JPH05301019A - Method for washing mist eliminator - Google Patents

Abstract

PURPOSE:To facilitate the control of a liquid level in an adsorber and to save a washing solution at the time of washing a mist eliminator. CONSTITUTION:In this method by which a mist eliminator installed in the upper part of an adsorber of a wet type flue gas desulfurizer is normally washed with washing liquid, when the liquid level in the adsorber is within the prescribed limits, a lot of industrial water is added to returned liquid in the equipment to use the total as washing liquid, and when the liquid level is beyond the prescribed limits, only the returned liquid is used as washing liquid. Further, when the liquid level is within the prescribed limit, returned liquid is used as washing liquid together with industrial water to control the liquid level in the adsorber so that it may be within the prescribed limit.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for cleaning a mist eliminator provided in an upper part of an absorption tower of a wet flue gas desulfurization apparatus.

[0002]

2. Description of the Related Art A wet flue gas desulfurization device is one of the devices for removing sulfur oxides in combustion exhaust gas discharged from power generation facilities and waste incineration facilities.

This wet flue gas desulfurization apparatus is, as shown in FIG. 3, an absorption tower a for desulfurizing exhaust gas G with a slurry liquid.
And sulfur oxide (SO ₂ ) in the desulfurized slurry liquid
Is mainly composed of an oxidation tower b for converting gypsum (CaSO ₄ ) into a gypsum separation part c for separating gypsum from the slurry liquid, and exhaust gas G from a boiler (not shown) is absorbed in the absorption tower a. The exhaust gas G and the slurry liquid containing the absorbent such as lime (CaCO ₃ ) stored in the absorption tower a are brought into gas-liquid contact therewith to remove the sulfur oxides in the exhaust gas G. It is desulfurized as calcium sulfite (CaSO ₃ ), and then the slurry liquid that has absorbed the sulfur oxides is introduced into the oxidation tower b to be air-oxidized and converted into gypsum, and the unreacted absorbent is mixed with sulfuric acid (oxidized in the oxidation tower b). After being made into gypsum with H ₂ SO ₄ ), it is sent to the gypsum separating section c and recovered as gypsum. Then, the returned liquid (H
₂ O + α) is again introduced into the absorption tower a, and the amount of the absorbent (CaCO ₃ ) corresponding to the flow rate of the exhaust gas is dissolved and reused as a slurry liquid.

Further, as shown in the drawing, a mist eliminator d for removing mist is provided in the upper part of the absorption tower a, and the droplets sprayed in the absorption tower a are exhaust gas G.
It prevents you from going outside without being accompanied by. Further, a cleaning spray e for injecting a cleaning liquid using industrial water supplied from outside the system is provided on the upper part of the mist eliminator d, and mist containing slurry adheres and is blocked. The mist eliminator d is constantly washed so as not to exist.

The cleaning liquid obtained by cleaning the mist eliminator d is stored in the absorption tower a as it is, and the absorbent (CaCO ₃ ) is dissolved together with the returned liquid and used as a slurry liquid.

[0006]

By the way, as described above, when the mist eliminator d is washed with industrial water, the liquid level in the absorption tower a rises when the water balance requires a larger amount than can be used. Therefore, a part of the returned liquid is withdrawn to return it to the absorption tower a to prevent the liquid level from rising. However, this method has a poor response of the liquid level control and a large amount of returned liquid. The liquid was wasted.

Therefore, it is possible to use the returned liquid as it is as a cleaning liquid for the mist eliminator d, but since the returned liquid contains impurities such as gypsum,
When it is used as a cleaning liquid for a long period of time, there arises a problem that the impurities are fixed to the mist eliminator d or the impurities in the slurry liquid increase, and a part of the water in the device is separated by the gypsum separation part c. The separated gypsum was discharged to the outside of the system and gradually decreased to lower the liquid level in the absorption tower a. Therefore, it was necessary to replenish the absorption tower a with water from outside the system as needed.

Therefore, the present invention has been devised to effectively solve these problems, and its purpose is to facilitate the control of the liquid level and to eliminate the waste of the cleaning liquid. To provide a cleaning method.

[0009]

In order to achieve the above object, the present invention provides a method for cleaning a mist eliminator in which a mist eliminator provided in an upper part of an absorption tower of a wet flue gas desulfurization apparatus is always cleaned with a cleaning liquid. When the liquid level in the absorption tower is below a predetermined range, a large amount of industrial water is added to the return liquid in the device to be used as the cleaning liquid, and when the liquid level is above the predetermined range, Only the returned liquid is used as the cleaning liquid, and when the liquid level is within the predetermined range, the returned liquid is used as the cleaning liquid together with the industrial water so that the liquid level in the absorption tower falls within the predetermined range. Controlled by.

[0010]

As described above, according to the present invention, when the liquid level in the absorption tower is below a predetermined range, the use of the cleaning liquid containing a large amount of industrial water as the returned liquid prevents the liquid level from being lowered, and When the liquid level is equal to or higher than the predetermined range, the rise of the liquid level can be prevented by using only the returned liquid as the cleaning liquid. Further, when the liquid level is within a predetermined range, it is used as a cleaning liquid together with the industrial water, so that the liquid level becomes constant and its fluctuation is prevented beforehand.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A preferred embodiment of the present invention will be described in detail below with reference to the accompanying drawings.

FIG. 1 shows an embodiment of a wet flue gas desulfurization apparatus according to the present invention. As shown in the figure, this wet flue gas desulfurization apparatus produces an absorption tower 1 that absorbs and removes sulfur oxide (SO ₂ ) in the exhaust gas G, and produces gypsum (CaSO ₄ ) from the sulfur oxide absorbed in the absorption tower 1. It mainly comprises an oxidation tower 2 and a gypsum separating part 3 for separating gypsum.

The absorption tower 1 has lime (CaCO ₃ ) at the bottom.
Slurry liquid 4 containing an absorbent such as
The slurry liquid 4 is sprayed from the spray nozzle 6 provided in the upper part of the absorption tower 1 by the circulation pump 5 and brought into gas-liquid contact with the introduced exhaust gas G, so that the sulfur oxides in the exhaust gas G are converted to calcium sulfite (CaSO ₃ ) Is designed to be absorbed and removed.

The oxidizing tower 2 extracts and introduces a part of the slurry liquid 4 that has absorbed the sulfur oxides in the exhaust gas G, and the slurry liquid 4 is blown from an oxidizing blower 7 into air and sulfuric acid (H ₂ SO 4). _The gypsum is produced from the sulfur oxides which are oxidized by ₄ ) and absorbed in the slurry liquid 4.

The gypsum separating section 3 is for treating the slurry liquid 4 containing the gypsum produced in the oxidation tower 2. The gypsum separating part 3 separates the gypsum in the slurry liquid 4 and the remaining liquid (H ₂ O +).
α) is returned to the absorption tower 1 via the return passage 8 as the return liquid H.

Further, a water supply passage 9 for supplying the industrial water K is connected to the return passage 8 so as to join, and the industrial water K is supplied into the return passage 8 as necessary. There is.

A mist eliminator 11 is provided in the upper part of the absorption tower 1 near the gas outlet 10 thereof, and the mist (slurry liquid) sprayed in the absorption tower 1 is entrained in the exhaust gas G. The mist is designed to be removed so as not to go outside as it is. Further, a cleaning spray nozzle 12 connected to the return passage 8 is provided above the mist eliminator 11, and the return liquid H and the industrial water K introduced from the return passage 8 are constantly sprayed. The mist eliminator 11 is designed to be washed.

In the figure, 13 is a gas inlet, 14 and 15 are flow rate adjusting valves for controlling the flow rates of the returned liquid H and the industrial water K, and 16 is a discharge valve for discharging the returned liquid H.

Next, the operation of the wet flue gas desulfurization apparatus according to the present invention will be described.

As shown in FIG. 1, the gas inlet 1 of the absorption tower 1
The exhaust gas G introduced from 3 comes into gas-liquid contact with the slurry liquid 4 in the absorption tower 1 sprayed from the spray nozzle 4, and at that time, is contained by a chemical reaction as shown in the following formula (1). Sulfur oxide is calcium sulfite (CaSO
₃ ) Absorbed and removed as a mist eliminator 1
1, the mist of the slurry liquid is removed, and then the gas outlet 12 is generated together with the generated carbon dioxide (CO ₂ ).
Is exhausted to the outside of the absorption tower 1.

(1) SO ₂ + CaCO ₃ + 1 / 2H ₂ O
→ CaSO ₃ .1 / 2H ₂ O + CO ₂ On the other hand, a part of the slurry liquid 4 which has absorbed sulfur oxide as calcium sulfite is introduced into the oxidation tower 2 by the circulation pump 5 and the air and sulfuric acid supplied from the oxidation blower 7 are supplied. (H ₂ SO ₄ ) oxidation treatment,
Calcium sulfite (CaSO ₃ ) contained by the chemical reaction as shown in ( ₃ ) is deposited as gypsum (CaSO ₄ ), and the unreacted slurry liquid 4 is sulfuric acid (H ₂ SO ₄ ).
Is processed by reacting with.

(2) CaSO ₃ .1 / 2H ₂ O + 1/2
O ₂ + 3 / 2H ₂ O → CaSO ₄・ 2H ₂ O (3) CaSO ₃ + H ₂ SO ₄ + H ₂ O → CaSO ₄・
2H ₂ O + CO ₂ Then, the slurry liquid in which gypsum has been deposited is sent to the gypsum separating section 3 to be separated into gypsum and a supernatant liquid (H ₂ O + α), and the supernatant liquid (H ₂ O + α) is returned as a return liquid 8 The mist eliminator 11 is sprayed from the cleaning spray nozzle 12 as a cleaning liquid for the mist eliminator 11 in the absorption tower 1 via the above.

The cleaning liquid used to clean the mist eliminator 11 is stored as it is in the bottom of the absorption tower 1, and dissolves lime (CaCO ₃ ) injected in an amount commensurate with the exhaust gas G introduced into the absorption tower 1. To be used as the slurry liquid 4 again.

Next, the cleaning method of the present invention will be described.

As described above, the returned liquid H from which the gypsum has been separated
Will be used as a cleaning liquid for the mist eliminator 11, but a part of the returned liquid H will be contained in the gypsum separated by the gypsum separating section 3 and will be discharged out of the system together with the gypsum. The slurry liquid 4 in the tower 1 gradually decreases, and its liquid level gradually decreases in proportion to this. Then, as shown in FIG. 2, when the liquid level falls below a predetermined range, the return liquid H is returned into the return passage 8.
At the same time, by flowing a large amount of industrial water K, the liquid level in the absorption tower 1 will be increased. In addition, this industrial water K
Since this is clean water with less impurities than the returned liquid H, the cleaning effect of the mist eliminator 11 is also improved.

Next, as shown in the figure, when the liquid level in the absorption tower 1 falls within a predetermined range, the flow rate adjusting valve 14
Is controlled so that the flow rate of the industrial water K is reduced, the rise of the liquid level is suppressed, and the liquid level is controlled to fall within a predetermined range. However, as shown in the figure, when the liquid level in the absorption tower 1 exceeds a predetermined range, the flow rate adjustment valve 14
To stop the flow of industrial water K and return the cleaning liquid to the liquid H
The rise in the liquid level is suppressed by paying only for it. And
The liquid level gradually decreases due to the reasons described above,
If it falls within the predetermined range, as shown in the figure, the industrial water K is caused to flow together with the returned liquid H to prevent the liquid level from dropping below that.

As described above, according to the present invention, the liquid in the absorption tower 1 is simply controlled by controlling the flow rate of the industrial water K added to the return liquid H used as the cleaning liquid for the mist eliminator 11 according to the liquid level in the absorption tower 1. The level can be easily controlled, and the returned liquid H can be effectively used without wasting it during normal operation.

If necessary, the flow control valve 15 of the return passage 8 is closed and the discharge valve 16 is opened to discharge the return liquid H out of the system, and only the industrial water K is mist eliminator 11.
It is also possible to use it as the cleaning liquid of the above, and in this case, the cleaning effect of the mist eliminator 11 is enhanced.

[0029]

In summary, according to the present invention, the liquid level in the absorption tower can be easily controlled by controlling only the flow rate of the industrial water used as the cleaning liquid for the mist eliminator, and the returned liquid can be used. Since it is not wastefully discharged, it has an excellent economical effect.

[Brief description of drawings]

FIG. 1 is a schematic view showing an embodiment of a wet flue gas desulfurization apparatus according to the present invention.

FIG. 2 is a graph showing an embodiment of the present invention.

FIG. 3 is a schematic view showing an embodiment of a conventional wet flue gas desulfurization apparatus.

[Explanation of symbols]

 1 Suction tower 11 Mist eliminator K Industrial water H Return liquid

Claims (1)

[Claims] 1. A method for cleaning a mist eliminator in which a mist eliminator provided in an upper part of an absorption tower of a wet flue gas desulfurization apparatus is always washed with a cleaning liquid, when the liquid level in the absorption tower is below a predetermined range, When a large amount of industrial water is added to the returned liquid in the device and used as the cleaning liquid, and when the liquid level is above a predetermined range,
Only the returned liquid is used as the cleaning liquid, and when the liquid level is within the predetermined range, the returned liquid is used as the cleaning liquid together with the industrial water so that the liquid level in the absorption tower falls within the predetermined range. A method for cleaning a mist eliminator, which is characterized in that