JP2007284557A - Method for pretreatment of coal for coke - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for the pretreatment of coal for coke, enabling loaded coal density in a coke oven to be controlled within a proper range while preventing dust generation and carryover and suppressing segregation when the coal is dried beforehand and to be loaded into the chamber-type coke oven. <P>SOLUTION: The method for the pretreatment of coal for coke comprises the following procedure: Stock coal is dried and classified into powdered coal containing 40-95 mass% of coal particles 0.3 mm or smaller in size and the other coarse granular coal. Thereafter, a binder is added to the pulverized coal to form it into transversely grooved or corrugated board or the like. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a pretreatment method for coking coal. More specifically, when coal is dried in advance and charged into a chamber-type coke oven, dust generation and carryover are prevented, segregation is suppressed, and the charging density in the coke oven is set appropriately. The present invention relates to a pretreatment method for coking coal that can be controlled within a range.

  The coal raw material charged into the chamber-type coke oven usually has a moisture of about 9% by mass. When this coal raw material is dried, not only can the heat of carbonization during coking be reduced, but also the coal charging density can be increased to increase coke quality and production. Since coke quality should just maintain a level required for blast furnace operation, if coke quality is improved, it will become possible to increase the mixture ratio of cheap non-caking coal with low caking property.

  Since high-quality caking coal tends to be insufficient worldwide, it is very important to increase the blending ratio of non-minor caking coal. With the aim of these effects, humidity-controlled coal charging methods for drying coal raw materials have been implemented in many coke ovens.

  However, when the dryness of coal is increased, there arises a problem that dust generation and carryover become severe when coal is transported to a coke oven or charged. This is because the pseudo particles disintegrate due to drying and the fine powder increases. For this reason, the moisture conditioning coal charging method can only dry coal moisture to about 5% by mass.

  Therefore, the dusting fine powder that becomes a problem during coal drying is separated, kneaded with a binder, molded, pseudo-particles, mixed with the remaining coarse coal and charged into a coke oven, etc. A method has been proposed.

  The technique disclosed in Patent Document 1 is a coke oven in which a binder is added to molding raw coal, kneaded and pressure-molded to prepare a plurality of types of molded coal having different strengths and replaced with conditioned coal. However, since a plurality of types of molding machines are required, the equipment cost becomes high, and the coal coal is segregated, resulting in variations in the amount of coke oven charged and the coke quality.

  The technique disclosed in Patent Document 2 adjusts the coal moisture to less than 3% by mass, separates fine particles by applying agitation and / or vibration, agglomerates by adding a binder to the fine particles, Although it is a method of mixing, the equipment is complicated and the equipment costs are high, and there are problems that the dusting fine powder cannot be sufficiently separated by the agitation and vibration while consuming a large amount of power.

  The technique disclosed in Patent Document 3 classifies raw coal into pulverized coal and coarse coal, and adjusts the moisture and particle size of coarse coal when compressing and molding pulverized coal and mixing it with coarse coal. This is a method of adding a binder, but the problem that the moisture of the coal cannot be dried to 2% or less, the problem that classification control is difficult, and the problem that it is difficult to uniformly mix the binder with a large amount of coarse coal have.

  The method disclosed in Patent Document 4 is a method in which raw coal is dried, classified into pulverized coal and coarse coal, a binder is kneaded with pulverized coal, and mixed with coarse coal. When mixed with coarse coal and conveyed to a coke oven, the pseudo-particles collapse and pulverize, so there is a problem that dust generation and carry-over cannot be prevented.

  The method disclosed in Patent Document 5 is a method in which raw coal is dried, classified into pulverized coal and coarse coal, a binder is kneaded into pulverized coal, briquetted, and mixed with coarse coal. Segregates and the coke oven charge and coke quality vary. Further, in this method, there is a concern that the charging density at the time of charging into the coke oven becomes too large and damages the furnace wall of the coke oven.

  The technique disclosed in Patent Document 6 is to dry coal to reduce moisture to 2 to 5%, classify it into pulverized coal and coarse coal, further dry only pulverized coal, and reduce moisture to 2% or less. Although it is a method of reducing and molding and mixing with coarse coal, there are problems that the equipment is complicated and equipment costs are high, and that the moisture of the coal cannot actually be reduced to 2% or less.

JP-A-57-80480 Japanese Patent Laid-Open No. 58-80387 JP-A-5-65487 JP-A-10-183136 JP-A-10-130653 JP-A-1-252694

  It is an object of the present invention to provide a coking coal pretreatment method that can solve the above-described problems of the prior art. That is, in the present invention, when coal is dried in advance and charged into a chamber-type coke oven, dust generation and carry-over prevention are prevented, segregation is suppressed, and an appropriate charging density in the coke oven is achieved. An object of the present invention is to provide a pretreatment method for coking coal that can be controlled within a wide range.

  When the dryness of the coal is increased, the pseudo particles collapse, and there arises a problem that dust generation and carryover become intense when the coal is transported to the coke oven or charged. For this reason, the moisture conditioning coal charging method can reduce coal moisture only to about 5% by mass.

  On the other hand, the particle size of fine powder that causes dust generation and carry-over, which is a problem when drying coal, is clarified in Patent Document 5, and is about 0.1 mm or less for dust generation and 0 for carry-over. .3 mm or less.

  Therefore, the present inventors diligently devised a method for reducing particles of 0.3 mm or less by quasi-particles in order to solve both problems of dust generation and carryover while reducing coal moisture to 5% or less. The present invention has been studied and made the present invention.

The means will be described below.
(1) Drying the raw coal, classifying it into pulverized coal containing 40 to 95% by mass of particles of 0.3 mm or less and other coarse coal, and then adding a binder to the pulverized coal A pretreatment method for coke coal, which is molded into a plate shape such as a lateral groove shape or a corrugated plate shape.

  (2) The pretreatment method for coke coal according to (1), wherein the pulverized coal after molding is mixed with the coarse coal and charged into a coke oven.

  (3) The pretreatment method for coke coal according to (1) or (2), wherein the drying and classification are performed in a fluidized bed.

  (4) The amount of the binder added to the pulverized coal is 5 to 15% by mass with respect to the amount of pulverized coal before the addition of the binder, according to any one of (1) to (3), Pre-treatment method for coking coal.

  (5) In the drying of the raw coal, the moisture content ([moisture mass in raw coal / raw coal mass−wet] × 100) is 5% or less, (1) to (4) above The pre-processing method of the coal for cokes in any one of.

  According to the pre-treatment method for coke coal of the present invention, while suppressing the generation of dust and carry-over at the time of transportation to and charging into a chamber-type coke oven, which is a problem when the coke coal is dried in advance. It is possible to suppress segregation and control the charging density in the coke oven to an appropriate range. As a result, the dryness of the coal charged into the chamber-type coke oven is increased, the heat of carbonization during coking is reduced, and the coal charging density is increased to improve the coke quality and increase the production volume. I can expect that.

Hereinafter, the best mode for carrying out the present invention will be described with reference to the drawings.
FIG. 1 is a diagram showing a flow of a pretreatment method for coke coal according to the present invention. The raw coal having moisture of about 9% by mass (also referred to as raw coal) is dried by the drying classifier 1, reducing the moisture to 5% by mass or less, and pulverized coal mainly having a particle size of 0.3 mm or less, Classify and collect.

  As a means for drying and classifying, a means for drying with a kiln or the like and then classification with a vibrating sieve or the like is possible, but industrially, a fluidized bed that can be dried and classified at the same time is most reasonable and preferable.

  In dry classification using a fluidized bed, first, raw coal whose particle size is adjusted within a predetermined particle size (for example, 10 mm or less) by pulverization or the like is introduced into a fluidized bed classification dryer, and hot air of about 100 to 350 ° C. In addition, the coal is fluidized and dried until the surface moisture disappears, the pseudo particles are destroyed by collision of the flowing raw material coal, the pulverized coal is discharged from the upper part together with the exhaust gas, and the remaining coarse coal is discharged from the side part, etc. Can be classified efficiently.

  Moreover, it is possible to control the particle size of the fine powder to be classified by adjusting the superficial velocity above the fluidized bed. The particle size of the pulverized coal is controlled by adjusting the superficial velocity so that the mass ratio of particles of 0.3 mm or less is 40 to 95% from the viewpoint of securing the strength of the molded product.

  Whether the mass ratio of particles of 0.3 mm or less is 40 to 95% can be confirmed by, for example, sieving with a 0.3 mm sieve and calculating the ratio under the sieve. Once it has been classified at a predetermined empty equal velocity and confirmed to be within the above range, it is possible to keep the mass ratio within the above range by classification at the empty equal velocity. .

  The classified pulverized coal is collected by the dust collector 2. As the dust collector, a solid-air centrifugal type dust collector such as a cyclone or a bag filter can be used, but a bag filter having a high dust collection capability is more desirable.

  The recovered pulverized coal is supplied to the kneader 4 using the screw conveyor 3, and is kneaded by adding a binder. The kneading machine 4 may be of any type as long as pulverized coal to which a binder is added can be kneaded, but a continuous kneader such as a pin mixer or a kneader is more preferable.

  As the binder, tar, heavy oil, pitches, quicklime, and the like can be used, but it is desirable to use tar soot generated from a chamber furnace coke oven or crude tar. The appropriate amount of the binder to be added by the kneading machine 4 varies depending on the type of the binder and the like, but from the viewpoint of securing the strength of the molded product and the stability of molding (based on the mass of the pulverized coal before the binder addition) It is preferable to control to be 5 to 15% by mass (in terms of the external number with respect to pulverized coal).

  Next, the pulverized coal kneaded with the binder is molded by the molding machine 5. As the molding machine 5, a biaxial roll molding machine can be used. By using molding rolls having various surface shapes (unevenness), the shape of the molded product can be adjusted.

  For example, as shown in FIG. 2 (a), by using a biaxial forming roll whose surface shape is a transverse groove shape, two roll surfaces for compacting pulverized coal are set so that the convexity and convexity face each other. A lateral groove-shaped (convex convex) molded product as shown in FIG. 2B can be molded.

  An example of the shape of the molded product according to the present invention is shown in FIG. 2 (b). From the viewpoint of suppressing pulverization, preventing segregation, and charging density into the coke oven, a plate-shaped molding such as a lateral groove shape or a corrugated plate shape is used. It is a thing. In the case of molding into a plate shape, grooves are formed on the roll surface so that the pulverized coal does not slip on the surface of the molding roll, thereby improving the moldability. The shape of the molded product can be selected from a shape in which grooves on the roll surface are combined with an uneven surface or a convex surface, either of which may be selected.

  The average size of the sheet-like molded product of the transverse wave shape or the corrugated plate shape varies depending on the molding roll conditions, the coal raw material conditions, the drop height immediately after molding, the conveyance conditions, etc., but the thickness is 2 to 25 mm and the width. When the length is 3 to 50 mm and the length is 10 to 300 mm, segregation is suppressed and the charging density in the coke oven is within an appropriate range while suppressing dust generation and carryover, which are the problems of the present invention. It is preferable because it can be stably controlled.

  More preferably, the thickness is 3 to 15 mm, the width is 5 to 20 mm, and the length is 40 to 100 mm.

  The average value can be obtained by sampling about 100 to 1000 molded products immediately after molding and averaging the values measured by measuring the thickness, width and length with calipers.

  After the pulverized coal is molded by the molding machine 5, it is transported to the coke oven together with the remaining coarse coal classified by the dry classifier 1. It is possible to transport the pulverized coal and coarse coal alone to the coke oven, but in order to stabilize the coke quality, both should be mixed in advance, and also to reduce the cost of the transport equipment It is desirable to transport both to the coke oven.

  Moreover, it is an effective means for reducing fine powder to install a vibration sieve in the subsequent stage of the molding machine 5 and sieve the molded product to return the fine powder under the sieve to the kneading machine 4 or the molding machine 5. If necessary, a vibration sieve may be installed.

  In addition, although the linear pressure of a roll influences the intensity | strength of a molding, since the linear pressure required in order to maintain required intensity | strength changes with roll diameters, roll rotation speeds, etc., it sets suitably.

  According to the present invention, the dryness of coal charged in a chamber-type coke oven is increased, the heat of carbonization during coking is reduced, the charging density of coal is increased, and the coke quality and production volume are increased. It becomes possible.

Example 1
Fig. 3 shows the measurement results of the strength of the molded product when the molding test was carried out by changing the particle size of classified pulverized coal with a moisture content of 2% ([moisture content in raw coal / mass of raw material coal-wet] x 100). Indicates. A fluidized bed was used as a dry classifier, and the hot air temperature and air volume were changed to change the particle size of the classified pulverized coal. Further, the moisture was adjusted by adding water or drying so that the moisture content of the classified pulverized coal became 2%.

  As a binder, tar was added in an external number of 10% by mass, and kneaded for 3 minutes with a proshear mixer. The shape of the molded product was a horizontal groove shape with convex and convex surfaces combined, and was molded with a horizontal groove roll having a diameter of 224 mm under the conditions of a linear pressure of 1.5 t / cm and a roll rotation speed of 12 rpm, and used as a sample.

  The strength index was evaluated based on a particle ratio of 0.3 mm or more after the molded product was dropped by a drop test simulating a drop condition during actual conveyance. The target of the drop strength is 80% or more from the viewpoint of dust generation and carry-over prevention.

  As can be seen from FIG. 3, in order to maintain the strength of the molded product, the mass ratio of particles of 0.3 mm or less in the pulverized coal after classification may be controlled to be 40 to 95%.

  Furthermore, it can be seen that when the mass ratio of particles of 0.3 mm or less in the pulverized coal is less than 40% and more than 95%, the drop strength rapidly decreases.

  In order to produce a molded product with high strength by granulation or molding, it is important to fill a gap between coarse particles as a core with fine particles to form a dense structure. If the particle size is less than 40%, there are few fine particles filling the gap, and if it is more than 95%, there are few coarse particles serving as nuclei, and it is considered that the strength cannot be increased.

  In addition, even if the same test is performed under the condition where the moisture content is further reduced to the equilibrium moisture content, the mass ratio of particles of 0.3 mm or less in the pulverized coal is less than 40%, as in the case of the moisture content of 2%. Or, it has been found that the drop strength suddenly drops when it exceeds 95%.

(Example 2)
In FIG. 4, the measurement result of the intensity | strength of a molding at the time of implementing a molding test by changing the amount of binder addition is shown. A fluidized bed is used as a dry classifier, so that the moisture content of the classified pulverized coal is 2%, and the particle size of the classified coal is hot air so that particles of 0.3 mm or less are 60 to 80% by mass. Temperature and air volume were adjusted.

  Tar was used as a binder, the amount added was changed, and the mixture was kneaded for 3 minutes with a pro-share mixer. The shape of the molded product was a horizontal groove shape with convex and convex surfaces combined, and a sample molded with a horizontal groove roll having a diameter of 224 mm under the conditions of a linear pressure of 1.5 t / cm and a roll rotation speed of 12 rpm was used. The intensity index and target are the same as those in the first embodiment.

  As can be seen from FIG. 4, the strength of the molded product can be increased as the amount of binder added is increased. However, in order to increase the strength of the molded product beyond the target, Add 5% or more. On the other hand, if it is added more than 15%, the kneaded raw material adheres to the roll of the molding machine 5 and cannot be stably molded.

  Therefore, it is preferable to control the additive amount of the binder to be 5 to 15% by mass with respect to the classified pulverized coal.

(Example 3)
In order to optimize the shape of the molded product, various types of molded products with different shapes and sizes were used, and a conveyance test simulating the conditions for conveyance to an actual coke oven was conducted. A fluidized bed is used as a dry classifier, so that the moisture content of the classified pulverized coal is 2%, and the particle size of the classified coal is hot air so that particles of 0.3 mm or less are 60 to 80% by mass. Temperature and air volume were adjusted.

  As a binder, 10% of tar was added to the classified pulverized coal and kneaded for 3 minutes with a pro-share mixer. The groove shape of a roll having a diameter of 224 mm was changed and molded under the conditions of a linear pressure of 1.5 t / cm and a roll rotation speed of 12 rpm, and used as a sample.

  As samples, seven types of unmolded kneaded material, 50 cc Macek type, 15 cc Macek type, 15 cc almond type, 5 cc almond type, lateral groove type and corrugated plate type were prepared and evaluated. Each appearance photograph is shown in FIG.

  The unmolded kneaded material is a product obtained by adding 10% of tar to the above pulverized coal and kneading for 3 minutes with a professional shear mixer. The Macek type is a shape in which the bottoms of a quadrangular pyramid are pasted together, the almond type is an oval shape, the horizontal groove type is a shape in which V-shaped grooves are combined with convex and convex surfaces, and the corrugated plate type is a corrugated plate shape. It is the shape which matched the groove | channel on the uneven surface.

  The Macek type and almond type were also evaluated for different sizes, but the shape is the same, so the appearance photograph is omitted. These moldings and 2% moisture coarse coal are mixed at a mass ratio of 3 to 7, and a conveyance test simulating the conditions for conveyance to an actual coke oven is performed, and the amount of pulverization, segregation, and charging are performed. Density was evaluated.

  FIG. 6 compares the amount of pulverization during conveyance for each type of coal. The amount of increase in particles of 0.3 mm or less was defined as the amount of pulverization, and the target was set to 6% or less from the viewpoint of dust generation and carryover suppression. From the viewpoint of preventing pulverization, a 15 cc macek type, a 15 cc almond type, a 5 cc almond type, a lateral groove shape, and a corrugated plate shape are desirable.

  Since the kneaded product is simply a mixture of the classified fine powder with the binder to make pseudo particles, it is mixed with the coarse coal when transported, and the binder in the kneaded product moves to the coarse coal side to simulate It is presumed that the amount of pulverization increased due to particle collapse. In addition, the 50cc Macek type has a large molded product, so it is difficult to ensure the strength because the pressure is not sufficiently transmitted to the inside of the molded product, and it is easy to break due to a large impact when dropped, increasing the amount of powder. It is estimated that

  Therefore, in order to prevent pulverization, a small pocket type or plate-like molded product is desirable.

  It is important to reduce segregation because segregation of the molded product during conveyance to the coke oven causes variations in the amount of coke oven charged and coke quality. FIG. 7 compares the segregation during transport for each type of coal.

  In order to evaluate segregation, a mixture of a molded product and coarse coal in a mass ratio of 3 to 7 was charged into a container simulating a coke oven, divided into 5 parts in the longitudinal direction, 3 parts in the width direction, top and bottom Divided into two in the direction, the standard deviation of the mass ratio of particles of 9.5 mm or more was used as an index. The reason for focusing on the particles of 9.5 mm or more is that the abundance ratio of the formed charcoal can be roughly expressed because it is hardly present in the coarse coal.

  The target value is set to 5% or less in order to reduce variations in the amount of coke oven charged and coke quality. From the viewpoint of preventing segregation, a kneaded material, a lateral groove shape, and a corrugated plate shape are desirable. A pocket type such as a Macek type or almond type tends to roll off a slope and segregate into a corner when charged in a coke oven, a coal tower, etc., and segregation becomes more pronounced as the size increases.

  On the other hand, a horizontal groove-like or corrugated plate-like molded product is presumed to have small segregation because it is cracked appropriately during the conveyance process and is not easily rolled by being stuck between coarse coal. Moreover, since there are no particles of 9.5 mm or more in the kneaded product, segregation of the kneaded product is caused by particles of 9.5 mm or more in the coarse coal.

  When charging coke coal into a chamber-type coke oven, a higher charging density is desirable because coke production increases and coke quality improves, but the coal expands during the dry distillation process. Therefore, if the charging density is too large, there is a concern that the coke oven will be damaged. Therefore, it is important to control the charging density within an appropriate range.

FIG. 8 compares the bulk density when charging the coke oven for each type of coal. The target value of the charging density is desirably controlled in the range of 0.76 to 0.84 t / m ³ from the viewpoints of coke production and quality improvement and furnace damage. As the molded product is larger, the charging density tends to increase. In order to control the charging density within an appropriate range, a plate-shaped molded product having a lateral groove shape or a corrugated plate shape is desirable.

  The reason why the charging density increases as the molding increases is that the particle size distribution of the charging increases as the molding increases. On the other hand, a plate-like molded product such as a lateral groove shape or a corrugated plate shape is easy to break and is appropriately cracked in the conveying process. Therefore, it is considered that the particle size distribution falls within an appropriate range and the charging density does not become too large.

  As described above, from the viewpoint of suppression of powdering, prevention of segregation, and charging density, the shape of the molded product is preferably a plate-shaped molded product such as a lateral groove shape or a corrugated plate shape.

It is a figure which shows the flow of the pre-processing method of the coal for cokes of this invention. It is a figure which shows the shape of the molding of this invention. It is a figure which shows the relationship between -0.3mm particle | grain weight ratio in a classification fine powder, and a molding strength. It is a figure which shows the relationship between a binder addition ratio and molding strength. It is a figure which shows the shape of the various charcoal used by the conveyance test. It is a figure which shows the pulverization amount at the time of the conveyance test of various charcoal. It is a figure which shows the segregation at the time of the conveyance test of various charcoal. It is a figure which shows the coke oven charging density at the time of the conveyance test of various charcoal.

Explanation of symbols

1 Drying classifier (fluidized bed dryer)
2 Dust collector (bug filter)
3 Screw conveyor 4 Kneading machine 5 Molding machine (horizontal groove or corrugated plate)

Claims (5)

  The raw coal is dried and classified into pulverized coal containing 40 to 95% by mass of particles of 0.3 mm or less and other coarse coal, and then a binder is added to the pulverized coal to form a horizontal groove. A method for pretreatment of coal for coke, which is formed into a plate shape such as a sheet or corrugated plate.   The pre-treatment method for coke coal according to claim 1, wherein the pulverized coal after molding is mixed with the coarse coal and charged into a coke oven.   The method for pretreating coal for coke according to claim 1 or 2, wherein the drying and classification are performed in a fluidized bed.   The amount of the binder to be added to the pulverized coal is 5 to 15% by mass with respect to the amount of pulverized coal before the addition of the binder. Pre-processing method.   5. The moisture content ([moisture content in raw material coal / mass of raw material coal−wet] × 100) is set to 5% or less when the raw material coal is dried. 5. The pre-processing method of the coal for cokes as described.