JPH07126653A - Method for producing coke for blast furnace - Google Patents

Abstract

PURPOSE:To provide a method for producing cake for blast furnaces, capable of maintaining the quality of coke, improving productivity, reducing installation costs, and using a large amount of general coal as a raw material coal. CONSTITUTION:In this method for producing coke for blast furnaces by rapidly heating coal to a temperature just under the softening temperature of the coal and subsequently carbonizing the coal, the coal is heated indirectly or with microwaves to a temperature of 500-600 deg.C in a carbonization chamber having an oven width of <=200mm, while the expansion of the coal is limited with the walls of the oven, again solidified, carbonized, and subsequently cooled.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing blast furnace coke. More specifically, productivity improvement,
It relates to the production of blast furnace coke in order to reduce equipment costs and diversify raw coal.

[0002]

2. Description of the Related Art Conventionally, blast furnace coke has been manufactured in a chamber type coke oven. However, since the room-type coke oven indirectly heats coal through the furnace wall, the heat transfer is slow, and the carbonization time is usually 15 hours or longer, and even if various coal pretreatment techniques are adopted, it takes 10 hours or more to improve productivity. Is low. Therefore, it is also necessary to construct a large facility in order to produce a certain amount of coke, and the facility cost is high. Further, it is necessary to use coking coal as the raw material coal, and the usable amount of steam coal that is inexpensive and has a large reserve is only at most 30% even when various coal pretreatment techniques are adopted.

In order to solve these problems, coal is heated to a temperature immediately before the softening start temperature of the coal, that is, to a temperature between the softening start temperature and a temperature 50 ° C. lower than the softening start temperature, 10 ² to 10 ⁶ ° C. Preheat by rapid heating at a temperature rising rate of 1 / min, dry-distill to 700-900 ° C after molding, and then CDQ
A method has been proposed in which coal containing steam coal can be produced in a short time within 10 hours by firing with a (coke dry fire extinguisher).

[0004]

However, the coal rapidly heated to just before the softening start temperature undergoes a thermal decomposition reaction even if kept at that temperature, and begins to soften and further solidify over time. , Loses stickiness. Therefore, the coal that has been rapidly heated up to just before the softening start temperature needs to be carbonized in a short time. It is an object of the present invention to provide a blast furnace coke manufacturing method capable of solving the above-mentioned problems in the prior art. That is, it is an object of the present invention to provide a method for producing blast furnace coke, which makes it possible to greatly improve productivity, reduce equipment cost accordingly, and use a large amount of steam coal as a raw material coal.

[0005]

[Means for Solving the Problems] The above objects are achieved by a manufacturing method in which coal is rapidly heated to a temperature around its softening temperature, then the coal is restrained by the furnace wall until resolidification, and the coal is rapidly heated, followed by carbonization and cooling. To be done. That is, the present invention rapidly heats the raw coal from a softening start temperature of the raw coal to a predetermined temperature within a range of 50 ° C lower than the softening start temperature at a heating rate of 100 ° C / min or more, and then a furnace width of 200 mm or less. 500 ~ 6 coal while restraining the expansion of coal by the furnace wall in the carbonization chamber of
High strength coke by indirect heating to a temperature of 00 ° C or by heating the coal to a temperature of 500 to 600 ° C by microwave while restraining the expansion of the coal to re-solidify, and then carbonizing and cooling. Is a way to get.

[0006]

In the present invention, 10 ² to 10 ⁶ ℃ until a predetermined temperature within the range from the softening start temperature of the raw material coal to a temperature 50 ° C. lower than the softening start temperature, that is, until the state immediately before the softening start. Rapid heating at a heating rate of / min.
The softening temperature of coal in the present invention is 100
It is the softening start temperature when the fluidity is measured by a plastometer after rapid heating at a temperature rising rate of ° C / min or more. Due to the effect of this rapid heating, coal does not soften in this step due to the lack of pyrolysis reaction time, but it softens in the next step, and its fluidity and expandability are compared with the case of carbonization in a chamber furnace. ,
improves. Further, even in coal which does not exhibit fluidity or expandability in a chamber furnace, fluidity or expandability is exhibited.

In this step, if the temperature is heated to a temperature higher than the softening start temperature, coal softens and agglomerates to cause troubles such as blocking the heating device. Further, when heating is performed only to a temperature lower than the softening start temperature by 50 ° C. or more, the effect of rapid heating that the fluidity and expandability in the next step are improved cannot be obtained. Therefore, in this step, it is necessary to heat to a predetermined temperature within the range from the softening start temperature to a temperature 50 ° C. lower than the softening start temperature. As the rapid heating method in this step, generally used gas stream heating, fluidized bed heating, or the like is used.

Then, the rapidly heated coal is heated to 500 to 600 while restraining the expansion of the coal by the furnace wall in the carbonization chamber.
Heat to a temperature of ° C to resolidify. In this step, the coal becomes a semi-coke having an appropriate porosity and a strong pore wall structure, so that the temperature will be further increased in the next step to become a high-strength coke. The porosity and pore wall structure of coke are determined in the process of coal resolidifying into semi-coke, and do not change in the process after resolidifying. In addition,
When the semi-coke is heated, residual volatiles are generated and shrinkage occurs, but the shrinkage causes the semi-coke to basically transform into a similar shape, so that the pores also shrink at the same time and the porosity does not decrease.

Since the coal that has been rapidly heated to just before the softening start temperature in the previous step is undergoing a thermal decomposition reaction, it softens due to the progress of the reaction over time even if it is maintained at a constant temperature, and further time elapses. Since it loses its heat softening property, it is necessary to heat it to at least the resolidification temperature in a short time. It is possible to heat up to a higher temperature in this coal resolidification process, but since the coal resolidification process is a process that handles softened coal and the equipment becomes complicated, the productivity is increased as much as possible and the equipment is not made compact. And equipment costs will rise, so
In this process, it is advantageous to re-solidify the coal to form a semi-coke having an appropriate porosity and a strong pore wall structure, and then perform the carbonization in another simpler furnace. .

In order to form a semi-coke having an appropriate porosity and a strong pore wall structure, first, the process from the start of softening of coal to the resolidification must be carried out under the condition that the coal particles expand sufficiently. , Coal particles do not adhere well and a strong pore wall structure cannot be obtained. In the present invention, since the coal is rapidly heated to the temperature immediately before the softening start temperature in the previous rapid heating step, in the step of resolidifying the coal, it exhibits high expandability as compared with the case of carbonization in a chamber furnace. To do. Alternatively, coal that does not exhibit fluidity or expandability in a chamber furnace will develop fluidity or expandability. Due to these effects, a large amount of steam coal having no or almost no expandability in a normal furnace can be used. Further, in the present invention, in this coal resolidification step, heating up to resolidification is carried out in a short time, so the rate of temperature rise becomes high. This also improves the fluidity and expandability.

Further, in the process from the start of softening of coal to the re-solidification, it is necessary to restrain the coal layer and prevent the porosity of the semi-coke produced by the coal layer expanding as a whole during carbonization from increasing. There is. In the present invention, since the coal bed is heated while restraining the expansion of the coal bed, the porosity of the generated semi-coke does not increase. As a result, high-strength coke is obtained by heating in the subsequent carbonization process. When heating from the start of softening to the re-solidification of coal without constraining expansion, it is necessary to prevent the coal layer from expanding and increasing the porosity of coke, limiting the expansivity of coal to below a certain limit. Therefore, the coal blending is very limited. In the present invention, there is no limitation on the blending of coal, and the expandability of coal can be utilized.

In the step of resolidifying the coal, it is necessary to resolidify the coal into a semi-coke to form a coke structure, and therefore, it is necessary to heat the coal to at least 500 ° C. Since the process of resolidifying coal is a process of handling softened coal and the device becomes complicated, the equipment cost will increase unless productivity is increased and the device is made compact. Therefore, the heating temperature in the step of resolidifying coal needs to be at most 600 ° C, more preferably up to 550 ° C.

As a heating method in the step of resolidifying coal, indirect heating by ordinary gas combustion can be used. In the case of indirect heating, if the coal in the central part of the carbonization chamber is kept at a constant temperature for a long time, it may deteriorate before the temperature starts to be raised, so the heating must be completed within 60 minutes. For this reason, the furnace width (distance between two heating surfaces) is 200 mm or less,
It should preferably be 150 mm or less. further,
Microwave heating can also be used as the heating method.
In this case, the heating time can be shortened, and at the same time, the temperature gradient in the semi-coke layer can be reduced to prevent the increase of cracks.

In any case, since the generated semi-coke has hardly shrunk, it cannot be extruded and discharged from the carbonization chamber as in the case of the chamber furnace. The furnace wall, for example, as shown in FIG.
The semi-coke is continuously and sequentially discharged as a moving wall such as a caterpillar shape as shown in Fig. 2, or as a batch type, a certain amount of coal is heated to a predetermined temperature, and then the furnace wall is moved in the width direction of the furnace. It is necessary to make the structure wider so that semi-coke is discharged.

Then, the semi-coke is subjected to dry distillation and cooling. As the carbonization method, direct gas heating by a normal shaft furnace or the like can be used. As a cooling method, a normal dry fire extinguishing method or the like can be used. Further, for example, as described in Japanese Patent Application Laid-Open No. 2-194087, CDT (coke dry fire extinguisher) can be used to carry out dry distillation and fire extinguishing in one facility. Also,
It is also possible to connect all or some of the above steps into a single facility, which is particularly effective for facilitating the inter-step transportation of heated coal or semi-coke.

[0016]

EXAMPLE Caking coal 40 having a volatile content of 26% and a water content of 9% by weight
Blended coal consisting of 60% by weight of steam coal and 60% by weight of steam coal was crushed to 3 mm or less and used. The softening start temperature of this coal measured with a rapid heating plastometer at a temperature rising rate of 500 ° C / min was 450 ° C. This coal was rapidly heated to 430 ° C., which is 20 ° C. lower than the softening start temperature, for a total of 3 minutes by a three-stage air flow heating device. 500 ° C in the third stage of the air flow heating device
The heating was performed at a heating rate of / min. This coal rapidly heated to 430 ° C. is introduced into a carbonization chamber composed of two moving walls, and while moving, it is fed with a microwave of 2450 MHz for 1 hour.
Heated to 530 ° C. in 5 minutes. The generated semi-coke was introduced into a CDQ (coke dry fire extinguisher) provided directly below the carbonization chamber. Here, air is blown in to burn the gas generated from the semi-coke, and the heat of the semi-coke 1000
Coke by heating to ° C. I also extinguished the coke at the bottom of the CDQ. The coke thus obtained had a porosity of 49% and a drum strength index (15 mm index after 150 rotations) of 85.0 according to JIS K2151 and had sufficient properties as a blast furnace coke.

[0017]

Industrial Applicability According to the present invention, coal is rapidly heated until just before the start of softening, the rapidly heated coal is converted into semi-coke in a short time, and the semi-coke can be carbonized in a short time to form coke. Productivity is greatly improved. Therefore, the equipment becomes compact and the equipment cost can be significantly reduced. Further, the rapid heating of the coal and the formation of semi-coke in a short time improve the fluidity and expandability of the coal, so that a large amount of steam coal can be used as the raw material coal.

[Brief description of drawings]

FIG. 1 is a moving wall carbonization furnace according to one embodiment of the carbonization furnace of the present invention.

[Explanation of symbols]

 1 Moving wall 2 Coal charging device 3 Coke discharge device

Claims (2)

[Claims] 1. A method of rapidly heating coal to a temperature immediately before the softening start temperature of the coal, followed by carbonization, wherein the coal after the rapid heating is indirectly heated to a temperature of 500 to 600 ° C. in a carbonization chamber having a furnace width of 200 mm or less and re-heated. A method for producing coke for a blast furnace, which comprises solidifying, followed by dry distillation and cooling. 2. A method of rapidly heating coal to a temperature immediately before the softening start temperature of the coal and then performing carbonization, wherein the coal after rapid heating is heated to a temperature of 500 to 600 ° C. by microwave to re-solidify, and then carbonization is performed. A method for producing blast furnace coke, which comprises cooling.