JPH0727330A - Method for controlling ignition of pilot burner - Google Patents

Abstract

PURPOSE:To prevent a flame failure of a pilot burner, make its ignition easy and prevent its explosion in case a flame failure occurs. CONSTITUTION:When the ignition operation of a pilot burner is effected, the pressure of the main pipe of pilot COG is kept constant by using an automatic pressure adjusting valve V3. Because of a rapid response, the pressure of the main pipe can be prevented from becoming unstable relative to a sharp pressure fluctuation caused by the opening operation of a cutoff valve V4 and the pilot burner is hard to cause flame failure. When the pilot burner is ignited, the exhaust system is made negative in pressure, and only air supplied from a main AIR pipe to a radiant tube.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to ignition control of a pilot burner, and for example, it is used for ignition control of a pilot burner that ignites a radiant tube of a heating furnace installed in a continuous steel sheet processing line. sell.

[0002]

2. Description of the Related Art For example, in a heating furnace installed in a continuous processing line for steel plates, there are many heating furnaces (for example, 300).
It is indirectly heated by the radiant tube. Each radiant tube has, for example, coke gas (CO
Fuel gas and air called G) are supplied. It is ignited on the inlet side of the radiant tube and burns in the tube of the radiant tube to generate heat which heats the furnace. The exhaust gas after combustion is sucked and exhausted by the blower.

In order to ignite the mixed gas of the radiant tube which is the main burner, a pilot burner is installed at the inlet side of each radiant tube. A mixed gas of coke gas and air is supplied to each pilot burner. When the pilot burners are actually ignited, the operation of manually opening the shut-off valves installed for each group of ten or more pilot burners and igniting each pilot burner one by one is repeated. Ignite the pilot burners in sequence.

A conventional specific configuration will be described. Pilot C that supplies coke gas to multiple pilot burners
As shown in FIG. 3, a pressure detector and a pneumatic control valve are installed in the OG main piping and the pilot AIR main piping for supplying air, and each pneumatic control valve has a digital controller. The feedback control is performed by the laser.

When the pilot burner is actually ignited, coke gas and air control systems are used to control the automatic mode.
In the digital mode, the pneumatic control valve is automatically adjusted so that the pressure detected by the pressure detector by the digital controller matches the predetermined target value.In the manual mode, the digital controller The operation is stopped and the valve opening of the pneumatic control valve is kept constant.

[0006]

In this type of equipment, it is extremely important to facilitate ignition of each pilot burner and to prevent each pilot burner from misfiring after ignition. That is, since the number of pilot burners to be ignited is very large, if ignition is difficult, it takes a huge amount of time to ignite all the pilot burners. Further, when the pilot burner misfires, unburned gas accumulates in the pipe, causing a danger of explosion.

However, when the pilot burner is ignited while the coke gas control system is controlled by the automatic mode, the coke gas pressure in the pipe becomes unstable especially at the initial stage of ignition. The pilot burner may easily misfire.

Further, when the pilot burner is ignited by setting the coke gas control system in the manual mode (constant valve opening), a small number of pilot burners are provided especially in the initial stage of ignition. Since coke gas concentrates and flows, it is difficult to ignite, and unburned gas easily accumulates in the exhaust gas system, which may cause explosion.

Therefore, it is an object of the present invention to facilitate ignition of each pilot burner and prevent misfire of each pilot burner after ignition.

[0010]

In order to solve the above problems, in the present invention, a plurality of main burners, main burner piping for supplying fuel gas and air to the main burners, and each main burner are ignited. Equipment equipped with a plurality of pilot burners, a pilot burner fuel gas main pipe for supplying fuel gas to the plurality of pilot burners, and a pilot burner air main pipe for supplying air to the plurality of pilot burners In the ignition control method of the pilot burner, the ignition side pressure of each pilot burner is controlled to be constant by using a self-powered pressure control valve when igniting each pilot burner. The pressure in the pilot burner air main pipe is controlled to be constant or the valve opening of the pressure control valve in the pilot burner air main pipe is fixed.

Further, in a preferred aspect of the present invention, when the pilot burners are ignited, the plurality of main burners are used.
The internal pressure of the exhaust gas pipe arranged on the outlet side of the nozzle is controlled to a constant negative pressure.

In a preferred embodiment of the present invention, when each pilot burner is ignited, only air is flowed through the main burner pipe and fuel gas is shut off.

[0013]

In the present invention, when the pilot burner is ignited, the outlet side pressure of the pilot burner fuel gas main pipe is controlled to be constant by the self-powered pressure control valve, and the pilot burner air main pipe is The pressure is controlled to be constant, or the valve opening of the pressure control valve in the pilot burner main air piping is fixed.

When the pilot burner is ignited in the conventional automatic mode, especially in the initial stage of ignition,
The coke gas pressure in the pipe becomes unstable, and it is thought that the cause is that the control system cannot follow the rapid pressure fluctuation accompanying the opening / closing operation of the shutoff valve at the end of the pilot burner. To be That is, in the conventional control system, the signal from the pressure detector is sampled at a constant cycle, the sampled feedback signal is processed by the digital controller, and the difference is calculated according to the difference between the target value and the feedback signal. Although a controlled variable is generated and the pneumatic control valve is controlled, the response speed of this type of control system is relatively slow and cannot follow a rapid pressure change.

On the other hand, the self-powered pressure control valve is a so-called pressure reducing valve, which is operated by a mechanical operation regardless of fluctuations in the primary pressure or changes in the usage amount on the secondary side.
The secondary pressure is maintained stable. This self-powered pressure control valve does not require a control device and has extremely good responsiveness, and can follow abrupt pressure changes such as when the shutoff valve is opened and closed. In the present invention, the output pressure of the pilot burner fuel gas main pipe is controlled to be constant by this self-powered pressure control valve, so that the pilot burner end is shut off when the pilot burner is ignited. Even if a sudden pressure fluctuation occurs due to the opening / closing operation of the valve, the self-propelled pressure control valve quickly follows the change to control the outlet pressure of the pilot burner fuel gas main pipe to a constant value. For this reason,
Even in the initial stage of ignition work, the coke gas pressure in the tube does not become unstable, and misfire is unlikely to occur.

Further, when each pilot burner is ignited, the internal pressure of the exhaust gas pipe arranged on the outlet side of the main burner is controlled to a constant negative pressure, so that some pilots should be protected. Even if the burner misfires, it is possible to prevent the unburned gas from staying in the pipe, which improves safety.

Further, when each pilot burner is ignited, even if some pilot burners are misfired by flowing only air into the main burner piping to cut off the fuel gas, The air passing through the main burner pipe can reduce the concentration of unburned gas emitted from the pilot burner, thus improving safety.

[0018]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows the configuration of the main part of equipment for carrying out the present invention in one mode. The equipment shown in FIG. 1 is used for a heating furnace installed in a continuous steel plate processing line. That is, coke gas (COG) and air (AIR) are supplied into the pipe of each radiant tube (main burner) installed in the heating furnace, and the radiant tube is burned in the pipe. Heat and heat the furnace. Although only a single radiant tube is shown in FIG.
00 radiant tubes are installed in the heating furnace, and each radiant tube has coke gas (CO).
G) and air (AIR) are supplied.

The gas (exhaust gas) burned in each radiant tube is mixed with dilution air and collected in a plenum chamber. Due to the function of the exhaust gas blower, the inside of the plenum chamber is maintained at a negative pressure, and this negative pressure sucks the exhaust gas from each radiant tube and enters the plenum chamber. The exhaust gas passes through the plenum chamber, is exhausted from the chimney through the pressure control valve V1, the exhaust heat recovery device, and the exhaust gas blower. Digital controller C1 connected to the pressure control valve V1 of the exhaust gas passage
Usually has a constant pressure in the plenum chamber (target value)
The pressure control valve V1 is adjusted so that

A pilot burner is installed on the entrance side of each radiant tube. This pilot bar
A mixed gas of coke gas (COG) and air (AIR) is supplied to the nozzle. That is, the pilot A through which the air passes
IR main pipe and pilot COG through which coke gas passes
Each main pipe is connected to a large number of branch pipes,
Each branch pipe has a mixer installed at each end.
It is connected to a pilot burner via M1, and a cutoff valve V4 is installed on the branch pipe of the pilot COG on the upstream side of the mixer M1.

A pneumatic pressure regulating valve V2 and a pressure detector D2 are installed in the pilot AIR main pipe, and the pneumatic pressure regulating valve V2 is controlled by a digital controller C2. The digital controller C2 normally adjusts the opening degree of the pneumatic pressure regulating valve V2 so that the pressure detected by the pressure detector D2 matches a predetermined target value.

A self-powered pressure control valve V3 is installed in the pilot COG main pipe. This self-powered pressure control valve V
The structure of 3 is shown in FIG. The valve V3 is a so-called pressure reducing valve, and the secondary pressure is stably maintained by the mechanical operation regardless of the fluctuation of the primary pressure or the change of the usage amount on the secondary side. Not only does this self-powered pressure control valve not require a control device, but it also has extremely good responsiveness, and it follows well even sudden changes in pressure, such as when the shut-off valve is opened and closed, and the secondary pressure Is controlled to be constant.

Prior to igniting each radiant tube which is a main burner, ignition is first performed for each pilot burner. Ignition of the pilot burner is a manual operation, and an operator sequentially opens all the shutoff valves V4 and ignites all the pilot burners. After the pilot burner is ignited, the main COG
When coke gas COG is supplied to the radiant tube from the pipe, the pilot burner ignites the main burner (radiant tube).

By the way, when the pilot burner is ignited, the opening operation of each shutoff valve V4 is repeated, so that the pressure of the pilot COG main pipe changes stepwise each time the shutoff valve V4 is opened. However, the pressure change in the pilot COG main pipe is suppressed by the operation of the self-powered pressure control valve V3.

In this embodiment, there is a special reason for installing the self-powered pressure control valve V3 in the pilot COG main pipe. That is, a conventional general pressure control system consisting of a pressure detector, a digital controller, and a pneumatic pressure regulating valve is installed in the pilot COG main pipe to ignite the pilot burner. Then, especially in the initial stage of ignition, the coke gas pressure in the pipe becomes unstable, and misfire of the pilot burner is likely to occur. It is considered that this is because the control system cannot follow the rapid pressure fluctuation associated with the opening / closing operation of the shutoff valve V4. That is, in the conventional control system, the signal from the pressure detector is sampled at a constant cycle, the sampled feedback signal is processed by the digital controller, and the difference is calculated according to the difference between the target value and the feedback signal. Although a controlled variable is generated and the pneumatic control valve is controlled, the response speed of this type of control system is relatively slow and cannot follow a rapid pressure change. Further, for example, when the control of the pressure control system is stopped and the ignition work is performed with the valve opening kept constant, coke gas concentrates and flows to a small number of pilot burners, especially at the initial stage of ignition, so that ignition is performed. However, there is a risk of explosion because unburned gas easily stays in the exhaust gas system. However, the self-powered pressure control valve V3 has an extremely high responsiveness and maintains a stable secondary pressure by following a rapid pressure change. Therefore, as in this embodiment, the self-powered pressure control valve V3 is used. When the pilot burner is ignited while controlling the outlet pressure of the pilot COG main pipe, even if the ignition work is in the initial stage, the pipe inside the pipe
The gas pressure does not become unstable and misfiring is less likely to occur.

In this embodiment, when the pilot burner is ignited, the exhaust gas blower is operated and the digital controller C1 is used to adjust the pressure so that the negative pressure in the plenum chamber becomes constant. Valve V1
The valve V6 of the main COG pipe is closed and the valve V6 of the main AIR pipe is opened, and only the air is supplied to the radiant tube by a computer (not shown). There is. As a result, even if some pilot burners misfire, the main AI
The air supplied from the R pipe lowers the concentration of unburned gas, and since the unburned gas is sucked into the exhaust system,
Unburned gas is prevented from accumulating in the pipe, eliminating the risk of explosion.

In the above embodiment, the pressure in the pilot AIR main pipe is controlled to be constant by the digital controller C2, but a self-regulating valve may be used. But,
Since there is almost no pressure fluctuation in the pilot AIR main pipe when the shutoff valve V4 is opened / closed, it should be determined in consideration of the total cost of both types. Further, the ignition work of the pilot burner can be carried out even when the valve opening of the pneumatic pressure regulating valve V2 of the pilot AIR main pipe is kept constant. However, more preferable results can be obtained by controlling the pressure as in the embodiment.

Further, in the above embodiment, each pilot bar
Although the case where the ignition to the engine is manually performed is shown, the present invention can be applied to the case where the ignition is automatically performed using an igniter or the like.

[0029]

As described above, according to the present invention, when each pilot burner is ignited, the outlet pressure of the pilot burner fuel gas main pipe is made constant by using the self-powered pressure control valve (V3). Since the control is performed, the fuel gas (COG) pressure of the pilot burner can be stably maintained in response to a rapid pressure change associated with the opening operation of the shutoff valve (V4), and the pilot burner can be maintained. -It is extremely effective in preventing misfires in the fire.

Further, as in the embodiment, when the pilot burner is ignited, the internal pressure of the exhaust gas pipeline is controlled to a constant negative pressure, and only the air is flown into the main burner piping to cut off the fuel gas. As a result, some pilot bar
Even if the engine is misfired, the air supplied from the main burner pipe reduces the concentration of unburned gas, and since unburned gas is sucked into the exhaust system, unburned gas stays in the pipe. Is prevented and there is no danger of explosion.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration of a main part of equipment of an embodiment.

FIG. 2 is a vertical sectional view showing the configuration of a self-powered pressure control valve V3.

FIG. 3 is a block diagram showing a configuration of conventional equipment.

[Explanation of symbols]

V1: Pressure control valve V2: Pneumatic pressure control valve V3: Self-powered pressure control valve V4: Shutoff valve V5, V6: Valve C1: Digital controller C2: Digital controller D1: Pressure detector D2: Pressure detector M1: mixer

Claims (3)

[Claims] 1. A plurality of main burners, a main burner pipe for supplying fuel gas and air to the main burners, a plurality of pilot burners for igniting each of the main burners, and a fuel for the plurality of pilot burners. Pilot bar that supplies gas
In the ignition control method of the pilot burner for equipment equipped with a fuel gas main pipe and a pilot burner air main pipe for supplying air to a plurality of pilot burners: when igniting each pilot burner, The outlet side pressure of the pilot burner fuel gas main pipe is controlled to be constant by using a self-powered pressure control valve, and the pressure of the pilot burner air main pipe is controlled to be constant or the pilot burner air main pipe. A method for controlling ignition of a pilot burner, characterized in that the valve opening of the pressure control valve is fixed. 2. When igniting each pilot burner, the internal pressure of the exhaust gas pipes arranged on the outlet side of the plurality of main burners is controlled to a constant negative pressure.
An ignition control method for the described pilot burner. 3. The ignition control method for a pilot burner according to claim 1, wherein when igniting each pilot burner, only air is flowed through the main burner pipe and fuel gas is shut off.