JP2003055667A - Production method for blast furnace coke - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for producing blast furnace coke from bony coal (e.g. brown coal). SOLUTION: After bony coal (e.g. brown coal) is subjected to heat treatment in a liquid medium under a pressure of 1-20 MPa at 400 deg.C or lower, the treated coal is separated from the liquid medium, charged as a part of a coal blend into a coke oven, and carbonized. The treated coal can be mixed with a caking additive. Water or a substance of which the vapor pressure exceeds 1 MPa at 400 deg.C or lower can be used as the liquid medium.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing blast furnace coke, and particularly to poor quality coal such as brown coal (poor quality coal).
The present invention relates to a method of producing good quality coke by using a large amount of coke.

[0002]

2. Description of the Related Art A chamber furnace type coke oven for producing blast furnace coke is a furnace in which a carbonization chamber for carbonizing coal and a combustion chamber for supplying heat to the carbonization chamber are alternately arranged in a sandwich form. is there. The size of the carbonization chamber is, for example, 6 in height.
~ 7m, length is 15 ~ 17m, width is about 0.45m, all made of bricks. In such a coke oven, for example, 20 to 40 tons of raw material coal is charged into the carbonization chamber at one time, heated at a temperature of about 1000 ° C. for about 24 hours, and carbonized,
It becomes coke and is discharged from the furnace. The red hot coke discharged from the coke oven was then wet-cooled by sprinkling water,
Alternatively, extinguishing and cooling are performed by dry cooling with an inert gas.

Coal, which is a raw material for the production of coke, is classified into various forms depending on its properties and uses. The most frequently used classification methods are by degree of coalification and by caking. The classification according to the degree of coalification is classified into lignite, bituminous coal and anthracite. The classification based on caking property is classified into non-light caking coal and caking coal. The degree of coalification indicates the degree of progress of a process in which a root plant is converted to coal by receiving a coalification action, and changes from brown coal to anthracite as coalification progresses. On the other hand, caking property is a classification standard used when aiming at the production of blast furnace coke.

One of the properties that the coke for a blast furnace should have is that it is lumpy. In order to obtain this massive coke, coal needs to be melted once in the carbonization process. Coal that has the property of melting (softening and melting) is called coking coal, and coal that does not melt at all or hardly melts is called non-fine coking coal. Coal having softening and melting properties, which is indispensable for the production of high-quality blast furnace coke, is a part of bituminous coal among coals classified by the degree of coalification, and other bituminous coal (also called subbituminous coal).
Alternatively, anthracite and lignite have no caking properties at all.

Therefore, the coals that can be used to produce blast furnace coke are very limited, and attempts have been made to use a wider range of coals. For example, in Japanese Patent Laid-Open No. 6-184544, as a method for producing a binder (caking filler) for using coal having low caking property as a coke raw material, tar is irradiated with radiation in an oxidizing or inert atmosphere. An invention of a method of applying is disclosed. Further, in Japanese Patent Laid-Open No. 8-165474, fine powder is separated and collected during drying of coal, the fine powder is agglomerated, and the agglomerated coal is mixed with the remaining dry coal and loaded into a coke oven. The invention of a method of increasing the bulk density of the charge by charging is disclosed. However, these inventions are improvements in the method of using coal and are not aimed at improving the properties of the coal itself. Therefore, the amount of non-cohesive coal that can be used is naturally limited.

[0006]

[Problems to be Solved by the Invention] Low-rank coals (such as lignite coal and sub-bituminous coal) (which are collectively referred to as "poor coals" in this specification) that occupy about half of coal resources are It has a high content of hetero elements such as sulfur and nitrogen, and has a high porosity. When low-rank coal (poor quality coal) having such properties, especially brown coal, is used as a part of blended coal for producing blast furnace coke, the strength of the product coke is improved even if the addition amount is small. It drops sharply. Therefore, the process of using such inferior coal as a raw material for blast furnace coke has not been practically used so far.

An object of the present invention is to provide a method for producing blast furnace coke, which uses inferior coal, which is considered unsuitable for the production of coke, as blended coal.

[0008]

[Means for Solving the Problems] The present inventors examined the cause of the decrease in coke strength when poor quality coal is used as the blended coal for producing coke.

Caking coal (good quality coal) from which high quality blast furnace coke can be obtained exhibits a softening and melting state at a carbonization temperature of 400 to 500 ° C., and in this temperature range, it is converted from macromolecular solid coal by a pyrolysis reaction. A liquid low-molecular component is produced. It is considered that the low-molecular component is generated by stabilizing the low-molecular radical initially generated by the thermal decomposition reaction with hydrogen. Therefore, whether or not a softened and molten state is exhibited is hydrogen that can contribute to radical stabilization (also called mobile hydrogen).
However, how much it exists in coal is a big key.

In poor quality coal, since the content of oxygen or oxygen functional group contained in a large amount in the molecule is high, oxygen or oxygen functional group preferentially reacts with mobile hydrogen. For this reason, the amount of mobile hydrogen that should act effectively in the softening and melting region (pyrolysis reaction region) is insufficient. That is, oxygen or oxygen functional groups in inferior coal cannot generate liquid low-molecular components that inhibit radical stabilization. In addition, since being porous generally causes an increase in reaction active sites (thermal decomposition reaction active sites), consumption of mobile hydrogen is further accelerated, and radical stabilization for softening and melting property development is inhibited. it seems to do.

As described above, it has been clarified that the high oxygen content and porous nature of inferior coal have an adverse effect on the softening and melting property for producing high quality blast furnace coke.

The reason why lignite cannot be used as a blended coal for producing blast furnace coke is that lignite has a high oxygen content and is highly reactive because it is porous. Therefore, it was thought that if the reactivity of inferior coal could be suppressed, it could be used as blended coal for producing blast furnace coke. Based on this idea, various experiments were conducted, and it was found that the reactivity can be suppressed by heat-treating inferior coal in a high-pressure liquid, and the present invention was completed.

The gist of the present invention resides in the following method for producing blast furnace coke.

After heat-treating inferior coal in a medium liquid having a pressure of 1 to 20 MPa and a temperature of 400 ° C. or less, the heat-treated coal and the medium liquid are separated, and then the heat-treated coal is added to the blended coal and loaded into a coke oven. A method for producing blast furnace coke, which is charged by dry distillation.

It is desirable to add a caking filler to the mixture of the above-mentioned heat-treated coal and blended coal, and it is desirable to use a medium liquid or water whose vapor pressure exceeds 1 MPa and whose temperature is 400 ° C. or less.

The poor-quality coal to be subjected to the heat treatment of the method of the present invention is brown coal or sub-bituminous coal whose degree of coalification is higher than that of brown coal. These inferior coals are appropriately crushed if necessary,
It is mixed with the medium liquid and subjected to heat treatment.

[0017]

BEST MODE FOR CARRYING OUT THE INVENTION The present inventors have compared and examined the behaviors of a poor quality coal and a good quality coal during a thermal decomposition reaction, and have clarified the following.

FIG. 1 (a) is a diagram showing a cross section of poor quality coal, (b) is a diagram showing a cross section of good quality coal, and (c) is a schematic diagram for explaining a thermal decomposition reaction of poor quality coal.

Poor coal 1 has pores 3 as shown in FIG. 1 (a).
There are many. On the other hand, high-quality coal has few pores, as shown in Fig. 1 (b). Further, the poor quality coal has a higher content of oxygen or oxygen functional groups 5 than the good quality coal, and therefore has high thermal decomposition reactivity. FIG. 1 shows an example in which the oxygen functional group is (-COOH, carboxyl group).

As shown in FIG. 1 (c), in the thermal decomposition reaction of inferior coal, in the pores 3 where reaction sites are easily formed, the oxygen functional group 5 is released, the tar 4 is generated, and the tar exudation phenomenon occurs. Occur. And, usually, these pyrolysis reaction products are easily released to the outside of inferior coal. In order to prevent this, in the present invention, it was considered to suppress the main reaction of the thermal decomposition reaction. That is, the inferior coal is produced by the precursor reaction as shown in FIG.
As shown in (c), a part of the tar 4 is exuded and the pore outlet is closed or made small so that the thermal decomposition reaction is hard to occur. Another method is to build a barrier at the outlet of the opening, and to make the medium liquid have a high pressure.

The medium liquid has the following functions (1) to (3). In other words, it should be a heat transfer medium to coal for heat treatment, capable of generating high pressure, suppressing diffusion of thermal decomposition products, and capable of transporting inferior coal to the reaction system in the case of a continuous process.

Such a medium liquid may be a liquid whose vapor pressure exceeds 1 MPa and whose temperature is 400 ° C. or lower. Examples of the liquid exhibiting such properties include water and methylnaphthalene oil. The vapor pressure of a substance can be measured, but it generally correlates well with the boiling point of a liquid.
A substance at 20 ° C has a vapor pressure of about 1 MPa at a temperature of 350 ° C. Water has a vapor pressure of about 1 MPa at a temperature of 180 ° C,
It is about 20MPa at around 60 ℃.

The inferior carbon mixed with the medium liquid is heat treated into a slurry. Next, the reason for limiting the heat treatment conditions will be described.

Heat treatment temperature: 400 ° C. or less In the heat treatment of the poor quality coal of the present invention, as described above with reference to FIG. 1 (c), part of the tar 4 is exuded by the precursory reaction and the pore outlet is discharged. It is to make it small. For this reason,
When the heat treatment temperature exceeds 400 ° C, the thermal decomposition of inferior coal (coal) becomes too active, which is not preferable. The lower limit of the treatment temperature is not particularly limited, but if it is too low, the reaction does not occur, so it is desirable to set it to about 250 ° C or higher.

Heat treatment time: The heat treatment time is determined in consideration of the heat treatment temperature. When the temperature is high, it is short, and when it is low, a long time is required. Therefore, the heat treatment time is not particularly limited, but from the viewpoint of productivity, it is preferably 1
Within time.

Pressure during heat treatment: 1 to 20 MPa When heat treatment is performed on inferior coal (brown coal), a decomposition reaction occurs from the most reactive portion of the coal structure. Most of the initial reactions are reactions involving oxygen or oxygen functional groups. As a result of the reaction, a gas (H, mobile hydrogen) or a liquid product (tar 4) is produced as shown in FIG. 1 (c). These products are a poor quality coal during heat treatment unless diffusion is restricted.
It will be easily separated from (brown coal).

According to the method of the present invention, this reaction product,
In particular, most of the liquid product remains in the poor quality coal during the heat treatment. The remaining of these acts to close the pores in the poor quality coal during the heat treatment. The mechanism of this pore blockage is not clear, but the tar-like liquid that is generated and oozes out by thermal decomposition fills the pores, but the outlet of the pores closes the outlet with medium liquid having pressure. It is considered that the solidification occurs in the pores.

In the method of the present invention, the reaction zone is maintained at a high pressure in order to prevent the liquid matter produced by the heat treatment from diffusing and dissipating. If the pressure in the reaction zone is less than 1 MPa, the effect of suppressing the diffusion of the liquid material cannot be exhibited. The higher the pressure in the reaction zone is, the more effective it is. However, since the apparatus cost becomes high and the diffusion suppressing effect is saturated as the pressure becomes higher, the upper limit was set to 20 MPa. Therefore, the pressure in the reaction zone was set to 1 to 20 MPa.

The high pressure in the reaction zone can be maintained by introducing a high pressure gas (for example, nitrogen gas) as a third substance into the reaction system. Further, it is economical and preferable that the reaction material itself can generate a high pressure (autogenous pressure due to vapor pressure). Since the coal does not undergo a large phase change at a temperature of 400 ° C or lower, such generation of autogenous pressure cannot be expected. On the other hand, the medium liquid can generate a vapor pressure according to the temperature.

When the inferior coal is introduced into the reaction zone (reaction vessel) set to the above heat treatment conditions, the highly reactive portion of the inferior coal is thermally decomposed and is derived from a carboxyl group, a carbonyl group, an ether group or the like. A small amount of gas components containing COx as a main component are generated, and the oxygen content in inferior coal decreases. In addition, the reactivity decreases due to the blockage of some of the pores. In this way, inferior coal is reformed by thermal decomposition, and consumption of mobile hydrogen in the softening and melting process is suppressed. Hereinafter, it will be described in more detail with reference to examples.

[0031]

Example 1 Inferior coal (crushed brown coal) shown in Table 1 and the medium liquid shown in Table 2 were mixed at a mass ratio of 1: 2 to form a slurry, which had an internal volume of It was filled in a 5 liter autoclave and heat-treated at various reaction temperatures, pressures (basically autogenous pressure consisting of vapor pressure of the medium liquid) and time. The heat-treated sample was quantitatively recovered from the autoclave, centrifuged and washed with acetone as necessary to recover the heat-treated charcoal. The autoclave test under the same conditions was repeated until the amount of recovered heat-treated coal under the same heat treatment conditions became 5 kg or more. The heat-treated coal thus obtained and the blended coal for producing ordinary blast furnace coke were uniformly mixed in a mass ratio of 15:85, and a small carbonization test with a coal filling amount of 30 kg was carried out. The coke was filled in a furnace and subjected to dry distillation under conditions of a furnace temperature of 1150 ° C. and a dry distillation time of 20 hours to produce coke. The blended coal was blended so as to have the values shown in Table 3.

[0032]

[Table 1]

[0033]

[Table 2]

[0034]

[Table 3]

The coke thus obtained was subjected to a conventional cold rotary drum test, and the coke strength (D
I) was measured. The results are shown in Table 4. Coke with a coke strength (DI) of 80% or more was used as blast furnace coke. The coke obtained by dry distillation of only the blended coal shown in Table 3 had a strength of 84.5%.

[0036]

[Table 4]

The coke of Test No. 1 of the invention example was subjected to a heat treatment in which brown coal was kept at 350 ° C. (internal pressure: 16.5 MPa) for 0.5 hours with water as a medium liquid, and the heat treated coal was mixed with blended coal and dry-distilled. Manufactured. The coke strength DI of this coke is 8
It was 2.3%.

The coke of Test No. 2 of the invention example was subjected to a heat treatment in which brown coal was held at 330 ° C. (internal pressure: 12.8 MPa) for 1.0 hour using water as a medium liquid, and this heat treated coal was mixed with blended coal and dry-distilled. Manufactured. The coke strength DI of this coke is 8
It was 1.6%.

The coke of Test No. 3 of the invention example was prepared by using brown nacre at 400 ° C. (internal pressure: 1.3
Heat treatment was carried out for 0.5 hour in a), and the heat-treated coal was mixed with blended coal and carbonized to produce. The coke strength DI of this coke was 82.2%.

The coke of the test No. 4 of the invention example has an initial pressure in the autoclave of 0.2 MPa with nitrogen gas and a medium solution of methylnaphthalene oil at 360 ° C. (internal pressure: 1.2 MPa).
Was heat-treated for 0.5 hour, and this heat-treated charcoal was mixed with blended charcoal and carbonized to produce. The coke strength DI of this coke was 82.1%.

The coke shown in these invention examples can be used as blast furnace coke.

On the other hand, the coke of the test No. 5 of the comparative example was produced by mixing the brown coal shown in Table 1 with the blended coal as it was without treatment and carrying out dry distillation. The coke strength DI of this coke is 7
It was 3.4%.

Coke of Test No. 6 was produced by heat-treating the medium liquid as methylnaphthalene oil at 420 ° C. (internal pressure: 2.0 MPa) for 0.5 hour, mixing the heat-treated carbon with blended carbon, and dry-distilling. . The coke strength DI of this coke is 7
It was 3.3%. It is considered that this is because the heat treatment temperature was as high as 420 ° C. and the brown coal was excessively decomposed. To support this, we measured the volatile content of the heat-treated charcoal,
In the case of heat-treated coal in the case of test No. 3, the volatile content was 48.7%, which was almost the same as the value of raw coal (poor quality coal shown in Table 1).
In the heat-treated coal of Test No. 6, the volatile matter content was 42.1%, which was clearly lower than that of the raw coal (poor quality coal shown in Table 1). From this, in the case of Test No. 6, it was confirmed that the thermal decomposition reaction occurred by heat-treating the poor quality coal.

Coke of Test No. 7 was produced by heat-treating the medium liquid as methylnaphthalene oil at 360 ° C. (internal pressure: 0.8 MPa) for 0.5 hour, mixing the heat-treated coal with blended coal, and dry-distilling. . The coke strength DI of this coke is 7
It was 3.6%. This is probably because the treatment pressure was as low as 0.8 MPa and the reforming of inferior coal did not proceed.

Coke of Test No. 8 was produced by heat treating the medium liquid as anthracene oil at 400 ° C. for 0.5 hour, mixing the heat treated coal with the blended coal, and carbonizing. The coke strength DI of this coke was 73.8%. This is because the temperature when the vapor pressure of anthracene oil is 1MPa is as shown in Table 2.
This is because the internal pressure is as low as 0.5 MPa at 400 ° C because it is 445 ° C.

The coke of these comparative examples could not be used for a blast furnace. (Example 2) 10% by mass of a caking filler (petroleum-based pitch shown in Table 5) was further added to and mixed with the mixture of the heat-treated coal and the blended coal obtained in Test No. 1 of Example 1. , A dry distillation test was conducted. When the strength of the coke obtained here was measured, the DI was 85.0%, and coke having a higher strength than in the case of test No. 2 was obtained. It has been found that the mixing of such a caking filler with heat-treated coal and blended coal is very effective for coke strength.

[0047]

[Table 5]

[0048]

INDUSTRIAL APPLICABILITY In the method of the present invention, inferior coal such as brown coal is reformed by heat treatment in a liquid medium at a pressure of 1 to 20 MPa and a temperature of 400 ° C. or less. When this heat-treated coal is used as a part of blended coal, the consumption of mobile hydrogen is suppressed during the softening and melting process during dry distillation. As a result, coke having a cold rotary drum test strength DI of 80% or more can be obtained, and inferior coal such as brown coal can be used in the production of blast furnace coke. Further, according to the method of the present invention,
By mixing the heat-treated charcoal with a caking additive, the cold rotating drum test strength DI can be further increased.

[Brief description of drawings]

FIG. 1 (a) is a diagram showing a cross section of poor quality coal, (b) is a diagram showing a cross section of high quality coal, and (c) is a schematic diagram for explaining a thermal decomposition reaction of poor quality coal.

[Explanation of symbols]

1. Poor coal 2. High quality charcoal 3. Pores 4. tar 5. Oxygen functional group

Claims (4)

[Claims] 1. After inferior coal is heat-treated in a medium liquid having a pressure of 1 to 20 MPa and a temperature of 400 ° C. or less, the medium liquid and the heat-treated coal are separated, and the heat-treated coal is added to the blended coal to a coke oven. A method for producing blast furnace coke, which comprises charging and carbonizing. 2. The inferior coal is heat-treated in a medium liquid having a pressure of 1 to 20 MPa and a temperature of 400 ° C. or less, the medium liquid and the heat-treated coal are separated, and the mixture is mixed with the mixture of the heat-treated coal and blended coal. A method for producing coke for a blast furnace, which comprises adding a property-improving material and charging the coke oven to dry distillation. 3. The method for producing a blast furnace coke according to claim 1, wherein a medium liquid having a vapor pressure of more than 1 MPa and a temperature of 400 ° C. or less is used. 4. The method for producing blast furnace coke according to claim 1, wherein the medium liquid is water.