness/brightness is a key index in the industrial purpose feldspar. In the run of mine, ferrous substances are the main coloration compositions, which exist in the form of biotite, ilmenite, chlorite and tourmaline.

Test Report: Remove Fe & Ti in Coal-series Kaolin

Test Report: Remove Fe & Ti in Coal-series Kaolin

The sample is coal-series kaolin from Xiangtan, black powder blocks, with small stones and other impurities in it. Purpose of the test is to remove Fe and Ti in it. Coal-series kaolin mainly existed in the top/bottom/interlayer of coal layers of coal-series stratum formed in the Permian of carbon and the coal series of Carboniferous, Triassic, Jurassic and Tertiary, with hard texture. Crystalloids are compact microcrystal, mostly plate-shaped, smaller than that of non-coal-based kaolin; darker, generally containing organic carbon, and natural whiteness is usually 20 to 50 degree. There are black, gray black, gray, brown, gray green, gray white and other different colors, with high iron and titanium content. In kaolin ores, in addition to kaolin, there are often quartz, feldspar, boehmite, pyrite and anatase, with a small amount of marcasite, magnetite, limonite, hematite, ilmenite, rutile, zircon, tourmaline and water mica, etc. The Al2O3 in coal-based kaolin is much higher than soft soil, which is between 35% and 39%. To remove Fe & Ti in Kaolin 1. Reverse Flotation Test See the following test flow. After initial grinding, dispersing agents, kaolin inhibitors, activator vector to activate iron and titanium for flotation are added in the slurry, and finally collector is added for reverse flotation. Flotation test results are shown in Table 1. Reverse Flotation Test for Kaolin Test Result of Reverse flotation test for Kaolin Yield (%) Grade (%) Recovery (%) Fe Ti Fe Ti Concentrates 58.4 0.65 0.71 32.79 25.71 Tailings 41.6 1.87 2.88 67.21 74.29 Run-of-mine 100 1.16 1.61 100 100 We can see from the Table 1 that Fe and Ti can’t be lowered below 0.5% simply by reverse flotation. Wet high gradient high intensity magnetic separation is considered before reverse flotation. 2. High Gradient High Intensity Magnetic Separation – Reverse Flotation Test High gradient high intensity magnetic separation is added in the flow sheet to reduce some parts of Fe and Ti. Result is shown in Table 2. Yield (%) Grade (%) Recovery (%) Fe Ti Fe Ti Concentrates 55.3 0.48 0.61 21.41 20.26 Tailings 44.7 2.18 2.97 78.59 79.74 Run-of-mine 100 1.24 1.66 100 100 3. Further test is recommended Conditions of flotation Optimize the grinding size, dispersing agent, activator, collector, etc, to find the most suitable flotation conditions. Conditions of magnetic separation Optimize the magnetic intensity of high intensity magnetic separation, and the test result of magnetic separation with flocculant.

Useful minerals vs Gangue

Useful minerals vs Gangue

Useful minerals are minerals, ores and rocks that can be used (with economic benefits).

Gangue: In addition to the useful minerals, there are some minerals in the ore that can not be enriched or used at present, which are called gangue, such as hematite, biotite, amphibole in feldspar; high gradient magnetic separator is used to separate feldspar and gangue.

Feldspar after removing magnetic gangues by HGMS

Rock vs Ore vs Mineral

Rock vs Ore vs Mineral

Minerals are integral part of the rock or ore; they are elements of nature or natural compounds with fixed chemical composition and physical and chemical properties, after natural physical and chemical effects and biochemical effects in the earth's crust. Most of the minerals are natural compound, such as magnetite (Fe3O4), quartz (SiO2), a small parts are natural elements, such as the nature of gold (Au), silver (Ag), copper (Cu), graphite (C), etc.

Industrial Standard of Iron Ores

Industrial Standard of Iron Ores in China

1.       Iron ores for Steel-making

Iron Ores	TFe (%)	Max. content of impurities (%)			Other impurities (%)
		SiO2	S	P
Magnetite	≥56	≤13	≤0.15	≤0.15	Cu≤0.2 Ag≤0.1
Hematite

What is beneficiation

Definition of Beneficiation

Definition: through the physical or chemical diversity of minerals, separating ore into valuable substances and waste (gangue) by any of a variety of mining equipment, to enrich the useful minerals.

Usually run-of-mine ores are composed of useful minerals and gangues. Grade of useful minerals is not high enough for industrial purpose. Beneficiation is to purify and enrich them to make them concentrates.

e.g.

Beach placer (beach sand) contains a variety of minerals, such as quartz, zircon sand, ilmenite, rutile, garnet, monazite, hematite, hornblende, silimanite, etc. If the grade of zircon is relatively high and has a value of market development, we can use washing, spiral separation, magnetic separation, flotation, and other processes, to move other minerals, especially the radioactive monazite, and get upgraded zircon concentrate. 

By wet high gradient magnetic separator, beach sands are separated into three parts: non-magnetic silica sands, feebly magnetic ilmenite and weaker magnetic garnet