How do I use a blast furnace - part 3

Blast furnace's loading system

According to the type of charging equipment, furnace capacity, raw materials, fuel conditions and ratio, determine the batch weight, charging line, loading sequence, distributor rotation angle and working procedures of bell less furnace top rotary chute: multi ring distribution, spiral distribution or single ring distribution, opening of material flow control valve, working procedures of furnace throat guide plate, etc. The purpose of formulating the charging system is to make the charge distribution in the furnace reasonable. Reasonable burden distribution combined with appropriate wind speed can obtain reasonable gas distribution, which is the basis of stable operation of blast furnace. The marks of reasonable burden distribution are: the thickness of coke layer and ore layer is appropriate; Uniform circumferential distribution; Radial distribution: the ore coke ratio in the center of the furnace is the lowest. The ore coke ratio increases gradually from the center to the edge, and decreases slightly near the edge. The thickness of coke layer and ore layer is determined by the batch weight. According to experience, the batch weight of coke (T) is about 0.03dt3 (DT is the throat diameter, m) or the thickness of coke layer is 450 ~ 650mm at the throat. After the coke batch weight is determined, the ore batch weight can be calculated according to the coke ratio. The circumferential uniform distribution of furnace charge is realized by the correct operation of rotary distributor or rotary chute on bell less furnace top; The reasonable radial distribution is realized by adjusting the feed line, loading sequence and the gear of the throat guide plate or the inclination of the rotary chute on the top of the bell less furnace.

The distribution of charge and gas flow in the furnace is difficult to observe directly. It is usually judged according to the distribution of gas temperature and composition. On the same plane, if the gas temperature at each point in the same ring is close, it indicates that the circumferential distribution of charge and gas is uniform; On the contrary, it is uneven. The distribution of radial charge and gas is generally judged according to the distribution curve or temperature distribution curve of gas composition (CO2% or CO2 / (CO2 + CO)) at each point along the radius of furnace throat.

At the height of CO2% or CO2 / (CO2 + CO)%, the ore coke ratio of the material layer is high and the gas flow is weak; On the contrary, the ore coke ratio is low and the gas flow is strong. The gas temperature is high, the ore coke ratio of the material layer is low and the gas flow is strong; On the contrary, the ore coke ratio is high and the gas flow is weak. The normal gas distribution curve is generally double peaked M-shaped or bell shaped; On the contrary, the normal temperature distribution curve is generally in the shape of double Valley w or inverted bell shaped. After the gas flow distribution pattern is determined, the required charge distribution and gas flow distribution can be obtained by using the distribution characteristics of batch weight, material line, loading sequence and the distribution function of rotary distributor, throat guide plate or bell less furnace top rotary chute (see blast furnace distribution). Judgment and adjustment of furnace condition

When the blast furnace operates well, the blanking is stable, the charging speed meets the regulations and is uniform, the gas flow distribution is normal, the air volume, air pressure and static pressure curve of each layer are stable, the pressure curve of the furnace top does not appear upward peak, the temperature curve of each layer of the furnace body is stable, the temperatures in all directions on the same horizontal plane are close, the temperatures of each tuyere are uniform and active, the tuyere and slag mouth are rarely burned out, the molten iron quality is good, the fluidity of molten iron and slag is good, and the temperature is high and uniform, Blast furnace has high utilization coefficient and low fuel ratio. This normal and good furnace condition means that the furnace condition is smooth. The fluctuation of blast furnace operation parameters and the instability of blast furnace fuel are often caused by the fluctuation of blast furnace operation parameters. If this change can not be found and adjusted in time, it will lead to abnormal furnace condition, even blast furnace failure or accident. Therefore, it is necessary to monitor and control the furnace condition frequently. The main items monitored are the movement of furnace temperature, charge and gas flow, slag alkalinity and lining erosion.