JPS6339035B2 - - Google Patents

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention is an improved method for deashing solvent-purified coal in a coal liquefaction process, and more specifically, in carrying out a sedimentation separation method by contacting with an organic solvent. This has been improved so that sediment can be easily discharged.

[Conventional technology]

In the liquefaction process of coal by hydrogenation, one of the important issues is the removal of ash from raw coal. For example, in the solvent refining method for coal, a hydrocarbon solvent with high hydrogen donating property is used to turn the crushed raw material coal into a slurry, which is then subjected to a hydrogenation reaction.The hydrogenation reaction product is then subjected to distillation. Coal-derived ash and liquefaction catalyst will inevitably be mixed into the residue after the light oil is recovered or the medium oil is also recovered.

The above residue is generally called solvent-refined coal, and since it contains components that can be liquefied by hydrogenation, it can be returned to the hydrogenation reaction tower and re-hydrogenated together with the raw materials, or it can be used as a catalyst for high-grade catalysts. Efforts are being made to improve the recovery rate of liquefied oil by supplying it to a packed secondary hydrogenation reaction tower. However, if it is handled while containing ash, there is a risk of clogging the piping system or reaction tower, so it has become a common practice to incorporate a deashing process following the distillation process.

There are various methods that can be applied to this deashing process, but the most commonly used method is the solvent deashing method, which involves bringing an organic solvent into contact with solvent-refined charcoal, separating dissolved substances and insoluble substances, and precipitating the latter. There is. The solvent used in this solvent deashing method has been researched in various fields, and the present applicant has also made proposals such as JP-A-59-84977 and JP-A-58-161043 (JP-A-60-51785). However, depending on the solvent used here, the so-called BI content (benzene insoluble content) and PI content (pyridine insoluble content) may also be added to the insoluble substances side and removed together with the ash content. Therefore, the above-mentioned solvent is sometimes referred to as a deasphalting solvent, and the above-mentioned deashing process is sometimes referred to as a deashing/deasphalting process, but these are all subject to the present invention regardless of the solvent. include.

[Problem that the invention seeks to solve]

Ash, which is an insoluble substance, is in the form of a fine powder, and ash is a highly viscous substance, so when they settle and accumulate at the bottom of the settling tank in a mixed state, the whole becomes viscous and semi-fluid. It has become an object. Therefore, even if the sludge discharge port provided at the bottom of the settling tank is opened, it is difficult to discharge the sludge smoothly, and the sludge must be discharged in a state that involves a considerable amount of the organic solvent present in the upper layer. Must be. However, the sludge discharged in this way contains a considerable amount of organic solvent and substances dissolved in the solvent (low-molecular organic substances), and it is difficult to recover them. Therefore, a method of preparing a separate organic solvent and introducing it into the sedimentation layer to increase fluidity and discharge it (hereinafter referred to as the solvent dilution method)
was proposed, and the emissions of low-molecular-weight organic substances have been reduced.

However, the organic solvent introduced into the settling tank has the ability to dissolve the low-molecular-weight organic substances, and its discharge cannot be completely eliminated, and almost all of the introduced organic solvent is discharged together with the sludge. A problem arises as to how efficiently the organic solvent can be recovered from the sludge after it has been discharged. In other words, the cost of recovering organic solvents (even if vacuum distillation is performed, a high temperature of around 150°C is required) increases, and even then, problems such as odor problems due to the presence of residual organic solvents and problems with the treatment of the recovered solids themselves remain. Although sludge discharge may seem like a trivial matter at first glance, there are many practical inconveniences.

The present invention was developed in consideration of this situation, and it not only improves sludge discharge performance, but also reduces entrainment of low-molecular organic substances and organic solvents into discharged sludge compared to the solvent dilution method. We have conducted various studies in order to provide a method that can reduce the amount of damage as much as possible.

[Means for solving problems]

The present invention, which has succeeded in solving the above problems, is a method for deashing the residue after recovering at least light oil from the hydrogenation reaction product by a solvent deashing method. introducing water into the sedimentation layer formed after contacting the organic solvent;
The gist is that insoluble substances are discharged as an aqueous sludge.

[Effect]

In the present invention, water is introduced into the sedimentation layer, but the actual introduction is carried out during (a) the initial stage of sedimentation separation by adding an organic solvent for deashing and deassignment, and (b) during the progress of sedimentation separation. In either the intermediate stage where the sedimentation separation is completed, or (c) the final stage after the sedimentation separation is completed, the upper part of the sedimentation tank,
It can be fed either from the middle or from the bottom and by any means.

Since the water supplied in this manner has no affinity with the organic solvent and has a high specific gravity, it sinks downward together with insoluble substances. That is, the insoluble substances and the organic solvent are separated, and the insoluble substances are dispersed in water to form a highly fluid aqueous sludge. Therefore, the sludge can be discharged smoothly and the amount of organic solvent mixed into the sludge can be reduced. A part of the organic solvent is discharged together with the aqueous sludge because it is adsorbed by insoluble matter such as ash or particulate matter, or because it is dragged in when the aqueous sludge is discharged. Furthermore, when water is supplied to the bottom of the settling tank, the organic solvent in the sludge layer is also discharged. At this time, since the organic solvent is easily separated from the aqueous layer, the amount of organic solvent attached or adsorbed into the solid content is extremely small, and the treatment after separating the sludge becomes simple.
That is, the conventional organic solvent recovery operation such as vacuum distillation becomes unnecessary, and the handling of the solid content itself is improved.

Next, the temperature of the water introduced into the sedimentation layer will be explained.

The internal environment of a sedimentation separation tank is generally high temperature and high pressure for the purpose of promoting sedimentation separation. The pressure is usually about 5 kg/cm ² G or more, and the temperature varies depending on the type of organic solvent, but it is the critical temperature of the organic solvent.
It is selected from within the range of Tc ~ (Tc - 150℃). Under such conditions, the organic substances attached to or adsorbed on the solid content become softened, causing the solid content to adhere to each other and reducing the fluidity of the sludge. This consideration is also supported by the results of basic experiments shown below.

Figure 2 is a graph showing the relationship between sludge dispersibility and solvent temperature. Solvent refined charcoal and an organic solvent are added to an autoclave, and stirring is continued while gradually changing the temperature inside the autoclave. The liquid (supernatant liquid) was extracted and the solid content concentration was determined. The vertical axis indicates (solid content concentration in supernatant liquid/solid content concentration in all raw materials). A value of 1 on the vertical axis indicates good dispersibility of solids;
This means that the particle size of the solid content is small and the tendency for coarsening due to mutual adhesion is small. On the other hand, a value of 0 on the vertical axis indicates that the dispersibility of the solid content is poor and almost all of the solid content has settled, which means that there is a strong tendency for the solid content to become coarse due to mutual adhesion. Judging from the results of these basic experiments, lowering the temperature inside the settling tank by introducing water is a meaningful means of suppressing the mutual adhesion of solids and improving the fluidity of sludge. It seemed like it would happen.

For these reasons, the present inventor considered it desirable to introduce water at a temperature lower than at least the internal temperature of the sedimentation tank. However, if the temperature of the introduced water is too low and the temperature of the organic solvent layer becomes low, the solids to be settled will not enter the water layer and will remain in the organic solvent layer, making it difficult to achieve the purpose of sedimentation separation. Considering that the temperature of the organic solvent layer is quite high as mentioned above, hot water is generally introduced. There is no problem if the temperature of the organic solvent is the same as the temperature of the water introduced, but if they are different, the temperature after water introduction will be determined by the temperature and amount of both, so the temperature and amount of water introduced should be determined based on these. It should be determined as follows. As a guideline, it is desirable to determine the temperature and amount of water introduced so that the temperature after introducing the water is in the range of (150 to Tc)°C.

〔Example〕

FIG. 1 is an explanatory diagram showing the flow of a deashing process incorporating the method of the present invention, in which an organic solvent and solvent-refined charcoal are introduced into a mixing section and mixed, and then introduced into a sedimentation separation section. Ash and other undissolved substances settle here, and the supernatant liquid is treated separately as deashed and desalted refined coal, but hot water is introduced into the lower part of the sedimentation layer to create a sludge with increased fluidity. Sediment is discharged as At this time, it is advisable to stir the mixture to promote mixing of the sludge and hot water. The extracted sludge is introduced into the oil/water separation section. Here, solids and water are separated as sediment, and the organic solvent is recycled and used. The oil-water separation operation is preferably carried out at a high temperature; at low temperatures, there is a risk that the solid content will migrate to the organic solvent layer.

An example of the material balance in the example was as follows.

Amount of solvent refined coal initially supplied: 20 parts Breakdown [solid content (BI content) 10 parts, BS content 10 parts] Amount of organic solvent initially supplied: 80 parts Amount of hot water (250℃) supplied : 25 parts Supernatant liquid: 75 parts...Breakdown Solvent refined charcoal: 10 parts Organic solvent: 65 parts Discharge sludge (250℃): 25 parts + hot water 25 parts Breakdown Solid content: 15 parts Organic solvent: 15 parts Hot water: 25 parts Solid content in recovered organic solvent from discharged sludge:
0.1% [Effects of the Invention] Since the present invention is configured as described above, the sedimentation layer formed at the bottom of the sedimentation separation section can be smoothly discharged as a sludge with good fluidity. Further, since the discharged sludge is smoothly separated into the aqueous layer and the solvent layer, not only is it easy to recover the solvent from the sludge, but the separated solid content also has a low organic solvent content.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram of the implementation flow of the present invention, and FIG. 2 is a graph showing the relationship between solid content dispersibility and temperature.

Claims (1)

[Claims] 1. After recovering at least light oil from the hydrogenation reaction product, the residue is introduced into a sedimentation tank and brought into contact with an organic solvent, and the precipitated insoluble materials are extracted from the sedimentation tank as discharge sludge. A method for deashing solvent-refined coal using an ash method, the method comprising introducing water into a sedimentation layer and discharging insoluble substances as an aqueous sludge.