JPH1190172A - Control method and controller for absorbing liquid level in flue gas desulfurizer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a control method for the absorbing liquid level in a flue gas desulfurizer and a controller using the same enabling miniaturization of a liquid pump for supplying absorbing liquid to an absorber and level control of absorbing liquid with good responsibility and high accuracy. SOLUTION: In a flue gas desulfurizer in which oxidizing air is forcibly fed into absorbing liquid K stored in an absorber 1 and also waste gas is forcibly fed to subject them to gas-liquid contact in the absorber 1, thereby absorbing gaseous SO2 in the waste gas by reaction, a level gauge 20 for detecting the level of the absorbing liquid K in the absorber 1, a tightly closed tank 30 for storing replenishing absorbing liquid, a pressurized gas introducing pipe 36 for introducing a part of the oxidizing air into the closed tank 30 through a valve 37, and a controller 40 for opening the valve 37 according to the output of the level gage 20 are provided. This controller 40 controls the absorbing liquid level in the absorber 1 by opening the valve 37 to introduce a part of the oxidizing air into the closed tank 39 and forcibly feed absorbing liquid K in the closed tank 30 to the absorber 1 by the pressure of the oxidizing air.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a method for absorbing and reacting sulfur dioxide in an exhaust gas by bringing the exhaust gas containing the sulfur dioxide into gas-liquid contact in an absorption tower with an absorbing solution comprising a sulfur dioxide neutralizer slurry solution. The present invention relates to a flue gas desulfurization apparatus and, more particularly, to an absorbent level control method and a controller for controlling a liquid level of an absorbent in an absorption tower.

[0002]

2. Description of the Related Art Conventionally, as one type of flue gas desulfurization apparatus for detoxifying a large amount of exhaust gas generated in a boiler or the like of a thermal power plant, sulfur dioxide gas (SO ₂ ) contained in the exhaust gas is converted into limestone (CaCO ₃ ). It is widely known that a solution is made to come into contact with an absorbing solution composed of an aqueous solution (sulfurous acid gas neutralizing agent slurry solution) in which the solution is dissolved or suspended, and is absorbed in the absorbing solution.

FIG. 2 shows the structure of a main part of a conventional flue gas desulfurization apparatus of this type. The absorption tower 1, which is a main part of this flue gas desulfurization apparatus, has a circular or square horizontal cross section, and an upper deck 3 and a lower deck 2 are arranged in the upper space at an interval in the vertical direction. Have been. These decks 3 and 2 are provided as partition walls for airtightly defining the internal space of the absorption tower 1. The lower space of the lower deck 2 is a storage tank 4, and the space between the upper deck 3 and the lower deck 2 is an entrance. The plenum 6 and the upper space of the upper deck 3 form an exit plenum 8. Inside the storage tank 4, an absorption liquid K made of limestone slurry is stored at a predetermined level. Also,
The inlet plenum 6 is connected to an inlet duct 5 for introducing exhaust gas into the absorption tower 1, while the outlet plenum 8 is connected to an outlet duct 7 for guiding treated exhaust gas in the absorption tower 1 to the outside. .

A large number of openings are formed in the lower deck 2 in a distributed manner, and each opening has a sparger pipe (exhaust gas introduction pipe) suspended from the lower surface of the lower deck 2.
9 are connected to each other. The sparger pipe 9 has a lower end inserted into the absorbing liquid K in the storage tank 4 and a large number of exhaust gas discharge holes 9a that open in the horizontal direction are formed in the outer periphery of the lower end along the circumferential direction. Have been.
The exhaust gas discharge hole 9a is opened at a predetermined depth below the liquid level of the absorbing liquid K, and discharges exhaust gas horizontally below the liquid level of the absorbing liquid K.

A gas riser 10 is provided between the lower deck 2 and the upper deck 3 so as to communicate an upper space 4 a above the absorbent surface of the storage tank 4 with the outlet plenum 8 so as to penetrate the inlet plenum 6. Have been. Further, at the bottom of the storage tank 4, a supply pipe 11 for oxidizing air for blowing out oxidizing air (oxidizing gas) and a stirrer 12 for stirring the absorbing liquid K are provided. The end side is connected to a blower 15 for pumping oxidizing air. A slurry pump 13 is connected to the storage tank 4.

Further, a supply line 14 for supplying a replenishing absorbing liquid into the absorption tower 1 is connected to the absorption tower 1. The base end of the supply line 14 is connected to a liquid pump 23 via a valve 23, and the suction side of the liquid pump 23 is introduced into a slurry tank 21 for absorbing liquid. Further, the storage tank 4 of the absorption tower 1 is provided with a level meter 20 for measuring the liquid level of the absorbing liquid K, and a valve 23 and a liquid pump 22 according to the level of the absorbing liquid measured by the level meter 20. Is controlled so that the level of the absorbing liquid K in the storage tank 4 is kept constant.

In the absorption tower 1 having the above structure,
When supplying exhaust gas from the inlet duct 5 to the inlet plenum 6 while supplying oxygen into the absorbing liquid K through the supply pipe 11,
The exhaust gas is ejected from the ejection holes 9a at the lower end of each sparger pipe 9, and vigorously mixes with the absorbing liquid K to form a liquid phase continuous jet bubbling layer. At this time, the stirrer 1
2 is rotated to stir the absorbing liquid K, and the supply pipe 11
Is supplied continuously from the nozzle at the tip into the absorbing liquid K. Thereby, high-efficiency gas-liquid contact is performed in the jet bubbling layer, and SO ₂ + CaCO ₃ + 1/2 · O ₂ + H ₂ O → CaSO ₄
・ As shown by 2H ₂ O ↓ + CO ₂硫酸, sulfurous acid gas (S
O ₂ ) is oxidized and neutralized by the limestone in the absorbing solution K, and the sulfurous acid gas is absorbed and absorbed.
Removed. The desulfurized and detoxified exhaust gas is discharged from the gas riser 10 through the outlet plenum 8 and the outlet duct 7 to the outside through the chimney.

On the other hand, gypsum (CaSO ₄₎ generated in the absorbing solution by oxidizing and neutralizing sulfur dioxide gas (SO ₂ )
2H ₂ O) becomes an absorbent gypsum slurry by growing crystals to form coarse particles, and when it reaches a predetermined concentration, it is extracted from the reaction tank 1 by the slurry pump 13 and a gypsum separator (not shown) Is separated into mother liquor and gypsum. The mother liquor thus separated is stored in the slurry tank 21 as a replenishing absorbent. Then, in accordance with the detection signal from the level meter 20, the absorption liquid for replenishment is appropriately supplied into the absorption tower 1 through the supply line 14.

According to the flue gas desulfurization apparatus using such an absorption tower 1, the stirrer 1 is supplied while oxidizing air is supplied into the absorbing solution.
2 and the exhaust gas is blown out from the lower end of each sparger pipe 9 to form a jet bubbling layer that is continuous with the absorbing liquid, so that sulfur dioxide gas (SO ₂ ) in the exhaust gas is absorbed and oxidized. -The entire process of neutralization and gypsum crystallization can be performed in one tank, and there is an advantage that sulfur dioxide gas can be removed at a very high rate.

[0010]

By the way, in the absorption tower 1, if the level of the absorbing liquid K is too high, the air supply pressure for ejecting the exhaust gas from the sparger pipe 9 becomes relatively high, and the air supply If the load on the blower is excessive and uneconomical, on the other hand, if the above level is too low, exhaust gas will be ejected near the liquid level, and a sufficient jet bubbling layer cannot be formed, so that It is not suitable because highly efficient desulfurization cannot be obtained. As described above, the level of the absorbing solution K in the storage tank 4 is a very important factor in forming a jet bubbling layer and performing highly efficient reaction absorption.

Therefore, in the above-mentioned conventional flue gas desulfurization apparatus, the absorption liquid is supplied from the slurry tank 21 to the absorption tower 1 by using a large liquid pump 22 in accordance with the detection signal from the level meter 20.
To control the level of the absorbing solution in the absorption tower 1. However, in the above-mentioned conventional flue gas desulfurization apparatus, the absorption tower 1 is generally large, having a diameter of about several tens of meters, and the amount of absorption liquid to be replenished is large. For this reason, this has been one of the causes of an increase in the cost of the entire apparatus. In addition, when the level meter 20 detects a decrease in the liquid level, the valve 23 is opened to feed the absorbing liquid into the absorption tower 1, and the level meter detects that the liquid level has reached a certain value. In this case, the supply of the absorbing liquid is controlled by repeatedly opening and closing the valve 23, such as controlling the liquid level to a constant level by the operation of closing the valve 23, so that the responsiveness to a change in the level of the absorbing liquid is improved. Therefore, it is necessary to further increase the size of the pump 22, and improvement thereof has been desired.

The present invention has been made to effectively solve the problem of the level control of the absorbent in such a conventional flue gas desulfurization apparatus, and has a small liquid pump for supplying the absorbent to the absorption tower. It is an object of the present invention to provide an absorbent level control method for a flue gas desulfurization apparatus and a control apparatus used for the same, which can achieve high-level control of the absorbent with high responsiveness and high accuracy. Things.

[0013]

According to the first aspect of the present invention, there is provided a method for controlling an absorbent level, comprising: sending an oxidizing gas and an exhaust gas into an absorbing solution stored in an absorbing tower; In a flue gas desulfurization device that reacts and absorbs sulfurous acid gas in exhaust gas by gas-liquid contact in the tower, at least a part of the oxidizing gas is introduced into a closed tank storing a replenishing absorbent, The absorption liquid in the closed tank is pressure-fed into the absorption tower by the pressure of the oxidizing gas, whereby the level of the absorption liquid in the absorption tower is controlled. At this time, the invention according to claim 2 is characterized in that at least a part of the oxidizing gas is used as the gas.

According to a third aspect of the present invention, there is provided an absorption liquid level control device, wherein an oxidizing gas and an exhaust gas are pressure-fed into an absorption liquid stored in an absorption tower, and gas-liquid contact is performed in the absorption tower. By doing so, in a flue gas desulfurization device that reacts and absorbs sulfurous acid gas in exhaust gas, a level meter that detects the liquid level of the absorbing solution in the absorption tower, a closed tank that stores the absorbing solution for replenishment, A pressure gas introduction pipe for introducing at least a part of the oxidizing gas into the closed tank via a valve, and opening the valve in accordance with the output of the level meter, thereby causing at least a part of the oxidizing gas to the closed tank. And a control means for controlling the level of the absorbing solution in the absorption tower by introducing the absorbing solution into the absorbing tower by the pressure of the oxidizing gas. Here, the invention according to claim 4 is characterized in that at least a part of the oxidizing air is used as the gas by branching and connecting the supply pipe of the oxidizing gas to the closed tank. Is what you do.

According to the first aspect of the present invention, the absorption liquid in the closed tank is sent into the absorption tower by the pressurized gas, so that the conventional liquid pump for supplying the absorption liquid can be reduced in size. This makes it possible to reduce the cost of the entire apparatus including the cost of the apparatus itself and power consumption, and further facilitates maintenance and management. Also,
Since the absorption liquid in the closed tank is extruded with the gas pressure, the supply amount of the absorption liquid into the absorption tower can be adjusted very finely by adjusting the gas pressure, and a large amount of the absorption liquid is responsive. It becomes possible to supply well. In particular, if at least a part of the oxidizing gas that is constantly driven during operation is used as the pressurized gas as in the invention described in claim 2, a separate pressurized gas supply device is not required, This is preferable because it is more economical and can further reduce power consumption.

In the invention according to claim 3 or 4, when the level meter detects a decrease in the level of the absorbing solution in the absorption tower, the control means opens a valve to open at least a part of the oxidizing gas. The pressurized gas is introduced into the closed tank. Then, the absorbing liquid in the sealed tank is pushed out by the pressure of the gas and sent into the absorbing tower.
Therefore, the supply amount of the absorbing liquid into the absorption tower can be adjusted very finely by adjusting the gas pressure. When the level meter detects that the level of the absorbent in the absorption tower has reached a certain value, the control means closes the valve and stops the introduction of the oxidizing gas into the closed tank. Therefore, it is possible to promptly supply and stop the supply of the absorbing liquid in response to a change in the level of the absorbing liquid in the absorption tower, thereby improving the responsiveness.

[0017]

Embodiments of the present invention will be described below with reference to the drawings. The same components as those of the conventional example shown in FIG. 2 are denoted by the same reference numerals, and description thereof will be omitted. FIG. 1 shows a configuration of a main part of an embodiment of an absorption liquid level control device of a flue gas desulfurization device according to the present invention. In this flue gas desulfurization device, a closed type side tank (closed tank) 30 is provided as a means for storing the replenishing absorbent in the absorption tower 1. The absorption liquid K is stored in the side tank 30, and an air reservoir 32 for introducing oxidizing air is secured on the storage liquid surface. Note that the air reservoir 32 may hardly exist when the absorbing liquid K is fully filled.
The side tank 30 is provided with a pressure sensor 35 for detecting the air pressure in the air reservoir 32. Further, a supply pipe 44 provided with a valve 43 which is opened and closed by a liquid level meter 42 is provided, so that a shortage of the absorbing liquid can be appropriately supplied from outside.

On the other hand, a base end of a supply line 14 for supplying the replenishing absorbing liquid into the absorption tower 1 is connected to the bottom of the side tank 30 via a valve 23. A supply pipe 11 for supplying oxidizing air to the bottom of the flue gas desulfurization device 4 of the absorption tower 1 is directly connected to a discharge port of the blower 15.
Is connected to a base end of a pressure gas introducing pipe 36 for introducing at least a part of the oxidizing air for driving. The distal end of the pressure gas introduction pipe 36 is connected via a valve 37 to
It is connected to an opening 31 provided in the upper lid of the side tank 30. Although not shown, the side tank 30 is provided with an air vent having a valve through which air can be vented as necessary.

In the figure, reference numeral 40 denotes the valve 23,
A control device (control means) for controlling the opening and closing of 37. The control device 40 takes in the detection signal of the level meter 20 of the absorption tower 1 and the detection signal of the pressure sensor 35, and connects the valve 23 of the supply line 14 for the absorbing liquid and the pressure gas introduction pipe 3.
The opening and closing of the valve 37 is controlled.

Next, an embodiment of the absorption liquid level control method according to the present invention using the absorption liquid level control device having the above configuration will be described together with the operation of supplying the absorption liquid K to the absorption tower 1. First, when the absorption liquid K is not supplied to the absorption tower 1, the control device 40 has the valves 23 and 37 closed. As a result, the entire amount of the oxidizing air from the blower 15 is sent into the storage tank 4 through the supply pipe 11 as the oxidizing air.

Next, when the level meter 20 detects that the level of the absorbent in the absorption tower 1 has decreased, the control device 40
Opens the valves 23 and 37 based on the detection signal.
Then, at least a portion of the oxidizing air from the blower 15 is introduced into the air reservoir 32 at the upper end of the side tank 30, and the pressure PT of the air presses the stored liquid surface downward. Then, the absorption liquid corresponding to the lowering of the liquid level is sent into the absorption tower 1 through the supply line 14 connected to the bottom of the side tank 30. Thereby, the level of the absorbing liquid in the absorption tower 1 increases.

In this case, the flow rate of the absorbing liquid is adjusted according to the pressure of the air in the air reservoir 32, and the level meter 2
When the detected value of 0 detects approach to a predetermined value, the control device 4
While 0 monitors the detection signal from the pressure sensor 35, the pressure in the air reservoir 32 is reduced to reduce the supply flow rate, and the absorption liquid level is controlled so as to converge to a constant level while finely adjusting.

When the level meter 20 detects that the level of the absorbing solution in the absorption tower 1 has reached a certain value, the control device 40 closes the valves 23 and 37 and the side tank 3
The introduction of oxidizing air to zero is stopped.

As described above, in the above-described absorption liquid level control method and control device, the pressure of the oxidizing air is used as the driving force for supplying the absorption liquid into the absorption tower 1.
There is no need to use a special large liquid pump as in the past,
Therefore, the system configuration is simplified, and the equipment cost and the operating cost can be reduced. In addition, since the absorption liquid in the side tank 30 is sent into the absorption tower 1 by the pressure of the gas, the supply amount of the absorption liquid into the absorption tower 1 can be finely controlled by adjusting the pressure of the air introduced into the side tank 30. As a result, the level accuracy of the absorbing liquid in the absorption tower 1 can be improved.

[0025]

As described above, according to any one of the first to fourth aspects of the present invention, the size of the liquid pump for supplying the absorbing liquid into the absorption tower can be reduced.
Equipment costs and operating costs can be reduced.
Further, since a pressurized gas such as at least a part of the oxidizing gas supplied to the absorption tower is used, and the absorption liquid in the closed tank is sent into the absorption tower by the pressure of the gas, the gas is introduced into the closed tank. By adjusting the gas pressure, the supply amount of the absorbing liquid into the absorption tower can be finely adjusted, so that the level of the absorbing liquid in the absorption tower can be accurately controlled.

[Brief description of the drawings]

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

FIG. 2 is a system configuration diagram of a conventional example.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Absorption tower 20 Level meter 30 Sealed tank 36 Pressure gas introduction pipe 37 Valve 40 Control device (control means) K Absorbing liquid

Claims (4)

[Claims] An oxidizing gas and an exhaust gas are pressure-fed into an absorbing solution stored in an absorption tower, and gas-liquid contact is made in the absorbing tower, so that the sulfurous acid gas in the exhaust gas is reduced in the absorbing solution. In a flue gas desulfurization unit that absorbs and removes gas, the pressurized gas is introduced into a closed tank that stores the replenishing absorbent, and the pressure of the gas sends the absorbent in the closed tank into the absorption tower. Controlling the level of the absorbent in the absorption tower by controlling the level of the absorbent in the flue gas desulfurization apparatus. 2. The method according to claim 1, wherein the gas is at least a part of the oxidizing gas. 3. An oxidizing gas and an exhaust gas are pumped into the absorbing solution stored in the absorption tower, and gas and liquid are brought into contact in the absorbing tower. In a flue gas desulfurization device that absorbs and removes gas, a level meter that detects the liquid level of the absorbing solution in the absorption tower, a sealed tank that stores the absorbing solution for replenishment, and a valve for the pressurized gas are provided. By opening the valve according to the output of the level meter, and a pressure gas introduction pipe introduced into the closed tank via
Control means for controlling the level of the absorbing solution in the absorption tower by introducing the gas into the closed tank, causing the absorbing solution in the closed tank to be pressure-fed into the absorbing tower by the pressure of the gas, and controlling the level of the absorbing solution in the absorbing tower. Liquid level control device for flue gas desulfurization equipment. 4. The method according to claim 3, wherein at least a part of the oxidizing air is used as the gas by branching and connecting the supply pipe of the oxidizing gas to the closed tank. Absorbent liquid level control device for flue gas desulfurization equipment.