JP7095561B2 - Sintered ore manufacturing method - Google Patents

Description

The present invention relates to a method for producing a sinter.

Currently, the main raw material for blast furnace pig iron is sinter. Sintered ore is usually produced as follows. First, iron ore, return ore, steelmaking dust and other iron-containing raw material powders, carbonaceous materials, and auxiliary raw materials including CaO are mixed in a predetermined ratio, and the mixture is granulated or agglomerated to form a mixed raw material. And. Next, the granulated or agglomerated compounded raw material is placed on a pallet of a dwitroid (DL) type sintering machine that sucks downward from the hopper to form a packed raw material, and the packed raw material is placed. The carbonaceous material in the packed bed of raw material is ignited from the upper layer (surface layer) by an ignition furnace. Then, oxygen is supplied by sucking air from the lower part of the pallet while continuously moving the pallet, and the combustion of the carbonaceous material in the raw material filling layer proceeds from the upper layer to the lower layer, whereby the combustion of the carbonaceous material is carried out. Sequentially sintered by heat. The obtained sintered portion (sinter cake) is pulverized to a predetermined particle size, sized by sieving, etc. to obtain a sintered ore which is a raw material for blast furnace pig iron.

In the above manufacturing process, granulation is performed because the carbonaceous material is burned by suction of air at the time of sintering, and heat sintering is performed by this combustion. If the raw materials are not granulated, small raw material particles are clogged in the gaps between the raw materials, which hinders the air permeability and delays sintering.
At the time of granulation, water is added to the raw material to perform granulation. By adding water to the raw material and performing the granulation operation, water acts as a binder and relatively fine particles adhere around the relatively coarse particles. As a result, the apparent particle size of the compounded raw material increases, and when the compounded raw material is supplied to the sintering machine, the porosity and the void diameter of the packed bed of the raw material increase, and the air permeability is improved. If the air permeability is improved, the progress of sintering becomes faster and the productivity is also improved.

However, when granulating a raw material using water as a binder, when the carbonaceous material and other raw materials are mixed at the same time and granulated, the charcoal material that does not easily get wet with water is buried inside the granulated material, and the interior is decorated. Therefore, it may not be possible to obtain an apparent particle size of the compounded raw material having a sufficient size because it inhibits granulation. Then, the distance between the compounded raw materials (granulated materials) becomes narrow, the air permeability during sintering is hindered, and as a result, the productivity of the sinter is lowered.

To solve such a problem, there is a technique called powder coke split addition (for example, Non-Patent Document 1) or post-addition (for example, Patent Document 1) to improve productivity (hereinafter, these are collectively referred to as a generic technique). It is called "carbonate post-addition sintering method").
The post-carbonation addition sintering method prevents the charcoal material from being buried in the granulated material, increases the combustion rate of the carbonaceous material, and improves the combustion front descent rate (FFS). This improves the productivity of sintering.

Japanese Patent Application Laid-Open No. 2003-160815

Iron and Steel 100 (2014) No. 2 p. 180-188

However, in general, the improvement of FFS lowers the high temperature holding time (melting time), so that it also has a problem of deteriorating the yield of the sinter that has secured the required sinter strength. Even if the FFS is improved by the carbonaceous material post-addition sintering method, this problem of yield decrease is not completely solved.
There is a description that the method disclosed in Patent Document 1 was able to increase the particle size of the pseudo-particles, reduce the rate of decrease in yield, and significantly increase the production rate. The security was not enough.

The present invention provides a method for producing a sinter that not only improves FFS and improves productivity but also improves yield when carrying out a post-addition sinter method for carbonaceous materials. With the goal.

The gist of the present invention for solving the above problems is as follows.
(1) Granulated compounded raw materials are charged into a pallet constituting a dwitroid (DL) type sintering machine to form a raw material packing layer, ignited from the upper part of the raw material filling layer, and the atmosphere is blown from below. A method for producing a sinter that sinters the raw material packing layer, which is sintered by suction.
In the granulated compounding raw material, the raw material from which only a part or the whole amount of the charcoal material was removed was added to the raw material during or after granulation by adding water. It is a thing
The DL-type sintering machine includes an igniter and a frame heating device provided on the downstream side of the igniter at a distance and heating the upper surface of the raw material packed bed.
An atmospheric suction region is formed between the igniter and the frame heating device.
The upper surface of the raw material packed bed is heated by the frame heating device in which the distance d1 (mm) between the igniter and the frame heating device is set to a length distance of 2% or more and 10% or less with respect to the following L1. A method for producing a sintered ore characterized by.
L1: Machine length L2 (mm) -Pallet traveling direction length X1 (mm) of the igniter-Pallet traveling direction length X2 (mm) of the frame heating device
(2) The sintering according to (1), wherein the ratio of the carbonaceous material to be added later to the granulated compounding raw materials is 30% by mass or more with respect to the total mass of the carbonaceous material. How to make ore.
(3) The method according to (1) or (2), wherein the granulation time from the later addition of the charcoal material to the addition is 80% or more and 95% or less with respect to the total granulation time. How to make sinter.
(4) The sintering according to any one of (1) to (3), wherein the coal material to be added later is charcoal obtained by carbonizing coal having a logger index of 10 or less as raw coal. How to make ore.

According to the present invention, the raw material is filled by a carbon material post-addition sintering method in which the carbon material is added to the granulated product during or after granulation of a raw material other than a part or all of the carbon material. The breathability of the layer is improved. In addition, after ignition heating by the igniter, the frame heating by the frame heating device is performed at predetermined intervals, so that the combustion zone advances to the lower part due to the increase in the superficial velocity during atmospheric suction from ignition to frame heating. However, since the frame is heated after the thickness is expanded, a significant productivity improvement effect accompanied by a yield improvement effect can be obtained.

Constructive diagram of a sintering machine having a carbon post-addition process and having an igniter and a frame heating device. Overall schematic diagram of a general DL type sintering machine. Explanatory drawing of combustion front depth by operation example of a sintering machine. Explanatory drawing to calculate the arrangement location range of the frame heating device from the raw material packed bed and the captain. The figure which showed the influence which the post-addition sintering method of a carbonaceous material and the frame heating method have on the product yield. The figure which showed the influence which the carbon post-addition sintering method and the frame heating method have on the combustion front descent rate. The figure which showed the influence which the post-addition sintering method of a carbonaceous material and the frame heating method have on the production rate. The figure which showed the influence which the addition ratio after a coal material had on the product yield. The figure which showed the influence which the addition timing of the charcoal material in the post-addition coal material sintering method has on the product yield.

The process of solving the problem will be explained in detail below.
In a DL type sintering machine, when sintering is performed sequentially from the ignited upper layer to the lower layer, in general, the thermal distribution in the height direction of the raw material packed bed is such that the lower layer portion has a sufficient amount of heat, but the upper layer portion has a sufficient amount of heat. Then the amount of heat becomes insufficient. In the lower layer, the temperature gradually rises due to the progress of sintering in the upper layer, and after sufficient preheating, the carbonaceous material such as coke burns, and even after the combustion is completed, it is gradually cooled by the residual heat of the upper layer. On the other hand, in the upper layer portion, after the combustion of coke in the compounding raw material is completed, it is rapidly cooled by the low temperature air sucked from the upper layer.
When the amount of heat in the upper layer portion is insufficient, sintering does not proceed sufficiently in this portion, causing insufficient strength of the sinter in the upper layer portion, and the overall yield also deteriorates.

The present inventor investigated the yield and cold strength under the conditions for heating the upper surface of the raw material packed bed by various methods after ignition by the igniter. As a result, after the ignition by the igniter is completed, an atmospheric suction region in a predetermined range is provided, and the upper surface of the raw material packed bed is reheated by frame heating at a predetermined timing to secure the required sintering strength. We have found that the yield of sinter can be improved. The frame heating is performed for the purpose of igniting the charcoal material (coke) that has not been sufficiently ignited by the first stage ignition and sufficiently heating the upper layer to replenish the heat. The technique of performing the second stage frame heating (second stage ignition) at a predetermined interval after the first ignition (first stage ignition) is hereinafter referred to as a frame heating method.

According to the frame heating method, the frame heating device installed at a predetermined distance from the igniter keeps the upper space of the sintered layer at a high temperature, and the air in the upper space of the raw material packed bed kept at a high temperature is sintered. Since it is sucked into the layer, heat is not removed from the upper part of the sintered layer, and conversely, gas sensible heat is utilized for supplying heat to the raw material of the raw material packed bed. Therefore, heating with fuel is efficiently performed, sintering defects due to insufficient heat and insufficient high temperature holding time can be prevented, and it is effective in improving the yield of the upper part (upper layer) of the packed bed. Since the yield of the upper layer, which has lowered the overall yield, is improved, the overall yield is also improved.

This frame heating method is based on the principle of heating the upper layer, which tends to be insufficiently sintered, and regardless of the type of compounding raw material, if it is a normal compounding raw material, sintering that secures the required sintering strength. The yield of ore can be improved. Therefore, the frame heating method was applied for the purpose of improving the yield even in the post-addition sintering method for carbonaceous materials, which has a problem in yield.
As a result, it was clarified that the synergistic effect of the frame heating method and the carbonaceous material post-addition sintering method, which exceeded the prediction, can be obtained.

(Charcoal material post-addition sintering method)
The characteristics of the carbonaceous material post-addition sintering method will be described with reference to FIG.
In general granulation that does not use the post-addition sintering method for carbonaceous materials, powdered metal oxides (iron ore), raw lime, silicon oxide, fine powder ore (pellet feed, etc.), return ore, binder, etc. are used as raw materials. The entire amount is collectively granulated with a drum mixer 15 suitable for mass processing. On the other hand, in the post-additional sintering method of carbonaceous material, carbonaceous material such as coke breeze (solid carbon) is used from the outlet of the granulator from the outlet of the granulator during the process of granulation by adding water to the raw material or after the granulation is completed. The source) is added and used as the total amount of the compounded raw material.

According to this method, a solid carbon source such as coke breeze is externalized. That is, the solid carbon source exists as independent grains attached or not attached to the surface layer of the granulated product without being encapsulated in the granulated product. Therefore, at the time of sintering, the combustion reaction with oxygen in the circulating gas becomes active, and as a result, the yield is improved. In addition, when it is charged into the sintering machine, it tends to be concentrated (unevenly distributed) in the upper layer of the raw material packed bed. Therefore, the improvement of combustion efficiency by heating the frame is accelerated, and as a result, a synergistic effect on the improvement of yield can be obtained.

In addition, the post-granulation sintering method removes carbonaceous materials (solid carbon sources) such as coke breeze, which are difficult to granulate, so the sintering speed (FFS: combustion front descent speed) is improved by strengthening the granulation. You can expect the effect. In addition, since the carbonaceous material (solid carbon source) such as powdered coke is not included in the granulated product, the solid-solid reaction between carbon iron oxide is suppressed, and the effect of improving the reducibility by reducing the sintered ore FeO is also expected. can.

As described above, in the frame heating method, the yield is greatly improved when the carbonaceous material such as coke breeze is concentrated in the upper layer of the packed bed of the raw material, and the specific method is the post-carbonate material addition sintering method. Here, in order to exhibit the effect, the ratio of the carbonaceous material to be added later is preferably 30% by mass or more with respect to the total mass of the carbonaceous material. The charcoal material referred to here is a solid carbon source, and is generally a raw material containing a free carbon content of 75% by mass or more. A free carbon content of 75% or more means that C is 75% by mass in terms of carbon. Specific examples include coke and anthracite.

Further, in order to more sufficiently avoid encapsulation in the carbonaceous material granulated product, it is preferable that the granulation time until the addition of the charcoal material is 80% or more and 95% or less with respect to the total granulation time. By setting the granulation time within this range, the product yield is further improved.
As shown in FIG. 1, the granulation may be performed by using a single drum mixer 15 and supplying only the carbonaceous material from the terminal side of the drum mixer 15. Although not shown, two drum mixers 15 are used to perform granulation other than the carbonaceous material with the first drum mixer 15, and then the carbon material is exteriorized on the granulated material granulated with the first drum mixer 15 with the next drum mixer 15. Granulation may be done. If the granulation time until the addition of the carbonaceous material is 80% or more and 95% or less with respect to the total granulation time, in the case shown in FIG. 1, it is controlled by the position where the carbonaceous material is supplied, and two When the drum mixer 15 is used, it is controlled by the granulation time of each drum mixer 15.

(Frame heating method)
Subsequently, the frame heating method, which is a feature of the present invention, will be described in detail.
The present invention is a method using a DL type sintering machine.
FIG. 2 shows a general DL type sintering machine. The sintering machine used in the present invention also conforms to the configuration of such a general sintering machine. The characteristic points of the present invention will be described in detail later, but first, a general configuration will be described.
The sintering machine adds a coagulant such as fresh lime, silicon oxide, and coke breeze and fuel to powdered metal oxide (iron ore), adds water, and kneads the compounded raw material into a pallet. A device for producing sintered ore by igniting fuel powder coke from above with a burner flame and sintering it with the combustion heat of the ignited fuel. Hopper 7, pallet 9, rail or track guide 10, drive wheel 11, It includes a free wheel 12, a duct 13, a wind box 14, and an igniter 2.

The hopper 7 is a raw material supply unit in which the compounded raw material is supplied from the upper part and a predetermined amount of the compounded raw material is charged into the pallet 9 from the lower discharge port.
The pallet 9 is a dolly having a side wall and a bottom that are open at the top and front and back in the traveling direction, and a plurality of slit-shaped openings extending along the width direction of the pallet 9 are formed at the bottom. By arranging the plurality of pallets 9 without gaps in the traveling direction, a container over the entire length of the sintering machine is formed.

The pallet 9 is pushed out from the mining side by the drive wheels 11 and travels on the rail or the track guide 10 at a predetermined speed to reach the mining section. There, it is guided by the idler wheel 12 and the rail or track guide 10 to reverse, and returns to the drive wheel 11 along the lower rail or track guide 10.
Although not shown, the duct 13 is connected to a blower, and when the blower is operated, air in the space below the air box 14 arranged under the pallet 9 is sucked out, and accordingly, the air above the pallet 9 is sucked out. The air cooled from the air is introduced to maintain the combustion of the compounded raw material ignited by the igniter 2, and cool the sintered ore after combustion.
The igniter 2 is made of, for example, a box-shaped body that covers the upper part of the pallet 9, and is made into an ignition furnace having a plurality of burners for ignition inside.

In such a sintering machine, when the compounded raw material is supplied to the hopper 7, a predetermined amount of the compounded raw material is charged into the pallet 9 from the lower discharge port, and the pallets 9 are ignited together with the driving of the drive wheels 11. Proceed to the vessel 2, and the blended raw material is ignited by the igniter 2. After the ignition of the compounded raw material, the ignited compounded raw material is cooled by the air while the combustion is maintained by the air accompanying the suction of the duct 13 through the air box 14, and the sintered ore burning in the part of the idle wheel 12 is burned. While moving downward on the idler wheel 12, it breaks in the middle, then falls and is crushed by a crusher to produce a sintered ore having a predetermined diameter.

Next, the frame heating method, which is a feature of the present invention, will be described with reference to FIGS. 3 and 4. In the present invention, in the sintering machine, a frame heating device 4 for frame-heating the upper surface of the raw material packed bed 1 is provided on the downstream side of the igniter 2 at a predetermined interval from the igniter 2, and the igniter 2 is provided. An atmospheric suction region 3 is formed between the frame heating device 4 and the frame heating device 4. In FIGS. 3 and 4, the description of the pallet 9, the rail or track guide 10, the drive wheel 11, the free wheel 12, the duct 13, and the air box 14 shown in FIG. 2 is omitted. In FIGS. 3 and 4, the combustion zone 5 is shown as a relatively thick and large region. These figures are shown as conceptual diagrams with an exaggerated thickness that is easy to understand, and the combustion zone 5 does not actually occupy the illustrated ratio with respect to the raw material packed bed 1.
The sintering machine of the present invention is characterized in that it is provided with a frame heating device 4 arranged at a predetermined distance from the igniter 2. The specific distance d1 (mm) must be a length distance of 2% or more and 10% or less with respect to the following L1.
L1: Machine length L2 (mm) -Pallet traveling direction length X1 (mm) of the igniter-Pallet traveling direction length X2 (mm) of the frame heating device

Here, "frame heating" means heating using a frame, that is, a flame, and the frame (flame) is sprayed on the uppermost surface of the sintered layer, which is the object to be heated, and the flame comes into direct contact with the surface. It means to heat in the state of being. That is, the fuel is not blown into the packed bed 1 for combustion and heated in the packed bed 1, but the combustion is heated from the outside of the layer. Further, in the present invention, "frame heating" means a heating step in which ignition is performed by the igniter 2, suction is performed in a predetermined atmospheric suction region 3, and then reheating is performed.
In the present invention, since the frame is directly jetted onto the upper surface of the raw material packed bed 1 to heat the raw material packed bed 1, the raw material packed bed 1 itself can be sufficiently heated, and the combustion efficiency of the carbonaceous material in the raw material packed bed 1 can be improved, and at the same time. The air in the upper space of the raw material packed bed 1 can also be heated. Since the air in the upper space of the raw material packed bed 1 is heated, it is possible to prevent the temperature of the upper portion of the sintered layer from dropping due to cold air. Further, since the frame is directly sprayed on the upper surface of the raw material packed bed 1 and all the unburned charcoal material that could not be ignited by the igniter 2 can be ignited, the heating by the charcoal material in the raw material packed bed 1 can be ignited. The efficiency is excellent.
Further, the "atmospheric suction region 3" in the present invention is a region between the igniter 2 and the frame heating device 4, and although the atmosphere is sucked by downward suction, direct heating by a burner or the like is performed from the upper surface. It refers to the area that is not covered.
When ignited by the igniter 2, the raw material filling layer 1 is formed with a combustion zone 5, and is sintered from the upper layer to the lower layer by atmospheric suction in the atmospheric suction region 3 provided between the igniter 2 and the frame heating device 4. As the reaction proceeds, the combustion zone 5 in the upper layer is particularly expanded. On the other hand, if the burner is continuously heated immediately after ignition by the igniter 2, the oxygen concentration in the space above the raw material packed bed 1 decreases due to the flame of the burner. In the present invention, since the combustion heating of the flame burner or the like is not performed from the upper surface in the atmospheric suction region 3, sufficient oxygen is supplied to the combustion zone 5, so that the raw material filling layer 1 in the atmospheric suction region 3 Combustion of the carbonaceous material inside is promoted.

Since the timing for starting frame heating needs to be a predetermined timing, it is necessary to specify the interval between the initial ignition and frame heating. This interval can be expressed by the distance d1. The predetermined distance d1 must be in the range of 0.02L1 (mm) ≤ d1 (mm) ≤ 0.10L1 (mm). When it is less than 0.02L1, the position of the combustion front (lower surface of the combustion zone) becomes less than a predetermined depth, and when it exceeds 0.10L1, the depth position h of the combustion front (lower surface of the combustion zone) becomes a predetermined depth. This is because it becomes deeper than the depth. Since the depth position h of the combustion front (bottom surface of the combustion zone) and d1 are in a proportional relationship, if d1 is set to a predetermined range, h is also set to a predetermined range.
The significance of having to perform frame heating when h is in a predetermined position range will be described below.

This will be described with reference to FIG.
When the upper surface (surface) of the raw material packed bed 1 charged from the hopper 7 is ignited by the igniter 2, the charcoal material contained in the raw material packed bed 1 burns. In the combustion of the carbonaceous material during ignition, it may or may not be sucked downward, but this combustion ignites until the ignition by the igniter 2 is completed, but sintering does not proceed in the lower layer direction. .. This is because the oxygen concentration above the raw material filling layer 1 becomes thin due to the heating of the ignition burner, so that the supply of oxygen is restricted, and the carbonaceous material in the raw material filling layer 1 is not sucked downward, of course, even if it is sucked downward. This is because the combustion of oxygen is stagnant.
When ignition is completed, the pallet 9 is downstream from the igniter 2 (the raw material packed bed 1 is shown continuously in the longitudinal direction in FIGS. 3 and 4, but the raw material packed bed 1 is actually a box-shaped pallet 9). When the raw material packed bed 1 moves to the air suction region 3 as it is placed inside, the combustion zone 5 descends from the lower surface by sucking the air from below, and toward the lower surface from the upper surface. proceed.
At this time, not all the carbonaceous materials contained in the raw material packed bed 1 in the thickness direction start combustion at once. At first, only the surface carbonaceous material burns, and when the surface carbon material finishes burning, the fire surface moves downward in sequence. That is, during sintering, the portion of the raw material filling layer 1 where the charcoal material is burned (combustion zone 5) is filled with the sintered complete layer 6 where the charcoal material has finished burning and the raw material filling where the charcoal material is about to burn. It is sandwiched between layers 1 and has a certain thickness in the depth direction.
The "bottom surface of the combustion zone" means a combustion start portion at the lowermost portion of the combustion zone 5 in which the carbonaceous material is burned in red. Further, during heating by the frame heating device 4, the combustion front does not progress and is stagnant, with or without downward suction, as in the case of heating with the igniter 2. This is because the oxygen concentration above the raw material packed bed 1 becomes thin due to frame heating, so that the supply of oxygen is restricted and the combustion of the carbonaceous material in the raw material packed bed 1 is stagnant.

When the timing for starting frame heating exceeds a predetermined depth from the uppermost surface of the sintered layer at the depth position h of the combustion front (lower surface of the combustion zone), the upper surface of the sintered layer is cooled by atmospheric suction and the temperature is increased. Even if it is heated again, the effect of improving the yield by heating the frame will be reduced.
On the other hand, when the timing at which the frame heating is started is that the depth position h of the combustion front (lower surface of the combustion zone) is shallower than the predetermined depth from the uppermost surface of the sintered layer, the atmospheric suction region 3 having a necessary and sufficient length d1 is secured. This is not possible, and the high temperature holding time of 1100 ° C. or higher, which is a temperature sufficient to proceed with sintering, cannot be sufficiently secured on the upper surface of the raw material filling layer 1 and becomes shorter. Therefore, in order to indirectly specify h, d1 having a certain proportional relationship with h is used to determine a sufficient length d1 as described above. On the contrary, even if the material is continuously heated after ignition, or if the atmospheric suction region 3 having a necessary and sufficient length d1 is not provided, sufficient atmospheric suction is not performed on the carbonaceous material inside the raw material packed bed 1. As a result, oxygen becomes insufficient, and the heat at the time required for sintering the upper part of the packed bed 1 cannot be supplied.
Therefore, the timing for starting the frame heating can be realized by setting the distance d1 between the igniter 2 (ignition furnace) and the frame heating device 4 to a predetermined length.

Based on this, as the configuration of the sintering machine, the range of the length d1 of the atmosphere suction region 3 which is the distance between the igniter 2 and the frame heating device 4 is the machine length L2, the length X1 of the igniter 2, and the frame heating device 4. The reason why it is 2 to 10% of the length of L1 represented by the length X2 of the above will be described in detail with reference to FIG.
While the pallet 9 moves to the sintering end point, which is the end of the air box (not shown in FIGS. 3 and 4) that ignites the upper part of the raw material filling layer 1 and sucks from below, the combustion front is the air suction region 3. At a constant speed while passing through (distance d1 shown in FIG. 4) and while moving to the end point of the air box after heating by the frame heating device 4 (distance d2 shown in FIG. 4). proceed. The distance while being ignited by the igniter 2 (length X1 in the captain direction of the igniter 2) and the distance while the frame is being heated (length X2 in the captain direction of the frame heating device 4) are the raw material filling layer. Since the oxygen in the upper space of 1 is lowered by the burner heating of the igniter 2 and the frame heating device 4, the combustion front does not proceed.
Then, in total, the combustion front moves by the layer thickness H of the raw material packed bed 1. Normally, the point where the combustion front reaches the bottom of the packed bed is approximately the value (L1) obtained by subtracting the length (X1) of the ignition (device) and the length (X2) of the frame heating (device) from the captain L2. It is a 70% point. This is because even after the combustion front reaches the bottom layer of the raw material packed bed 1, it takes more time or distance to complete the sintering until the sinter can be completely discharged. The mine is discharged when the maximum combustion temperature position of the combustion zone 5, which reaches the bottom of the combustion zone 5 later than the front position, reaches the bottom of the raw material packed bed 1. Based on this, the combustion front depth h at the start of frame heating is proportional to (d1 + d2). Assuming that this is L1, d1 for defining the optimum h for starting frame heating can be expressed by multiplying L1 by a predetermined coefficient determined by the apparatus. When this ratio is applied to the actual machine and expressed, d1 corresponds to a ratio between 2% and 14% with respect to L1.
The captain L2 is the length from the start point of the igniter 2 (the most upstream point of the igniter 2) to the end point of sintering, which is the end of the air box.

As the igniter 2, the same igniter 2 as that conventionally used can be used. In order to efficiently ignite the surface of the raw material bed, it is preferable to use a burner having a combustion amount of about 25 MJ / raw material t. This amount of heat of combustion is at the level of the current actual machine. The air-fuel ratio is adjusted under appropriate conditions for combustion according to the type of gas (LPG, COG, etc.).
The frame heating device 4 also ignites the fuel gas to form a flame. The amount of combustion can be about 25 MJ / raw material t. An igniter having the same configuration as that of the igniter 2, that is, an igniter having the same specifications and scale may be provided (FIGS. 3 and 4). Since the existing igniter and igniter can be used as they are, it is possible to reduce the cost when installing the sintering machine. Further, for example, as shown in FIG. 4, in the atmospheric suction region 3, the igniter 2 and the frame heating device 4 are provided in independent hoods 8, and the respective hoods 8 are separated from each other in the pallet traveling direction of the sintering machine. It can be realized by providing it.

The frame heating device 4 has, for example, a plurality of burners arranged in the width direction orthogonal to the traveling direction of the pallet 9, and the entire width direction of the raw material packed bed 1 may be frame-heated by the frame heating device 4. preferable. By heating the entire width direction, the yield and cold strength are improved on the entire width direction surface of the upper surface.

As shown in FIG. 1, it is preferable that the igniter 2 and the frame heating device 4 are laid in the same hood 8. This is because the gas having a temperature higher than normal temperature is sucked, and the temperature inside the sintered layer can be increased by utilizing the sensible heat. At this time, in order to form the atmospheric suction region 3, a wall separating the atmospheric suction zone and both ignition zones may be provided in the hood 8.
(Embodiment of the present invention)

The present invention is a method of simultaneously carrying out the frame heating method and the above-mentioned carbonaceous material post-addition sintering method, and at that time, the timing at which the frame heating is started further limits the above range, and the distance of the above L1. Is 100%, and the distance d1 between the ignition end point (end point of the igniter 2) of the first stage and the frame heating start point (start point of the frame heating device 4) is a length distance of 2% or more and 10% or less. It is characterized by that. The rationale for this numerical limitation is based on the examples described later. By setting this range, the yield and productivity are improved at the same time due to the synergistic effect when the carbonaceous material post-addition sintering method is used in combination.

In the present invention, as shown in FIG. 1, the particle size of the obtained granulated product is expanded by the carbonaceous material post-addition sintering method to improve the air permeability of the sintered layer. As a result, the effect of improving productivity can be obtained. On the other hand, the combustion zone 5 in the upper layer is further expanded due to the increase in the superficial velocity in the atmospheric suction region 3 provided between the igniter 2 and the frame heating device 4. This action improves yield. That is, yield and productivity are improved at the same time. The timing of adding the carbonaceous material later may be during the granulation or after the granulation.
(Use of coal char)

Furthermore, it is better to use coal char as the coal material to be added later.
Coal char has a higher burning rate than ordinary coke breeze. By post-adding this coal char to the exterior, the high combustion rate is fully utilized, the combustion progress rate of sintering is increased, and the productivity is further improved.

Here, the coal char is a coal material obtained by carbonizing coal having low cohesiveness to remove volatile components. The carbonization temperature may be lower than that of the coke oven for blast furnace because it is sufficient to remove the volatile matter to about 5% or less suitable for sintering. Low-viscosity coals include lignite, subbituminous coals and some bituminous coals. The logger index can be used for the determination, and corresponds to coal having a logger index (according to the logger test method specified in JIS-M8801) of 10 or less.

(Example 1)
1. 1. Synergistic effect of frame heating method and post-addition sintering method of carbonaceous material.
The effect of the method of the present invention was confirmed in a pot test. In the pot test, sintering is performed under conditions simulating a DL-type sintering machine, and unlike the DL-type sintering machine, the conveyor does not move, but a container of a predetermined size that can be sucked downward contains fuel. This is a test in which a raw material is charged, ignited from the upper surface, and sucked downward to proceed with sintering.
The compounding conditions are described in Table 1.
The composition of all raw materials at the time of charging into the sintering machine was kept almost constant.
Formulation 1 is a normal batch granulation test, in which all the raw materials including the charcoal material (powdered coke) were put into a drum mixer and mixed for 4 minutes. Then, water was added so as to have a target water content (7.5% by mass; shown in Table 1), and these were further mixed for 4 minutes.
Formulation 2 is a case where the post-addition sintering method for carbonaceous material is adopted, and in the first granulation, the case where the entire amount of coke breeze is excluded, that is, the mass of the granulated compounding raw material is added later with respect to the total mass of the carbonaceous material. This is a case where the ratio of the charcoal material (addition ratio after the charcoal material) is 100%. That is, the raw materials obtained by removing the coke breeze from the raw materials were mixed for 4 minutes. Then, water was added so as to have a target water content (shown in Table 1), and the mixture was mixed for 3 minutes and 45 seconds. The drum mixer was once stopped, powdered coke was added, and then the mixture was mixed for 15 seconds. The target moisture value of the final compounded raw material was 7.5% by mass with respect to the total mass of the raw material including coke breeze and return ore.

Next, the ignition conditions will be described.
A pot test was carried out in which the frame heating time was changed to 0.5 minutes, 2.5 minutes, and 3.5 minutes after the ignition was completed. These are the length distances of 2%, 10%, and 14% of L1 (each value is shown in "heating interval" in Table 2) when converted into the distance in the actual machine as the frame heating timing. Further, a case where frame heating is not performed (indicated as "not performed" in "heating interval" in Table 2) is also provided.
The pot tester had a diameter of 300 mm and a height of 500 mm, and was sintered from below with a constant negative pressure of 1300 mmAq. The ignition and frame heating times were both set to 1 minute (heat amount 25 MJ / raw material t). The suction negative pressure at the time of sintering was adjusted by the valve opening on the suction side of the blower so that the measured value under the pan was constant at 1300 mmAq.
Under the pot, the temperature was measured with a thermocouple as well as the pressure. In sintering, when the combustion zone 5 reaches the bottom of the sintered layer, the temperature under the pan starts to rise, reaches a peak, and then falls when the combustion of coke is completed.
Three minutes after the exhaust gas temperature peaked, the suction of the blower was stopped. The sintering time was set to the time from the start of ignition to the peak of the exhaust gas temperature.

Regarding the test results, the results of the combustion front descent rate, the product yield, and the production rate are shown in Table 2 and FIGS. 5 to 7.
After sintering, the obtained sintered cake was dropped from a height of 2 m four times to obtain a sintered product having a particle size of +5 mm or more excluding the bedding ore. Then, the value obtained by dividing the weight of the sintered product by the weight of the sinter cake excluding the bedding was defined as the product yield.
The production rate was calculated by dividing the product quantity by the sintering time and the pot bottom area, with the time required from the start of ignition to the peak of the exhaust gas temperature as the sintering time.

As shown in FIG. 5, the product yields were those of Examples 1-1 and 1-2 and Comparative Examples 1-5 and 1-6 in which the carbonaceous material post-addition sintering method was carried out regardless of the frame heating conditions. However, it was better than Comparative Examples 1-1, 1-2, 1-3, and 1-4, which were not carried out. It is considered that this is the effect of promoting the combustion of the concentrated (unevenly distributed) carbon in the upper layer of the packed bed of the raw material by the addition after the carbon material. Comparing the effect of improving the yield of the product in the case where the post-addition sintering method for carbonaceous material was carried out, Examples 1-1 and 1-2 in which the ignition and frame heating intervals were 2% and 10% were 14 % And was larger than Comparative Examples 1-5 and 1-6 without frame heating.
As shown in FIG. 6, the combustion front descent rate (FFS) was carried out in Examples 1-1 and 1-2 and Comparative Examples 1-5 and 1-6 in which the carbonaceous material post-addition sintering method was carried out. Although it was improved as compared with Comparative Examples 1-1, 1-2, 1-3, and 1-4, the degree of improvement was almost constant regardless of the frame heating conditions.
As shown in FIG. 7, since the production rate is generally proportional to the product of the product yield and the FFS, the yield improving effect was large, and the ignition and frame heating intervals were 2% and 10% in Example 1-1. In 1-2, the production rate was significantly improved, that is, there was a synergistic effect on the product yield. Further, it can be estimated that a product yield synergistic effect equal to or higher than that in the case of 2% or 10% can be obtained even when the ignition-frame heating interval is more than 2% and less than 10%.

The above results are summarized in Table 2. From Table 2, by optimizing the ignition and frame heating interval, specifically, 2% or more and 10% or less, the effect of significantly improving productivity is obtained in the carbonaceous material post-addition sintering method to which the frame heating method is applied. It can be confirmed that it was obtained.

(Example 2)
2. 2. Optimization of post-charcoal addition ratio.
In the same experimental method as in Example 1, appropriate conditions were evaluated with the post-carbonation addition ratios of 0%, 20%, 30%, 50%, and 100% as shown in Table 3.
The granulation conditions were the same as in Example 1. That is, a predetermined amount of coke breeze was removed from the raw materials and mixed for 4 minutes. Then, water was added so as to have a target water content (shown in Table 3) and mixed for 3 minutes and 45 seconds. The drum mixer was once stopped, powdered coke was added, and then the mixture was mixed for 15 seconds. The target moisture value of the final compounding raw material was 7.5% by mass. The ratio of the time between ignition and frame heating to the total sintering time was fixed at 2%.
As shown in FIG. 8, the effect of improving the yield of the product was obtained even when the ratio of the post-added carbonaceous material was 20%, but it was greatly improved when the ratio was 30% or more.

The above results are summarized in FIG. From FIG. 8, it can be confirmed that by optimizing the post-addition ratio of the carbonaceous material, a significant effect of improving the yield was obtained in the post-additional coal material sintering method to which the frame heating method was applied.

(Example 3)
3. 3. Appropriate conditions for post-addition timing of charcoal.
The appropriate condition of the post-addition timing of the carbonaceous material was evaluated by the same experimental method as in Example 1 above.
The ratio of the time between ignition and frame heating to the total sintering time is constant at 2%, and the ratio of the time between ignition and frame heating is constant at 2%. The granulation time before and after the addition of was changed. Here, the total granulation time was set to a constant value (4 minutes).
The results are shown in FIG.
The product yield of Examples 3-3, 3-4, 3-5, in which the granulation time until the addition of the post-addition carbonaceous material was 80% or more and 95% or less with respect to the total granulation time, was 78%. Yes, it was higher than in Examples 3-1 and 3-6, which exceeded 95% or less than 80%. From this, it can be confirmed that the yield improvement effect was obtained by setting the granulation time until the addition of the post-addition coal material was 80% or more and 95% or less with respect to the total granulation time.

In this embodiment, both the ignition time and the frame heating time are 1 minute, but the present invention is not limited to this value. The reason is that the heating time in the examples takes into account the heat loss in the pan test. In an actual (commercial) sintering machine, for example, if the heating time is 30 seconds, it is not necessary to set this heating time to 1 minute at all, and the frame may be heated while maintaining the ignition time of the actual operation. Further, the frame heating time does not have to be 1 minute in the actual machine.

(Example 4)
4. Use of coal char The case where coal char was used as the coal material and post-addition was carried out in the drum mixer was examined.
As shown in Table 5, Example 4-1 of Formulation 2 is the same as Example 1-1 (reposted), and Example 4-2 of Formulation 6 is a case where coal char is used.
The raw coal of coal char is bituminous coal with a logger index of 1.9, but it is a general coal with low cohesiveness. A char obtained by carbonizing this at 700 ° C. was used. The volatile content remaining in the char was 4.5%.
In each of the cases of Examples 4-1 and 4-2, the coke breeze and coal char were completely removed from the raw materials and mixed for 4 minutes. Then, water was added so as to have a target water content (shown in Table 5), and the mixture was mixed for 3 minutes and 45 seconds. The drum mixer was stopped once, coke breeze and coal char were added, and then the mixture was mixed for 15 seconds. The target moisture value of the final compounded raw material was 7.5% by mass with respect to the total mass of the raw material including coke breeze or coal char and return ore.
The ratio of the time between ignition and frame heating to the total sintering time was constant at 2% (0.5 minutes).

Table 6 shows the results of the combustion front descent rate, production rate, and product yield.
The production rate of Example 4-2 is higher than that of Example 4-1 and it can be confirmed that the production rate is improved by using the coal char.

In the post-addition sinter method for sinter, after ignition by the igniter 2, atmospheric suction regions 3 are provided at predetermined intervals and reheated by frame heating to improve the productivity of the sinter. It is possible to provide a method for producing a sinter that improves the product yield of the sinter. By this method, the fuel cost can be suppressed because the amount of carbonaceous material such as coke breeze can be reduced by performing a constant operation of the product yield.
Further, if a product having a high combustion rate at the time of sintering using coal having a logger index of 10 or less and low cohesiveness as the raw coal as the coal material to be added later is used, the effect of this technique becomes large.

1 ... raw material filling layer, 2 ... igniter, 3 ... atmospheric suction region, 4 ... frame heating device, 5 ... combustion zone, 6 ... sintering completed layer, 7 ... hopper, 8 ... hood, 9 ... pallet, 10 ... rail Or track guide, 11 ... drive wheel, 12 ... idle wheel, 13 ... duct, 14 ... wind box, 15 ... drum mixer, 16 ... charcoal hopper

Claims (4)

A pallet constituting a Dwightroid (DL) type sintering machine is charged with granulated compounding raw materials to form a raw material packing layer, ignited from the upper part of the raw material filling layer, and sucks air from below. A method for producing a sinter that sinters the raw material packing layer.
In the granulated compounding raw material, the raw material from which only a part or the whole amount of the charcoal material was removed was added to the raw material during or after granulation by adding water. It is a thing
The DL-type sintering machine includes an igniter and a frame heating device provided on the downstream side of the igniter at a distance and heating the upper surface of the raw material packed bed.
An atmospheric suction region is formed between the igniter and the frame heating device.
The upper surface of the raw material packed bed is heated by the frame heating device in which the distance d1 (mm) between the igniter and the frame heating device is set to a length distance of 2% or more and 10% or less with respect to the following L1. A method for producing a sintered ore characterized by.
L1: Machine length L2 (mm) -Pallet traveling direction length X1 (mm) of the igniter-Pallet traveling direction length X2 (mm) of the frame heating device The production of the sinter according to claim 1, wherein the ratio of the carbonaceous material to be added later to the granulated compounding raw material is 30% by mass or more with respect to the total mass of the carbonaceous material. Method. The production of the sinter according to claim 1 or 2, wherein the granulation time until the addition of the carbonaceous material to be added later is 80% or more and 95% or less with respect to the total granulation time. Method. The method for producing sinter according to any one of claims 1 to 3, wherein the charcoal material to be added later is charcoal obtained by carbonizing coal having a logger index of 10 or less as raw coal.

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