JPH10324877A - Coal liquefaction method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To decrease the amt. of a solvent penetrating into feed coal in a slurried mixture in comparison with a conventional coal liquefaction method, to thereby enable the coal concn. in the mixture to be increased without causing troubles with liq. transport, and thus to increase the liquefaction yield, the amt. of coal treated per unit time and unit vol., and the vol. efficiency of an apparatus. SOLUTION: A mixed solvent having an oxygen content of 1.5 mass % or lower and comprising a light oil obtd. from a gas-liq. separator (3), etc., and a heavy oil obtd. by hydrogenating a coal liquefaction oil with a gas-phase hydrogenation apparatus (7), etc., is mixed with feed coal in a coal slurry preparation vessel (1). The resultant slurried mixture is sent to a hydrogenation reactor (4) to be hydrogenated or is sent to the gas-liq. separator (3) to be freed from a light oil to increase the slurry concn. and then sent to the hydrogenation reactor (4) to be hydrogenated.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for liquefying coal, and more particularly, to a raw material adjusting step of mixing a raw coal with a solvent to obtain a slurry-like mixture, and adding hydrogen to the mixture to form a coal. And a hydrogenation treatment step of hydrogenating coal.

[0002]

2. Description of the Related Art In the wake of the two oil crises, there has been a strong demand for technological development on alternative fuels to oil. In particular, since coal has abundant reserves, it is an important issue to establish a technology for efficiently liquefying coal to obtain fuel oil.

[0003] For this reason, various coal liquefaction methods have been conventionally proposed. As a typical coal liquefaction method, a raw material adjustment step of mixing a solvent and a catalyst with pulverized raw coal to obtain a slurry-like mixture, and adding hydrogen gas to the mixture under high temperature and high pressure to form a coal A hydrogenation step of hydrogenating
An oil separation step of separating an oil component from the hydrogenated product obtained in the hydrogenation step. Here, in the oil separation step, generally, a hydrogenated product is fed to a gas-liquid separator, and unnecessary gases such as CO and CO ₂ are removed by decompression operation in the gas-liquid separator. A gas-liquid separation step obtained by separating a gas-phase fraction and a liquid-phase fraction is employed. Then, the obtained liquid phase fraction is adjusted in the boiling range by a distillation step or the like, recovered as a product oil, a part of which is circulated and supplied to the raw material adjustment step, and mixed with the raw coal (a so-called circulating solvent). Used as

[0004] In such a coal liquefaction process, it is economically advantageous that the coal concentration in the slurry mixture is high. However, when the coal concentration is high, the viscosity of the slurry mixture becomes high, which makes handling difficult. Become. Therefore, the coal concentration in the slurry mixture is set to a concentration that does not hinder the handling of the mixture. In the case of the conventional coal liquefaction method, this coal concentration is low, and particularly in the case of lignite, since the pore structure is developed, a part of the solvent is absorbed in the pores of the lignite, and the viscosity of the slurry-like mixture is increased. Therefore, the concentration of coal in the slurry-like mixture is often limited to a low concentration of about 28 to 35% by mass, and it was necessary to set the concentration to such a low concentration. Therefore, in the case of the conventional coal liquefaction method, the amount of coal that can be treated with respect to the reactor volume was small, the volumetric efficiency of the apparatus was low, the contact efficiency between coal and the catalyst was low, and the liquefied oil yield was low.

That is, it is important to increase the coal concentration in a slurry mixture (hereinafter, slurry) containing a solvent and coal to be adjusted in the raw material adjustment step from the viewpoint of improving transport efficiency and volumetric efficiency. In addition, increasing the coal concentration in the slurry can be expected to improve the liquefaction reactivity in order to increase the contact efficiency between the catalyst and the coal. By the way, as a solvent for obtaining a slurry, a solvent (circulating solvent) whose boiling point is adjusted by distilling an oil component (coal liquefied oil) obtained by separating from a hydrogenated product is generally used. is there. However, a part of this solvent is absorbed in the pores of the raw coal, and the viscosity of the slurry becomes high. In particular, when lignite is used as the raw coal, the pore structure is developed inside the lignite. Is absorbed in the pores, and the viscosity of the slurry tends to be higher than when other types of coal are used.

Here, considering the discharge performance of a slurry feed pump from a raw material adjustment tank to a preheater and a reactor in an industrial scale plant of a coal liquefaction process, the viscosity of slurry that can be sent is approximately 100 ° C. at a temperature of 100 ° C. 500mPa
・ S or less. As a raw material coal, Australian lignite is used whose coal has been adjusted to a water content of 15% by mass or less and a particle size of 60 mesh or less.
When the slurry is adjusted using a fraction of ~ 420 ° C, the coal concentration in the slurry is as low as 28 to 35% by mass (solvent mass: based on the mass of coal supplied in terms of anhydrous ashless raw coal). It is confirmed that the viscosity of the slurry cannot be reduced below the limit of the slurry that can be sent. With the coal concentration in such a slurry, not only is the efficiency of contact between the coal and the catalyst during coal liquefaction lowered and the reactivity is low, but also because the amount of coal processed per unit time is small, the feed volume of the feed pump and hydrogenation The internal volume of the reactor becomes large and inefficient.

[0007]

DISCLOSURE OF THE INVENTION The present invention has been made in view of such circumstances, and has as its object the purpose of comparing the raw material in the slurry-like mixture with the conventional coal liquefaction method. The amount of solvent impregnated into the coal is reduced,
The amount of the solvent required to secure the viscosity within the limit viscosity of the slurry mixture that can be sent can be reduced, and the coal concentration in the slurry mixture can be increased without causing a problem in sending the slurry. As a result, the contact efficiency between the coal and the catalyst is improved, and the liquefied oil yield can be further improved, and the amount of coal treated per unit time per unit volume in hydrogenation increases,
Further, it is an object of the present invention to provide a coal liquefaction method capable of processing a large amount of coal with respect to the reactor volume and increasing the volumetric efficiency of the apparatus.

[0008]

Means for Solving the Problems To achieve the above object, a coal liquefaction method according to the present invention is a coal liquefaction method according to claims 1 to 8, which has the following configuration. Things. That is, the method for liquefying coal according to claim 1 includes a raw material adjustment step of mixing a raw material coal with a solvent to obtain a slurry mixture, and a hydrogenation step of adding hydrogen to the mixture to hydrogenate the coal. In the method for liquefying coal, the light oil and the heavy oil obtained by hydrogenating a coal liquefied oil obtained from coal are used as the solvent, and the oxygen content is 1.5 mass % Of a coal solvent is used (first invention).

According to a second aspect of the present invention, in the method for liquefying coal, the slurry mixture obtained in the raw material adjustment step is preheated, and light oil in the mixed solvent in the mixture is separated by a gas-liquid separation operation. The coal liquefaction method according to claim 1, wherein the mixture is fed to the hydrogenation step after increasing the slurry concentration of the mixture (second invention).

According to a third aspect of the present invention, in the method of liquefying coal, the mass of the solvent in the slurry mixture fed to the hydrogenation step is 0.3 to 1.0 of the mass of coal in terms of anhydrous ashless content of the raw coal.
The method for liquefying coal according to claim 2, wherein the method is doubled (third invention). The coal liquefaction method according to claim 4, wherein the amount of light oil in the mixed solvent of light oil and heavy oil used in the raw material adjustment step is 30 to 70% by mass. Method (fourth invention). The coal liquefaction method according to claim 5, wherein the mass of the solvent mixed with the raw coal in the raw material adjustment step is 1.0 mass of the anhydrous ashless coal mass of the raw coal.
The method for liquefying coal according to claim 1, wherein the ratio is 1.5 to 1.5 times (fifth invention). The coal liquefaction method according to claim 6, wherein the raw coal is lignite.
A coal liquefaction method according to 4 or 5 (Sixth invention). The method of liquefying coal according to claim 7, wherein the light oil is a light oil having a continuous boiling point distribution of 300 ° C or less, and the heavy oil has a continuous boiling point distribution of 300 to 420 ° C. The coal liquefaction method according to claim 1, 2, 3, 4, 5, or 6, which is an oil (seventh invention).

The method for liquefying coal according to claim 8, wherein the oxygen content of the oxygen-containing compound having oxygen as a hydroxyl group is based on the oxygen content of the oxygen-containing compound contained in the mixed solvent having an oxygen content of 1.5% by mass or less. The coal liquefaction method according to claim 1, wherein the proportion of the amount is 60% by mass or less (eighth invention).

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention relates to a method for liquefying coal, and is carried out, for example, as follows. A heavy oil obtained by hydrotreating a coal liquefied oil obtained from coal and a light oil obtained by distilling the coal liquefied oil are mixed so as to have an oxygen content of 1.5% by mass or less. To form a mixed solvent. The thus obtained mixed solvent and the catalyst for coal liquefaction are mixed with pulverized raw coal (raw lignite, etc.),
A slurry-like mixture is obtained. Next, hydrogen gas is added to the slurry-like mixture under high temperature and high pressure to hydrogenate the coal. Here, the hydrogenation treatment of coal liquefied oil is a treatment of reacting coal liquefied oil with hydrogen, and a hydrotreated oil (solvent) is obtained by this treatment. Heavy oil obtained by separating from this hydrotreated oil is heavy oil obtained by hydrotreating coal liquefied oil.

[0013] The heavy oil obtained by hydrotreating the above coal liquefied oil has a reduced oxygen-containing compound having a hydroxyl group, a carbonyl group, an ether group, etc., that is, an oxygen-containing compound, due to the hydrogenation treatment. I have. Therefore, when the heavy oil and the light oil are mixed to form a mixed solvent, and this is mixed with the raw coal to form a slurry mixture, a hydroxyl group, a carbonyl group, an ether group, and the like in the oxygen-containing compound of the solvent. The interaction between the oxygen-containing functional groups and the oxygen-containing functional groups such as the hydroxyl group, carbonyl group, and ether group of the constituent molecules of the coal is weak, and the amount of the solvent impregnated into the coal is reduced.

As can be seen from the embodiment of the present invention, according to the coal liquefaction method of the present invention, as compared with the conventional coal liquefaction method, the solvent for the raw coal in the slurry mixture is not used. Impregnation amount becomes small. That is, in the coal liquefaction method according to the present invention, unlike the conventional coal liquefaction method, a solvent (solvent for slurry preparation) in a raw material adjustment step of mixing a raw material coal with a solvent to obtain a slurry-like mixture.
As a mixed solvent, a light oil and a heavy oil obtained by hydrotreating a coal liquefied oil are mixed so that the oxygen content becomes 1.5% by mass or less. As compared with the case of the coal liquefaction method, the interaction between the solvent (solvent for slurry preparation) and the coal is reduced, and the amount of the solvent impregnated in the raw coal in the slurry-like mixture is reduced. Therefore, the amount of the solvent necessary for ensuring the viscosity within the limit viscosity of the slurry-like mixture that can be sent can be reduced, and the coal concentration in the slurry-like mixture can be increased without causing trouble in the solution sending. Will be able to do it. As a result, the transport efficiency is improved, the contact efficiency between the coal and the catalyst is improved, and the liquefied oil yield can be further improved. Further, the amount of coal processed per unit time and unit volume by hydrogenation is reduced. As a result, the amount of coal that can be processed with respect to the reactor volume can be increased, and the volumetric efficiency of the apparatus can be increased (first invention).

Further, in the raw material adjusting step, the slurry mixture obtained by using the mixed solvent as a slurry preparing solvent is preheated, and light oil in the mixed solvent in the mixture is separated by a gas-liquid separation operation. Thereby, the slurry concentration of the mixture can be further increased, and the slurry mixture having such a high slurry concentration can be fed to the hydrogenation step to be hydrogenated. As a result, the liquefied oil yield, It is possible to further improve the amount of coal processed per unit time per unit volume and the volumetric efficiency of the apparatus (second invention).

The details will be described below.

The present inventors have conducted intensive studies on the influence of the properties of the raw coal and the solvent on the viscosity of the slurry (slurry mixture). As a result, particularly when lignite is used as a raw coal, since lignite is a coal type having a low degree of carbonization, many hydroxyl groups, carbonyl groups, and oxygen-containing functional groups such as ether groups are present in the constituent molecules of the lignite. When the brown coal is mixed with a circulating solvent (solvent obtained by distilling coal liquefied oil and adjusting the boiling point range) used in the above-described conventional technology as a solvent to form a slurry, the oxygen-containing compound present in the solvent is contained in the brown coal. A hydroxyl group, a carbonyl group, an oxygen-containing functional group such as an ether group,
It has been found that the interaction with the oxygen-containing functional group in the brown coal is caused by a hydrogen bond or the like, so that the impregnation of the solvent into the brown coal is promoted and the viscosity of the slurry increases accordingly.

In particular, as a solvent to be mixed with the lignite, the coal liquefied oil obtained from the lignite as a raw material is distilled to obtain a boiling point range:
When using a solvent adjusted to a fraction of 180 ° C to 420 ° C,
The oxygen content in the solvent is 3% by mass or more, and these oxygens are mainly present in the solvent in the form of aromatic oxygen-containing compounds such as phenol, benzofuran and cresol. Therefore, the impregnation of the interior of the brown coal with the solvent is further promoted, and the viscosity of the slurry further increases. The high oxygen content of the solvent is due to the low carbonization of lignite, which is originally higher than sub-bituminous coal and bituminous coal, which has a high carbonization of 20% by mass or more. This is because a large amount of oxygen-containing compounds are contained in the coal liquefied oil to be obtained.

Therefore, the present inventors use the solvent as a solvent in order to reduce the interaction between the coal and the solvent in the slurry, reduce the amount of the solvent impregnated in the coal, and alleviate the increase in the viscosity of the slurry. An attempt was made to reduce the oxygen content in coal liquefied oil. As a method of reducing the oxygen content, the coal liquefied oil (solvent) is further hydrogenated, whereby the oxygen-containing compound in the solvent is decomposed and hydrogenated, and the oxygen atoms in the oxygen-containing compound are converted into water or CO, There is a method of removing in the form of CO ₂ . As a typical method of hydrotreating such coal liquefied oil, for example, a Ni-Mo based catalyst or a Co
Using a flow-type fixed-bed high-pressure reactor filled with -Mo catalyst, temperature: 300 to 400 ° C, hydrogen pressure: 10 to 20 MPa, LHSV
(Liquid space velocity): There is a method of treating a coal liquefied oil under the condition of 0.5 to 1.5 hr ^-1 to obtain a hydrotreated oil.

[0020] Coal liquefied oil obtained from brown coal is subjected to hydrotreating by the above-mentioned hydrotreating method, and the resulting liquid (hydrotreated oil) is distilled from 180 ° C to 420 ° C.
The product content was adjusted to obtain a product liquid, and the oxygen content in the product liquid was 0.5 to 1.5% by mass, depending on the hydrotreating conditions.

When a slurry was prepared by mixing a product liquid having an oxygen content of 1.2% by mass with Australian brown coal as a solvent, the coal concentration in the slurry was adjusted to 40% by mass (solvent mass:
100 when converted to 1.5 times the mass of coal in terms of anhydrous ashless content)
Slurry viscosity at about 200 ° C .: about 210 mPa · s.
When the coal concentration in the slurry was adjusted to correspond to the slurry viscosity at the liquid sending limit of 0 mPa · s, the coal concentration in the slurry was 48% by mass (solvent mass: 1.08 times the coal mass in terms of anhydrous ashless content). Thus, the coal concentration could be increased as compared with the case where coal liquefied oil was directly used as a solvent for slurry preparation (first invention).

The reason why the viscosity of the slurry is low even when the concentration of coal in the slurry is high is that the oxygen content in the coal liquefied oil (solvent) is reduced by hydrogenation treatment to reduce the oxygen-containing compound in the solvent. Therefore, the interaction between oxygen-containing functional groups such as hydroxyl group, carbonyl group, and ether group in the oxygen-containing compound of the solvent and oxygen-containing functional groups such as hydroxyl group, carbonyl group, and ether group of the constituent molecules of the lignite coal. It is considered that the action was reduced and the amount of the solvent impregnated inside the lignite was reduced.

When the hydrogenation conditions of the above coal liquefied oil (solvent) are relaxed to make the oxygen content in the solvent after the hydrogenation treatment more than 1.5% by mass and the slurry is prepared using the solvent, The coal concentration in the solution is 40% by mass or less
1.5 times the mass of coal in terms of anhydrous ashless content)
The slurry viscosity does not fall below the liquid sending limit. Even when a hydrogenation solvent having an oxygen content of 1.5% by mass or less is used, if the coal concentration in the slurry is 50% by mass or more (solvent mass: 1.0 times or less the mass of coal in terms of anhydrous ashless content), the above-mentioned feeding is performed. It is not preferable that the slurry viscosity is higher than the liquid limit. Therefore, when using a hydrogenation solvent having an oxygen content of 1.5% by mass or less, the coal concentration in the slurry in the raw material adjustment step is 50% by mass or less (solvent mass: at least 1.0 times the mass of coal in terms of anhydrous ashless content). Is desirable. At this time,
The coal concentration in this slurry is 40% by mass or more (solvent mass:
In this case, the concentration of coal in the slurry: 28 to 35 mass% (mass of solvent: the mass of coal in terms of anhydrous ashless raw coal)
(1.8 to 2.5 times), the coal concentration is much higher than in the prior art. From this point, it is desirable that the coal concentration in the slurry in the raw material adjustment step be 40 to 50% by mass (solvent mass: 1.0 to 1.5 times the mass of coal in terms of anhydrous ashless content) (fifth invention).

On the other hand, from the viewpoint of the coal liquefaction reaction, it is better to use heavy oil having a boiling point range of 300 to 420 ° C. as a solvent used in the liquefaction reaction, and to use a solvent having a boiling point range of 180 to 420 ° C. It has already been clarified that the obtained coal liquefied oil is rich in light fractions. Therefore, as a solvent used for preparing a slurry with coal in the raw material adjustment step, it is desirable to use heavy oil as a hydrotreating solvent. Then, the hydrotreating solvent is distilled to separate a fraction having a boiling point range of 300 to 420 ° C. to obtain a heavy oil of a hydrotreating solvent having an oxygen content of 1.7% by mass. When a slurry was prepared in the same manner using
Mass% (solvent mass: 1.5% of coal mass in terms of anhydrous ashless content)
), Slurry viscosity at 100 ° C: about 610m
When the coal concentration in the slurry was adjusted so as to correspond to the slurry viscosity at the liquid sending limit of 500 mPa · s, the coal concentration in the slurry was 35% by mass (solvent mass:
(1.8 times the mass of coal in terms of anhydrous ashless content), indicating that the coal concentration is lower than when a hydrotreating solvent having a boiling range of 180 to 420 ° C is used. At such a coal concentration, the contact efficiency between the catalyst and the coal is low, and the liquefaction reactivity is expected to decrease.

Therefore, in order to use heavy oil as a hydrotreating solvent and to keep the coal concentration in the slurry fed to the hydrogenation reactor high, the inventors of the present invention carried out the fractionation of the solvent in the slurry preparation step. Focusing on the composition, light oil with a boiling point range of 300 ° C or less is mixed with the heavy oil of the hydrotreating solvent during slurry preparation to lower the slurry viscosity and to remove the solvent before the slurry enters the hydrogenation reactor. It has been found that the solvent in the slurry can be substantially concentrated to only the heavy oil of the hydrotreating solvent by separating the light oil component therein by a gas-liquid separation operation (second invention). That is, a light oil having a boiling point range of 300 ° C. or less as a solvent for preparing a slurry and a boiling point range of 300 to 420.
Using a solvent mixed with heavy oil of the hydrotreating solvent at ℃, the light oil is fed from the raw material adjustment process to the preheating process,
By separating light oil in the gas-liquid separation process at a temperature of around 300 ° C, the slurry before being sent to the reactor is substantially composed of coal and heavy oil, and is under high temperature conditions of 300 ° C or more Because the coal concentration in the slurry is 40-50
It has been found that even if it is higher than the mass%, it has fluidity and can be fed. At this time, the mixed solvent of light oil and heavy oil used in the raw material adjustment step may have an oxygen content of 1.5% by mass or less in order to reduce the interaction with the raw coal as described above. is necessary. Here, boiling point range: 300 ° C
For the following light oils, it is desirable to use the light components of the hydrotreating solvent, but the properties and mixing of the light oil so that the oxygen content in the solvent after mixing with the heavy oil will be 1.5% by mass or less. If it is a ratio, it need not necessarily be a hydrotreating solvent.

The above-mentioned oxygen content: 1.7% by mass of the hydrotreating solvent heavy oil: 50% by mass, boiling point range: 180 to 300%
° C, oxygen content: 0.9 mass% of hydrogenated solvent light oil of 50 mass% is mixed to obtain a mixed solvent of oxygen content: 1.3 mass%, and slurry is prepared under the same conditions as the above-mentioned Australian lignite. As a result, when the coal concentration in the slurry was adjusted to 40% by mass (solvent mass: 1.5 times the mass of coal in terms of anhydrous ashless content), the slurry viscosity at 100 ° C. was approximately 350 mPa · s,
When the coal concentration in the slurry was adjusted to correspond to the slurry viscosity at the liquid sending limit of 500 mPa · s, the coal concentration in the slurry was 43% by mass (solvent mass: 1.3 times the mass of coal in terms of anhydrous ashless content). ), And the coal concentration could be higher than when heavy oil as the hydrotreating solvent was used.
Furthermore, when light oil was separated by gas-liquid separation operation after the preheating step using this slurry, the coal concentration of the slurry was 61% by mass (solvent mass: 0.65 times the mass of coal in terms of anhydrous ashless content).
Thus, the coal concentration in the slurry fed to the hydrogenation reactor could be significantly increased.

As described above, as a solvent for preparing a slurry in the raw material adjustment step, light oil and heavy oil obtained by hydrotreating coal liquefied oil have an oxygen content of 1.5 after mixing.
By using a mixed solvent that is mixed so as to be equal to or less than mass%, the impregnation amount of the solvent into the raw coal in the slurry is reduced, and therefore, the viscosity within the limit viscosity of the slurry mixture that can be sent is reduced. It has been found that the amount of the solvent necessary for securing the amount can be reduced, and the coal concentration in the slurry-like mixture can be increased without causing any trouble in liquid sending.

Further, the slurry-like mixture obtained in the raw material preparation step is preheated using the above-mentioned mixed solvent, and light oil in the mixed solvent in the mixture is separated by a gas-liquid separation operation. Coal concentration (slurry concentration) in the mixture
Was found to be able to be further enhanced.

At this time, the amount of the light oil in the mixed solvent of the light oil and the heavy oil used in the raw material adjusting step is desirably 30 to 70% by mass. That is, when the amount of light oil in the mixed solvent is less than 30% by mass, the coal concentration in the slurry after the light oil is separated by the gas-liquid separation operation after preheating is less than 48% by mass (solvent mass: anhydrous ashless content). (More than 1.05 times the converted coal mass), the coal concentration in the slurry fed to the hydrogenation reactor is not sufficiently high, the contact efficiency between the coal and the catalyst is low, and the liquefaction reaction efficiency tends to decrease. On the other hand, if the amount of light oil in the mixed solvent is more than 70% by mass, the coal concentration in the slurry after light oil separation in the gas-liquid separation operation after preheating is more than 77% by mass (solvent mass: in terms of anhydrous ashless content). (Less than 0.3 times the mass of coal)
The fluidity of this slurry is poor even at a temperature of 300 ° C. or higher, and it tends to be difficult to feed the slurry to the hydrogenation reactor. Therefore, the amount of light oil in the mixed solvent is 30 to 70% by mass.
(4th invention). As can be seen from these facts, it is desirable that the mass of the solvent in the slurry mixture fed to the hydrogenation step be 0.3 to 1.0 times the mass of coal in terms of anhydrous ashless content of the raw coal. (Third invention).

In the present invention, the mixed solvent having an oxygen content of 1.5% by mass or less used as a slurry preparation solvent in the raw material adjustment step is obtained by hydrogenating light oil and coal liquefied oil, as can be seen from the above. And a heavy oil to be mixed so that the oxygen content after mixing is 1.5% by mass or less. That is, it is a mixed solvent mixed so that the amount of the oxygen-containing compound (oxygen-containing compound) after mixing becomes 1.5% by mass or less in terms of oxygen amount.

The oxygen-containing compound is a compound having oxygen, that is, a compound having an oxygen-containing group (eg, a hydroxyl group, a carbonyl group, an ether group, etc.). Such oxygen-containing compounds include compounds having oxygen as a hydroxyl group, a carbonyl group, an ether group, or the like. Therefore, the mixed solvent having an oxygen content of 1.5% by mass or less can be said to be a mixed solvent in which the amount of an oxygen-containing compound having oxygen as a hydroxyl group, a carbonyl group, an ether group, or the like is 1.5% by mass or less in terms of oxygen.

As described above, when a brown solvent is mixed with a circulating solvent such as that used in the prior art as a solvent to form a slurry, the slurry contains hydroxyl groups, carbonyl groups, ether groups, etc. in the oxygen-containing compound present in the solvent. Since the interaction between the oxygen functional group and the oxygen-containing functional group in the lignite is caused by a hydrogen bond or the like, the impregnation of the solvent into the lignite is promoted, and the viscosity of the slurry increases accordingly. As a result of further research, among the oxygenated functional groups in these oxygenated compounds, the hydroxyl group has the strongest interaction with the oxygenated functional group in the lignite by hydrogen bonding, etc., and promotes the impregnation of the solvent into the lignite. It has the function of increasing the viscosity of the slurry. Therefore, among the oxygen-containing compounds (oxygen-containing compounds) of the solvent, it is particularly important to reduce the amount of oxygen-containing compounds having oxygen as a hydroxyl group. It was found to be effective in reducing the action, and in turn, reducing the amount of solvent impregnated inside the lignite. In the case of the mixed solvent having an oxygen content of 1.5% by mass or less, the amount of the oxygen-containing compound having oxygen as a hydroxyl group is set to be 60% by mass or less based on the total amount of the oxygen-containing compound. The amount of solvent impregnated into the lignite decreases, so that the amount of solvent required to secure the viscosity within the limit viscosity of the slurry-like mixture that can be sent can be further reduced, causing problems in sending the solution. It was found that the concentration of coal in the slurry mixture could be higher.

From these findings, the ratio of the oxygen content of the oxygen-containing compound having oxygen as a hydroxyl group to the oxygen content of the oxygen-containing compound having oxygen contained in the mixed solvent having an oxygen content of 1.5% by mass or less is considered. Is desirably 60% by mass or less (the eighth invention). That is, in the mixed solvent having an oxygen content of 1.5% by mass or less, the amount of the oxygen-containing compound having oxygen as a hydroxyl group is based on the amount of the oxygen-containing compound having oxygen as an oxygen-containing functional group such as a hydroxyl group, a carbonyl group, or an ether group. Is desirably 60% by mass or less in terms of the amount of oxygen.

More specifically, the coal liquefaction method according to the present invention is performed, for example, by the apparatus and process flow shown in FIG. 1, and is performed by the apparatus and process flow shown in FIG. The details will be described below with reference to these drawings.

When the apparatus shown in FIG. 1 is used, the operation is performed as follows. In a coal slurry preparation tank (1), dry and pulverized raw coal, light oil separated from a gas-liquid separator (3) after a preheater (2), and coal After the hydrogenation treatment in (7), the heavy oil obtained by separation in the gas-liquid separator (8) is supplied, and these are mixed to obtain a slurry mixture. This slurry mixture is fed to a preheater (2) to be preheated. The pre-heated slurry mixture is separated into a gas-liquid separator (3).
To a gas component and a liquid component at a temperature of about 300 ° C.
After cooling, the gas component is supplied to the coal slurry preparation tank (1) as light oil (circulating solvent).

A catalyst (including a co-catalyst such as sulfur) and hydrogen gas are added to the slurry mixture after separating the gas component (light oil), and the mixture is fed to a hydrogenation reactor (4). Here, the hydrogenated product is obtained. At this time, a typical example of the hydrogenation reactor (4) is a bubble column reactor. Typical hydrogenation reaction conditions are temperature: 450 ° C., pressure: 15 MPa, and time: 1 hr.

The obtained hydrogenated product is introduced into a gas-liquid separator (5), where gas phase components at high temperature and high pressure are separated. This gas phase component is directly fed to a gas phase hydrogenation apparatus (7) and subjected to hydrogenation treatment to obtain a hydrogenation treatment solvent. At this time, a flow-type tubular reactor filled with a fixed-bed hydrotreating catalyst is typically used as the gas-phase hydrogenation device (hydrotreating device). Typical conditions for the hydrogenation treatment are as follows: temperature: 350 ° C., pressure: 15 MPa, LHSV (liquid hourly space velocity): 1 hr ⁻¹ .

The obtained hydrotreating solvent was used in a gas-liquid separator.
Light oil with a boiling point of 300 ° C or less and a boiling point of 300
The separated heavy oil is fed to the coal slurry preparation tank (1) as a circulating solvent.

A part of the liquid phase portion containing the catalyst separated by the gas-liquid separator (5) is directly circulated to the hydrogenation reactor (4), and a part thereof is circulated to the oil separator (6). ) And is separated into residues containing oil and solids.

The apparatus shown in FIG. 2 does not have the gas-liquid separator (3) and differs from the apparatus shown in FIG. 1 in that point, but the other points are the same as the apparatus shown in FIG. is there. When the apparatus shown in FIG. 1 is used, the gaseous component (light oil) is separated from the slurry mixture after preheating in the preheater (2) by the gas-liquid separation operation in the gas-liquid separator (3). After the slurry concentration of the mixture is increased, the mixture is fed to the hydrogenation reactor (4). On the other hand, when the apparatus shown in FIG.
The gas mixture (light oil) is not separated by the gas-liquid separation operation of the slurry mixture and the slurry concentration of the slurry mixture is not increased, and the slurry mixture after preheating in the preheater (2) is directly subjected to water. It will be sent to the additional reactor (4).

In the present invention, sub-bituminous coal and bituminous coal can be used as coal in addition to low-carbon coal such as lignite, and particularly, lignite can be advantageously used (sixth invention). It is because brown coal is likely to be impregnated with a solvent due to the development of the pore structure as described above, and the viscosity of the slurry mixture is likely to be high. It is difficult for the viscosity to increase,
This is because the effect is remarkable. From this point, among lignite, calorific value defined by JIS M 1002: 7300 Kcal / Kg
(Based on anhydrous mineral-free substances) The following lignite coals can be advantageously used. These coals usually have a moisture of 15
% Or less, and then used after being ground to a particle size smaller than about 60 mesh. In this case, coal liquefaction can be performed more efficiently by the method of the present invention.

The method of separating the solvent, oil or solid in the gas-liquid separation step or the oil separation step is not particularly limited, and means other than distillation, such as filtration, may be employed. In the case of distillation, distillation conditions suitable for a desired object can be appropriately selected.

[0043]

EXAMPLES Examples of the present invention will be described below, but the present invention is not limited to these examples unless it exceeds the gist. Type of raw coal, type of slurry preparation solvent (mixing ratio of light oil and heavy oil, oxygen content), ratio of mass of slurry preparation solvent to mass of anhydrous ashless coal ( S / C ratio): Slurry viscosity at 1.5 (viscosity of slurry mixture), Slurry viscosity at 100 ° C: 500 mPa · s (Slurry viscosity at liquid transfer limit)
S / C after separating a light oil from a slurry mixture with a C ratio, slurry viscosity at 100 ° C: 500 mPa · s by distillation
Table 1 shows the ratio and the results of the liquefaction reaction of the slurry mixture after light oil separation. Table 1 also shows those of Comparative Examples performed for comparison.

Example 1 Lignite A (calorific value 5930 Kcal / Kg based on anhydrous mineral-free substance, fuel ratio 0.89) was used as raw material coal, pyrite: 3 mass% was used as a catalyst, and in the presence of the catalyst, temperature: A liquefaction reaction was carried out at 450 ° C. and a hydrogen pressure of 15 MPa to obtain a coal liquefied crude oil. The coal liquefied crude oil was cut (separated) by distillation into coal liquefied oil having a boiling point range of 180 ° C. to 420 ° C. Using this coal liquefied oil, using a flow-type fixed-bed high-pressure reactor filled with a Ni-Mo catalyst, hydrogenated at a temperature of 350 ° C., a hydrogen pressure of 15 MPa, and an LHSV of 1.0 hr ⁻¹ , A hydrotreated solvent was obtained. By distilling this hydrotreating solvent, light oil having a boiling point range of 180 ° C to 300 ° C is obtained,
Heavy oils having boiling points ranging from 300 ° C to 420 ° C were obtained by separation. As shown in Table 1, the light oil of the hydrotreating solvent and the heavy oil of the hydrotreating solvent were mixed at a ratio of 50% by mass to 50% by mass to obtain a mixed solvent. When the oxygen content of the obtained mixed solvent was determined by elemental analysis, it was 1.25% by mass as shown in Table 1.

Using this mixed solvent as a solvent for slurry preparation, a coal slurry was prepared by using the brown coal A obtained by drying and pulverizing (water content: 14.54% by mass, particle size: 60 mesh or less) as raw coal. When the slurry was prepared with the ratio (S / C ratio) of the mass of the mixed solvent to the mass of coal in terms of anhydrous ashless content (coal concentration in the slurry: 40% by mass), a double cylindrical rotary viscometer was used. When the slurry viscosity was measured, the slurry viscosity at 100 ° C. was about 32 as shown in Table 1.
It was 0 mPa · s. Also, the slurry viscosity at 100 ℃
When the mixing ratio (S / C ratio) of the mixed solvent and the mass of coal was adjusted to 500 mPa · s (slurry viscosity at the liquid sending limit), the S / C ratio was 1.25 (slurry as shown in Table 1). (Coal concentration in the sample: 44.4% by mass).

Using the slurry having the S / C ratio of 1.25, light oil having a boiling point range of 300 ° C. or less was separated by distillation, and as shown in Table 1, the S / C ratio was 0.63 (coal concentration in the slurry: 6).
1.3% by mass). Using 10 cc of this slurry, a pyrite catalyst was added to an autoclave (internal volume: 30 cc) in an amount of 3% by mass based on the weight of coal in terms of anhydrous ashless content, and liquefaction was performed under the conditions of hydrogen pressure: 15 MPa and temperature: 450 ° C. Was done. After the reaction was completed, the product was separated and separated using a solvent fractionation method. As shown in Table 1, the oil content (n
-Hexane soluble matter) was 77.1% by mass. or,
Gas component yield 14.2% by mass, hydrogen consumption 5.8% by mass
Met.

[0047]

[Table 1]

Example 2 In the same manner as in Example 1, a hydrotreating solvent was obtained, and its boiling point range was from 180 to 300.
A light oil at a temperature of 300 ° C. and a heavy oil having a boiling point range of 300 to 420 ° C. were separated, and the light oil and the heavy oil were mixed at a ratio of 70% by mass to 30% by mass to obtain a mixed solvent. The oxygen content of the obtained mixed solvent was 1.03% by mass. This mixed solvent was used as a slurry preparation solvent, and the same dry and ground brown coal as in Example 1 was used as a raw coal to prepare a coal slurry. When the slurry was prepared at an S / C ratio of 1.5 and the slurry viscosity was measured, the slurry viscosity at 100 ° C. was about 250 mPa · s. When the S / C ratio was adjusted so that the slurry viscosity at 100 ° C was 500 mPa · s, the S / C ratio was 1.10 (coal concentration in the slurry: 47.6% by mass).

Using a slurry having the above S / C ratio: 1.10, light oil having a boiling point range of 300 ° C. or less was separated by distillation to obtain a S / C ratio.
A slurry having a C ratio of 0.33 (coal concentration in the slurry: 75.1% by mass) was obtained. A liquefaction reaction was performed using 10 cc of this slurry under the same conditions as in Example 1, and the yield of the oil component was 80.1% by mass. The gas component yield was 14.8% by mass, and the hydrogen consumption was 6.1% by mass.

Example 3 In the same manner as in Example 1, a hydrotreating solvent was obtained, and its boiling point range was from 180 to 300.
A light oil at a temperature of 300 ° C. and a heavy oil having a boiling point range of 300 to 420 ° C. were separated, and the light oil and the heavy oil were mixed at a ratio of 30% by mass to 70% by mass to obtain a mixed solvent. The oxygen content of the obtained mixed solvent was 1.47% by mass. This mixed solvent was used as a slurry preparation solvent, and the same dry and ground brown coal as in Example 1 was used as a raw coal to prepare a coal slurry. When the slurry was prepared at an S / C ratio of 1.5 and the slurry viscosity was measured, the slurry viscosity at 100 ° C. was about 410 mPa · s. When the S / C ratio was adjusted so that the slurry viscosity at 100 ° C. was 500 mPa · s, the S / C ratio was 1.40 (coal concentration in the slurry: 41.6% by mass).

Using a slurry having the above S / C ratio: 1.40, light oil having a boiling range of 300 ° C. or less was separated by distillation,
A slurry having a C ratio of 0.98 (coal concentration in the slurry: 50.5% by mass) was obtained. A liquefaction reaction was performed using 10 cc of this slurry under the same conditions as in Example 1, and the yield of the oil component was 73.6% by mass. The gas component yield was 13.1% by mass and the hydrogen consumption was 5.6% by mass.

Example 4 A hydrogenation solvent was obtained in the same manner as in Example 1 using lignite B (calorific value 6640 Kcal / Kg based on anhydrous mineral-free substances, fuel ratio 0.94) as raw coal.
From this, light oil with a boiling range of 180 to 300 ° C and a boiling range of 300
A heavy oil at ~ 420 ° C was obtained by separation, and the light oil and the heavy oil were mixed at a ratio of 50% by mass to 50% by mass to obtain a mixed solvent. The oxygen content of the obtained mixed solvent was 0.86% by mass. This mixed solvent was used as a slurry preparation solvent, and the above brown coal B was dried and pulverized as raw coal (having a water content of 13.90).
% By mass, particle size of 60 mesh or less) to prepare a coal slurry. A slurry was prepared at an S / C ratio of 1.5, and the slurry viscosity was measured.
It was 0 mPa · s. The slurry viscosity at 100 ° C is 500m
When the S / C ratio was adjusted to Pa · s, the S / C
The ratio was 1.15 (coal concentration in the slurry: 46.5% by mass).

Light oil was separated by distillation from the slurry having the S / C ratio of 1.15 to obtain a slurry having an S / C ratio of 0.58 (coal concentration in the slurry: 63.3% by mass). A liquefaction reaction was carried out using 10 cc of this slurry under the same conditions as in Example 1, and the yield of oil was 77.9% by mass. The gas component yield was 14.5% by mass, and the hydrogen consumption was 5.
It was 9% by mass.

COMPARATIVE EXAMPLE 1 Coal liquefied crude oil was obtained in the same manner as in Example 1, and this crude oil was cut into a coal liquefied oil having a boiling point range of 180 ° C. to 420 ° C. by distillation. Using this coal liquefied oil, a flow-type fixed-bed high-pressure reactor packed with a Ni-Mo catalyst was used. The temperature was 250 ° C, the hydrogen pressure was 15 MPa,
Hydrotreating was performed under the condition of LHSV: 1.0 hr ^-1 to obtain a hydrotreating solvent. This hydrotreating solvent is distilled to have a boiling point range of 180.
Light oils having a boiling point in the range of 300 ° C to 420 ° C were separated and obtained. The light oil of the hydrotreating solvent and the heavy oil of the hydrotreating solvent were mixed at a ratio of 50% by mass to 50% by mass to obtain a mixed solvent. The oxygen content of the obtained mixed solvent was 1.80% by mass.

This mixed solvent was used as a slurry preparation solvent, and the same dry and pulverized lignite as in Example 1 was used as a raw coal to prepare a coal slurry. A slurry was prepared at an S / C ratio of 1.5 and the slurry viscosity was measured. The slurry viscosity at 100 ° C. was 1200 mPa · s. When the S / C ratio was adjusted so that the slurry viscosity at 100 ° C was 500 mPa · s, the S / C ratio was 2.30 (coal concentration in the slurry:
30.3% by mass), which is a higher value than in Examples 1 to 3.

Light oil was separated from the slurry having the S / C ratio of 2.30 by distillation to obtain a slurry having an S / C ratio of 1.15 (coal concentration in the slurry: 46.5% by mass). A liquefaction reaction was performed using 10 cc of this slurry under the same conditions as in Example 1, and the yield of the oil component was 64.3% by mass.
The values were lower than those in Examples 1 to 3.

COMPARATIVE EXAMPLE 2 A hydrogenated solvent was obtained in the same manner as in Example 1, and its boiling point range was 180-300.
A light oil at a temperature of 70 ° C. and a heavy oil having a boiling point range of 300 to 420 ° C. were obtained by separation, and the light oil and the heavy oil were mixed at a ratio of 80% by mass to 20% by mass to obtain a mixed solvent. The oxygen content of the obtained mixed solvent was 0.92% by mass. This mixed solvent was used as a slurry preparation solvent, and the same dry and ground brown coal as in Example 1 was used as a raw coal to prepare a coal slurry. A slurry was prepared at an S / C ratio of 1.5, and the slurry viscosity was measured. The slurry viscosity at 100 ° C. was 180 mPa · s.
Also, adjust the slurry viscosity at 100 ° C to 500 mPa · s.
When the S / C ratio was adjusted, the S / C ratio was 0.97 (coal concentration in the slurry: 50.8% by mass).

Light oil was separated from the slurry having the S / C ratio of 0.97 by distillation to obtain a slurry having an S / C ratio of 0.19 (coal concentration in the slurry: 84.0% by mass). Using 10 cc of this slurry, a liquefaction reaction was carried out under the same conditions as in Example 1. Even when the temperature was raised to 450 ° C., the slurry was viscous and could not be stirred, so that the liquefaction reaction could not be carried out.

COMPARATIVE EXAMPLE 3 A hydrogenated solvent was obtained in the same manner as in Example 1, and its boiling point range was from 180 to 300.
A light oil at a temperature of 200 ° C. and a heavy oil having a boiling point range of 300 to 420 ° C. were obtained by separation, and the light oil and the heavy oil were mixed at a ratio of 20% by mass to 80% by mass to obtain a mixed solvent. The oxygen content of the obtained mixed solvent was 1.58% by mass. This mixed solvent was used as a slurry preparation solvent, and the same dry and ground brown coal as in Example 1 was used as a raw coal to prepare a coal slurry. A slurry was prepared at an S / C ratio of 1.5, and the slurry viscosity was measured. The slurry viscosity at 100 ° C. was 950 mPa · s.
When the slurry viscosity at 100 ° C becomes 500 mPa
The S / C ratio was 2.12 (coal concentration in the slurry: 32.0% by mass).

Light oil was separated from the slurry having the S / C ratio of 2.12 by distillation to obtain a slurry having an S / C ratio of 1.70 (coal concentration in the slurry: 37.0% by mass). A liquefaction reaction was carried out using 10 cc of this slurry under the same conditions as in Example 1, and the yield of the oil component was 63.2% by mass.
Liquefaction reactivity was lower than in Examples 1-3.

Example 5 Lignite C (calorific value: 6520 Kcal / Kg, based on anhydrous minerals, fuel ratio: 0.91) was used as a raw coal, pyrite: 3% by mass was used as a catalyst, and the temperature was: A liquefaction reaction was carried out at 450 ° C. and a hydrogen pressure of 15 MPa to obtain a coal liquefied crude oil. This coal liquefied crude oil was cut by distillation into coal liquefied oil having a boiling point range of 180 ° C to 420 ° C. Using this coal liquefied oil, a flow-type fixed-bed high-pressure reactor filled with a Ni-Mo catalyst was used.
Hydrogen treatment under the conditions of hydrogen pressure: 15 MPa, LHSV: 1.0 hr ^-1
A hydrotreated solvent was obtained. The hydrotreated solvent is distilled to obtain a light oil having a boiling point range of 180 ° C to 300 ° C and a boiling point range of 30 ° C.
Heavy oils at 0 ° C to 420 ° C were separated and obtained. The light oil of the hydrotreating solvent and the heavy oil of the hydrotreating solvent were mixed at a ratio of 50% by mass to 50% by mass to obtain a mixed solvent. When the oxygen content of the obtained mixed solvent was determined by elemental analysis, it was 1.23% by mass as shown in Table 1. Further, with respect to the amount of the oxygen-containing compound having oxygen contained in the solvent,
The ratio of the amount of the oxygen-containing compound having oxygen as a hydroxyl group was 55% by mass in terms of the amount of oxygen.

Using this mixed solvent as a slurry-preparing solvent, the above-mentioned brown coal C was dried and pulverized (water content: 13.5% by mass, particle size: 60 mesh or less), and a coal slurry was prepared. When a slurry is prepared with the ratio (S / C ratio) of the mass of the mixed solvent to the mass of coal in terms of anhydrous ashless content (coal concentration in coal slurry: 40% by mass), use a double cylindrical rotary viscometer. The slurry viscosity at 100 ° C. was about 240 mPa · s as shown in Table 1. The mixing ratio (S / C ratio) of the mixed solvent and coal was adjusted so that the slurry viscosity at 100 ° C was 500 mPa · s. The S / C ratio was 1.12 (as shown in Table 1). Coal concentration: 44.4% by mass).

Using a coal slurry having the above S / C ratio: 1.12, light oil having a boiling point range of 300 ° C. or less was separated by distillation, and the S / C ratio was 0.56 (coal concentration in the slurry: 64.1% by mass). A coal slurry was obtained. Using 10 cc of this slurry, a pyrite catalyst was added in an autoclave (internal volume: 30 cc) in an amount of 3% by mass based on the mass of coal in terms of anhydrous ashless content.
The liquefaction reaction was performed under the conditions of hydrogen pressure: 15 MPa and temperature: 450 ° C. After the reaction was completed, the product was separated and separated by a solvent fractionation method. As shown in Table 1, the yield of oil (soluble matter in n-hexane) was 79.2% by mass. The gas component yield was 13.8% by mass, and the hydrogen consumption was 5.9% by mass.

[0064]

According to the coal liquefaction method of the present invention,
Compared with the conventional coal liquefaction method, the amount of solvent impregnated in the raw coal in the slurry mixture is reduced, and therefore, it is necessary to secure the viscosity within the limit viscosity of the slurry mixture that can be sent. And the concentration of coal in the slurry-like mixture can be increased without causing problems in liquid feeding, and as a result, the contact efficiency between coal and the catalyst is improved, and consequently liquefied oil The yield can be further improved,
The amount of coal processed per unit time and unit volume in hydrogenation increases, and thus the amount of coal that can be treated with respect to the reactor volume is large, and the equipment volume efficiency can be increased, or the reactor volume can be reduced. Therefore, a sufficient amount of coal can be secured, and the size of the reactor can be reduced.

[Brief description of the drawings]

FIG. 1 is a diagram showing an outline of an example of a coal liquefaction method according to the present invention.

FIG. 2 is a diagram showing an outline of an example of a coal liquefaction method according to the present invention.

[Explanation of symbols]

(1)-coal slurry preparation tank, (2)-preheater, (3)-gas-liquid separator, (4)-hydrogenation reactor, (5)-gas-liquid separator, (6 )-
Oil separator, (7)-gas-phase hydrogenator, (8)-gas-liquid separator.

Claims (8)

[Claims] 1. A coal liquefaction method comprising: a raw material adjustment step of mixing a raw material coal with a solvent to obtain a slurry mixture; and a hydrogenation step of adding hydrogen to the mixture to hydrogenate the coal. As the solvent, light oil and heavy oil obtained by hydrotreating coal liquefied oil obtained from coal as a raw material,
A coal liquefaction method using a mixed solvent having an oxygen content of 1.5 mass% or less. 2. The slurry mixture obtained in the raw material adjustment step is preheated, and light oil in a mixed solvent in the mixture is separated by a gas-liquid separation operation to increase the slurry concentration of the mixture. The coal liquefaction method according to claim 1, wherein the mixture is fed to the hydrogenation step thereafter. 3. The coal liquefaction according to claim 2, wherein the mass of the solvent in the slurry mixture fed to the hydrogenation step is 0.3 to 1.0 times the mass of the raw coal in terms of anhydrous ashless content. Method. 4. The coal liquefaction method according to claim 2, wherein the amount of light oil in the mixed solvent of light oil and heavy oil used in the raw material adjusting step is 30 to 70% by mass. 5. The mass of the solvent to be mixed with the raw coal in the raw material adjusting step is a mass of coal in terms of anhydrous ashless content of the raw coal.
5. The coal liquefaction method according to claim 1, wherein the ratio is 1.0 to 1.5 times. 6. The method according to claim 1, wherein the raw coal is lignite.
The method for liquefying coal according to 2, 3, 4 or 5. 7. The light oil is a light oil having a continuous boiling point distribution of 300 ° C. or less, and the heavy oil is 300 to 420 ° C.
A heavy oil having a continuous boiling point distribution of
7. The coal liquefaction method according to 2, 3, 4, 5, or 6. 8. The ratio of the oxygen content of the oxygen-containing compound having oxygen as a hydroxyl group to the oxygen content of the oxygen-containing compound having oxygen contained in the mixed solvent having an oxygen content of 1.5% by mass or less is 60% by mass or less. Claims 1, 2, 3,
The method for liquefying coal according to 4, 5, 6, or 7.