JPH06292839A - Method for controlling smoke concentration of boiler - Google Patents

Abstract

PURPOSE:To provide the method for controlling the smoke concn. of a boiler which suppresses the smoke concn. without delay and maintains the smoke concn. always at a prescribed value or below when the load of the boiler increases sharply. CONSTITUTION:This method includes a DC high-voltage power source device 8 for sending the charge quantity of a DC high voltage to an electrostatic precipitator 1 and a dust counter 3 for detecting the smoke dust quantity in the outlet of this electrostatic precipitator 1. The load increase of the boiler equipped with a controller 6a to set and command the charge quantity of the DC high voltage to be supplied to the electrostatic precipitator 1 in the DC high-voltage power source device 8 by processing the smoke concn. signal outputted from the dust counter 3 is detected by a load signal 9s of the boiler and the charge quantity is increased stepwise at the point of the time when the smoke concn. signal 4s exceeds a prescribed value so as to prevent the rapid increase of the smoke concn. The next charge quantity is calculated from the change rate of the charge quantity and the change rate of the smoke concn. after the smoke concn. is rapidly suppressed. The charge quantity is further corrected by the momentary value of the smoke concn. at the point of this time just before the output of the charge quantity, and thereafter, this charge quantity is freshly outputted as the charge quantity.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a boiler dust concentration control method applied to an outlet dust concentration control of an electric dust collector for a boiler.

[0002]

2. Description of the Related Art FIG. 5 shows the configuration of an outlet dust concentration control apparatus of a conventional electric dust collector for a boiler. A dust densitometer 3 is provided at the outlet flue 2 of the electric dust collector 1. The output of the soot and dust concentration meter 3 is sent to the control device 6.
The output of the control device 6 is sent to the DC high-voltage current device 8 for charging the electrostatic precipitator 1.

In the above, the dust concentration meter 3 detects the dust concentration in the exhaust gas from the outlet flue 2. Then, it is input to the control device 6 as the dust concentration signal 4s having a correlation with the dust amount. Based on the input signal, the control device 6 controls the DC high-voltage power supply device 8 to charge the DC high voltage so that the amount of dust collected at the outlet of the electrostatic precipitator 1 falls within a predetermined range (continuous charge amount or intermittent charge amount). The amount of charge depending on the charging rate is calculated, and the setting command 7s is calculated, and the direct current high voltage power supply 8
Output to. The DC high-voltage power supply device 8 supplies a DC high-voltage and current corresponding to the command 7s to the electrostatic precipitator 1. In FIG. 5, 5 is a dust densitometer failure signal.

The charge amount calculation calculation of the DC high-voltage power supply device 8 performed in the control device 6 is based on the flow chart shown in FIG. As can be seen from the figure, the control is performed under the condition that the amount of change in the dust concentration at the entrance of the electrostatic precipitator is constant, and the same method is used throughout the boiler operation.

[0005]

SUMMARY OF THE INVENTION In the above conventional technique,
This is a feedback control in which the charge amount of the electrostatic precipitator is controlled by using only the dust concentration detected at the outlet of the electrostatic precipitator. For this reason, as shown in FIG. 7, when the boiler load increases, the dust concentration at the inlet of the electrostatic precipitator increases sharply, the control cannot follow, and the dust concentration at the outlet temporarily increases rapidly and exceeds the set value. There is a problem called the shaded area in the figure.

[0006]

The present invention takes the following means in order to solve the above problems.

That is, as a dust concentration control method for a boiler, an electric dust collector, a DC high-voltage power supply device for charging the electric dust collector with a DC high voltage, and a dust quantity for detecting the outlet dust amount of the electric dust collector. A densitometer and a control device for processing the dust and soot concentration signal output from the soot and dust concentration meter to instruct the DC high voltage power supply device to set the charge amount of the DC high voltage to be supplied to the electrostatic precipitator In the boiler, a load increase is detected by the load signal of the boiler, and when the dust concentration signal exceeds a predetermined value, the charge amount is increased stepwise to prevent the dust concentration from rapidly increasing, and the dust concentration is rapidly increased. After suppressing to
The next charge amount is calculated from the change amount of the charge amount and the change amount of the dust concentration, and immediately before the same charge amount is output, the same charge amount is corrected by the instant dust concentration instantaneous value at that time, and then the new charge is newly added. A soot and dust concentration control method for a boiler, which is characterized by outputting as a quantity.

[0008]

By the above means, when the load of the boiler increases, the increase of the load signal of the boiler is detected. As the load on the boiler increases, the dust concentration signal increases,
When this signal exceeds a predetermined value, the amount of charge on the electrostatic precipitator is increased in a predetermined amount stepwise. Then, the dust collection rate of the electrostatic precipitator is improved, and the increase in the dust concentration is suppressed. Next, the next charge amount is calculated from the change amount of the charge amount and the change amount of the dust concentration by a predetermined estimation formula. Immediately before outputting the calculated charge amount, the same charge amount is corrected by the warming-up value of the dust concentration at that time, and then output as a new charge amount. After that, feedback control is performed as usual based on this new charge amount.

As described above, even when the load on the boiler suddenly increases, the increase in the dust concentration is suppressed without delay, and the control is always maintained below a predetermined value.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described with reference to FIGS. It should be noted that the parts described in the conventional example are denoted by the same reference numerals and the description thereof is omitted, and the parts relating to the present invention will be mainly described.

In FIG. 1, a dust densitometer 3 is installed at the outlet flue 2 of the electrostatic precipitator 1. This detects the amount of dust in the exhaust gas in the outlet flue 2, and the control device 6a
The dust concentration signal 4s is input. The boiler load signal 9s is also input to the control device 6a.

In the control device 6a having the above structure,
The boiler load signal 9s is sampled at regular intervals, and the increase in boiler load is detected by one of the following methods. Whether the load has increased by a certain value or more compared to the boiler load one cycle before. Whether or not the boiler load continues to rise above a certain level for several consecutive cycles.

While the boiler load is increasing, the instantaneous value (SO) of the soot and dust concentration signal 4s is compared with the upper limit value (SN) of the range, and when the instantaneous value of the soot and dust concentration exceeds (SO ≧ S
N) Immediately, the charge rate of the intermittent charge is set to 4 steps (normal 4
Double) raise.

Further, the control period timer of the normal electrostatic precipitator charging control is cleared and the count is increased from zero.

The increase amount (RcUP) of the charge rate of the intermittent charge differs depending on the plant and is determined in advance by the following method. step1. Confirm the sudden increase (A) of the maximum outlet dust concentration in the conventional control when the boiler load increases in normal operation. step2. The change amount (B) of the outlet dust concentration when the charge rate of the intermittent charge is increased by one step before the boiler load is increased is confirmed. step3. From the values obtained in steps 1 and 2, the following equation (1)
Calculate the amount of rise.

(RcUP) = (A) ÷ (B) …………………………… (1) Next, when the control cycle timer counts up, the average value (Save) of the exit dust concentration is If it is below the lower limit value (SNl) of the range (Save <SNl), the charge rate decrease amount (RcDOWN) of intermittent charge is calculated from the following equation (2).

(RcDOWN) = (SNl-Save) ÷ (SN-Smin) × 4 (2) RcDOWN; charge amount or decrease amount of charge ratio of intermittent charge SNl; of a predetermined value or range Lower limit value Save: Average value of outlet dust concentration during one control cycle after charge rise SN: Upper limit value of specified value or range Smin: Minimum value of outlet dust concentration during one control cycle after charge rise RcUP: Boiler load rise Medium charge amount or increase amount of charge amount ratio of intermittent charge Smin; minimum value of outlet dust concentration in the current control cycle However, the calculation result (RcDOWN) is rounded up to the nearest decimal point. Furthermore, when the instantaneous value (SOl) of the exit dust concentration immediately before the output of the charge rate exceeds the average value (SOl>
Save) is corrected by the equation (3), and is decreased by the decrease amount (RcDOWN) of the obtained charge rate of the intermittent charge.

(RcDOWN) = (RcDOWN) -1 (3) It should be noted that after the boiler load is increased, the same charge control as usual is performed,
Again, the above control is not performed until it is detected that the boiler load is increasing.

A detailed flow chart of the above calculation is shown in FIGS.

FIG. 2 is a flow chart of the first half and FIG. 3 is a flow chart of the second half. A time chart of each signal is shown in FIG. As can be seen from the figure, even when the boiler load signal is rising, the dust concentration signal at the outlet of the electrostatic precipitator is controlled and maintained below the set value (SN).

In the above embodiment, the charge amount is based on the charge ratio of intermittent charge, but it may be a continuous charge amount.

[0022]

As described above in detail, according to the present invention,
Even when the boiler load increases, the dust concentration can be controlled and maintained below a predetermined value without delay.

[Brief description of drawings]

FIG. 1 is a configuration system diagram of an embodiment of the present invention.

FIG. 2 is a flow chart of the first half of the embodiment.

FIG. 3 is a flow chart of the latter half of the embodiment.

FIG. 4 is an operation explanatory view of the same embodiment.

FIG. 5 is a configuration system diagram of a conventional example.

FIG. 6 is a flowchart of the conventional example.

FIG. 7 is an explanatory view of the operation of the conventional example.

[Explanation of symbols]

 1 Electrostatic precipitator 2 Flue 3 Dust concentration meter 4s Dust concentration signal 6,6a Control device 7s Charge amount or charge rate command signal 8 DC high voltage power supply device 9s Boiler load signal

Claims (1)

[Claims] 1. An electrostatic precipitator, a high-voltage direct current power supply for charging the electric precipitator with a high DC voltage, and a dust densitometer for detecting the amount of dust in the outlet of the electrostatic precipitator.
A boiler equipped with a controller for processing a dust concentration signal output from the same dust concentration meter and setting a command for setting a charge amount of a DC high voltage to be supplied to the electrostatic precipitator to the DC high voltage power supply device. Detecting a load increase by the load signal of the boiler, and increasing the charge amount stepwise when the dust concentration signal exceeds a predetermined value so as to prevent a rapid increase in the dust concentration, after rapidly suppressing the dust concentration. , The next charge amount is calculated from the change amount of the charge amount and the change amount of the dust concentration, and immediately before the same charge amount is output, the same charge amount is corrected by the dust concentration instantaneous value at that time, and the new charge amount is newly added. A soot and dust concentration control method for a boiler, which is characterized by outputting as a charge amount.