JP5334433B2 - Production method of ashless coal - Google Patents

Description

  The present invention relates to a method for producing ashless coal, and in particular, to a method for producing ashless coal for obtaining ashless coal from which ash is removed from coal.

  Coal is widely used as a fuel for thermal power generation and boilers, or as a raw material for chemical products, and development of a technique for efficiently removing ash in coal is strongly desired as one of environmental measures. For example, in a high-efficiency combined power generation system using gas turbine combustion, an attempt has been made to use ashless coal from which ash has been removed as a fuel to replace liquid fuel such as LNG. Attempts have also been made to use ashless coal as coking coal for ironmaking coke such as blast furnace coke.

The following methods have been proposed as methods for producing ashless coal.
For example, a coal raw material and a solvent are mixed to prepare a slurry, and the obtained slurry is heated to extract a coal component soluble in the solvent, and from the slurry, a solution portion containing a coal component soluble in the solvent A method for producing ashless coal is known, in which a ashless coal is obtained by separating the solvent from the solution portion and then separating the solvent from the solution portion (Patent Document 1).

However, when a filtration method or a centrifugal separation method is used as a method for separating the solution portion and the non-solution portion from the slurry, it is difficult to implement industrially. For example, when a filtration method is used, frequent replacement of the filter aid is necessary, and continuous treatment is difficult. Further, for example, when a centrifugal separation method is used, clogging with a coal component (RC) insoluble in a solvent is likely to occur, and continuous treatment is difficult.
Japanese Patent Laid-Open No. 2005-120185

  Therefore, when ashless coal was produced using gravity sedimentation method, in which solvent-insoluble components such as ash are gravity settled, and the separation process is performed continuously, the problem is that depending on the brand of coal, the sedimentation rate is extremely slow. occured. For this reason, fine solvent-insoluble components that have not settled stay in the upper part of the sedimentation tank, and as a result, ash cannot be removed sufficiently. In order to solve such problems, the sedimentation tank area and height are increased, the sedimentation tank is enlarged, the liquid ascending flow rate is decreased, the sedimentation time is secured sufficiently, or the coal concentration is lowered to reduce the particle size. Although measures such as suppressing interference between the two can be considered, there were technical difficulties and production cost increase in manufacturing a large sedimentation tank.

  The present invention has been made in view of the above circumstances, and can improve the sedimentation rate of solvent-insoluble components in the gravity sedimentation method, and can produce ashless coal from which ash is sufficiently removed with high efficiency and low cost. It aims at providing the manufacturing method of ash coal.

The present invention provides a slurry preparation step of preparing a slurry by mixing a coal raw material in which caking coal is mixed with coal having a slow sedimentation rate of a solvent-insoluble component and a solvent;
An extraction step of heating the slurry obtained in the slurry preparation step to extract a coal component soluble in a solvent;
A separation step of separating, from the slurry obtained in the extraction step, a solution portion containing a coal component soluble in a solvent and a non-solution portion containing a coal component insoluble in a solvent by gravity sedimentation; and the separation step Ashless coal acquisition step of obtaining ashless coal by separating the solvent from the solution portion separated in step;
It is related with the manufacturing method of ashless charcoal characterized by including.

  According to the method for producing ashless coal according to the present invention, the sedimentation rate of the solvent-insoluble component is improved when the gravity sedimentation method is performed. Therefore, ashless coal from which the ash has been sufficiently removed can be produced with high efficiency and at low cost.

The method for producing ashless coal according to the present invention is a method for producing ashless coal by sufficiently removing solvent-insoluble components such as ash inevitably contained in the coal from the coal. The method for producing ashless coal according to the present invention will be described in detail with reference to FIG. FIG. 1 is a schematic view showing an example of an ashless coal production apparatus for carrying out the ashless coal production method of the present invention.
In the present specification, the solvent-insoluble component is a coal component such as ash that remains without being dissolved in the solvent or coal containing the ash (that is, ash coal) even when the coal is dissolved / extracted with a solvent. It is an inorganic component contained in or coal components that are not extracted by the solvent, and is derived from organic components that have a relatively high molecular weight and developed a crosslinked structure. Hereinafter, the solvent-insoluble component may be referred to as “RC component”. On the other hand, a solvent-soluble component is a coal component that can be dissolved in a solvent, and is mainly derived from an organic component in coal that has a relatively small molecular weight and has not developed a crosslinked structure.

  The method for producing ashless coal according to the present invention includes a slurry preparation step, an extraction step, a separation step, and an ashless coal acquisition step, and further includes a by-product coal acquisition step as desired. Hereinafter, each step will be described.

<Slurry preparation process>
The slurry preparation step is a step of preparing a slurry by mixing a coal raw material and a solvent, and is performed in the slurry preparation tank 1 in FIG.

  The coal raw material used is a mixture of caking coal and caking coal. Thereby, RC component which appears in the extraction process mentioned later can be quickly settled in a separation process. The details of the mechanism of such a phenomenon are not clear, but are thought to be based on the following mechanism. When coking coal is used alone as raw material to produce ashless coal, in the separation process by gravity sedimentation method, the sedimentation rate of RC component is sufficiently fast, clarification in the upper part of the sedimentation tank proceeds, and the ash concentration is very high. Less ashless coal can be produced. This is because the cohesiveness of the RC component of caking coal is good. The inventors of the present invention have discovered, after diligent efforts, that such a cohesiveness-promoting factor lies in the adhesive component that is relatively contained in the coking coal together with the RC component. The adhesive component is in a semi-dissolved state in the extraction step and has high adhesiveness, so that it adheres to the RC component and further promotes the adhesion between the RC components. Specifically, the adhesive component has a property of softening and melting in the extraction temperature range and is present in the slurry in a semi-dissolved state (semi-extracted state) in the extraction process, and as a result, acts as a binder that aggregates RC component particles. Therefore, by adhering caking coal to coal with poor RC component agglomeration, the adhesive component (binder substance) that emerges from caking coal during the extraction of mixed coal adheres to and agglomerates between RC components. It is thought that it promotes.

  The caking coal is caking coal used for coke production, and has a softening start point of 420 ° C. or less, particularly 360 ° C. to 420 ° C., and a maximum fluidity in a Gieselar plastometer test. Is a logarithmic representation of 2 or more, especially 2-5 coal. Even if coal whose softening start point is too high or the maximum fluidity is too low is used, the expected binder effect cannot be obtained, and as a result, the sedimentation rate of the RC component cannot be improved effectively.

  In the present specification, the softening start point and the maximum fluidity are values measured by the Gieseller Plastometer test.

As the caking coal, those classified into categories B ₁ , B ₂ , and C defined by the Japanese coal classification method (JIS M 1002-1978) can be used.
For example, the coal classified into the categories B ₁ and B _{2 represents} a calorific value of 8400 kcal / kg or more among so-called “rubber blue coal”.
Further, for example, the coal classified into the category C indicates a calorific value of 8100 or more and less than 8400 kcal / kg among so-called “brick blue coal”.

The calorific value specified by the coal classification method (JIS M 1002-1978) is a value calculated based on the following equation.
Calorific value (corrected anhydrous ashless base) = calorific value / (100-1.08 x ash-moisture) x 100

  The mixing ratio of caking coal is not particularly limited as long as the object of the present invention is achieved. Usually, the binder effect is recognized at a ratio of 4% by weight or more in the total coal supplied (general coal + caking coal). It is done. From the viewpoint of more effectively exhibiting the binder effect, the mixing ratio is preferably 5% by weight or more, particularly preferably 5 to 50% by weight, more preferably 5 to 20% by weight, and further preferably 5 to 10% by weight. . Even if the mixing ratio is set to a value exceeding 50% by weight, the effect of addition only becomes saturated.

  Steam coal is usually used for power generation, blast furnace pulverized coal injection (PCI), so-called caking coal or non-slightly caking coal used for coke production, etc. Coal that is not coking coal. Such steaming coal is, in particular, a coal that has poor softening meltability or no softening meltability, and does not show softening fluidity in the Gieseller Plastometer test, or the maximum fluidity is logarithmically displayed. It is less than 2 coal.

As steam coal, those classified into categories D, E, F ₁ and F ₂ defined by Japanese coal classification method (JIS M 1002-1978) can be used.
For example, the coal classified into Category D indicates a calorific value of 7800 or more and less than 8100 kcal / kg among so-called “subbituminous coal”.
Further, for example, coal classified into Category E indicates a calorific value of 7300 kcal / kg or more and less than 7800 kcal / kg in so-called “subbituminous coal”.
Further, for example, the coal classified into the category F ₁ indicates a calorific value of 6800 or more and less than 7300 kcal / kg among so-called “brown coal”.
Further, for example, the coal classified into the category F ₂ indicates a calorific value of 5800 or more and less than 6800 kcal / kg among so-called “brown coal”.

  A solvent will not be restrict | limited especially if coal can be melt | dissolved, For example, the oil component derived from coal is used preferably. The oil component derived from coal is an oil component born from coal, and as such an oil component derived from coal, for example, a non-hydrogen donating solvent mainly containing a bicyclic aromatic compound is preferably used.

  The non-hydrogen donating solvent is a coal derivative which is a solvent mainly composed of a bicyclic aromatic compound purified mainly from a carbonization product of coal. Since this non-hydrogen donating solvent is stable even in a heated state and has excellent affinity with coal, the proportion of coal components extracted into the solvent (hereinafter also referred to as “extraction rate”) is high. It is a solvent that can be easily recovered by methods such as distillation. The recovered solvent can be recycled for improving economic efficiency.

  The main components of the non-hydrogen donating solvent include naphthalene, methylnaphthalene, dimethylnaphthalene, trimethylnaphthalene, etc., which are bicyclic aromatic compounds, other naphthalenes having an aliphatic side chain, biphenyl, Alkylbenzenes with long aliphatic side chains are included.

  The boiling point of the solvent is not particularly limited. For example, from the viewpoint of pressure reduction in the extraction step and the separation step, extraction rate in the extraction step and solvent recovery rate in the ashless coal acquisition step, etc., 180 to 300 ° C. In particular, those of 240 to 280 ° C. are preferably used.

  The density | concentration of the coal raw material (mixed coal) with respect to a solvent is not restrict | limited in particular, Usually, the range of 10-50 weight% is preferable on a dry coal basis, and the range of 20-35 weight% is more preferable.

<Extraction process>
The extraction step is a step of heating the slurry obtained in the slurry preparation step to extract a coal component (solvent soluble component) soluble in the solvent. In FIG. To be implemented. Specifically, the slurry prepared in the slurry preparation tank 1 is once supplied to the preheater 3 by the pump 2 and heated to a predetermined temperature, then supplied to the extraction tank 4 and stirred at the predetermined temperature while being stirred by the stirrer 40. And extraction is performed.

The heating temperature of the slurry in the extraction step is not particularly limited as long as the solvent-soluble component can be dissolved. For example, from the viewpoint of sufficient solubilization of the solvent-soluble component and improvement of the extraction rate, preferably 300 to 420 ° C. In particular, the range is 360 to 400 ° C.
The heating time (extraction time) is not particularly limited, but is preferably 10 to 60 minutes from the viewpoint of sufficient dissolution and extraction rate. The heating time is the total heating time in the preheater 3 and the extraction tank 4 in FIG.

  The extraction process is performed in the presence of an inert gas. Contact with oxygen in the extraction process is dangerous because it may ignite. As the inert gas used in the extraction step, inexpensive nitrogen is preferably used, but is not particularly limited.

  The pressure in the extraction step is preferably 1.0 to 2.0 MPa, although it depends on the temperature at the time of extraction and the vapor pressure of the solvent used. When the pressure is lower than the vapor pressure of the solvent, the solvent is volatilized and is not trapped in the liquid phase and cannot be extracted. In order to confine the solvent in the liquid phase, a pressure higher than the vapor pressure of the solvent is required. On the other hand, if the pressure is too high, the cost of the equipment and the operating cost increase, which is not economical.

<Separation process>
The separation step is a step of separating the solution portion and the non-solution portion from the slurry obtained in the extraction step by gravity sedimentation. Here, the solution portion refers to a solution portion in which a solvent-soluble component is dissolved, and is hereinafter also referred to as a supernatant. A non-solution part means the slurry part containing a solvent insoluble component, and is also hereafter called solid content concentrate. In FIG. 1, the separation step is performed in the gravity settling tank 5. Specifically, the slurry is separated into a supernatant liquid as a solution part and a solid concentrate as a non-solution part. The supernatant liquid in the upper part of the gravity sedimentation tank 5 passes through the filter unit 6 as needed, and is discharged to the solvent separator 7, and the solid content concentrate settled in the lower part is discharged to the solvent separator 8.

  The gravitational sedimentation method is a method in which a slurry is retained in a tank to settle and separate solvent-insoluble components using gravity. A continuous separation process is possible by continuously discharging the supernatant from the top and the solid concentrate from the bottom while continuously supplying the slurry into the tank.

  The time for maintaining the slurry in the gravity settling tank 5 is a time required for separating the slurry into a supernatant and a solid concentrate, and is not particularly limited, but in the present invention, it is 30 to 120 minutes. Sufficient separation can be achieved in a relatively short time. This is because in the present invention, precipitation of solvent-insoluble components is promoted.

  The gravity sedimentation tank 5 is preferably heated or / and pressurized in order to prevent reprecipitation of solvent-soluble components eluted from the raw coal. The heating temperature is usually preferably in the range of 300 to 370 ° C. Usually, the pressure is preferably in the pressure range of 1.0 to 2.0 MPa.

<Ashless coal acquisition process>
The ashless charcoal acquisition step is a step of separating the solvent from the solution portion separated in the separation step to obtain ashless coal that is a modified coal, and is performed by the solvent separator 7 in FIG.

  As a method for separating the solvent from the solution part (supernatant liquid), a general distillation method, an evaporation method (spray drying method, etc.), etc. can be used. The separated and recovered solvent is circulated to the slurry preparation tank 1. Can be used repeatedly. By separating and collecting the solvent, ashless coal (HPC) substantially free of ash can be obtained from the supernatant. Ashless coal contains little ash, has no moisture, and exhibits a higher calorific value than raw coal, such as steam coal. Furthermore, the softening and melting property, which is a particularly important quality as a raw material for iron-making coke, has been greatly improved, so that the obtained HPC has a good softening and melting property even if the raw material coal does not have a softening and melting property. Become. Therefore, ashless coal can be used as a blended coal for coke raw materials. Moreover, it can also be used as a combination charcoal by mixing with the byproduct charcoal mentioned later.

<By-product coal acquisition process>
The byproduct charcoal acquisition step is performed as necessary, and is a step of separating the solvent from the non-solution part separated in the separation step to obtain byproduct charcoal, and is performed by the solvent separator 8 in FIG.

  The method for separating the solvent from the non-solution part (solid concentrate) can use a general distillation method or evaporation method as in the ashless coal acquisition step described above. It can be circulated to the slurry preparation tank 1 and used repeatedly. By separation and recovery of the solvent, by-product coal (RC) in which solvent-insoluble components including ash and the like are concentrated can be obtained from the solid concentrate. By-product charcoal contains ash, but has no water and has a sufficient calorific value. Although the by-product coal does not show softening and melting properties, the oxygen-containing functional groups are eliminated, so that when used as a blended coal, it inhibits the softening and melting properties of other coals contained in this blended coal. It is not a thing. Therefore, this by-product coal can be used as a part of the blended coal of coke raw material in the same way as ordinary non-slightly caking coal, and is used for various fuels without being used as coke raw coal. It is also possible. The by-product coal may be discarded without being collected.

  Although the present invention is as described above, in carrying out the present invention, within the range that does not adversely affect the respective steps, for example, during or before and after each step, for example, a coal pulverizing step for pulverizing a coal raw material, Other steps such as a removal step of removing unnecessary substances such as garbage and a drying step of drying the obtained ashless coal may be included.

<Experimental example 1>
Coal A (general coal) or coal B (caking coal) shown in Table 1 was used as the raw material coal. Coal A and Coal B were classified into Category D and B1 in the Japanese coal classification method (JIS M 1002-1978), respectively.
As the solvent, a coal-derived dry distillation oil component (Mechinaf-H, manufactured by Seachem Corporation) having a boiling point of 254 ° C. was used. The composition was a bicyclic aromatic compound mainly composed of 1-methylnaphthalene.

  A solvent was mixed with raw material coal to prepare a slurry (slurry preparation step). The mixing ratio of the raw coal was such a ratio that the initial RC concentration in the slurry used for the separation step became a predetermined value. This slurry was pressurized with 1.2 MPa of nitrogen and extracted in an autoclave with an internal volume of 30 L under the conditions of 380 ° C. and 1 hour (extraction process). This slurry was allowed to stand for 60 minutes in a batch-type gravity settling tank maintained at 350 ° C., and the sedimentation behavior of the insoluble component (RC) was examined (separation step). The initial RC concentration in the slurry subjected to the separation step was 10% by weight when either coal was used.

The concentration distribution of RC in the sedimentation tank height direction when it was allowed to stand for 60 minutes in a batch gravity sedimentation tank was measured and compared between Coal A and Coal B. The results are shown in FIG. H is the height of the measurement position from the sedimentation tank bottom, H ₀ represents the sedimentation tank height.
The RC of coal A has a slow sedimentation rate, and the RC concentration in the upper part of the sedimentation tank was as high as about 1% by weight even after standing for 60 minutes.
The RC of coal B had a fast sedimentation rate, the RC concentration in the upper part of the sedimentation tank was 0.02% by weight, and was clarified 50 times as compared with coal A.

<Experimental example 2>
The same coal A, coal B, and solvent as in Experimental Example 1 were used.
Experimental example, except that coal A and coal B were mixed and used at a predetermined ratio, and the concentration of the mixed coal was adjusted so that the initial RC concentration when the mixed coal was extracted was 10% by weight. In the same manner as in No. 1, the slurry preparation step, the extraction step and the separation step were performed, and the sedimentation behavior of the insoluble component (RC) was examined. The results are shown in FIG. From FIG. 3, it is clear that the mixing of coal B has the effect of promoting aggregation and sedimentation, and clarification is significantly promoted. When coal B was mixed, clarification progressed about 10 times compared to coal A alone, and the effect of improving the sedimentation rate of RC by coal B mixing could be confirmed.

Thereafter, from the supernatant obtained in the separation step, the solvent was separated and removed by distillation to obtain ashless coal. The ash content in the obtained ashless coal was measured.
When coal B was mixed, the ash content in the ashless coal was less than 0.5% by weight.
When coal B was not mixed, the ash content in ashless coal was about 2% by weight.

  The ashless coal produced by the method according to the present invention is useful as a raw material for thermal power generation and boiler fuel, a high-efficiency combined power generation system, and steelmaking coke.

It is a schematic diagram of the manufacturing apparatus for demonstrating each process in the manufacturing method of ashless coal of this invention. 6 is a graph created in Experimental Example 1. 10 is a graph created in Experimental Example 2.

Explanation of symbols

  1: slurry preparation tank, 2: pump, 3: preheater, 4: extraction tank, 5: gravity settling tank, 6: filter unit, 7: 8: solvent separator, 40: stirrer.

Claims (6)

A slurry preparation step in which caking coal is mixed with general coal, and a slurry is prepared by mixing a coal raw material and a solvent in which the mixing ratio of caking coal in the total coal is 4 to 50% by weight ;
An extraction step of heating the slurry obtained in the slurry preparation step to extract a coal component soluble in a solvent;
A separation step of separating, from the slurry obtained in the extraction step, a solution portion containing a coal component soluble in a solvent and a non-solution portion containing a coal component insoluble in a solvent by gravity sedimentation; and the separation step Ashless coal acquisition step of obtaining ashless coal by separating the solvent from the solution portion separated in step;
The manufacturing method of the ashless coal characterized by including.   The method for producing ashless coal according to claim 1, wherein the mixing ratio of caking coal in the total coal is 5 to 50% by weight.   The method for producing ashless coal according to claim 1 or 2, wherein the softening start point of the caking coal by the Gisela plastometer test is 420 ° C or less, and the maximum fluidity is 2 or more in logarithm.   The manufacturing method of the ashless coal in any one of Claims 1-3 using the oil component derived from coal whose boiling point is 180-300 degreeC as a solvent.   The manufacturing method of the ashless coal in any one of Claims 1-4 which further includes the byproduct ash coal acquisition process which isolate | separates a solvent from the non-solution part isolate | separated at the said isolation | separation process, and obtains byproduct coal.   The method for producing ashless coal according to any one of claims 1 to 5, wherein the separated solvent is circulated to the slurry preparation step.

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