JP6079142B2 - Coke production method - Google Patents

Description

  The present invention relates to a method for producing coke for blast furnace using a horizontal chamber type coke oven, and particularly relates to a method for producing coke that can reduce the extrusion load when extruding a coke cake after dry distillation from a carbonization chamber.

  In recent coke oven operations, many methods have been adopted to reduce the moisture content of coal charged into the carbonization chamber with the aim of improving coke quality and productivity, and the coal charging (packing) density tends to increase. is there. As a result, when the coke cake is extruded, the load applied to the side wall (furnace wall) of the carbonization chamber increases, and the force (extrusion load) required to extrude the coke tends to increase accordingly.

In addition, the number of coke ovens that have been operating for a long time and the aging of the furnace bodies is increasing, and in the carbonization chamber of such coke ovens, when carbon is attached to the furnace wall and projections are formed Is increasing.
At the place where the protrusion is formed, the furnace width (distance between furnace walls) is narrowed by that amount, and when the coke cake passes through it, the interaction between the furnace wall surface and the coke cake surface is large. Thus, the load acting on the furnace wall and the extrusion load are further increased.

  In such a situation, the extrusion load exceeds the capacity of the extruder, and there is an increased possibility of clogging or leading to major troubles such as a furnace wall brick being broken during extrusion. Yes. For this reason, extruding the coke after coal dry distillation from the carbonization chamber with a lower extrusion load not only stabilizes the operation and secures the amount of coke produced, but also reduces the load on the furnace wall of the carbonization chamber to reduce the furnace body. This is very important from the viewpoint of extending the service life.

The extrusion load when extruding coke after dry distillation from the carbonization chamber is evaluated by Rankine coefficient.
This Rankine coefficient is defined as the rate at which the force of pushing coke in the extruder is converted to the force pushing the furnace wall. It is also called the side pressure conversion rate, but the smaller the Rankine coefficient, the more the extrusion during coke extrusion. The lateral pressure is reduced, indicating that extrusion can be performed with a smaller extrusion force (extrusion load).

  Conventionally, it is known that the Rankine coefficient decreases as the gap between coke and the furnace wall increases. In order to reduce the Rankine coefficient, the amount of shrinkage (burn-out amount) caused by dry distillation is devised in order to reduce the Rankine coefficient. And a method for increasing the clearance between the coke and the furnace wall, and a method for changing the operating condition by predicting the Rankine coefficient from the operating condition and the amount of clearance between the coke and the furnace wall. Yes.

  For example, Patent Document 1 discloses that coal at the center of a coke oven chamber is regenerated by mixing 0.5 to 10% by weight of lump coke having a particle size of 40 to 200 mm with blended coal, charging the mixture into a coke oven, and performing dry distillation. Disclosed is a method for reducing the gap in the center of the carbonization chamber after solidification, increasing the amount of horizontal burn-out defined by the gap between the coke oven wall and the coke cake surface, and increasing the gap between the coke and the oven wall. Yes.

  Patent Document 2 discloses that the average length of the coke mass in the direction parallel to the furnace wall is added to the charging coal in the range of 5% to 10% with a powder coke having a particle size of 0.5 mm or less. A coke oven operating method is disclosed that reduces the extrusion resistance during medium-to-low temperature dry distillation.

  Further, Patent Document 3 describes in advance the relationship between the furnace temperature and the coke shrinkage rate and the furnace temperature based on the knowledge that the coke particle size is important for the coke extrusion load in addition to the gap between the coke and the furnace wall. And the coke particle size, and from the actual furnace temperature of the coking chamber, calculate the gap between the furnace wall and the coke particle size based on the coke shrinkage, and predict the Rankine coefficient based on these values. And when Rankine coefficient is more than a preset value, the operation method of the coke oven which adjusts furnace temperature and the placing time after dry distillation is indicated.

JP-A-11-228971 Japanese Patent Laid-Open No. 08-2833731 JP 2008-255299 A

  In the method of Patent Document 1, since coke is added to the entire charged coal, there is a problem that the production amount of coke is reduced and an influence on the strength of the obtained coke is not studied. Patent Document 2 describes that if coke breeze having a particle size of 0.5 mm or less is added to the charging coal in a range of 5% to 10%, the coke quality is not deteriorated. As a result of detailed investigations by the inventors, it was confirmed that the coke strength may be lowered depending on conditions. Furthermore, in the method of Patent Document 3, it is necessary to obtain the relationship between the furnace temperature and the contraction rate and particle size of the coke by experiment for each brand of the coal blend used as a raw material. There is a problem.

  Therefore, in the present invention, a carbon material having a low shrinkage coefficient at the time of dry distillation (low-shrinkage carbon material) such as coke disclosed in Patent Documents 1 and 2 above is used to reduce coke with reduced extrusion load. It is an object of the present invention to provide a method for producing coke that can produce coke with reduced extrusion load without substantially reducing coke strength by reducing the amount of carbonaceous material added.

The present inventors have studied a method for producing coke that can reduce the extrusion load when extruding the coke cake after carbonization from the carbonization chamber of the coke oven.
As a result, it was found that by charging the blended coal added with the low shrinkage carbonaceous material to a predetermined height at the lower part of the coke oven, the Rankine coefficient can be reduced and the extrusion load can be reduced while suppressing the reduction in coke strength. .
The gist of the present invention is as follows.

(1) When blended coal is charged into the coking chamber of the coke oven and coke is produced by dry distillation, the blended coal is charged to a height in the range of 0.5 m to less than 1 m from the bottom of the coking chamber. In addition, a low shrinkage carbon material having a shrinkage rate of 6% or less at 500 to 1000 ° C. is added in the range of 8% or more and 25% or less by mass ratio as the external number ,
The addition rate of the low-shrinkage carbon material is obtained by calculating the relationship between the addition rate of the low-shrinkage carbon material and the Rankine coefficient for each average particle size of the low-shrinkage carbon material. Accordingly, with respect to the Rankine coefficient when the low shrinkage carbonaceous material addition rate is 0%, the addition rate that is reduced by a factor of 0.8 is set as the lower limit, and the addition rate that decreases most is selected from the above range as the upper limit. Coke production method.
(2) The method for producing coke according to (1), wherein the low-shrinkage carbon material is one or both of powdered coke and anthracite.

  In the present invention, it is possible to obtain a higher extrusion load reduction effect with the same amount of low shrinkage carbonaceous material as in the past, and reduce the coke extrusion load almost without reducing the coke strength regardless of the type of blended coal. can do.

It is a figure which shows the relationship between the addition amount of a powder coke, and a Rankine coefficient. It is a figure which shows the relationship between the addition amount of a powder coke, and coke intensity | strength DI. It is a figure which shows the relationship between the height of the furnace height direction from the furnace bottom of the charging range of the blended coal which added the powder coke, and coke intensity | strength DI. It is a figure which shows the relationship between the height of the furnace height direction from the furnace bottom of the charging range of the blended coal which added the powder coke, and an extrusion load.

In the present invention, when coal is charged into a coking chamber of a coke oven to a height of, for example, 6 m, and coke is produced by dry distillation, the blended coal is charged to the lower portion of the carbonizing chamber. By further adding a low shrinkage carbonaceous material as a part, a coke cake with reduced extrusion load is obtained.Hereinafter, in the present invention, an example in which powdered coke is used as the low shrinkage carbonaceous material is used in the present invention. The background of the investigation and the basic principle of the present invention will be described.
In addition, below, the addition rate (mass%) of low shrinkage carbonaceous materials, such as a powder coke, is shown by an external number.

First, in order to confirm the effect of addition of powder coke, the relationship between the amount of powder coke added and Rankine coefficient and the relationship between the amount of powder coke added and coke strength were examined.
Regarding the Rankine coefficient, as described in FIG. 6 of Patent Document 3, the furnace wall that becomes the heating surface is a fixed wall that does not move even when an external force is applied, and a movable wall that is structured to move when an external force is applied. After the coal was co-distilled into coke using the configured dry distillation test furnace, one furnace lid of the test furnace was opened, the coke was pushed out toward the other furnace lid with a ram, and attached to the movable wall and ram The load cell measures the compression pressure in the furnace length direction and the pressure in the furnace width direction transmitted to the furnace wall (the sum of the pressures on the furnace walls on both sides), and calculates from these measured values.

  In the measurement, test coal blends prepared by adding powder coke with average particle diameters of 0.1 mm, 0.4 mm, and 0.7 mm to the coal blends at various ratios of 30% or less were prepared. Then, the coke was manufactured and subjected to an extrusion test to measure the Rankine coefficient. As the base of the Rankine coefficient, the Rankine coefficient when the addition rate of powdered coke was 0% in the blended coal of the same conditions was used, and the ratio of the obtained Rankine coefficient to the base was obtained.

The obtained result is shown in FIG. 1, and it was confirmed that the value of Rankine coefficient becomes small by adding the powder coke at any particle size. However, it was recognized that the Rankine coefficient increased conversely when the amount of powdered coke added was excessive, and that the Rankine coefficient decreased as the powdered coke particle size increased.
As shown in FIG. 1, when powder coke having an average particle size of 0.1 to 0.7 mm is added, the upper limit of the amount of addition at which an almost minimum Rankine coefficient value is obtained is 25% of 0.1 mm diameter powder coke. When it was.

Next, the relationship between the amount of powder coke added and the coke strength DI was examined. The coke strength DI was measured using coke produced using the same test furnace as described above.
The obtained results are shown in FIG. 2, and in the particle size of 0.1 to 0.7 mm, the result that the coke strength DI is reduced by adding the powder coke was obtained. The rate at which the coke strength DI decreased as the average particle size decreased.

  As a result of the dry distillation test using the above test furnace, the relationship between the added amount of coke breeze and Rankine coefficient and the relationship between the added amount of coke breeze and the strength of coke were obtained. The method of adding coke breeze at the time of charging was examined.

Generally, in the lower part of the carbonization chamber, the bulk density of coal is higher than that of the upper part and the furnace temperature is higher, so that it is known that coke having higher strength than that of the upper part can be obtained. Therefore, the present inventors considered that coke strength reduction due to addition of powdered coke hardly occurs in the lower part of the carbonization chamber, and focused on adding powdered coke to the lower part of the carbonization chamber.
In addition to the fact that the lower part of the furnace has a high bulk density and a lower porosity, the coke particle size is smaller than that of the upper part of the carbonization chamber, so that the frictional force with the furnace wall is larger. In the lower part, the coke's own load is applied, so the friction force at the bottom of the furnace is generated. Therefore, it is known that the extrusion load at the lower part of the carbonization chamber is higher than that at the upper part of the carbonization chamber.

Then, the present inventors considered that the extrusion load of the whole coke oven can be suppressed by adding the powder coke to the lower part of the carbonization chamber.
And, as a result of examination based on that idea, by introducing the blended coal added with powdered coke to a predetermined height at the lower part of the coke oven, while suppressing the decrease in coke strength, the Rankine coefficient is reduced and the extrusion load is reduced. We found that it can be reduced.

First, the content which examined about the relationship of the range of the height direction which adds a powder coke, coke intensity | strength, and an extrusion load is demonstrated.
Prepare 0.4mm powder coke, and add the powder coke by adding 3%, 10% and 20% by mass ratio to the coal mix with 0% powder coke addition rate as the standard The blended coal was prepared and charged into the coking chamber of the coke oven to various heights from the bottom of the furnace. Subsequently, the charged coal was changed to a reference blended coal and charged to a height of 6 m. In addition, as an example of the reference, only the reference blended coal was charged to a height of 6 m. Thereafter, coke was produced by dry distillation, and the coke strength DI of the entire carbonization chamber was measured.

FIG. 3 shows the relationship between the charging range in the furnace height direction (distance from the furnace bottom) of the blended coal to which powdered coke is added and the strength DI of the obtained coke. From FIG. 3, regardless of the amount of powdered coke added, if the charging range of the blended coal to which powdered coke is added is less than 1 m from the furnace bottom, that is, the range of charging of the blended coal to which powdered coke is added. Was less than 1 m from the bottom of the furnace, it was confirmed that the decrease in coke strength DI ¹⁵⁰ ₁₅ could be suppressed. From the viewpoint of coke strength, the charging range in the furnace height direction of the blended coal to which powder coke is added is preferably 0.9 m or less, and more preferably 0.8 m or less.

  Subsequently, the relationship between the charging range in the furnace height direction of the blended coal to which powder coke was added and the extrusion load was examined. The result is shown in FIG. As an example, this will be described in detail below using the plot of ◇ in FIG.

  First, a method for adjusting the blended coal will be described. The blended coal A normally charged in the coke oven (no added powder coke) is blended coal A, and the blended coal added with the powder coke charged in the lower portion of the coke oven is referred to as blended coal B. The plot of ◇ in FIG. 4 is a case where as blended coal B, 10% of powdered coke having a particle diameter of 0.4 mm is added to blended coal A.

Next, a method for charging the blended coal into the coke oven will be described.
When blended coal B was charged to a height of 0.5 m from the bottom of the furnace, and then blended coal A was charged into a portion of 0.5 m to 6.0 m, the coke cake extrusion load was 35.0 tons. It was. When only blended coal A was charged up to 6 m from the furnace bottom (plot at the left end of FIG. 4), the extrusion load of the coke cake was 36.4 tons, and the 1.4 ton extrusion load decreased.
When blended coal B was charged to a height of 0.97 m from the bottom of the furnace, and then blended coal A was charged into the 0.97 m to 6.0 m portion, the extrusion load of coke cake was 34.7 tons. It was.
When blended coal B was charged to a height of 1.48 m from the bottom of the furnace, and then blended coal A was charged into a portion of 1.48 m to 6.0 m, the coke cake extrusion load was 34.3 tons. It was. From this result, when the charging height of blended coal B to which powder coke was added was 1 m or more from the furnace bottom, the extrusion load was reduced, but the effect was small.

  The Rankine coefficient of these blended coals was measured by charging the blended coals A and B into a test furnace and dry-distilling them, and then performing an extrusion test of the produced coke. As a result, the Rankine coefficient (base) of the coke cake of blended coal A was 0.040, and the Rankine coefficient of the coke cake of blended coal B was 0.032. That is, Rankine coefficient / Rankin coefficient (base) at the lower part of the coke oven was 0.8.

In cases other than Rankine coefficient / Rankine coefficient (base) = 0.8, the Rankine coefficient was adjusted by changing the powder coke addition rate while keeping the powder coke particle diameter constant.
Moreover, from FIG. 4, the extrusion load became low, so that the Rankine coefficient of the coke of the coal blend which added the powder coke was low.
From the results of FIGS. 3 and 4, it was confirmed that the coal blend to which the powder coke was added was effective to be charged at a height of less than 1 m from the furnace bottom.

  As a result of the above experiments, if a low-shrinkage carbon material is added to the blended coal charged in the lower part of the carbonization chamber, the extrusion load when the coke cake is extruded from the carbonization chamber can be reduced, and the strength reduction is also suppressed. It has been confirmed that coke can be produced.

Next, individual requirements and preferable requirements constituting the present invention will be described.
Adding low-shrinkage coal to the blended coal charged in the lower part of the carbonization chamber reduces the Rankine coefficient when the coke cake pushes the furnace wall by increasing the particle size of the coke obtained after dry distillation. This is to reduce the extrusion load when extruding the coke cake.
Here, the low shrinkage carbonaceous material is defined as shrinkage at 500 to 1000 ° C. ≦ 6%, and anthracite coal can be used in addition to the powder coke exemplified above. These may be used alone or at the same time.

When the anthracite coal is added, the Rankine coefficient reduction effect is smaller than when the powder coke having the same particle size is added, and when the addition ratio to each blended coal is the same, the relationship of the following equation is obtained. This equation is obtained as a result of investigating the Rankine coefficient lowering effect when anthracite is added, as in the experiment with the powder coke shown in FIG.
[Rachinkin coefficient reduction effect by anthracite] = 0.588 x [Rankine coefficient reduction effect by powdered coke]

The range in which anthracite is added is also less than 1 m from the furnace bottom. The reason for this is that, as in the case of adding coke breeze, it was confirmed that the range from the furnace bottom to 1 m had the greatest influence on the extrusion load of the entire coke cake.
As described above, if the low shrinkage carbonaceous material is added to less than 1 m from the furnace bottom, the decrease in the coke strength DI can be reduced, and the lower extrusion load is effective for reducing the overall coke extrusion resistance. Even if 1 m or more is added, the effect of reducing the extrusion load is reduced, while the coke strength is significantly reduced.

If adding a low shrinkage carbonaceous material, the effect according to the height direction of the range to be added Ru obtained, in order to obtain a Rankine coefficient lowering effect of coke particle diameter enlargement sufficiently, coke block of one minute It is preferable to charge the blended charcoal to which the low shrinkage carbonaceous material is added to a height exceeding the height. Therefore, it charged with coal blend obtained by adding coke in a range from the furnace bottom in the furnace height direction than 0.5 m.

  The particle size of the low shrinkage carbon material to be added is 0.1 to 0.7 mm in terms of average particle size in the powder coke. When the average particle size is smaller than 0.1 mm, the effect of decreasing the Rankine coefficient by increasing the coke particle size decreases, and when the average particle size exceeds 0.7 mm, the coke strength DI decreases significantly. . In addition, about anthracite, the thing about 0.4-0.7 mm is normally handled as an average particle diameter in many cases.

The addition ratio of the low shrinkage carbon material is in the range of 8 to 25%, although the optimum range varies depending on the average particle size of the low shrinkage carbon material to be added.
As shown in FIG. 1, the reduction effect of Rankine coefficient due to the addition of the low shrinkage carbon material decreases as the amount of the low shrinkage carbon material increases as the maximum effect is obtained (the lowest point). Moreover, because the coke strength decreases due to the increase in the amount of low shrinkage carbon material added, even if low shrinkage carbon material is added beyond the position of the lowest point, only the disadvantage due to the reduction in coke strength increases. It is reasonable to set the maximum amount of addition at the lowest point. For this reason, the upper limit of the powder coke addition amount is 25% from FIG.

  Moreover, about the lower limit of the amount of powder coke addition, when it tested on various conditions, the conditions from which the significant extrusion load reduction effect (about 1t) is obtained are the conditions of coke which consists of coal blends with which the Rankine coefficient is a standard. It was found to be less than 0.8 times the Rankine coefficient. As an example, as shown in FIG. 4, if the Rankine coefficient is 0.8 times, when coke made of blended coal with added powder coke is present from the bottom to 0.5 m, the extrusion load reducing effect is about 1t. Therefore, it can be seen from FIG. 1 that the lower limit of the powder coke addition rate is 8%.

  For anthracite, as described above, the average particle size is about 0.4 to 0.7 mm, so the same test as in the case of powdered coke was performed, particle size 0.4 mm, 0.7 mm. As a result, it was confirmed that the lower limit of the addition amount is preferably about 15%. In addition, since anthracite has a higher shrinkage rate than powdered coke of the same particle size, the maximum Rankine coefficient reduction effect is obtained compared to the case of powdered coke shown in FIG. Shift to. However, as described above, since anthracite does not handle those having a small average particle size (about 0.1 mm), the one having an average particle size of 0.4 to 0.7 mm was considered. As a result, it was confirmed that the upper limit of the addition amount was about 25% as the point where the effect of lowering the Rankine coefficient was maximized when the average particle size was 0.4 mm.

In addition, since the upper limit and the lower limit of the addition rate of the low shrinkage carbon material change according to the following relationship depending on the particle size of the low shrinkage carbon material, the position of the lowest point is experimentally obtained for each blended coal used, and the coefficient a to d are obtained.
[Upper limit of low shrinkage carbonaceous material addition rate] = a × [particle diameter of low shrinkage carbonaceous material] + b
[Lower limit of low shrinkage carbonaceous material addition rate] = c × [particle diameter of low shrinkage carbonaceous material] + d
Incidentally, in the case of FIG. 1, it was a: -16.67, b: 26.667, c: -11.67, d: 15.667. In the case of anthracite, a: -16.67, b: 31.667, c: -16.67, d: 26.667.

  As mentioned above, although the example of the embodiment of this invention was demonstrated, the implementation possibility and effect of this invention are further demonstrated by an Example.

Prepare powdered coke with an average particle size of 0.1 mm, 0.4 mm, and 0.7 mm and anthracite with 0.4 mm and 0.7 mm, and add them at various addition rates to the standard blended coal. A low-shrinkage coal is added to the coke oven, and charged to the coke oven's carbonization chamber from the bottom to 0.97m and 1.46m in height. Changed to charcoal and charged to a height of 6m. In addition, as a conventional example, a standard blended coal was charged into a carbonization chamber to a height of 6 m.
As a blended coal serving as a reference, the raw coal is blended and mixed so that its properties are a total expansion rate (ΣTD) = 51.0 and a volatile content (ΣVM (dry)) = 25.1% Was used.

In each of the above cases, when extruding the coke cake from the carbonization chamber after dry distillation, a load cell was attached to the extruder ram and the extrusion force was measured. Further, the coke strength DI ¹⁵⁰ ₁₅ of the obtained coke was measured.
The Rankine coefficient was separately measured using the aforementioned dry distillation test furnace.

Table 1 summarizes the conditions of the blended coal to which powder coke was added and the measured values obtained. In addition, when charging the coal blend used as a reference and dry distillation, Rankine coefficient: 0.04, coke strength DI ¹⁵⁰ ₁₅ : 86.0, extrusion load: 36.4t, this value is used to determine the effect It was set as a reference value when
In the present invention, a sufficient effect of reducing the extrusion force was obtained while suppressing a decrease in the coke strength DI ¹⁵⁰ ₁₅ . On the other hand, in the comparative example, the coke strength DI ¹⁵⁰ ₁₅ was reduced by 0.5 or more, and the reduction amount of the extrusion load was less than 1 t.

Claims (2)

When blended coal is charged into the carbonization chamber of the coke oven and coke is produced by dry distillation, the blended coal charged to a height in the range of 0.5 m or more and less than 1 m from the bottom of the carbonization chamber is 500 A method for producing coke in which a low shrinkage carbonaceous material having a shrinkage rate at ˜1000 ° C. of 6% or less is added in a range of 8% to 25% by mass ratio as an external number ,
The addition rate of the low-shrinkage carbon material is obtained by calculating the relationship between the addition rate of the low-shrinkage carbon material and the Rankine coefficient for each average particle size of the low-shrinkage carbon material. Accordingly, with respect to the Rankine coefficient when the low shrinkage carbonaceous material addition rate is 0%, the addition rate that is reduced by a factor of 0.8 is set as the lower limit, and the addition rate that decreases most is selected from the above range as the upper limit. Coke production method.   The method for producing coke according to claim 1, wherein the low shrinkage carbonaceous material is one or both of powdered coke and anthracite.

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