JP5255303B2 - Production method of ashless coal - Google Patents

Description

  The present invention relates to a method for producing ashless coal that produces ashless coal from coal.

  Coal is widely used as a fuel for thermal power generation and boilers, or as a raw material for chemicals. In this coal, ash is contained, but in recent years, as one of environmental measures, development of a technique for efficiently removing ash in the coal is strongly desired. Further, in a high efficiency combined power generation system using gas turbine combustion, an attempt has been made to use so-called ashless coal (hypercoal) as a fuel to replace liquid fuel such as LNG (Liquid Natural Gas). Establishing the technology to obtain is an important issue.

  Here, ashless coal is produced by extracting coal with a solvent, separating only the components soluble in the solvent, and then removing the solvent (see, for example, Patent Document 1). ). Because this ashless coal does not dissolve in the solvent, the ashless coal does not substantially contain ash, so it can be used for gas turbine direct injection fuel applications, improving combustion efficiency, reducing coal ash, etc. Attention has been focused on environmentally friendly coal utilization technology. In addition, since this ashless coal exhibits high fluidity under heating and is excellent in thermal fluidity, its applicability to various uses is being studied, such as expected application as a coke raw material. .

In such a general production method of ashless coal, slurry obtained by solvent extraction of coal is subjected to solid-liquid separation by gravitational sedimentation or the like, and ash that is solid content is gravity settled. The ash contained in the liquid component is removed by filtering. By such a manufacturing method, the ash content concentration in ashless coal is reduced to about 0.06 mass% (for example, refer nonpatent literature 1).
JP 2001-26791 A Abstracts of the 50th Annual Meeting of the Japan Institute of Energy Kansai Branch p19-22

However, the conventional method for producing ashless coal has the following problems.
As described above, in the conventional method for producing ashless coal, after the solid-liquid separation, a process of filtering the liquid component is performed. Here, in the solid-liquid separation in which the solid ash is gravity settled, the ash with small particles is the supernatant liquid due to the rise with the rising flow velocity and the dispersion due to the Brownian motion in the solution. Collected in the overflow. Then, by filtering this overflow with a filter, the ash that could not be removed in the solid-liquid separation can be removed to some extent. However, it is difficult to remove particularly ash having a small particle diameter by filtration.

  Even when multistage filtration using a plurality of filters is performed, ash with a small particle diameter passes through the filter and cannot be removed. In particular, ash having a particle size of about 0.5 μm or less, which is less than the mesh length of the filter, is difficult to remove by filtration, and is eventually contained in ashless coal. As a result, with the conventional technology, the ash concentration in ashless coal can be reduced only to about 0.06% by mass. Therefore, in order to further improve the quality of ashless coal, development of a technology for further reducing the ash concentration in the ashless coal is desired.

  The present invention has been made in view of the above-mentioned problems, and its purpose is to remove even ash having a particularly small particle size by filtration to remove ash contained in the liquid component from which the coal component has been extracted. It is providing the manufacturing method of ashless coal which manufactures low ashless coal.

In order to solve the above-mentioned problems, the inventors of the present application have studied the matters described below.
The method for producing ashless coal according to the present invention performs filtration twice, but first, by removing in advance a material that can be removed by filtration in a high temperature state, the recovery rate of ashless coal finally obtained is improves. This is because the rate of loss of coal components due to filtration is constant with respect to the amount of ash to be removed, but the rate of loss of coal components increases as the temperature decreases. Therefore, in order to improve the recovery rate of ashless coal, it is very advantageous to use low ash conditions at the time of low temperature filtration. In addition, when the filtrate contains only ash particles that have been filtered once, the extraction component is deposited only on the fine particles that can pass through the filter, and the particle size of the fine particles increases. When only one filtration is performed, the precipitation of the extracted components occurs evenly from fine particles to huge particles, so the growth rate of the fine particle size of the fine particles that can pass through the filter is reduced and removed by filtration. There is a concern that it will not be possible.
Therefore, as a result of intensive studies, the inventors of the present application conducted filtration twice, and by making the temperature of the filtrate filtered in the second filtration lower than the temperature of the liquid component filtered in the first filtration, the ash concentration The inventors have invented a method for producing ashless coal that produces ashless coal with a very low ash.

  That is, the method for producing ashless coal according to the present invention includes a slurry heating step, a separation step, a first filtration step, a second filtration step, and an ashless coal acquisition step, and the second filtration step. The temperature of the filtrate to be filtered is lower than the temperature of the liquid component to be filtered in the first filtration step.

  According to such a manufacturing method, in the slurry heating step, a slurry in which coal and an aromatic solvent are mixed is heat-treated, and in the separation step, the slurry heat-treated in the slurry heating step is a liquid component in which coal is dissolved. And a solid component containing ash and insoluble coal. Then, in the first filtration step, the liquid component separated in the separation step is filtered, and ash having a particle size of a predetermined size or more contained in the liquid component is removed. Further, by making the temperature of the filtrate filtered in the second filtration step lower than the temperature of the liquid component filtered in the first filtration step, the extracted component in the filtrate is precipitated around the ash content, and the particle size of the fine particles containing the ash content Becomes larger. Thus, in the second filtration step, the filtrate filtered in the first filtration step is further filtered to remove fine particles containing ash, and the ash that could not be removed in the first filtration step is removed. And in an ashless coal acquisition process, an aromatic solvent is removed from the filtrate filtered at the 2nd filtration process, and ashless coal is manufactured.

  According to the method for producing ashless coal according to the present invention, it is possible to remove even ash having a particularly small particle size, which is contained in the liquid component subjected to solid-liquid separation. And it can be manufactured at low cost.

  Next, a method for producing ashless coal according to the present invention will be described in detail with reference to the drawings. In the drawings to be referred to, FIG. 1 is a flowchart for explaining the steps of the method for producing ashless coal, and FIG. 2 is a schematic diagram showing a solid-liquid separation device for performing a gravity sedimentation method.

≪Production method of ashless coal≫
As shown in FIG. 1, the method for producing ashless coal includes a slurry heating step (S1), a separation step (S2), a first filtration step (S3), a second filtration step (S4), and an ashless coal. A charcoal acquisition step (S5).
Hereinafter, each step will be described.

<Slurry heating step (S1)>
The slurry heating step (S1) is a step of preparing a slurry by mixing coal and an aromatic solvent, and heating the slurry containing the coal and the aromatic solvent. And a coal component is heat-extracted by the aromatic solvent by heat-processing a slurry.

  Coal to be used as raw material (hereinafter also referred to as “raw coal”) should be non-slightly caking coal that has little softening and melting properties, or low quality coal such as lignite or sub-bituminous coal. Is preferred. By using inexpensive coal such as these, ashless coal can be produced at a lower cost, so that economic efficiency can be further improved. However, the coal used is not limited to these inferior coals, and bituminous coals may be used.

  In addition, inferior coal here means coals, such as a non-slightly caking coal, a general coal, and a low grade coal. The low-grade coal is coal that contains 20% by mass or more of water and is desired to be dehydrated. Examples of such low-grade coal include lignite, lignite, and sub-bituminous coal. For example, lignite coal includes Victoria coal, North Dakota coal, Belga coal, etc., and sub-bituminous coal includes West Banco coal, Binungan coal, Samarangau coal, and the like. The low-grade coal is not limited to those exemplified above, and any coal containing a large amount of water and desired to be dehydrated is included in the low-grade coal referred to in the present invention.

  Generally, aromatic solvents that dissolve coal include monocyclic aromatic compounds such as benzene, toluene, and xylene, and bicyclic aromatic compounds such as naphthalene, methylnaphthalene, dimethylnaphthalene, and trimethylnaphthalene. . The bicyclic aromatic compound includes other naphthalenes having an aliphatic side chain, and biphenyl and alkylbenzene having a long aliphatic side chain. A bicyclic aromatic compound which is a non-hydrogen donating solvent is preferable.

  The non-hydrogen donating solvent is a coal derivative which is a solvent mainly composed of a bicyclic aromatic and purified mainly from a coal carbonization product. 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 circulated and used repeatedly in order to improve economy.

  The aromatic solvent preferably has a boiling point of 180 to 330 ° C. When the boiling point is less than 180 ° C., the required pressure in the heat extraction or in the separation step (S2) described later increases, and the loss due to volatilization increases in the step of recovering the aromatic solvent. Solvent recovery is reduced. Furthermore, the extraction rate in the heat extraction decreases. On the other hand, when it exceeds 330 ° C., it becomes difficult to separate the aromatic solvent from the liquid component and solid component described later, and the recovery rate of the aromatic solvent is lowered.

  Although the coal density | concentration with respect to an aromatic solvent is based also on the kind of raw material coal, the range of 10-50 mass% is preferable on the basis of dry coal, and the range of 11-25 mass% is more preferable. When the coal concentration with respect to the aromatic solvent is less than 10% by mass, the proportion of the coal component extracted into the aromatic solvent is less than the amount of the aromatic solvent, which is not economical. On the other hand, the higher the coal concentration, the better. However, when it exceeds 50% by mass, the viscosity of the slurry becomes high, and it becomes difficult to move the slurry and separate the liquid component and the solid component in the separation step (S2).

  The slurry heat treatment (heat extraction) in the slurry heating step (S1) is preferably in the range of 300 to 420 ° C. By setting the heating temperature within this range, the bonds between the molecules constituting the coal are loosened, mild thermal decomposition occurs, and the extraction rate becomes the highest. If heating temperature is less than 300 degreeC, it is inadequate to weaken the coupling | bonding between the molecules which comprise coal, and an extraction rate falls. On the other hand, if it exceeds 420 ° C., the pyrolysis reaction of coal becomes very active, and recombination of the generated pyrolysis radical occurs, so that the extraction rate decreases.

  The heating time (extraction time) is a criterion for reaching the dissolution equilibrium, but it is economically disadvantageous to realize it. Therefore, since it varies depending on conditions such as the particle size of the coal, the type of aromatic solvent, etc., it can not be said unconditionally. Usually, after passing through a preheater and reaching a predetermined extraction temperature, it is about 10 to 60 minutes. . If the heating time is less than 10 minutes, the extraction of the coal component tends to be insufficient, while if it exceeds 60 minutes, the extraction does not proceed any further, which is not economical.

  Further, before the transition to the separation step (S2), this heated slurry may be cooled to a temperature at which the solute eluted from the coal does not reprecipitate, for example, about 200 to 360 ° C. By cooling the slurry, subsequent handling becomes easy and excessive thermal decomposition can be avoided. In addition, the pressure in the sedimentation tank can be lowered, and the specification level of valves and the like can be lowered. In addition, about the cooling temperature of a slurry here, the temperature of the liquid component filtered by the 1st filtration process (S3) mentioned later and the temperature of the filtrate filtered by the 2nd filtration process (S4) are considered suitably. Adjust it.

  In this heating extraction, the coal is thermally decomposed to produce aromatic-rich components mainly having an average boiling point (Tb50: 50% distillation temperature) of 200 to 300 ° C. Can be used as part.

  Heat extraction is preferably performed in a non-reducing atmosphere. Specifically, it is performed in the presence of an inert gas. This is because contact with oxygen during heating extraction is dangerous because it may ignite, and the cost increases when hydrogen is used.

  As the inert gas used in the heat extraction, inexpensive nitrogen is preferably used, but is not particularly limited. The pressure in the heat extraction is preferably 1.0 to 2.0 MPa, although it depends on the temperature at the time of heat extraction and the vapor pressure of the aromatic solvent used. When the pressure is lower than the vapor pressure of the aromatic solvent, the aromatic solvent volatilizes and is not trapped in the liquid phase and cannot be extracted. In order to confine the aromatic solvent in the liquid phase, a pressure higher than the vapor pressure of the aromatic 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 step (S2)>
The separation step (S2) is a step of separating the slurry heat-treated in the slurry heating step (S1) into a liquid component and a solid component.
Here, the liquid component means a solution in which coal is dissolved, that is, a solution containing a coal component extracted into an aromatic solvent, and the solid component means a slurry containing ash and insoluble coal insoluble in an aromatic solvent. Say.

  The method for separating the slurry into a liquid component and a solid component in the separation step (S2) is not particularly limited, but it is preferable to use a gravity sedimentation method (the gravity sedimentation method will be described later).

  As a method for separating a slurry into a liquid component and a solid component, various filtration methods and centrifugal separation methods are generally known. However, the filtration method requires frequent replacement of the filter, and the centrifugation method tends to cause clogging with undissolved coal components, and it is not easy to implement these methods industrially. Therefore, it is preferable to use a gravity sedimentation method that allows continuous operation of fluid and is suitable for a large amount of processing at low cost. Thus, from the upper part of the gravity sedimentation tank, the liquid component (hereinafter also referred to as “supernatant liquid”), which is a solution containing the coal component extracted into the aromatic solvent, is transferred to the aromatic solvent from the lower part of the gravity sedimentation tank. A solid component (hereinafter also referred to as “solid content concentrate”) that is a slurry containing insoluble ash and insoluble coal can be obtained.

  In addition, before the liquid component is transferred to the first filtration step (S3), the liquid component in the heated state is cooled to a temperature at which the solute eluted from the coal does not reprecipitate, for example, about 200 to 360 ° C. It may be cooled. By cooling the liquid component, subsequent handling becomes easy and excessive thermal decomposition can be avoided. In addition, the pressure at the time of filtration can be lowered, and the specification level of valves and the like can be lowered. In addition, what is necessary is just to adjust suitably about the cooling temperature of the liquid component here in consideration of the temperature of the filtrate filtered by the 2nd filtration process (S4) mentioned later.

<First filtration step (S3)>
The first filtration step (S3) is a step of filtering the liquid component separated in the separation step (S2).
The method for filtering the liquid component is not particularly limited, and a commonly used filtration method may be used. For example, as will be described later, by providing a filter unit in the solid-liquid separator, it is possible to perform filtration simply and continuously.

As a filter used for filtration, a material such as paper, cloth, membrane, ceramics, stainless steel, or copper can be used. The filter may be of a cartridge type, but in the case of continuous operation, it is preferable that the filter can be continuously supplied in consideration of filter replacement. In addition, as filter paper, filter cloth, membrane filter, ceramics filter, stainless steel filter, copper filter, etc. used as a filter, for example, use a fine filter with a pore size of about 0.5 μm. Can do.
By the filtration in the first filtration step (S3), ash content exceeding about 0.5 μm in particle size contained in the liquid component can be removed.

<Second filtration step (S4)>
The second filtration step (S4) is a step of further filtering the filtrate (first filtrate) filtered in the first filtration step (S3).
The method for filtering the first filtrate is not particularly limited, and may be performed in the same manner as in the first filtration step (S3).
Also in the second filtration step (S4), as in the first filtration step (S3), by providing a filter unit in the solid-liquid separator, it is possible to perform filtration simply and continuously. What is necessary is just to carry out according to a 1st filtration process (S3) also about other conditions other than the temperature described below.
By the filtration in the second filtration step (S4), the following ash can be removed from the particle size of about 0.5 μm contained in the liquid component (first filtrate).

  Here, in the second filtration step (S4), the temperature of the filtrate filtered in the first filtration step (S3) is filtered in a state lower than the temperature of the liquid component to be filtered in the first filtration step (S2). (Filtrate cooling step).

  In the ashless coal production process, generally, the extraction rate of coal takes a maximum value in the vicinity of 380 ° C. (see, for example, JP-A-2005-120185). That is, by lowering the temperature, the solubility of the extracted component in the aromatic solvent is reduced and it is precipitated as a solid content. Since the precipitation of the extracted component occurs around the ash which is a solid content in the solution, the particle size of the fine particles containing the ash is increased by the precipitation of the extracted component. By increasing the particle size of the fine particles, the filterability of the ash content is lowered, and the ash content in the first filtrate can be removed by filtration. Thereby, ashless coal with extremely low ash concentration (for example, 0.020% by mass or less) can be produced.

The temperature of the filtrate (first filtrate) to be filtered in the second filtration step (S4) is preferably 100 ° C. or lower and more preferably 150 ° C. or lower than the temperature of the liquid component. Furthermore, it is preferably 190 ° C. or lower. Further, the lower limit value of the temperature of the first filtrate is preferably about 20 ° C.
However, the lower the temperature of the first filtrate, the more the extracted components are deposited, which is advantageous in ash removal, but the extracted components are also deposited more frequently, causing a reduction in the ashless coal recovery rate. Therefore, it is preferable that the temperature of the first filtrate is as high as possible in the range where ash removal is possible.

As will be described later, a cooler can be used to lower the temperature. In addition, in order to cool a filtrate, you may provide the cooling mechanism in the supernatant liquid receiver (refer FIG. 2).
However, when the filtrate is once put into the supernatant liquid receiver, it is naturally cooled to some extent, so that a configuration without a cooler, a cooling mechanism, or the like may be used. Moreover, after collecting a filtrate in a supernatant liquid receiver, it may be naturally cooled to a desired temperature by leaving it for a while.

  Further, as a method for enhancing the effect of removing ash by filtration, there is a method of adding coal, in which a large amount of extracted components are precipitated, to the raw material due to a decrease in temperature. By doing in this way, when raw coal with little precipitation amount is used, the precipitation amount of an extraction component can be increased and the permeability of the filter of an ash content can be made low. Preferably, coal in which precipitation occurs in a high temperature region is used. In this case as well, the temperature condition is adjusted as appropriate in consideration of the recovery rate of ashless coal.

Such a 1st filtration process (S3) and a 2nd filtration process (S4) can be performed continuously to a separation process (S2), for example in a solid-liquid separation device for performing gravity sedimentation. it can.
Hereinafter, an example of the gravity sedimentation method will be described with reference to FIGS.
As shown in FIG. 2, in the gravity sedimentation method, in the solid-liquid separation device 100, first, coal in a powder that is a raw material of ashless coal and an aromatic solvent are mixed in a coal slurry preparation tank 1, Prepare. Next, a predetermined amount of slurry is supplied from the coal slurry preparation tank 1 to the preheater 3 by the pump 2, and the slurry is heated to 300 to 420 ° C. Then, a predetermined amount of the heated slurry is supplied to the extraction tank 4 and heated at 300 to 420 ° C. for a predetermined time while being stirred by the stirrer 10, and then cooled to a predetermined temperature by the cooler 7a as necessary (slurry). Heating step (S1)). Note that a cooling mechanism may be provided in the extraction tank 4 in order to cool the slurry. And the slurry which performed this extraction process is supplied to the gravity sedimentation tank 5, and a slurry is isolate | separated into a supernatant liquid and solid content concentrated liquid (separation process (S2)), and settled in the lower part of the gravity sedimentation tank 5. The solid concentrate is discharged to the solid concentrate receiver 6 and the upper supernatant liquid is discharged to the filter unit 8a by a predetermined amount.

  Here, in the gravity settling tank 5, in order to prevent reprecipitation of the solute eluted from the raw material coal, when the slurry is heated, and when the slurry is cooled after being cooled, the temperature is maintained after being heated. The pressure is preferably in the range of 1.0 to 2.0 MPa. Further, in the gravity settling tank 5, the time for maintaining at a predetermined temperature is the time required to separate the slurry into a supernatant and a solid concentrate, and is generally 60 to 120 minutes. It is not particularly limited.

  It should be noted that by increasing the number of gravity sedimentation tanks 5, it is possible to recover components that are soluble in the aromatic solvent accompanying the solid concentration liquid. It is appropriate to arrange in steps.

  Then, the supernatant discharged from the gravity settling tank 5 is cooled to a predetermined temperature by the cooler 7b as necessary, and then filtered by the filter unit 8a to receive the supernatant as a filtrate (first filtrate). Is collected in a container (first filtrate receiver) 9a (first filtration step (S3)). And the supernatant liquid (1st filtrate) collect | recovered by the supernatant liquid receiver 9a is cooled to predetermined temperature with the cooler 7c as needed. In addition, in order to cool a supernatant liquid or a 1st filtrate, you may provide the cooling mechanism in the gravity sedimentation tank 5 or the supernatant liquid receiver 9a. Further, natural cooling may be performed without using the coolers 7b and 7c and the cooling mechanism. The first filtrate recovered in the supernatant liquid receiver 9a is further discharged to the filter unit 8b and filtered to obtain a supernatant (second filtrate) as a supernatant liquid receiver 9b (second filtrate receiver). (Second filtration step (S4)).

Then, as described below, the aromatic component is separated and recovered from this liquid component (second filtrate) and the solid component (solid content concentrate) using a distillation method or the like, and the liquid component (second filtrate) is collected. ) To obtain ashless coal having an extremely low ash concentration (ashless coal acquisition step (S5)). Moreover, by-product charcoal with which ash content was concentrated can be obtained from a solid component as needed.
The aromatic solvent separated and recovered from the solid concentrate discharged to the solid concentration receiver 6 and the aromatic solvent separated and recovered from the supernatant recovered in the supernatant receiver 9b are necessary. Accordingly, it is circulated to the coal slurry preparation tank 1 (shown by a dotted line portion in FIG. 2 for convenience).

<Ashless charcoal acquisition process (S5)>
The ashless charcoal acquisition step (S3) is a step of acquiring ashless charcoal by removing the aromatic solvent from the filtrate (second filtrate) filtered in the second filtration step (S4).

  As a method for separating and removing the aromatic solvent from the second filtrate (supernatant liquid), a general distillation method or evaporation method (spray drying method, etc.) can be used, and the aromatic solvent separated and recovered. Can be circulated to the coal slurry preparation tank 1 (see FIG. 2) and repeatedly used. By separating and collecting the aromatic solvent, ashless coal having an extremely low ash concentration can be obtained from the second filtrate. This ashless coal contains almost no ash, has no moisture, and exhibits performance (thermal fluidity) far superior to that of raw coal.

  In addition, in the said ashless coal acquisition process (S5), in addition to acquiring the ashless coal which is modified coal from the filtrate filtered by the said 2nd filtration process (S3) as needed, the said separation process The aromatic solvent may be removed from the solid component separated in (S2) to produce by-product coal that is modified coal (by-product coal acquisition step).

  This by-product charcoal is free of oxygen-containing functional groups, has ash, has no water, and has a sufficient calorific value. Therefore, this byproduct charcoal can be used for various fuels.

  The method for separating and removing the aromatic solvent from the solid component (solid content concentrate) is similar to the above-described ashless coal acquisition step (S5) for acquiring ashless coal from the liquid component, The evaporation method can be used, and the aromatic solvent separated and recovered can be circulated to the coal slurry preparation tank 1 (see FIG. 2) and repeatedly used. By separation and recovery of the aromatic solvent, by-product charcoal enriched in ash can be obtained from the solid concentrate.

In addition, only the ashless coal without ash is produced from the liquid component separated in the separation step (S2), only the aromatic solvent is recovered from the solid component, and the by-product coal enriched in ash is discarded. Good.
Moreover, although solid-liquid separation in acquisition of the above-mentioned ashless coal and by-product coal can be performed sequentially using the same apparatus, you may perform it using a respectively different apparatus. Moreover, in the acquisition of ashless coal and byproduct coal, you may make it acquire simultaneously, and you may make it acquire either one previously.

  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, a coal pulverization step of pulverizing raw coal between or before and after the respective steps, 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.

Next, an example is given and the manufacturing method of ashless coal concerning the present invention is explained concretely.
The following experiment was conducted using coal having the properties shown in Table 1.

[First embodiment]
As raw material coal, coal obtained by mixing 30% by mass of bituminous coal O with bituminous coal B was used.
A slurry was prepared by mixing 6 kg (30 kg) of an aromatic solvent (1-methylnaphthalene (manufactured by Nippon Steel Chemical Co., Ltd.)) with 5 kg of this raw material coal. This slurry was pressurized in nitrogen at a pressure of 2.0 MPa and heat-treated (heat extraction) in an autoclave with an internal volume of 30 liters at 380 ° C. for 40 minutes. The slurry was cooled to 350 ° C. and separated into a supernatant and a solid concentrate in a gravity sedimentation tank maintained at a pressure of 2.0 MPa and 350 ° C.

  About a part of this supernatant liquid, the aromatic solvent was separated and recovered by distillation to produce ashless coal (ashless coal after solid-liquid separation). Moreover, about the remainder, the supernatant liquid was cooled to 250 degreeC, and it filtered with the filtration filter (1st filtration), and obtained the filtrate (1st filtrate).

  About this 1st filtrate, the aromatic solvent was isolate | separated and collect | recovered with the distillation method about one part, and the ashless coal (the ashless coal after 1st filtration) was manufactured. For the rest, the first filtrate is cooled to 60 ° C., filtered through a filter (second filtration) to obtain a filtrate (second filtrate), and an aromatic solvent is obtained from this second filtrate by distillation. Was separated and recovered to produce ashless coal (ashless coal after second filtration).

  The ash content of the ashless coal after solid-liquid separation, the ashless coal after the first filtration, and the ashless coal after the second filtration thus obtained was measured by the method defined in JISM8812. In addition, the ash concentration of raw material coal was also measured. The ash content was 0.020% by mass or less, and the ash content was very low.

Moreover, the decreasing rate of ash was calculated by the following formula.
Ash reduction rate of ashless coal after solid-liquid separation (mass%) = [1- (ash concentration of ashless coal after solid-liquid separation (mass%) / ash concentration of raw coal (mass%))] × 100
Ash reduction rate (mass%) of first ashless coal after first filtration = [1- (ash concentration of ashless coal after first filtration (mass%) / ash concentration of raw coal (mass%))] × 100
Ash reduction rate (mass%) of ashless coal after second filtration = [1- (ash concentration of ashless coal after second filtration (mass%) / ash concentration of raw coal (mass%))] × 100
These results are shown in Table 2.

[Second Embodiment]
As raw coal, coal obtained by mixing 30% by mass of bituminous coal O with bituminous coal M was used.
Using this raw material coal, a supernatant and a solid concentrate were obtained in the same manner as in the previous example.
About a part of this supernatant liquid, the aromatic solvent was separated and recovered by distillation to produce ashless coal (ashless coal after solid-liquid separation). Moreover, about the remainder, the supernatant liquid was cooled to 250 degreeC and filtered with the filtration filter (1st filtration), and the filtrate was acquired. About this filtrate, about one part, the aromatic solvent was isolate | separated and collect | recovered with the distillation method, and the ashless coal (the ashless coal after the 1st filtration) was manufactured.

The ash content of the ashless coal after solid-liquid separation and the ashless coal after the first filtration thus obtained were measured by the method defined in JIS M8812. In addition, the ash concentration of raw material coal was also measured. The ash content was 0.02% by mass or less and the ash content was very low, so that the quality of ashless coal was good.
Also, the reduction rate of ash was calculated. The ash content reduction rate of the ashless coal after solid-liquid separation and the ash content reduction rate of the ashless coal after the first filtration were obtained by the same formulas as in the first example.
These results are shown in Table 2.

  As shown in Table 2, in the first example, in the ashless coal after solid-liquid separation, the reduction rate of ash was 94.86% by mass, and the ash concentration was 0.380% by mass. Moreover, in the ashless coal after the first filtration, the reduction rate of ash was 99.46% by mass, and the ash concentration was 0.040% by mass. And in the ashless coal after the 2nd filtration, the decreasing rate of ash was 99.73 mass%, and the ash concentration was 0.020 mass%. Therefore, by performing the first filtration and the second filtration, it was possible to obtain a good quality ashless coal having an extremely low ash concentration.

  In the second example, in the ashless coal after solid-liquid separation, the reduction rate of ash was 95.36% by mass, and the ash concentration was 0.510% by mass. In the ashless coal after the first filtration, the reduction rate of ash was 99.64% by mass, and the ash concentration was 0.040% by mass. However, since the second filtration was not performed, the final ash concentration was 0.040% by mass, and good quality ashless coal with an extremely low ash concentration was not obtained.

  As mentioned above, although the best embodiment and the example were shown and explained in detail about the manufacturing method of ashless coal concerning the present invention, the meaning of the present invention is not limited to the above-mentioned contents, and the scope of right is patent. It should be interpreted broadly based on the claims. Needless to say, the contents of the present invention can be widely modified and changed based on the above description.

It is a flowchart explaining the process of the manufacturing method of ashless coal. It is a schematic diagram which shows the solid-liquid separator for performing a gravity sedimentation method.

Explanation of symbols

S1 Slurry heating step S2 Separation step S3 First filtration step S4 Second filtration step S5 Ashless coal acquisition step 1 Coal slurry preparation tank 2 Pump 3 Preheater 4 Extraction tank 5 Gravity sedimentation tank 6 Solid concentration receiver 7a, 7b , 7c Cooler 8a 8b Filter unit 9a Supernatant liquid receiver (first filtrate receiver)
9b Supernatant receiver (second filtrate receiver)
10 Stirrer 100 Solid-liquid separator

Claims (1)

A slurry heating step in which a slurry in which coal and an aromatic solvent are mixed is heat-treated;
A separation step of separating the slurry heat-treated in the slurry heating step into a liquid component in which coal is dissolved and a solid component containing ash and insoluble coal;
A first filtration step of filtering the liquid component separated in the separation step;
A second filtration step of further filtering the filtrate filtered in the first filtration step;
Removing the aromatic solvent from the filtrate filtered in the second filtration step to obtain ashless coal,
A method for producing ashless coal, wherein the temperature of the filtrate filtered in the second filtration step is lower than the temperature of the liquid component filtered in the first filtration step.

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