JPH07120171A - Method of operating heating oven including heat storage alternate combustion burner system - Google Patents

Abstract

PURPOSE:To prevent condensation from being produced and shorten the start-up time of an oven without deteriorating the advantage of a heat storage alternate combustion burner system. CONSTITUTION:In a heating oven 1 including a heat storage alternate combustion burner system 100 wherein a pair of burners 9 are alternately burned and heat of combustion waste gas is recovered by a heat storage structure through a non-combustion burner keeping the temperature of the gas at a high temperature for use in a preheating source of combustion air, upon the system being started when the oven is interrupted and the oven is again started, temperature rise is performed in an ordinary continuous combustion system until predetermined oven temperature is attained. All combustion waste gas produced thereupon is exhausted through a flue 8 not including a heat storage structure provided in the oven, and after the predetermined temperature is attained, the temperature rise is achieved by a heat storage alternate combustion system.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a furnace operation method capable of preventing dew condensation of exhaust gas generated at the time of temperature rising start-up of a heating furnace equipped with a regenerative alternating combustion burner system and shortening the start-up time. .

[0002]

2. Description of the Related Art A heat storage type alternating combustion burner system developed in recent years has a structure in which a pair of burners are alternately burned and the heat of the combustion exhaust gas is recovered as a high temperature through a non-combustion burner by a heat storage body to preheat combustion air. Being used as a source, the thermal efficiency is much higher than that of the conventional heating burner system. That is, the temperature of the combustion exhaust gas discharged from the heat storage outlet to the outside of the system can be set to a considerably low temperature of about 100 to 150 ° C., and as a result, exhaust gas heat loss is reduced.

However, this property, which is excellent in terms of thermal efficiency, causes a problem when starting the furnace. Here, the startup of the furnace means that some time has passed after the furnace was stopped,
When starting the operation of the furnace again, it means a step of raising the temperature from a cold state to a target furnace temperature by a burner installed in the furnace. At the time of this start-up, the inside of the furnace is in a cold state (when it is stopped for a long time, it will be near room temperature),
The temperature of the combustion exhaust gas is likely to drop, and the temperature of the combustion exhaust gas sucked into the heat storage body is considerably lower than that during normal operation. Further, since the heat storage body itself is also cooled like the furnace body, the amount of cooling heat of the combustion exhaust gas flowing in the heat storage body becomes larger than usual and the temperature tends to decrease. Further, the heat storage body itself is designed to sufficiently absorb the sensible heat of the combustion exhaust gas, and the synergistic effect combined with the above-mentioned two effects makes the heat storage body outlet temperature of the combustion exhaust gas during steady-state operation. Temperature (100
Temperature is much lower than about 150 ° C). Therefore, the temperature is below the dew point of the temperature at which the water in the exhaust gas condenses,
Condensation is very likely to occur.

When dew condensation occurs in the pipe, the condensed water oxidizes the metal on the inner surfaces of the pipe and the valve to generate scale. This scale piece is clogged in the gap of the movable portion of the valve, etc., and becomes caught, making normal operation of the valve difficult. If this condition progresses, the valve will not operate,
The valve body will be damaged. In addition, if the scale is locally concentrated, the pipe is significantly damaged, and cracks or holes are generated in the pipe.

This problem is greatly affected when a fuel containing a relatively large amount of sulfur and nitrogen is used. That is, the sulfur oxide, the nitrogen oxide and the water in the combustion exhaust gas react with each other when dew condensation occurs to generate an acid liquid. This acid solution rapidly corrodes the metal inside the pipe and valve. The rate of corrosion by this acid solution is
The rate of damage is much faster than the rate of corrosion by water alone, and the damage progresses faster. In particular, when the furnace is stopped for a long time, the condensed water is likely to be accumulated in the pipes and valves as a drain, and the influence is further increased.

Therefore, as a countermeasure against such a problem,
Conventionally, a method of intermittently burning a burner to suppress the generation of drain during the shutdown of the furnace or a system in which the generated drain is physically connected as disclosed in, for example, Japanese Patent Laid-Open No. 62-155922 is disclosed. We are trying to solve the problem by adopting a method of removing it to the outside.

[0007]

However, in the intermittent operation while the operation is stopped, it is not possible to completely prevent the occurrence of drain by an emergency measure, and the intermittent operation itself is always possible. Not necessarily.

Further, it is impossible to discharge all the drains even when the drains are removed from the system.
There are also problems such as clogging and corrosion of the drain valve itself.

In any case, the conventional countermeasures against exhaust gas dew condensation have not been sufficient to solve the problem, so that the repair of the piping of the system through which the combustion exhaust gas flows and the replacement of valves have to be carried out in a short period.

In view of the above points, the present invention is a regenerative alternating combustion burner which does not cause dew condensation and shortens the furnace start-up time without impairing the advantages of the regenerative alternating combustion burner system. An object of the present invention is to provide a method of operating a heating furnace equipped with a system.

[0011]

A method of operating a heating furnace having a regenerative alternating combustion burner system according to the present invention has the following constitution. That is, in a heating furnace equipped with a regenerative alternating combustion burner system in which a pair of burners are alternately burned and the heat of the combustion exhaust gas is recovered as a high temperature through a non-combustion burner in a regenerator and used as a preheat source for combustion air. When the furnace is stopped and the operation of the furnace is started again, in the furnace operation method in which the furnace temperature is raised to a predetermined temperature and started before starting the operation, at the time of rising the temperature, until the predetermined furnace temperature is reached. , The temperature is raised by the normal continuous combustion method, and all the combustion exhaust gas generated at this time is discharged from the flue that is not equipped with the heat storage body provided in the furnace body, and the heat is stored after reaching the predetermined furnace temperature. The temperature is raised by an alternating combustion method.

At the time of raising the temperature, all burners installed in the heating furnace are continuously burned.

Further, as the heating furnace, a continuous heating furnace having a plurality of zones is used, and the zone where the predetermined furnace temperature is reached by the temperature increase by the continuous combustion method is sequentially switched to the heat storage alternating combustion method. To do.

[0014]

In the present invention, when the temperature is raised, the temperature is raised by the normal continuous combustion method until the temperature reaches a predetermined furnace temperature (for example, the lower limit temperature at which dew condensation of combustion exhaust gas does not occur). All combustion exhaust gas is discharged from the flue that does not have a heat storage body provided in the furnace body, and after reaching the constant furnace temperature, the temperature is raised by the heat storage alternating combustion method, so that the thermal efficiency is improved. It is possible to prevent the occurrence of dew condensation without impairing the advantages of the excellent heat storage type alternating combustion burner system.

Further, in the present invention, since all burners installed in the heating furnace are made to continuously burn when the temperature is raised, in principle, a maximum of half of the total number of burners installed in the furnace is set. It is possible to increase the number of burners to be burned (maximum can be doubled) as compared with the heat storage alternating combustion method in which only the burner of No. 1 can burn. Therefore, the heating time up to the predetermined furnace temperature can be shortened, and thus the total heating time can also be shortened.

Further, in the present invention, a continuous heating furnace having a plurality of zones is used as the heating furnace, and from the zone where a predetermined furnace temperature is reached by the temperature rise by the continuous combustion method,
The reason for switching to the heat storage alternating combustion method is that when the temperature is raised, the combustion exhaust gas is discharged from the flue provided in the furnace body so that, for example, the combustion exhaust gas is entirely at one end of the continuous heating furnace. Since it can flow near the butt (near the charging part of the object to be heated), even if it is a continuous heating furnace that uses a regenerative alternating combustion burner system that does not easily generate gas flow between each zone, Similar to a continuous heating furnace consisting of a burner system (not a regenerative alternating combustion burner system), the distance or time for the combustion exhaust gas to flow can be set to be relatively long, and the regenerative alternating combustion method can be used after reaching a predetermined furnace temperature. This is because by switching, the effect of utilizing the advantage of the heat storage type alternating combustion burner system which is excellent in terms of thermal efficiency is great. Therefore, as long as the heating furnace is equipped with the regenerative alternating combustion burner system, the furnace operating method of the present invention can be applied to a single furnace heating furnace or a batch heating furnace.

[0017]

The present invention will be described below with reference to the illustrated embodiments. FIG. 1 is a block diagram showing a schematic configuration of a continuous heating furnace for explaining a method of operating a heating furnace equipped with a regenerative alternating combustion burner system according to an embodiment of the present invention. 2 and 3 are schematic configuration diagrams showing a regenerative alternating combustion burner system provided for each unit furnace of the continuous heating furnace, FIG. 2 is a side sectional view of the unit furnace, and FIG. 3 is a unit furnace. FIG.

The continuous heating furnace 1 has a charging port 3 for the object W to be heated.
And a plurality of unit furnaces 2 each having a carry-out port 4 are connected. In this embodiment, it is composed of four unit furnaces 2 and therefore has four zones for continuously heating the object to be heated. The unit furnace 2 includes a pair of regenerative combustion burners 9 on the upper and lower parts of the furnace body and on the left and right of each part.
Are installed facing each other in the furnace length direction. As shown in FIGS. 2 and 3, each burner 9 has a space 10 for mixing the combustion preheated air supplied through the heat storage body 11 provided in the burner body with the fuel, and each pair of burners 9 has a space. 9
Is designed to perform combustion and exhaust alternately in a cycle.
One of the burners 9 stops burning, and one of the four-way valves 14 draws the exhaust gas from the furnace through the heat storage body 11 of the burner, while the other burner 9 starts burning and the hot combustion gas is burned. It is designed to blow out toward the inside.
In FIG. 3, reference numeral 12 is an air supply system for supplying combustion air by a pushing fan 15, and 13 is an induction fan 16.
A four-way valve 14 is provided in the air supply system 12 and the exhaust gas exhaust system 13 in the exhaust gas exhaust system for exhausting the exhaust gas. Reference numeral 18 denotes a fuel supply system for supplying fuel via a slide spool type directional control valve 17. Direction control valve 17
As shown in FIGS. 4 to 6, the spool 17a can be switched in three stages. That is, a position for supplying fuel to both the pair of burners 9 (FIG. 4), and a position for supplying fuel to one of the pair of burners 9 (FIG. 5),
It is possible to switch to a position (FIG. 6) for supplying fuel to the other of the pair of burners 9. Further, in FIGS. 1 and 2, reference numeral 5 is a furnace pressure control means provided for each unit furnace 2, which adjusts the opening degree of a damper 6 provided in a duct 7 communicating with the stack chimney 8 and is adjusted during normal operation. The furnace pressure in the zone is controlled to be constant, and the continuous heating furnace 1 is used when the furnace is started up.
Only the damper 6 near the bottom of the furnace is opened to control all the combustion exhaust gas to flow in the vicinity of the bottom of the furnace.

At least one pair of the heat storage type alternating combustion burner system 100 configured as described above is installed in each unit furnace 2 to configure the continuous heating furnace 1 as shown in FIG. Therefore, each zone of the continuous heating furnace 1 has a unit furnace 2
The exhaust gas does not almost flow out to the front and rear adjacent zones by the heat storage type alternating combustion burner 9 during combustion by the heat storage alternating combustion system. Further, for each heat storage type alternating combustion burner system 100 of each zone, a fuel flow rate control device 101 for controlling the fuel supplied to the burner 9.
Is provided. The fuel flow rate control device 101 outputs a fuel flow rate control signal to the regenerative alternating combustion burner system 100 based on the combustion pattern signal from the fuel injection setting means 102, and also outputs the current fuel injection pattern to the reactor pressure control means 5. Is a continuous combustion pattern (furnace startup) or a heat storage alternating combustion pattern (normal operation).

The fuel injection setting means 102 comprises a startup determination means 103 and a fuel injection pattern calculation means 104. The start-up determination means 103 uses the temperature information (not shown) provided in each zone for each furnace temperature information 10 from each temperature sensor.
5 is sequentially compared with the switching temperature set value (for example, the lower limit temperature at which dew condensation of combustion exhaust gas does not occur), and when the furnace temperature is lower than the switching temperature set value, it is determined to be started, and the fuel injection pattern calculation means 104. To the zone number and a signal notifying that it is starting up,
When the furnace temperature is higher than the switching temperature set value, the zone number and the alternate combustion permission signal are output to the fuel injection pattern calculation means 104. When the number of the zone corresponding to the signal notifying the start-up is input from the start-up determination means 103, the fuel injection pattern calculation means 104 causes the fuel flow rate control device 101 of the regenerative combustion burner system 100 in the zone to be input. On the other hand, when the fuel injection pattern is set to be a normal continuous combustion pattern and the zone number corresponding to the alternating combustion permission signal is input from the start-up determination means 103, the heat storage type alternating combustion burner system 100 in the zone is input. The fuel flow rate control device 101 is set so that the fuel injection pattern is a heat storage alternating combustion pattern.

Therefore, in this embodiment, when the furnace is stopped and the operation of the furnace is started again after a lapse of a certain time, it is the startup determination means 1 that the heating is startup.
03, and based on the determination result, the fuel injection pattern calculation means 104 determines the fuel injection pattern for the fuel flow rate control device 101 of each regenerative combustion burner system 100 as a normal continuous combustion pattern. Set to. And the fuel flow control device 101
The fuel supplied to the burner 9 of the regenerative alternating combustion burner system 100 is controlled by the control described above, and the temperature rise by the normal continuous combustion method is started. At this time, in this embodiment, all the burners 9 are set to burn continuously so that the heating time to the lower limit temperature at which dew condensation of the combustion exhaust gas does not occur can be shortened as much as possible, but this is not the only option. Instead, some of the burners 9 or some of the burners 9 in the zones may be burned continuously. In short, it is important to prevent the combustion exhaust gas from being discharged to the outside of the system through the non-combustion burner when the temperature is raised, and the intended purpose is achieved.

When the temperature rise by the normal continuous combustion system is started, in synchronization with this, the furnace pressure control means 5 controls the continuous heating furnace among the dampers 6 provided in the ducts 7 communicating with the collective chimney 8. Only the damper 6 in the vicinity of the furnace bottom of No. 1 is opened, all the other dampers 6 are closed, and the combustion exhaust gas is controlled so as to flow through all the zones to the vicinity of the furnace bottom. As a result, the distance or time during which the combustion exhaust gas flows can be made relatively long, and the inside of the furnace body at the time of temperature rise and start-up is cold,
Since the efficiency of heat absorption from the combustion exhaust gas passing through the furnace body is extremely high, the temperature can be raised efficiently. Further, the combustion exhaust gas is discharged from the damper 6 near the furnace bottom at a high temperature through the collective chimney 8 having no heat storage body, so that the occurrence of dew condensation in the collective chimney 8 is also prevented.

Since the start-up determination means 103 is constantly comparing the furnace temperature information 105 for each zone with the switching temperature set value, the furnace temperature is higher than the switching temperature set value due to the temperature increase by the continuous combustion method. Whether or not the temperature has become higher can be determined for each zone, and it is possible to sequentially notify the fuel injection pattern calculation means 104 from the zone in which it has been determined that the furnace temperature has become higher than the switching temperature set value. The fuel injection pattern calculation means 104 sequentially sets the fuel injection pattern to be set in the fuel flow rate control device 101 of the heat storage type alternating combustion burner system 100 in the zone where the switching temperature set value is reached based on the determination result of the startup determination means 103. The normal continuous combustion pattern is switched to the heat storage alternating combustion pattern.
Then, the fuel supplied to the burner 9 of the heat storage type alternating combustion burner system 100 is controlled by the control of the fuel flow rate control device 101, and sequentially from the zone where the switching temperature set value is reached,
The combustion method is switched to the heat storage alternating combustion method. In this way, the combustion method is sequentially switched from the normal continuous combustion method to the heat storage alternating combustion method, and when the last zone reaches the switching temperature set value, all zones are heated by the heat storage alternating combustion method and the thermal efficiency is increased. In this respect, the advantage of the excellent heat storage type alternating combustion burner system is utilized, and the total heat-up time is shortened compared to the conventional one.

When the burners 9 in some zones are made to continuously burn at the time of rising the temperature, the furnace temperature in the combustion zone reaches the switching temperature set value, and the combustion method in this combustion zone is continuous burning. When the system is switched to the heat storage alternating combustion system, a part of the non-combustion zone is ignited and burned in the normal continuous combustion system, and this system is sequentially switched and ignited, and the last zone is switched. When the temperature set value is reached, all zones may be brought into a heat-up state by the heat storage alternating combustion method.

By the way, in the above-mentioned embodiment, the one in which the furnace operating method of the present invention is used in the continuous heating furnace is shown. However, if the heating furnace is equipped with the regenerative alternating combustion burner system, the heating method of other methods is used. The furnace operation method of the present invention can also be applied to a furnace, for example, a single furnace type heating furnace or a batch type heating furnace. In this case, the distance that the combustion exhaust gas flows by the continuous combustion method at the time of temperature rise startup cannot be taken long, but if the combustion amount is reduced, the capacity of the combustion exhaust gas decreases, so the passage time in the furnace increases and the heat exchange amount increases. Can be increased. as a result,
Improvement of thermal efficiency can be expected. That is, the heat efficiency can be adjusted while shortening the heat-up time, and the priority specific gravity of both can be arbitrarily selected within a certain range. Even if the thermal efficiency becomes poor, it is only within the range of heating up to a certain furnace temperature (switching temperature setting value), and the thermal efficiency for the overall heating up to the final target furnace temperature is Substantially no difference from the conventional heating method (total heating is due to heat storage type alternating combustion).

FIG. 7 shows a concrete comparison of how long it took to apply the furnace operation method of the present invention and the conventional heating method until the final target furnace temperature was reached. Is. FIG. 7 shows the furnace temperature on the vertical axis and the time on the horizontal axis. The solid line shows the furnace operating method of the present invention, and the broken line shows the conventional heating method. Further, the switching temperature set value is set to 600 ° C. and the final target furnace temperature is set to 1200 ° C., and in the furnace operating method of the present invention, all burners in each zone are continuously burned at the time of starting up to the switching temperature set value,
In the conventional heating method, all the heat rising until the final target furnace temperature is reached is performed by regenerative combustion of all the burners in each zone. As is clear from the figure, the conventional heating method required 8 hours to reach the final target furnace temperature (1200 ° C.), whereas the furnace operating method of the present invention required 7 hours. A time saving effect of more than 10% was obtained.

[0027]

As described above, according to the present invention, when the temperature is raised, the temperature is raised by the normal continuous combustion method until the temperature reaches the predetermined furnace temperature, and all combustion exhaust gas generated at this time is raised. Is discharged from the flue that does not have a heat storage body provided in the furnace body, and after reaching the constant furnace temperature, the temperature is raised by the heat storage alternating combustion method, so a heat storage method that is excellent in terms of thermal efficiency Condensation can be prevented without compromising the advantages of the alternating combustion burner system.

Further, according to the present invention, all the burners installed in the heating furnace are made to burn continuously when the temperature is raised, so that, in principle, the maximum half of the total number of burners installed in the furnace is set. It is possible to increase the number of burners to burn (maximum double) as compared with the heat storage alternating combustion method, which can burn only the burner, and to shorten the heating time to the predetermined furnace temperature. The heating time can also be shortened.

Further, according to the present invention, a continuous heating furnace having a plurality of zones is used as the heating furnace, and the zones in which a predetermined furnace temperature is reached by the temperature increase by the continuous combustion system are sequentially
Since the system switches to the heat storage alternating combustion method, the combustion exhaust gas generated by continuous combustion when the temperature rises and rises, for example, near the bottom of the continuous heating furnace (near the charging part of the object to be heated).
Even if it is a continuous heating furnace that uses a regenerative alternating combustion burner system that can flow to each other and does not easily generate a gas flow between each zone, it consists of a conventional burner system (not a regenerative alternating combustion burner system). Similar to the continuous heating furnace, the distance or time for the combustion exhaust gas to flow can be set relatively long, and the advantages of the heat storage type alternating combustion burner system, which is excellent in terms of thermal efficiency, can be utilized.

[Brief description of drawings]

FIG. 1 is a block diagram showing a schematic configuration of a continuous heating furnace for explaining a method of operating a heating furnace having a regenerative alternating combustion burner system according to an embodiment of the present invention.

FIG. 2 is a sectional side view of a unit furnace of the continuous heating furnace of FIG.

FIG. 3 is a front view of the unit furnace shown in FIG.

4 is an enlarged cross-sectional view showing a directional control valve arranged in a fuel supply system of the unit furnace of FIG.

5 is a cross-sectional view showing another mode of the directional control valve of FIG.

6 is a cross-sectional view showing a different aspect of the directional control valve of FIG.

FIG. 7 is a diagram showing a comparison of the time required to reach the final target furnace temperature between the furnace operating method of the present invention and the conventional heating method.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Continuous heating furnace 6 Damper 7 Duct 8 Stack chimney 9 Heat storage type combustion burner 11 Heat storage body 100 Heat storage type alternating combustion burner system 101 Fuel flow rate control device 102 Fuel injection setting means 103 Startup determination means 104 Fuel injection pattern calculation means

Front Page Continuation (72) Inventor Ryoichi Tanaka 2-3-1, Shirute, Tsurumi-ku, Yokohama-shi, Kanagawa Japan Furnace Industry Co., Ltd. Within Japan Furnace Industry Co., Ltd. (72) Inventor Atsushi Sudo 2-53, Shirate, Tsurumi-ku, Yokohama-shi, Kanagawa Inside Furnace Industry Co., Ltd.

Claims (3)

[Claims] 1. A regenerative alternating combustion burner system is provided, wherein a pair of burners are burned alternately and the heat of the combustion exhaust gas is recovered as a high temperature through a non-combustion burner by a regenerator and used as a preheat source for combustion air. When stopping the furnace in the heating furnace and restarting the operation of the furnace again, in the furnace operation method that raises the furnace temperature to a predetermined temperature and starts it before starting the operation, Until the temperature is reached, the temperature is raised by the normal continuous combustion method, and all the combustion exhaust gas generated at this time is exhausted from the flue provided with no heat storage body in the furnace body, and after reaching the predetermined furnace temperature. Is a method of operating a heating furnace equipped with a heat storage type alternating combustion burner system, wherein the temperature is raised by a heat storage type alternating combustion system. 2. The method of operating a heating furnace equipped with a regenerative alternating combustion burner system according to claim 1, wherein all the burners installed in the heating furnace are burned continuously when the temperature is raised. 3. A continuous heating furnace having a plurality of zones is used as the heating furnace, and the heat storage alternating combustion method is sequentially switched from the zone where a predetermined furnace temperature is reached by the temperature increase by the continuous combustion method. A method of operating a heating furnace comprising the regenerative alternating combustion burner system according to claim 1 or 2.