JP3429375B2 - Thermal storage type alternating combustion device - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a regenerative alternating combustion device used for a metal heating furnace or the like. 2. Description of the Related Art FIG. 1 shows a regenerative alternating combustion apparatus of this type, in which a pair of burners 1a and 1b is provided with a charging chamber 3 filled with a heat storage material, and an air supply blower 4 is provided. And the exhaust blower 5 via the flow path switching valve 6 to both burners 1a, 1
b, and both burners 1a, 1b are alternately burned,
During the combustion of one burner 1a, the exhaust gas in the furnace 8 is discharged through the other burner 1b, and the exhaust heat is recovered in the regenerator charging chamber 3, and the burner 1b is subsequently burned by the exhaust heat. The combustion air at the time is preheated.
FIG. 2 shows an example of the structure of the charging chamber 3, in which reference numeral 7 denotes a pilot burner, and reference numeral 9 denotes a cooling air supply port for protecting the fuel supply pipe 10 from high temperature during recovery of exhaust heat. As the heat storage body, ceramic small balls are usually used. In FIG. 1, 10a and 10b are fuel supply pipes, 11a and 11b.
b is a fuel gas shutoff valve. Conventionally, as a method of igniting the burner 1, a pilot continuous combustion system in which the pilot burner 7 shown in FIG. 2 is burned through a combustion cycle and an exhaust heat recovery cycle has been adopted. FIG. 5 (a) shows a time chart thereof. Since the pilot burner 7 is constantly burning, fuel can be supplied to each main burner 1 simultaneously with the end of the exhaust heat recovery cycle. There is an advantage that there is no time delay between the combustion and the combustion cycle. On the other hand, a counter wind is applied to the pilot burner 7 to make combustion unstable, and the flame goes up, so that the nozzle of the pilot burner is rapidly worn. There was a disadvantage.
Therefore, recently, as shown in FIG. 5B, a pilot timed combustion system in which the pilot burner 7 is ignited after the end of the exhaust heat recovery cycle is also performed. However, this method is also excellent in terms of pilot flame stability, but has the following disadvantages. In general, in a regenerative alternating combustion device, the combustion air or exhaust gas has a very high ventilation resistance when passing through the regenerator filling chamber 3, so that, as shown in FIG. Each time, the pressure inside the furnace fluctuates rapidly.
Therefore, in a furnace having low hermeticity, suction of outside air and blowing of furnace air occur every time switching is performed, which causes a reduction in thermal efficiency. In the pilot constant combustion system as shown in FIG.
Since the period in which both the main burners 1a and 1b are not burning is instantaneous, the rapid decrease in the furnace pressure due to the extinguishing of the burner 1a and the rapid increase in the furnace pressure due to the ignition of the burner 1b occur almost simultaneously, and as a result, they cancel each other out. Although there was an effect that the rapid fluctuation of the furnace pressure was suppressed, in the pilot timed combustion system, there was a slight delay between the extinguishing and the ignition of both burners 1a and 1b, so that the furnace pressure suddenly dropped and suddenly increased. Has a drawback in that heat loss occurs as described above. The present invention can solve the above-mentioned drawbacks of the prior art, prevent the burnout of the nozzle of the pilot burner 7, and minimize the blowout of furnace air and the suction of outside air accompanying the ignition and extinguishing of the burner. It is an object of the present invention to provide a regenerative alternating combustion device that can be suppressed. According to the present invention, as shown in FIGS. 1 and 2, a pair of burners 1a and 1b are provided with filling chambers 3 each filled with a heat storage material. An exhaust blower 5 is connected to both burners 1a and 1b via a flow path switching valve 6, and during combustion of one burner 1a (or 1b), exhaust heat is discharged from a charging chamber 3 of the other burner 1b (or 1a). As shown in FIG. 3, in the regenerative alternating combustion device that can be recovered, immediately after the pilot burner 7 attached to each burner 1a (or 1b) is ignited, the burner 1a (or 1b)
Is switched from the exhaust heat recovery cycle to the combustion cycle, and the pilot burner 7 is extinguished after ignition of the burner 1a. Note that the flow path switching valve 6 is 1 in FIG.
Although it is composed of four four-way switching valves, it may be composed of four on-off valves. According to the above configuration, as shown in FIG. 3, the pilot burner 7 is ignited immediately before the end of the exhaust heat recovery cycle of the main burner 1, so that the operation from the exhaust heat recovery cycle to the combustion cycle is started. The fuel supply to the main burner 1 can be started at the same time as the switching, thereby shortening the difference between the fire extinguishing of the burner 1 and the ignition timing of the other burner 1a as in the case of FIG. The rapid change of the internal pressure can be suppressed to a minimum, and the combustion time of the pilot burner 7 can be reduced to several tenths of the case of FIG. At the same time, it is possible to prevent wear of the pilot burner nozzle due to the run-up of the pilot flame, and it is possible to stabilize the flame by making the pilot flame sufficiently large because the combustion time is short. FIG. 1 shows an embodiment of a regenerative alternating combustion apparatus according to the present invention. Each of the burners 1a and 1b has a structure shown in FIG.
As shown in FIG. 1, a filling chamber 3 filled with ceramic balls (for example, a diameter of 10 to 20 mm) is integrally connected, and is supplied to these filling chambers 3 via a four-way switching valve 6. The air blower 4 and the exhaust blower 5 are connected so that the air supply passage 2b (or 2a) of the other burner 1b (or 1a) is used as an exhaust passage while one burner 1a (or 1b) is burning. The combustion air is preheated by the heat of the exhaust gas via the heat storage body. At this time furnace 8
The temperature of the exhaust gas inside reaches 1000-1300 ° C., and the duration of the combustion cycle or the exhaust heat recovery cycle of the burners 1a and 1b is, for example, about several tens seconds to several minutes. As shown in the time chart of FIG. 3, each burner 1 is switched from the exhaust heat recovery cycle to the combustion cycle immediately after the ignition of the pilot burner 7 attached thereto, and is supplied with fuel immediately. After the ignition of the burner 1 is confirmed, the pilot burner 7 is extinguished. Therefore, the combustion time of the pilot burner 7 is within several seconds, and the combustion time of the pilot burner 7 in the prior art shown in FIG.
It is about 1/0. FIG. 4 (a) is a graph showing the pressure change in the furnace of the pilot timed combustion system before the improvement according to the present invention, and FIG. 4 (b) is a graph showing each measured value of the pressure change after the improvement. 1 or less. According to the present invention, as described above, fuel supply to the main burner 1 can be started simultaneously with switching from the exhaust heat recovery cycle to the combustion cycle, thereby extinguishing the fire of the burner 1. And the other side of the burner 1a can shorten the ignition timing shift and minimize the sudden change in the furnace pressure, thereby minimizing the decrease in the thermal efficiency due to the suction of the outside air and the blowout of the furnace air. 5A, and the combustion time of the pilot burner 7 can be reduced to, for example, several tenths of that in the case of FIG. 5A. The advantage is that the burner nozzle can be prevented from being worn, and the combustion time is short, so that the pilot flame can be made sufficiently large to stabilize the flame. There is a point.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a system diagram of an alternating combustion device showing one embodiment of the present invention. FIG. 2 is a cross-sectional view showing an example of the structure of a heat storage element charging chamber used in the first embodiment. FIG. 3 is a time chart showing an operation state of the above. 4 (a) is a graph showing measured values of the pressure in each furnace before the improvement according to the present invention, and FIG. FIGS. 5 (a) and (b) are time charts showing operating states of a conventional pilot constant combustion system and a pilot timed combustion system, respectively. FIG. 6 is a graph showing a change in furnace pressure in a conventional pilot timed combustion system. [Description of Signs] 1, 1a, 1b (Main) burners 2a, 2b Air supply path 3 Heat storage material filling chamber 4 Air supply blower 5 Exhaust blower 6 Flow path switching valve or four-way switching valve 7 Pilot burner 8 Furnace body 9 Cooling air supply ports 10, 10a, 10b Fuel supply pipes 11a, 11b Fuel gas shutoff valve

Claims (1)

(57) [Claims 1] A pair of burners are provided with filling chambers each filled with a heat storage body, and a supply air blower and an exhaust blower are connected to the respective burners via on-off valves, respectively. In a regenerative alternating combustion device in which exhaust heat can be recovered in a charging chamber of the other burner during combustion of one burner, the burner is burned from an exhaust heat recovery cycle immediately after ignition of a pilot burner attached to each burner. A regenerative alternating combustion device characterized in that the cycle is switched to a cycle and the pilot burner is extinguished after the burner is ignited.