JP2007302916A - Method for recovering waste heat from tuyere in blast furnace, and tuyere for blowing air into blast furnace - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for recovering waste heat from a tuyere in a blast furnace, which recovers the waste heat caused by cooling the blast furnace to decrease energy to be consumed in a blast furnace operation, and thereby reduces the amount of carbon to be used, and to provide a tuyere for blowing air into a blast furnace, which is suitable for recovering the waste heat. <P>SOLUTION: The method for recovering the waste heat from the tuyere in the blast furnace comprises the steps of: cooling the tuyere by passing a fluid into a body of the tuyere of the blast furnace to heat fluid; and blowing the heated fluid into the blast furnace. The tuyere for blowing air into the blast furnace has a blowing passage inside the body, through which the fluid passes and then is blown into the blast furnace. The blowing passage is formed in a spiral shape. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an energy recovery method in a blast furnace, and relates to a method for recovering waste heat from a tuyere and a tuyere for blast furnace blowing.

In recent years, the reduction of carbon dioxide generation has been considered the most important issue in the steel industry because of global warming concerns. In particular, reduction of carbon usage in the blast furnace, where the largest amount of carbon (coal) is used as reduction energy and heat energy at the steelworks, is regarded as the most important. Since the blast furnace is a process for reducing and melting iron ore, which is Fe ₂ O ₃ , the energy required for pure reduction and melting is thermodynamically constant. In addition to this, energy input as carbon is reduced as oxides other than iron (metalloid reduction) and melting, melting of slag, calorie-containing gas discharged from the top of the furnace, and heat load (waste heat from cooling water). used. Such a blast furnace material, the flow of thermal energy, and the approximate temperature are schematically shown in FIG. In FIG. 1, coke (C), iron ore (Fe ₂ O ₃ ), and sintered ore (Fe ₂ O ₃ ) are charged from the upper part of the blast furnace 1, and hot air (1200 ° C.) from the tuyere 2 at the lower part of the furnace. O ₂ -containing gas) is injected. The calorie-containing gas 3 composed of CO and CO ₂ is 100 ° C., and the hot metal (Fe) and the slag 4 are 1500 ° C. Reference numeral 5 denotes a combustion focus, which is 2000 ° C. Furnace upper waste heat in furnace cooling is A, tuyere waste heat due to tuyere cooling is B, and furnace lower waste heat in furnace cooling is C.

Of these, metalloid reduction and slag melting are quantitatively fixed by the input raw material quality and cannot be controlled. In addition, the energy of the calorie-containing gas 3 from the top of the furnace is recovered and used as heat or electric power in the lower process in the factory, so it is not wasted and the reduction is operational for both the blast furnace and the lower process. The burden of is great. Therefore, in order to reduce the amount of energy used in the blast furnace, it is considered most preferable to recover the waste heat A, B, and C. Cooling of the furnace body and tuyere is performed using cooling water (for example, refer to Patent Document 1). Therefore, in order to recover waste heat A, B, and C, heat recovery is performed from the cooled drainage after cooling.
Japanese Patent No. 3151803

  The blast furnace is a huge high-temperature reaction vessel, and in the lower part where hot air is blown in, there are places where the temperature exceeds 2000 ° C., and it is essential to protect the equipment by cooling. Steam recovery is common for high-temperature waste heat, and it can also be recovered as electricity using a steam turbine, but the blast furnace cooling water is a low-temperature wastewater of tens of degrees Celsius, although the amount of water is abundant. Recovery by these means is not possible at present. Research is also progressing on the method for recovering low-temperature exhaust heat, but the feasibility is low at steelworks due to problems such as cost and space.

  Therefore, the object of the present invention is to solve such problems of the prior art, recover waste heat used for cooling the blast furnace, and reduce the energy consumed in blast furnace operation, thereby reducing the amount of carbon used. It is an object of the present invention to provide a method for recovering waste heat from tuyere in a blast furnace and a tuyere for blast furnace blowing suitable for use in waste heat recovery.

  The present inventors have found that most of the waste heat of the blast furnace is due to tuyere cooling, studied heat recovery methods at the tuyere, let the fluid pass inside the main body of the tuyere of the blast furnace, A method of recovering waste heat from a tuyere in a blast furnace, wherein the tuyere is cooled by raising the temperature and heat recovery is performed by blowing the heated fluid into the blast furnace, and a fluid The present invention of a tuyere for blast furnace blowing characterized in that it has a blowing passage for blowing into the blast furnace after passing through the inside of the main body, and the blowing passage is formed in a spiral shape.

  According to the present invention, energy saving in a blast furnace is possible, and the amount of carbon dioxide generated can be reduced.

The furnace body of the blast furnace consists of refractories, bricks, cooling equipment (stave) from the inside, and the inner wall is formed with a deposit layer mainly composed of coke powder and zinc. Waste heat via circulating water is small for its large area. On the other hand, although the tuyere is small in area, it is near the combustion focal point (about 2000 ° C.) and is exposed to high temperatures. As measured by a 4000 m ³ class blast furnace by the present inventors, as shown in FIG. 2, the furnace body upper waste heat A is 34%, the furnace body lower waste heat C is 21%, and the waste heat from the tuyere It was found that B reached 45% of the total waste heat and nearly half of the waste heat was generated at the tuyere.

  The higher the temperature of the target, the higher the heat recovery efficiency. In this sense, it is presumed that the tuyere is a promising heat recovery target. The tuyere is regarded as a high-grade consumable and is made of copper casting for durability, with cooling water circulating at an ultra-high speed inside. Therefore, the present inventors reviewed the tuyere cooling facility, which has traditionally focused on durability, as a heat recovery source, and developed it with the goal of efficiently recovering heat.

  As described above, normal tuyere cooling is performed using water. A chemical solution may be used to prevent corrosion, but the main component is water. Since the boiling point of water at atmospheric pressure is 100 ° C., it is necessary to circulate a large amount of cooling water so that the temperature is sufficiently lower than that, for example, about 60 ° C. on the outlet side. This is because if the cooling water boils in the tuyere and bubbles are generated, both the specific heat and the thermal conductivity are rapidly reduced, and the tuyere melts rapidly. However, it is difficult to recover heat unless the waste water is hot.

  Therefore, the present inventors considered that it is possible to reduce waste heat by returning the thermal energy of the tuyere to the inside of the furnace instead of discharging it outside the furnace. In normal blast furnace operation, reducing materials such as pulverized coal are blown from the tuyere. The reducing material is not normally preheated, and is blown into the space at the center of the tuyere through a pipe called a blowing lance and blown into the furnace together with hot air (a temperature similar to the copper melting point of 1083 ° C.). The inventors raise the temperature of the reducing material through the inside of the tuyere body, thereby cooling the tuyere, and blowing the heated reducing material into the blast furnace to simultaneously cool the tuyere. We found that preheating of the reducing material is possible. In other words, if the tuyere is cooled by exchanging heat with the material blown into the furnace, the waste heat from the tuyere is recovered and used in the blast furnace, and as a result, it is possible to reduce the waste heat. The title and the present invention have been completed. That is, the present invention relates to a blast furnace in which a fluid is allowed to pass through the body of the tuyere of the blast furnace, the tuyere is cooled by raising the temperature of the fluid, and the heated fluid is blown into the blast furnace. This is a method for recovering waste heat from the mouth.

  A fluid is used as the material to be blown into the furnace after cooling the tuyere. It is preferable to use a reducing material that is normally blown into the furnace from the tuyere of the blast furnace as the blowing fluid. As the reducing material, in addition to liquid and gaseous reducing materials such as heavy oil, LNG, coke oven by-product gas (COG), etc., solid reducing materials can also be suitably used. The pulverized coal, plastic particulates, etc., which are solid reducing materials, are blown into the blast furnace as a fluid by using nitrogen or the like as a carrier gas. It is preferable to use water cooling in combination for cooling the tuyere. In this case, the water is discharged after being circulated through the tuyere as normal cooling water without being blown into the furnace.

  Next, a tuyere suitable for use in the implementation of the method for recovering waste heat from the tuyere in the blast furnace will be described.

  When carrying out the method of the present invention, for example, a blast furnace blower characterized in that it has a blow passage in the body for allowing the fluid to pass through and then blows into the blast furnace, and the blow passage is formed in a spiral shape. A tuyere can be used.

  When the fluid is passed through the tuyere body to raise the temperature and the heated fluid is blown into the blast furnace, the tuyere body has a blowing passage that is a hole penetrating between the inside of the furnace and the outside of the furnace, When using a tuyere in which the blowing passage forms a coil shape with the space part (hot air blowing part) at the center of the tuyere as a core, the fluid turns spirally inside the tuyere body, and then the blast furnace Will be blown into. In order to maintain a predetermined blowing speed and to ensure a sufficient time for heat exchange between the fluid and the tuyere, it is preferable that the blowing passage is long, and for this purpose, the blowing passage is made spiral as described above. It is appropriate to do.

  A reducing material blowing test was conducted using the tuyere shown in FIG. FIG. 3 is a schematic view of the cross section of the tuyere in a direction parallel to the blowing direction, and a blowing passage 7 that spirally turns inside the main body 6 of the tuyere 2 is formed. 8 is a cooling water channel, and 9 is a lance for blowing the reducing material into the tuyere.

  Heavy oil, LNG, and COG were used as reducing materials, respectively. For comparison, a reducing material blowing test using a conventional lance was also performed.

  The blowing test was performed using a combustion furnace that can simulate the vicinity of the tuyere of the blast furnace. A schematic diagram of the combustion furnace is shown in FIG. Coke was charged into the furnace through a coke charging hole 11 at the top of the combustion furnace 10 to form a coke packed bed 12. Hot air at 1200 ° C. was blown from the blow pipe 13 connected to the tuyere 2, and the exhaust gas was discharged from the exhaust gas outlet hole 14. Cooling water was allowed to flow through the cooling water passage 8 formed inside the tuyere body, and heavy oil, LNG, and COG were blown into the tuyere main body from the blowing passage entrance side 7a and into the combustion furnace from the blowing passage exit side 7b. . In addition, heavy oil, LNG, and COG are blown directly into the center of the tuyere through the lance 9 and burned together with hot air so that the amount blown into the combustion furnace per unit time is the same as when using the blowing passage. It was blown into the furnace.

  When the reducing material was blown into the combustion furnace through the lance, the temperature difference between the inlet side and the outlet side of the tuyere cooling water was 12.2 ° C. Was blown into the combustion furnace, the temperature difference between the inlet side and the outlet side of the tuyere cooling water decreased to 10.5 ° C.

  The decrease in the temperature rise of the cooling water indicates that a part of the heat that should have become waste heat from the tuyere was effectively used for preheating the reducing material. It decreased by 14%.

  Although FIG. 3 shows an example in which the blowing passage 7 is provided on the outer cylinder side of the tuyere 2, it may be on the inner cylinder side.

Schematic of the flow of blast furnace material and thermal energy. The graph which shows the example of the waste heat in a blast furnace. The schematic of the cross section of a tuyere which is one Embodiment of this invention. The schematic diagram of a testing apparatus.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Blast furnace 2 tuyere 3 Calorie containing gas 4 Hot metal, slag 5 Combustion focus 6 Main body 7 Blowing passage 8 Cooling water passage 9 Reducing material blowing lance 10 Combustion furnace 11 Coke charging hole 12 Coke filling layer 13 Blow pipe 14 Exhaust gas outlet A Furnace upper waste heat B Feather waste heat C Furnace lower waste heat

Claims (2)

  From the tuyere in the blast furnace, the fluid is passed through the main body of the tuyere of the blast furnace, the tuyere is cooled by raising the temperature of the fluid, and the heated fluid is blown into the blast furnace Waste heat recovery method.   A blast furnace blower tuyere having a blow passage for blowing into a blast furnace after passing a fluid inside the main body, wherein the blow passage is formed in a spiral shape.

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