JP5978807B2 - Blast furnace operation method - Google Patents

Description

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

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. As a result, in recent blast furnace operations, the ratio of low reducing agent ratio (low RAR: Abbreviation for Reduction Agent Ratio, the total amount of reducing material blown from the tuyere and coke charged from the top of the furnace per 1 ton of pig iron production. ) Operation is strongly promoted. Blast furnaces mainly use coke and pulverized coal blown from the tuyere as a reducing material. In order to achieve a low reducing material ratio, and in turn, to suppress carbon dioxide emission, coke is used as waste plastic, LNG, heavy oil and other hydrogen. A method of replacing with a reducing material having a high content is effective. In the following Patent Document 1, it is proposed that coal containing crystallization water is blended with pulverized coal blown from the tuyere, and the pulverized coal is dispersed by utilizing the vaporization expansion of crystallization water to improve the combustibility of the pulverized coal. ing.

Japanese Patent No. 3450206

  The blast furnace operation method described in Patent Document 1 is more effective in improving the combustion temperature and reducing the reduction material basic unit than the conventional method of blowing only pulverized coal from the tuyere. It is effective when blowing in. However, when coal containing crystallization water is used as described in Patent Document 1, energy is required for the decomposition and evaporation of crystallization water, and the reduction effect of the reducing material basic unit is reduced.

  The present invention has been made paying attention to the above problems, and an object of the present invention is to provide a blast furnace operating method capable of improving the combustion rate of a solid reducing material without loss of energy. .

In order to solve the above problems, a blast furnace operating method of the present invention is a blast furnace operating method in which a solid reducing material is blown from a tuyere, and a melting point is 100 ° C. or higher and a boiling point is 400 with respect to the solid reducing material blown from the tuyere It is characterized in that 1 to 15% by weight of a dispersing material having a temperature of not more than 0 ° C. is mixed.
Furthermore, the dispersion material is characterized in that a compound-carbon, hydrogen, oxygen, a combination of any of the elements of nitrogen.

  The compound is benzoic acid or phthalic anhydride.

Thus, according to the blast furnace operating method of the present invention, when the solid reducing material is blown from the tuyere, by mixing 1 to 15% by weight with respect to the solid reducing material blown from the tuyere, The combustibility of the solid reducing material can be improved without losing heat energy.
Further, the dispersion material has a melting point of 100 ° C. or more and a boiling point of 400 ° C. or less, and is a compound composed of a combination of any element of carbon, hydrogen, oxygen, and nitrogen, so that a solid reducing material such as pulverized coal The flammability can be further improved.

  Further, when the compound is benzoic acid or phthalic anhydride, the combustibility of a solid reducing material such as pulverized coal can be further improved.

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 of a combustion mechanism when only pulverized coal and pulverized coal and a dispersion material are blown. It is explanatory drawing of a combustion experiment apparatus. It is explanatory drawing of a combustion experiment result. It is explanatory drawing of a combustion experiment result. It is explanatory drawing of a combustion experiment result.

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.

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. The hot air velocity at the tip of the tuyere 3 in the direction of blowing hot air is about 200 m / sec, and the region where O ₂ exists in the raceway 5 from the tip of the lance 4 is about 0.3 to 0.5 m. In particular, it is necessary to improve the temperature rise of the pulverized coal particles and the contact efficiency (dispersibility) with O ₂ at a level of 1/1000 second.

  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.

  FIG. 4 shows a combustion mechanism when the dispersion material 9 is blown together with the pulverized coal 6 from the lance 4 into the blower pipe 2. FIG. 4 a blows only the pulverized coal 6 from the lance 4, and FIG. 4 b blows the pulverized coal 9 and the dispersion material 9 mixed from the lance 4. When only the pulverized coal 6 is blown from the lance 4, the pulverized coal flow is concentrated inside the blower pipe 2, and the mixing region 10 where the pulverized coal 6 mixes with the oxygen being blown is narrow. On the other hand, when the pulverized coal 6 and the dispersion material 9 are mixed and blown from the lance 4, the pulverized coal 6 is dispersed as the dispersion material 9 is vaporized and expanded, and the pulverized coal 6 is mixed with the oxygen being blown. It is considered that the region 10 spreads and the dispersion material 9 burns, and the pulverized coal 6 is heated and heated rapidly by this combustion heat, whereby the combustion temperature further rises at a position close to the lance 4.

  The dispersion material preferably has a melting point of 100 ° C. or higher and a boiling point of 400 ° C. or lower. When the melting point of the dispersion material is less than 100 ° C., the dispersion material melts at the temperature of the pulverized coal, and the pulverized coal adheres to the lance and causes clogging. On the other hand, when the boiling point of the dispersing material exceeds 400 ° C., the timing of releasing the volatile matter of the pulverized coal becomes the same, and the effect of promoting the dispersion of the pulverized coal is low. The dispersing material is preferably a compound composed of a combination of any of carbon, hydrogen, oxygen, and nitrogen, and examples thereof include benzoic acid and phthalic anhydride. Benzoic acid has a melting point of 122.35 ° C and a boiling point of 249 ° C. Further, phthalic anhydride has a melting point of 131 ° C. and a boiling point of 284 ° C.

  Based on such knowledge, a combustion experiment was performed using the combustion experiment apparatus shown in FIG. The experimental furnace 11 is filled with coke, and the inside of the raceway 15 can be observed from the viewing window. A lance 14 is inserted into the blower tube 12, and hot air generated in the combustion burner 13 can be blown into the experimental furnace 11 with a predetermined blowing amount. Moreover, in this ventilation pipe 12, it is also possible to adjust the oxygen enrichment amount of ventilation. The lance 14 can blow either one or both of pulverized coal and a dispersing material into the blower pipe 12. When the pulverized coal and the dispersion material are simultaneously blown from the lance 14, the pulverized coal and the dispersion material are blown in a mixed state. Further, the exhaust gas generated in the experimental furnace 11 is separated into exhaust gas and dust by a separation device 16 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 17. The

In the combustion experiment, a single pipe lance was used as the lance 14, and only the pulverized coal was blown using the single pipe lance, and the combustion position and unburned char were each mixed and blown into the mixture. The diffusivity was measured. Unburned char was collected from the rear of the raceway 15 with a probe and measured. The specifications of pulverized coal are 71.3% of fixed carbon (FC), 19.6% of volatile matter (VM), 9.1% of ash (Ash), and the blowing condition is 50 kg / h ( 158 kg / t equivalent). Moreover, the blowing conditions of the dispersing material were 3.6 kg / h (5.0 Nm ³ / h, corresponding to 11 kg / t in the ironmaking base unit). The blowing conditions are as follows: blowing temperature 1100 ° C., flow rate 350 Nm ³ / h, flow rate 80 m / s, O ₂ enrichment +3.7 (oxygen concentration 24.7%, air oxygen concentration 21%, 3.7% wealth) ). The evaluation of the experimental results is based on the combustion position and combustion rate when only pulverized coal is blown from a single pipe lance (using N ₂ as the medium), and the mixing ratio of the dispersion material with respect to pulverized coal is variously changed. Then, the dispersion angle of pulverized coal, the combustion position of pulverized coal, and the combustion rate of pulverized coal were evaluated. The combustion rate was calculated from the difference from the weight ratio of the ash before combustion, with the weight ratio of the collected char ash measured by chemical analysis, assuming that this ash was unchanged.

  In FIG. 6, the result of the mixing rate of the dispersing material by the combustion experiment and the dispersion angle of pulverized coal is shown. FIG. 7 shows the results of the mixing ratio of the dispersion material and the combustion position (ignition distance) of the pulverized coal in the combustion experiment. The combustion position of the pulverized coal is represented by the distance from the blowing tip of the lance 14 to the ignition position of the pulverized coal. In FIG. 8, the result of the mixing rate of the dispersion rate by the combustion experiment and the combustion rate of pulverized coal is shown. From FIG. 6, the dispersion angle of pulverized coal increases when the mixing ratio of the dispersing material is 1% or more, and is saturated at a mixing ratio of about 10%. This tendency is similar to the combustion rate of pulverized coal in FIG. This is because when the mixing ratio of the dispersing material is about 10%, the spread of the pulverized coal flow reaches the inner diameter of the tuyere, and the dispersion becomes impossible. On the other hand, the combustion position (ignition distance) of pulverized coal also increases when the mixing ratio of the dispersing material is 1% or more, and is saturated when the mixing ratio of the dispersing material is about 15%. From these results, it is preferable that the mixing ratio of the dispersion material with respect to the pulverized coal blown from the lance is 1 to 15%.

Thus, in the blast furnace operating method of the present embodiment, when the pulverized coal (solid reducing material) 6 is blown from the tuyere 3, the dispersion material 9 is applied to the pulverized coal (solid reducing material) 6 blown from the tuyere 3. By mixing 1 to 15% by weight, the combustibility of the solid reducing material can be improved without losing heat energy.
Dispersant 9 has a melting point of 100 ° C. or higher and a boiling point of 400 ° C. or lower, and is a compound composed of a combination of any of carbon, hydrogen, oxygen, and nitrogen, so that solids such as pulverized coal 6 can be obtained. The combustibility of the reducing material can be further improved.

  Moreover, when the compound is benzoic acid or phthalic anhydride, the combustibility of a solid reducing material such as pulverized coal 6 can be further improved.

  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 (solid reducing material), 7 is coke, 8 is char, 9 is a dispersion material

Claims (3)

In the blast furnace operating method in which a solid reducing material is blown from a tuyere , a dispersion material having a melting point of 100 ° C. or higher and a boiling point of 400 ° C. or lower is mixed by 1 to 15% by weight with respect to the solid reducing material blown from the tuyere. A blast furnace operating method characterized by the above. The dispersed material is blast furnace operation method according to claim 1, characterized in that a compound-carbon, hydrogen, oxygen, a combination of any of the elements of nitrogen.   The method for operating a blast furnace according to claim 2, wherein the compound is benzoic acid or phthalic anhydride.

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