JPH11117009A - Blast furnace operation method - Google Patents

Abstract

(57) [Summary] [Problem] To suppress the heat fluctuation in the blast furnace even when the coal type or coke ratio is changed, and to prevent [Si]
To provide a blast furnace operating method capable of suppressing the concentration. SOLUTION: This is a blast furnace operating method in which pulverized coal is blown together with hot air from a blowing tuyere. When a plurality of pulverized coals of different coal types are injected into a blast furnace or when the amount of coke per ton of pig iron (hereinafter referred to as “coke ratio”) is changed, the components of the Find the amount of heat used in Then, the amount of pulverized coal injected and the amount of oxygen enrichment are changed so that the calorific value in the blast furnace before and after the change of the coal type and the coke ratio becomes equal. [Effect] A rise in [Si] in hot metal can be suppressed by suppressing furnace heat fluctuation.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method of operating a blast furnace in which pulverized coal is blown together with hot air from a blowing tuyere, in the case of using a plurality of types of coal, particularly when changing the type of coal or changing the coke ratio. It relates to a blast furnace operating method.

[0002]

2. Description of the Related Art Generally, in the operation of pulverized coal injection into a blast furnace, the calorific value of coal is measured by a calorimeter or Dulo.
The heat exchange rate was calculated from the calorific value calculated by the ng formula, and the amount of pulverized coal injected was determined.However, since carbon and hydrogen were not completely burned in the blast furnace, they were actually used in the blast furnace. The calorific value is lower than these calorific values, and if the conventional calorific value is used, the heat exchange rate cannot be accurately expressed.

Conventionally, to solve such a problem, for example, Japanese Patent Application Laid-Open No. Hei 6-212217 discloses a method in which the calorific value and volatile content of pulverized coal are used as indices, and the relative replacement ratio of pulverized coal and relative To increase blast furnace gas generation,
A method of mixing and pulverizing pulverized coal has been proposed.

In Japanese Patent Application Laid-Open No. 6-240320, a difference in the amount of oxygen in each coal is determined in advance, and the amount of oxygen enrichment corresponding to the difference in the amount of oxygen is increased or decreased based on the difference in the amount of oxygen. A pulverized coal injection operation method has been proposed in which the production rate of pig iron is kept constant.

[0005]

However, in any of the above-described methods, an accurate heat exchange rate that is appropriate for the reaction in the blast furnace cannot be expressed in any case. When the ratio changes, it causes heat fluctuation,
Accordingly, there is a problem that the [Si] concentration in the hot metal increases.

The present invention has been made in view of the above-mentioned conventional problems, and is intended for use in the case where a plurality of types of coal are used as pulverized coal blown from a blowing tuyere, especially when changing the type of coal. It is an object of the present invention to provide a blast furnace operating method capable of suppressing the heat fluctuation in the blast furnace even when the coke ratio is changed and suppressing the [Si] concentration in the hot metal.

[0007]

According to the method for injecting pulverized coal into a blast furnace according to the present invention, the amount of heat used in the blast furnace is determined in advance from the components of the pulverized coal, and the amount of coal used in the blast furnace before and after the change in the coal type and coke ratio is determined. The amount of pulverized coal injected and the amount of oxygen enrichment are changed so that the calorific value in the furnace becomes equal to suppress the furnace heat fluctuation. By doing so, it is possible to suppress an increase in [Si] in the hot metal when a plurality of types of coal are used, particularly when the type of coal is changed or the coke ratio is changed.

[0008]

DETAILED DESCRIPTION OF THE INVENTION The present inventors have invented a method for accurately estimating the heat exchange rate in a blast furnace by the method described below. First, the carbon monoxide utilization rate [ηCO], the hydrogen utilization rate [ηH ₂ ], and the heat flow ratio [HFR = (solid heat capacity) / (gas heat capacity)] in the blast furnace are given as initial values, and the effective heat generation in the blast furnace is given. The quantity [Qef] is determined from the coke and coal composition by the following equation (1).

[0009]

[Number 1] Qef = (Q1 + Q2 × ηCO ) × (% C) ÷ 100 + Q3 × {(% H) × ηH 2 - (% O) ÷ 8} ÷ 100 (kcal / kg) , however, C + (1/2 ) 0 ₂ = CO + Q1 CO + (1/2) 0 ₂ = CO ₂ + Q2 H ₂ + (1/2) 0 ₂ = H ₂ O + Q3 Q1: Heat value per unit mass of C Q2: In CO Calorific value per unit mass of C in Q3: Calorific value per unit mass of H (% C): Carbon concentration in coke and coal (% H): Hydrogen concentration in coke and coal (% O): Coke and Carbon concentration in coal

Next, the effective calorific value of coke and pulverized coal after changing the brand and coke ratio [(Qef, COKE), (Qef, PC)]
, And the heat loss of the furnace body and the top (the sensible heat of the top gas) [Heat L
oss / R], the coke ratio [C / R] and the pulverized coal ratio [PC / R] are set as follows so that the sum of the effective heating value and the heat loss before changing the brand and coke ratio is equal. Determined by Equation 2.

[0011]

[Equation 2] (C / R) × (Qef, COKE) + (PC / R) × (Qef, PC) − (Heat
(Loss) / R = (C / R ') × (Qef', COKE) + (PC / R ') × (Qef', PC)
− (Heat Loss) / R 'where C / R', PC / R ', (Heat Loss) / R' and Qef 'are the coal brand, coke ratio before coke ratio change, pulverized coal ratio, furnace body It is the heat loss and effective calorific value of the furnace top (the sensible heat of the furnace gas).

Here, the heat loss [Heat Loss / R] between the furnace body and the furnace top (furnace gas sensible heat component) is calculated by the following equation (3) from the heat flow ratio HFR.
Ask by.

[0013]

[Equation 3] (Heat Loss) / R = HFR × a + b (kg / pt) where a is a coefficient obtained from actual operating conditions b: A coefficient obtained from actual operating conditions

Then, the carbon ratio [Carbon / R] and the hydrogen ratio [Hydroge] are determined from the coke ratio, the pulverized coal ratio, and the humidity control component [BM / R] during blowing.
n / R] is calculated by the following Expressions 4 and 5.

[0015]

[Equation 4] Carbon / R = (C / R) × (% C) inCOKE ÷ 100 + (PC / R) ×
(% C) inPC ÷ 100 (kg / pt)

[0016]

[Equation 5] Hydrogen / R = (C / R) × (% H) inCOKE ÷ 100 + (PC / R)
× (% H) inPC ÷ 100 + (BM / R) × 2 ÷ 18 ÷ 1000 (kg / pt)

From Equations 4 and 5, ηCO and ηH ₂ are newly obtained by Equations 6 and 7 below.

[0018]

ΗCO = c + d × (Carbon / R) + e × HFR where c: coefficient obtained from actual operating conditions d: coefficient obtained from actual operating conditions e: coefficient obtained from actual operating conditions

[0019]

ΗH ₂ = f + g × (Hydrogen / R) + h × HFR where f: coefficient obtained under actual operating conditions g: coefficient obtained under actual operating conditions h: coefficient obtained under actual operating conditions

Next, the oxygen amount [Wo] in the furnace top gas (CO, CO ₂ )
Is calculated by the following equation (8).

[0021]

[Equation 8] Wo = 4 ÷ 3 × (1 + ηCO) × ｛(Carbon / R) − (Dust / R) × (% C) inDust ÷ 100 −1000 × (% C) inPig ÷ 100 kg (kg / pt) However, Dust / R: Basic unit of dust discharged from the furnace top (kg /
pt) (% C) inDust: Carbon concentration in dust (% C) inPig: Carbon concentration in hot metal

Further, of the oxygen in the furnace top gas, the amount of oxygen (Oxygen / R) from the blast is calculated by the following equation (9).

[0023]

(Equation 9) Oxygen / R = ｛Wo−OinOre−OinPC × (1−ηH ₂ )
｝ ÷ 32 × 22.4−O ₂ / R where OinOre: Oxygen derived from ore (k
g / pt) OinPC: PC-derived oxygen _{(kg / pt) O 2 /} R: oxygen consumption rate (kg / pt)

Based on the blowing conditions (blowing amount, oxygen amount, humidity control amount), the basic unit of air blowing (BV / R) and the basic unit of furnace gas generation (BG /
R) is calculated from Equations 10 and 11 below.

[0025]

BV / R = (Oxygen / R) ÷ (% O ₂ ) inBV (Nm ³ / pt) where (% O ₂ ) inBV is the volume ratio of oxygen in the blast air

[0026]

BG / R = (BV / R) × (% N ₂ ) inBV + (PC / R) × (% N) inPC ÷ 28 × 22.4 + (Carbon / R) ÷ 12 × 22.4 + (Hydrogen / R) ÷ 12 × 22.4 (Nm ³ / pt) where (% N ₂ ) inBV: Volume ratio of nitrogen in blast air
(% N) inPC: Nitrogen concentration in pulverized coal

Finally, the heat flow ratio HFR is calculated again from the ore ratio (Ore / R), the coke ratio, and the unit gas generation rate by the following equation (12).

[0028]

HFR = ｛(C / R) × i + (Ore / R) × j｝ / (BG / R ×
k) where i to k are constant values

[0029] When the heat flow ratio HFR by the equation 12 is newly determined, newly determined ItaCO, the ItaH ₂ from Equation 6 described above. Then, the obtained ItaCO, the the ItaH ₂ Equation 1
And the convergence calculation is performed until the effective calorific value of coke and pulverized coal obtained by equation 2 becomes equal before and after the change of the coal type and coke ratio. The amount of pulverized coal to be injected and the amount of oxygen enrichment are determined based on the obtained amount.

As a result of the investigation by the present inventors, there is a correlation between the hot metal temperature and the [Si] concentration in the hot metal, as shown in FIG. 1. When the hot metal temperature rises by 10 ° C., the [Si] ] It was found that the concentration increased by 0.06%.

Therefore, according to the present invention as described above,
Convergence calculation is performed until the effective calorific value of coke and pulverized coal becomes equal before and after the change of coal type and coke ratio.
Since the C / R is calculated and the pulverized coal injection amount and oxygen enrichment amount are adjusted based on this, heat fluctuations can be suppressed even when the coal type is changed or the coke ratio is changed, and hot metal accompanying the heat fluctuations can be suppressed. It is possible to suppress an increase in the concentration of [Si] therein.

[0032]

EXAMPLES The results of experiments conducted to confirm the effects of the present invention will be described below. In a blast furnace with an inner volume of 2700 m ³ , pulverized coal B
Figure 3 shows the transition of the hot metal temperature and the [Si] concentration in the hot metal when the pulverized coal injection rate was changed at the conventional replacement rate based on the total calorific value when the brand was changed to It is.

In the conventional method, the hot metal temperature of the base is set to 1510
Although it was operating at ℃, the hot metal temperature began to fall at the time of since the injection amount of pulverized coal was underestimated.
Therefore, when the humidity was lowered, and the increase in the pulverized coal injection amount and the decrease in the oxygen injection amount were responded to, the hot metal temperature rapidly increased to 1540 ° C as shown in FIG. The concentration of [Si] rose 0.18% at a stretch.

On the other hand, when the amount of pulverized coal injected was adjusted using the effective calorific value in the blast furnace in the present invention (base hot metal temperature 1510 ° C., [Si] concentration in hot metal: 0.48% As shown in FIG. 2, the fluctuation of the hot metal temperature was less than 20 ° C., and the rise of the [Si] concentration in the hot metal could be suppressed to about 0.06% or less (standard deviation 0.062). Also, when the pulverized coal injection amount is changed due to the change in the coke ratio, the same effect can be obtained by applying the method of the present invention.

[0035]

[Table 1]

[0036]

As described above, according to the present invention,
When changing the coal type or coke ratio,
By changing the amount of pulverized coal injected and the amount of oxygen enrichment based on the amount of heat effectively used in the blast furnace, heat fluctuations in the blast furnace can be suppressed, and fluctuations in the [Si] concentration in the hot metal can be suppressed. I can do it.

[Brief description of the drawings]

FIG. 1 is a diagram showing a relationship between hot metal temperature and [Si] concentration in hot metal.

FIG. 2 is a diagram showing changes in the hot metal temperature and the [Si] concentration in the hot metal when the method of the present invention is applied when changing the coal brand.

FIG. 3 is a diagram showing transitions of hot metal temperature and [Si] concentration in hot metal when a conventional method is applied when changing coal brands.

Claims (1)

[Claims] In a blast furnace operating method in which pulverized coal is blown together with hot air from a blowing tuyere, when a plurality of pulverized coals of different coal types are blown into a blast furnace, or the amount of coke per ton of pig iron (hereinafter referred to as “coke Ratio).), The amount of heat used in the blast furnace is determined in advance from the components of the pulverized coal, and the calorific value in the blast furnace before and after the change in the coal type and coke ratio is equalized. A blast furnace operating method characterized by changing the amount of pulverized coal injected and the amount of oxygen enrichment to suppress furnace heat fluctuations and suppress the rise of [Si] in hot metal.