KR100389240B1 - Gas density control method of blast furnace bottom - Google Patents

Abstract

The present invention relates to a method for efficiently controlling the gas density at the bottom part in response to an increase in the amount of combustion gas generated in the blast furnace when a large amount of pulverized coal is injected. The aim is to secure stable coal dust injection conditions by minimizing the increase in gas density.

In the present invention, low volatility coal is used to reduce the amount of combustion gas generated during volatile combustion in the furnace, while pure oxygen is supplied together with air in the atmosphere and moisture is blown in the blowing air supplied to the furnace +5 g / Nm ^2. Managing the supply below, increasing the nodal pressure to 2.80kg / cm ² level; In order to increase the combustion gas residence space in the lower part of the furnace, the shape of the fusion zone is formed into the inverted "V" shape, the softening melting temperature is lowered to within 1450 ° C, the amount of secondary raw materials in the furnace is suppressed to within 2% of the iron ore use, and the molten slag generated in the furnace Adjusting the basicity of the level to 1.20, and opening the two exit ports at the same time to perform the rap starting work.

Description

Gas density control method of blast furnace bottom}

The present invention relates to a method for efficiently controlling the gas density in the lower part in response to an increase in the amount of combustion gas generated when a large amount of pulverized coal is blown in a blast furnace. This is to secure stable high pulverized coal injection conditions by minimizing the increase in gas density under the furnace.

In general, as shown in FIG. 1, the pulverized coal blown into the furnace through the pulverized coal blowing lance 13 in the lower part of the blast furnace 10 is subjected to hot air (high temperature air) of 1200 ° C. or higher introduced into the tuyere 14 through a blower pipe. It reacts with oxygen and burns to gasify.

At this time, the gasification of pulverized coal is divided into a temperature rising stage, an ignition stage, a volatile combustion stage, and a fixed carbon combustion stage, as shown in FIG. 2. It will fall at a constant speed.

Therefore, as the amount of pulverized coal blown into the furnace increases, the amount of volatiles entering the furnace also increases proportionately, thus increasing the amount of gas at the bottom of the furnace, which increases the gas density at the bottom of the furnace, which directly affects the pressure rise at the bottom of the furnace. Therefore, the hot air supply pressure (blowing pressure) of the blast furnace 10 also increases, thereby causing a phenomenon in which the in-furnace charges fly upward in the blast furnace 10 (Fludizing, Flooding), thereby preventing a stable blast furnace operation.

Conventional methods for lowering the gas density of the lower part of the furnace include a method of forming a coke (12) layer gas passage in the center of the blast furnace in which a large amount of coke (12) is charged in the center of the blast furnace so that the lower part gas can easily escape to the hearth part. There is a lowering method, and a wind blowing method of lowering the amount of hot air introduced through the lower part tuyere 14 has been used.

However, the conventional method for lowering the furnace gas density has the following problems. First, the method of forming a coke layer gas passage by charging a large amount of coke at the center of the blast furnace has high temperature CO and H ₂ generated in the furnace part. Reducing gases easily escaped through this passage to the hearth, reducing the time for reaction with iron ore in the furnace. Therefore, thermal efficiency and gas reduction rate are reduced by shortening the contact time between the furnace gas and the charges, which ultimately increases fuel costs.

Secondly, the method of lowering the pressure at the top of the blast furnace increases the pressure difference between the lower part and the upper part, and increases the gas volume from the lower part of the lower part to increase the gas flow rate from the lower part to the hearth. As a result, a floating phenomenon in which the charges of the lower part is blown up has occurred, thereby preventing stable blast furnace operation.

Third, the method of lowering the air flow in the blast furnace for lowering the gas density of the furnace lowers the amount of sensible heat flowing into the furnace, reducing the iron ore in the blast furnace. As a result, the pulverized coal combustibility is lowered and the amount of reducing gas in the furnace is also reduced, thereby lowering the blast furnace productivity.

Fourth, in order to maintain the constant moisture content even in the state of rising atmospheric moisture in summer, it consumes a large amount of heat to steam the moisture in the combustion zone in front of the tuye-gu so that it can burn pulverized coal in a short time (0.2 seconds). Temperature management was difficult.

Fifth, since the conventional method only takes measures to reduce the gas density of the lower part of the furnace, the gas is reduced even if the amount of gas remaining in the lower part is not secured. Density increased.

In other words, due to the increase in the ore / coke ratio due to the increase in the amount of pulverized coal, the slag generation amount increased in the lower part of the furnace because the usage ratio between the sintered slag with a large amount of slag and the pellet with the small amount of slag was not increased. This has resulted in a reduction of the area where the combustion gases can stay.

The present invention has been invented to solve this problem in view of the above problems, and its object is to secure stable high pulverized coal injection conditions by minimizing the increase in the bottom gas density caused by the increase in pulverized coal combustion gas when pulverized coal is blown. First, minimization of combustion gas increase through low volatility coal injection, decrease of inert nitrogen gas volume in furnace through increase of oxygen enrichment, decrease of evaporation gas volume of underfloor from lowering of humidity, lowering of gas volume of underfloor due to rise of nominal pressure, etc. This is to reduce the gas density at the bottom of the furnace and to increase the gas reaction time at the bottom of the furnace to improve the blast furnace thermal efficiency and lower the fuel cost.

Another object of the present invention is to secure the lower gas area represented by the reverse V-type softening fusion zone, slag volume reduction in the blast furnace, and the lap outgoing operation, which can increase the amount of gas generated by the increase in the amount of pulverized coal injection. In providing a place.

1 is a schematic view showing a state of blowing coal in a blast furnace

2 is a graph showing changes in the amount of combustion gas generated during pulverized coal combustion

Figure 3 is a conventional furnace gas density control diagram when a large amount of pulverized coal injection

Figure 4 is a furnace gas density control diagram of the present invention when a large amount of pulverized coal injection

※ Explanation of symbols on main parts of drawing ※

10: blast furnace 11: iron ore

12: coke 13: pulverized coal injection lance

14: Fenggu 15: Furnace combustion gas retention zone

16: reverse V type softening zone

The technical configuration of the method for controlling the lower gas density in the blast furnace of the present invention for achieving the above object is as follows.

The present invention uses low volatile coal to reduce the amount of combustion gas generated during volatile combustion in the furnace, while supplying pure oxygen with air in the air and reducing moisture in the blowing air supplied to the furnace to +5 g / Nm ² or less. Managing and supplying, increasing the notch pressure to the level of 2.80 kg / cm ² ;

In order to increase the combustion gas residence space in the lower part of the furnace, the shape of the fusion zone is formed into the inverted "V" shape, the softening melting temperature is lowered to within 1450 ° C, the amount of secondary raw materials in the furnace is suppressed to within 2% of the iron ore use, and the molten slag generated in the furnace Adjusting the basicity of the level to 1.20, and opening the two exit ports at the same time to perform the rap starting work.

In addition, low volatile coal used to reduce the amount of combustion gas generated during combustion of the volatile in the furnace is less than 15% of low volatile coal 60% or more is used, pure oxygen used to reduce the amount of combustion gas generated during the volatile combustion in the furnace. The supply amount is 30 ± 5% of the amount of atmospheric air supplied into the furnace, and the time for opening the two exit ports at the same time and performing the rap start operation is 20 minutes or more.

Referring to the accompanying drawings in the bottom of the blast furnace gas density control method of the present invention having such characteristics as follows.

The present invention is divided into a method of reducing the amount of combustion gas generated at the bottom of the furnace even under a large amount of pulverized coal injection and a method of ensuring the maximum area in which the combustion gas can stay at the bottom of the furnace. As shown in Table 1, there is a functional relationship between the size of gas generating factors such as air flow, oxygen enrichment, humidity, pulverized coal injection, pulverized coal properties, and the size of the area where gas may be present in the lower part of the furnace. .

Table 1

VBG = VB [1.21 + O ₂ Load / (VB × 60) + 22.4 / 1000 {WH ₂ O / 9 + (KPC × PCB) / 100}] VBG (Volume of Bosh Gas): Within the lower part (Bosh) Total gas generation volume of VB (Volume of Blast): Air flow rate of high temperature air (Hot air flow rate: Nm ² / min)

WH ₂ O (Weight of H ₂ O): Humidity (g / Nm ² )

KPC: it generated per unit of coal to be blown gas production _{(% H 2 O / 9 +} % H 2/2 +% H 2/28 + O 2/16)

PCB (Pulverized Coal of Blast): The amount of fine coal blown per blowing amount [(16666 × Pulverized coal injection) / VB]

First, as a method of keeping the combustion gas generation at the bottom of the furnace at a minimum, the use of low volatility coal and the reduction of the blowing amount were adopted to increase the amount of oxygen enrichment, decrease the humidity level, and increase the pressure of the top.

In order to increase the combustion gas retention area (15) at the bottom of the furnace, inverted V-type softening fusion zone (16) formation type distribution control was carried out, slag generation in the blast furnace by adjusting the use ratio of sintered or pellets and the use of low slag volume sintered ore The lowering, Lap taping operation to discharge the melt from the two taping openings for a short time was promoted.

The use of low volatile coal as a method of minimizing the increase in the amount of combustion gas generated serves to lower the gas density of the furnace by lowering the amount of combustion gas which is rapidly increased during volatile combustion. As such, the amount of low volatile coal used to lower the gas density of the lower part uses 60 to 80% of the volatile matter content in the pulverized coal.

The reason for using 60 to 80% of the volatile matter content of 10 ± 5% is that the use of less than the amount of gas in the furnace occurs more than the target value, the use of more than the amount of gas generated in the furnace is less economical.

Increasing the amount of oxygen enrichment increases the oxygen supply even under conditions where the airflow is lowered by substantially replacing nitrogen in the blowing air with oxygen because the oxidizing agent of the pulverized coal and coke combustion reaction is oxygen around the air vent. It serves to lower the gas density of the lower part by lowering the amount of nitrogen gas, which is an inert gas, which accounts for%.

The amount of oxygen, which serves to lower the gas density of the lower part of the furnace, is 30 ± 5% of the amount of air in the air blown into the blast furnace. The reason is that the use of more oxygen generates less gas, but due to the excessive use of oxygen. If the economical efficiency is lowered and less than that is used, there is a problem that the gas generation amount is more than the target value.

In addition, the decrease in humidity level induces a decrease in the amount of gas generated by the evaporation of moisture and at the same time, it minimizes the amount of heat lost from the endothermic reaction caused by the vaporization of moisture in the pulverized coal combustion zone, thereby contributing to ensuring a stable pulverized coal combustion condition.

The crude moisture content decreases, which contributes to the same combustion conditions to typically blown by managing the atmosphere within the + 20g / Nm ² small + 5g / Nm than ² contained in the air, because that is lost from the heat absorbing reaction in accordance with the vaporization of the moisture Minimize calories.

And the increase in top pressure is based on the principle that the volume of gas is inversely proportional to the pressure. The pressure rise in the furnace, which results from the increase in the top pressure, serves to reduce the combustion gas volume at the bottom of the furnace. At this time, the pressure rise in the furnace is 2.80kg / cm ² level.

In addition, the formation of a reverse V-type softening fusion zone is used to increase the area where gas can stay in the furnace side as a measure to expand the combustion gas retention area in the lower part of the furnace. The reduction of the slag amount and the short run of the rap in the short time drove out the melt stored in the bottom of the furnace to the outside of the furnace, thereby lowering the melt retention level in the furnace to increase the retention area of the combustion gas.

As a condition, first, the shape of the fusion zone is formed in the inverted "V" shape through the charge distribution control so that the position of the softening fusion zone where iron ore is reduced-melted in the blast furnace can be moved to the upper side side as much as possible. By lowering the softening melting temperature to within 1450 ℃ to provide a basis for the softening melting zone can be raised.

Second, the slag of sintered ore, which is the main supply factor of slag in the blast furnace, can expand the gas retention space at the lower side of the tuyere by reducing slag generation amount that occupies 60% of the volume of the melt (slag + molten iron) in the bottom of the blast furnace. It reduces the components to less than 15% and suppresses the amount of secondary raw materials (gyuseok, limestone; containing about 90% of slag components) within 2.0% of iron ore consumption.

Third, the basicity of the molten slag produced in the blast furnace is adjusted to 1.20 so that the bottom gas retention area can be expanded through the rapid discharge of slag generated from the bottom of the furnace to improve the fluidity and the slag can easily flow out of the furnace. Lap out work that opens two outlets at the same time should be carried out for more than 20 minutes.

The present invention as described above is as shown in Table 2 when compared with the conventional method.

Table 2

Comparison of gas density control methods in the lower part

division Species The present invention Lower gas generation Coal High Volatility Coal Low volatile coal Air condition Decreased amount of hot air (no increase in oxygen enrichment) Decreased amount of hot air (oxygen enrichment) Pressure Lowering Increase Humidity Fine tune Humidity reduction Increased gas retention zone Slag volume Fine tune Lowering Sintered Light Ratio Fine tune Lowering Sintered ore slag volume Fine tune Lowering Softening zone Fine tune Increase Underfloor Melt Level Fine tune Deterioration (Lap starting work)

As described above, the present invention minimizes combustion gas increase through low volatile coal injection, decreases the amount of inert nitrogen gas in the furnace by increasing the amount of oxygen enrichment, lowers the amount of evaporation gas from the lower part of the furnace by lowering the humidity level, and lower the gas volume by increasing the pressure of the furnace. The lowering of the gas density at the lower part by lowering, etc., induces an increase in gas reaction time at the lower part, thereby improving thermal efficiency in the blast furnace and lowering fuel costs.

In addition, the present invention provides a place for absorbing the gas generation increase due to the increase in the amount of pulverized coal blown by the method of securing the lower part gas area, which is represented by securing a reverse V-type softening fusion zone, slag volume reduction in the blast furnace, and lap outing work. It is effective.

Claims (4)

The low volatile coal is used to reduce the amount of combustion gas generated in the combustion of volatile gas in the furnace, and pure oxygen is supplied together with the air in the atmosphere, and the moisture is controlled to +5 g / Nm ² or less in the blowing air supplied to the furnace. Increasing the stationary pressure to a level of 2.80 kg / cm ² ; In order to increase the combustion gas residence space in the lower part of the furnace, the shape of the fusion zone is formed into the inverted "V" shape, the softening melting temperature is lowered to within 1450 ° C, the amount of secondary raw materials in the furnace is suppressed to within 2% of the iron ore use, and the molten slag generated in the furnace Adjusting the basicity of the level to 1.20 level and opening the two outlets at the same time to perform the lab outgoing; lower gas density control method in the blast furnace, characterized in that consisting of. The method according to claim 1, wherein the low volatile coal used for lowering the amount of combustion gas generated during combustion of the volatile in the furnace is used by using 60% or more of low volatile coal of 10% or less. The method of claim 1, wherein the pure oxygen supply amount used to reduce the amount of combustion gas generated during volatile combustion in the furnace is 30 ± 5% of the amount of atmospheric air supplied into the furnace. 2. The method according to claim 1, wherein the opening of the two exit ports at the same time and the time for the rap starting work are 20 minutes or more.