2.1.4. Burden Evaluation Model

In order to gain a reasonable material distribution and help the operation of the blast furnace, it is necessary to evaluate the distribution of the layers. The particle average size and strength of coke are much larger and higher than those of sinter. Coke remains in a solid state to 1500 ◦C while sinter softens and melts below the cohesive zone in the furnace. In the blast furnace, coke has better permeability than sinter. Therefore, the mass ratio of ore to coke is used to evaluate the burden of the coke state and is calculated as follows:

$$\mathbf{K}\_{\rm O/C} = \frac{\Delta \mathbf{M}\_{\rm O}}{\Delta \mathbf{M}\_{\rm C}} = \frac{[f\_{\rm O}(r)\_{n} - f\_{\rm C}(r)\_{n}]\rho\_{\rm O}}{[f\_{\rm C}(r)\_{n} - f\_{\rm O}(r)\_{n-1}]\rho\_{\rm C}},\tag{23}$$

where Δ*MO* is the mass of the ore layer (kg), Δ*MC* is the mass of the coke layer (kg), *fO*(*r*)*<sup>n</sup>* is the function of ore in the nth layer, and *fC*(*r*)*<sup>n</sup>* is the function of coke in the nth layer. ρ*<sup>O</sup>* and ρ*<sup>C</sup>* are the ore bulk density (kg/m3) and coke bulk density (kg/m3), respectively.

#### *2.2. Radar Detection Measurement*

Rotating radar detection measurement is an integration system, including a mechanical radar device, signal transmission device, and signal processing system. Two rotating radars are installed on the top of the blast furnace (see Figure 7). One of them only measures half of the burden surface profile from the centerline of the furnace to the periphery. They are symmetrically distributed in the top of the furnace and can detect the full material surface together.

**Figure 7.** Schematic diagram of the radar installation in the top of the blast furnace.

After a new burden layer has been formed, the two radars are used to get the radar of the full surface. A combination of the mathematical model and radar data is divided into radar data processing and mathematical model calculation and is shown in Figure 8. After radar data processing, the burden profile function is obtained. The burden descent velocity is gained by two methods: The calculation descent function from the mathematical model and the fitting function of radar data. After the descent function, the burden profiles will present the layer structure. Then, we can evaluate the burden distribution through calculation of the ratio of ore to coke.

**Figure 8.** Procedure of the combination of the mathematical model and radar data in a software implementation.
