JP5971165B2 - Blast furnace operation method - Google Patents

Description

  The present invention relates to a method for operating a blast furnace in which pulverized coal is blown from a blast furnace tuyere and the combustion temperature is increased to improve productivity and reduce the basic unit of reducing material.

In recent years, global warming due to an increase in carbon dioxide emission has become a problem, and the suppression of exhausted CO ₂ is an important issue even in the steel industry. In response to this, in recent blast furnace operations, the ratio of low reducing agent (low RAR: Abbreviation for Reduction Agent Ratio) is the sum of the reducing material injected from the tuyere and the coke charged from the top of the furnace per 1 ton of pig iron. Volume) Operation is being strongly promoted. For stable and efficient operation of the blast furnace, it is necessary to minimize variations in the tuyere tip temperature in the blast furnace circumferential direction. However, since the amount of pulverized coal injection at each tuyere varies, the temperature at the tuyere tip is greatly varied in the circumferential direction. Therefore, Patent Document 1 below describes that the amount of pulverized coal injection from the tuyere is controlled based on the deviation amount in the circumferential direction of the furnace temperature. Further, in Patent Document 2 below, the pulverized coal blowing air is measured so that the pulverized coal blowing amount is uniform by measuring the pulverized coal blowing amount with a capacitance type flow meter provided in the blower pipe (blow pipe). A method for controlling the flow rate is described.

Japanese Patent Laid-Open No. 11-124609 JP 2004-300504 A

However, since it is difficult to stably control the flow rate of pulverized coal, it is possible to sufficiently suppress the variation in the blast furnace circumferential direction of the tuyere tip temperature by the method described in Patent Document 1 and Patent Document 2. Can not. When blowing air to the blast furnace tuyere, oxygen-enriched hot air is evenly blown to each tuyere, but in such cases, if the amount of pulverized coal blown in each tuyere varies in the blast furnace circumferential direction, Since the pulverized coal / oxygen ratio changes, the tip temperature difference occurs in the blast furnace circumferential direction. The tuyere where the flow rate of pulverized coal increased and the pulverized coal / oxygen ratio increased increased the temperature at the tip of the tuyere, deteriorated the combustibility of the pulverized coal, generated unburned char, and increased the gas permeability in the furnace. Getting worse. When the flow rate of pulverized coal decreases and the pulverized coal / oxygen ratio decreases, the combustion of coke at the tuyere tip increases relatively, and the tuyere tip temperature rises. And if there is a tuyere tip temperature deviation, the reduction reaction in the furnace will be biased, inducing deterioration of the operating state such as an abnormal drop of the charge, and as a result, the reducing material ratio increases. Moreover, when a tuyere tip temperature difference arises, the blast furnace circumferential direction difference of hot metal temperature will arise. When the hot metal temperature is higher than 1530 ° C., the wear of surrounding refractories is accelerated. On the other hand, when the hot metal temperature is below 1500 ° C., hot metal, slag outflow and outflow cannot be smoothly performed, which causes deterioration of furnace conditions.
This invention is made paying attention to the above problems, and it aims at providing the blast furnace operating method which can suppress the dispersion | variation in the blast furnace peripheral direction of tuyere tip temperature. .

  In order to solve the above problems, the blast furnace operating method of the present invention includes a lance for blowing pulverized coal and oxygen from different blowing paths into hot air blown to each tuyere, and the lances of the blast furnace are fed from the lance. A blast furnace operation method in which pulverized coal and oxygen are simultaneously blown into the mouth, and the amount of pulverized coal injected is measured for each tuyere or each tuyere group, and the measured amount of pulverized coal injected is measured. A value is used to set the amount of oxygen blown from the lance for each corresponding tuyere or each tuyere group.

Further, the pulverized coal ratio per 1 ton of hot metal, which is the total amount of pulverized coal blown from all tuyere per 1 ton of hot metal, is 150 kg / t-hot metal or more.
Further, pulverized coal and oxygen are simultaneously blown into the tuyere with one lance that can blow pulverized coal and oxygen from different blowing routes per tuyere.
Further, for each tuyere, pulverized coal and oxygen are blown into the tuyere at the same time with two lances, a lance for blowing pulverized coal and a lance for blowing oxygen.

Further, when the gas reducing material is simultaneously blown into the tuyere, the amount of oxygen blown from the lance is set so that the theoretical tuyere tip temperature given by the following formula 1 becomes a preset target value. It is what.
Theoretical tuyere tip temperature (° C.) = Constant term (° C.) + B × blast temperature (° C.) + C × lance oxygen enrichment rate (%) + D × blast moisture (g / Nm ³ ) + E × pulverized coal ratio (g / Nm ³ −O ₂ ) + F × Gas reducing material ratio (g / Nm ³ −O ₂ ) (1)

However, the lance oxygen enrichment rate (%) = the amount of oxygen blown from the lance (Nm ³ / unit time) / air flow rate (Nm ³ / unit time) × 100, pulverized coal ratio = the amount of pulverized coal injected from the lance (G / unit time) / (oxygen blown amount from lance (Nm ³ / unit time) + oxygen flow rate during blowing (Nm ³ / unit time)), gas reducing material ratio = gas reducing material blowing amount from lance (G / unit time) / (amount of oxygen blown from the lance (Nm ³ / unit time) + oxygen flow during blowing (Nm ³ / unit time)), B to F are preset coefficients

The tuyere group is characterized in that two to five tuyere are adjacent to each other, and the amount of oxygen blown from the lance is set for each corresponding tuyere group. is there.
In addition, when the pulverized coal blowing from the lance is stopped for each tuyere, the oxygen blowing from the lance to the same tuyere is stopped.

  Thus, according to the blast furnace operating method of the present invention, the hot air blown to each tuyere has a lance that blows pulverized coal and oxygen from different blowing paths, and from the lance to the tuyere tuyere When blowing pulverized coal and oxygen simultaneously, measure the amount of pulverized coal blown for each tuyere or each tuyere group, and use the measured value of the amount of pulverized coal blown from the lance. The amount of oxygen to be blown is set for each corresponding tuyere or each tuyere group. Therefore, it is possible to suppress variations in tuyere tip temperature in the blast furnace circumferential direction. When the variation in the blast furnace circumferential direction of the tuyere temperature is suppressed, the combustion of pulverized coal becomes stable, the variation in the circumferential direction of the descending rate of the charge is eliminated, and the gas permeability in the furnace is improved. Increases and heat loss from the furnace wall decreases, so that stable operation with a low reducing material ratio can be realized. Further, since the temperature of the hot metal is stabilized, the effect of stabilizing the hot metal quality and the effect of extending the life of the refractory at the bottom of the furnace can be obtained. These effects are remarkable when the total amount of pulverized coal injected from all tuyere per 1 ton of hot metal, that is, the ratio of pulverized coal per 1 ton of hot metal is 150 kg / t-hot metal or more.

It is a longitudinal cross-sectional view which shows one Embodiment of the blast furnace to which the blast furnace operating method of this invention was applied. It is explanatory drawing of a combustion state when only pulverized coal is blown in from the lance of FIG. It is explanatory drawing of the combustion mechanism of the pulverized coal of FIG. It is explanatory drawing which shows an example of the lance which blows in pulverized coal and oxygen from a tuyere. It is explanatory drawing which shows the other example of the lance which blows in pulverized coal and oxygen from a tuyere. It is a sequence diagram of an oxygen blowing path. It is explanatory drawing of the relationship between a pulverized coal ratio, the amount of blowing oxygen, and tuyere temperature. It is a block diagram for lance oxygen blowing amount setting. It is explanatory drawing of an effect | action of oxygen blowing amount control.

  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 combustion space called a raceway 5 exists in the coke deposit layer in the hot air blowing direction ahead of the tuyere 3, and iron ore is reduced, that is, ironmaking is mainly performed in this combustion space. In the present embodiment, there are 40 tuyere 3 in the circumferential direction of the blast furnace 1.

  FIG. 2 shows a combustion state when only pulverized coal 6 is blown from the lance 4. The pulverized coal 6 that has passed through the tuyere 3 from the lance 4 and is blown into the raceway 5, together with the coke 7, combusts its volatile matter and fixed carbon, and remains unburned, generally called char. The aggregate of ash is discharged as unburned char 8 from the raceway. When the unburned char 8 is discharged from the raceway into the charge, the air permeability in the furnace deteriorates.

  FIG. 3 shows a combustion mechanism when only pulverized coal (PC: Pulverized Coal in the figure) 6 is blown into the blow pipe 2 from the lance 4. The pulverized coal 6 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 6 is rapidly increased by the radiant heat transfer and conduction heat transfer. The thermal decomposition starts when the temperature is raised to 300 ° C. or more, and the volatile matter is ignited to form a flame, and the combustion temperature reaches 1400 to 1700 ° C. When the volatile matter is released, the above-described char 8 is obtained. Since the char 8 is mainly fixed carbon, a reaction called a carbon dissolution reaction occurs along with a combustion reaction.

In this embodiment, in order to improve the combustibility of pulverized coal, oxygen is blown into the tuyere using a lance. In addition, gas reducing materials such as LNG (Liquefied Natural Gas) and city gas are blown into the tuyere as needed from the lance. For example, when pulverized coal, LNG, and oxygen are injected at the same time, the pulverized coal is dispersed as the gas diffuses, and LNG is combusted by the contact of LNG and O ₂ , and the pulverized coal is rapidly heated and raised by the combustion heat. It is thought that it warms, and, thereby, the combustibility of pulverized coal can be improved further.

  In FIG. 4, an example of the lance 4 which blows in pulverized coal and a lance separately is shown. The lance 4 is a so-called single pipe lance, and the lance 4 for blowing in pulverized coal and the lance 4 for blowing in oxygen are set into two sets and blown into each tuyere 3. FIG. 5 shows another example of the lance 4 in which the pulverized coal and the lance are individually blown. This lance 4 is a so-called double pipe lance in which a large-diameter blow pipe is concentrically stacked on the outside of a small-diameter blow pipe. For example, pulverized coal is blown from an inner blow pipe, and the inner blow pipe and the outer Oxygen is blown from the gap between the blow 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. In the present embodiment, oxygen is blown only from the lance in order to bring pulverized coal and oxygen closer to each other, and oxygen is not enriched in the blown air. Moreover, the above-mentioned LNG and city gas are also blown into the tuyere using a lance (not shown).

  FIG. 6 is a sequence diagram of the oxygen blowing path. Oxygen branches from the high-pressure main pipe 11 to the header pipe 13 via the shut-off valve 12 and is distributed to the branch pipes 14 to each tuyere connected to the header pipe 13. Accordingly, there are a total of 40 branch pipes 14. Each branch pipe 14 is provided with a flow control valve 15, a shut-off valve 16, and a check valve 17 from the upstream side to finely control the amount of oxygen blown from each branch pipe 14 to the lance 4. it can. Each branch pipe 14 is also connected with a purge nitrogen supply pipe. In the figure, symbol PT indicates a pressure gauge, FT indicates a flow meter, and TI indicates a thermometer.

  FIG. 7 shows the relationship between the amount of pulverized coal blown from the lance and the amount of oxygen blown and the tuyere tip temperature. FIG. 7a shows the tuyere temperature when the amount of oxygen blown from the lance is constant and the pulverized coal ratio, that is, the amount of pulverized coal blown from the lance is changed. In addition, the pulverized coal ratio of the horizontal axis of FIG. 7a was represented with the sum total of the amount of pulverized coal injected from all tuyere per 1t of hot metal. Moreover, FIG. 7 b shows the tuyere tip temperature when the amount of pulverized coal injection is constant and the amount of oxygen injection is changed. According to these figures, it is shown that the tuyere tip temperature decreases as the amount of pulverized coal injection relative to the amount of oxygen injection increases, and the tip temperature increases as the amount of oxygen injection relative to the amount of pulverized coal injection increases. ing.

FIG. 8 shows a block diagram of an oxygen blowing amount setting device that sets the amount of oxygen blown from the lance for each tuyere. In the present embodiment, for example, the blowing temperature sensor 21 detects the blowing temperature (° C.), the blowing moisture sensor 22 detects the blowing moisture (g / Nm ³ ), and the LNG (or city gas) ratio sensor 23 detects LNG. (Or city gas) ratio (g / Nm ³ -O ₂ ) is detected, the pulverized coal ratio sensor 24 detects the pulverized coal ratio (g / Nm ³ -O ₂ ), and the blast flow rate sensor 25 detects the blast flow rate (Nm ³ / min) and the detection results are input to the arithmetic processing unit 26. In the arithmetic processing unit 26, in addition to these detection results, a constant term (° C.) and a target tuyere tip temperature (° C.) are input. The blowing amount, Nm ³ / min) is set. In accordance with the lance oxygen blowing amount, the oxygen blowing control circuit controls the amount of oxygen blown from each tuyere lance. The LNG (or city gas) ratio is the amount of LNG (or city gas) injected per unit oxygen injection amount. For detecting the amount (flow rate) of pulverized coal, a flow meter such as a differential pressure measuring method or an ultrasonic method can be used in addition to the capacitance method.

Theoretical tuyere tip temperature (° C.) = Constant term (° C.) + B × blast temperature (° C.) + C × lance oxygen enrichment rate (%) + D × blast moisture (g / Nm ³ ) + E × pulverized coal ratio (g / Nm ³ −O ₂ ) + F × LNG (or city gas) ratio (g / Nm ³ −O ₂ ) (1)
However, the lance oxygen enrichment rate (%) = the amount of oxygen blown from the lance (Nm ³ / min) / the flow rate of air flow (Nm ³ / min) × 100. B to F are coefficients set in advance.

  Incidentally, the flow rate of the pulverized coal ratio in the above formula 1 varies depending on the properties of the pulverized coal even if the conditions such as the carrier gas are constant. On the other hand, the air temperature, air humidity, and LNG (or city gas) ratio in the above formula 1 have small fluctuations at each tuyere, so that, for example, the pulverized coal blowing amount and the oxygen blowing amount become the tuyere tip temperature. The relationship of the influence, for example, the map of FIG. 7, may be used to determine the oxygen injection amount that achieves the target tuyere tip temperature according to the pulverized coal injection amount, and set it as the lance oxygen injection amount.

Next, as an example of the blast furnace operating method of the present embodiment, in a large blast furnace having a volume of about 5000 m ³ and a number of tuyere of 40, an operation was performed in which the ratio of pulverized coal per 1 ton of hot metal was blown at 145 kg / t-hot metal. The pulverized coal and oxygen were blown from individual lances as shown in FIG. The operating conditions are an air volume: 7800 m ³ / min, and an air temperature: about 1100 ° C. Conventionally (before control), oxygen was blown evenly into each tuyere, but in the examples (after control), oxygen blowing amount control using the above-described formula 1 was applied. Both results are shown in FIG. 9a, and the pulverized coal injection amount and the oxygen injection amount by the oxygen injection amount control are shown in FIG. 9b. In addition, tuyere number 25 tuyere was operated without blowing pulverized coal because the blowing lance for pulverized coal was clogged. For example, in this tuyere number 25 tuyere, when the blowing of pulverized coal is stopped and oxygen is blown in the same manner as the other tuyere, the tuyere tip temperature rises extremely, but the tuyere tip temperature is the target. When the oxygen blowing amount control is performed so as to coincide with the tuyere temperature, since the pulverized coal is not blown, the oxygen blowing is also stopped. As a result, variation in tuyere temperature is suppressed when the oxygen injection amount control is performed. As a result, the variation of the tuyere tip temperature in the blast furnace circumferential direction and the temperature difference of the tapping were improved, and the reduction of the coke ratio was achieved.

Next, while changing the pulverized coal ratio, the blast furnace operating state before continuously performing the blast furnace operating method of the present embodiment (conventional example) and when continuously performed (example) is shown in Table 1 below. . The variation of the tuyere tip temperature in the table indicates the standard deviation of the theoretical tuyere tip temperature obtained by the above-mentioned formula 1 of 40 tuyere. Moreover, the output temperature difference shows the difference between the average values of the output temperatures at the two outlets. The CO gas utilization rate is expressed by CO ₂ / (CO ₂ + CO). As is apparent from the above, the variation in the tuyere temperature is significantly lower in the example than in the conventional example, and as a result, the difference in the average value of the tapping temperature at the two tapping holes is also reduced. ing. Further, since the coke ratio is lowered, the reducing material ratio is lowered. As a result, the CO gas utilization rate is improved, and as a result, the CO ₂ emission amount is lowered. Further, since the CO gas utilization rate has been improved, the coke ratio and the reducing material ratio are reduced, and as a result, the CO ₂ emission amount is reduced. And this tendency is remarkable when the ratio of pulverized coal is large, especially when the ratio of pulverized coal per 1 ton of hot metal is 150 kg / t-molten iron or more, and the decrease in the temperature difference of the molten iron, the coke ratio and the reducing material ratio is remarkable. is there.

  As described above, in the blast furnace operating method of the present embodiment, the hot air blown to each tuyere 3 has the lance 4 that blows pulverized coal and oxygen from different blowing paths, and the wings of the blast furnace 1 from the lance 4. When pulverized coal and oxygen are simultaneously blown into the mouth 3, the amount of pulverized coal blown is measured for each tuyere 3, and the measured value of the measured amount of pulverized coal blown from the lance 4 The amount of oxygen to be injected is set for each corresponding tuyere 3. Therefore, it is possible to suppress variations in tuyere tip temperature in the blast furnace circumferential direction. When the variation in the blast furnace circumferential direction of the tuyere temperature is suppressed, the combustion of pulverized coal becomes stable, the variation in the circumferential direction of the descending rate of the charge is eliminated, and the gas permeability in the furnace is improved. Increases and heat loss from the furnace wall decreases, so that stable operation with a low reducing material ratio can be realized. Further, since the temperature of the hot metal is stabilized, the effect of stabilizing the hot metal quality and the effect of extending the life of the refractory at the bottom of the furnace can be obtained. These effects are remarkable when the total amount of pulverized coal injected from all tuyere per 1 ton of hot metal, that is, the ratio of pulverized coal per 1 ton of hot metal is 150 kg / t-hot metal or more.

  In the above embodiment, the oxygen injection amount control corresponding to the pulverized coal injection amount is performed for each tuyere, but for example, two to five adjacent tuyere are taken as a group and the lance is blown from the lance. Even if the amount of oxygen to be injected is set for each corresponding tuyere group, the same effect can be obtained, and for example, the number of flow rate adjusting valves in the oxygen blowing path and the control system can be reduced. .

  1 is a blast furnace, 2 is a blow pipe, 3 is a tuyere, 4 is a lance, 5 is a raceway, 6 is pulverized coal, 7 is coke, 8 is char, 11 is a main pipe, 12 is a shut-off valve, 13 is a header pipe 14 is a branch pipe, 15 is a flow regulating valve, 16 is a shut-off valve, and 17 is a check valve.

Claims (5)

A blast furnace operation method in which pulverized coal and oxygen are blown into the hot air blown to each tuyere through different blowing paths, and pulverized coal and oxygen are simultaneously blown into the tuyere tuyeres from the lance. Then , the gas reducing material was simultaneously blown into the tuyere, the amount of pulverized coal was measured for each tuyere or each tuyere group, and the measured value of the measured amount of pulverized coal was used . A method for operating a blast furnace, wherein an amount of oxygen blown from the lance is set so that a theoretical tuyere tip temperature given by the following formula 1 is a preset target value.
Theoretical tuyere tip temperature (° C.) = Constant term (° C.) + B × blast temperature (° C.) + C × lance oxygen enrichment rate (%) + D × blast moisture (g / Nm ³ ) + E × pulverized coal ratio (g / Nm ³ −O ₂ ) + F × Gas reducing material ratio (g / Nm ³ −O ₂ ) (1)
However, the lance oxygen enrichment rate (%) = the amount of oxygen blown from the lance (Nm ³ / unit time) / air flow rate (Nm ³ / unit time) × 100, pulverized coal ratio = the amount of pulverized coal injected from the lance (G / unit time) / (oxygen blown amount from lance (Nm ³ / unit time) + oxygen flow rate during blowing (Nm ³ / unit time)), gas reducing material ratio = gas reducing material blowing amount from lance (G / unit time) / (amount of oxygen blown from the lance (Nm ³ / unit time) + oxygen flow during blowing (Nm ³ / unit time)), B to F are preset coefficients   The blast furnace operating method according to claim 1, wherein the ratio of pulverized coal per 1t of hot metal is 150kg / t-hot metal or more. Per tuyere one, was blown into the pulverized coal and oxygen and the potential was blown from different blowing pathways one lance simultaneously tuyere pulverized coal and oxygen, which further can only blow the gas reducing material wherein 1 blast furnace method according to claim 1 or 2, characterized in blown Mukoto simultaneously tuyere said gaseous reducing agent at a different other of the lance and the lance. Per tuyere one, of the pulverized coal blown free lance and oxygen blown lance two lances in sparging pulverized coal and oxygen simultaneously tuyere, further wherein the gas reducing agent blowing viewed possible the two blast furnace method according to claim 1 or 2, characterized in simultaneously blow Mukoto the gas reducing material tuyere Reims different other lances. The said tuyere group makes 2 to 5 tuyere adjacent to one group, and the amount of oxygen blown from the lance is set for each corresponding tuyere group. The blast furnace operating method according to any one of 4 .

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