JP5724659B2 - Apparatus and method for injecting reducing material into blast furnace - Google Patents

Description

  The present invention relates to an apparatus and method for injecting a reducing material into a blast furnace, and more particularly to an apparatus and method for injecting a reducing material into a blast furnace in a stable and reliable manner while preventing a backflow to an injection lance.

In general, in recent blast furnaces, gas reducing materials such as city gas (LNG) are often injected into the furnace as a means to achieve high output ratio and low coke ratio operation. At the same time, blowing of a solid (powdered) reducing material such as pulverized coal is often performed. The blowing of these reducing materials is important not only from the operational advantage as described above, but also from the viewpoint of reducing the burden on the global environment due to the effect of suppressing the generation of CO ₂ .

  In general, the reducing material is injected into the blast furnace as shown in FIG. 1 (a), an overall view of the blast furnace, FIG. 1 (b), a partially enlarged view of FIG. 1 (a), and FIG. As shown in FIG. 2, the reduction material is blown into the blow pipe 4 attached to the furnace wall 2 of the blast furnace 1 from a blow lance (hereinafter also simply referred to as “lance”) 10. . The blow pipe 4 is directly connected to the tuyere 5 and is a pipe through which high-temperature high-speed air supplied from a hot stove (not shown) via the annular pipe 3 flows. Since the injection of the reducing material is achieved in relation to the pressure in the furnace, operational troubles due to insufficient pressure, etc., abnormal combustion due to backflow of high-temperature high-speed air into the lance 10, etc. Careful consideration should be given to avoiding the danger phenomenon.

  Therefore, in order to stably and reliably blow the reducing material into the blast furnace, techniques described in Patent Documents 1 and 2 have been disclosed so far.

JP 2006-241585 A JP 2006-274341 A

  However, as a result of investigations by the present inventors, it has been found that the techniques described in Patent Documents 1 and 2 have the following problems.

  Patent Document 1 basically describes the arrangement of the lance, but hardly mentions the reducing material supply pressure, the flow rate, and the like, which are the preconditions for blowing in, and the pressure in the furnace in the range of normal operation. Even if the operation status changes, the lance arrangement is not necessarily optimal.

  Patent Document 2 describes maintaining the predetermined blowing pressure of the reducing gas with respect to the pressure in the furnace, the contents of implementation when the blowing pressure falls below a predetermined value, and the like. It is coping therapy because there is no mention of how to eliminate the cause of the declining situation. In addition, if the lance is blocked for some reason, it may be detected that the blowing pressure exceeds a predetermined value even though the blowing is actually impossible. I can't handle anything.

  The present invention has been made in view of the circumstances as described above, and when the reducing material is blown into the blast furnace, the high-speed high-speed air backflow to the blowing lance is accurately prevented, and the blast furnace is stable. It is an object of the present invention to provide a reducing material blowing apparatus and method that can reliably blow the reducing material.

  As a result of various studies to solve the above problems, the present inventors have obtained the following knowledge.

  That is, first, as a precondition for the reducing material to be blown from the lance into the furnace without backflow of the high-temperature high-speed air, it is necessary to always satisfy the relationship of “lance tip pressure> furnace pressure”. In addition, in order to accurately prevent the backflow of the high-temperature high-speed air to the lance, a throttling mechanism may be provided in the lance itself or a piping system upstream of the lance. Furthermore, the reducing material may be blown continuously instead of intermittently. In addition, the number of lances into which the reducing material is blown may be increased or decreased according to the supply amount of the reducing material.

  The present invention is based on the above findings and has the following characteristics.

  [1] An apparatus for blowing a reducing material into a blow pipe of a blast furnace, wherein the blowing lance itself or a piping system upstream of the lance includes a throttle mechanism.

  [2] The reducing material blowing device into the blast furnace according to [1], wherein the reducing material is continuously blown.

  [3] The above [1] or [2], wherein the number of lances into which the reducing material is blown is increased or decreased in accordance with the supply amount of the reducing material so that the lance tip pressure becomes larger than the furnace pressure. Equipment for injecting reducing material into the blast furnace.

  [4] A method for injecting a reducing material into a blow pipe of a blast furnace, wherein a reducing mechanism is provided in the injecting lance itself or a piping system upstream of the lance.

  [5] The method of injecting the reducing material into the blast furnace according to [4], wherein the reducing material is continuously injected.

  [6] The above-mentioned [4] or [5], wherein the number of lances into which the reducing material is blown is increased or decreased according to the supply amount of the reducing material so that the lance tip pressure becomes larger than the furnace pressure. Of reducing material into the blast furnace.

  In the present invention, the backflow to the lance can be accurately prevented, and the reducing material can be stably and reliably injected into the blast furnace. As a result, the furnace condition becomes more stable. In addition, since the frequency of troubles related to lances is greatly reduced, there are also merits of avoiding a blast furnace wind-down, that is, a reduction in the amount of dredging due to the occurrence of trouble, and reducing repair costs for damaged parts.

It is a figure explaining the part to which this invention relates in a blast furnace installation. It is a figure explaining the difference of the blowing lance used by one Embodiment of this invention, and the conventional blowing lance. In one Embodiment of this invention, it is a figure explaining the installation location of the flow regulating valve of a reducing material. It is a figure explaining the Example of this invention.

  An embodiment of the present invention will be described with reference to the drawings.

  As shown in FIG. 1, in general, in a blast furnace 1, hot air supplied from a hot stove via an annular pipe 3 is arranged in a tuyere evenly arranged on the circumference of the lower part of the furnace body through a blow pipe 4. 5 is blown into the furnace. Also in the present invention, the reducing material is supplied into the furnace through the lance 10 inserted into the blow pipe 4.

In a blast furnace, raw materials are basically charged from the top of the furnace, and hot air and a reducing material are supplied from the bottom. The raw material is finally discharged from the hearth as molten iron, and the high-temperature air and the reducing material are finally discharged from the top of the furnace as blast furnace gas. The inside of the furnace is roughly a packed bed with ore and coke stacked alternately (however, there is no clear layer at the bottom of the furnace because the layers are fused), and a stable furnace One of the operation parameters for maintaining the internal state is the furnace pressure _PBF . In actual operation, since the state of the packed bed changes from moment to moment, the ventilation resistance of the packed bed also changes accordingly. As a result, the furnace pressure P _BF is
P _ave −ΔP ≦ P _BF ≦ P _ave + ΔP
It fluctuates in the range. Here, P _ave : furnace pressure average value, ΔP: half of the furnace pressure fluctuation range.

Therefore, first, the lance tip pressure P _L always need to satisfy the following relationship.
Lance tip pressure P _L > Furnace pressure P _BF

Because the fluid flows along the pressure gradient,
Lance tip pressure P _L <furnace pressure P _BF
This is because the high-temperature high-speed air may flow back into the lance and backfire in the reducing material supply piping system.

  In addition, in the present invention, by providing the lance 10 with a throttle mechanism, the backflow of the high-temperature high-speed air to the lance 10 is accurately prevented.

FIG. 2 shows a comparison between the blowing lance 10A used in the present invention and the conventional blowing lance 10Z. The conventional blowing lance 10Z shown in FIG. 2 (a) is a lance pipe 11 alone, but the blowing lance 10A used in the present invention shown in FIG. 2 (b) has a throttle mechanism 12 inside the lance pipe 11. I have. The throttle mechanism 12 may simply be a restricted orifice. In other words, the throttle mechanism (orifice) 12 has a pressure loss ΔP _o , and the downstream pressure becomes P _BF with respect to the upstream pressure P _BF + ΔP _o due to the installation of the orifice 12. As a result, the backflow from the downstream side to the upstream side of the orifice 12 does not occur as shown in FIG. As for the installation position of the orifice 12, the tip of the lance tube 11 is most desirable for the reasons described above. This is because the backflow into the lance tube 11 can be effectively suppressed.

  In the present invention, the throttle mechanism 12 is provided in the lance 10 itself, but the throttle mechanism 12 may be provided in the reducing material supply piping system upstream of the lance 10.

  In the present invention, the reducing material is blown continuously instead of intermittently. When the reducing material is blown intermittently, the pulverized coal flows back into the lance pipe 11 due to the pressure fluctuation in the blow pipe 4 at the moment when the blowing is stopped or while the blowing is stopped, and the frequency of occurrence of fusion is high. There is a possibility. This also applies to the possibility of increasing the frequency of malfunctions due to the backflow of reducing materials other than pulverized coal. Furthermore, since the reducing material is often at room temperature, and the lance cooling effect is often expected in the reducing material blowing itself, the lance cooling cannot be performed while the blowing is stopped, and the temperature of the lance tube 11 is increased. The temperature rises to about 1100 ° C., and the material deteriorates and melts down (in addition, when the reducing material blowing is stopped, an inert gas is often blown instead for cooling the lance). From this point of view, it is desirable that the reducing material be continuously blown.

  Moreover, although it is necessary to change the supply amount of a reducing material according to an operation condition, in this invention, the number of the lances blown in according to the supply amount is selectable.

In general, several tens of tuyere 5 are installed in the blast furnace 1 according to the inner volume, and the lance 10 is basically installed for each tuyere 5, that is, the blow pipe 4. When the reducing material supply amount decreases, if the reducing material is uniformly supplied to all of the tens of lances 10, the flow rate of each lance 10 becomes too small, and the furnace pressure _PBF fluctuates. May flow back into the lance tube 11.

Therefore, in order to avoid this, in the present invention, the reducing material is supplied only from the predetermined lance 10A in accordance with the reduction of the reducing material supply amount, and falls below the minimum flow rate per lance 10A. In other words, the lance tip pressure P _L is made larger than the furnace pressure P _BF . For this purpose, as shown in FIG. 3, a flow rate adjusting valve 24 is provided for each of several tens of lances 10A, or a flow rate adjusting valve 23 is provided for each group of several lances 10A. . In FIG. 3, reference numeral 21 denotes a reducing material supply pipe, and 22 denotes a ring pipe that serves as a header by collecting several lances 10A.

  In this way, in the present invention, since the lance 10A provided with the throttle mechanism (orifice) 12 is used in the lance pipe 11, the backflow to the lance pipe 11 is prevented, and the blast furnace is stably and reliably reduced. The material can be blown.

  Note that the present invention is not limited to the above-described embodiment, and various modifications can be made without departing from the scope of the invention.

  Examples of the present invention are shown below.

First, as a conventional example, a reducing material was injected using a conventional lance 10Z as shown in FIG. At that time, a manual flow rate adjusting valve was installed upstream of the lance 10Z. In addition, there is a timing when the lance tip pressure P _L <furnace pressure P _BF , the reducing material is blown intermittently (inert gas was blown during the stop), and the reducing material supply amount changes. In addition, the reducing material was blown from all the lances 10Z.

On the other hand, as an example of the present invention, a reducing material was injected using a lance 10A as shown in FIG. At that time, as shown in FIG. 4A and a partial enlarged view in FIG. 4B, the lance 10A group is divided into five groups using the ring pipe 22 as a header, and the reducing material upstream of the ring pipe 22 An automatic flow control valve 23 that can be operated from the blast furnace cab is installed in the supply pipe 21. Further, the relationship of lance tip pressure P _L > in-furnace pressure P _BF is always maintained, the reducing material is continuously blown, and when the reducing material supply amount is lower than a predetermined value, the automatic flow control valve 23 Thus, the specific lance 10A was automatically stopped. Otherwise, the operating conditions were the same as in the conventional example.

  As a result, in the example of the present invention, it was possible to prevent the occurrence of backflow accurately compared to the conventional example. As a result, it was able to greatly contribute to the stable operation of the blast furnace.

DESCRIPTION OF SYMBOLS 1 Blast furnace 2 Furnace wall 3 Annular pipe 4 Blow pipe 5 Tuyere 10 Blow lance 10A Blow lance 10Z Blow lance 11 Lance pipe 12 Throttle mechanism (orifice)
21 Reducing Material Supply Pipe 22 Ring Pipe 23 Flow Control Valve 24 Flow Control Valve

Claims (4)

An apparatus for continuously blowing a reducing material into a blow pipe attached to a plurality of blast furnaces,
The blower lance itself installed for each blow pipe or the piping system upstream of the lance has a throttle mechanism,
The relationship of lance tip pressure P _L > furnace pressure P _BF is always maintained,
When the reducing material supply amount decreases and falls below the minimum flow rate, a part of the plurality of lances is stopped, and the reducing material is blown into a lance other than the stopped lances. A reductant injection device for the blast furnace. 2. The blast furnace according to claim 1, wherein the number of lances into which the reducing material is blown is increased or decreased in accordance with a supply amount of the reducing material so that the lance tip pressure P _L becomes larger than the furnace pressure P _BF . Reducing material blowing device. A method in which a reducing material is continuously blown into a blow pipe attached to a plurality of blast furnaces,
A throttle mechanism is provided in the blowing lance itself installed in each blow pipe or the piping system upstream of the lance,
The relationship of lance tip pressure P _L > furnace pressure P _BF is always maintained,
When the reducing material supply amount decreases and falls below the minimum flow rate, a part of the plurality of lances is stopped, and the reducing material is blown into a lance other than the stopped lances. A method for injecting reducing material into the blast furnace. 4. The blast furnace according to claim 3, wherein the number of lances into which the reducing material is blown is increased or decreased according to the amount of the reducing material supplied so that the lance tip pressure P _L becomes larger than the furnace pressure P _BF . Reducing material blowing method.

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