Method for producing sintered ore

Abstract

To provide a method for producing sintered ore capable of stably improving productivity of the sintered ore.SOLUTION: A method for producing sintered ore includes a charging chute 11 that charges sintered raw material supplied from a drum feeder onto a sintering pallet and includes a plurality of bars 13 to 16 spaced apart in the width direction and extending in the direction in which the sintered raw material flows downward, and further includes a bar screen 10 disposed downstream of the charging chute 11, in which the vertical spacing between adjacent bars 13 to 16 in the width direction increases in the direction in which the sintered raw material flows downward, thereby classifying the sintered raw material flowing down from the charging chute 11 while charging it onto the sintering pallet and sintering it, wherein the bar screen 10 has a plurality of upper tier bars 13 whose tips are positioned higher than the tips of the adjacent bars 14 to 16 on both sides in the width direction, and the upper tier bars 13 are arranged at an arrangement pitch of 35 mm to 75 mm. Before sintering the sintering raw material loaded on the sintering pallet, the protrusions on the surface of the raw material layer are flattened by the cut plate 12.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a method for producing sintered ore. [Background technology]

[0002] Sintered ore is produced by igniting the surface layer (hereinafter also referred to as the upper layer) of the sintering raw material loaded on a sintering pallet, and sintering the lower layer of the sintering raw material while sucking it from below and transporting it to the end of the sintering pallet. The productivity of sintered ore is proportional to the product of the sintered ore yield and the firing rate, and by improving either or both of the yield and the firing rate, the productivity of sintered ore can be stabilized at a high level. The firing rate is the speed at which sintering progresses from the upper layer to the lower layer of the sintered raw material on the sintering pallet (the speed at which the combustion reaction surface in the sintered layer progresses downward).

[0003] In the sintering process, the surface layer of the sintering raw material layer loaded onto the sintering pallet is cooled by the outside air that is sucked in from below the sintering pallet and flows in from above, resulting in insufficient temperature rise and a tendency for the sintered ore yield to decrease.On the other hand, the lower layer of the sintering raw material layer tends to form a thicker combustion fusion zone (also called red zone) with greater air resistance than the upper layer, resulting in a slower sintering speed. Therefore, in sintering, the average particle size of the sintering raw material in the upper layer is reduced to increase the temperature reached after oxidation heat generation ends, and the average particle size of the sintering raw material in the lower layer is increased to ensure air permeability and increase the firing speed. In this way, segregation charging is carried out as a method for reducing the average particle size of the sintering raw material in the upper layer and increasing the average particle size of the sintering raw material in the lower layer.

[0004] For example, Patent Document 1 proposes a technology in which a bar screen consisting of multiple bars extending in the direction in which the sintering raw material flows is provided downstream of a charging chute for the sintering raw material, and the sintering raw material flowing down from the charging chute is classified by the bar screen while being charged onto a sintering pallet. Here, the multiple bars are arranged at intervals in the width direction of the charging chute, and the intervals between adjacent bars in the vertical direction in side view increase toward the downstream side. The method described in Patent Document 1 above realizes segregated charging of sinter raw materials, improves the yield of sintered ore, and increases productivity. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2014-129570 [Patent Document 2] Japanese Patent Application Publication No. 1-309929 Summary of the Invention [Problem to be solved by the invention]

[0006] In order to further improve the productivity of the method of Patent Document 1, the present inventors have investigated the use of a cut plate as described in Patent Document 2, for example. Generally, cut plates are used to flatten convex portions that appear on the surface of the raw material layer (hereinafter simply referred to as the surface) of the sintering raw material layer, but as described in Patent Document 2, they are also used as a means to actively create unevenness. The present inventors conducted tests using various cut plates in the method of Patent Document 1, and although a predetermined effect of improving productivity was obtained, the stability of this effect was not necessarily sufficient.

[0007] An object of the present invention is to provide a method for producing sintered ore that can stably improve the productivity of sintered ore. [Means for solving the problem]

[0008] The inventors used the bar screen 10 shown in Figures 1 and 2 to investigate the factors that cause the effect to be unstable. As a result, it became clear that the arrangement of the bars 13 to 16 that make up the bar screen 10 increases the firing unevenness of the sintering raw material layer, resulting in low yields and low firing speeds.

[0009] Specifically, after a detailed investigation of the bar screen arrangement and the sintering raw material layer within the sintering pallet, we found that raw material tends to fall below bar 13 (hereinafter also referred to as the upper bar), which is located above bars 14-16 adjacent to each other in the width direction of the sintering pallet, and that relatively small raw material tends to accumulate there. Specifically, as shown in Figure 3, we found that ridge-like convex portions are formed on the surface of the sintering raw material layer loaded onto the sintering pallet according to the arrangement pitch L of the upper bar. Furthermore, we found that coarse particles, which tend to roll off more easily than fine particles, gather near the center between the upper bars (hereinafter also referred to as the concave portion), resulting in particle size segregation in the width direction of the sintering pallet (coarse particles tend to segregate in the concave portion). Note that for ease of explanation, the distinction between fine and coarse particles is exaggerated in Figure 3 and Figure 4 (described later).

[0010] In particular, it was found that when the arrangement pitch L of the upper row bars in the width direction of the sintering pallet exceeds 75 mm, the height of the ridge-like convex portions increases, and the segregation of the sintering raw material layer in the width direction of the sintering pallet is strengthened (the concentration of coarse particles in the concave portions is promoted). The convex parts with increased height are less able to ensure ventilation than the concave parts, which causes a decrease in yield. Therefore, we attempted to improve the yield by flattening them with a cut plate. However, as shown in Figure 4, this resulted in compaction of the convex parts (the convex parts are pressed into the sintering pallet and compacted, creating compacted parts). Therefore, although the concave parts where coarse particles segregate were able to ensure ventilation and improve yield, the breathability of the convex parts deteriorated, the impact of uneven ventilation became greater, and the yield overall worsened.

[0011] Regarding the firing speed, which is related to productivity, the ventilation provided by the recesses where coarse particles segregate and the lower parts of the recesses allows air to be supplied to the lower parts of the protrusions where fine particles segregate in the sintering raw material layer, and as a result, the firing speed was improved overall, despite the presence of compacted parts.

[0012] As described above, when the arrangement pitch L of the upper bars exceeds 75 mm, the firing speed improves but the yield deteriorates, and as a result, the productivity, which is the product of the two, deteriorates.

[0013] On the other hand, when the arrangement pitch L of the upper bar is less than 35 mm, the height of the convex part is reduced, the compacted part that occurs after passing through the cut plate is reduced, and the yield is improved. However, the segregation of the sintering raw material layer in the width direction of the sintering pallet is reduced, and the air permeability in the concave part and below the concave part is not improved, so the firing speed is deteriorated.

[0014] As described above, when the arrangement pitch L of the upper bars is less than 35 mm, the yield improves but the firing speed deteriorates, and as a result, the productivity, which is the product of the two, deteriorates.

[0015] Based on the above, the inventors have come to the conclusion that by setting the arrangement pitch L of the upper bars to 35 mm or more and 75 mm or less and setting the height of the ridge-like convex portions to a certain level, it is possible to reduce the compacted areas caused by the use of cut plates and improve yield.Furthermore, by ensuring ventilation in the concave portions, which are mainly composed of coarse particles due to a certain degree of segregation of the sintering raw material layer in the width direction of the sintering pallet, and in the areas below the concave portions, the firing speed of the entire sintering raw material layer is improved, thereby stabilizing productivity at a high level.

[0016] That is, the present invention is as follows. A method for producing sintered ore, comprising: a charging chute for charging sintered raw material supplied from a drum feeder onto a sintering pallet; a plurality of bars spaced apart in the width direction of the charging chute and extending in the direction in which the sintered raw material flows downward; a bar screen, the vertical spacing between adjacent bars in the width direction of which increases in the direction in which the sintered raw material flows downward, is disposed downstream of the charging chute; the sintered raw material flowing down from the charging chute is charged onto the sintering pallet while being classified by the bar screen; and the sintered raw material on the sintering pallet is sintered, The bar screen includes a plurality of upper bars whose tips are arranged at a position higher than the tips of the adjacent bars on both sides in the width direction, and the arrangement pitch of the upper bars is 35 mm or more and 75 mm or less, A method for producing sintered ore, characterized in that, before sintering the sintered raw materials charged on the sintering pallet, convex portions on the surface of the raw material layer of the sintered raw materials are flattened by a cut plate. [Effects of the Invention]

[0017] According to the method for producing sintered ore of the present invention, it is possible to stably improve the productivity of sintered ore. [Brief explanation of the drawings]

[0018] [Figure 1] FIG. 2 is an explanatory diagram showing the positional relationship between a bar screen and a cut plate when the sintering machine is viewed from the side. [Figure 2] FIG. 2 is an explanatory diagram showing the positional relationship of the tips of the multiple bars that make up the bar screen. [Figure 3] 1 is an explanatory diagram showing the behavior of the sintering raw material charged onto the sintering pallet by the bar screen and the charging state of the raw material layer. FIG. [Figure 4] This is an explanatory diagram showing the state of the raw material layer of sintering raw material loaded onto a sintering pallet when using a bar screen with an arrangement pitch of upper bars exceeding 75 mm, as it passes through the cut plate. [Figure 5] FIG. 10 is an explanatory diagram showing the positional relationship of the tips of multiple bars that make up another bar screen. [Figure 6]1 is a graph showing the relationship between the arrangement pitch L of upper bars that make up the bar screen and the sinter yield. [Figure 7] 10 is a graph showing the relationship between the arrangement pitch L of the upper bars that make up the bar screen and the firing speed. [Figure 8] 1 is a graph showing the relationship between the arrangement pitch L of upper bars constituting the bar screen and sintering productivity. DETAILED DESCRIPTION OF THE INVENTION

[0019] The method for producing sintered ore of the present invention comprises a charging chute that charges sintered raw material supplied from a drum feeder onto a sintering pallet, the charging chute being provided with a plurality of bars spaced apart in the width direction and extending in the direction in which the sintered raw material flows downward, and a bar screen in which the vertical spacing between adjacent bars in the width direction increases in the direction in which the sintered raw material flows downward is disposed downstream of the charging chute, the sintered raw material flowing down from the charging chute is charged onto the sintering pallet while being classified by the bar screen, and the sintered raw material on the sintering pallet is sintered, The bar screen includes a plurality of upper bars whose tips are arranged at a position higher than the tips of the adjacent bars on both sides in the width direction, and the arrangement pitch of the upper bars is 35 mm or more and 75 mm or less, Before the sintering raw material loaded on the sintering pallet is sintered, the protrusions on the surface of the raw material layer of the sintering raw material are flattened by a cut plate.

[0020] Sintered ore is produced by igniting the surface layer of sintering raw materials loaded onto a sintering pallet, and then sintering the raw materials down to the bottom layer while sucking them from below the sintering pallet and transporting them to the end of the sintering pallet.

[0021] The charging chute 11 shown in FIG. 1 is arranged below a storage hopper (not shown) that stores sintering raw materials, and is inclined downward in the opposite direction to the traveling direction of the sintering pallet into which the sintering raw materials are charged through a bar screen 10 arranged downstream of the charging chute 11.

[0022] The cut plate 12 is used to flatten (eliminate unevenness in the surface) the convex portions on the surface of the raw material layer of sintering raw material that has been loaded onto the sintering pallet from the loading chute 11 through the bar screen 10, and normally has a straight lower end when viewed from the front. However, it can also have a shape in which the lower end that comes into contact with the resulting convex portion protrudes downward more than the other parts (such as a wavy lower end), or a shape in which the lower end protrudes downward from both ends of the sintering pallet width direction toward the center (V-shape), etc.

[0023] 1 and 2, the bar screen (also referred to as a segregation charging member) 10 is provided with a plurality of bars 13-16 that extend in the direction of the flow of the sintering raw material at intervals in the width direction of the charging chute 11 (the same as the width direction of the sintering pallet). Each of these bars 13-16 is inclined downward toward the direction of the flow of the sintering raw material, and the base end of each bar is attached to the back side (underside) of the downstream end of the charging chute 11 with the vertical intervals between adjacent bars 13 and 14, between bars 14 and 15, and between bars 15 and 16 in the width direction of the charging chute 11 widening toward the direction of the flow of the sintering raw material.

[0024] Each bar 13 to 16 is made of a metal rod such as iron (diameter: approximately 5 mm to 30 mm, length: approximately 500 mm to 1500 mm), and rotates around its axis. Its cross section is usually circular, but is not particularly limited as long as it is a shape that can classify the sintering raw material, and it may be, for example, elliptical, egg-shaped, or polygonal such as triangular or rectangular.

[0025] Of the multiple bars 13-16 described above, bar 13 (hereinafter also referred to as the upper bar) has its tip positioned higher than the tips of the adjacent bars 14-16 on both sides of the width of the sintering pallet. Specifically, bar 13 is arranged in four rows: bar 13 in the first row, bar 14 in the second row, bar 15 in the third row, and bar 16 in the fourth row. As shown in FIG. 2, when the bar screen 10 is viewed from the tip side, the imaginary lines connecting the tips of adjacent bars 13-16 in the width direction form a W shape, i.e., a valley, a peak, and a valley. The arrangement of the tips of bars 13-16 shown in FIG. 2 is a partial illustration of multiple bars arranged in the width direction of the sintering pallet. Generally, bar screens used are those in which the illustrated arrangement is repeated multiple times to form a width approximately equal to the width of the sintering machine pallet.

[0026] A plurality of the bars 13 are arranged in the width direction of the sintering pallet (the width direction of the charging chute 11), and in the present invention, the arrangement pitch L of the bars 13 is set to 35 mm or more and 75 mm or less. The arrangement pitch L of the bars 13 is the distance between the axial centers of the bars 13 adjacent to each other in the width direction.

[0027] As mentioned above, by setting the arrangement pitch L of the upper tier bars to 75 mm or less, the increase in the height of the ridge-like protrusions formed according to the arrangement pitch L of the upper tier bars can be suppressed. This suppresses the increase in segregation of the sintering raw material layer in the width direction of the sintering pallet and reduces the compacted areas caused by the use of cut plates, thereby reducing uneven ventilation in the width direction and stabilizing the yield at a high level. On the other hand, by setting the arrangement pitch L of the upper bars to 35 mm or more, it is possible to form ridge-like convex portions to a certain degree, causing a minimum amount of segregation in the width direction, and by ensuring ventilation in the concave portions, which are mainly composed of coarse particles, and below the concave portions, it is possible to improve the ventilation of the entire raw material layer of the sintering raw material, and to stabilize the firing speed at a high level. From the above, by setting the arrangement pitch L of the upper bars to 35 mm or more and 75 mm or less, productivity can be stabilized at a high level, taking into consideration both yield and firing speed.

[0028] The effect of the present invention does not necessarily require that the heights of the upper bars be the same (they are the same height), and for example, as shown in Figure 5, even if some of the upper bars (here, bar 16) are not the topmost bar (even if they are not the same height as bar 13), roughly the same effect can be obtained. As shown in Figure 5, bar 16 is an upper bar of the present invention because its tip is positioned higher than the tips of bars 15 adjacent to it on both sides in the width direction, and the arrangement pitch L of bars 13 and 16 is set to 35 mm or more and 75 mm or less. There is also no particular limit to the number of rows of bars that make up the bar screen, as long as there are two or more rows, but in reality it is around three to five rows.

[0029] As described above, by limiting the spacing of the upper bars (bar 13 in Figures 2 and 3, and bars 13 and 16 in Figure 5) of the multiple bars 13 to 16 that make up the bar screen 10, whose tips are positioned higher than the bars adjacent to them on both sides, and controlling the position at which the sintering raw material falls in the width direction of the sintering pallet, it is possible to maintain a high firing rate by improving the permeability of the sintering raw material layer by imparting segregation in the width direction of the sintering pallet, while the cut plate 12 has the effect of suppressing an increase in uneven permeability in the width direction of the sintering pallet, which is a problem unique to the bar screen 10.By maintaining a high sinter yield, it is possible to maintain a high level of sintering productivity. [Example]

[0030] Next, examples carried out to confirm the effects of the present invention will be described.

[0031] 1. Experimental Conditions The specifications of the bar screen used are shown in Table 1, and the experimental conditions for the comparative example and the inventive example are shown in Table 2.

[0032] [Table 1]

[0033] [Table 2]

[0034] The bar screen of Comparative Example 1 shown in Table 2 has two rows of bars, but these two rows of bars are made up of the first and second rows of bars shown in Figure 1. Similarly, the bar screens of Invention Examples 1 and 2 have three rows of bars, but are made up of the first to third rows of bars shown in Figure 1. In addition, the bar screens of Invention Examples 1 and 3 have some of the upper rows of bars not in the top row, so that the arrangement pitch L of the upper rows of bars is changed to three or four rows. The bar arrangement (arrangement of the bar tips) shown in Table 2 is a partial illustration, and the bar screen used in the experiment was 4 m long (the width of the sinter machine pallet) by repeating the illustrated arrangement.

[0035] In Comparative Example 1, the arrangement pitch L of the upper bars was set to 28 mm (less than 35 mm). In Comparative Example 2, the arrangement pitch L of the upper bars was set to 84 mm (more than 75 mm). In Examples 1 to 3, the arrangement pitch L of the upper bars was set to 42 mm, 56 mm, and 70 mm (within the range of 35 mm to 75 mm), respectively.

[0036] The sintering raw materials used in the actual machine test consisted of fine ore with 20% to 80% by mass of particles under 500 μm, coagulants such as fine coke, and auxiliary materials such as limestone. The moisture content of the sintering raw material was 7.0% to 10.0% by mass. This moisture content (mass%) was calculated by the formula "amount of water (kg) / {amount of water (kg) + sintering raw material (kg)} × 100". The supply rate of sintering raw materials to the sintering machine (sintering pallet) was set to 200 ton / h per 1 m width of the charging chute.

[0037] Sinter productivity (T / day / m 2 ) is the amount of sintered ore produced per unit time divided by the effective area of ​​the sinter machine (= sinter machine width x machine length). The yield (mass%) is the percentage of sintered ore recovered when the sintered ore produced in the sintering machine is crushed in a crusher and sieved, i.e., the percentage of the mass of sintered ore with a particle size of 5 mm or more recovered to the mass of the total sintered ore. The firing rate (mm / min) is the speed at which the combustion reaction surface in the sintered layer progresses downward, and is calculated by dividing the layer thickness by the time it takes for the exhaust gas temperature of the sintering machine to reach its maximum temperature.

[0038] 2. Test Results The sinter yield, firing speed, and sinter productivity obtained when the above-mentioned actual machine test was carried out are shown in Figure 6, Figure 7, and Figure 8, respectively. The firing rate and sintering productivity were corrected values, with the values ​​of Comparative Example 2 being set at 1. In terms of productivity improvement effect, the arrangement pitch L of the upper bars that was improved by 1.5% or more (sintering productivity 1.015) compared to Comparative Example 2 was defined as the appropriate range.

[0039] As shown in Figure 6, the sinter yield improved as the arrangement pitch L of the upper bars became smaller. As shown in FIG. 7, the firing speed improved as the arrangement pitch L of the upper bars increased. As shown in FIG. 8, the sintering productivity improved by 1.5% or more when the arrangement pitch of the upper bars was 35 mm or more and 75 mm or less.

[0040] Here, the test was carried out with the bar screen specifications shown in Table 1 above. However, if the specifications of the segregation charging member are such that the gap d between adjacent bars in the horizontal direction in a plan view is 3 mm or more and 12 mm or less, and the opening angle between adjacent bars in the vertical direction in a side view is 1.2° or more and 3.0° or less, the same effect as that of the present invention can be obtained.

[0041] From the above, it was confirmed that by using the method for producing sintered ore of the present invention, it is possible to stably improve the productivity of sintered ore.

[0042] Although the present invention has been described above with reference to the embodiments, the present invention is not limited to the configurations described in the above embodiments and includes other embodiments and modifications that are conceivable within the scope of the claims. For example, the scope of the present invention also includes a case where the method for producing sintered ore of the present invention is configured by combining some or all of the above embodiments and modifications. [Industrial Applicability]

[0043] INDUSTRIAL APPLICABILITY The present invention provides a method for producing sintered ore that can stably improve the productivity of sintered ore, and is therefore industrially useful. [Explanation of symbols]

[0044] 10, 10a: Bar screen, 11: Charging chute, 12: Cut plate, 13-16: Bar

Claims

[Claim 1] A method for producing sintered ore, comprising: a charging chute for charging sintered raw material supplied from a drum feeder onto a sintering pallet; a plurality of bars spaced apart in the width direction of the charging chute and extending in the direction in which the sintered raw material flows downward; a bar screen, the vertical spacing between adjacent bars in the width direction of which increases in the direction in which the sintered raw material flows downward, is disposed downstream of the charging chute; the sintered raw material flowing down from the charging chute is charged onto the sintering pallet while being classified by the bar screen; and the sintered raw material on the sintering pallet is sintered, The bar screen includes a plurality of upper bars whose tips are arranged at positions higher than the tips of the adjacent bars on both sides in the width direction, and the arrangement pitch of the upper bars is 35 mm or more and 75 mm or less, A method for producing sintered ore, characterized in that, before sintering the sintered raw materials charged on the sintering pallet, convex portions on the surface of the raw material layer of the sintered raw materials are flattened by a cut plate.

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