JPH0931470A - Preliminary treatment of coal charged to coke oven - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for preliminary treating coal charged to a coke oven, capable of increasing coke forming capacity by adjusting the water content of the coal for coke oven with an input heat value to the drier at the discharging port of a drier, separating the coal into fine powdery coal and coarse grain coal with maintaining the separating ratio of the dried coal at a prescribed value, and absorbing the variations in the properties of supplied coal. SOLUTION: This method for preliminary treating coal charged to a coke oven capable of absorbing the variety in the properties of supplied coal and keeping the dust suppressing property and suppression in carrier-over at objective levels to increase the coke forming capacity of the coal for coke oven is constituted by supplying a raw material coal for a coke oven to a drier 1 and adjusting the water content of the dried coal at the discharging port of the drier within 1.0-6.0%, further adjusting the flow rate of a gas in separating the dried coal with an air-flow screening machine 2 separating the dried coal by maintaining the separating ratio at the prescribed value to obtain fine powdery coal and coarse grain coal. The fine powdery coal is recovered by a dust collecting machine 3, weighed by a fine powdery coal weighing tool 5, blended and kneaded with added additives, blended with the coarse grain coal 6 weighed by a coarse grain coal weighing tool 7, and charged to the coke oven.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pretreatment method for coke oven coal, in which coke oven coal is dried, classified, and charged into a coke oven.

[0002]

2. Description of the Related Art In order to increase the packing density of coal charged into a carbonization chamber and to produce dense, high-quality coke of high quality, with a small amount of energy and in a short time in the coke oven, to efficiently produce the coke. A technique of previously drying and reducing the adhering water content and charging is already proposed. However, there is a problem that dust is increased in the process of transferring the dry coal to the coke oven.

Therefore, as a method of preventing dust generation in the carrying process, a method of providing a classifier after the dryer and providing a classifier for classifying pulverized coal that easily generates dust and coarse grain coal that does not generate dust is proposed. Has been implemented.

In Japanese Patent Laid-Open No. 59-4680, a raw material coal is dried in a rotary fluid type drying and classifying machine having a double structure to separate fine agglomerates into agglomerates and return them to the remaining coarse-grained coal. Discloses that the work of charging coal is facilitated and the charging coal is adjusted. In addition, JP-A 1-2526
According to Japanese Patent Publication No. 94, coal has an average water content of 2.0 to 5.0.
%, After being initially dried to a fine powder portion and a coarse grain portion while blowing hot air, only the fine powder portion is further dried to a water content of 2.0% or less to agglomerate, and then coarse grain coal. It is disclosed that they are merged with each other and conveyed to a coke oven.

[0005]

All of the above techniques are aimed at preventing dust generation and / or enhancing the coking property of the pulverized coal portion. It is a technique of classifying to a specific target particle size and collecting fine powder having a particle size equal to or smaller than the particle size to agglomerate.

However, in the case of a weight classifier which does not work to sufficiently rub and loosen the inside of the coal bed in the classifying operation,
Due to the presence of particle size distribution variation and water segregation due to the blending of the supplied coal, the pulverized coal part, which is easy to dry with water, has a low water content, and the coarse coal part has a high water content, and the collapse of pseudo particles is stable. Disappear. When the classified particle diameter is set to a certain target value, the classifier gas flow rate is set to a constant value according to the Allen's terminal velocity formula. Therefore, due to the particle size distribution of the raw coal and the variation of the water content within the lot, the classification rate cannot be controlled to be constant.

Although the particle size distribution varies depending on the coal composition and lot, the coal moisture value at the dryer outlet is 1% to 6%.
If it is attempted to keep it constant at a certain value within the range, the amount of pulverized coal after classification will not be constant, and the classification rate will fluctuate.

If the classification rate fluctuates, the amount of binder added for agglomeration and the capacity of agglomeration equipment must be set with a margin. Further, when the classification rate changes, the coal supply amount to the kneading equipment with the binder will vary, but from the characteristics of the kneading device, it is desirable that the coal amount supplied to this be a constant weight speed. It is a general characteristic of a kneader that the kneading property changes depending on the capacity of the adding and kneading equipment, regardless of whether the supplied coal amount is large or small (Fig. 3).

Further, the charging bulk density is influenced by the particle size distribution of the charging coal and changes when the particle size distribution and the ratio of the granulated material to be mixed change (FIG. 2), but the classification amount is If it fluctuates, the amount of the pseudo-granulated product formed by adding and kneading the binder will fluctuate, and the purpose of increasing the bulk density of coal charging to the coke oven and stably improving the quality of coke will not be secured. .

In operation, one of the goals is to suppress dust generation and carryover, and to stabilize the quality of coke. As a means for that, in addition to reducing the water content of dry coal, the classification rate of pulverized coal is adjusted to knead. There is a problem of stabilizing the quantity ratio.

The present invention provides a method for solving these operational problems based on the concept of coke quality and the self-contained recycling operation of tar, which is a by-product of coke oven operation. That is, it is intended to provide a method for suppressing the variation in coke quality, adjusting the amount of classified pulverized coal to a target value, controlling the amount of coal supplied to the kneader to a target amount that is assumed in advance, and making the amount of pseudo particles by the binder constant. is there.

[0012]

Means for Solving the Problems In order to solve the above-mentioned problems, (1) after drying the raw material coal for a coke oven, it is classified into pulverized coal and coarse-grained coal, and an additive is added to the pulverized coal. In the pretreatment method for coke oven coal, which is mixed with the coarse-grained coal and then charged into a coke oven after kneading, the water content in the dry coal at the dryer outlet is adjusted by the amount of heat input to the dryer. And maintaining the classification rate of the dry coal at a set value, a pretreatment method for coke oven coal.

(2) Further, the raw material coal for the coke oven is dried, the water content of the coal at the dryer outlet is changed from 1.0% to 6.0%, and then classified to obtain pulverized coal and coarse-grained coal. In the pretreatment method of coke oven coal to be charged into a coke oven by mixing with the coarse coal after kneading by adding an additive to pulverized coal,
Coke characterized in that when the water content of coal at the outlet of the dryer is 1.0% to 6.0%, the crushed particle size of the raw coal is adjusted to maintain the classification rate of the dry coal at a set value. This is a pretreatment method for furnace coal.

(3) Further, the raw material coal for the coke oven is dried, and the water content of the coal at the outlet of the dryer is changed from 1.0% to 6.0%, and then air classification is carried out to obtain fine coal and coarse coal. In a pretreatment method for coke oven coal, which comprises adding an additive to the pulverized coal, kneading the mixture, and then charging the pulverized coal with the coarse-grained coal into a coke oven, the coal water content at the dryer outlet is 1.0% to 6%. It is a pretreatment method for coke oven coal, characterized in that the gas flow rate of the airflow classifier is adjusted to maintain the classification rate of the dry coal at a set value when the content is set to 0.0%.

Here, the classification ratio of the dry coal indicates the ratio of the weight of the pulverized coal after the classification to the total weight of the dry coal at the dryer outlet.

Pulverized coal refers to coal having a particle size of 0.05 to 0.5 mm or less as a boundary, although it is slightly different depending on the purpose of classification, and coarse coal is the above. It is the remaining dry coal except pulverized coal.

[0017]

The operation of the method for drying coal according to the present invention will be described in detail below.

In order to shorten the dry distillation time of the coke oven, it is necessary to dry the adhering water content of the raw material coal for the coke oven to 1.0 to 6.0%. Here, if the adhered water content exceeds 6.0%, the effect of shortening the carbonization time is small, and if the adhered water content of the raw material coal for the coke oven is reduced to 6% or less, the pulverized coal that has been made into pseudo particles as the adhered water content decreases in adhesive strength. Lost and become loosely separated. If the attached water content is reduced to less than 1.0%, dust is remarkably generated from the transportation device while the dry coal is transported to the coke oven, which is a serious environmental problem.

Generally, pulverized coal of -0.1 mm or less is inferior in fluidity in terms of coal properties as compared with coarse-grained coal, and becomes a cause of dust generation during transportation of coal by a belt conveyor or the like. Also −
Pulverized coal with a size of 0.3 mm or less is entrained in the generated gas when it is charged into the carbonization chamber and is mixed into tar, which is a by-product, and causes a phenomenon that deteriorates the property of tar (this is generally called carryover). In addition, there is a drawback that the charging bulk density of the coal bed in the carbonization chamber is lowered. As a result, the coke quality is reduced, but as a way to avoid these drawbacks,
A technique has been proposed in which the coal discharged from the dryer is subjected to a fluidized bed classifier to classify it into pulverized coal and coarse-grained coal to agglomerate the pulverized coal.

Coal is produced by the method and hardness when it is mined in Yamamoto.
The true particle size distribution differs depending on the characteristics of each type of coal, such as the ease of cracking and the microcracks caused by the generation process. The true particle size is the particle size found when measuring the particle size in a state in which the water content is completely dried and the content of the adhered water content is 0% (when absolutely dry), but the adhered water content remains. In this case, the fine powder portion is converted into pseudo particles and adheres around the large particles, or the fine coal particles are aggregated to form apparently large particles.

In the case of coal types having the same handling history such as brand, mining method, lot, crushing, etc., the agglomeration state is almost determined by the water state.

When classifying with a certain particle size as a boundary,
The classification rate is almost regulated by the water content of coal (Fig. 4).

In the raw material coal charged into the coke oven, the particle size distribution can be roughly estimated by the value of the adhering water content, but since many brands with different histories are blended, the accuracy is a single brand. It is considerably inferior to the case of.

When the above-mentioned raw material coal charged into the coke oven leaving the dryer is subjected to the fluidized bed classifier to classify it into pulverized coal and coarse particle coal, if the target of the classified particle diameter is set in advance, coal adhesion will occur. The classification rate can be almost determined by the water content.

Conventionally, the target classifying particle size of a classifier has been determined to be 0.3 mm from the viewpoint of preventing dust generation, or a large amount of a binder is added when the blended coal tends to have insufficient fluidity. 5 mm
It is often determined from the viewpoints of classifying, carrying-over suppression and charging bulk density. On the other hand, as a measure against these, when the priority is given to the classification rate due to restrictions from the capacity of equipment for adding and kneading binders and additives, and the bulk density of charged coal and the quality effect when kneading is compounded. Is in actual operation.

The classification ratio, which is the ratio of the weight of pulverized coal to the weight of dry coal, is substantially determined by the operating conditions of the classifier and the coal conditions. As an operating condition that affects the classification rate, in the case of an air stream classifier, there is the amount of flowing gas supplied to the classifier, that is, the gas velocity of the classification section gas. The classification rate can be controlled to be constant even if the adhering water content of the supplied coal and the particle size distribution change by adjusting the classification part gas flow velocity, but if the classification rate fluctuates ± 5% or more, the air flow classifier Adjustment of the flowing gas is not preferable because the amount of change in classified particles becomes too large.

The coal conditions include characteristics such as particle size, coal collecting method, carbon washing method, true specific gravity according to brand, and adhering water condition. The adjustment in the coal mining work cannot be performed in the operation at the coke factory, which is the user, and the factors that can adjust the classification rate as the operating conditions are the pulverized particle size distribution and the water content of coal.

The classifier used in the classification of the present invention is preferably an air stream classifier from the viewpoint that a kneading and washing effect can be expected.
Regarding the amount of gas supplied to the classifier, the classification gas flow velocity is calculated when the target classification particle size is determined. Therefore, a preset constant amount is fed to the classification unit. The actual classification rate is calculated by measuring the amount of pulverized coal or coarse coal at the outlet of the classifier, and the water content in the dryer outlet coal is adjusted by the amount of heat input to the dryer based on the difference between the target classification rate and the actual classification rate. However, the classification rate can be controlled to the target value.

In the case of adjusting with the water content of coal, the water content is reduced in order to increase the pulverized coal classification rate, and pseudo particles due to the water content adhering to the particle surface are disintegrated. When lowering the classification rate, increase the water content of coal. The crushed particle size is set in consideration of coke quality, and it is better not to change the raw coal particle size distribution especially when crushing by brand.

When the water content of coal is changed, the amount of heat of dry distillation after charging into the coke oven increases or decreases, and further the time required for dry distillation and the temperature adjustment of the coke oven are required, which may make the operation difficult.

Therefore, when adjusting the crushed particle size of coal, if the crushing is strengthened so that the peak of the particle size distribution is on the fine powder side, the classification rate increases, and the crushing is weakened and the peak of the particle size distribution is changed to the coarse particle side. If this is set, the classification rate will decrease.

The particle size distribution adjustment method and the water content adjustment method should be selected from all the surrounding equipment conditions and operating conditions.

[0033]

Embodiment 1 An embodiment of the present invention will be described in detail with reference to the drawings.

In FIG. 1, the raw material coal has a water content of 7 to 12%.
Is already blended in the wet coal state, and is put into the coal dryer 1. Many types of dryer 1 have been devised,
The method of drying by indirect heating with steam having a pressure of 1 kg / cm ² or more, the method of heating and drying by directly contacting coal with combustion exhaust gas having high sensible heat, the method of drying by using exhaust heat of flue gas, etc. Are known.

The dryer used here is a coal blend 1 having a water content of 10%.
00t / h (wet charcoal base) is used for the dryer outlet moisture 3.8-
A tumble dryer with a coal passage through a heating pipe with a capacity of drying up to 6.5% was used. This exit coal has a large amount of dust generation during transportation to the coke oven, suppresses entrainment of pulverized coal in the gas generated when charging the coke oven carbonization chamber (generally called carryover), and In order to improve the coking property of coal by adding a binder to the pulverized coal portion that is the cause and kneading it to perform pseudo-granulation, a process of classifying into pulverized coal and coarse-grained coal is started.

As the classifier, there are a method using an inertial force such as a cyclone and a cyclone type classifier, a method for gravity classification such as a louver type, and a gravity classifier by fluidization. In order to accurately classify the pseudo particles according to the particle size, a fluid floating type (fluidized bed type) classifier was used here.

The kneading machine for pulverized coal and the binder used was a horizontal axis paddle stirring type kneader, but this kneading machine has the characteristic that the kneading property changes depending on the level of the amount of coal retained in the machine.
A good kneading property is exhibited at a supply amount of 1 t / h.

The target classified particle size was set to 0.3 mm in order to eliminate the above-mentioned negative effect of pulverized coal. The target classification rate is set within the range of 10% to 40% depending on the relationship between the coke quality requirement and the type of coal to be blended, the acceptable dust generation level, the capacity of the binder kneading and granulating equipment or the mixing characteristics. However, here, considering the facility capacity and quality effect, aiming at the operation of the range in which the kneading performance of the binder kneader can be maintained at a high level, 20% was set as the target classification rate here.

The binder is added in an amount of 6% to the classified pulverized coal.
If 20% is added, both dust generation and carryover can be suppressed and the coke quality effect is exhibited, but if 10% or more is added, the effect is great. In this example, 12% was added for kneading and pseudo-granulation.

When this granulation is mixed with coal, the charging bulk density when charging into the carbonization chamber changes depending on the amount of pseudo-granulated material. Therefore, it is necessary to control the amount of the pseudo-granulated product by the kneading of the binder to be constant, but as the means for adjusting the classification rate, that is, the amount of pulverized coal while keeping the classified particle size constant, the moisture content of the coal leaving the dryer The method of suppressing

A specific method for controlling water content will be described below.

Of the coal classified by the classifier, the pulverized coal is captured by the bag filter and fed into the kneader, and the coarse grain coal is conveyed as it is toward the coke oven by the belt conveyor.
Both of these are weighed with a belt scale to calculate the classification rates of pulverized coal and coarse-grained coal. The water content and particle size of coal vary within the lot, and the classification rate fluctuates especially when there is water segregation or particle size segregation. In this example, the target classification rate was set to 20%, and the moisture content at the outlet of the dryer was adjusted based on the difference from the calculated actual classification rate.

According to the results of this test, the target average water content at the dryer outlet was set to 4.6% and the gas flow velocity corresponding to the classified particle diameter of 0.3 mm was applied to the classifier for 100 t / h of the raw coal supply. did. On the other hand, the actual pulverized coal classification rate is 15%
From 23%. It was thought that this was due to the particle size distribution of the fed raw coal, but we decided to adjust the moisture content of the dryer and adjust the steam pressure for heating the dryer. When the coal moisture and the classification rate in this coal lot are illustrated as an example, there is a relationship as shown in FIG. 5, but since the classification rate fluctuates, the following actions were taken. When the classification rate dropped to 15%, the water content was adjusted to 4.0%, and when the classification rate increased to 23%, the water content was adjusted to 5.2%. Although there was a delay of several tens of seconds in the action with steam, it showed the effect of suppressing the classification rate fluctuation, and was 18%.
To 21% fluctuation range.

As a result, the blending amount of the kneaded granulated product becomes stable,
The charging bulk density into the coke oven is 0.76 ± 0.02t / m
^Although there was a variation of ^3, it could be adjusted to approximately 0.76 t / m ³ .

[0045]

Example 2 In the above example, the crushed particle size of the coal fed into the dryer was adjusted while the moisture content at the dryer outlet was kept constant with respect to the variation of the classification rate.

When the particle size distribution is fine, even if the water content of coal is the same, the amount of pulverized coal which is in a free state without forming pseudo particles increases, and when it is subjected to a classifier, the pulverized coal is released. The higher the classification rate, the higher the classification rate.

On the other hand, when the particle size distribution is coarse, the proportion of pulverized coal which has been made into pseudo particles becomes high, and the classification rate at the same gas amount in the classifier decreases. In this example, there is a coal crusher that is added before it is added to the dryer. This particle size control is usually controlled at 78% to 80% under 3 mm, but the rotation speed of this hammer crusher type crusher is feedback-controlled by the actual classification rate. FIG. 6 shows an example of changes in the classification rate due to the operation of the pulverizer. The classification rate target was set to 20% and the moisture content at the dryer outlet was adjusted to 4%. In this operation, the actual classification rate fluctuated within a range of ± 3% in the average value for 30 minutes. On the other hand, when the classification rate decreased, crushing was strengthened and the 3 mm lower ratio was increased by 2%. As a result of performing the operation of lowering the rotation speed of the crusher so that the lower ratio of 3 mm is lowered by 1.5% when the classification ratio is increased, the actual classification ratio can be stably controlled to 20% ± 1%. As a result, variations in tar kneading properties were reduced, stable pseudo-granulated products were obtained, and it became possible to control the charging bulk density to the target of 0.76 t / m ³ .

[0048]

[Example 3] In Example 1, a method in which the crushed particle size of the coal fed to the dryer is kept constant against the fluctuation of the classification rate, and the classified particle size is changed while the dryer outlet moisture remains constant. It was adopted.

Even if the water content and particle size distribution of coal are the same, the classification rate may change. This may be caused by the humidity or temperature of the classification gas, or partial deformation due to material fatigue inside the classifier or deformation / clogging of the gas blowing holes. In daily operations, it may not be possible to improve such fluctuations due to the constraint that facility operation cannot be stopped. When the classification rate is adjusted under such a condition, the classified particle size can be varied within the allowable range of operation. Specifically, this is by increasing or decreasing the flow velocity of gas fed into the classifier, that is, the amount of gas.

In Example 1, a classification rate of 20% was targeted with 0.3 mm as the classification point, but the pulverized coal classification rate fluctuated from 15 to 23% with respect to the supply of 100 t / h of raw coal.
FIG. 7 shows an example of the change in the classification rate depending on the classification particle size. The target classified particle diameter was made to have a width of about ± 0.03 mm, and when the classification ratio was lowered, the supply gas amount was increased so that the classified particles were classified to 0.33 mm. On the other hand, when the classification ratio fluctuated to a high level, the amount of gas was adjusted to reduce the classification particle size. In this operation, the actual classification ratio can be stably controlled to 20% ± 1%. The allowable classification particle size varies depending on the purpose. In the case of dust generation prevention, it can be lowered to 0.1 mm if dust collector equipment is fully equipped, but in the case of carryover prevention 0.2 mm
It is effective to lower the Further, under operating conditions where the amount of the binder is small, it becomes difficult to granulate when the particle size becomes large, so the upper limit particle size for classification may be limited.

In the above-mentioned Examples 1 to 3, tar was used as a binder to be added to the classified pulverized coal, but both of them were added by 12% based on the classified pulverized coal.

It has already been widely known that the addition of tar has the effect of enhancing the coking property of coal having low fluidity. In addition to the method of adding a fixed amount to classified pulverized coal, regardless of the classification rate. There is also a method of adding a fixed amount to the amount of raw coal.

Further, as a binder, tar slag or pitch which is softened at elevated temperature to improve fluidity is also effective. Further, even if the oil is drained, the effect of improving the quality of coke is small, but it can be used.

In the test operation carried out, under the condition that a large amount of non-cohesive coal is blended and the variation in the particle size distribution of the raw material coal within the lot is large, it cannot be controlled only by adjusting the water content. The method of adjusting both distributions was effective.

[0055]

EFFECTS OF THE INVENTION As is apparent from the above-mentioned examples, the present invention aims to suppress dusting and carry-over of coal charged to a coke oven which has been crushed and dried, and at the same time improve the coking property of coal. In the process of classifying only the pulverized coal portion and kneading it with a binder and granulating, feed back the dry water content and / or the crushed particle size of the raw coal in order to control the classification rate constant while keeping the particle size to be classified constant. To control.

Further, as a method of controlling the classification rate constant while keeping the dry water content and / or the crushed particle size of the raw material coal constant, the classified particle diameter is changed and adjusted.

The method of the present invention is a technology for setting the operating conditions of the classifier and the target classified particle size while carefully checking the operating conditions, and absorbing the fluctuations in the properties of the supplied coal. It is a technology that can improve coking properties while maintaining the temperature at a high level, and has a great effect on operation.

[Brief description of drawings]

FIG. 1 is a diagram showing a configuration of a dryer and a fluidized bed classifier.

FIG. 2 is a view showing a relationship between a mixing ratio of a kneaded granulated material and a charging bulk density.

FIG. 3 Amount of coal supplied to the kneader and kneading property (-0.1 mm
The figure which shows the relationship of residual amount.

FIG. 4 is a diagram showing a particle amount ratio due to water adhering to coal.

FIG. 5 is a diagram showing a relationship between a pulverized coal classification rate and coal moisture in Example 1.

FIG. 6 is a diagram showing a relationship between a pulverized coal classification rate and a classified particle diameter in Example 2.

FIG. 7 is a diagram showing a relationship between a pulverized coal classification rate and a classified particle diameter in Example 3.

[Explanation of symbols]

1 ... Dryer 2 ... Fluidized Bed Classifier 3 ... Dust Collector 4 ... Pulverized Coal Transportation Equipment 5 ... Pulverized Coal Meter 6 ... Classified Coarse Coal 7 ... Coarse Coal Meter

Claims (3)

[Claims] 1. A raw material coal for a coke oven is dried and then classified to obtain pulverized coal and coarse-grained coal, an additive is added to the pulverized coal, and the mixture is kneaded and then mixed with the coarse-grained coal and loaded into a coke oven. In the pretreatment method for entering the coke oven coal, the moisture content in the dry coal at the dryer outlet is adjusted by the amount of heat input to the dryer, and the classification rate of the dry coal is maintained at a set value. Pretreatment method for coke oven coal. 2. A raw material coal for a coke oven is dried, the water content of the coal at the outlet of the dryer is changed from 1.0% to 6.0%, and then classified to obtain pulverized coal and coarse-grained coal. In the pretreatment method for coke oven coal, which comprises adding an additive and kneading and then mixing with the coarse-grained coal and charging the coke oven into a coke oven, the coal water content at the dryer outlet is set to 1.0% to 6.0%. In this case, a method for pretreatment of coal for a coke oven, characterized in that the pulverized particle size of the raw coal is adjusted to maintain the classification rate of the dry coal at a set value. 3. The raw coal for a coke oven is dried, the water content of the coal at the dryer outlet is changed from 1.0% to 6.0%, and then air classification is performed to obtain pulverized coal and coarse-grained coal. In the pretreatment method of the coal for a coke oven, in which an additive is added and kneaded and then mixed with the coarse grain coal and charged into the coke oven, the water content of the coal at the outlet of the dryer is 1.0% to 6.0%. In this case, the gas flow rate of the airflow classifier is adjusted to maintain the classification rate of the dry coal at a set value, the pretreatment method for coke oven coal.