JPH07318050A - Combustion system using heat storage burner - Google Patents

Abstract

PURPOSE:To prevent the generation of NOx and to regulate a flame temperature by selectively switching the state that the exhaust gas sucked from one heat accumulator is supplied to the other heat accumulator and the state that the exhaust gas sucked from the other accumulator to the one accumulator, and regulating the concentration of oxygen to be supplied to the exhaust gas to be supplied to the accumulator. CONSTITUTION:A first heat accumulation burner 2 supplies fuel, sucks its exhaust gas via the burner 5 of a second heat accumulation burner 3 and a heat accumulator 7, and supplies low-temperature exhaust gas 40 from which heat is derived by the accumulator 7 is supplied toward the heat accumulator 6 of the burner 2 and a burner 4. Oxygen is supplied to the exhaust gas supplied to the burner 2, the mixed gas in which the oxygen is mixed with the exhaust gas at a predetermined ratio is supplied to the burner 2, preheated by the accumulator 6, and then burned together with fuel. In this case, the oxygen concentration of the mixed gas is measured. The exhaust gas suction amount is regulated based on the measured result, and the oxygen concentration is suitably regulated.

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 for alternately burning fuel and preheating a gas for burning fuel by utilizing heat of exhaust gas.
The present invention relates to a combustion system that saves energy.

[0002]

2. Description of the Related Art Conventionally, as a combustion system using a regenerative burner, for example, there is one disclosed in Japanese Utility Model Laid-Open No. 4-33825. As shown in FIG. 5, the combustion system 50 includes a regenerative burner 5 including a regenerator and a burner.
1,52 is applied to the 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, 52 are provided with fuel injection nozzles 56, 57 and combustion air injection nozzles 58, 59 formed around them, and the combustion air injection nozzles 58, 59 store heat. Media 60, 61 are provided. The fuel injection nozzles 56 and 57 are provided with an opening / closing valve 62,
It is connected to the fuel gas supply source 64 via 63. The combustion air injection nozzles 58, 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, as shown in the figure. The combustion air supplied from the one burner 51 is supplied to the one burner 51, and the exhaust gas discharge fan 67 exhausts the exhaust gas from the other burner 52. Conversely, the exhaust gas discharge fan 67 exhausts the exhaust gas from the one burner 51. The combustion air supplied from the air supply fan 66 can be switched to a state in which the combustion air is supplied to the other burner 52.

Therefore, the combustion system 50 is operated by alternately switching the heat storage type burners 51 and 52 between the combustion state and the non-combustion state based on the operation of the four-way valve 65 and the on-off valves 62 and 63. That is, when burning fuel with 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 the fuel and combustion air are supplied to the burner 51 for combustion. In addition, the exhaust gas generated in the radiant tube 53 flows in the direction of the arrow (solid line), and the heat is removed by the heat storage medium 61 and exhausted. On the other hand, burner 5
When the fuel is burned at 2, the on-off valve 62 is closed, the on-off valve 63 is opened, the four-way valve 65 is set to the dotted line state, and the burner 52 is supplied with fuel and combustion air 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 radiant tube 53 in the arrow (dotted line) direction to heat the heat storage medium 60, and this heat is used for preheating the combustion air at the time of 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 above combustion system 50, the fuel is burned using the air in the atmosphere, and since the atmosphere naturally contains nitrogen, NO.
The occurrence of x is unavoidable. 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, but the combustion flame of pure oxygen becomes extremely high in temperature, and there is a fear of adverse effects on the material to be treated. Therefore, it was not used in general industrial furnaces.

[0006]

Therefore, 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 the thermal efficiency and preventing the generation of NOx. The exhaust gas is sucked from the fuel supply source connected to the burner of each heat storage burner through an on-off valve, and (b) one of the regenerators, and the exhaust gas remains. Exhaust gas suction / supply means capable of selectively switching between a state of supplying the other heat accumulator and a state of sucking exhaust gas from the other heat accumulator and supplying the exhaust gas to the remaining one heat accumulator, (c) An oxygen supply source for supplying oxygen to the exhaust gas supplied from the exhaust gas suction / supply means to the heat accumulator, and (d) an oxygen concentration adjusting device for a mixed gas of the exhaust gas and oxygen are provided.

Various applications can be considered for the combustion system using the heat storage type burner. Among them, a slit type burner is used as the burner, and these burners are installed on the furnace wall of the muffle furnace so that the slits are oriented vertically. It has been found that a very large effect can be obtained when attached and used.

[0008]

In the combustion system having the above structure, when the first regenerative burner burns fuel, the burner is supplied with fuel from the fuel supply source. At this time, exhaust gas suction
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 in the regenerator to the regenerator and the burner of the first regenerative burner. Is set accordingly. Oxygen is supplied from the oxygen supply means to the exhaust gas supplied to the first regenerative burner, and a mixed gas for fuel combustion in which the oxygen and the exhaust gas are mixed at a predetermined ratio is supplied to the first regenerative burner. It is preheated in a regenerator and then 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 / supply means is operated to adjust the exhaust gas suction amount, 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 system diagram of a combustion system 1 using a heat storage type burner according to the present invention.
Is equipped with two sets of regenerative burners 2 and 3, and each regenerative burner 2 and 3 is composed of burners 4,5 and regenerators 6 and 7, respectively. The burners 4 and 5 are the furnace wall 8
And is connected to the fuel supply source 11 via the on-off valves 9 and 10, respectively. The heat accumulators 6 and 7 house heat accumulating media such as alumina balls inside, and in this embodiment, a combustion gas supply pipe (hereinafter referred to as “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 the first port 19 and the second port 20 of the four-way valve 18, respectively. One ends of exhaust gas pipes 23 and 24 are connected to the third port 21 and the fourth port 22 of the four-way valve 18, respectively, and the other end of one exhaust gas pipe 23 is a fan 25.
Of the exhaust gas pipe 24 and the fan 25
Is connected to the exhaust gas discharge pipe 26 connected to the exhaust part of the. The exhaust gas discharge pipe 26 is provided with a discharge amount adjustment valve 27 on the downstream side of the connection portion of the exhaust gas pipe 26 in the exhaust gas transportation direction, and the exhaust gas discharge amount of the fan 25 is adjusted by adjusting the opening degree of the adjustment valve 27. 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,
Open / close valves 31, 32 provided in the oxygen supply pipes 28, 29
Pure oxygen can be supplied to the gas supply pipes 16 and 17 based on the opening / closing operation. 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, and the other ends of the gas extraction pipes 34 and 35, one end of which is connected to the oxygen concentration adjusting device 33, are connected, respectively. ing.

The oxygen concentration adjusting device 33 is provided with an oxygen concentration measuring device, and opens / closes the opening / closing valves 36 and 37 provided in the gas extraction pipes 34 and 35 to open and close the respective gas supply pipes 16 and 17.
The oxygen concentration of the mixed gas flowing through the chamber can be appropriately measured. Further, 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, a variable voltage frequency converter (VVV).
F) depending on the number of revolutions of the fan 25 or the emission control valve 27
The opening degree or both of them can be adjusted. The emission control valve 27 is a regenerative burner 2, 3
It is preferable to use a system that can be fully closed in case of maintaining both of them in a non-combustion state. Note that instead of the gas extraction pipes 34, 35 and the opening / closing valves 36, 37, the oxygen concentration meters 12, 13 are directly provided in the gas supply pipes 16, 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 of No. 2 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 and the oxygen on-off valve 31 are opened, and the fuel on-off valve 10 and the oxygen on-off valve 3 forming a pair with these are opened.
Close 2 Further, the valve 39 of the four-way valve 18 is set to the position shown by the solid line. As a result, the exhaust gas in the furnace 38 (residual oxygen concentration of about 2%) is transferred to the burner 5 of the second regenerative burner 3.
And is sucked into the gas supply pipe 17 through the heat storage device 7. At this time, when passing through the heat storage device 7, the heat of the exhaust gas 40 is recovered by the heat storage device 7 and discharged to the gas supply pipe 17.
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 discharged from the exhaust gas discharge pipe 26 via the exhaust gas adjusting valve 27. The remaining exhaust gas passes through the exhaust gas pipe 24, the fourth port 22 of the four-way valve 18 and the first port 19 to the first exhaust gas.
It is sent to the gas supply pipe 16 leading to the regenerative burner 2 and mixed there with a predetermined amount of pure oxygen supplied from the oxygen supply source 30 to adjust the mixed gas to have an oxygen concentration of 15 to 21%.
Then, this mixed gas is preheated to a high temperature through the heat storage unit 6 and sent to the burner 4, and is 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 heat storage type burner 2 is continued for a predetermined time, and thereafter, the fuel is burned by the burner 5 of the second heat storage type burner 3 to burner 4 of the first heat storage type burner 2.
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 opening / closing valve 10 and the oxygen opening / closing valve 32 are opened, and the fuel opening / closing valve 9 and the oxygen opening / closing valve 31 paired with these are closed. Further, the valve 39 of the four-way valve 18 is set from the state shown in FIG. 1 to the solid line position in FIG. As a result, 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 which has passed through the heat accumulator 6 and has a lowered temperature 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 the exhaust gas discharge pipe 26 through the exhaust gas adjusting valve 27, and the rest is exhausted through the exhaust gas transport passage 24, the fourth port 22 and the second port 20 of the four-way valve 18. Is sent to the gas supply pipe 17 leading to the second heat storage type burner 3, where the oxygen supply source 30
The mixed gas is mixed with a predetermined amount of pure oxygen supplied from to prepare a mixed gas having an oxygen concentration of 15 to 21%. Then, the mixed gas is preheated by the regenerator 7 and then sent to the burner 5, and is injected and burned in the furnace 38 together with the fuel supplied from the fuel supply source 11.

The combustion state by the second heat storage type burner 3 is continued for a predetermined time, and thereafter, the fuel is burned by the burner 4 of the first heat storage type burner 2 again, and the burner 5 of the second heat storage type burner 3 in the furnace. The combustion state in which the exhaust gas 40 of 38 is sucked is switched. In this way, the above two combustion states are repeated at predetermined time intervals.

The exhaust gas 4 sucked into the burners 2 and 3
No. 0 has its temperature lowered due to heat being taken by the heat accumulators 6 and 7, respectively. Therefore, it is not necessary to use expensive heat resistant ones 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 the fuel is burned by the first heat storage type burner 2, the on-off valve 36 is opened as shown in FIG. 1, a part of the mixed gas composed of the exhaust gas and pure oxygen is extracted through the gas extraction pipe 34, and the oxygen concentration thereof is extracted. Is measured by the oxygen concentration adjusting device 33 and set to an appropriate value. next,
Based on the set value, the exhaust gas suction amount or the exhaust gas discharge amount of the fan 25 is adjusted by adjusting the rotation speed of the fan 25 or the opening degree of the exhaust gas adjusting valve 27, or by adjusting both of them. 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 in the furnace 38 is adjusted. Second heat storage type burner 3
Similarly, when the fuel is combusted with, the opening / closing valve 37 is opened, a part of the mixed gas is extracted through the gas extraction pipe 35, and the oxygen concentration thereof is measured by the oxygen concentration adjusting device 33, and based on the measurement result, it is appropriate. A set value is selected to adjust the oxygen concentration of the mixed gas and the temperature inside the furnace.

The oxygen concentration of the mixed gas is adjusted by the fan 2
5 and / or the opening degree of the exhaust gas adjusting valve 27 is adjusted, and the oxygen supply amount from the oxygen supply source 30 or the opening / closing of the oxygen opening / closing valves 31 and 32 is performed based on the measurement result of the oxygen concentration. The oxygen concentration and the furnace temperature may be adjusted by adjusting the temperature.

When any of the regenerative burners 2 and 3 is set to the non-combustion state in order to adjust the temperature in the furnace, the fuel opening / closing valves 9 and 10, the oxygen opening / closing valves 31 and 32, and the exhaust gas adjusting valve 2 are set.
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 pipes 23,
The exhaust gas 40 is injected from the other burner 5 or one burner 4 via the 24 and the four-way valve 18, and the exhaust gas 40 convects in the furnace 38. Further, 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 atmosphere stirring effect in the furnace becomes active, the temperature in the furnace is kept uniform, and the processing material is heated uniformly.

In the above description, the combustion system 1 is provided with only one set of regenerative burners, but it is clear 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 refractory material. The inner cover 43
A base plate 44 is provided inside the
A plurality of metal strip coils 45, which is a processing material, are stacked on No. 4. A fan 46 is rotatably provided below the base plate 44 by a motor 47. Then, the atmosphere enclosed in the inner cover 43 is circulated by the rotation of the fan to uniformly heat the metal strip coil 45.

The furnace body 42 is provided with vertically elongated slit-shaped flame ports 48, 49, and the flame ports 48, 49 are respectively provided with the regenerative burners 2, 3 respectively.
Is attached.

In the cover type annealing furnace 41 having the above structure, since the flame ports 48 and 49 are formed in the slit type, the first type
Of the heat storage type burner 2 or the second heat storage type burner 3 is burned by the furnace body 42 and the inner cover 4
Spread in the vertical direction between 3. Therefore, the inner cover 4
3, the heat dissipation area can be increased uniformly.
In addition, the exhaust gas generated by combustion is the inner cover 4
3 above, after the temperature has dropped, it moves below and is discharged from either the non-combusting side flame port 48 or 49. In this way, the flame does not come into contact with the inner cover 43 and heat is radiated from a wide flame area, so that the life of the inner cover 43 is extended.
Furthermore, since pure oxygen can be used as a fuel, the combustion products are only CO ₂ , H ₂ O and residual oxygen, the partial pressure of CO ₂ , H ₂ O is increased, the gas radiative capacity is improved, and the heat transfer efficiency is also improved. To do.

Incidentally, as shown in FIGS. 6 and 7, in the conventional cover-type annealing furnace 70, since the steady combustion flame is formed from the circular flame port 71, the temperature uniformity in the circumferential direction of the muffle is maintained. In addition, multiple burners 72 were required. However, in the cover type annealing furnace 41, since the flame spreads in the vertical direction between the furnace body 42 and the inner cover 43 and the method of switching combustion and exhaust by the heat storage type burner is adopted, two sets of the heat storage type burner 2, It is only necessary to provide 3. Regarding the structure of the cover-type annealing furnace 70, the same members as those of the cover-type annealing furnace 41 are designated by the same reference numerals, and the description thereof will be omitted.

[0027]

As is apparent from the above description, according to the combustion system of the regenerative burner of the present invention, the mixed gas of oxygen and exhaust gas is used as the fuel combustion gas, so that the energy saving can be achieved. The generation of NOx is completely prevented while improving the efficiency. Further, since there is no nitrogen in the path of the combustion system, it is not necessary to design the burner structure to take measures against NOx as in the conventional case, and the structure of the burner becomes extremely simple.

Further, since the flame temperature can be freely adjusted by adjusting the oxygen concentration of the mixed gas, it is possible to use pure oxygen as a fuel in a furnace for various purposes, for example, a general industrial furnace.

Further, combustion is stopped by keeping both heat storage type burners forming a pair in a non-combustion state, injecting the exhaust gas sucked from one burner from the other burner, and by appropriately switching the circulation direction of the exhaust gas. Occasionally, convection of exhaust gas is formed in the furnace, and the treatment material can be heated uniformly.

Furthermore, in the case where the combustion system of the regenerative burner is used in the muffle furnace, the slit-type port is provided in the muffle furnace, so that the flame spreads in the longitudinal direction of the furnace body and the muffle, and Therefore, the heat radiation area can be uniformly increased. Further, since the flame or 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 drawings]

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

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

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

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

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

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

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

[Explanation of symbols]

1 ... Regenerative burner combustion system, 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)

[Claims] 1. A combustion state in which two sets of regenerative burners including a burner and a regenerator are provided, and these regenerative burners burn the fuel supplied to the burner with combustion gas supplied through the regenerator. And the first heat storage burner by alternately setting the exhaust heat recovery state in which exhaust gas in the furnace is exhausted through the heat storage unit while stopping the supply of fuel and combustion gas to the burner and heat storage unit, respectively. In a combustion device that alternately combusts fuel with a second regenerative burner, (a) a fuel supply source connected to the burner of each regenerative burner via an on-off valve, and (b) from one regenerator Exhaust gas suction that can be selectively switched between a state in which exhaust gas is sucked and is supplied to the other remaining regenerator and a state in which exhaust gas is sucked from the other regenerator and is supplied to the remaining one 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 heat storage unit, and (d) an oxygen concentration adjusting device for a mixed gas of the exhaust gas and oxygen. A combustion system using a regenerative burner characterized by the above. 2. A combustion system for a heat storage type burner according to claim 1, wherein a slit type burner is used for the burner, and these burners are attached to a furnace wall so that the slits are oriented vertically. A muffle furnace.