JP3701550B2 - Auxiliary fuel injection operation method - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
TECHNICAL FIELD The present invention relates to a technique in which, for example, a vertical metallurgical furnace such as a blast furnace is blown through a tuyere as pulverized coal as main auxiliary fuel and various plastic (waste synthetic resin) particles discarded as auxiliary fuel. Specifically, the present invention relates to an auxiliary fuel injection operation method in which operation is performed while maintaining the optimum combined condition of pulverized coal and waste synthetic resin particles.
[0002]
[Prior art]
In recent years, from the viewpoint of environmental protection, treatment of waste synthetic resin discharged in large quantities has been regarded as a problem. From this point of view, a processing method in which waste synthetic resin is recycled and used as an auxiliary fuel for metallurgical furnaces such as blast furnaces, coke ovens, boilers, cement kilns, and the like is in the spotlight.
[0003]
As a utilization method in a blast furnace, for example, a technique of blowing into a furnace through a tuyere like pulverized coal has been proposed, and has been put into practical use in some blast furnaces. Since waste synthetic resin is mainly composed of hydrocarbons, when it is blown into the furnace from the tuyere, it burns in high-temperature air and becomes a heat source and generates reducing gases such as high-temperature CO and H _2. The metal oxide charged from the top of the furnace is quickly heated, reduced and melted.
[0004]
For example, in Japanese Patent Application Laid-Open No. 8-178254, as shown in FIG. 3, a combustible material such as waste plastic, waste tire, municipal waste, sludge, coal, or a mixture 101 is placed inside a combustion furnace 102 including a blast furnace with a screw feeder. An apparatus and a method are described in which stable combustion can be ensured by supplying hot air 105 supplied from the tuyere 104 through the tuyere 104 via the hot air 105 and being sent outside the screw feeder 103.
[0005]
In addition, in order to increase the amount of pulverized coal that has been conventionally used as the main auxiliary fuel and to achieve stable injection, 5 to 15 weight of waste plastic having a maximum particle size of 1.0 mm is added to coarse coal. A technique of using a mixture of 2% is reported (Japanese Patent Laid-Open No. 7-278621).
[0006]
[Problems to be solved by the invention]
By the way, the following two problems are assumed when pulverized coal and waste synthetic resin particles are used in combination.
[0007]
The first problem is the difference in fuel characteristics, which is due to the fact that ordinary waste synthetic resin granules are overwhelmingly coarse compared to pulverized coal. The latter is practically reduced to a size of several millimeters at most even though it undergoes a plurality of crushing and grinding processes. Therefore, since the optimum conditions for air-conveying them to the tuyere are naturally different, the waste synthetic resin granules and the pulverized coal are blown from the dedicated tuyere through different paths, but the resin granules The oxygen consumption rate in the hot air when the body is blown into the furnace from the dedicated tuyere and heated is different from that of pulverized coal. That is, the size of the raceway combustion zone near the tuyere, the stability, and the coke flow speed at the top of the raceway vary greatly between the dedicated tuyere.
[0008]
The second problem is the difference in the amount of processing, which is accompanied by equipment factors that ensure a circumferential balance in a normal large blast furnace and inject pulverized coal from multiple tuyere. By doing so, the load in the furnace interior is lowered and the circumferential balance of the gas flow is maintained in a healthy manner. However, if waste synthetic resin granules and pulverized coal having different combustion characteristics are blown from their dedicated tuyere, there is a concern that the circumferential balance of the blast furnace will be adversely affected for the reasons described above. On the other hand, as described in JP-A-7-278621, when waste synthetic resin granules are mixed with coal, they are pulverized to the extent that they do not affect the transportability of pulverized coal, or blow pipes and tuyere It is not realistic because it requires major equipment modifications to modify the structure itself.
[0009]
Therefore, there is an operation method that can follow the conventional pulverized coal injection operation, and also stably use the conventional injection tuyere and injection equipment to inject waste synthetic resin particles into the furnace stably. It should be explored and there was room for improvement in this regard.
[0010]
The present invention has been made in view of the problems of the prior art as described above, and can follow conventional pulverized coal blowing operation, and also uses waste blowing peripheral equipment as it is, and waste synthetic resin granules. It is an object of the present invention to provide an auxiliary fuel injection operation method capable of performing the injection.
[0011]
[Means for Solving the Problems]
The auxiliary fuel injection operation method of the present invention is an auxiliary fuel injection operation method in which pulverized coal and waste synthetic resin particles are injected as auxiliary fuel into the furnace through respective dedicated tuyere, and the furnace operation is performed. , The average pulverized coal ratio of the pulverized coal injection tuyere is PCR [kg / tp], the average waste synthetic resin particle blasting ratio of the waste synthetic resin particle blowing tuyere is PLR [kg / tp], When the calorific value is Qpc and the calorific value of the waste synthetic resin particles is Qpl, the waste synthetic resin particles are injected under the following conditions.
[0012]
PLR = PCR × (Qpc / Qpl) × A
However, in the method of the present invention, A = 0.7 or more and 1.2 or less, because the operating conditions in the waste synthetic resin granule blowing tuyere with respect to the operating conditions in the pulverized coal blowing tuyere are adjusted, The conventional pulverized coal injection operation can be followed, and the conventional peripheral equipment can be used as it is, and it is possible to suitably maintain the circumferential balance of the in-furnace situation, for example, the unloading behavior in the blast furnace Become.
[0013]
Here, the average pulverized coal ratio (PCR) of the pulverized coal injection tuyere means the average value of the weight of the pulverized coal injected when producing 1 ton of pig iron at the pulverized coal injection tuyere. The average waste synthetic resin particle injection ratio (PLR) of the resin particle blowing tuyere is the weight of the waste synthetic resin particle blowing when producing 1 ton of pig iron. Say the average value.
[0014]
However, when operating in the range of A = 0.7 or more and 1.0 or less (when the amount of waste synthetic resin granules blown is relatively small), the number of waste synthetic resin granules blown tuyere is the total number of tuyere It is preferable to make it 20% or less. This is because if it exceeds 20%, the amount of heat in the vicinity of the waste synthetic resin granule blowing tuyere tends to be insufficient, and the unloading circumferential balance in the furnace is lost.
[0015]
In the auxiliary fuel injection operation method of the present invention, the appropriate particle size range of the waste synthetic resin granules for the operation conditions having different average pulverized coal ratios is that of the waste synthetic resin granules when the average pulverized coal ratio is less than 180 kg / tp. When the average particle diameter is smaller than 5 mm and the average pulverized coal ratio is in the range of 180 kg / tp to 230 kg / tp, the average particle diameter of the waste synthetic resin granules is set to 5 mm to 9 mm, and the average pulverized coal ratio is 230 kg / tp. When it is larger, the average particle diameter of the waste synthetic resin granules is made larger than 9 mm. In other words, it means that it is allowed to enlarge the waste synthetic resin granules as the average pulverized coal ratio increases.
[0016]
If it does in this way, it will become possible to maintain suitably the situation inside a furnace, for example, the circumference balance of the gas flow position in a furnace in a blast furnace.
[0017]
DETAILED DESCRIPTION OF THE INVENTION
The present inventors obtained the following first knowledge through the operation of blowing into the actual blast furnace.
[0018]
Hot air, enriched oxygen, and auxiliary fuel are supplied from a number of tuyere into the blast furnace while maintaining a balance in the circumferential direction at the bottom of the furnace. At this time, if the coke flow speed to the raceway before the tuyere is different for each tuyere, the oxygen consumption rate of the auxiliary fuel competing with the coke in the raceway will greatly deviate in the circumferential direction. There is a strong possibility that the material will drop abnormally, such as slips and shelves in the raw material charge, and that the unloading will become uneven and that the furnace condition will deteriorate.
[0019]
Therefore, the present inventors have not yet fully understood the consumption mechanism of the waste synthetic resin particles in the vicinity of the tuyere. Focusing on the lower gas flow behavior, we searched the operating range to maintain the circumferential balance appropriately.
[0020]
Specifically, the following examination was conducted. The waste synthetic resin granules are estimated to have a longer residence time in the raceway than pulverized coal, but the consumption efficiency in the actual furnace cannot be generally compared only with the particle size. Therefore, only waste synthetic resin particles are supplied to a specific tuyere and only pulverized coal is fed to the remaining tuyere, and the descending behavior near each tuyere of the raw material charged from the top of the furnace is investigated, Separately, the descending behavior of the raw material charge in the vicinity of all tuyere during normal operation where only pulverized coal was supplied from all tuyere was compared. At this time, the waste synthetic resin granule blowing conditions are as follows: the average pulverized coal ratio of the pulverized coal blowing tuyere is PCR [kg / tp], and the average waste synthetic resin granule of the spent synthetic resin granulated blowing tuyere. When the blowing ratio is PLR [kg / tp], the calorific value of pulverized coal is Qpc [kcal / kg], and the calorific value of the waste synthetic resin particles is Qpl [kcal / kg], the following (1) regarding the calorific value The coefficient A in the equation is changed.
[0021]
PLR = PCR × (Qpc / Qpl) × A (1)
The waste synthetic resin granules are produced by crushing or by melt granulation for cutting the rod-shaped resin extruded by an extruder or the like.
[0022]
FIG. 1 shows the obtained results. When the coefficient A is changed, the waste synthetic resin particles are blown with respect to the circumferential deviation of the descending speed of the raw material charge during normal operation (only pulverized coal is blown). It is a graph which shows the ratio of the circumferential direction deviation of the descent | fall speed of a raw material charge at the time of pouring (pulverized coal and waste synthetic resin granule blowing). The vertical axis represents the ratio of the circumferential speed deviation of the descending speed, and the horizontal axis represents the coefficient A.
[0023]
As can be understood from FIG. 1, when the waste synthetic resin particles are blown, the furnace operation similar to that during normal operation is possible by setting the coefficient A in the range of 0.7 to 1.2. become.
[0024]
The reason why the coefficient A is in the range of 0.7 or more and 1.2 or less is that there is little waste synthetic resin granules under the condition that the coefficient A is smaller than 0.7, so that the oxygen blown in the vicinity of the tuyere becomes redundant. As a result of burning a large amount of coke above it, the amount of coke flowing into the waste synthetic resin particle blowing tuyere becomes larger than the average value of the amount of coke flowing (unloading amount) at the pulverized coal blowing tuyere. On the other hand, when the charge lowering balance is lost and the coefficient A is larger than 1.2, the amount of waste synthetic resin particles staying in the raceway is increased. This is because the coke flow speed at the waste synthetic resin granule blowing tuyere is smaller than the coke flow speed of the coke, and the coke stagnation and the circumferential balance deteriorates.
[0025]
Therefore, based on the 1st knowledge demonstrated above, when implementing this invention in a real blast furnace, since the operation conditions in the waste synthetic resin granule injection tuyere with respect to the operation conditions in a pulverized coal injection tuyere are adjusted, In addition, the conventional pulverized coal injection operation can be followed, and waste synthetic resin particles can be injected using the conventional peripheral equipment as it is, and the coke flow velocity (load) in the furnace It is possible to favorably maintain the circumferential balance of the descending behavior.
[0026]
However, in the auxiliary fuel injection operation method of the present invention, when the coefficient A is operated in the range of 0.7 to 1.0, the amount of heat near the waste synthetic resin particle injection tuyere may be insufficient. Therefore, since the circumferential balance of the coke flow speed in the furnace may be lost, it is preferable that the number of waste synthetic resin particles blown tuyere is 20% or less of the total tuyere.
[0027]
In the above description, the range of the coefficient A at the time of blowing the waste synthetic resin granules is defined as 0.7 or more and 1.2 or less, but it may be set within the range of 0.9 or more and 1.1 or less. preferable. In this case, the circumferential balance of the coke flow speed in the furnace can be adjusted with higher accuracy.
[0028]
Furthermore, the present inventors made the following study and obtained a second finding.
[0029]
Generally, when the ratio of pulverized coal increases, the position where oxygen is completely consumed at the tuyere tip is close to the furnace wall. Similarly, the position showing the maximum gas temperature in the raceway also tends to approach the furnace wall, which increases the heat load on the furnace body. Therefore, severe control of the furnace bottom gas flow must be implemented. In other words, with regard to waste synthetic resin granule injection tuyere, combustibility management according to the pulverized coal ratio level was introduced to balance the oxygen consumption behavior on the raceway with pulverized coal injection tuyere as much as possible. It is necessary to do.
[0030]
Therefore, the present inventors have three levels with different pulverized coal ratios, when the pulverized coal ratio is smaller than 180 kg / tp, when the pulverized coal ratio is 180 kg / tp or more and 230 kg / tp or less, and when the pulverized coal ratio is 230 kg / tp. For the larger case, various changes were made to the average particle size of the waste synthetic resin granules, and the change in the circumferential balance of the gas flow in the lower part of the furnace was investigated. At this time, the circumferential balance of the gas flow in the lower part of the furnace is obtained as the circumferential deviation of the brick temperature above the tuyere, and the circumferential deviation of the brick temperature during the waste synthetic resin granule blowing and the brick temperature during normal operation. Evaluation was made by comparing the circumferential deviation.
[0031]
FIG. 2 is a graph showing the ratio of the deviation in the circumferential direction of the furnace bottom brick temperature when the waste synthetic resin granule is blown to the circumferential deviation of the furnace bottom brick temperature during normal operation. . The vertical axis represents the ratio of the circumferential deviation of the furnace lower brick temperature, and the horizontal axis represents the average particle diameter [mm] of the waste synthetic resin granules. FIG. 2 (a) shows that when the pulverized coal ratio is smaller than 180 kg / tp, FIG. 2 (b) shows that when the pulverized coal ratio is 180 kg / tp or more and 230 kg / tp or less, (c) shows that the pulverized coal ratio is 230 kg / tp or less. It ’s a big time.
[0032]
As understood from FIG. 2, when the pulverized coal ratio is smaller than 180 kg / tp, the average particle diameter of the waste synthetic resin particles is preferably smaller than 5 mm. If the size is larger than this, the residence time of the waste synthetic resin particles in the raceway becomes long, and the coke flow to the raceway is stagnant compared to the pulverized coal tuyere.
[0033]
Moreover, when operating in the range of pulverized coal ratio of 180 kg / tp or more and 230 kg / tp or less, it is desirable to adjust the average particle diameter of the waste synthetic resin particles to 5 mm or more and 9 mm or less. When the average particle size is smaller than 5 mm, the oxygen consumption in the raceway in front of the waste synthetic resin particle blowing tuyere is smaller than that in the pulverized coal blowing tuyere, and therefore the coke flow down This is because if the speed becomes too high and exceeds 9 mm, the residence time in the raceway in front of the waste synthetic resin particle blow-in tuyere becomes excessive, and none of them can maintain the circumferential balance soundly.
[0034]
In addition, when used under ultra-large quantity blowing conditions where the pulverized coal ratio is greater than 230 kg / tp, it is preferable to maintain the average particle size of the waste synthetic resin granules larger than 9 mm. This is because, under conditions of 9 mm or less, it is difficult to achieve sufficient oxygen consumption with the waste synthetic resin particle blow-in tuyere against the pulverized coal blow-in tuyere.
[0035]
Therefore, based on the first knowledge and the second knowledge described above, when the present invention is implemented in an actual blast furnace, the circumferential balance of the furnace temperature is preferably maintained, that is, the position where the furnace gas flows. It is possible to make the distance from the furnace wall uniform at each position in the circumferential direction.
[0036]
In the above description, the size of the blast furnace and the number of tuyere are not clearly stated, but the present invention can be applied regardless of the size of the blast furnace and the number of tuyere. is there.
[0037]
Further, although the above description does not clearly state the blow-in facility into the blast furnace, the present invention applies to any blow-in facility such as that shown in FIG. 3 and other blow-in facilities not shown. Can be applied to.
[0038]
Further, in the above description, the injection into the blast furnace is given as an example, but the present invention is not limited to the blast furnace, but other vertical furnaces such as vertical metallurgical furnaces, coke ovens, boilers, cement kilns, etc. Of course, it can also be applied to a vertical furnace.
[0039]
【The invention's effect】
As described above in detail, in the case of the present invention, since the operating conditions in the waste synthetic resin granule blowing tuyere with respect to the operating conditions in the pulverized coal blowing tuyere are adjusted, the conventional pulverized coal blowing operation is performed. In addition, waste synthetic resin granules can be blown using conventional blowing peripheral equipment as it is, and the circumferential balance of the in-furnace situation can be suitably maintained.
[Brief description of the drawings]
FIG. 1 shows waste synthetic resin particles with respect to the amount of deviation in the circumferential direction of the raw material charge descending speed during normal operation when the coefficient A of the operating conditions used in the auxiliary fuel injection operation method according to the present invention is changed. It is a graph which shows the ratio of the circumferential direction deviation | shift amount of the raw material charge fall speed | rate at the time of blowing.
FIG. 2 shows waste synthetic resin particles blown with respect to the circumferential deviation of the furnace bottom brick temperature during normal operation when the pulverized coal ratio of the operation conditions used in the auxiliary fuel injection operation method according to the present invention is changed. It is a graph which shows the ratio of the circumferential direction deviation amount of the furnace lower brick temperature at the time of pouring.
FIG. 3 is a front cross-sectional view showing the blowing equipment used in the prior art.
[Explanation of symbols]
101 Combustible material (mixture)
102 Combustion furnace 103 Screw feeder 104 Tuyere 105 Hot air

Claims (3)

Auxiliary fuel injection operation method in which pulverized coal and waste synthetic resin particles are injected into the furnace as auxiliary fuel through dedicated tuyere, respectively,
The average pulverized coal ratio of the pulverized coal injection tuyere is expressed as PCR [kg / tp (tp indicates hot metal ton. The same shall apply hereinafter)], the average waste synthetic resin particle injection ratio of the waste synthetic resin particle injection tuyere. When the PLR [kg / tp], the calorific value of the pulverized coal is Qpc, and the calorific value of the waste synthetic resin particles is Qpl, the auxiliary synthetic resin particles are injected under the following conditions. Fuel injection operation method.
PLR = PCR × (Qpc / Qpl) × A
However, A = 0.7 or more and 1.2 or less The auxiliary fuel according to claim 1, wherein when operating in the range of A = 0.7 or more and 1.0 or less, the number of waste synthetic resin particles blown tuyere is 20% or less of the total tuyere. Blow operation method. The appropriate particle size range of waste synthetic resin granules for operating conditions with different average pulverized coal ratio is
When the average pulverized coal ratio is smaller than 180 kg / tp, the average particle diameter of the waste synthetic resin granules is made smaller than 5 mm,
When the average pulverized coal ratio is in the range of 180 kg / tp or more and 230 kg / tp or less, the average particle diameter of the waste synthetic resin granules is 5 mm or more and 9 mm or less,
The auxiliary fuel injection operation method according to claim 1 or 2, wherein when the average pulverized coal ratio is larger than 230 kg / tp, the average particle diameter of the waste synthetic resin particles is larger than 9 mm.

Images