JP2013185181A - Blast furnace operating method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a blast furnace operating method for making ore reduction and permeability in a furnace diameter direction be proper when blowing a hydrogen-containing reducing gas into a blast furnace shaft part.SOLUTION: In a blast furnace operating method, when blowing a hydrogen-containing reducing gas from a blast furnace shaft part, a blowing amount of a hydrogen gas is 20 Nmor more and 150 Nmor less per ton of pig iron, and O/C in a radial direction in a blast furnace top part satisfies the following expressions (1) and (2). The expression (1) is (0.003×VH+1.2)≥a≥(0.003×VH+0.85) and the expression (2) is a≥1.0, provided that: (a) is (O/C)/(O/C), and it is a ratio of O/C of a furnace peripheral part and a furnace intermediate part when the radial direction of the furnace top part is divided into three and defined as 1, 2 and 3 from a furnace center to a furnace wall; and VHis a blowing amount (Nm/tp) of the hydrogen gas.

Description

  The present invention relates to a blast furnace operating method.

In recent years, from the viewpoint of protecting the global environment, the need for reducing carbon dioxide emissions has increased, and measures for reducing carbon dioxide in a blast furnace have been studied. Coke and pulverized coal (hereinafter referred to as PC) burned in the blast furnace burns carbon, the main component, into carbon monoxide in the front tuyere raceway, reducing iron ore when ascending in the blast furnace. Then it becomes carbon dioxide and is discharged from the top of the furnace.
Here, coke oven gas containing a large amount of hydrogen and methane (hereinafter referred to as COG) and natural gas containing methane as the main component (hereinafter referred to as LNG) instead of coke and PC containing carbon as the main component. Alternatively, a reduction in carbon dioxide discharged from the blast furnace can be expected by blowing a reducing gas containing hydrogen such as reformed COG having a high hydrogen content by reforming COG.

  There is a technique in which a reducing gas containing hydrogen such as COG, LNG, or reformed COG is blown from the tuyere of a blast furnace. This method is an effective means by using a fuel containing a large amount of hydrogen gas and suppressing emission of carbon dioxide from the blast furnace. However, when these gases burn in front of the tuyere, the temperature at the tuyere decreases. If the blast temperature is increased or the oxygen blowing rate is increased as a countermeasure, the heat flow ratio is increased, resulting in insufficient heat in the blast furnace shaft. In addition, there is a limit to burning a large amount of gas in a limited space called the tuyere front raceway.

  A conceivable method is to blow a reducing gas containing hydrogen such as COG, LNG, or reformed COG into the lower part of the blast furnace shaft. This method reduces the ore with hydrogen before the ore in the blast furnace melts, and is an effective means for suppressing the discharge of carbon dioxide from the blast furnace. There are no problems such as a decrease in temperature before the tuyere and an increase in the heat flow ratio.

However, even if reducing gas containing hydrogen is blown into the lower shaft of the blast furnace, the furnace is filled with ore and coke, and the blown gas stays in the vicinity of the furnace wall and reaches the furnace center. It does not penetrate. As a result, there is a problem that the ore reduction in the radial direction in the furnace and the maintenance of air permeability become inappropriate.
Conventionally, there is a disclosure of a technique in which reducing gas is blown from a lower portion of a blast furnace shaft.
In view of the fact that the blown gas does not diffuse uniformly into the furnace, a method of blowing the gas vertically from the top of the furnace through a pipe is disclosed (Patent Document 1).
Next, an invention is disclosed in which hydrocarbon fluid is blown from the lower part of the furnace (tuyere) by an oxygen injection device, and reducing gas mainly containing preheated CO and H ₂ is blown from the lower part of the shaft above the furnace (patent). Reference 2).
Further, there is disclosed an invention in which a gas that has been burned with fuel gas and whose temperature is increased is blown into a furnace shaft portion by a gas combustion / blowing device (Patent Document 3).
Also, there is a disclosure of a technique in which the temperature of the reducing gas is raised with a plasma arc heater and a high-temperature reducing gas is blown into the peripheral portion when the ratio of ore and coke in the peripheral portion (hereinafter referred to as O / C) is high. Yes (Patent Document 4).
Also disclosed is a technique in which heavy oil is pyrolyzed and a reducing gas having a high hydrogen content (H ₂ : 46%, CO: 44%) is blown into a test blast furnace (non-patent document 1).

Japanese Unexamined Patent Publication No. 47-3404 JP-A-47-9104 Japanese Patent No. 4760985 Japanese Patent Laid-Open No. 5-195027

Iron and Steel 58th (1972) No.5 P68-P80 CAMP-ISIJ Vol. 23 (2010) -879 CAMP-ISI Vol.23 (2010) -94 Iron and steel Vol.87 (2001) No5 P154

However, the invention described in Patent Document 1 requires very high equipment technology such as sealing performance, and in the blast furnace of the bell-less charging device, the vertical pipe interferes with the turning chute, and only the bell-type charging device. Limited application. In addition, it is difficult to install the vertical pipe at the center of the furnace, and there is a problem that stable blast furnace operation is difficult because the placement of the charge in the furnace is greatly disturbed.
The invention described in Patent Document 2 supplements the heat shortage in the upper part of the furnace due to fuel blowing from the furnace lower part (feather) with a preheating reducing gas. In order to compensate for the lack of temperature at the upper part of the shaft due to the operation of the ratio, a dilution gas having a higher temperature is blown into the lower part of the shaft. In addition, the invention described in Patent Document 4 compensates for insufficient heat reduction in the peripheral portion when the peripheral portion O / C becomes high. The inventions described in these documents are measures against heat shortage of the shaft portion, and there is no mention that the reducing gas containing hydrogen does not penetrate to the furnace center.
Non-Patent Document 1 describes that the permeability of the reducing gas blown into the upper part of the shaft into the furnace is investigated using a glass sphere packed bed, and the blown gas stays around the furnace. However, there is no examination or description of countermeasures against this. The reducing gas injection is intended to compensate for the heavy oil blowing from the tuyere and to inject the reducing gas modified from the heavy oil, and the amount of injection is limited to a maximum of 29.6 kg / tp in terms of heavy oil. .
This invention makes it a subject to suppress the discharge | emission of the carbon dioxide from a blast furnace by blowing in reducing gas containing hydrogen, such as COG, LNG, or reforming COG, from the lower part of a blast furnace shaft.
When reducing gas containing hydrogen is blown into the lower part of the shaft of the blast furnace, the reducing gas stays in the vicinity of the furnace wall and does not penetrate to the furnace center. As a result, the ore reduction in the radial direction in the furnace changes, making it difficult to maintain air permeability and hindering blast furnace operation.
An object of the present invention is to provide a blast furnace operating method in which ore reduction and air permeability in the furnace radial direction are appropriate when reducing gas containing hydrogen is blown into the lower part of the shaft of the blast furnace.

  The present inventor conducted an experiment in which a reducing gas containing hydrogen was blown into the lower portion of the shaft of the blast furnace using a blast furnace reaction simulator (hereinafter referred to as a BIS furnace). As a result, the O / C in the furnace radial direction was adjusted. And found that smooth blast furnace operation is possible. The present invention has been made to solve the above problems based on this finding, and the gist of the present invention is as follows.

(1) A blast furnace operation in which reducing gas containing hydrogen is blown from a blast furnace shaft portion,
Blowing amount of the hydrogen gas contained in the reducing gas pig iron per ton of 20 Nm ³ or more and 150 Nm ³ or less,
A blast furnace operating method characterized in that a distribution coefficient a of O / C in the radial direction at the top of the blast furnace furnace satisfies the following expressions (1) and (2).
(0.003 × VH ₂ +1.2) ≧ a ≧ (0.003 × VH ₂ +0.85) (1)
a ≧ 1.0 ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ (2)
However,
a; (O / C) ₃ / (O / C) ₂ . Ratio of the furnace peripheral part (O / C) ₃ and the furnace intermediate part (O / C) ₂ when the radial direction at the top of the blast furnace furnace is divided into three and 1, 2, 3 from the furnace center toward the furnace wall It is.
VH ₂ ; amount of hydrogen gas blown (Nm ³ / tp)

  INDUSTRIAL APPLICABILITY The present invention can provide a blast furnace operating method capable of performing ore reduction and air permeability in an appropriate furnace radial direction when reducing gas containing hydrogen is blown into the lower part of the shaft of the blast furnace.

The figure which shows the experimental apparatus of the actual blast furnace 1/10 which investigates the flow of blowing gas. The figure which shows the flow of the shaft blowing gas in the experimental apparatus of actual blast furnace 1/10. The figure which shows the pressure loss of the sintered ore by modified COG. The relationship between the injection amount of the modified COG and the maximum pressure loss of the sintered ore is shown. The figure which shows the outline of a heat insulation type BIS furnace. The figure which shows the relationship between charging O / C and a 1100 degreeC reduction rate. _{a = (O / C) 3} / (O / C) 2 and illustrates the relationship of the discharge CO _2. The figure which shows the relationship between the shaft blowing amount and the distribution coefficient a.

[Composition of reducing gas containing hydrogen]
The reducing gas blown from the shaft portion for suppressing the discharge of carbon dioxide from the blast furnace is a gas containing hydrogen such as COG, LNG, or modified COG.
LNG (CH ₄ ) contains up to 75% hydrogen by steam reforming (CH ₄ + H ₂ O = 3H ₂ + CO), with the remainder being CO.
_{H 2} in COG is 57%, the sum of _{H 2} when all 32% methane COG steam reforming is increased to 78%.
In order to exert the CO ₂ reduction effect, the H ₂ concentration of the reformed reducing gas blown from the shaft is set to 50% or more and a maximum of 78%.
The COG reforming method does not affect the effect of the present invention. As a method for reforming methane (CH ₄ ) contained in COG, a reforming method combined with steam, partial oxidation, or the like can be applied, and a gas having a predetermined H ₂ concentration may be obtained after predetermined reforming.

[Blowing amount of hydrogen-containing reducing gas]
Blowing amount of reducing gas containing hydrogen, represents hydrogen amount ^{_{(VH 2) Nm 3 / tp}} , and 20 Nm ³ / tp to 150 Nm ³ / tp. This is because the lower limit is less than the CO ₂ reduction effect. The upper limit is determined by the mass balance in the steelworks. The amount of COG (CH ₄ : 32%, H ₂ : 57%) produced from the coke oven is 156 Nm ³ / tp. Considering COG supply to the bottom step, the 100 Nm ³ / tp of the generation amount as steam ^reforming, _{H 2} of 153Nm 3 /tp(100*(0.57+0.32*3)) is generated.

[Flow in shaft when hydrogen-containing reducing gas is blown]
When reducing gas containing hydrogen is blown into the lower part of the shaft of the blast furnace, the reducing gas stays in the vicinity of the furnace wall and does not penetrate to the furnace center. The present inventors have investigated and already published the distribution of the gas in the shaft when the gas is blown into the lower part of the shaft using the experimental apparatus of an actual blast furnace 1/10 (Non-patent Document 2).
FIG. 1 shows an experimental apparatus for an actual blast furnace 1/10 for investigating the flow of injected gas. Filled with 2-5 mm coke, sampled the furnace gas from the sampling hole 3 on the back of the device by blowing air from the tuyere 1 at 800 L / min and CO ₂ from the gas blowing nozzle 2 at the shaft at 80 L / min or 160 L / min. The gas flow was investigated by measuring the concentration of carbon dioxide. FIG. 2 shows the flow of shaft blowing gas in the experimental apparatus for an actual blast furnace 1/10. The blown gas rises in a range where the distance from the furnace wall is 150 mm with respect to the model width of 1000 mm.
Assuming that the shaft width (radius) of the 5000 m ³ class is 8000 mm, in an actual furnace, the reducing gas blown into the lower part of the shaft rises in the shaft within a range of the peripheral part at a distance of about 1200 mm from the furnace wall. Conceivable.

[Ore reduction when blowing hydrogen-containing reducing gas]
The present inventors have investigated and already published the influence of blowing hydrogen-containing reducing gas on the high-temperature reducing properties of iron ore (Non-patent Document 3).
FIG. 3 shows the pressure loss of the sintered ore by the modified COG. This is an investigation of the ventilation resistance of an ore packed bed due to reduction, softening, and melting of a sintered ore when a sintered ore is reduced with a hydrogen-containing reducing gas while simulating an actual furnace and applying a load. The temperature pattern was 10 ° C./min up to 900 ° C., held at 900 ° C. for 30 minutes, 5 ° C./min from 900 to 1600 ° C., and a load of 9.8 × 10 ⁻² MPa was applied from 800 ° C. The gas composition was H ₂ 60%, CO 30%, N ₂ 10% gas was blown at a position of 900 ° C. or higher. The amount of gas blown was 0, 100, or 300 Nm ³ / tp. The gas distribution ratio is a case where the radial direction in the furnace at the blowing position is equally divided into three, and the blowing amount V ₁ at the intermediate portion and the blowing amount V _{W at the} peripheral portion are 1: 5.
In FIG. 3, the reduction of the sinter progresses by the modified COG, and the pressure loss of the sinter packed bed is greatly reduced by blowing the modified COG. It shows that the reducing power of hydrogen is great.
FIG. 4 shows the relationship between the amount of reformed COG injected and the maximum pressure loss of the sintered ore. By blowing the modified COG, the pressure loss in the peripheral portion is greatly reduced.
This is presumed that the reduction of the sintered ore progressed due to the blowing of the modified COG, the amount of the melt in the cohesive zone at the periphery decreased, and the cohesive zone became extremely thin. As a result, it is considered that the pressure loss in the peripheral portion is significantly reduced.

[Relationship between charging O / C and 1100 ° C reduction rate]
As described above, when the reformed COG is blown from the lower part of the shaft, the blown reducing gas rises in the peripheral part of the furnace. Since H ₂ containing reformed COG has a strong reducing power, the ore in the peripheral part is remarkably reduced. As a result, the pressure loss in the peripheral part is reduced, and knitting flow to the peripheral part of the furnace gas is assumed. The The drift of the in-furnace gas to the periphery may cause modulation of blast furnace operation. Therefore, the present inventors considered increasing the O / C of the peripheral portion and suppressing the peripheral flow when the hydrogen-containing reducing gas is blown from the lower portion of the shaft.
The present inventors first investigated the relationship between the charging O / C and the ore reduction rate using an adiabatic BIS furnace.

  The adiabatic BIS furnace is a heating type blast furnace reaction simulator (BIS furnace) modified to an adiabatic type. FIG. 5 shows an outline of the heat insulation type BIS furnace. The reaction tube 4 is filled with ore 5 and coke 6 in layers, the heater 7 is moved, and the gas is introduced into the reaction tube 4 to form a countercurrent moving layer. For heat insulation, heat dissipation from the reaction tube 4 is prevented by the heat insulation layer 8, the temperature is detected from the thermometer 9 in contact with the inside and the outer wall of the reaction tube 4, and both temperatures are matched by the control unit 10. The electric furnace is controlled (Non-Patent Document 4).

FIG. 6 shows the relationship between the charging O / C and the 1100 ° C. reduction rate when the hydrogen-containing reducing gas is blown. This was investigated using an adiabatic BIS furnace.
The charging O / C is managed by O / C at each of the divided parts when the radial direction at the top of the blast furnace furnace is divided into three and is 1, 2, 3 from the center toward the furnace wall.
In FIG. 6, a straight line of VH ₂ = 0 Nm ³ / tp is indicated as charging (O / C) ₂ (hereinafter referred to as (O / C) ₂ ) in the middle part of the furnace where hydrogen in the blowing reducing gas does not permeate. ) And the 1100 ° C. reduction rate. On the other hand, the straight line of VH ₂ = 100 Nm ³ / tp is charged (O / C) ₃ (hereinafter referred to as (O / C) ₃ ) and 1100 ° C. reduction at the periphery of the furnace where the reducing gas is infiltrated. It means rate relationship.

For example, consider a case where the charging O / C is 5.0 and the intermediate part (O / C) ₂ and the peripheral part (O / C) ₃ are 5.0. When the hydrogen in the blowing reducing gas is VH ₂ = 100 Nm ³ / tp, the 1100 ° C. reduction rate of the peripheral portion where the reducing gas penetrates increases to 69% (point B), but the reducing gas does not penetrate. The 1100 ° C. reduction rate in the middle part remains at 52% (point A). As a result, as shown in FIG. 4, the pressure loss of the ore packed bed in the peripheral portion decreases, and the gas in the furnace concentrates in the peripheral portion, which may lead to a malfunction due to a change in the furnace condition.

In FIG. 6, in order to avoid gas concentration in the peripheral part due to a decrease in pressure loss in the peripheral part, (O / C) ₃ in the peripheral part may be set to 5.9 (point C). If the intermediate part (O / C) _{2 is set} to 5.0, the peripheral part (O / C) _{3 is set} to 5.9, and the respective 1100 ° C. reduction rates are set to 52%, the furnace gas in the peripheral part and the intermediate part is reduced. It is considered that the unbalance can be eliminated and a stable furnace condition can be maintained.

[A peripheral portion, the relationship between the CO ₂ emissions and the intermediate portion O / C]
When the hydrogen-containing reducing gas is injected as described above, the ore reduction state in the furnace is changed by the peripheral part (O / C) ₃ and the intermediate part (O / C) ₂ of the furnace, and the exhaust CO ₂ (kg / kg) is changed. tp) is affected.
Changes in exhaust CO ₂ (kg / tp) when (O / C) ₃ and (O / C) ₂ were changed were investigated using the adiabatic BIS furnace.

The ratio of O / C between the peripheral part and the intermediate part was defined as a distribution coefficient a. That is, a = (O / C) ₃ / (O / C).
FIG. 7 shows the relationship between a = (O / C) ₃ / (O / C) ₂ and exhaust CO ₂ .
When the hydrogen injection is VH ₂ = 0 Nm ³ / tp, when a = (O / C) ₃ / (O / C) ₂ is 1.0, the exhaust CO ₂ (kg / tp) is the lowest value ( P point).
When hydrogen injection is VH ₂ = 50 Nm ³ / tp, when a = (O / C) ₃ / (O / C) ₂ is 1.0 (P point) to 1.35 (Q point), Hydrogen injection is smaller than the exhaust CO ₂ (kg / tp) when VH ₂ = 0 Nm ³ / tp. That is, when the hydrogen injection is VH ₂ = 50 Nm ³ / tp, a = (O / C) ₃ / (O / C) ₂ is changed from 1.0 (P point) to 1.35 (Q point). Then, CO ₂ (kg / tp) emission can be reduced.

When hydrogen injection is VH ₂ = 100 Nm ³ / tp, when a = (O / C) ₃ / (O / C) ₂ is 1.3 (point R) to 1.65 (point S), Hydrogen injection is smaller than the exhaust CO ₂ (kg / tp) when VH ₂ = 0 Nm ³ / tp. That is, when the hydrogen injection is VH ₂ = 100 Nm ³ / tp, a = (O / C) ₃ / (O / C) ₂ is changed from 1.3 (R point) to 1.65 (S point). Then, CO ₂ (kg / tp) emission can be reduced.

[To reduce emissions CO _2, the hydrogen blow amount _VH 2 and ^{(Nm 3 / tp) a =} (O / C) 3 / (O / C) Introduction of the relational expression _2]
In FIG. 7, if the point P _(VH ² = 50Nm 3 _/tp,a=1.0),R point ^{_{(VH 2 = 150Nm 3 /tp,a=1.3)}} , discharged _CO 2 (kg / tp) can be reduced.
From the point P and the point R, the following formula (3), which is a lower limit capable of reducing exhaust CO ₂ (kg / tp), is derived.

[Formula]
a ≧ (0.003 × VH ₂ +0.85) (3)

Reduction Similarly, Q point _(VH ² = 50Nm 3 _{/tp,a=1.35),S} point than ^{_{(VH 2 = 150Nm 3 /tp,a=1.65)}} , _CO 2 emissions of (kg / tp) The following formula (4) which is the upper limit that can be obtained is derived.

[Formula]
(0.003 × VH ₂ + 1.2) ≧ a (4)

  By synthesizing the above formula (3) and the above formula (4), and a is limited to 1.0 or more, the following formulas (1) and (2) can be derived.

[Formula]
(0.003 × VH ₂ +1.2) ≧ a ≧ (0.003 × VH ₂ +0.85) (1)

[Formula]
a ≧ 1.0 ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ (2)

[O / C control when blowing hydrogen-containing reducing gas]
In the present invention, the distribution coefficient a of O / C is performed according to the above formulas (1) and (2) according to the hydrogen content of the hydrogen-containing reducing gas.
FIG. 8 shows the distribution coefficient a of the charge when the hydrogen-containing reducing gas is blown. The control method is adjusted by changing the cut-out position for each charging batch as usual.
In the present invention, since there is a central coke at the furnace center and the volume contribution is small, the central portion is not controlled from the viewpoint of control accuracy.
In the method of operating a blast furnace in which the shaft is blown according to the present invention, the larger the number of circumferential blow ports installed, the more desirable uniform blow in the circumferential direction becomes. On the other hand, the installation of an excessive number of blowing ports causes an increase in equipment costs, so it is desirable that the circumferential interval between the blowing ports be 5 m or less.

  Next, examples of the present invention will be described, but the present invention is not limited thereto.

Using a test blast furnace (two tuyere, internal volume 8 m ³ ) equipped with one blowing port in the shaft part, an operation evaluation test was conducted by blowing modified COG having a H ₂ concentration of 65%. The results are shown in Table 1.
(Comparative Example 1)
The operation of the base condition where the shaft of reducing gas is not blown is 420 kg / tp for input C and 1357 for discharged CO ₂ (Nm ³ / tp) at a distribution coefficient of a = 1.0, and the airflow resistance index (K value) ), Operation management indicators such as furnace body heat dissipation and slip frequency were also good.
(Example 1)
The hydrogen blowing amount was set to 50 Nm ³ / tp, and the distribution coefficient a was set to 1.15 that satisfies the formula (1). The blast furnace operation was stable and the exhausted CO ₂ was reduced by 66 kg / tp.
(Example 2)
The hydrogen blowing amount was 150 Nm ³ / tp, and the distribution coefficient a was 1.45 that satisfies the formula (1). The blast furnace operation was stable, and the exhausted CO ₂ was reduced by 132 kg / tp.
(Comparative Example 2)
The amount of hydrogen blown was 18 Nm ³ / tp. Hydrogen blowing amount is small, significant CO ₂ reduction is not exerted.
(Comparative Example 3)
The blowing amount was 50 Nm ³ / tp, and the distribution coefficient a was 1.40 exceeding the upper limit of the formula (1). As a result of excessive reduction load at the wall, the gas flow to the intermediate portion was excessively promoted and the ventilation was not stable. As a result, since coke had to be increased, the amount of exhausted CO ₂ was not reduced and increased by 73 kg / tp relative to the comparative example 1 of the base.

  When reducing gas containing hydrogen is blown into the lower part of the shaft of the blast furnace, a blast furnace operating method in which ore reduction and air permeability in the furnace radial direction are appropriate can be provided.

DESCRIPTION OF SYMBOLS 1 ... tuyere, 2 ... gas injection nozzle, 3 ... sampling hole, 4 ... reaction tube, 5 ... ore, 6 ... coke, 7 ... heater, 8 ... heat insulation layer, 9 ... thermometer, 10 ... control part.

Claims (1)

A blast furnace operation in which reducing gas containing hydrogen is blown from a blast furnace shaft portion,
Blowing amount of the hydrogen gas contained in the reducing gas pig iron per ton of 20 Nm ³ or more and 150 Nm ³ or less,
A blast furnace operating method characterized in that a distribution coefficient a of O / C in the radial direction at the top of the blast furnace furnace satisfies the following expressions (1) and (2).
(0.003 × VH ₂ +1.2) ≧ a ≧ (0.003 × VH ₂ +0.85) (1)
a ≧ 1.0 ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ (2)
However,
a; (O / C) ₃ / (O / C) ₂ . Ratio of the furnace peripheral part (O / C) ₃ and the furnace intermediate part (O / C) ₂ when the radial direction at the top of the blast furnace furnace is divided into three and 1, 2, 3 from the furnace center toward the furnace wall It is.
VH ₂ ; amount of hydrogen gas blown (Nm ³ / tp)

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