阅读说明：本技术 成型煤的制造方法 (Method for producing shaped coal ) 是由 森英一朗 安田和真 小菅克志 藤吉旭 浦田裕介 有吉大辅 于 2018-10-03 设计创作，主要内容包括：提供一种成型煤的制造方法,其具有将包含粉状的干馏煤和粘结剂的成型原料成型并以60～100℃干燥来得到水分为5重量％以下的成型煤的工序。粘结剂含有皂化度大于99.3mol％且聚合度为1700以上的聚乙烯醇的水溶液。粉状的干馏煤是对包含褐煤和次烟煤中的至少一种的煤进行干燥并干馏而得到的粉煤。(Provided is a method for producing a shaped coal, which comprises a step for shaping a shaped raw material comprising a powdery carbonized coal and a binder and drying the shaped raw material at 60-100 ℃ to obtain a shaped coal having a moisture content of 5 wt% or less. The binder contains an aqueous solution of polyvinyl alcohol having a saponification degree of more than 99.3 mol% and a polymerization degree of 1700 or more. The pulverized dry-distilled coal is pulverized coal obtained by drying and dry-distilling coal containing at least one of lignite and subbituminous coal.)

1. A process for producing a shaped coal, which comprises a step of shaping a shaped raw material comprising a powdery carbonized coal and a binder and drying the shaped raw material at 60 to 100 ℃ to obtain a shaped coal having a moisture content of 5 wt% or less,

the binder contains an aqueous solution of polyvinyl alcohol having a saponification degree of more than 99.3 mol% and a polymerization degree of 1700 or more,

the pulverized dry-distilled coal is obtained by drying and dry-distilling coal containing at least one of lignite and subbituminous coal.

2. The method for producing molded coal according to claim 1, wherein the degree of polymerization of the polyvinyl alcohol is 2500 or more.

3. The method for producing molded coal according to claim 1 or 2, wherein the content of the polyvinyl alcohol in the aqueous solution is 1 to 10% by weight.

4. The method for producing briquette coal according to any one of claims 1 to 3, wherein the polyvinyl alcohol is contained in an amount of 1 part by weight or more per 100 parts by weight of the carbonized coal.

5. The method for producing molded coal according to any one of claims 1 to 4, wherein the binder contains alpha starch.

6. The method for producing formed coal according to any one of claims 1 to 5, wherein the formed coal has a compressive strength of 50N or more after being immersed in water at 20 ℃ for 24 hours.

7. The method for producing briquette coal according to any one of claims 1 to 6, wherein neither calcium oxide nor magnesium oxide is added to the briquette raw material.

Technical Field

The present invention relates to a method for producing shaped coal.

Background

In the coal production process, pulverized coal in a powdery state is produced. Pulverized coal can be a cause of dust generation in addition to being difficult to handle. Accordingly, effective use of pulverized coal by molding the pulverized coal into molded coal has been studied. For example, patent document 1 proposes a technique in which starch is added to pulverized coal as a binder and mixed, and the surface of a molded article obtained by molding is covered with a heavy oil component such as heavy oil or tar. Patent document 2 proposes a technique of adding tar or tar residue to pulverized coal and then molding the mixture.

Documents of the prior art

Patent document

Patent document 1: japanese patent laid-open publication No. 2003-64377

Patent document 2: japanese patent laid-open publication No. 9-3458

Disclosure of Invention

Problems to be solved by the invention

In order to effectively utilize low-quality coal such as lignite and subbituminous coal, modification techniques including drying and carbonization have been studied. Pulverized coal is produced when this modification process is performed. From the viewpoint of improving safety and preventing liquefaction, it is preferable that the produced pulverized coal is not pulverized but is transported as molded coal. Here, the molded coal is required to have high strength so that it is not easily damaged by vibration, impact, or the like during transportation. In addition, in the case of transporting and storing coal by sea, since the molded coal is exposed to wind and rain, it is required to maintain high strength without collapsing even when wetted with water.

Pulverized coal of carbonized coal is difficult to mold compared with raw coal, and therefore a binder is required for producing molded coal. When a heavy oil such as tar is used as a binder, heating is necessary for kneading with pulverized coal. However, pulverized coal generated during dry distillation is liable to self-ignite, and therefore heating is not preferable from the viewpoint of safety. Further, since a heating facility is required and it is difficult to heat uniformly in the case of large-volume kneading, there is a fear that kneading becomes non-uniform and the strength of the molded coal becomes non-uniform.

In addition, when starch is used as a binder and the surface is covered with an oil-based binder, if the molded coal is broken and the inside is exposed, the starch is water-soluble, and therefore, there is a concern that the strength when wetted with water is lowered. Under such circumstances, it is required to establish a technique for producing a molded coal having high safety and excellent water resistance.

Accordingly, an object of one aspect of the present invention is to provide a method for producing a molded coal which is excellent in safety and can maintain high strength even when wetted with water.

Means for solving the problems

In one aspect, the present invention provides a method for producing formed coal, comprising a step of forming a forming material comprising pulverized dry-distilled coal and a binder, the binder containing an aqueous solution of polyvinyl alcohol having a saponification degree of more than 99.3 mol% and a polymerization degree of 1700 or more, and drying the formed material at 60 to 100 ℃ to obtain formed coal having a moisture content of 5 wt% or less, wherein the pulverized dry-distilled coal is pulverized coal obtained by drying and dry-distilling coal comprising at least one of lignite and subbituminous coal.

In this production method, a binder containing an aqueous solution of polyvinyl alcohol having a saponification degree of more than 99.3 mol% is used. This shows that the aqueous solution is used as a binder, and therefore, the safety is excellent. In addition, when polyvinyl alcohol having a high degree of saponification is dried, hydroxyl groups in the respective molecules are hydrogen-bonded to each other, and excellent water resistance is exhibited. That is, the molecules of polyvinyl alcohol contained as a binder in the molded coal are strongly bonded to each other, and thus high strength can be maintained even when the molded coal is wetted with water.

The polymerization degree of the polyvinyl alcohol is preferably 2500 or more. This can further improve the strength of the molded coal particularly during drying.

In the above step, the molded product of the molding material is dried to obtain molded coal having a moisture content of 5 wt% or less. By reducing the moisture content of the molded product in this way, the formation of hydrogen bonds is promoted, and the strength of the molded coal when wetted with water can be improved.

The content of polyvinyl alcohol in the aqueous solution of polyvinyl alcohol is preferably 1 to 10% by weight. This improves the dispersibility of the powdery carbonized coal and the binder, and improves the uniformity of the molding material. Therefore, the strength unevenness of the molded coal can be reduced.

The content of the polyvinyl alcohol is preferably 1 part by weight or more based on 100 parts by weight of the carbonized coal. This can further improve the strength of the molded coal.

The binder may contain both polyvinyl alcohol and alpha starch. Since alpha-starch is inexpensive, the production cost can be reduced. Further, if alpha starch is used, the strength of the molded coal at the time of drying can be sufficiently improved. Therefore, α starch is useful for applications where strength at the time of drying is more important than water resistance.

The briquette obtained by the above-mentioned production process preferably has a compressive strength of 50N or more after being immersed in water at 20 ℃ for 24 hours. This can sufficiently prevent the coal from collapsing due to exposure to wind and rain during transportation and storage.

Preferably, neither calcium oxide nor magnesium oxide is added to the molding material. Thus, when the molded coal is used as a solid fuel, the calorific value can be sufficiently increased.

The compression strength of the molded coal after being immersed in water at 20 ℃ for 24 hours is preferably 50N or more. This can sufficiently prevent the coal from collapsing due to exposure to wind and rain during transportation and storage. Therefore, the coal can be safely transported and stored on the sea, and the formed coal obtained by the above-described production method is suitable for use as a solid fuel.

ADVANTAGEOUS EFFECTS OF INVENTION

The present invention can provide a method for producing a molded coal which is excellent in safety and can maintain high strength even when wetted with water.

Drawings

FIG. 1 is a schematic view of a measuring apparatus for measuring compressive strength of a shaped coal.

FIG. 2 is a semilogarithmic graph showing the relationship between the impregnation time and the compressive strength of the shaped coals of examples 2, 3 and comparative examples 2, 3.

FIG. 3 is a semilogarithmic graph showing the relationship between the dipping time and the compressive strength of the molded coals according to reference examples 4 to 6.

FIG. 4 is a graph in which the vertical axis represents the compressive strength and the horizontal axis represents the polymerization degree of polyvinyl alcohol, and the molded coal of reference examples 4 to 6 was immersed in water before (after drying) and after 24 hours (1440 minutes) of immersion.

FIG. 5 is a semilogarithmic graph showing the relationship between the dipping time and the compressive strength of the molded coals according to reference examples 6 to 10.

FIG. 6 is a semilogarithmic graph showing the relationship between the dipping time and the compressive strength of the molded coals according to reference examples 11 to 13.

FIG. 7 is a graph in which the vertical axis represents the compressive strength and the horizontal axis represents the blending ratio of alpha-starch, and data before (after drying) and after 24 hours (1440 minutes) immersion of the molded coals according to reference examples 8 and 11 to 13 are plotted

Detailed Description

Embodiments of the present invention will be described below with reference to the drawings. However, the following embodiments are examples for illustrating the present invention, and the present invention is not intended to be limited to the following.

The method for producing a shaped coal according to the present embodiment includes a step of shaping a shaped raw material including a powdery carbonized coal and a binder and drying the shaped raw material to obtain a shaped coal. The pulverized dry-distilled coal is pulverized coal obtained by drying and dry-distilling coal containing at least one of lignite and subbituminous coal. This enables efficient use of low-quality lignite and subbituminous coal as well as coal. The particle size of the carbonized coal is not particularly limited, and may be undersize pulverized coal obtained by sieving with a sieve of 1 to 10mm, for example. When the coal is sieved with a 1mm sieve, the undersize fraction with respect to the whole dry-distilled coal may be 80 wt% or more in view of improving the moldability.

The binder contains an aqueous solution of polyvinyl alcohol (PVA) having a saponification degree of more than 99.3 mol% and a polymerization degree of 1700 or more. Pulverized coal obtained by drying and dry-distilling low-quality coal such as lignite and subbituminous coal has more pores than coke powder produced from high-quality coal. Therefore, the molded product of the pulverized coal has a low density and tends to have a low strength. However, in the present embodiment, the strength can be improved by using the above-described binder.

The saponification degree of polyvinyl alcohol (PVA) indicates the proportion of units that can be actually saponified into vinyl alcohol units among units that can be converted into vinyl alcohol units by saponification. The degree of saponification can be measured by a neutralization titration method in accordance with JIS K6726-1994. Specifically, a phenolphthalein solution was added to polyvinyl alcohol, and sodium hydroxide was added dropwise until it became pale red. The residue (residual acetoxy group) was determined from the amount of the residue added dropwise, and the degree of saponification was calculated.

That is, in the polyvinyl alcohol having a molecular structure represented by the following formula (1), the degree of saponification is calculated by the numerical expression of n/(m + n) × 100. The partially saponified polyvinyl alcohol has a molecular structure represented by the following formula (1), while the completely saponified polyvinyl alcohol has an acetic acid group almost substituted with a hydroxyl group represented by the following formula (2).

When polyvinyl alcohol having a saponification degree of more than 99.3 mol% is dried, hydroxyl groups in each molecule are strongly bonded to each other by hydrogen bonds. Once formed, such a bond is not easily dissociated even if it is again contacted with water. Therefore, the molded coal obtained by molding and drying using a binder comprising an aqueous solution of polyvinyl alcohol having a saponification degree of more than 99.3 mol% is excellent in water resistance. From the viewpoint of further improving the strength of the molded coal during drying and wetting with water, the saponification degree of the polyvinyl alcohol is preferably 99.5 mol% or more.

Commercially available polyvinyl alcohols can be used. In particular, the polymerization degree of the polyvinyl alcohol is 1700 or more, preferably 2500 or more, and more preferably 3300 or more, from the viewpoint of improving the strength of the molded coal at the time of drying. The polymerization degree of polyvinyl alcohol can be measured by a solution viscometry method according to JIS K6726-1994.

The content of polyvinyl alcohol in the aqueous solution of polyvinyl alcohol is preferably 1 to 10% by weight, more preferably 2 to 10% by weight. This facilitates kneading with the pulverized carbonized coal, and can improve dispersibility. Therefore, the homogeneity of the molding material is improved, and the variation in the strength of the molded coal can be reduced. The viscosity (20 ℃) of the aqueous solution of polyvinyl alcohol may be, for example, 20 to 500 mPas.

Since the binder contains an aqueous solution, it is superior in safety as compared with a binder composed of only combustible materials. Further, since the carbonized coal and the binder can be kneaded at room temperature without heating, the kneaded coal can be kneaded with high safety even if it is a carbonized coal having spontaneous combustibility. However, kneading by heating is not excluded.

The molding material can be prepared by mixing and kneading powdery carbonized coal and a binder containing an aqueous solution of polyvinyl alcohol. Water may be added and kneaded together depending on the viscosity of the aqueous polyvinyl alcohol solution or the content of polyvinyl alcohol in the aqueous solution. From the viewpoint of achieving both moldability and kneading property at a sufficiently high level, the mixing ratio of the aqueous solution of polyvinyl alcohol may be, for example, 5 to 50 parts by weight or 5 to 30 parts by weight per 100 parts by weight of the pulverized carbonized coal.

The content of the polyvinyl alcohol in the molding material is preferably 0.5 wt% or more, and more preferably 1.5 wt% or more, from the viewpoint of sufficiently improving the strength of the molded coal. On the other hand, from the viewpoint of reducing the production cost of the molding coal, the content of the polyvinyl alcohol in the molding material is preferably 10% by weight or less. From the viewpoint of achieving both moldability and kneading property at a sufficiently high level, the water content in the molding material is preferably 20 to 40% by weight.

The binder may contain ingredients other than polyvinyl alcohol and water. The component may be a water-soluble component. As the water-soluble component, α starch is preferable from the viewpoint of production cost. Since alpha starch is generally cheaper than polyvinyl alcohol, the production cost of the molded coal can be reduced by replacing a part of polyvinyl alcohol with alpha starch. In addition, when alpha starch is used, the strength of the molded coal during drying can be sufficiently improved. In the molding material, the α starch is preferably added in a ratio of 1 to 9 parts by weight to 100 parts by weight of the carbonized coal, from the viewpoint of sufficiently improving the strength during drying while maintaining the water resistance.

From the viewpoint of sufficiently increasing the calorific value when the molding coal is used as a solid fuel, it is preferable that neither calcium oxide nor magnesium oxide is added as a molding raw material.

Examples of the apparatus for molding the molding material include a general twin-roll molding machine and a single-screw press molding machine. The shape of the molded article obtained by molding the molding material is not particularly limited, and may be, for example, a mosaic type, or a spherical, cylindrical or prismatic shape. The molded coal may have a density of 1.0 to 2.0g/ml, for example. The molding pressure is, for example, 1 to 10 tons/cm in a line pressure gauge and 40 to 390MPa in a surface pressure gauge.

Next, the obtained molded article is dried by, for example, an electric furnace or a dryer to reduce moisture. The molded product is dried to obtain a molded coal. The drying may be performed, for example, in an atmosphere of 60 to 100 ℃ or in an inert gas atmosphere. The drying time may be, for example, 1 to 20 hours. By drying at such a low temperature of 60 to 100 ℃, molded coal which can maintain high strength even when wetted with water can be produced. Drying may also be carried out in the exhaust gases of the burner. By this drying, the moisture content of the molded coal is preferably reduced to 5% by weight or less. By setting the water content to this amount, hydrogen bonding between the polyvinyl alcohol molecules (between the hydroxyl groups) is sufficiently promoted, and the strength of the molded coal can be further improved. The moisture content of the molded coal can be measured by a heat drying method (a method of measuring the weight before and after heat drying) using a moisture measuring machine.

The molded coal comprises a carbonized coal and a binder containing polyvinyl alcohol having a saponification degree of more than 99.3 mol% and a polymerization degree of 1700 or more. From the viewpoint of excellent water resistance and sufficient strength improvement, the content of the polyvinyl alcohol in the formed coal is preferably 1 part by weight or more, and more preferably 2 parts by weight or more, per 100 parts by weight of the carbonized coal. From the viewpoint of production cost, the content of the polyvinyl alcohol in the coal briquette is, for example, 10 parts by weight or less per 100 parts by weight of the carbonized coal. From the viewpoint of improving the strength, the moisture content of the molded coal is 5 wt% or less, preferably 4 wt% or less. When the binder contains polyvinyl alcohol and alpha starch, the content of the alpha starch in the coal briquette is preferably 1 to 9 parts by weight and the total content of the polyvinyl alcohol and the alpha starch is preferably 2 to 10 parts by weight, based on 100 parts by weight of the carbonized coal.

The strength of the molded coal can be quantified by measuring the compressive strength using the measuring apparatus 10 shown in fig. 1. As a sample, a columnar shaped coal 16 (φ 15 mm. times.height 15mm) was prepared. On the support plate 17 disposed on the bottom plate of the holder 18, the molded coal 16 is disposed such that the peripheral surface of the molded coal 16 to be measured contacts the upper surface of the support plate 17. Then, the movable plate 14 attached to the holder 18 so as to be movable up and down is lowered, and the coal briquette 16 is sandwiched between the movable plate 14 and the support plate 17. Then, by operating the movable plate 14, a load is applied in the radial direction of the shaped coal 16. Finally, the compressive strength is determined from the load at the time of fracture of the formed coal 16.

The compression strength of the molded coal is preferably 100N or more, more preferably 150N or more, when dried (moisture: 2 to 4% by weight). The compression strength of the molded coal after being immersed in water at 20 ℃ for 24 hours is preferably 40N or more, and more preferably 50N or more. It is seen that the molded coal of the present embodiment can maintain high strength not only when dried but also when wetted with water.

While the present invention has been described with reference to the embodiments, the present invention is not limited to the embodiments.

Examples

The present invention will be described in more detail with reference to examples, reference examples and comparative examples, but the present invention is not limited to the following examples.

[ investigation of the kind of Binder ]

(example 1 and comparative example 1)

< preparation of Molding raw Material >

The following 12 binders were prepared.

(1) Aqueous solution of polyvinyl alcohol (degree of polymerization: 1700, degree of saponification: 99.7 mol%) (polyvinyl alcohol content: 10% by weight)

(2) Alpha starch (from corn)

(3) Alpha starch (from cassava)

(4) Straight-run asphalt

(5) Soft asphalt (SOP)

(6) Asphalt A

(7) Asphalt B

(8) Vinyl acetate emulsion

(9) Waste molasses A (without hydrated lime)

(10) Waste molasses B (hydrated lime added)

(11) Pulp waste liquor

(12) Alkaline aqueous solution of humic acid

(13) Bentonite clay

The carbonized coal obtained by carbonization was sieved with a 1mm sieve to obtain undersize carbonized coal, and the undersize carbonized coal was kneaded with the binders (1) to (13), respectively, to obtain a molding material. The binders (1) and (8) to (13) may be kneaded at room temperature to prepare a molding material. On the other hand, since the binders (4) to (7) have high viscosity, it is difficult to knead at room temperature (20 ℃ C.). Therefore, the binders (4) to (7) are kneaded with the carbonized coal while being heated to 120 to 130 ℃ to prepare a molding material.

< production of shaped coal and evaluation of moldability >

The prepared molding material was molded by a single-screw pressure molding machine at a molding pressure of 283MPa to prepare a molded coal. The amount of binder to be mixed for making the compression strength of the molded coal 50N or more was examined for each binder. Further, moldability of each binder was evaluated by the following criteria. That is, the case where the binder content of the whole molded coal was 10 wt% or less was evaluated as "a", the case where the binder content was more than 10 wt% and 40 wt% or less was evaluated as "B", and the case where the molding could not be performed even if the binder content was 40 wt% or the compressive strength was not more than 50N was evaluated as "C". The evaluation results are shown in table 1.

< evaluation of Water resistance of molded coal >

The water resistance of the sample whose moldability was evaluated as "A" or "B" was evaluated by the following procedure. The shaped coal was immersed in water for 1440 minutes. Then, the molded coal was taken out from the water, and the shape before the impregnation was maintained was evaluated as "a", and the shape before the impregnation could not be maintained was evaluated as "B". The evaluation results are shown in table 1.

[ Table 1]

	Kind of the Binder	Whether or not heating is required	Formability	Water resistance
					Example 1	(1)	Does not need to use	A	A
Comparative example 1-1	(2)	Does not need to use	A	B
					Comparative examples 1 to 2	(3)	Does not need to use	A	B
Comparative examples 1 to 3	(4)	Need to make sure that	B	A
					Comparative examples 1 to 4	(5)	Need to make sure that	B	A
Comparative examples 1 to 5	(6)	Need to make sure that	C	-
					Comparative examples 1 to 6	(7)	Need to make sure that	C	-
Comparative examples 1 to 7	(8)	Does not need to use	C	-
					Comparative examples 1 to 8	(9)	Does not need to use	C	-
Comparative examples 1 to 9	(10)	Does not need to use	C	-
					Comparative examples 1 to 10	(11)	Does not need to use	C	-
Comparative examples 1 to 11	(12)	Does not need to use	C	-
					Comparative examples 1 to 12	(13)	Does not need to use	C	-

As shown in Table 1, in example 1 in which polyvinyl alcohol was used as a binder, molded coal having excellent moldability was obtained as compared with comparative examples 1-3 to 1-12 in which binders (4) to (13) were used. The molded coal of example 1 was also excellent in water resistance. Comparative examples 1-1 and 1-2 using binders (2) and (3) had excellent moldability, but they disintegrated when immersed in water and could not maintain the original shape.

[ influence of saponification degree ]

(example 2)

An aqueous solution (binder aqueous solution) containing polyvinyl alcohol (degree of saponification: 99.85 mol%, degree of polymerization: 1700) at a concentration of 10% by weight, water and the dry distilled coal used in example 1 were mixed to obtain a mixture. The mixing ratio based on the weight at this time was 30 parts by weight of the binder aqueous solution and 10 parts by weight of water per 100 parts by weight of the carbonized coal. The mixture was molded by a single-screw compression molding machine (molding pressure: 283MPa), and a plurality of molded coals were produced (before drying). The moisture content of the molded coal was 27.6% by weight, and the compressive strength (average value of N: 2) was 66N. The compressive strength was measured by using the measuring apparatus of FIG. 1.

The molded coal obtained was dried in air at 80 ℃ for 15 hours. The moisture content and compressive strength of the dried molded coal are shown in Table 2. The moisture content of the molded coal before and after drying was measured by a heat drying method using a commercially available moisture measuring machine.

The dried molded coal pieces were immersed in water at about 20 ℃ for a predetermined period of time. After the predetermined impregnation time shown in table 2 had elapsed, the molded coal was taken out from the water, and the compressive strength was measured by measuring the moisture (some of the molded coal was not measured for moisture). The results of the measurement of the impregnation time and the moisture and the compressive strength are shown in Table 2.

The shaped coal, which was immersed in water for 1440 minutes, was dried in air at 80 ℃ for 15 hours. The moisture content of the molded coal after redrying was measured, and the compressive strength was measured. The results of moisture and compressive strength are shown in table 2.

[ Table 2]

As shown in Table 2, the briquette of example 2 maintained a compressive strength of 90N or more even after 24 hours had elapsed.

(example 3)

Shaped coal was produced and measured in the same manner as in example 2, except that polyvinyl alcohol (degree of saponification: 99.3 mol%, degree of polymerization: 1700) was used in place of the polyvinyl alcohol used in example 2. The results are shown in Table 3.

[ Table 3]

As shown in Table 3, the briquette of example 3 maintained a compressive strength of 70N or more even after 24 hours had elapsed. Example 2 having a high degree of saponification had a higher compressive strength and excellent water resistance than example 3.

Comparative example 2

Shaped coal was produced and measured in the same manner as in example 2, except that polyvinyl alcohol (degree of saponification: 94.5 to 95.5 mol%, degree of polymerization: 1700) was used in place of the polyvinyl alcohol used in example 2. The results are shown in Table 4.

[ Table 4]

As shown in table 4, the compression strength of the molded coal of comparative example 2 after drying was significantly reduced as compared with examples 2 and 3. Further, since the molded coal gradually disintegrates when immersed in water, the measurement after 30 minutes of immersion time was not possible.

Comparative example 3

Shaped coal was produced and measured in the same manner as in example 2, except that polyvinyl alcohol (degree of saponification: 87 to 89 mol%, degree of polymerization: 1700) was used in place of the polyvinyl alcohol used in example 2. The results are shown in Table 5.

[ Table 5]

As shown in Table 5, the compression strength of the molded coal of comparative example 3 after drying was lower than that of comparative example 2. Further, since the molded coal gradually disintegrates when immersed in water, the measurement after the immersion time of 1 minute was not possible.

FIG. 2 is a semilogarithmic graph showing the relationship between the impregnation time and the compressive strength of the shaped coals of examples 2, 3 and comparative examples 2, 3. The compressive strength of a sample disintegrated by immersion in water is plotted as 0 in the graph.

[ Effect of polymerization degree ]

(reference example 4)

Shaped coal was produced and measured in the same manner as in example 2, except that polyvinyl alcohol (degree of saponification: 99 mol%, degree of polymerization: 2500) was used in place of the polyvinyl alcohol used in example 2. The results are shown in Table 6.

[ Table 6]

As shown in Table 6, the molded coal of reference example 4 maintained a compressive strength of 100N or more even after 24 hours of immersion.

(reference example 5)

Shaped coal was produced and measured in the same manner as in example 2, except that polyvinyl alcohol (degree of saponification: 99 mol%, degree of polymerization: 3300) was used in place of the polyvinyl alcohol used in example 2. The results are shown in Table 7.

[ Table 7]

As shown in Table 7, the molded coal of reference example 5 maintained a compressive strength of 100N or more even after 24 hours of immersion. Reference example 5, in which the degree of polymerization of polyvinyl alcohol was large, showed higher compressive strength both before and after immersion in water, compared to reference example 4.

(reference example 6)

Shaped coal was produced and measured in the same manner as in example 2, except that polyvinyl alcohol (degree of saponification: 99 mol%, degree of polymerization: 4000) was used in place of the polyvinyl alcohol used in example 2. The results are shown in Table 8.

[ Table 8]

As shown in Table 8, the briquette of reference example 6 maintained a compressive strength of 100N or more even after 24 hours had elapsed. The compression strength before impregnation (before and after drying) and after redrying was particularly high in the molded coal of reference example 6 in which the polymerization degree of polyvinyl alcohol was high, as compared with reference examples 4 and 5.

FIG. 3 is a semilogarithmic graph showing the relationship between the dipping time and the compressive strength of the molded coals according to reference examples 4 to 6. FIG. 4 is a graph in which the vertical axis represents the compressive strength and the horizontal axis represents the polymerization degree of polyvinyl alcohol, and the molded coal of reference examples 4 to 6 was immersed in water before (after drying) and after 24 hours (1440 minutes) of immersion. As shown in fig. 3 and 4, as the degree of polymerization of polyvinyl alcohol increases, both the compressive strength and the water resistance before immersion in water increase. In addition, the compressive strength of the molded coal after drying is greatly improved by increasing the degree of polymerization of polyvinyl alcohol.

[ Effect of the content of polyvinyl alcohol ]

(reference example 7)

A mixture was prepared by mixing an aqueous binder solution containing the polyvinyl alcohol (degree of saponification: 99 mol%, degree of polymerization: 4000) used in reference example 6 at a concentration of 10 wt%, water and the dry distilled coal used in example 1. The mixing ratio based on the weight at this time was 3 parts by weight of the binder aqueous solution and 34.3 parts by weight of water per 100 parts by weight of the carbonized coal. Using this mixture, molded coal was produced in the same manner as in example 2, and measurement was performed. The results are shown in Table 9.

[ Table 9]

(reference example 8)

Shaped coal was produced and measured in the same manner as in reference example 7, except that a mixture was prepared by setting the mixing ratio of the binder aqueous solution, water and dry distilled coal based on the weight to 10 parts by weight of the binder aqueous solution and 28 parts by weight of water with respect to 100 parts by weight of dry distilled coal. The results are shown in Table 10.

[ Table 10]

(reference example 9)

Shaped coal was produced and measured in the same manner as in reference example 7, except that a mixture was prepared by setting the mixing ratio of the binder aqueous solution, water and dry distilled coal based on the weight to 100 parts by weight of dry distilled coal, 15 parts by weight of the binder aqueous solution and 23.5 parts by weight of water. The results are shown in Table 11.

[ Table 11]

(reference example 10)

Shaped coal was produced and measured in the same manner as in reference example 7, except that a mixture was prepared by setting the mixing ratio of the binder aqueous solution, water and dry distilled coal based on the weight to 20 parts by weight of the binder aqueous solution and 19 parts by weight of water with respect to 100 parts by weight of dry distilled coal. The results are shown in Table 12.

[ Table 12]

FIG. 5 is a semilogarithmic graph showing the relationship between the dipping time and the compressive strength of the molded coals according to reference examples 6 to 10. It was confirmed that the compressive strength was increased as the content of polyvinyl alcohol was increased. It was confirmed that the ratio of polyvinyl alcohol to 100 parts by weight of the carbonized coal was required to be 1.5 parts by weight or more in order to obtain a compressive strength of 100N or more both before and after the impregnation into water.

[ Complex addition of polyvinyl alcohol and alpha-starch ]

(reference example 11)

An aqueous polyvinyl alcohol solution containing polyvinyl alcohol (degree of saponification: 99 mol%, degree of polymerization: 4000) at a concentration of 10 wt%, alpha starch used in comparative example 1-1, water, and the dry distilled coal used in example 1 were mixed to obtain a mixture. The weight-based blending ratio in this case was 10 parts by weight of the polyvinyl alcohol aqueous solution, 1 part by weight of the α -starch, and 28 parts by weight of water, based on 100 parts by weight of the carbonized coal. Except for using the mixture, briquettes were manufactured and measured in the same manner as in example 2. The results are shown in Table 13.

[ Table 13]

(reference example 12)

Shaped coal was produced and measured in the same manner as in reference example 11, except that a mixture was prepared by setting the blending ratio of the polyvinyl alcohol aqueous solution, the α starch, the water and the dry distilled coal based on the weight basis to 10 parts by weight, 3 parts by weight and 28 parts by weight of the water with respect to 100 parts by weight of the dry distilled coal. The results are shown in Table 14.

[ Table 14]

(reference example 13)

Shaped coal was produced and measured in the same manner as in reference example 11, except that a mixture was prepared by setting the blending ratio of the polyvinyl alcohol aqueous solution, the α starch, the water and the dry distilled coal based on the weight basis to 10 parts by weight, 5 parts by weight and 28 parts by weight of the water with respect to 100 parts by weight of the dry distilled coal. The results are shown in Table 15.

[ Table 15]

FIG. 6 is a semilogarithmic graph showing the relationship between the dipping time and the compressive strength of the molded coals according to reference examples 11 to 13. FIG. 7 is a graph in which the vertical axis represents the compressive strength and the horizontal axis represents the α -starch blending ratio (parts by weight), and data before (after drying) and after 24 hours (1440 minutes) of immersion of the molded coals according to reference example 8 and reference examples 11 to 13 are plotted. From these data, it was confirmed that the addition of alpha starch did not improve the water resistance, but significantly improved the compressive strength of the molded coal before immersion in water (after drying) and after further drying.

[ influence of immersion time ]

(example 14)

Shaped coal was produced and measured in the same manner as in example 2, except that polyvinyl alcohol (degree of saponification: 99.7 mol%, degree of polymerization: 1700) was used in place of the polyvinyl alcohol used in example 2. The immersion in water was carried out for a maximum of 72 hours. The results are shown in Table 16.

[ Table 16]

As shown in table 16, it was confirmed that although the compressive strength decreased when the immersion in water was started, the compressive strength hardly decreased when the immersion time exceeded 30 minutes. Thus, the compressive strength after 24 hours of immersion can be easily evaluated with the immersion time set to 30 minutes.

Comparative example 4

Shaped coal was produced and measured in the same manner as in example 2, except that polyvinyl alcohol (degree of saponification: 87 to 88 mol%, degree of polymerization: 1700) was used instead of the polyvinyl alcohol used in example 2. The results are shown in Table 17.

[ Table 17]

The molded coal disintegrated after 1 minute of immersion in water. Therefore, the compressive strength after immersion in water cannot be measured.

Comparative example 4

Shaped coal was produced in the same manner as in example 2, except that polyvinyl alcohol (degree of saponification: 98.0 to 99.0 mol%, degree of polymerization: 1700) was used in place of the polyvinyl alcohol used in example 2. The compressive strength of the molded coal obtained was measured by the same procedure as in example 2 (after drying and after 24 hours of immersion in water at 20 ℃). The results are shown in Table 18. Table 18 also shows the results of comparative example 2, comparative example 3, example 2, and example 3.

[ Table 18]

As shown in table 18, in comparative example 4, the compressive strength was only slightly increased as compared with comparative examples 2 and 3. On the other hand, in examples 2 and 3 using polyvinyl alcohol having a saponification degree falling within the range of more than 99.3 mol%, the compressive strength after drying and water immersion was significantly increased as compared with comparative examples 2 to 4. In each of the examples and comparative examples, polyvinyl alcohol was added in a proportion of 3 parts by weight based on 100 parts by weight of the carbonized coal. From this result, it was confirmed that even when the blending ratio of polyvinyl alcohol was low, high compressive strength could be obtained by using polyvinyl alcohol having a high saponification degree and a polymerization degree of not less than a predetermined value.

Industrial applicability

According to the present invention, a method for producing molded coal which is excellent in safety and can maintain high strength even when wetted with water can be provided. Further, it is possible to provide a molded coal which can maintain high strength even when wetted with water.

Description of the reference numerals

10 … measuring device, 14 … movable plate, 16 … molding coal, 17 … support plate and 18 … support.