JP2000212572A - Preheating of coal - Google Patents

Abstract

PROBLEM TO BE SOLVED: To surely suppress thermal decomposition of coal, when coal is preheated at elevated temperature in the coal-preheating step. SOLUTION: Before coal is charged in a coke furnace for producing metallurgical coke, the coal is preheated by heat exchange with the hot gas. In this preheating, the coal is preheated until the coal reaches in the temperature ranges from 200 deg.C to 300 deg.C so that the coal is perfectly dried in the first step. Then, without the cooling step the dried coal is led to the solid-gas separator and separated from the hot gas and directly introduced into the coal preheater and further heated over 300 deg.C, preferably at 340-430 deg.C.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement in a method of preheating coal by bringing it into contact with a heating gas and exchanging heat before charging the coal into a coke oven for the production of metallurgical coke. It is.

[0002]

2. Description of the Related Art In a process for producing coke for metallurgy, raw coal is preliminarily added to a coke oven before it is charged into a coke oven.
A technique of preheating to about ° C and then dry distillation is widely practiced (the temperature of the gas itself for preheating is as high as 400 to 600 ° C). This is because by increasing the heating rate of the raw coal as fast as possible in the preheating step, not only the carbonization can be efficiently performed in the coke oven, but also the coking property of the raw coal can be improved.

Japanese Patent Application Laid-Open No. 9-48977 discloses that raw coal comprising 0 to 60% by weight of non-coking coal and the remaining coking coal being 350 to 450 at a heating rate of 100 to 1000 ° C./sec.
℃, then classified into pulverized coal and coarse coal, hot coal agglomeration (that is, molding), after mixing the preheated coarse coal and the compacted coal, coke oven A method for producing coke for a blast furnace, in which the coke is charged and carbonized, is shown. In this example, the raw coal blended with caking coal and non-fine caking coal was heated to 150 ° C. by a coal drying preheater and dried, and then transferred to a coal hopper. An example is shown in which an apparatus is charged into a coal heater of a formula and rapidly heated to 400 ° C. at 500 ° C./sec by the coal heater to preheat.

[0004] The next application in the applicant's application is to exchange heat by contacting the coal with a heated gas prior to charging the coal into a coke oven for the production of metallurgical coke. It is disclosed that the preheating is performed by devising the preheating as follows.

JP-A-9-221677: Preheating,
(a) performing the contact by bringing coal into the heating gas stream; (b) controlling the oxygen concentration in the heating gas to less than 3%; and (c) controlling the coal temperature by the heat exchange. The temperature of 340 to 400 ° C. is satisfied.

JP-A-9-221678: Preheating,
(a) performing the contact by entraining coal with the heated gas stream; (b) performing the contact under pressurized conditions;
(c) controlling the oxygen concentration in the heating gas to less than 3%, and (d) setting the coal temperature to 340 to 340 by the heat exchange.
It is performed so as to satisfy all the conditions of bringing the temperature to 400 ° C.

JP-A-9-227875: Preheating
(a) performing the contact by bringing coal into the heating gas stream; (b) controlling the oxygen concentration in the heating gas to less than 3%; and (c) controlling the contact in the heating gas. The procedure is performed in such a manner that the conditions of vaporizing the tar and (d) bringing the coal temperature to 340 to 400 ° C. by the heat exchange are all satisfied. In this case,
It is particularly desirable that the condition of (e) performing the contact under pressurized conditions is also satisfied.

In addition, Japanese Unexamined Patent Application Publication No. 9-272873 filed by the present applicant discloses that waste gas containing a combustible component after heat exchange used for high-temperature preheating of coal is supplied to a pre-chamber of a coke dry-fire extinguishing system. A method for treating gas used for high-temperature preheating of coal, which is guided to the upper space of the pre-chamber and burned by air introduced at a ratio equal to or higher than the theoretical combustion equivalent of the waste gas in the upper space in the pre-chamber, is shown. I have.

[0009]

As described above, in the production process of metallurgical coke, a technique of preheating and then carbonizing raw coal before charging it into a coke oven is widely practiced. In this case, in order to efficiently preheat the coal, the coal particles are exposed to a rapid rise in temperature due to heat exchange with a high-temperature gas, and therefore, the coal particles are easily thermally disintegrated and pulverized. Coalization of coal particles causes a decrease in coke strength due to a decrease in bulk density (charge density) in a coke oven, and causes various troubles due to entrainment of the fines in the generated gas. Need to be avoided.

[0010] In the above-mentioned application, various improved methods relating to the preheating of coal have been proposed, but suppression of thermal collapse in the preheating step of coal has not always been sufficiently solved.

In view of such circumstances, the present invention provides a method for performing preheating at a high temperature in a coal preheating step, and provides a technique capable of reliably suppressing thermal collapse in the preheating step. It is intended for.

[0012]

The method for preheating coal according to the present invention involves exchanging heat by bringing the coal into contact with a heating gas prior to charging the coal into a coke oven for the production of metallurgical coke. Preheating the coal by 200
The first stage of preheating, in which the preheating is carried out until the temperature becomes not less than 300 ° C and less than 300 ° C, is carried out completely. Then, this is led to a solid-gas separator without cooling, separated from the heating gas, and immediately preheated coal A second stage of preheating in which the coal is further preheated to a high temperature of 300 ° C. or higher.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail.

As the coal which is widely used at present, one having a particle size of about 3 mm or less, particularly one having an average particle size of about 1 mm is used. The coal type may be any of caking coal, fine caking coal, non-coking coal, or a mixture thereof.

The heating gas is optional, but industrially, a combustible component (H ₂₎ generated in steelmaking or a steelworks-related factory is used.
And CO), for example, a gas obtained by burning a coke oven gas, a blast furnace gas, a converter gas, or a mixed gas thereof with a limited ratio of air.

In the present invention, the first stage of preheating is performed in which the coal is preheated to a temperature of 200 ° C. or higher and lower than 300 ° C., and is completely dried. Immediately after the introduction and separation from the heating gas, the mixture is introduced into a coal preheater to perform a second stage of preheating in which the coal is preheated to a high temperature of 300 ° C. or more.

FIG. 1 is an explanatory view showing an example of an apparatus for carrying out the preheating method of the present invention, wherein (1) is a first hot air generator, (2) is a coal feeder, and (3) is 1st coal preheater, (4)
Is the first solid-gas separator, (5) is the second coal preheater, (6) is the second
The solid-gas separator (7) is a second hot air generator. Although not shown, an oxygen concentration meter, a combustion control device, and the like can be additionally provided as necessary.

In the first hot air generator (1), a gas containing a combustible component is burned with air to produce a high-temperature heating gas having an oxygen concentration of less than 3% (preferably 2.5% or less, particularly 2% or less). generate. The heating gas generated from the first hot air generator (1) is guided to the first coal preheater (3), and the coal supplied from the coal feeder (2) is dried, heated, and preheated. The temperature of the heating gas entering the first coal preheater (3) is preheated so that the coal is at a temperature of 200 ° C. or more and less than 300 ° C. according to the supply amount of coal, and is increased to a temperature of 300 ° C. or more. Strictly controlled so as not to be heated. The preheated coal preheated to a temperature in the above range and from which water has been completely removed is supplied to the first solid-gas separator.
The gas is separated from the heating gas by (4), guided to the second coal preheater (5), and further heated and preheated to a high temperature of 300 ° C. or more. The preheated coal exiting the second coal preheater (5) is separated from the heated gas by the second solid-gas separator (6), transported to a coke oven and carbonized. The heating gas generated from the second hot air generator (7) is introduced into the second coal preheater (5).

In the first coal preheater (3), 2
It is important to preheat to a temperature above 00 ° C and below 300 ° C. If the temperature is lower than 200 ° C., water remains in the coal particles, and the water rapidly escapes at the time of high-temperature preheating in the second coal preheater (5) in the next step, so that the coal particles collapse. Further, when preheating is performed to a high temperature of 300 ° C. or more, the same coal particles are disintegrated and pulverized in the first coal preheater (3). The temperature rise in the first coal preheater (3) is desirably performed in a short time as possible (for example, within 10 seconds, particularly within 7 seconds, and more preferably within 5 seconds).

In the second coal preheater (5), 3
It is preheated to a high temperature of 00 ° C. or higher. If the temperature is lower than 300 ° C., the strength of coke produced from the coal by dry distillation is not sufficiently improved. The preheating temperature of the coal by the second coal preheater (5) is preferably 340 to 430 ° C (more preferably 350 to 410 ° C).
It is desirable that the temperature rise at this time is also performed in a short time as possible (for example, within 10 seconds, particularly, within 7 seconds, and more preferably, within 5 seconds). The above temperature range corresponds to the softening and melting temperature of coal, at which temperature the micellar structure of the coal is thermally dissociated, and the dissociated micelles generated in the coal particles act as a kind of solvent, The coking properties of coal are improved. However, unless the oxygen concentration in the heating gas is controlled to less than 3%,
As the oxidation proceeds, the coking properties decrease.

The first solid-gas separator (4) and the second solid-gas separator (6)
Part of the exhaust gas after solid-gas separation by the furnace is transferred to the first hot air generator (1) and the second hot air generator (7) to control the gas temperature and gas volume and to effectively use waste gas in the actual equipment. You can go back.

<Action> In the present invention, coal is used for 200 times.
The first stage of preheating, in which the preheating is carried out until the temperature becomes not less than 300 ° C and less than 300 ° C, is carried out completely. Then, this is led to a solid-gas separator without cooling, separated from the heating gas, and immediately preheated coal In the second stage, the coal is preheated until it reaches a high temperature of 300 ° C. or more. By doing so, it is possible to heat to a high temperature while avoiding cracking of the coal particles. this is,
When heated to 300 ° C. or more in a single step, the particles are destroyed because the inherent moisture present inside the particles explosively escapes when they go out of the particles. However, if the temperature is lower than 300 ° C., this phenomenon is avoided. This is because if the first stage preheating is performed at a temperature lower than 300 ° C. and the presence of moisture inside disappears, the particles will no longer crack even if rapidly heated to a high temperature of 300 ° C. or higher. On the other hand, if the preheating in the first stage is lower than 200 ° C., the inherent moisture present in the coal particles remains without being completely removed and explosively comes out of the particles during the preheating in the second stage of the next process. Collapses. Preheating in the first stage at 200 ° C. or higher and lower than 300 ° C. prevents coal particles from collapsing, increases the heating efficiency of the second stage high-temperature preheating, and has the effect of improving coke strength.

[0023]

The present invention will be further described with reference to the following examples.

<Coal> Coal having a volatile content of 32.9% and an average particle size of 1.02 mm was used.

<Preheating Condition> The above-mentioned coal was heated from room temperature to a predetermined temperature under the condition of a contact time of 1 second. As the heating gas, N ₂ gas at a temperature of 360 ° C. was used as a model gas. Ratio of heated gas to coal (solid-gas ratio) is 0.89 g / L
And

<Comparative Example, Reference Example, Example> Blank: In order to check the equipment characteristics, coal particles are flowed from the coal feeder (2) to the second solid-gas separator (6) without heating, and treated. The average particle size of the subsequent particles was measured to determine the degree of cracking.

First, the first stage preheating was carried out under the following three conditions. Comparative Example 1: Coal particles were heated in one stage from room temperature to 380 ° C. Comparative Example 2: Coal particles were heated in one stage from room temperature to 320 ° C. Reference Example 1: Coal particles were heated in one stage from room temperature to 250 ° C.

Next, the steps from the first stage preheating to the second stage preheating were continuously performed. Comparative Example 3: After heating the coal particles from room temperature to 250 ° C. in one stage (first stage preheating), once allowed to cool to 100 ° C.
It was cooled to below and then heated to 380 ° C. (second
Stage preheating). Comparative Example 4: After heating the coal particles from room temperature to 150 ° C. in one stage (first stage preheating), the coal particles were guided to a solid-gas separator without cooling to be separated from the heated gas, and then immediately to 400 ° C.
(Second stage preheating). Example 1: After heating coal particles from room temperature to 250 ° C. (first stage preheating), the coal particles were guided to a solid-gas separator without cooling, separated from a heated gas, and immediately heated to 380 ° C. Two stages of preheating).

<Results> Table 1 shows the conditions and results.

[0030]

[Table 1]  Preheating condition Average particle size after treatment  Blank 0.95 mm without preheating  Comparative Example 1 From room temperature to 380 ° C (1 step) 0.85 mm Comparative Example 2 From room temperature to 320 ° C (1 step) 0.88 mmReference Example 1 From room temperature to 250 ° C (1 step) 0.94 mm  Comparative Example 3 Room temperature → 250 ° C. → Cooling → 380 ° C. (2 steps) 0.87 mm Comparative Example 4 Room temperature → 150 ° C. → 400 ° C. (2 steps) 0.86 mmExample 1 Room temperature → 250 ° C. → 380 ° C. (two steps) 0.93 mm

<Analysis> As shown in Table 1, when the coal particles are heated at over 300 ° C., such as 380 ° C. and 320 ° C., in the first stage preheating, the average particle diameter is considerably reduced due to collapse by heat. (Comparative Examples 1 and 2) It can be seen that at less than 300 ° C., particularly at about 250 ° C., the occurrence of collapse can be suppressed (Reference Example 1). Even if the first stage preheating is performed at a temperature lower than 300 ° C., and further preheating is performed at a temperature of 300 ° C. or higher (for example, up to 380 ° C.) without cooling, collapse by heat no longer occurs and the particle size is maintained. (Example 1). However, once cooled after the first-stage preheating, the particle size becomes smaller even when the second-stage preheating is performed (Comparative Example 3). Further, when the preheating of the first stage is as low as 150 ° C., the particle diameter becomes small even if the preheating of the second stage is further performed without cooling (Comparative Example 4).

As described above, the conditions for heating the coal particles to 380 ° C. while avoiding collapse by heating include (1) preheating to a temperature of less than 300 ° C. in the first stage, and (2) Without cooling, in the second stage 3
It can be seen that preheating is performed until the temperature becomes higher than 00 ° C.

[0033]

According to the present invention, the first stage of preheating is performed in which the coal is preheated to a temperature of 200 ° C. or more and less than 300 ° C. and completely dried. Immediately after the heating and separation from the heating gas, the heat is guided to a coal preheater, and a second stage of preheating is further performed to preheat the coal to a high temperature of 300 ° C. or more, so that the heat in the coal preheating process is improved. The target collapse can be more reliably suppressed.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram showing an example of an apparatus for performing a preheating method of the present invention.

[Explanation of symbols]

 (1) ... first hot air generator, (2) ... coal feeder, (3) ... first coal preheater, (4) ... first solid-gas separator, (5) ... second coal preheater, ( 6) ... second solid-gas separator, (7) ... second hot air generator

Claims (2)

[Claims] 1. Prior to charging coal into a coke oven for the production of metallurgical coke, the coal is preheated by contacting it with a heating gas and exchanging heat at a temperature of 200.degree. It was preheated to a temperature below ℃ performs preheating of the first stage to completely dry and then was separated from the heated gas is guided to without solid-gas separator to cool it, immediately led to coal preheater And 300 more coals
A method for preheating coal, wherein a second stage of preheating of preheating to a high temperature of at least ℃ is performed. 2. The first stage preheating is performed at a temperature of 200 ° C. or more and 300 ° C.
At a temperature of less than 340 ° C. to 430 ° C.
The method for preheating coal according to claim 1, wherein