WO2003020987A1

WO2003020987A1 - Method of treating steelmaking waste, and movable hearth furnace therefor

Info

Publication number: WO2003020987A1
Application number: PCT/JP2002/008885
Authority: WO
Inventors: Hiroshi Ichikawa; Yasushi Oba
Original assignee: Nippon Steel Corporation
Priority date: 2001-09-03
Filing date: 2002-09-02
Publication date: 2003-03-13
Also published as: JP2003147442A

Abstract

A treating method that, when recycling a steelmaking waste containing iron oxides, is capable of easily collecting zinc from a dust containing much volatile substance, such as chlorine, thus making it possible to recycle even a waste that has heretofore been considered to have no choice but to be discarded; and a movable hearth furnace therefor. A steelmaking waste charging device and a carbonaceous material charging device are separately installed in a movable hearth furnace, and a steelmaking waste and carbonaceous material are charged into the furnace, in which they are mixed, the mixture being reduced. It is preferable that the movable hearth furnace be provided with a first exhaust port between the steelmaking waste charging device and the carbonaceous material charging device so as to exhaust the volatile gas generated from the steelmaking waste, and that a second exhaust port be provided between the carbonaceous material charging device and the exhaust device so as to exhaust the gas generated from the mixture of steelmaking waste and carbonaceous material. Further, it is preferable that a mixer be installed behind the carbonaceous material charging device.

Description

Description Steelmaking waste treatment method and mobile hearth furnace therefor

TECHNICAL FIELD The present invention relates to a treatment method and equipment capable of reducing iron-manufacturing waste including iron oxide such as scale, sludge, and dust generated in a steel mill and the like, and reusing the waste as a steelmaking raw material and the like. Background art

In order to reduce and recycle steelmaking waste including iron oxide such as scale, sludge, and dust generated in steelworks and reuse it as steelmaking raw materials, etc., mix a solid reducing agent such as coats powder with these steelmaking wastes. It is known as a direct reduction method that a pelletized product is formed into an agglomerate and then charged into a reduction furnace for reduction treatment. A moving hearth furnace such as a rotary hearth furnace is used for the reduction treatment. In a rotary hearth furnace, the charged agglomerate is placed on the hearth, and the agglomerate is moved by rotating the hearth, while being heated by a panner arranged in the rotary hearth furnace. To reduce. As a method of reducing iron oxide using a rotary hearth furnace, Japanese Patent Application Laid-Open No. 5-125454 discloses a method in which a carbonaceous substance and a binder are added to waste generated in a steelmaking plant, mixed, and further mixed with water. A method is disclosed in which a wet mixture is formed into an agglomerate, which is dried in a rotary hearth furnace at 900 ° C for 15 minutes, and then reduced by heating at 1150 ° C for 20 to 30 minutes. I have.

JP-A-8-337827 discloses that a mixture containing an oxygen-bonded metal and a reducing agent is placed as a first layer on a rotary hearth furnace, and the hearth is rotated to produce a first layer by an oxidizing flame. The layer is heated, and a second layer of reducing agent is supplied and heated so as to cover the first layer, and the second layer is partially reduced in the furnace. A method is disclosed for preventing oxidation of a given mixture.

Japanese Patent Application Laid-Open No. 11-310832 discloses a method for separating and recovering iron, zinc and lead from waste oxide generated from a steelmaking plant by mixing dry waste oxide and sludge with carbon, iron, zinc, and the like. A mixture containing lead is formed, and fine coke is added to the mixture to have a total carbon content of 16 to 22% by weight to form an agglomerate, which exceeds 1093 ° C in a rotary hearth furnace It is disclosed that firing at a temperature reduces iron oxides and releases zinc and lead.

Also, Japanese Patent Application Laid-Open No. 10-287933 discloses a process of heating a zinc-containing dust alone under reduced pressure to obtain a dust mainly composed of iron oxide and zinc oxide, and mixing a reducing agent with the obtained dust. A method of reducing and evaporating zinc by heating under reduced pressure, and a method of cooling the generated steam zinc under vacuum to form metallic zinc.

Generally, steelmaking waste contains volatile substances such as Cl, Pb, Na, and K. Most of Pb, Na, and K are in the form of chlorides (PbCl ₂ , NaCl, KC1). Since these have a high saturated vapor pressure above 1000 ° C, they evaporate at a high rate when heated above 1000 ° C as shown in Figure 1.

Most of the Zn is contained in the dust in the form of oxide (ZnO). ZnO has a high boiling point and is difficult to volatilize as it is. However, when a reducing agent is mixed and heated and reduced, it becomes metallic zinc by the reaction of ZnO + C → Zn + C0, and its boiling point is 903 ° C, so it evaporates at 1000 ° C or higher.

Therefore, if the agglomerates obtained by kneading a reducing agent into steelmaking waste containing these volatile substances are charged into a rotary hearth furnace and reduced by heating, dust generated in the rotary hearth furnace is collected by a dust collector. According to the conventional method as described in JP-A-5-125454, JP-A-8-337827, and JP-A-11-301832, the dust collected in the collected dust is as described above. Contains volatile substances. For this reason, to recover zinc from dust, it is necessary to separate volatile substances from zinc, which requires enormous costs, so that the unit cost of zinc recycling rises and there is no recycling advantage. On the contrary, there is a problem that equipment costs increase due to recycling.

Therefore, in the past, it was not possible to reuse iron-making waste containing a small amount of volatile substances and recycle those containing a large amount of volatile substances such as chlorine.

On the other hand, in the method disclosed in Japanese Patent Application Laid-Open No. 10-287933, a step of heating a dust containing zinc alone to obtain a dust mainly composed of iron oxide and zinc oxide, and adding a reducing agent to the obtained dust. Mixing and heating under reduced pressure to reduce and evaporate zinc allows separation and recovery of zinc and other volatile substances (Cl, Pb, Na, K, etc.) .

However, in this method, the multi-stage hearth is fixed, and the dust-containing dust containing dust on the hearth is moved while stirring with a stirring arm. As a result, there was a problem that the purity of the recovered zinc decreased due to being transported to the metal recovery unit together with the exhaust gas and the metal zinc vapor.

In addition, since the stirring arm is exposed to the high-temperature atmosphere in the furnace, there is a problem that the stirring arm has high wear, high temperature corrosion, and large thermal distortion, and the life of the stirring arm is short. Water cooling of the stirring arm was also required, and there was a problem that the heat removal of the cooling water was large.

In addition, there was a problem that the structure was complicated due to the multi-stage furnace, and the equipment cost was high.

Accordingly, the problem to be solved by the present invention is to reduce and recycle iron-made waste by making it possible to easily recover zinc even from a dust containing a lot of volatile substances such as chlorine. Recycling of materials that had to be discarded in the past was realized. And Disclosure of the invention

The method of the present invention for solving the above-mentioned problems is directed to a method for treating steelmaking waste, in which ironmaking waste is charged into a moving hearth furnace and reduced, and discharged from a discharge device as a reduced product. The steelmaking waste charging device for charging steelmaking waste into the floor furnace and the carbon material charging device for charging carbonaceous material are separately installed, and the steelmaking waste and carbonaceous material are transferred to the moving hearth. This is a method for treating steelmaking waste, which is charged into a furnace.

In the above method of the present invention, a first exhaust port is provided between the steelmaking waste charging device and the carbonaceous material charging device, and volatile gas generated from the steelmaking waste is discharged from the first exhaust port. Is preferred.

In addition, it is preferable that a second exhaust port is provided between the carbon material charging device and the discharge device, and gas generated from the mixture of the steelmaking waste and the carbon material is discharged from the second exhaust port.

Further, the facility of the present invention for solving the above-mentioned problem is a moving hearth furnace for reducing charged steelmaking waste and discharging it as a reductant from a discharge device. An iron-making waste loading device for loading materials and a carbon material loading device for loading carbon materials are arranged at intervals in the moving direction of the moving floor. It is a processing facility.

In the above-mentioned facility of the present invention, it is preferable that a first exhaust port for discharging volatile gas generated from steelmaking waste is provided between the ironmaking waste charging device and the carbonaceous material charging device.

Further, it is preferable that a second exhaust port for discharging gas generated from a mixture of steelmaking waste and carbonaceous material is provided between the carbonaceous material charging device and the discharge device. Further, it is preferable to provide a mixing device for mixing the steelmaking waste and the carbonaceous material in the moving hearth furnace in front of the moving direction of the moving floor of the carbonaceous material charging device.

Furthermore, it is preferable to provide a reduction device for reducing the mixture of the steelmaking waste and the carbonaceous material in front of the moving floor of the mixing device in the moving direction.

Further, in any one of the carbon material charging device, the mixing device, and the pressing device, or two or more of them, a ceiling of a portion where these devices of the moving hearth furnace are attached may be replaced with a ceiling of another portion. It is preferable to make it lower than the ceiling.

Alternatively, in any one of the carbon material charging device, the mixing device, and the pressing device, or two or more of them, a partition wall is provided before and after a portion of the moving hearth furnace to which these devices are attached, and It is preferable to provide a gap between the lower end of the partition and the hearth. BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 is a graph showing the relationship between the heating temperature of a specific element contained in the steelmaking waste subject to the present invention and the characteristics of volatilization and removal.

FIG. 2 is a circumferential cross-sectional development view of a rotary hearth furnace which is an example of the moving hearth furnace of the present invention.

FIG. 3 is a development in a circumferential cross section of another rotary hearth furnace which is an example of the moving hearth furnace of the present invention.

FIG. 4 is a perspective view showing an example of a rotary hearth furnace which is an example of a moving hearth furnace to which the present invention is applied.

FIG. 5 is a cross-sectional view illustrating an example of the mixing device according to the present invention.

FIG. 6 shows an example of the mixing device according to the present invention, and is a cross-sectional view taken along the line AA of FIG.

FIG. 7 shows an example of the mixing apparatus according to the present invention, and is taken along the line BB in FIG. It is a perspective sectional view.

FIG. 8 shows an example of a mixing apparatus according to the present invention, and is a perspective sectional view taken along the line C-C in FIG.

FIG. 9 is a cross-sectional view showing another example of the mixing device according to the present invention. FIG. 10 shows another example of the mixing device according to the present invention, and is a front view of FIG.

FIG. 11 shows another example of the mixing device according to the present invention, and is a perspective view of FIG. BEST MODE FOR CARRYING OUT THE INVENTION

In the present invention, a steel hearth waste charging device 2 and a carbon material charging device 6 are separately provided in a moving hearth furnace such as a rotary hearth furnace 1 as shown in FIG. After heating before mixing with the material, the Pb, Na, K, etc. are volatilized in the form of chlorides, and the steelmaking waste and the carbon material are mixed in the rotary hearth furnace 1 by the mixing device 7 etc., and reduced. Reaction: Zn in the steelmaking waste is volatilized in the form of metallic zinc by {η} + C → Zn + C0.

The hearth rotates in the direction of the arrow, and the charged steelmaking waste and the carbonaceous material are placed on the hearth, mixed while moving, heated and reduced, and discharged from the discharge device 19.

FIG. 2 is an exploded view of an example of a cross section in the circumferential direction of the rotary hearth furnace 1. In this example, the steelmaking waste 3 charged from the steelmaking waste charging device 2 moves in the direction of the arrow, is heated by the first combustion device 9, and then is loaded from the carbon material charging device 6. The mixed carbon material 5 and the carbon material charging device 6 are mixed by the mixing device 7 provided in the moving direction of the moving hearth of the carbon material charging device 6, and the mixture 11 is mixed in front of the moving direction of the moving hearth of the mixing device 7. The pressure is reduced by the provided pressure reduction device 20, reduced by heating in the second combustion device 10, and discharged as the reductant 12 from the discharge device 19. Fig. 3 shows the combustion device of the existing rotary hearth furnace 1 divided into a first combustion device 9 and a second combustion device 10 by a partition wall 13, and a carbon material charging device between the two partition walls 13. This is an example in which a mixing device 7 and a pressing device 20 are provided in front of the moving hearth 6 and the moving hearth in the moving direction.

The purpose of mixing the steelmaking waste 2 and the carbonaceous material 5 with the mixing device 7 is to promote the reduction reaction by bringing the zinc oxide in the steelmaking waste into close contact with the carbon in the carbonaceous material. .

The purpose of reducing the mixed material 11 by the whirling reduction device 20 is to promote the reduction reaction by bringing the zinc oxide in the steelmaking waste into close contact with the carbon in the carbonaceous material.

In the rotary hearth furnace 1 as shown in FIGS. 2 to 4, a first gas discharge device for discharging volatile gas generated from steelmaking waste 3 is provided between the ironmaking waste charging device 2 and the carbon material charging device 6. It is preferable to provide an exhaust port 4, and a second exhaust port 8 for discharging gas generated from the mixture 11 of the steelmaking waste 3 and the carbonaceous material 5 between the carbon material charging device 6 and the discharging device 19. It is preferable to provide The first exhaust port 4 and the second exhaust port 8 are respectively connected to separate gas cooling devices and dust collecting devices.

In the case of using waste with a low volatile substance content that has been conventionally used for recycling as ironmaking waste 3, the above-mentioned first exhaust port 4 is not particularly provided, and the usual It is sufficient if there is an exhaust port and the second exhaust port 8.

However, when steelmaking waste containing a large amount of volatile substances is used, the first exhaust port 4 is provided, and the volatile matter generated when the steelmaking waste 3 is heated by the first combustion device 9 is removed.

After removing volatile substances from the first exhaust port 4, the steelmaking waste 3 and the carbonaceous material 5 are mixed, and the mixture 11 is reduced by heating in the second combustion device 10. Although the exhaust at this time can be performed from the normal exhaust port, By providing the second exhaust port 8 between the carbon material charging device 6 and the discharge device 19 as described above, zinc can be effectively recovered from the second exhaust port 8 in the form of high-purity zinc oxide. it can.

Incidentally, Pb in steel waste, Na, many K is chloride _{(PbCl 2, NaCl, KC1)} , the first combustion device 9, steelmaking about 1050 prior to mixing the carbonaceous material at 1250 ° C By heating the waste 3, harmful substances such as Cl, Pb, Na, and K can be volatilized and removed from the first exhaust port 4 with almost no evaporation of zinc. The reason why the temperature is set to 1250 ° C or lower is that a sufficiently high volatility is obtained at 1200 ° C as shown in Fig. 1, and even if heating to more than 1250 ° C, heat loss and wear of refractories only increase. If the temperature is lower than ° C, the volatility is low.

In the second combustion device 10, the mixture 11 of the steelmaking waste 3 and the carbonaceous material 5 is heated in a relatively high-temperature iron oxide reduction region to be reduced. At this time, zinc oxide and the like in the steelmaking waste 3 are reduced, volatilized as vapor of metallic zinc, sucked from the second exhaust port 8, and re-oxidized by oxygen in the exhaust gas in the furnace and the duct. Thus, high-purity zinc oxide is recovered.

Further, in the present invention, the ceiling between the first combustion device 9 and the second combustion device 10 is a ceiling lower than the ceiling of the combustion furnace as shown in FIG. 2, or an isolation wall is provided between both combustion devices as shown in FIG. The provision of 13 can prevent volatile substances and carbonaceous material 5 from being sucked from the second exhaust port 8, and can recover higher-purity zinc.

If the lower end of the isolation wall on the second exhaust port side 8 is lower than the lower end of the isolation wall on the first exhaust port side 4 as shown in FIG. 3, the above effect is further improved.

Further, in the present invention, as shown in FIG. 3, by providing a separating wall 13 between the mixing device 7 and the first combustion device 9 and / or between the second combustion device 10, steelmaking waste that rises into the furnace during mixing is provided. Material 3, carbonaceous material 5, or mixture 11 is drawn from first exhaust port 4 and / or second exhaust port 8. Thus, problems such as a decrease in the purity of the recovered zinc and an increase in the load on the dust collector do not occur, and the heat load on the mixing device 7 is reduced.

Next, a specific example of the mixing device 7 in the hearth furnace of the present invention will be described. Fig. 5 is a cross-sectional view of the rotary hearth furnace 1 as viewed from the rotating direction. Blades 14 and 15 are mounted on a shaft 16 supported on both furnace wall sides, and an opening 17 is provided in each blade 14 and 15. It is. As shown in Fig. 6, the blades 14, 15 are fixed to the shaft 16 so as to be shifted substantially perpendicular to each other, and have a hook-shaped tip with a sharp tip in the rotation direction. The shape is as shown in the perspective views of FIG. 7 and FIG.

By rotating the shaft 16 by a driving device (not shown) as shown in FIG. 6, the steelmaking waste 3 and the carbonaceous material 5 are effectively mixed into a mixture 11, and FIG. An example in which the mixing plate 18 is employed will be described. As shown in FIGS. 10 and 11, the mixing plate 18 has irregularities formed on the upper part, and as shown in FIG. 9, the steelmaking waste 3 and the carbon material 5 fall from the recesses as the hearth progresses, and both are mixed. Are mixed to form a mixture 11. The mixing plate 18 has both ends fixed to both furnace walls, but may be fixed by being inclined at an appropriate angle as shown in FIG. 9 or may be vibrated while being inclined. Industrial applicability

As described above, according to the present invention, when ironmaking waste including iron oxide such as scale, sludge, dust, etc. is subjected to reduction treatment and re-synthesized into steelmaking raw materials, it contains a large amount of volatile substances such as chlorine. By making it possible to easily recover zinc from dust, it is possible to widely recycle steelmaking waste that had to be disposed of before. Therefore, there are significant environmental and cost benefits such as effective use of resources and reduction of waste.

Claims

Range of request

1. A method for treating steelmaking waste by charging and reducing ironmaking waste into a moving hearth furnace and discharging the steelmaking waste from a discharge device as a reductant. The steelmaking waste charging device and the carbon material charging device for charging the carbon material are separately installed, and the steelmaking waste and the carbon material are charged into the moving hearth furnace. Wastewater treatment methods

2. A first exhaust port is provided between the iron waste charging device and the carbon material charging device, and volatile gas generated from the iron waste is discharged from the first exhaust port. The method for treating steelmaking waste according to claim 1, wherein

3. A second exhaust port is provided between the carbon material charging device and the discharge device, and gas generated from a mixture of steelmaking waste and carbon material is discharged from the second exhaust port. 3. The method for treating steelmaking waste according to claim 1 or 2, wherein:

4. A moving hearth furnace for treating steelmaking waste, which reduces the charged steelmaking waste and discharges it as a reductant from a discharge device, wherein the steelmaking waste is charged into the moving hearth furnace. And a carbon material charging device for charging carbonaceous materials are provided at intervals in the moving direction of the moving hearth. Moving hearth furnace.

5. A first exhaust port for discharging volatile gas generated from steelmaking waste is provided between the ironmaking waste charging device and the carbonaceous material charging device. A moving hearth furnace for treating steelmaking waste according to paragraph 4.

6. A second exhaust port for discharging gas generated from a mixture of steelmaking waste and carbonaceous material was provided between the carbonaceous material charging device and the discharge device. 6. The moving hearth furnace for treating steelmaking waste according to claim 4 or claim 5, characterized in that:

7. A mixing device for mixing steelmaking waste and carbonaceous material in the moving hearth in front of the moving hearth in the moving hearth of the carbon material charging device. 7. The moving hearth furnace for treating steelmaking waste according to any one of items 4 to 6.

8. The steelmaking waste according to claim 7, wherein a reduction device for reducing a mixture of the steelmaking waste and the carbonaceous material is provided in front of the moving hearth of the mixing device in the moving direction. Moving hearth furnace for material processing.

9. In any one or more of the carbon material charging device, the mixing device, and the pressing device, the moving hearth furnace may be configured such that a ceiling of a portion to which these are attached is lower than ceilings of other portions. The moving hearth furnace for treating steelmaking waste according to any one of claims 4 to 8, characterized in that:

10. In any one or two or more of the carbon material charging device, the mixing device, and the pressing device, a partition is provided before and after a portion of the moving hearth furnace to which these are attached, and a lower end of the partition and 10. The moving hearth furnace for treating steelmaking waste according to any one of claims 4 to 9, wherein a gap is provided between the hearth and the hearth.