JPS5834107A - Operating method for blowing-in of blast furnace - Google Patents

Abstract

PURPOSE:To prevent the generation of spalling cracks surely by forecasting and operating the infurnace surface temps. of bricks after the start of blowing-in operations with time in accordance with the numerical models wherein filling conditions prior to starting of the blowing-in operations, the blasting conditions after the start of the blowing-in and the conditions for charging materials are used as factors. CONSTITUTION:Thermocouples 1a, b, c are provided in blast furnace bricks, and the temps. of the bricks are measured actually with thermometers 2a, b, c by using said thermocouples, whereby the infurnace surface temps. of the bricks are estimated. A coefft. correcting operator 3 compares these values and the forecast values in accordance with the numerical models that an operation planning system 4 determines by using the filling conditions prior to starting of the blowing-in operations, the blasting conditions after the start of the blowing-in and the conditions for charging materials as factors, and operates the correction quantity to eliminate the deviations thereof. The correction values are outputted to a hot wind regulator 5. The regulator 5 regulates the flow rate, blasting temp. and moisture of the hot wind through tuyeres 1d.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention proposes a method for preventing spalling cracks that occur in bricks during blast furnace firing operations.

Conventionally, in the blast furnace firing operation, in the charging process before the firing operation, the ore to be charged first is charged with enough sleepers and coke to heat and melt the ore before the ore is charged.
Next, ore, auxiliary raw materials and coke are charged and charged alternately.
After the firing operation, the ore is melted and the amount of FC hot metal accumulated at the bottom of the furnace reaches the height of the tap hole VC, for example, 24 hours later, making it possible to tap the iron for the first time. The operating conditions are mainly based on light experience.

In addition, the occurrence of spalling cracks in bricks in blast furnaces is thought to be caused by stress caused by changes over time in the temperature gradient from the inner surface of the blast furnace brick furnace to the surface of the blast furnace shell due to temperature rise. It is known that the occurrence of spalling cracks depends on the temperature rise rate of the brick, as shown in FIG. 1. In other words, Figure 1 shows the area where spalling cracks occur (shaded area) with the horizontal axis representing the internal temperature of the brick furnace and the vertical axis representing the brick heating rate. It can be said that the higher the internal temperature of the brick furnace is, the lower the critical brick heating rate at which spalling cracks occur.

However, during the firing operation, the temperature rise rate of the furnace and wall bricks is extremely high, and therefore the bricks are in a state where spalling cracks are very likely to occur. At this stage, spalling cracks occur in the furnace wall bricks, and the bricks When the blast furnace is worn out, the subsequent wear on the blast furnace shell becomes significant, shortening the life of the blast furnace.

Therefore, during the firing operation, it is very important to perform the operation properly so that spalling cracks do not occur in the bricks.

The method of the present invention was made in view of such circumstances,
We proposed a blast furnace firing operation method that prevents spalling cracks from occurring in the furnace wall bricks, and by preventing wear on the furnace wall bricks, we also prevent wear on the blast furnace shell, which in turn extends the life of the blast furnace. The purpose is to measure.

The method of blast furnace firing operation according to the present invention uses a mathematical model in which the charging conditions before the start of the blast furnace firing operation, the air blowing conditions and the charge conditions after the start of the blast furnace operation are variables. The furnace inner surface temperature is predicted and calculated over time, and the spalling crack generation area, which is predefined based on the furnace inner surface temperature and temperature increase rate of the furnace wall bricks, is avoided by referring to the predicted settlement result. The method is characterized in that an operation plan is created for each element of the mathematical model, and a burning operation is carried out based on the operation plan.

First, the mathematical model used in the present invention will be explained. The mathematical model is based on the following three equations, that is, the basic equation regarding heat: % equation % When ε and εl are the porosity of the packed layer and the liquid retention rate, respectively, Eg:ε(1−εl).

E:1-εeF'/:εε1 'rj: Temperature of j phase ? To: Temperature of h phase v: j-phase superficial column flow velocity h] heat transfer coefficient between cj second phase and j phase a: Representative length Reaction heat and heat loss in Q@j phase 11 t, g: coordinates of time and furnace height Basic equations for reactions: % formula % (2) (1・ξ1:mass fraction of 1 component M = molar weight of formula 11 R□: Reaction rate for 1 formula Basic formula for the law of conservation of mass: %formula% It is possible to simulate unsteady behavior based on .

− +Qj 'j TjΣR, Ml) = y("rj)
-(4) Equations (2) and (3) are both first-order partial differential equations, and since the rising speed vg is fast for gas, a steady equation is sufficient for gas.

Therefore, in the unsteady simulation of a blast furnace, it is sufficient to focus on the descending behavior of the charge and perform the integration of equations (4) and (5) as follows.

”’lTj　za=z, -V8dtj　j　z=z.

-(cT) (ξ1)・-・. -vmd, -(ξ□)2=2゜where, v8: Solids unloading speed Thus, the time-dependent change in the temperature distribution inside the furnace during the firing operation is determined, and therefore the time-dependent change in the internal temperature of the brick furnace is determined. However, this adjustment includes the charging conditions before the start of the burn-in operation (method of charging sleepers, coke, iron ore, and coke into the furnace), as well as the blowing conditions (air amount and temperature) and charging after the start of the burn-in operation. It was found that changing material conditions (charging (ore/coke) ratio) was effective.

On the other hand, as mentioned above, the area where spalling cracks occur in bricks depends on the internal temperature of the brick furnace and its rate of temperature rise, and is predefined as shown in FIG. Therefore, an operation plan is created to avoid the above-mentioned spalling crack generation region by referring to the temporal change in the temperature inside the brick furnace predicted and calculated using the mathematical model, and the firing operation is performed based on the plan. It can prevent spalling cracks from occurring in bricks.

Furthermore, in actual reactor operation, unexpected abnormalities within the reactor may occur, so correcting the predicted values based on the mathematical model during operation for such abnormalities will be more reliable. Fig. 2 schematically shows the method, in which thermocouples 1a, lb, and lc are embedded in the blast furnace brick (it is better to embed thermocouples at two or more points in the thickness direction of the brick at each location), Using this, the internal temperature of the brick furnace is estimated by actually measuring the temperature of the bricks with the thermometers 2a, 2b, and 2c, and the value is compared with the value predicted by the mathematical model obtained by the operation planning system 4. In order to eliminate the deviation, it is preferable that the coefficient correction calculator 3 calculates the correction amount from time to time, and the hot air regulator 5 adjusts the amount of hot air blown from the tuyere 1d, the blown temperature, and the humidity.

Next, examples of the method of the present invention will be described. Figure 3 is based on the method of the present invention.
a) #-i This is the charging condition before the start of the burning operation. The bottom of the furnace below the tuyere (shaded area with broken line) is filled with sleepers, and the area from the morning glory above that to the hearth belly (shaded area) is filled with coke. The upper part is filled with ore, auxiliary raw materials, and coke at the (ore/coke) ratio shown by the dashed line.

(1)) in the figure shows the operating conditions after the start of the burning operation, with time on the horizontal axis and each condition on the vertical axis.
The solid line shows the air flow rate, the broken line shows the air blowing temperature, the chain 1 shows the moisture content, and the two-dot chain line shows the charging (ore/coke) ratio.

Figure 4 is a graph showing the relationship between the internal temperature of the brick furnace and its heating rate (predicted values and measured values) in comparison with the area where spalling cracks occur; (a) 18 m above the ti tuyere;
, (b) is the part 13m above the tuyere, (0) is the part above the tuyere, 5ffi, (d) is 4m above the tuyere.
The shaded area in Figure 0, which shows the area shown in Figure 1, is the area where spalling cracks occur, as in Figure 1, and the solid line shows the internal temperature of the brick furnace and its rise when the firing operation is performed according to the plan shown in Figure 3. The black circles show the predicted values of the temperature-speed relationship, and the actual values when the firing operation was actually carried out according to the plan. The firing operation plan shown in Figure 3 was created so that the relationship between the predicted brick furnace inner surface temperature and its temperature increase rate would avoid the spalling crack occurrence area, and the blast furnace firing operation was actually performed according to the plan. The values also roughly matched the predicted values, and no spalling cracks occurred in the bricks.In this actual operation, we also used the method of correcting during actual furnace operation as shown in Figure 2. As mentioned above, the blast furnace firing operation method according to the present invention includes:
The internal temperature of the brick furnace after the start of the burning operation is predicted and calculated over time using a mathematical model that uses the charging conditions before the start of the burning operation and the blowing conditions and charge conditions after the start of the burning operation as fluctuation factors, and the calculated results are calculated. Since spalling cracks are prevented from occurring in the bricks based on this method, the occurrence of spalling cracks is reliably suppressed, and this has a great effect on improving the life of the blast furnace.

[Brief explanation of drawings]

Figure 1 is a graph showing the area where spalling occurs.
The figure is a schematic diagram showing the method of correction during the firing operation, and Figure 3 (a), (t)) is a graph showing the firing operation plan based on the method of the present invention; Figure 4 (a), (t)) , (
Q) and (d) are graphs showing the relationship between the inner surface temperature of a brick furnace and its temperature increase rate, and the comparison between the subbo + IJ crack occurrence area and -. la, l b, l c ---Thermocouple agent Patent attorney Noboru Kono

Claims (1)

[Claims] 1. Predicting the furnace inner surface temperature of the furnace wall bricks over time after the start of the blast furnace burning operation using a mathematical model that takes into account the charging conditions before the start of the blast furnace burning operation, and the blowing conditions and charge conditions after the start of the blast furnace operation. The operation plan is calculated for each element of the mathematical model in order to avoid the spalling crack occurrence area, which is predefined based on the furnace inner surface temperature and temperature increase rate of the furnace wall bricks, with reference to the predicted calculation results. A blast furnace firing operation method 0 characterized by creating a blast furnace firing operation and carrying out a firing operation based on the operation plan.