How to directly judge the quality of coal with the naked eye

How to directly judge the quality of coal by the naked eye - coal quality testing. The quality of coal is determined by the calorific value of coal, the content of vermiculite, the amount of sulfur in coal and the amount of moisture in coal. First of all, the judgment of coal quality should start from the strength and hardness. The vermiculite is divided into flakes and granules according to the depth of color. The sulfur content in coal is distinguished by high, medium and low, and the moisture content of coal is bounded by 5%. For example, an anthracite pulverized coal having a sulfur content of 1 or less and 3 cm or less is used as an example.
1. Sampling: Sampling in coal piles should not be less than 20 points. The depth of each point is not less than 50 cm, and the sample taken at the end is not less than 5 kg. Grab a forceful pinch, generally the better the strength and hardness, the better the coal quality.
2, meteorite: grab a hand in the palm of your hand to look carefully, if there are meteorites and meteorites are granulated, then look at a few more than 1 cm of meteorites. If there are more than 3, there is no 6000 for fever. If there is no big one, look at a few stones less than 1 cm, if there are more than 7, there is no 6000. If the meteorite is flaky, don't look, there is no 6000. The darker the color of the vermiculite, the higher the sulfur content, and vice versa.
3. Sulfur is mainly seen by the copper wire and the individual copper crystals in the coal block. Sulfur containing less than 0.5 does not show significant sulfur; 0.5-0.7, there are 1-2 filaments of copper wire or a small section of dark sulfur on the coal block; 0.7-0.99, there are less than three wires of copper wire or less than 2 bars Dark sulfur; 1-1.5, with obvious copper wire, copper crystal or 3 to 4 dark sulfur; 1.5-2, with obvious copper crystals, a single copper crystal appears, dark sulfur is not less than 5 knots. 2-3 has obvious large copper crystals.
Generally, coal is divided into high 2 or more, medium 1-2, and low 1 or less. How to make a simple distinction? The method is: grab a handful of coal, pinch it a few times, throw it away, look at the residual coal powder on your hand, and then lick it a few times. The darker the color, the higher the sulfur. Black is shiny, not to mention high-sulfur coal, tile gray, light color, is medium sulfur. The color 搓 is unchanged, it is 1 or less, and the lower the sulfur, the less coal powder remains on the hand. Grab a lot, rinse it out, face the sun, you will see the rainbow, the more beautiful and beautiful the rainbow. The higher the sulfur content, the lower the reverse. Grab a hand, throw it in the burning fire, and quickly stretch your head. Below 0.5, there is basically no taste, low 0.5-1 has no great taste, 1-2, has a sultry taste, high sulfur, and awkward.
4, the identification of moisture, grab a hand, pinch, naturally loose. If the coal in the palm of your hand spreads naturally and leaks from the gap of your finger, there is no obvious moist feeling. This moisture should be 5%. If the coal has sputum, but no more than 1/3, it should be 6%, more than 2/3 is 7%, there are fingerprints on the coal gangue, 8%, and water is ≥9%.
5. The elements that make up the organic matter of coal are mainly carbon, hydrogen, oxygen, nitrogen and sulfur. In addition, there are very few elements such as phosphorus, fluorine, chlorine and arsenic. Carbon, hydrogen and oxygen are the main bodies of coal organic matter, accounting for more than 95%; the deeper the degree of coalification, the higher the carbon content, the lower the content of hydrogen and oxygen. Carbon and hydrogen are elements that generate heat during the combustion of coal, and oxygen is a combustion-supporting element. When coal is burned, nitrogen does not generate heat, and is converted into nitrogen oxides and ammonia at a high temperature to precipitate in a free state. Sulfur, phosphorus, fluorine, chlorine and arsenic are harmful components in coal, of which sulfur is the most important. When coal is burned, most of the sulfur is oxidized into sulfur dioxide (SO2), which is emitted with flue gas, pollutes the atmosphere, endangers movement, plant growth and human health, and corrodes metal equipment; when sulfur-containing coal is used for metallurgical coking, It also affects the quality of coke and steel. Therefore, the "sulfur" content is one of the important indicators for evaluating coal quality.
The flammable gas produced by the decomposition of organic matter in coal under certain temperature and conditions is called "volatile matter". It is a mixed gas composed of various hydrocarbons, hydrogen, carbon monoxide and other compounds. Volatile matter is also the main coal quality index. Volatile matter has an important reference role in determining the processing and utilization of coal and process conditions. Coal with a low degree of coalification has more volatiles. If the combustion conditions are not suitable, the coal with high volatile content will easily produce unburned carbon particles, commonly known as "black smoke"; and produce more carbon monoxide, polycyclic aromatic hydrocarbons, aldehydes and other pollutants, and the thermal efficiency is reduced. Therefore, it is necessary to select appropriate combustion conditions and equipment based on the volatile matter of the coal.
6. The content of inorganic substances in coal is very small, mainly including water and minerals, and their presence reduces the quality and utilization value of coal. Minerals are the main impurities of coal, such as sulfides, sulfates, carbonates, etc., most of which are harmful components.
“Moisture” has a great impact on the processing and utilization of coal. When the water turns into steam, it absorbs heat, thus reducing the calorific value of the coal. The moisture in coal can be divided into external moisture and internal moisture, and the internal moisture is generally used as an indicator for evaluating coal quality. The lower the degree of coalification, the larger the internal surface area of ​​coal and the higher the moisture content.
7. “Ashes” is the solid residue left after the complete combustion of coal carbon, which is an important indicator of coal quality. Ash is mainly derived from incombustible minerals in coal. Minerals should absorb heat when ashing, and a large amount of slag should take away heat. Therefore, the higher the ash, the lower the thermal efficiency of coal combustion. The more ash, the more ash generated by coal combustion, the more fly ash is discharged. . In general, the ash content of high quality coal and clean coal is relatively low. Fixed carbon (FC) for coal
The fixed carbon content refers to the residue after removal of moisture, ash and volatiles, and is an important indicator for determining the use of coal. The difference between the moisture, ash and volatiles of the coal is subtracted from 100 to be the fixed carbon content of the coal. Based on the basis of the calculated volatiles used, the fixed carbon content of different benchmarks such as dry basis and dry ashless basis can be calculated.
8. Calorific value refers to the heat generated by the unit mass of coal when it is completely burned. It is mainly divided into high calorific value and low calorific value. The high calorific value of coal minus the heat of vaporization of water is the low calorific value. The national unit of calorific value is 10,000 joules per kilogram (MJ/KG) commonly used units kilocalories/kg, and the conversion relationship is: 1MJ/KG=239.14Kcal/kg; 1J=0.239cal; 1cal=4.18J. Such as calorific value 5500Kcal / kg, 5500Kcal / kg = 5500 / 239.14 = 23MJ / kg.