Method for manufacturing molded charcoal

Abstract

To provide molded charcoal with improved combustion performance that allows for easy ignition, and a method for manufacturing the molded charcoal. [Solution] Molded charcoal is constructed using aggregate containing graphite powder and wood powder, and a binder containing carboxymethylcellulose or starch.

Description

Technical Field

[0001] The present invention relates to molded charcoal containing graphite powder and a method for producing the same.

Background Art

[0002] Charcoal produces less smoke, flames, and odors during combustion, and can create a charred surface on food ingredients by the action of radiant heat including infrared rays (near-infrared rays, far-infrared rays), thereby confining umami components. Also, since no moisture is generated during the combustion of charcoal, the surface of the food ingredient becomes crisply roasted. Thus, charcoal has favorable characteristics for cooking and is widely used as a solid fuel for cooking.

[0003] For example, charcoal with excellent combustion performance such as Binchotan is produced by carbonizing wood at a high temperature to remove components other than carbon as much as possible, so the production cost is high and it becomes expensive. Therefore, although, for example, sawdust charcoal is commercially available as a substitute for Binchotan, the same level of combustion performance as Binchotan has not been obtained.

[0004] Here, for example, charcoal for cooking is required to have a large calorific value and a certain combustion time. In particular, charcoal used in general households or camping requires high combustion performance including easy ignition in addition to these.

[0005] For example, Patent Document 1 discloses producing fuel molded charcoal by mixing 5 to 25% of artificial graphite powder with carbon powder as a raw material composed of carbide with 80% or more carbonaceous matter. The addition of artificial graphite powder can be expected to improve the calorific value and combustion time, and to improve the bulk density of the molded charcoal. Therefore, by controlling the density of the molded charcoal, various characteristics such as, for example, bringing the combustion performance close to that of Binchotan and enabling easy ignition can be imparted to the molded charcoal.

Prior Art Documents

Patent Documents

[0006] [Patent Document 1] Japanese Patent Publication No. 2006-306925 [Overview of the Initiative] [Problems that the invention aims to solve]

[0007] Patent Document 1 discloses that in order to obtain charcoal as a raw material, it is necessary to dry-distill organic materials such as coniferous trees, sawdust, and bark at around 400-700°C. Furthermore, it discloses the use of wood vinegar tar and polyvinyl alcohol as binders (binding agents) in the molding process. However, there was a problem in that potassium and calcium had to be attached to the surface of the molded charcoal to facilitate ignition. In addition, since the artificial graphite powder content was a maximum of 25%, the improvement in combustion performance was limited.

[0008] This invention has been made in view of the above problems, and aims to provide molded charcoal with improved combustion performance that can be easily ignited, and a method for manufacturing the molded charcoal. [Means for solving the problem]

[0009] The molded charcoal of the invention of claim 1 is characterized by being composed of aggregate containing graphite powder and wood powder, and a binder containing carboxymethylcellulose or starch.

[0010] According to the above configuration, a binder containing carboxymethylcellulose or starch can be used to bond the aggregate containing graphite powder and wood powder together, thereby forming a robust molded charcoal. Since this molded charcoal contains wood powder, which has a lower ignition temperature than graphite powder, it can be easily ignited. Furthermore, because this molded charcoal contains graphite powder, its combustion performance can be improved.

[0011] The molded charcoal of the invention of claim 2 is characterized in that, in the invention of claim 1, the graphite powder is 30 to 50 parts by mass of the aggregate 100 parts by mass. According to the above configuration, the proportion of graphite powder in the aggregate is large, which improves the calorific value and burning time, thereby improving the combustion performance of the molded charcoal.

[0012] The molded charcoal of the invention of claim 3 is characterized in that, in the invention of claim 1, the wood powder and the binder are carbonized. According to the above configuration, the amount of fixed carbon in the molded charcoal increases, which improves the calorific value and thus the combustion performance.

[0013] The method for producing molded charcoal according to claim 4 is characterized by comprising: a mixing step of forming a mixture by mixing aggregate, wherein the aggregate is composed of 100 parts by mass of graphite powder and wood powder, with 30 to 50 parts by mass of graphite powder, and a binder containing carboxymethylcellulose or starch, in an amount of 3 to 15 parts by mass per 100 parts by mass of the aggregate; a kneading step of kneading the mixture at 110 to 200°C while adding water to form a kneaded product; and a molding step of forming the kneaded product into a molded product of a predetermined shape.

[0014] According to the above configuration, a binder containing carboxymethylcellulose or starch can be used to bind the aggregate containing graphite powder and wood powder together, thereby forming robust molded charcoal. Since this molded charcoal contains wood powder, which has a lower ignition temperature than graphite powder, it can be easily ignited. Furthermore, because the proportion of graphite powder in the aggregate is large, the calorific value and burning time can be improved, thereby enhancing combustion performance.

[0015] The method for producing molded charcoal according to claim 5 is characterized in that, in the invention of claim 4, it includes a heat treatment step of heat-treating the molded product in a non-oxidizing atmosphere at 700 to 1000°C. According to the above configuration, the amount of fixed carbon in the molded charcoal increases through heat treatment, thereby improving the calorific value and thus the combustion performance. [Effects of the Invention]

[0016] According to the formed charcoal and its manufacturing method of the present invention, the formed charcoal can be easily ignited, and the combustion performance of the formed charcoal can be improved.

Brief Description of the Drawings

[0017] [Figure 1] It is the formed charcoal according to Example 1 of the present invention. [Figure 2] It is a diagram showing the forming process of the formed charcoal of the present invention. [Figure 3] (a) is a chart showing the TG curve of Example 1, and (b) is a chart showing the DTA curve of Example 1. [Figure 4] (a) is a chart showing the TG curve of Example 2, and (b) is a chart showing the DTA curve of Example 2. [Figure 5] (a) is a chart showing the TG curve of Comparative Example 1, and (b) is a chart showing the DTA curve of Comparative Example 1. [Figure 6] (a) is a chart showing the TG curve of Comparative Example 2, and (b) is a chart showing the DTA curve of Comparative Example 2. [Figure 7] (a) is a chart showing the TG curve of Comparative Example 3, and (b) is a chart showing the DTA curve of Comparative Example 3. [Figure 8] It is a chart showing the change in combustion temperature of Examples 1 and 2 and Comparative Examples 1 to 3.

Modes for Carrying Out the Invention

[0018] Hereinafter, the modes for carrying out the present invention will be described in detail, but the present invention is not limited to the following embodiments.

[0019] The formed charcoal shown in FIG. 1 is obtained by binding and molding powdery aggregates containing graphite powder and wood powder with a binder. As the graphite powder, powder of artificial graphite or powder of natural graphite such as flake graphite or soil graphite can be used. The powder of artificial graphite is the shaving powder generated when shaving graphite products from artificial graphite blocks, and is usually discarded. By using such shaving powder, waste or by-products can be effectively utilized at low cost.

[0020] As for wood powder, for example, crushed discarded wood or sawdust generated when cutting timber from logs or processing wood can be used. Coniferous trees such as cedar, cypress, and hemlock are widely used as timber, and wood powder from these conifers is readily available. When molded charcoal containing wood powder burns, it releases a scent characteristic of the wood used to make the powder, so it is possible to adjust the scent to one's preference by selecting the type of tree. However, wood powder from hardwoods such as cherry can also be used, and the type of tree is not particularly limited.

[0021] Carboxymethylcellulose is preferred as a binder, but starch can also be used. Alternatively, a mixture of carboxymethylcellulose and starch may be used as a binder. These are available in food additive grades, do not produce harmful components during combustion, and are safe for use in heating food.

[0022] Molded charcoal consists of 30 to 50 parts by mass of graphite powder out of 100 parts by mass of aggregate. Because of the high proportion of graphite powder, which contains almost no components other than carbon, the combustion performance (calorific value, burning time, etc.) of the molded charcoal is improved. Furthermore, because this molded charcoal contains wood powder, ignition is easier.

[0023] Next, the process of forming molded charcoal will be described based on Figure 2. The first mixing step involves mixing graphite powder and wood powder, which are the aggregates, with a powdered binder in predetermined proportions. For 100 parts by mass of aggregate, 30 to 50 parts by mass of graphite powder and the remainder being wood powder may be used. The binder should be mixed in a ratio of 3 to 15 parts by mass per 100 parts by mass of aggregate. Mixing may be done manually, for example, using a stirring rod, or it may be done using a V-type mixer or a double-cone type mixer. The mixing method is not particularly limited as long as the graphite powder, wood powder and binder are thoroughly mixed so that they are uniformly combined.

[0024] The kneading process involves kneading the mixture prepared in the mixing process while adding water to bond the aggregates together with a binder. Kneading is performed using a commercially available kneading machine, for example, by applying friction to the mixture through the rotation of a screw while adding water as needed to form a kneaded product. The temperature during kneading depends on the type of aggregate and binder, but is preferably 110 to 200°C, and more preferably around 120 to 170°C.

[0025] In the molding process, the kneaded material formed in the kneading process is molded using a commercially available compression molding machine. The kneaded material is extruded from, for example, the nozzle of the compression molding machine and cut to an appropriate length by a rotating blade, resulting in molded charcoal. The shape of the molded charcoal is not particularly limited, but it can be made cylindrical with a diameter of 20 to 40 mm and a length of 20 to 100 mm to facilitate molding and handling.

[0026] The molded product (molded charcoal) thus formed may be heat-treated in a heat treatment process to carbonize the wood powder and binder. This heat treatment is preferably carried out in a non-oxidizing atmosphere (reducing atmosphere or an inert gas atmosphere such as nitrogen gas), and the heat treatment temperature is preferably 700 to 1000°C. Although the aroma released from the wood powder during combustion is eliminated by the heat treatment, the amount of moisture released during combustion is reduced, the amount of fixed carbon increases, and the combustion performance is improved.

[0027] Next, the molded charcoal of Examples 1 and 2 of the present invention will be described. 62 parts by mass (31 kg) of sawdust from coniferous trees such as cedar was used as wood powder, and 38 parts by mass (19 kg) of graphite powder obtained by cutting artificial graphite was used as aggregate. In addition, 5 parts by mass (2.5 kg) of commercially available carboxymethylcellulose was used as a binder per 100 parts by mass of aggregate.

[0028] In the mixing process, the aggregate and binder were uniformly mixed in a metal container using a metal stirring rod. In the kneading process, the aggregate and binder mixture was kneaded at approximately 150°C using a screw-type kneader, while water was added as needed. In the molding process, a commercially available compression molding machine was used to extrude the kneaded mixture from the mixing process through a cylindrical nozzle with an inner diameter of 30 mm, forming it into a cylindrical shape, and then cutting it into lengths of approximately 30 to 100 mm with a rotating blade.

[0029] Example 1 is molded charcoal in its original, unmolded form, with a bulk density of 0.83 g / cm³. 3 The result was as follows. Example 2 is molded charcoal in which the wood powder and binder contained in the molded product are carbonized in a heat treatment process, and the bulk density is 0.73 g / cm³. 3 In the heat treatment process, a commercially available vertical tubular furnace was used, and the material was heat-treated at 920°C for 10 minutes in a nitrogen atmosphere.

[0030] The molded charcoal of Examples 1 and 2, as well as commercially available products (Comparative Examples 1-3), underwent industrial analysis in accordance with JIS M 8812 (measurement of moisture content, ash content, volatile matter, and fixed carbon), measurement of calorific value in accordance with JIS M 8814, and measurement using a differential thermal balance. A calorimeter C5000 2 / 12 (manufactured by IKA) was used to measure calorific value.

[0031] Thermogravimetric differential thermal analysis (TG-DTA) was performed in an air atmosphere at a heating rate of 10°C / min in the temperature range of 30 to 800°C using a differential thermal balance TG-DTA7200 (manufactured by SII Nanotechnology Inc.). The TG curve shows a mass loss due to vaporization of water and volatile components before combustion of the sample in the low-temperature region, and a large mass loss due to combustion after the start of combustion. In addition, the DTA curve shows an exothermic peak due to the combustion of the sample.

[0032] Table 1 shows the industrial analysis results (moisture content, ash content, volatile matter, fixed carbon), calorific value, and ignition temperature for Examples 1 and 2 and Comparative Examples 1-3. The ignition temperature was defined as the point where the extension of the linear portion of the mass change in the temperature region before combustion intersects with the extension of the initial linear portion of the mass change due to combustion in the TG curves for Examples 1 and 2 and Comparative Examples 1-3 shown in Figures 3-7, and the temperature at that point was defined as the ignition temperature. Comparative Example 1 is Kishu Binchotan charcoal (bulk density 1.03 g / cm³). 3 Comparative Example 2 is sawdust charcoal (bulk density 1.06 g / cm³). 3 Comparative Example 3 is charcoal made from mangrove wood used by the Malaysian Forestry Agency (bulk density 0.87 g / cm³). 3 These are all readily available, commercially produced items.

[0033] [Table 1]

[0034] The molded charcoal of Example 1 contained uncarbonized wood powder and a binder, resulting in a high volatile content of 26.9% by mass and an ignition temperature of 260°C. This is considered to indicate a lower ignition temperature and easier ignition compared to Example 2 and Comparative Examples 1-3. Furthermore, three exothermic peaks were observed in the DTA curve (see Figure 3). The two lower-temperature peaks are thought to be due to the wood powder and binder, while the highest-temperature peak is thought to be due to the graphite powder.

[0035] The molded charcoal of Example 2 had an ignition temperature and calorific value approximately equivalent to that of the Binchotan charcoal of Comparative Example 1. Furthermore, compared to Comparative Example 1, Example 2 is considered to be easier to ignite due to its higher volatile content of 7.5% by mass. In addition, two exothermic peaks were observed in the DTA curve (see Figure 4); the lower-temperature exothermic peak is thought to be due to carbonized wood powder and binder, while the higher-temperature exothermic peak is thought to be due to graphite powder. In contrast, Reference Examples 1 to 3 each showed only one exothermic peak in the DTA curve (see Figures 5, 6, and 7).

[0036] Next, combustion experiments were conducted using Examples 1 and 2 and Comparative Examples 1 to 3 as fuels. Here, approximately 140 g of fuel was placed in a commercially available stove (Hida stove 14 cm, manufactured by Wahei Freiz Co., Ltd.) and ignited with a gas burner to initiate combustion. Figure 8 shows the changes in combustion temperature for Examples 1 and 2 and Comparative Examples 1 to 3. Combustion temperature was measured at five points on the surface of the fuel every 5 minutes from immediately after ignition (0 minutes) until 30 minutes had passed, and the highest temperature was recorded as the temperature at that time. A radiation thermometer (model number IR-309, manufactured by Custom Co., Ltd.) was used to measure the combustion temperature.

[0037] In Example 1, ignition occurred in about 3 minutes without the need for special ventilation, and very little ash was produced after combustion. In Example 2, ignition occurred in about 3 minutes without the need for special ventilation, burned at a higher temperature than in Example 1, and very little ash was produced after combustion.

[0038] Comparative Example 1 was difficult to ignite without a fan, and ignition took about 5 minutes when ignition was performed with a fan. After ignition, it burned more stably at a higher temperature than Example 2, and more ash remained after combustion compared to Examples 1 and 2. Comparative Example 2 ignited in about 3 minutes without the need for a fan, burned at a similar temperature to Example 1, and more ash remained after combustion compared to Examples 1 and 2. Comparative Example 3 ignited in about 3 minutes without the need for a fan, the temperature during combustion fluctuated greatly, and more ash remained after combustion compared to Examples 1 and 2.

[0039] Example 1 exhibits good ignition properties, can produce fragrances corresponding to the type of wood used to make the wood powder, burns at a temperature comparable to Comparative Example 2, and produces very little ash, making cleanup easy. Example 2, while slightly less than Comparative Example 1, has a high calorific value, a high combustion temperature, good ignition properties, and produces very little ash, making cleanup easy.

[0040] Furthermore, those skilled in the art can implement the present invention in various forms with modifications to the above embodiments without departing from the spirit of the invention, and the present invention encompasses such modifications.

Claims

1. Molded charcoal characterized by being composed of aggregate containing graphite powder and wood powder, and a binder containing carboxymethylcellulose or starch.

2. The molded charcoal according to claim 1, characterized in that of the 100 parts by mass of aggregate, the graphite powder is 30 to 50 parts by mass.

3. The molded charcoal according to claim 1, characterized in that the wood powder and the binder are carbonized.

4. A mixing step to form a mixture by mixing aggregate containing graphite powder and wood powder in an aggregate of which 30 to 50 parts by mass are graphite powder in 100 parts by mass of aggregate, and a binder containing carboxymethylcellulose or starch in an amount of 3 to 15 parts by mass per 100 parts by mass of aggregate, A kneading step in which water is added to the mixture and kneaded at 110 to 200°C to form a kneaded product, A method for producing molded charcoal, characterized by having a molding step to form the kneaded material into a molded product of a predetermined shape.

5. The method for producing molded charcoal according to claim 4, characterized by having a heat treatment step of heat-treating the molded product in a non-oxidizing atmosphere at 700 to 1000°C.

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