JP4954949B2 - Coke reactivity evaluation method - Google Patents

Description

  The present invention relates to a coke reactivity evaluation method for evaluating coke reactivity under conditions closer to an actual furnace.

In the blast furnace operation in the iron making process, iron-containing raw materials such as lump iron ore and sintered ore and coke are charged from the top of the blast furnace furnace so as to form layers alternately in the furnace, and the iron-containing raw material descends in the furnace. Then, by blowing air from the lower tuyere, the iron-containing raw material is reduced by the reducing gas generated by the combustion reaction of coke and further by the solution loss reaction to form hot metal, and the tapping is performed. At this time, a heat storage zone having a temperature of about 950 to 1000 ° C. is formed in the upper part of the shaft in the blast furnace, where coke is gasified by a solution loss reaction (C + CO ₂ → 2CO) with coke and CO ₂ gas. Indirect reduction of lump iron ore and sintered ore by gas proceeds, and lump iron ore and sintered ore start to soften and melt at a temperature of about 1100 ° C or more below this heat preservation zone, forming a cohesive zone Here, in addition to the indirect reduction of the massive iron ore and sintered ore with CO gas, a direct reduction reaction with coke (C) also proceeds. In general, in order to reduce the reducing material ratio by improving the reduction efficiency of massive iron ore and sintered ore, it is desirable to reduce the temperature of the heat preservation zone, and by using highly reactive coke as this means coke. A method for promoting the gasification reaction is known (Patent Document 1).

  This highly reactive coke, as shown in Patent Document 1, blends non-slightly caking coal into raw coal, blends iron with a role as a catalyst for promoting the gasification reaction of coke, into raw coal. Furthermore, a method of manufacturing using a method such as adding an alkaline earth metal such as Ca to raw coal has been proposed.

In addition, as one of the evaluation methods for coke reactivity, a coke reactivity index (CRI) is known in which the reactivity between coke and CO ₂ is expressed by the weight loss percentage of coke in a CO ₂ atmosphere. .

The coke quality evaluation method based on the coke reactivity index (CRI) is a method in which a coke sample is reacted with a reaction gas of CO ₂ for a certain period of time at a high temperature in an experimental furnace, and the ratio of the weight of the coke sample after reaction to the weight of the coke sample before reaction Is expressed as.

In this case, the weight of the coke sample is measured, and the weight of the coke sample after the reaction is measured.
JP 2005-232348 A

  Incidentally, alkali is circulating in the blast furnace, and it is known that the reactivity of coke is improved by the influence of this alkali.

  However, the coke weight after the reaction, which is the basis for calculating the above-described coke reactivity index (CRI), is not based on the weight reduction in an alkaline atmosphere, but about the evaluation of the properties of coke to be charged in the blast furnace. Is not necessarily clearly shown. In particular, in order to further reduce the reducing agent ratio by further improving highly reactive coke, it is necessary to create a state in which alkali is attached to the coke and evaluate the properties of the coke.

  The present invention has been made in view of such a viewpoint. For example, a weight reduction amount of coke used when evaluating the quality of coke using a coke reactivity index (CRI) can be obtained under conditions closer to those of an actual furnace. An object of the present invention is to provide a method for evaluating coke reactivity.

  The present invention has been made to solve the above problems, and the gist thereof is as follows.

(1) The temperature range and reaction gas concentration in the coke reaction state in an actual blast furnace are reproduced in the reaction vessel in which the sample coke layer is charged, and the weight of the reaction vessel is measured, and the reaction vessel is charged. In the coke reactivity evaluation method for determining the weight reduction amount of the sample coke layer, the primary vapor was measured after alkali vapor generation by reacting the alkali vapor generation layer with KOH and coke as the primary sample coke layer in the reaction vessel. the weight loss of the sample coke layer as the correction value, is reacted in the reaction vessel then those arranged alkali deposition coke on the freshly prepared a alkali vapor generating layer as a secondary sample coke layer The amount of weight reduction of the secondary sample coke layer measured after the generation of alkali vapor is used as this measurement value, and the weight reduction amount of the correction value is subtracted from the weight reduction amount of the above measurement value. The coke reactivity evaluation method is characterized in that the value obtained by setting the value is a net coke weight reduction amount of the coke for alkali vapor deposition.
(2) The coke reactivity evaluation method according to (1), wherein the alkali vapor generation layer is configured by mixing KOH powder and coke.
(3) The coke reactivity evaluation method according to (1), wherein the alkali vapor generation layer is configured by adhering a KOH solution to coke.

(4) The coke according to (3), wherein the sample coke layer has a structure in which a lower coke layer to which a KOH solution dripping from the alkali vapor generation layer is attached is disposed below the alkali vapor generation layer. Reactivity evaluation method.

  (5) The weight reduction amount may be obtained by increasing the temperature at a constant temperature within the temperature range and measuring the weight at each temperature increase temperature, according to any one of (1) to (4) Coke reactivity evaluation method as described.

  (6) The coke reactivity evaluation method according to any one of (1) to (5), wherein the temperature range is 800 ° C to 1200 ° C.

According to the present invention, the alkali vaporized from the alkali vapor generation layer is deposited on the alkali vapor deposition coke, and this alkali vapor deposition sample coke is reacted with the reaction gas (CO ₂ ), under conditions close to an actual furnace. It became possible to evaluate the reactivity of coke. Since the weight reduction amount reduced by the reaction between the alkali vapor generation layer and the reaction gas (CO ₂ ) is measured in advance as a correction value, the value obtained by subtracting the correction value from the weight reduction amount of this measurement value is A net coke weight reduction amount of the alkali vapor deposition coke can be obtained.

  It can also contribute to the creation of highly reactive coke with even higher reactivity.

  FIG. 1 is a schematic longitudinal sectional view of a measuring apparatus which is an experimental furnace for carrying out a coke reactivity evaluation method according to the present invention.

In FIG. 1, a measuring device 1 stores a coke sample, and a reaction tube 2 as a reaction vessel for reacting the stored coke sample with a reaction gas (CO ₂ ) is disposed in a thermostat 3 so as to be movable in the vertical direction. Yes. The reaction tube 2 is suspended from a balance-type balance 5 via a wire 4 so that the weight of the stored item in the reaction tube 2 can be measured by the balance 5.

  A heating device 6 for heating the inside of the thermostat 3 to the same temperature as that of the actual furnace is disposed in the thermostat 3 so as to surround the reaction tube 2, and temperature control is performed by a controller (not shown).

  The reaction tube 2 is formed in a double tube structure in which an inner reaction tube 9 is disposed concentrically with a gap 8 in a bottomed outer reaction tube 7, and a vent 9 b is formed in the bottom 9 a of the inner reaction tube 9. Thus, the gap 8 communicates with the inside of the inner reaction tube 9.

The top of the outer reaction tube 7 from a thermostat 3 is exited upward, the reaction gas (CO ₂₎ introduction pipe 10 is provided, the reaction gas (not shown) (CO ₂₎ reaction gas from the supply device (CO ₂₎ As shown by an arrow, the reaction gas (CO ₂ ) is supplied into the gap 8 through the reaction gas (CO ₂ ) introduction pipe 10, and further, the reaction gas (CO ₂ ) passes through the vent 9 b formed in the bottom portion 9 a of the inner reaction pipe 9. 9 is supplied.

  An upper portion of the reaction tube 2 is provided with a flange portion 11 that fixes the upper ends of the outer reaction tube 7 and the inner reaction tube 9 and has an inner diameter hole 11 a that communicates with the inner reaction tube 9. An exhaust hole 12 a is provided in the flange portion 11. A lid 12 having a detachable attachment is attached. An exhaust pipe 13 connected to the exhaust hole 12 a is attached to the upper surface of the lid 12.

The inner reaction tube 9 is placed on a lower alumina ball layer 14 in which a large number of alumina spheres (alumina balls) are spread over a plurality of stages in order to disperse the reaction gas (CO ₂ ) introduced from below. The sample layer 15 is provided, and the temperature of the sample layer 15 is measured by a thermocouple 16. Then, the reaction gas (CO ₂ ) in contact with the sample of the sample layer 15 in the inner reaction tube 9 is discharged from the inner diameter hole 11a through the exhaust hole 12a to the outside from the exhaust pipe 13.

  The lower alumina ball layer 14 is disposed on the lower partition plate 17 having a plurality of vent holes 17a.

  As shown in FIG. 2A, the sample layer 15 is a mixed layer of KOH powder and coke obtained by mixing KOH powder and coke on the lower coke layer 18 (hereinafter referred to as KOH powder / coke mixed layer). When composed of an alkali vapor generation layer 15a carrying 19 (this is referred to as a primary sample layer), as shown in FIG. 2 (b), an evaporation target for depositing alkali on the alkali vapor generation layer 15a There is a case where the coke layer 20 is provided (this is referred to as a secondary sample layer). The coke layer 20 to be deposited is disposed on the upper alumina ball layer 22 similar to the lower alumina ball layer 14 on the upper partition plate 21 having the same configuration as the lower partition plate 17. Further, on the lower alumina ball layer 14, a middle partition plate 23 having the same configuration as the lower partition plate 17 is disposed, and a lower coke layer 18 is disposed thereon.

  The KOH powder / coke mixed layer 19 constituting the alkali vapor generating layer 15a is composed of a mixture of granular coke and KOH powder. This is because alkali is circulating in the blast furnace and coke reactivity is improved by the influence of the alkali.

However, when high-temperature reaction gas (CO ₂ ) is brought into contact with the alkali vapor generation layer 15a, the reaction between the deposited KOH and coke (2KOH + 2C⇒2K + 2CO + H2) occurs, and the target reaction gas (CO ₂ ) and In addition to the weight reduction associated with the reaction with coke (C + CO ₂ → 2CO), the weight reduction amount of the gasification (gasified K, 2CO, H2) due to the reaction (2KOH + 2C) is included. It cannot be said that this is a strict reaction of CO ₂ . Furthermore, in the actual blast furnace, the alkali adheres to the coke in the form of steam, so that the adherence of the alkali to the coke in the actual furnace can be essentially different from attaching the alkali to the coke in the powder state. It is thought that there is sex.

In addition, the reaction gas (CO ₂ ) is contacted with coke on which alkali has been vapor-deposited in advance, the reaction gas (CO ₂ ) is reacted, and the weight before the reaction is measured to calculate the weight reduction rate of the coke. In this case, a certain amount of potassium is vapor-deposited even at a low temperature, which is not a reaction in a situation close to an actual furnace.

Therefore, the KOH powder / coke mixed layer 19 of the alkali vapor generation layer 15a evaporates potassium by contact with a high-temperature reaction gas (CO ₂ ) and deposits the evaporated potassium on the coke of the deposition target coke layer 20. It plays a role in creating a situation close to.

In the alkali vapor generation layer 15a, the lower coke layer 18 is disposed under the KOH powder / coke mixed layer 19, but if the lower coke layer 18 is not present, the KOH powder / coke mixed layer 19 The KOH adhering to the coke becomes liquid and drips downward and reaches the lower alumina ball layer 14 to form unreacted KOH. However, the lower coke layer 18 is formed below the KOH powder / coke mixed layer 19. Such a problem is solved by arranging. The coke particle size used in the KOH powder / coke mixed layer 19 and the lower coke layer 18 in order to suppress liquefaction of KOH adhering to the coke and dripping onto the lower alumina ball layer 14 is determined by the evaporation target. It is preferable to make it smaller than the coke particle size of the coke layer 20.
For this reason, the coke particle size used in the KOH powder / coke mixed layer 19 and the lower coke layer 18 is more preferably 2 to 3 mm.

As shown in FIG. 2 (a), the measurement method using the measurement apparatus 1 is such that only the alkali vapor generation layer 15a forming the primary sample layer is disposed in the inner reaction tube 9, and the temperature is changed under the temperature condition of the blast furnace. And a correction value measurement is performed in which the weight of the reaction tube 2 is measured with a scale 5 in an atmosphere in which the CO ₂ gas concentration of the reaction gas at the temperature is adjusted.

FIG. 3 shows the relationship between the weight reduction amount (g) of the inner reaction tube 9 and the temperature, and the weight obtained by subtracting the weight (Wt) during the reaction at each temperature from the weight (W) of the inner reaction tube 9 before the reaction. Each is a weight reduction amount (ΔW = W−Wt). The weight reduction amount (ΔW) shown in FIG. 3 includes K ₂ CO gasified by the reaction of 2KOH + 2C described above in addition to the weight reduced by the reaction between the coke and the reaction gas (CO ₂ ) in the alkali vapor generation layer 15a. Includes a H2 minute weight.

Next, the lid 12 is removed, the alkali vapor generation layer 15a in the inner reaction tube 9 is replaced with a new one, and an upper partition plate 21 and an upper alumina ball layer 22 are further disposed as shown in FIG. 2 (b). Then, the deposition target coke layer 20 having a weight of m is disposed thereon, the secondary sample layer 15 is constructed, the lid body 12 is closed, and the main measurement is performed under the same conditions as the correction value measurement described above. Then, the weight of the reaction tube 2 is measured by the balance 5 before the reaction. In this case, when the weights of the upper partition plate 21 and the upper alumina ball layer 22 are subtracted, the weight is increased by m from the weight (W) before the reaction during the correction measurement. Then, the concentration of the reaction gas (CO ₂ ) is adjusted while raising the temperature of the sample layer 15, and the weight of the reaction tube 2 at each temperature is measured with a scale 5. FIG. 4 shows the weight loss (g) at each temperature in this measurement.

In this measurement, vapor potassium from the alkali vapor generation layer 15a is vapor-deposited on the coke of the coke layer 20 to be deposited, and at this time, the existence ratio of vapor potassium changes with temperature change. Thus, potassium is deposited on the coke of the deposition target coke layer 20 and reacts with the reaction gas (CO ₂ ).

In this measurement, potassium is deposited on the coke of the deposition target coke layer 20, and the deposited coke reacts with contact with the reaction gas (CO ₂ ) to reduce the deposition target coke by ΔW2, and the alkali vapor generation layer. The weight ΔW is reduced from 15a.

Therefore, if the weight loss in this measurement is ΔW1,
ΔW1 = ΔW2 + ΔW
Thus, the weight ΔW2 (ΔW2 = ΔW1−ΔW) in which the alkali-deposited coke is reduced by the reaction with the reaction gas (CO ₂ ) in a state where alkali is vapor-deposited in an atmosphere close to an actual furnace is calculated.

Therefore, the net coke weight reduction rate of the coke in the deposition target coke layer 20 can be calculated only by subtracting the correction value obtained by the correction value measurement from the weight reduction amount obtained by the main measurement. It becomes.
In place of the KOH powder / coke mixed layer 19, a KOH-immersed coke layer having a structure in which granular coke is immersed in a KOH aqueous solution may be used.
In this case, the alkali vapor generation layer 15a has the lower coke layer 18 disposed below the KOH-immersed coke layer. If the lower coke layer 18 is not present, the alkali coke generation layer 15a is a coke forming the KOH-immersed coke layer. The adhering KOH liquefies and falls down and reaches the lower alumina ball layer 14 to form unreacted KOH. However, by placing the lower coke layer 18 below the KOH-immersed coke layer, Such a problem is solved. Further, in order to prevent KOH adhering to the coke from liquefying and dripping onto the lower alumina ball layer 14, the coke particle size used in the KOH-immersed coke layer and the lower coke layer 18 is the coke layer 20 to be deposited. It is preferable to make it smaller than the coke particle size.
For this reason, the coke particle size used in the KOH immersion coke layer and the lower coke layer 18 is more preferably 2 to 3 mm.

1) As dimensions of the reaction tube 2,
Inner reaction tube 9 inner diameter 70 mm, length 880 mm
Outer reaction tube 7 inner diameter 90mm, length 910mm
2) Particle size of alumina balls constituting the alumina ball layer: 10 mm
The weight of the lower alumina ball layer 14 is 258 g.
The weight of the upper alumina ball layer 22 is 172 g.
3) As sample coke,
Weight of lower coke layer 18 (average particle size of coke: 2.5 mm): 120 g
Weight of KOH powder / coke mixed layer 19 (average particle diameter of coke: 2.5 mm): 150 g (sample coke 100 g + KOH (50 g))
Deposition target coke layer 20 (average particle size of coke: 20 mm): 200 g
4) The gas concentration (ηCO = [CO ₂ / (CO + CO ₂ )] × 100) is
Temperature 800 ° C to 900 ° C, ηCO: 40% to 30%
At a temperature of 900 ° C. to 1200 ° C., ηCO: 30% to 5%
5) The heating rate is 5 ° C / min.
6) Reactant gas (CO ₂ ) flow rate of 20 L / min
As a result, the correction value measurement and the main measurement were performed.

In the correction value measurement and the main measurement, the reaction gas (CO ₂ ) is introduced into the reaction tube 2 under the above-mentioned conditions, and the weight loss at that time is measured. This measurement was performed in the same manner 5 times including reproducibility.

In the correction value measurement, the reaction between the coke in the lower coke layer 18 and the reactive gas (CO ₂ ) and the reaction between the coke in the KOH powder / coke mixed layer 19 and the reactive gas (CO ₂ ) proceed at each temperature. The measurement result is shown in FIG.

Further, in this measurement, in the state where the coke of the deposition target coke layer 20 deposited potassium as alkali, the reaction between the deposition target coke layer 20 and the coke of the alkali vapor generation layer 15a and the reactive gas (CO ₂ ) is performed at each temperature. The measurement result of this measurement is shown in FIG.

  In this way, the correction value measurement and the main measurement are performed, and by subtracting the measurement result shown in FIG. 3 from the measurement result shown in FIG. 4, a net coke weight reduction rate of the coke in the deposition target coke layer 20 is obtained. Will be.

  FIG. 5 shows the results of this measurement when the above-described coke reactivity test was performed on the coke sample A, the coke sample B, and the coke sample C.

  Coke sample A uses non-slightly caking coal (100%) as coking coal, 1% Ca is added as a catalyst thereto, and coke obtained by carbonization in a coke oven, coke sample B is coking coal. Coke and coke sample C obtained by dry distillation in a coke oven using non-slightly caking coal: 80% and caking coal: 20% are non-slightly caking coal: 30% and caking coal: This is coke obtained by dry distillation in a coke oven using 70%. The JIS reactivity is high in the order of coke C <coke B <coke A, and gasification reaction easily occurs.

The schematic longitudinal cross-sectional view of the measuring apparatus which can implement this invention. Explanatory drawing of the sample layer of FIG. The figure which shows the measurement result of correction value measurement The figure which shows the measurement result of this measurement. The figure which shows this measurement result of sample A, B, and C. FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Measuring device 2 Reaction tube 3 Constant temperature bath 4 Wire 5 Scale 6 Heating device 7 Outer reaction tube 8 Clearance 9 Inner reaction tube 9a Bottom part 9b Vent hole 10 Reactive gas introduction pipe 11 Gutter part 11a Inner diameter hole 12 Cover body 12a Exhaust hole 13 Exhaust Tube 14 Lower alumina ball layer 15 Sample layer Alkali vapor generation layer 15a
16 Thermocouple 17 Lower partition plate 17a Vent 18 Lower coke layer 19 Mixed layer of KOH powder and coke (KOH powder / coke mixed layer)
20 Deposition target coke layer 21 Upper partition plate 22 Upper alumina ball layer 23 Middle partition plate

Claims (6)

Sample coke charged in the reaction vessel by reproducing the temperature range and reaction gas concentration in the coke reaction state in the actual blast furnace in the reaction vessel charged with the sample coke layer and measuring the weight of the reaction vessel In the coke reactivity evaluation method for determining the weight loss of the layer,
The alkali vapor generation layer equipped with KOH and coke is reacted as the primary sample coke layer in the reaction vessel, and the weight loss of the primary sample coke layer measured after the generation of alkali vapor is used as a correction value. weight loss was a alkali vapor generating layer secondary sample coke layer are reacted in the reaction vessel which was placed alkali deposition coke as a secondary sample coke layer was measured after alkaline steam generation on the Coke reactivity evaluation, wherein the value obtained by subtracting the weight reduction amount of the correction value from the weight reduction amount of the main measurement value is the net coke weight reduction amount of the alkali vapor deposition coke. Method. The coke reactivity evaluation method according to claim 1, wherein the alkali vapor generation layer is configured by mixing KOH powder and coke. The coke reactivity evaluation method according to claim 1, wherein the alkali vapor generation layer is configured by attaching a KOH solution to coke. The coke reactivity according to claim 3, wherein the sample coke layer has a structure in which a lower coke layer to which a KOH solution dripping from the alkali vapor generation layer is attached is disposed below the alkali vapor generation layer. Evaluation methods.   The coke reactivity according to any one of claims 1 to 4, wherein the weight reduction amount is obtained by increasing the temperature at a constant temperature within the temperature range and measuring the weight at each temperature increase temperature. Evaluation methods.   The coke reactivity evaluation method according to any one of claims 1 to 5, wherein the temperature range is 800 ° C to 1200 ° C.

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