JP3564040B2 - Exhaust heat recovery equipment in melting furnace - Google Patents

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention is used in a melting treatment facility provided with a melting furnace for melting a substance to be melted such as incineration residue and fly ash discharged from a refuse incinerator or sewage sludge or crushed incombustible material. The present invention relates to an exhaust heat recovery device in a melting furnace having both a function as a secondary combustion tower for secondary combustion of exhaust gas discharged from a furnace and a function as an air preheater for recovering heat from high-temperature exhaust gas.
[0002]
[Prior art]
In recent years, in order to reduce the volume and harmlessness of incineration residues and fly ash (hereinafter referred to as “melted material”) discharged from refuse incinerators, a method of melting and solidifying the material to be melted has attracted attention, and it has actually been put to practical use. Have been. This is because by melting and solidifying the material to be melted, its volume can be reduced to 1/2 to 1/3, and it is physically and chemically stable to prevent elution of harmful substances such as heavy metals and dioxins. This makes it possible to completely disassemble, reuse as concrete filler materials, roadbed materials, blocks, etc., extend the life of the final landfill site, etc.
[0003]
Thus, in the method of melting and solidifying the material to be melted, an electric melting furnace such as an arc melting furnace, a plasma arc furnace, or an electric resistance furnace is used, and the material to be melted is melted by electric energy. Using a method of solidifying by water cooling or air cooling and a surface melting furnace, a swirling melting furnace, a combustion type melting furnace such as a coke bed furnace, and melting the material to be melted by the combustion energy of fossil fuel such as kerosene or natural gas, The method of solidifying this by water cooling or air cooling is often used, and when the power generation equipment is installed in the melting treatment facility for the material to be melted, the former method using electric energy, When not juxtaposed, the latter method using combustion energy is often adopted.
[0004]
FIG. 5 is a schematic system diagram showing an example of a melting treatment facility for a material to be melted using a surface melting furnace. In FIG. 5, reference numeral 40 denotes a surface melting furnace, 41 denotes a high-temperature flue, and 42 denotes a secondary combustion tower. , 43 is a secondary combustion air blowing nozzle, 44 is a secondary combustion air supply pipe, 45 is a secondary combustion air blower, 46 is a gas cooling blower, 47 is an air preheater, and 48 is a surface melting furnace. A combustion air supply pipe to the burner 62, 49 is a push-in blower, 50 is a gas cooling device, 51 is cooling water, 52 is a supply pipe for activated carbon, slaked lime and auxiliary, 53 is a dust collector, 54 is a fly ash conveyer. Reference numeral 55 denotes a catalytic denitration tower, reference numeral 56 denotes an induction ventilator, and reference numeral 57 denotes a chimney.
[0005]
The surface melting furnace 40 uses combustion heat of fossil fuel such as kerosene or natural gas as a heat source, and is provided with a material to be melted from four directions into the furnace to form a four-sided molten surface. The structure or the furnace has a face-to-face structure in which a material to be melted is supplied from two facing directions to form an inclined molten surface.
That is, as shown in FIG. 1, the surface melting furnace 40 includes a furnace body 58, hoppers 59 provided in four directions or two facing directions around the furnace body 58, and a material W to be distributed and charged into each hopper 59. A melt distributing / supplying device 60, a melt extruding device 61 for supplying the melt W supplied to each hopper 59 into the furnace, and one unit for heating and melting the melt W in the furnace from the front side or A plurality of burners 62, a slag tap 63 for discharging molten slag, a water-sealed slag conveyor 64 (or air-cooled slag conveyor) for granulating (or air cooling) and discharging molten slag flowing down from the slag tap 63, and the like. , And a secondary combustion tower 42 and an air preheater 47 are sequentially connected to the surface melting furnace 40 via a high-temperature flue 41.
[0006]
The secondary combustion tower 42 has a cylindrical refractory structure having a secondary combustion chamber S therein, and a secondary revolving section that gives a swirl into the secondary combustion chamber S is provided at a lower position of the secondary combustion tower 42. A combustion air blowing nozzle 43 is provided.
As shown in FIG. 6, the air preheater 47 has a double cylindrical structure in which an inner cylinder 65 and an outer cylinder 66 made of steel plates having different diameters are arranged concentrically. When the high temperature exhaust gas G flows, the combustion air A for the burner 62 flowing between the inner cylinder 65 and the outer cylinder 66 is heated. This air preheater 47 absorbs the thermal expansion between the inner cylinder 65 and the outer cylinder 66 caused by the temperature rise by the expansion joint 67.
[0007]
Thus, in the melting processing equipment, the melted material W such as incineration residues distributed and injected into the respective hoppers 59 by the melted material distribution and supply device 60 is moved into the furnace body 58 by the melted material extruding device 61. And is deposited on the furnace bottom in a state where the surface becomes a substantially mortar-shaped inclined surface centering on the slag tap 63, and is sequentially heated and melted from the surface side by the combustion heat of the burner 62, thereby melting the film. It becomes slag. The molten slag flows down a mortar-shaped inclined surface, falls from a slag tap 63 onto a water-sealed slag conveyor 64, is cooled and solidified by cooling water to form granulated slag, and then is cooled by a water-sealed slag conveyor 64. It is discharged by.
[0008]
On the other hand, the high-temperature combustion exhaust gas G in the furnace main body 58 is discharged from the slag tap 63 together with the molten slag, and is sent into the secondary combustion tower 42 through the high-temperature flue 41. The combustion exhaust gas G sent into the secondary combustion tower 42 is injected into the secondary combustion chamber S by the secondary combustion air A ′ blown into the secondary combustion chamber S from the secondary combustion air injection nozzle 43. Secondary combustion. Thereby, the unburned gas contained in the exhaust gas G is completely burned in the secondary combustion chamber S with a sufficient residence time and temperature.
The exhaust gas G that has been completely burned continues to enter the air preheater 47, where the combustion air A for the burner 62 sent from the forced blower 49 to the air preheater 47 is heated to about 350 ° C. After passing through the cooling device 50, the dust collecting device 53, the catalytic denitration tower 55, the draft ventilator 56 and the chimney 57, it is released as clean gas into the atmosphere.
[0009]
[Problems to be solved by the invention]
By the way, when the secondary combustion tower 42 and the air preheater 47 are installed as separate devices as in the above-mentioned melting processing equipment, there are the following problems (1) to (4).
{Circle around (1)} The secondary combustion tower 42 needs to have a sufficient size to completely burn unburned gas in the exhaust gas G, and the air preheater 47 also has a sufficient size to recover heat from the exhaust gas G. A heat transfer area is required, and the secondary combustion tower 42 and the air preheater 47 are both large devices. As a result, a space for separately installing the secondary combustion tower 42 and the air preheater 47 is inevitably large, and there is a problem that construction costs and equipment costs increase.
{Circle around (2)} Since the inner cylinder 65 of the air preheater 47 comes into direct contact with the exhaust gas G, the temperature of the exhaust gas G is set to around 650 ° C. so that the inner peripheral surface temperature of the inner cylinder 65 becomes lower than the maximum use temperature of the material of the inner cylinder 65. Need to be lowered to However, since the temperature of the exhaust gas near the outlet of the secondary combustion tower 42 is close to 900 ° C., cooling air or cooling water must be blown before the air preheater 47 to cool the exhaust gas G. The problem is that the amount increases.
{Circle around (3)} The secondary combustion tower 42 decomposes dioxins by completely burning the exhaust gas G at a high temperature of 850 ° C. or higher with a sufficient residence time, while the air preheater 47 degrades the dioxin between the inner cylinder 65 and the outer cylinder 66. However, there is a problem that a temperature range (around 300 ° C.) where dioxins are easily re-synthesized in the boundary layer of the exhaust gas G flowing near the inner peripheral surface of the inner cylinder 65 due to the temperature of the combustion air A flowing through the inner cylinder 65.
{Circle around (4)} In the exhaust gas G discharged from the surface melting furnace 40, HCl contained in the exhaust gas G is as high as several thousand ppm depending on the properties of the material to be melted W, and the inner peripheral surface of the inner cylinder 65 of the air preheater 47. Therefore, there is a problem that corrosion dust is caused on the inner peripheral surface of the inner cylinder 65 of the air preheater 47 because the molten dust mainly containing the molten salts adheres to the inner surface.
[0010]
The present invention has been made in view of such a problem, and its purpose is to integrate a secondary combustion tower and an air preheater that are installed as separate devices having different applications, thereby reducing the size of the equipment and reducing the size of the equipment. It is an object of the present invention to provide an exhaust heat recovery device in a melting furnace, which can reduce costs, prevent resynthesis of dioxins, and prevent corrosion due to exhaust gas.
[0011]
[Means for Solving the Problems]
In order to achieve the above object, the invention according to claim 1 of the present invention is to completely burn unburned gas in exhaust gas discharged from a melting furnace and to recover heat from the exhaust gas to heat combustion air. Heat recovery equipment in a molten furnaceIn the exhaust heat recovery device, combustion air is provided between an inner cylinder that forms a secondary combustion chamber into which exhaust gas from a melting furnace is fed and an outer peripheral surface of the inner cylinder that is disposed outside the inner cylinder. And an outer cylinder forming an annular preheating passage that passes therethrough.The unburned gas in the exhaust gas is subjected to secondary combustion in the secondary combustion chamber with secondary combustion air to complete combustion, and passes through the preheating passage. Heat recovery device in a melting furnace in which the combustion air to be heated is heated by the high temperature exhaust gas in the secondary combustion chamber through the inner cylinder, wherein the inner cylinder forming the secondary combustion chamber is formed of a metal cylinder. The inner cylinder is made of a refractory having excellent corrosion resistance and heat conductivity on the inner peripheral surface, and an air injection nozzle for secondary combustion is provided at a position upstream of the secondary combustion chamber to provide secondary combustion. Secondary combustion along the inner peripheral surface of the inner cylinder from the air blowing nozzle It is to that so as to form a swirling flow in the secondary combustion chamber by blowing air and the basic structure of the invention.
[0012]
The invention of claim 2 of the present inventionIn the exhaust heat recovery device in the melting furnace in which the unburned gas in the exhaust gas discharged from the melting furnace is completely burned and heat is recovered from the exhaust gas to heat the combustion air, The recovery device includes an inner cylinder forming a secondary combustion chamber into which exhaust gas from the melting furnace is fed, and an annular preheating passage through which combustion air passes between the inner cylinder and an outer peripheral surface of the inner cylinder. The secondary combustion chamber comprises an outer cylinder that forms unburned gas. The unburned gas in the exhaust gas is subjected to secondary combustion in the secondary combustion chamber with secondary combustion air to complete combustion, and the combustion air passing through the preheating passage is subjected to secondary combustion. An exhaust heat recovery device in a melting furnace in which a high temperature exhaust gas in a combustion chamber heats through an inner cylinder, wherein an inner cylinder forming a secondary combustion chamber is formed in a cylindrical shape from a porous refractory. The combustion air passing through the preheating passage from the refractory The basic structure of the invention is to heat by conduction and to allow a part of the combustion air in the preheating passage to flow into the secondary combustion chamber from the porous refractory hole as the secondary combustion air. It is.
[0013]
The invention of claim 3 of the present invention provides:A secondary combustion air blowing nozzle is provided at an upstream position of the secondary combustion chamber, and secondary combustion air is blown from the secondary combustion air blowing nozzle along the inner peripheral surface of the inner cylinder in a tangential direction thereof. Thus, a swirling flow is formed in the secondary combustion chamber.
[0014]
According to the invention of claim 4 of the present invention, the inner cylinder forming the secondary combustion chamber is formed in a cylindrical shape by a porous refractory, and the combustion air passing through the preheating passage is transferred by heat conduction from the refractory. In addition to the heating, a part of the combustion air in the preheating passage flows as secondary combustion air from the porous refractory hole into the secondary combustion chamber.
[0016]
The exhaust heat recovery apparatus 1 completely burns the unburned gas in the high-temperature combustion exhaust gas G that has passed through the high-temperature flue 10 from the surface melting furnace 2, and recovers heat from the exhaust gas G for the burner 7. It heats the combustion air A (or both the combustion air A for the burner 7 and the secondary combustion air A ') and has both a function as a conventional secondary combustion tower and a function as an air preheater. Things.
[0017]
That is, the exhaust heat recovery device 1 includes an inner cylinder 24 that forms a secondary combustion chamber S having a circular cross-sectional shape into which the high-temperature flue gas G that has passed through the high-temperature flue 10 is sent, and an outer periphery of the inner cylinder 24. An outer cylinder 25 that forms an annular preheating passage S ′ through which combustion air A for the burner 7 passes between the outer combustion surface A and the secondary combustion chamber B that blows the secondary combustion air A ′ into the secondary combustion chamber S The secondary combustion chamber S includes an air injection nozzle 11 and the like, and the unburned gas in the exhaust gas G is secondary-combusted by the secondary combustion air A 'in the secondary combustion chamber S and completely burned. The combustion air A for the burner 7 is heated by the exhaust gas G in the secondary combustion chamber S through the inner cylinder 24.
[0018]
Specifically, as shown in FIG. 2, the inner cylinder 24 is formed by lining a refractory 26 having excellent corrosion resistance and heat conductivity on the inner peripheral surface of a steel plate cylinder 24a. The refractory 26 has corrosion resistance to corrosive gas such as HCl and adhered dust mainly including molten salts such as NaCl and KCl, and has excellent thermal conductivity. And refractory bricks and other fixed refractories are used.
[0019]
As shown in FIG. 2, the outer cylinder 25 is formed of a steel plate into a cylindrical shape having a larger diameter than the inner cylinder 24, and is disposed concentrically around the outer periphery of the inner cylinder 24 to form an outer peripheral surface of the inner cylinder 24. And an annular preheating passage S 'through which the combustion air A for the burner 7 passes.
An inlet 27 for supplying fresh combustion air A to the preheating passage S 'is formed at the lower end of the outer cylinder 25, and the inlet 27 is connected to the push-in blower 15 via the combustion air supply pipe 14. Have been. An outlet 28 through which the combustion air A heated in the preheating passage S 'flows out is formed at the upper end of the outer cylinder 25, and the outlet 28 is connected to the burner 7 through the combustion air supply pipe 14. It is connected to the.
[0020]
The upper end of the inner cylinder 24 and the outer cylinder 25 are connected in an airtight manner, and the lower ends thereof are connected in an airtight manner via an expansion joint 29. The expansion joint 29 absorbs thermal expansion generated between the outer cylinder 25 and the outer cylinder 25.
[0021]
As shown in FIGS. 2 and 3, the secondary combustion air blowing nozzle 11 is provided at several positions upstream of the secondary combustion chamber S (lower position in FIG. 2). The secondary combustion air A 'is blown in the tangential direction along the inner peripheral surface of the secondary combustion chamber to form a swirling flow in the secondary combustion chamber S. The secondary combustion air blowing nozzle 11 is connected to a forced air blower 15 via a secondary combustion air supply pipe 12.
[0022]
The exhaust heat recovery device 1 has an upstream end (lower end in FIG. 2) connected to a high-temperature flue 10 through which high-temperature combustion exhaust gas G discharged from the surface melting furnace 2 flows. The downstream end (upper end in FIG. 2) is connected to the cooling device 16 so as to communicate with the exhaust gas G sent from the high-temperature flue 10 in the secondary combustion chamber S. After the secondary combustion by the secondary combustion air A ', the air is sent into the gas cooling device 16 and the combustion air A for the burner 7 flowing in the preheating passage S' is heated.
[0023]
Next, a case in which the material to be melted W such as incineration residues is melted using the melting processing equipment provided with the above-described exhaust heat recovery device 1 will be described.
The molten material W such as incineration residue discharged from the refuse incinerator is distributed and charged into each hopper 4 by the molten material distributing and supplying device 5, and then sequentially into the melting furnace main body 3 by the molten material extruding device 6. It is fed and deposited on the furnace bottom in a state where the surface is a substantially mortar-shaped inclined surface centering on the slag tap 8.
[0024]
The material to be melted W deposited on the furnace bottom is heated to a high temperature of 1300 ° C. to 1400 ° C. by the combustion flame from the burner 7 and is sequentially melted from the surface side to become a film-like molten slag. The molten slag flows down the mortar-shaped inclined surface, falls from the slag tap 8 onto the water-sealed slag conveyor 9, is cooled and solidified by the cooling water to form granulated slag, and then becomes the water-sealed slag conveyor 9. It is discharged by.
[0025]
As the molten slag flows down the inclined surface, new molten materials W are successively exposed on the inclined surface, and the exposed new molten materials W are successively formed into films by the combustion flame from the burner 7. Going to be melted.
When the melted inclined surface recedes with the progress of melting, the molten material extruding device 6 operates to push the new molten material W in the hopper 4 into the furnace. As a result, the melted inclined surface of the material W layer is maintained at an angle of repose or an angle close to the angle of repose of the material W to be melted. As a result, the molten slag that has been melted in the form of a film easily flows down the inclined surface, so that a new material to be melted W is immediately exposed, and the melting process is rapidly performed.
[0026]
On the other hand, the high-temperature combustion exhaust gas G generated in the furnace main body 3 is discharged from the slag tap 8 together with the molten slag, is sent to the exhaust heat recovery device 1 through the high-temperature flue 10, and is subjected to secondary combustion therein. As well as heat recovery.
That is, the combustion exhaust gas G sent into the secondary combustion chamber S of the exhaust heat recovery device 1 is generated by the secondary combustion air A ′ blown into the secondary combustion chamber S from the secondary combustion air blowing nozzle 11. Secondary combustion is performed in the secondary combustion chamber S. At this time, the secondary combustion air A 'is blown from the secondary combustion air blowing nozzle 11 along the inner peripheral surface of the inner cylinder 24 in the tangential direction to form a swirl flow in the secondary combustion chamber S. Therefore, the unburned gas contained in the exhaust gas G is stirred and burned in the secondary combustion chamber S with a sufficient residence time and temperature. As a result, the unburned gas in the exhaust gas G discharged from the surface melting furnace 2 is completely burned.
In addition, fresh combustion air A (temperature: about 20 ° C.) is fed into the preheating passage S ′ of the exhaust heat recovery device 1 from the forced air blower 15 and the combustion air supply pipe 14. The combustion air A flowing in the preheating passage S ′ is heated to about 350 ° C. by heat conduction from the refractory 26 forming the inner cylinder 24, and then supplied to the burner 7 through the combustion air supply pipe 14. It is used for combustion.
[0027]
Then, the exhaust gas G after the secondary combustion in the secondary combustion chamber S of the exhaust heat recovery device 1 is continuously sent to the gas cooling device 16, where the temperature is reduced to 200 ° C. or less by injection of the cooling water 17. After that, the gas passes through the dust collecting device 19, the catalytic denitration tower 21, the induction ventilator 22, and the chimney 23 and is released as clean gas into the atmosphere.
[0028]
As described above, the exhaust heat recovery device 1 has both a function as a secondary combustion tower and a function as an air preheater. Without separately installing the air preheater, the installation space can be halved and the construction cost and equipment cost can be significantly reduced.
Further, in the exhaust heat recovery device 1, since the inner cylinder 24 is formed by lining the refractory 26 on the inner peripheral surface of the metal cylinder 24 a, the high temperature and high corrosiveness flowing in the secondary combustion chamber S The exhaust gas G or dust does not directly contact the cylinder 24a, which is a metal member, so that corrosion of the inner cylinder 24 can be prevented. Needless to say, by lining the refractory material 26, there is no need to lower the temperature of the exhaust gas G to be lower than the maximum operating temperature of the inner cylinder material unlike the conventional air preheater. At the same time, it is not necessary to blow cooling air before the air preheater, and the amount of exhaust gas G discharged does not increase.
Further, the exhaust heat recovery device 1 heats the combustion air A of the burner 7 passing through the preheating passage S 'by heat conduction from the refractory 26 lining the inner peripheral surface of the inner cylinder 24. In addition, the surface temperature of the refractory 26 in contact with the exhaust gas G does not drop significantly. As a result, a temperature range (around 300 ° C.) where dioxins are easily re-synthesized is not created in the exhaust gas G flowing near the inner peripheral surface of the inner cylinder 24, and an effect as a measure against dioxins is obtained.
[0029]
FIG. 4 is a schematic cross-sectional view of an exhaust heat recovery apparatus 1 according to another embodiment of the present invention. The exhaust heat recovery apparatus 1 includes a high-temperature flue gas G that has passed through a high-temperature flue 10. And the like, which forms an annular preheating passage S 'through which combustion air A for the burner 7 passes between the inner cylinder 24 forming the secondary combustion chamber S into which the air is sent, and the outer peripheral surface of the inner cylinder 24. The inner cylinder 24 forming the secondary combustion chamber S is formed in a cylindrical shape by a porous refractory 26 ', and the combustion air A for the burner 7 passing through the preheating passage S' is refractory 26 ′, And a part of the combustion air A in the preheating passage S ′ flows into the secondary combustion chamber S from the hole of the porous refractory 26 ′ as the secondary combustion air A ′. It has become.
[0030]
The inner cylinder 24 is formed by stacking porous block-shaped refractories 26 'in a cylindrical shape, and each refractory 26' is supported by the outer cylinder 25 via a plurality of hooks 30 made of steel. Have been. That is, each refractory 26 ′ is formed by embedding one end of a steel hook 30 in each refractory 26 ′ and fixing the other end of the hook 30 to the inner peripheral surface of the outer cylinder 25 by welding or the like. It is supported by the outer cylinder 25. As the refractory 26 ', a refractory 26' having excellent heat conductivity and capable of allowing a part of the combustion air A flowing in the preheating passage S 'to flow into the secondary combustion chamber S is used. I have.
[0031]
The outer cylinder 25 is formed of a steel plate into a cylindrical shape having a larger diameter than the inner cylinder 24, is disposed concentrically around the outer periphery of the inner cylinder 24, and is disposed between the outer cylinder 25 and the outer peripheral surface of the inner cylinder 24. To form an annular preheating passage S 'through which the combustion air A passes.
An inlet 27 for supplying fresh combustion air A to the preheating passage S 'is formed at the lower end of the outer cylinder 25. The inlet 27 is connected to the push-in blower 15 through the combustion air A supply pipe 14. It is connected. An outlet 28 through which the combustion air A heated in the preheating passage S 'flows out is formed at the upper end of the outer cylinder 25, and the outlet 28 is connected to the burner 7 through the combustion air supply pipe 14. It is connected to the.
[0032]
The upper end of the inner cylinder 24 and the outer cylinder 25 are connected in an airtight manner, and the lower ends thereof are connected in an airtight manner via an expansion joint 29. The expansion joint 29 absorbs the thermal expansion generated between the outer cylinder 24 and the outer cylinder 25.
In FIG. 4, reference numeral 31 denotes a damper interposed in the combustion air supply pipe 14, and 32 denotes a damper so that the temperature and the flow rate of the combustion air A flowing in the combustion air supply pipe 14 become predetermined values. 31 is a controller that controls 31.
[0033]
Thus, in the exhaust heat recovery device 1, the heat of the combustion exhaust gas G sent into the secondary combustion chamber S of the exhaust heat recovery device 1 through the high-temperature flue 10 forms the inner cylinder 24. The combustion air A transmitted to the refractory 26 'and flowing in the preheating passage S' by heat conduction from the refractory 26 'is heated to about 350C. The heated combustion air A is supplied to the burner 7 through the combustion air supply pipe 14 and used for combustion.
A part of the combustion air A in the preheating passage S 'flows into the secondary combustion chamber S from the hole of the porous refractory 26', and is used as the secondary combustion air A '. As a result, the combustion exhaust gas G in the secondary combustion chamber S is subjected to secondary combustion in the secondary combustion chamber S by the secondary combustion air A ', and the unburned gas contained in the exhaust gas G is converted to the secondary combustion air. It is completely burned in the combustion chamber S. The exhaust gas G that has been completely burned is continuously sent to the gas cooling device 16, where the temperature of the exhaust gas G is reduced to 200 ° C. or less by injection of the cooling water 17, and then the dust collecting device 19, the catalytic denitration tower 21, the induction draft fan 22, It is released as clean gas through the chimney 23 into the atmosphere.
[0034]
The exhaust heat recovery device 1 can achieve the same operation and effect as the exhaust heat recovery device 1 shown in FIG. 2 described above. Naturally, the exhaust heat recovery apparatus 1 is a porous refractory in which a part of the combustion air A for the burner 7 flowing in the preheating passage S 'forms the inner cylinder 24 as the secondary combustion air A'. Since the gas flows from the inner peripheral surface of the inner cylinder 24 into the secondary combustion chamber S through the hole 26 ', dust can be prevented from adhering to the inner peripheral surface of the inner cylinder 24.
[0035]
【The invention's effect】
As described above, in the exhaust heat recovery apparatus of the first aspect of the present invention, the outer cylinder is disposed around the inner cylinder forming the secondary combustion chamber, and the combustion air passes between the inner cylinder and the outer cylinder. An annular preheating passage is formed, and the unburned gas in the exhaust gas is subjected to secondary combustion in the secondary combustion chamber with the secondary combustion air to complete combustion, and the combustion air passing through the preheating passage is subjected to secondary combustion. The hot exhaust gas in the combustion chamber is heated through the inner cylinder. That is, since the exhaust heat recovery device of the present invention has both the function as a secondary combustion tower and the function as an air preheater, the secondary combustion tower and the air preheater, which have different uses like conventional melting processing equipment, are separated. The installation space can be halved, and construction costs and equipment costs can be greatly reduced.
[0036]
Further, claim 1 of the present inventionThe exhaust heat recovery device of the present invention has the following effects in addition to the above effects.That is, the exhaust heat recovery device isSince the inner cylinder is formed by lining a refractory material on the inner peripheral surface of a metal cylinder, high-temperature and highly corrosive exhaust gas and dust flowing in the secondary combustion chamber come into direct contact with the metal cylinder. Without saying, corrosion of the inner cylinder can be prevented. Also, by lining the refractory, it is not necessary to lower the temperature of the exhaust gas to be lower than the maximum operating temperature of the inner cylinder material unlike a conventional air preheater, and heat recovery from high-temperature exhaust gas becomes possible. Further, unlike the conventional air preheater, there is no need to blow cooling air before the air preheater, and the amount of exhaust gas discharged does not increase. Furthermore, since the combustion air passing through the preheating passage is heated by heat conduction from the refractory lining the inner peripheral surface of the inner cylinder, the surface temperature of the refractory in contact with the exhaust gas is significantly reduced. Nothing. As a result, a temperature range in which dioxins are easily re-synthesized is not generated in exhaust gas flowing near the inner peripheral surface of the inner cylinder, and an effect as a measure against dioxins can be obtained.Besides,A secondary combustion air blowing nozzle is provided at an upstream position of the secondary combustion chamber, and secondary combustion air is blown from the secondary combustion air blowing nozzle along the inner peripheral surface of the inner cylinder in a tangential direction thereof. As a result, a swirling flow is formed in the secondary combustion chamber, so that the unburned gas contained in the exhaust gas is stirred and burned in the secondary combustion chamber with a sufficient residence time and temperature. As a result, the unburned gas in the exhaust gas discharged from the surface melting furnace is completely burned.
In addition, claim 2 of the present inventionIn the exhaust heat recovery device, the inner cylinder is formed in a cylindrical shape with a porous refractory, and the combustion air passing through the preheating passage is heated by heat conduction from the refractory, and the combustion air in the preheating passage is heated. Because part of the air flows into the secondary combustion chamber through the porous refractory holes as secondary combustion air,Claim 1The same operation and effect as those of the exhaust heat recovery device can be obtained, and the adhesion of dust to the inner peripheral surface of the inner cylinder can be prevented.
In the invention of claim 3,A secondary combustion air blowing nozzle is provided at an upstream position of the secondary combustion chamber, and secondary combustion air is blown from the secondary combustion air blowing nozzle along the inner peripheral surface of the inner cylinder in a tangential direction thereof. As a result, a swirling flow is formed in the secondary combustion chamber, so that the unburned gas contained in the exhaust gas is stirred and burned in the secondary combustion chamber with a sufficient residence time and temperature. As a result, the unburned gas in the exhaust gas discharged from the surface melting furnace is completely burned.
[Brief description of the drawings]
FIG. 1 is a schematic system diagram of a melting processing facility using an exhaust heat recovery device according to an embodiment of the present invention.
FIG. 2 is a schematic longitudinal sectional view of the exhaust heat recovery device according to the embodiment of the present invention.
FIG. 3 is a schematic cross-sectional view of the exhaust heat recovery device.
FIG. 4 is a schematic longitudinal sectional view of an exhaust heat recovery device according to another embodiment of the present invention.
FIG. 5 is a schematic system diagram of a conventional melting processing facility using a surface melting furnace.
FIG. 6 is a schematic longitudinal sectional view of an air preheater used in a conventional melting processing facility.
[Brief description of reference numerals]
1 is an exhaust heat recovery device, 2 is a surface melting furnace, 11 is a secondary combustion blowing nozzle, 24 is an inner cylinder, 24a is a cylinder, 25 is an outer cylinder, 26 and 26 'are refractories, G is exhaust gas, S Is a secondary combustion chamber, S 'is a preheating passage, A is combustion air, and A' is secondary combustion air.

Claims (3)

The unburned gas in exhaust gas discharged from the melting furnace causes complete combustion, at exhaust heat recovery device in the melting furnace so as to heat the combustion air by heat recovery from the exhaust gas, the exhaust heat The recovery device includes an inner cylinder forming a secondary combustion chamber into which exhaust gas from the melting furnace is fed, and an annular preheating passage through which combustion air passes between the inner cylinder and an outer peripheral surface of the inner cylinder. The secondary combustion chamber comprises an outer cylinder that forms unburned gas. The unburned gas in the exhaust gas is subjected to secondary combustion in the secondary combustion chamber with secondary combustion air to complete combustion, and the combustion air passing through the preheating passage is subjected to secondary combustion. An exhaust heat recovery device in a melting furnace in which a high temperature exhaust gas in a combustion chamber heats through an inner cylinder, wherein an inner cylinder forming a secondary combustion chamber is provided with corrosion resistance and an inner peripheral surface of a metal cylinder. Inner cylinder lined with refractory with excellent thermal conductivity In both cases, a secondary combustion air injection nozzle is provided at an upstream position of the secondary combustion chamber, and the secondary combustion air is injected from the secondary combustion air injection nozzle in the tangential direction along the inner peripheral surface of the inner cylinder. Exhaust heat to form a swirl flow in the secondary combustion chamber . The unburned gas in exhaust gas discharged from the melting furnace causes complete combustion, at exhaust heat recovery device in the melting furnace so as to heat the combustion air by heat recovery from the exhaust gas, the exhaust heat The recovery device includes an inner cylinder forming a secondary combustion chamber into which exhaust gas from the melting furnace is fed, and an annular preheating passage through which combustion air passes between the inner cylinder and an outer peripheral surface of the inner cylinder. The secondary combustion chamber comprises an outer cylinder that forms unburned gas. The unburned gas in the exhaust gas is subjected to secondary combustion in the secondary combustion chamber with secondary combustion air to complete combustion, and the combustion air passing through the preheating passage is subjected to secondary combustion. An exhaust heat recovery device in a melting furnace in which a high temperature exhaust gas in a combustion chamber heats through an inner cylinder, wherein an inner cylinder forming a secondary combustion chamber is formed in a cylindrical shape from a porous refractory. The combustion air passing through the preheating passage from the refractory While heating by conduction, at a melting furnace, characterized in that as part of the combustion air in the preheating passage flows from the pores of the porous refractory as secondary combustion air into the secondary combustion chamber Waste heat recovery equipment. A secondary combustion air blowing nozzle is provided at an upstream position of the secondary combustion chamber, and secondary combustion air is blown from the secondary combustion air blowing nozzle along the inner peripheral surface of the inner cylinder in a tangential direction thereof. 3. The exhaust heat recovery device in a melting furnace according to claim 2, wherein a swirling flow is formed in the secondary combustion chamber .

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