JPS6332839B2 - - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to a method for reforming low-rank coal, and more specifically, it involves reducing the moisture content of low-rank coal such as peat, lignite, and sub-bituminous coal, and further combining rapid heating, compression molding, and oxidation treatment. This invention relates to a method for modifying low-rank coal that reduces activity, prevents spontaneous combustion, and improves transportability and storability. Low-grade coal such as lignite has a high moisture content, which makes it uneconomical to transport.It is also highly active and tends to spontaneously ignite during transportation and storage. Limited to nearby areas. In view of these circumstances, various methods have been proposed to remove as much water as possible from these low-rank coals and prevent spontaneous combustion. For example, after drying, heat treatment is carried out in the presence of steam, followed by heat molding under atmospheric pressure to form briquettes (Japanese Unexamined Patent Publication No. 104996/1983), and a method of rapid heating after drying and then rapid cooling (Japanese Unexamined Patent Publication No. 1986-104996). 56−
149494). In addition, the present inventors have already developed a method of compression molding under high temperature (Japanese Patent Application No. 1983-
32983 specification) and a method for preventing spontaneous combustion by oxidizing coking coal after drying (Japanese Patent Application No. 57-182789)
(No. 3 Specification). The present inventors further conducted intensive research on methods for reforming low-rank coal, and as a result, completed the present invention. In the present invention, low-rank coal is dried at 85-150°C until the moisture content becomes substantially 0%, then heated to a forming temperature of 200-400°C within 10 minutes, and at this temperature, immediately Compression molding is performed at a pressure of 5ton/ ^cm2 , and the briquette is further heated to an oxygen concentration of 1 to 21 at 100 to 200℃.
This is a low-rank coal reforming method characterized by carrying out oxidation treatment using air or a mixed gas of oxygen and nitrogen at a volume percent. It is known that among coals, peat is the most likely to spontaneously ignite, followed by lignite, subbituminous coal, and bituminous coal. In addition, low-grade coal such as peat, lignite, sub-bituminous coal, and bituminous coal has a high moisture content and therefore has poor transportation efficiency. Therefore, in the present invention, these low-rank coals are targeted for modification. In carrying out the present invention, it is preferable that the raw coal be pulverized in advance into granules, and it is particularly preferable that the particle size is 3 mm or less. Coal is also dried in the sun to reduce its moisture content to 15 to 20.
It is desirable to reduce it to % by weight. Drying of the coal is carried out by heating at a temperature of 85 to 150°C, preferably in an inert gas such as nitrogen gas, until the moisture content becomes substantially 0%. The drying time is determined by considering the type of coal, heating temperature, etc. This drying removes most of the moisture in the coal and also removes some of the combustible gases. Dry coal has a forming temperature i.e. 200-400
Heat rapidly to a temperature of °C. Rapid heating is performed to a predetermined temperature within 10 minutes, preferably within 5 to 7 minutes. The reason for performing such rapid heating is to prevent deterioration in moldability due to long-term treatment at high temperatures. After rapid heating, compression molding is instantaneously carried out at a predetermined temperature of 200 to 400°C under a pressure of 1 to 5 t/cm ² , preferably 2 to 3 t/cm ² . Further, when compression molding is normally performed, it is necessary to add a binder such as pitch from the outside, but in the present invention, since self-by-produced tar is used as the binder, no external binder is required. Subsequently, the high-temperature compression molded coal is oxidized. This operation is aimed at improving spontaneous ignition resistance, and excellent effects are obtained when carried out at temperatures of 100-200°C. Oxidation treatment has an oxygen concentration of 1
~21% by volume, preferably 4-10% by volume for 30 minutes ~5
The heating time is preferably 2 to 3 hours. Although the oxidation treatment can be performed using air, it is preferable to use a mixed gas containing oxygen and nitrogen in a predetermined ratio. By the method of the present invention, which combines rapid heating, compression molding, and oxidation treatment, coal having a 1% carbon dioxide generation temperature of 115° C. or higher, a crushing strength of 80 Kg·f/cm or higher, and a bulk density of 1.1 g/cm ³ can be obtained. . The coal thus obtained has excellent spontaneous ignition resistance and dust generation resistance, and can sufficiently maintain these properties even when pulverized. Furthermore, since the crushing strength and bulk density are high, the transport efficiency is also extremely high. Furthermore, when used as fuel, it has a high calorific value and has properties suitable as fuel coal. Next, examples of the present invention will be shown. Examples 1 to 4 Australian Yalloon coal was crushed to 3 mm or less and dried at 120°C for 3 hours in a nitrogen gas atmosphere to reduce the moisture content to 0%.
And so. Thereafter, 8 g of the dried charcoal (properties shown in Table 1) was placed in a mold with an inner diameter of 25 mm, and rapidly heated to the specified molding temperature for the time shown in Table 2, followed by a compression pressure of 3 t/cm ^2. Instantly molds to a thickness of 15
~20 mm briquettes were obtained. Thereafter, the briquettes were subjected to oxidation treatment at a temperature of 150° C. for 3 hours in an oxygen-nitrogen mixed gas with an oxygen concentration of 6% by volume. Thereafter, the temperature was lowered to room temperature, the charcoal was taken out, and the charcoal was stored in an airtight container. The results are shown in Table 2. The spontaneous ignition resistance was evaluated based on the 1 volume % CO ₂ generation temperature. Comparative Examples 1 to 8 Example 1 except that oxidation treatment was not performed
It was carried out in the same manner as in 4. The results are shown in Table 2. Comparative example 9 Rapid temperature rise to 300℃, and then 3
The same procedure as in Example 3 was carried out except that compression molding was carried out after holding for a certain period of time. The results are shown in Table 2. Table 1 a Analysis values of dry coal for industrial analysis (dry base) Ash content: 1.2% by weight Volatile content: 50.9% by weight Fixed carbon: 47.9% by weight b Elemental analysis (dry ash free) Carbon: 64.0% by weight Hydrogen: 4.5 Weight% Nitrogen: 1.0% by weight Oxygen: 30.3% by weight Sulfur: 0.2% by weight [Table]

Claims (1)

[Claims] 1. Low-rank coal with substantially 0% moisture content at 85 to 150°C
The charcoal is then dried to a temperature of 200 to 400°C within 10 minutes, and at this temperature it is immediately compression molded at a pressure of 1 to 5 ton/cm ² . A method for reforming low-rank coal, characterized by carrying out oxidation treatment using air or a mixed gas of oxygen and nitrogen with an oxygen concentration of 1 to 21% by volume. 2. The reforming method according to claim 1, wherein the low-rank coal is lignite.