JP2003286510A - Method for mixing pulverized coal to be blown into blast furnace - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To simultaneously solve such problems of both abrasion and plugging that a hard pulverized coal employed for being blown into a blast furnace, abrades the pipe wall of a transport pipe, and a soft pulverized coal clogs in the transport pipe due to the viscosity. <P>SOLUTION: In the figure, ○ indicates excellence, μ plugging, and Δ abrasion, of which the latter two signs mean failure. This method is characterized by mixing different sorts of pulverized coals so as to satisfy the condition of 3X-105≤Y≤3X+50. Then, the method makes a protective layer of an appropriate amount of the pulverized coal adhere onto the pipe wall of a transport pipe, and restrains the pipe wall from being abraded due to the protective layer. The pulverized coal simultaneously has an effect of grinding the pipe wall as well, because of having an appropriately lowered Hardglove index. For that reason, the method prevents both plugging and the abrasion for a long term, because the pulverized coal balances growth of the protective layer in the pipe with an action of grinding the protective layer. <P>COPYRIGHT: (C)2004,JPO

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of mixing pulverized coal for blowing into a blast furnace, and more particularly to a method of mixing pulverized coal capable of reducing clogging and abrasion of a transport pipe. 2. Description of the Related Art For example, in FIG. 1 of Japanese Unexamined Patent Publication No. Hei 5-214417, "Method of Injecting Pulverized Coal into Tuyere of Blast Furnace", a transportation pipe to blast furnace 11 (the reference numeral is described in the gazette; the same applies hereinafter). 7 shows a technique for injecting pulverized coal. Such pulverized coal injection into the blast furnace is a technique aimed at reducing the cost of iron making by directly using inexpensive coal in the blast furnace. Pulverized coal is obtained by crushing coal, but as is well known, coal has different types of coal depending on the production area, and different types of coal have different chemical and physical properties such as calorific value, specific gravity, hardness, and adhesion. . If the hardness is too high, there will be a problem that a hole is formed in the transport piping. Therefore, in the above-mentioned Japanese Patent Application Laid-Open No. 5-214417, the particle size of the pulverized coal is set in a predetermined range, or the friction coefficient is set in a predetermined range, so as to reduce the abrasion in the transportation pipe. [0004] However, even with pulverized coal whose grain size or coefficient of friction is kept within a predetermined range, if the adhesive force is high, it adheres to the inner wall of the transport pipe and grows. The tube may be clogged. Therefore, it can be said that measures for controlling the particle size or the friction coefficient are insufficient. Accordingly, an object of the present invention is to provide a technique capable of simultaneously reducing both clogging and abrasion of a transport pipe. [0005] To achieve the above object, the present inventors have repeated various experiments and found that the hard glove index shows not only the abrasion but also the clogging of the transport pipe. Is also a strong influence factor. The hard globe index is an index indicating the friability of coal defined by JIS M8801, and a larger value indicates that crushing is easier, and a smaller value indicates that crushing is more difficult. [0006] Therefore, if the hard glove index is large, the material is soft and wear in the transport pipe is slight, and conversely,
If the index is small, it is hard and wear on the transport pipe becomes significant. Therefore, the present inventors prepared a large number of pulverized coals having different coal types, mixed these variously, and examined clogging and wear. The details will be described below. Table 1 is a table showing the prepared pulverized coal and its hard glove index (hereinafter abbreviated as "HGI"). The prepared coal types are A coal to G coal. Yes,
The HGIs are different from each other, such as 87, 44, 66. [Table 1] [0009] Table 2 shows specific examples in which the above-mentioned coal types are appropriately mixed in order to investigate clogging and wear of the transport pipe. [Table 2] The table lists, from left to right, the samples, mixing ratios, average HGI and results. That is, the sample is 1
~ 14 were prepared. Since sample 1 was 100% F coal, the average HGI from Table 1 remains at 84. Sample 2 is 80% coal A, 5% coal B,
The mixing ratio was 15% for C coal. Average HGI = (H of A charcoal
GI × 80%) + (HGI of coal B × 5%) + (H of coal C
(GI × 15%) = 87 × 0.8 + 44 × 0.05 + 66
× 0.15 = 81.7 = about 82, the average HGI of Sample 2 was set to 82. The average HGI of Samples 3 to 14 was determined by the same calculation, and the average HGI was described in the table. Next, using each of these samples,
The blast furnace was blown. The ultrasonic clogging detector periodically checks the pipe for local clogging phenomena. If a clogging phenomenon is observed, it is judged as "blockage" and the HGI is set to low H.
Changed to GI to eliminate clogging. In addition, the thickness of the pipe is measured every week with an ultrasonic thickness gauge. If no more than a certain amount of wear is observed after one month, there is no wear and the wear exceeds a certain value before that. Is judged as "wear" and HGI is set to high H.
GI was changed to reduce wear. After one month, the pipe was disassembled and the inside of the pipe was visually inspected. When it was judged that there was no wear, the pulverized coal layer having a constant thickness was stuck to the pipe wall, and it was found that this pulverized coal layer exerts the abrasion resistance. If neither blockage nor wear is recognized, it is judged as “good”. When evaluated according to the above criteria, as shown in the results column of [Table 2], samples 1 to 3 were determined to be "closed", samples 4 to 11 were determined to be "good", and samples 12 to 14 were determined to be "wear". We were able to. The above results will be discussed in the form of a graph. FIG.
Is a dispersion graph of the average HGI obtained in the experiment of the present invention,
The horizontal axis indicates the sample number, and the vertical axis indicates the average HGI. The average HGI for each sample was plotted on the graph as a black point. Next, when a dashed line was started up from the boundary between “occlusion” and “good”, it was possible to distinguish between occlusion and good at the point where the scale on the vertical axis was 80. From this, it was found that the average HGI = 80 had a threshold value for partitioning between closed and good. Similarly, when a broken line is set up from the boundary between “good” and “wear”, the scale on the vertical axis is 60
In terms of the above, good and abrasion could be distinguished vertically.
From this, it was found that the average HGI = 60 had a threshold value for separating good from abrasion. From the above, the average HGI is 60-80.
It is only necessary to control the mixing ratio of the pulverized coal so that If the average HG
In order to obtain I = 70, it is conceivable to mix equal amounts of HGI = 60 and HGI = 80 or to mix equal amounts of HGI = 90 and HGI = 50. The former (HGI = 60 and H
It can be easily estimated that a good mixture of GI = 80 and GI = 80 gives good results, but the latter (HGI = 90 and HGI = 5).
(Equivalent mixture of 0) has a strong possibility that any one of clogging and abrasion occurs, and it is hard to say that good results are obtained as in the former case. This is a bottleneck. Then, the following experiment was performed in order to perform more correct management. FIG. 2 is a principle diagram of the experimental apparatus used in the present invention. The experimental apparatus 10 includes a pulverized coal tank 12 for storing mixed pulverized coal 11 and a transport extending from the bottom of the pulverized coal tank 12. A pipe 13, a cyclone 14 provided at the end of the transport pipe 13, a collection tank 15 connected to the bottom of the cyclone 14, and a discharge valve 16 disposed at the bottom of the collection tank 15.
And an exhaust pipe 17 extending from the upper part of the cyclone 14.
And a bag filter 18 attached at the end of the exhaust pipe 17, and a first nitrogen blowing pipe 2 connected to supply transportation energy.
The first and second nitrogen blowing pipes 22 are provided. Then, A coal having an HGI of 87 and HG
B coal having an I of 44 and C coal having an HGI of 66 (all shown in Table 1) are prepared, and a mixture of these in various ratios is supplied to the pulverized coal tank 12, and the first and second coals are prepared. By supplying high-pressure nitrogen gas from the 2 nitrogen blowing pipes 21 and 22, the pulverized coal is moved to the collection tank 15 via the transport pipe 13 and the cyclone 14. The moved pulverized coal accumulates at the bottom of the recovery tank 15, and the nitrogen gas is discharged to the atmosphere through the exhaust pipe 17 and the bag filter 18. Bag filter 1
At 8, only fine gas is released to capture the fine particles of charcoal. The pulverized coal accumulated in the recovery tank 15 is discharged
Can be released to the outside of the tank by opening as appropriate. Therefore, pulverized coal can be continuously flowed into the transport pipe 13,
In the manner described above, the presence or absence of blockage or wear of the transport pipe 13 can be checked. FIGS. 3 (a) to 3 (c) are graphs showing the results of experiments using AC coal. In (a), the experiment was carried out under the condition of A coal ratio + B coal ratio = 100%. If the horizontal axis is the B coal ratio and the vertical axis is the A coal ratio, the results can be displayed on a straight line of Y = −X + 100. X (obstruction), ○
(Good) or △ (wear) are indicated. In (b), the C coal ratio is fixed at 20%,
The remaining 80% was tested as the ratio of coal A to the ratio of coal B. The result can be displayed on a straight line of Y = −X + 80. The experimental results are indicated by X (closed), （(good) or Δ (wear). In (c), the C coal ratio is fixed at 40%,
The remaining 60% was tested as the ratio of coal A to the ratio of coal B. The result can be displayed on a straight line of Y = −X + 60. The experimental results are indicated by X (closed), （(good) or Δ (wear). Considering the above, in (a), Y =
Assuming that the length of the straight line of −X + 100 in the first quadrant is L1, and the length of the group of ○ thereon is L2, this L2 is L
1 is about 40%. The ratio of A and B coals must be determined so as not to deviate from L2, and the control becomes troublesome. This is the HGI of coal A is 87 and that of coal B is 4
4, which is out of the preferred HGI value (60-80). On the other hand, in (c), if the length of the straight line of Y = −X + 60 in the first quadrant is L3 and the length of the group of ○ on it is L4, this L4 is about 60% of L3. Become. It is not so difficult to determine the A and B coal ratios without deviating from L2. Preferred C coal (HG
I = 66) is 40%, so that coal A (HGI =
87) or B coal (HGI = 44) means that the degree of freedom is increased. FIG. 4 is a composite graph of FIGS. 3 (a) to 3 (c), and three graphs of FIGS. 3 (a) to 3 (c) are composited.
Then, the boundary between the group ○ and the group X can be separated by a straight line of Y = 3X + 50. Similarly, the boundary between the group ○ and the group Δ can be divided by Y = 3X−
It can be divided by 105 straight lines. FIG. 1 shows that pulverized coal having an HGI of more than 80 and pulverized coal having an HGI of less than 60 must be strictly controlled in terms of clogging and abrasion, and FIG.
It has been found that the area of 3X + 50 and the area of Y <3X-105 cause troubles of blockage and wear. From these, the present invention can be summarized as follows. [0027] More specifically, when pulverized coal of two or more different coal types is mixed and injected into a blast furnace, the sum of the ratios of pulverized coal having a hard globe index of less than 60 is defined as X%, Assuming that the sum of the ratios of the globe indexes exceeding 80 is Y, 3X−105 ≦ Y ≦ 3
It is characterized in that pulverized coal of different coal types is mixed so as to satisfy the condition of X + 50. When the total ratio of pulverized coal having a hard globe index of less than 60 is X% and the total ratio of pulverized coal having a hard globe index of more than 80 is Y,
By mixing pulverized coal of different coal types so as to satisfy the condition of 3X−105 ≦ Y ≦ 3X + 50, a pulverized coal having an HGI of more than 80 allows an appropriate amount of pulverized coal protective layer to be adhered to the pipe wall of the transport pipe. This pulverized coal layer serves as a protective layer, and abrasion can be suppressed. At the same time, pulverized coal having a hard glove index of less than 60 has an effect of shaving the pipe wall. Therefore, the growth of the protective layer in the pipe by the pulverized coal and the action of shaving this protective layer are balanced, and it is possible to prevent both blockage and wear for a long period of time. EXAMPLE A verification for confirming whether the present invention can be applied to an actual machine (blast furnace) is performed. The following [Table 3] is the same as the above [Table 1], and [Table 4] is the above [Table 2]
Approximately the same as above, but reprinted for convenience. [Table 3] [Table 4] From Table 3 above, those having an HGI of 60 to 80 are removed. The following Table 5 summarizes those with an HGI below 60 as "low HGI coal" and those with an HGI above 80 as "high HGI coal".
It is. [Table 5] Based on this [Table 5], the columns of the mixing ratio in [Table 4] are arranged. That is, from Table 4, it can be seen that the low HG
The following [Table 6] was created by leaving coal I and high HGI coal and deleting the rest. [Table 6] Table 6 shows, from left to right, samples, low HG
I coal, high HGI coal, (low HGI coal, high HGI coal) and the notation column were provided. For example, A in sample 2 of Table 4
Among coal, coal B and coal C, coal 1 not present in [Table 5]
Exclude 5%. Then, 5% of coal B is allocated to the column of low HGI coal in the row of sample 2 of [Table 6], and 80% of coal A is allocated to the column of high HGI coal of [Table 6]. Similarly, sorting work was performed on other samples. Next (low HGI, high H
In the column of (GI), each percentage is represented in the form of coordinates (X, Y). For example, sample 2 is (5,80). The notation in the rightmost column is represented by × 1 to × 3 since Samples 1 to 3 were “closed” (see [Table 4]). Similarly, samples 4-1
1 is ４4 to 、 11, samples 12 to 14 are △ 12 to △ 1
4 is assumed. In addition, ○ means “good” and Δ means “wear”. FIG. 5 is a dispersion graph of the experimental results according to the present invention. The horizontal axis represents the low HGI coal ratio, the vertical axis represents the high HGI coal ratio, and (low HGI, high HGI) in [Table 6]. ×,
プ ロ ッ ト and △ were plotted. This plot is shown in Table 6
Matches the notation. And the graph shows Y = 3X-105
And a straight line of Y = 3X + 50 was added. As a result,
All groups were between Y = 3X-105 and Y = 3X + 50, and groups X and △ were all outside. From the above, it is assumed that the sum of the ratios of pulverized coal having a hard globe index of less than 60 is X%, and the sum of the ratios of pulverized coal having a hard globe index of more than 80 is Y%.
It was confirmed that good results could be obtained by mixing pulverized coal of different coal types so as to satisfy the condition of 3X−105 ≦ Y ≦ 3X + 50. According to the present invention, the following effects can be obtained by the above-described structure. Claim 1 shows that when the sum of the ratios of the pulverized coal whose hard glove index is less than 60 is X% and the sum of the ratios of the hard glove index exceeding 80 is Y, 3X−105 ≦ Y ≦ 3X + 50. By mixing pulverized coal of different coal types so as to satisfy the conditions of the above, the pulverized coal having an HGI of more than 80 enables a protective layer of an appropriate amount of pulverized coal to be adhered to the pipe wall of the transport pipe. Can serve as a protective layer to suppress wear. At the same time, pulverized coal having a hard glove index of less than 60 has an effect of shaving the pipe wall. Therefore, the growth of the protective layer in the pipe by the pulverized coal and the action of shaving this protective layer are balanced, and it is possible to prevent both blockage and wear for a long period of time.

[Brief description of the drawings] FIG. 1 is a dispersion graph of an average HGI obtained in an experiment of the present invention. FIG. 2 is a diagram illustrating the principle of the experimental apparatus used in the present invention. FIG. 3 is a graph showing the results of experiments using AC coal. FIG. 4 is a composite graph of FIGS. 3 (a) to 3 (c). FIG. 5 is a dispersion graph of experimental results according to the present invention. [Explanation of symbols] 10: experimental apparatus, 11: pulverized coal ", 13: transport pipe.

Claims (1)

Claims 1. When mixing and pulverized coal of two or more different types of coal into a blast furnace, the total of the pulverized coal whose hard glove index is less than 60 is defined as X%. , The sum of the ratios of those with a hard globe index exceeding 80 is Y
Wherein pulverized coal of a different coal type is mixed so as to satisfy the condition of 3X−105 ≦ Y ≦ 3X + 50.