JPS63238195A - Liquefaction of coal - Google Patents

Abstract

PURPOSE:To improve liquid yield of coal liquefaction and simultaneously con trive stabilization of a liquefaction plant, by recycling a residue of a coal lique faction product removing ash from the residue to a liquefaction process and further subjecting the residue to hydrocracking. CONSTITUTION:Ash is removed by a method such as solvent extraction, supercritical extraction, centrifugal separation, gravitational sedimentation or gravity separation from a distillation residue obtained when coal liquefaction product is distilled. Then the ash-removed distillation residue is recycled to directly before the distillation process, liquefaction process or hydrogenation process. The liquefaction process is preferably carried out at 430-470 deg.C for 0.5-2hr in hydrogen pressure of 100-200atm. and as the liquefaction catalyst, an inexpensive iron based catalyst is preferably used together with a cocatalyst such as sulfur compound.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a method of operating a distillation step in a coal liquefaction process.

(Prior art and its problems) The coal liquefaction process includes a liquefaction reaction step to liquefy coal, a distillation step to separate the liquefied product into liquefied oil and residue,
It consists of a solvent hydrogenation process in which hydrogen is added to liquefied oil to reform it into a solvent suitable for liquefaction.

In the liquefaction reaction step, a solvent containing coal and coal liquefied oil as main components and a catalyst that promotes the liquefaction of coal are supplied.
Liquefaction is carried out by holding at a high temperature of about 400 to 500° C. for about 0.5 to 2.0 hours under hydrogen pressure of about 300 atm.

In the distillation process, the liquefied product is distilled after gas, raw material hydrogen, etc. have been separated, and light oil (BP: IBP ~ 200 ° C.
), medium oil (BP: 200-350℃), heavy oil (B
P; 350-538°C) is extracted from the top of the distillation column,
Distillation residue is extracted from the bottom. In the solvent hydrogenation step, hydrogen is added to medium oil and heavy oil using a high-grade catalyst (for example, N i -Mo/A 1203), and the oil is modified to have properties suitable for a solvent for coal liquefaction.

It is desired that such a coal liquefaction process be applicable to all types of coal, since its construction costs are high and it is difficult to secure a large amount of raw material coal for one type of coal.

In addition, in the coal liquefaction process, it is important to ensure the separation of distillation residue during the distillation process and ensure stable operation of the process.
It is equally important to improve the liquid yield in the coal liquefaction process.

In other words, when coal is liquefied using a known process with a cut temperature of 538°C in the distillation column, the distillation process is stable when liquefying coal that has a low ash content and produces a large amount of distillation residue; In the liquefaction of coal, which produces only a small amount of coal, ash concentrates in the distillation residue during the distillation process, reducing the fluidity of the distillation residue, making it difficult to extract it from the bottom of the distillation column, and hindering the stable operation of the liquefaction process. There is a problem with this.

As a method to solve this problem, a method can be considered: (1) to remove ash in advance from coal that has a high ash content and produces a small amount of distillation residue. However, this method has the following drawbacks.

(a) Since deashing equipment is required that has a processing capacity greater than the amount of coal required for the coal liquefaction process, its construction and operating costs are high.

(b) Ash, which has the effect of promoting coal liquefaction, must be removed in advance, and a new catalyst must be added.

In addition, it is possible to remove ash in advance by methods such as solvent extraction, centrifugation, supercritical extraction, and addition of anti-solvents prior to the distillation process, but this method requires new equipment and the construction cost. , operating costs are high.

Thus, with conventional operating methods, it has been difficult to liquefy coal with high ash content and little distillation residue.

(Objective of the Invention) The object of the present invention is to achieve stable operation of a coal liquefaction process, particularly a distillation process, regardless of the type of coal used.

(Structure of the Invention) The present inventors have discovered that stable operation of the distillation process can be achieved by removing ash from the distillation residue that has passed through the distillation process and recycling this distillation residue back into the coal liquefaction process. I found it.

The gist of the present invention is a coal liquefaction method characterized by removing ash from a distillation residue obtained when distilling a coal liquefaction product, and re-adding this distillation residue from which the ash content has been removed to a coal liquefaction process. It is.

The reaction temperature, reaction time, hydrogen pressure, liquefaction catalyst, etc. in the liquefaction process are not particularly different from known methods. Preferred conditions are a reaction temperature of 430-470°C and a reaction time of 0.5-470°C.
The hydrogen pressure is approximately 100 to 200 atm for 2.0 hours.

As the liquefaction catalyst, it is preferable to use an inexpensive iron-based catalyst in combination with a promoter (sulfur compound).

The accompanying drawing is a flow sheet illustrating one embodiment of the invention.

In the present invention, ash is removed from the distillation residue after the distillation process. The method for removing and separating ash is not particularly limited, and solvent extraction, supercritical extraction, centrifugation, gravity sedimentation, specific gravity separation, etc. can be used. Furthermore, the solvent used is not particularly limited, and light oil produced in the process can also be used.

In the embodiment shown, the distillation residue obtained after removing the ash is recycled back to the distillation process. Medium oil and heavy oil that have passed through the distillation process are supplied to the hydrogenation process.

The place where the distillation residue from which the ash content has been removed is added is not particularly limited, and it can be added immediately before the distillation process, at the liquefaction process, at the hydrogenation process, or the like. In addition, the ash removal rate is not particularly limited, but
In order to reduce the amount of distillation residue to be added and increase the amount of distillation throughput, it is desirable that the ash removal rate be as high as possible. By circulating the distillation residue from which ash has been removed in the liquefaction and hydrogenation processes,
The distillation residue from which the ash has been removed is further hydrocracked to produce liquefied oil, which ultimately improves the yield of liquid from coal.

(Example) Next, the present invention will be explained by examples.

Badr River coal having the analytical values shown in Table 1 was liquefied using a coal liquefaction facility with a processing capacity of 52/h under the operating conditions shown in Table 2, and the material balance and properties of the resulting distillation residue were investigated. The results are shown in Table 3 as a comparative example.

Table 3 (Comparative Example) Table 4 shows, as an example, the material balance when 15 wt% of the distillation residue from Table 3 from which ash was removed was added to raw coal and recycled to the coal liquefaction process. Note that the operating conditions are the same as in Table 2.

Comparing Table 3 and Table 4, it is seen that in Table 4 of the present invention, the liquid yield is increased by circulating the distillation residue from which ash has been removed to the coal liquefaction process.

Figure 2 shows the properties of distillation residue when varying amounts of distillation residue from which ash has been removed immediately before the distillation process are added as another example, and as a comparative example, coal that has been deashed in advance is shown. The properties of the distillation residue obtained when liquefying the ash were shown by varying the deashing level.

From Figure 2, the softening point and pour point, which are indicators of the fluidity of the distillation residue, are closely related to the amount of toluene solubles in the distillation residue, and as the amount of toluene solubles increases, the softening point and pour point It is observed that the fluidity of the remaining residue is improved. Furthermore, from FIG. 2, it is recognized that the example exhibits almost the same effect as the comparative example. On the other hand, the size of the equipment required for these deashing is 1.00 per 100 pieces of raw coal, whereas in the comparative example, 200 pieces of equipment are required for a yield of 50%. Approximately 30 installations are sufficient in the exemplary embodiment. Therefore, it is possible to reduce the size of the processing equipment required for deashing,
It is recognized that this method is effective in reducing equipment costs and operating costs.

(Effects of the Invention) According to the present invention, the following effects are observed.

(a) Stable operation of the liquefaction plant can be achieved at the same time as liquid yield and solvent for coal liquefaction are secured.

(b) Since it can be supplied to the ash liquefaction process which has the effect of promoting coal liquefaction, it is effective in reducing the amount of catalyst used.

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

(d) Compared to the case of deashing in advance or the case of deashing immediately before the distillation process, the processing equipment can be made smaller and its operating cost can be reduced.

(e) By circulating the distillation residue to the liquefaction process, a liquid is generated from the distillation residue and the liquid yield is improved.

[Brief explanation of the drawing]

FIG. 1 is a flow sheet of one embodiment of the present invention. FIG. 2 is an explanatory diagram showing the properties of distillation residues obtained in Examples and Comparative Examples.

Claims (1)

[Claims] A method for liquefying coal, comprising removing ash from a distillation residue obtained when distilling a coal liquefaction product, and re-adding the distillation residue from which the ash has been removed to a coal liquefaction process.