CN116066840A

CN116066840A - Sludge incineration rotary incinerator

Info

Publication number: CN116066840A
Application number: CN202111292915.0A
Authority: CN
Inventors: 徐军松; 荒井正太郎
Original assignee: Yamato Sanko Mfg Co ltd; Shanghai E&t Environment Engineering Co ltd; Sinochem Environmental Holdings Ltd
Current assignee: Yamato Sanko Mfg Co ltd; Shanghai E&t Environment Engineering Co ltd; Sinochem Environmental Holdings Ltd
Priority date: 2021-11-03
Filing date: 2021-11-03
Publication date: 2023-05-05

Abstract

The invention relates to the technical field of sludge incineration, and discloses a sludge incineration rotary incinerator. The sludge incineration rotary incinerator comprises an incinerator body, a stirring device and a flue gas introducing device, wherein an incineration part and a deodorization part are arranged in the incinerator body, a gas outlet is formed in the upper part of the incinerator body, a supporting platform is arranged at the bottom of the incinerator body, and a combustor is arranged on the side wall of the incinerator body; the stirring device comprises a hollow rotating shaft penetrating through the middle of the supporting platform, the rotating shaft can rotate relative to the supporting platform, a slag discharging port is formed in the position, close to the rotating shaft, of the supporting platform, a plurality of hollow rotating arms are arranged on the periphery of a part of the rotating shaft above the supporting platform, a plurality of hollow stirring rods are arranged at intervals at the bottom of the rotating arms and used for stirring sludge at the top of the supporting platform, an air inlet is formed in the bottom of the rotating shaft, a first air distribution port is formed in the stirring rods, and a plurality of second air distribution ports are formed in the periphery of the upper part of the rotating shaft; the flue gas introducing device is used for introducing odor generated in the sludge drying process towards the deodorizing part.

Description

Sludge incineration rotary incinerator

Technical Field

The invention relates to the technical field of sludge incineration, in particular to a sludge incineration rotary incinerator.

Background

The dewatered sludge has high water content and low heat value, and is generally dried before incineration, and the drying and incineration are the most thorough method for harmless, recycling and reducing the sludge. The incineration method has outstanding advantages compared with other methods: the burning can reduce the full burning volume of the combustible components of the residual sludge to the minimum at high temperature, so that few substances which are finally required to be disposed of can meet the requirement of reduction; after the sludge is burnt, the malodor in the sludge is thoroughly eliminated, and the harmless requirement is met. In most of the current sludge drying and incineration, the combustion effect of the sludge is poor, and the odor generated by the sludge drying requires a set of independent condensation and deodorization device, so that a large amount of high-concentration wastewater and high-concentration odor are generated to be treated.

Disclosure of Invention

In order to solve the technical problems or at least partially solve the technical problems, the invention provides a sludge incineration rotary incinerator.

The invention provides a sludge incineration rotary incinerator, comprising:

the device comprises a furnace body, wherein an incineration part and a deodorization part are sequentially arranged in the furnace body from bottom to top, a gas outlet is arranged at the upper part of the furnace body, a supporting bottom plate for placing sludge to be incinerated is arranged at the bottom of the furnace body, and a combustor for incinerating the sludge is arranged on the side wall of the furnace body;

the stirring device comprises a hollow rotating shaft penetrating through the middle of the supporting bottom plate, the rotating shaft can rotate relative to the supporting bottom plate, a slag discharging port for discharging incinerated sludge is formed in the position, close to the rotating shaft, of the supporting bottom plate, a plurality of hollow rotating arms are arranged on the periphery of a part of the rotating shaft above the supporting bottom plate, a plurality of hollow stirring rods are arranged at intervals at the bottom of each rotating arm and used for stirring sludge at the top of the supporting bottom plate, the inside of the rotating shaft, the inside of each rotating arm and the inside of each stirring rod are sequentially communicated, an air inlet is formed in the bottom of the rotating shaft, a first air distribution port is formed in each stirring rod, and a plurality of second air distribution ports are formed in the periphery of the upper part of the rotating shaft; and

and the flue gas introducing device is used for introducing odor generated in the sludge drying process towards the deodorizing part.

Preferably, the incinerator further comprises a support frame, the support frame is supported at the bottom of the support bottom plate, the rotating shaft downwards extends out of the support bottom plate, the extending end of the rotating shaft is rotatably arranged at the bottom of the support frame, and the air inlet is formed in the side wall of the extending section of the rotating shaft.

Preferably, the periphery of the part of the rotating shaft provided with the air inlet is sleeved with an air box, the rotating shaft can rotate relative to the air box, and the support frame is provided with a fan communicated with the air box.

Preferably, the support frame is provided with a slag discharging device, the slag discharging device comprises a chute with a water-cooling jacket, the chute is obliquely arranged, one end of the chute is connected with a slag discharging port, and the other end of the chute is connected with a screw conveyor with the water-cooling jacket.

Preferably, the inner ring of the supporting bottom plate extends upwards to be provided with an annular baffle plate, the annular baffle plate is sleeved on the periphery of the rotating shaft, and a slag discharge port is formed between the annular baffle plate and the rotating shaft.

Preferably, a feeding hole is arranged at a position of the side wall of the furnace body corresponding to the supporting bottom plate, and the feeding hole is connected with a conveying device for conveying sludge towards the top of the supporting bottom plate.

Preferably, the rotary arms are disposed in a horizontal direction, and the plurality of rotary arms are disposed at intervals along a circumferential direction of the rotating shaft.

Preferably, the flue gas introduction device comprises:

the first air entraining device comprises first air inlets which are arranged on the side wall of the furnace body at intervals along the circumferential direction of the furnace body; and

the second air entraining device comprises second air inlets which are arranged on the side wall of the furnace body at intervals along the circumferential direction of the furnace body;

the first air entraining device and the second air entraining device are arranged at intervals along the axial direction of the furnace body, and the first air inlet and the second air inlet are opposite to the deodorizing position.

Preferably, the first air inlet is opposite to the second air inlet in position along the axial direction of the furnace body.

Preferably, the number of the first air inlets is eight, and angles between the eight first air inlets and the axis of the radial direction of the furnace body are 25 °, 20 °, 15 °, 10 °, 5 °, 40 °, 35 ° and 30 ° in order;

the number of the second air inlets is eight, and the angles between the eight second air inlets and the axis of the radial direction of the furnace body are 5 degrees, 40 degrees, 35 degrees, 30 degrees, 25 degrees, 20 degrees, 15 degrees and 10 degrees in sequence.

Compared with the prior art, the technical scheme provided by the embodiment of the invention has the following advantages:

according to the invention, the first air distribution opening is arranged on the stirring rod, so that the stirring rod can supply air for the combustion of the sludge in the stirring process, each position of the sludge can be fully combusted, the incineration effect of the sludge is improved, the air supplementing is carried out on the unburned gas part at the upper part of the furnace body and the introduced odor through the second air distribution opening, the thorough combustion is further ensured, the generation of harmful substances is avoided, in addition, the odor generated in the drying process is deodorized in the deodorization part of the incinerator by utilizing the waste heat of the sludge combustion, no additional odor treatment equipment is required, the equipment cost is saved, the treatment problems of condensed water and odor are solved, and the environmental pollution is avoided.

Drawings

The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments consistent with the invention and together with the description, serve to explain the principles of the invention.

In order to more clearly illustrate the embodiments of the invention or the technical solutions in the prior art, the drawings which are used in the description of the embodiments or the prior art will be briefly described below, and it will be obvious to a person skilled in the art that other drawings can be obtained from these drawings without inventive effort.

FIG. 1 is a schematic view showing the structure of an incinerator according to an embodiment of the present invention;

FIG. 2 is a front view of an incinerator according to an embodiment of the present invention;

FIG. 3 is a schematic structural view of a stirring device according to an embodiment of the present invention;

FIG. 4 is a schematic view of the positional relationship between a stirring rod and a supporting base plate according to an embodiment of the present invention;

fig. 5 is a schematic view of an arrangement mode of a supporting frame according to an embodiment of the invention.

Description of the reference numerals

1. A furnace body; 11. a gas outlet; 12. a burner; 13. a feed inlet; 14. a first air inlet; 15. a second air inlet; 2. a support base plate; 21. an annular baffle; 3. a stirring device; 4. a rotating shaft; 41. an air inlet; 42. a second air distribution port; 43. a wind box; 44. a blower; 5. a slag discharge port; 6. a rotary arm; 7. a stirring rod; 71. a first air distribution port; 8. and (5) supporting frames.

Detailed Description

In order that the above objects, features and advantages of the invention will be more clearly understood, a further description of the invention will be made. The embodiments of the present invention and the features in the embodiments may be combined with each other without collision.

In the following description, numerous specific details are set forth in order to provide a thorough understanding of the present invention, but the present invention may be practiced otherwise than as described herein; it is apparent that the embodiments in the specification are only some embodiments of the present invention, but not all embodiments.

Referring to fig. 1 to 4, the sludge incineration rotary incinerator according to the embodiment of the present invention includes a furnace body 1, a stirring device 3, and a flue gas introduction device.

The inside of the furnace body 1 is sequentially provided with an incineration part and a deodorization part from bottom to top, the upper part of the furnace body 1 is provided with a gas outlet 11, and the upper part of the furnace body 1 can be the top of the furnace body 1 or the side wall of the upper part of the furnace body 1. The bottom of furnace body 1 is equipped with the supporting baseplate 2 that is used for placing the mud that waits to burn, and wherein, the axis of supporting baseplate 2 coincides with the axis of furnace body 1, and supporting baseplate 2 sets up along the horizontal direction promptly, and supporting baseplate 2 comprises 10mm thick platelike structure to lay the flame retardant coating at the upper portion of the supporting baseplate 2 of platelike structure, the flame retardant coating can adopt the refractory material preparation of wear-resisting high temperature resistant, plays thermal-insulated and increase of service life's effect. The side wall of the furnace body 1 is provided with a plurality of burners 12 for burning sludge in the burning portion, the plurality of burners 12 are uniformly distributed along the circumferential direction of the furnace body 1, preferably 4 burners 12, and the burners 12 are the usual components of the burning furnace, and thus, not described here too much.

As shown in fig. 3, the stirring device 3 includes a hollow rotating shaft 4 penetrating through the middle of the supporting base plate 2, the rotating shaft 4 is arranged along the vertical direction, the rotating shaft 4 can rotate relative to the supporting base plate 2, a slag discharging port 5 for discharging the incinerated sludge is arranged at a position, close to the rotating shaft 4, of the supporting base plate 2, a plurality of hollow rotating arms 6 are arranged on the periphery of a part of the rotating shaft 4 above the supporting base plate 2, specifically, the rotating arms 6 are arranged along the horizontal direction, and the rotating arms 6 are arranged at intervals along the circumferential direction of the rotating shaft 4. The bottom interval of gyration arm 6 is equipped with a plurality of hollow stirring bars 7, stirring bar 7 sets up along vertical direction for the stirring is in the mud at supporting baseplate 2 top, and, for the surface stirring mud in-process, mud removes towards supporting baseplate 2's middle part, the part stirring bar 7 that is close to the limit portion setting is flat tubulose, preferably, 2-3 stirring bars 7 that are close to the limit portion setting are flat tubulose, and flat tubulose stirring bar 7 inclines towards the direction of rotation of pivot 4, ensure the stirring effect of mud, simultaneously, make mud can remove towards supporting baseplate 2's middle part direction. The rest of the stirring rod 7 is in a circular tube shape so as to reduce resistance. In the burning process, the rotating shaft 4 rotates at the speed of 1 minute and 3 revolutions, so that the burning effect is ensured, and the cooling effect of the rotating arm 6 and the stirring rod 7 when the burning gas passes through can effectively prolong the service life.

As shown in fig. 4, the inside of the rotating shaft 4, the inside of the rotating arm 6 and the inside of the stirring rod 7 are sequentially communicated, the bottom of the rotating shaft 4 is provided with an air inlet 41, the stirring rod 7 is provided with a first air distribution opening 71 for distributing air for burning sludge, the burning effect of the sludge is ensured, the number of the first air distribution openings 71 is multiple, the first air distribution openings 71 are uniformly distributed on the periphery of the stirring rod 7, and the uniformity of gas distribution is ensured. The periphery of the upper portion of the rotating shaft 4 is provided with a plurality of second air distribution openings 42 for distributing air for insufficiently combusted gas at the top of the sludge and odor combustion entering the deodorizing part, ensuring that the gas is sufficiently combusted and avoiding the generation of harmful gas. In use, combustion gas enters the rotary shaft 4 through the air inlet 41 and flows in the rotary shaft 4, part of the combustion gas is discharged through the second air distribution opening 42, the other part of the combustion gas flows to the inner wall of the rotary arm 6, the combustion gas is respectively distributed into each stirring rod 7 through the rotary arm 6, and finally the combustion gas is discharged through the first air distribution opening 71 of the stirring rod 7 for the combustion of sludge, wherein the combustion gas is preferably air. The flue gas introducing device is used for introducing odor generated in the sludge drying process towards the deodorizing part.

According to the invention, the first air distribution opening 71 is arranged on the stirring rod 7, so that the stirring rod 7 can supply air for the combustion of the sludge in the stirring process, each position of the sludge can be fully combusted, the generation of fly ash is greatly reduced, the incineration effect of the sludge is improved, more than 90% of sludge incombustible is discharged in the form of slag, the recycling of the sludge is realized, the air supplementing is carried out on the unburned gas part at the upper part of the furnace body 1 and the introduced odor through the second air distribution opening 42, the thorough combustion is further ensured, the generation of harmful substances is avoided, and in addition, the odor generated in the drying process is deodorized in the deodorization part of the incinerator by utilizing the waste heat of the sludge combustion, so that equipment cost is saved, the treatment problems of condensed water and the odor are solved, and the environmental pollution is avoided.

As shown in fig. 1, 2 and 5, the incinerator further comprises a support frame 8, wherein the support frame 8 is supported at the bottom of the support bottom plate 2 and plays a role in supporting the incinerator body 1, and meanwhile, the incinerated sludge can be discharged through the bottom of the incinerator body 1. The rotating shaft 4 downwards extends out of the supporting bottom plate 2, the extending end of the rotating shaft 4 is rotatably arranged at the bottom of the supporting frame 8, the air inlet 41 is formed in the side wall of the extending section of the rotating shaft 4, and the driving device and the air blowing device of the rotating shaft 4 are conveniently arranged in the design mode, so that the structural distribution is more reasonable.

The setting mode of the driving device can comprise the following embodiments, specifically, the driving device for driving the rotating shaft 4 to rotate can be arranged on the supporting frame 8, the driving device comprises a driving motor and a reduction gear set, specifically, the driving motor can be arranged on the supporting frame 8, the reduction gear set comprises a driving wheel, a reduction wheel and a driven wheel, the driving wheel, the reduction wheel and the driven wheel are all arranged in a bottom plate of the supporting frame 8, the driving wheel is arranged on an output shaft of the driving motor, the driving wheel is driven to rotate through rotation of the driving wheel, the driven wheel is arranged at the bottom end of the rotating shaft 4, the reduction wheel is driven to rotate through rotation of the driving wheel, the rotating shaft 4 is driven to rotate, and the reduction ratio can be controlled through specific sizes of the driving wheel, the reduction wheel and the driven wheel, so that the rotating speed of the rotating shaft 4 is controlled.

As shown in fig. 5, the arrangement mode of the blower device may include the following embodiments, specifically, the part of the periphery of the rotating shaft 4 provided with the air inlets 41 is sleeved with the air bellows 43, the plurality of air inlets 41 are arranged at intervals along the circumferential direction of the rotating shaft 4. The pivot 4 can rotate for bellows 43, and bellows 43 fixes on support frame 8 promptly, in addition, be equipped with on the support frame 8 with bellows 43 intercommunication's fan 44, fan 44 carries combustion gas (air) towards bellows 43, combustion gas is full of bellows 43, combustion gas rethread air intake 41 after full bellows 43 enters into in pivot 4 to distribute combustion gas through pivot 4, under this kind of design mode, bellows 43 can not influence pivot 4's rotation, and no matter be in the air intake 41 rotation to any angle on pivot 4, combustion gas in bellows 43 all can enter into pivot 4 through air intake 41.

The support frame 8 is provided with a slag discharging device which comprises a chute with a water-cooling jacket and arranged in an inclined way, one end of the chute is connected with a slag discharging port 5, and the other end of the chute is connected with a screw conveyor with the water-cooling jacket. So that the burnt sludge can enter the chute through the slag discharge port 5 and slide to the screw conveyor through the obliquely arranged chute for distributing the dry sludge.

As shown in fig. 4, the inner ring of the supporting bottom plate 2 is provided with an annular baffle 21 in an upward extending manner, the annular baffle 21 is sleeved on the periphery of the rotating shaft 4, so that the rotating shaft 4 can rotate relative to the annular baffle 21, and a slag discharging port 5 is formed between the annular baffle 21 and the rotating shaft 4. When the sludge incinerator is used, sludge gradually moves towards the middle of the supporting bottom plate 2 through rotation of the stirring rod 7 and is compared with the side surface of the annular baffle plate 21, when the sludge is accumulated to a certain volume, the incinerated sludge is turned out from the top of the annular baffle plate 21 and is discharged from the slag discharge port 5. Further optimally, an opening can be arranged on the annular baffle plate 21, and the incinerated sludge can enter the slag discharging opening 5 through the opening so as to be discharged, so that the design can be carried out according to actual use requirements.

The side wall of furnace body 1 is equipped with feed inlet 13 with the corresponding position department of supporting baseplate 2, and feed inlet 13 is connected with the conveying equipment who is used for carrying mud towards the top of supporting baseplate 2, and conveying equipment carries the mud behind feed inlet 13 to fall in the limit position of supporting baseplate 2, along with the rotation of revolving arm 6, while pushing away mud, stirs mud through stirring rod 7 gradually screeds mud for mud evenly burns, and pushes away mud towards the middle part of supporting baseplate 2 gradually through stirring rod 7, ensures the combustion effect.

As shown in connection with fig. 1 and 2, the flue gas introduction device comprises a first bleed air device and a second bleed air device. The first air entraining device comprises first air inlets 14 arranged on the side walls of the furnace body 1 at intervals in the circumferential direction of the furnace body 1. The second bleed air device comprises second air inlets 15 arranged on the side walls of the furnace body 1 at intervals in the circumferential direction of the furnace body 1. The first air entraining device and the second air entraining device are arranged at intervals along the axial direction of the furnace body 1, and the first air inlet 14 and the second air inlet 15 are opposite to the deodorizing position, wherein the first air entraining device is arranged between the feeding hole 13 and the second air entraining device. Preferably, the first air intake 14 is opposed to the second air intake 15 in position along the axial direction of the furnace body 1. The number of first air inlets 14 is eight, and angles between the eight first air inlets 14 and the axis of the furnace body 1 in the radial direction are 25 °, 20 °, 15 °, 10 °, 5 °, 40 °, 35 °, and 30 ° in order. The number of the second air inlets 15 is eight, and the angles between the eight second air inlets 15 and the axis of the furnace body 1 in the radial direction are 5 °, 40 °, 35 °, 30 °, 25 °, 20 °, 15 °, and 10 ° in order. By adopting the arrangement mode and the first air inlet 14 and the second air inlet 15 which are arranged at the angle, spiral vortex-shaped air flows can be generated, the turbulence degree inside the furnace body 1 can be enhanced, the air can be better mixed, the combustion temperature inside the furnace body 1 is more uniform, and the combustion deodorization effect of odor is ensured.

It should be noted that in this document, relational terms such as "first" and "second" and the like are used solely to distinguish one entity or action from another entity or action without necessarily requiring or implying any actual such relationship or order between such entities or actions. Moreover, the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus. Without further limitation, an element defined by the phrase "comprising one … …" does not exclude the presence of other like elements in a process, method, article, or apparatus that comprises the element.

The foregoing is only a specific embodiment of the invention to enable those skilled in the art to understand or practice the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other embodiments without departing from the spirit or scope of the invention. Thus, the present invention is not intended to be limited to the embodiments shown and described herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A sludge incineration rotary incinerator, comprising:

the device comprises a furnace body (1), wherein an incineration part and a deodorization part are sequentially arranged in the furnace body (1) from bottom to top, a gas outlet (11) is formed in the upper part of the furnace body (1), a supporting bottom plate (2) for placing sludge to be incinerated is arranged at the bottom of the furnace body (1), and a combustor (12) for incinerating the sludge is arranged on the side wall of the furnace body (1);

stirring device (3), stirring device (3) are including wearing to establish hollow pivot (4) at bottom plate (2) middle part, pivot (4) can rotate for bottom plate (2) are supported, bottom plate (2) are close to the position of pivot (4) is equipped with and supplies mud exhaust sediment mouth (5) after burning, be in the part of bottom plate (2) top the periphery of pivot (4) is equipped with a plurality of hollow revolving arms (6), the bottom interval of revolving arms (6) is equipped with a plurality of hollow stirring rod (7), stirring rod (7) are used for stirring and are in the mud at bottom plate (2) top, the inside of pivot (4) the inside of revolving arm (6) with the inside of stirring rod (7) communicates in proper order, the bottom of pivot (4) is equipped with air intake (41), be equipped with first air distribution mouth (71) on stirring rod (7), the periphery of the upper portion of pivot (4) is equipped with a plurality of second air distribution mouths (42); and

and the flue gas introducing device is used for introducing odor generated in the sludge drying process to the deodorizing part.

2. The sludge incineration rotary incinerator according to claim 1, further comprising a supporting frame (8), wherein the supporting frame (8) is supported at the bottom of the supporting base plate (2), the rotating shaft (4) downwardly extends out of the supporting base plate (2), the extending end of the rotating shaft (4) is rotatably arranged at the bottom of the supporting frame (8), and the air inlet (41) is arranged on the side wall of the extending section of the rotating shaft (4).

3. The sludge incineration rotary incinerator according to claim 2, wherein a bellows (43) is sleeved on the periphery of the part of the rotating shaft (4) provided with the air inlet (41), the rotating shaft (4) can rotate relative to the bellows (43), and a fan (44) communicated with the bellows (43) is arranged on the support frame (8).

4. The sludge incineration rotary incinerator according to claim 2, wherein the support frame (8) is provided with a slag discharging device, the slag discharging device comprises a chute with a water cooling jacket, the chute is obliquely arranged, one end of the chute is connected with the slag discharging port (5), and the other end of the chute is connected with a screw conveyor with the water cooling jacket.

5. The sludge incineration rotary incinerator according to claim 1, wherein an annular baffle plate (21) is arranged on the inner ring of the supporting bottom plate (2) in an upward extending mode, the annular baffle plate (21) is sleeved on the periphery of the rotating shaft (4), and a slag discharging port (5) is formed between the annular baffle plate (21) and the rotating shaft (4).

6. The sludge incineration rotary incinerator according to claim 1, characterized in that a feed inlet (13) is arranged at a position of the side wall of the incinerator body (1) corresponding to the supporting bottom plate (2), and the feed inlet (13) is connected with a conveying device for conveying sludge towards the top of the supporting bottom plate (2).

7. The sludge incineration rotary incinerator according to claim 1, characterized in that the rotary arms (6) are arranged in a horizontal direction, and a plurality of the rotary arms (6) are arranged at intervals along a circumferential direction of the rotary shaft (4).

8. The sludge incineration rotary incinerator according to any one of claims 1 to 7, wherein the flue gas introduction device comprises:

the first air entraining device comprises first air inlets (14) which are arranged on the side wall of the furnace body (1) at intervals along the circumferential direction of the furnace body (1); and

the second air entraining device comprises second air inlets (15) which are arranged on the side wall of the furnace body (1) at intervals along the circumferential direction of the furnace body (1);

the first air entraining device and the second air entraining device are arranged at intervals along the axial direction of the furnace body (1), and the first air inlet (14) and the second air inlet (15) are opposite to the deodorizing position.

9. The sludge incineration rotary incinerator according to claim 8, characterized in that the first air inlet (14) is opposite to the second air inlet (15) in position along the axial direction of the furnace body (1).

10. The sludge incineration rotary incinerator according to claim 8, characterized in that,

the number of the first air inlets (14) is eight, and angles between the eight first air inlets (14) and the axis of the furnace body (1) in the radial direction are 25 degrees, 20 degrees, 15 degrees, 10 degrees, 5 degrees, 40 degrees, 35 degrees and 30 degrees in sequence;

the number of the second air inlets (15) is eight, and the angles between the eight second air inlets (15) and the axis of the radial direction of the furnace body (1) are 5 degrees, 40 degrees, 35 degrees, 30 degrees, 25 degrees, 20 degrees, 15 degrees and 10 degrees in sequence.