JP2009299089A - Operating method of vertical furnace, and apparatus for preventing in-furnace powdering - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an operating method of a vertical furnace and an apparatus for preventing in-furnace powdering, which are applicable even when coke of any kind is used, and sufficiently suppresses powdering of coke to be charged in the vertical furnace such as a blast furnace, for allowing the smooth and consistent operation of the vertical furnace. <P>SOLUTION: In the operating method of the vertical furnace, a step part is formed in a conveying line of coke to be charged in a vertical furnace, the coke is separated into lump portion and powder portion when the coke drops on the stepped part, and the separated lump portion is charged in the vertical furnace. A stair-like chute 1 is installed in the step part. The apparatus for preventing in-furnace powdering comprises a carrying conveyor 5, a feeding conveyor 6, a discharging conveyor 4, a sifting apparatus 2 for sifting the coke discharged from the discharging conveyor 4, and a conveyor 11 for the vertical furnace which conveys the coke sifted by the sifting apparatus 2 on the sift and charges the coke from the top of the vertical furnace, and further comprises a bypass line 8 for conveying the coke carried by the carrying conveyor 5 to the discharging conveyor 4. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a method for operating a vertical furnace using a method for preventing in-furnace powdering of coke for charging a vertical furnace used in a blast furnace and the like, and an in-furnace powdering prevention facility.

  In the blast furnace for producing hot metal, iron ore such as sintered ore and lump ore, and massive coke as a heat source and reducing material source are alternately charged from the top of the furnace, and the upper part of the furnace (shaft) Part) are deposited in layers. And the high-temperature air blown into the furnace from the tuyeres at the bottom of the furnace burns the coke accumulated in the furnace to generate high-temperature gas, and the high-temperature gas is between the iron ores and coke particles. The gap flows toward the top of the furnace, and the iron ore and coke are heated, and at the same time, the iron ore is reduced and melted. Therefore, if the gap between the particles is not properly secured, the distribution of the gas flow in the furnace becomes inappropriate for operation, the situation in the furnace becomes worse, and stable and smooth operation cannot be performed. Or, the productivity of the blast furnace decreases. That is, it is very important to ensure the air permeability of the raw material layer for blast furnace operation. When powder is mixed into the raw material charged from the top of the furnace, air permeability is hindered. Therefore, it is necessary to prevent the powder from being mixed as much as possible.

  In addition to the powder mixed into the raw material and charged into the furnace, there is also a problem of powder generated in the furnace. Coke exists in a lump until it is combusted by oxygen supplied from the tuyere at the bottom of the furnace after being charged from the top of the furnace, but lacks fragile parts due to physical contact with other raw materials. As a result, coke powder is generated. This powder becomes clogged between the raw material particles and causes deterioration of the stability and controllability of the gas flow in the furnace. For this reason, it is important to suppress pulverization while coke descends in the furnace.

In order to prevent the occurrence of chipping of the fragile portion, many attempts have been made to keep the coke strength high. For example, even if a large amount of non-caking coal that causes a reduction in coke strength is added to the coking coal, a non-caking furnace tar (generated during coke production) with reduced lightness is not used as a device that does not reduce the coke strength. A method of preventing strength reduction of the obtained coke by adding to caking coal and then charging and coking into a coke oven is known (see, for example, Patent Document 1). There is also a method for producing coke having a high porosity and a certain level of strength by adding a pore-forming agent and a binder during blending of raw coal, and then charging and coking into a coke oven. It is known (for example, refer to Patent Document 2).
JP 2000-8047 A JP-A-11-236573

  The methods described in Patent Document 1 and Patent Document 2 are techniques for improving coke strength by adding an additive to raw coal to improve the average substrate strength of the coke produced.

  However, even when the average substrate strength of coke is improved by blending such an additive, local blending variation (segregation) occurs in the raw material charged into the coke oven. Therefore, in part, coke with a weak substrate is manufactured, and when coke is charged into a blast furnace, the weak coke is pulverized in the furnace.

  Although it is conceivable to use only coal that can produce high-strength coke as the raw material for coke, such coal is expensive, and it is not practical to produce coke using only such varieties of coal. . Even if the strength of the produced coke is low, it is desirable to prevent the coke from being pulverized.

  Therefore, the object of the present invention is to solve such problems of the prior art, and can be applied to any kind of coke, and sufficiently suppresses the pulverization of vertical furnace charging coke such as a blast furnace. An object of the present invention is to provide a vertical furnace operating method and furnace powdering prevention equipment that enables smooth and stable vertical furnace operation.

The features of the present invention for solving such problems are as follows.
(1) A step portion is provided in the conveying line of the vertical furnace charging coke, and when the coke falls, the coke is separated into a lump portion and a powdery portion, and the separated lump portion is A method for operating a vertical furnace characterized by being charged in a mold furnace.
(2) The operation method of a vertical furnace as described in (1), wherein the sieve is made into a lump by screening.
(3) The method for operating a vertical furnace according to (1) or (2), wherein the coke subjected to the drying treatment is separated into a lump part and a powdery part.
(4) A method for operating a vertical furnace according to any one of (1) to (3), wherein a stepped chute is installed at the stepped portion.
(5) The method for operating a vertical furnace according to (4), wherein the coke is dried in a chute.
(6) Used when charging coke into a vertical furnace, and is conveyed from the chute, a conveyer that conveys coke, a chute, a supply conveyor that supplies the coke conveyed by the conveyer to the chute, and the chute A discharge conveyor that conveys the coke, a sieving device that sifts the coke discharged from the discharge conveyor, and the sieving device screened by the sieving device is conveyed for charging from the top of the vertical furnace. And a bypass line that conveys coke conveyed by the conveyor to the discharge conveyor.

  According to the present invention, pulverization of coke charged into a vertical furnace such as a blast furnace can be suppressed within a certain range regardless of the strength of the coke used. This enables smooth and stable furnace operation, and improves the productivity of the furnace.

  Conventional handling of coke for vertical furnace charging has been made in order to minimize the impact on the coke and prevent coke pulverization. In other words, the handling that prevents the coke from being damaged due to the force applied to the coke during the process of conveying the coke to the vertical furnace has been considered good. However, when the coke has a fragile portion, pulverization occurs in the furnace no matter how small the impact applied to the coke before charging the vertical furnace. Therefore, the present inventors conversely increase the impact applied to the coke before charging the vertical furnace, thereby preliminarily pulverizing the fragile part of the surface of the coke, and removing the powdery part into the vertical furnace. It is thought that by charging, coke pulverization in the furnace can be suppressed, and the coke is subjected to a drop impact more than usual during the coke transport process, and the coke is separated into a lump part and a powdery part and separated. The present inventors have found that powdering in the furnace can be prevented by using the lump portion in a vertical furnace and completing the present invention. By adding a drop impact to the frictional force applied during coke conveyance, not only the brittle part of the coke surface, but also the destruction of coke due to cracks existing inside the coke is promoted, generating a larger amount of powdery parts. This can be separated.

  In order to apply a drop impact in the transport process, it is possible to obtain a certain effect simply by dropping it from a hopper, etc., but to promote the pulverization of the fragile part, use the connecting part of the belt conveyor used for coke transport. Is preferred. A stepped portion having a larger step than that of the connecting portion is provided, and the coke is separated into a massive portion and a powdery portion by the impact of the coke dropping. It is preferable to provide a chute at the step portion to guide the falling coke from the upper belt conveyor onto the lower belt conveyor. At this time, it is more preferable that the shape of the chute has a structure that easily gives an impact to the coke. By making the shape of the chute easy to give an impact to the coke, the impact force given to the coke can be increased even if the step height of the connecting portion of the belt conveyor is about the conventional level. Further, the coke of the upper belt conveyor can be dropped to a device that separates the coke into a lump part and a powdery part instead of the lower belt conveyor.

  Separation of the massive part and the powdery part is preferably performed using a sieve. The mass portion charged in the furnace preferably has a particle size of about 6 mm or more, and preferably has a screen size of 6 mm or more.

  If the water content of the coke is high, the sieving efficiency is reduced, and there is a case where the lumpy part and the powdery part are not sufficiently separated, so the coke that has been dried is separated into the lumpy part and the powdery part. It is preferable to do. It is efficient to dry the coke while applying a frictional force and a drop impact in a rotating drum described later.

  Used to charge coke into vertical furnaces to apply frictional force and drop impact to coke, and to separate and remove powdered parts. From supply conveyor, chute, discharge conveyor, and discharge conveyor In-furnace pulverization prevention comprising a sieving device for sieving discharged coke and a charging device for charging the top of the sieve screened by the sieving device from the top of the vertical furnace Equipment can be used. Further, a conveyor having a bypass line, which conveys coke, a chute, a supply conveyor that supplies the coke conveyed by the conveyer to the chute, a discharge conveyor that conveys coke discharged from the chute, A sieving device for sieving the coke discharged from the discharge conveyor, and a conveyor for a vertical furnace for conveying the top of the sieved by the sieving device for charging from the top of the vertical furnace And it is preferable to use the in-furnace powdering prevention equipment characterized by having a bypass line which conveys the coke conveyed by the said conveyance conveyor to the said discharge conveyor. The chute preferably has a structure having a large number of steps in the chute to impart frictional force and drop impact to the coke. In particular, in order to give an appropriate drop impact, the step per step is 1 m or more to 5 m. The following is preferable. Further, it is preferable to provide a downward inclination between the steps to impart a frictional force to the coke, and it is particularly preferable to provide a downward inclination of 10 degrees to 45 degrees. Further, by removing the powdery part generated during the chute dropping as needed, it is possible to positively apply a frictional force or a drop impact to the massive coke. It is preferable to have a structure with a gap as shown in FIG.

  In addition, it can be considered that the coke yield decreases and the coke cost increases by separating and removing the powdery part, but powdered coke is used in various applications as a high value-added product in steelworks and others. Therefore, the coke as a whole can be used effectively, and the cost increase does not become a problem.

  The vertical furnace used in the present invention is a blast furnace, a shaft furnace, a gasification melting furnace, or the like, and is used by charging massive coke from the top of the furnace.

  Hereinafter, an embodiment when the present invention is used in a blast furnace will be described based on the circumstances leading to the present invention.

  The red hot coke pushed out from the coke oven is lowered to a discharge place on a belt conveyor called a wharf after sprinkling fire. Then, after cutting out from the wharf, the mass is crushed with a coke cutter (a type of roll crusher), and only the desired size is used in the blast furnace through a sieve under the hopper (storage tank) of the blast furnace. . In recent years, in view of energy saving and environmental measures, there is a case where reddish coke is cooled with gas and called “dry fire extinguishing” and then sent to the blast furnace through the same route.

  First, the present inventors consider that in such conventional coke treatment, the weak portions of coke are not completely removed, but are charged into the blast furnace, and after applying sufficient impact force between the cokes, sieving is performed. I thought that the weak part could be removed by doing. And as shown in FIG. 1, about the chute 1 provided in the connection part of the belt conveyor in the path | route which sends a coke from a coke factory or a coke product yard to a storage tank, many level | step differences are inside chute 1. The fragile part was separated there, passed through sieve 2 and adjusted to a predetermined particle size (for example, 6 to 75 mm), and then sent to a blast furnace storage tank. At that time, a coke sample is collected between the chute 1 and the sieve 2, the strength test of the coke sample is performed, the strength data is fed back, and the transport process is adjusted as described later, and the strength and particle size are related. The coke that satisfies the charging standards (for example, in-house standards) was charged into the blast furnace.

  Here, the chute supplies coke from the upper supply port 7, the coke falls in the chute 1, and the coke is subjected to friction and drop impact by contact between the cokes, and the lower discharge port 3. From which coke is discharged. The chute 1 has a bottom portion 1a which is a stepped slide structure, and has a side wall 1b so that at least coke does not fall out of the chute. In the case of FIG. 1, it further has an upper lid 1c and has a structure as a cylindrical passage. The entire amount of coke that exits the discharge port 3 is sent to the subsequent process by the discharge conveyor 4.

  When such a dropping process is repeated, the fragile portion in the coke structure is almost destroyed and turned into powder, and the portion remaining in a lump is almost free from the fragile portion.

  The chute 1 has a heated gas supply duct 9 in the upper part thereof, and the heated gas 10 is sent into the chute 1 through the heated gas supply duct 9, so that the chute 1 can be dropped while drying the coke. Further, by forming at least a part of the bottom 1a of the chute 1 with a mesh structure, the generated powdery part can be removed.

  In the present embodiment, as described above, the coke discharged from the chute 1 is sent to the sieve 2 so as to have a particle size used in the blast furnace, and a part of the coke is sampled before being sent to the sieve 2. The strength test is performed, and this strength test method may be a test method appropriately determined for each blast furnace. As an example, there is a drum strength defined in JIS K 2151 (Chapter 9, “Coke Test Methods”, 9.2: Drum Method). Of course, a tumbler method described in the same standard or the like, which is generally used as a test method for coke strength, may be used.

  If the result of this strength test is higher than the upper limit of the control value of the target strength in the blast furnace that supplies coke, the bypass line 8 provided in place of the supply conveyor 6 is used and the chute 1 is not used. Convey coke.

  By adjusting the extent to which the brittle part of the coke is destroyed using the chute 1 or the bypass line 8 in this way, the strength of the coke is adjusted to a certain value or more without changing the composition of the raw coal during the production of the coke. Therefore, smooth and stable blast furnace operation can be performed. In the present invention, even when the bypass line 8 is used, if the coke strength is higher than the upper limit of the target strength, the blending of coal supplied to the coke oven may be changed to provide a cheaper blend. Moreover, when the chute | shoot 1 is passed and the intensity | strength exceeding a target is obtained, it can also be set as the cheap mixing | blending which intensity | strength falls to this target intensity | strength.

  As described above, the case of using a chute installed at the connecting portion of the belt conveyor as a means for forcibly removing the weak portion of coke has been given as an example. If it is before, it can be installed at any position. As in the present invention, if the fragile portion is removed in advance, the amount of powder coke below the sieve 2 that cannot be used in the blast furnace increases. In general, in steelworks, the powder coke is effective as a fuel for sintering raw materials, etc. Since it can be used, it will not be wasted.

  Next, separation of the coke that has been subjected to the drying process into a lump part and a powdery part will be described.

  The coke powder generated when dropping impact is applied to the coke, if the coke used contains a large amount of water, the generated coke powder tends to adhere to the coke agglomerate and is sieved for separation. Is used, there is a problem that the powdery part cannot be sufficiently separated and removed by this sieve, or a problem that the sieve itself is clogged and the powdery part of coke cannot be removed. The powdery part that adheres to the coke lump and cannot be separated and removed by sieving is transported to the top of the vertical furnace while being attached to the coke lump, and is dried by the heat in the furnace. Since the coke lump is separated from the surface of the coke lump, a large amount of powdery coke is charged into the furnace, and the powdery part flows through the gap between the raw materials in the furnace and clogs the gap between the raw materials. When the present invention is used for coke having a high water content, such as inhibiting the stable gas flow, there is a concern that the effects of the present invention cannot be sufficiently exhibited.

  It is known that a phenomenon in which a powdery part adheres to a coke-like part and separation thereof becomes difficult increases in proportion to the water content of the coke. Therefore, it is preferable to sieve the coke in a dry state, and it is preferable that the amount of water contained in the coke is as small as possible. For that purpose, when applying frictional force or drop impact to the surface of coke, it is arranged at the downstream side to reduce the coke-containing water content by applying constant heat to coke in advance, at the same time or after application. Therefore, it is preferable to dry the coke before sieving.

  The heating method for drying the coke is preferably performed by introducing a heating gas into a container containing coke, and various heating gases generated in a factory are preferably used. In order to remove moisture contained in coke, it is desirable to use hot-blast furnace combustion exhaust gas and heating furnace exhaust gas with low oxygen concentration. However, a heating gas as a dedicated hot-air generation source by installing a combustion furnace, electric furnace, etc. Can also be generated. In addition, as long as nitrogen for controlling the oxygen concentration is introduced, a heated gas such as a cooler exhaust heat of a sintering machine can be used. As described above, it is efficient and preferable to dry the coke in the chute. As described above, the chute can have a structure with an open top, but when drying in the chute, it has a duct-like closed structure, supplying heated gas from the top of the chute and exhausting from the bottom of the chute. Is preferably performed.

  The temperature of the heated gas is sufficient if the coke can be dried, and 60 ° C. or higher is sufficient for drying the coke, and it is desirable to set it to 200 ° C. or lower. This is because moisture contained in coke, which is a carbonaceous material, is dried, so that it is difficult to prevent fire and explosion if the temperature of the heated gas is too high.

  One embodiment of the in-furnace powdering prevention facility of the present invention will be described with reference to FIG. The in-furnace pulverization prevention equipment includes a transport conveyor 5 that transports coke, a supply conveyor 6 that supplies coke transported by the transport conveyor 5 to the chute 1, and a discharge conveyor 4 that transports coke discharged from the chute 1. , A sieving device 2 for sieving the coke discharged from the discharge conveyor 4, and a vertical furnace conveyor 11 for transporting the top of the sieve screened by the sieving device 2 for charging into the vertical furnace. And a bypass line that conveys coke conveyed by the conveyor 5 to the discharge conveyor 4. 13 is a dust collecting bag filter, 14 is a dust collecting fan, and 15 is an exhaust gas chimney.

  In FIG. 1, coke supplied into the chute 1 via the supply conveyor 6 falls while being dried by the heated gas 10 sent into the chute 1 from the heated gas supply duct 9, and is weakened by friction and drop impact. Becomes powdery. The heated gas 10 is exhausted from the lower part of the chute 1 through a dust collecting bag filter 13 by a dust collecting fan 14 and is discharged from an exhaust gas chimney 15. The coke discharged from the coke discharge port 3 is conveyed to the sieve 2 by the discharge conveyor 4 and separated into a lump part and a powdery part by sieving. The lump portion on the sieve is conveyed by the vertical furnace conveyor 11 and then charged from the upper portion of the vertical furnace. The powdery part under the sieve is conveyed by the powder extraction conveyor 12 and can be used separately. Depending on the strength of the coke sampled on or downstream of the discharge conveyor 4, the strength of the coke produced by transporting the coke transported by the transport conveyor 5 directly to the discharge conveyor 4 using the bypass line 8. Can be adjusted.

  A test for conveying coke to a blast furnace was performed using equipment similar to that shown in FIG. 1 in which a step-like chute is installed at the connecting portion of the belt conveyor and a bypass line that does not pass through the chute is provided. The height of the chute was about 10 m, the inclination of the slope portion was 10 degrees downward from the horizontal direction, and the step portion was formed in four steps.

Sampling was performed on the discharge conveyor on the upstream side of the sieve at regular intervals, and the coke strength was measured when the chute was passed and when the bypass line was passed. Strength of the coke was measured at prescribed in JIS K 2151 "drum strength", the particle size of the coke sample when strength measurement 15 mm, as 150rpm rotational speed of the test drum, the so-called "drum intensity (symbol DI ^0.99 ₁₅ ) ”. The sieve mesh was 6 mm.

  When not passing through the chute but passing through the bypass line, the coke strength sampled on the upstream side of the sieve was 84.3 on average, but the chute was passed through to give friction force and drop impact to the coke. As a result, the drum strength of the coke increased to 84.9. That is, the strength of the coke charged into the blast furnace could be increased by 0.6 points by removing the weak part of the coke by dropping with a chute.

  When the operation method of the present invention in which the top of the sieve sieve is charged into the blast furnace after passing through the chute, compared with the case where the operation of charging the sieve top into the blast furnace is performed through the bypass line. The coke pulverization in the furnace of the blast furnace was suppressed, so the air permeability of the blast furnace was improved, the gas flow distribution in the furnace could be maintained properly, the furnace condition was stabilized, and smooth operation was possible, The amount of hot metal discharged increased by 5% under the same operating conditions.

  The same equipment as shown in FIG. 1 is used, and when a friction force and a drop impact are applied to the surface of the coke by dropping on the chute without using a bypass line, a heating gas is introduced into the chute. In the case where drying was performed by applying constant heat to the coke with a heated gas (combustion exhaust gas) at 150 ° C. to reduce the water content of the coke, and in the case where drying was not performed, each was processed and sieved. The separation of the coke and the powdery coke after sieving was compared when the coke on the chute exit side was in a dry state and the moisture content was high without applying heat.

  In FIG. 2, for example, when the coke with a moisture content of more than 4 mass% when not dried is reduced to a moisture content of 0 mass% by drying, the separation situation differs greatly, and when a sieve with a mesh size of 6 mm is used, The mixing ratio of coke (-6 mm) having a particle size of 6 mm or less to the upper side was reduced from the 3 mass% level to about 0.5 mass%. The reduction in the water content of coke greatly affected the separation of the powdery portion of coke, and it was found that the drying treatment is very effective in preventing in-furnace powdering for coke having a high water content.

It is a flowchart which shows one Embodiment of this invention. The graph which shows the effect of drying of coke.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Chute 1a Bottom part 1b Side wall 1c Top cover 2 Sieve 3 Coke discharge port 4 Discharge conveyor 5 Conveyor 6 Supply conveyor 7 Coke supply port 8 Bypass line 9 Heating gas supply duct 10 Heating gas 11 Vertical furnace 12 Powder extraction Conveyor 13 Dust collection bug filter 14 Dust collection fan 15 Exhaust gas chimney

Claims (6)

  A step portion is provided in the coke transfer line for vertical furnace charging, and when the coke falls, the coke is separated into a lump portion and a powdery portion, and the separated lump portion is put into a vertical furnace. A method of operating a vertical furnace characterized by being charged and used.   The method for operating a vertical furnace according to claim 1, wherein, by sieving, a sieve having a particle diameter of 6 mm or more is formed into a lump.   The method for operating a vertical furnace according to claim 1 or 2, wherein the coke subjected to the drying treatment is separated into a lump part and a powdery part.   The method for operating a vertical furnace according to any one of claims 1 to 3, wherein a stepped chute is installed at the step portion.   The method for operating a vertical furnace according to claim 4, wherein coke is dried in a chute.   Used when charging the coke into the vertical furnace, a transport conveyor for transporting the coke, a chute, a supply conveyor for supplying the coke transported by the transport conveyor to the chute, and a coke discharged from the chute Conveying discharge conveyor, sieving device for sieving the coke discharged from the discharging conveyor, and vertical mold for conveying the top of the sieve screened by the sieving device for charging from the top of the vertical furnace An in-furnace powdering prevention facility comprising a conveyor for a furnace and having a bypass line for transporting coke transported by the transport conveyor to the discharge conveyor.

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