Views: 0 Author: Site Editor Publish Time: 2025-12-02 Origin: Site
1. Coal is a solid combustible mineral formed by the burial of ancient plants and subsequent complex biochemical and physical chemical changes. Coal is a solid combustible organic rock, mainly formed by the biochemical action of plant remains, burial, and subsequent geological transformation.
2. Coke is produced by heating bituminous coal to a temperature range of 950 - 1050℃ under an oxygen-free environment. Through stages such as drying, pyrolysis, melting, bonding, solidification, and contraction, it is finally formed. This process is called high-temperature coking (high-temperature dry distillation).
3 The coke obtained from high-temperature coking is used in blast furnaces for smelting, casting and gasification. The coke oven gas produced during the coking process, after being recovered and purified, is not only a high-calorific fuel but also an important raw material for the organic synthesis industry.
Coke is a type of solid fuel. It is obtained by dry distillation of coal at a temperature of approximately 1000℃. Its main component is fixed carbon, followed by ash. The contents of volatile matter and sulfur are very low. It is silver-gray in color, has a metallic luster, is hard and porous.
Its calorific value is mostly between 26,380 and 31,400 kJ/kg (6,300 to 7,500 kcal/kg). Depending on the application, there are three main types: metallurgical coke, casting coke, and chemical coke. According to size, it can be divided into lump coke, broken coke, and coke dust. It is mainly used for smelting iron and other metals, and can also be used as raw materials for manufacturing water gas, gasification, and chemical industries.
The physical properties of coke include coke sieve composition, coke bulk density, true relative density of coke, apparent relative density of coke, porosity of coke, specific heat capacity of coke, thermal conductivity of coke, thermal stress of coke, ignition temperature of coke, thermal expansion coefficient of coke, shrinkage rate of coke, resistivity of coke and permeability of coke.
The average specific heat capacity is 0.808 kj/(kg·K) (at 100℃), and 1.465 kj/(kg·K) (at 1000℃).
The thermal conductivity is 2.64 kj/(m·K) (at room temperature), and 6.91 kj/(m·K) (at 900℃).
The ignition temperature (in the air) is 450 - 650℃.
The low calorific value of the dry ash-free basis is 30 - 32 KJ/g;
1. Sulfur content in coke: Sulfur is one of the harmful impurities in the smelting of pig iron, which reduces the quality of pig iron. In pig iron produced by steelmaking, if the sulfur content exceeds 0.07%, it is considered a defective product. The sulfur content brought into the furnace from the blast furnace feedstock accounts for 11% of the sulfur from the ores; 3.5% from limestone; and 82.5% from coke. Therefore, coke is the main source of sulfur in the feedstock. The level of sulfur content in coke directly affects the ironmaking production in the blast furnace. When the sulfur content in coke is greater than 1.6%, for every 0.1% increase in sulfur content, the coke usage increases by 1.8%, the limestone addition increases by 3.7%, and the ore addition increases by 0.3%. As a result, the blast furnace output decreases by 1.5 - 2.0%. The sulfur content of metallurgical coke is specified not to exceed 1%, and the sulfur content of metallurgical coke used in medium and large blast furnaces is less than 0.4 - 0.7%.
2. Phosphorus content in coke: The phosphorus content in metallurgical coke used for ironmaking should be below 0.02 - 0.03%.
3. Ash content in coke: The ash content of coke has a significant impact on the smelting process in the blast furnace. If the ash content of coke increases by 1%, the amount of coke required will increase by 2 - 2.5%. Therefore, reducing the ash content of coke is very necessary.
4. Volatile matter in coke: The content of volatile matter in coke can be used to determine the maturity of the coke. If the volatile matter is greater than 1.5%, it indicates that the coke is still immature; if the volatile matter is less than 0.5 - 0.7%, it indicates that the coke has been over-fired. Generally, the volatile matter of mature metallurgical coke is around 1%.
5. Moisture content in coke: Fluctuations in moisture levels can cause inaccurate coke measurement, leading to fluctuations in the furnace condition. Moreover, an increase in coke moisture will result in a higher M40 value and a lower M10 value, thereby introducing errors to the drum indicators.
6. Screening composition of coke: In the process of blast furnace smelting, the particle size of coke is also very important. In the past, China required the particle size of coke for large blast furnaces (1300 - 2000 square meters) to be greater than 40 millimeters; for medium and small blast furnaces, the particle size should be greater than 25 millimeters. However, some steel mills' experiments have shown that a particle size range of 40 - 25 millimeters is preferable. Coals larger than 80 millimeters should be ground into uniform pieces to keep the particle size range relatively stable. This ensures uniform coke size, large voids, low resistance, and good operation of the blast furnace.
According to the "China Coal Classification Scheme" recommended by the National Science and Technology Commission, China's coal is classified into ten categories. Generally, lean coal, coking coal, rich coal, gas coal, weakly adhesive coal, non-adhesive coal, and long-flame coal are collectively referred to as bituminous coal; lean coal is called semi-animal coal; and coal with a volatile matter content greater than 40% is called lignite.
Anthracite can be used to produce gas or directly as fuel. Bituminous coal is used for coking, blending coal, power boilers and gasification industries; Lignite is generally used in gasification, liquefaction industries, power boilers, etc.
Charcoal: It is a porous substance. The surface area of a porous substance is necessarily very large. The larger the surface area of a substance, the more molecules of other substances it can adsorb, and the stronger the adsorption effect will be. If during the production of charcoal, high-temperature steam is continuously introduced to remove the oily substances adhering to the surface of the charcoal and to make the countless internal channels unobstructed, then the surface area of the charcoal will be even larger. Charcoal processed in this way is called activated carbon. Obviously, activated carbon has a stronger adsorption effect than charcoal.
2. Coke: In the absence of air, bituminous coal is heated to 950 - 1050℃. After going through stages such as drying, pyrolysis, melting, bonding, solidification, and contraction, it is finally transformed into coke. This process is called high-temperature coking (high-temperature dry distillation). The coke obtained from high-temperature coking is used in blast furnace smelting, casting, and gasification. The coke oven gas recovered and purified from the coking process is not only a high calorific value fuel but also an important raw material for organic synthesis industries.
3. Activated Carbon: It is an extremely excellent adsorbent. It is made by using materials such as charcoal, bamboo charcoal, various fruit shells, and high-quality coal as raw materials. Through a series of processes including crushing, sieving, catalyst activation, rinsing, drying, and screening, these raw materials are processed and manufactured.
It possesses the dual characteristics of physical adsorption and chemical adsorption, and can selectively adsorb various substances in the gaseous and liquid phases to achieve purposes such as decolorization and purification (sugar decolorization), disinfection, deodorization, and purification. Before use, burning can enhance its adsorption effect. The principle is that burning can remove the oil or other impurities adhered inside the internal pipes, in accordance with standards such as the American ASTM, Japanese JIS, German DIN standards, etc.
4. Carbon black: A form of amorphous carbon. It is a light, soft and extremely fine black powder with a very large surface area ranging from 10 to 3000 m2/g. It is the product obtained from the incomplete combustion or thermal decomposition of organic substances (such as natural gas, heavy oil, fuel oil, etc.) under conditions of insufficient air.
