JPS6244735Y2 - - Google Patents

Description

[Detailed description of the invention] The present invention relates to a wet exhaust gas treatment equipment equipped with a dust removal tower, an absorption tower, etc., and in particular, the amount of discharge of the treatment liquid is limited according to the Cl concentration in the treatment liquid. The present invention relates to a wet exhaust gas treatment device that can reduce water consumption and effectively utilize water resources.

Generally, the exhaust gas emitted from combustion equipment such as boilers contains fly ash and sulfur oxides, so the exhaust gas is treated to remove these before it is released into the atmosphere. .

There are two types of exhaust gas treatment methods: a dry treatment method and a wet treatment method that uses water.The latter, the wet treatment method, has been particularly popular due to its high treatment efficiency. If hydrogen chloride gas, which is a trace component in exhaust gas, concentrates and accumulates in the processing liquid, the materials used will be more susceptible to chlorine corrosion and the desulfurization performance will decrease.
In order to always maintain the Cl concentration of the processing liquid within the system below the allowable concentration, the circulating processing liquid within the apparatus is appropriately discharged to the outside of the system.

A conventional example of this wet-type exhaust gas treatment device will be explained based on FIG. Dust, hydrogen chloride gas (HCl), and hydrogen fluoride gas (HF) that come into contact with the circulating treatment liquid 3 and are contained therein
etc. are removed.

The exhaust gas from which dust, chlorine compounds, etc. have been removed in this way is further introduced into the absorption tower 4, where it is desulfurized by contacting with an absorption liquid 5 made by dissolving limestone in water, for example, and released into the atmosphere as it is. released to.

On the other hand, since the soot and dust and hydrogen chloride (HCl) that have been adsorbed and removed are concentrated in the treated liquid 3 in the dust removal tower 2, a part of this liquid is transferred to the dust removal tower blow pump 6.
The treated liquid is discharged through the treatment liquid discharge passage 7 toward, for example, a wastewater treatment device (not shown). The discharge amount of the processing liquid is controlled by a flow rate controller 8 interposed in the passage 7 and automatically adjusting a flow rate control valve 9, so that a predetermined flow rate is discharged. Water is supplied to the treated liquid 3 in the column via the water supply passage 10 in an amount corresponding to the amount insufficient due to discharge or evaporation in the column, and the amount of treated liquid in the system is maintained constant.

By the way, the discharge amount of the above-mentioned processing liquid is determined to be below a predetermined Cl concentration in order to protect the material of the equipment, but in the past, the discharge amount was determined in accordance with the maximum possible amount of chlorine, and the discharge amount was constantly maintained. Processing liquid was being discharged even at a constant discharge rate. Therefore,
For example, if the load on the boiler decreases and the amount of fuel being combusted decreases, or if the quality of the fuel improves and the chlorine content in the exhaust gas decreases, the Cl concentration in the treated liquid becomes much lower than the allowable Cl concentration. However, a large amount of treatment liquid was discharged, and water resources were wasted.

Therefore, it is possible to detect the HCl concentration in the exhaust gas and control the discharge amount of the processing liquid based on this detected value, but in this case, the HCl concentration in the gas
When the HCl concentration is extremely low, detection accuracy is poor and controllability is poor, making it impractical.

This invention was devised to effectively solve the above-mentioned problems, and its purpose is to reduce the Cl concentration in the processing liquid used in dust removal towers and absorption towers. To provide a wet exhaust gas treatment device capable of detecting and limiting the discharge amount of a treatment liquid so as to always maintain a substantially constant value, thereby reducing the amount of water used and effectively utilizing water resources. It is in.

Hereinafter, a preferred embodiment of the present invention will be described in detail with reference to the accompanying drawings.

First, FIG. 2 is a schematic system diagram showing a first embodiment of the exhaust gas treatment apparatus according to the present invention.

As shown in the figure, reference numeral 2 denotes a dust removal tower as an exhaust gas treatment tower. A treatment liquid tank 11 is provided in the lower part of the tower, and the treatment liquid 3 stored in this tank is transferred to the upper part of the tower through a treatment liquid circulation passage 12. At the same time, the spray 13 provided at the top sprays onto the surface 3a of the processing liquid stored in the tank. Further, a flue gas inlet 14 is provided in the lower side wall of the dust removing tower 2, and a flue gas outlet 15 is provided in the upper part of the tower for discharging the treated flue gas. By contacting the above-mentioned spray treatment liquid within the chamber, dust removal treatment and adsorption removal of HCl gas, HF gas, etc. can be accomplished.

On the other hand, an absorption tower 4 for desulfurizing the exhaust gas is provided on the downstream side of the dust removal tower 2.
The exhaust gas after the dust removal treatment is treated with limestone 16, for example.
This can be desulfurized by contacting it with an absorption liquid 5 made by dissolving it in water.

On the other hand, the treated liquid tank 11 of the dust removal tower 2 is connected with a treated liquid discharge passage 7 for appropriately discharging the treated liquid 3 therein to the outside of the tower, and a blow pump is interposed in the middle of this passage. 6 allows the processing liquid 3 to be transferred to the outside of the tower.

Further, the processing liquid tank 11 is provided with a Cl concentration detector 17 for detecting the Cl concentration of the processing liquid stored therein, and the detected value obtained here is used as a feature of the present invention. 1 flow rate control means 18. The flow rate control means 18 mainly includes a calculation unit 19 that performs calculation processing, and a flow rate control valve 20 provided in the discharge passage 7 to control the discharge amount of the processing liquid based on the calculation results. . Specifically, this calculation unit 19
The set value set to the desired Cl concentration is stored in advance, and this set value and the detected value transmitted from the detector 17 are compared and processed to determine if the detected value exceeds the set value. In response to this, the control valve 20 is opened or its opening degree is increased to start discharging the processing liquid or to increase the discharge amount of the liquid. If the value becomes smaller than the set value, in response, the control valve 20 is closed or its opening degree is reduced to stop discharging the processing liquid or to reduce the amount of discharged liquid. It is composed of Here, set an upper limit value and a lower limit value with a certain width for the set value, and when the detected value exceeds the upper limit value, discharge of the processing liquid is started, and conversely, when the detected value increases The discharge of the processing liquid may be stopped when the value becomes smaller than the lower limit value. At this time, even if the detected value is located within the width of the set value, the control valve 20 does not operate at all, and this width of the set value constitutes a so-called insensitive zone.

Note that this set value is normally set to an allowable concentration of the treatment liquid Cl concentration.

On the other hand, the dust removal tower 2 is provided with a second flow rate control means 21 that supplies water in order to maintain a constant amount of the processing liquid 3 in the processing liquid tank 11, which tends to be insufficient. This control means 21 is mainly composed of a water level gauge 22 that detects the position of the liquid level in the processing liquid tank 11, and a water supply passage 23 that supplies insufficient water. When the amount of water decreases by more than 1, the opening/closing valve 24 provided in the water supply passage 23 is opened to supply water into the processing liquid tank 11.

The operation of the present invention configured as above will be described.

Exhaust gas 1 discharged from combustion equipment (not shown)
is introduced into the dust removal tower 2 through the exhaust gas inlet 14, and is brought into contact with the treatment liquid 3 that is being circulated and sprayed in this tower to perform dust removal treatment, and at the same time, the HCl gas and HF contained in this gas are removed. Impurities such as gas are removed. The dust-removed exhaust gas is discharged through the exhaust gas outlet 15, and then introduced into the absorption tower 4, where it is desulfurized and discharged into the atmosphere as cree gas.

On the other hand, as the dust removal process progresses in the dust removal tower 2, the Cl concentration of the treatment liquid in the treatment liquid tank 11 increases and exceeds a predetermined value.
This Cl concentration is detected by the Cl concentration detector 17 and transmitted to the calculation section 19 as a detected value. In this calculation section 19, a comparison calculation process is performed between a set value set in advance to a desired Cl concentration and the above-mentioned detected value. For example, this set value has a certain width, and in response to the detected value rising to exceed the upper limit of the set value, the processing liquid discharge passage 7
The flow control valve 20 provided in the is opened, and the processing liquid 3
will be discharged outside the tower. As the treatment liquid is discharged, the water level in the treatment liquid tank 11 decreases, and this water level is constantly detected by the water level gauge 22. Here, when this water level decreases beyond a certain value, an on-off valve 24 installed in the water supply passage 23
is opened, and water supply into the processing liquid tank 11 is started. Along with this water supply, the processing liquid tank 1
The Cl ions in 1 are diluted and the Cl concentration gradually decreases, and when this concentration decreases beyond the lower limit of the set value, the flow control valve 20
is closed and the discharge of the processing liquid is stopped, thereby making it possible to maintain the Cl concentration of the processing liquid 3 at a substantially constant allowable concentration. Therefore, the collected Cl
As the volume increases, the amount of wastewater increases accordingly,
In addition, if the amount of collected Cl decreases, the amount of wastewater will decrease correspondingly, and the amount of wastewater collected will be reduced.
It can be increased or decreased depending on the amount of Cl.

Note that when the water level in the treatment liquid tank 11 reaches a predetermined level, this water level is detected by the water level gauge 22 and the water supply is stopped by closing the on-off valve 24 interposed in the water supply passage 23. The water level will be maintained at a nearly constant level.

Next, a second embodiment of the present invention will be described.

FIG. 3 is a schematic system diagram showing a second embodiment of the exhaust gas treatment device according to the present invention.

As shown in the figure, this processing apparatus employs a desulfurization method without a dust removal tower, and dust removal processing and desulfurization processing are performed simultaneously in an absorption tower 4 provided as an exhaust gas treatment tower. A flue gas inlet 25 is provided in the lower side wall of the absorption tower 4, and a flue gas outlet 26 is provided in the upper portion for discharging the flue gas that has been subjected to dust removal and desulfurization treatment.
Further, an absorption liquid tank 27 for storing an absorption liquid as a processing liquid is provided at the lower part of the tower, and the absorption liquid 28 stored in this tank is transferred to a processing liquid circulation passage 29.
The absorbent liquid surface 28a is transferred to the upper part of the column through the tank, and is stored in the tank from the spray 30 provided at the upper part.
It is designed to be sprayed on top. This absorption liquid 28
For example, it is produced by dissolving limestone CaCo ₃ in water, and when it comes into contact with exhaust gas, it absorbs and removes sulfur oxide SOx as shown in the formula below, and also removes impurities such as soot, dust, HCl gas, HF gas, etc. contained in exhaust gas. can be removed at the same time.

CaCO ₃ + SO ₂ + 1/2H ₂ O → CaSO ₃ 1/2H ₂ O + CO ₂ ↑ An oxidation tower 31 is provided downstream of this absorption tower 4, and an oxidation tower 31 is provided from the absorption liquid tank 27 in the absorption tower through a passage 32. Calcium sulfite (CaSO ₃ .1/2H ₂ O), which is transferred and supplied by the pump, is reacted with air 33 as shown in the following formula to produce gypsum.

CaSO ₃・1/2H ₂ O + 1/2O ₂ + 3/2H ₂ O →CaSO ₄・2H ₂ O The slurry gypsum introduced can be separated into solid and liquid. A dehydrator 36 is provided further downstream of the thickener 34, and further removes moisture from the gypsum transferred from the thickener 34 through a passage 37 to recover gypsum 38, and also separates the gypsum. The moisture is returned to the strainer 34 via the passage 39.

On the other hand, a stiffener overflow water passage 40 is provided from the stiffener 34 to the treated liquid tank 27 of the absorption tower 4, and the overflow water from which solids have been removed is returned to the absorption tower 4 and circulated. It is ready for use.

And this Shitsukuna overflow water passage 4
In the middle of 0, there is a Cl to detect the Cl concentration of the overflow water (processing liquid) flowing through this.
A concentration detector 17 is provided, and a processing liquid discharge passage 7 is provided in a branched manner in the middle of this passage for discharging a portion of the overflow water (processing liquid) flowing therein to the outside of the system. It is being

Furthermore, the detected value obtained by the Cl concentration detector 17 is determined by the first flow rate control means 18 which is a feature of the present invention.
It has become possible to transmit information to This flow rate control means 18 includes a calculation unit 19 that mainly performs calculation processing as in the first embodiment, and the discharge passage 7 that controls the discharge amount of the processing liquid (stiffener overflow water) based on the calculation result. Flow control valve 2 installed in
0.

In addition, the absorption liquid 28 which is becoming insufficient in the absorption tower 4
The first step is to supply water to maintain a constant amount of water.
A second flow rate control means 21 similar to the embodiment is provided.

Next, the operation of the second embodiment configured as above will be described.

First, the exhaust gas 1 discharged from the combustion equipment (not shown) is introduced into the absorption tower 4 through the exhaust gas inlet 25, and is desulfurized by contacting with the absorption liquid 28 that is circulated and sprayed into the tower. At the same time, impurities such as HCl gas and HF gas are also removed. The calcium sulfite slurry produced here is introduced into the oxidation tower 31 through the passage 32, where it is oxidized to produce gypsum.
The produced gypsum slurry is further introduced into a thickener 34 via a passage 35, where it is concentrated.

The concentrated gypsum is then introduced into a dehydrator 36 via a passage 37, where it is dehydrated to obtain dry gypsum 38, and at the same time, the removed separated liquid is passed through a passage 39. Shitsukuna 3 again
It will be introduced into 4.

On the other hand, the overflow water in the water tanker 34 is a supernatant liquid from which the solid content has been removed. As the process progresses, the Cl concentration in this overflow water increases. This Cl concentration is detected by the Cl concentration detector 17 provided in the passage 40 and transmitted to the calculation unit 19. This detected value is compared with a set value having a preset constant width as in the previous embodiment, and in response to the detected value exceeding the upper limit of the set value, the processing liquid discharge passage 7
The flow control valve 20 provided in the flow control valve 20 is opened or the degree of opening thereof is increased to start discharging the processing liquid (overflow water) or to increase the discharge amount. Conversely, when the detected value becomes smaller than the lower limit of the set value, the flow control valve 20 is closed or its opening degree is reduced to stop discharging the processing liquid, or Reduce emissions.

Here, the water level in the absorption liquid tank 27 will decrease as the treatment liquid is discharged, but this fluctuation in the water level is detected by the water level gauge 22, and if the water level falls below a certain level, the water level in the water supply passage 27 will decrease. On-off valve 2 installed in
4 is opened to supply water into the absorption liquid tank 27. As a result, the Cl ion content is diluted and water is supplied in an amount commensurate with the amount of discharge, and the amount of absorption liquid is always maintained at a substantially constant amount.

In this way, by detecting the Cl concentration in the processing solution,
We decided to control the amount of processing liquid discharged so that this detected value always maintains a nearly constant value (set value), so as the amount of Cl recovered from the exhaust gas increases, the amount of treatment liquid discharged increases accordingly. If the amount of recovered Cl increases and the amount of Cl recovered decreases, the amount of treated liquid discharged will decrease accordingly, and there will be no need for wasted water supply.

In short, according to the present invention, the following excellent effects can be achieved.

(1) We decided to detect the Cl concentration in the processing solution and control the discharge amount of the processing solution so that this detected value maintains an approximately constant allowable concentration. It can be increased or decreased depending on the amount.

(2) Therefore, a large amount of treatment liquid is not discharged even if the Cl concentration falls significantly below the permissible concentration as in the conventional example, and water resources can be used effectively.

(3) Even if the Cl content in the exhaust gas fluctuates due to a change in the combustion amount or a difference in the Cl content in the fuel, the amount of processing liquid discharged will automatically change accordingly, making maintenance easy. be.

(4) Since the structure is simple, it can be easily adopted into existing equipment.

[Brief explanation of the drawing]

Fig. 1 is a schematic system diagram showing a conventional wet exhaust gas treatment device, Fig. 2 is a schematic system diagram showing a first embodiment of the present invention, and Fig. 3 is a schematic system diagram showing a second embodiment of the present invention. be. In addition, in the figure 2...dust removal tower, 4...absorption tower, 3...
...Processing liquid, 28...Absorbing liquid, 7...Processing liquid discharge passage, 11...Processing liquid tank, 27...Absorbing liquid tank, 17
...Cl concentration detector, 18...First flow rate control means, 19...Calculation unit, 20...Flow rate control valve, 21
...Second flow rate control means, 22...Water level gauge, 23
...Water supply passage, 40...Shitsukuna overflow water passage.

Claims (1)

[Scope of utility model registration request] The treatment liquid stored in the treatment liquid tank provided at the bottom of the flue gas treatment tower is transferred to the upper part of the treatment tower and is sprayed and circulated on the surface of the treatment liquid, so that this sprayed treatment liquid and exhaust gas containing chlorine compounds are transferred. In a wet exhaust gas treatment device that processes exhaust gas by bringing it into contact, a treatment liquid discharge passage for discharging the treatment liquid to the outside of the tower, a Cl concentration detector for detecting the Cl concentration in the treatment liquid, and the detector a first flow rate control means that compares a detected value obtained from the above with a preset set value and discharges the processing liquid from the discharge passage in response to the detected value exceeding the set value; A second system that supplies water to maintain a constant amount of processing liquid in the liquid tank.
A wet exhaust gas treatment device comprising a flow rate control means.