1 Introduction
The blast furnace is the main furnace used by steel mills today. The volume of the furnace determines the size of the furnace. The furnace capacity ratio (FR) is the most commonly used performance index for the blast furnace. The ratio reflects the production capacity of the furnace, its average operation load, and the efficiency of its charge system. The furnace capacity ratio (FR) is defined as the ratio of the active volume of the hearth to the total volume of the hearth and the bosh before charged at the beginning of the campaign. This paper will discuss the factors that affect the FR in blast furnaces and strategies for optimizing FR to maximize furnace productivity.
2 Factors affecting furnace capacity ratio (FR)
2.1 Fuel ratio and air rate
The air supply and fuel ratios used in the blast furnace directly affect the overall productivity of the furnace. For example, if too much fuel is used or the air rate is increased, the furnace will be overloaded, resulting in a reduction of the furnace capacity ratio. On the other hand, if the fuel ratio is too low or the air rate is too low, the blast furnace will become cold and the capacity ratio will decrease. So it is important to control the fuel ratio and air rate to maintain an optimal furnace capacity ratio.
2.2 Hearth stock shape
The shape of the hearth stock is an important factor influencing the capacity ratio of the blast furnace. If the hearth stock is even and the stock distribution is uniform, the height of the hearth will be even, but if the hearth stock is too low or too high, or has a random shape, the heat efficiency of the furnace will be reduced, and the capacity ratio will be reduced. Therefore, it is important to control the hearth stock shape to maintain an optimal hearth capacity ratio.
2.3 Refractory linings
The refractory linings of the blast furnace are also an important factor affecting the furnace capacity ratio. Generally, the furnace capacity ratio will be higher when using high-quality, high-intensity refractory linings. But if the refractory linings are too low-quality or low-intensity, it will result in a loss in heat efficiency and thus a reduction in furnace capacity ratio. So it is important to select proper refractory linings when constructing a blast furnace to maximize the capacity ratio.
3 Strategies for optimizing furnace capacity ratio (FR)
3.1 Using the right fuel ratio and air rate
The fuel ratio and air rate used in the blast furnace should be carefully controlled to maintain the optimal furnace capacity ratio. Generally, a fuel ratio of 1.5 to 2 and an air rate of 5 to 7 cubic meters per second can be used to achieve an optimal furnace capacity ratio.
3.2 Maintaining even hearth stock shape
The hearth stock shape should be maintained as even and as uniform as possible to maintain the optimal furnace capacity ratio. If the hearth stock shape is uneven or non-uniform, corrective measures, such as changing the hearth material, changing the charging pattern, or using a slag-breaker, should be taken to maintain an even hearth shape.
3.3 Using correct refractory linings
The refractory lining of the blast furnace should be carefully selected for good quality and high intensity to ensure a good furnace capacity ratio. Generally, the refractory lining should be at least 3-6 cm thick, and the maximum temperature should not exceed 1100℃.
4 Conclusion
The furnace capacity ratio (FR) is a crucial performance index for blast furnaces, and is affected by several factors such as the fuel ratio, air rate, hearth stock shape, and refractory linings. Strategies such as using the right fuel ratio and air rate, maintaining an even hearth stock shape, and using correct refractory linings can be used to optimize the furnace capacity ratio and maximize its productivity.
