JP5392229B2 - Combustion method of low calorific value gas by combustion burner - Google Patents

Description

  The present invention relates to a combustion method for stably burning a low calorific gas such as a blast furnace gas produced as a by-product in a steel production process by a combustion burner, and a blast furnace for carrying out a stable low reducing material ratio operation. It relates to the operation method.

In recent years, global warming due to an increase in carbon dioxide emissions has become a problem, and the suppression of emitted CO ₂ is an important issue even in the steel industry. In response to this, in recent blast furnace operations, low-reducing material ratio (low RAR) operations are being strongly promoted.
In blast furnace operation, reducing gas such as CO generated by the combustion of coke at the blast furnace tuyere is used for the reduction of iron ore. RAR (Reduction Agent Ratio: This leads to a reduction in the total amount of injected fuel and coke charged from the top of the furnace.
Originally, the blast furnace gas is a low calorific value gas. However, when the RAR is reduced as described above, the calorific value of the generated blast furnace gas is further reduced. In the steel manufacturing process, as part of exhaust heat recovery, sensible heat of red hot coke discharged from a coke oven is recovered by a coke dry fire extinguishing equipment (CDQ). CDQ cools coke with an inert gas, but gas generated from coke at the time of recovery is also mixed and recovered as a low calorific value gas of about 300 kcal / Nm ³ .

  Gas burners used industrially are roughly divided into diffusion combustion type (external mixing) type and premixed combustion type (internal mixing type) depending on the mixing type of fuel gas and supporting gas (oxygen-containing gas). However, each burner has a structure in which a flame is formed in front of the burner tip. The diffusion combustion method (external mixing) is a method in which fuel gas and supporting gas are mixed and burned at the burner tip, and a high-temperature flame can be obtained and widely used. Further, the premixed combustion type has the advantage that a relatively short flame can be formed. However, these conventional burners have a problem that since a flame is formed in front of the burner tip, it is necessary to secure a wide space for combustion in front of the burner, which inevitably increases the size of the combustion equipment.

On the other hand, as fuel gas used in conventional burners, in addition to LNG and propane gas, coke oven gas produced as a by-product in the steel manufacturing process, blast furnace gas, MIX gas mixed with blast furnace gas and converter gas, etc. However, among these, when a low calorific value gas such as blast furnace gas is used alone, the stability of the flame may not be sufficient due to the change of the air ratio or the increase or decrease of the gas calorific value, and the flame may be extinguished. Therefore, a pilot burner is separately installed for maintaining the flame and combustion, or a method of preheating the fuel gas and the combustion supporting gas in advance. Also, when a low calorific value gas, depending on the combustion conditions, or increased production of harmful substances such as NO _X, unburned content or discharge of hydrocarbons, the problem of soot is produced It is likely to occur, and there is concern that it will become one of the sources of environmental pollution.

  In order to solve the above problems, Patent Document 1 introduces a tubular flame burner to burn a low calorific value gas, and swirls fuel gas and oxygen-containing gas (combustion gas) into the combustion chamber. The method of burning is shown. The method of Patent Document 1 is carried out using an oxygen-containing gas having an oxygen concentration of 60 vol% or more as a combustion support gas and the ratio of the supplied oxygen amount to the theoretical oxygen amount is 1.0 to 1.4. is there.

JP 2007-271188 A JP 2008-214735 A JP-A-62-27509

Ohno et al., “Iron and Steel” The Japan Steel Association 75 (1989), p.1278

However, the method of Patent Document 1 has the following problems.
(1) An oxygen-containing gas having an oxygen concentration of 60 vol% or more is required as a combustion support gas. In order to obtain such a high concentration of oxygen, a separate oxygen separation process such as cryogenic separation or membrane separation is required. Is required.
(2) When burning a low calorific value gas with a high concentration of oxygen, locally heated to a high temperature, generation of the thermal NO _X to be environmental problem is concerned. In addition, when the S content is contained in the fuel gas, the generation of SO _X is promoted.
(3) When high-concentration oxygen is introduced through piping, etc., degreasing treatment, etc., piping with stainless steel pipes, etc. and valves are required. For this reason, expensive materials are required, and the equipment cost is increased.

On the other hand, in the low RAR operation of the blast furnace, when the RAR is lowered, the amount of blown air is reduced in principle. As a result, the temperature rise of the charged material is delayed at the upper part of the shaft, and smooth reduction cannot be achieved. In addition, there is a concern that a wall of zinc compound or the like will be promoted, leading to poor furnace conditions such as wind pressure fluctuations and unloading abnormalities. Further, in the case where the furnace top temperature is lowered and falls below 100 ° C., there arises a problem that moisture in the exhaust gas is condensed in the pipe.
In normal blast furnace operation, the following countermeasures are usually taken to prevent the above-mentioned various furnace conditions, particularly poor temperature rise of the charge in the upper part of the furnace.
(A) Decreasing the oxygen enrichment rate and increasing the gas volume (lowering the heat flow ratio and increasing the gas temperature).
(B) Increasing the amount of pulverized coal or other fuel injected (decreasing the heat flow ratio and increasing the gas temperature).
(C) Reduce the reduction efficiency (shaft efficiency) and increase the ratio of reducing material.

However, the measure (a) is not desirable because it leads to a decrease in production. The above (b) depends on the margin of blowing capacity, but the amount of increase is limited at steelworks operating near the capacity limit. In addition, when the amount of fuel injected is increased, the amount of Bosch gas increases and the production volume decreases, so it is necessary to perform oxygen enrichment simultaneously. However, the amount of oxygen that can be used is limited in terms of supply capacity. The above (c) goes back to the original purpose of CO ₂ reduction by aiming at the operation with reduced efficiency.
As described above, when low RAR operation is performed in a normal blast furnace, it is difficult to avoid various furnace condition malfunctions, particularly temperature rise failures in the upper part of the furnace, by changing the operation conditions within the normal operation range.

  Patent Document 2 describes the above-mentioned problem, that is, when the low RAR operation is performed in a normal blast furnace (a blast furnace that blows tuyere hot air with an oxygen enrichment rate of 10% by volume or less), In order to solve the problem that the temperature rise is delayed, when the furnace top temperature is 110 ° C. or lower, a gas of 10 volume% or less of the furnace top gas amount is blown into the furnace as the shaft gas from the upper part of the shaft. It is shown. Further, this document shows that after being discharged from the top of the furnace, a part of the blast furnace gas that has passed through the gas cleaning device is extracted, heated in a combustion furnace, and then used as the shaft gas.

In the method of Patent Document 2, the blast furnace gas is heated (preheated) in the combustion furnace and then blown into the furnace, but the blown gas is sufficiently preheated and has a pressure higher than the pressure in the furnace at the blowing position. There is a need.
However, unlike the so-called oxygen blast furnace process that performs pure oxygen blowing (see, for example, Patent Document 3 and Non-Patent Document 1), the blast furnace gas generated in the normal blast furnace process has a low calorific value, so that a desired temperature in the combustion furnace. In some cases, it is difficult to raise the temperature up to, for example, measures such as using auxiliary fuel with a high calorific value may be required. In addition, since blast furnace gas has a low calorific value, variations in combustion temperature are likely to occur in a normal combustion furnace, and for this reason, oxygen remains in the combustion gas and is oxidized during reduction when blown into the furnace. There is a problem that the product (Fe ₂ O ₃ , FeO) is reoxidized. It is also difficult to stably inject preheated gas into a blast furnace having a predetermined furnace pressure.

Therefore, the first object of the present invention is to solve the problems of the prior art when low calorific value gas is burned by a combustion burner, and to use low calorific value gas without using high oxygen concentration supporting gas in the combustion burner. An object of the present invention is to provide a combustion method capable of stably burning.
In addition, the second object of the present invention is to prevent the malfunction of the furnace during low RAR operation, especially the temperature rise failure of the charge in the upper part of the furnace, and to prevent the blast furnace gas etc. To provide a blast furnace operating method capable of stably burning such a low calorific value gas into a preheated gas and stably blowing the preheated gas into a blast furnace having a predetermined furnace pressure. is there.

First, as a result of investigations to solve the first problem, the present inventors have conducted stable combustion of a low calorific value gas of 1000 kcal / Nm ³ or less (particularly 800 kcal / Nm ³ or less). It has been found that it is effective to use a tubular flame burner and add hydrogen to the fuel gas.
In addition, in order to solve the above second problem, as a result of investigation mainly on the preheating gas generation / blowing means, the method of the tubular flame burner conventionally used in heating furnaces and combustion equipment was used. A gas combustion / blowing device is installed on the shaft, hydrogen is added to the low calorific value gas used as the fuel gas of the gas combustion / blowing device, and the combustion gas is blown into the furnace as a preheating gas, so that blast furnace gas, etc. It has been found that a low calorific value gas can be stably combusted into a preheated gas, and that the preheated gas can be stably blown into a blast furnace having a predetermined furnace pressure.
The present invention has been made based on such findings, and the gist thereof is as follows.

[1] A premixed gas of fuel gas and combustion support gas is injected into the inner wall surface of a tubular combustion chamber with an open end so that a gas swirl flow is generated in the combustion chamber or fuel gas and combustion support gas are mixed. In a combustion burner having an opening for blowing, when a gas having a calorific value of 1000 kcal / Nm ³ or less is used as a fuel gas, the fuel gas before being blown into the combustion chamber and / or the fuel gas blown into the combustion chamber In addition to adding hydrogen (including the case where it is added as a hydrogen-containing gas) , the combustion chamber is a gas containing at least one of CO and H ₂ , and the combustion gas is diluted to obtain a gas composition or a gas composition and a gas temperature. A method for combusting a low calorific value gas by a combustion burner, characterized in that a dilution gas for adjusting the temperature is supplied .
[2] A fuel gas and a combustion-supporting gas are blown into the inner wall surface of the tubular combustion chamber having an open end so that a gas swirl flow is generated in the combustion chamber in a direction substantially tangential to the inner wall surface, In a combustion burner in which an opening for injecting a premixed gas of combustion support gas is used, when a gas having a calorific value of 1000 kcal / Nm ³ or less is used as the fuel gas, the fuel gas and / or combustion before being injected into the combustion chamber Hydrogen is added to the fuel gas blown into the chamber (including the case where it is added as a hydrogen-containing gas) , and the combustion chamber is a gas containing one or more of CO and H ₂ , and the combustion gas is diluted. A combustion method of a low calorific value gas by a combustion burner, characterized by supplying a gas composition or a dilution gas for adjusting the gas composition and gas temperature .

[3] In the combustion method of [1] or [2] above, hydrogen is added to the fuel gas containing CO so that the adiabatic flame temperature is 750 ° C. or higher (including the case where it is added as a hydrogen-containing gas). A combustion method of low calorific value gas using a combustion burner.
[4] In the combustion method of any one of [1] to [3], a gas nozzle or a fuel gas for supplying fuel gas and combustion support gas to the combustion chamber through an opening formed in the inner wall surface of the combustion chamber, A combustion method of a low calorific value gas by a combustion burner, wherein a gas nozzle for supplying a premixed gas of combustion-supporting gas uses a combustion burner composed of a plurality of nozzle tubes arranged in parallel in the burner axial direction.
[5] In the combustion method according to any one of [1] to [4 ] above, combustion in which another opening for injecting gas is formed on the inner wall surface of the combustion chamber so that a gas swirl flow is generated in the combustion chamber A combustion method of a low calorific value gas by a combustion burner, characterized in that a burner is used and hydrogen is blown into the combustion chamber from the opening (including the case of blowing in as a hydrogen-containing gas).

[6] In the combustion method according to any one of [1] to [4 ] above, gas is blown into the inner wall surface of the combustion chamber further in a direction substantially tangential to the inner wall surface so that a gas swirl flow is generated in the combustion chamber. A combustion method of a low calorific value gas using a combustion burner, characterized in that a combustion burner having another opening is used and hydrogen is blown into the combustion chamber from the opening (including the case where it is blown as a hydrogen-containing gas).
[7] In the combustion method of [5] or [6 ] above, a plurality of nozzles in which gas nozzles for supplying hydrogen into the combustion chamber through other openings formed in the inner wall surface of the combustion chamber are arranged in parallel in the burner axial direction A combustion method of low calorific value gas by a combustion burner, characterized by using a combustion burner composed of a tube.
[8] A combustion method of a low calorific value gas by a combustion burner according to any one of the above [1] to [7] , wherein the swirl number Sw of the gas flow in the combustion chamber is 3 to 10.
[9] In the combustion method according to any one of [1] to [8] above, fuel gas and combustion support gas are blown into the inner wall surface on the rear end side of the combustion chamber so that a gas swirl flow is generated in the combustion chamber. The gas composition or the gas composition and the gas are obtained by diluting the combustion gas at a position closer to the front end of the combustion chamber than the opening and closer to the front end of the combustion chamber than the center position in the longitudinal direction of the combustion chamber. A combustion method of a low calorific value gas by a combustion burner, characterized by using a combustion burner provided with a gas nozzle for supplying a dilution gas for adjusting temperature into the combustion chamber.

According to the combustion method of low calorific value gas by the combustion burner according to the present invention, low calorific gas such as blast furnace gas or gas recovered from CDQ can be stably burned, It can be effectively used as fuel.
Further, according to the blast furnace operation method according to the present invention, in the operation of a normal blast furnace, it is possible to prevent the temperature rise of the charge in the upper part of the furnace during the low RAR operation, and moisture condensation and zinc compounds due to a decrease in the furnace top temperature. As a result, the low RAR operation can be carried out stably. In addition, a low calorific value gas such as a blast furnace gas can be stably burned into a preheated gas, and the preheated gas can be stably blown into a blast furnace having a predetermined furnace pressure.

The partially notched top view which shows one Embodiment of the combustion burner used by this invention Sectional view along line II-II in FIG. The other embodiment of the combustion burner used by the present invention is shown, and the sectional view which meets the section line similar to FIG. Partial cutaway plan view showing another embodiment of the combustion burner used in the present invention Bottom view partially showing the combustion burner of FIG. Sectional view along line VI-VI in FIG. Sectional drawing which follows the VII-VII line of FIG. Explanatory drawing which shows typically one Embodiment of the blast furnace operating method of this invention Explanatory drawing which shows the combustion burner used by the combustion test of the Example In the combustion burner used by this invention, explanatory drawing which shows typically the radial direction cross section of the combustion chamber inside in the position in which opening 2a, 2b was formed In the combustion burner used by this invention, explanatory drawing which shows typically the radial direction cross section of the combustion chamber inside in the position in which opening 2a, 2b was formed

1 and 2 show an embodiment of a combustion burner (tubular flame burner) used in the present invention. FIG. 1 is a partially cutaway plan view, and FIG. 2 is taken along the line II-II in FIG. It is sectional drawing.
In the figure, 1 is a tubular (cylindrical) combustion chamber having an open end, 3a is a gas nozzle for fuel gas, and 3b is a gas nozzle for combustion support gas.
Fuel gas (and hydrogen) and an inner wall surface 100 on the inner side (rear end side) of the combustion chamber 1 so that a gas swirl flow (a gas swirl flow along the circumferential direction of the inner wall surface 100) is generated in the combustion chamber. Openings 2a and 2b (nozzle ports) for injecting combustion-supporting gas are formed, and the gas nozzles 3a and 3b are connected to the openings 2a and 2b, respectively. The openings 2a and 2b (nozzle ports) are formed so as to blow gas in a direction (eccentric direction) in which the axial center of the combustion chamber 1 is removed so that the gas blown into the combustion chamber 1 becomes a swirling flow. . The openings 2a and 2b of the present embodiment are formed so as to blow fuel gas and combustion-supporting gas substantially in the tangential direction of the inner wall surface 100, respectively.
The openings 2a and 2b are formed in a slit shape along the tube axis direction, and are provided at positions facing the inner wall surface 100 (inner peripheral surface) by 180 °. A plurality of these openings 2a and 2b may be provided. In this case, gas nozzles 3a and 3b are connected to the openings 2a and 2b.

A gas introducing portion of the gas nozzle 3 a is provided with a mixing chamber 4 for mixing fuel gas and hydrogen, and a fuel gas supply pipe 5 and a hydrogen supply pipe 6 are connected to the mixing chamber 4. On the other hand, a combustion supporting gas supply pipe 7 is connected to the gas introduction part of the gas nozzle 3b.
In other drawings, 8 to 10 are flow rate adjusting valves provided in the fuel gas supply pipe 5, the hydrogen supply pipe 6 and the combustion support gas supply pipe 7, respectively, 11 is a flow meter provided in the hydrogen supply pipe 6, and 12 is a combustion chamber 1. A combustion state detection device 13 for detecting the combustion state in the inside, 13 is a spark plug. The combustion state detection device 12 may be, for example, a method in which a thermocouple is inserted in a flame to measure temperature, an optical method in which ultraviolet light in the flame is detected using Ultravision or the like. Further, x is a furnace body provided with a combustion burner.

Here, from the openings 2a and 2b (nozzle ports), if fuel gas and combustion-supporting gas are blown into the combustion chamber 1 so that a gas swirl flow (gas swirl flow along the circumferential direction of the inner wall surface 100) is generated, respectively. In particular, the gas swirl flow of the gas from the openings 2a and 2b is set so that the swirl number Sw (a dimensionless number representing the strength of swirl in the flow of fluid with swirl) as described later is in the range. It is preferable to set the blowing direction. FIG. 10 schematically shows a radial section of the inside of the combustion chamber at the position where the openings 2a and 2b are formed. In the radial cross section of the combustion chamber 1, among the ends of the openings 2 a and 2 b in the circumferential direction of the inner wall surface 100, the tip side in the swirling (rotating) direction of the gas flow discharged from the openings 2 a and 2 b and swirling Is the point p, the tangent line of the inner wall surface 100 at this point p is x, the center line of the gas flow discharged from the openings 2a, 2b (= the axis of the gas nozzles 3a, 3b) is y, the tangent line x and the gas flow When the angle formed by the center line y is the gas blowing angle θ, it is preferable to set the gas blowing angle θ so as to be within a preferable swirl number Sw range (Sw: 3 to 10). That is, when the fuel gas velocity at the opening 2a calculated from the inner diameter of the gas nozzle 3a is Vf and the support gas velocity at the opening 2b calculated from the inner diameter of the gas nozzle 3b is Va, the fuel gas velocity in the tangential x direction. The component Vf1 and the combustion support gas velocity component Va1 are as follows.
Vf1 = Vf × cosθ
Va1 = Va × cosθ
Then, it is preferable to determine the gas blowing angle θ so that the swirl number Sw calculated by using the Vf1 and Va1 as the gas velocity at the openings 2a and 2b falls within a predetermined preferable range. The method for obtaining the swirl number Sw is as described later.

  On the other hand, in terms of the structure of the combustion burner, the combustion burner has openings 2a and 2b for injecting fuel gas and supporting gas in the tangential direction of the inner wall surface on the inner wall surface 100 of the combustion chamber 1, respectively. A structure is preferred. This is because with such a structure, a preferable swirl number Sw can be realized regardless of changes or changes in the gas amount or gas speed. Specifically, it is desirable that the gas blowing angle θ shown in FIG. 10 is 30 ° or less, more preferably 10 ° or less. When the gas blowing angle θ is increased, there is a possibility that a gas swirl flow along the inner wall surface 100 cannot be properly formed depending on the gas amount and the gas velocity. In the present embodiment, the embodiment of FIG. 3 to be described later, and the embodiment of FIGS. 4 to 7, the gas blowing angle θ is approximately 0 ° to 5 °.

In the tubular flame burner as described above, the present invention has a low heat generation with a calorific value of 1000 kcal / Nm ³ or less (particularly 800 kcal / Nm ³ or less) such as blast furnace gas, CDQ gas, exhaust gas containing a small amount of combustible components, and the like. When a quantity gas is used as a fuel gas, hydrogen is added to the fuel gas in order to stably burn it. This hydrogen may be added as pure hydrogen gas or as a hydrogen-containing gas (hereinafter referred to as “hydrogen (added to fuel gas)” in this specification, “hydrogen-containing gas” is referred to as “hydrogen”. Meaning to include). The hydrogen concentration of the hydrogen-containing gas must naturally exceed the hydrogen concentration of the fuel gas when the fuel gas originally contains hydrogen. Accordingly, when blast furnace gas (usually H ₂ concentration: _{2 to 3} vol%) is used as the fuel gas, it is necessary to use a hydrogen-containing gas having a higher hydrogen concentration than the blast furnace gas. Other than this point, the hydrogen concentration of the hydrogen-containing gas is not particularly limited, but it is generally preferable to use a hydrogen-containing gas having a hydrogen concentration of 20 vol% or more. Among the gases generated in the steel production process, for example, a coke oven gas obtained when producing coke has a particularly high hydrogen concentration (usually about 55 vol%) and is suitable as a hydrogen-containing gas.

  In order to add hydrogen to the fuel gas, in the combustion burner shown in FIGS. 1 and 2, fuel gas and hydrogen are supplied to the mixing chamber 4 of the gas nozzle 3a through the fuel gas supply pipe 5 and the hydrogen supply pipe 6, where the fuel gas Hydrogen is mixed with this, and this hydrogen-mixed fuel gas (fuel gas mixed with hydrogen; the same applies hereinafter) enters the nozzle body. On the other hand, a combustion support gas is supplied to the gas nozzle 3b through the support gas supply pipe 7. The hydrogen mixed fuel gas and the combustion support gas supplied to the gas nozzles 3a and 3b in this way are blown into the combustion chamber 1 from the openings 2a and 2b (nozzle ports). The hydrogen-mixed fuel gas and the combustion support gas burn while forming a swirling flow along the inner wall surface 100 of the combustion chamber 1 to form a flame. In addition, the above combustion is started by the ignition by the spark plug 13, and when combustion continues, the ignition by the spark plug 13 is complete | finished at that time.

When the combustion state detected by the combustion state detection device 12 is not stable because the calorific value of the fuel gas fluctuates and becomes a lower calorific value, for example, the flow meter 11 provided in the hydrogen supply pipe 6 The supply amount of hydrogen is increased by the flow rate adjusting valve 9.
The combustion burner may use a gas (premixed gas) in which fuel gas and combustion support gas are mixed in advance. In this case, gas swirling is performed on the inner wall surface 100 of the combustion chamber 1 in the combustion chamber 1. One or more openings 2 (nozzle ports) for injecting a premixed gas of fuel gas and supporting gas are formed so as to generate a flow (a gas swirl flow along the circumferential direction of the inner wall surface 100). The gas nozzle 3 for supplying premixed gas is connected to The opening 2 is gas in a direction (eccentric direction) in which the axial center of the combustion chamber 1 is removed so that the gas blown into the combustion chamber 1 becomes a swirling flow, like the openings 2a and 2b in FIGS. In particular, it is preferably formed so as to blow gas (premixed gas) substantially in the tangential direction of the inner wall surface 100. Then, the hydrogen is added to the fuel gas or the premixed gas before being premixed with the combustion support gas, and the premixed gas thus added with hydrogen is blown into the combustion chamber 1 from the opening 2 through the gas nozzle 3. It is. The gas may be blown from the opening 2 so that a gas swirl flow (a gas swirl flow along the circumferential direction of the inner wall surface 100) is generated in the combustion chamber 1, but a preferable method for setting the gas blowing direction, The gas blowing angle θ preferred for the burner structure is the same as that of the openings 2a and 2b described above with reference to FIG.

  In the combustion burner as described above, the hydrogen mixed fuel gas and the combustion support gas (or the premixed gas of both) are blown into the combustion chamber 1 from the gas nozzles 3a and 3b and the openings 2a and 2b to form a swirl flow. Gas layers with different densities are formed on both sides of the flame. That is, high-temperature combustion exhaust gas exists on the axis side where the turning speed is low, and unburned gas exists on the inner wall surface 100 side where the turning speed is high. Further, in the vicinity of the inner wall surface 100, the turning speed exceeds the flame propagation speed, so that the flame cannot remain in the vicinity of the inner wall surface. For this reason, a tubular flame is stably generated in the combustion chamber 1. In addition, since unburned gas is present near the inner wall surface of the combustion chamber 1, the inner wall surface of the combustion chamber 1 is not heated to a high temperature by direct heat transfer. Then, the gas in the combustion chamber 1 flows to the tip side while swirling, and during that time, the gas on the inner wall surface 100 side sequentially burns and moves to the axial center side, and the combustion gas is discharged from the open tip.

The burning rate of hydrogen is extremely faster than other flammable gases such as CO. Therefore, it is possible to stably burn a low calorific value gas by adding hydrogen. Here, the gas combustion rate (MCP: maximum combustion potential) is determined by its composition and is calculated by the following equation.

The MCP calculated by the above formula is 282 for hydrogen and 100 for CO, and hydrogen is 2.8 times faster than CO. Therefore, by adding hydrogen, it becomes possible to stably burn the low calorific value gas. In order to continue the combustion of the low calorific value gas, theoretically, the adiabatic flame temperature of the low calorific value gas is equal to or higher than the ignition point of the gas species contained in the fuel gas (CO ignition point: 609 ° C., H ₂ (Ignition point: 500 ° C.) or the concentration of the combustible gas contained in the fuel gas is not less than the lower explosion limit concentration (CO explosion lower limit concentration: 12.5 vol%, H ₂ : 4 vol%) Good. However, as a result of investigation by the present inventor, in a low calorific value gas containing CO such as blast furnace gas, when the adiabatic flame temperature after adding hydrogen becomes 750 ° C. or higher, stable combustion becomes possible. I understood. For example, a gas with CO of 10.1 vol% (the balance being an inert gas such as N ₂ and / or CO ₂ ) has a calorific value of 305 kcal / Nm ³ and an adiabatic flame temperature of 645 ° C., which is stable in this state However, the combustion does not continue, and a pilot burner for supplementary combustion is required separately. By adding 3.0 vol% of hydrogen to this gas, the adiabatic flame temperature becomes 750 ° C., and stable combustion can be continued. The adiabatic flame temperature is a temperature calculated theoretically as being used for increasing the temperature of the combustion gas without losing heat generated by combustion to the outside.

Therefore, in a low calorific value gas containing CO such as blast furnace gas, it is preferable to add hydrogen so that the adiabatic flame temperature is 750 ° C. or higher. On the other hand, if the amount of hydrogen added is large, the stability of combustion increases accordingly, but if the amount of hydrogen added is too large, the economy is impaired.
As described above, the present invention can also be applied to the case where a low calorific value gas originally containing hydrogen is used as a fuel gas, and of course, the hydrogen concentration depends on the hydrogen concentration originally contained. The amount added is adjusted.
In the combustion method of the present invention, if the combustion chamber 1 is in a pressurized state, the gas density increases and the apparent heat generation amount increases, so that stable combustion is possible even with a fuel gas having a lower heat generation amount. Is possible.

In the present invention, an oxygen-containing gas such as air or oxygen gas can be used as the combustion support gas, but the present invention is particularly useful when air is used as the combustion support gas. The supply amount of the combustion support gas is an amount necessary to maintain a stable combustion state. When air is used as the combustion support gas, it is usually supplied so that the air ratio is 1 or more. The air ratio is the ratio of the theoretical amount of air required for fuel combustion to the amount of air actually supplied (actual air amount / theoretical air amount). ₂ and H ₂ O. When the air ratio is less than 1, incomplete combustion occurs, and stable combustion cannot be continued. In addition, when the air ratio is excessive, lean combustion occurs, and even in this case, a stable combustion state cannot be maintained. Therefore, it is usually preferable to supply the combustion support gas in an air ratio range of 1.0 to 1.5.
There is no particular limitation on the ejection speed of the fuel gas and the combustion-supporting gas from the nozzle (opening), but it is preferable that both of them have the same speed.

1 and 2, hydrogen is added to the fuel gas before being blown into the combustion chamber 1, but hydrogen is added to the fuel gas blown into the combustion chamber 1 (that is, within the combustion chamber 1). Hydrogen may be added to the fuel gas). FIG. 3 is a cross-sectional view (a cross-sectional view along the same cross-sectional line as FIG. 2) showing an embodiment of the combustion burner used in this case. In this combustion burner, openings 2a and 2b similar to those in FIG. 2 are formed on the inner wall surface 100 on the inner side (rear end side) of the combustion chamber 1, and between the openings 2a and 2b in the circumferential direction of the inner wall surface 100. In the combustion chamber 1 so that a gas swirl flow (a gas swirl flow along the circumferential direction of the inner wall surface 100) is generated in the combustion chamber 1 at the center position (ie, at a position of 90 ° with respect to the openings 2a and 2b in the circumferential direction). Openings 2c ₁ and 2c ₂ (nozzle ports) for blowing (hydrogen gas or hydrogen-containing gas; the same applies hereinafter) are formed, and hydrogen gas nozzles 3c ₁ and 3c ₂ are connected to the openings 2c ₁ and 2c ₂ , respectively. ing. Similarly to the openings 2a and 2b, the openings 2c ₁ and 2c ₂ (nozzle ports) also have a direction in which the axial center of the combustion chamber 1 is removed (eccentric direction) so that the gas blown into the combustion chamber 1 becomes a swirling flow. It is formed so that gas (hydrogen) is blown into. The openings 2c ₁ and 2c ₂ of the present embodiment are formed so as to blow hydrogen substantially in the tangential direction of the inner wall surface 100.
Similar to the openings 2a and 2b, the openings 2c ₁ and 2c ₂ are formed in a slit shape along the tube axis direction. Note that only _{one of} these openings 2c ₁ and 2c ₂ may be provided, or three or more of them may be provided. In this case, a gas nozzle 3c is connected to each opening 2c.
Gas (hydrogen) may be blown from the openings 2c ₁ and 2c ₂ so that a gas swirl flow (gas swirl flow along the circumferential direction of the inner wall surface 100) is generated in the combustion chamber 1. A preferable setting method of the inlet direction and a gas injection angle θ preferable for the burner structure are the same as those of the openings 2a and 2b described above with reference to FIG.

In such a combustion burner, hydrogen is added to the fuel gas in the combustion chamber 1 by blowing hydrogen into the combustion chamber 1 from the openings 2c ₁ and 2c ₂ through the gas nozzle 3c.
Since the other structures and functions of the combustion burner of the embodiment of FIG. 3 are the same as those of the combustion burner of the embodiment shown in FIGS. 1 and 2, detailed description thereof is omitted. As in the combustion burner of the embodiment shown in FIGS. 1 and 2, a gas (premixed gas) obtained by premixing fuel gas and combustion supporting gas may be used. In this case, as described above, Instead of the openings 2a and 2b, one or more openings 2 (nozzle ports) for injecting a premixed gas of fuel gas and supporting gas are formed, and a gas nozzle 3 for supplying the premixed gas is formed in the opening 2 Is connected.

In the present invention, the fuel gas to which hydrogen is added and the combustion support gas form a swirling flow in the combustion chamber 1 of the combustion burner, so that the fuel gas having a low calorific value can be stably combusted. However, when the fuel gas is a gas mainly composed of CO, CO ₂ , and N ₂ such as blast furnace gas, hydrogen has a lower gas density than these gas components, so that the embodiment shown in FIG. When hydrogen is blown into a swirl flow, hydrogen moves to the axial center side due to the density difference and burns preferentially to promote combustion of other gases. For this reason, the combustibility of the fuel gas with a low calorific value can be further enhanced.

4 to 7 show another embodiment of a combustion burner (tubular flame burner) used in the present invention. FIG. 4 is a partially cutaway plan view of the combustion burner, and FIG. 5 is a partial view of the combustion burner. 6 is a cross-sectional view taken along line VI-VI in FIG. 4, and FIG. 7 is a cross-sectional view taken along line VII-VII in FIG.
In the embodiment of FIGS. 4 to 7, the gas nozzle 3a for fuel gas and the gas nozzle 3b for combustion-supporting gas are each composed of a plurality of nozzle tubes 300a and 300b arranged in parallel in the burner axial direction. The gas nozzles 3a and 3b are configured by the plurality of nozzle pipes 300a and 300b as described above, while an appropriate swirl flow is formed in the combustion chamber 1 by the gas nozzles 3a and 3b, as will be described later. This is to make Sw a predetermined preferred range.

Similar to the embodiment of FIGS. 1 and 2, the inner wall surface 100 on the inner side (rear end side) of the combustion chamber 1 has a gas swirl flow (gas swirl along the circumferential direction of the inner wall surface 100) in the combustion chamber 1. Openings 2a and 2b (nozzle ports) for injecting fuel gas and combustion-supporting gas are formed so as to generate a flow, and these openings 2a and 2b are also constituted by a plurality of openings 200a and 200b, respectively. The nozzle pipe 300a is connected to each opening 200a, and the nozzle pipe 300b is connected to each opening 200b. The openings 200a and 200b are formed so as to blow gas in a direction (eccentric direction) in which the axial center of the combustion chamber 1 is removed so that the gas blown into the combustion chamber 1 becomes a swirl flow. The openings 200a and 200b of the present embodiment are formed so as to blow fuel gas and combustion-supporting gas substantially in the tangential direction of the inner wall surface 100, respectively.
Further, in order to supply a dilution gas into the combustion chamber 1 for diluting the combustion gas and adjusting its temperature and / or composition at a position closer to the tip of the combustion chamber than the gas nozzles 3a, 3b (openings 2a, 2b). The gas nozzle 14 is provided. Since the gas nozzle 14 supplies gas for diluting the combustion gas, the gas nozzle 14 may be provided at a position where the gas combustion in the combustion chamber 1 is not hindered. The gas nozzle 14 is specially provided at an installation (connection) position in the longitudinal direction of the combustion chamber. Although there is no particular limitation, in this embodiment, it is provided at a position closer to the front end of the combustion chamber than the center position in the longitudinal direction of the combustion chamber.

The gas nozzle 14 may be composed of a single nozzle tube, but in the present embodiment, the gas nozzle 14 is composed of a plurality of nozzle tubes 140 arranged in parallel in the burner axis direction. On the inner wall surface 100 of the combustion chamber 1 at the position where the gas nozzle 14 is installed, a gas swirl flow (gas swirl flow along the circumferential direction of the inner wall surface 100) is generated in the combustion chamber 1. An opening 15 (nozzle port) for blowing dilution gas in the tangential direction is formed, and the gas nozzle 14 is connected to the opening 15. In the present embodiment, the opening 15 is composed of a plurality of openings 150, and the nozzle pipe 140 is connected to each opening 150, but the opening 15 is a single slit-shaped opening along the tube axis direction. A single gas nozzle 14 may be connected to this. Note that the dilution gas opening 15 does not necessarily have a structure in which gas is blown so that a swirling gas flow is generated in the combustion chamber 1.
Since the other structures and functions of the combustion burner of the embodiment of FIGS. 4 to 7 are the same as those of the combustion burner of the embodiment shown in FIGS. 1 and 2, detailed description thereof is omitted.
Further, the gas may be blown from the openings 200a and 200b so that a gas swirl flow (gas swirl flow along the circumferential direction of the inner wall surface 100) is generated in the combustion chamber 1, but a preferable setting of the gas blowing direction is preferable. The gas blowing angle θ preferable for the method and the burner structure is the same as that of the openings 2a and 2b described above with reference to FIG.

In the combustion burner used in the present invention, high-temperature combustion gas is generated in the combustion chamber 1, and for example, the theoretical combustion temperature of blast furnace gas is about 1300 ° C. at an air ratio of 1.0. When the present invention is applied to a blast furnace operating method as described later and the combustion gas of the combustion burner is blown into the blast furnace as a preheating gas, the coke in the furnace is consumed by the CO ₂ in the blown combustion gas, or the furnace It is preferable to dilute the combustion gas and manage its temperature and composition so that the iron ore (magnetite) reduced in step 1 is not reoxidized. In the present embodiment, for such a purpose, a dilution gas for adjusting the temperature and / or composition of the combustion gas is supplied from the gas nozzle 14 into the combustion chamber 1.

The type of dilution gas to be used may be appropriately selected according to the purpose (gas temperature adjustment and / or gas composition adjustment) to be added to the combustion gas. From the aspect of adjusting the composition of the combustion gas, CO, H Those containing a reducing gas such as ₂ are preferred. For example, one or more of blast furnace gas, converter gas, coke oven gas, and the like can be used, and it is particularly preferable to extract a part of the blast furnace gas and use it as a dilution gas.
Further, when the combustion gas of the combustion burner is blown into the blast furnace as a preheating gas, the temperature of the preheating gas is preferably 500 ° C. or higher, and preferably 800 ° C. or higher as described later. It is preferred that the gas temperature and supply rate be selected.
It should be noted that a combustion burner having a gas nozzle for injecting a premixed gas of fuel gas and supporting gas, and a combustion burner having a gas nozzle 3c for injecting hydrogen as in the embodiment of FIG. 3 are also connected to the burner shaft. It can be composed of a plurality of nozzle tubes arranged in parallel in the direction. Also in these combustion burners, the gas nozzle 14 and the opening 15 for the dilution gas as described above can be provided.

In the combustion method of the present invention, the swirl number Sw of the gas flow in the combustion chamber 1 is preferably in the range of 3-10. The swirl number is a dimensionless number that represents the strength of swirl in the flow of fluid with swirl. The larger the swirl number, the stronger the swirl flow. If the swirl number is too small, the mixing of the fuel gas and the combustion supporting gas becomes insufficient, and the ignition of the fuel gas becomes unstable. On the other hand, if the swirl number is too large, the combustion flame may blow off. From the above viewpoint, the swirl number Sw is preferably in the range of 3-10.
The swirl number Sw can be calculated according to a known basic formula for calculating the swirl number Sw by a formula corresponding to the type of combustion burner to be used and its usage. For example, as in the embodiment of FIGS. When a combustion burner having an opening 2a for blowing fuel gas and an opening 2b for supporting combustion gas is used, the swirl number Sw can be obtained by the following equation. In the following formula, the fuel gas is a hydrogen mixed fuel gas.

さらに、図３の実施形態のような、燃料ガス吹き込み用の開口２aと支燃ガス吹き込み用の開口２bに加えて、水素吹き込み用の開口２cを有する燃焼バーナを用いる場合には、スワール数Ｓwは下式により求めることができる。

Further, when a combustion burner having an opening for injecting a premixed gas of fuel gas and combustion support gas is used, the swirl number Sw can be obtained by the following equation. In the following formula, the premixed gas is “fuel gas + hydrogen + combustion gas”.

Further, in the case of using a combustion burner having an opening 2c for blowing hydrogen gas in addition to the opening 2a for blowing fuel gas and the opening 2b for supporting combustion gas as in the embodiment of FIG. 3, the swirl number Sw Can be obtained by the following equation.

When the swirl number Sw is set to the preferred range as described above, a plurality of gas nozzles 3a for fuel gas and gas nozzles 3b for combustion gas are arranged in parallel in the burner axial direction as in the embodiment of FIGS. The nozzle pipes 300a and 300b are preferably used. This is due to the following reasons. For example, combustion chamber diameter: 50 mm, combustion gas amount (blast furnace gas): 30 Nm ³ / h (gas density: 1.34 kg / Nm ³ ), air amount: 21.4 Nm ³ / h (gas density: 1.29 kg / Nm) ³ ), air ratio: 1.1, furnace pressure: 245 kPa (furnace pressure when the combustion burner is installed in the blast furnace as a gas combustion / blowing device a as in the blast furnace operating method described later), the gas nozzle 3a, If each 3b is composed of a single (one) nozzle tube, the inner diameter of the nozzle tube with a swirl number Sw of 3 (inner diameter in terms of a circle. In other words, the cross-sectional area inside the nozzle tube is converted into the area of the circle. The diameter of the circle at the time of the gas nozzle 3a (hereinafter referred to as “the inner diameter of the nozzle tube” is the same meaning) is 21 mm for the gas nozzle 3a (fuel gas velocity at the opening 2a: 7 m / s) and the gas nozzle 3b. 21mm (opening Combustion-supporting gas velocity at b: 5m / s) to become. However, when the gas nozzles 3a and 3b are configured by a single nozzle tube in this way, the inner diameter of the nozzle tube is about 4/10 of the combustion chamber diameter in the section taken along the line II-II in FIG. With the combustion support gas, the flow toward the center of the combustion chamber (axial center) increases, and it becomes difficult to form a good swirl flow. For this reason, there exists a possibility that the high temperature combustion exhaust gas which exists in the shaft center side may be cooled, and the effect of this invention may fall. FIG. 11 schematically shows a radial cross section of the inside of the combustion chamber at the position where the openings 2a and 2b are formed. The radius of the combustion chamber 1 is R and the inside of the gas nozzles 3a and 3b in the combustion chamber radial direction. When the width or the actual inner diameter is t, the center position of the gas flow blown from the openings 2a and 2b (= the axial center of the gas nozzles 3a and 3b) is a position (R−t / 2) from the center of the combustion chamber 1. It is in. Here, when t becomes large with respect to R, the flow toward the center of the combustion chamber (axial center) increases and it becomes difficult to form a favorable swirl flow, and the tubular flame is formed at a position away from the tube wall. Combustion tends to be unstable. From such a viewpoint, (R−t / 2) /R≧0.8 is preferable. However, in the above example, this preferable condition is not satisfied.

  On the other hand, when the gas nozzles 3a and 3b are composed of a plurality of nozzle tubes 300a and 300b arranged in parallel in the burner axial direction, the inner diameter per nozzle tube is reduced, and thus the above-described problems are unlikely to occur. A good swirl flow can be generated while keeping the swirl number Sw within a preferable range. Therefore, the gas nozzle 3a for fuel gas and the gas nozzle 3b for combustion-supporting gas are preferably configured by a plurality of nozzle tubes 300a and 300b arranged in parallel in the burner axial direction. For the same reason, a combustion burner having a gas nozzle for injecting a premixed gas of fuel gas and supporting gas, and a combustion burner having a gas nozzle 3c for injecting hydrogen gas as in the embodiment of FIG. The gas nozzle is preferably composed of a plurality of nozzle tubes arranged in parallel in the burner axial direction.

The low calorific value gas used as fuel gas in the present invention has a calorific value of 1000 kcal / Nm ³ or less. In general, a gas having a calorific value exceeding 1000 kcal / Nm ³ can be combusted by a conventional method without particularly applying the present invention. Therefore, in the present invention, it is a substantial requirement that the calorific value of the fuel gas to which hydrogen is added is also 1000 kcal / Nm ³ or less. In addition, since a gas having a calorific value of 800 kcal / Nm ³ or less is particularly difficult to obtain stable combustibility, the utility of the present invention is particularly high when it is used as a fuel gas. On the other hand, if the calorific value of the fuel gas is less than 300 kcal / Nm ³ , it may be difficult to stably burn even if the present invention is applied. Therefore, the fuel gas used in the present invention has a calorific value of 300 kcal / N Nm ³ or more is preferable.

Next, a blast furnace operating method to which the above-described combustion method of the low calorific value gas by the combustion burner will be described.
This blast furnace operation method of the present invention is intended for blast furnace operation in which air or oxygen-enriched air is blown through, that is, operation of a normal blast furnace. When the oxygen-enriched air is blown into the tuyere, the operation is usually performed at an oxygen enrichment rate of 20% by volume or less, preferably 10% by volume or less. As the oxygen enrichment rate increases, the amount of gas passing through the furnace decreases, and the amount of blown gas required to raise the temperature of the upper portion of the shaft significantly increases. From this point as well, Operation at an oxygen enrichment rate is preferred.

FIG. 8 is an explanatory view schematically showing an embodiment of the blast furnace operating method of the present invention. In the figure, 20 is a blast furnace, and 21 is a tuyere, from which hot air and auxiliary reducing materials (for example, pulverized coal, LNG, etc.) are blown into the furnace.
Blast furnace gas (furnace top gas) discharged from the top of the blast furnace 20 is dust-removed by a dust catcher 22 which is a gas cleaning device, and moisture is removed by a mist separator 23, and then a top gas generator 24. After the pressure of the furnace top gas is recovered as electricity, it is led out of the system.

In the present invention, gas is blown into the blast furnace from the gas blowing portion A provided in the shaft portion (preferably the middle portion to the upper portion of the shaft). In this way, the main purpose of blowing gas into the furnace is to make up for the decrease in the amount of air flow due to low RAR operation and to secure the gas flow rate at the top of the furnace, but to lower the furnace top gas temperature unnecessarily. Blowing a temperature gas is contrary to the gist of the invention, so a preheated gas is used as the blown gas.
In this way, when the preheating gas is blown into the blast furnace from the gas blowing section A, in the present invention, the gas blowing section A is used as a combustion burner as described above (for example, the combustion burner of FIGS. 1 and 2 and FIG. 3). Combustion burner, one of the combustion burners of FIGS. 4 to 7) is configured by a gas combustion / blowing device a in which the tip of the combustion chamber communicates with the inside of the blast furnace, and the combustion gas of this gas combustion / blowing device a is preheated gas It is blown into the blast furnace. That is, in FIG. 1 and FIG. 4, x is the furnace body of the blast furnace 20, and the combustion burner is attached to the furnace body x so that the tip of the combustion chamber 1 communicates with the inside of the blast furnace, thereby constituting the gas combustion / blowing device a To do.

  The basic structure of such a gas combustion / blowing device a is known as a tubular flame burner. However, this tubular flame burner has been developed and used for heating furnaces and combustion equipment, and has not been studied at all for application to gas blowing means for blast furnaces. In addition, blast furnace operation in recent years is performed under high pressure conditions, and the preheating gas needs to be blown up to a pressure higher than the furnace pressure at the blowing position, but the tubular flame burner is assumed to be used at normal pressure, The use under the above pressure conditions has not been studied at all. On the other hand, in the present invention, a tubular flame burner type gas combustion / blowing device a is used as a means for preheating by burning a low heating value gas such as blast furnace gas and blowing it into the furnace from the shaft portion of the blast furnace. Has been found to have an excellent function. Moreover, when low calorific value gas, such as blast furnace gas, is used as fuel gas, it discovered that stable combustion became possible by adding hydrogen to fuel gas as mentioned above.

  In the embodiment of FIG. 8, after being discharged from the top of the furnace, a part of the blast furnace gas that has passed through the gas cleaning device (dust catcher 22 and mist separator 23) and the top gas generator 24 is extracted and boosted by the booster 25a. Then, it introduce | transduces into the gas combustion and blowing apparatus a which comprises the gas blowing part A as fuel gas. In order to mix hydrogen with the fuel gas, hydrogen is introduced directly into the fuel gas pipe, or hydrogen is mixed into the fuel gas using a mixer (not shown) to obtain a hydrogen mixed fuel gas. Of the blast furnace gas flow path 27 discharged from the top of the blast furnace 20, a part of the blast furnace gas is supplied to the gas combustion / blowing apparatus a from the downstream flow path portion of the furnace top gas power generation device 24. The flow path 28 is branched.

Further, the gas combustion / blowing device a is supplied with a combustion support gas which is an oxygen-containing gas (air, oxygen-enriched air, high oxygen concentration gas, etc.), and the combustion support gas is also pressurized by the booster 25b. Then, it introduce | transduces into the gas combustion and blowing apparatus a. When a premixed gas of fuel gas and combustion support gas is used in the gas combustion / blowing device a, the pressure of the fuel gas and combustion support gas may be separately increased in advance by the boosters 25a and 25b. The mixed gas may be boosted with a single booster 25. In this case, hydrogen is introduced into the fuel gas before being premixed with the combustion supporting gas (or hydrogen is mixed with a mixer), or hydrogen is introduced into the premixed gas (or hydrogen is mixed with the mixer).
In the case of the combustion burner shown in FIG. 3, hydrogen is boosted by a booster, introduced into the gas combustion / blowing device a separately from the fuel gas, and blown into the combustion chamber.

In the case of the combustion burner shown in FIGS. 4 to 7, coke is consumed by CO ₂ in the combustion gas blown into the blast furnace, or iron ore (magnetite) reduced in the furnace is reoxidized. In order to dilute the combustion gas and manage its temperature and composition, the dilution gas is supplied from the gas nozzle 14 into the combustion chamber 1. As described above, the diluent gas preferably includes a reducing gas such as CO or H ₂ , and for example, one or more of blast furnace gas, converter gas, coke oven gas, etc. can be used. However, it is preferable to extract a part of the blast furnace gas and use it as a dilution gas. Further, since the temperature of the preheating gas is 500 ° C. or higher, preferably 800 ° C. or higher, the temperature and the supply amount of the dilution gas are selected so as to be such a preheating gas temperature.

Next, hydrogen is added to the low-calorific value gas that is a fuel gas (especially when using a blast furnace gas generated by operation with a low reducing material ratio) using the tubular flame burner type gas combustion / blowing device a in the present invention. The effect obtained by doing this will be described in comparison with the case of using another type of conventional gas burner.
Conventionally, most gas burners used industrially have a structure in which a flame is formed in front of the burner tip. Therefore, when such a gas burner is used as a gas combustion / blowing device a, the flame directly hits the charge (iron ore, coke) descending from the upper part of the blast furnace, causing a coke solution loss reaction, and coke is unnecessary. This causes problems such as being consumed.

In addition, the top gas of the oxygen blast furnace process that performs pure oxygen blowing has a low amount of nitrogen and is mainly CO, and therefore has a high calorific value (for example, about 1200 kcal / Nm ³ ). For this reason, even the conventional general gas burner as described above can be used as a fuel gas without any particular problem. On the other hand, the blast furnace gas generated in the ordinary blast furnace process targeted by the present invention has a low calorific value (for example, about 800 kcal / Nm ³ ), and stable combustion even when applied to the conventional gas burner as described above. Is difficult. In addition, when directed to low RAR operation, the amount of heat generated by the blast furnace gas further decreases. For example, when calculating with the blast furnace internal material heat balance model, the heat generation amount of the blast furnace gas is (1) 722 kcal / Nm ³ in the operation equivalent to RAR494 kg / t (PCR: 130 kg / t, blowing temperature: 1150 ° C.), (2) 620kcal for operation equivalent to RAR 450kg / t (PCR: 130kg / t, blast temperature: 1200 ° C, high-reactive coke used, heat loss reduced by 43%, shaft efficiency increased by 2% compared to operation (1) above) / Nm ³ , (3) Operation equivalent to RAR 412 kg / t (PCR: 130 kg / t, blast temperature: 1200 ° C., use of highly reactive coke, heat loss reduced by 57%, shaft efficiency compared to the operation of (1) above 4% up), it is 517 kcal / Nm ³ . In the calculation, in the operations (2) and (3) above, the temperature of the blast furnace top gas is 110 ° C. or less. Therefore, for example, when a part of the blast furnace gas discharged from the top of the furnace is extracted and preheated gas burned with oxygen is injected into the furnace from the shaft part, and the blast furnace top gas temperature is maintained at 110 ° C. or higher, The gas heating value further decreases. For example, in the operation of the above (2), if a 800 ° C. preheated gas's crowded 100 Nm ³ / t blown, the blast furnace gas calorific value 590kcal / Nm ^3, and the addition, in the operation of the above (3), preheating of 800 ° C. When gas is blown at 150 Nm ³ / t, the blast furnace gas heating value is 477 kcal / Nm ³ . Such a decrease in the amount of heat generated by the blast furnace gas due to the low RAR operation makes it more difficult to perform stable combustion with the conventional general gas burner as described above.
Further, a normal blast furnace is operated under a pressure of 4 to 5 kg / cm ² , and there is a constant pressure fluctuation because the charged material descends from the upper part of the blast furnace. In addition, blow-by due to the generation of deposits on the blast furnace wall occurs. In the conventional general gas burner as described above, the stability of the flame is hindered by these factors, and there is a possibility that blowout or the like may occur.

In order to solve the problems of the conventional gas burner as described above, hydrogen is used for a low calorific value gas such as a blast furnace gas which is used as a fuel gas and a tubular flame burner type gas combustion / blowing device a in the present invention. In addition, the following effects can be obtained by stable combustion.
(A) Gas burns in the combustion chamber 1 and there is no flame outside the combustion chamber 1, so the charge (iron ore, coke) descending from the upper part of the blast furnace is not directly exposed to flame, and the charge There is little influence on. Similarly, since there is no flame outside the combustion chamber 1, a stable flame is formed without being affected by the furnace pressure in the blast furnace, its fluctuation, or blow-through, and the combustion gas at a desired temperature is stabilized in the furnace. Can be blown in.

(B) The preheated gas to be blown into the furnace needs to have a pressure higher than the pressure in the furnace at the position to be blown, and therefore gas combustion occurs substantially under pressure in the combustion chamber 1 of the gas combustion / blowing device a. However, when the combustion chamber 1 is in a pressurized state in this way, it becomes an advantageous condition for stably combusting a low calorific value gas such as a blast furnace gas. In the gas combustion / blowing device a, since a stable flame is formed in the combustion chamber 1 and the mixing property of the fuel gas and the combustion support gas is good, the gas can be burned efficiently and homogeneously. In particular, when the combustion chamber 1 is in a pressurized state as described above, the apparent heat generation amount increases because the gas density increases with respect to the heat generation amount in the standard state. For this reason, even if the fuel gas is a low calorific value gas such as blast furnace gas or the concentration of the fuel gas component is very low, coupled with the addition of hydrogen to the fuel gas, It becomes possible to burn stably.

(C) Similarly, when the combustion chamber 1 is in a pressurized state, the gas density is increased, and the amount of heat held by the fuel gas can be effectively transmitted to the combustion gas. In particular, since unburned gas and supporting gas exist near the inner wall surface 100 of the combustion chamber 1, the inner wall surface 100 of the combustion chamber 1 is not heated to a high temperature by direct heat transfer, The effect is further enhanced by the small heat loss from the tube wall.
(D) It is preferable that the preheating gas blown from the gas blowing section A does not contain oxygen (oxygen gas as O ₂ ; the same applies hereinafter) or has a low oxygen concentration. This is because if the preheating gas contains oxygen, iron oxide (Fe ₂ O ₃ , FeO) being reduced in the furnace is reoxidized. In this respect, the gas combustion / blowing device a has a high oxygen utilization efficiency by forming a stable flame in the combustion chamber 1, and further increases the oxygen utilization efficiency when the combustion chamber 1 is in a pressurized state. Therefore, stable combustion is possible with an oxygen amount smaller than the theoretical oxygen amount. Therefore, a preheating gas that does not contain oxygen or has a very low oxygen concentration can be blown into the furnace.
(E) Since a stable flame is formed in the combustion chamber 1, the temperature variation of the preheating gas (combustion gas) blown into the furnace is small, and the blast furnace gas from the lower part of the furnace and the charging that descends from the upper part of the furnace The temperature of the object can be raised without variation.

Usually, the flow path 28 for guiding the blast furnace gas to the booster 25, the composition of the blast furnace gas, is installed a sensor 26 _A that measures such as temperature and pressure, also the pressure inside the furnace in the vicinity of the gas blowing part A, the temperature A sensor 26 _{B to} be measured is installed, and based on the measured values of these sensors 26 _A and 26 _B , the gas pressure to be boosted by the boosters 25 a and 26 b, the amount of combustion support gas to be introduced into the gas combustion / blowing device a, and the hydrogen amount Etc. are controlled.
Blowing of the preheating gas from the gas blowing section A may be performed constantly or only when the furnace top gas temperature is lowered. In the latter case, for example, the furnace top gas temperature is measured by a sensor, and when the furnace top gas temperature is equal to or lower than a predetermined temperature (for example, 110 ° C. or lower), the preheating gas is blown from the gas blowing portion A. .
Although there is no special restriction | limiting in the temperature of the preheating gas blown in from the gas blowing part A, since it will cool the inside of a furnace conversely if lower than the furnace gas temperature of the blowing position, it will be higher than the furnace gas temperature of the blowing position. A high temperature is preferred, generally 500 ° C. or higher, preferably 800 ° C. or higher.

There is no particular limitation on the amount of preheated gas blown, and generally the gas blown amount may be set so that the furnace top gas temperature can be maintained at 100 ° C. or higher.
The installation position of the gas blowing part A (preheating gas blowing position) in the furnace height direction is preferably from the middle to the upper part of the shaft. In particular, the position where the furnace port radius is R ₀ and the depth from the stock line is R ₀ is p. _1, when the height from the shaft portion the lower end has a position of 1/3 of the total height shaft and p _2, established the gas injection portion a between the position p ₁ and the position p ₂ in the furnace height direction, the Preheating gas is preferably blown from the gas blowing portion A. If the preheating gas blowing position is too shallow (too high), the load of the raw material packed bed is small, so that the raw material is fluidized and stirred, which may reduce the stability of the raw material drop. On the other hand, if the blowing position of the preheating gas is too deep (too low), it may be applied to the softened fusion zone in the furnace, which is not preferable.

  The number of installed gas blowing portions A and the installation form in the furnace circumferential direction are not particularly limited, but are preferably provided at a plurality of locations at equal intervals in the furnace circumferential direction. In particular, at least n places (where n is an even number of 4 or more) at equal intervals in the furnace circumferential direction, and depending on the total amount of preheated gas blown, the preheated gas is discharged from the n gas blowing portions A. It is preferable to select the gas blowing parts A for blowing at equal intervals in the furnace circumferential direction. In this case, the number of gas blowing portions A installed at equal intervals is 4, 8, 16, 32, 64, or the like. In actual equipment, it may be difficult to provide the gas blowing parts A at exactly equal intervals in the furnace circumferential direction because of the relationship with the furnace body cooling structure, etc. Is done.

  The present invention is a preferred embodiment in which a blast furnace gas that has a low calorific value and can be introduced from a nearby location is used as the fuel gas of the gas combustion / blowing device a, and in particular, the blast furnace gas discharged from the top of the furnace It is a particularly preferable embodiment from the viewpoint of effective use of energy (gas sensible heat can be used as it is) and from the viewpoint of equipment, by extracting a part of the gas from an appropriate flow path position and using it as a fuel gas. I can say that. However, gas other than blast furnace gas may be used as the fuel gas, or blast furnace gas and other gas may be mixed and used. The blast furnace gas includes blast furnace gas extracted from the downstream side of the gas cleaning device (dust catcher 22, mist separator 23), blast furnace gas extracted from between the top of the furnace and the gas cleaning device, and blast furnace gas stored in the gas holder. Etc. may be used.

[Example 1]
A combustion test using a fuel gas (low calorific value gas) to which hydrogen was added and a combustion-supporting gas (air) was performed under the conditions shown in Table 2 using the combustion burner test apparatus having the structure shown in FIG. The combustion chamber of this test apparatus has an inner diameter of 50 mm and an overall length of 300 mm, and an opening (nozzle slit) for injecting fuel gas formed on the inner wall surface has a length of 48 mm, a width of 5 mm, and an inflow of combustion supporting gas. The opening (nozzle slit) has a length of 31 mm and a width of 5 mm.

In Invention Examples 1 to 4, a low calorific value gas (CO: 10.1 vol%, CO ₂ : 10.4 vol%, N ₂ : 79.5 vol%) of about 300 kcal / Nm ³ is prepared as the fuel gas. Hydrogen was added to the gas at concentrations of 3.7 vol%, 4.0 vol%, 6.0 vol%, and 2.0% in the fuel gas, and a combustion test was performed. In Invention Examples 5 and 6, a blast furnace gas at an operation equivalent to RAR 412 kg / t was used as the fuel gas, and hydrogen was added thereto to conduct a combustion test. In Examples 7 and 8, a blast furnace gas at an operation equivalent to RAR 450 kg / t was used as the fuel gas, and hydrogen was added thereto to conduct a combustion test. In any case, air was supplied so that the theoretical oxygen amount was 1.1 with respect to 30 Nm ³ / h of a fuel gas mixed with hydrogen. As a comparative example, a combustion test using a fuel gas not mixed with hydrogen was also conducted.

In this combustion test, the combustion stability was evaluated according to the following criteria.
○: Stable combustion (excellent) following pressure fluctuation without pulsation of flame
△: Flame pulsates, but no misfire is recognized (good)
×: Flame pulsates and misfires due to pressure fluctuation (impossible)
The results are shown in Table 2 together with the test conditions. According to this, all of the inventive examples realize stable combustion, and particularly when hydrogen is added so that the adiabatic flame temperature becomes 750 ° C. or higher, very stable combustion is realized. Yes.

[Example 2]
Fuel gas (hydrogen-mixed fuel gas) and combustion-supporting gas (air) under the conditions shown in Table 3 using a combustion burner test apparatus in which the number of nozzle tubes constituting the gas nozzle for fuel gas and the gas nozzle for combustion-supporting gas is different. ) Was used to conduct a combustion test. Here, the combustion burner in which each gas nozzle is composed of one (single) nozzle tube is a burner having a gas nozzle having a structure as in the embodiment of FIGS. 1 and 2, and each gas nozzle has a plurality of gas nozzles. The combustion burner constituted by the nozzle tube is a burner having a gas nozzle having a structure as in the embodiment of FIGS.
The combustion chamber of each combustion burner has an inner diameter of 50 mm and an overall length of 700 mm. The number of nozzle tubes constituting the gas nozzle for fuel gas and the gas nozzle for combustion support gas is Test Example 1: 5 and Test Example 2 : 4, Test Example 3: 2, Test Example 4: 1, Test Example 5: 4, Test Example 6: 2

  In the combustion burners used in Test Examples 1 to 4, the inner diameter of the nozzle tube constituting the gas nozzle for injecting fuel gas is 10 mm, and the inner diameter of the nozzle tube constituting the gas nozzle for injecting combustion gas is also 10 mm. In the combustion burner used in Test Example 5, the inner diameter of the nozzle tube constituting the gas nozzle for fuel gas blowing is 6 mm, and the inner diameter of the nozzle tube constituting the gas nozzle for blowing combustion gas is also 6 mm. In the combustion burner used in Test Example 6, the inner diameter of the nozzle tube constituting the gas nozzle for fuel gas blowing is 10 mm, and the inner diameter of the nozzle tube constituting the gas nozzle for supporting combustion gas blowing is 10 mm.

The blast furnace gas used as the fuel gas (blast furnace gas mixed with hydrogen) has a gas composition of CO: 22 vol%, CO ₂ : 21 vol%, H ₂ : 5 vol%, N ₂ : 52 vol%, and a calorific value of 792 kcal / Nm ^3. Air: 19.5 Nm ³ / h was supplied as a combustion support gas so that the theoretical oxygen amount was 1 with respect to this fuel gas: 30 Nm ³ / h. The furnace pressure of the applied test furnace is 245 kPa.
In Test Example 6, combustion exhaust gas discharged from the combustion chamber using a combustion burner provided with a gas nozzle for dilution gas (inner diameter 20 mm) at a position 500 mm away from the center of the fuel gas / support gas injection position in the burner axial direction A dilution gas (blast furnace gas) was supplied at 33.8 Nm ³ / h so that the temperature became 800 ° C. By adding this dilution gas, the combustion gas composition contained 10.3 vol% of CO (reducing gas).

In Test Examples 1 to 6, observation in the combustion chamber (observation from a viewing window as shown in FIG. 9) and gas composition analysis of the combustion exhaust gas were performed, and the combustion state was evaluated according to the following criteria. The results are shown in Table 3 together with the configuration of the gas nozzle, the gas flow rate, the swirl number Sw, the combustion gas composition (in Test Example 6, the gas composition after adding the dilution gas), and the like.
X: Pulsation was observed in the combustion state, and a considerable amount of unburned CO was measured.
○: Stable combustion continued and almost no unburned CO was measured (however, the CO concentration in Test Example 6 is due to the mixing of dilution gas)

[Example 3]
In a blast furnace having a furnace internal volume of 5000 m ³ , the present invention was implemented in an embodiment as shown in FIG. 8 using a gas combustion / blowing device a as shown in FIGS. 1 and 2. The operating conditions were pulverized coal blowing rate: 130 kg / t, coke ratio: 320 kg / t, blowing temperature: 1150 ° C. (humidity: 10 g / Nm ³ ), and highly reactive coke was used. Blast furnace gas extracted from the downstream side of the top gas turbine generator _{24 (CO: 17.7vol%, CO} 2: 23.1vol%, H 2: 2.4vol%, H 2 O: 3.6vol%, N 2: 53.2 vol%) was boosted to a pressure 0.2 atm higher than the furnace pressure by the booster 25a, and introduced into the gas combustion / blowing apparatus a constituting the gas blowing section A as fuel gas. At that time, hydrogen was added to the blast furnace gas so that the hydrogen concentration was 4.0 vol% to obtain a hydrogen mixed fuel gas. Further, the air was boosted by the booster 25b and introduced into the gas combustion / blowing device a as a combustion support gas.

In the gas combustion and purging means a, a hydrogen fuel gas mixture 100 Nm ³ / t to produce a 800 ° C. combustion gas is burned with air 37.8Nm ³ / t, was blown into the furnace so as preheating gas. The oxygen ratio in the gas combustion / blowing apparatus a is 0.736 (relative to the theoretical oxygen amount), and the composition of the preheating gas is CO: 3.5 vol%, CO ₂ : 27.3 vol%, H ₂ : 0. _{.8vol%, H 2 O: 5.0vol} %, N 2: a 63.3vol%. By blowing such preheated gas, the furnace top gas temperature became 149 ° C., and condensation of moisture into the piping during blast furnace operation was completely avoided, and stable operation became possible. When preheating gas is not injected, it is calculated as 97 ° C. from the calculation of material heat balance.

[Example 4]
In a blast furnace having a furnace internal volume of 5000 m ³ , the present invention was implemented in an embodiment as shown in FIG. 8 using a gas combustion / blowing device a as shown in FIGS. The blast furnace operating conditions were the same as in Example 3. Blast furnace gas extracted from the downstream side of the top gas turbine generator _{24 (CO: 17.7vol%, CO} 2: 23.1vol%, H 2: 2.4vol%, H 2 O: 3.6vol%, N 2: 53.2 vol%) was boosted to a pressure 0.2 atm higher than the furnace pressure by the booster 25a, and introduced into the gas combustion / blowing apparatus a constituting the gas blowing section A as fuel gas. At that time, hydrogen was added to the blast furnace gas so that the hydrogen concentration was 4.0 vol% to obtain a hydrogen mixed blast furnace gas. Further, the air was boosted by the booster 25b and introduced into the gas combustion / blowing device a as a combustion support gas.

In the gas combustion / blowing device a, hydrogen-mixed blast furnace gas 73.6 Nm ³ / t is combusted with air 37.8 Nm ³ / t (oxygen ratio 1.0), and dilution gas (BFG) is 26.4 Nm in the combustion chamber. ^By supplying ³ / t, a combustion gas of 800 ° C. was generated, and this was blown into the furnace as a preheating gas. The composition of the preheating gas is the same as in Example 3. By blowing such preheated gas, the furnace top gas temperature became 147 ° C., and condensation of moisture into the piping during blast furnace operation was completely avoided, and stable operation became possible. When preheating gas is not injected, it is calculated as 97 ° C. from the calculation of material heat balance.

1 the combustion chamber _{2a, 2b, 2c 1, 2c} 2 openings _{3a, 3b, 3c 1, 3c} 2 gas nozzle 4 mixing chamber 5 fuel gas supply pipe 6 a hydrogen supply pipe 7 the oxidizing gas supply pipe 8, 9 and 10 flow regulating valve 11 flow meter 12 the combustion status sensor 13 ignition plug 14 gas nozzle 15 opening 20 blast furnace 21 birds port 22 dust catcher 23 mist separator 24 top gas generator device 25a, 25b booster 26 _A, 26 _B sensors 27, 28 the channel 100 in the wall 140 Nozzle pipe 150 Opening 200a, 200b Opening 300a, 300b Nozzle pipe A Gas blowing part a Gas combustion / blowing device

Claims (9)

For injecting fuel gas and supporting gas into the inner wall surface of the tubular combustion chamber with the open end so that a gas swirl flow is generated in the combustion chamber or for injecting a premixed gas of fuel gas and supporting gas When a gas having a calorific value of 1000 kcal / Nm ³ or less is used as a fuel gas in a combustion burner having an opening, hydrogen is added to the fuel gas before being blown into the combustion chamber and / or the fuel gas blown into the combustion chamber (Including the case where it is added as a hydrogen-containing gas) and a gas containing one or more of CO and H _{2 in} the combustion chamber, and adjusting the gas composition or gas composition and gas temperature by diluting the combustion gas A method for burning a low calorific value gas by a combustion burner, characterized in that a dilution gas is supplied . A fuel gas and a combustion-supporting gas are blown into the inner wall surface of a tubular combustion chamber having an open end so that a gas swirl flow is generated in the combustion chamber in a direction substantially tangential to the inner wall surface. When a gas having a calorific value of 1000 kcal / Nm ³ or less is used as a fuel gas in a combustion burner having an opening for injecting a premixed gas, the fuel gas before being blown into the combustion chamber and / or blown into the combustion chamber Hydrogen is added to the fuel gas (including the case where it is added as a hydrogen-containing gas) , and is a gas containing at least one of CO and H _{2 in} the combustion chamber , wherein the combustion gas is diluted to have a gas composition or A combustion method of a low calorific value gas by a combustion burner, characterized in that a dilution gas for adjusting a gas composition and a gas temperature is supplied .   The combustion burner according to claim 1 or 2, wherein hydrogen is added to the fuel gas containing CO so that the adiabatic flame temperature is 750 ° C or higher (including the case where hydrogen is added as a hydrogen-containing gas). Low calorific gas combustion method.   A gas nozzle for supplying fuel gas and combustion-supporting gas into the combustion chamber through an opening formed on the inner wall surface of the combustion chamber, or a gas nozzle for supplying premixed gas of fuel gas and combustion-supporting gas, in the burner axial direction, 4. A combustion method of a low calorific value gas using a combustion burner according to claim 1, wherein a combustion burner comprising a plurality of nozzle tubes arranged in parallel is used.   Using a combustion burner in which another opening for injecting gas is further formed on the inner wall surface of the combustion chamber so that a gas swirl flow is generated in the combustion chamber, hydrogen is blown into the combustion chamber from the opening (however, hydrogen-containing gas The combustion method of the low calorific value gas by the combustion burner according to any one of claims 1 to 4, wherein   A combustion burner having another opening for injecting gas in a substantially tangential direction of the inner wall surface so that a gas swirl flow is generated in the combustion chamber is formed on the inner wall surface of the combustion chamber. The method for combusting a low calorific value gas by the combustion burner according to any one of claims 1 to 4, wherein the gas is burned (including a case where the gas is blown as a hydrogen-containing gas).   The gas nozzle for supplying hydrogen into the combustion chamber through another opening formed in the inner wall surface of the combustion chamber uses a combustion burner composed of a plurality of nozzle tubes arranged in parallel in the burner axial direction. A combustion method of a low calorific value gas by a combustion burner according to 5 or 6.   The method for combusting low calorific gas with a combustion burner according to any one of claims 1 to 7, wherein the swirl number Sw of the gas flow in the combustion chamber is 3 to 10. An opening is formed in the inner wall surface on the rear end side of the combustion chamber so as to blow each of the fuel gas and the combustion support gas so that a gas swirl flow is generated in the combustion chamber. A gas nozzle is provided at a position closer to the front end of the combustion chamber than the center position in the longitudinal direction of the combustion chamber to dilute the combustion gas and supply a dilution gas for adjusting the gas composition or gas composition and gas temperature into the combustion chamber. The combustion method of the low calorific value gas by the combustion burner according to any one of claims 1 to 8, wherein a combustion burner is used.

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