KR19980044912A - Theoretical combustion temperature calculation method of combustion zone in blast furnace coal injection operation - Google Patents

Abstract

The present invention relates to a method for calculating the theoretical combustion temperature of the combustion zone in the pulverized coal blowing operation in the blast furnace, the step of inputting the thermal parameters and blast furnace operating conditions,

It consists of establishing the mass balance for the reaction system and the production system, and calculating the enthalpy in the combustion zone to calculate the theoretical combustion temperature of the combustion zone when the pulverized coal is blown.

Description

Theoretical combustion temperature calculation method of combustion zone in blast furnace coal injection operation

The present invention relates to a method for calculating the theoretical combustion temperature of the combustion zone during the pulverized coal blowing operation in the blast furnace, comprising the steps of: inputting thermodynamic data and blast furnace operating conditions;

It consists of establishing a mass balance for the reaction system and the production system, and calculating the enthalpy in the combustion zone to calculate the theoretical combustion temperature of the combustion zone when blowing pulverized coal.

Conventional blast furnace combustion zone is a high temperature blowing into the furnace through the air vents, blowing evaporation moisture, oxygen blown for the oxygen incubation operation, and the pulverized coal causes a combustion reaction, CO and hydrogen and nitrogen required to reduce the heat and iron ore required for operation It is a reaction zone to produce.

1 is a schematic diagram schematically showing a combustion zone of a blast furnace.

The temperature of the combustion reaction in these combustion zones is an important index for determining the thermal state of the blast furnace in the blast furnace operation and requires thorough management for smooth blast furnace operation.

However, since it is difficult to directly measure the temperature of the furnace, either indirectly estimates the furnace temperature or theoretically calculate the combustion temperature (see The Iron Blast Furnace Theory and Practice, JGPeaceu and WG Davenport). ).

The theoretical calculation of the combustion temperature is derived by treating the combustion zone as an insulator with no heat loss to the surroundings and by setting up the mass balance and the heat balance for the combustion reaction.

The theoretical combustion temperature equation of the representative combustion zone currently used in the blast furnace is as follows.

Tf (° C) = 1,559 + 0.839TB-6.003WH20-3.0PCB + 4,973VO2 ------ (1)

From here to be.

In the pulverized coal injection operation, the blown coal species is selected by taking into account various coal types in consideration of supply and demand problems and cost problems.

Table 1 is a table of the analysis of the representative coal used for pulverized coal blowing.

TABLE 1

Table of Elements of Pulverized Coal

When the theoretical combustion temperature of the combustion zone is calculated according to the conventional method, the blowing temperature, the blowing amount, the blowing moisture amount, the oxygen load and the pulverized coal blowing amount are constant and the coal type to be blown can be determined from Equation (1). As shown in FIG. 3, the pulverized coal affects the theoretical combustion temperature, so the theoretical combustion temperature was the same even if the pulverized coal species were injected as shown in FIG. 3.

However, as shown in Table 1, since the composition and calorific value of coal are different depending on the type of coal, the theoretical combustion temperature is different depending on the type of coal injected, even if the same amount is injected.

However, in the theoretical combustion temperature calculation method according to the conventional method, it is not possible to consider the pulverized coal of these different coal species.

On the other hand, in the pulverized coal blowing operation, increasing the coal pulverized coal decreases the theoretical combustion temperature, thereby reducing the heat supplied to the blast furnace.

When the theoretical combustion temperature is calculated by the conventional method, even if the blown coal species is different, the theoretical combustion temperature is calculated. Therefore, proper thermal compensation cannot be performed.

Therefore, the theoretical combustion temperature calculation method that can accurately estimate the change of theoretical combustion temperature brought about by the change of coal type is needed for the actual heat compensation when the coal type is different.

In order to simplify the calculation, the theoretical combustion temperature calculation method according to the conventional method assumes that the enthalpy of the material participating in the reaction is constant regardless of temperature, and the operation data of each blast furnace is substituted into the equation in the middle of the derivation process. Correlation was obtained and expressed by linear equation.

Equation (1) is a formula expressed by linear equation.

However, the conventional method of calculating the theoretical combustion temperature using such a linear equation is useful for rapid calculation, but has a disadvantage in that it cannot accommodate a variety of operating conditions.

In particular, even if the coal type of pulverized coal is changed, the previous method is calculated to have the same theoretical combustion temperature when the pulverized coal is blown in the same amount.

The present invention has been invented to solve the above problems in consideration of the above problems, the theoretical combustion temperature can be calculated according to the type of pulverized coal by calculating the theoretical combustion temperature, by using this to effectively analyze the blast furnace operation and appropriate thermal compensation The purpose is to be able to grasp the degree of and to ensure stable operation.

Features of the present invention having such an object include the steps of: inputting bloating data and blast furnace operating conditions;

Establishing a mass balance for the reaction system and the production system;

It consists of calculating the enthalpy in the combustion zone by calculating the theoretical combustion temperature of the combustion zone when blowing pulverized coal.

1 is a schematic view of a combustion table

2 is a flowchart of a program for calculating the theoretical combustion temperature

Figure 3 is a graph of the theoretical combustion temperature change calculated by the conventional method when the amount of fine coal injection

Figure 4 is a graph of the theoretical combustion temperature change calculated by the method of the present invention when the amount of fine coal injection is increased

5 is a graph of the decrease in the theoretical combustion temperature when increasing the amount of fine coal injection;

6 is a graph of theoretical combustion temperature and lower ventilation index.

7 is a graph of the theoretical combustion temperature and the average temperature of the S1 stage

The enthalpy of the present invention does not assume that it is a constant, it is a function of temperature that changes with temperature, and the theoretical combustion temperature is calculated by calculating a system of equations by setting up a system of equations without simplifying the induction process. Even in the case of different coal types, the same blowing amount solves the problem of calculating the same theoretical combustion temperature.

The theoretical combustion temperature in the combustion zone is as follows.

As shown in FIG. 1, the materials entering the combustion zone include blowing air, blowing moisture, oxygen supplied for an oxygen load operation, and pulverized coal blown during a pulverized coal blowing operation. These reactants are converted into CO, H ₂ and N ₂ gases by the following combustion reactions in the combustion zone.

O _{2 (blowing air, oxygen enrichment)} + 2C _{(coke, pulverized coal)} = 2CO (2)

H ₂ O _{(blowing moisture)} + C _{(coke, pulverized coal)} = H ₂ + CO (3)

N _{2 (in air)} = N ₂ (4)

H _{2 (in pulverized coal)} = H ₂ (5)

The theoretical combustion temperature is calculated by the method according to the present invention as follows.

The first step in finding the theoretical combustion temperature is to read the thermodynamic data of the materials involved in the reaction.

Table 2 below is the thermodynamic data of the materials required for the calculation of the theoretical combustion temperature. In Table 2, a, b, and c are coefficients of heat capacity of the material.

Cp is the heat capacity of the isostatic reaction ΔH ₂₉₈ is the standard production enthalpy of the material at ₂₉₈ K at 1 atmosphere and is in cal.

TABLE 2

Thermodynamic data

See: O. Kubaschewski, C.B.Alcock; Metallurgical Thermochemistry 5th Pergamon Press PP340-356

The second step in calculating the theoretical combustion temperature is to read the operating conditions. The operating conditions required for the calculation of theoretical combustion temperature are the blowing amount, blowing temperature, blowing moisture, oxygen load, and the amount of pulverized coal blown and blown pulverized coal.

The third step in calculating the theoretical combustion temperature is to obtain the mass balance of the combustion reaction in the combustion zone. The mass balance of the combustion reaction is derived from the fact that the mole of the reaction system reactant and the mole of the product of the product system must be equal. When calculating the mass balance, for the convenience of calculation, the amount of the mass participating in the reaction is calculated based on the unit of 1kgmol-O based on oxygen in the blowing air.

The reactants of the reaction system participating in the combustion reaction are oxygen during blowing, nitrogen during blowing, oxygen from the oxygen load, blowing moisture, blown coal and carbon in the burning coke.

In order to calculate the mass balance of the combustion zone, the amount of material in the reaction system is calculated based on 1kg / mole of oxygen in the air as follows.

(A) Oxygen volume during blowing (XO2) = 1 [kgmol-O] (6)

The amount of oxygen in the blow is 1 kg mol-O as a standard of calculation.

In the following formula, the oxygen amount during blowing is expressed as XO2.

B) Nitrogen content during blowing (7)

The amount of nitrogen in the blow is determined using the composition ratio of air when the amount of oxygen is 1 kg / mol-O.

In the following formula, the nitrogen content during blowing is expressed as XN2.

C) Oxygen amount by oxygen load (OXY)

Here, the oxygen loading rate is calculated as follows.

The amount of oxygen due to the oxygen load is expressed as the oxygen load ratio by adding the oxygen contained in the air during the entire blowing and the oxygen loaded oxygen under the operating conditions, so that the amount of purely oxygen loaded oxygen is calculated by the above equation (8).

In the following equation, the oxygen amount due to the oxygen load is expressed as OXY.

D) Blowing moisture content (WET)

Blowing moisture content is calculated by the formula (10) because the unit value (g / N ㎥) as the amount of moisture (moisture) contained in the blowing air.

In the following formula, the blowing moisture amount is expressed as WET.

E) fine coal injection (XFA)

The pulverized coal injection is expressed by the equation (11) because it is expressed as the blowing amount per unit production charterage under the operating conditions.

In the following formula, the pulverized coal injection amount is represented by XFA.

F) Carbon in the burned coke (XCC)

= (XO2 + WET + OXY)-(carbon in pulverized coal) (12)

Carbon in the coke required for combustion is the amount of carbon excluding carbon supplied by pulverized coal in the carbon required to generate CO gas by reacting with oxygen in the air, blowing moisture, and oxygen by the oxygen load.

Carbon, oxygen, hydrogen and nitrogen in the pulverized coal blown are calculated by the formulas (13), (14), (15) and (16) using the component analysis table in Table 1 above.

Carbon in the coke burned by the following formula is represented by XCC.

The material of the reaction system is changed into three types of CO gas, H ₂ gas and N ₂ gas by the combustion reaction of the combustion zone. The amount of three substances produced is calculated on the basis of 1kgmole-O of oxygen in the air as follows.

A) CO gas amount (YCO)

= XO2 + (WET) + (OXY × 2) + (Oxygen in Pulverized Coal) (17)

CO gas is produced by the combustion of oxygen in the air, blowing moisture, oxygen loaded oxygen and oxygen in pulverized coal.

The amount of CO gas generated is 1 mole of oxygen when 1 mole of oxygen is generated. Since the unit of oxygen-loaded oxygen is kgmol-O ₂ / kgmol-O, the CO gas generates twice the amount of oxygen-loaded oxygen. In the following equation, the amount of CO gas in the production system is expressed as YCO.

I) H ₂ gas (YH2)

= (Hydrogen in Blowing Air) + (Hydrogen in Pulverized Coal) (18)

The H ₂ gas does not react with hydrogen during blowing and hydrogen in pulverized coal, and is included in the generated gas as it is.

In the following formula, the amount of H ₂ gas is expressed as YH ₂ .

C) N ₂ gas amount is (YN2)

= (Nitrogen in blowing) + (nitrogen in pulverized coal) (19)

N ₂ gas does not change by combustion reaction, so the amount of reaction system and the amount of production system are the same. The source of N ₂ gas is nitrogen in blowing and nitrogen in pulverized coal.

In the following formula, the N ₂ gas amount is expressed as YN ₂ .

The theoretical combustion temperature is the fourth step to find the reaction system enthalpy in the combustion zone.

Enthalpy H _input of a reaction system can be represented as following Formula (20).

H _input = H _{O2, (air)} + H _{O2, (oxygen enrichment)} + H _{H2O, (blowing moisture)} + H _{N2, (air)} + H _{C, (pulverized coal)} + H _{C, (coke)} (20)

In the above formula, H _{O, (air)} is the enthalpy of oxygen during blowing, H _{O, (oxygen enrichment)} represents the enthalpy of oxygen supplied by the oxygen load.

And H _{N, (air)} represents the enthalpy of nitrogen in the blowing, H _{C, (pulverized coal)} represents the enthalpy of the pulverized coal blown, and H _{C, (coke)} represents the enthalpy of carbon in the _coke burned.

If the enthalpy of the substance of the reaction system is shown in detail, it can be represented by the following formula (21) to formula (26).

In the above formula, T _B represents the blowing temperature.

Reaction System Enthalpy In the above equations, the enthalpy of coke is a function of theoretical combustion temperature. Therefore, the enthalpy of the reaction system can be obtained if the air flow rate, the blowing temperature, the blowing moisture, the oxygen load, the pulverized coal injection and the pulverized coal powder are given as operating conditions except for the enthalpy of the coke.

Therefore, the enthalpy of the reaction system can be expressed simply as follows.

H _intput = H ₁ + H _coke (27)

H ₁ is the sum of the enthalpy remaining in the enthalpy of the reaction system except for the enthalpy of the coke.

The final step to find the theoretical combustion temperature of the combustion zone is to find the temperature that satisfies the enthalpy resin by using the formula derived so far. Satisfying the enthalpy resin is that the sum of the enthalpy of the reaction system and the sum of the enthalpy of the production system is the same.

That is, the enthalpy resin in a combustion zone is as follows.

H _intput = H _output (29)

Where H _input is the enthalpy of the reaction system and H _output is the enthalpy of the production system.

H _input = is represented by the following formula (27) and (28).

1) H _input = H ₁ + H _coke (27)

(2) H _output

In order to calculate the enthalpy resin of the combustion zone, the enthalpy of the production system must be calculated.

The enthalpy H _output of the generation system is

H _output = H _CO + H _H2 + H _N2 (30)

The products of the production system are three kinds of CO gas, H ₂ gas and N ₂ , and each enthalpy is represented by the following formulas (31), (32) and (33).

In the above formula, Tf is the theoretical combustion degree. The enthalpy H _output of the reaction system is expressed as follows by substituting Eqs. (31), (32) and (33) into Eq. (30).

Therefore, when the enthalpy resin of a combustion zone substitutes Formula (27) and Formula (30) in said Formula (29), it is as follows.

H ₁ + H _coke = H _CO + H _H2 + H _N2 (35)

Substituting Eq. (28) and Eq. (34) into Eq. (35), the final equation of the enthalpy equation for calculating the theoretical combustion temperature is given by Eq. (36).

As can be seen from equation (36), the enthalpy of the production system is a function of the theoretical combustion temperature. Therefore, the temperature which satisfy | fills said Formula (36) which is an enthalpy resin formula of a combustion zone is a theoretical combustion degree.

As described above, the theoretical combustion temperature can be obtained by setting the mass balance and the enthalpy balance in the combustion zone. It can be calculated easily using BASIC or FORTRAIN, which is a language for computing, and FIG. 2 is a flowchart of a program for calculating theoretical combustion temperature using such a language.

Example

FIG. 3 shows the change in theoretical combustion temperature calculated by the conventional method when the blowing amount of pulverized coal of different types is increased to 200 kg / t-p in a blast furnace having an internal volume of 3800 m 3.

The pulverized coal used was calculated for four coals having the components shown in Table 1 above. At this time, the other operating conditions were fixed at a constant rate, the blowing amount was 6324 Nm 3 / min, the temperature blowing temperature was 1107 ℃, the blowing moisture was 23g / Nm, the oxygen load was 11646Nm / Hr. As shown in the figure, the theoretical combustion temperature calculated by the conventional method shows the same theoretical combustion temperature regardless of the carbon type.

4 is a change in the theoretical combustion temperature at the time of increasing the pulverized coal injection amount calculated according to the method of the present invention for the above conditions.

When the pulverized coal injection amount is 0, the calculated theoretical combustion temperature is calculated to be about 80 ° C. lower than the conventional theoretical combustion temperature calculation method.

The difference in the calculated temperature is caused by the conventional method because the material is treated as enthalpy as a constant independent of temperature and linearized for simplicity.

When the theoretical combustion temperature is calculated according to the present invention as shown in the figure, the theoretical combustion temperature varies depending on the coal type charged.

When the blowing amount is 100 kg / t-p, the theoretical combustion temperature when the blowing coal type is D is 2106 ° C, which is about 85 ° C lower than that of the A coal.

The difference in theoretical combustion temperature was increased at 150 kg / t-p, so that coal type D was about 100 ° C lower than that of coal A, and the difference was about 150 ° C at 200 kg / t-p.

5 is a change in the theoretical combustion temperature when the amount of fine coal injection is increased by 10 kg / t-p at an arbitrary injection amount.

In the calculation by the conventional method, the amount of fine coal injection is increased by 10 kg / t-p irrespective of the amount, and the theoretical combustion temperature decreases by approximately 29 ° C.

When the theoretical combustion temperature is calculated by the method of the present invention, the amount of decrease in the theoretical combustion temperature varies depending on the type of coal. In the case where the blowing amount is small, the blowing amount is a large decrease in theoretical combustion temperature when the increase is 10 kg / t-p, but in the case of a high blowing amount, the reduction in the theoretical combustion temperature is smaller.

6 is a view showing the relationship between the theoretical combustion temperature and the lower ventilator blast furnace operation index.

The lower airflow index is the main index to know the air permeability of the bottom of the blast furnace.

(37)

Here, the SPI stage pressure is the temperature of the pressure gauge located at GL + 17485 mm of the blast furnace, and the amount of bosh gas is defined as the amount of gas generated in the combustion zone.

The lower ventilation index increases the theoretical combustion temperature, so that the combustion efficiency of the pulverized coal blown is increased, so that the amount of unburned powder is deposited in the furnace, so that the ventilation is good.

Therefore, theoretical combustion temperature and lower ventilation index will be positively correlated.

As shown in the figure, the correlation between the theoretical combustion temperature calculated by the conventional method and the lower ventilation index has no correlation as 0.09, but the correlation between the theoretical combustion temperature calculated by the method according to the present invention and the lower K appears as 0.71. .

7 is a graph showing the correlation between the theoretical combustion temperature and the average temperature of the S1 stage, which is a thermometer installed under the furnace body of the blast furnace.

The position of the S1 stage is GL + 17798mm, which shows the furnace temperature at the position closest to the tuyere with the position GL + 14600mm.

When the theoretical combustion temperature rises, the temperature of the S1 stage rises. Therefore, the theoretical combustion temperature and the temperature of the S1 stage show a positive correlation. The correlation between the theoretical combustion temperature calculated by the method of the present invention and the average temperature of the S1 stage is 0.66, which shows a correlation higher than 0.22 which is the correlation between the theoretical combustion temperature calculated by the conventional method and the average temperature of the S1 stage.

The theoretical combustion temperature of the combustion zone of the present invention as described above is the theoretical maximum temperature that can be reached by the combustion reaction in the combustion zone is an index that can know the thermal state in the blast furnace. Therefore, an appropriate level of thermal state must be maintained for stable and smooth operation. Increasing the amount of pulverized coal blown decreases the theoretical combustion temperature.

Increasing the amount of blowing becomes thermally low, so heat must be compensated in an appropriate manner. In order to determine the degree of thermal compensation, it is important to accurately calculate the combustion temperature. When various types of coal are used as pulverized coal blowing coal, the calculation of theoretical combustion temperature according to the conventional method is calculated at the same theoretical combustion temperature even if the coal type is changed.

By calculating the theoretical combustion temperature by the method according to the present invention as described above, it is possible to calculate the correct theoretical combustion temperature according to the type of pulverized coal, and it is possible to effectively analyze the blast furnace operation, to grasp the appropriate degree of thermal compensation, and to operate stable There is an effect that can be done.

Claims (1)

Inputting the following table of materials participating in the reaction, ie thermodynamic data, Table of Elements of Pulverized Coal Inputting the blowing conditions, the blowing temperature, the blowing moisture, the oxygen load, the pulverized coal injection amount and the pulverized coal pulverization component which are operating conditions together with the thermodynamic data; Oxygen enrichment rate determined by the amount of oxygen during blowing (XO ₂ ), formula (6), the amount of nitrogen during blowing (XO ₂ ) formula (7), oxygen amount by oxygen enrichment (OXY) formula (8) And carbon in the burned coke (XCC) calculated by the blowing moisture content (WET) equation (10) and the pulverized coal injection amount (XFA) equation (11). = (XO2 + WET + OXY)-(carbon in pulverized coal) (12) And carbon, oxygen, hydrogen and nitrogen in the pulverized coal blown into the reaction system obtained by formulas (13), (14), (15) and (16) using the component classification table of the above table; Establishing a mass balance for the generation system of the Co gas amount (YCO) equation (17), the H ₂ gas amount (YH2) equation (18), and the N ₂ gas amount (YN2) equation (19); Equations (20) to (35) for calculating the enthalpy in the combustion zone are derived and finally the enthalpy equation Method for calculating the theoretical combustion temperature of the combustion zone in the blast furnace coal injection operation, characterized in that consisting of a step consisting of.