JPH081287B2 - Heat storage type combustion device - 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 type combustion apparatus 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, about 1 million times / year (= 6000 × 3600/2)
The switching operation of 0) is repeated, and in order to make such a huge number of switching functions without malfunction even once, high reliability is required not only in the control method but also in the mechanical structure of the switching valve itself. There was a problem. For example,
If the fuel system valve malfunctions or fuel leaks, the leaked fuel flows into the exhaust gas line and is wasted, or an explosion occurs. Further, when the fuel gas containing impurities is used, the impurity components are gas switching valves F1 and F2.
There is a risk of sticking to the inside of the and not maintaining a sufficient seal.

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]

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and the heat storage type combustion apparatus according to the present invention alternately supplies combustion air and exhausts combustion exhaust gas. And a fuel injection nozzle arranged in the middle of these air passages, and a burner having a central air passage, and two air passages for supplying the combustion air and exhausting the combustion exhaust gas. And a breathable heat storage body housed in each of the connecting pipes.

[0012]

In the above heat storage type combustion apparatus, the burner is attached to the furnace wall with the fuel injection nozzle and the air outlet of the air passage facing the inside of the furnace. Further, the fuel injection nozzle is connected to the fuel supply source. Further, the connecting pipe is connected to the combustion air supply source and the exhaust gas device via the switching means, respectively. Then, during fuel combustion, fuel is continuously supplied to the fuel injection nozzle. Combustion air is supplied from a combustion air supply source to one of the air passages, exhaust gas in the furnace is exhausted from the other remaining air passage, and the heat storage body provided in the connecting pipe is preheated.
The air flow path for supplying the combustion air and the air flow path for exhausting the exhaust gas are switched every predetermined time, and the heat recovered from the exhaust gas by the heat storage body is used for preheating the combustion air.

[0013]

Embodiments of the heat storage type combustion apparatus according to the present invention will be described below with reference to the accompanying drawings. In FIGS. 1 and 2, 1 is a burner and 2 is a burner body of the burner 1, which is made of a known refractory material. 3a is the first air flow path, 3
Reference numeral b is a second air flow path, and these air flow paths 3a and 3b are formed by penetrating the burner body 2 in the front-rear direction. 4a, 4b
Is a heat storage material, which is made of a honeycomb-shaped or heat-resistant material such as ceramics or a container-shaped breathable member that accommodates a large number of ceramic pellets, and is connected to the air flow paths 3a and 3b in the connection pipes 5a and 5b. 6a and 6b are provided and housed in the heat storage boxes 6a and 6b, respectively. Although the regenerator boxes 6a and 6b are separated from each other in the drawing, the accommodating portions of the regenerators 4a and 4b may be formed by partitioning one regenerator box with a partition wall. Reference numeral 7 denotes a central air passage, which is formed in the middle of the two air passages 3a and 3b so as to penetrate the burner body 2 and has a connecting pipe 8 at the rear end. Reference numeral 9 denotes a fuel nozzle, which penetrates the rear end of the connecting pipe 8 and is inserted into the central air passage 7. Reference numeral 10 is a flame monitoring window, which is provided on the side of the central air passage 7.

The burner 1 having the above-mentioned structure is provided with the air passage 3
The front parts of a and 3b are attached to the furnace wall with the front parts facing the inside of the furnace, and the pipes are connected as shown in FIG. That is, the fuel nozzle 9 is connected to the gas supply source 14 via the gas supply line 13 having the shutoff valve 11 and the regulating valve 12. The connecting pipe 8 of the central air flow path 7 is connected to an air blower 17 via a center air supply line 16 having a shutoff valve 15. The connecting pipe 5a of the first air flow path 3a is connected to the air blower 17 via an air supply line 19a having a switching valve 18a, and an exhaust gas line 21a having a switching valve 20a.
It is connected to the attraction fan 22 via. Similarly, the connecting pipe 5b of the second air flow path 3b is connected to the air blower 17 via the air supply line 19b having the switching valve 18b, and is connected to the induction fan 22 via the exhaust gas line 21b having the switching valve 20b. Be connected.

The burner 1 connected to the pipe as described above is
Based on the external control signal, the following operation modes M1 and M
The operation is repeated by repeating 2 every predetermined time. Valve mode M1 mode M2 18a open closed 20a closed open 18b closed open 20b open closed The switching times of the operation modes M1 and M2 are set in consideration of the heat storage capacity of the heat storage bodies 4a and 4b, the air preheating capacity, and the like.
It is set to obtain the most efficient combustion. Also,
Valve 11 of gas supply line 13 and center air supply line 1
The valve 15 of No. 6 is maintained in the open state in any operation mode and is closed only when the furnace is stopped or at a specific time.

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 14 to the fuel nozzle 9 through the gas supply line 13, 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 7 from an air blower 17 through a center air supply line 16. Then, the fuel jet injected from the fuel nozzle 9 is mixed with the center air injected from the central air flow path 7 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 9
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 fuel nozzle 9 unless the shutoff valve 11 is forcibly closed due to some abnormality or a furnace shutdown, and the center air is also continuously supplied with the valve 15 kept open. To be done.

In the operation mode M1, the switching valve 18a is opened and the switching valve 18b is closed, so that the first
Combustion air is supplied to the air flow path 3a from the air blower 17 through the air supply line 19a, and the combustion air is mixed and burned with the fuel gas to form a flame F. Further, the switching valve 20a is closed and the switching valve 20b is opened, and the exhaust gas in the furnace is sucked into the exhaust gas line 21b through the second air flow path 3b based on the drive of the induction fan 22, and is discharged from the chimney 23 into the atmosphere. Is discharged. Furthermore, the connecting pipe 6
The heat storage body 4b of b 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 18a is closed and the switching valve 18b is opened, contrary to the operating mode M1, and the combustion air is supplied from the air blower 17 to the second air flow through the air supply line 19b. 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 is deprived of the heat stored in the heat storage body 4b when passing through the heat storage body 4b heated during the operation of 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 21a based on the drive of the induction fan 22, and the heat storage body 4a is heated by contact with the high temperature exhaust gas at that time. Then, when the operation mode is switched from the mode M2 to the mode M1, the heat storage body 4 of the connecting pipe 5a is
The combustion air is preheated by the heat stored in a, and the combustion efficiency in mode M1 is maintained at a high level.

That is, in the operation mode M1, the heat storage body 4
b is heated, and the combustion air is preheated in the operation mode M2 by the heat stored in the heat storage body 4b. vice versa,
The heat storage body 4a 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 9 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.

FIG. 4 shows an example in which the above heat storage type combustion device is applied to a walking beam type heating furnace. In the walking beam type heating furnace 25 shown in this figure, a walking beam 29 is composed of a plurality of movable posts 27 penetrating the hearth wall 26 and a skid pipe 28 connecting these movable posts 27. Performs a rectangular motion indicated by arrow X, and thereby the heating material M is conveyed in the direction of arrow Y. Further, in the above walking beam type heating furnace 25, the furnace side wall 30 and the vertical wall 32 formed by bending a part of the ceiling wall 31 downward are substantially vertical to the material conveying direction.
The burner 1 is attached to the. 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 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. The same effect can be obtained by heating furnace 25
It is also obtained when a burner is attached to the side wall of the lower strip of the.

[0022]

As is apparent from the above description, the heat storage type combustion apparatus according to the present invention can simultaneously supply the combustion air and exhaust the exhaust gas by one unit, so that a predetermined heat input can be secured. The number of burners required to achieve this is halved compared to conventional heat storage burners, which reduces the required space in the furnace and increases 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 type combustion apparatus of the present application, the fuel is continuously supplied to the fuel nozzle, and the switching valve is not required. Therefore, two switching valves are provided in the combustion air supply system and two in the exhaust gas system. , 4 in total 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 each set of two heat storage burners, but the burner of the present invention requires no flame monitoring device as the number of burners decreases. Become.

Further, since the high temperature exhaust gas is sucked in the vicinity of the flame, the sucked exhaust gas is mixed with the flame and the combustion air. Therefore, due to the above mixing action, an appropriate flame temperature is maintained even if the temperature of the combustion air supplied into the furnace rises, and low NOx performance can be ensured.

Further, since the heat storage body is arranged outside the burner, maintenance and inspection and replacement of the heat storage body are easy. In addition, when the heat storage body is housed in the air flow path, it is not easy to properly secure the sealing property of both, but in the case of the present invention,
Since the heat storage body is housed in the heat storage box outside the burner, it is easy to secure the sealing property between both.

[Brief description of drawings]

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

FIG. 2 is a front view of a heat storage type combustion apparatus according to the present invention.

FIG. 3 is a piping diagram of a heat storage type combustion apparatus 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]

1 ... Burner, 2 ... Burner body, 3a, 3b ... Air flow path,
4a, 4b ... Heat storage body, 7 ... Central air flow path, 9 ... Fuel nozzle.

Claims (1)

[Claims] 1. A burner having two air passages for alternately supplying combustion air and exhausting combustion exhaust gas, a fuel injection nozzle arranged in the middle of these air passages, and a central air passage. And connecting pipes respectively connected to the two air flow paths for supplying the combustion air and exhausting the combustion exhaust gas, and a breathable heat storage body housed in each of the connecting pipes. Heat storage type combustion device.