JPS6051784A - Method of liquefying brown coal - Google Patents

Abstract

PURPOSE:To allow secondary hydrogenation to proceed efficiently by removing efficiently pre-asphaltene component, by carrying a gravity precipitation treatment by using a specified org. solvent in a solvent-refined coal deashing stage after the primary hydrogenation in a two-stage hydrogenation method for brown coal. CONSTITUTION:Brown coal is mixed with a solvent, the resulting slurry is subjected to a primary hydrogenation in the presence of an iron catalyst at a high temp. under a high pressure, and distillation (1) is carried out. In the distillation (1), the solvent-refined coal is recovered by recovering an equilibrium solvent, and naphtha can be obtd. as a product. Since ash is still contained in the solvent-refined coal obtd. by the distillation (1), a gravity precipitation treatment is carried out by using an org. solvent having a delta value of 7.4-8.5 as a deashing solvent to thereby reduce the quantity of pre-asphaltene component therein to 20wt% or below, thus preventing the hydrogenation catalyst in the second hydrogenation stage from being deactivated.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for liquefying lignite, and in particular, in a liquefaction method using a two-stage hydrogenation method, solvent refined coal (S
This invention relates to a lignite liquefaction method that efficiently removes pre-asphaltene components along with ash in the deashing process of RC, and allows secondary hydrogenation to proceed efficiently.

Due to the recent resource and energy situation, j! The technology to liquefy the abundant coal of U-Zangjing has attracted attention and the liquefaction technology for lignite, which accounts for most of the coal reserves, is being rapidly advanced. Among them, one of the representative methods is the hydrogenation and liquefaction method in which lignite is mixed with a solvent and a catalyst and hydrogenated at high temperature and pressure in the presence of hydrogen to obtain SRC and liquefied oil.

By the way, in order to obtain a high yield of liquefied oil using the hydrogenation liquefaction method, it is possible to increase the hydrogen decomposition from SRC to liquefied oil by making the reaction conditions harsher, but in this method, the liquefied oil produced is further decomposed. The yield of liquefied oil actually decreases. As a solution to these problems, a two-stage hydrogenation and liquefaction method has been proposed, in which the hydrogenated product is distilled to recover liquefied distillate oil, and then the remaining SRC is hydrogenated again, and has achieved certain results. In other words, the two-stage hydrogenation and liquefaction method involves mixing lignite powder with a suitable solvent, adding a Fet-based catalyst to the mixture, performing primary hydrogenation at high temperature and pressure in the presence of hydrogen, and distilling the product. Separation into liquefied oil and residual oil (including ash and catalyst). After deashing the residual oil to obtain SRC, it is added to MO% W% C0% Ni, which has higher hydrogenation activity than Fe-based catalysts.
The SRC that was not completely liquefied in the primary hydrogenation is further decomposed and the liquefied oil is recovered. As is well known, the above-mentioned deashing treatment is carried out to prevent a decrease in the activity of the secondary hydrogenation catalyst due to ash content, but according to what the present inventors have confirmed through experiments, the secondary water It was confirmed that the catalytic activity of the added catalyst was significantly reduced not only by the ash content but also by the pre-asphaltene component in the SRC. Based on this confirmation result, the S obtained by primary hydrogenation
We established a method of performing secondary hydrogenation after once removing pre-asphaltene from RC, and filed a patent application (Japanese Patent Application No. 57-284541).

The present invention was carried out as part of research to improve the efficiency of secondary hydrogenation and liquefaction in the two-stage hydrogenation and liquefaction method, and in particular, in the deashing step performed after the first hydrogenation step,
By specifying the solubility parameter (δ) of the deashing solvent and setting the deashing conditions appropriately, the pre-asphaltene component, which is the main cause of deactivation of the secondary hydrogenation catalyst, is removed together with the ash content, thereby increasing the hydrogenation and liquefaction efficiency. It is intended to increase the That is, the composition of the hydrogenation and liquefaction method according to the present invention is that lignite is mixed with a liquefaction solvent and a hydrogenation catalyst, and primary hydrogenation is performed at high temperature and high pressure in the presence of hydrogen, resulting in a hydrogenated product. S
In the two-stage hydrogenation and liquefaction method for lignite in which RC is deashed and then subjected to secondary hydrogenation, in the deashing step, 2
The solubility parameter (δ) at 5°C is 7.4 to 8.
5 using an organic solvent and carrying out gravity sedimentation to remove the above S.
The gist of this method is to reduce the pre-asphaltene component in RC to 20% by weight or less.

In the present invention, the pre-asphaltene component is, for example, “
It is defined as a substance that is soluble in pyridine, quinoline, or tetrahydrofuran and insoluble in benzene or toluene, as shown in ``Catalyst Vol. ) Also, if a large amount is contained in SRC, the secondary hydrogenation catalyst will be deactivated in a short time as described above, making it impossible to increase the recovery rate of liquefied oil. However, as detailed below, if an organic solvent with a solubility parameter (δ) in a specific range is used as a deashing solvent and deashing is carried out by gravity sedimentation under specific temperature conditions, the deashing process can be completed. The pre-asphaltene component is removed as an insoluble matter, and a decrease in the activity of the secondary hydrogenation catalyst is prevented as much as possible.

By the way, as mentioned above, from the sole purpose of removing pre-asphaltene components in the primary hydrogenation product, it is sufficient to select and use an organic solvent with a low solubility parameter (δ). If it is too low, a considerable amount of the shellfish among the benzene soluble components (BS) and hexane soluble components (H5) in the SRC, which are to be supplied as secondary hydrogenation raw materials, will be removed as insoluble matter, making it difficult to recover liquid water and oil. The display will be significantly reduced. Therefore, in order to effectively utilize the above idea industrially, it is necessary to use a deashing solvent to dissolve as much of the BS and H5 components as possible without dissolving the ash and pre-asphaltene in the primary hydrogenation product. It is necessary to select a solvent that can suppress the loss of the secondary hydrogenation raw material as much as possible.

Therefore, the present inventors investigated the solubility parameters of each mild organic solvent for SRCC with a typical component composition obtained by primary hydrogenation, but with the ash removed in advance and only organic substances (pyridine soluble component (PS)). (value at 8225°C) and the solubility of the above SRC component was investigated. S used
The component ratios based on the solubility of RC in pyridine, benzene, and hexane are shown in Table 1 below. In addition, in the experiment, the SRC was 4 times the SRC (weight ratio).
Dispersed in a solvent of 25% at a temperature of -80°C, the critical temperature of the solvent.
After standing for a minute, the soluble and insoluble components were collected.

Table 1 Component ratio of SRC However, PS: Pyridine soluble component Bl: Benzene insoluble component BS: Benzene soluble component Hl: Hexane insoluble component H5: Hexane soluble component The results are as shown in Figure 1, and the solubility of the solvent As the parameter (δ) increases, the amount of solvent-soluble components in the SRC increases. In other words, when using a solvent with (δ) of 7.8, the soluble content is only 8o96, but when (δ) is 9.0
When this solvent is used, 95% of the SRC is dissolved. Here, it can be seen that (δ) of a solvent in which the BI component corresponding to the pre-asphaltene component of 5RC (PS) is insoluble and suitable as a secondary hydrogenation raw material, and the S component is soluble is approximately 8.2. . However, as is well known, SRC is a complex mixture of many types of hydrogen cracked products, and it is not possible to completely separate the BI and BS components, and even the BI component contains a small amount of BS. Even if it is a BS component, a small amount of BI component will also be mixed in. Moreover, the component ratio of SRC itself varies depending on the type of lignite used as the starting material, primary hydrogenation conditions, etc. The range of fluctuation in the SRC component ratio is considered to be about 2,595 above and below the average component ratio shown in Table 1. Therefore, when this fluctuation range is applied to FIG. 4 to determine the preferred range of the solubility parameter (δ), the range (δ) is 7.4 to 8.5, as shown by the broken line in FIG. By the way, if (δ) is less than 7.4, a large amount of BS and BI will be simultaneously removed as insoluble components along with BI in the deashing process, resulting in a large loss as a raw material for secondary hydrogenation, resulting in a loss of liquefied oil. Collection amount decreases. On the other hand, when (δ) exceeds 8.5, a considerable amount of BI in the SRC is transferred to the SRC for secondary hydrogenation.
Since it gets mixed into the water, it becomes impossible to effectively prevent the deactivation of the secondary hydrogenation catalyst. As is clear from the above, the optimum solubility parameter (δ) of the deashing solvent is selected from the above-mentioned suitable range according to the component ratio of SRC obtained by primary hydrogenation. The most common is S with the average component ratio as shown in Table 1 (and Figure 1) above.
A solvent (e.g. cyclohexane) with a solubility parameter of approximately 8.2, with an optimal (δ) value corresponding to the RC number.
It is. Although it is of course possible to use a general industrial organic solvent as the deashing solvent, it is also possible to use naphtha with an appropriate (δ) value obtained by distillation after secondary hydrogenation, as detailed below. For example, it is very advantageous that the deashing solvent can be supplied in a closed system from the hydrogenation and liquefaction plant itself. That is, the purified SRC after deashing is subjected to a secondary hydrogenation treatment as described above, and then the liquefied oil is recovered by distillation.
Since the value can be kept within the above-mentioned preferred range by controlling the secondary hydrogenation conditions, this naphtha component can be recycled and used as a deashing solvent.

Incidentally, FIG. 2 shows a comparison of solvent-soluble components in primary hydrogenated SRC when cyclohexane or secondary naphtha is used as a deashing solvent. However, the secondary naphtha has a (δ) value of 8.1 obtained by performing secondary hydrogenation at 400°C and distilling it, and the secondary naphtha obtained by performing secondary hydrogenation at 860°C and distilling it (δ). ) A secondary naphtha with a value of 8.9 was used. As is clear from Figure 2, when cyclohexane or secondary naphtha with a (δ) value of 8.1 is used, there is almost no loss of BS or I (S) in the primary hydrogenated SRC. The BI content can be reduced to about 115. However, if a secondary naphtha with too high a δ) value is used, the BI content will be reduced to 6
Approximately 5% f has been mixed into purified SRC as a soluble component, making it impossible to achieve the object of the present invention.

By the way, as mentioned above, in the present invention, a considerable amount of pre-asphaltene components are removed as insoluble matter in the deashing process, so the sludge is higher in viscosity than the sludge to be separated in the normal deashing process, and as a result, There is a tendency for the gravity settling efficiency of ash to decrease. Therefore, we investigated the treatment conditions to allow gravity sedimentation to progress efficiently.
It has been found that the ash can be efficiently separated by performing gravity sedimentation at a temperature higher than [the critical temperature of the dehulling solvent -80°C]. However, as the deashing treatment temperature falls below the above temperature, the viscosity of the deashing treatment liquid increases, the sedimentation rate of the sludge decreases, and the efficiency of gravity sedimentation deteriorates. There is no particular upper limit for the deashing temperature, but if the temperature is too high, it will be necessary to heat it to prevent the temperature from falling due to evaporation of the deashing solvent, and convection of the processing liquid in the tank will occur, causing sludge to settle. Since there is a possibility that the temperature may be inhibited on the contrary, it is desirable to suppress the critical temperature to -5°C or lower.

Even if the treatment temperature is set as described above, if a large amount of fine ash is contained, it may be difficult to perform sufficient sedimentation and separation. Therefore, in such a case, prior to the deashing step, the overflow liquid is separated into an overflow liquid containing fine particles of 100 μmφ or less and a bottom flow liquid containing coarse particles using a hydroclone or the like, and the overflow liquid is subjected to primary hydrogenation. A method of reducing the deashing load by returning the bottom effluent to the reaction system and subjecting only the bottom effluent to the deashing process is extremely effective. In this case, since the activity of the iron-based catalyst contained in the fine particles returned to the primary hydrogenation process is quite high, there is almost no possibility that the primary hydrogenation efficiency will be inhibited; It functions as a seed crystal within the strain,
It can also have the secondary effect of contributing to coarsening of fine particles, suppressing coking within the reaction system, and further reducing the deashing load. On the other hand, catalyst components in coarse particles exceeding 100 μmφ have a small specific surface area, so their hydrogenation activity is low, and in addition to not being able to enjoy the above-mentioned advantages of recycling, their sedimentation rate during deashing is also high. After separation, it is sent to the demineralization process.

As described above, the present invention is characterized in that pre-asphaltene components are simultaneously removed during the deashing process, but as a result of various experiments, the pre-asphaltene content in SiC sent to the secondary hydrogenation process must necessarily be zero. It was confirmed that it is not necessary and that a small amount of pre-asphaltene is allowed to be mixed in. Therefore, further research was conducted to clarify the upper limit of the permissible pre-asphaltene content from the viewpoint of preventing deactivation of the secondary hydrogenation catalyst, and the results shown in FIG. 8 were obtained. That is, Fig. 8 shows that using raw SRC with the solvent fractionation composition shown in Table 2 below, five types of refined SRC with different BI component values were extracted using solvents with different (δ) values, and Ni-Mo based It is an experimental graph showing the change in catalyst activity over time when secondary hydrogenation is performed at 400° C. using a catalyst.

Table 2 Raw material SRC components PS, BI, BS, HI, H5 As is clear from Figure 8, which is the same as Table 1, BIffi in SiC is 2
If the amount is less than 0% by weight, there is hardly any decrease in the activity of the secondary hydrogenation catalyst, but if it exceeds 20% by weight, the activity of the catalyst will clearly decrease over time.

From these experimental facts, in order to effectively exhibit the pre-asphaltene removal effect during deashing according to the present invention at an actual operational level, it is necessary to set the (δ) value of the deashing solvent so that the pre-asphaltene content is 20% by weight or less. It is understood that the conditions for the decalcification treatment should be set.

Next, a series of hydrogenation and liquefaction processes including the above-mentioned deashing and pre-asphaltene treatment will be briefly explained based on the flow diagram in Figure 4. The embodiments are not limited, and all modifications and implementations that do not go against the spirit of the above and below are included within the technical scope of the present invention. In the figure, square frames represent processing details, and parentheses represent substances. That is, a slurry obtained by mixing raw material lignite with a solvent is preheated if necessary, and then subjected to primary hydrogenation at high temperature and pressure in the presence of an iron-based catalyst. The type and amount of slurry-forming solvent, conditions for preheating and primary hydrogenation reaction, etc. are not limiting requirements of the present invention. After the primary hydrogenation is completed, gas-liquid separation is performed under reduced pressure if necessary, followed by distillation (1), in which the equilibrium solvent is recovered and SR
C is recovered and naphtha (mixed oil consisting of aromatic compounds, naphthenes, paraffins, etc.) is obtained as a product. Since the SRC obtained by distillation i11 contains ash as described above, it is subsequently subjected to deashing treatment by gravity sedimentation. In the present invention, an organic solvent with a (δ) value of 7.4 to 8.5 is used as a deashing solvent in the deashing process, and at the same time as deashing, the pre-asphaltene component in the SRC is removed to reduce its content. is reduced to 20% by weight or less to prevent deactivation of the hydrogenation catalyst in the next secondary hydrogenation step. In addition, when performing distillation (2) again after deashing and adding a step of recovering the deashing solvent added at the time of deashing, the recovered solvent can also be recycled as the deashing solvent.

In addition, as a deashing solvent, naphtha obtained by distillation (3) after secondary hydrogenation can be used as described later, but initially, naphtha with a predetermined (δ) value left at the end of the previous operation can be used. naphtha,
Alternatively, a separately prepared organic solvent may be used, and after entering a certain running state, secondary naphtha may be supplemented to the extent that it makes up for the shortage of recovered solvent obtained in distillation (2). Furthermore, if fine particles and coarse particles are separated prior to deashing, the overflow containing fine particles should be returned to the primary hydrogenation step (two-dot chain line in Figure 4) as described above, and the bottom containing coarse particles should be It is sufficient to send only the effluent to the deashing process.

The conditions for distillation ftl and distillation (2) are not particularly restricted, but as is clear from Figure 4, at least naphtha fraction (low boiling point fraction), equilibrium solution ts (medium temperature fraction), and
It is desired that it can be fractionated into RC (high temperature distillate).

In the above deashing step, if the pre-asphaltene component in SRC is reduced to 20% by weight or less as described above, a decrease in the activity of the secondary hydrogenation catalyst in the next step is almost prevented, and the refined SRC is
The secondary hydrogenation efficiency of RC can be maintained at a high level. Therefore, by subjecting the obtained secondary hydrogenation product to distillation (3) to recover naphtha and medium oil, it is possible to significantly increase the yield of liquefied oil from raw brown coal. The equilibrium solvent recovered in distillation (3) is used as a secondary hydrogenation solvent, and a portion of the secondary naphtha is returned and used as a deashing solvent. Here, the secondary naphtha (δ
) value is 7.4 to 8.5, as is clear from the above explanation.
Needless to say, it should be within the range of .

The flow diagram of fs5 diagram shows another example, in which the equilibrium solvent obtained in distillation (3) is returned to the primary hydrogenation step, and the distillation (
The example is substantially the same as the example shown in FIG. 4, except that a part of the equilibrium solvent separated in step 1) is extracted as a product.

Next, the hydrogenation conditions are not a limiting requirement of the present invention, and may be determined appropriately taking into consideration the properties of the raw coal, the type of equilibrium solvent, the consumption amount of IA, H2, the type of catalyst, etc. Examples of conditions are as follows.

<Primary hydrogenation> Temperature: 480-480°C Pressure = 150-280Kf/2G Catalyst: Fe2O3 <Secondary hydrogenation> Temperature: 400°C or higher Pressure 150-280Ky/1yn2G catalyst: Co-
Degree of hydrogenation of metal catalysts such as Mo type, Ni MO type, etc.: 8 to 4% The present invention is roughly configured as described above, and the deashing process
Pre-asphaltene, which causes a decrease in the activity of the secondary hydrogenation catalyst, is 2
Since the pre-asphaltene removal treatment was carried out until the amount of asphaltene was reduced to 0.02iffi% or less, the secondary hydrogenation efficiency could be maintained at a high level, and the recovery rate of liquefied oil from raw brown coal could be significantly increased. Furthermore, pre-asphaltenes can be removed simultaneously during the deashing process by simply setting the (δ) value of the deashing solvent appropriately, and the decrease in gravity settling efficiency that occurs due to the simultaneous removal of pre-asphaltenes can be This can be easily dealt with by appropriately adjusting the temperature, so there is no fear that maneuverability will deteriorate. In addition, secondary naphtha is used as a deashing solvent, and there is no need to recycle the solvent, making it economical and providing an extremely practical technology.

[Brief explanation of drawings]

Figure 1 shows the solubility parameter (δ) and SR of the deashing solvent.
A graph showing the relationship between the amount of solvent-soluble components in SRC, Figure 2 is a graph showing the proportion of soluble components in SRC when the deashing solvent dishes are changed, and Figure 8 is a graph showing the relationship between the amounts of solvent-soluble components in SRC. Figure 4.5 is a flowchart showing an example of the present invention.

Claims (1)

[Claims] (1) Brown coal is mixed with a liquefaction solvent and a hydrogenation catalyst, and subjected to primary hydrogenation at high temperature and high pressure in the presence of hydrogen, and the resulting hydrogenated product is solvent-refined coal. After deashing, is it subjected to secondary hydrogenation using a regular hydrogenation catalyst? In the two-stage hydrogenation and liquefaction method of d-coal,
In the above deashing process, an organic solvent having a solubility parameter (δ) at 25°C of 7.4 to 8.5 is used as a deashing solvent, and gravity sedimentation is performed to remove the pre-asphaltene component in the solvent-refined coal. A method for liquefying lignite, characterized by reducing the amount to less than ffi%. (2. In claim 1, prior to the demineralization process by gravity sedimentation, the overflow liquid is separated into an overflow liquid containing fine solid particles of 100 μm or less and a bottom flow liquid containing coarse solid particles,
In this lignite liquefaction method, the overflow liquid is returned to the primary hydrogenation reaction system, and the bottom effluent is subjected to a deashing process. (3) A method for liquefying lignite according to claim 4 or 2, in which naphtha obtained by distillation after secondary hydrogenation is used as a deashing solvent.