JP2900283B2 - Control method of exhaust gas ventilator of flue gas desulfurization unit - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a method for controlling an exhaust gas ventilator of a flue gas desulfurization device that reduces sulfur oxides in exhaust gas from combustion equipment such as a boiler.

[Conventional technology]

In a conventional flue gas desulfurization apparatus, as shown in FIG. 3, a boiler blower 6 blows air to a combustion facility such as the boiler 1,
After burning in the boiler 1 and untreated exhaust gas discharged from the boiler 1 is attracted by the exhaust gas blower 4, the temperature is lowered through the heat recovery unit 7 of the gas / gas heater, and then, the desulfurization as the flue gas desulfurization device is performed. It is sent to a tank 8 where the desulfurized treated exhaust gas is passed through a reheater 7 ′ of a gas heater to exchange heat with high-temperature untreated exhaust gas, and the heated treated exhaust gas is discharged from the chimney 2. I have to.

As a result, sulfur oxides in exhaust gas from combustion equipment such as the boiler 1 are reduced to a certain level, and the generation of white smoke when discharged from the chimney 2 is prevented.

Further, in case of an emergency such as when an accident of the flue gas desulfurization device occurs, a bypass duct 3 for discharging untreated exhaust gas directly to the chimney 2 is provided.

Therefore, when the amount of the exhaust gas blower 4 attracted is large, the amount of recycling increases, and the size of each device is increased. When the amount of attracted air is small, a short pass is performed by the bypass duct 3, which causes a problem in performance. A bypass damper 5 is provided in the bypass duct 3.

Further, the bypass damper 5 must be fully opened in an emergency, but may not operate due to accumulation of dust on the sliding portion. Therefore, the open / close test is performed at a certain frequency during operation. .

Here, since the internal pressure of the boiler 1 fluctuates within a range of ± 5 to 20 mm water column depending on the combustion state of the boiler 1, a bypass damper 5 having a high hermeticity is provided, or the set pressure of the exhaust gas ventilator inlet is set to a range without leakage. Therefore, it is necessary to reduce the pressure of the untreated exhaust gas path side.

The exhaust gas ventilator 4 is controlled based on the inlet pressure of the exhaust gas ventilator 4, the exhaust gas flow rate, or the differential pressure of the bypass damper 5.

Further, the signal of the boiler blower 6 or the boiler induction fan may be used as a preceding signal.

Among these methods, the method using the exhaust gas ventilator 4 inlet pressure is different because the chimney draft changes depending on the outside air temperature.
Selection increases, and the ventilation efficiency during operation deteriorates.

In order to solve this, it is common to control by the differential pressure of the bypass damper 5.

In the method using the exhaust gas flow rate, the exhaust gas flow rate changes even with the same boiler load due to seasonal changes in the outside temperature, and when coal is used as fuel, the exhaust gas flow rate also changes depending on the coal component, so large equipment using short paths and recycling Is concerned.

However, conventionally, it is often seen that the exhaust gas ventilator 4 is controlled at a flow rate by using a bypass damper 5 having a low hermeticity or by not using the bypass damper 5 at all.

On the other hand, as shown in FIG. 3, when there are a plurality of exhaust gas ventilators 4, there may be a slight difference in fan performance,
Duct arrangement may be different.

Therefore, if controlled by the bypass differential pressure, the amount of exhaust gas will be unbalanced, and the difference may be large.When processing high-capacity exhaust gas, it is difficult to perform desulfurization, cooling, heat recovery, etc. On the other hand, when processing a low-capacity exhaust gas under a low load, a problem occurs in the controllability of the exhaust gas ventilator 4, the desulfurization tank 8, and the like.

[Problem to be solved by the invention]

The present invention has been made in order to solve the conventional problems, and the same flow rate of the exhaust gas without regard to the difference in fan performance and the arrangement of the duct when a plurality of exhaust gas ventilators are provided. It is an object of the present invention to provide a method for controlling an exhaust gas ventilator of a flue gas desulfurization device capable of stably operating the flue gas desulfurization device.

[Means for Solving the Problems] As a means for solving the above problems, a method for controlling an exhaust gas ventilator of a flue gas desulfurization apparatus according to the present invention comprises an untreated exhaust gas passage discharged from a combustion facility such as a boiler. A plurality of flue gas that connects untreated flue gas discharged from a flue gas desulfurization unit such as a desulfurization tank with a bypass duct interposed with a bypass damper and sends untreated flue gas from the boiler etc. to the desulfurization tank etc. For the ventilator, the differential pressure before and after the bypass damper is increased by 5% from the exhaust gas path side after the untreated exhaust gas path side is processed.
, And the flow rate of each exhaust gas ventilator 4 or the difference between the output signals to each exhaust gas ventilator is added to or subtracted from the control of the exhaust gas ventilator.

〔Example〕

Hereinafter, an embodiment of the present invention will be described with reference to the drawings. An embodiment of a flue gas desulfurization apparatus to which the control method of the present invention is applied has substantially the same configuration and function as that described with reference to FIG. It comprises a boiler 1, two exhaust gas ventilators 4, a gas / gas heater heat recovery unit 7 and a reheater 7 ', a desulfurization tank 8, a chimney 2, etc., and connects between an untreated exhaust gas passage and a treated exhaust gas passage. , Connected by a bypass duct 3 provided with a bypass damper 5 interposed therebetween, and the operation thereof is the same as that described above, and will not be described here.

Therefore, FIG. 1 is a block diagram of a control circuit of the exhaust gas ventilator 4 of the flue gas desulfurization apparatus according to the embodiment, and FIG.
Pressure difference of the bypass damper 5 so that the untreated exhaust gas passage side on the inlet side of the desulfurization tank 8 is lower than the treated exhaust gas passage side on the exit side of the desulfurization tank 8 by 5 to 50 mm water column.
And controlling the D _P, further feeding the exhaust gas flow rate 1 of the two exhaust gas ventilator 4 and the exhaust gas flow 2 in the proportional-integral controller 21, calculates a difference of the exhaust gas flow rate of each gas ventilator 4, the flow rate The difference correction signal is sent to the adder 16 so that the control of each exhaust gas ventilator 4 is appropriately added and subtracted.

On the other hand, each opening signal of the two boiler blowers 6 is sent to the related converter 15 to determine the control drive amount of each exhaust gas ventilator 4, and the adder 16 and each of the two exhaust gas ventilators 4 are controlled. adder 17 of the proportional plus integral controller 21 to signal the pressure difference D _P of the bypass damper 5 of the controller 1 and the controller 2 is sent
Send to one of

Thereby, the difference between the output signal of the exhaust gas blower 4 and the signal of the exhaust gas flow 2 of the other exhaust gas blower 4 is used as a reference, and the difference is adjusted as a correction signal.

Next, in another embodiment shown in FIG. 2, the difference between the output signals to the two exhaust gas blowers 4 is added to or subtracted from the control of the exhaust gas blowers 4, which is almost the same as the embodiment shown in FIG. They have functions and the same parts are indicated by the same part numbers.

〔The invention's effect〕

According to the control method of the exhaust gas ventilator of the flue gas desulfurization apparatus of the present invention described above, the exhaust gas flow rate can be the same, regardless of the difference in performance between the plurality of exhaust gas ventilators and the arrangement of the ducts. There is an effect that all the facilities of the flue gas desulfurization device can be safely operated.

Further, since the pressure on the untreated exhaust gas path side of the bypass damper is made lower than that on the treated exhaust gas path side, there is an advantage that even when the load is stabilized, the opening / closing test of the bypass damper can be performed as it is.

[Brief description of the drawings]

FIG. 1 is a block diagram of one embodiment of a control circuit of an exhaust gas ventilator of a flue gas desulfurization apparatus to which the control method of the present invention is applied,
FIG. 2 is a block diagram of another embodiment different from FIG. 1, and FIG. 3 is a flow chart for explaining a conventional flue gas desulfurization apparatus. 1 boiler 3 bypass duct 4 exhaust gas ventilator 5 bypass damper 7 heat recovery unit 7 ′
… Reheater, 8… desulfurization tank, 16,17 …… adder, D _P ……
Differential pressure.

Claims (1)

(57) [Claims] An untreated exhaust gas is connected to a flue gas desulfurization device connected between a non-treated flue gas passage from a combustion facility and a flue gas passage treated by a flue gas desulfurization device by a bypass duct provided with a bypass damper. For a plurality of exhaust gas ventilators to be sent, the untreated exhaust gas side is treated and the differential pressure before and after the bypass damper is controlled so that the water column is lower by 5 to 50 mm than the exhaust gas side, and the flow rate of each exhaust gas ventilator or each exhaust gas A method for controlling an exhaust gas ventilator of a flue gas desulfurization device, in which a difference between output signals to the ventilator is added to and subtracted from control of the exhaust gas ventilator.