Coal tar and wood tar

November 21, 2019

(1) In the case of dry distillation coal , shale , peat and wood, various tars such as coal tar (high temperature and low temperature), shale oil, peat tar and wood tar can be obtained. The composition of tar is generally not complicated, and it varies with the distillation raw materials and temperature. In addition to various hydrocarbon compounds, there are also bipolar materials such as phenol, alcohol, organic acid and organic alkali. In the early stage of the development of flotation process, tar was used as a collector for sulfide ore. The repolarized substance contained in it was the active component of flotation, and the hydrocarbon oil only had an auxiliary collection effect. Because there are only a small fraction of effective repolarizing substances, and most of them are hydrocarbon oils, they are used in large amounts (500 to 5000 g/ton). Later, after the chemically synthesized collector (such as xanthate) was applied, the tar was replaced. Nowadays, tar is an important chemical raw material. It is no longer used directly in the flotation industry. Its fractions are divided into different products and used comprehensively. Only fractions with little value are used as mineral processing agents.

Table 1 lists the distillation temperatures and components of each of the coal tar fractions:

The distillation temperature and composition of each fraction of coal tar

Fraction	Fractionation temperature (Â°C)	Yield(%)	Specific gravity	Component
Light fraction (light oil)	<170	0.5 to 1.5	0.91ï½ž0.98	Benzene, toluene, xylene, benzofuran, naphthalene, phenol and its homologues
Middle fraction (medium oil)	170ï½ž230	2.5~9	1.026~1.03	Naphthalene, methylnaphthalene, dimethylnaphthalene. Phenol, methyl, xylenol, etc.
Heavy fraction (heavy oil)	230~270	11~13	1.05~1.07	Naphthalene, anthracene, phenanthrene, tar acids and basic compounds
è’½ fraction (è’½ oil)	270-360	20-25	1.08â€”1.13	Anthraquinone, phenanthrene, carbazole, acridine
Levy	>360	-	-	asphalt

Most of the fractionated products of coal tar can be used as collectors for coal. The light oil has weaker ability to capture, but has strong foaming performance. The dosage is generally 200-2000 g/ton, and it can also be mixed with kerosene and solar oil. use. Heavy oil is a foaming agent for coal capture, but the foaming performance is lower than that of medium oil, and the amount is slightly larger. Heavy oil can be used as a substitute Coban xanthate selected from copper sulfide ore flotation even multiple metal poured sulfur ore. The combination of heavy oil and xanthate can obtain better indicators and can reduce your medicinal amount. The production of eucalyptus oil is large, the price is low, and the application is less. It can also replace some xanthate in the flotation polymetallic sulphide ore; the eucalyptus oil and sulphur are co-cooked, and the sulphide sulphate oil can be used as a substitute for xanthate, but flotation The indicator is slightly lower. Medium oil is used as a raw material for extracting phenolic foaming agents.

Coal tar and its fraction products contain a large amount of phenol and cresol. When used as a mineral processing agent, the tailing water is poisonous, so the wastewater should be handled well to prevent pollution.

White shale tar used in the flotation of lead ore, stibnite and coal, to get good results.

(2) Wood tar is a wood retorting product that heats the wood from the air. When it is more than 100 degrees Celsius, the water is first released, and the distillation begins to occur at 150 Â°C. When the temperature reaches 400 Â°C, the heat released by the distillation can be stopped. The reaction continues with heat until the dry distillation is completed. The remaining product of the dry distillation is carbon, and the gas released during the dry distillation is cooled to obtain water and wood tar. [next]
The composition of wood tar varies depending on the type of wood used and the place of production. In general, it is a relatively complicated substance. Here are some examples.
From the two examples in Tables 2 and 3, the composition of wood tar is complex, but in general, the main components

Composition with birch tar Table 2

name	content(%)
water Volatile acid (such as acetic acid) phenol Neutral substance Acid (non-volatile acid)	1.5~2 1.7~2.5 21~27 55~58 15 to 18 (of which 80% is high molecular acid, 25% of these polymers are stearic acid, and 25% are aromatic acids.

Neutral substances (refer to some other reports, these neutral substances are mainly hydrocarbons), phenol and carboxylic acid, so take the appropriate part of the wood tar, can be used as a flotation agent.

1. Neutral oil floating coal The tar obtained by retorting from softwood is placed in a distiller for separation and separation into oil and asphalt. The obtained oil is treated with sodium hydroxide. The phenols in the oil react with sodium hydroxide to form sodium phenolate. The water is separated from the oil to give a neutral oil. Neutral oil is a homogeneous liquid with a specific gravity close to 1, a boiling range of 160 to 360 Â° C, containing more than 51% of aromatic hydrocarbons, alcohols, carbonyl compounds and ethers, used for flotation indicators.

Ranunculus tar properties and composition Table 3

Name or composition	Value or content (%)
proportion Acid value Soap value water Volatile acid Water soluble acid phenol Neutral Ash Mechanical impurities	1.21 111.63 65~69 11.5 4.34 5.63 41.55 20.0 0.95 0.095

2, the floating portion for phenol Lu iron ore will wood tar fractionation, distillation range taken fried 240 ~ 350 â„ƒ fraction, containing 50% or more acidic substance (mainly phenolic acids and their biological transgression), hematite and false Like hematite collectors, and no ability to capture calcium and magnesium silicates and carbonates, it has high selectivity to hematite. The trapping mechanism is that the iron ions on the surface of hematite form a complex with the hydroxyl group of the phenol and are fixed to the hematite hydrophobic and floating; the Ca ²⁺ and Mg ²⁺ plasmas cannot form a complex with the hydroxyl group of the phenol, so the phenol Its mites and organisms cannot be anchored to the surface of calcium and magnesium silicates and carbonates, so there is no capture effect on these minerals.

3, the flotation separation of lead from the zinc oxide ore in a kind of wood tar oil, wherein a boiling point of â‰¤240 â„ƒ is 10%, the boiling point of â‰¤340 â„ƒ 80%, an acid value of 19.6, this oil dialogue galena ( PbCO ₃ ), molybdenum- lead ore (PbMoO ₄ ), lead (PbSO ₄ ), and other lead oxides have good capture, but have no ability to capture quartz , feldspar, and other silicates. Using this flotation oil to crudely select Pb-Zn mixed ore, the recovery of Pb, Zn and Cu in coarse concentrate increased by 7.5%, 14.5% and 6.15%, respectively, and Pb was lost in tailings, from 0.44%. Dropped to 0.27%.

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