JP4660399B2 - Carbon material preheating injection blast furnace operation method - Google Patents

Description

  The present invention relates to a method for operating a blast furnace in which a carbon material is heated and blown from a tuyere.

  Conventionally, in blast furnace operation, in order to reduce the coke ratio, operation has been performed in which pulverized coal is blown into the furnace together with hot air from the tuyere (for example, see Non-Patent Document 1). Pulverized coal burns in the raceway in front of the tuyere, and the combustion heat and combustion gas contribute to the reduction of the coke ratio. However, pulverized coal does not burn completely in the raceway and is usually called “char”. A so-called unburned portion accumulates in the furnace core.

  When the amount of “char” deposited is large, the effect of reducing the coke ratio by blowing pulverized coal is small, and further, the air permeability in the furnace is deteriorated, so that the operation becomes unstable. As a result, the heat balance at the lower part of the furnace is not stable, the hot metal temperature is unbalanced, or the output ratio is lowered.

  Therefore, a method for improving flammability by heating the pulverized coal blown from the tuyere has been proposed (see, for example, Patent Documents 1 and 2). For example, Patent Document 1 discloses a pulverized coal blowing method in which pulverized coal is heated to 200 ° C. or higher in advance and blown into a blast furnace together with hot air.

  However, even if the pulverized coal is heated to increase the combustibility and the blowing amount is increased, the coke ratio may not be reduced and other operational effects may not be obtained.

  This is because the actual gas volume in the tuyere becomes large and the pressure loss in the furnace becomes large, and as a result, high-high ratio operation becomes difficult.

Japanese Patent Laid-Open No. 04-354810 Japanese Unexamined Patent Publication No. 01-028311 Japan Iron and Steel Institute: 146th, 147th Nishiyama Memorial Technology Course Recent Progress and Future of Steelmaking Technology

  In view of the above-mentioned demands, the present invention has an object to reduce the coke ratio and stably extract hot metal at a predetermined temperature in pulverized coal injection blast furnace operation.

  In order to stably extract hot metal at a predetermined temperature, it is necessary to stably maintain the heat balance in the lower part of the furnace. When substituting coke with pulverized coal, the effective amount of heat in the lower part of the furnace (hereinafter referred to as “furnace calorific value”) is greater than that of pulverized coal. is there.

  The heat value at the bottom of the furnace is an index defined by subtracting the amount of heat required to raise the temperature up to 1400 ° C from the partial combustion heat until the charcoal burns and generates CO. If it blows in, it can increase the calorific value of the lower part of the pulverized coal. As a result, the substitution rate of pulverized coal with coke can be increased, and the coke ratio can be reduced even if the reducing material ratio is constant.

  And if this inventor preheats pulverized coal in the temperature range where the volatile matter in pulverized coal does not volatilize, it can remove or fully reduce the moisture in pulverized coal, and as a result, in the lower part of the furnace It has been found that the amount of heat input to the lower part of the furnace can be increased and the substitution rate between pulverized coal and coke can be increased without changing the actual gas volume.

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

(1) In a blast furnace operation method in which a carbon material is blown from a tuyere, the carbon material is preheated to a temperature equal to or higher than a temperature at which moisture in the carbon material vaporizes and less than a temperature at which volatile components in the carbon material start to volatilize. The carbonaceous material preheating blow-in blast furnace operating method is characterized in that the water content is 0.5% or less and blown from the tuyere.

(2) The carbon material preheating according to (1) , wherein a temperature at which moisture in the carbon material vaporizes is 100 ° C., and a temperature at which a volatile component in the carbon material starts to volatilize is 200 ° C. Blow blast furnace operation method.

( 3 ) The carbonaceous material preheating blowing blast furnace operating method according to any one of (1) to ( 2 ), wherein the carbonaceous material is preheated in heated carbonaceous material conveying air or nitrogen.

( 4 ) The carbonaceous material preheating blowing blast furnace operation according to any one of (1) to ( 2 ), wherein the carbonaceous material is preheated by a heating device disposed in a carbonaceous material conveyance line immediately before the tuyere. Method.

( 5 ) The carbonaceous material preheating blow-in blast furnace operating method according to any one of (1) to ( 4 ), wherein the carbonaceous material is pulverized coal.

  According to the present invention, pulverized coal with reduced moisture can be blown to the furnace core, so that the heat input to the lower part of the furnace can be substantially reduced by suppressing the endothermic reaction caused by moisture and sensible heat of the pulverized coal. Can be increased. Therefore, according to the present invention, the hot metal can be stably brewed at a predetermined temperature while reducing the coke ratio, and the brewing ratio can be maintained at a high level.

  In order to stably extract the hot metal at a predetermined temperature, it is necessary to maintain the heat balance in the lower part of the furnace. The inventor considered that the endothermic reaction caused by moisture in the carbonaceous material is a cause of imbalance in the heat balance in the lower part of the furnace, and tried to remove the moisture in the carbonaceous material.

  In order to remove moisture from the carbonaceous material, it is necessary to heat the carbonaceous material. Will decline. In addition, if the volatile components are volatilized during the heating of the pulverized coal, there is a danger in handling the pulverized coal.

  In order to avoid this danger, a method of rapidly heating the carbonaceous material to a high temperature immediately before blowing may be considered, but the moisture in the carbonaceous material cannot be sufficiently reduced.

  Therefore, in order to remove or reduce the moisture in the carbonaceous material, it is necessary to preheat the carbonaceous material for a predetermined time at a temperature equal to or higher than the temperature at which the moisture vaporizes and below the temperature at which volatile components start to volatilize from the carbonaceous material. is there.

  The temperature at which the volatile matter starts to volatilize from the charcoal varies depending on the brand and type of the charcoal, so it cannot be specified at a specific temperature, but if it is 200 ° C or less, the combustible volatile matter is It hardly volatilizes.

  The inventor experimentally investigated the relationship between the degree of reduction of the coke ratio and the preheating temperature by changing the heating temperature of the pulverized coal at a temperature range of 200 ° C. or less and blowing it from the tuyere. The result is shown in FIG. From the figure, it is understood that when the pulverized coal is heated to a low temperature range of 100 to 200 ° C., the coke ratio can be greatly reduced by 10 to 16 Kg / t.

  Since the preheating temperature of 100 to 200 ° C. is lower than the pulverized coal heating temperature of Patent Document 1, it is difficult to think that the flammability of pulverized coal has been further improved by preheating, so a significant reduction in the coke ratio is 100 to 200 ° C. This is probably because the moisture causing the endothermic reaction was removed or sufficiently reduced by the low-temperature preheating at.

  Furthermore, by blowing pulverized coal from which moisture has been removed or sufficiently reduced, the sensible heat of the pulverized coal is brought to the furnace core, and the amount of heat input to the lower part of the furnace has increased. Contributes to a significant reduction in

  Thus, the present inventors have found that the coke ratio can be significantly reduced by increasing the amount of heat input to the lower part of the furnace substantially by low-temperature preheating of the pulverized coal.

  In the above preheating, pulverized coal was preheated to a temperature of 200 ° C. or lower (a temperature at which volatile components do not volatilize). However, in preheating, volatilization of volatile components must be avoided from the viewpoint of maintaining combustibility and preventing danger. Therefore, the upper limit of the preheating temperature is set to be lower than the temperature at which the volatile components start to volatilize.

  As described above, the temperature at which the volatile component starts to volatilize differs depending on the brand and type, and thus cannot be specified as a specific temperature.

The lower limit of the preheating temperature, in order to remove or sufficiently reduce the efficiency better moisture, moisture in the carbonaceous material is to 100 ° C. or higher to evaporate.

  According to the present invention, water in pulverized coal can be removed or sufficiently reduced, so that the amount of heat input to the lower part of the furnace can be increased without changing the actual gas volume at the lower part of the furnace. As a result, the substitution rate between pulverized coal and coke can be increased.

  The preheating of the charcoal material blown from the tuyere is not limited to a specific preheating method or preheating means, but is performed by heating the charcoal carrier air or nitrogen that feeds the charcoal to the tuyere to the required temperature, or It is preferable to use a heating device arranged in the carbonaceous material transport line immediately before the mouth in that the current blast furnace equipment can be used.

  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 1
In a blast furnace with an internal volume of 4800 m ³ , operation was initially performed at a coke ratio of 340 kg / t and a pulverized coal ratio of 155 kg / t. The blowing temperature of pulverized coal was 50 ° C. Although the pulverized coal contained 2% of moisture, the carrier air was heated to preheat the pulverized coal to 150 ° C.

  As a result, the water content in the pulverized coal decreased to 0.5%, and the coke ratio could be reduced by 9 kg / t while stably maintaining the hot metal temperature of 1525 ° C.

(Example 2)
In a blast furnace with an internal volume of 4800 m ³ , operation was initially performed at a coke ratio of 340 kg / t and a pulverized coal ratio of 155 kg / t. The blowing temperature of pulverized coal was 50 ° C. Although the pulverized coal contained 2% of water, a heater was installed in the pulverized coal conveyance line after the distributor to preheat the pulverized coal to 200 ° C.

  As a result, there was no water in the pulverized coal, and the coke ratio could be reduced by 14 kg / t while stably maintaining the hot metal temperature of 1525 ° C.

  According to the present invention, as described above, pulverized coal with reduced water content can be blown up to the furnace core, so that a substantial furnace can be obtained by suppressing endothermic reaction caused by moisture and sensible heat brought in by pulverized coal. The amount of heat input to the lower part can be increased. Therefore, according to the present invention, since the hot metal can be stably brewed at a predetermined temperature, the brewing ratio is high and the applicability is high in blast furnace operation.

It is a figure which shows the relationship between pulverized coal preheating temperature and reduction of coke ratio.

Claims (5)

In the blast furnace operation method in which the carbon material is blown from the tuyere, the carbon material is preheated to a temperature equal to or higher than the temperature at which moisture in the carbon material evaporates and below the temperature at which the volatile matter in the carbon material starts to volatilize, and the moisture in the carbon material is reduced. Carbonaceous material preheating blow-in blast furnace operation method characterized by being 0.5% or less and blowing from the tuyere. The temperature at which moisture in the carbonaceous material vaporizes is 100 ° C, and the temperature at which the volatile matter in the carbonaceous material starts to volatilize is 200 ° C. Method. The carbonaceous material preheating blowing blast furnace operating method according to any one of claims 1 to 2 , wherein the carbonaceous material is preheated in heated carbonaceous material conveying air or nitrogen. The carbonaceous material preheating blow-in blast furnace operating method according to any one of claims 1 to 2 , wherein the carbonaceous material is preheated by a heating device disposed in a carbonaceous material conveyance line immediately before the tuyere. The said carbonaceous material is pulverized coal, The carbonaceous material preheating blowing blast furnace operating method of any one of Claims 1-4 characterized by the above-mentioned.

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