JPS5825357B2 - Method for manufacturing molded coke - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing molded coke, in which different heating methods are used in the upper and lower regions at a predetermined carbonization temperature within the range of 650 to 850°C. This technology was developed based on new knowledge that superior molded coke can be obtained by this method.

Conventionally, two methods have been proposed and implemented as carbonization methods for forming layers: a direct heating method and an indirect heating method.The former is superior in terms of productivity, and the latter is superior in terms of coke quality. It was thought to be a method.

However, there is not necessarily a clear difference between the two mentioned above, but rather they are in a complementary relationship with each other, and this complementary relationship becomes even more pronounced especially at the carbonization temperature. They have discovered that depending on the combination of heating methods, the advantages and disadvantages of each can be offset to produce excellent molded coke.

Next, the conventional carbonization method will be described.

(1) First, in the conventional direct heating method, combustion waste gas is used as a heating medium as it is, and no consideration is given to the gas composition in the heating medium, and attention is paid to the content of oxidizing gas in the heating medium gas. However, there are heating methods in which (1) a heating medium gas with a low content of oxidizing gas is used, or (2) the oxidizing gas is converted into a reducing gas.

In the former case, as is clear from FIG. 2, if the temperature of the flue exceeds 900° C., the yield will drop significantly, making it unsuitable for high-temperature carbonization.

In addition, when a vertical furnace is used, the temperature distribution in the vertical direction of the formed coal bed is difficult to control (and when looking at individual formed layers, uneven heating occurs in areas that are exposed to heating medium gas and areas that are not). There is.

On the other hand, in the latter case (cases ■ and ■ above), it was developed to improve the former method, but the carbonization furnace has many structural defects and is uneconomical, and especially in the case of ■ Although it is suitable for low temperature carbonization below 800°C, it is unsuitable for higher temperature carbonization.

That is, in a high temperature range, an endothermic reaction such as C+CO□→2CO C+HO−+H2+CO occurs between the heat transfer gas and coal, which prevents the flue temperature from rising.

In order to raise the flue temperature, the flow rate of the heating medium gas may be increased, but this results in an increase in the amount of unreduced oxidizing gas in the heating medium gas, making it impossible to achieve the original purpose.

FIG. 1 shows a temperature rise curve when an oxidizing gas is converted into a reducing gas by coke plea, as an example of the above-mentioned method.

As is clear from this figure, in the low-temperature carbonization region of 800°C or less, coke pleat effectively acted as a heat dispersant, and the temperature increase rate could be ideally controlled.

However, at temperatures above 800°C, the above-mentioned endothermic reaction occurred violently on the surface of the porous coke pleat, and the flue temperature did not reach 1000°C.

From the above, it can be seen that the conventional direct heating method is unsuitable for high-temperature carbonization.

In contrast, the conventional indirect heating method requires a long time (approximately 10 hours) for carbonization, and the bulk density of briquette coal is approximately 700 kg/m
However, the charging density is slightly lower than that of powdered coal.

In addition, since rapid heating is not possible at carbonization temperatures below 600°C, softening and melting properties are not promoted, resulting in coke with poor melting properties and low strength.However, to improve this, a large amount of binder is required, and furthermore, molded coal particles The disadvantage is that mutual sway and baby booming are likely to occur.

The purpose of this invention is to eliminate the drawbacks of the conventional heating method as described above, and the carbonization temperature is 650°C.
This paper proposes a method for producing briquette coal with good properties by directly heating the lower temperature region around ~800° C. and indirectly heating the higher temperature region.

The details of the structure of the present invention will be explained below based on the comparison results between the direct heating method and the indirect heating method based on the inventors' experimental results.

(1) Regarding the influence of both heating methods on coke yield: - Molded coal having the properties shown in Table 1 was carbonized by the indirect heating method and the direct heating method, respectively.

The results are shown in FIG. 2 as the difference in yield between the indirect method and the direct method.

As can be seen from this figure, in the temperature range below the carbonization temperature of 850°C, the difference in yield between the two heating methods is only a small difference of about 1.5% or less.

These differences are due to the fact that in the indirect heating method, heavy VM is deposited on the surface of the briquette.
This is because (volatile matter) is vapor-deposited, whereas in the direct heating method, the VM is carried away by the heating medium gas.

Therefore, it can be said that this difference is not caused by burnout of the briquette coal.

On the other hand, at temperatures above 900° C., the curve moves upward with temperature, which indicates that in the case of the direct method, the yield rapidly decreases due to burnout of the briquette coal.

That is, it is clear that the burnout of briquette coal due to the oxidizing gas in the heating medium gas hardly occurs at temperatures below 850°C, but becomes rapidly significant at temperatures above 900°C.

As shown in Table 2, even when directly heated using a heating medium gas containing a large amount of oxidizing gas, the
The fact that the yield of molded coal is essentially the same as that of the indirect heating method at temperatures below 0°C, and the fact that the yield of the direct heating method decreases rapidly at temperatures above 900°C, This is a more important point than the structure of the method of the present invention.

(2) Effects of both heating methods in temperature increase pattern 1 In order to obtain coke with high strength, it is necessary for the temperature increase pattern to satisfy the following three conditions.

(b) In order to maximize the softening and melting properties of briquette coal, the heating rate of briquette coal is rapidly heated to about 550 ml.
reach ℃.

(b) In order to moderate the shrinkage rate after the briquette coal is solidified again, the temperature of the briquette coal is raised as slowly as possible from about 550 to 650°C.

(c) The flue temperature must reach 1000°C or higher.

Therefore, in order to satisfy the conditions (a) and (b) above, molten coal was charged into a carbonization furnace that was auxiliary heated (electrically heated) to a wall surface temperature of 650°C, and molten coal was used for each method of direct heating and indirect heating. Temperature was measured.

Thereafter, the furnace temperature was raised and the briquette coal was carbonized at high temperature.

The briquette temperature at this time was also measured.

The results are shown in FIG.

As is clear from FIG. 3, in the temperature range of 900° C. or lower, the direct heating method increased the temperature more quickly and stopped at the set furnace temperature.

In other words, the direct heating method can easily satisfy the requirements (a) and (b) above.

On the other hand, in the high temperature range of 900°C or higher, the indirect heating method has a faster temperature increase rate and the flue temperature is 1030-1050°C.
reach °C.

On the other hand, in the case of the direct heating method, the rate of temperature increase is slow, and the flue temperature often reaches 1000'C.

This is because, in the case of the direct heating method, the oxidizing gas and the shaped carbon primarily undergo the following endothermic reaction in the high-temperature carbonization temperature range of 900° C. or higher.

C+C02→2 CO C+H20→CO+H2 Therefore, in order to increase the flue temperature using the direct heating method, (
b) Increase the concentration of 02 in the heat transfer gas and exothermic reaction C+02→
Possible methods include performing C02 to compensate for the endothermic component and increasing the heat transfer gas flow rate to supply sufficient heat to the briquette coal. I can't think of it as practical.

Therefore, the above conditions (/→) can be better achieved by the indirect heating method than by the direct heating method.

From the above, the heating pattern for producing high-strength and high-quality blast furnace coke is 800°C.
It can be seen that the direct heating method is better in the following cases, and the indirect heating method is better in the case of 900°C or higher.

(3) Regarding the thermal conductivity and specific heat of briquette coal in both heating methods, Figure 4 shows the relationship between carbonization temperature and thermal conductivity of briquette coal.

The following can be seen from this figure. (a) Carbonization temperature 600℃
In the following, the thermal conductivity of briquette coal is extremely low and does not change with temperature, but remains almost constant.

(b) At carbonization temperatures of 600° C. or higher, the thermal conductivity of briquette coal increases rapidly as the carbonization temperature increases.

FIG. 5 shows the relationship between carbonization temperature and constant pressure specific heat (cp) of briquette coal.

The following can be seen from this figure. (c) Carbonization temperature approximately 600
Up to °C, the specific heat of briquette coal increases rapidly with carbonization temperature.

b) The specific heat of briquette coal decreases extremely as the carbonization temperature increases from about 600°C to 700°C.

(This is due to heat generation due to resonance stabilization energy released when the aromatic structure in the briquette releases H2 and undergoes polycondensation.

) (E) At carbonization temperatures of 700°C or higher, the specific heat of briquettes increases again as the temperature rises;
It is much smaller than the specific heat at temperatures below 0°C.

To summarize the above facts, the thermal properties of briquette coal change significantly at about 600°C.

That is, (3) at temperatures below about 600°C, the thermal conductivity is extremely low and the specific heat is extremely high.

For this reason, it can be seen that the direct heating method is more rational than the indirect heating method in rapidly heating briquette coal at a temperature of 600° C. or less.

(B) On the other hand, at a temperature of about 600°C or higher, 600°
In contrast to the case below C, the thermal conductivity becomes significantly higher,
Specific heat is low.

Therefore, even if indirect heating method, which is said to have poor thermal efficiency, is used, it is expected that carbonization can be carried out with sufficient efficiency at a temperature of 6 GO° C. or higher.

Moreover, FIG. 6 shows another basis for thinking that indirect heating may be sufficiently practical in the carbonization temperature range of about 600° C. or higher.

This figure shows the actual measurement of the relationship between humidity in the center between the furnace walls and time in a conventional chamber furnace for pulverized coal carbonization (indirect heating method).

Despite the furnace wall spacing of approximately 40CTl, it took more than 13 hours for the core temperature to reach 600°C.

On the other hand, the temperature increase between 600 and 1000°C was completed in about 2 hours.

Although there are differences between powdered coal and briquette coal, even if briquette coal is carbonized by indirect heating in a temperature range of 600° C. or higher, the carbonization is completed in a sufficiently short time.

(4) Regarding the shape of the product coke, it is important that the molded coke has a constant particle size and a uniform shape.

This is because if the particle size is not constant and the particle size distribution is wide, the bulk density during charging into the blast furnace will increase, which is undesirable.

For this reason, the narrower the particle size distribution range of the molded coke, the better.

During the carbonization of the briquettes, the surface of the briquettes softens and melts, causing the briquettes to stick together and form agglomerates, and sometimes these agglomerates become extremely large, often making it difficult to discharge product coke from the carbonization furnace.

For this reason, it is preferable that the molded coke briquettes do not stick together.

From the above viewpoint, FIG. 7 shows the influence of the carbonization method on the particle size distribution of molded coke.

As is clear from the figure, in the case of the direct heating method, the particle size distribution is biased toward the fine particle side.

This is because, in the case of the direct heating method, the briquette coal is burned out by the heating medium gas at high temperatures.

On the other hand, in the case of the method of the present invention, the particle size is mostly 38 to 407n.
m, and the distribution width is narrow.

On the other hand, in the case of the indirect heating method, the briquettes stick to each other, so the distribution tends to be biased towards large lumps.

Table 3 shows the strength of cohesion between product coke particles in each carbonization method using an index.

This index is subjective, and its criteria are shown in Table 4.

As is clear from Table 4, if the yield strength index is 2 or less, it means that there is no yield in actual carbonization and discharge operations, but if the yield strength index is 3, some kind of prevention measure should be taken. It is necessary to apply

As shown in Table 3, the binding force index in the direct heating method and the method of the present invention is 2 or less.

This is because the surface of the molded coal came into contact with the oxidizing gas in the heating medium gas and became inert in the early stage of carbonization.

On the other hand, in the case of the indirect heating method, the surface of the briquettes was not inactivated, so the briquettes strongly stuck to each other.

From the above, it can be seen that the carbonization method according to the present invention is superior.

(5) Strength of Molded Coke Comparing the crushing and abrasion strength of the matrix portion between the direct heating method and the indirect heating method from FIGS. 8 and 10, the following is found.

At temperatures of 400°C or higher, the strength of the matrix part of briquette formed by the direct heating method is higher than that of the indirect heating method.

This is due to the direct heating method as mentioned in (2) above.
This shows that the promotion of softening and melting properties of briquette coal at temperatures between 400 and 600°C and the subsequent adjustment of the shrinkage rate have the strongest influence on improving the strength of the matrix.

In other words, the strength of the matrix part of molded coke is 400 to 600.
This means that it is mostly determined by the quality of the treatment at °C, and the subsequent carbonization conditions have almost no effect.

In the case of the method of the present invention, carbonization was carried out by direct heating up to around 700°C, and indirect heating was performed in the temperature range above around 700°C, but the substrate strength was equivalent to or higher than that of the direct heating method, as shown in Figures 8 and 10. It is extremely good.

Figures 9 and 11 show the passion and abrasion strength for the epidermis.

In the case of the direct heating method, the skin strength is slightly lower than that in the indirect heating method due to the effect of the heating medium gas.

In the case of the method of the present invention, the skin strength is between the direct heating method and the indirect heating method, but is relatively close to that of the indirect heating method.

(See Figures 9 and 11).

In addition, the decrease in skin strength in the direct heating method is 1000
Significant at temperatures above ℃.

As is clear from the above explanation, direct heating in the temperature range of 600°C or lower and indirect heating in the temperature range of 1000°C or higher is essential from the perspective of improving coke strength, and in the case of the method of the present invention, All of these conditions were satisfied, and coke with higher strength than either the direct heating method or the indirect heating method could be obtained.

The strength display of molded coke shown in this invention is a method developed by the inventors, and its characteristics will be explained below.

Crushing strength refers to the strength when a relatively large drop impact is applied to molded coke.

That is, 50 pieces of molded coke are placed in a rotating drum for normal JIS coke strength measurement.

This rotating drum is rotated 210 times at a rotation speed of 15 rpm.

During this process, the coke yield with a particle size of 15 g or more in the rotating drum is measured every 30 revolutions.

On the other hand, the abrasion strength refers to the strength of the coke pore walls caused by the rubbing of formed coke lumps without applying a large drop impact.

That is, 10 pieces of molded coke are placed in a rotating drum for so-called loga testing.

This rotating drum is rotated 3000 times at a rotation speed of 5 Orpm.

The yield of coke with a particle size of 5 or more is measured every 500 revolutions during the process.

Since the loga test drum has a diameter of 30 degrees and a width of 10 degrees and has an extremely small volume, when 10 pieces of molded coke are added, approximately half of the internal volume of the rotating drum is occupied by molded coke.

For this reason, even when the drum is rotated, the molded coke does not fall to the bottom of the drum even though it is scraped up by the blades inside the drum, and the movement of the molded coke lumps rubbing against each other is the main movement, and Wear occurs.

Next, a more detailed explanation will be given using wear strength as an example.

When molded coke is charged into a loga test range rotary drum and the relationship between drum rotation speed and coke yield is determined, the relationship shown in FIG. 12 is obtained.

As is clear from this figure, (1) the yield of molded coke decreases smoothly as the drum rotation speed increases; (2)
It was found that the coke strength cannot be expressed by the coke yield at a specific drum rotation speed.

(For example, in Fig. 1, in the range from 0 to 1000 revolutions, the coke in reservoir 6 is strong and the coke in reservoir 2 is weak, but above 2000 revolutions, this relationship is completely reversed.) In short, in this invention, these points are taken into consideration regarding the strength display. This has been considered.

Therefore, (1) the surface of molded coke is surrounded by a strong shell due to erosion caused by heat transfer gas and expansion cracks; (2)
It was determined that a homogeneous and strong coke matrix was formed under this weak shell.

Moreover, when the molded coke is charged into a drum and rotated, the fragile outer skin quickly peels off due to the rotational impact.

When a homogeneous matrix is exposed after the skin is peeled off, the coke lump yield decreases at a constant rate depending on the strength of the matrix.

That is, the strength of molded coke can be considered separately into the strength of the outer shell and the strength of the matrix.

In order to make molded coke with high strength, both the outer shell and the matrix must be strong.

The same thing can be said about the crushing strength as well.

From the above, it was found that an approximate relationship expressed by the following equation (1) exists between the coke yield and the drum rotation speed.

However, for the coke yield at rotational speed Y(r) of r Ni drum: constant (strength of matrix part) A: constant (strength of shell part) As is clear from the above, whether it is crushing strength or abrasion strength In any case, the process by which the lump yield of molded coke decreases in the rotating drum is as the number of rotations of the drum increases.
It can be considered in stages.

That is; The first stage is the initial stage of Nidram rotation.

This is the period when coke lumps mainly become smaller due to external shape defects of molded coke (erosive scratches due to gasification, cracks, pointed protrusions, etc.).

2nd stage: In the 1st stage, the defective external shape of the briquette is lost and the briquette surface, which has become spherical, undergoes a reduction in the size of coke lumps based on the uniform pulverization of the coke matrix.

In the second stage, it is considered that the drum rotation speed r and the amount of under-sieve fine powder generated are proportional.

That is, in fact, in the crushing strength test, r = 90 or more, and in the abrasion test, r = 500 or more, (2)
The formula holds true well.

That is, in the second stage, equation (1) obtained by solving equation (2) holds true.

Therefore, the size of K has a large influence on the reduction of coke lump size and can be regarded as an index representing the difficulty of pulverizing the briquette matrix.

In this sense, when the drum rotation speed is low, where K is defined as the substrate strength, equation (1) and the actual measured value deviate.

Originally, it should be Y(0)-1, which is the coke yield when the drum rotation speed r=0.

However, Y(0) obtained by extending equation (1) to drum rotation speed r=O usually satisfies Y(0)<1.

Especially in the early stages of drum rotation due to poor shape of briquettes, etc.
If r is small, Y(0) tends to be small if it is easily pulverized.

We believe that this can be a measure of the fragility of the formed coke skin, and in equation (1), when r = 0, A =
1 n was defined as the epidermis strength and Y(0).

Example The briquette shown in Table 1 above was directly heated to a briquette temperature of 700°C using a heating medium gas having the composition shown in Table 2.
The heating pattern at which the supply of the heating medium gas was stopped at ℃ and then heated to 1030 ℃ by indirect heating method is shown in FIG. 13, and is almost the same pattern as the heating pattern of the direct heating method shown in FIG. Became.

On the other hand, molded coke was produced by carbonizing molded coal with the same properties only by a direct heating method and by carbonizing only by an indirect heating method.

A comparison of this with the molded coke produced by the method of the present invention described above is as follows.

(a) Strength of anchoring force As shown in Table 3, in the case of the method of the present invention, it is small as in the case of the direct heating method.

(b) Particle size distribution: As shown in Figure 7, the method of the present invention has a narrow distribution range and good particle size uniformity.

(c) Coke yield 2 As is clear from the coke yield shown in Table 5, the method of the present invention is close to that of the indirect heating method, and the gasification loss of carbonaceous material due to the heating medium gas is relatively small.

B) Coke strength2 As is clear from the crushing and abrasion test results shown in Table 6, the substrate strength in the method of the present invention is much better than other heating methods, regardless of crushing and abrasion. .

In addition, the skin strength showed a high value almost equivalent to that of the indirect heating method.

From these points, it can be seen that the molded coke produced by the method of the present invention becomes a product with much higher strength than the molded coke produced by the conventional method.

From the above points, the molded coke produced by the method of the present invention exhibits more preferable properties than any of the conventional carbonization methods.

As is clear from the above explanation, the present invention has the following effects.

(1) Effects obtained by directly heating a temperature range in which the temperature of briquette coal is 750°C or lower using a heating medium gas containing an oxidizing gas.

(a) Since the surface of the molded carbon is inactivated by the oxidizing gas in the early stage of carbonization, it is possible to produce molded coke with a uniform shape and less mutual sticking and deformation of the molded coals.

(b) In a temperature range of 800°C or less, the burning of briquette coal by oxidizing gas is extremely slight, and the use of oxidizing gas has almost no negative effect on briquette coal; therefore, temperatures below 800°C A heating medium gas containing an oxidizing gas can be used even in the temperature range of .

Moreover, an inexpensive fuel can be selected as the fuel source for direct heating.

(c) Molded coal has a high specific heat and extremely low thermal conductivity in a temperature range of 700° C. or lower.

Therefore, the direct heating method has higher thermal efficiency than the indirect heating method and can shorten the carbonization time.

2) To produce high-strength, high-quality molded coke for metallurgy, it is necessary to rapidly heat the semi-coke to a carbonization temperature of approximately 500°C or less to promote softening and melting properties, and carbonization to moderate the shrinkage rate of semi-coke. It is necessary to heat slowly to a temperature of about 500-700°C.

As described above, in the low-temperature carbonization temperature range of 800° C. or lower, it is necessary to appropriately adjust the heating rate, but this adjustment can be easily achieved by the direct heating method.

In particular, a direct heating method is suitable for rapid heating to promote softening and melting properties.

(2) Effects obtained by indirectly heating briquette coal in a temperature range of 750℃ or higher; The indirect heating method can prevent this.

(b) In the range of 700 to 1000°C, the specific heat of briquette coal decreases, but the thermal conductivity significantly improves.

Therefore, even if high-temperature carbonization of briquette coal is performed by indirect heating, thermal efficiency is high and high productivity can be maintained.

As described above, according to the method of the present invention, it is possible to produce molded coke of excellent quality as coke for blast furnaces, which has a uniform shape with little deformation or sagging of briquettes.

[Brief explanation of drawings]

Figure 1 of the drawing shows the temperature increase pattern when oxidizing gas is converted to reducing gas by coke breeze, and Figure 2 shows the relationship between the difference in yield between the direct heating method and indirect heating method and the briquette temperature. Figure 3 is a diagram showing the temperature pattern showing the carbonization method of the present invention, Figure 4 is a diagram showing the change in thermal conductivity during the carbonization process of briquette coal, and Figure 5 is a diagram showing the change in specific heat during the carbonization process of briquette coal. Figure 6 is a diagram showing the relationship between the core temperature and coking time in the chamber furnace, Figure 7 is a diagram showing the product coke particle size distribution for each carbonization separation, and Figures 8 and 10 are diagrams showing the changes. Figures 9 and 11 are diagrams showing changes in the crushing strength or abrasion strength of the matrix part of molded coke during the carbonization process; Figures 9 and 11 are diagrams showing changes in the crushing strength or abrasion strength of the skin part of molded coke; FIG. 13 is a graph showing the relationship between the coke yield, which represents the strength index, and the drum rotation speed. FIG. 13 is a graph showing the heating pattern of the example.

Claims (1)

[Claims] 1. In a method of producing molded coke with uniform particle size and high strength by carbonization in which the molded layer is slowly heated in the range of 700 to 500°C, but rapidly heated in the range of 500°C or less, the carbonization temperature of the molded layer is determined during the carbonization. is 650-850°C
Direct heating is performed using a heating medium gas in the temperature range below the selected temperature within the range, while indirect heating without heating gas is applied in the temperature range above this temperature range. Characteristic method for producing molded coke 6