JPH021875B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] This invention relates to a method for producing solvent refined coal.
More specifically, by evaporating the solvent from a solution containing a dilute concentration of solvent refined coal, hereafter abbreviated as SRC (Solvent Refined Coal), in a single evaporation step, The present invention relates to a method for manufacturing SRC that allows obtaining SRC with a high softening point.

[Problems with the prior art] As is well known, coal powder is dispersed in a solvent, hydrogenated with a small amount of hydrogen at high temperature and pressure, and dissolved in the solvent. After the dissolved matter is removed, the solvent is evaporated in a multi-stage evaporation process to obtain SRC as a residue after evaporation.

When producing SRC industrially, it is difficult to obtain a large amount of solvent, so it is necessary to balance the material balance of the manufacturing process only by recycling the recovered solvent without additionally supplying new solvent. is desirable, and for this purpose it is necessary to improve the solvent recovery rate.

The softening point of SRC itself is 200 to 300°C, which is high, but as the amount of residual solvent in SRC increases, the softening point becomes lower.

Therefore, the softening point of SRC after solvent recovery is an indicator of the solvent recovery rate.

Conventionally, the method exclusively used for solvent recovery is multistage evaporation, but multistage evaporation is a method to increase the recovery rate of solvent from a dilute SRC solution and obtain SRC with a high softening point. It cannot be said that the method is advantageous in terms of its equipment and its operation. An object of the present invention is to provide a method for obtaining SRC with a high softening point from a dilute solution of SRC in one step.

[Structure of the Invention] The method for producing SRC of the present invention is to thermally decompose coal under hydrogen pressure in a solvent, and to remove insoluble matter from the resulting reaction mixture.
To obtain SRC by removing the solvent from an SRC solution of 30% by weight or less, the SRC solution is heated to a temperature not exceeding 430°C and sent to a flashing area under reduced pressure to flash and separate the solvent. By refluxing a portion of this melt into the SRC solution that is newly fed to the solvent separation step, the amount of SRC in the SRC solution that is fed to the vacuum flash zone through the heating step is SRC concentration 30% by weight
It is characterized by maintaining the concentration above .

The inventors conducted various studies in order to obtain SRC with a high softening point, that is, a high solvent recovery rate by evaporating the solvent from a dilute solution of SRC in one step, and discovered the following facts, and arrived at this invention. .

That is, assuming that the desired softening point of SRC and the pressure in the flash region are constant, the more dilute the concentration of the SRC solution, the higher the temperature of the solution supplied to the flash region needs to be. For example, to obtain SRC with a softening point of 160°C when the flash region pressure is 80 mm of mercury, the concentration of the SRC solution must be 50 mm.
% by weight, the temperature of the feed SRC solution is approximately 385
℃, but if the concentration is 20% by weight,
It is necessary that an SRC solution heated to about 460° C. be supplied to the flash zone.

On the other hand, when the SRC solution is heated above 430° C., thermal decomposition reactions occur in the SRC itself and in the solvent, resulting in deterioration of its properties.

In addition, not only will the SRC quality of the product deteriorate, but the formation of polymers or carbides in the heating tubes installed in the heating furnace will cause clogging of the heating tubes, which will cause serious operational problems. This will promote

The temperature of the SRC solution supplied to the flash area
It is absolutely necessary to avoid temperatures exceeding 430℃.

Therefore, no matter how large the capacity of the SRC solution heating furnace is, it is impossible to obtain SRC having a high softening point from a dilute SRC solution.

However, this difficult problem was surprisingly solved by an extremely simple method of refluxing and mixing a portion of the SRC taken out as a melt from the flash zone with the SRC solution to be supplied to the flash zone. .

By doing this, the concentration of SRC in the SRC solution increases, and the heating temperature of the SRC solution supplied to the flash area can be kept at a temperature that does not exceed 430°C.

To explain with reference to FIG. 1, conventionally, the SRC solution from line 1 is stored in reservoir 2 and line 3
The pressure is increased to the required pressure by the pump 4,
After passing through the heating tube in the heating furnace 5 and the line 6, it is transferred to the evaporation tower 7.
was introduced into the country and flashed here,
Solvent via line 8 and SRC via line 9
However, in the method of the present invention, a part of the SRC is refluxed to the reservoir 2 through the line 10, increasing the SRC concentration of the SRC solution sent to the heating furnace 5. be.

In the method of this invention, the concentration of the SRC solution supplied from line 1 to be treated is 30% by weight or less.

The pressure in the flash zone is preferably 30 to 30 mercury.
100 mm, particularly preferably 50 to 80 mm.

The temperature of SRC supplied to the flash area is 430℃
The lower temperature limit should not be exceeded, but the lower temperature limit is determined by the desired softening point of the SRC, the concentration of the SRC solution, and the flash zone pressure.

In order to reflux mix the SRC melt into the SRC solution, it is preferable to reflux only by position difference without using a pump in order to prevent mixing of the solvent to be flashed. It is preferable to adjust so that a sufficient positional difference is obtained for reflux.

[Effects of the Invention] According to the present invention, the solvent is evaporated from a dilute solution having an SRC concentration of 30% by weight or less, and SRC that is recovered and has a predetermined softening point is converted into SRC and SRC by one-step evaporation. It can be obtained by an extremely simple method without impairing the properties of the solvent.

Comparative examples and examples are shown below, but the invention is not limited to these examples.

[Comparative Example] An SRC solution with a concentration of 24% by weight obtained from Miike bituminous coal by a conventional method was passed through a heating furnace and heated so that its outlet temperature was 430°C.

The heated SRC solution is then fed into a vacuum solvent recovery column at a flow rate of 100 parts by weight per hour to a pressure of 80%.
It was flashed in a vacuum solvent recovery column held in a column of mm mercury.

Through this flashing, the solvent is evaporated and extracted from the top of the column and recovered, while from the bottom of the column it is
A melt of SRC at 66°C was obtained with a flow rate of 34 parts by weight per hour; this SRC melt with a softening point of 66°C was
It consists of 24 parts by weight of SRC with a softening point of 160°C and 10 parts by weight of solvent, and although the load on the vacuum solvent recovery tower is not large, the separation of the solvent is incomplete, and 10 parts by weight of solvent is lost to the product every hour. This resulted in it getting mixed into the SRC, which should have been treated as waste, and being discharged outside the system.

[Example] According to the method of the invention, 105 parts by weight per hour are refluxed to a reservoir of SRC solution by position difference, and from the reservoir of SRC solution is refluxed per hour into a vacuum solvent recovery column.
SRC solution was introduced and flushed at a flow rate of 205 parts by weight.

Even though the amount of SRC solution fed to the vacuum solvent recovery tower was doubled, the softening point of the SRC melt obtained from the bottom of the tower was 160°C after the solvent separation process reached a steady state.

[Brief explanation of the drawing]

FIG. 1 is a flow sheet for explaining the method of the present invention. 1... Line (SRC solution), 2... Reservoir, 3
...Line, 4...Pump, 5...Heating furnace, 6...Line, 7...Evaporation tower (flash area/vacuum solvent recovery tower), 8...Line (solvent), 9...Line (SRC),
10...Line (SRC), 11...Detection end, 12...Control valve.

Claims (1)

[Claims] 1. Solvent refined coal is obtained by removing the solvent from a solvent refined coal solution with a concentration of 30% by weight or less obtained by thermally decomposing coal under hydrogen pressure in a solvent and removing insoluble matter from the resulting reaction mixture. To obtain the solution, the solvent-refined coal solution is heated to a temperature not exceeding 430°C and sent to a vacuum flashing zone to flash, separating the solvent and producing a melt of solvent-refined coal; By refluxing some of the substances into the solvent refined coal solution newly supplied to this solvent separation process, the solvent refined coal in the solvent refined coal solution that is sent to the vacuum flashing area after the heating process is removed. A method for producing solvent refined coal, characterized by maintaining the concentration at a concentration exceeding 30% by weight.