JP2584193B2 - Combustion system using a regenerative burner - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention comprises two sets of regenerative burners, in which fuel is alternately burned by these regenerative burners, and a gas for fuel combustion is preheated by utilizing heat of exhaust gas.
This relates to a combustion system that saves energy.

[0002]

2. Description of the Related Art A conventional combustion system using a regenerative burner is disclosed, for example, in Japanese Utility Model Laid-Open No. 4-33825. As shown in FIG. 5, the combustion system 50 includes a regenerative burner 5 composed of a regenerator and a burner.
1 and 52 are applied to a radiant tube 53,
The regenerative burners 51 and 52 are connected to the openings at both ends of the radiant tube 53.

The regenerative burners 51 and 52 have fuel injection nozzles 56 and 57 and combustion air injection nozzles 58 and 59 formed therearound. The combustion air injection nozzles 58 and 59 store heat. Mediums 60 and 61 are provided. The fuel injection nozzles 56 and 57 are provided with on-off valves 62,
It is connected to a fuel gas supply source 64 via 63. The combustion air injection nozzles 58 and 59 are connected to an air supply fan 66 and an exhaust gas discharge fan 67 via a four-way valve 65. Based on the operation of the four-way valve 65, the air supply fan 66 is Is supplied to the one burner 51 and exhaust gas is exhausted from the other burner 52 by the exhaust gas discharge fan 67, and exhaust gas is exhausted from the one burner 51 by the exhaust gas discharge fan 67, The state can be switched to a state in which the combustion air supplied from the air supply fan 66 is supplied to the other burner 52.

Accordingly, the combustion system 50 is operated such that the regenerative burners 51, 52 are alternately switched between a combustion state and a non-combustion state based on the operation of the four-way valve 65 and the on-off valves 62, 63. That is, when fuel is burned by the burner 51, the open / close valve 62 is opened, the open / close valve 63 is closed, and the four-way valve 65 is set to the solid line state, and fuel and combustion air are supplied to the burner 51 for combustion. The exhaust gas generated in the radiant tube 53 flows in the direction of the arrow (solid line), and the heat is taken out by the heat storage medium 61 and exhausted. Meanwhile, burner 5
When fuel is burned in 2, the on-off valve 62 is closed, the on-off valve 63 is open, the four-way valve 65 is set in the dotted line state, and fuel and combustion air are supplied to the burner 52 for combustion. At this time, the combustion air comes into contact with the heat storage medium 61 and is preheated, so that efficient combustion can be obtained. Further, the combustion exhaust gas flows in the direction of the arrow (dotted line) in the radiant tube 53 to heat the heat storage medium 60, and this heat is used for preheating the combustion air at the next combustion by the burner 51. As described above, in the combustion system 50, the heat contained in the exhaust gas is recovered, and this heat is used for preheating the combustion air.
Energy saving and improvement of thermal efficiency can be achieved at the same time.

[0005]

However, in the combustion system 50, fuel is burned using air in the atmosphere, and since the atmosphere naturally contains nitrogen, NO
The occurrence of x is inevitable. Further, a method of using pure oxygen as a fuel combustion gas in order to prevent the generation of NOx is known in the field of combustion. However, the combustion flame of pure oxygen becomes extremely high temperature, and there is a concern that there is an adverse effect on the material to be treated. Therefore, it was not used in general industrial furnaces.

[0006]

SUMMARY OF THE INVENTION Accordingly, the present invention provides a combustion system using a regenerative burner which enables the use of pure oxygen in a general industrial furnace, thereby improving thermal efficiency and preventing generation of NOx. (A) a fuel supply source connected to each burner of each regenerative burner via an on-off valve, and (b) an exhaust gas is sucked from one of the heat accumulators, and the exhaust gas remains. Exhaust gas suction / supply means for selectively switching to a state of supplying the other regenerator and a state of sucking exhaust gas from the other regenerator and supplying the exhaust gas to the remaining regenerator; An oxygen supply source for supplying oxygen to exhaust gas supplied from the exhaust gas suction / supply means to the regenerator, and (d) an oxygen concentration adjusting device for a mixed gas of the exhaust gas and oxygen are provided.

[0007] The combustion system using the regenerative burner can be used for various purposes. Among them, slit burners are used as burners, and these burners are mounted on the furnace wall of a muffle furnace so that the slits extend in the vertical direction. It has been found that a very large effect can be obtained when used by mounting.

[0008]

In the combustion system having the above configuration, when fuel is burned by the first regenerative burner, the burner is supplied with fuel from a fuel supply source. At this time,
The supply means sucks the exhaust gas through the burner and the regenerator of the second regenerative burner, and supplies the low-temperature exhaust gas deprived of heat by the regenerator to the regenerator and the burner of the first regenerative burner. It is set as follows. Oxygen is supplied to the exhaust gas supplied to the first regenerative burner from an oxygen supply means, and a mixed gas for fuel combustion obtained by mixing the oxygen and the exhaust gas at a predetermined ratio is supplied to the first regenerative burner. After being preheated in the regenerator, it is burned with fuel. The oxygen concentration of the mixed gas is measured by the measuring means, and based on the measurement result, for example, the exhaust gas suction amount is adjusted by operating the exhaust gas suction / supply means, and the oxygen concentration is appropriately adjusted.

[0009]

Embodiments of the present invention will be described below with reference to the accompanying drawings. FIG. 1 is a piping diagram of a combustion system 1 using a regenerative burner according to the present invention.
Is provided with two sets of regenerative burners 2 and 3, each of which is constituted by burners 4 and 5 and regenerators 6 and 7, respectively. The burners 4 and 5 are connected to the furnace wall 8.
And are connected to a fuel supply source 11 via on-off valves 9 and 10, respectively. The heat accumulators 6 and 7 house a heat storage medium such as alumina balls therein, and in this embodiment, a combustion gas supply pipe (hereinafter, referred to as a “gas supply pipe”) 16 connected to the burners 4 and 5. , 17 are provided.

The ends of the gas supply pipes 16 and 17 are connected to a first port 19 and a second port 20 of a four-way valve 18, respectively. One end of exhaust gas pipes 23 and 24 is connected to the third port 21 and the fourth port 22 of the four-way valve 18, respectively.
The exhaust gas pipe 24 is connected to a fan 25
Is connected to an exhaust gas discharge pipe 26 connected to an exhaust part of the exhaust gas. The exhaust gas discharge pipe 26 is provided with an emission control valve 27 downstream of the connection part of the exhaust gas pipe 26 in the exhaust gas transport direction. It can be adjusted. In the present invention, the gas supply pipes 16 and 17 and the four-way valve 1 are used.
8, the exhaust gas pipes 23 and 24 and the fan 25 constitute exhaust gas suction / supply means.

The gas supply pipes 16 and 17 are connected to an oxygen supply source 30 via oxygen supply pipes 28 and 29,
On-off valves 31, 32 provided on these oxygen supply pipes 28, 29
Pure oxygen can be supplied to the gas supply pipes 16 and 17 based on the opening / closing operation of. The gas supply pipes 16 and 17 are connected to the burner side of the connection parts of the oxygen supply pipes 28 and 29, respectively, and the other end parts of the gas extraction pipes 34 and 35 each having one end connected to the oxygen concentration adjusting device 33, respectively. ing.

The oxygen concentration adjusting device 33 includes an oxygen concentration measuring device, and opens and closes on-off valves 36 and 37 provided in the gas extraction tubes 34 and 35, respectively.
The oxygen concentration of the mixed gas flowing through the sample can be appropriately measured. The oxygen concentration adjusting device 33 is connected to the fan 25 and the discharge amount adjusting valve 27, respectively, and based on the measurement result of the oxygen concentration, the variable voltage frequency converter (VVV
F), the rotation speed of the fan 25 or the discharge amount adjusting valve 27
, Or both of them can be adjusted. The emission control valve 27 is provided with regenerative burners 2 and 3
It is preferable to use a method in which both can be fully closed in case both are maintained in a non-combustion state. Instead of the gas extraction tubes 34 and 35 and the on-off valves 36 and 37, the oxygen concentration meters 12 and 13 are directly provided in the gas supply tubes 16 and 17 and the measured values are sent to the oxygen concentration adjusting device 33 as signals. Good.

The operation of the combustion system 1 having the above configuration will be described. As shown in FIG. 1, the first regenerative burner 2
When the fuel is burned by the burner 4 and the exhaust gas in the furnace 38 is sucked from the burner 5 of the second regenerative burner 3, the fan 2
5, the fuel on / off valve 9, the oxygen on / off valve 31 are opened, and the fuel on / off valve 10, the oxygen on / off valve 3
Close 2. Further, the valve 39 of the four-way valve 18 is set at the position indicated by the solid line in the figure. As a result, the exhaust gas (residual oxygen concentration of about 2%) in the furnace 38 is transferred to the burner 5 of the second regenerative burner 3.
Is sucked into the gas supply pipe 17 through the heat accumulator 7. At this time, when passing through the regenerator 7, the heat of the exhaust gas 40 is recovered by the regenerator 7 and the exhaust gas 4 discharged to the gas supply pipe 17 is discharged.
The temperature of 0 is decreasing.

Next, the exhaust gas 40 is sent to the fan 25 via the second port 20 and the third port 21 of the four-way valve 18 and the exhaust gas pipe 23. Part of the exhaust gas discharged from the fan 25 is exhausted from an exhaust gas discharge pipe 26 via an exhaust gas control valve 27. The remaining exhaust gas passes through the exhaust gas pipe 24, the fourth port 22 and the first port 19 of the four-way valve 18,
The gas is sent to a gas supply pipe 16 communicating with the regenerative burner 2, where it is mixed with a predetermined amount of pure oxygen supplied from an oxygen supply source 30 so that the oxygen concentration is adjusted to a gas mixture of 15 to 21%.
Then, the mixed gas is preheated to a high temperature via the regenerator 6, sent to the burner 4, injected into the furnace 38 together with the fuel supplied from the fuel supply source 11, and burned.

The above-mentioned combustion state by the first regenerative burner 2 is continued for a predetermined time, after which the fuel is burned by the burner 5 of the second regenerative burner 3 and the burner 4 of the first regenerative burner 2 is burned.
Is switched to a combustion state in which the exhaust gas in the furnace 38 is sucked. In this new combustion state, as shown in FIG. 2, the fuel on-off valve 10 and the oxygen on-off valve 32 are opened, and the fuel on-off valve 9 and the oxygen on-off valve 31, which are paired with them, are closed. Further, the valve 39 of the four-way valve 18 is set to the position shown by the solid line in FIG. 2 from the state shown in FIG. Thereby, the exhaust gas in the furnace 38 is sucked into the gas supply pipe 16 via the burner 4 of the first regenerative burner 2 and the regenerator 6, and the heat of the exhaust gas 40 is recovered in the regenerator 6.

The exhaust gas 40 whose temperature has dropped after passing through the regenerator 6 is sucked by the fan 25 through the first port 19 and the third port 21 of the four-way valve 18 and the exhaust gas pipe 23. Exhaust gas 40 discharged from the fan 25 is partially exhausted from an exhaust gas discharge pipe 26 through an exhaust gas control valve 27, and the rest is discharged through an exhaust gas transport path 24, a fourth port 22 and a second port 20 of the four-way valve 18. To the gas supply pipe 17 leading to the second regenerative burner 3 where the oxygen supply source 30
Is mixed with a predetermined amount of pure oxygen supplied from the above to adjust the oxygen concentration to a mixed gas having a concentration of 15 to 21%. Then, the mixed gas is preheated by the regenerator 7, sent to the burner 5, injected into the furnace 38 together with the fuel supplied from the fuel supply source 11, and burned.

The combustion state of the second regenerative burner 3 is continued for a predetermined period of time, after which the fuel is burned again by the burner 4 of the first regenerative burner 2, and then burned from the burner 5 of the second regenerative burner 3. The combustion state is switched to a state in which the exhaust gas 40 is sucked. Thus, the above two combustion states are repeated every predetermined time.

The exhaust gas 4 sucked by the burners 2 and 3
In the case of 0, the heat is taken away by the heat accumulators 6 and 7, respectively, so that the temperature is lowered. Therefore, it is not necessary to use expensive heat-resistant materials for the four-way valve 18 and the fan 25.

The adjustment of the oxygen concentration of the mixed gas and the adjustment of the furnace temperature are performed as follows. That is, when fuel is burned by the first regenerative burner 2, the on-off valve 36 is opened as shown in FIG. 1, and a part of the mixed gas composed of exhaust gas and pure oxygen is extracted through the gas extraction pipe 34, and the oxygen concentration thereof is increased. Is measured by the oxygen concentration adjusting device 33 and set to an appropriate value. next,
Based on the set value, the rotation speed of the fan 25 or the opening degree of the exhaust gas control valve 27 is adjusted, or both of them are adjusted, so that the exhaust gas suction amount or the exhaust gas discharge amount of the fan 25 is adjusted. As a result, the amount of exhaust gas mixed with pure oxygen and the oxygen concentration of the mixed gas are adjusted, and the temperature of the furnace interior 38 is adjusted. Second regenerative burner 3
Similarly, when fuel is burned, the on-off valve 37 is opened, a part of the mixed gas is extracted from the gas extraction pipe 35, and the oxygen concentration is measured by the oxygen concentration adjusting device 33. An appropriate set value is selected, and the oxygen concentration of the mixed gas and the furnace temperature are adjusted.

The oxygen concentration of the gas mixture is adjusted by the fan 2
5 and / or the degree of opening of the exhaust gas control valve 27 is adjusted. Based on the measurement result of the oxygen concentration, the amount of oxygen supplied from the oxygen supply source 30 or the opening and closing of the oxygen on-off valves 31 and 32 is performed. The temperature may be adjusted to adjust the oxygen concentration or the furnace temperature.

When any of the regenerative burners 2 and 3 is set to a non-combustion state to adjust the furnace temperature, the fuel on / off valves 9 and 10, the oxygen on / off valves 31 and 32, and the exhaust gas control valve 2
Close 7. In this case, when the fan 25 is driven, the exhaust gas in the furnace sucked from one of the burners 4 or the other burner 5 is supplied to the gas supply pipes 16 and 17, the exhaust gas pipe 23,
The fuel is injected from the other burner 5 or one of the burners 4 through 24 and the four-way valve 18, and the exhaust gas 40 convects in the furnace 38. The convection direction is switched by switching the valve 39 of the four-way valve 18 from the state shown in FIG. 1 to the state shown in FIG. 2 and vice versa at predetermined time intervals. As a result, the effect of stirring the atmosphere in the furnace becomes active, the temperature in the furnace is kept uniform, and the processing material is uniformly heated.

In the above description, only one set of regenerative burners is provided in the combustion system 1. However, it is apparent that a plurality of sets of regenerative burners may be provided.

Next, an example in which the combustion apparatus 1 is applied to a muffle furnace, for example, a cover-type metal strip coil annealing furnace (hereinafter, referred to as "cover-type annealing furnace") will be described. Figure 3,
As shown in FIG. 4, the cover-type annealing furnace 41 is configured by installing an inner cover 43 which is a metal muffle inside a furnace body 42 made of a refractory. The inner cover 43
Is provided with a base plate 44.
4, a plurality of metal strip coils 45 as processing materials are mounted. A fan 46 is provided below the base plate 44 so as to be rotatable by a motor 47. Then, the atmosphere enclosed in the inner cover 43 is circulated by the rotation of the fan, and the metal strip coil 45 is heated uniformly.

The furnace body 42 is provided with vertically elongated slit-type flame ports 48, 49 facing each other. The flame ports 48, 49 are respectively connected to the regenerative burners 2, 3 respectively.
Is attached.

In the cover-type annealing furnace 41 having the above-described structure, the flame ports 48 and 49 are formed in a slit shape.
The flame generated when the regenerative burner 2 or the second regenerative burner 3 is burned is a furnace body 42 and an inner cover 4.
Spreads vertically between three. Therefore, the inner cover 4
3, the heat radiation area can be increased uniformly.
Exhaust gas generated by combustion is supplied to the inner cover 4.
3 and moves down after the temperature drops, and is discharged from either the non-combustion side flame port 48 or 49. As described above, since the flame does not contact the inner cover 43 and heat is radiated from a wide flame area, the life of the inner cover 43 is extended.
Furthermore, pure oxygen can be used as a fuel, so that the combustion products are only CO ₂ and H ₂ O and residual oxygen, the partial pressure of CO ₂ and H ₂ O is increased, the gas radiating ability is improved, and the heat transfer efficiency is also improved. I do.

As shown in FIGS. 6 and 7, in the conventional cover type annealing furnace 70, since a steady combustion flame is formed from the circular flame port 71, the uniformity of the temperature in the circumferential direction of the muffle is maintained. In addition, a plurality of burners 72 were required. However, the cover-type annealing furnace 41 employs a method in which the flame spreads in the vertical direction between the furnace body 42 and the inner cover 43 and switches between combustion and exhaust by a regenerative burner. 3 only needs to be provided. In the structure of the cover-type annealing furnace 70, the same members as those of the cover-type annealing furnace 41 are denoted by the same reference numerals, and description thereof is omitted.

[0027]

As is apparent from the above description, according to the regenerative burner combustion system according to the present invention, since a mixed gas of oxygen and exhaust gas is used as a fuel combustion gas, energy can be saved. While preventing the generation of NOx. In addition, since nitrogen does not exist in the path of the combustion system, it is not necessary to design the burner structure to take measures against NOx as in the prior art, and the structure of the burner becomes extremely simple.

Further, since the temperature of the flame can be freely adjusted by adjusting the oxygen concentration of the mixed gas, pure oxygen can be used as a fuel in a furnace for various uses, for example, a general industrial furnace.

Further, by keeping both regenerative burners forming a pair in a non-combustion state, the exhaust gas sucked from one burner is injected from the other burner, and the circulation direction of the exhaust gas is appropriately switched to stop the combustion. In some cases, convection of exhaust gas is formed in the furnace, so that the processing material can be uniformly heated.

Further, in the case where the combustion system of the regenerative burner is used in the muffle furnace, the flame is spread in the longitudinal direction of the furnace body and the muffle by providing the muffle furnace with the slit-type port, so that the flame is spread to the muffle. As a result, the heat radiation area can be increased uniformly. Further, since the flame or the exhaust gas does not come into contact with the muffle, there is no thermal deformation of the muffle, and the service life of the muffle can be extended.

[Brief description of the drawings]

FIG. 1 is a piping diagram of a combustion system for a regenerative burner according to the present invention.

FIG. 2 is a piping diagram of a regenerative burner combustion system according to the present invention.

FIG. 3 is a longitudinal sectional view of a muffle furnace using a regenerative burner combustion system according to the present invention.

FIG. 4 is a cross-sectional view of a muffle furnace using a regenerative burner combustion system according to the present invention.

FIG. 5 is a piping diagram of a conventional regenerative burner.

FIG. 6 is a longitudinal sectional view of a conventional muffle furnace.

FIG. 7 is a cross-sectional view of a conventional muffle furnace.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Combustion system of regenerative burner, 2,3 ... Regenerative burner, 4,5 ... Burner, 6,7 ... Regenerator, 11 ... Fuel supply source, 18 ... Four-way valve, 25 ... Fan, 27 ... Emission control Valve, 30: oxygen supply source, 33: oxygen concentration adjusting device.

Claims (2)

(57) [Claims] 1. A combustion state in which two regenerative burners each having a burner and a regenerator are provided, and the regenerative burners are burned together with the fuel supplied to the burners and the combustion gas supplied via the regenerator. The first regenerative burner by stopping the supply of fuel and combustion gas to the burner and the regenerator and alternately setting the exhaust heat recovery state to exhaust the exhaust gas in the furnace via the regenerator. In a combustion apparatus for burning fuel alternately with a second regenerative burner, (a) a fuel supply source connected to a burner of each regenerative burner via an on-off valve, and (b) one of the regenerators Exhaust gas suction that can selectively switch between a state in which the exhaust gas is sucked and the exhaust gas is supplied to the remaining regenerator and a state in which the exhaust gas is sucked from the other regenerator and the exhaust gas is supplied to the remaining regenerator.・ Supplier A stage, (c) an oxygen supply source for supplying oxygen to the exhaust gas supplied from the exhaust gas suction / supply means to the regenerator, and (d) an oxygen concentration adjusting device for a mixed gas of the exhaust gas and oxygen. A combustion system using a regenerative burner. 2. A regenerative burner combustion system according to claim 1, wherein a slit-type burner is used as the burner, and these burners are attached to a furnace wall such that the slits extend in a vertical direction. Muffle furnace.