fuel

Fuel is one of the main raw materials for sinter. It is a source of heat for sinter ore. It is required to have low fuel ash, low volatile content and suitable particle size.
Too high will reduce the ash content of the sintered iron-containing ore, some plants containing Fe60% magnetic sintered ore, coke ash containing up to 20% can be obtained only ordinary containing Fe56% of sinter. Because the high ash coke is easily broken, the small coke contains higher ash, and the ash in the general coke is 2 to 4% higher than the large coke.
If the volatiles are too high, it will affect the permeability of the coating. It escapes at high temperatures and re-cools at lower temperatures. Therefore, these volatiles may condense in the lower portion of the sintered layer to affect the gas permeability of the layer. It may also condense on the exhaust pipe, the dust removal system and the fan blade to reduce the vacuum negative pressure and dust removal effect. Thus volatiles fuel should not exceed 3-5%, the reason not be used for cigarette coal fuel are sintered thereto.
The most suitable particle size is less than 3 mm, which accounts for 80 to 90%. Therefore, the fuel for sintering is processed.
Currently used fuels for sintering are coke and anthracite.
(1) Fragmentation: It is the undersize of blast furnace coke, generally below 25 mm. The coke ash and volatiles are higher than the block coke, but the price is cheaper and the use is more economical. Requirements for coke: fixed carbon > 80%, volatiles < 5%, ash < 15%. Fragmentation chemical composition of several plants in China. Some plants have ash content of more than 20%, and the fixed carbon content is relatively reduced. Sulfur is generally lower.
(2) Anthracite: As the sintering production develops rapidly, the amount of coke can not meet the requirements of sintering. Anthracite is a good fuel that can replace coke. Generally, anthracite contains higher volatile matter, but with the degree of carbonization of coal, the content of volatile matter is also very different. For anthracite requirements, calorific value >25.12 million joules / kg (6000 kcal / kg), volatile matter <10%, ash <15%, sulfur <2.5%. Into the plant particle size <40 mm.
In addition to the higher volatile content of anthracite, anthracite is similar to coke, and some sulfur and ash are not high.
Shougang once commissioned the Beijing Research Institute of the Beijing Coal Research Institute to inspect the Mentougou and Yangquan anthracite used for sintering.
(1) Calorific value: For the sintering process, it is desirable to have a fuel having a high calorific value, and a calorific value calorimeter is used for measurement.
(2) Reactivity: refers to the reaction speed of fuel and CO ₂ at a certain temperature. That is, the ability of the fuel to reduce CO ₂ , or the activity of the fuel. According to the composition of gas generated by reaction of CO ₂ with anthracite under certain temperature conditions, the reaction ability (R) is calculated.

Usually: R = 30 ~ 50% is a low reactivity coke,
R=50～100% is moderately reactive coke,
R = 100 to 200% is a coke having high reactivity.
It can be seen that the reactivity of the door coal to the coal is poor. As the temperature increases, the difference gradually decreases. Under sintering temperature conditions (generally at 1350 ° C), the effect of fuel reactivity on the sintering process may not be significant.
(3) Thermal stability: It indicates that the coal bursts after being heated. The anthracite with layered or flaky structure is easy to split and produce powder after being heated. The fracture has a shell-like thermal stability, and the thermal stability of the two coals is good. Measurement data.
Since the coal for sintering is broken to <3 mm, the thermal stability is much less than the effect of using lump coal in the blast furnace. From the above measurement results, the thermal stability of the door coal is poor.
(4) Ash melting point: The method for measuring the ash melting point of the laboratory is to prepare the ash to be measured into a triangular cone and heat it in a carbon grain electric furnace having a semi-reducing atmosphere. When the cone tip is rounded or tilted, it is the starting deformation temperature (T ₁ ), the upper part of the cone is inclined to the substrate, and even when the ball is formed into a ball, it is a softening temperature (T ₂ ). When the cone is melted, it is melted when it is formed into a beach. The temperature (T ₃ ), the temperature of T ₁ -T ₂ is referred to as the softening stage, and the temperature range of T ₂ -T ₃ is referred to as the melting stage. Ash having a melting point of less than 1200 ° C is called fusible ash, 1200 to 1300 ° C is called fusible ash, 135 to 1500 ° C is called refractory, and above 1500 ° C is actually not melting. The ash melting point of the fuel has a large influence on the sintering process. The fusible ash is easy to form a liquid phase, which is beneficial to the sintering of the ore and further improves the quality of the sintered ore. The door coal contains more alkaline substances (mainly calcite ) due to ash, and the melting point is about 1200 °C. Yangquan coal ash has strong acidity and melting point above 1500 °C, which is refractory. It relies on the alkaline material in the flux to form a slag to lower its melting point.

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