Quality indicators of coke (coke quality indicators)

[Quality indicators of coke] Coke is a solid product of high-temperature dry distillation, mainly composed of carbon, and is a porous structure with cracks and irregularities. The number of cracks directly affects the strength and crushing strength of coke, and its indicators are generally measured by crack degree (referring to the length of cracks per unit volume of coke). The main indicator for measuring pore spore structure is porosity (the percentage of coke pore volume to total volume), which affects the reactivity and strength of coke. Different types of coke have different requirements for porosity indicators. Generally, metallurgical coke requires a porosity of 40-45%, casting coke requires a porosity of 35-40%, and export coke requires around 30%. The degree of cracking and porosity of coke is directly related to the type of coal used in coking. For example, coke produced mainly from gas coal has more cracks, higher porosity, and lower strength; The coke produced from coking coal as the base coal has fewer cracks, lower porosity, and higher strength. The strength of coke is usually represented by two indicators: crushing strength and wear resistance. The crushing strength of coke refers to its ability to resist external impact forces without breaking along cracks or defects in the structure, expressed as M40 value; The wear resistance of coke refers to its ability to resist external friction without the formation of surface glass debris or powder, expressed as an M10 value. The cracking degree of coke affects its crushing strength M40 value, and the pore structure of coke affects its wear resistance M10 value. There are many methods for determining the values of M40 and M10, and China mostly uses the method of the German Migonne drum test. As shown in Table 31-1.

After the conversion test is completed, sieve with a diameter of 40mm and 10mm. The percentage of particles larger than 40mm is M40, and the percentage of particles smaller than 10mm is M10. The strength indicators specified for metallurgical coke in China are shown in Table 31-2.

Table 31-1 Experimental Methods for Coke Drum

Drum characteristics

Coke sample

screening

Strength index

Diameter/length (mm), rotational speed (rpm), number of revolutions (rpm), weight (kg), particle size (mm), perforated sieve (mm), wear resistance (particle size mm/index), crushing strength (particle size mm/index)

1000/1000 25 100 50>60 circular 40, 10<10/M10>40/M40

Table 31-2 Strength Index of Metallurgical Cokes in China (%)

Strength index

Grade I metallurgical coke

Grade II metallurgical coke

Grade III metallurgical coke

M40>80.0>76.0>72.0

M10<8.0<9.0<10.0

Table 31-3 National Standards for Ash Content of Metallurgical Coke and Clean Coal in Several Countries (Ad)

different countries

China

United States

Former Soviet Union

Germany

France

Japan

Grade I, II, III

Coke ash content (%)

≤ 12.0

≤ 13.5 ≤ 15.0<7.0<10.0<8.0<9.0<10.0

Clean coal ash content (%)<12.5 5.5-6.5 8.0-8.5 6.0-7.0<7.0 6.6-8.0