JP2591945B2 - Boiler ON-OFF operation control device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial application field> The present invention relates to ON-OFF in a boiler having a drum.
The present invention relates to a boiler control device that optimizes restart timing during operation.

<Prior Art> FIG. 4 shows an example of pressure characteristics during ON-OFF operation in a conventional boiler having a drum.

During the constant pressure control operation of the drum pressure (or the main steam pressure), if the load usage decreases, the fuel control valve is throttled to be held at the lowest fuel position.

In such an operation, when the drum pressure increases and reaches a certain set pressure (a '), the burner is extinguished and the boiler operation is stopped. After stopping the boiler, since the steam is consumed, the drum pressure gradually decreases in accordance with the consumption amount. When the pressure drops to a certain set pressure value (d '), the burner is ignited again and restarted.

When the load (steam consumption) is below the minimum load, this ON-
The OFF operation is repeated to supply the necessary steam. That is, the operation is continued while repeating the vertical movement between the set values of the drum pressure. However, the cycle of the ON-OFF operation differs depending on the load condition, and the ON-OFF cycle becomes longer as the steam consumption decreases. However, in the past, almost no furnace purge was taken into account when ON-OFF was repeated, and the burner ignition was started immediately after the set pressure was detected, and the operation was restarted.

However, in this prior art, sufficient consideration was not given to the furnace purge at the time of restarting the ignition, and the boiler was restarted while the furnace purge was insufficient, which was regarded as a problem in boiler security.

Regarding boiler furnace purge, NFPA (NATIONAL FI
RE PROTECTION ASSOSIATION) states that "at 25% MCR airflow, (a) a single burner replaces 8 times the furnace volume (2) multiple burners replace the furnace volume 5 times or purging for 5 minutes" Is recommended.

Considering the furnace purging for safety in accordance with this recommendation, if the pressure at the time of boiler restart (point C in the figure) is not uniform due to the steam consumption as shown in FIG. 3, the boiler restart timing (1 T / H steam extraction C point) changes depending on the evaporation amount. As an example, the steam consumption 1 in FIG.
As shown in the case of T / H, when restarting at the d point of the ON set value, the drum pressure drops to the e point beyond the d point (d−
During the period e), there is a problem that the steam is not supplied.

<Object of the Invention> An object of the present invention is to perform reignition at a minimum necessary pressure as viewed from the load side after sufficiently purging the furnace.
An object of the present invention is to provide a boiler ON-OFF operation control device in which ON-OFF set values are specified.

<Summary of Means> In the present invention, the ignition timing changes depending on the degree of the load. Therefore, by making the characteristics of the ignition timing a function, a restart command is issued at a point corresponding to the state of the load to perform a suitable ON-OFF operation. Try to achieve.

In other words, a diagram based on the steam extraction amount drum pressure shown in FIG. 2 in which the evaporation amount is converted based on the elapsed time from the stop of FIG. 3 to the start of the boiler “ignition command value curve”
The above object is achieved by determining the ignition drum pressure from the above and determining the boiler ignition timing.

<Operation> FIG. 2 shows an ignition command value curve used in the embodiment of the present invention. In this diagram, a burner ignition command is issued when the drum pressure with respect to the boiler steam consumption falls below the ignition command value curve, and the furnace purge is started. By setting the characteristics of the diagram in the burner ignition command setter 9, a burner ignition command can be issued at an optimum timing for each boiler steam consumption. That is, de in FIG.
Does not cause an excessive pressure drop.

More specifically, according to the conventional drum pressure characteristic curve at a low load in FIG. 3, when the burner purge is performed for 5 minutes after reaching the boiler digestion set pressure value, the pressure decreases thereafter due to boiler steam consumption and natural heat dissipation. Then, when the boiler ignition set pressure value is reached (ON set value in the figure), an ignition command is issued and restart is performed. However, in the conventional apparatus, when the furnace is purged for 5 minutes at point d, the burner is ignited at a pressure lower than the set pressure after 5 minutes (point e). Therefore, the steam is not supplied until the pressure rises to the set pressure (point d), which is inconvenient. In order to avoid this state, in the present invention, a point (point C) at which the restart set pressure (ON line position) is reached when the furnace purge for 5 minutes is completed is determined. Although this point differs depending on the boiler steam consumption, these points are represented by a fixed function. By setting this function as a set point, even if the boiler steam consumption is changed, the ignition start command is issued at the set pressure. Can be issued. Therefore, set immediately after furnace purge for 5 minutes
Operation can be started by firing the burner at ON pressure.

In addition, what shows this function as a characteristic curve is an ignition command curve in FIG.

Further, in FIG. 3, the solid line shows the case of the embodiment of the present invention in which the furnace was purged for 5 minutes, and the dashed line shows the pressure characteristics (FIG. 4) by the conventional operation method.

Embodiment 1 The overall configuration of the present invention will be described as a first embodiment with reference to FIG.

Water supplied from a water supply pump (hereinafter abbreviated as BFP) 8 enters the drum 4 through a water supply flow control valve 6. The feed water heated in the furnace 5 is heated by the evaporation tube of the furnace 5 and enters the drum 4 as steam, and the generated steam is sent to the steam header 1.

Here, the boiler steam consumption is measured by the main steam flow transmitter 2, and the value thereof is calculated by the burner ignition command setter 9 to calculate a pressure set value when an ignition command is issued in accordance with the boiler steam extraction amount. (The characteristics of FIG. 2 are incorporated in the pressure setting device.) On the other hand, the actual pressure of the drum 4 is measured by the drum pressure transmitter 3, and the difference between the actual pressure and the set pressure is calculated by the drum pressure subtractor 10. The calculated pressure difference is applied to the drum pressure high / low selector 11
When the actual pressure becomes equal to or lower than the set pressure, a command signal 13 is issued from the burner ignition command signal transmitter 12, the furnace is purged, the sequence is sequentially prepared for ignition, and the burner ignition is performed.

Here, the control box 14 includes a drum pressure transmitter 3, a main steam flow transmitter 2, a burner ignition command setting device 9, and a drum pressure subtractor 1.
0, a drum pressure high / low selector 11, and a burner ignition command signal transmitter 12.

<Embodiment 2> Another embodiment of the present invention will be described with reference to FIG.

In the first embodiment, the steam consumption of the boiler is detected by the main steam flow transmitter 2, but when no auxiliary steam or the like is extracted in the drum boiler, the main steam flow rate and the feed water flow rate are equal. Therefore, instead of the main steam flow rate, the feed water flow rate is detected by the feed water flow rate transmitter 7 and the burner ignition command setting device 9 is detected.
The same effect as in the first embodiment can be obtained by sending a signal to.

That is, the boiler ignition timing can be set using the feedwater flow rate.

<Effect of the Invention> By practicing the present invention, when the pressure becomes equal to or less than the set pressure stored in accordance with the boiler steam consumption, the forced draft fan is started, the furnace is purged for 5 minutes, and the burner can be ignited.

As a result, steam can be stably supplied within the ON-OFF set pressure range without an excessive pressure drop, and a sufficient purge can be performed, so that sufficient safety can be obtained from the viewpoint of security.

[Brief description of the drawings]

FIG. 1 is a system diagram of a burner ignition command setting control apparatus according to one embodiment of the present invention, FIG. 2 is a setting curve of an ignition command value, FIG. 3 is a pressure characteristic curve after burner extinguishing by steam consumption, FIG. FIG. 4 is a diagram showing the relationship between the conventional drum pressure drop and time. 1 steam head 2 main steam flow transmitter 3 drum pressure transmitter 4 drum 5 furnace 6 water supply flow control valve 7 water supply flow transmitter 8 water supply Pump 9 Burner ignition command setting device 10 Drum pressure subtractor 11 Drum pressure high / low selector 12 Burner ignition command signal transmitter 14 Control box

Claims (4)

(57) [Claims] 1. A method for performing an ON-OFF operation for extracting a smaller amount of steam than a continuous low-load operation of a boiler using a drum pressure as a signal, in consideration of a drum pressure drop speed corresponding to a set furnace barge time. A control box was created to create an ignition command value curve for the drum pressure versus the amount of steam extracted per unit time, receive a signal of the amount of steam extracted per unit time, and issue an ON ignition command using the drum pressure as a signal. A boiler ON-OFF operation control device. 2. The control box includes a drum pressure transmitter, a main steam flow transmitter, a burner ignition command setting device, a drum pressure subtractor, a drum pressure high / low setting device, and a burner ignition command signal transmitter. Boiler ON according to claim 1
-OFF operation control device. 3. An on-off operation for extracting a smaller amount of steam than a continuous minimum load operation of a boiler by using a drum pressure as a signal, in consideration of a drum pressure drop speed corresponding to a set furnace barge time. A control box was created to create an ignition command value curve for drum pressure vs. boiler water supply per unit time, receive a signal of boiler water supply per unit time, and specify ON for ignition using drum pressure as a signal. A boiler ON-OFF operation control device. 4. The control box includes a drum pressure oscillator, a feed water flow rate oscillator, a burner ignition command setting device, a drum pressure calculator, a drum pressure high / low setting device, and a burner ignition command signal oscillator. Boiler ON according to item 3
-OFF operation control device.