JPH09194846A - Method for thermal decomposition of coal - Google Patents

Abstract

PROBLEM TO BE SOLVED: To increase the light-oil content of coal tar and improve the yields of BTX. SOLUTION: In recovering by-products, such as coal tar and BTX, obtained by the thermal decomposition of coal, coal is subjected to a primary thermal decomposition at a temperature of below 600 deg.C, and the formed primary product is mixed with a gaseous or liquid hydrogen-donating organic compound under agitation, led to a zone at a temperature of 600 deg.C or above, and subjected to a secondary thermal decomposition. As a result, the increase in the light-oil content of coal tar and the improvement in the yields of BTX can be done while stable coke quality can be assured without any special pretreatment of coal.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for thermally decomposing coal, and more particularly to lightening coal tar and B.
The present invention relates to a method for thermally decomposing coal capable of improving the yield of TX.

[0002]

BACKGROUND ART Conventional coal pyrolysis technology has been developed mainly for the purpose of producing coke used in ironmaking blast furnaces, so that the yield of useful coal byproducts such as coal tar and BTX is low. I had a fault. For this reason, there has been a demand for a more economically superior pyrolysis technique for coal by improving the yield of by-products.

Japanese Patent Laid-Open No. 6-108056 (Prior Document 1) discloses that when pyrolyzing coal, an organic compound having a hetero atom such as pyridine or tetralin is pre-absorbed by the coal, and thereafter, at a temperature of 300 ° C. or higher. A technique for improving the yield of coal tar by thermally decomposing at temperature is disclosed.

[0004]

Although the method of the prior art document 1 improves the yield of useful coal tar, it requires a complicated pretreatment of absorbing the above-mentioned organic compound having a hetero atom into coal. Becomes Therefore, complicated pretreatment work, relatively expensive raw materials, equipment investment, etc. are required, resulting in an increase in manufacturing cost.

Further, according to this method, a large amount of an organic compound is added into the coal from the outside, so that the components and structure of the obtained solid content are different from those obtained when only coal is pyrolyzed. Therefore, when this method is applied to coke production, it is difficult to estimate the components and structure of the coke quality based on conventional coal carbonization data without pretreatment, and stable coke quality cannot be secured.

The present invention was proposed in order to solve the above-mentioned problems of the prior art, and when pyrolyzing coal, stable coke quality is obtained without special pretreatment of coal. It is an object of the present invention to provide a method for thermally decomposing coal that enables lightening of coal tar and improvement of the yield of BTX while ensuring the above.

[0007]

According to the present invention, when coal is pyrolyzed to recover by-products such as coal tar and BTX, the coal is subjected to primary pyrolysis in a temperature range of less than 600 ° C.
A gas or liquid organic compound having a hydrogen donating property is added to and mixed with the produced primary product, and the produced mixture is introduced into a temperature range of 600 ° C. or higher for secondary thermal decomposition. It is a method of pyrolyzing coal.

As a result of intensive studies to solve the above problems, the present inventors have focused on the thermal decomposition behavior of coal in the blast furnace coke manufacturing process.

The temperature of the furnace wall of the blast furnace coke oven is higher than the temperature of the center of the furnace, and the coal charged near the furnace wall is heated by the heat from the furnace wall (in other words, the temperature gradient in the coke layer is The coal is heated and pyrolyzed,
Carbonization progresses.

That is, in the vicinity of the central part of the furnace having a temperature range of less than 600 ° C., various fragments of a large amount of hydrocarbon gas such as carbon monoxide, hydrogen, methane and tar components (this is called a primary product). Are generated and released outside the coal particles (this is called primary pyrolysis).

These primary products are discharged near the higher temperature furnace wall (mainly the gap between the furnace wall and the coke layer) and the rising pipe (these regions have a temperature of 600 ° C. or higher). Then, it is further decomposed by heat to be reduced in molecular weight. (This is called secondary pyrolysis, and the product formed at this time is called the secondary product.)

However, in the coke manufacturing process for a blast furnace, primary products (various fragments) generated by pyrolysis of coal and secondary products produced by secondary pyrolysis are recombined and polymerized. As a result, tar and BTX yields are poor.

Therefore, the present inventors have further studied to prevent the recombination of secondary products. As a result, in the secondary thermal decomposition process, radicals are generated from the primary product,
Some of these radicals are polymerized between the radicals to be self-stabilized, but most of the radicals receive hydrogen from these organic compounds when an organic compound having a hydrogen donating property is added and mixed, so that a low molecular weight compound is obtained. It was found that the radicals do not re-polymerize and the heavier state is suppressed by the stable reaction, that is, by the presence of the organic compound having a hydrogen donating property.

In addition, some organic compounds having a hydrogen donating property may generate low molecular weight radicals such as hydrogen radicals when themselves are thermally decomposed. This low-molecular radical reacts with a primary product such as a tar component, decomposes the primary product, lowers the molecular weight (this is called lightening of the tar component), or generates a low-molecular organic compound such as BTX. It has been found that it is possible to contribute to the lightening of the tar component and the improvement of the yield of BTX, and these yields are improved.

Based on the above findings, in the present invention, coal 6
Primary thermal decomposition is performed in a temperature range of less than 00 ° C. At this time,
Organic compounds that have a hydrogen donating property in the form of gas or liquid to the primary products (gaseous or liquid organic compounds such as hydrocarbon gas and tar components) that are volatilized and released from coal after primary thermal decomposition. Both are rapidly and uniformly mixed to form a gaseous or liquid mixture.

Next, when this mixture is introduced into a temperature range of 600 ° C. or higher, thermal energy necessary for causing thermal decomposition is imparted and secondary thermal decomposition proceeds, but an organic compound having a hydrogen donating property. By the presence of, the recombination of the secondary product is prevented, and the low molecular weight radical generated when the organic compound having hydrogen donating property is thermally decomposed reacts with the primary product to lighten the tar component. , Low-molecular-weight organic compounds such as BTX are produced, so tar components are lightened and BT
It can contribute to the improvement of the yield of X, and these yields are improved.

When the primary thermal decomposition is carried out in the temperature range of 600 ° C. or higher, the generated primary product immediately undergoes the secondary thermal decomposition, and the secondary product is produced to promote the recombination. Therefore, even if an organic compound having a hydrogen donating property is added thereafter, the effect of the present invention is reduced.

Further, even if an organic compound having a hydrogen donating property in a temperature range of less than 600 ° C. is added to cause secondary thermal decomposition, recombination of the secondary product in the present invention cannot be sufficiently prevented. Therefore, it is not preferable.

[0019]

BEST MODE FOR CARRYING OUT THE INVENTION When the hydrogen-donating organic compound is in a liquid state, as a method of addition, it is added to the gaseous or liquid mixture fluid by means of, for example, spraying or jetting from a nozzle. . This allows a homogeneous and rapid mixture to be produced. Also,
It may be added continuously or at appropriate intervals,
It does not require complicated pretreatment of coal unlike the prior art.

Specific examples of the organic compound having a hydrogen donating property include hydrogenated tar obtained by adding hydrogen to coal tar, a lower alcohol having a molecular weight of 60 or less, tetrahydronaphthalene, or decahydronaphthalene. It is desirable to use a cyclic compound saturated with hydrogen, or a mixture of two or more thereof.

[0021]

EXAMPLES In order to confirm the effects of the present invention, a coal pyrolysis test was carried out using the coal pyrolysis apparatus shown in FIG.

Here, 1 is a primary pyrolysis furnace, 2 is a secondary pyrolysis furnace, 3 is a cooler, 4 is a coal tar recovery device, and 5 is BT.
X recovery device, 6 is a hydrogen donating organic compound supply tank. The test conditions are described below.

First, about 50 kg of coal weighing 2.5 kg is used.
Coal is loaded into the primary pyrolysis furnace 1 whose temperature is controlled to 0 ° C., the coal is primarily pyrolyzed, and the generated hydrocarbon gas and gas components such as tar components are guided to the secondary pyrolysis furnace 2. It was

When the coal is thermally pyrolyzed in the primary pyrolysis furnace 1, hydrogenated tar (hereinafter referred to as hydrogen donating organic compound) having a hydrogen donating property is fed from the hydrogen donating organic compound supply tank 6 to the secondary It was continuously sprayed and supplied into the thermal decomposition furnace 2. The amount of hydrogenated tar supplied at this time was 5w based on the weight of coal.
The ratio was t%.

In the secondary pyrolysis furnace 2, the gas component (primary product) generated from coal and the hydrogenated tar (hydrogen-donating organic compound) are mixed, and the mixed gas is 900 ° C. to 1000 ° C. It was heated in the temperature range of ° C and secondarily pyrolyzed.

The gas component (secondary product) generated by the thermal decomposition in the secondary pyrolysis furnace 2 is guided to the cooler 3, and water is added to the gas component (secondary product) in the cooler 3. Was sprayed to 90 ° C. to 100 ° C., and the tar content was recovered in the coal tar recovery device 4. By further cooling the gas component (secondary product) from which tar is removed, B
BTX was collected by the TX collector 5.

Table 1 shows tar and BT in this test.
The amount of X recovered is shown. However, the obtained recovery amount is obtained by previously measuring the weights of tar and BTX obtained when pyrolyzing the hydrogenated tar supplied under the same conditions except that coal is not charged in the experimental apparatus. Every other, and the value is subtracted. The recovered tar was separated into 6 boiling points by a distillation operation and weighed.

Similarly, Table 1 shows comparative examples in which coal was pyrolyzed without supplying hydrogenated tar. However, the other conditions were the same as the test conditions of the example.

[0029]

[Table 1]

From Table 1, the BTX recovery amount in the example was 23% higher than that of the comparative example, and the tar recovery amount was higher than that of the comparative example in the low boiling point range of 250 ° C. or lower, which has a high market value. A higher yield was obtained and the yield of light tar was improved.

[0031]

EFFECTS OF THE INVENTION According to the method of the present invention, coal tar can be lightened and BTX yield can be reduced at a low cost while ensuring stable coke quality by a simple method without special pretreatment of coal. Can be improved.

[Brief description of the drawings]

FIG. 1 is a view showing an embodiment of a coal pyrolysis apparatus for carrying out the method of the present invention.

[Explanation of symbols]

 1 Primary pyrolysis furnace 2 Secondary pyrolysis furnace 3 Cooler 4 Tar recovery device 5 BTX recovery device 6 Hydrogen donating organic compound supply tank

Claims (1)

[Claims] 1. Coal tar, B by thermal decomposition of coal
When recovering by-products such as TX, coal is subjected to primary thermal decomposition in a temperature range of less than 600 ° C., and a gaseous or liquid organic compound having a hydrogen donating property is added to and mixed with the resulting primary product. A method for thermally decomposing coal, which comprises introducing the produced mixture into a temperature range of 600 ° C. or higher for secondary thermal decomposition.