Method for manufacturing a binder for coke production and method for manufacturing coke

Abstract

The present invention provides a method for producing a coke binder with softening and melting properties using biomass, and a method for producing coke using the same binder. [Solution] A method for producing a binder for coke production, characterized by semi-carbonizing biomass at a semi-carbonization temperature of 240°C to 285°C, heating a mixture of the semi-carbonized biomass, alkali, and alcohol at 215°C to 240°C for 10 minutes or more, cooling, separating the cooled reaction product into solid and liquid under acidic conditions, and using the separated solid as a binder.

Description

Technical Field

[0001] The present invention relates to a method for producing a binder for coke production and a method for producing coke using the binder.

Background Art

[0002] Conventionally, development of production technologies for blast furnace coke using low-grade coal has been carried out. For example, coke is produced by blending a binder with low-grade coal. Patent Document 1 describes a method of modifying a non-caking coal into a binder by adding and mixing a metal salt of a fatty acid or a metal salt source of a fatty acid to the non-caking coal, followed by heat treatment. It is described that when this binder is added to coal at 30% and the mixture is calcined, the strength is improved compared to the case where the binder is added at 10%.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of Invention

Problems to be Solved by the Invention

[0004] Meanwhile, utilization of biomass, which is a carbon-neutral resource, is also being studied in coke production. However, biomass does not exhibit softening and melting properties during the carbonization process. Therefore, when biomass is added as a raw material (including a binder) for producing blast furnace coke, the strength of coke is significantly reduced, so biomass could not be used as a binder.

[0005] Accordingly, the present application aims to provide a method for producing a binder for coke production that has softening and melting properties using biomass, and a method for producing coke using the binder.

Means for Solving the Problems

[0006] This application was made to solve the above-mentioned problems, and its gist is as follows.

[0007] (1) A method for producing a binder for coke production, characterized by: semi-carbonizing biomass at a semi-carbonization temperature of 240°C to 285°C; heating a mixture of the semi-carbonized biomass, alkali, and alcohol at 215°C to 240°C for 10 minutes or more; cooling the mixture; separating the cooled reaction product into solid and liquid under acidic conditions; and using the separated solid as a binder.

[0008] (2) The method for producing a binder for coke production according to (1) above, characterized in that the alkali is at least one of KOH, NaOH, and Ca(OH)2.

[0009] (3) The method for producing a binder for coke production according to (1) above, characterized in that the alcohol is at least one of ethanol, butanol, and isopropyl alcohol.

[0010] (4) A method for producing coke, characterized by adding the binder produced by the method in (1) above to coal having a maximum fluidity of 0 ddpm or more and 10 ddpm or less, compressing and molding to produce a molded product, and carbonizing the molded product to produce coke. [Effects of the Invention]

[0011] According to this application, it is possible to provide a method for producing a coke binder with softening and melting properties using biomass, and a method for producing coke using the same binder. [Brief explanation of the drawing]

[0012] [Figure 1] This is a flowchart of the manufacturing method for the binder according to the embodiment. [Modes for carrying out the invention]

[0013] <Method for manufacturing binders> This embodiment will be described with reference to the drawings. Figure 1 is a flowchart of the method for producing a binder for blast furnace coke production using biomass according to this embodiment. The method for producing the binder according to this embodiment involves semi-carbonizing biomass at 240°C to 285°C, heating a mixture of the semi-carbonized biomass, alkali, and alcohol at 215°C to 240°C for 10 minutes or more, cooling, separating the cooled reaction product into solid and liquid under acidic conditions, and using the separated solid as the binder. By semi-carbonizing the biomass, cellulose and hemicellulose in the biomass are decomposed, and lignin-like substances are increased. Then, by heating the semi-carbonized biomass in an alkali-alcohol solution within a predetermined temperature range, the components in the biomass are further decomposed and reduced in molecular weight, thereby obtaining a binder suitable for coke production. The binder obtained by this method has the softening and melting properties necessary for coke production during the carbonization process when mixed with coal to produce coke. In the following description of embodiments, the mixing ratios and addition rates are given as mass fractions (%) unless otherwise specified.

[0014] First, the biomass used in the method for producing the binder of this embodiment will be described. Various types of biomass can be used and are not particularly limited. Examples of biomass that can be used include woody biomass (pine, cedar, beech, cypress, etc.), herbaceous biomass (grasses, legumes, etc.), agricultural residues (rice straw, rice husks, almond shells, walnut shells, etc.), oil extraction residues (palm kernel shells (PKS), empty palm fruit clusters (EFB), etc.), waste biomass (sewage sludge, municipal solid waste, etc.), and food biomass (coffee grounds, etc.). Biomass other than those exemplified above can also be used. The form and state of the biomass are not particularly limited. For example, in the case of woody biomass, sawdust or chips can be used. Among these biomass, woody biomass containing a larger amount of lignin-like substances that are the basis of low molecular weight components that exhibit softening and melting properties during the carbonization process to coke is preferred.

[0015] The biomass before partial carbonization preferably has a particle size of less than 50 mm. Particle size adjustment can be performed, for example, using a sieve, and the material below a 50 mm sieve can be used in the production of the binder. Alternatively, the biomass can be crushed to adjust the particle size.

[0016] The steps in the manufacturing method of the binder are described below. First, the biomass with adjusted particle size is semi-carbonized (S1). Semi-carbonization is a heat treatment also called torrefaction. Semi-carbonization can be performed by heating in an inert atmosphere (oxygen-free or low-oxygen atmosphere) using a general heating furnace to a predetermined heat treatment temperature (hereinafter also referred to as the "semi-carbonization temperature"). In this embodiment, the semi-carbonization temperature can be 240°C or higher and 285°C or lower. Semi-carbonization at this semi-carbonization temperature results in a binder with a better yield when the subsequent heat treatment in an alkali-alcohol solution is performed at the predetermined heat treatment temperature. In addition, when coke is produced using this binder by the method described later, coke with better strength can be obtained. If the semi-carbonization temperature is below 240°C, at least one of the binder yield and coke strength may be insufficient. If the semi-carbonization temperature is above 285°C, the strength of the coke produced may decrease. The heating time (holding time) at the above semi-carbonization temperature can be between 1 minute and 10 minutes.

[0017] As mentioned above, partial carbonization can decompose cellulose and hemicellulose, which are polysaccharides contained in biomass. Furthermore, it can increase the proportion of lignin-like substances, which are aromatic polymers contained in biomass. Components that exhibit softening and melting properties in binders can be obtained from these lignin-like substances. Therefore, by increasing the content of lignin-like substances through partial carbonization treatment, binders can be manufactured with a higher yield.

[0018] Here, the yield of the binder in this embodiment is the yield calculated by the following formula (1). Yield of binder (%) = Mass of binder obtained (g) / Mass of semi-carbonized biomass (g) × 100 ... (1)

[0019] The semi-carbonized biomass has improved grindability compared to the original biomass. It is preferable to adjust the particle size of the semi-carbonized biomass to less than 3 mm, preferably less than 0.5 mm. The particle size adjustment can be performed using a crusher and a sieve, and the fraction passing through the predetermined sieve may be used for producing the binder.

[0020] Next, an alkali and an alcohol are added to and mixed with the semi-carbonized biomass (S2). A strong alkaline substance can be used as the alkali. Specifically, at least one of KOH, NaOH, and Ca(OH)2 can be used. A lower alcohol having 5 or less carbon atoms can be used as the alcohol. Specifically, at least one of ethanol, butanol (including isomers), and isopropyl alcohol can be used. The mixing of the biomass, alkali, and alcohol can be carried out using an appropriate reactor. A plurality of types of alkalis or alcohols may be used in combination.

[0021] The mass ratio of the biomass to the alkali to be mixed can be set such that the alkali is 0.5 to 3 relative to 1 of the biomass. The ratio of the biomass to the alcohol can be set to an amount that allows the entire biomass to be immersed in the alcohol in the reactor.

[0022] Next, a mixture of biomass, alkali and alcohol is subjected to heat treatment (S3). That is, the biomass is heat-treated in an alkali-alcohol solution. The inside of the reactor is heated at a predetermined temperature rising rate to a predetermined heat treatment temperature and held there. The heat treatment can be performed after the gas in the reactor is replaced with nitrogen. The temperature rising rate of the reactor is not particularly limited, but can be 3°C / min or more and 30°C / min or less. In addition, the heat treatment temperature can be 215°C or more and 240°C or less. When biomass is semi-carbonized, the decomposition of cellulose and hemicellulose proceeds, and the biomass is polymerized through cross-linking formation between oxygen-containing functional groups. That is, although the semi-carbonized biomass has a higher molecular weight than the state before semi-carbonization, it can be thermally decomposed in the alkali-alcohol solution to reduce its molecular weight by performing the heat treatment within the above temperature range. This is because when the heat treatment temperature falls within the said range, coke with excellent strength can be obtained when coke is produced using the produced binder. The heat treatment time (holding time) at the heat treatment temperature is preferably 10 minutes or more. The upper limit of the heat treatment time is not particularly limited, but can be, for example, 60 minutes or less.

[0023] Next, the reaction product obtained by the heat treatment is cooled (S4). The cooling method is not limited, and can be performed, for example, by immersing the reactor in a water bath. In this cooling step, it is sufficient to cool to room temperature.

[0024] Next, an acid is added to the reaction product (S5). By making the solution acidic through the addition of the acid, the components with high softening and melting properties dissolved in the solution are precipitated on the solid side. Examples of the acid include inorganic acids such as hydrochloric acid and sulfuric acid, and organic acids such as acetic acid and formic acid. The concentration of each of hydrochloric acid and sulfuric acid can be 0.2 mol / L or more and 5.0 mol / L or less. The concentration of acetic acid can be 9.0 mol / L or more and 17.5 mol / L or less, and the concentration of formic acid can be 13.0 mol / L or more and 26.5 mol / L or less. The solution can also be made acidic by blowing CO₂ gas into the solution.

[0025] Next, the reaction product after adding the acid is subjected to solid-liquid separation (S6). The solid and liquid can be separated by filtration, and the solid is recovered and used in the next step. The filtration method is not particularly limited as long as it can separate the solid and liquid, but it can be carried out by natural filtration using filter paper.

[0026] Next, the solid obtained by solid-liquid separation is vacuum-dried (S7). Moisture is removed from the solid by vacuum drying. The material obtained by vacuum drying is the binder of this embodiment. The above describes the method for manufacturing the binder of this embodiment.

[0027] <Method of producing coke> Next, the method for producing coke according to this embodiment will be described. Coke can be produced by mixing coal and the binder produced as described above in a predetermined ratio, compressing and molding the mixture, and then carbonizing the molded product.

[0028] The type of coal used is not particularly limited, but coal with little or no softening and melting properties can be used. Such coal, when carbonized to produce coke, lacks sufficient softening and melting properties and therefore has insufficient strength. Combining it with the binder of this embodiment, which possesses softening and melting properties, allows for a greater enjoyment of the binder's softening and melting effect. As an example of coal with little or no softening and melting properties, coal with a maximum fluidity (MF) of 0 ddpm or more and 10 ddpm or less can be used. This MF is the Gieseler maximum fluidity measured using the fluidity test method (Giesler plastometer method) in accordance with JIS M 8801. Examples of such coal include non-caking coal, slightly caking coal, semi-anthracite, and anthracite. It is preferable to crush the coal to less than 500 μm before use. Of course, coke can also be produced by blending the binder of this embodiment with coal that possesses softening and melting properties.

[0029] The specified mixing ratio of the binder can be 3% to 50% when the total mass of the coal and binder mixture is considered to be 100%. Adding the binder within this range allows for the production of coke with sufficient indirect tensile strength for blast furnaces when mixed with coal that has little or no softening and melting properties. If the ratio is less than 3% (lower limit) or more than 50% (upper limit), sufficient strength of the coke may not be obtained.

[0030] Compression molding is not limited to any particular method, as long as it can be molded into a shape and dimensions suitable for blast furnace coke. For example, it can be molded into the desired shape and size (dimensions, volume) using a uniaxial compression molding machine, briquetting machine, or pelletizer. The shape can be, for example, cylindrical, masec type, or pillow type. The size can be, for example, between 0.5 cc and 100 cc. By compression molding, the density of the molded product is 800 kg / m³. 3 More than 1300kg / m 3 The following range is possible.

[0031] The carbonization of the molded material can be carried out in the same manner as the conventional carbonization of coal to coke. That is, carbonization is performed by blocking out air and, if necessary, maintaining an inert gas atmosphere at a carbonization temperature of 900°C to 1200°C for 10 to 120 minutes. The heating rate to the carbonization temperature can be 0.5°C / min to 20°C / min. The coke obtained by carbonizing the molded material is the coke of this embodiment. The above describes the method for producing coke of this embodiment.

[0032] The method for producing a binder for coke production according to this embodiment makes it possible to produce a binder that exhibits softening and melting properties from biomass that does not show softening and melting properties during the carbonization process to coke. By adding the prepared binder to coal that has little or no softening and melting properties according to the coke production method of this embodiment, it is possible to produce coke with sufficient strength for use in blast furnaces.

[0033] The reason why a binder produced by heating biomass in an alkali-alcohol solution exhibits softening and melting properties during the carbonization process to coke is thought to be as follows: Biomass has more oxygen-containing functional groups than coal, which exhibits softening and melting properties. Therefore, even if low-molecular-weight components (components that soften and melt) are generated by the thermal decomposition of biomass during the carbonization process, these generated low-molecular-weight components polymerize again via ether bonds formed by oxygen-containing functional groups, causing the softening and melting properties to be lost. As a result, even if biomass is used directly in a mixture with coal, the biomass does not exhibit softening and melting properties during the carbonization process, and the resulting coke lacks sufficient strength. In contrast, by semi-carbonizing the biomass and heating the semi-carbonized biomass in an alkali-alcohol solution at a temperature between 215°C and 240°C, the ether bonds can be cleaved, and low-molecular-weight components can be generated. Since these low-molecular-weight components have softening and melting properties during the carbonization process, the binder of this embodiment can be used to produce blast furnace coke with sufficient strength.

[0034] Furthermore, if the heat treatment temperature is below 215°C, the cleavage of the ether bonds is insufficient, and the softening and melting properties are reduced. Also, if the heat treatment temperature exceeds 240°C, the low-molecular-weight components undergo polymerization reactions, which reduces the softening and melting properties during the carbonization process. [Examples]

[0035] Samples of binders were prepared at various semi-carbonization temperatures and various heat treatment temperatures using the method of the embodiment. Coke was also produced using each binder sample.

[0036] <Manufacturing of adhesives> Pine chips (sieved through a 20mm sieve) were used as biomass and partially carbonized. The partial carbonization process was carried out in a heating furnace under an inert atmosphere, heating to predetermined partial carbonization temperatures. The partial carbonization temperatures were 225°C, 250°C, 275°C, 300°C, and 325°C. The partially carbonized material was pulverized and sieved to adjust the particle size to less than 500 μm. 5 g of partially carbonized material, 5 g of NaOH, and 50 mL of ethanol were placed in a reactor. After replacing the gas in the reactor with nitrogen, the reactor was heated at approximately 10°C / min to the respective heat treatment temperatures. The heat treatment temperatures were 160°C, 180°C, 200°C, 220°C, and 240°C, and binders were prepared at each temperature. Of these, the binder obtained by semi-carbonizing at a semi-carbonization temperature of 250°C to 275°C and then heat-treating at a heat-treatment temperature of 220°C to 240°C corresponds to the binder of the embodiment. After being held at the heat-treatment temperature for 30 minutes, it was cooled in a water bath. 200 mL of a 2 mol / L aqueous HCl solution was added to the reaction product (a mixture of solid and liquid) in the reactor, and then the solid and liquid were separated and recovered by natural filtration using filter paper. The recovered solid was vacuum-dried to remove moisture and obtain the binder for each sample.

[0037] The yield was determined for each sample of binder. The yield was calculated using the above formula (1). Specifically, it is as shown below. Yield of binder (%) = Mass of binder obtained (g) / Mass of semi-carbonized biomass (g) × 100 ... (1)

[0038] <Coke production> Non-caking coal (MF: 0ddpm, volatile matter VM: 50%) that does not soften or melt was crushed to less than 500 μm, and 20% (internal percentage) of the prepared binder was added and mixed (i.e., 80% coal, 20% binder). The mixture was compressed and molded using a uniscrew compression molding machine under conditions of 30 MPa to obtain a cylindrical molded product with a diameter of 15 mm and a thickness of 10 mm. The molded product was heated in an inert gas atmosphere at 5°C / min to 900°C, held for 30 minutes, and then carbonized to produce coke.

[0039] <Strength Test> The strength of the prepared coke was evaluated using the crushing strength test method, and the indirect tensile strength was calculated using the following formula (2). This method is the evaluation method described in Miyagawa, Yoshio and Fujishima, Ichiro, "Investigation of coke strength by indirect tensile strength test method (I) - Matrix strength of blast furnace coke -", "Journal of the Japan Fuel Association", Vol. 54, No. 584 (1975), pp. 983-993. f = 2·P / (π·d·l) (2) Here, f is the indirect tensile strength [MPa], P is the crushing strength [N], d is the sample diameter [mm], and l is the thickness [mm]. That is, based on the crushing strength test method described above, the crushing strength P at which the sample fractured was determined, and the indirect tensile strength f was calculated from the determined crushing strength P using equation (1).

[0040] Table 1 shows the yield of the manufactured binders and the results of the coke strength tests. Table 1 shows the yield (%) of each binder produced by semi-carbonizing biomass at each semi-carbonization temperature and then heat-treating it at each heat treatment temperature, and the strength [MPa] of each coke produced using each binder. Samples without a semi-carbonization temperature listed (indicated by "-") are examples where the binder was produced by heat-treating unsemi-carbonized biomass directly in alkali and alcohol. "na" in the strength column indicates that the crushing strength was below the detection limit and could not be measured.

[0041] [Table 1]

[0042] As can be seen from the results in Table 1, when coke was produced by adding binders obtained under conditions where the biomass was semi-carbonized at 250°C and 275°C, and the heat treatment temperature in the alkali-alcohol solution was 220°C and 240°C, the indirect tensile strength of the coke was a good strength of 4.2 MPa to 5.5 MPa. Furthermore, the yield was also higher (over 12%) compared to when semi-carbonization was not performed. Therefore, it was confirmed that pre-semi-carbonizing the biomass increases the coke strength-improving effect of the resulting binder and also improves the yield of the binder. In other words, it was confirmed that semi-carbonization treatment can achieve both improved coke strength and improved binder yield.

[0043] On the other hand, for samples of biomass that were not partially carbonized and were heat-treated in an alkali-alcohol solution, the coke strength was highest at a heat treatment temperature of 220°C, but it remained at 3.0 MPa. Furthermore, the yield of the binder was only 8%. In addition, even when the heat treatment temperature in the alkali-alcohol solution was 220°C or 240°C, the strength was lower when the partial carbonization temperature was 300°C or higher compared to when it was between 250°C and 275°C.

Claims

1. A method for producing a binder for coke production, characterized by semi-carbonizing biomass at a semi-carbonization temperature of 240°C to 285°C, heating a mixture of the semi-carbonized biomass, alkali, and alcohol at 215°C to 240°C for 10 minutes or more, cooling, separating the cooled reaction product into solid and liquid under acidic conditions, and using the separated solid as a binder.

2. The alkalis mentioned above are KOH, NaOH, and Ca(OH) ２ A method for producing a binder for coke production according to claim 1, characterized in that it is at least one of the following.

3. The method for producing a binder for coke production according to claim 1, characterized in that the alcohol is at least one of ethanol, butanol, and isopropyl alcohol.

4. A method for producing coke, characterized by adding the binder produced by the method of claim 1 to coal having a maximum fluidity of 0 ddpm or more and 10 ddpm or less, compressing and molding to produce a molded product, and carbonizing the molded product to produce coke.

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