JPH086906B2 - Heat storage burner - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heat storage burner for recovering heat of exhaust gas in a furnace to preheat combustion air.

[0002]

2. Description of the Related Art Conventionally, as a burner for saving energy by preheating combustion air with the heat of combustion exhaust gas, as shown in FIG. 5, a burner body 101, a fuel injection nozzle 102, and a burner throat portion are provided. A heat storage burner 100 including an air flow passage 104 communicating with 103 and an air permeable heat storage body 105 arranged in the air flow passage 104 is known.

The burner 100, as shown in FIG.
Two units (100a, 100b) are attached to the furnace wall 106 as one set. The fuel injection nozzles 102, 102 of the burners 100a, 100b are provided with the switching valves F1, F, respectively.
A gas supply source 108 is connected via gas supply lines 107a and 107b having two. Also, the burner 100
The air flow paths 104 and 104 of a and 100b are air supply lines 109a and 109 having switching valves A1 and A2, respectively.
exhaust gas line 111 connected to the air blower 110 via b and having switching valves W1 and W2, respectively.
It is connected to the induction fan 112 via a and 111b.

A pair of burners 100a and 100b connected to the line in this way is used for combustion of fuel gas and exhaust of exhaust gas at predetermined time intervals, and at the same time when one gas burns with the other burner. It is operated while exhausting exhaust gas. That is, as shown in the figure, when burning gas with the burner 100a, the switching valves F1 and A1 are opened and the switching valve W1 is closed with respect to the burner 100a, and the fuel gas is supplied from the gas supply source 108 to the nozzle 102. The combustion air is supplied to the air passage 104 from the air blower 110, and the fuel gas and the combustion air are injected from the burner throat portion 103 into the furnace 114 and burned.
Regarding the other burner 100b, the changeover valves F2, A2 are closed and the changeover valve W2 is opened, and the induction fan 112 is opened.
The exhaust gas in the furnace 114 is driven by the
Is discharged from the chimney 113 through the heat storage body 10 at this time.
5 is heated by contact with the high temperature exhaust gas passing through the heat storage body 105.

On the contrary, when burning gas with the burner 100b, the changeover valves F2 and A2 are used for this burner 100b.
And the switching valve W2 is closed and the gas supply source 10
The fuel gas is supplied from the nozzle 8 to the nozzle 102, the combustion air is supplied from the air blower 110 to the air passage 104, and the fuel gas and the combustion air are injected from the burner throat portion 103 into the furnace 114 and burned. At this time, in the burner 100b, heat is accumulated in the heat storage body 105 during gas combustion by the burner 100a, so that the combustion air supplied from the air blower 110 to the air flow passage 104 contacts the heat storage body 105. It is preheated and the fuel gas is combusted with this preheated combustion air. Therefore,
The combustion efficiency of the fuel is significantly improved as compared with the case where the fuel gas is burned with the air at room temperature. On the other hand, regarding the burner 100a, the switching valves F1 and A1 are closed and the switching valve W
1, the exhaust gas in the furnace 114 is exhausted through the air flow path 104, and the heat of the high-temperature exhaust gas is recovered by the heat storage body 105 and used for preheating the combustion air at the next fuel combustion of the burner 100a.

[0006]

However, the burners 100a and 100b must be used as a set of two burners as described above, and when one burner burns, the other burner is kept in a non-burning state. Must.
In addition, there is a limit to how close the burners can be in order to secure the required piping space. Therefore, in order to secure a predetermined amount of combustion (heat input to the furnace), the number of burners to be installed increases, and there is a problem in that it is unavoidable to increase the size of the furnace and increase the cost.

Further, in the burner, the temperature of the heat storage body 105 gradually decreases as the combustion air is supplied, and the preheating force of the combustion air decreases. Therefore, in order to maintain a high combustion efficiency, the switching valves F1, A1, W1, F2, A2, W2
Must be opened and closed frequently. In reality, the valve is switched about every 20 seconds, and if the furnace is operated for 6000 hours a year, 1 million times / year (= 6000 × 3600/20)
The switching operation of is repeated. In order to make such a huge number of switching functions without any malfunction,
There is a problem that not only the control method but also the mechanical structure of the switching valve itself is required to have high reliability. For example, if the valve of the fuel system malfunctions or fuel leaks, the leaked fuel flows into the exhaust gas line and is wasted, or an explosion occurs.

Further, since the air passage 104 is connected to the burner throat portion 103, that is, the fuel gas can enter the air passage 104, the switching valve for combustion air and exhaust gas malfunctions. Then, there is a risk that fuel gas may flow into the exhaust gas lines 111a and 111b to cause an explosion.

Furthermore, in order to confirm the state of flame, it is necessary to monitor the flames of two systems for one set of burners (two burners), and to distinguish between the "combusting" and "exhausting" modes. The condition to monitor must be incorporated into the control. In addition, a burner for ignition is required for each burner.
Therefore, there is a problem that the design and configuration of the control system and the piping system become complicated and the cost required for them becomes high.

Further, since the fuel injection nozzle 102 is located close to the heat storage body 105 and is designed to burn while being surrounded by the high temperature preheated air, the NOx exhausted due to the temperature rise. There was a problem that the cost was high. Specifically, when the preheating temperature of the air by the heat storage body 105 rises to 1000 ° C., the exhausted NOx is 1000 p
It was over pm.

[0011]

The present invention has been made to solve the above problems, and a heat storage burner of the present application uses two air for alternately supplying combustion air and exhausting combustion exhaust gas. It is provided with a flow path, a fuel injection nozzle arranged in the middle of these air flow paths, a central air flow path, and an air permeable heat storage material arranged in each of the two air flow paths.

[0012]

The heat storage burner of the present invention having the above-described structure is attached to the furnace wall with the nozzle for fuel injection and the jet outlet of the air flow path facing the inside of the furnace. The nozzle is connected to the fuel supply source, and the air flow path is connected to the combustion air supply source and the exhaust gas device via the switching means. And when burning fuel,
Fuel is continuously supplied to the nozzle. Further, one of the air flow paths is supplied with combustion air from a combustion air supply source, and the other exhaust gas in the furnace is exhausted from the other air flow path.
The air flow path for supplying the combustion air and the air flow path for exhausting the exhaust gas are switched at predetermined time intervals, and the heat recovered from the exhaust gas by the heat storage body is used for preheating the combustion air.

[0013]

Embodiments of the present invention will be described below with reference to the accompanying drawings. 1 and 2, 1 is a heat storage burner,
Reference numeral 2 denotes a burner body 2 of the heat storage burner 1, which is made of a known refractory material. Reference numeral 3a is a first air flow passage, 3b is a second air flow passage, and these air flow passages 3a and 3b are formed by penetrating the burner body 2 in the front-rear direction. 4a and 4b are heat storage bodies,
A honeycomb-shaped or container-shaped breathable member made of a heat-resistant material such as ceramics or containing a large number of ceramics pellets is provided in the two air flow paths 3a and 3b. Connection pipes 5a and 5b are connected to the rear ends of the air flow paths 3a and 3b, respectively. Reference numeral 6 denotes a central air flow passage, which is formed in the middle of the two air flow passages 3a and 3b so as to penetrate the burner body 2 and has a connecting pipe 7 at the rear end. 8
Is a fuel nozzle, which penetrates the rear end of the connecting pipe 7 and is inserted into the central air passage 6. Reference numeral 9 is a flame monitoring window, which is provided on a side portion of the central air passage 6.

The heat storage burner 1 having the above structure is attached to the furnace wall with the front portions of the air flow paths 3a and 3b facing the inside of the furnace, and the pipes are connected as shown in FIG. That is, the fuel nozzle 8 is connected to the gas supply source 13 via the gas supply line 12 having the shutoff valve 10 and the regulating valve 11. The connecting pipe 7 of the central air flow path 6 is connected to the air blower 16 via a center air supply line 15 having a shutoff valve 14. The connecting pipe 5a of the first air flow path 3a is connected to the air blower 16 via an air supply line 18a having a switching valve 17a, and is connected to the induction fan 21 via an exhaust gas line 20a having a switching valve 19a. . Similarly,
The connecting pipe 5b of the second air flow path 3b is connected to the air blower 16 via an air supply line 18b having a switching valve 17b, and an exhaust gas line 20 having a switching valve 19b.
It is connected to the induction fan 21 via b.

The heat storage burner 1 connected to the pipe as described above.
Is based on an external control signal, and the operation mode M1 described below
And M2 are alternately repeated at predetermined time intervals. The switching time between the operation modes M1 and M2 is set in consideration of the heat storage capacity of the heat storage bodies 4a and 4b and the air preheating capacity.
It is set to obtain the most efficient combustion. Also,
Valve 10 of gas supply line 12 and center air supply line 1
The valve 14 of No. 5 is maintained in the open state in any operation mode. Further, these valves 10 and 14 are closed only during a shutdown or an emergency.

The operation of the burner 1 will be described in detail. Regardless of the operation mode during burner combustion, fuel gas is supplied from the gas supply source 13 to the fuel nozzle 8 through the gas supply line 12, and the central air flow path is supplied. A part of the combustion air (hereinafter, this combustion air is referred to as “center air”) is supplied to 6 through a center air supply line 15 from an air blower 16. Then, the fuel jet injected from the fuel nozzle 8 is mixed with the center air injected from the central air flow path 6 and comes into contact with the high temperature preheated air ejected from the air passage 3a or 3b, so that the flame F is stabilized. Retained. The center air is the fuel nozzle 8
And has a function of stabilizing the flame F, and its amount is about 3 to 10% of the total combustion air. Further, the fuel gas is continuously supplied to the combustion burner 8 unless the shutoff valve 10 is forcibly closed due to some abnormality or furnace shutdown, and the center air is also continuously supplied with the valve 14 always maintained in the open state. To be done.

In the operation mode M1, the switching valve 17a is opened and the switching valve 17b is closed, so that the first
Combustion air is supplied from the air blower 16 to the air flow path 3a through the air supply line 18a, and the combustion air is mixed and burned with the fuel gas to form a flame F. Further, the switching valve 19a is closed and the switching valve 19b is opened, so that the exhaust gas in the furnace is sucked into the exhaust gas line 20b from the second air flow path 3b based on the drive of the induction fan 21, and is discharged from the chimney 22 into the atmosphere. Is discharged. Further, the heat storage body 4b of the second air flow path 3b is heated by contact with the high temperature exhaust gas passing through the heat storage body 4b.

When switching to the operating mode M2, the switching valve 17a is closed and the switching valve 17b is opened, contrary to the operating mode M1, and the combustion air is supplied from the air blower 16 to the second air flow through the air supply line 18b. The combustion air is supplied to the passage 3b, and the combustion air is mixed and burned with the fuel gas to form the flame F. The combustion air supplied to the second air flow path 3b takes away the heat stored in the heat storage body 4b when passing through the heat storage body 4b heated during the operation in the mode M1, and becomes high temperature preheated air. Become. Therefore, the combustion efficiency of the fuel gas mixed with the high temperature preheated air is highly maintained. Further, the exhaust gas in the furnace is sucked and exhausted from the first air flow path 3a to the exhaust gas line 20a based on the drive of the induction fan 21, and at that time, the heat storage body 4a is heated by contact with the high temperature exhaust gas. Then, when the operation mode is switched from the mode M2 to the mode M1, the combustion air is preheated by the heat stored in the heat storage body 4a of the first air passage 3a, and the combustion efficiency in the mode M1 is maintained at a high level. .

That is, the heat storage body 4b of the second air passage 3b is heated in the operation mode M1, and the combustion air is preheated in the operation mode M2 by the heat stored in the heat storage body 4b. On the contrary, the heat storage body 4a of the first air flow passage 3a is heated in the operation mode M2, and the combustion air is preheated in the operation mode M1 by the heat stored in the heat storage body 4a.

By the way, the fuel gas and the combustion air supplied from the air flow path 3a or 3b start mixing at a position separated from the tip of the fuel nozzle 8 by a predetermined distance. Further, on the opposite side of the contact mixing surface of the fuel gas and the combustion air, the in-furnace gas sucked into the air flow path is caught in the flame and mixed.
Therefore, the temperature of the combustion air supplied into the furnace is changed to the furnace temperature (generally the air flow paths 3a and 3b) by the mixing action of these.
It is equal to the temperature of the exhaust gas sucked into. ) Of about 90% (for example, 1170 ° C. if the furnace temperature is 1300 ° C.), combustion is continued gently. In addition, good low NOx performance can be obtained by the mixing action.

Next, an example in which the heat storage burner 1 is arranged in a walking beam type heating furnace is shown in FIG. In the walking beam type heating furnace 25 shown in this figure, a plurality of movable posts 27 penetrating the hearth wall 26 and the movable posts 27 are provided.
Walking beam 2 with a skid pipe 28
9, the heating material M is conveyed in the direction of the arrow Y by the movable post 27 performing the rectangular movement indicated by the arrow X. In addition, the above walking beam type heating furnace 2
In 5, the heat storage burner 1 is attached to the furnace side wall 30 and the vertical wall 32 formed by bending a part of the ceiling wall 31 downward and being substantially vertical to the material conveying direction. Therefore, in this walking beam heating furnace 25,
The flame formed in the furnace dissipates heat and is then returned to the exhaust air flow path of the heat storage burner 1. Therefore, compared to the conventional walking beam type heating furnace in which the combustion exhaust gas is made to flow uniformly toward the outlet of the furnace, it is not necessary to specially provide a hot air duct or an exhaust gas duct, and space efficiency and cost are reduced. It can be reduced. Similar effect,
It is also obtained when a burner is attached to the side wall of the lower strip of the heating furnace 25.

[0022]

As is apparent from the above description, the heat storage burner according to the present invention can simultaneously supply the combustion air and exhaust the exhaust gas, so that a predetermined heat input can be secured. The number of burners required for the above is halved as compared with the conventional heat storage burner, thereby reducing the required space of the furnace and increasing the heat input density to the furnace.

Further, in the conventional heat storage burner used in a set of two units, there are two switching valves for each set, which are repeatedly opened and closed in the fuel system, two in the combustion air supply system, and two in the exhaust gas system.
A total of 6 pieces were required. However, in the heat storage burner of the present application, the fuel is continuously supplied to the fuel nozzle, and the switching valve is not required. Therefore, there are two switching valves in the combustion air supply system and two in the exhaust gas system. Four is enough. Therefore, the piping and control system are simplified, the incidence of accidents due to malfunction of the switching valve is significantly reduced, and safety and reliability are improved even for long-term use.

Further, since the air flow path and the fuel gas supply path are completely separated, even if the switching valve for combustion air or exhaust gas malfunctions or fuel leaks, the fuel flows back to the exhaust gas line. It will not explode and the safety will be improved.

Furthermore, in the conventional heat storage burner, two flame monitoring devices were required for one set of two heat storage burners, but in the heat storage burner of the present invention, the flame monitoring device is not necessary due to the reduced number of units. Becomes

Further, in the heat storage burner of the present invention, since the high temperature exhaust gas is sucked in the vicinity of the flame, this intake exhaust gas is mixed with the flame and the combustion air. Therefore, due to the above-described mixing action, even if the temperature of the combustion air supplied into the furnace becomes high, the proper flame temperature is maintained and low NOx
Performance can be secured.

[Brief description of drawings]

FIG. 1 is a vertical sectional view of a heat storage burner according to the present invention.

FIG. 2 is a front view of a heat storage burner according to the present invention.

FIG. 3 is a piping diagram of a heat storage burner according to the present invention.

FIG. 4 is a partial cross-sectional view of a walking beam type heating furnace.

FIG. 5 is a vertical cross-sectional view of a conventional heat storage burner.

FIG. 6 is a piping diagram of a conventional heat storage burner.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Heat storage burner, 2 ... Burner main body, 3a, 3b ... Air flow path, 4a, 4b ... Heat storage body, 6 ... Central air flow path, 8 ... Fuel nozzle.

Claims (1)

[Claims] 1. An air flow path for alternately supplying combustion air and exhausting a combustion exhaust gas, a fuel injection nozzle and a central air flow path arranged in the middle of these air flow paths, and 2. A heat storage burner, comprising: an air-permeable heat storage body disposed in each of the two air flow paths.