JP2006022156A - Method for molding finely-powdered charcoal - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for molding finely-divide charcoal, capable of decreasing internal pressure in a finely-divided charcoal layer in the neighborhood of a screw feeder, when the finely-divided charcoal is molded, without deteriorating productivity, and capable of maintaining good strength and yield. <P>SOLUTION: This method for molding the dust coal comprises classifying raw material coal for producing coke for a blast furnace and then molding the dust coal smaller than a classification point, wherein the dust coal is beforehand subjected to preliminary consolidation and then the consolidated dust coal is supplied to a molding machine by the screw feeder, so that the dust coal is molded. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a method of molding pulverized coal having a classification point less than the classification point after classifying raw coal for producing blast furnace coke.

  Conventionally, high quality coal (strongly caking coal, caking coal) has been used as coking coal for blast furnace coke production. However, in recent years, high quality coal has been depleted and low quality coal (non-fine coal) Coking coal) must be used in large quantities as the main raw coal.

  However, although low-quality coal (non-coking coal) is inexpensive and can be supplied stably, when used in large quantities as the main raw coal, coke strength in the coke oven is inferior, resulting in reduced coke strength. There was a problem to do.

  In the past, in order to suppress the reduction in coke strength, the coking coal for blast furnace coke production was dried to reduce moisture, and the coal bulk density was improved to improve coking properties, and the generation due to moisture reduction. In order to suppress dust, many methods for classifying dry coal and forming pulverized coal that causes dust generation have been disclosed.

  Conventionally, as a method for molding pulverized coal, a method is used in which pulverized coal is supplied to a molding machine by a screw feeder and is pressure-molded by two opposed flat rolls or grooved rolls.

  However, such a pulverized coal pressure molding method has the following problems. That is, since the pulverized coal has a narrow particle size distribution, the coal filling structure when supplied to the molding machine is in a depopulated state with many voids. For this reason, when molding with a roll, the internal pressure in the molding machine increases due to the air in the gaps between the coal particles as the coal throughput (supply) increases.

  In this case, if the deaeration is insufficient, the internal pressure of the powder layer immediately above the roll will rise, and when supplying coal with a screw feeder, the springback phenomenon becomes prominent, reducing the strength and yield of the coal. This causes a decrease. Moreover, in order to enable stable molding, it has been necessary to limit the number of roll rotations of the molding machine and reduce the productivity of the molding charcoal.

  For such a problem in pulverized coal molding, Patent Document 1 discloses a screw feeder casing constituting a roll molding machine, or a steel plate having a large number of apertures in the structure of a hopper wall around the screw tip. A roll forming machine having a ventilation structure including an outer filter is disclosed.

  However, in this roll molding machine, it is necessary to make the filter mesh incapable of permeating the coal, so during molding, the filter is likely to be clogged with pulverized coal, and in order to maintain sufficient air permeability, Filter maintenance is required.

  Further, in Patent Document 2, a plurality of deaeration paths are provided in the lower part of the hopper for supplying coal in the roll molding machine, a suction box is provided in the outer opening of each deaeration path, and the deaeration path is provided via the suction box. A roll molding machine having a structure for collecting pulverized coal leaked from a dust collector is disclosed.

  However, this device requires a complicated structure to return the dust collector and the pulverized coal collected by the dust collector to the hopper again, so that the equipment becomes larger, the maintenance is poor, and the pulverized powder is excellent in workability and productivity. It was not a charcoal molding method.

JP-A-5-69198 JP-A-5-331471

  Based on the above-mentioned problems of the prior art, the present invention reduces the internal pressure in the pulverized coal layer in the vicinity of the screw feeder and maintains good strength and yield when molding pulverized coal without reducing productivity. An object is to provide a method for forming pulverized coal.

  The pulverized coal has a narrow particle size distribution, and the filling structure when supplied to the molding machine has a large number of gaps. Therefore, the internal pressure in the molding machine increases due to air in the gaps between the coal particles during roll molding. Since the filling structure is depopulated, the bulk density of the powder immediately before being bitten by the molding machine is lowered.

  Therefore, the present inventor diligently studied a method for increasing the bulk density of the pulverized coal layer and reducing the internal pressure in the molding machine during roll molding before molding the pulverized coal. As a result, after compacting the pulverized coal in advance and supplying it to the molding machine with a screw feeder, the bulk density of the pulverized layer immediately before being bitten by the molding roll increases, and the internal pressure in the molding machine is reduced. I found out.

  This invention was made | formed based on the said knowledge, and the summary is as follows.

  (1) In the method of molding pulverized coal below the classification point after classifying raw coal for blast furnace coke production, after pre-consolidating the pulverized coal, the pulverized coal is put into a molding machine by a screw feeder. A method for molding pulverized coal, comprising supplying and molding pulverized coal.

  (2) The preliminary compaction of the pulverized coal is characterized in that the linear pressure of the compacted roll is increased by 0.3 t / cm or more and less than 1.2 t / cm using two opposing compacted rolls. The method for molding pulverized coal according to 1).

(3) The molding of pulverized coal according to (1) or (2) above, wherein the bulk density of the pulverized coal in the vicinity of the tip of the screw feeder is 0.76 t / m ³ or more. Method.

  According to the present invention, when molding pulverized coal, the internal pressure in the pulverized coal layer in the vicinity of the screw feeder is reduced when molding pulverized coal without lowering productivity, and good strength and yield are obtained. Can be maintained.

  As a result, pulverized coal that causes dust generation contained in dry coal is classified and molded to obtain sufficiently strong coal, and dust generation due to collapse is suppressed when charging into a coke oven. Further, it is possible to prevent the dust-derived carbon from adhering to the upper part of the furnace, the riser, etc., and the dust coal from being mixed into the by-product.

  The present invention will be described with reference to the drawings. FIG. 1 shows an example of an apparatus for carrying out the present invention. After classifying the pulverized raw coal, the pulverized coal 1 below the classification point is supplied into the compacting roll 2 at a predetermined supply amount, and the pulverized coal 1 is continuously preconsolidated.

  The pre-consolidated compacted coal 3 is supplied to the storage tank 4 and further supplied to the pushing tank 5 provided at the lower part thereof, and then the compacted coal 3 is supplied to the forming roll 7 by the screw feeder 6 and pressurized. Molding is performed to produce the charcoal 8.

  According to the above-described embodiment, the filling structure of the pulverized coal layer supplied into the pushing tank 5 of the molding machine is densified by the preliminary compaction of the pulverized coal 1 performed before the molding of the pulverized coal 1, and in particular, the molding roll The bulk density of the pulverized coal 1 immediately before biting 7, that is, in the vicinity of the tip of the screw feeder 6 (region (a) in the figure) is improved.

  As a result, even if the processing amount (supply amount) of pulverized coal is increased, the internal pressure in the molding machine during molding can be reduced and the springback phenomenon during molding can be suppressed without reducing productivity. Charcoal strength and yield can be improved.

  In the above embodiment, the classification point when classifying the pulverized raw coal is determined from the fine particle size that causes dust generation according to the properties of the raw coal and the amount of water in the raw coal.

  If the classification point is excessively small, the particle size distribution becomes narrow, and the bulk density of the fine coal layer in the molding machine may be reduced during molding. On the other hand, if the classification point is too high, the dust generation suppressing effect due to the molding of the pulverized coal may be reduced, the moldability may be reduced, and the strength and yield of the coal may be reduced.

  Therefore, the classification point is preferably selected in the range of 0.2 mm to 0.7 mm.

  The shape of the compacting roll 2 is not particularly limited, but a flat roll is preferable in order to pressurize pulverized coal uniformly.

  The coking coal means a single brand of coal or a mixture of multiple brands of coal.

  In the above embodiment, in order to improve the strength and yield of the coal, the linear pressure of the compacting roll 2 when pre-compacting the pulverized coal 1 and the molding machine 8 when press-molding the compacted coal 3 The bulk density of pulverized coal in the vicinity of the screw feeder tip (region (a) in FIG. 1) is particularly important.

  These preferable conditions will be described with reference to FIGS. The results shown in FIGS. 2 to 4 are obtained after pre-consolidating pulverized coal below the classification point after the pulverized raw coal is classified at a classification point of 0.5 mm using the apparatus shown in FIG. The results of molding are organized.

  FIG. 2 shows the relationship between the linear pressure of the compacting roll and the bulk density of pulverized coal in the vicinity of the tip of the screw feeder of the molding machine.

When the pulverized coal is not pre-consolidated before molding (when the linear pressure of the compacting roll is 0 t / cm), the bulk density of the pulverized coal in the vicinity of the tip of the screw feeder of the molding machine is as low as about 0.72 t / m ^3. .

Even when the linear pressure of the compacting roll is 0.1 t / cm, the effect of improving the bulk density due to the preliminary compaction of the pulverized coal is slightly seen, but the effect is small. Under the condition that the linear pressure of the compacting roll is 0.3 t / cm or more, the bulk density of the pulverized coal in the vicinity of the tip of the screw feeder of the molding machine is 0.76 t / m ³ or more, compared with the case without conventional pre-consolidation Thus, the bulk density immediately before the forming roll bites is remarkably improved.

  FIG. 3 shows the relationship between the bulk density of pulverized coal near the tip of the screw feeder of the molding machine and the gas pressure of the pulverized coal layer.

When the pulverized coal is not pre-consolidated before molding (when the bulk density of the pulverized coal in the vicinity of the tip of the screw feeder is 0.72 t / m ³ ), the gas pressure of the pulverized coal layer in the molding machine is as high as about 3 kPa.

Pre-compacting the pulverized coal before molding, and setting the bulk density of the pulverized coal in the vicinity of the tip of the screw feeder of the molding machine to 0.76 t / m ³ or more, the gas pressure of the pulverized coal layer in the molding machine during molding Can be reduced to 1.2 kPa or less.

  FIG. 4 shows the relationship between the bulk density of pulverized coal in the vicinity of the tip of the screw feeder of the molding machine, and the yield and strength of the molded coal. In addition, the yield of molding coal was shown as a mass ratio (mass%) with a particle size of 1 mm or more with respect to the total amount of coal discharged from the molding machine.

  Moreover, the strength of the coal was shown as a mass ratio of 1 mm or more in particle diameter with respect to the total amount of coal after 60 rotations by putting 200 g of coal into a cylinder having a length of 700 mm and a diameter of 130.8 mm.

By pre-compacting the pulverized coal before molding, and making the bulk density of the pulverized coal in the vicinity of the tip of the screw feeder of the molding machine 0.76 t / m ³ or more, the yield of the molded coal and The strength can be sufficiently improved.

Based on the knowledge shown in FIG. 2 to FIG. 4, in the present invention, at the time of molding pulverized coal, productivity is improved by improving the bulk density immediately before biting the molding roll and reducing the gas pressure of the pulverized coal layer in the molding machine. In order to sufficiently improve the strength and yield of the coal as compared with the conventional method, the linear pressure of the compacting roll is set to 0.3 or more, and the volume of the pulverized coal in the vicinity of the tip of the screw feeder of the molding machine. The density is preferably 0.76 t / m ³ or more.

  In order to further improve the bulk density of pulverized coal at the time of molding without further reducing the productivity and further improve the strength and yield of the formed coal, the linear pressure of the compacting roll is 0.5 t / cm or more. Is more preferable.

  On the other hand, when the linear pressure of the compacting roll is 1.2 t / cm or more, the preconsolidated compacted coal becomes a lump and the fluidity when supplying to the molding machine is reduced, so the tip of the screw feeder of the molding machine Fluctuations in the bulk density of pulverized coal in the vicinity of the part increase.

  As a result, the moldability of the pulverized coal becomes unstable, the yield and strength of the coal coal fluctuate, and the required strength cannot be obtained stably. Therefore, in the present invention, the upper limit of the linear pressure of the consolidation roll is set to less than 1.2 t / cm.

  In the present invention, the linear pressure of the consolidated roll means the pressure per unit roll width (t / cm) in the roll axis direction.

  Next, examples of the present invention will be described. The conditions of the examples are one example of conditions adopted for confirming the feasibility and effects of the present invention, and the present invention is limited to this one example of conditions. Is not to be done. The present invention can adopt various conditions as long as the object of the present invention is achieved without departing from the gist of the present invention.

(Example)
After classifying the pulverized raw coal at a classification point of 0.5 mm using the apparatus shown in FIG. 1, the pulverized coal 1 below the classification point is pre-consolidated with a compacting roll 2, and then the pre-consolidated compacted coal. 3 was supplied to the storage tank 4 and further to the indentation tank 5 and supplied to the forming roll 7 by the screw feeder 6 and subjected to pressure molding.

  As an example for comparison, the pulverized coal 1 was supplied to the forming roll 7 by the screw feeder 6 and subjected to pressure molding without pre-consolidating.

  A sample is taken from the coal 8 obtained 60 minutes after the start of the molding machine operation (the time required for the stability of the equipment), and the yield, strength, and throughput (productivity) of the coal are measured. ,evaluated. Table 1 shows the test conditions and results. In addition, although not shown in Table 1, the linear pressure of the molding roll at the time of pulverized coal molding was made constant at 3.0 t / cm.

  Inventive Examples 1 to 4 were formed after the pulverized coal was pre-consolidated and then molded. Therefore, compared to Comparative Examples 1 and 2 in which neither pulverized coal was pre-consolidated, the vicinity of the tip of the screw feeder of the molding machine ((a) in FIG. The bulk density of the pulverized coal in this area) increased, and the yield and strength of the formed coal could be improved without lowering the productivity (maintaining the treatment amount at 3.5 t / h).

  In these invention examples, the linear pressure of the compacting roll and the bulk density of the pulverized coal in the vicinity of the tip of the screw feeder of the molding machine (region (a) in FIG. 1) are within a more preferable range defined in the present invention. Inventive Example 1 and Inventive Example 2 performed in 1 were improved in yield and strength of the coal as compared to Inventive Example 3 and Inventive Example 4 in which either or both of these conditions were removed.

  On the other hand, since Comparative Example 1 did not pre-consolidate the pulverized coal, the pulverized coal in the vicinity of the tip of the screw feeder of the molding machine (area (a) in FIG. 1) was low compared with the same processing amount as the invention example. As a result, the yield of coal and the strength of coal were greatly reduced.

  Moreover, Comparative Example 2 is also an example in which pulverized coal was not pre-compacted like Comparative Example 1, and the number of rotations of the molding roll of Comparative Example 1 was decreased from 7.0 rpm to 4.5 rpm, and the throughput was reduced. Even under the condition of decreasing to 2.4 t / h, the results were lower than the yield and strength of the coals of Invention Examples 1 to 4.

  From the above results, application of the example of the present invention makes it possible to stably produce coal with good yield and strength without reducing productivity as compared with the conventional case.

  As described above, according to the present invention, when molding pulverized coal, the internal pressure in the pulverized coal layer in the vicinity of the screw feeder is reduced when molding pulverized coal without reducing productivity, and good strength is achieved. And maintain yield.

  As a result, pulverized coal that causes dust generation contained in dry coal is classified and molded to obtain sufficiently strong coal, and dust generation due to collapse is suppressed when charging into a coke oven. Further, it is possible to prevent the dust-derived carbon from adhering to the upper part of the furnace, the riser, etc., and the dust coal from being mixed into the by-product.

  Therefore, the present invention greatly contributes to the development of blast furnace coke production technology, which involves a pretreatment process of raw coal that classifies dry coal with reduced moisture content and classifies pulverized coal, and has great industrial applicability. Is.

It is a figure which shows the example of 1 apparatus which implements this invention. It is a figure which shows the relationship between the linear pressure of a compacting roll, and the bulk density of pulverized coal in the screw feeder front-end | tip part vicinity of a molding machine. It is a figure which shows the relationship between the bulk density of pulverized coal in the screw feeder front-end | tip part vicinity of a molding machine, and the gas pressure of a pulverized coal layer. It is a figure which shows the relationship between the bulk density of pulverized coal in the screw feeder front-end | tip part vicinity of a molding machine, and the yield and intensity | strength of molded coal.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Pulverized coal 2 Consolidation roll 3 Consolidation coal 4 Storage tank 5 Pushing tank 6 Screw feeder 7 Forming roll 8 Forming charcoal (a) Screw feeder near the tip

Claims (3)

  In the method of forming pulverized coal below the classification point after classifying the raw coal for blast furnace coke production, after pre-consolidating the pulverized coal, the pulverized coal is supplied to the molding machine by a screw feeder. A method for molding pulverized coal, comprising molding charcoal.   The preliminary compaction of the pulverized coal uses two opposing compaction rolls, and pressurizes the compaction roll with a linear pressure of 0.3 t / cm or more and less than 1.2 t / cm. Pulverized coal molding method. ^{3. The} method for molding pulverized coal according to claim 1, wherein a bulk density of the pulverized coal in the vicinity of the tip of the screw feeder is 0.76 t / m ³ or more.

Images