JP2008190010A - Method for removing copper from copper-containing molten iron - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a safe and efficient method which can selectively remove copper that has once dissolved in steel from the steel, and can regenerate the steel into a high-quality steel for automobile use and the like. <P>SOLUTION: The method includes charging polyvinyl chloride as a chlorine source or a high grade of bleaching powder into a molten iron which contains copper as an impurity to convert the copper in the molten iron into copper chloride of a gas, and thereby removing the copper from the molten iron. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a method of selectively removing vapor by, for example, selective vapor separation of copper from molten iron of steel scrap, which contains copper element as an impurity.

  End-of-life vehicles (hereinafter referred to as “ELV”) are collected and recycled according to the Automobile Recycling Law. In general, in ELV, a part that can be directly used is separated by dismantling, and the remaining part that cannot be used directly is pressed or crushed to become a steelmaking raw material. The main material constituting the disassembled ELV is steel. ELV steel scrap is recycled as steel by an electric furnace or converter-type new steelmaking method. However, in this steel scrap, copper derived from wiring in automobiles and other parts often remains, causing the quality of steel products to be recycled to deteriorate. For this reason, it is requested | required that the copper content in the iron-making raw material derived from ELV should be 0.3% or less. In order to satisfy this requirement, car dismantling companies are conducting careful material sorting operations including hand sorting, but there are still oversights and the requirements may not be met.

  Chemical thermodynamics teaches that once an iron-making raw material containing copper is dissolved, copper cannot be removed by the current oxidative refining method using oxygen. Non-Patent Document 1 describes several methods in which copper removal is considered to be possible by chemical thermodynamics. One of them is a method using a sulfide flux. However, this method has a problem in the treatment of flux after absorbing copper in iron and has not been put into practical use. In the same document, a method using iron chloride is described. However, this method has not been put into practical use because of poor reaction efficiency.

Patent Document 1 describes a treatment method using chlorine for selectively removing copper from iron scrap containing copper. In this method, in order to selectively react copper with iron and remove it as a gas, the scrap heating temperature is 700 to 1100 ° C., the chlorine concentration (1 to 90%) of the gas, and the oxygen partial pressure ( 10 ^-3 atm or higher) and atmospheric pressure conditions are specified. Further, after the metal chloride is deposited from the exhaust gas by cooling, the chlorine concentration and the oxygen partial pressure are adjusted and used again for the scrap treatment. When gaseous chlorine is used in industry, it has the following disadvantages. That is, firstly, gaseous chlorine is toxic and not easy to handle in the atmosphere, and secondly, gaseous chlorine is highly corrosive, and the chlorine source input device must be protected against corrosion. Due to these disadvantages, this method has not been put into practical use.

The current technique for reducing the copper concentration in steel products produced using iron-containing raw materials containing copper is a method of diluting with high-grade steel mills that do not contain copper. However, since a small amount of copper naturally remains in the steel product obtained by this method, it cannot be used as a high-grade steel such as an automobile material. As long as this dilution method is continued, there will be a shortage of high-grade iron raw materials that can be used for dilution, and the day will soon come when automobile recycling will not be successful.
Japan Iron and Steel Association, issued in February 1996, "Basic study on the separation method of playing element in scrap iron" JP-A-6-248364

  The present invention provides a safe and efficient method that makes it possible to selectively remove high-grade steel that can be used for automobiles and the like by selectively removing copper once dissolved in the steel. This is the issue.

  In the present invention, by introducing polyvinyl chloride (hereinafter referred to as “PVC”) or advanced bleaching powder (hereinafter also collectively referred to as “copper removal agent”) as a chlorine source into molten iron containing copper as an impurity, The copper in the molten iron is removed from the molten iron as gaseous copper chloride.

  When PVC as a chlorine source is introduced into molten iron containing copper, PVC is vaporized and reacts with copper in the molten iron to become gaseous copper chloride, which is removed from the molten iron by the carrier gas. In addition, when advanced bleaching powder is introduced into the molten iron as a chlorine source, the advanced bleaching powder decomposes and releases gaseous chlorine into the molten iron. Gaseous chlorine reacts with the copper in the molten iron to form gaseous copper chloride and is removed from the molten iron.

  Embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a schematic cross-sectional view of a reaction apparatus used for carrying out the present invention.

In FIG. 1, an alumina reaction tube 2 is arranged in a vertical direction in an electric furnace 1 using molybdenum silicide as a heating element. In this embodiment, the reaction tube 2 has an outer diameter of 60 mm, an inner diameter of 52 mm, and a length of 1000 mm, and its upper and lower ends are sealed with silicone rubber plugs 3 and 4. In the reaction tube 2, an alumina crucible base 5 supported at the lower part by an alumina support rod 6 is disposed, and an alumina crucible 7 is disposed thereon. In this embodiment, the crucible 7 has an outer diameter of 35 mm, an inner diameter of 30 mm, and a height of 150 mm, and an alumina tube 8 for preventing spillage is disposed on the upper edge thereof. In this embodiment, the alumina tube 8 has an outer diameter of 35 mm, an inner diameter of 30 mm, and a height of 150 mm. The capsule guide tube 9 and the carrier gas introduction tube 10 are introduced into the reaction tube 2 through the upper silicon rubber plug 3 in an airtight manner. The capsule guide tube 9 is an alumina tube having an outer diameter of 20 mm, an inner diameter of 16 mm, and a length of 300 mm, and its lower end is disposed above the crucible 7. The support rod 6 protrudes outside through the lower silicon rubber stopper 4 in an airtight manner, and the carrier gas discharge pipe 11 is led out of the reaction pipe 2. In the crucible 7, 100 g of steel-copper alloy or pig iron-copper alloy 21 (hereinafter referred to as “molten iron”) containing 2% copper is accommodated and melted at 1650 ° C. The From the carrier gas introduction tube 10, argon gas as a carrier gas is always introduced into the reaction tube 2 and discharged from the carrier gas discharge tube 11.
Filling the iron capsule 12 shown in FIG. 2 with 0.3 g of commercially available granular reagent PVC having a diameter of 100 μm or 1 g of commercially available reagent high-grade bleaching powder, the required number is charged into the molten iron alloy in the crucible through the capsule guide tube 9. . The upper end of the capsule guide tube 9 is closed with a rubber stopper or the like except when the capsule is inserted.

  Since PVC and highly bleached powder (copper removal agent) have a relatively low boiling point, if they are directly introduced into the crucible 7, they cannot be vaporized before reaching the surface of the molten iron and put into the molten iron. Does not occur. The reason for encapsulating in the capsule 12 is to ensure that the molten iron is charged. The capsule 12 may be made of aluminum or other appropriate metal.

  The capsule 12 was cut to a length of 30 mm from a commercially available soft iron tube having an outer diameter of 8 mm and an inner diameter of 6 mm, and one end thereof was caulked and closed, and after filling a predetermined amount of the copper removal agent 13 from the other end side, It is produced by caulking and sealing. The tare mass of the capsule 12 is 5 g.

  The gaseous copper chloride produced by the reaction is discharged from the reaction tube 2 through the carrier gas discharge pipe 11 together with the carrier gas. As the carrier gas, an inert gas commonly used in steelworks such as nitrogen and argon is used. Since the temperature of the copper chloride carried out of the apparatus decreases, it becomes powdered copper chloride. Powdered copper chloride can be recovered and used as a raw material for high-purity copper.

  FIG. 3 is a graph showing the copper removal rate (copper removal rate) when PVC is introduced into a 1650 ° C. molten steel-copper alloy or pig iron-copper alloy (molten iron) containing 2% copper by mass percentage. It is. The horizontal axis represents the mass of the added PVC, and the vertical axis represents the copper removal rate. The copper removal rate is defined as follows.

Copper removal rate = (mass of copper removed by reaction / mass of copper present in molten iron) × 100
FIG. 3 shows that copper is removed from both the steel-copper alloy and the pig iron-copper alloy.

  FIG. 4 is a graph showing the copper removal rate (copper removal rate) when highly bleached powder is introduced into a 1650 ° C. molten pig iron-copper alloy containing 2% copper by mass percentage. The horizontal axis is the number of moles of high-grade bleaching powder introduced, and the vertical axis is the copper removal rate. FIG. 4 shows that advanced bleaching powder can also serve as a copper removal agent. If the number of moles is the same, the copper removal rate of PVC and advanced bleaching powder is equivalent.

  PVC and highly bleached powder are both chlorine sources that are solid at room temperature, and can be handled in the air without protective measures, and the anticorrosive treatment of the chlorine source input device is not necessary.

  Since the good quantitative relationship between the molten iron and the chlorine source varies depending on the characteristics of the apparatus used, it is determined empirically for each apparatus used.

  The PVC to be input may be a new product or a collected used product. When processing used PVC as waste, there is a concern that environmental pollution will occur. However, if used PVC is used as a copper removal agent, there is an effect of reducing the risk of environmental pollution.

FIG. 5 shows an example of a reaction apparatus in the case of transporting the copper removal agent into the molten iron by the carrier gas. In FIG. 5, an alumina reaction tube 32 is arranged in a vertical direction in an electric furnace 31 using silicon carbide as a heating element. In this embodiment, the reaction tube 32 has an outer diameter of 60 mm, an inner diameter of 52 mm, and a length of 1000 mm, and the upper and lower ends are sealed with silicon rubber plugs 33 and. A sampling glass tube 35 passes through the upper silicon rubber plug 33. The sampling glass tube 35 is always sealed with a silicone rubber plug 36 except during sampling. In the reaction tube 32, a graphite crucible 38 supported at the lower part by an alumina support 37 is disposed. In this embodiment, the crucible 38 has an outer diameter of 35 mm, an inner diameter of 30 mm, and a height of 150 mm. About 50 g of pig iron-copper alloy (molten iron) 21 is accommodated therein and melted at 1350 ° C. An alumina inner cylinder 39 for protecting the reaction tube 32 is disposed in the gap between the crucible 38 and the reaction tube 32. In this embodiment, the alumina inner cylinder 39 has an outer diameter of 46 mm, an inner diameter of 40 mm, and a height of 500 mm. The alumina inner cylinder 39 is inserted into the reaction product collecting tank 41 through the lower silicon rubber plugs 34 and 40 in an airtight manner. The inert gas introduction pipe 42 is a quartz pipe having an outer diameter of 10 mm, an inner diameter of 8 mm, and a length of 300 mm, and its lower end is connected to a graphite nozzle 43. The graphite nozzle 43 has an outer diameter of 12 mm and an inner diameter of 10 mm, and the lower end of an inert gas introduction pipe 42 is inserted into the upper end. The graphite nozzle 43 is introduced into the molten iron 21, and the lower end thereof reaches the vicinity of the bottom of the crucible 21.
A storage tank 44 of the copper removal agent 13 is attached to the upper part of the inert gas introduction pipe 42, and a copper removal agent cutting device 45 is installed at the lower part of the copper removal agent storage tank 44. An inert gas (N _{2 in} this embodiment) is introduced from the upper part of the inert gas introduction pipe 42, and the powder in the decopper storage tank 44 is removed into the inert gas by the decopper removal apparatus 45. Copper agent 13 is supplied at a rate of about 0.2 g / min. The copper removal agent is conveyed to the bottom of the crucible 7 by the inert gas. Since the copper removal agent 13 has a relatively low boiling point and decomposition temperature, the copper removal agent that has reached the molten iron 21 near the bottom of the crucible 38 is vaporized and mixed with an inert gas to form bubbles and rise in the molten iron 21. While reacting with copper in molten iron. The inert gas and the gaseous copper removal agent after coming into contact with the molten iron reach the reaction product collection tank 41 and are cooled to release copper chloride as the reaction product as a solid. The inert gas that has released the reaction product is discharged from the inert gas discharge pipe 46 into the atmosphere.
The method of transporting the copper removal agent into the molten iron by the carrier gas is not limited to this method, and for example, it can be included in the inert gas for reflux in the RH device, which is a secondary refining device for steel.

It is a schematic sectional drawing of the reactor used for implementation of this invention. It is a schematic sectional drawing of the metal capsule which encloses PVC or highly bleached powder. It is a graph which shows the removal rate (copper removal rate) of copper when PVC is thrown into 1650 degreeC melted steel-copper alloy or pig iron-copper alloy (molten iron) containing 2% of copper by mass percentage. FIG. 4 is a graph showing the copper removal rate (copper removal rate) when highly bleached powder is introduced into a 1650 ° C. molten pig iron-copper alloy containing 2% copper by mass percentage. It is a schematic sectional drawing of the reaction apparatus used for other embodiment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Electric furnace 2 Reaction tube 3 Silicon rubber plug 4 Silicon rubber plug 5 Crucible base 6 Support rod 7 Crucible 8 Alumina tube 9 Capsule guide tube 10 Carrier gas introduction tube 11 Carrier gas discharge tube 12 Capsule 13 Copper removal agent 21 Molten iron 31 Electric furnace 32 Reaction tube 33 Silicon rubber plug 34 Silicon rubber plug 35 Sampling glass tube 36 Silicon rubber plug 37 Crucible base 38 Crucible 39 Inner cylinder 40 Silicon rubber plug 41 Reaction product collection tank 42 Inert gas introduction pipe.
43 Nozzle made of graphite.
44 Copper removal agent storage tank 45 Copper removal agent cutting device 46 Inert gas discharge pipe

Claims (6)

  A method of removing copper from molten iron containing copper, wherein the copper is removed from molten iron as gaseous copper chloride by introducing polyvinyl chloride as a chlorine source into molten iron containing copper as an impurity .   2. The method for removing copper from molten copper-containing iron according to claim 1, wherein the polyvinyl chloride is filled in a metal sealed container and poured into molten iron.   The method for removing copper from the copper-containing molten iron according to claim 1, wherein the polyvinyl chloride is introduced into the molten iron by being conveyed with a carrier gas.   A method for removing copper from molten iron containing copper, wherein the copper is removed from molten iron as gaseous copper chloride by introducing highly bleached powder as a chlorine source into molten iron containing copper as an impurity.   The method for removing copper from the copper-containing molten iron according to claim 1, wherein the highly bleached powder is filled into a metal sealed container and poured into the molten iron.   The method for removing copper from the copper-containing molten iron according to claim 1, wherein the advanced bleaching powder is fed into the molten iron by being conveyed with a carrier gas.

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