Thermal Reactivity and Thermal Reaction Strength

Coke is an indispensable fuel for traditional blast furnace ironmaking process. In recent years, with the development of blast furnace blowing fuel technology, the coke ratio is decreasing, and the influence of coke quality on blast furnace smelting is becoming more and more obvious, which is one of the factors limiting the development of blast furnace production. The coke used in blast furnace smelting usually needs to meet the quality requirements of composition, particle size and strength, such as high fixed C content, low ash, low content of harmful elements, uniform particle size of 40~60 mm and high cold strength. In order to ensure the coke's ability to resist crushing and abrasion under the temperature and atmosphere conditions in the furnace, it is also required to have a certain thermal strength (Coke Strength After Reaction) and a weak reactivity (CRI: Coke Reactivity Index).

The thermal strength of coke is a mechanical strength index reflecting the thermal properties of coke. It shows the ability of coke to resist breakage and abrasion when subjected to both thermal and mechanical stresses at the temperature and atmosphere of the environment in which it is used.

Usually, blast furnace smelting has the following requirements on coke quality:

1, chemical composition

Requirement for high fixed carbon content, low ash. Fixed carbon content is high, the coke provides more heat and reducing agent, coke ash is high, blast furnace slag will increase; ash and coke quality expansion of different, heated in the blast furnace, the ash particles around the cracks, so that the coke strength is reduced; ash in the alkali metals, etc. on the coke carbon-soluble reaction catalytic effect on the coke reactivity, affecting the strength of the reaction. In addition, it is also required that the content of volatile matter of coke is low, the moisture of coke is stabilized at a low level, and the content of harmful elements such as sulfur, phosphorus and alkali metals is low.

2, cold mechanical strength

Including coke shattering strength M40 and abrasion strength M10 indicators, cold strength and the wind mouth coke particle size composition, the average particle size has a strong correlation, the overall reflection of the coke's ability to maintain the particle size in the blast furnace, and therefore used as a daily production inspection indicators.

3, particle size

The coke particle size is required to be uniform, and the average particle size is kept at the level of 40~50 mm. Specific requirements according to the volume of the blast furnace, the level of operation and the level of indicators vary slightly.

4 High-temperature performance

The high-temperature performance of coke includes reactivity CRI and post-reaction strength CSR. Reactivity is a stability index to measure the ability of coke to react with CO2 carbon solution at high temperature, and post-reaction strength is a measure of coke's ability to maintain its high-temperature strength under the condition of CO2 and alkali metal erosion. It is generally recognized that the coke's post-reaction strength, CSR, is a better indicator of coke quality than cold strength.