JP3297350B2 - Treatment system for waste generated from steelworks - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a system for treating waste generated from steelworks.

[0002]

2. Description of the Related Art For example, iron ore powder, iron or steelmaking dust, electric furnace dust, rolling sludge, pickling sludge, etc.
Waste containing, for example, Ni such as stainless steel scrap
As a technique for recycling waste containing and recoverable metal-containing waste including Zn-containing waste such as scraps of galvanized steel sheets, the applicants disclosed in Japanese Patent Application Laid-Open No. Hei 8-33050.
In the patent application No. 5, while moving the recoverable metal-containing waste from upstream to downstream of the high-temperature reduction melting rotary kiln, reducing the metal oxide in the recoverable metal-containing waste to obtain a metal or an alloy, A method and an apparatus for recycling a waste generated at a steel mill, which melts the metal or alloy and recovers the molten metal or alloy downstream of the high-temperature reduction melting rotary kiln, are proposed.

[0003] The high-temperature reduction melting rotary kiln according to the patent application has the following components. 1) The ratio of the length L to the inner diameter D is L / D ≦ 5. 2) Its central axis is inclined by 1 to 2 degrees with respect to the horizontal. 3) The recoverable metal-containing waste and the reducing agent are charged from the input port and heated by a burner from the input port side. It is a so-called co-current type. 4) The inside of the high-temperature reduction melting rotary kiln is heated by the burner to a temperature higher than the melting point of iron. 5) The discharge end of the high-temperature reduction melting rotary kiln is connected to the secondary combustion chamber. 6) Further, a slag forming substance may be charged from the charging port. And, by the high-temperature reduction melting rotary kiln according to the patent application, it is possible to easily treat the recoverable metal-containing waste which has been conventionally buried, and economically recover a high-grade metal or alloy. It became so. Further, the high-temperature reduction melting rotary kiln is relatively small and hard to cause trouble, and can be operated for a long time with almost no repair.

[0004]

However, the above-mentioned high-temperature reduction melting rotary kiln is heated to about 1200 ° C. or higher, but the discharged exhaust gas remains at a high temperature.
There is a problem that energy loss is large. Further, it is necessary to further reduce the total cost of processing and recovering the waste containing the recoverable metal.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a system for treating waste generated from a steel mill, which can reduce the total cost by effectively utilizing energy.

[0006]

SUMMARY OF THE INVENTION The object of the present invention is to provide a system for treating waste generated from a steelworks according to the present invention, that is, (1) a hollow cylindrical shape, the center axis of which is horizontal. On the other hand, it is tilted and rotated so as to become lower from upstream to downstream, and the recoverable metal-containing waste, the reducing agent, and the slag forming material are charged from the input portion at the upstream open end, and the combustion gas is introduced, and the metal is introduced. Drying, reducing and melting the metal while moving the recoverable metal-containing waste and the reducing agent toward the outlet at the downstream open end.
A high-temperature reduction melting rotary kiln that sequentially performs preferential evaporation and oxidation of zinc and generation of zinc oxide powder, and discharge of molten metal and molten slag, and (2) an upright cylindrical shape having a molten metal and molten slag outlet at its lower end. The rotary kiln is provided on its side with a joint with the discharge part of the rotary kiln, and a fuel oil burner is provided inside the secondary kiln to mainly burn the exhaust gas discharged from the high-temperature reduction melting rotary kiln. A combustion chamber; (3) an electric furnace disposed in close proximity to the outlet of the molten metal and molten slag of the secondary combustion chamber; and (4) a hot gas, water and air discharged from the secondary combustion chamber. (5) saturated steam from the waste heat boiler,
A superheater that generates superheated steam by taking in fuel oil and air; (6) a power generation turbine that generates power using superheated steam from the superheater; and (7) air using exhaust gas from the superheater. An air preheater for preheating, (8) a cooling tower for cooling high-temperature exhaust gas discharged from the waste heat boiler, and (9) a bag filter for removing dust from the cooled exhaust gas from the cooling tower.
The molten metal and the molten slag which fall from the discharge part of the rotary kiln and are discharged from the outlet of the molten metal and the molten slag of the secondary combustion chamber are hot-charged to the electric furnace and discharged from the electric furnace. The electric furnace gas is introduced into the secondary combustion chamber to combust waste materials in the electric furnace gas, and uses the thermal energy in the electric furnace gas to generate saturated steam in the waste heat boiler subsequent to the secondary combustion chamber. Is generated, and the preheated air from the air preheater is introduced into the input section of the rotary kiln and the secondary combustion chamber, and is used for heating, and the electric power generated by the power generation turbine is used as the electric furnace and This is achieved by a system for treating waste generated from steelworks, which is supplied to other equipment of the steelworks.

[0007]

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, an embodiment of a system for treating waste generated from steelworks according to the present invention will be described in detail with reference to the accompanying drawings.

FIG. 1 is a schematic diagram of a system for treating waste generated from a steelworks according to an embodiment of the present invention. A known dry process of recoverable metal-containing waste such as iron ore powder, pig iron or steelmaking dust, electric furnace dust, rolling sludge, pickling sludge, stainless steel scrap, galvanized steel sheet scrap, and reducing agents such as pulverized coal and coke powder. Alternatively, they are mixed by a wet mixing method. The product obtained by the dry treatment is directly put into a rotary kiln or, after further mixing with a dewatered cake or the like obtained separately by a wet method, is put into a rotary kiln. On the other hand, the product obtained by the wet treatment is dewatered to form a dewatered cake, which is directly put into a rotary kiln or, after further mixing with pulverized coal or the like, is put into the rotary kiln. Paper waste, wood waste, plastic waste, pulp waste, pulp residue, waste oil, etc. can be used as secondary fuel and secondary reducing agent.
Like the reducing agent such as coke powder, it is mixed with the recoverable metal-containing waste and mixed, and then charged into the rotary kiln, or when mixing is difficult, directly charged into the rotary kiln. In order to increase the recovery rate of iron and iron alloy, it is preferable to introduce a slag forming substance such as incineration ash into the rotary kiln.

The charging section of the rotary kiln is heated to 500 to 700 ° C. by a heating burner. In order to heat the rotary kiln, the waste heat of the air preheater is effectively used. The waste heat supplied from the air preheater to the rotary kiln is 32000 Nm3 / h at 185 ° C.

The mixture of the above-mentioned easily pretreated dewatered cake-like recoverable metal-containing waste and a reducing agent or a secondary reducing agent is heated at a charging section of the rotary kiln, dried and directed downstream. (Drying step).
The mixture may be granulated in advance.

In the reduction step following the drying step, iron, nickel, chromium, zinc,
An oxide such as lead is reduced by a reducing agent or a secondary reducing agent. The mixture of the reduction step forms a pool bed at the bottom of the rotary kiln, and the temperature of the bed of the reduction step reaches about 1000 ° C to 1200 ° C. In bed,
In a gas-solid reaction mode, the reduction reaction starts and is almost completed. That is, the carbon of the reducing agent or the secondary reducing agent partially reacts directly with the solid metal oxide, or in most cases, carbon monoxide gas generated from carbon reacts with the solid metal oxide. I do. The reduction products include solid reduced iron, solid ferronickel alloy, molten zinc, molten lead, molten cadmium, and the like.

[0013] Molten zinc, molten lead, and molten cadmium have a low boiling point and thus evaporate preferentially. The gaseous zinc and the like move to the space of the oxidizing atmosphere above the reducing bed, and the zinc and the like are oxidized in the oxidizing atmosphere to generate fine powder such as zinc oxide. The fine powder such as zinc oxide exits the rotary kiln together with the exhaust gas, passes through the secondary combustion chamber, the waste heat boiler, and the quenching tower, and is collected by the bag filter.

On the other hand, the reduced iron and ferronickel remain in the bed. The carbon monoxide gas remaining after the reduction reaction burns above the bed and contributes to heating the bed and the inner wall of the rotary kiln. This combustion flame of carbon monoxide also contributes to maintaining the bed in a reducing atmosphere.

In the melting step subsequent to the reduction step, the mixture is heated to 1200 ° C. or higher, and the reduced iron is melted while taking in carbon, so that molten iron carbide having a substantially carbon-saturated composition, that is, a composition close to pig iron, is obtained. can get. Nickel, chromium, and the like are also dissolved in the molten iron carbide. Further, when the mixture contains a slag-forming substance such as incineration ash, molten slag is also obtained. Due to a difference in specific gravity, the molten slag floats above the molten metal and forms separate layers. A large amount of chromium, a small amount of iron, and a small amount of nickel are incorporated in the molten slag.

The molten metal and molten slag are 1250-1
It is sent toward the discharge of a rotary kiln maintained at 300 ° C. The molten slag covers the surface of the molten metal,
This prevents the molten metal from being oxidized. The molten metal and the molten slag fall from the discharge part of the rotary kiln and are accommodated in a receiving pan disposed directly below the molten metal and molten slag outlet at the lower end of the secondary combustion chamber. Even in the saucer, the molten slag floats on the molten metal due to the specific gravity difference, covers the surface of the molten metal, and prevents the molten metal from being oxidized.

The molten metal and molten slag in the pan are at about 1275 ° C. and are charged hot to an adjacent electric furnace. Molten iron carbide is melted together with iron scrap, which is the main raw material of the electric furnace, and the iron scrap starts to be melted in the electric furnace after being preheated from 20 ° C to about 800 ° C. In the embodiment already about 1
Since molten iron carbide at 275 ° C. is used, preheating of raw materials can be partially omitted from the viewpoint of operation of the electric furnace, and operation costs can be reduced.

The processing capacity of the molten metal and the molten slag discharged from the rotary kiln is as follows.
2000 tons.

The secondary combustion chamber has an upright cylindrical shape, and a lower end thereof is provided with a molten metal and molten slag outlet.
A connection port is provided for connection with the discharge section at the downstream open end of the rotary kiln. A fuel oil burner is provided inside the secondary combustion chamber 2 to heat the inside of the secondary combustion chamber. In order to heat the secondary combustion chamber, the waste heat of the air preheater is effectively used. The waste heat supplied to the air preheater in the secondary combustion chamber is 29000 Nm3 / h at 185 ° C.
Further, a waste oil lance is provided on a side surface of the secondary combustion chamber, and an air inlet 205 and a waste liquid lance 20 are provided above the waste oil lance.
6 are provided. The ambient temperature in the secondary combustion chamber is approximately 1
It is kept at 351 ° C.

The exhaust gas discharged from the secondary combustion chamber is 963
° C and kept at 75000 Nm3 / h. Since there is a high possibility that a halogen element is mixed in the exhaust gas, it is regulated to keep the tube wall temperature at about 450 ° C. or less. When the temperature is about 450 ° C. or more, corrosion of the metal pipe duct becomes remarkable, and normal operation cannot be performed.

Exhaust gas, water and air from the secondary combustion chamber are introduced into the waste heat boiler at 276 ° C. and 60 kg / c.
37,700 tons / h of saturated steam of m2G was generated, and the heat energy in the exhaust gas from the secondary combustion chamber, which was conventionally discarded, has been effectively used. The saturated steam is introduced into a super heater, and the remaining exhaust gas from the waste heat boiler is 75500 Nm 3 / h at 190 ° C., but is sent to a quenching tower.

In the quenching tower, the exhaust gas of the waste heat boiler is washed and cooled by the cooling spray water, and cooled to about room temperature. Thereafter, the 190 ° C. air from the air preheater is mixed with the cooled waste heat boiler exhaust gas,
00Nm3 / h, which is sent to the bag filter.

From the waste heat boiler exhaust gas treated as described above, solid dust 1800 is filtered by a bag filter.
0 tons / year was recovered, 70% of which was zinc oxide powder. 102000 Nm3 / h of gas after filtration is released from the chimney.

On the other hand, the saturated steam together with the heavy oil A and the combustion air is introduced into a super heater,
36000 kg / h of superheated steam of 8 kg / cm2G was generated. A part of the superheated steam was supplied to the steam type air preheater in front of the air preheater, but most of the superheated steam was supplied to the power generation turbine to generate electric power equivalent to 8000 kW.

FIG. 2 is a schematic diagram of iron recovery from recoverable metal-containing waste in an embodiment of the present invention. When the waste containing the recoverable metal containing iron is put into the rotary kiln, it is reduced and melted, the molten metal and the molten slag are discharged, and the powder is scattered in the exhaust gas. Iron is 94% in molten metal, 3% in slag, and 3% in fly ash. That is, almost all of the recoverable metal-containing waste is recovered, and 94% of the molten iron carbide can be recovered.

FIG. 3 is a schematic view of recovering zinc, lead, and cadmium from recoverable metal-containing waste according to an embodiment of the present invention. When recyclable metal-containing waste containing zinc, lead, and cadmium is put into a rotary kiln, it is reduced and melted, the molten metal and molten slag are discharged, and molten zinc, lead, and cadmium are given priority. It evaporates and is oxidized in an oxidizing gas atmosphere to produce powder, which is scattered in exhaust gas. Zinc, lead and cadmium are 1% in molten metal, 1% in slag, and 9% in fly ash.
8% is included. That is, almost all of the recoverable metal-containing waste is recovered.
Can be recovered. On the other hand, high quality iron carbide or ferronickel in which a trace amount of zinc or the like is dissolved in the molten metal can be obtained. On the other hand, the obtained powder of zinc oxide or the like has high purity and can be sold at high cost to a non-ferrous smelter.

FIG. 4 is a schematic diagram of nickel recovery from recoverable metal-containing waste in an embodiment of the present invention.
When the recoverable metal-containing waste containing nickel is put into a rotary kiln, it is reduced and melted, the molten metal and the molten slag are discharged, and the powder is scattered in the exhaust gas. Nickel is 95% in molten metal, 4% in slag, and 1% in fly ash. That is, almost all of the recoverable metal-containing waste is recovered, and 95% of the recovered ferronickel can be recovered.

FIG. 5 is a schematic diagram of chromium recovery from recoverable metal-containing waste according to an embodiment of the present invention. When a chromium-containing waste containing a recoverable metal is put into a rotary kiln, it is reduced and melted, the molten metal and the molten slag are discharged, and the powder is scattered in the exhaust gas. Chromium is 47% in molten metal and 50% in slag
% And 3% in fly ash. That is, almost all of the recoverable metal-containing waste is recovered, but most of the molten slag can be removed.

[0029]

According to the first and second systems for treating waste generated from steelworks according to the present invention, steam is generated using exhaust gas from a secondary combustion furnace which has been conventionally discarded, Since power is generated by the steam turbine, energy can be effectively used. Furthermore, by using the generated electric power for an electric furnace or other equipment of a steelworks, it is possible to contribute to cost reduction of the steelworks. In addition, income can be obtained by selling power to a power company.

According to the second aspect of the present invention, a system for treating waste generated from a steel mill can hot-charge molten iron carbide to an electric furnace, thereby eliminating the need for preheating of input materials and reducing operating costs. You. If the electric furnace is operated using the electric power obtained by the system, the operating cost can be further reduced.

[Brief description of the drawings]

FIG. 1 is a schematic diagram of a system for treating waste generated from a steelworks according to an embodiment of the present invention.

FIG. 2 is a schematic diagram of iron recovery from recoverable metal-containing waste in an embodiment of the present invention.

FIG. 3 is a schematic diagram of recovery of zinc, lead, and cadmium from recoverable metal-containing waste according to an embodiment of the present invention.

FIG. 4 is a schematic diagram of nickel recovery from recoverable metal-containing waste in an embodiment of the present invention.

FIG. 5 is a schematic diagram of chromium iron recovery from recoverable metal-containing waste in an embodiment of the present invention.

Continuation of the front page (51) Int.Cl. ⁷ identification code FI F23G 5/44 ZAB F23G 5/44 ZABZ (58) Field surveyed (Int.Cl. ⁷ , DB name) F23G 5/00, 5/16, 5/20 F01K 27/02

Claims (1)

(57) [Claims] (1) A hollow cylindrical shape, the center axis of which is inclined and rotated so as to become lower from upstream to downstream with respect to the horizontal, and the metal-containing waste that can be recovered from the input portion at the upstream open end. The material, the reducing agent, and the slag-generating substance are charged, and the combustion gas is introduced.
Drying, reduction and melting of metal, preferential evaporation and oxidation of zinc and generation of zinc oxide powder while moving the recoverable metal-containing waste and reducing agent towards the discharge at the downstream open end;
A high-temperature reduction melting rotary kiln for sequentially discharging molten metal and molten slag; and (2) an upright cylindrical shape, the lower end of which is provided with a molten metal and molten slag discharge port, and a discharge portion of the rotary kiln on a side surface thereof. A secondary combustion chamber mainly provided with a fuel oil burner for burning exhaust gas discharged from the high-temperature reduction melting rotary kiln; and (3) melting of the secondary combustion chamber. (4) a waste heat boiler configured to take in high temperature gas, water and air discharged from the secondary combustion chamber to generate saturated steam, and 5) a superheater that generates superheated steam by taking in saturated steam, fuel oil and air from the waste heat boiler; and (6) using superheated steam from the superheater. (7) an air preheater that preheats air using exhaust gas from the super heater, (8) a cooling tower that cools high-temperature exhaust gas discharged from the waste heat boiler, (9) A) a bag filter for removing dust from the cooled exhaust gas from the cooling tower; and a molten metal that falls from the discharge part of the rotary kiln and is discharged from the molten metal and molten slag outlet of the secondary combustion chamber. And the molten slag is hot-charged into the electric furnace, the electric furnace gas discharged from the electric furnace is introduced into the secondary combustion chamber to burn off waste materials in the electric furnace gas, and heat energy in the electric furnace gas The saturated steam is generated in the waste heat boiler following the secondary combustion chamber by using the preheated air, and the preheated air from the air preheater is supplied to the input section of the rotary kiln and A waste generated at a steel mill, which is introduced into the secondary combustion chamber and used for each heating, and the electric power generated by the power generation turbine is supplied to the electric furnace and other equipment of the steel mill. Etc. processing system.