KR860002068B1 - Process for modification of coal - Google Patents

Abstract

No content.

Description

Coal Improvement Method

The present invention relates to a method for the improvement of coal, and more particularly to stabilizing coal by reducing the activity of low-grade coal such as peat, lignite and cold bituminous coal and reducing its activity to protect coal from natural combustion. It is about how to.

The present invention also relates to a method for the reforming of coal, and more particularly to reducing the water content of lower coals such as peat, lignite and sub-bituminous coal and reducing the activity by appropriately performing rapid heating, compression molding and oxidation treatment. It is a method for improving coal to prevent spontaneous ignition and improve transportation and storage.

Low lank coals, such as lignite, are generally used in confined areas near coal mines because their high water content increases transport costs, which is disadvantageous from an economic point of view, and is therefore more likely to spontaneously ignite transport or storage due to their high activity. do.

In such circumstances, various proposals have been made to reduce the water content of such low-grade coal and protect it from natural combustion.

For example, as a technique for reducing the water content of coal, (1) evaporation method, (2) mechanical dehydration method, and the like are known. In addition, technologies to prevent natural combustion of coal include: (1) coating air protection methods (coal storage in water or coal surface) or covering coal surfaces, extruding storage of coal, inert gas sealing, and (2) cooling methods ( 3) How to remove fine coal powder (4) It is known how to make coal briquettes.

In more detail, a method of heating and drying coal in the presence of steam, a method of thermoforming under atmospheric pressure to produce coal briquettes (see Japanese Patent Application Publication No. 104996/1981), and the like are known.

However, these methods are not satisfactory because they do not achieve effective results and are complicated to operate.

It is an object of the present invention to provide a method for the improvement of coal in which dehydration of low dry coal and prevention of natural combustion are simultaneously achieved by a relatively simplified procedure.

The process for improving coal quality comprises (1) heating the coal at a temperature between 100 and 350 ° C. until the water content of the coal is substantially zero and then oxidizing the coal.

(2) Processes for coal reforming including drying coal until the water content of coal is practically zero, rapidly heating coal to forming temperature, forming under elevated pressure, and oxidizing the coal. will be.

With regard to coal, peat is known to spontaneously ignite, and lignite and sub-bituminous coal also spontaneously ignite. The transport efficiency of lower coal such as peat, lignite and sub-bituminous coal is poor due to their water content. Thus, the present invention mainly prays for the improvement of such low coal. In the practice of the present invention, the supply of coal is preferably pulverized into an acquaintance type.

It is particularly desirable for the diameter of the particles to be 3 millimeters or less. In addition, the water content of coal is preferably reduced by 15% to 20% by weight by drying in the form of solar drying.

The process (1) of this invention is demonstrated below.

Coal is first heated in a closed gas such as nitrogen gas at a temperature of 100 to 350 ° C. until the water content is substantially zero. The time for this heat treatment is determined in consideration of the type of coal, the heating temperature and the like, and is generally 10 minutes to 3 hours. This heat treatment removes steam and flammable gases, and increases the natural flammability of coal. However, if the heating temperature is higher than 350 ℃, the temperature at which carbon dioxide is generated falls and the amount of oxygen increases as it is absorbed. The desired effect is only inadequate.

After the heat treatment, coal is formed if necessary. This molding is achieved by heating and compressing the heated coal. If necessary, a binder such as wet tarna bitumen can be used. The oxidation process applied after the heat treatment aims at enhancing the natural combustion power (or self-ignition characteristics) of the coal. This oxidation is usually done during heating. It produces excellent results in oxidizing in the rising temperature range between 100 ° C and 200 ° C. The oxidation process is carried out at an oxygen concentration of at least 1% by volume and is usually carried out at 1 to 21% by volume, more preferably at 4 to 10% for 30 minutes to 5 hours, more preferably for 2 to 3 hours. . Air can be used in this oxidation process, but it is preferable to use a mixture of oxygen and nitrogen at a given rate.

The following describes the process (2) of the present invention in detail.

Coal is typically dried by heating at a temperature of 85 to 150 ° C., and better with inert gas such as nitrogen gas until the moisture content is substantially zero. The drying time is determined by considering the type of coal and the heating temperature. This drying removes the combustible gas and the like in the coal.

The coal thus dried is then rapidly heated to an elevated temperature, such as from 200 ° C to 400 ° C. This heat treatment is carried out so that the predetermined temperature is achieved within 1 to 10 minutes, more preferably within 5 to 7 minutes.

This rapid heating is carried out for the reason that long-term heating at elevated temperature reduces the molding ability.

After rapid heating, the coal is compacted at a predetermined temperature in an instant, preferably at 200 to 400 under a pressure of 1 to 5 ton / cm 2, and more preferably at a pressure of 2 to 3 ton / cm 2. In this compression molding it is usually necessary to add external binders such as bitumen. In the present invention, however, its external by-product tar is used as the binder, so such external binder does not need to be added.

At this elevated temperature, the compacted coal is then oxidized. This oxidation is carried out for the purpose of enhancing the self-ignition properties of coal. The oxidation conditions are the same as the oxidation process described in the process (1) of the present invention.

Steaming is preferred after the oxidation process. This steam load is carried out in saturated humidity at 80 to 150 ° C., preferably at 90 ° C. for 2 to 8 hours. These oxidation treatments and steam steaming can be carried out at the same time, no problem.

The process of the present invention produces carbonaceous coals which significantly reduce the water content of coal and have improved natural combustibility compared to raw coals or crude coals supplied from Australia. The reformed coal in which carbon quality is improved by the method of the present invention has a high exothermic value and is therefore suitable for fuel use. In particular, process (2) of the invention typically produces reformed coal having a temperature of generating 115% or more of carbon dioxide 1% and a bulk density of at least 80 kg · f / cm of compressive strength.

In this way, the reformed coal is greatly improved in natural combustion power and powder production characteristics, and can maintain improved characteristics even when pulverized. Moreover, the transportation efficiency of reformed coal is very high because of its high compressive strength and bulk density. Steam steam produces reformed coal with high water resistance.

In other words, the ammunition ammunition coal does not lose its original form even if it is hit by diarrhea and is easy to handle and store. Moreover, steam loads increase the compressive strength of coal-reforming coal.

The present invention will be described in more detail with reference to the following examples and comparative examples.

[Examples 1 to 5]

Two kilograms of Yallourn lignite (pulverized to 5 mm or less in diameter) of air-dried australian acid are loaded into the packaged cylinder and dried by passing preheated nitrogen through the cylinder at a rate of 2 liters per minute.

The coal is then heated for 3 hours after reaching a predetermined temperature. At the end of time, coal is cooled to room temperature, taken out of the cylinder and stored in a closed container. The moisture content of lignite was 0%.

Moisture content was specified throughout the entire example by the humidity measurement method (heat drying method) specified in Japanese Industrial Standard JIS M 8811-1976. The packed column was loaded with 200 g of the heated lignite described above, and the mixed gas of oxygen and nitrogen adjusted to 6 vol% oxygen concentration was preheated and passed through the column at a rate of 500 milliliters per minute. At the end of this time, the temperature of the coal is lowered to room temperature and then the coal is removed from the circumference and stored in a closed container.

The above lignite is pulverized and sieved in order to crush fragments having a particle diameter of 0.15 to 0.5 mm and a particle diameter of 0.15 mm or less. The temperature of gaseous carbonate generation and the amount of absorbed burnt on the fragments of electrons are measured to evaluate their natural combustion power.

The final analysis and calorie values for the latter fractions are presented in Tables 1 and 2.

[Comparative Examples 1 to 5]

The procedures of each of Comparative Examples 1 to 5 were repeated except that the oxidation process was omitted. The results are shown in Tables 1 and 2.

[Table 1]

Notice :

* 1: Coal under air dry conditions is pulverized and sieved to obtain fragments of 60 to 150 mesh.

50 g of the above fragments are then placed in a lower absorption tube of a combustion sulfur analyzer for petroleum products as defined in the reactor (JIS K-2818) and placed in an oil bath.

The atmosphere in the tube is replaced by oxygen blown into the tube at a rate of 30 milliliters per minute at a lower share than air. After confirming that the atmosphere is almost replaced by oxygen by chromatography, the temperature of the oil tank is raised at a rate of about 0.7 ° C. per minute while maintaining the oxygen flow rate as described above. The composition of the generated gas is measured by chromatography at about 1 minute intervals.

* 2: The bioboot (made of aluminum) in which 1-2 grams of 60-100 mesh pieces were put in it was put in the room. The atmosphere in rooms and cylinders is completely replaced by oxygen from atmospheric pressure. The experiment began when the temperature in the room reached the measured temperature. The pressure change corresponding to the amount of oxygen absorbed by the sample was recognized by the gas rectifier and oxygen was introduced from the cylinder into the room by the injection pump at a volume comparable to the consumption. The amount of oxygen absorbed was determined by the reduced amount of oxygen in the cylinder.

[Table 2]

Notice :

* 1: Coal is dried at 50 ° C under reduced input.

* 2: The numerical value was based on the coal free content, not based on the equilibrium moisture at 95% humidity specified by JIS M8811-1976.

[Examples 6 to 10]

In this example, the effect of oxidation time was tested. The procedure of Example 1 was repeated with a heating temperature of 200 ° C., an oxidation temperature of 150 ° C., an oxygen concentration of 6% by volume, and an oxidation time as shown in Table 3.

The results are shown in Table 3.

[Table 3]

Note: * mark is same as the first table.

[Examples 11 to 15]

In this example, the effect of oxygen concentration on the oxidation process was tested. The procedure of Example 1 was repeated with varying heating temperatures of 300 ° C., oxidation temperatures of 150 ° C. and oxygen concentrations as indicated in Table 4. The results are shown in Table 4.

[Table 4]

Note: * 1 and * 2 are the same as the first table.

EXAMPLES 16-20

In this example, the effect of oxidation temperature was tested. The procedure of Example 1 was repeated with a heating temperature of 300 ° C. and an oxidation temperature of 6% by volume of the oxygen concentration axis as indicated in Table 5. The results are shown in Table 5.

[Table 5]

Note: The * mark is the same as in the first table.

[Comparative Examples 6 and 7]

Under reduced pressure (Comparative Example 6), coal (Yallourn lignite) and australian clam coal (Example 7), dried at 50 ° C., respectively, are ground and sieved to obtain fragments of 0.15-9.5 mm in diameter. The annealing was tested for carbon dioxide evolution temperature and oxygen uptake.

The results are shown in Table 6.

[Comparative Examples 8 and 9]

The procedure of Example 1 was repeated except for the heating temperature of 400 ° C. and the oxidation process (Comparative Example 8).

The procedure of Example 1 was repeated at a heating temperature of 400 ° C. and an oxidation temperature of 150 ° C. The results are shown in Table 6.

[Table 6]

Note: 1 and 2 are the same as in the first table.

[Examples 21 to 24]

Yallourn lignite is pulverized to 3 mm or less in particle diameter and completely dried at 120 ° C. in a stream of nitrogen.

The above-mentioned dry coal (the characteristics of which are indicated in the seventh table) is then placed in a mold (inner diameter of 25 millimeters) and rapidly heated to the predetermined forming temperature indicated in the seventh table, and 3 ton / Molded in seconds under pressure of cm ² . The molding thus obtained is separated from the mold and oxidized for 3 hours at a temperature of 150 ° C. in a mixed gas (oxygen concentration 6%) with oxygen. At the end of this time the shaped coal is cooled off at room temperature and taken out and stored in an airtight container. The results are shown in Table 8. The natural combustion power of coal-reforming coal was evaluated at 1% carbon dioxide generation temperature.

[Comparative Examples 10 to 17]

The procedures of Examples 21-24 were repeated except that the oxidation process was omitted. The results are shown in Table 8.

[Table 7]

[Table 8]

Note: * 1. Measured at a compression rate of 20 mm in the radial direction of the cylindrical mold.

For standardization, compressive strength per unit strength is measured by dividing each measurement by thickness.

* 2. After grinding

[Examples 25 to 27]

Oxidized coal was prepared in the same manner as in Example 22 and placed in a flask containing distilled water. The flask is infiltrated with the heat maintained at 100 ° C. and the inside of the flask is saturated with steam by distilled water being heated at 90 ° C. Steam the coal briquettes in this saturated steam. The coal briquettes thus obtained were measured for compressive strength and water content (measured after immersion in water as described below in Examples 26 and 27). Compressive strength is calculated by the following equation.

Where the specimen is compressed from its radial direction

Compressive strength of specimen = compressive strength

Equation: compressive strength (kgf / cm)

In Examples 26 and 27, the coal briquettes were deposited for 100 hours, after which the compressive strength was measured. Protective retention rate was calculated from the following equation.

The results are shown in Table 9.

[Examples 28 to 30]

Oxidized coal was prepared in the same manner as in Example 23 and steam steamed for a predetermined time in the same manner as in Examples 25 to 27. The coal briquettes thus obtained were measured for compressive strength and water content (in Example 29 and after immersion in water as described above). The protection retention was measured for the coal briquettes of Examples 29 and 30.

The results are shown in Table 9.

[Table 9]

Reference Example 1

Oxidized charcoal was prepared in the same manner as in Example 22 and deposited in water for 100 hours without being steamed. At the end of this time, the compressive strength of the above described shots was attempted, but could not be measured because the above shots swelled and disintegrated.

The water content after infiltration in water was 12.5%.

Reference Example 2

Oxidized briquettes were prepared in the same manner as in Example 23 and were deposited in water for 100 hours without steaming. At the end of this time, the compressive strength of the above described coals was measured and found to be 128 kg · f / cm.

Protection retention rate was 71%. The water content after immersion in water was 12.5%. The shot had cracks.

Claims (6)

The coal is heated and dried at a temperature of 100 ° C. to 350 ° C. until the water content substantially reaches zero, and the dried coal is rapidly heated to a forming temperature of 200 ° C. to 400 ° C. for 1 to 10 minutes. A method for improving coal, comprising compression molding under reduced pressure and oxidizing the coal briquettes. The method for reforming coal according to claim 1, wherein the coal is a low quality coal such as lignite. The method for reforming coal according to claim 1, wherein the oxidation is carried out at a temperature condition of 100 to 200 ° C and an oxygen concentration of 1 to 21% by volume. The method of claim 1, wherein the coal is dried by heating at a temperature of 85 ° C to 150 ° C. The method for reforming coal according to claim 1, wherein the compression molding is instantaneously performed at a pressure of 1 to 5 tons / cm ² and a temperature of 200 to 400 ° C. A method for reforming coal, wherein the coal briquettes oxidized according to claim 1 are steamed in a saturated humidifier at a temperature of 80 to 150 ° C. for 2 to 8 hours.