JP7335513B2 - coke production method - Google Patents

Description

The present invention relates to a method for producing coke using modified coal.

In the chamber hearth coke oven, highly caking coal is used as the main raw material, and it is expected that this highly coking coal will be depleted in the future as well as being expensive. Blended coal containing a large amount of low-cost inferior coal (for example, high volatile inferior coal) has a higher shrinkage rate in the coking process as the volatile content increases, so that many cracks are likely to form in the coke. As a result, there is a problem that the coke particle size becomes smaller due to the decrease in coke strength. _The coke strength in this specification means coke strength DI ^150-15 unless otherwise specified.

Here, a method is known in which the low-quality coal is heat-treated before being charged into a coking chamber to remove volatile matter, charred, and used as a raw material for coke.

Patent Document 1 discloses a pretreatment method for obtaining char suitable for producing molded coke from high volatile non-slightly coking coal, in which tar is added to the high volatile non-slightly coking coal in a mixer and mixed. After that, it is heated at 450 to 600 ° C. in an externally heated rotary kiln to produce char, and the tar separated from the dry distillation gas discharged from the rotary kiln is used as the tar added to the mixer described above. . In addition, FIG. 3 of Patent Document 1 describes that coke with high coke strength can be obtained by blending 20 to 40% of char produced by this method with raw coal.

JP-A-56-136879

However, even if the blended coal containing char described in Patent Document 1 is dry distilled in a chamber-type coke oven, coke with high coke strength cannot be produced due to insufficient caking properties. That is, since the chamber furnace type coke production method has a lower coal packing bulk density than the molded coke method, if a large amount of char with poor cohesion is blended, the blended coal will have insufficient cohesion, resulting in coke Strength decreases.

The inventor of the present invention has discovered a technology that can reform inferior coal into coking coal with excellent cohesiveness by directly bringing the dry distillation gas generated during the dry distillation of inferior coal into contact with the inferior coal and then cooling it. .

That is, the method for producing coke according to the present invention includes: (1) a char production step of dry-distilling inferior coal having a volatile content of 30% by mass or more and a total expansion coefficient of 15% or less to produce char; , a reforming step of producing modified coal by contacting inferior coal having the properties described above with the carbonization gas generated in the char production step; and at least the char obtained in the char production step and the reforming step. A mixing step of producing a mixed coal by mixing the modified coal obtained in (1) with a strongly coking coal containing 15% by mass or more and less than 30% of volatile matter and having a total expansion rate of 20% or more; and a reformed coal cooling step of cooling the reformed coal obtained in the reforming step before mixing in the mixing step.

(2) Further, it has a dry distillation gas cooling step for cooling the dry distillation gas generated in the char production step, and the dry distillation gas cooled in the dry distillation gas cooling step is used as the dry distillation gas in the reforming step. The method for producing coke according to the above (1).

(3) The method for producing coke according to (1) or (2) above, wherein the coal mixed in the mixing step further contains inferior coal having the properties described above.

(4) When the mixed coal is 100% by mass, the blending ratio of the char is 10% by mass or more and 30% by mass or less, and the blending ratio of the modified coal is 10% by mass or more and 40% by mass or less. , The method for producing coke according to any one of the above (1) to (3), wherein the blending ratio of the strongly caking coal is 10% by mass or more and 30% by mass or less.

ADVANTAGE OF THE INVENTION According to this invention, modified coal with excellent caking property can be obtained by contacting inferior coal with dry distillation gas and then cooling. Further, coke with high coke strength can be produced by mixing the modified coal with char and strongly coking coal and subjecting the mixture to dry distillation in a chamber-type coke oven.

It is process drawing which shows the manufacturing method of coke. It is a schematic diagram of a dry distillation apparatus (for char production).

(Definition of terms)
In this specification, inferior coal is defined as "coal having a volatile matter (VM) content of 30% by mass or more and a total expansion coefficient (TD) of 15% or less". The inferior coal may be single coal or mixed coal in which multiple brands of inferior coal are mixed. Strong coking coal is defined as "coal having a volatile matter (VM) content of 15% by mass or more and less than 30% by mass and a total expansion coefficient (TD) of 20% or more". The strong coking coal may be single coal or mixed coal in which multiple brands of strong coking coal are mixed. The total expansion rate (TD) is the sum of the contraction rate and the expansion rate measured by the expansion test method (dilatometer method) specified in JIS M 8801 (the same shall apply hereinafter).

The present inventors discovered that by contacting inferior coal with carbonization gas generated during char production and then cooling the coal, the coal can be reformed into coal with excellent caking properties. Hereinafter, the method for producing coke according to the present embodiment will be described in detail with reference to the drawings. FIG. 1 is a process drawing showing the method for producing coke according to the present embodiment.

The method for producing coke according to the present embodiment includes:
(1) a char production process of dry-distilling inferior coal to produce char;
(2) a reforming step of bringing the inferior coal into contact with the carbonization gas generated in the char production step to produce the reformed coal;
(3) a mixing step of mixing the char obtained in the char production step, the modified coal obtained in the reforming step, the inferior coal, and the strongly coking coal;
(4) a modified coal cooling step of cooling the modified coal before mixing in the mixing step;
(5) A dry distillation step of dry-distilling the mixed coal obtained in the mixing step in a chamber-type coke oven.
In addition, when inferior coal used in the char manufacturing process is referred to as inferior coal for char manufacturing, inferior coal modified in the reforming process is referred to as inferior coal for reforming, and inferior coal mixed in the mixing process is referred to as inferior coal for mixing. There is

(About the char manufacturing process)
Inferior coal for char production is dry distilled in a dry distillation apparatus 1 to produce char. The dry distillation temperature is exemplified by 600° C. or higher and 900° C. or lower. Char is a carbonaceous substance that is produced without softening or melting when coal is heated (see JIS0104 Coal Utilization Technical Terms).

Although the dry distillation apparatus 1 is not particularly limited, for example, an externally heated double rotary kiln can be used. Dry distillation of inferior coal for char production generates dry distillation gas containing tar. This dry distillation gas is sent to the reformer 2 after being cooled to a predetermined temperature in the primary gas cooler 11 (corresponding to the dry distillation gas cooling step). The predetermined temperature is preferably 200° C. or higher and 400° C. or lower. When the temperature of the dry distillation gas drops below 200° C., liquid tar may be condensed and generated, and as described later, the tar becomes difficult to permeate into the inferior coal for reforming. If the temperature of the dry distillation gas remains above 400° C., the inferior coal for reforming in contact with the dry distillation gas undergoes a thermal decomposition reaction, and the reforming effect tends to decrease. In addition, the modification effect in this specification is to improve the caking property of inferior coal.

The char produced in the dry distillation apparatus 1 is sent to the mixing apparatus 4 after being cooled in the char cooler 12 .

(Regarding the reforming process)
FIG. 2 is a schematic diagram of a reformer. The reformer 2 is a counter-type reformer in which gas and solid flow in opposite directions, and is formed in a tubular shape and rotates around a longitudinal axis L. As shown in FIG. The inferior coal for reforming is charged from one end side of the rotating reformer 2 and discharged from the other end side. The dry distillation gas cooled by the primary gas cooler 11 is blown in from the other end side of the rotating reformer 2 and exhausted from one end side. That is, the inferior coal for reforming rolls in the reformer 2 and moves in the direction opposite to the direction in which the dry distillation gas flows. Thereby, the inferior coal for reforming can be brought into contact with the dry distillation gas efficiently.

The inferior coal for reforming has a large number of pores, and the dry distillation gas (mainly tar in a gas phase state) at a predetermined temperature flows into these pores to relax the structure of the coal, thereby reforming the coal. Poor quality coal for quality can be suitably reformed. That is, since the tar in the gaseous state whose temperature has been adjusted to the predetermined temperature permeates into the interior of the inferior quality coal for reforming, the structure of the coal can be relaxed efficiently.

The residence time of the inferior coal for reforming in the reformer 2 is preferably 5 minutes or more and 30 minutes or less. By setting the residence time to 5 minutes or longer, the tar can be sufficiently permeated into the interior of the inferior coal for reforming, so the residence time is preferably set to 5 minutes or longer. By setting the residence time to 30 minutes or less, the reforming of the inferior coal for reforming can be progressed more appropriately, so the residence time is preferably set to 30 minutes or less.

(Regarding modified coal cooling process)
The reformed coal cooler 3 cools the reformed coal discharged from the other end side of the reformer 2 . Here, if the reformed coal is carbonized in a chamber-type coke oven without being cooled, the reformed coal cannot exhibit sufficient caking properties. The reason for this is that the modified coal is in a highly reactive state where the structure is relaxed, and the thermal decomposition reaction proceeds in this state, so the thermal decomposition reaction proceeds excessively and the caking property decreases. guessed. On the other hand, if the reformed coal that has been reformed by the reformer 2 is once cooled and then carbonized in a chamber-type coke oven, the coking property of the reformed coal can be fully developed. It is presumed that this is because the thermal decomposition starts after the structure-relaxed modified coal is once stabilized, so excessive progress of the thermal decomposition can be suppressed.

The cooling temperature in the modified coal cooler 3 is preferably less than 200°C, and the cooling time is preferably 3 hours or more. The dry distillation gas introduced into the reformer 2 is cooled by the secondary gas cooler 21 so as not to interfere with subsequent transportation and processing.

(Mixing process)
In the mixing step, mixed coal is produced by mixing the char obtained in the char producing step, the modified coal obtained in the reforming step, the inferior coal for mixing, and the strongly coking coal. When the total mixed coal is 100% by mass, the blending ratio of the strongly coking coal is preferably 10% by mass or more. If the blending ratio of the highly coking coal is less than 10%, the coking property of the mixed coal may be lowered, and the coke strength may be lowered. Moreover, the upper limit of the blending ratio of strongly coking coal is not particularly limited. However, the present invention is based on the premise that a large amount of inexpensive inferior coal is blended after reforming to reduce the blending ratio of expensive hard-coking coal, so the blending ratio of hard-coking coal is 30% by mass or less. It is preferable to keep it to

When the total mixed coal is 100% by mass, the blending ratio of char is preferably 10% by mass or more and 30% by mass or less. Since char is a raw material with a low volatile content, if the char blending ratio is reduced to less than 10% by mass, the volatile content contained in the mixed coal becomes excessively high. As a result, cracks occur during carbonization, and coke strength decreases. may decrease. Since char is a raw material with a very small total expansion coefficient, if the blending ratio of char exceeds 30% by mass, the coke strength of the mixed coal may be lowered and the coke strength may be lowered.

When the entire mixed coal is 100% by mass, the blending ratio of the modified coal is preferably 10% by mass or more. Modified coal has better caking properties than inferior coal and char, so if the blending ratio of modified coal is reduced to less than 10% by mass, the coking properties of the mixed coal may decrease and the coke strength may decrease. . Moreover, the upper limit of the blending ratio of the modified coal is not particularly limited. However, if the blending ratio of the reformed coal is increased, the equipment costs and operating costs of the reformer 2 and the reformed coal cooler 3 increase, so it is preferable to keep the blending ratio to 40% by mass or less. Also, by suppressing the modified coal to 40% by mass or less, it is possible to suppress the generation of cracks due to excessive volatile matter.

As the inferior coal for mixing mixed in the mixing step, the inferior coal for char production and the remaining inferior coal that cannot be completely treated as the inferior coal for reforming are used. That is, the inferior coal that cannot be processed by the carbonization unit 1 and the reformer 2 due to the problem of processing capacity or the like is mixed in the mixing step. Therefore, if all of the inferior coal can be processed in the dry distillation unit 1 and the reformer 2, the inferior coal may be excluded from the coal mixed in the mixing step.

(About dry distillation process)
The mixed coal obtained in the mixing step is charged into the carbonization chamber of the chamber-type coke oven 5 and carbonized. The carbonized coke is extruded from the coking chamber, cooled by the coke dry quenching equipment, and used as a reducing agent for charging into the blast furnace.

EXAMPLES Next, the present invention will be described in detail with reference to examples. Table 1 shows the properties of the hard coking coal, inferior coal, char, and modified coal used in this example. A method for producing char and modified coal will be described later.

The cohesive strength index CI is an index indicating the strength of cohesiveness of coal obtained from the strength of the coke button after carbonizing a mixture of coal and an inert substance, and in this embodiment, it is 0.25 mm or less. 1 g of coal is mixed with 9 g of coke powder of 0.25 to 0.3 mm, carbonized in a magnetic crucible at 900 ° C for 7 minutes, then the product is sieved with a sieve mesh of 0.42 mm, and the percentage of the sieve mass was taken as the cohesive strength index CI (see page 255, published by the Japan Fuel Association, 1983). The higher the caking strength index CI, the higher the caking properties.

Mixed coal blended according to the blending conditions shown in Table 2 was carbonized in a test coke oven to measure coke strength. Here, the dry distillation temperature was 1250° C. and the dry distillation time was 18.5 hours.

In Comparative Example 3, the blending ratio of strongly coking coal was set to 20% by mass, and the remainder was used as inferior coal. Also, the inferior coal was equally divided into inferior coal for char production and inferior coal for mixing, respectively. The char was produced by applying the char production method described in Patent Document 1. Specifically, inferior coal for char production was charged into a rotary kiln, heated to 550°C at a temperature elevation rate of 5°C/min, held at 550°C for 20 minutes, and then cooled. The amount of tar to be added was set to 1% by mass with respect to the inferior coal. Comparative Example 2 was the same as Comparative Example 3, except that no tar was added. In Comparative Example 1, all the inferior coal for mixing was used as the inferior coal for mixing (that is, the inferior coal for char production and the inferior coal for reforming were set to 0% by mass).

In Invention Example 1, the blending ratios of the inferior coal for mixing, char, and modified coal were 40% by mass, 20% by mass, and 20% by mass, respectively. Char was produced by heating inferior coal for char production (no tar added) in a rotary kiln under the same conditions as described above. Further, the inferior coal for reforming was charged into the reformer, and the carbonized gas cooled to 350° C. in the primary gas cooler was blown into the reformer. The outlet temperature of the dry distillation gas reformer was 300°C. The residence time of the inferior coal for reforming in the reformer was set to 10 minutes. The reformed coal reformed by the reformer was cooled to 30° C. by a reformed coal cooler, and then mixed with strong coking coal, poor quality coal for mixing and char in a mixing device. The time until the reformed coal was charged into the coke oven after cooling was set to 8 hours. In Invention Example 2, the blending ratios of the inferior coal for mixing, char, and modified coal were 30% by mass, 20% by mass, and 30% by mass, respectively. The method for producing the modified coal was the same as in Invention Example 1.

With reference to Comparative Examples 2 and 3, the coke strength increased only to 82 even with the addition of tar. As shown in Invention Examples 1 and 2, coke strength was greatly improved by including char and modified coal in the mixed coal.

REFERENCE SIGNS LIST 1 dry distillation device 2 reformer 3 reformed coal cooler 4 mixing device 5 chamber-type coke oven 11 primary gas cooler 12 char cooler 21 secondary gas cooler

Claims (4)

a char production process for producing char by carbonizing inferior coal having a volatile content of 30% by mass or more and a total expansion coefficient of 15% or less;
a reforming step of bringing the inferior coal having the properties described above into contact with the carbonization gas generated in the char production step to produce modified coal;
At least the char obtained in the char production step, the modified coal obtained in the reforming step, and strongly coking coal containing 15% by mass or more and less than 30% of volatile matter and having a total expansion rate of 20% or more. A mixing step of producing mixed coal by mixing
a dry distillation step of dry-distilling the mixed coal in a chamber-type coke oven;
a modified coal cooling step of cooling the modified coal obtained in the modifying step before mixing in the mixing step;
A method for producing coke, comprising: Furthermore, it has a dry distillation gas cooling process for cooling the dry distillation gas generated in the char production process,
2. The method for producing coke according to claim 1, wherein the dry distillation gas cooled in the dry distillation gas cooling step is used as the dry distillation gas in the reforming step. 3. The method for producing coke according to claim 1, wherein the coal mixed in the mixing step further contains inferior coal having the properties. When the mixed coal is 100% by mass, the blending ratio of the char is 10% by mass or more and 30% by mass or less, and the blending ratio of the modified coal is 10% by mass or more and 40% by mass or less. 4. The method for producing coke according to any one of claims 1 to 3, wherein the blending ratio of caking coal is 10% by mass or more and 30% by mass or less.