1 coal is a solid combustible mineral gradually formed by complex biochemical and physicochemical changes of ancient plants buried underground. Coal is a kind of solid combustible organic rock, which is mainly transformed from plant remains by biochemical, burial and geological processes.
Coke is made of bituminous coal heated to 950- 1050℃ under the condition of air isolation, and then dried, pyrolyzed, melted, bonded, solidified and shrunk. This process is called high temperature coking (high temperature dry distillation).
Coke obtained by high temperature coking is used for blast furnace smelting, casting and gasification. The recovered and purified coke oven gas produced in coking process is not only a high calorific value fuel, but also an important raw material for organic synthesis industry.
Extended data:
Coke is a solid fuel. It is obtained by dry distillation of coal at a high temperature of 1000℃. The main component is fixed carbon, followed by ash, which contains almost no volatile matter and sulfur. Silver gray with metallic luster. Hard and porous.
Its calorific value is mostly 26380 ~ 31400 kj /kg (6300 ~ 7500 kcal/kg). According to different uses, there are metallurgical coke, casting coke and chemical coke. According to the size, there are lump coke, broken coke and coke chips. It is mainly used for smelting steel or other metals, and can also be used as raw materials for making water gas, gasification and chemical industry.
Physical properties of coke include coke screening composition, coke bulk density, coke true relative density, coke apparent relative density, coke porosity, coke specific heat capacity, coke thermal conductivity, coke thermal stress, coke ignition temperature, coke thermal expansion coefficient, coke shrinkage, coke resistivity and coke permeability.
The physical properties of coke are closely related to its mechanical strength, thermal strength and chemical properties at room temperature. The main physical properties of coke are as follows:
The average specific heat capacity is 0.808kj/(kgk)( 100℃),1.465kJ/(kgk) (1000℃).
The thermal conductivity is 2.64kj/(mhk) (room temperature) and 6.91kj/(mhk) (900℃);
Ignition temperature (in air) is 450-650℃;
Low calorific value of dry ash-free base is 30-32kJ/g;
quality index
1. Sulfur content in coke: Sulfur is one of the harmful impurities in pig iron smelting, which reduces the quality of pig iron. When the sulfur content in steelmaking pig iron is more than 0.07%, it is waste. 1 1% of the sulfur brought into the furnace by blast furnace burden comes from ore; 3.5% comes from limestone; 82.5% comes from coke, so coke is the main source of sulfur in charge. The sulfur content of coke directly affects the blast furnace ironmaking production. When the sulfur content of coke is more than 65438 0.6%, for every 0.65438 0% increase in sulfur content, the consumption of coke increases by 65438 0.8%, the addition of limestone increases by 3.7%, the addition of ore increases by 0.3%, and the output of blast furnace decreases by 65438 0.5-2.0%. The sulfur content of metallurgical coke is not more than 1.
2. Phosphorus content in coke: The phosphorus content in metallurgical coke for ironmaking should be below 0.02-0.03%.
3. Ash in coke: The ash in coke has a significant influence on blast furnace smelting. The ash content of coke increased by 65438 0%, and the consumption of coke increased by 2-2.5%. Therefore, it is very necessary to reduce the ash content of coke.
4. Volatiles in coke: The maturity of coke can be judged according to the volatile content of coke. If the volatile matter is greater than 1.5%, it means coking; If the volatile content is less than 0.5-0.7%, it means overheating. Generally, the volatile content of mature metallurgical coke is about 65438 0%.
5. Moisture in coke: Moisture fluctuation will make the measurement of coke inaccurate, thus causing furnace condition fluctuation. In addition, the increase of coke moisture will make M40 higher and M 10 lower, which will bring errors to drum index.
6. Screening composition of coke: The particle size of coke is also very important in blast furnace smelting. In the past, there were requirements for coke particle size in China: the coke particle size of large coke oven (1300-2000 square meters) was more than 40mm, and that of small and medium blast furnace was more than 25 mm. However, tests in some steel mills show that the particle size of coke is 40-25mm. Coke larger than 80 mm should be complete, so that its particle size range does not change much. In this way, the coke is broken evenly, the gap is large, the resistance is small, and the furnace runs well.
Coal is the most widely distributed fossil energy resource in the world, which is mainly divided into four categories: bituminous coal and anthracite, sub-bituminous coal and lignite. 60% of the world's recoverable coal reserves are concentrated in the United States (25%), the United States (23%) and China (12%). In addition, Australia, India, Germany and South Africa account for 29%, and the coal production of the above seven countries or regions accounts for 80% of the world's total output, with proven coal reserves.
Coal classification table
According to the China coal classification scheme recommended by the State Science and Technology Commission, China coal can be divided into ten categories. Generally, lean coal, coking coal, fat coal, gas coal, weakly bonded, unbonded and long-flame coal are collectively referred to as bituminous coal; Lean coal is called semi-anthracite coal; More than 40% of the volatile matter is called lignite.
Anthracite can be used to make gas or directly as fuel, while bituminous coal can be used in coking, coal blending, power boiler and gasification industry. Lignite is generally used in gasification, liquefaction industry, power boilers and so on.
coal
1.？ Charcoal: It is a porous substance, and the surface area of the porous substance is bound to be large. The larger the surface area of a substance, the more molecules it adsorbs to other substances, and the stronger the adsorption. If high-temperature steam is continuously introduced in the process of preparing charcoal, the oil attached to the surface of charcoal will be removed and countless internal pipes will be dredged, then the surface area of charcoal will be larger. Charcoal processed in this way is called activated carbon. Obviously, the adsorption of activated carbon is stronger than charcoal.
2.？ Coke: Bituminous coal is heated to 950- 1050℃ without air, and then dried, pyrolyzed, melted, bonded, solidified and shrunk, and finally made into coke. This process is called high temperature coking (high temperature dry distillation). Coke obtained by high temperature coking is used for blast furnace smelting, casting and gasification. The recovered and purified coke oven gas produced in coking process is not only a high calorific value fuel, but also an important raw material for organic synthesis industry.
3. Activated carbon: It is an excellent adsorbent. It is made of charcoal, bamboo charcoal, various fruit shells and high-quality coal by physical and chemical methods, and through a series of processes such as crushing, sieving, catalyst activation, rinsing, drying and sieving.
It has the dual characteristics of physical adsorption and chemical adsorption, and can selectively adsorb various substances in gas phase and liquid phase, so as to achieve the purposes of decoloration and refining (sucrose decoloration), disinfection and deodorization, decontamination and purification. Burning before use can improve the adsorption effect. The principle is that burning can make grease or other national standards adhere to the internal pipeline, such as American ASTM, Japanese JIS and German DIN standards.
4.？ Carbon black: an amorphous carbon. Light, loose and extremely fine black powder with a very large surface area of 10-3000m2/g is the product of incomplete combustion or thermal decomposition of organic matter (natural gas, heavy oil, fuel oil, etc.). ) in the case of insufficient air.
References:
Baidu Encyclopedia-Coal? Baidu encyclopedia-cola