JP4171408B2 - Method and apparatus for supplying molten material to melting furnace - Google Patents

Description

  The present invention relates to a melting furnace for melting incineration residue, fly ash, etc. (hereinafter referred to as a material to be melted) that is discharged when municipal waste and industrial waste are incinerated in an incinerator. The present invention relates to a melt supply technology.

  Conventionally, incineration residue, fly ash, etc. (melted material) discharged when incineration of municipal waste and industrial waste in an incinerator is plasma-melted for the purpose of resource recycling, detoxification, and volume reduction. It is melted using a melting furnace such as a furnace and taken out as slag. In order to melt the melted material in the furnace body using the melting furnace in this way, the melted material discharged from the incinerator is subjected to pretreatment steps such as a screen, a magnetic separator, and a measuring instrument, and then melted. While being put into the hopper provided in the screw feeder connected to the furnace, it is supplied into the melting furnace from the screw feeder and melted.

  By the way, when the melted material is supplied to the melting furnace by the screw feeder as described above, the tip portion of the screw feeder facing the melting furnace is exposed to the high temperature atmosphere in the melting furnace. It is known that there is a problem that the melted material is melted and fixed before being supplied to the melting furnace, and the function of the screw feeder is impaired. As an improvement measure for this problem, for example, there is one proposed in Japanese Patent Laid-Open No. 2000-304226 (Patent Document 1).

  The above proposed method is a method of supplying a melt to a melting furnace in which the melt is supplied into the furnace by a melt supply apparatus having a screw feeder connected to a melt supply port of the melting furnace. In this case, when the melt is supplied into the furnace by the melt supply device, the tip of the outer cylinder of the screw feeder (referred to as a supply pipe in the present invention) is slid in the melt supply port. The material supply device is periodically moved back and forth with respect to the melting furnace, the melted material at the melt feed port is pushed into the furnace at the tip of the screw feeder, and the melt is fixed to the melt feed port It is something that breaks things down.

  In the proposed method, when the melt is supplied into the furnace by the melt supply apparatus, the melt supply apparatus is connected to the melting furnace while sliding the outer cylinder tip of the screw feeder in the melt supply port. The melted material at the melt feed port is extruded into the furnace at the tip of the screw feeder, and the melted material fixed to the melt feed port is broken down. Therefore, it is expected that the melt at the melt supply port can be easily removed, and that the melt is prevented from sticking to the melt feed port. In addition, even if the melt is fixed to the melt supply port, it is expected that the fixed melt can be removed without stopping the operation of the melting furnace.

However, in the proposed method, the above effect is expected. However, since the melt supply device such as a screw feeder and a hopper is moved back and forth with respect to the melting furnace, the drive device is necessary and the facility is large. In addition, since the tip of the outer cylinder of the screw feeder is slid within the melt supply port, its wear and maintenance are required, and there is a concern that the facility becomes complicated as a whole.
JP 2000-304226 A

  In view of the above circumstances, the present invention has been achieved by searching for means that can solve the above problems without causing the above-mentioned concerns, and the object thereof is not to use large-scale equipment. And, without requiring maintenance of the equipment due to wear, etc., it is possible to prevent the screw burnout of the screw feeder and the trouble that the melted material adheres to the tip of the supply pipe of the screw feeder with simple methods and means. A method and an apparatus for supplying a material to be melted to a melting furnace are provided.

In order to achieve the above object, a melt supply method to a melting furnace according to the present invention (Claim 1) is to supply a melt with a screw feeder connected to a melt supply port of the melting furnace. A method for supplying a material to be melted into a melting furnace having a negative pressure inside the furnace using an apparatus, wherein the void ratio in the screw feeder between the wall surface of the furnace and the hopper (screw feeder at the time of supplying the material to be melted) the rate) as well as at least 20% occupied by the void portion in the longitudinal plane containing the axis of the supply pipe, the gap portion of the screw feeder, an air flow toward the furnace which is a negative pressure formation The material to be melted is supplied while the material is melted.

  Generally, in a melting furnace, exhaust gas is sucked in order to prevent the exhaust gas generated during the melting process of the melted material from leaking to the outside, and the furnace pressure is slightly negative. Therefore, by using the melt supply method as described above, air or forced through the gap in the screw feeder between the furnace inner wall surface and the hopper from the hopper opening (melt input). A gas such as nitrogen blown into the hopper can be introduced into the hopper, and the introduced air can prevent the tip of the screw feeder from being heated more than necessary due to the furnace atmosphere, etc. It is possible to prevent the burning and the trouble that the material to be melted is melted and fixed in the supply pipe. And in order to acquire such an effect, it is desirable that the porosity is 20% or more. Further, the upper limit is not particularly limited, but is preferably about 80%. If the porosity becomes larger than this, there is a concern about a decrease in the atmospheric temperature in the furnace, and a decrease in the melt processing amount of the melted material in the melting furnace. Is concerned. Therefore, a desirable porosity is 20 to 80%. Further, in order to obtain the porosity as described above in the screw feeder between the furnace inner wall surface and the hopper, it is performed by controlling the amount of melt to be supplied from the pretreatment process to the hopper of the screw feeder, This can be achieved by operating the melting furnace without filling the hopper, for example, by controlling the supply speed of the screw feeder within the processing capacity range of the melting furnace.

  In the invention described in claim 1, the tip of the screw shaft of the screw feeder may be disposed so as to recede at least 20 mm or more from the inner wall surface of the melting furnace (invention 2). By comprising in this way, the heat which a screw shaft and the front-end | tip part of a blade | wing combine with ventilation | gas_flowing from the said space | gap part can reduce the heat received from the inside of a furnace, and a screw burnout and a to-be-melted material are more effective. Can be prevented from melting and adhering to the supply pipe. Further, the upper limit of the backward arrangement is not particularly limited, but is preferably about 200 mm, and if it is larger than this, there is a concern that the melted material accumulates in the supply pipe between the furnace inner wall surface and the tip of the screw shaft. In the case of deposition, there is a concern that the void ratio at the tip portion becomes insufficient and melted and fixed. Therefore, the preferable range of the backward arrangement is 20 to 200 mm.

In the invention described in claim 1 or 2, the pitch of the screw blade of the screw feeder is made of formed so as to be or stepwise increase continuously due to go to the tip from the rear (Claim 3). By configuring in this way, the gap can be enlarged as it goes to the tip of the screw shaft of the screw feeder, and the melted material can be supplied into the furnace. The received heat can be reduced, and it is possible to more effectively prevent troubles caused by screw burning and melting and fixing of the material to be melted to the supply pipe.
Furthermore, in the invention according to the first to third aspects, the negative pressure of the furnace pressure is formed by sucking exhaust gas through a tap cover attached to the melting furnace (claim). Item 4).

In order to achieve the above object, a melt supply apparatus for a melting furnace according to the present invention (Claim 5 ) is connected to a hopper that receives the melt and a melt supply port of the melting furnace. Oite to be melt supply device provided with a screw feeder, the tip of the screw shaft of the screw feeder is arranged to retract at least 20mm or more from the furnace wall of the melting furnace, the pitch of the screw blade of the screw feeder However, as it goes from the rear part to the tip, it is formed continuously or stepwise, and an outlet cover is attached to the outlet of the melting furnace, and exhaust gas is sucked through the outlet cover. Thus, the furnace pressure is configured to be a negative pressure, and a gas supply hole is formed in the upper part of the supply pipe of the screw feeder. By configuring in this way, a gas such as air can be supplied from the gas supply hole into the supply pipe, and a gap can be formed in the supply pipe from the gas supply hole to the furnace inner wall surface. The heat received by the gas such as the supplied air from the inside of the furnace by the screw shaft and blade tips can be reduced, and the trouble of screw burning and melting of the melted material to the supply pipe can be prevented.

  As described above, according to the melt supply method to the melting furnace according to the present invention, the burnout of the screw of the screw feeder can be performed without using large-scale equipment and without requiring equipment maintenance due to wear or the like. In addition, it is possible to prevent a problem that the material to be melted adheres to the tip of the supply pipe of the screw feeder.

  In addition, according to the melt supply device to the melting furnace according to the present invention, it is possible to prevent the burnout of the screw of the screw feeder and the trouble that the melt is stuck to the tip of the supply pipe of the screw feeder. Can be melted

  Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a schematic longitudinal sectional view of an apparatus for supplying a melt to a melting furnace according to the present invention. In the figure, reference numeral 1 denotes a melt supply device, 2 denotes a melting furnace, and the melt supply device 1 is connected to a side wall portion of the melting furnace 2.

  The melt supply apparatus 1 includes a hopper 3 and a screw feeder 4 provided in communication with a lower portion of the hopper 3. The screw feeder 4 includes an outer cylinder serving as a supply pipe 5, a screw shaft 6 inside thereof, and screw blades 7 formed in a spiral shape on the outer peripheral surface of the screw shaft 6, and the screw shaft 6 is rotationally driven by a drive motor 8. It is comprised so that. The tip of the supply pipe 5 of the screw feeder 4 is airtightly attached and fixed to an opening 10 opened in the side wall 9 of the melting furnace 2. In this melt supply device 1, the melt A cut out from the supply device 11 in the previous process is received in the hopper 3, and the melt shaft A is rotated into the supply pipe 5 by the screw shaft 6 and the screw blade 7. Is fed to the melting furnace 2.

  The melting furnace 2 is an example of a plasma melting furnace, and the structure of the furnace itself generally includes a plasma torch 12 charged from the upper center of the plasma melting furnace 2 and a furnace installed on the furnace bottom side as shown in the figure. A plasma arc 15 that includes a bottom electrode 13, a DC power source 14 that supplies a DC voltage to the plasma torch 12 and the furnace bottom electrode 13, and serves as a heat source for melting the material A to be melted, As mentioned above, it is configured to flow to the molten slag bath 16 and the furnace bottom electrode 13 which is a cathode. The melt A supplied to the melting furnace 2 from the screw feeder 4 is heated to a melting temperature by a high-temperature plasma arc 15 irradiated from the plasma torch 12 to form molten slag, thereby forming a molten slag bath 16. At the same time, the molten slag overflows from the outlet 17 of the melting furnace 2 and is discharged outside the furnace. Reference numeral 18 denotes an outlet cover, which exhausts exhaust gas and the like to a chimney or the like through a dust removal device (not shown).

The method of supplying the melt A to the melting furnace 2 by the melt supply apparatus 1 having the above-described configuration is performed as follows. That is, the material A to be melted cut out from the supply device 11 in the previous process and received in the hopper 3 is conveyed and supplied to the melting furnace 2 in the supply pipe 5 by the rotating screw shaft 6 and the screw blade 7 of the screw feeder 4. However, at that time, the cutting amount of the melt A from the supply device 11 to the hopper 3 is controlled, and the transport amount of the melt A in the screw feeder 4 from the furnace inner wall surface 19 to the hopper 3 is As shown in FIG. 3 , it supplies so that the space | gap part B which becomes 20% or more in the porosity in the cross section in the supply pipe | tube 5 may be formed. The void ratio C is a ratio (C = B / D) of the void portion B to the cross-sectional area D obtained by removing the cross-sectional area of the screw shaft 6 from the cross-sectional area of the supply pipe 5.

  By supplying the melt A to the melting furnace 2 as described above, in the melting furnace 2, the exhaust gas generated in the melting process of the melt A is generally not leaked to the outside through the outlet cover 18. As the exhaust gas is sucked and the furnace pressure is slightly negative, as indicated by an arrow X from the opening of the hopper 3 through the gap B in the screw feeder 4 between the furnace inner wall surface 19 and the hopper 3. Air is introduced, and the introduced air can prevent the tip portion of the screw feeder 4 from being heated more than necessary by the furnace atmosphere or the like. A trouble that A is melted and fixed in the supply pipe 5 can be prevented.

  FIG. 3 is an enlarged vertical cross-sectional view of a main part of the melt supply apparatus applied to the melt supply method to the melting furnace according to the present invention. In FIG. 3, a melt supply device 20 is used instead of the melt supply device 1 shown in FIG. 1, and the melt supply device 20 is a screw blade 7 in the melt supply device 1. The pitch of the screw blades 21 is continuously increased from the rear to the tip (see FIG. 3a) and gradually increased (see FIG. 3b). ) Formed.

  In the melt supply device 20, when the melt A is supplied to the melting furnace 2, the gap B in the screw feeder 4 increases as it goes to the tip of the screw shaft 6. It becomes easy to introduce air from the void B, and is introduced in the same manner as or more than when the melt A is supplied to the melting furnace 2 by the melt supply apparatus 1 described above. It is possible to prevent the tip of the screw feeder 4 from being heated more than necessary by the atmosphere in the furnace due to air, and the screw shaft 6 and the screw blade 21 are burned out and the melted material A is melted and fixed in the supply pipe 5. Can prevent trouble.

  In order to obtain the above-mentioned effects more effectively, in FIG. 1 and FIG. 3, the distance L between the tip of the screw shaft 6 of the screw feeder 4 and the furnace inner wall surface 19 of the melting furnace 2 is at least 20 mm. It is preferable to dispose the above. By comprising in this way, the heat | fever which the front-end | tip part of the screw shaft 6 or the screw blade | wings 7 and 21 receives from the inside of a furnace combined with ventilation | gas_flowing from the space | gap part B can be reduced, and a screw shaft can be made more effective. 6 and screw blades 7 and 21 can be prevented from being burned out and troubles in which the material A is melted and fixed in the supply pipe 5 can be prevented.

  FIG. 4 is an enlarged vertical cross-sectional view of a main part of an apparatus for supplying a melt to a melting furnace according to another embodiment of the present invention. The melt supply device 22 shown in FIG. 4 is used in place of the melt supply device 1 shown in FIG.

  The melt supply device 22 includes a hopper 23 and a screw feeder 24 provided in communication with a lower portion of the hopper 23. The screw feeder 24 has the same configuration as the screw feeder 4, and includes an outer cylinder serving as a supply pipe 25, a screw shaft 26 inside thereof, and a screw blade 27 formed in a spiral shape on the outer peripheral surface of the screw shaft 26. The screw shaft 26 is rotationally driven by the drive motor 28. The screw blades 27 are formed so that the pitch increases in three steps as the pitch goes from the rear part to the tip of the screw shaft 26. A gas supply hole 29 through which air or the like can be introduced is formed in the upper part of the supply pipe 25. The tip of the supply pipe 25 of the screw feeder 24 is airtightly attached and fixed to the opening 10 opened in the side wall 9 of the melting furnace 2, but the tip of the screw shaft 26 is melted during the fixing. A distance L (L = 20 mm or more) is opened from the furnace inner wall surface 19 of the furnace 2 so as to be retracted.

  According to the melt supply device 22 having the above-described configuration, the melt A cut out from the supply device 11 in the previous process and received in the hopper 23 is supplied by the rotating screw shaft 26 and the screw blade 27 of the screw feeder 24. 25 is conveyed and supplied to the melting furnace 2. Gas supply holes that are formed so that the pitch of the screw blades 27 increases in three stages as the screw shafts 26 move from the rear part to the tip of the screw shaft 26 and air or the like can be introduced into the upper part of the supply pipe 25 during the conveyance and supply 29 is formed, the height of the melt A to be transported and fed decreases toward the melting furnace 2 in the supply pipe 25, and the upper part of the melt A and the top of the supply pipe 25 are increased. A gap B is formed between the peripheral surface and the air, and air is introduced into the melting furnace 2 through the gap B and the gas supply hole 29 from the opening of the hopper 23 (the inlet of the melt A). Thus, the introduced air can prevent the tip portion of the screw feeder 24 from being heated more than necessary due to the atmosphere in the furnace, etc., and the screw shaft 26 and the screw blades 27 are burned out, and the melted material A Supply pipe The trouble to melted and fixed can be prevented in the 5.

It is a schematic longitudinal cross-sectional view of the to-be-melted material supply apparatus to the melting furnace which concerns on this invention. It is a partial explanatory view of the screw feeder concerning the present invention, Comprising: a is an expanded longitudinal section, b is a YY sectional view of a. It is a principal part expanded longitudinal cross-sectional view of the to-be-melted material supply apparatus applied to the to-be-melted material supply method to the melting furnace which concerns on this invention, Comprising: When a is the pitch of screw blades becoming large continuously, b is a screw This is a case where the pitch of the blades increases stepwise. It is a principal part expansion longitudinal cross-sectional view of the to-be-melted material supply apparatus to the melting furnace of another embodiment which concerns on this invention.

Explanation of symbols

1: Melted material supply device 2: Melting furnace 3: Hopper 4: Screw feeder 5: Supply pipe 6: Screw shaft 7: Screw blade 8: Drive motor 9: Side wall 10: Opening portion 11: Supply device 12: Plasma torch 13 : Furnace bottom electrode 14: DC power supply device 15: Plasma arc 16: Molten slag bath 17: Outlet port 18: Outlet port cover 19: Furnace inner wall surface 20: Molten material supply device 21: Screw blade 22 Melted material supply Device 23: Hopper 24: Screw feeder 25: Supply pipe 26: Screw shaft 27: Screw blade 28: Drive motor 29: Gas supply hole A: Material to be melted B: Cavity part L: Tip of screw shaft and inside of furnace Distance between walls X: Arrow indicating air flow

Claims (5)

A method for supplying a material to be melted into a melting furnace having a negative pressure inside the furnace by means of a melt feeding device provided with a screw feeder connected to a melt feeding port of the melting furnace, the inner wall surface of the furnace the porosity of the screw feeder between the to the hopper with the (proportion of void portions in the longitudinal plane containing the axis of the supply tube of the screw feeder at the time of immersion in the melt supplied) is 20% or more, the screw feeder A method of supplying a material to be melted to a melting furnace, wherein the material to be melted is supplied while forming an air flow toward the inside of the furnace in which a negative pressure is formed in the gap.   The method for supplying a material to be melted to the melting furnace according to claim 1, wherein the tip of the screw shaft of the screw feeder is disposed so as to be retracted by at least 20 mm from the inner wall surface of the melting furnace.   The method for supplying a material to be melted to a melting furnace according to claim 1 or 2, wherein the pitch of the screw blades of the screw feeder is formed so as to increase continuously or stepwise from the rear to the tip.   The melting furnace according to any one of claims 1 to 3, wherein the negative pressure of the furnace pressure is formed by sucking exhaust gas through a tap cover attached to the melting furnace. The melt supply method. Oite to be melt supply device provided with a screw feeder which is connected to the melt supply port of the melting furnace hopper for receiving an object to be melt, the tip of the screw shaft of the screw feeder, from the furnace wall of the melting furnace The screw blade pitch of the screw feeder is formed to increase continuously or stepwise as it goes from the rear part to the tip, and is output to the outlet of the melting furnace. A port cover is attached, and the exhaust gas is sucked through the outlet port cover so that the furnace pressure becomes negative, while a gas supply hole is formed in the upper part of the supply pipe of the screw feeder. An apparatus for supplying a material to be melted to a melting furnace.