JPH08285272A - Air blowing control method for 3 position combustion control boiler - Google Patents

Abstract

PURPOSE: To shorten the pre-purging period of time, to shorten a period of time from the decrease of a steam pressure to the start of a combustion. CONSTITUTION: A 3 position combustion control boiler is equipped with an air blower of which the rotation speed is adjusted, and a damper which adjusts the ventilation quantity from the air blower, and a combustion control is performed at 3 positions of high combustion, low combustion and stoppage. For such a boiler, the rotation speed when the air blower is operated is set in 3 stages of air volume for purging, air volume for high combustion and air volume for low combustion, and the opening degree of the damper is also set in two stages of opening degree for high combustion and opening degree for low combustion. Then, when a pre-purging is performed, the rotation speed of the air blower is set at the air volume for purging, and the damper opening degree is set at a maximum air feeding quantity of the opening degree for high combustion, and at the time of ignition after the pre-purging and at the time of an initial low combustion, the damper opening degree is set at the opening degree for low combustion.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a blower control method for a boiler in which a blower whose rotation speed is adjusted and a damper which adjusts the amount of ventilation from the blower are combined to adjust the amount of blown air.

[0002]

2. Description of the Related Art In the case of a boiler performing three-position combustion control, the supply amount of combustion air is also adjusted according to the fuel supply amount. In the past, the amount of air blown from the blower was constant, and the amount of air blown was adjusted by adjusting the opening of a damper installed in the middle of the air passage. A method has been proposed in which the speed is adjusted and the air flow rate is adjusted. When adjusting the rotation speed of the blower, when the rotation speed is reduced, the effect of reducing power consumption and noise can be obtained, but there is a problem that the amount of air blown at the time of ignition becomes unstable. As described in (3), the adjustment by the blower rotation speed and the adjustment by the damper opening degree are combined to maintain the blower rotation speed at the high combustion air volume during the pre-purge, at the time of ignition, and during the first low combustion after ignition, and at the time of ignition. A method has been proposed in which the damper opening is set to the low combustion side only during the first low combustion after ignition.

Further, the boiler is controlled so that combustion is started when the steam pressure is lowered. However, when the boiler starts combustion, it is dangerous if unburned mixed gas exists in the boiler. It is necessary to send a fixed amount of air into the furnace and perform pre-purge to ventilate the inside of the furnace.
The start of combustion is delayed by that time. If the time until the start of combustion becomes long, the steam pressure will drop significantly and the ability to follow the load will deteriorate, so it is desirable to start combustion as soon as possible.

[0004]

The problem to be solved by the present invention is to shorten the pre-purge time and to shorten the time from when the vapor pressure is lowered to when combustion is started.

[0005]

[Means for Solving the Problems] In a boiler having a blower whose rotation speed is adjusted and a damper which adjusts the amount of ventilation from the blower, combustion control is performed at three positions: high combustion, low combustion, and stop. , The rotation speed when the blower is operated is set to three levels: purge air volume, high combustion air volume, and low combustion air volume, and the damper opening also has a high combustion opening and a low combustion opening. When setting and performing pre-purge, the rotation speed of the blower is the purge air flow rate, the damper opening is the maximum air flow rate for the high combustion opening, and the damper opening is set during the subsequent ignition and the first low combustion. Is the opening for low combustion.

[0006]

[Operation] The air flow rate during combustion needs to be adjusted so that proper combustion can be performed with respect to the fuel supply rate, but since prepurging is intended to send in a fixed amount of air for ventilation, It is not necessary to limit the pre-purge time, and the pre-purge time can be shortened by performing the pre-purge with the purge air volume higher than the normal blower rotation speed. The pre-purge time can be shortened by setting the purge opening to the damper opening with a powerful blower and controlling the air flow rate with the damper even during high combustion, but in that case, the air flow from the blower is other than pre-purge. Is wasted. However, when the rotation speed is increased only during the pre-purge, no waste occurs, and the pre-purge time can be shortened.

[0007]

An embodiment of the present invention will be described with reference to the drawings.
The upper part is a control chart of the fan rotation speed, the middle part is a damper opening control chart, and the lower part is an explanation of the operating state of the boiler. Burner combustion is controlled in three positions: high combustion, low combustion, and stop. At the start of combustion, pre-purge for ventilation in the furnace is performed, and low combustion is maintained until the flame becomes stable after ignition to the burner. High combustion after being done. The blower rotation speed is set to purge air volume, high combustion air volume, and low combustion air volume in addition to stop.The damper opening is fully closed, as well as high combustion opening and low combustion opening. Is set. The air flow rate at this time is as follows: purge air volume> high combustion air volume> low combustion air volume, and high combustion opening> low combustion opening.

Description will be made with reference to FIG. When the combustion of the burner is stopped, the fan rotation speed is stopped and the damper opening is also fully closed. When the start of combustion is output, the blower rotation speed is set to the maximum air flow for purging and the damper opening is set to the maximum opening for high combustion, so that a large amount of air is blown in a short time by the boiler. Sent in,
The prepurge is completed in a shorter time than usual.

When the time set for the prepurge elapses, the blower rotation speed is changed to a high combustion air flow rate, the damper opening is changed to a low combustion air flow rate to reduce the air flow rate, and ignition is performed. During the first low combustion after ignition, both the blower rotation speed and damper opening are kept as they are to stabilize the flame.
When transitioning combustion to high combustion, the blower rotation speed remains the same and the damper opening is set to the high combustion opening to increase the air flow rate, and the damper opening is not changed in the subsequent combustion fluctuation, and the high combustion position is changed. Hold and adjust the blower rotation speed according to the combustion condition.

Post-purge is performed when the boiler stops combustion. In this case, the rotation speed of the blower becomes the amount of air for purging, the blower is stopped after the end of the post-purge, and the damper is fully closed to prevent the boiler from cooling.
However, in the case of post-purging, it is not necessary to reduce the time, and therefore the post-purging may be performed with a high combustion air volume or a low combustion air volume as the blower rotation speed.

Even when the output to the blower is changed from the purge air flow rate to the high combustion air flow rate at the time of ignition, it takes a long time for the actual air flow rate to change from the purge air flow rate to the high combustion air flow rate. If the air volume is not stable, output is made to change the fan rotation speed to a high combustion air volume during the pre-purge, or the fan rotation speed is set to the purge air volume during ignition and after low combustion even after the completion of the pre-purge. It is also possible to maintain and adjust the ventilation volume sent to the burner by the damper, change the blower rotation speed to the high combustion air volume when the combustion shifts to high combustion, and change the damper opening to the high combustion position. .

[0012]

By implementing the present invention, the pre-purge time can be shortened, and the time from the steam pressure drop to the steam generation is shortened, so that the load followability can be improved.

[Brief description of drawings]

FIG. 1 is a control chart of an embodiment of the present invention.

FIG. 2 is a control chart of another embodiment of the present invention.

FIG. 3 is a control chart of another embodiment of the present invention.

Claims (1)

[Claims] 1. A blower having a blower whose rotation speed is adjusted and a damper which adjusts the amount of ventilation from the blower, and which operates a blower in which combustion control is performed at three positions: high combustion, low combustion, and stop. When the rotation speed is set, it is set to three levels of purge air volume, high combustion air volume, low combustion air volume,
When pre-purging is performed by setting the opening for high combustion and the opening for low combustion to the opening of the damper, the rotation speed of the blower is set to the air volume for purging, and the damper opening is set to the opening for high combustion. A blower control method for a three-position combustion control boiler, wherein the damper opening is set to a low combustion opening during the subsequent ignition and the first low combustion.