JPS60235627A - Level controlling process of absorption tower in stack gas desulfurization apparatus for wet slaking gypsum production - Google Patents

Abstract

PURPOSE:To control the level of an absorption tower at a fixed level for the sudden change of a boiler load by inputting into a function generator values obtd. by multiplying the flow rate of the waste gas introduced into an absorption tower by the measured values of the concn. of SOX, and operating a control valve in a discharging pipe line of washing liq. with the output signal of the function generator and a level controller. CONSTITUTION:The flow rate of the waste gas introduced into the absorption tower 3 and the concn. of SOX of the gas are sensed by a flow meter 11 and a densitometer for SOX 12. The sensed values are multiplied and inputted into the function generator 14. An amt. of CaCO3 as the absorbent equivalent to the absorbed SO2 is fed to the washing liq. in the absorption tower 3 from a pipe 7. The level of the washing liq. in the absorption tower 3 is sensed and fed to a level sensing controller 9. The sensed signal and the output signal from the function generator 14 are added in an adder 15. The control valve 10 provided to a pipe line 8 for discharging the washing liquid from the absorption tower 3 is operated by the output signal from the adder 15, thus, the level of the absorption tower is held almost at a fixed level.

Description

Detailed Description of the Invention The present invention uses calcium hydroxide (Cm(O)I)2) and/or calcium carbonate (CaCO5) to remove sulfur oxides (hereinafter referred to as sox) contained in flue gas. The present invention relates to a method for controlling the absorption tower level of a wet flue gas desulfurization equipment.

Conventionally, as this type of control method, the method shown in FIG. 1 is known. For example, exhaust gas from a coal-fired gage is introduced into an absorption tower 3 through an exhaust gas inlet duct 1, and is cooled and dust-removed by a cleaning liquid at the entrance of the absorption tower 3. Of course, a method is also known in which the exhaust gas is cooled and dust removed using a separate cooling and dust removal device before entering the absorption tower 3.

Due to the cooling of the exhaust gas, some of the water in the K and cleaning liquid evaporates, but is replenished by makeup water from the pipe 2.

Next, the exhaust gas is further cooled and dust removed in the main body of the absorption tower 3, and at the same time, SOx in the exhaust gas reacts with the cleaning liquid.
Absorbed.

Using the absorbent and 1-CaC0 in the cleaning solution, SOX is absorbed by the following reaction process.

Ca5O, +SO2+H2O-+Ca +zuso,-
(1) ISO, ''' 1002 → H+5O4 (2) Ca2
++502-→C&5O4 4(3) CaCO+I(So-+r-+cmso, +a2+co
2 (4) 3 In other words, the 90 aSO5 produced in the absorption tower 3 is the absorbed SO
In equation (1), Cm and H3O3- are obtained, but this H3
A part of O5- is oxidized by 0□ in the exhaust gas (2)
As shown in the formula, the needle + So4"K. Also, H8O, -
As shown in equation (4), C* SO5, H2O, and CO2 are neutralized with C aCOs, which is an absorbent.
02 is emitted as a gas from the outlet 4 in FIG. When the concentration of 90a and 8042- increases, (3)
As shown in (CaSO4 and CaSO3, it is precipitated in the solid phase.The production ratio of CaSO4 and CaSO3 is determined by the amount of SO4"- produced by O2 in the exhaust gas.

Cleaning liquid circulates 3j! It is supplied to the absorption tower 3 through the circulation pipe 6t by the pump 5, and comes into contact with the exhaust gas.

The cleaning liquid in the absorption tower 3 is supplied from the pipe 7 in an amount equal to the amount of SO2 absorbed by the Ca COs (or Ca(OH)2) absorbent, and the amount increases or decreases in proportion to the absorbed SO2.

A part of the cleaning liquid passes through the entire pipe 8 and is extracted out of the system. This withdrawal amount is controlled by a level detection controller 9 and a control valve 10 so as to keep the cleaning liquid level in the absorption tower 3 constant.

By the way, recent power generation mailers vary the amount of power generated and the load of the boiler according to the power demand, so the amount of exhaust gas generated by the boiler also changes, and when the amount of exhaust gas fluctuates, the amount of SO absorbed by the absorption tower 3 increases. □The amount also fluctuates, and the flow rate of the absorbent in the pipe 7 to be supplied also fluctuates in proportion to the S02 amount.

When the boiler load changes, it is not only the flue gas flow rate that changes, but also the concentration in the flue gas.In the case of mailers, the product of the flue gas flow rate and SOx concentration and the absorption tower The flow rate of absorbent supplied to is approximately proportional to the flow rate.

Therefore, the above-mentioned level detection controller 9 and control valve 10
The method of controlling the level in the absorption tower 3 solely by the above method had the disadvantage that it could not respond quickly enough to the fluctuations in the boiler load.

This will be specifically explained below using a 300,000 kW Geira exhaust gas desulfurization device for exhaust gas treatment as an example.

The holding up amount of cleaning liquid in absorption tower 3 is approximately 500 m'
The cross-sectional area is approximately 100 m2.

Further, the amount of absorbent supplied from the pipe 7 is about 25 m3/'H when the boiler load is low. However, since the amount of makeup water supplied from the pipe 2 is smaller than the amount of absorbent supplied, it will be ignored here.

Assume that from this state, the boiler load doubles and the absorbent supply flow rate suddenly increases to s o m371x. The cross-sectional area is 10
The liquid level, which is close to 0 m2, is undulating under normal pressure, and the detected level value is thought to fluctuate by about 10 cIn even if there is no change in hold up.

Therefore, it is not until a fluctuation of about 20 cm is detected that it can be determined that there has been a fluctuation in the hold up amount, and the control valve 10 can be operated.

Here, 20c! The time required for the n level to rise is 148 years.

The 48 minute delay between when a change in hold up occurs and when the control valve 10 is operated poses a major problem in terms of level controllability.

When the above-mentioned Boi 2 load fluctuated and the absorbent flow rate changed significantly, the mechanism fluctuated greatly.

The present invention was made to solve the above-mentioned drawbacks of the conventional method, and measures the flow rate of the exhaust gas introduced into the absorption tower and the sulfur oxide concentration in the exhaust gas, and inputs these measurement signals into a multiplier. Multiplication is performed, and the output signal of the multiplier is inputted to a function generator that generates a preset function, while the cleaning liquid level in the absorption tower is detected, and this level detection signal is inputted as a control variable to a level controller. Then, the output signal of the level controller and the output signal of the function generator are input to an adder and added, and the output signal of the adder operates a control valve installed in a pipe for extracting the cleaning liquid from the absorption tower. Kotoyoshi,
However, the present invention aims to provide a method that can control the level of the absorption tower to be almost constant even if the absorbent flow rate fluctuates due to sudden changes in the blast load.

Hereinafter, embodiments of the present invention will be described in detail with reference to FIG.

First, the exhaust gas from the mailer is introduced into the absorption tower JIC through the exhaust gas inlet duct 1, and is cooled and dust removed by a cleaning liquid at the entrance of the absorption tower 30. Make-up water is replenished from piping 2 because part of the cleaning liquid evaporates when the exhaust gas is cooled. At this time, the flow rate of the exhaust gas introduced into the absorption tower 3 is measured by the flow meter 11, and the SOx concentration in the exhaust gas is measured by the SOx concentration meter 12.
These detection signals are input to a multiplier 13 for multiplication, and the output No. 1 of the multiplier 13 is input to a function generator 14. The function generator 14 generates the function f(
x) is set to occur. In other words, the output of the function generator 14 is approximately equivalent to the amount of absorbent and makeup water supplied to the absorption tower 3.

Next, the exhaust gas is further cooled and dust removed in the main body of the absorption tower 3, and at the same time, SOx in the exhaust gas is reacted and absorbed by the cleaning liquid.

The cleaning liquid is supplied to the absorption tower through the circulation piping 5 by the circulation pipe 5, and comes into contact with the exhaust gas.

The cleaning liquid in the absorption tower 3 is supplied with CaCO3 from the pipe 7.
An equivalent amount of SO2 absorbed by the absorbent (OH) ) is supplied, and the amount increases or decreases in proportion to the absorbed SO2. At this time, the cleaning liquid level in the absorption tower 3 is detected by a detector, and its detection signal is input to the level detection controller 9, and the output signal of the function generator 14 is input to the detection signal of the controller 9. It is output to the adder 15.

A part of the cleaning liquid passes through the entire pipe 8 and is extracted out of the system. This extraction amount is determined by an adder 1r which receives the output signals of the function generator 14 and the level detection controller 9 and adds them.
The control valve 10Vc is controlled by an output signal from the control valve 10Vc.

Therefore, even if the load on the mailer suddenly changes and the flow rate of the absorbent supplied from the pipe 1 changes, the output signal of the function generator 14, which is almost equivalent to the flow rate supplied to the absorption tower 3, and the level detection controller 9 The output signal from the adder 15 is input, and the output signal from the adder 15 is added to the output pipe 8 from the absorption tower 3.
Since the control valve 10 equipped with Vc is operated, it is possible to draw out almost the same amount as the flow rate supplied to the absorption tower 3 at any time. At this time, the adder 15 adds the output signal of the level detection controller 9 to the output signal of the function generator 14. This is because if there is a slight difference between the estimated supply flow rate to the absorption tower 3 by the function generator 14 and the actual supply flow rate, the level will gradually increase if controlled only by the output signal of the function generator 14. come. For this purpose, the cleaning liquid level in the absorption tower 3 is detected, a correction signal is calculated by the level detection controller 9 so as to eliminate the deviation from the set value, and the signal is inputted to the adder 15VC to generate an estimate by the function generator 13VC. Correcting errors.

Therefore, according to the present invention, the level of the absorption tower 30 can be controlled to be substantially constant.

In the above embodiment, the output signal of the adder 15 directly operates the control valve 10t, but the present invention is not limited thereto. For example, as shown in FIG.
The setting of the flow rate detection controller 16 that detects the amount of discharge ([
The controller 16 may operate the control valve 10 so that the flow rate is set by the output signal of the adder 15.

As detailed above, according to the present invention, the absorber level control method in a wet lime-gypsum flue gas desulfurization apparatus is capable of controlling the absorber level at a nearly constant level even if the boiler load suddenly changes and the absorbent supply flow rate fluctuates. can provide

[Brief explanation of the drawing]

Fig. 1 is a schematic diagram for explaining the entire absorption tower level control method of a conventional flue gas desulfurization equipment, and Fig. 2 is an embodiment for explaining the entire absorption tower level control method of the flue gas desulfurization equipment of the present invention. The third factor is a diagram showing the relationship between the product of exhaust gas flow rate and BOX 11 degrees and the supply flow rate of absorbent and makeup water to the absorption tower. Figure 4 is the absorption tower level control of the present invention. FIG. 6 is a schematic diagram showing another example for explaining the method. J...Exhaust gas inlet duct, 3...Absorption tower, 5...
Circulation pump, 6... Circulation piping, 7... Piping for absorbent supply, 8... Piping for cleaning liquid extraction, 9... Level detection controller, 10... Control valve, 1 No...exhaust gas flow meter, 12...SOx concentration meter, 13...multiplier,
14...Function generator, 15...Adder, 16...
Flow rate detection controller. Figure 1 To1 Figure 2

Claims (1)

[Claims] In the absorption level control method of a wet flue gas treatment device, which cleans flue gas using a slurry containing calcium hydroxide and/or calcium carbonate to remove sulfur oxides from the flue gas, the flue gas introduced into the absorption tower. and the sulfur oxide concentration in the exhaust gas, input these measurement signals to a multiplier to perform multiplication, and input the output signal of the multiplier to a function generator that generates a preset function. On the other hand, the level of the cleaning liquid in the absorption tower is detected, this level detection signal is inputted as a control amount to a level controller, and the output signal of the level controller and the output signal of the function generator are inputted to an adder. A method for controlling the level of an absorption tower in a wet lime-gypsum flue gas desulfurization apparatus, characterized in that the output signal of the adder is used to operate a control valve installed in a pipe for extracting cleaning liquid from the absorption tower.