KR100804948B1 - Methods for Increasing Solid/Gas Ratio and Estimating Transportability of Pulverized Coal - Google Patents

Abstract

The present invention relates to a method for increasing solids / gas ratio and a method for evaluating transportability of pulverized coal blown into a blast furnace. The present invention relates to a method for increasing the solid / gas ratio of pulverized coal by adjusting the flow rate ratio of auxiliary air for transporting pulverized coal to 0.6 to 0.7. The purpose of the present invention is to provide a method for evaluating transportability in advance by calculating the fluidity index of pulverized coal through physical properties such as average particle size of pulverized coal, volatile matter, ash and moisture content.

The present invention comprises the steps of setting the total transport air flow rate and the auxiliary air flow rate of the pulverized coal blown into the blast furnace; Calculating an auxiliary air flow rate ratio from the set total transport air flow rate and the auxiliary air flow rate; And maintaining the calculated auxiliary air flow rate ratio at 0.6 to 0.7; measuring a solid / gas ratio during transportation of pulverized coal, and measuring average particle size, volatile matter, moisture, and ash content of pulverized coal. And calculating a fluidity index such as the following formula from the measured average particle size, volatile matter, water content and ash content.

Fluidity Index = 0.476 * Average Particle Size + 0.417 * Volatile Content-5.476 * Water Content +

6.371 * ash content-50.86

Solid / gas ratio, transportability, auxiliary gas flow ratio, flow index

Description

Method for Increasing Solid / Gas Ratio and Estimating Transportability of Pulverized Coal {Methods for Increasing Solid / Gas Ratio and Estimating Transportability of Pulverized Coal}             

1 is a structural diagram showing an example of blast furnace pulverized coal injection facility;

2 is a structural diagram showing an example of a pulverized coal transport test apparatus;

Figure 3 is a graph showing an example of the solid / gas ratio measurement results according to the transport air flow rate

Figure 4 shows an example of the solid / gas ratio measurement results according to the secondary air flow rate ratio

graph

5 is a flow chart of the secondary air flow rate ratio and solid / gas ratio measurement results according to the types of pulverized coal;

Graph showing an example

6 is a graph showing the correlation between the measured value and the calculated value of the pulverized coal liquidity index

Explanation of symbols on the main parts of the drawings

5. Pulverized coal storage hopper, 7. Supply hopper, 8. Distributor, 9. Pick-up unit,

10, 19. Transport piping, 11. Fenggu, 12. Blast furnace, 14. Transport air pressure regulator,                 

15. Transport air flow regulator, 18. Transport hopper, 20. Auxiliary air flow control valve

The present invention relates to a method for increasing the solid / gas ratio representing the weight of pulverized coal transported to unit transport air when blowing pulverized coal into a blast furnace and a method for evaluating the transportability of pulverized coal. More specifically, it is possible to increase the solid / gas ratio by appropriately adjusting the flow ratio of total transport air and auxiliary air, and to use physical properties such as average particle size, volatile content, ash content and moisture content of pulverized coal. The present invention relates to a method for evaluating transportability according to pulverized coal type.

In the steelmaking process to produce molten iron, pulverized coal blowing is performed to replace coke, which serves as a heat source and a reducing material. Conventionally, it has been common to use crushed coal having a volatile content of about 30%, but it is becoming increasingly difficult to secure coal of such quality, and also inferior in combustibility in order to increase the coke replacement rate, which is a coke reduction effect due to blowing coal. Operation is progressing toward the use of low volatile coal. As the coal injected into the blast furnace is diversified, technology development to actively increase the blowing amount is actively progressed, and steel mills with fine coal injection records of more than 200kg / t-melt coal are increasing. However, in order to inject a large amount of such pulverized coal, related technologies such as a technology for allowing the pulverized coal to be sufficiently combusted in a combustion zone, and an appropriate charge distribution control technique should be made together as the amount of ingot coke is reduced. Along with this operation technology, the pulverized coal is dried and crushed, and then smoothly transported through a transport pipe is a major problem.

The technology to reduce the transportation air used to transport pulverized coal reduces not only the power required for transportation of pulverized coal, but also the effect of reducing the combustion temperature by mixing the hot air with hot air through a lance inserted into the air vent. It is necessary in that point. As a method of improving such transportability, Japanese Patent Application No. 1995-989821 (Method for Improving Pulverized Coal Transport) discloses a method of mixing solid compounds such as silicon dioxide and aluminum oxide of 5 μm or less with finely divided coal. For example, in 1995 CAMP-ISIJ (p.247) proposed a plug transport method for high concentration transport. However, in the former case, the method of effectively mixing particulate solid powder with coal is unclear, and as the oxides are blown together, it may affect the slag formation behavior in the combustion zone, which may adversely affect the liquid flow and aeration. This is expected to be a lot. In addition, in the latter case, not only a separate device for forming pulverized coal in the form of a plug is required but also a problem of increasing the pressure of transport air when transporting long distances is expected.

On the other hand, in the current blast furnace operation using various coals, it is necessary to prepare a method to improve the transportability in advance by evaluating transportability and to use it as one of the criteria for selecting coal species by mutually evaluating transportability. There is a situation. At present, a device capable of detecting a blockage of a transportation system due to the use of poorly transportable coal or a poor transport condition and a method for removing the same are Korean Application No. 1999-059958 (Clock detection of a pulverized coal injection pipe of a furnace), respectively. Apparatus) and Application No. 1997-054541 (Method for removing pulverized coal clogging of blast furnace), but such apparatus or method is only applicable when a problem occurs in the transportation system.

In addition, the present inventors have applied for a method for calculating an angle of repose using an analysis value of an average particle diameter, volatile matter content, and an inert component content of coal and estimating the transportability of pulverized coal from the angle of reclamation application (1998-021268). As described in, however, this method is not normally included in the analysis of ordinary coal dust operation coal because a separate cumbersome procedure is required for the analysis of inert materials. Therefore, a method that can be easily estimated from the results of the industrial analysis (water, volatile matter, ash and fixed carbon content), which is a conventional coal analysis, is needed.

The present inventors have proposed the present invention to solve the problems of the prior art, the present invention provides a method that can increase the solid / gas ratio during the transportation of pulverized coal so that its transportability is improved when the pulverized coal blowing operation in the blast furnace. In addition, the purpose of the present invention is to provide a method for easily evaluating transportability in advance by using an analysis value of pulverized coal properties.

EMBODIMENT OF THE INVENTION Hereinafter, this invention is demonstrated.

The present invention comprises the steps of setting the total transport air flow rate and the auxiliary air flow rate of the pulverized coal blown into the blast furnace; Calculating an auxiliary air flow rate ratio from the set total transport air flow rate and the auxiliary air flow rate; And maintaining the calculated secondary air flow rate ratio of 0.6 to 0.7. The method for increasing the solid / gas ratio during transportation of pulverized coal, and measuring the average particle size, volatile content, moisture content and ash content of pulverized coal step; And calculating a fluidity index such as the following formula from the measured average particle size, volatile content, water content and ash content.

Fluidity Index = 0.476 * Average Particle Size + 0.417 * Volatile Content-5.476 * Water Content +

6.371 * ash content-50.86

Hereinafter, the present invention will be described in detail with reference to the drawings and examples.

1 is a structural diagram showing an example of blast furnace pulverized coal injection facility. The pulverized coal transported through the conveyor belt 1 is stored in the raw coal storage hopper 2 and then crushed into pulverized powder (about 80% or less below 200mesh) in the crusher 3 and passed through the intermediate hopper 4 to the pulverized coal storage hopper 5. Stored. The pulverized coal caught in the filtration device 6 is also periodically supplied to the pulverized coal storage hopper. The pulverized coal is transported to the feed hopper 7 and then transported by nitrogen to the distribution device 8 located at the top of the blast furnace, in the middle of which a pick-up is accompanied by high-pressure air to control the transport amount. The apparatus 9 is installed. In the distribution device, the pulverized coal is uniformly supplied into the blast furnace 12 through the transport pipe 10 and the tuyere 11.

In the pulverized coal blowing operation of the blast furnace, the transportation capacity of the pulverized coal through the transportation pipe 10 from the distribution device 8 to the tuyere 11 is important. In the same transport air flow and pressure through the same transport pipe, the transport speed of the pulverized coal varies depending on the type of pulverized coal. In particular, in the case of pulverized coal having poor transportation properties, there is a problem that clogging occurs in the transportation pipe 10.

2 is a structural diagram showing an example of a pulverized coal transport test apparatus capable of evaluating the transportability of pulverized coal. The transport air supplied from the compressor 13 has a certain amount of air present in the transport hopper 18 via the transport air pressure regulator 14, the transport air flow regulator 15, the control valve 16, and the safety valve 17. The pulverized coal is transported through the transport pipe 19. In the pulverized coal transport facility, auxiliary air is used to increase the transportation effect, and an auxiliary air flow control valve 20 is installed to measure the effect. The transport pipe 19 is attached with a pressure gauge 21 capable of measuring the pressure during transport. After the transportation of the pulverized coal is recovered in the cyclone 22 and then transferred to the relay hopper 23 and the discharge hopper 24 is contained in the transport hopper 18 can be transported continuously. The transportability of pulverized coal was calculated based on the time required for transporting a certain amount of pulverized coal to the pressure of the transport air, and the change of air flow rate was also measured.

Table 1 below summarizes the main physical properties of the pulverized coal measured using the pulverized coal transport test apparatus, and shows the representative values of each measured before and after the experiment. In particular, B and J shots used classified particle size to see the effect of particle size change.                     

Pulverized coal type Volatile Content (%) Moisture content (%) Ash content (%) Average particle size (μm) B 36 1.7 9.2 29, 53, 70 J 9 0.8 10.6 35, 72, 98 Y 37 1.4 7.7 55 G 28 1.4 9,3 43

Figure 3 is a graph measuring the change in the solid / gas ratio according to the flow rate of the transport air experiments for the B bullet with a particle size of 53 μm in Table 1 in the transport pipe diameter 17mm, the number in the legend is the flow rate of auxiliary air (l / min). As can be seen, the lower the flow rate of the auxiliary air, the higher the solids / gas ratio, and the same solids / gas ratio under the same auxiliary air flow conditions.

The same results were obtained for other types of pulverized coal and transport piping, and the variable of auxiliary air flow rate was defined as follows, considering that the flow rate of auxiliary air had a great influence on the change of solid / gas ratio.

Auxiliary Air Flow Rate = Auxiliary Air Flow Rate / Total Transport Air Flow

FIG. 4 is a graph showing the measurement results of the solid / gas ratio of FIG. 3 according to the auxiliary air flow rate ratio defined above. As the flow rate of the auxiliary air increases, the solid / gas ratio decreases and the maximum solids for each auxiliary air flow rate. It can be seen that the condition indicating the / gas ratio is clearly shown. That is, since the maximum solid / gas ratio is shown based on the condition that the secondary air flow rate ratio is 0.6 to 0.7, from this result, the secondary air flow is reduced as much as possible, and the ratio of the secondary air flow rate to the total transport air flow rate is 60%. It can be seen that maintaining the range of ˜70% is a condition that maximizes the amount of coal transported per unit air.

FIG. 5 is a graph showing solid / gas ratio measurement results for an auxiliary air flow rate ratio under conditions of an auxiliary air flow rate of 50 l / min with respect to the four coal types (53 μm for B coal and 72 μm for J coal) shown in Table 1 above. , Legend G, Y, J, B shows the type of coal in Table 1. In this figure, although there is a difference in the solid / gas ratio according to the type of coal, as shown in Figure 4 it can be seen that the maximum value under the condition that the secondary air flow rate ratio is 0.6 ~ 0.7.

As such, the transportation characteristics of pulverized coal are greatly affected by the conditions of the transport air, and also by the physical properties of the pulverized coal itself. In the present invention, the effect of physical properties on the transport properties of such pulverized coal was found. As shown in Table 2, the physical properties of the powders were measured for all 11 types of coal samples having different types and particle sizes.

Sample coal Volatile Content (%) Water content (%) Ash content (%) Average particle size (μm) B (mixed) 31.6 1.11 9.4 54.1 B (-200mesh) 30.6 1.43 10.4 30.0 B (+ 200mesh) 32.3 1.23 8.6 73.8 J (mixed) 7.6 0.70 10.8 65.2 J (-200mesh) 8.5 1.62 12.4 34.8 J (+ 200mesh) 7.5 0.82 9.3 92.7 G (mixed) 25.2 0.99 9.5 44.9 Y (mixed) 32.1 1.15 8.0 63.1 Y1 (mixed) 9.2 1.23 8.6 43.0 B + Y1 (8: 2) 27.2 1.14 9.5 58.7 B + Y1 (4: 6) 17.9 0.80 9.9 49.6

The physical properties of the powders measured were angle of repose, compression, spatula and cohesion, and the fluidity index was calculated based on these values. And the suitability of the fluidity index was evaluated from the relationship between the calculated fluidity index and the results of the pulverized coal transportability test.

Hereinafter, a method of measuring the physical properties of each powder will be described. First, the angle of repose is defined as the angle between the inclined plane and the horizontal plane of the conical pile formed by the powder dropped from a specific vertical distance. Therefore, the angle of repose can be an indicator of the fluidity of the powder and is the most widely used factor because the measuring method is very simple.

Another index for assessing the fluidity of the powder is its compressibility, which can be calculated from the following powder density measurements:

Compression degree = (fill density-aeration density) * 100 / fill density

Here, the aerated bulk density is a measure of the volume and weight of the powder by pouring it into a container of a certain volume, and the packing density is the mass per unit volume by shaking the container itself or compacting the powder when the powder is contained in the container. This is the density value that increased. In this way, the compressibility is influenced by the density of the powder, as defined by the index indicating the compactness of the powder, which in turn is directly influenced by the basic physical properties of the powder such as particle size distribution, particle shape, particle surface area, hardness, moisture content, etc. . Generally, highly compressible powders exhibit poor transport properties.                     

Spatula angle is a property to evaluate the relative internal friction angle (or collapse angle) of powder. Usually, 5 × 7/8 inch size spatula is inserted into the bottom of the powder pile and lifted vertically to measure the angle with the horizontal direction formed by the powder pile formed on the spatula outside the powder pile. Then tap the spatula lightly and measure the angle formed by the powder pile to define the average value of these two angles as spatula. This spatula should be measured several times and its average value should be taken, and can be used as useful information to determine the flow characteristics of the powder rather than the angle of repose. The larger the spatula, the worse the fluidity, or transportability, of the powder.

Cohesiveness refers to the apparent cohesive force acting on the surface of fine particles composed of millions of atoms and molecules, not those studied in the inside or in solid physics. In a general method of measuring the degree of cohesion, the powders agglomerated under specific conditions are evaluated based on the degree to which the powder is broken by applying a mechanical external force. Usually, three types of sieves (60, 100, 200 mesh) and a bottom sample plate are used to measure the apparent surface cohesion. After placing a certain amount of powder sample (usually 2g) on the upper 60mesh sieve, three kinds of sieves are vibrated for 20 to 120 seconds according to the working apparent density of the powder, and the amount of powder remaining on each sieve is measured. If the initial sample is 2g, the cohesiveness is 100% when both 2g are present on the upper 60mesh sieve, while the coagulation degree is 0% when all the lowermost 200mesh sieves exit. Then, the degree of aggregation of the final powder is calculated by applying a score set for each unit of the weight of the powder remaining on each sieve.                     

Table 3 summarizes the results of the measurement of the physical properties and the fluidity index values in the same manner as described above.

Sample coal Repose Compression Spatula Cohesion Liquidity Index B (mixed) 42.25 37.58 66.55 41.66 45 B (-200mesh) 43.00 42.93 81.48 40.56 32 B (+ 200mesh) 38.50 35.25 69.28 39.75 49 J (mixed) 43.65 38.59 70.70 41.44 45 J (-200mesh) 43.60 40.00 82.25 40.43 41 J (+ 200mesh) 41.35 29.26 76.23 42.24 50 G (mixed) 46.80 41.44 75.62 40.57 31 Y (mixed) 46.95 38.59 75.08 41.20 36 Y1 (mixed) 45.03 38.43 74.34 40.76 39 B + Y1 (8: 2) 42.60 39.71 69.97 39.81 42 B + Y1 (4: 6) 45.78 40.60 65.88 39.52 41

As a result of measuring the physical properties of the various coals, changes in the angle of repose, compression, spatula, and cohesion were found, and the fluidity index values ranged from 31 to 50. In order of good fluidity through the results of Table 3, J (+ 200mesh)> B (+ 200mesh)> J (mixing) = B (mixing)> B + Y1 (8: 2)> B + Y1 (6: 4 ) = J (-200mesh)> Y (mixed)> Y1 (mixed)> B (-200mesh)> G (mixed).

This order of fluidity can be compared with the transport test results. That is, in FIG. 5, the transportability under the condition that the auxiliary air flow rate ratio having the maximum solid / gas ratio is about 0.6 is in the order of J (mixing)> B (mixing)> Y (mixing)> G (mixing). It can be seen that the order of the exponents is consistent.

On the other hand, as a result of applying the four physical properties of Table 2 to the influence of the physical properties on the fluidity index of these powders, the following correlations were obtained.                     

Fluidity Index = 0.476 * Average Particle Size + 0.417 * Volatile Content-5.476 * Water Content +

6.371 * ash content-50.86

In other words, to calculate the liquidity index, it is possible to have only the results of the industrial analysis (water, volatile matter, ash and fixed carbon content), which are the basic analysis values of coal, and the particle size value which is important in operation.

FIG. 6 is a graph showing a correlation between the liquidity index calculated using the relational expression and the measured liquidity index, and it can be seen that the correlation is excellent. Therefore, these liquidity index values can be usefully used to manage the transportability of a new kind of pulverized coal. That is, the content of water, ash and volatile matter is determined according to the type of pulverized coal and it may be possible to control the appropriate fluidity index value by adjusting the particle size of pulverized pulverized coal.

Among the 11 types of measurement samples listed in Table 3, the actual coal species operated in the blast furnace were four types of B (mixing), J (mixing), G (mixing), and Y (mixing). Among them, B (mixed) and J (mixed) were transported stably, whereas in the case of G (mixed) and Y (mixed), blockages frequently occurred. In this regard, the liquidity index of 45 or more was judged to be appropriate. As a result of measuring powder physical properties to use the new carbon type Y1 (mixed), the transportability was deteriorated. Therefore, as a result of mixing with B (mixing) having good transportability, as shown in Table 3, the fluidity was improved and there was no problem in transportability as a result of actual operation. From these results, it is judged that it is desirable to set the liquidity index to 40 on the condition that there is no problem in transportability.

As described above, according to the present invention, by adjusting the flow rate ratio of the auxiliary air for transporting pulverized coal, it is possible to increase the solid / gas ratio during transportation of pulverized coal so as to transport a larger amount of pulverized coal while using the same transport air. In addition, the fluidity index of the pulverized coal is calculated through physical properties such as the average particle size of the pulverized coal injected into the blast furnace, the volatile content, the ash content, and the water content, so that the transportability can be evaluated in advance.

Claims (3)

Setting a total transport air flow rate and an auxiliary air flow rate of pulverized coal blown into the blast furnace; Calculating an auxiliary air flow rate ratio from the set total transport air flow rate and the auxiliary air flow rate; And, Maintaining the calculated auxiliary air flow rate ratio at 0.6 to 0.7; Solid / gas ratio increase method for transportation of pulverized coal, characterized in that consisting of Measuring the average particle size, volatile content, water content and ash content of the pulverized coal; And, Calculating a fluidity index such as the following formula from the measured average particle size, volatile content, water content and ash content; Transportability evaluation method of pulverized coal, characterized in that Fluidity Index = 0.476 * Average Particle Size + 0.417 * Volatile Content-5.476 * Water Content + 6.371 * ash content-50.86 3. The method for evaluating the transportability of pulverized coal according to claim 2, wherein the liquidity index is maintained at 40 or more.

Images