JPH06299164A - Method for pyrolyzing coal - Google Patents

Abstract

PURPOSE:To provide a method for pyrolyzing coal, capable of massively producing relatively useful pyrolysis products. CONSTITUTION:Coal powder is subjected to a supercritical extraction treatment at a temperature higher than the critical temperature of a hydrocarbon such as toluene, that is 300-450 deg.C under such a condition that the retention time of the hydrocarbon solvent is <=600sec in a reactor, thus pyrolyzing the coal and simultaneously extracting and recovering the pyrolyzed products. Useful chemical components such as the toluene can not only be extracted and recovered in high yields, but also liquid products and volatile products can be produced in large amounts. Even when a catalyst and a donor are not used, the coal can be converted in a high conversion rate. The coal pyrolyzing method is a technique for enhancing the usefulness of the coal as a chemical raw material.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a method for thermally decomposing coal, and more particularly to a method for thermally decomposing coal to obtain a useful compound or mixture.

[0002]

2. Description of the Related Art Supercritical fluids are characterized by higher diffusivity and lower viscosity than ordinary liquids, and their ability as a solvent can be easily changed by controlling temperature or pressure. You can Therefore, the method of extracting coal with a supercritical fluid is expected to be able to control coal decomposition or components produced thereby (Fuel, 1975, 54, 227, 1984, 6).
3, 1174, 1991, 70, 545 and J, Ch.
em, Eng, Japan, 1991, 24 (6), 7
15). It is known to perform supercritical extraction of pitch and coal to carry out decomposition, recovery and purification of useful components, and the like (JP-A-63-122787). Also, JP-A-63-2
Japanese Patent No. 58983 describes a method of supercritically extracting coal using a solvent such as toluene or quinoline.
This method mixes coal and solvent in a supercritical state,
It is a method of obtaining an ashless extract by holding for a certain period of time of about a minute, and is not intended to actively pyrolyze coal and recover useful components therefrom. The present invention focuses on adjusting the temperature and pressure so as to easily separate the residual coal or ash while recovering the extract, making the most of the characteristics of the supercritical liquid and more positively useful. It was designed with the intention of developing a method for recovering the components.

[0003]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a coal thermal decomposition method capable of obtaining a large amount of useful components.

[0004]

The present invention provides coal powder,
In the method of thermally decomposing coal by supercritical extraction using a hydrocarbon solvent at a temperature of 300 to 450 ° C., which is not lower than the critical temperature of the hydrocarbon solvent, in the reactor of the hydrocarbon solvent in the supercritical extraction zone. A method for thermally decomposing coal is characterized in that the residence time is 600 seconds or less.

As the coal which can be used in the present invention, those containing volatile components other than water can be used. Bituminous coal, lignite,
Peat and the like are preferred. The smaller the size of the coal powder, the larger the proportion of the liquid product as it becomes smaller. When using a supercritical liquid, the mass transfer rate is higher than in the case of a normal liquid solvent, so even if coal of the same particle size is used, the secondary reaction of the pyrolysis primary product in the coal particle is suppressed. However, the smaller the particle size is, the more the polymerization of the primary product in the coal particles is suppressed, so that the high coal conversion rate and the liquid yield can be obtained.

As the hydrocarbon solvent, a liquid at room temperature is 45
Although those having a critical temperature of 0 ° C. or lower can be used, aromatic hydrocarbons, aliphatic hydrocarbons and alicyclic hydrocarbons having good thermal stability are preferable, and specifically, benzene, toluene and xylene. And a mixture of one or more selected from cyclohexane. Further, when alicyclic hydrocarbons such as cyclohexane are used as a solvent, it is observed that a large amount of toluene is produced and dibenzyl is not produced compared to when aromatic hydrocarbons such as toluene are used. Also, the production amount of the intended useful component can be changed by selecting the kind of the solvent. If the critical temperature and critical pressure of these solvents are shown, for example, benzene is 289 ° C. and 4.9 MPa, toluene is 319 ° C. and 4.0 MPa, xylene is 343 ° C.
It is 3.6 MPa.

Since the supercritical extraction carried out in the present invention is carried out at a temperature of 300 to 450 ° C., which is higher than the thermal decomposition temperature of coal, thermal decomposition of coal occurs simultaneously with extraction. Therefore, the thermal decomposition referred to in the present invention includes extraction. The supercritical extraction is carried out under the conditions of the critical temperature of the solvent or higher and the critical pressure or higher, and the temperature needs to be in the range of 300 to 450 ° C.
If it is less than 300 ° C, thermal decomposition does not occur sufficiently, and if it exceeds 450 ° C, decomposition proceeds too much to reduce the production of useful components. The temperature is preferably 320 to 400 ° C. Further, although the pressure may be high, if the pressure is too high, the diffusion rate in the particles is reduced to promote secondary decomposition and polymerization in the coal particles, and not only the production of useful components is reduced, Since it is necessary to make the equipment expensive, the critical pressure ~ 40MP
It is better to stop at about a.

In the present invention, the residence time of the hydrocarbon solvent in the supercritical extraction zone is 600 seconds or less, preferably 60 seconds or less. If the residence time is too long, the useful components extracted from the coal will be decomposed too much. Thus, the shorter the time, the less stable, but the higher the yield of useful ingredients.

The supercritical extraction can be carried out by any method as long as the above conditions are satisfied, but preferably, a pressure vessel for carrying out the extraction is filled with coal powder, and a hydrocarbon solvent is continuously flowed therein. Is preferred. The residence time t of the hydrocarbon solvent in this case is represented by t = XΦ / F, where XΦ is the void in the pressure vessel and F is the flow rate of the hydrocarbon solvent. In addition, it is preferable to shorten the time until the temperature is reduced after the pressure is reduced after leaving the extraction zone composed of the pressure vessel. Further, although the thermal decomposition of coal is usually completed within 30 minutes depending on the temperature, the time for flowing the hydrocarbon solvent is about 30 minutes, but it may be longer than this.

In this supercritical extraction, coal is pyrolyzed and extracted, liquid products and volatile products flow out together with the solvent,
When the pressure is reduced and the temperature is lowered, the volatile product is separated as a gas, and the liquid product is taken out as a liquid. Also, the solid product is recovered separately. The solvent is recovered with the volatile or liquid product, which can be separated by distillation or the like. The recovered solvent can be reused. The useful component in the present invention is a relative one, a compound such as toluene useful as a chemical raw material, a liquid product useful as a fuel or various raw materials, and these are coal itself or a solid product. It is more valuable than things.

[0011]

The present invention will be specifically described below. In the examples, the experiment was conducted as follows. A stainless steel tube having an inner diameter of 8 mm and a length of 60 mm was used as a pressure vessel, and about 8 g of dried coal powder was filled in the stainless steel tube. Glass wool was set above and below the coal powder layer to prevent the coal powder from flowing out. The solvent was pressurized with a pump, heated with a preheater, and charged into the supercritical extraction zone in the pressure vessel. The pressure vessel is heated from the outside and heated at 10 K / min. The temperature rises at a rate of
After reaching the predetermined reaction temperature, the temperature was maintained for 2 hours. The fluid was continuously withdrawn from the supercritical extraction zone, the temperature was lowered by a cooler, and then the pressure was reduced to normal pressure. The gas generated at this time was recovered as a volatile product, but the amount was negligibly small. The liquid product was recovered with the solvent.
The solvent used was separated from the extract by distillation, and the extract was vacuum dried to separate the volatile product and the liquid product. Also, the solid product was recovered from the pressure vessel after completion. The gas and liquid were analyzed using GC-MS and GC-FID.

The coal used was subbituminous coal (Pacific Ocean), and the value of industrial analysis (wt% db: dry base) was used.
Is ash 14.2, volatile 45.0, fixed carbon 40.8
Then, the value of the elemental analysis (wt% daf: dry ash
free basis) is carbon 77.5, hydrogen 6.4,
Nitrogen 1.2, sulfur 0.3, oxygen (diff.) 1
At 4.6, the H / C is 0.99. The size of the powder was between 0.076 and 4 mm.

Coal consumption Ws [g-daf], solid product recovery amount Wr [g-daf], liquid product recovery amount
When Wq [g-daf] is set, the coal conversion rate x, the liquid product yield Yq, and the volatile product yield Yv can be calculated by the following equations. x = (Ws-Wr) / Ws * 100 Yq = Wq / Ws * 100 Yv = x-Yq

Example 1 Using toluene as a solvent, 653 K, 20 MPa,
Coal powder average particle size 0.8 mm, solvent flow rate 0.05-
Under the condition of 70 cc / min, the relationship between the residence time t in the solvent extraction zone and the production ratio of the liquid product, the volatile product, and the solid product when the coal was pyrolyzed by supercritical extraction is shown. As shown in FIG. From FIG. 1, it can be seen that the shorter the residence time, the larger the amount of liquid products produced. It is considered that this is because the unstable liquid product decomposes when the residence time becomes long. Further, it can be seen from FIG. 1 that about 20 wt% daf is a stable liquid product.

Example 2 A coal powder was prepared by pyrolyzing coal under the same conditions as in Example 1 except that the flow rate of the solvent was fixed at 10 cc / min and the particle size of the coal powder was changed. FIG. 2 shows the relationship between the particle size and the production ratio of liquid products, volatile products, and solid products. It can be seen from FIG. 2 that the smaller the particle size of the coal powder, the larger the amount of liquid products produced.

Example 3 The solvent flow rate was 0.1 cc / min, and the coal powder particle size was 1
Other than 6 to 24 mesh (1.0 to 0.7 mm),
When the same experiment as in Example 1 was performed, the results were: coal conversion 45.3 wt% daf, liquid product yield 30.9 w.
t% daf and volatile product yield were 14.4 wt% daf. When analyzed for a gas content of 138 cc in the volatile product, hydrogen was 92.86 cc, methane was 20.94.
cc, carbon dioxide 22.52cc, ethane 1.28c
c and propane were 0.40 cc. This is 0.
It hits 070 g. In addition, when the liquid content was analyzed, it was 0.761 g of a component other than toluene as a solvent and having a peak at a position close to toluene, and 0.176 g of a heavier component. This corresponds to a mass balance of 90.5%. Referring to the results of Example 4, it is suggested that this remaining about 10% is toluene.

Example 4 Cyclohexane was used as the solvent, and the flow rate of the solvent was 15
An experiment similar to that of Example 1 was carried out, except that the particle size of the cc / min was 60 to 100 mesh (0.25 to 0.15 mm) and the coal conversion rate was 46.9.
wt% daf, liquid product yield 24.6 wt% daf,
The volatile product yield was 22.3 wt% daf. When the liquid content in the volatile product was analyzed, 0.323 g of toluene, 0.197 g of a component having a GC peak position slightly lighter than toluene, and 0.552 g of a heavier component
Met. The gas content was extremely small. This is 1
It corresponds to a mass balance of 00%.

Example 5 The solvent flow rate was 15 cc / min, and the coal powder particle size was 0.
An experiment similar to that of Example 4 was conducted except that the thickness was set to 2 mm, and the liquid content in the volatile product was analyzed and found to be 40 wt%.
Is toluene, 25 wt% is gas such as CO and methane, 3
5 wt% was a slightly lighter component than toluene.

Example 6 Toluene was used as a solvent and the flow rate of the solvent was 2.5 cc.
/ Min, the same experiment as in Example 1 was performed except that the particle size of the coal powder was 16 to 24 mesh.

Example 7 The same experiment as in Example 6 was carried out except that a toluene-tetralin (1: 1) mixed solvent was used as the solvent. By using tetralin, which is a hydrogen donating solvent, as a solvent,
The thermal decomposition primary product radicals were stabilized by hydrogenation, recombination to coal or polymerization char was suppressed, and high coal conversion and liquid yield were obtained.

Example 8 Toluene was used as a solvent, and the flow rate of the solvent was 60 cc /
The same experiment as in Example 6 was performed except that min and the particle size of the coal powder were 60 to 100 mesh. By reducing the particle size, the primary product is extracted before the polymerization char within the particles occurs, so that a high conversion and a liquid yield were obtained without using expensive tetralin.

The results of Examples 6 to 8 are shown in FIG. From FIG. 3, it can be seen that the higher the flow velocity (retention time is shorter) and the smaller the particle size is, the more the liquid product is generated, and the use of the supercritical fluid having a high mass transfer rate is similar to the case of using the hydrogen donating solvent. It can be seen that the coal conversion rate and liquid yield of the same degree can be obtained.

From each figure, it can be inferred that the products can be roughly classified as follows. a Unstable liquid product that easily changes to volatiles About 10 wt% daf b Stable liquid product about 20 wt% daf c Volatile directly generated from coal about 10 wt% daf d Polymerizable liquid product about 15 wt% daf e Solid product about 45 wt% daf

When the volatile components directly generated from coal were analyzed, it was found that the gas component was composed mainly of carbon monoxide, carbon dioxide and methane, and the liquid component was composed mainly of ethylbenzene, para-xylene, meta-xylene and toluene. found. Especially, for toluene, several wt per unit weight of coal
The yield is as high as%.

When the stable liquid product was analyzed by GC-MS, it was found that the acetone-soluble matter mainly contained 1-2 ring aromatic hydrocarbons and aliphatic hydrocarbons. The stable liquid product produced almost the same amount even when the reaction temperature was changed to 340 ° C., 360 ° C., and 380 ° C. Therefore, it is considered that this stable liquid product is a component produced at 340 ° C. or lower. To be

GC-MS for polymerizable liquid products
And GC-FID analysis revealed that a significant amount of the acetone solubles was dibenzyl.
The production amount of dibenzyl was 380 ° C. and 20 MPa.
Then, under the following conditions, it was as follows. Fineness (mesh) Flow rate (cc / min) Amount of production (wt% daf) 16-24 0.1 0.38 16-24 4.2 0.40 60-100 0.14 3.60

The formation of an unstable liquid product which was liable to change to a volatile component decreased at lower temperatures, and this was due to the large amount of components insoluble in acetone.

[0028]

EFFECTS OF THE INVENTION According to the pyrolysis method of coal of the present invention, useful chemical components such as toluene and dibenzyl can be obtained in a high yield, and the production amount of liquid products and volatile products can also be increased. Many. It is also possible to obtain a high coal conversion rate without using a catalyst or a donor. It can be said that this is one technique that enhances the usefulness of coal as a chemical raw material.

[Brief description of drawings]

FIG. 1 is a graph showing the relationship between the residence time of a solvent and the production amount of each product.

FIG. 2 is a graph showing the relationship between the particle size of coal powder and the amount of each product produced.

FIG. 3 is a graph showing the production amount of each product of Examples 6 to 8.

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[Procedure amendment]

[Submission date] June 30, 1993

[Procedure Amendment 1]

[Document name to be amended] Statement

[Correction target item name] 0006

[Correction method] Change

[Correction content]

As the hydrocarbon solvent, a liquid at room temperature is 4
Those having a critical temperature of 50 ° C. or lower can be used, but aromatic hydrocarbons, aliphatic hydrocarbons having good thermal stability,
Alicyclic hydrocarbons are preferable, and specific examples thereof include one kind or a mixture of two or more kinds selected from benzene, toluene, xylene and cyclohexane. At the same temperature and pressure
Even if the solvent is changed, the mass transfer rate and the dissolving power will be different.
Then, the route of the secondary reaction in the coal particles is changed, and as a result , the production amount of the intended useful component can be changed by selecting the kind of the solvent. If the critical temperature and critical pressure of these solvents are shown, for example, benzene is 28
9 ℃, 4.9 MPa, toluene is 319 ℃, 4.0MP
a and xylene are 343 ° C. and 3.6 MPa.

[Procedure Amendment 2]

[Document name to be amended] Statement

[Correction target item name] 0007

[Correction method] Change

[Correction content]

The supercritical extraction according to the present invention is performed at a temperature of 300 to 450 ° C., which is higher than the thermal decomposition temperature of coal, so that thermal decomposition of coal occurs simultaneously with extraction. Therefore, the extraction referred to in the present invention includes thermal decomposition . The supercritical extraction is carried out under the conditions of the critical temperature of the solvent or higher and the critical pressure or higher, and the temperature needs to be in the range of 300 to 450 ° C.
If it is less than 300 ° C, thermal decomposition does not occur sufficiently, and if it exceeds 450 ° C, decomposition proceeds too much to reduce the production of useful components. The temperature is preferably 320 to 400 ° C. Further, although the pressure may be high, if the pressure is too high, the diffusion rate in the particles is reduced to promote secondary decomposition and polymerization in the coal particles, and not only the production of useful components is reduced, Since it is necessary to make the equipment expensive, the critical pressure ~ 40MP
It is better to stop at about a.

[Procedure 3]

[Document name to be amended] Statement

[Correction target item name] 0014

[Correction method] Change

[Correction content]

Example 1 Using toluene as a solvent, 653 K, 20 MPa,
Coal powder average particle size 0.8 mm, solvent flow rate 0.05-
Under the condition of 70 cc / min, the relationship between the residence time t in the solvent extraction zone and the production ratio of the liquid product, the volatile product, and the solid product when the coal was pyrolyzed by supercritical extraction is shown. As shown in FIG. From FIG. 1, it can be seen that the shorter the residence time, the larger the amount of liquid products produced. It is considered that this is because the unstable liquid product decomposes when the residence time becomes long. Also, exposed from high temperature for a long time from Figure 1.
However, it can be seen that about 20 wt% daf recovered as a liquid product is a stable liquid product.

[Procedure amendment 4]

[Document name to be amended] Statement

[Correction target item name] 0017

[Correction method] Change

[Correction content]

Example 4 Cyclohexane was used as the solvent, and the flow rate of the solvent was 15
An experiment similar to that of Example 1 was carried out, except that the particle size of the cc / min was 60 to 100 mesh (0.25 to 0.15 mm) and the coal conversion rate was 46.9.
wt% daf, liquid product yield 24.6 wt% daf,
The volatile product yield was 22.3 wt% daf. Analysis for the liquid content of the volatile product, in toluene
0.323 g of the closest component, 0.197 g of which the GC peak position is a little lighter than toluene, and the heavier component of 0.
It was 552 g. The gas content was extremely small. This corresponds to a mass balance of about 100%.

[Procedure Amendment 5]

[Document name to be amended] Statement

[Correction target item name] 0018

[Correction method] Change

[Correction content]

Example 5 The solvent flow rate was 15 cc / min, and the coal powder particle size was 0.
An experiment similar to that in Example 4 was conducted except that the thickness was set to 2 mm, and the liquid content in the volatile product was analyzed and found to be 70 wt%.
Was toluene and components lighter than toluene, and 25 wt% was gas components such as CO and methane.

[Procedure correction 6]

[Document name to be amended] Statement

[Name of item to be corrected] 0024

[Correction method] Change

[Correction content]

When the volatile matter generated directly from coal was analyzed, it was found that the gas content was composed mainly of carbon monoxide, carbon dioxide, and methane, and the liquid content was composed mainly of ethylbenzene, paraxylene, metaxylene, and toluene. found. In particular, the yield of toluene and components having a structure close to it is as high as several wt% based on the weight of coal.

[Procedure Amendment 7]

[Document name to be amended] Statement

[Correction target item name] 0026

[Correction method] Delete

[Procedure Amendment 8]

[Document name to be amended] Statement

[Correction target item name] 0028

[Correction method] Change

[Correction content]

[0028]

According to the coal thermal decomposition method of the present invention ,
In addition to being able to obtain useful chemical components such as ruene in high yield, it also produces a large amount of liquid products and volatile products. It is also possible to obtain a high coal conversion rate without using a catalyst or a donor. It can be said that this is one technique that enhances the usefulness of coal as a chemical raw material.

[Procedure Amendment 9]

[Document name to be corrected] Drawing

[Name of item to be corrected] Figure 1

[Correction method] Change

[Correction content]

[Figure 1]

[Procedure Amendment 10]

[Document name to be corrected] Drawing

[Name of item to be corrected] Figure 3

[Correction method] Change

[Correction content]

[Figure 3]

Claims (5)

[Claims] 1. A method of thermally decomposing coal by supercritically extracting coal powder with a hydrocarbon solvent at a temperature of 300 to 450 ° C. above the critical temperature of the hydrocarbon solvent, in the supercritical extraction zone. The method for thermally decomposing coal, wherein the residence time of the hydrocarbon solvent in the reactor is 600 seconds or less. 2. The residence time of the hydrocarbon solvent in the reactor is 6
The method for thermally decomposing coal according to claim 1, which is set to 0 seconds or less. 3. The method for thermally decomposing coal according to claim 1, wherein the average particle diameter of the coal powder is 1 mm or less. 4. The method for thermally decomposing coal according to claim 1, wherein the hydrocarbon solvent is benzene, toluene, xylene or cyclohexane. 5. The thermal decomposition method for coal according to claim 1, wherein the supercritical extraction is carried out while continuously flowing a hydrocarbon solvent.