阅读说明：本技术 一种湿法烟气脱硫系统和湿法烟气脱硫方法 (Wet flue gas desulfurization system and wet flue gas desulfurization method ) 是由 郑岩峰 杨丁 郑进朗 张仲梁 于 2021-11-02 设计创作，主要内容包括：本发明属于环保领域,尤其涉及一种湿法烟气脱硫系统和湿法烟气脱硫方法。本发明提供的脱硫系统包括：石灰石制浆池、石灰石-石膏法烟气脱硫塔、石膏浆分离设备、石膏脱水设备、回收水池、废水分离设备、化学沉淀设备、高级氧化反应器和外排水管道。本发明提供的系统通过增设高级氧化反应器,并将高级氧化去除LAS的脱硫废水返回到脱硫塔中,能够将脱硫塔内的LAS浓度控制在较低水平,从而消除脱硫塔起泡的根源因素,进而可以使脱硫系统在高氯离子浓度条件下正常运行,即实现脱硫系统的高浓缩倍率运行,显著减少脱硫废水的排放量。此外,该系统的排外废水COD值较低,具有良好的环境效益。(The invention belongs to the field of environmental protection, and particularly relates to a wet flue gas desulfurization system and a wet flue gas desulfurization method. The desulfurization system provided by the invention comprises: the system comprises a limestone-gypsum method flue gas desulfurization tower, gypsum slurry separation equipment, gypsum dehydration equipment, a recovery water tank, wastewater separation equipment, chemical precipitation equipment, an advanced oxidation reactor and an external drainage pipeline. According to the system provided by the invention, the advanced oxidation reactor is additionally arranged, and the desulfurization wastewater with the LAS removed by advanced oxidation is returned to the desulfurization tower, so that the concentration of the LAS in the desulfurization tower can be controlled at a lower level, the bubbling root factor of the desulfurization tower is eliminated, the desulfurization system can normally operate under the condition of high chloride ion concentration, namely, the high-concentration multiple operation of the desulfurization system is realized, and the discharge amount of the desulfurization wastewater is remarkably reduced. In addition, the COD value of the discharged wastewater of the system is lower, and the system has good environmental benefit.)

1. A wet flue gas desulfurization system, comprising:

a limestone pulping tank;

the limestone-gypsum method flue gas desulfurization tower is connected with the slurry outlet of the limestone pulping tank;

the gypsum slurry separation equipment is connected with a gypsum slurry outlet of the limestone-gypsum method flue gas desulfurization tower;

gypsum dewatering equipment connected with the underflow port of the gypsum slurry separation equipment;

a recovery water tank connected to the overflow port of the gypsum slurry separation apparatus and the water discharge port of the gypsum dewatering apparatus, respectively; the recovery water tank is provided with a first water outlet and a second water outlet, and the first water outlet is connected with the limestone pulping tank;

the waste water separation equipment is connected with the second water outlet of the recovery water tank; the bottom flow port of the wastewater separation equipment is connected back to the recovery water tank;

the chemical precipitation equipment is connected with the overflow port of the wastewater separation equipment;

the advanced oxidation reactor and the external drainage pipeline are connected with a clear liquid outlet of the chemical precipitation equipment; and the water outlet of the advanced oxidation reactor is connected with the limestone pulping tank or the limestone-gypsum method flue gas desulfurization tower.

2. The wet flue gas desulfurization system of claim 1, wherein the advanced oxidation reactor is an ozone oxidation reactor, a UV-Ti photocatalytic oxidation reactor, a UV-H₂O₂A photocatalytic oxidation reactor or a fenton reactor.

3. The wet flue gas desulfurization system of claim 1, wherein the gypsum slurry separation device is a gypsum cyclone.

4. The wet flue gas desulfurization system of claim 1, wherein the wastewater separation device is a wastewater cyclone.

5. The wet flue gas desulfurization system of claim 1, wherein the chemical precipitation equipment comprises a wastewater treatment triple box and a settling tank;

the wastewater treatment triple box comprises a neutralization tank, a reaction tank and a flocculation tank which are arranged in series, wherein a water inlet of the neutralization tank is connected with an overflow port of the wastewater separation equipment;

and the water inlet of the sedimentation tank is connected with the water outlet of the flocculation tank, and the clear liquid outlet of the sedimentation tank is respectively connected with the water inlet of the advanced oxidation reactor and the external drainage pipeline.

6. The wet flue gas desulfurization system of claim 1, further comprising a process water delivery conduit;

and the water outlet end of the process water conveying pipeline is respectively connected with the desulfurization absorption tower and the gypsum dehydration device.

7. The wet flue gas desulfurization system of claim 1, further comprising a wastewater collection tank;

the waste water collecting tank is arranged between an overflow port of the waste water separating equipment and a water inlet of the chemical precipitation equipment, the water inlet of the waste water collecting tank is connected with the overflow port of the waste water separating equipment, and a water outlet of the waste water collecting tank is connected with the water inlet of the chemical precipitation equipment.

8. A wet flue gas desulfurization method, which is performed in the wet flue gas desulfurization system of claim 1, comprising the steps of:

preparing limestone slurry from limestone powder in a limestone slurry preparation tank, and conveying the limestone slurry serving as a desulfurization absorbent to a limestone-gypsum method flue gas desulfurization tower;

raw flue gas enters a limestone-gypsum method flue gas desulfurization tower from a raw flue gas inlet and is in countercurrent contact with slurry sprayed on the top of the tower; in the process of countercurrent contact, the slurry absorbs sulfur dioxide in the original flue gas, then falls into the bottom of the tower, and the desulfurized clean flue gas is discharged from a clean flue gas outlet at the top of the tower; the slurry falling into the tower bottom reacts with air blown into the tower through an air inlet, so that calcium sulfite in the slurry is oxidized into gypsum; a part of the tower bottom slurry is sent to the tower top through a slurry circulating pipeline and is sprayed out again, and the other part of the tower bottom slurry is discharged through a gypsum slurry outlet arranged at the tower bottom;

the discharged tower bottom slurry enters gypsum slurry separation equipment for separation to respectively obtain wet gypsum and gypsum slurry separation wastewater;

discharging the wet gypsum through a bottom flow port of gypsum slurry separation equipment, and dehydrating in gypsum dehydration equipment to respectively obtain dry gypsum and dehydrated water;

the gypsum slurry separation wastewater is discharged through an overflow port of the gypsum slurry separation equipment, and converges with the dehydrated water discharged by the gypsum dehydration equipment into a recovery water tank, and part of the water in the recovery water tank is returned to the limestone slurry making tank as recovered water to participate in slurry making; the other part is conveyed to a wastewater separation device for separation, the underflow obtained by separation is returned to a recovery water tank, and the overflow obtained by separation enters a chemical precipitation device;

carrying out chemical precipitation on overflow from the wastewater separation equipment in chemical precipitation equipment to obtain clear liquid;

discharging the clear liquid through a clear liquid port of chemical precipitation equipment, continuously treating a part of clear liquid in an advanced oxidation reactor, and returning the treated effluent to a limestone pulping pool to participate in pulping or to a limestone-gypsum flue gas desulfurization tower to participate in desulfurization; the other part of clear liquid is taken as discharged wastewater and enters a discharged water discharging pipeline;

in the period, process water is periodically added into the wet flue gas desulfurization system to maintain the material balance of slurry in the limestone-gypsum flue gas desulfurization tower.

9. The wet flue gas desulfurization method of claim 8, wherein the effluent of the advanced oxidation reactor has a concentration of sodium linear alkylbenzene sulfonate of 0.5mg/L or less.

10. The wet flue gas desulfurization method of claim 8, wherein the chloride ion concentration of the effluent wastewater is not less than 30000 mg/L.

Technical Field

The invention belongs to the field of environmental protection, and particularly relates to a wet flue gas desulfurization system and a wet flue gas desulfurization method.

Background

With the increasing environmental protection in China, a flue gas desulfurization device is generally arranged in the thermal power industry. Limestone-gypsum Wet Flue Gas Desulfurization (WFGD) technology becomes the leading technology of flue gas desulfurization at home and abroad due to a series of advantages of wide coal application range, high desulfurization efficiency and the like. In the process of washing flue gas by wet desulphurization, flue gas fly ash is washed and enters limestone-gypsum slurry, harmful substances such as chloride ions, heavy metal ions and the like contained in the flue gas fly ash also enter a flue gas desulphurization system, and in the process of gypsum treatment, the flue gas fly ash enters a desulphurization wastewater link along with washing water, so that the desulphurization wastewater rich in heavy metals and chloride ions is formed. In order to maintain the mass balance of the slurry circulation system of the desulfurization apparatus, prevent the corrosion of desulfurization equipment, and ensure the quality of gypsum, a certain amount of wastewater must be discharged from the system.

At present, most of desulfurization wastewater of power plants is directly discharged after being treated by a conventional method, and the conventional desulfurization wastewater treatment mainly adopts a triple-box process of neutralization, reaction and flocculation or a new process of electric flocculation and the like, so that wastewater containing more salt substances is finally discharged. The wastewater contains more cations such as calcium, magnesium, copper, iron, manganese and the like and Cl^-、SO₄ ^2-Although the plasma can be discharged after reaching the standard, the direct discharge still causes serious pollution to the water body. Only a few domestic power plants are forced to require zero discharge of the desulfurization wastewater due to special reasons, and the advanced treatment technology of the desulfurization wastewater is still in a groping stage, so that the method is a plant side. It can be seen that the discharge amount of the desulfurization wastewater directly affects the difficulty of zero discharge and the investment cost.

Cl in desulfurization wastewater^-The chlorine element contained in the coal is converted into HCl after being combusted in a hearth of a boiler, the HCl is absorbed by desulfurization slurry, the limestone serving as an absorbent can be ground into fine powder, and the contained chlorine element, heavy metal and the like can be quickly dissolved out in a slurry pool. Due to Cl^-Has very stable chemical property and does not change the concentration caused by chemical reaction, so that Cl is often used in the circulating concentration process of the slurry^-The concentration change of the slurry is used for judging the concentration degree of the slurry and determining whether pollution discharge is needed or not, so that the Cl in the desulfurization wastewater at present^-The concentration is the main parameter for determining whether the desulfurization waste water is discharged or not. Under the condition that the conditions allow, the discharge amount of the waste water can be reduced by increasing the concentration multiple as much as possible.

Because coal quality, limestone components, make-up water quality, the operation mode of a desulfurization absorption tower and the like all have direct influence on the water quality of desulfurization wastewater, representative water quality data of the desulfurization wastewater are difficult to provide, the water quality of the desulfurization wastewater of different thermal power plants has great difference, even if the same wet desulphurization system is used, the water quality can be changed frequently due to frequent change of the coal quality and the make-up water, and even different water qualities can be obtained in different time intervals. The industry standard DL/T1477-2015 technical supervision and guide rule of desulfurization unit of thermal power plant also clearly requires strict control of Cl in the slurry of the absorption tower^-The content is less than 10000mg/L, and the commonly recognized water balance calculation of the current design unit is based on Cl of the desulfurization wastewater^-The content is not higher than 20000 mg/L. After actual research, the domestic wet desulphurization waste water Cl is^-The content is generally less than 10000mg/L, mainly because Cl is taken as a nominal parameter of desulfurized wastewater^-Once the content is high, the desulfurization efficiency is reduced, and even the operation parameters of desulfurization operation are influenced, and the Cl can be reduced by discharging wastewater in advance^-The content of the sulfur-containing compound can easily maintain the desulfurization performance, so that the emission of most of desulfurization wastewater is higher, and a great burden is added to subsequent zero emission.

From the above analysis, it can be seen that the prior art generally recognized Cl of desulfurized wastewater^-The content is a direct cause of the influence on the desulfurization operation.In order to reduce the discharge of the desulfurization waste water, various methods for reducing or removing Cl from the desulfurization waste water are provided^-Content techniques, e.g. reverse osmosis, forward osmosis, electrodialysis, or desalination by membrane methods, or reduction of Cl by ion exchange, extraction, or the like^-The content of HCl in the flue gas is even removed by adopting NaOH powder from the flue gas side so as to reduce Cl in the desulfurization wastewater^-Content of Cl is generally considered as only the desulfurized wastewater Cl^-The content is reduced, so that the wastewater can be returned to the tower for recycling, and Cl is actually treated^-The content reduction, particularly the membrane method desalination method, can realize the return recycling of the desulfurization waste water to the tower and the reduction of the desulfurization waste water. However, due to Cl^-Chemical property of itself is extremely stable, and Cl is added^-The removal from the waste water is very difficult, so the method has high investment cost and brings great economic burden to enterprises.

Disclosure of Invention

In view of the above, the present invention provides a wet flue gas desulfurization system and a wet flue gas desulfurization method, and the desulfurization system provided by the present invention can realize high concentration multiple operation, so as to effectively reduce the discharge amount of desulfurization wastewater.

The invention provides a wet flue gas desulfurization system, comprising:

a limestone pulping tank;

the limestone-gypsum method flue gas desulfurization tower is connected with the slurry outlet of the limestone pulping tank;

the gypsum slurry separation equipment is connected with a gypsum slurry outlet of the limestone-gypsum method flue gas desulfurization tower;

gypsum dewatering equipment connected with the underflow port of the gypsum slurry separation equipment;

a recovery water tank connected to the overflow port of the gypsum slurry separation apparatus and the water discharge port of the gypsum dewatering apparatus, respectively; the recovery water tank is provided with a first water outlet and a second water outlet, and the first water outlet is connected with the limestone pulping tank;

the waste water separation equipment is connected with the second water outlet of the recovery water tank; the bottom flow port of the wastewater separation equipment is connected back to the recovery water tank;

the chemical precipitation equipment is connected with the overflow port of the wastewater separation equipment;

the advanced oxidation reactor and the external drainage pipeline are connected with a clear liquid outlet of the chemical precipitation equipment; and the water outlet of the advanced oxidation reactor is connected with the limestone pulping tank or the limestone-gypsum method flue gas desulfurization tower.

Preferably, the advanced oxidation reactor is an ozone oxidation reactor, a UV-Ti photocatalytic oxidation reactor or a UV-H photocatalytic oxidation reactor₂O₂A photocatalytic oxidation reactor or a fenton reactor.

Preferably, the gypsum slurry separation device is a gypsum cyclone.

Preferably, the wastewater separation device is a wastewater cyclone.

Preferably, the chemical precipitation equipment comprises a wastewater treatment triple box and a precipitation tank;

the wastewater treatment triple box comprises a neutralization tank, a reaction tank and a flocculation tank which are arranged in series, wherein a water inlet of the neutralization tank is connected with an overflow port of the wastewater separation equipment;

and the water inlet of the sedimentation tank is connected with the water outlet of the flocculation tank, and the clear liquid outlet of the sedimentation tank is respectively connected with the water inlet of the advanced oxidation reactor and the external drainage pipeline.

Preferably, the system also comprises a process water conveying pipeline;

and the water outlet end of the process water conveying pipeline is respectively connected with the desulfurization absorption tower and the gypsum dehydration device.

Preferably, the system also comprises a waste water collecting tank;

the waste water collecting tank is arranged between an overflow port of the waste water separating equipment and a water inlet of the chemical precipitation equipment, the water inlet of the waste water collecting tank is connected with the overflow port of the waste water separating equipment, and a water outlet of the waste water collecting tank is connected with the water inlet of the chemical precipitation equipment.

The invention provides a wet flue gas desulfurization method, which is carried out in the wet flue gas desulfurization system in the technical scheme and comprises the following steps:

preparing limestone slurry from limestone powder in a limestone slurry preparation tank, and conveying the limestone slurry serving as a desulfurization absorbent to a limestone-gypsum method flue gas desulfurization tower;

raw flue gas enters a limestone-gypsum method flue gas desulfurization tower from a raw flue gas inlet and is in countercurrent contact with slurry sprayed on the top of the tower; in the process of countercurrent contact, the slurry absorbs sulfur dioxide in the original flue gas, then falls into the bottom of the tower, and the desulfurized clean flue gas is discharged from a clean flue gas outlet at the top of the tower; the slurry falling into the tower bottom reacts with air blown into the tower through an air inlet, so that calcium sulfite in the slurry is oxidized into gypsum; a part of the tower bottom slurry is sent to the tower top through a slurry circulating pipeline and is sprayed out again, and the other part of the tower bottom slurry is discharged through a gypsum slurry outlet arranged at the tower bottom;

the discharged tower bottom slurry enters gypsum slurry separation equipment for separation to respectively obtain wet gypsum and gypsum slurry separation wastewater;

discharging the wet gypsum through a bottom flow port of gypsum slurry separation equipment, and dehydrating in gypsum dehydration equipment to respectively obtain dry gypsum and dehydrated water;

the gypsum slurry separation wastewater is discharged through an overflow port of the gypsum slurry separation equipment, and converges with the dehydrated water discharged by the gypsum dehydration equipment into a recovery water tank, and part of the water in the recovery water tank is returned to the limestone slurry making tank as recovered water to participate in slurry making; the other part is conveyed to a wastewater separation device for separation, the underflow obtained by separation is returned to a recovery water tank, and the overflow obtained by separation enters a chemical precipitation device;

carrying out chemical precipitation on overflow from the wastewater separation equipment in chemical precipitation equipment to obtain clear liquid;

discharging the clear liquid through a clear liquid port of chemical precipitation equipment, continuously treating a part of clear liquid in an advanced oxidation reactor, and returning the treated effluent to a limestone pulping pool to participate in pulping or to a limestone-gypsum flue gas desulfurization tower to participate in desulfurization; the other part of clear liquid is taken as discharged wastewater and enters a discharged water discharging pipeline;

in the period, process water is periodically added into the wet flue gas desulfurization system to maintain the material balance of slurry in the limestone-gypsum flue gas desulfurization tower.

Preferably, the concentration of the linear alkyl benzene sodium sulfonate in the effluent of the advanced oxidation reactor is less than or equal to 0.5 mg/L.

Preferably, the chloride ion concentration of the discharged wastewater is more than or equal to 30000 mg/L.

Compared with the prior art, the invention provides a wet flue gas desulfurization system and a wet flue gas desulfurization method. The desulfurization system provided by the invention comprises: a limestone pulping tank; the limestone-gypsum method flue gas desulfurization tower is connected with the slurry outlet of the limestone pulping tank; the gypsum slurry separation equipment is connected with a gypsum slurry outlet of the limestone-gypsum method flue gas desulfurization tower; gypsum dewatering equipment connected with the underflow port of the gypsum slurry separation equipment; a recovery water tank connected to the overflow port of the gypsum slurry separation apparatus and the water discharge port of the gypsum dewatering apparatus, respectively; the recovery water tank is provided with a first water outlet and a second water outlet, and the first water outlet is connected with the limestone pulping tank; the waste water separation equipment is connected with the second water outlet of the recovery water tank; the bottom flow port of the wastewater separation equipment is connected back to the recovery water tank; the chemical precipitation equipment is connected with the overflow port of the wastewater separation equipment; the advanced oxidation reactor and the external drainage pipeline are connected with a clear liquid outlet of the chemical precipitation equipment; and the water outlet of the advanced oxidation reactor is connected with the limestone pulping tank or the limestone-gypsum method flue gas desulfurization tower. The invention overcomes the technical prejudices that the excessive concentration of chloride ions generally believed in the field can cause the foaming of the desulfurization slurry and the virtual high liquid level of the slurry, thereby influencing the operation of a desulfurization system, reducing the desulfurization efficiency and increasing the power consumption, and finds that the inevitable linear alkyl sodium benzenesulfonate (LAS) in the process water for desulfurization is the root cause of slurry bubbles, and the concentration of the chloride ions only reflects the level of the LAS on the side surface. Based on this, the invention no longer focuses on the reduction of the concentration of chloride ions in the desulfurization slurry, and the concentration of chloride ions is only a nominal parameter of the concentration ratio of the desulfurization absorption tower. The system provided by the invention can control the LAS concentration in the desulfurizing tower at a lower level by returning the desulfurizing wastewater from which the LAS is removed by advanced oxidation to the desulfurizing tower, thereby eliminating the root factor of foaming of the desulfurizing tower, further enabling the desulfurizing system to normally operate under the condition of high chloride ion concentration, namely realizing the high-concentration multiple operation of the desulfurizing system, and remarkably reducing the discharge amount of the desulfurizing wastewater. Moreover, by arranging the advanced oxidation reactor, the COD value of the desulfurization wastewater of the system can be obviously reduced, so the system has more obvious technical advantages in the areas with higher raw water COD value and COD limit value discharge.

Drawings

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, it is obvious that the drawings in the following description are only embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to the provided drawings without creative efforts.

FIG. 1 is a process flow diagram of a wet flue gas desulfurization system provided by an embodiment of the present invention;

FIG. 2 is a process flow diagram of a wet flue gas desulfurization system in accordance with a comparative example of the present invention.

Detailed Description

The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

The invention provides a wet flue gas desulfurization system, comprising:

a limestone pulping tank;

the limestone-gypsum method flue gas desulfurization tower is connected with the slurry outlet of the limestone pulping tank;

the gypsum slurry separation equipment is connected with a gypsum slurry outlet of the limestone-gypsum method flue gas desulfurization tower;

gypsum dewatering equipment connected with the underflow port of the gypsum slurry separation equipment;

a recovery water tank connected to the overflow port of the gypsum slurry separation apparatus and the water discharge port of the gypsum dewatering apparatus, respectively; the recovery water tank is provided with a first water outlet and a second water outlet, and the first water outlet is connected with the limestone pulping tank;

the waste water separation equipment is connected with the second water outlet of the recovery water tank; the bottom flow port of the wastewater separation equipment is connected back to the recovery water tank;

the chemical precipitation equipment is connected with the overflow port of the wastewater separation equipment;

the advanced oxidation reactor and the external drainage pipeline are connected with a clear liquid outlet of the chemical precipitation equipment; and the water outlet of the advanced oxidation reactor is connected with the limestone pulping tank or the limestone-gypsum method flue gas desulfurization tower.

Referring to fig. 1, fig. 1 is a process flow diagram of a wet flue gas desulfurization system provided by an embodiment of the invention. In fig. 1, 1 is a limestone pulping tank, 2 is a limestone-gypsum method flue gas desulfurization tower, 2-1 is a raw flue gas inlet, 2-2 is a clean flue gas outlet, 2-3 is a slurry circulating pipeline, 2-4 is a gypsum slurry outlet, 2-5 is an air inlet, 2-6 is an oxidation fan, 3 is a gypsum slurry separation device, 4 is a gypsum dewatering device, 5 is a recovery water tank, 6 is a wastewater separation device, 7 is a wastewater collection tank, 8 is a wastewater treatment triple box, 8-1 is a neutralization tank, 8-2 is a reaction tank, 8-3 is a flocculation tank, 9 is a sedimentation tank, 10 is an advanced oxidation reactor, and 11 is an external drainage pipeline.

The wet flue gas desulfurization system provided by the invention comprises: the system comprises a limestone-gypsum method flue gas desulfurization tower 1, a limestone-gypsum method flue gas desulfurization tower 2, gypsum slurry separation equipment 3, gypsum dehydration equipment 4, a recovery water tank 5, waste water separation equipment 6, chemical precipitation equipment, an advanced oxidation reactor 10 and an external drainage pipeline 11.

In the desulfurization system provided by the invention, a limestone slurry preparation tank 1 is used for preparing limestone slurry, and is provided with a limestone powder feed inlet, a water inlet and a slurry outlet, and a stirring device is preferably arranged in the tank.

In the desulfurization system provided by the invention, a limestone-gypsum method flue gas desulfurization tower 2 is reaction equipment for performing flue gas desulfurization and generating gypsum, a raw flue gas inlet 2-1 is arranged on the side wall of a tower kettle, a purified flue gas outlet 2-2 is arranged at the top of the tower, a circulating slurry outlet, a gypsum slurry outlet 2-4 and an air inlet 2-5 are arranged at the bottom of the tower, the circulating slurry outlet is connected with a liquid inlet end of a slurry circulating pipeline 2-3 of the desulfurization tower, a liquid outlet end of the slurry circulating pipeline 2-3 is connected with a slurry spraying device arranged at the top of an inner cavity of the desulfurization tower, and the air inlet 2-5 is connected with an oxidation fan 2-6 matched with the air inlet.

In the desulfurization system provided by the invention, the gypsum slurry separation equipment 3 is used for carrying out solid-liquid separation on the discharged gypsum slurry of the limestone-gypsum method flue gas desulfurization tower 2, a feed inlet, an overflow port and a bottom flow port are arranged on the gypsum slurry separation equipment, and the feed inlet of the gypsum slurry separation equipment 3 is connected with the gypsum slurry outlet of the limestone-gypsum method flue gas desulfurization tower 2. In one embodiment provided by the present invention, the gypsum slurry separation device 3 is specifically selected to be a gypsum cyclone.

In the desulfurization system provided by the invention, the gypsum dewatering equipment 4 is used for dewatering wet gypsum discharged from the underflow port of the gypsum slurry separation equipment 3, and is provided with a feed inlet, a dry material outlet and a water outlet, wherein the feed inlet of the gypsum dewatering equipment 4 is connected with the underflow port of the gypsum slurry separation equipment 3. In one embodiment provided by the present invention, the gypsum dewatering device 4 is specifically selected from a vacuum belt conveyor.

In the desulfurization system provided by the invention, the recovery water tank 5 is used for recovering overflow separated by the gypsum slurry separation equipment 3 and dewatering water of the gypsum dewatering equipment 4, and indirectly returning part of the recovery water to the tower for recycling, a water inlet, a first water outlet and a second water outlet are arranged on the recovery water tank, a stirring device is preferably arranged in the recovery water tank, the water inlet of the recovery water tank 5 is respectively connected with an overflow port of the gypsum slurry separation equipment 3 and a water outlet of the gypsum dewatering equipment 4, and the first water outlet of the recovery water tank 5 is connected with a water inlet of the limestone slurry making tank 1.

In the desulfurization system provided by the invention, the wastewater separation equipment 6 is used for circularly treating the recovered water in the recovery water tank 5, the treated underflow returns to the tank, a water inlet, an overflow port and a underflow port are arranged on the underflow return, and the water inlet of the wastewater separation equipment 6 is connected with the second water outlet of the recovery water tank 5. In one embodiment provided by the present invention, the waste water separating device 6 is specifically selected as a waste water cyclone.

In the desulfurization system provided by the invention, the chemical precipitation device is used for chemically precipitating the overflow of the wastewater separation device 6, a water inlet and a clear liquid outlet are arranged on the chemical precipitation device, and the water inlet of the chemical precipitation device is connected with the overflow port of the wastewater separation device 6. In one embodiment provided by the present invention, the chemical precipitation apparatus comprises a wastewater treatment triple box 8 and a precipitation tank 9; the wastewater treatment triple box 8 specifically comprises a neutralization tank 8-1, a reaction tank 8-2 and a flocculation tank 8-3 which are arranged in series, wherein a water inlet of the neutralization tank 8-1 is connected with an overflow port of the wastewater separation equipment 6; the water inlet of the sedimentation tank 9 is connected with the water outlet of the flocculation tank 8-3. In the invention, the neutralization tank 8-1 is used for adding alkali liquor to adjust the pH value of the wastewater, preferably, the pH value is adjusted to be more than 8.5, and more preferably, the pH value is 8.5-9.5; the reaction tank 8-2 is used for carrying out mixed reaction of the wastewater and organic sulfides, wherein the organic sulfides include but are not limited to TMT-15, and the adding concentration of the organic sulfides is preferably controlled to be 1-5 wt%; the flocculation tank 8-3 is used for carrying out mixed reaction of the wastewater and a flocculating agent, and the adding amount of the flocculating agent is preferably controlled to be 0.1-0.3 wt%.

In the desulfurization system provided by the invention, a wastewater collecting tank 7 is preferably arranged between the overflow port of the wastewater separation equipment 6 and the water inlet of the chemical precipitation equipment and used for caching the overflow of the wastewater separation equipment 6, a water inlet and a water outlet are arranged on the wastewater collecting tank, a stirring device is preferably arranged in the tank, the water inlet of the wastewater collecting tank 7 is connected with the overflow port of the wastewater separation equipment 6, and the water outlet of the wastewater collecting tank 7 is connected with the water inlet of the chemical precipitation equipment. In the embodiment of the chemical precipitation equipment provided by the invention comprising the wastewater treatment triple box 8 and the precipitation tank 9, the water outlet of the wastewater collection tank 7 is connected with the water inlet of the neutralization tank 8-1.

In the desulfurization system provided by the invention, the advanced oxidation reactor 10 is used for performing advanced oxidation treatment on part of effluent after the chemical precipitation treatment, destructively removing linear alkyl sodium benzenesulfonate (LAS) in a water body, and directly or indirectly returning the treated effluent to the tower for recycling, a water inlet and a water outlet are arranged on the advanced oxidation reactor 10, the water inlet of the advanced oxidation reactor 10 is connected with a clear liquid outlet of the chemical precipitation equipment, and the water outlet of the advanced oxidation reactor 10 is connected with a water inlet of a limestone-gypsum method flue gas desulfurization tower 2 or a water inlet of a limestone-gypsum method pulping tank 1. In the embodiment of the present invention where the chemical precipitation apparatus comprises a wastewater treatment triple box 8 and a precipitation tank 9, the water inlet of the advanced oxidation reactor 10 is connected to the clear liquid outlet of the precipitation tank 9. In one embodiment provided by the present invention, the advanced oxidation reactor 10 is specifically selected from an ozone oxidation reactor, a UV-Ti photocatalytic oxidation reactor, and a UV-H catalytic oxidation reactor₂O₂A photocatalytic oxidation reactor or a fenton reactor.

In the desulfurization system provided by the invention, the external drainage pipeline 11 is used for discharging part of the effluent after the chemical precipitation treatment out of the desulfurization system, and the water inlet end of the external drainage pipeline 11 is also connected with the clear liquid outlet of the chemical precipitation equipment. In the embodiment of the chemical precipitation equipment provided by the invention, which comprises the wastewater treatment triple box 8 and the precipitation tank 9, the water inlet end of the external drainage pipeline 11 is connected with the clear liquid outlet of the precipitation tank 9.

In the desulfurization system provided by the invention, the system also comprises a process water conveying pipeline which is used for periodically supplementing process water to the desulfurization system so as to maintain the material balance of slurry in the limestone-gypsum method flue gas desulfurization tower; the water outlet end of the process water conveying pipeline is preferably connected with the desulfurization absorption tower and the gypsum dehydration device respectively.

The invention also provides a wet flue gas desulfurization method, which is carried out in the wet flue gas desulfurization system in the technical scheme and comprises the following steps:

limestone powder is prepared into limestone slurry in a limestone slurry preparation tank 1, and the limestone slurry is used as a desulfurization absorbent and is conveyed to a limestone-gypsum method flue gas desulfurization tower 2;

raw flue gas enters a flue gas desulfurization tower 2 by a limestone-gypsum method from a raw flue gas inlet 2-1 and is in countercurrent contact with slurry sprayed on the top of the tower; in the process of countercurrent contact, the slurry absorbs sulfur dioxide in the original flue gas, then falls into the bottom of the tower, and the desulfurized clean flue gas is discharged from a clean flue gas outlet 2-2 at the top of the tower; the slurry falling into the bottom of the tower reacts with air blown into the tower through an air inlet 2-5, so that calcium sulfite in the slurry is oxidized into gypsum; a part of the tower bottom slurry is sent to the tower top through a slurry circulating pipeline 2-3 to be sprayed out again, and the other part of the tower bottom slurry is discharged through a gypsum slurry outlet 2-4 arranged at the tower bottom;

the discharged tower bottom slurry enters a gypsum slurry separation device 3 for separation, and wet gypsum and gypsum slurry separation wastewater are respectively obtained;

discharging the wet gypsum through a bottom flow port of the gypsum slurry separation equipment 3, and dehydrating the wet gypsum in gypsum dehydration equipment 4 to respectively obtain dry gypsum and dehydrated water;

the gypsum slurry separation wastewater is discharged through an overflow port of the gypsum slurry separation equipment 3 and converged into a recovery water tank 5 together with the dehydrated water discharged by the gypsum dehydration equipment 4, and part of the water in the recovery water tank is returned to the limestone slurry making tank 1 as recovered water to participate in pulping; the other part is conveyed to a wastewater separation device 6 for separation, the underflow obtained by the separation is returned to a recovery water tank 5, and the overflow obtained by the separation enters a chemical precipitation device;

carrying out chemical precipitation on the overflow from the wastewater separation equipment 6 in chemical precipitation equipment to obtain clear liquid;

discharging the clear liquid through a clear liquid port of chemical precipitation equipment, continuously treating a part of clear liquid in an advanced oxidation reactor 10, and returning the treated effluent to a limestone pulping pool 1 for pulping or a limestone-gypsum method flue gas desulfurization tower 2 for desulfurization; the other part of clear liquid is taken as discharged wastewater and enters a discharged water discharging pipeline 11;

in the period, process water is periodically added into the wet flue gas desulfurization system to maintain the material balance of slurry in the limestone-gypsum flue gas desulfurization tower.

In the wet flue gas desulfurization method provided by the invention, linear alkyl benzene sulfonic acid sodium (LAS) inevitably exists in the process water, and the concentration of the linear alkyl benzene sulfonic acid sodium in the process water can be more than or equal to 1 mg/L. In one embodiment provided by the invention, the concentration of the linear alkyl benzene sulfonic acid sodium in the process water is 1.5-2 mg/L. In one embodiment provided by the invention, the concentration of chloride ions in the process water is 100-500 mg/L, more specifically 300 mg/L. In one embodiment of the invention, the COD value of the process water is 50-300 mg/L, more specifically 100-200 mg/L.

In the wet flue gas desulfurization method provided by the invention, the concentration of the effluent linear alkyl sodium benzenesulfonate of the advanced oxidation reactor 10 is preferably less than 1mg/L, more preferably less than or equal to 0.7mg/L, and most preferably less than or equal to 0.5 mg/L.

In the wet flue gas desulfurization method provided by the invention, the maximum value of the concentration of the linear alkyl benzene sulfonic acid sodium in the slurry in the limestone-gypsum flue gas desulfurization tower 2 is preferably controlled to be 5-10 mg/L, and specifically can be 5mg/L, 5.5mg/L, 6mg/L, 6.5mg/L, 7mg/L, 7.5mg/L, 8mg/L, 8.5mg/L, 9mg/L, 9.5mg/L or 10 mg/L. In one embodiment provided by the invention, the concentration of the linear alkyl benzene sulfonic acid sodium in the slurry in the limestone-gypsum method flue gas desulfurization tower 2 is preferably controlled to be 1-3 mg/L, and specifically can be 2 mg/L.

In the wet flue gas desulfurization method provided by the invention, the chloride ion concentration of the discharged wastewater is preferably controlled to be more than or equal to 30000mg/L, more preferably to be 30000 mg/L-the highest chloride ion corrosion resistant concentration of equipment of a desulfurization system, and most preferably to be 30000-50000 mg/L.

In the wet flue gas desulfurization method provided by the invention, the concentration of the linear alkyl benzene sulfonic acid sodium in the discharged wastewater is basically consistent with that of the linear alkyl benzene sulfonic acid sodium in the slurry in the limestone-gypsum flue gas desulfurization tower 2.

In the wet flue gas desulfurization method provided by the invention, the COD value of the discharged wastewater can be controlled to be less than or equal to 200mg/L, more preferably less than or equal to 150mg/L, and most preferably less than or equal to 100 mg/L.

The technical scheme provided by the invention starts from reducing the LAS concentration of the slurry, and can perform destructive removal on the LAS in the desulfurization wastewater by additionally arranging the advanced oxidation reactor, and then directly or indirectly returning the desulfurization wastewater without the LAS to the tower for circulation. According to the technical scheme provided by the invention, the desulfurization wastewater from which the LAS is removed by advanced oxidation is returned to the desulfurization tower, so that the concentration of the LAS in the desulfurization tower can be controlled at a lower level, the root factor of foaming of the desulfurization tower is eliminated, the desulfurization system can normally operate under the condition of high chloride ion concentration, namely, the high-concentration-ratio operation of the desulfurization system is realized, and the discharge amount of the desulfurization wastewater is remarkably reduced. In addition, by arranging the advanced oxidation reactor, the COD value of the discharged desulfurization wastewater in the technical scheme of the invention can be obviously reduced, so that the technical scheme of the invention has more obvious technical advantages in areas with higher raw water COD value and COD limit value discharge.

In addition, in the preferred technical scheme provided by the invention, the advanced oxidation reactor is an ozone oxidation reactor, and the ozone oxidation reactor has the advantages of low equipment investment, simple structure, no need of medicament consumables, no sludge byproducts and the like while having excellent LAS and COD removal capacity, and is very suitable for the desulfurization system.

For the sake of clarity, the following examples are given in detail.

Example 1

(1) The wet flue gas desulfurization system provided in this embodiment as shown in fig. 1 includes: the system comprises a limestone-gypsum method flue gas desulfurization tower 1, a limestone-gypsum method flue gas desulfurization tower 2, gypsum slurry separation equipment 3, gypsum dehydration equipment 4, a recovery water tank 5, wastewater separation equipment 6, a wastewater collection tank 7, a wastewater treatment triple box 8, a sedimentation tank 9, an advanced oxidation reactor 10 and an external drainage pipeline 11; the side wall of a tower kettle of the limestone-gypsum method flue gas desulfurization tower 2 is provided with a raw flue gas inlet 2-1, the top of the tower is provided with a clean flue gas outlet 2-2, the bottom of the tower is provided with a circulating slurry outlet, a gypsum slurry outlet 2-4 and an air inlet 2-5, the circulating slurry outlet is connected with the liquid inlet end of a slurry circulating pipeline 2-3 of the desulfurization tower, the liquid outlet end of the slurry circulating pipeline 2-3 is connected with a slurry spraying device arranged at the top of an inner cavity of the desulfurization tower, and the air inlet 2-5 is connected with an oxidation fan 2-6 matched with the air inlet; the gypsum slurry separation equipment 3 specifically selects a gypsum cyclone; the gypsum dewatering equipment 4 specifically selects a vacuum belt conveyor; the wastewater separation equipment 6 specifically selects a wastewater cyclone; the wastewater treatment triple box 8 specifically comprises a neutralization tank 8-1, a reaction tank 8-2 and a flocculation tank 8-3 which are arranged in series; the advanced oxidation reactor 10 is specifically an ozone oxidation reactor; the specific connection relationship of each device is shown in fig. 1, and is not described again.

(2) The embodiment also provides a process method for performing flue gas desulfurization in the system, which comprises the following steps:

limestone powder is prepared into limestone slurry in a limestone slurry preparation tank 1, and the limestone slurry is used as a desulfurization absorbent and is conveyed to a limestone-gypsum method flue gas desulfurization tower 2;

raw flue gas enters a flue gas desulfurization tower 2 by a limestone-gypsum method from a raw flue gas inlet 2-1 and is in countercurrent contact with slurry sprayed on the top of the tower; in the process of countercurrent contact, the slurry absorbs sulfur dioxide in the original flue gas, then falls into the bottom of the tower, and the desulfurized clean flue gas is discharged from a clean flue gas outlet 2-2 at the top of the tower; the slurry falling into the bottom of the tower reacts with air blown into the tower through an air inlet 2-5, so that calcium sulfite in the slurry is oxidized into gypsum; a part of the tower bottom slurry is sent to the tower top through a slurry circulating pipeline 2-3 to be sprayed out again, and the other part of the tower bottom slurry is discharged through a gypsum slurry outlet 2-4 arranged at the tower bottom;

the discharged tower bottom slurry enters a gypsum slurry separation device 3 for separation, and wet gypsum and gypsum slurry separation wastewater are respectively obtained;

discharging the wet gypsum through a bottom flow port of the gypsum slurry separation equipment 3, and dehydrating the wet gypsum in gypsum dehydration equipment 4 to respectively obtain dry gypsum and dehydrated water;

the gypsum slurry separation wastewater is discharged through an overflow port of the gypsum slurry separation equipment 3 and converged into a recovery water tank 5 together with the dehydrated water discharged by the gypsum dehydration equipment 4, and part of the water in the recovery water tank is returned to the limestone slurry making tank 1 as recovered water to participate in pulping; the other part is conveyed to a wastewater separation device 6 for separation, the underflow obtained by the separation is returned to a recovery water tank 5, and the overflow obtained by the separation enters a chemical precipitation device;

the overflow from the wastewater separation equipment 6 is conveyed into a wastewater collection tank 7, then enters a wastewater treatment triple box 8 to be sequentially subjected to neutralization, organic sulfide mixing reaction and flocculation, and then is precipitated in a precipitation tank 9 to obtain clear liquid;

the clear liquid is discharged through a clear liquid port of the sedimentation tank 9, a part of clear liquid enters the advanced oxidation reactor 10 for continuous treatment, and the effluent obtained after treatment returns to the limestone pulping tank 1 to participate in pulping; the other part of clear liquid is taken as discharged wastewater and enters a discharged water discharging pipeline 11;

and during the operation period of the system, periodically supplementing process water to the limestone-gypsum method flue gas desulfurization tower 2 so as to maintain the material balance of slurry in the limestone-gypsum method flue gas desulfurization tower.

In the flue gas desulfurization process method provided by the embodiment, the adopted process water is the reclaimed water of which town sewage does not meet the reuse standard, and the concentration of chloride ions in the raw water is 300mg/L, LAS and is 1.5-2 mg/L, COD and is 100-200 mg/L;

in the above flue gas desulfurization process method provided by this embodiment, during the operation of the system, the LAS concentration of the effluent from the advanced oxidation reactor 10 is 0.5 mg/L;

in the above flue gas desulfurization process provided by this embodiment, during the operation of the system, the LAS concentration in the slurry in the limestone-gypsum flue gas desulfurization tower 2 is controlled at 2 mg/L;

in the flue gas desulfurization process method provided by the embodiment, during the operation period of the system, the chloride ion concentration of the discharged wastewater is 30000mg/L, the LAS concentration is 2mg/L, the COD value is 100mg/L, and the discharge amount of the wastewater is 5 t/h;

in the above-mentioned flue gas desulfurization process provided in this embodiment, during the operation of the system, the slurry bubbling in the limestone-gypsum flue gas desulfurization tower 2 is observed, and the results are: no obvious foaming is seen, the liquid level of the absorption tower is clear and accurate, the flow and the current of the slurry circulating pump are stable, and the operation is stable without cavitation.

It can be seen that the concentration of chloride ions in the discharged wastewater reaches 30000mg/L when the wet flue gas desulfurization system provided by the embodiment operates, stable operation with high concentration ratio can be realized, the COD of the wastewater is as low as 100mg/L, the wastewater is not increased due to concentration of the absorption tower, and the industrial wastewater discharge standard in most areas can be met.

Comparative example 1

(1) The comparative example provides a wet flue gas desulfurization system as shown in fig. 2, including: the system comprises a limestone-gypsum method flue gas desulfurization tower 1, a limestone-gypsum method flue gas desulfurization tower 2, gypsum slurry separation equipment 3, gypsum dehydration equipment 4, a recovery water tank 5, wastewater separation equipment 6, a wastewater collection tank 7, a wastewater treatment triple box 8, a sedimentation tank 9 and an external drainage pipeline 11; the side wall of a tower kettle of the limestone-gypsum method flue gas desulfurization tower 2 is provided with a raw flue gas inlet 2-1, the top of the tower is provided with a clean flue gas outlet 2-2, the bottom of the tower is provided with a circulating slurry outlet, a gypsum slurry outlet 2-4 and an air inlet 2-5, the circulating slurry outlet is connected with the liquid inlet end of a slurry circulating pipeline 2-3 of the desulfurization tower, the liquid outlet end of the slurry circulating pipeline 2-3 is connected with a slurry spraying device arranged at the top of an inner cavity of the desulfurization tower, and the air inlet 2-5 is connected with an oxidation fan 2-6 matched with the air inlet; the gypsum slurry separation equipment 3 specifically selects a gypsum cyclone; the gypsum dewatering equipment 4 specifically selects a vacuum belt conveyor; the wastewater separation equipment 6 specifically selects a wastewater cyclone; the wastewater treatment triple box 8 specifically comprises a neutralization tank 8-1, a reaction tank 8-2 and a flocculation tank 8-3 which are arranged in series; the specific connection relationship of each device is shown in fig. 2, and is not described again.

(2) The comparative example also provides a process for flue gas desulfurization in the above system, comprising the steps of:

limestone powder is prepared into limestone slurry in a limestone slurry preparation tank 1, and the limestone slurry is used as a desulfurization absorbent and is conveyed to a limestone-gypsum method flue gas desulfurization tower 2;

raw flue gas enters a flue gas desulfurization tower 2 by a limestone-gypsum method from a raw flue gas inlet 2-1 and is in countercurrent contact with slurry sprayed on the top of the tower; in the process of countercurrent contact, the slurry absorbs sulfur dioxide in the original flue gas, then falls into the bottom of the tower, and the desulfurized clean flue gas is discharged from a clean flue gas outlet 2-2 at the top of the tower; the slurry falling into the bottom of the tower reacts with air blown into the tower through an air inlet 2-5, so that calcium sulfite in the slurry is oxidized into gypsum; a part of the tower bottom slurry is sent to the tower top through a slurry circulating pipeline 2-3 to be sprayed out again, and the other part of the tower bottom slurry is discharged through a gypsum slurry outlet 2-4 arranged at the tower bottom;

the discharged tower bottom slurry enters a gypsum slurry separation device 3 for separation, and wet gypsum and gypsum slurry separation wastewater are respectively obtained;

discharging the wet gypsum through a bottom flow port of the gypsum slurry separation equipment 3, and dehydrating the wet gypsum in gypsum dehydration equipment 4 to respectively obtain dry gypsum and dehydrated water;

the gypsum slurry separation wastewater is discharged through an overflow port of the gypsum slurry separation equipment 3 and converged into a recovery water tank 5 together with the dehydrated water discharged by the gypsum dehydration equipment 4, and part of the water in the recovery water tank is returned to the limestone slurry making tank 1 as recovered water to participate in pulping; the other part is conveyed to a wastewater separation device 6 for separation, the underflow obtained by the separation is returned to a recovery water tank 5, and the overflow obtained by the separation enters a chemical precipitation device;

the overflow from the wastewater separation equipment 6 is conveyed into a wastewater collection tank 7, then enters a wastewater treatment triple box 8 to be sequentially subjected to neutralization, organic sulfide mixing reaction and flocculation, and then is precipitated in a precipitation tank 9 to obtain clear liquid;

the clear liquid is discharged through a clear liquid port of the sedimentation tank 9 and enters an external drainage pipeline 11 as external wastewater;

and during the operation period of the system, periodically supplementing process water to the limestone-gypsum method flue gas desulfurization tower 2 so as to maintain the material balance of slurry in the limestone-gypsum method flue gas desulfurization tower.

In the flue gas desulfurization process method provided by the comparative example, the adopted process water is the reclaimed water of which the town sewage does not meet the reuse standard, and the concentration of the chloride ions in the raw water is 300mg/L, LAS and is 1.5-2 mg/L, COD and is 100-200 mg/L;

in the flue gas desulfurization process method provided by the comparative example, during the operation of the system, the chloride ion concentration of the discharged wastewater is 5000mg/L, the LAS is 10mg/L, COD and 1000mg/L, and the discharge amount of the wastewater is 30 t/h.

It can be seen that, as no source of slurry foaming is found, in order to avoid the influence of the desulfurization slurry foaming on the operation stability of the system, the concentration of the chloride ions in the slurry can only be controlled at a lower level during the operation of the desulfurization system of the comparative example, and the concentration of the chloride ions in the waste water discharged outside is only 5000mg/L, so that the discharge amount of the waste water is remarkably increased and is 6 times of that of the waste water in example 1; in addition, the COD of the wastewater is up to 1000 mg/L; can not meet the discharge standard of industrial wastewater, so the wastewater can reach the discharge standard after further treatment, which undoubtedly increases the cost of flue gas desulfurization.

Comparative example 2

Referring to the wet flue gas desulfurization system and the flue gas desulfurization process method of comparative example 1, the difference is only that the concentration ratio of the system operation is gradually increased. The result shows that when the chloride ion concentration of the discharged wastewater reaches 4000mg/L, obvious foam begins to appear in the inner slurry of the limestone-gypsum method flue gas desulfurization tower 2; when the chloride ion concentration of the discharged wastewater reaches 6000mg/L, a large amount of foam is generated in the inner slurry of the limestone-gypsum method flue gas desulfurization tower 2, and the normal operation cannot be realized.

It can be seen that, because the LAS in the slurry cannot be removed, the wet flue gas desulfurization system of the comparative example can only operate normally under the condition that the concentration of chloride ions in the waste water is lower than 5000mg/L, and the increase of the concentration ratio can cause the foaming of the inner slurry of the limestone-gypsum flue gas desulfurization tower 2 and cannot operate normally.

Comparative example 3

Referring to the wet flue gas desulfurization system and the flue gas desulfurization process method of comparative example 1, the difference is that purified water without linear alkyl sodium benzenesulfonate (LAS) is used as make-up water of the desulfurization system, and the concentration ratio of the system operation is gradually increased. As a result, when the concentration of chloride ions in the discharged wastewater reaches 40000mg/L, no obvious foaming condition still occurs in the limestone-gypsum method flue gas desulfurization tower 2. It follows that LAS is the root cause for slurry bubbling, and that desulfurization systems can be kept operating at high concentration ratios as long as there is no LAS in the slurry.

The foregoing is only a preferred embodiment of the present invention, and it should be noted that, for those skilled in the art, various modifications and decorations can be made without departing from the principle of the present invention, and these modifications and decorations should also be regarded as the protection scope of the present invention.