JP2014133943A - Method of setting oxygen enrichment rate and blast furnace operation method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method of setting an oxygen enrichment rate which can improve combustibility of powdered coal when hot air blown into a tuyere is enriched with oxygen and powdered coal and oxygen are blown into the tuyere.SOLUTION: A ratio of enriched oxygen in hot air to enriched oxygen blown from the vicinity of powdered coal, i.e. a tuyere blow oxygen ratio, is adjusted on the basis of a combustion state at the tip of the tuyere. Because the combustion state at the tip of the tuyere changes in response to a tuyere blow oxygen ratio, preliminary grasping of the relationship between the tuyere blow oxygen ratio and the combustion state at the tip of the tuyere enables determining an optimal value of the tuyere blow oxygen ratio for achieving a good combustion state at the tip of the tuyere. The relationship between tuyere blow oxygen ratio and the combustion state at the tip of the tuyere also depends upon the amount of blown powdered coal per unit pig iron, i.e. the powdered coal ratio. Preliminary determination of the relationship between tuyere blow oxygen ratio and the combustion state at the tip of the tuyere for every powdered coal ratio, therefore, enables determining an optimal value for achieving good combustion state even when the powdered coal ratio varies.

Description

  The present invention is a blast furnace in which oxygen can be enriched in hot air blown into the blast furnace from the tuyere, and pulverized coal can be blown into the tuyere and oxygen can be blown from the vicinity thereof. The present invention relates to an oxygen enrichment rate setting method and a blast furnace operation method.

  In the blast furnace method, while agglomerated raw materials such as iron ore, sintered ore and coke are charged from the top of the furnace, hot air is blown into the furnace from the tuyeres at the bottom of the furnace, and coke is produced at the tuyere tip. It is a method of producing pig iron by reducing and melting the raw material (ore) in the furnace in the process in which reducing gas is generated by combustion and the reducing gas is rising in the furnace toward the top of the furnace. In recent years, in order to reduce the cost of the coke agglomeration process, pulverized coal finely pulverized is directly blown into the tuyere, thereby replacing the coke and reducing the cost of hot metal production. doing. Here, at the tip of the tuyere (in front of the tuyere), a combustion space having a diameter of about 1 m called a raceway is formed by the impact of blowing hot air, and the pulverized coal that has been blown is the narrow combustion space. It is desirable to burn as much as possible during the short time of passing through. The reason is that unburned pulverized coal is accumulated in the furnace as unburned char, which causes deterioration of air permeability and hinders stable operation.

  In general, as a method of stabilizing the operation by efficiently burning this pulverized coal, 1) a method of increasing the temperature of the combustion space (improving the reaction rate), and 2) a method of increasing the oxygen concentration of the combustion space ( (Reaction rate improvement), 3) A method of adjusting the size of the combustion space (reaction time securing), 4) A method of adjusting the properties (volatile matter, particle size) of pulverized coal (reaction rate improvement), etc. are known. Among them, as one of the methods 2), for example, as described in Patent Document 1 below, there is a method in which pulverized coal is blown into the tuyere and at the same time oxygen or a gas having a high oxygen concentration is blown from the vicinity. is there. Moreover, as one of the methods of 3), as described in, for example, Patent Document 2 below, the size (depth) of the raceway for each tuyere is calculated from the air blowing conditions and the tuyere information, and those There is a method of adjusting the amount of pulverized coal injection so that the deviation of the raceway depth in the blast furnace circumferential direction becomes small.

JP 2003-286511 A Japanese Patent Publication No. 1-20202

However, in the oxygen blowing method described in Patent Document 1, in order to blow a large amount of oxygen into the high-pressure tuyere, it is necessary to increase the pressure of the blowing oxygen to a high pressure, which increases costs. Since the oxygen directly blown into the tuyere is not heated, the temperature is as low as about 100 ° C., and a large amount of tuyere oxygen blowing lowers the tuyere tip combustion temperature, which in turn reduces the flammability of pulverized coal. There's a problem. On the other hand, the pulverized coal injection method described in Patent Document 2 is not a technique for improving the combustion state of the tuyere by improving the flammability of the pulverized coal. As a result, the cost may be increased by using expensive coke to maintain the furnace temperature.
The present invention has been made paying attention to the above-described problems, and in the case where oxygen is enriched in the hot air blown to the tuyere and pulverized coal and oxygen are blown into the tuyere, the pulverized coal It is an object of the present invention to provide an oxygen enrichment rate setting method and a blast furnace operating method capable of improving the flammability.

  In order to solve the above problems, the oxygen enrichment rate setting method of the present invention is capable of enriching oxygen in hot air blown from the tuyere into the blast furnace, and adding pulverized coal to the tuyere. In the oxygen enrichment rate setting method in the case where it is possible to blow in and oxygen from the vicinity thereof, the hot air is blown from the vicinity of the enriched oxygen and the pulverized coal based on the combustion state of the tuyere The ratio with the enriched oxygen is adjusted.

  Further, a relationship between the ratio of the enriched oxygen to the hot air and the oxygen enrichment injected from the vicinity of the pulverized coal and the tuyere tip combustion state is obtained in advance, and based on the relationship, the combustion state of the tuyere tip And setting an optimum value of the ratio of the oxygen enriched to the hot air and the oxygen enrichment blown from the vicinity of the pulverized coal, and the oxygen enriched to the hot air and the pulverized coal to be the optimum value The ratio with the oxygen enrichment blown from the vicinity of is adjusted.

In addition, the relationship between the ratio of oxygen enriched to the hot air and oxygen enriched from the vicinity of the pulverized coal and the state of combustion at the tuyere is determined in advance for each amount of pulverized coal injected per unit pig iron. It is characterized by.
The blast furnace operating method of the present invention can enrich oxygen in hot air blown from the tuyere into the blast furnace, and blow pulverized coal into the tuyere and blow oxygen from the vicinity thereof. When it is possible, the relationship between the ratio of the oxygen enriched to the hot air and the oxygen enrichment injected from the vicinity of the pulverized coal and the state of combustion at the tip of the tuyere is obtained in advance. Based on the combustion state of the tip, an optimum value of the ratio of oxygen enriched to the hot air and oxygen enrichment blown from the vicinity of the pulverized coal is set, and the enrichment to the hot air is set to the optimum value. The ratio of oxygenated oxygen and oxygen enrichment injected from the vicinity of the pulverized coal is adjusted.

  Thus, according to the oxygen enrichment rate setting method and blast furnace operation method of the present invention, oxygen can be enriched in hot air blown from the tuyere into the blast furnace, and pulverized coal is formed in the tuyere. And the ratio of the enriched oxygen blown from the vicinity of the pulverized coal to the hot air is adjusted based on the combustion state of the tuyere. . The combustion state of the tuyere is blown from the vicinity of the oxygen and pulverized coal enriched in the hot air when the temperature of the hot air and the amount of moisture contained in the hot air are constant. Varies depending on the ratio of enriched oxygen. Therefore, if the relationship between the combustion state of the tuyere and the ratio of the enriched oxygen to the hot air and the enriched oxygen blown from the vicinity of the pulverized coal is grasped in advance, the combustion state of the tuyere is improved. The optimum value of the ratio of enriched oxygen to hot air and enriched oxygen blown from the vicinity of pulverized coal can be determined, and the enriched oxygen and pulverized coal By adjusting the ratio of the enriched oxygen blown from the vicinity, the combustibility of the pulverized coal at the tuyere can be improved.

  Further, the relationship between the ratio of oxygen enriched to hot air and oxygen enrichment injected from the vicinity of pulverized coal and the state of combustion at the tuyere changes depending on the amount of pulverized coal injected per unit pig iron. Therefore, if the relationship between the ratio of oxygen enriched to hot air and oxygen enrichment injected from the vicinity of pulverized coal and the state of combustion at the tuyere is determined in advance for each amount of pulverized coal injected per unit pig iron. Optimum ratio of enriched oxygen to hot air and enriched oxygen blown from the vicinity of pulverized coal to improve the combustion state of the tuyere even when the amount of pulverized coal injected per unit pig iron changes By adjusting the ratio of enriched oxygen to hot air and enriched oxygen blown from the vicinity of the pulverized coal so that the optimum value can be obtained, the combustibility of the pulverized coal at the tuyere is ensured. Can be improved.

It is a longitudinal cross-sectional view which shows one Embodiment of the blast furnace to which the oxygen enrichment rate setting method and blast furnace operation method of this invention were applied. It is explanatory drawing which shows the relationship between a tuyere blowing oxygen ratio and combustion temperature. It is a timing chart when adjusting the tuyere blowing oxygen ratio according to the tuyere tip combustion state in the blast furnace of FIG.

Next, an embodiment of the blast furnace operating method of the present invention will be described with reference to the drawings.
FIG. 1 is an overall view of a blast furnace to which the blast furnace operating method of the present embodiment is applied. As shown in the figure, a blast pipe 2 for blowing hot air is connected to the tuyere 3 of the blast furnace 1, and a lance 4 is installed through the blast pipe 2. A space called a raceway 5 exists ahead of the tuyere 3 in the direction of blowing hot air, and charcoal is mainly burned in this space. The pulverized coal (PC: Pulverized Coal in the figure) that passed through the tuyere 3 from the lance 4 and was blown into the raceway 5 burned together with coke, and its volatile matter and fixed carbon burned, and remained unburned. Aggregates of carbon and ash, commonly called char, are discharged from the raceway as unburned char. As described above, unburned char is accumulated in the furnace and deteriorates the air permeability of the furnace, so that the pulverized coal is burned as much as possible in the raceway 5, that is, the pulverized coal is required to be improved in combustibility.

The pulverized coal blown into the raceway 5 from the tuyere 3 is heated by the radiant heat transfer from the flame in the raceway 5, and the temperature of the pulverized coal rapidly rises by the radiant heat transfer and conduction heat transfer. Thermal decomposition starts when the temperature rises to 300 ° C. or more, ignites the volatile matter, forms a flame, and the combustion temperature reaches 1400 to 1700 ° C. When pulverized coal and oxygen are blown in parallel from the lance 4, it is considered that the pulverized coal comes into contact with O ₂ and burns, and the pulverized coal is heated and heated by the combustion heat. Charcoal begins to burn and the combustion rate also increases.

  In this embodiment, in order to improve the combustibility of pulverized coal in this way, oxygen is blown into the vicinity of pulverized coal using a lance. For example, when the lance 4 is a so-called single pipe lance, two sets of the lance 4 for blowing pulverized coal and the lance 4 for blowing oxygen are blown into each tuyere 3. Further, when the lance 4 is a so-called double pipe lance in which a small diameter blowing pipe is inserted inside a large diameter blowing pipe, for example, pulverized coal is blown from the inner blowing pipe, and the inner blowing pipe is used. And oxygen is blown from the gap between the outer blowing pipes. The pulverized coal and oxygen blowing in the double pipe lance may be reversed, but it is preferable to bring oxygen and pulverized coal closer to facilitate combustion. The lance is directly supplied with oxygen from an oxygen supply source.

  In the present embodiment, the hot air supplied to the blower pipe 2 is also enriched with oxygen. As the hot air, the wind generated by the blower 6 is sent to the hot air furnace 7, heated by the hot air furnace 7, and supplied to each blower pipe 2. Oxygen enriched in hot air is supplied to the upstream side of the hot air furnace 7. Therefore, the heated air blown from the blower tube 2 is enriched with heated oxygen. The oxygen enriched in the hot air and the oxygen blown from the lance 4 are supplied from the same oxygen supply source. And the ratio of oxygen enrichment to hot air and enrichment of oxygen blown from the lance 4 together with the pulverized coal described above can be freely adjusted.

  Sum of the enrichment rate of oxygen enriched in a single air duct 2 (the result is the same as a whole) and the enrichment ratio of oxygen blown from the lance 4 inserted into the air duct 2 (total oxygen enrichment) When the ratio of the oxygen enrichment ratio blown from the lance 4 to the total oxygen enrichment ratio is changed with the constant (concentration ratio) constant, the tuyere tip combustion temperature, that is, the tuyere tip combustion state changes. In general, for example, increasing the ratio of the lance (tuyere) blowing oxygen enrichment rate to the total oxygen enrichment rate is considered to improve the tuyere tip combustion state and increase the tuyere tip combustion temperature. However, for example, as shown in FIG. 2, the ratio of the tuyere blown oxygen enrichment rate to a certain total oxygen enrichment rate (in the figure, tuyere blown oxygen ratio, hereinafter also simply referred to as tuyere blown oxygen ratio) It became clear that the tuyere tip combustion temperature decreased when the tuyere tip combustion temperature was saturated.

  FIG. 2 shows the result of investigating the tuyere tip combustion temperature when the tuyere blown oxygen ratio is changed in the combustion experimental furnace. Like the actual blast furnace, the combustion experimental furnace is filled with coke so that the inside of the raceway can be observed from the viewing window. In addition, a lance is inserted into the blower tube, and hot air generated by, for example, a combustion burner can be blown into the experimental furnace with a predetermined blowing amount. Moreover, in this blower pipe, it is also possible to adjust the oxygen enrichment amount of the blown air. The lance can blow one or both of pulverized coal and oxygen into the blower pipe. The exhaust gas generated in the experimental furnace is separated into exhaust gas and dust by a separation device called a cyclone, the exhaust gas is sent to an exhaust gas treatment facility such as an auxiliary combustion furnace, and the dust is collected in a collection box. The tuyere tip combustion temperature, that is, the combustion temperature in the raceway, was measured from a viewing window with a two-color thermometer. As is well known, a two-color thermometer is a radiation thermometer that measures temperature using thermal radiation (electromagnetic wave movement from a high-temperature object to a low-temperature object). Paying attention to the shift, it is one of the wavelength distribution types to obtain the temperature by measuring the temperature change of the wavelength distribution, and in particular to measure the wavelength distribution, the radiant energy at two wavelengths is measured and the ratio The temperature is measured from

  As described above, when the pulverized coal injection basic unit, that is, the pulverized coal ratio is constant and the tuyere-blown oxygen ratio is increased, the tuyere tip combustion temperature peaks at a certain ratio, and thereafter The tuyere tip combustion temperature decreases as the oxygen concentration increases. This is, as described above, oxygen that is blown into the tuyere (lance) is not heated, is room temperature (low temperature) oxygen, and when blowing low temperature oxygen more than contributing to the improvement of pulverized coal combustibility, On the contrary, it is considered that the tuyere tip combustion temperature is lowered. Furthermore, as apparent from FIG. 2, changing the pulverized coal ratio and changing the tuyere blowing oxygen ratio not only changes the tuyere tip combustion temperature but also corresponds to the peak of the tuyere tip combustion temperature at each pulverized coal ratio. The value of the tuyere blowing oxygen ratio changes. Therefore, the tuyere blowing oxygen ratio at which the tuyere tip combustion temperature reaches a peak may be set and adjusted at the set pulverized coal ratio (pulverized coal blowing amount).

  Although the blast furnace conditions are kept constant, for example, the blowing rate of pulverized coal, etc., various other factors such as fluctuations in physical and chemical properties of raw materials (coke, iron ore, etc.) The combustion state of the tuyere changes due to (variation) or the like. That is, it means that the optimum value of the tuyere blowing oxygen ratio varies depending on the in-furnace situation. Therefore, the point of this technology is to find the optimum value by trial and error by grasping the “combustion state of the tuyere” from the sensor information. However, the method of searching the optimum point by changing the tuyere-blown oxygen ratio greatly in actual production facilities is not preferable for operation, so it is practical to find a desired value from the laboratory test results and set it. Operation method.

  In FIG. 2, the tuyere tip combustion temperature is used as the tuyere tip combustion state. For example, the tuyere tip combustion temperature tends to be opposite to the blowing pressure. That is, when the state of combustion at the tuyere is good and the tuyere tip combustion temperature is high, the blowing pressure is low. On the contrary, when the combustion state of the tuyere tip deteriorates and the tuyere tip combustion temperature is low, the blowing pressure becomes high. This agrees with the ventilation resistance index in the furnace. That is, as is well known, the ventilation resistance index in the furnace is obtained from the blowing pressure, the furnace top pressure, and the blowing volume. The higher the blowing pressure, the larger the ventilation resistance index in the furnace and the worse the ventilation state. The decrease in the aeration state is a decrease in the tuyere tip combustion temperature and the deterioration of the tuyere tip combustion state. Therefore, if the tuyere-injected oxygen ratio is adjusted while using the tuyere-tip combustion state information, the peak point of the tuyere-tip combustion temperature at the currently set pulverized coal ratio, that is, the optimum state of the tuyere-tip combustion state The optimum value of the tuyere blowing oxygen ratio that achieves the point can be searched and grasped, and the tuyere blowing oxygen ratio is adjusted to be the optimum value.

  Therefore, in the present embodiment, the temperature at the tip of the tuyere is detected by a thermometer T (feather embedding temperature) embedded in the tuyere 3, and the ventilation resistance index in the furnace is detected by a pressure gauge P attached to the blower tube 2. The tuyere-blown oxygen ratio was adjusted. An example is shown in FIG. In the example of FIG. 3, when pulverized coal was injected at a preset pulverized coal ratio and the operation was continued at the tuyere blowing oxygen ratio at which the tuyere tip combustion temperature was stable, the tuyere tip combustion temperature was due to some factor. As it decreased, the furnace ventilation resistance index deteriorated. This means that the tuyere-blown oxygen ratio currently set is no longer the optimum point due to fluctuations in the furnace conditions. Therefore, the tuyere-blown oxygen ratio was increased step by step in order to adjust to the optimum point according to the current in-furnace situation. First, due to the increase in the first stage, the tuyere tip combustion temperature increased and the furnace ventilation resistance index tended to decrease, so it was judged that the tuyere tip combustion state was improving. In addition, when the second stage was increased, the tuyere tip combustion temperature turned down and the in-furnace resistance index increased. This indicates that the state of combustion at the tip of the tuyere has deteriorated. In FIG. 2, it is considered that the tuyere tip combustion temperature has passed the optimum value of the tuyere-injected oxygen ratio at which the peak point is reached. That is, it can be determined that the setting of the tuyere blowing oxygen ratio in the first-stage increase action is an optimal value that matches the current in-furnace situation. Therefore, when returning to the first-stage action again, the tuyere tip combustion temperature rose, and stable tuyere tip combustion temperature and furnace ventilation resistance index could be obtained.

  Thus, in the blast furnace operating method of this embodiment, oxygen can be enriched in hot air blown from the tuyere into the blast furnace, and pulverized coal is blown into the tuyere and oxygen is introduced from its vicinity. When inhalation is possible, the ratio of the enriched oxygen to the hot air and the enriched oxygen that is injected from the vicinity of the pulverized coal, that is, the tuyere injecting oxygen ratio is adjusted based on the combustion state of the tuyere. The combustion state of the tuyere changes according to the tuyere blowing oxygen ratio. Therefore, if the relationship between the combustion state of the tuyere and the tuyere blowing oxygen ratio is known in advance, the optimum value of the tuyere blowing oxygen ratio for improving the tuyere tip combustion state is obtained. If the tuyere blowing oxygen ratio is adjusted so that the optimum value is obtained, the combustibility of the pulverized coal at the tuyere can be improved.

  The ratio between the oxygen enriched to hot air and the oxygen enrichment injected from the vicinity of the pulverized coal, that is, the relationship between the tuyere infused oxygen ratio and the state of the tuyere tip combustion is the blasted pulverized coal per unit pig iron. It depends on the quantity, ie the pulverized coal ratio. Therefore, if the relationship between the tuyere-injected oxygen ratio and the tuyere tip combustion state is obtained in advance for each pulverized coal ratio, it is possible to improve the tuyere tip combustion state even when the pulverized coal ratio changes. The optimum value of the tuyere blown oxygen ratio can be obtained, and if the tuyere blown oxygen ratio is adjusted so as to be the optimum value, the combustibility of the pulverized coal at the tuyere can be reliably improved.

1 is a blast furnace 2 is an air duct 3 is a tuyere 4 is a lance 5 is a raceway 6 is a blower 7 is a hot stove T is a thermometer P is a pressure gauge

Claims (4)

  Oxygen enrichment when oxygen can be enriched in hot air blown from the tuyere into the blast furnace, and pulverized coal can be blown into the tuyere and oxygen can be blown from the vicinity. In the rate setting method, the oxygen enrichment rate setting is characterized by adjusting the ratio of the enriched oxygen to the hot air and the enriched oxygen blown from the vicinity of the pulverized coal based on the combustion state of the tuyere Method.   The ratio between the enriched oxygen to the hot air and the oxygen enrichment blown from the vicinity of the pulverized coal, and the relationship between the tuyere tip combustion state in advance, from that relationship, based on the combustion state of the tuyere tip, Set the optimal value of the ratio of oxygen enriched to the hot air and oxygen enriched from the vicinity of the pulverized coal, and the vicinity of the oxygen enriched to the hot air and the pulverized coal to be the optimal value The oxygen enrichment rate setting method according to claim 1, wherein the ratio of oxygen enrichment blown from is adjusted.   The relationship between the ratio of oxygen enriched to the hot air and oxygen enriched from the vicinity of the pulverized coal and the state of combustion at the tip of the tuyere is obtained in advance for each amount of pulverized coal injected per unit pig iron The oxygen enrichment rate setting method according to claim 2.   When the hot air blown from the tuyere into the blast furnace can be enriched with oxygen, and when pulverized coal can be blown into the tuyere and oxygen can be blown from the vicinity thereof, the hot air The relationship between the ratio of oxygen enriched to oxygen and oxygen enrichment blown from the vicinity of the pulverized coal and the tuyere tip combustion state is obtained in advance, and from that relationship, based on the combustion state of the tuyere tip, the hot air The optimum value of the ratio of oxygen enriched to oxygen and oxygen enrichment blown from the vicinity of the pulverized coal is set, and the oxygen enriched to the hot air and the blown from the vicinity of the pulverized coal are set to the optimum value. A method for operating a blast furnace, characterized by adjusting a ratio of oxygen enrichment.

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