JP2013194942A - Metal melting furnace and metal melting method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a metal melting furnace and a metal melting method that can prevent exhaust gases containing carbon monoxide from being ignited in the vicinity of an exhaust outlet, and also can preheat a metal material supplied into a furnace to be effectively melted.SOLUTION: A metal melting furnace includes: a furnace 10 provided with a blowing port 31 and a hot water outlet 11; a material storage chamber 21 provided adjacent to the upper part of the furnace to store metal materials; a material loading door 23 openably and closably provided on the border between the furnace 10 and the material storage chamber 21; a combustion burner 16 provided near the bottom part of the furnace 10 for heating and melting the metal materials; an ignition burner 17 provided on the vertex part of the furnace 10; and a heat discharge passage 26 one end part of which is open into the furnace 10 and the other end part of which is open into the material storage chamber 21. The ignition burner 17 generates a secondary exhaust gas by reacting the carbon monoxide contained in the exhaust gas with the oxygen fed from the blowing port 31. The secondary exhaust gas is fed from the heat discharge passage 26 into the material storage chamber 21.

Description

  The present invention relates to a metal melting furnace for melting a metal material to create a molten metal, and a metal melting method using the same.

  There is known a metal melting furnace that melts a metal material charged into a furnace body with a hot gas obtained by burning liquefied natural gas or the like. When fuel such as liquefied natural gas is burned inside the furnace body, high-temperature exhaust gas containing carbon monoxide is generated. The hot exhaust gas rises in the furnace body, is introduced into an exhaust port provided in the upper part of the furnace body, and is discharged outside the furnace body. However, if the exhaust gas is mixed with outside air around the exhaust port, the contained carbon monoxide may ignite and burn. When carbon monoxide burns around the exhaust port, the pressure in the furnace body becomes negative, and the air around the exhaust port is pulled into the furnace body and air is sucked into the furnace from the outlet. When the outside air enters due to such suction, the pressure in the furnace becomes unstable. Moreover, since the external cold air enters the furnace body, the material temperature in the furnace is lowered, and nitrogen contained in the entered air brings out heat, so that the heat efficiency of the furnace is lowered. For this reason, it has been necessary to remove carbon monoxide from the exhaust gas to prevent combustion of the exhaust gas around the exhaust port.

  In addition to this, when external air enters the furnace, oxygen contained in the air may cause oxidation of the metal material. As a technique for preventing the entry of outside air and reducing oxidation of a metal material, for example, Patent Document 1 discloses a vertical furnace body having a material inlet that is opened and closed by a furnace lid at the top, and a bottom portion in the furnace body. A metal melting furnace having a plurality of oxyfuel combustion burners arranged in the vicinity is disclosed. The furnace body of the metal melting furnace of Patent Document 1 is provided with a non-oxidizing substance introduction section for introducing a non-oxidizing gas having a specific gravity larger than air into the furnace body at a position higher than the combustion burner. A technique is disclosed in which the non-oxidized gas that has been used functions as a gas barrier layer to suppress the entry of outside air when the material is charged.

  On the other hand, the non-oxidizing gas introduction technique of Patent Document 1 does not assume the entry of outside air except when the furnace lid is opened, and it is difficult to completely prevent the entry of outside air due to suction from the hot water outlet. Met. For this reason, there is still a possibility that the metal material is oxidized by the introduction of outside air containing a large amount of oxygen. The oxidation of the metal material contributes to the generation of slag, which lowers the quality and quantity of the molten metal and ultimately leads to material loss. For this reason, there is a need for technology that not only prevents the entry of outside air when materials are added, but also promotes the metal melting process as efficiently as possible to further reduce material loss (generally referred to as “oxidation loss”) due to oxidation of metal materials. It was done.

Japanese Patent Laying-Open No. 2010-230237 (paragraph 0010, FIG. 1)

  This invention is made | formed in view of this situation, The objective is to provide the metal melting furnace by which the fall of the pressure in a furnace and the fall of the thermal efficiency of a furnace were prevented beforehand. At the same time, it is an object of the present invention to provide a metal melting furnace capable of avoiding metal oxidation by preventing the outside air from entering the furnace. In addition, an object of the present invention is to provide a metal melting method in which the thermal efficiency of the furnace is high, the pressure in the furnace is stable, and at the same time, oxidation of the metal can be avoided as much as possible.

  The metal melting furnace according to the present invention has a vertical furnace body having a blower opening at the top and a tapping outlet at the bottom, a material storage chamber adjacent to the upper part of the furnace body for storing metal materials, and a furnace A material charging door that is openable and closable at the boundary between the body and the material storage chamber, and is opened to allow the furnace body and the material storage chamber to communicate with each other so as to input the metal material from the material storage chamber into the furnace body; Combustion burner provided near the bottom of the furnace body to heat and melt the metal material charged into the furnace body, exhaust gas containing carbon monoxide generated by combustion of the combustion burner, and oxygen supplied from the air outlet In order to reheat at the top of the furnace body, an ignition burner provided at the top of the furnace body and one end for supplying reheated exhaust gas to the material storage chamber and preheating the stored metal material Is open to the furnace body and the other end is a material storage chamber Characterized in that it comprises a heat discharge passage are opened, the.

  According to the present invention, the carbon monoxide contained in the exhaust gas generated by the combustion in the combustion burner is ignited at the upper part of the furnace body by the ignition burner, and reacts with the oxygen contained in the air supplied from the blower port to be completely It becomes carbon dioxide by burning. Since carbon monoxide in the exhaust gas is removed by this reaction, the exhaust gas is discharged from the exhaust port at a high temperature and does not burn even when mixed with air.

  In addition, the metal melting furnace of the present invention has an exhaust gas from which carbon monoxide has been removed by a heat exhaust passage having one end opened in the furnace body and the other end opened in the material storage chamber. The metal material stored in the material storage chamber is preheated. By introducing the preheated metal material into the furnace body, the metal material is efficiently dissolved.

  In the metal melting furnace of the present invention, the first exhaust duct including the first exhaust damper is connected to the upper portion of the furnace body, and the second exhaust duct including the second exhaust damper is the material storage. It is preferably connected to the upper part of the chamber. When the metal material is stored in the material storage chamber, the first exhaust damper is closed and the second exhaust damper is opened. When the metal material is introduced from the material storage chamber into the furnace body, the first exhaust damper is opened and the second exhaust damper is closed.

  In this way, by providing two exhaust ducts with exhaust dampers, the exhaust gas exhaust path from the furnace body is controlled, and when the metal material is stored in the material storage room and when the metal material is charged And an exhaust gas flow suitable for each can be selected. When the metal material is stored in the material storage chamber, the exhaust gas can be introduced into the material storage chamber and discharged from the second exhaust duct, so that the metal material is efficiently preheated. When the metal material is charged, the exhaust gas can be discharged from the first exhaust duct at the top of the furnace body, so that the pressure in the furnace is controlled to be constant.

  The present invention also provides an efficient metal melting method. The metal melting method of the present invention includes a vertical furnace body having a first exhaust duct having a first exhaust damper and a blower opening at the top, and a hot water outlet at the bottom, and adjacent to the top of the furnace body. And a material storage chamber provided with a second exhaust duct provided with a second exhaust damper, and provided at the boundary between the furnace body and the material storage chamber. A material charging door that communicates with the material storage chamber, a combustion burner provided near the bottom of the furnace body to heat and melt the metal material charged from the material storage chamber into the furnace body, and one generated by the combustion of the combustion burner In order to re-combust the exhaust gas containing carbon oxide and the oxygen supplied from the blower at the upper part of the furnace body, the ignition burner provided at the top of the furnace body, and the exhaust gas after the re-combustion are stored in the material storage chamber Metal materials that are supplied and stored in For heat, one end is a metal dissolution method using a metal melting furnace equipped with a heat discharge passage and the other end is open to the furnace body is open to the material storage chamber, the. In the metal melting method of the present invention, when the metal material is stored in the material storage chamber, the first exhaust damper is closed and the second exhaust damper is opened, so that the recombustion is performed via the heat exhaust passage. The exhaust gas is supplied to the material storage room. On the other hand, when the metal material stored in the material storage chamber is thrown into the furnace body, the first exhaust damper is opened and the second exhaust damper is closed, so that the reburned exhaust gas is removed from the first exhaust damper. The pressure inside the furnace is controlled by introducing it into the exhaust duct side.

  As described in detail above, according to the metal melting furnace and the metal melting method described in each claim, carbon monoxide in the exhaust gas generated by combustion in the combustion burner is ignited at the upper part of the furnace body by the ignition burner. Carbon dioxide is produced by a combustion reaction with oxygen supplied from the air blowing port. Since carbon monoxide in the exhaust gas is removed by this combustion reaction, the exhaust gas discharged from the exhaust port does not burn even when mixed with air. Since the combustion around the exhaust port does not occur, the inside of the furnace is always maintained at a positive pressure, and the possibility of outside air entering the furnace from both the exhaust port and the hot water outlet is avoided. As a result, the pressure in the furnace body is always stable and the thermal efficiency is kept constant.

  Moreover, according to the metal melting furnace and the metal melting method of the present invention, the exhaust gas supplied through the heat exhaust passage is used for preheating the metal material in the material storage chamber, thereby further improving the thermal efficiency of the furnace. it can.

  According to the metal melting furnace and the metal melting method of the present invention, by preventing the entry of outside air into the furnace body, metal oxidation in the melting process is avoided as much as possible. In addition, since the reburned exhaust gas is supplied from the furnace body to the material storage chamber through the heat exhaust passage, the metal material held in the material storage chamber is also prevented from being oxidized as much as possible. Avoidance of oxidation of the metal material leads to a decrease in slag discharge and contributes to an improvement in the quality and yield of the molten metal. Since the alloy addition cost in the subsequent process is suppressed by improving the quality and yield of the molten metal, it is possible to obtain a high-quality molten metal at a lower cost.

  The metal melting furnace of the present invention can improve the quality and yield of the molten metal simply by additionally installing an ignition burner, a heat discharge passage, and a second discharge duct in an existing furnace body.

It is a vertical direction sectional view showing an outline of a metal melting furnace according to an embodiment. It is an AA line horizontal sectional view of the metal melting furnace shown in FIG.

  Embodiments of the present invention will be described below with reference to the drawings.

  With reference to FIG.1 and FIG.2, one Embodiment of the metal melting furnace for producing the molten metal of cast iron is described. In FIG. 1, the vertical direction sectional view of the metal melting furnace of this embodiment is shown. As shown in FIG. 1, the metal melting furnace of the present embodiment includes a vertical furnace body 10, and the vertical furnace body 10 has a bottomed and covered cylindrical shape standing upright along the vertical direction. Yes. A hot water outlet 11 is provided at the bottom of the furnace body 10, and a material inlet 18 is provided at the upper side wall of the furnace body 10. An air blowing port 12 is provided at a position closer to the material charging port 18 than the center of the top of the furnace body 10. A blower passage 31 including a blower fan 32 is connected to the blower opening 12 and air is supplied in a state where the supply amount is controlled. A melting chamber 13 for melting an input M made of a metal material is defined in the furnace body 10. The hearth surface 15 corresponding to the bottom surface of the melting chamber 13 is formed as an inclined surface that descends toward the hot water outlet 11, and the hot water outlet 11 is located at the lowest place of the melting chamber 13.

  A material storage chamber 21 for storing a metal material is provided adjacent to the furnace body 10 outside the material input port 18 of the furnace body 10. The material storage chamber 21 includes a carry-in port 27 provided with a carry-in door 25 at the top, and a carry-out port 28 at a position corresponding to the material input port 18 of the furnace body 10. The floor surface 22 of the material storage chamber 21 descends linearly from the carry-in port 27 toward the carry-out port 28, and the carry-out port 28 is located at the lowest position of the material storage chamber 21. A material input door 23 is disposed at a location where the material outlet 28 on the material storage chamber 21 side and the material input port 18 on the furnace body 10 side are connected (that is, the boundary between the material storage chamber 21 and the furnace body 10). Yes. A hinge-type support structure 24 that rotates the material charging door 23 between an open position (a position indicated by a solid line) and a closed position (a position indicated by a two-dot chain line) is provided above the material charging door 23. The material input door 23 is supported by the support structure 24 so as to be opened and closed. The material input door 23 is normally in a closed position and functions as a bottom plate of the material storage chamber, and holds the metal material stacked in the material storage chamber 21. At the time of material charging, the material charging door 23 rotates to the furnace body 10 side and moves to the open position, the furnace body 10 and the material storage chamber 21 communicate with each other, and the held metal material is charged into the furnace body 10. To do.

  Near the bottom of the furnace body 10, there are provided a plurality of oxygen combustion burners 16 (11 in this example, 3 in the drawing) for burning fuel gas such as liquefied natural gas or fuel liquid using oxygen as a combustion aid. ing. A group of burners composed of eleven oxyfuel combustion burners 16 is arranged in the upper part of the passage from the melting chamber 13 of the furnace body 10 toward the hot water outlet 11. The combustion flames ejected from the respective oxygen combustion burners 16 form a hollow flame f (indicated by a two-dot chain line) having a hollow shape very similar to a cylinder. Since the oxygen combustion burner 16 uses a high-concentration oxygen gas (oxygen concentration of 90% or more) as an auxiliary combustion gas, the temperature of the hollow flame f reaches a high temperature of 1800 ° C. to 3300 ° C. Therefore, even when the input M is a refractory metal, the input M can be efficiently and rapidly dissolved.

  An ignition burner 17 (one in this example) that is an oxyfuel burner having the same specifications as the oxyfuel burner 16 is provided on the top of the furnace body 10. The ignition burner 17 is disposed in the vicinity of the air blowing port 12, and again burns exhaust gas containing carbon monoxide generated by the combustion of the combustion burner 16 and oxygen contained in the air supplied from the air blowing port 12. Let In the following, the exhaust gas ignited by the ignition burner 17 and recombusted is also referred to as secondary exhaust gas. The carbon monoxide initially contained in the exhaust gas reacts with oxygen during recombustion to become carbon dioxide, so it is hardly contained in the secondary exhaust gas.

  FIG. 2 schematically shows a cross section when the furnace body 10 and the material storage chamber 21 are cut in the horizontal direction at the center position in the height direction of the material charging port 18. In FIG. 2, the material charging door 23 is in the closed position. A first exhaust duct 33 is connected to a position facing the material charging port 18 in the diameter direction of the furnace body 10. A first exhaust damper 34 is provided inside the first exhaust duct 33. As shown in FIG. 1, a second exhaust duct 35 including a second exhaust damper 36 is connected to the upper part of the material storage chamber 21. In this embodiment, the exhaust dampers 34 and 36 are butterfly-shaped valve bodies, and the opening and closing thereof are controlled in synchronization with the material charging door 23 by a control means (not shown).

  As shown in FIG. 2, a heat exhaust passage 26 is provided at substantially the same height as the material storage chamber 21 in order to connect the upper portion of the side wall of the furnace body 10 and the side surface of the material storage chamber 21. One end of the heat exhaust passage 26 opens into the furnace body 10 as an exhaust gas inlet 19. The other end of the heat exhaust passage 26 opens into the material storage chamber 21 as an exhaust gas inlet 29. When the first exhaust duct 33 is opened and the second exhaust duct 35 is closed, most of the secondary exhaust gas generated in the furnace body 10 is discharged from the upper part of the furnace body 10 to the first exhaust gas. It is discharged via the duct 33 and further via the suction pipe 38. When the first exhaust duct 33 is closed and the second exhaust duct 35 is opened, the secondary exhaust gas generated in the furnace body 10 enters the material storage chamber 21 via the heat exhaust passage 26. It passes through and is discharged from the second exhaust duct 35.

  In the metal melting furnace of the present embodiment, the exhaust gas containing carbon monoxide generated by the combustion of the combustion burner 16 passes between the charged metal materials and rises to the top of the furnace body 10. The carbon monoxide contained in the exhaust gas that has reached the top of the furnace body 10 is ignited at the top of the furnace body 10 by the hollow flame f of the ignition burner 17, and oxygen contained in the air supplied from the blower port 12. It reacts with and completely burns to carbon dioxide. From the component analysis of the exhaust gas in the furnace, the amount of oxygen required around the ignition burner 17 is continuously calculated by an external analysis means (not shown), and the blower port 12 is controlled by controlling the blown amount of the blower fan 32. The amount of air supplied from is optimized. As a result of supplying an appropriate amount of air from the blower opening 12, almost no carbon monoxide and oxygen remain in the secondary exhaust gas.

  A metal melting method using the metal melting furnace of this embodiment will be described below. In the metal melting method of the present embodiment, the first exhaust damper 34, the second exhaust damper 36, and the material charging door 23 are opened and closed in a synchronized state by a control means (not shown). The opening amounts of the first exhaust damper 34 and the second exhaust damper 36 are adjusted so that the internal pressure of the furnace body 10 becomes a positive pressure (+ pressure) with respect to the outside air.

  The step of bringing the metal material into the material storage chamber 21 is appropriately performed according to the remaining amount of the metal material dissolved in the furnace body 10. The metal material is carried in from the carry-in port 27 at the upper part of the material storage chamber 21. At this time, the control means closes the material charging door 23, closes the first exhaust damper 34, closes the first exhaust duct 33, and opens the second exhaust damper 36 to open the second exhaust. The duct 35 is opened. As a result, the high-temperature secondary exhaust gas passes through the material storage chamber 21 via the heat discharge passage 26 and is discharged from the second exhaust duct 35. When the secondary exhaust gas passes through the material storage chamber 21, it heats the carried metal material. When opening / closing the carry-in door 25 provided at the carry-in entrance 27, the change in the pressure of the material storage chamber 21 and the furnace body 10 can be minimized by particularly reducing the opening amount of the second exhaust damper 36. .

  While the carried-in metal material is held in the material storage chamber 21, the control means maintains the material charging door 23 and the first exhaust damper 34 in a closed state, and the second exhaust damper is synchronized with this. 36 is kept open. The high-temperature secondary exhaust gas continues to pass through the material storage chamber 21 via the heat discharge passage 26 and is discharged from the second exhaust duct 35. The secondary exhaust gas warms the metal material stored in the material storage chamber 21. High-temperature secondary exhaust gas contains almost no oxygen or carbon monoxide, so metal materials that are exposed to secondary exhaust gas during storage maintain good quality without material deterioration due to oxidation In this state, it is fully preheated.

  In the material charging process in which the metal material is charged into the furnace body 10 from the material storage chamber 21, the control means opens the material charging door 23 and synchronizes with this to open the first exhaust damper 34. The exhaust duct 33 is opened. At the same time, the control means closes the second exhaust duct 35 by closing the second exhaust damper 36. The secondary exhaust gas is discharged from the upper part of the furnace body 10 via the first exhaust duct 33. At this time, the opening amount of the first exhaust damper 34 is controlled so that the internal pressure of the furnace body 10 becomes a positive pressure with respect to the outside air. Thereby, the fluctuation of the pressure in the furnace when the material is charged is minimized, and the inflow of outside air is prevented at the same time. Moreover, since the metal material thrown into the melting chamber 13 is sufficiently preheated, it can be efficiently melted to obtain a molten metal.

  Since the secondary exhaust gas discharged through the first exhaust duct 33 or the second exhaust duct 35 is burned again in the upper part of the furnace body 10 and carbon monoxide is removed, the secondary exhaust gas is in a high temperature state. It is not burned even if it is exhausted and mixed with air. By avoiding accidental combustion of carbon monoxide, the pressure in the furnace body is always maintained at a positive pressure, and the risk of air being sucked into the furnace from the exhaust ducts 33 and 35 and the outlet is previously avoided. Yes. From the above, the metal melting furnace of this embodiment and the metal melting method using the same provide a metal melting technique that has high thermal efficiency, stable pressure in the furnace, and can avoid metal oxidation as much as possible. Is done.

[Other changes]
The shape of the material storage chamber and the arrangement with respect to the furnace body described in the present embodiment can be appropriately changed. For example, the material storage chamber is disposed above the furnace body so that a part of the floor surface of the material storage chamber is adjacent to the upper portion of the furnace body, and the heat exhaust passage is provided as a passage rising from the furnace body to the material storage chamber. It is possible. By changing the positions of the exhaust gas inlet and the exhaust gas inlet so that the high-temperature secondary exhaust gas naturally rises from the furnace body to the heat exhaust passage, the metal material can be preheated more efficiently. In addition, other burners such as an air burner can be applied to the ignition burner. Moreover, although the case where air was supplied from a ventilation port was demonstrated, it is possible to manage the supply amount of oxygen more strictly by supplying oxygen alone.

  The present invention is applicable to a metal melting furnace for melting metal-based scrap and / or pig iron ingots.

DESCRIPTION OF SYMBOLS 10 Furnace 11 Outlet 12 Air outlet 13 Melting room 15 Furnace floor 16 Oxyfuel combustion burner 17 Ignition burner 18 Material inlet 19 Exhaust gas inlet 21 Material storage room 22 Material storage room floor 23 Material inlet door 24 Support structure
25 Loading door
26 Heat exhaust passage 27 Carry-in entrance
28 Unloading port 29 Exhaust gas introduction port 31 Blower passage 32 Blower fan 33 First exhaust duct 34 First exhaust damper 35 Second exhaust duct 36 Second exhaust damper 38 Suction piping
M Input f Combustion flame

Claims (3)

A vertical furnace body having an air outlet at the top and a tapping outlet at the bottom,
Adjacent to the top of the furnace body, a material storage chamber for storing metal materials,
It is provided at the boundary between the furnace body and the material storage chamber so as to be openable and closable, and is opened to allow the furnace body and the material storage chamber to communicate with each other so that the metal material is introduced into the furnace body from the material storage chamber. A material loading door,
A combustion burner provided near the bottom of the furnace body to heat and melt the metal material charged into the furnace body;
An ignition burner provided at the top of the furnace body in order to re-combust the exhaust gas containing carbon monoxide generated by the combustion of the combustion burner and oxygen supplied from the blower at the upper part of the furnace body; ,
One end is opened in the furnace body and the other end is in the material storage chamber for preheating the metal material stored by supplying the exhaust gas after reburning to the material storage chamber. An open heat exhaust passage,
A metal melting furnace comprising: A first exhaust duct comprising a first exhaust damper is connected to the upper part of the furnace body, and a second exhaust duct comprising a second exhaust damper is connected to the upper part of the material storage chamber;
When the metal material is stored in the material storage chamber, the first exhaust damper is closed and the second exhaust damper is opened, and the metal material is put into the furnace body from the material storage chamber. The metal melting furnace according to claim 1, wherein the first exhaust damper is sometimes opened and the second exhaust damper is closed. A vertical furnace body having a first exhaust duct having a first exhaust damper at the top and a blower opening, and having a tapping outlet at the bottom,
A material storage chamber adjacent to the top of the furnace body and provided with a second exhaust duct comprising a second exhaust damper;
A material charging door that is openably and closably provided at a boundary between the furnace body and the material storage chamber, and that opens and communicates the furnace body and the material storage chamber;
A combustion burner provided near the bottom of the furnace body to heat and melt the metal material charged from the material storage chamber into the furnace body;
An ignition burner provided at the top of the furnace body in order to re-combust the exhaust gas containing carbon monoxide generated by the combustion of the combustion burner and oxygen supplied from the blower at the upper part of the furnace body; ,
One end is opened in the furnace body and the other end is in the material storage chamber for preheating the metal material stored by supplying the exhaust gas after reburning to the material storage chamber. An open heat exhaust passage,
A metal melting method using a metal melting furnace comprising:
When the metal material is stored in the material storage chamber, the re-burned exhaust gas is closed via the heat exhaust passage by closing the first exhaust damper and opening the second exhaust damper. Supplying gas to the material storage chamber;
When the metal material stored in the material storage chamber is charged into the furnace body, the re-burned exhaust gas is opened by opening the first exhaust damper and closing the second exhaust damper. Is introduced into the first exhaust duct side to control the pressure in the furnace.

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