JPH01199629A - Flow rate restricting device for desulfurization treatment gas - Google Patents

Abstract

PURPOSE:To carry out a safe desulfurization control by providing an upper limit setting unit for exhaust gas, a rate restricting unit setting a treatment gas quantity at the starting of the desulfurization apparatus, and a low value selecting unit selecting the lower value between an output signal of the rate restricting unit and a treatment gas requiring signal. CONSTITUTION:In a normal operation, the treatment gas requiring signal 11 is compared with the output signal 27 of the rate restricting unit 26 (in this case, the output signal of an upper limit air quantity setting unit 22 in the state when the rate time is up.) by the low value signal selecting unit 28 where the lower value signal is selected to be made into a setting signal 29. On the other hand, the setting signal 29 is compared with the flow rate of the treated gas by a treated gas flow rate controller 12 to control the opening of the control damper 4 at the inlet of a desulfurization blower.

Description

[Detailed Description of the Invention] [Industrial Field of Application] The present invention relates to a desulfurization gas flow rate limiting system, and is particularly suitable for reducing draft fluctuations and preventing desulfurization equipment from being overloaded. Regarding desulfurization equipment.

[Conventional technology]

In the desulfurization equipment, exhaust gas from the boiler is drawn into the desulfurization equipment using a ventilator, and the air volume is controlled by a ventilator inlet control damper. It is important to smoothly and automatically control the ventilator inlet control damper in order to stabilize the processing gas flow rate, which is the demand signal for control, and to prevent the ventilator from becoming overloaded.

FIG. 3 is an overall system diagram of a desulfurization device to which a conventional flow rate restriction device is applied. In this device, exhaust gas 2 from a boiler 1 passes through a flue duct 3, is drawn by a ventilator 5, cools down by a gas heater 7, exchanges heat, and is introduced into a desulfurization device 8. The amount of processing gas sent to the desulfurization device 8 is controlled by adjusting the opening degree of the ventilator inlet control damper 4, and its flow rate is measured by the processing gas flow meter 6. The clean process gas desulfurized by the desulfurization device 8 undergoes heat exchange and temperature rise again by the gas heater 7, and is discharged into the atmosphere from the chimney 9.

FIG. 4 is a control system diagram in the prior art shown in FIG. A processing gas demand signal 11 commensurate with the amount of boiler exhaust gas is supplied as a setting signal for the processing gas flow rate controller 12, and the ventilator population control is performed so that the deviation between the signal 11 and the signal from the processing gas flowmeter 6 becomes zero. The opening degree of the tamper 4 is adjusted to control the flow rate of the processing gas.

The conventional control system described above has no problem with control during normal operation, but when starting the desulfurization equipment during boiler load operation, the processing gas request signal 11 has already become a high level setting signal, and this If the processing gas flow rate controller 12 is suddenly switched from manual to automatic mode in this state, the ventilator control damper 4 rapidly changes from the fully open state to the fully open state, causing a sudden change in the processing gas flow rate. For this reason, the draft of the boiler 1 and the flue duct 3 on the upstream side changes rapidly, and the overall control inside the desulfurization device 8 on the downstream side changes suddenly and drastically, and stabilization thereof becomes a major problem. Furthermore, performing the operation for stabilizing the fluctuations within a short period of time during the period when the amount of operation is large at the time of startup is a difficult task that requires great nerves and skill.

In addition, if multiple ventilators 5 are installed and one of them trips, a processing gas request signal for all desulfurization ventilators is sent to the remaining desulfurization ventilators, and the operating ventilators become overloaded. There was also a risk of this happening.

Therefore, when starting up the desulfurization device later during boiler load operation, there is a desire for a control device that can automatically control the draft so that the draft fluctuation is small and the ventilator 5 is not overloaded.

[Problem to be solved by the invention]

An object of the present invention is to solve the problems of the prior art, automatically prevent sudden changes in draft, and limit the desulfurization process gas flow rate to prevent the desulfurization ventilator from becoming overloaded. The goal is to provide equipment.

[Means to solve the problem]

The above purpose is a desulfurization treatment gas flow rate limiting device that guides the exhaust gas from the combustion equipment to the desulfurization equipment inlet through a flue duct, draws the exhaust gas into the desulfurization equipment using a ventilator, and controls the air flow rate with a ventilator inlet control damper. In,
Comparing the device that sets the upper limit of the exhaust gas flow rate, the rate limiting device that sets the processing gas amount at a constant rate up to the airflow rate at the control point when starting the desulfurization device, and the output signal of the rate limiting device and the processing gas request signal. This can be achieved by a desulfurization processing gas flow rate limiting device characterized by having a low signal selection device that selects a signal with a low value and outputs it as a processing gas flow rate setting signal.

[Effect]

In the desulfurization treatment gas flow rate limiting device of the present invention, the limit signal value, which automatically changes upward at a constant rate, is compared with the treatment gas request signal, the lower signal side is selected, and the flow rate is maintained at a constant rate until the air volume reaches the control point. Since the amount of gas to be processed is increased, sudden changes in draft can be prevented at startup. Also, compare the upper limit air volume limit signal value that prevents the desulfurization fan from overloading with the processing gas request signal, and select the lower signal side.
Since the desulfurization ventilator population control damper is operated using the selected lower signal as the processing gas flow rate set value, it is possible to prevent the desulfurization ventilator from becoming overloaded.

〔Example〕

FIG. 1 is an explanatory diagram showing one embodiment of the control system of the desulfurization treatment gas flow rate restriction device of the present invention. The difference from the conventional control system shown in FIG. 4 is that a desulfurization processing gas flow rate limiting device 21 is provided to convert a processing gas request signal 11 into a processing gas setting signal 29.

The desulfurization processing gas flow rate limiting device 21 includes an upper limit air setting device 22 that sets an air flow rate that does not overload the ventilator, and a ventilator inlet control damper that narrows down the processing gas amount when the ventilator is stopped. 4. Zero wind setting device 23 to prevent opening, and upper limit air volume setting device 2 when the ventilation fan is operating.
Select the signal on the 2 side and use the zero air volume setting device 23 when the ventilator is stopped.
a signal switch 24 that selects the side signal; and the signal switch 2
4, a rate limiter 26 for making a rate increase signal 27 which increases the switching signal 25 at a constant rate toward the target value (upper limit wind setting value) when the ventilation fan is started, and the processing gas request signal 11 and rate. It is comprised of a low signal selector 28 that compares the rising signal 26 and selects whichever signal is lower and uses it as the processing gas setting signal 29.

In the above configuration, during normal operation, the low signal selector 28
compares the processing gas request signal 11 and the output signal 27 of the rate limiter 2G (in this case, the output signal of the upper limit air volume setting device 22 whose rate time has increased), selects the lower signal, and sets the processing gas setting signal 29. shall be. On the other hand, the processing gas flow rate controller 12 compares the processing gas flow rate setting signal 29 with the processing gas flow rate, and controls the desulfurization ventilator inlet control damper 4.
By opening and closing , the wind ■ is adjusted so that the deviation becomes zero.

FIG. 2A is a diagram showing the relationship between the air volume and the elapsed time when the ventilator is started. In the figure, when starting the ventilation fan 5,
The processing gas setting signal 29 does not immediately take the value of the processing gas request signal 11, but between A and 8, the rate is M, and the signal 27
The processing gas request signal 11 and the output signal of the upper limit air volume setting device 22 are compared at point B, the closest signal 11 is selected, and the process of B-C is then performed. Take. Therefore, sudden draft fluctuations do not occur when the desulfurization fan is started.

FIG. 2B is a diagram showing the relationship between air volume and elapsed time when the processing gas request signal exceeds the upper limit air volume setting signal. Second
In figure B, if one of the multiple desulfurization fans trips while the processing gas setting signal 29 is DE and it is operating, the remaining desulfurization fans attempt to cover the amount of processing gas for all the desulfurization fans. When the processing gas request signal 11 exceeds the output signal of the upper limit air volume setting device 22 and becomes H at point E, and an overload is about to occur, the signals 11 and 22 are compared and the lower signal 22 is selected. The course will be E-F-G.

By using the above control device, it is possible to automatically prevent sudden changes in draft and overload of the desulfurization fan.

〔Effect of the invention〕

According to the present invention, it is possible to automatically prevent sudden changes in the draft when starting the desulfurization equipment and prevent overload of the desulfurization fan during operation, and by stabilizing the draft, the boiler furnace, flue, and desulfurization This makes it possible to prevent damage to the ventilation fan, and enables stable operation of the entire desulfurization equipment control. Therefore, the amount of operation by the operator can be reduced.

[Brief explanation of the drawing]

Fig. 1 is a control system diagram showing one embodiment of the desulfurization processing gas flow rate limiting device of the present invention, Figs. 2A and 2B are explanatory diagrams of the operation of the present invention, and Fig. 3 is an explanatory diagram of the entire system of the desulfurization device. , FIG. 4 is a control system diagram according to the prior art. 4... Desulfurization ventilator inlet control damper, 5...
Desulfurization ventilator, 6... Processing gas flow meter, 11... Processing gas request signal, 21... Desulfurization processing gas flow rate restriction device,
22... Upper limit air volume setting device, 26... Rate limiter,
28...Low signal selector, 29...Processing gas setting signal, 12...Processing gas flow rate controller. Agent Patent Attorney Takeshi Kawakita 21: Desulfurization processing gas flow rate limiter 22: Upper limit air flow setting device 23: Zero air flow setting device 26: Rate limiter 27: Rate 1-up signal 28: Low signal selector 29: Processing gas Setting signal 11: Processing gas request Y signal 12: Processing gas flow rate controller Fig. 2B: Time 3: Desulfurization equipment): Chimney Fig. 4

Claims (1)

[Claims] (1) In a desulfurization treatment gas flow rate limiting device that guides exhaust gas from the combustion equipment to the desulfurization equipment inlet through a flue duct, draws the exhaust gas into the desulfurization equipment using a ventilator, and controls the air volume with a ventilator inlet control damper. , a device for setting the upper limit of the exhaust gas flow rate; a rate limiting device for setting the processing gas amount at a constant rate up to the airflow rate at the control point when starting the desulfurization device; and an output signal of the rate limiting device and a processing gas request signal. A desulfurization processing gas flow rate limiting device characterized by having a low signal selection device that selects a signal with a comparatively low value and outputs it as a processing gas flow rate setting signal.