JP5256982B2 - Operation method of vertical melting furnace - Google Patents

Description

  The present invention relates to a method for operating a vertical melting furnace for producing pig iron by melting or dissolving and reducing an iron source such as iron waste.

  In the blast furnace method in which pig iron is produced using iron ore as an iron source, while iron ore charged from the top of the furnace descends in the furnace, iron oxide in the iron ore is blown from the tuyere with oxygen and coke. It reduces with the high temperature reducing gas (CO) produced | generated by reaction of these.

In the blast furnace method, in order to secure an indirect reduction rate of about 60% or more, the blast temperature is set to 1000 ° C. or more, and the blast speed is increased to form a raceway in front of the tuyere in the furnace. Gas utilization rate: Reducing gas (CO) is generated so that η _CO (= CO ₂ / (CO + CO ₂ )) becomes zero.

  On the other hand, the cupola method is a vertical melting furnace with a small internal volume compared to the blast furnace, melting the iron source mainly composed of iron scrap, foundry scrap, pig iron, etc., which has a higher metalization rate than iron ore, Produces pig iron. In the vertical melting furnace, an iron source having a high metallization rate that does not require reduction is used. Therefore, it is necessary to secure an amount of heat that can sufficiently melt the iron source in the furnace.

In the operation of a vertical melting furnace, when a raceway was formed in front of the tuyere as in the blast furnace method, heat was generated by the combustion reaction of oxygen (O ₂ ) and coke (C) (C + O ₂ → CO ₂ ) Thereafter, the heat absorption by the solution loss reaction (CO ₂ + C → 2CO) of CO ₂ gas and coke (C) reduces the amount of heat in the furnace and makes it difficult to sufficiently dissolve the iron source.

  Therefore, when melting an iron source with a high metallization rate in a vertical melting furnace, cold air enriched with oxygen or hot air of 600 ° C. or less from the tuyere does not form a raceway before the tuyere, Coke for casting is used as a solid fuel in order to blow into the furnace at a low blowing speed and to suppress a decrease in the amount of heat in the furnace.

  Since the coke for castings has a larger particle size and lower reactivity than the coke for blast furnace, it does not easily cause a solution loss reaction (endothermic reaction). In addition, since the coke for casting has high strength and low ash content, the amount of pulverization in the furnace and the amount of slag generated are small, which contributes to maintaining the air permeability in the furnace.

  By the way, in recent years, there is a tendency to use a large amount of iron-making dust that contains a large amount of iron oxide and has a low metallization rate compared to pig iron scrap, and the vertical melting furnace has a melting function for melting the iron source. In addition, a reduction function that reduces iron oxide in the iron source is required.

  Against this backdrop, as iron sources, in addition to iron sources that do not require reduction (sintering iron scraps, foundry scraps, pig iron, etc.) (iron sources with a high metallization rate), dust agglomerates, self Several methods have been proposed for operating vertical melting furnaces that use iron sources (low-metallization and iron sources that require reduction) such as reducible ores (agglomerates with a high carbon content). (See Patent Documents 1 to 3).

  However, when the properties of the iron source are diversified, the dissolution and / or reduction of the iron source is difficult to proceed evenly, and deposits are generated and grow on the furnace wall, resulting in an increase in the frequency of shelf hanging.

  Even when only an iron source with a high metallization rate is used, if a large amount of thin scrap such as shredder scrap is mixed with pig iron scrap or heavy scrap, and used as an iron source, the melting position of the iron source in the furnace is reduced. It becomes non-uniform, deposits are generated and grow on the furnace wall, and the frequency of shelf hanging increases.

Japanese National Publication No. 01-501401 Japanese Patent Application Laid-Open No. 10-036906 JP 09-203584 A

  As described above, when the properties of the iron source are diversified, the melting and / or reduction of the iron source does not easily progress in the furnace, and the furnace condition is not stable. If the melting and / or reduction of the iron source does not proceed evenly, the temperature distribution in the furnace becomes non-uniform, and the dissolved iron source contacts the furnace wall and solidifies to become deposits.

  The deposit generated on the furnace wall may melt and disappear when the furnace temperature near the deposit increases, but in many cases, the deposit generated on the furnace wall grows and enters the furnace interior. This prevents the descent of the rack and causes the shelf to hang. Moreover, the growth of the deposits causes the temperature distribution in the furnace to become more non-uniform and contributes to a more unstable furnace condition.

  The present inventors have confirmed in actual operation that the above phenomenon appears in the operation method of the vertical melting furnace.

  Therefore, the present invention aims to suppress the generation of deposits on the furnace wall in the furnace, suppress the growth of the deposits, stabilize the furnace condition, and suppress the occurrence of shelf hanging. It aims at providing the operation method of a vertical melting furnace which solves this.

  In order to solve the above-mentioned problems, the present inventors diligently investigated the manner of generation and growth of furnace wall deposits in the operation of a vertical melting furnace. As a result, (x) deposits are generated on the furnace wall above the tuyere, and (y) the furnace wall temperature of the portion where the deposits are generated decreases as the deposits grow. found.

  This invention was made | formed based on the said knowledge, and the summary is as follows.

( 1 ) In a method for operating a vertical melting furnace that uses solid fuel blended with coke for blast furnace, blows from the tuyere, melts the iron source, or melts and reduces it to produce pig iron.
(I-1) One or more thermometers are embedded in the furnace wall above the tuyere in the furnace height direction, with the same height and buried in the furnace circumferential direction, and the furnace wall temperature in the furnace circumferential direction is measured. ,
(I-2) A thermometer is installed at the top of the furnace to measure the furnace top temperature,
(Ii-1) When at least one of the furnace wall temperatures falls below the reference furnace wall temperature and the furnace top temperature is equal to or higher than the reference furnace top temperature, the furnace wall deposits grow greatly, Determine that shelves are hanging, (d2)
(Ii-2) A method for operating a vertical melting furnace, characterized in that the operating conditions are changed to reduced operating conditions or meltdown operating conditions .

( 2 ) The method for operating a vertical melting furnace according to (1 ), wherein the tuyere is arranged in two upper and lower stages.

(3) the thermometer, above, wherein the embedding two stages or three stages in the furnace height direction (1) or (2) vertical melting furnace method operations of any one of.

The method for operating a vertical melting furnace according to any one of (1) to ( 3 ), wherein the thermometer is embedded in at least four rows in the furnace circumferential direction.

  According to the present invention, in the operation of a vertical melting furnace, the generation and growth of deposits on the furnace wall are suppressed, the furnace condition is stabilized, and the shelf suspension can be quickly eliminated without causing the shelf suspension. The operation can be continued.

  The present invention will be described with reference to the drawings.

  FIG. 1 shows an embodiment of a vertical melting furnace. The vertical melting furnace 1 includes a furnace body 2, a tuyere 6 provided at the lower part of the furnace body 2, a gas suction part 4 provided at the upper part of the furnace body 2, and a furnace top part 3 provided in the gas suction part 4. It is configured. As for the tuyere 6, the upper tuyere 6a is usually provided at a height position directly above the surface of the coke bed 8 constructed in the lower part of the furnace, and the lower tuyere 6b is provided at a height position in the coke bed 8. ing.

  The raw fuel 10 (iron source and solid fuel) in the bucket 7 is loaded from the top 3 of the furnace onto the coke bed 8 below the furnace body 2 so that the iron source and solid fuel are deposited in layers or in a mixed state. Entered. The raw fuel 10 is charged up to the upper part in the furnace top 3, and the furnace top 3 is sealed (material seal).

  The iron source in the raw fuel 10 is dissolved by the reaction heat between oxygen in the air blown from the tuyere 6 and coke (solid fuel) while descending the furnace, and the iron oxide in the iron source is CO, Reduced with solid carbon and carbon in hot metal. The hot metal produced by melting and reduction descends the coke bed 8 and is stored in the storage part 11 of the furnace bottom 5.

  On the upper surface of the bottom plate of the furnace bottom 5, a connecting pipe 12 that communicates with the spout 9 is provided, and the hot metal stored in the storage section 11 flows out through the connecting pipe 12. The hot metal is separated into a hot metal in the upper layer part and a hot metal in the lower part, and the hot metal in the lower part is taken out from the outlet 9.

  When blowing from the upper tuyere 6a and the lower tuyere 6b, the lower tuyere 6b blows in air at room temperature or 600 ° C. or lower, mainly combusts coke (solid fuel), and the heat of combustion generates an iron source. Dissolve.

From the upper tuyere 6a, air at room temperature was blown, and a portion of the combustion gas (CO ₂ ) and CO gas generated by the solution loss reaction (endothermic reaction) of coke were burned, and the inside of the furnace generated by the solution loss reaction Compensates for heat loss.

  However, if operating factors such as the air blowing conditions fluctuate and the amount of heat in the furnace that melts the iron source suddenly decreases, or the drop or accumulation of raw fuel is disturbed, causing a deviation in the gas flow in the furnace, In this case, the melt height in the steel becomes non-uniform, and a part of the melted zone where the temperature decreases starts to solidify, or a part of the iron source that has been melted adheres to the furnace wall and solidifies to become a deposit.

  If the temperature of the melting zone is uneven and / or the amount of heat in the furnace continues, deposits grow. As the deposit grows, the iron source entangles and accumulates on the deposit, causing shelf hanging. When shelves are generated, the portion of the furnace that can be vented is narrowed. As a result, the rising speed of the in-furnace gas increases and the top temperature of the furnace rises rapidly.

  Normally, the temperature at the top of the furnace is measured, so the occurrence of shelf hanging can be detected. However, when it is detected, shelf hanging has already occurred. Even if the conditions are changed, it takes time to eliminate the shelves.

  If it is possible to detect signs that contribute to shelf hanging, the operating conditions can be changed to suppress the occurrence of shelf hanging, so the present inventors can detect the generation and growth of deposits. It was investigated.

As described above, in the case of a two-stage upper and lower tuyere, air at room temperature was blown from the upper tuyere and generated by a solution loss reaction (endothermic reaction) of a part of combustion gas (CO ₂ ) and coke (C). CO gas is burned to compensate for the decrease in the amount of heat in the furnace caused by the solution loss reaction. However, in the operation using the upper and lower two-stage tuyere, deposits are easily generated on the upper furnace wall of the upper tuyere.

  The inventors of the present invention noticed that the temperature of the furnace wall where the deposits were generated was naturally lower than the temperature of the surrounding furnace wall, and embedded a thermometer in the furnace wall above the tuyere, The temperature of the furnace wall at the top of the mouth was measured. A part of the measurement result is shown in FIG. 2 together with the measurement result of the furnace top temperature.

  In FIG. 2, shelves are generated at the marks “◯” and “◎”. From the time elapsed of the furnace wall temperature, the shelves (i) the furnace wall temperature gradually decreases to 600 ° C. It can be seen that it occurs when the process or (ii) rapidly drops below 600 ° C. It should be noted that the temperature at the top of the furnace was significantly increased due to the shelves, where the ◎ marks (see arrows in the figure) temporarily suspended the wind.

  This means that the temperature of the furnace wall to which the deposits adhere decreases as the deposits that contribute to the shelf hanging grow. That is, the present inventors have found that a sign of occurrence of shelf hanging can be detected from the transition of the furnace wall temperature.

  Based on the above findings, the present inventors measure the temperature of the furnace wall at the top of the tuyere in the furnace circumferential direction, detect signs of shelf hanging at an early stage, and suppress the occurrence of shelf hanging. Were embedded in the furnace wall in the furnace circumferential direction with one or more pieces aligned in the furnace height direction in the furnace wall above the tuyere.

  FIG. 3 shows an embodiment in which a thermometer is embedded in the furnace wall at the top of the tuyere, and FIG.

  3 and 4, thermometers are provided on the upper furnace walls of the eight lower tuyere 6b and the four upper tuyere 6a directly above the eight lower tuyere 6b arranged at equal intervals in the furnace circumferential direction. 13a, 13b, and 13c are embedded in the furnace circumferential direction at a predetermined height interval in the furnace height direction.

  FIG. 3 shows an embedding mode in which a thermometer is embedded in three stages in the furnace height direction in order to measure the change in the furnace wall temperature also in the furnace height direction. As long as growth can be detected, it may be one stage or two stages. In order to ensure accuracy of detection, four or more thermometers may be provided.

  FIG. 4 shows an embodiment in which the thermometers 13a, 13b, and 13c are embedded in one row in the furnace height direction. However, as long as the generation and growth of deposits can be detected, the furnace is not necessarily used. There is no need for one row in the high direction.

  Since deposits are most easily generated on the upper furnace wall of the upper tuyere, the thermometer is preferably embedded in the upper furnace wall of the upper tuyere rather than between the tuyere. However, if there is a restriction on the equipment structure at the position where the thermometer is to be embedded, avoid that position and embed it at another position. In addition, the embedding position of a thermometer should just be a position which can detect the production | generation and growth of a deposit | attachment fundamentally.

  In FIG. 5, in a vertical furnace in which four upper tuyere 6a are arranged between eight lower tuyere 6b, the thermometer is placed between tuyere (that is, between upper tuyere 6a). And the embedding aspect embed | buried in the upper furnace wall of between the lower tuyere 6b) is shown.

  Although the description has been given above with the two-stage tuyere vertical melting furnace, the present invention can also be applied to a one-stage tuyere vertical melting furnace. In the case of a 1-stage tuyere vertical melting furnace, the tuyere is usually installed at the same height as the lower tuyere in the case of a 2-stage tuyere. What is necessary is just to embed in an upper furnace wall.

  In the present invention, generation / growth of furnace wall deposits is determined based on the measured furnace wall temperature. The deposits are generated on the furnace wall having a low furnace wall temperature, and when the generated deposits grow, the furnace wall temperature decreases as shown in FIG. It is possible to grasp the generation of deposits and the growth of deposits at an early stage.

  Therefore, in the present invention, the reference furnace wall temperature is set, and the formation mode of deposits and the growth mode of deposits in the furnace are determined by comparing the decrease in the furnace wall temperature with the reference furnace wall temperature.

  For example, when at least one furnace wall temperature is equal to or higher than (a) the reference furnace wall temperature, it is determined that deposits generated on the furnace wall are growing, and (b) the reference furnace temperature When the temperature falls below the wall temperature, it is determined that the furnace wall deposits are growing greatly, and (d1) the operating conditions are changed to operating conditions that dissolve the deposits.

  The operating conditions for melting the deposits may be any, but increasing the coke ratio and / or introducing blank coke is effective for melting the deposits by raising the coke bed height in the furnace. It is. In addition, it is also effective to change the air blowing conditions (air blowing amount, oxygen flow rate, etc.).

  In this way, the operating conditions are changed to dissolve the furnace wall deposits or reduce the size, thereby eliminating the cause of the shelf hanging. It can be confirmed by measuring the furnace top temperature that the cause of the shelves has been removed.

  The determination of the deposit generation mode and the deposit growth mode in the furnace may be performed in consideration of changes in the furnace top temperature. In this case, the reference furnace top temperature is set, and the generation mode of the deposit and the growth mode of the deposit are determined based on the reference furnace top temperature and the reference furnace wall temperature.

  For example, when at least one furnace wall temperature decreases to (c) a reference furnace wall temperature or lower and the furnace top temperature is equal to or higher than the reference furnace top temperature, the furnace wall deposit grows greatly and is suspended from a shelf. (D2) The operating condition is changed to a reduced scale operating condition or a meltdown operating condition.

  As described above, after the shelf suspension is detected, the shelf suspension can be quickly eliminated by largely changing the operation itself.

  Next, examples of the present invention will be described. The conditions of the examples are one example of conditions adopted for confirming the feasibility and effects of the present invention, and the present invention is limited to this one example of conditions. Is not to be done. The present invention can adopt various conditions as long as the object of the present invention is achieved without departing from the gist of the present invention.

(Example)
An iron source having various properties was melted and reduced in a vertical melting furnace (maximum output capacity: 55 t / hr) shown in Table 1. Table 2 shows the operating conditions at the initial stage of operation. The reference furnace wall temperature was 600 ° C., and the reference furnace top temperature was 150 ° C.

  If the furnace wall temperature is 600 ° C. or more, but the downward trend continues for 12 hours or more, 1 t of blank coke is temporarily added, and if the furnace wall temperature falls to 600 ° C. or less, coke The ratio was increased by 2 kg / t for operation, and the shelf suspension suspension period during the operation period was measured.

  The result is shown in FIG. After September, when the present invention was implemented, the monthly shelf suspension time decreased to less than half of the conventional suspension time (5 hr / month). In the month of zero downtime, the operating conditions were changed in consideration of the furnace top temperature.

  As described above, according to the present invention, in the operation of the vertical melting furnace, the generation and growth of the furnace wall deposits are suppressed, the furnace condition is stabilized, and the shelf suspension is not generated. Can be resolved quickly and operation can be continued. Therefore, the present invention has great applicability in the steel manufacturing industry.

It is a figure which shows the one aspect | mode of a vertical melting furnace. It is a figure which shows the time course of the temperature of the furnace wall of a tuyere upper part, and a furnace top temperature. It is a figure which shows the one aspect | mode which embedded the thermometer in the furnace wall of the tuyere upper part. It is a figure which shows the embedment aspect seen in the AA cross section of FIG. It is a figure which shows another aspect which embedded the thermometer in the furnace wall of the tuyere upper part. It is a figure which shows the effect of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Vertical melting furnace 2 Furnace main body 3 Furnace top part 4 Gas suction part 5 Furnace bottom 6 tuyere 6a Upper tuyere 6b Lower tuyere 7 Bucket 8 Coke bed 9 Outlet 10 Raw fuel (iron source, solid fuel)
11 Storage Department 12 Communication Pipe

Claims (4)

In the operation method of the vertical melting furnace using solid fuel blended with coke for blast furnace, blowing from the tuyere, melting the iron source, or melting and reducing to produce pig iron
(I-1) One or more thermometers are embedded in the furnace wall above the tuyere in the furnace height direction, with the same height and buried in the furnace circumferential direction, and the furnace wall temperature in the furnace circumferential direction is measured. ,
(I-2) A thermometer is installed at the top of the furnace to measure the furnace top temperature,
(Ii-1) When at least one of the furnace wall temperatures falls below the reference furnace wall temperature and the furnace top temperature is equal to or higher than the reference furnace top temperature, the furnace wall deposits grow greatly, Determine that shelves are hanging,
(Ii-2) A method for operating a vertical melting furnace, characterized in that the operating conditions are changed to reduced operating conditions or meltdown operating conditions . Operation method of a vertical furnace according to claim 1, wherein the tuyere, characterized in that it is arranged vertically in two stages. The thermometer, vertical melting furnace method operations of any one of claims 1 or 2, characterized in that embedded in two stages or three stages in the furnace height direction. The method for operating a vertical melting furnace according to any one of claims 1 to 3 , wherein at least four rows of the thermometers are embedded in the circumferential direction of the furnace.

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