JPH0813969B2 - Liquefaction method of coal - Google Patents

Description

TECHNICAL FIELD The present invention relates to a coal liquefaction method capable of simplifying the operation of a liquefaction reactor in a coal liquefaction process.

(Conventional technology and its problems) The liquefaction process of coal includes a liquefaction reaction step for liquefying coal, a distillation step for distilling and separating the liquefied product into liquefied oil and the like, and hydrogen for liquefied oil from the distillation step. It is composed of a solvent hydrogenation step of adding and reforming to a solvent suitable for liquefaction.

In the liquefaction reaction step, a solvent containing coal and coal liquefied oil as main components and a catalyst for promoting liquefaction of coal are supplied, and
0 ~ 300atm under hydrogen pressure, 400 ~ 500 ℃ high temperature 0.
Liquefaction is carried out by holding for about 5 to 2.0 hours. In the liquefaction reaction process in which the raw materials are continuously supplied, in order to prevent the outflow of unreacted coal due to complete mixing and to obtain an extruded flow in which the reaction raw materials flow at a uniform average flow rate, usually multiple reactors are connected in series. Used by connecting.

In the distillation process, the liquefied product is distilled after the gas, the raw material hydrogen, etc. are separated, and the light oil (BP: IBP to 200 ° C), the medium oil (BP: 200 to 350 ° C), the heavy oil ( (BP: 350-538 ° C) is extracted from the top of the distillation column, and the distillation residue is extracted from the lower part. In order to improve energy efficiency and the like, atmospheric distillation is used for distillation of light oil, and vacuum distillation is used for distillation of heavy oil. When distilling off heavy oil having a boiling point of 538 ° C, the distillation column is usually kept at a temperature of about 400 ° C and a pressure of 10 mmHg or less in order to prevent thermal alteration of the oil content in the distillation column.

In the solvent hydrogenation process, a high-grade catalyst (for example, Ni-Mo / Al
₂ O ₃ ) is used to add hydrogen to medium and heavy oils, and it is reformed to properties suitable for coal liquefaction solvent.

In such a coal liquefaction process, construction cost is high, and it is difficult to secure a large amount of raw material coal with one kind of coal.

Further, in the coal liquefaction process, it is as important as surely separating the distillation residue in the distillation step to ensure stable operation of the process, as well as to improve the liquid yield in the coal liquefaction step.

In other words, if coal is liquefied by a known process with a distillation column cut temperature of 538 ° C, the distillation process will operate stably in the liquefaction of coal with a small amount of ash and a large amount of distillation residue, but with a high ash content When coal is liquefied with a small amount of residue produced, ash is concentrated in the distillation residue and the fluidity of the distillation residue is reduced, making it difficult to extract from the bottom of the distillation column, which hinders the stable operation of the coal liquefaction process. There is a problem of coming.

As a method of solving this problem, a method of removing the ash in advance from coal having a high ash content and a small amount of distillation residue produced can be considered. However, this method has the following drawbacks.

(A) Since the decalcification equipment having a treatment capacity equal to or more than the amount of coal required for the coal liquefaction process is required, the construction cost and operating cost are high.

(B) Ash that has the action of promoting the liquefaction of coal will be removed in advance, and a new catalyst must be added.

In addition, a method of removing ash in advance by a method such as solvent extraction, centrifugation, or addition of antisolvent prior to the distillation step can be considered, but this method requires new equipment, and its construction cost and operation cost are high. Becomes

In a liquefaction process consisting of a plurality of reactors, a method in which a solid-concentrated layer and a dilute layer are mainly separated in an upstream liquefaction reactor and the solid-concentrated layer is constantly taken out of the system (JP-A-52-145408). Issue).

A process flow chart of this method is shown in FIG. Raw materials such as coal, a solvent, a catalyst and hydrogen are sequentially charged into three liquefaction reaction vessels from below, and a solid concentrated layer is extracted from each reactor and sent to a deashing process. The liquefied oil from the final reactor and the liquefied oil from the deashing step are then sent to a distillation step where they are separated by distillation into light oil, medium oil, heavy oil and a residue as shown.

According to this method, a solid content concentrated layer is generated in the reactor, and the progress of the hydrocracking reaction is promoted in the concentrated layer,
Compared with a distillation column, it has an advantage that the solid concentrated layer is extracted from the reactor at high temperature and high pressure, so that the solid layer can be easily separated.

 However, this method also has the following drawbacks.

(A) As shown in FIG. 2, the supply port 2 at the bottom of the reactor 1
Since the raw material slurry + gas consisting of coal, solvent, catalyst and hydrogen gas as raw materials is supplied from inside the reactor, it is in a state where it is sufficiently stirred with the gas components supplied from the lower part of the reactor inside the reactor. It is easy to form a complete mixed flow. In order to maintain the equilibrium state between the solid-rich layer and the lean layer, it is necessary to delicately control the flow rates of coal, solvent, and hydrogen gas to be supplied.

(B) In the upstream part of the liquefaction process composed of a plurality of reactors, unreacted coal is easily contained in the solid-rich layer due to the complete mixed flow. As a result, the liquefied oil yield, which is also intended for the coal liquefaction process, tends to decrease.

(C) It is desirable that the solid content extracted outside the reactor does not contain solvent and liquefied oil, but in this method, the solid content and liquefied oil and solvent are not separated because the inside of the reactor is agitated. Sufficient and a large percentage of these are lost in the solids rich layer.

(D) In order to continuously extract the concentrated solid layer outside the reactor, it is necessary to perform a solid-liquid separation operation for the concentrated solid layer in order to secure the solvent and liquefied oil necessary for the liquefaction process. Requires a solid separation device.

(E) When a distillation device is adopted as a new solid separation device, the ash is concentrated, so that it is difficult to extract the distillation residue containing the solid from the lower part of the distillation column.

As described above, it has been difficult to liquefy coal having a high ash content and a small amount of distillation residue by the conventional operation method.

(Problem to be Solved by the Invention) An object of the present invention is to provide a coal liquefaction method capable of achieving stable operation of a coal liquefaction process, particularly a distillation step, regardless of the type of coal used.

(Means for Solving the Problems) The present inventors prefer to produce a precipitate rather than a liquefaction reactor which has been conventionally designed not to produce a precipitate, because the distillation residue has a high ash content. It has been found that the coal liquefaction reactor is suitable for the liquefaction of coal with a small amount of liquefied coal, and by extension is suitable for the liquefaction of any coal.

In addition, the inventors tried to quantify the coal liquefaction method, and found that the catalyst has a small effect of promoting the liquefaction reaction in the latter stage of the reaction.

Here, the essence of the present invention is a liquefaction reaction step of liquefying a raw material consisting of coal, a solvent, a catalyst and hydrogen gas to obtain a reaction product, which is composed of two or more liquefaction reactors, and the liquefaction reaction product obtained is distilled. A method for continuously liquefying coal comprising a distillation step of separating, a hydrogenation process of liquefied oil from the distillation step and supplying the liquefaction reaction step as a solvent to a liquefaction reaction step,
In the latter stage of the liquefaction reaction, the liquefaction reaction product from the liquefaction reactor upstream of the liquefaction reactor is provided from the supply port provided in the middle stage of at least the most downstream liquefaction reactor. To accelerate the formation of a precipitate, and the precipitate thus formed is discharged to the outside of the liquefaction reactor through a discharge port provided at the bottom of the liquefaction reactor by using the pressure difference inside the liquefaction reactor. And a method for liquefying coal, which facilitates solid-liquid separation in the subsequent steaming step.

Regarding the reaction temperature, reaction time, hydrogen pressure, liquefaction catalyst and the like in the liquefaction process in the present invention, those of known methods can be used as they are. Preferred conditions are reaction temperature 430-470
C, reaction time 0.5 to 2.0 hours, hydrogen pressure 100 to 200 atm. As the liquefaction catalyst, it is preferable to use an inexpensive iron-based catalyst in combination with the co-catalyst (sulfur compound).

A known reactor in a coal liquefaction process is a reactor of a complete mixing tank connected in series. It may be used in the present invention. The reactor of the complete mixing tank is preferable because it prevents the accumulation of solids in the reactor and at the same time promotes the diffusion of the catalyst to promote the progress of the liquefaction reaction.

As described above, according to the present invention, the production of the precipitate is actively promoted in the reactor in the latter stage of the liquefaction reaction, and the operation in the distillation step after the liquefaction reaction step is facilitated.

(Operation) Next, the present invention will be described in more detail together with its operation with reference to the accompanying drawings.

FIG. 3 shows a flow chart of the method for liquefying coal according to the present invention. As in the case of FIG. 1, coal, solvent,
A liquefied oil obtained by liquefying a raw material composed of a catalyst and hydrogen gas in three liquefaction reactors is sent to the next distillation step to be separated into respective fractions by distillation. However, in the case of the present invention, particularly in the illustrated example, all the reaction products from the upstream liquefaction reactor in the most downstream liquefaction reactor corresponding to the latter stage of the liquefaction reaction are charged into the reactor through the supply port provided in the middle stage, In the downstreammost reactor, the ash settles and is separated as a precipitate. The remaining liquefied oil is extracted from the top of the column and sent to the distillation step.

FIG. 4 is a drawing showing an example of a preferable reactor shape for promoting the formation of a precipitate.

Explaining the shape of the reactor 3 in terms of the fourth surface, the slurry of the liquefied product using coal, solvent, catalyst and hydrogen gas as raw materials is fed into the reactor 3 through the raw material supply port 4 provided in the middle stage of the reactor 3. Is supplied to. The inside of this reactor is maintained so as to satisfy predetermined reaction conditions.

As shown in FIG. 4, above the raw material supply port 4, the gaseous product supplied is sufficiently agitated to form a complete mixed flow, thereby promoting the liquefaction reaction. After the completion of the reaction, the slurry is constantly discharged from the reactor through the slurry discharge port 5. On the other hand, stirring is insufficient because there is no gas supply in the reactor below the raw material supply port 4, and solid and liquid products are mainly present. The solid product sequentially forms a precipitate due to the difference in specific gravity from the liquid product. When the accumulated amount of the precipitate reaches a certain level, the high temperature and high pressure valve 6 is opened and the precipitate is discharged to the outside of the reactor using the pressure difference between the inside and outside of the reactor. When the discharge is completed, the high temperature and high pressure valve 6 is closed again, and the precipitate is accumulated again from the lower part of the reactor. The high-pressure valve 6 is closed until the precipitate reaches a certain level, as compared with the case where the concentrated solid layer is constantly discharged, and during that time, the solvent or the liquefied oil of the product is discharged from the precipitate discharge port. Can be prevented.

Needless to say, the opportunity to extract the precipitate depends on the type of coal, reaction conditions, and the like.

As is clear from this example, as the shape of the reactor 3 that positively promotes the formation of precipitates, the raw material supply opening for coal, solvent, catalyst, hydrogen gas, etc., that is, the supply port 4 is used as the reactor. The structure is provided in the middle section.

As a method for removing the generated precipitate to the outside, it is desirable to use a physical method when necessary.

As the installation place of the liquefaction reactor having such a shape, in the coal liquefaction process having a plurality of reactors, it is preferable to install it in the final reactor.

This is because when the raw material coal is installed in the upstream reactor, unreacted coal easily precipitates, and it becomes difficult to secure the liquefied oil yield, which is the purpose of the coal liquefaction process.

On the other hand, in the final reactor, the rate of unreacted coal flowing in is decreasing and the coal liquefaction reaction is almost complete, so it is easy to secure the liquefied oil yield, which is the purpose of the coal liquefaction process. It can be carried out.

Further, compared with the case of separating the distillation residue in the distillation column, the separation in the liquefaction reactor can be carried out under the conditions of high temperature and high pressure. Due to the action of the solvent at a high temperature, the liquefied product having a high molecular weight can be dissolved in the solvent, so that the amount of the precipitate produced is smaller than that in the distillation column. Also,
In the vacuum distillation column, the distillation residue is discharged only by the action of gravity, but when it is carried out in the reactor, the action of the reaction pressure is also added, so that the precipitate can be separated more easily.

Next, the product of this liquefaction reactor is subjected to a distillation step, light oil, medium oil, and heavy oil are extracted from the top of the distillation column, and a distillation residue is extracted from the lower part of the distillation column.

The operating conditions of this distillation column are preferably carried out at a temperature of 400 ° C. or lower in order to prevent thermal deterioration of the product. The upper limit of the temperature of the distillation column limits the ability to extract the distillation residue from the lower part of the distillation column. It is self-evident that the lower the softening point and pour point of the distillation residue, the better the extractability of the distillation residue.

The inventors diligently studied the relationship between the amount of toluene-soluble matter in the distillation residue and the withdrawal property, and when the amount of the toluene-soluble matter was 20% or less, the withdrawal property from the lower part of the distillation column was lowered and the pipe was often clogged. Found out. Further, when the amount of toluene-soluble matter is small, the pipe is blocked. On the other hand, 30%
When it exceeds, the distillation residue can be smoothly extracted without blocking the pipe.

Here, some of the light oil and medium oil withdrawn from the top of the tower are taken out as products, and the rest of the medium oil and heavy oil are circulated and used as solvents in the coal liquefaction process after undergoing a hydrogenation process. To be done. The hydrogenation step in the present invention is not particularly limited, including the treatment conditions, and the conventional method may be used as it is.

(Examples) Next, the present invention will be described more specifically by way of examples.

A coal liquefaction process composed of a liquefaction facility and a distillation facility in which four reactors of a complete mixing tank whose reaction volume was adjusted to 1.25 liters were connected in series was used.

Battle River coal having the analytical values shown in Table 1 was supplied to the above coal liquefaction process at a flow rate of 5 l / h under the operating conditions shown in Table 2. From the reaction volume and the operating conditions, the average residence time in the coal liquefaction process is 1 hour. The material balance and the properties of the obtained distillation residue were investigated. The results are shown in Table 3 as a comparative example.

From Table 3, this coal liquefaction facility produces about 360 g / h of coal liquefied oil from 2000 g of coal. The amount of the distillation residue produced was about 770 g / h, but the toluene-soluble content in this distillation residue was as small as 20%, and due to its high softening point and pour point, the extraction pipe for the distillation residue was often blocked. Every time, the supply of coal to the coal liquefaction process was stopped, and the operation of the solvent was performed while removing the blockage of the distillation residue withdrawing pipe. As a result, the initial target of producing 360g / h of coal liquefied oil could not be secured.

Next, as an example, a reactor at the most downstream part of the series liquefaction reactor used relatively was provided with a raw material slurry supply port in the middle stage of the coal liquefaction reactor, and the inside of the reactor was precipitated using the solid-liquid gravity difference. Was exchanged with a reactor capable of promoting the formation of the above and removing the precipitate using a pressure difference between the inside and the outside of the reactor. The average residence time in the liquefaction reaction step of the raw material slurry at this reactor supply port was about 45 minutes. The other reaction conditions were the same as those of the comparative example.

Every hour after starting the supply of coal, the high temperature and high pressure valve was opened to remove about 520 g of the deposit accumulated in the reactor, and then the high temperature and high pressure valve was closed. Analysis of this precipitate revealed that the ash content was up to about 40% and that the product, coal liquefied oil, was included at about 50 g. On the other hand, the distillation residue from the bottom of the distillation column was produced at 300 g / h. The analytical values are shown in Table 4. It contained 30% of toluene-soluble content, had a softening point and a pour point at a lower temperature than the comparative examples, and had good residue extraction properties in the distillation column. Furthermore, the coal supply to the coal liquefaction process was not stopped due to a pipe clogging trouble. The material balance of this coal liquefaction process is shown in Table 4.

The amount of coal liquefied oil produced was about 310 g / h, and although the amount produced was smaller than in the comparative example, the coal liquefaction process could be operated stably and the initial target could be achieved.

In the conventional example, it is necessary to install a new deashing step to secure the solvent and product necessary for the operation of the process, but as shown in this example, the solvent and product of the process are secured by the distillation column. can do. The liquefied oil in the precipitate extracted from the lower part of the reactor can be partially recovered by an operation such as filtration, but for that purpose, it is necessary to install new separation equipment. In that case, the liquefied oil recovered from this new separation facility is added as a product.

(Effect of the Invention) According to the present invention, the following effects occur.

(B) The liquid yield and the solvent for coal liquefaction are secured, and at the same time, stable operation of the liquefaction plant can be achieved.

(B) Since ash having the action of promoting coal liquefaction can be supplied to the liquefaction process, it is effective in reducing the amount of catalyst used.

(C) The entire amount of raw material coal can be supplied to the liquefaction process.

(D) In the case of continuous discharge, solid separation operation is necessary to secure the solvent product, but since the present invention is a batch type, the amount of these extracted is small and a new solid separation operation is required. do not do.

(E) Since most of the ash can be removed in advance in the liquefaction process,
The distillation process can be operated stably.

[Brief description of drawings]

FIG. 1 is a process flow diagram according to a conventional example; FIG. 2 is a schematic explanatory diagram of a shape of a reactor according to a conventional example; FIG. 3 is a process flow diagram according to the present invention; and FIG. FIG. 3 is a schematic explanatory view of the shape of the reactor according to FIG.

Claims (1)

[Claims] 1. Coal, solvent, comprising two or more liquefaction reactors,
A liquefaction reaction step of liquefying a raw material consisting of a catalyst and hydrogen gas to obtain a reaction product, a distillation step of distilling and separating the obtained liquefaction reaction product, and a solvent for the liquefaction reaction step by hydrogenating the liquefied oil from the distillation step. A method for continuously liquefying coal consisting of a solvent hydrogenation process, which is supplied as a liquefaction from a liquefaction reactor upstream from a supply port provided at the middle stage of at least the most downstream liquefaction reactor in the latter stage of the liquefaction reaction. The reaction product is supplied, and in the liquefaction reactor, the formation of the precipitate is promoted simply by using the gravity difference between the solid and the liquid, and the precipitate thus produced is separated by using the pressure difference inside the liquefaction reactor. A coal liquefaction method, characterized in that the liquefaction reactor is discharged to the outside of the liquefaction reactor when necessary through a discharge port provided at the bottom of the liquefaction reactor to facilitate solid-liquid separation in the subsequent distillation step.