System and method for realizing zero emission of flue gas desulfurization wastewater

Abstract

The invention belongs to the field of pollutant control of coal-fired power plants, and particularly relates to a system and a method for realizing zero emission of flue gas desulfurization wastewater. Comprising a fan, a storage bin and an ejector which are connected in sequence, and the fan ejects an adsorbent in the storage bin to a flue; the tail gas treatment device comprises an electrostatic dust collector, a desulfurization tower, a wastewater treatment system and a chimney; the electrostatic dust collector is connected with the tail end of the flue and then connected with the desulfurization tower; the desulfurization wastewater recovery device comprises a sedimentation tank, a feeding tank and a nozzle, the sedimentation tank is respectively connected with the desulfurization tower and the feeding tank, after desulfurization wastewater flows out of the desulfurization tower, one part of the desulfurization wastewater enters the wastewater treatment system, the other part of the desulfurization wastewater enters the sedimentation tank, and the nozzle sprays clear liquid on the upper layer of the sedimentation tank into a flue for treatment. The adsorbent is sprayed before the flue gas enters the electrostatic dust collector, the concentration of Cl <-> in the flue gas is reduced, the desulfurization wastewater is precipitated and then circulated to the flue for treatment, and zero emission of the desulfurization wastewater is achieved.

Description

Technical Field

[0001] The present invention belongs to the field of pollutant control in coal-fired power plants, and particularly relates to a system and method for realizing zero discharge of flue gas desulfurization wastewater. Background Art

[0002] At present, the limestone-gypsum wet desulfurization process is widely used in the flue gas desulfurization process of domestic coal-fired power plants due to its high desulfurization efficiency, stable operation of equipment, and good reliability. However, when the concentration of chloride ions in the flue gas is too high, the limestone solution is inhibited, and it is necessary to regularly discharge the desulfurization wastewater containing heavy metals, high salts, and high suspended solids to ensure the stability of the system and the flue gas desulfurization efficiency. This desulfurization wastewater is difficult to treat, and if directly discharged, it will cause secondary pollution to the environment.

[0003] Currently, existing power plants pay more and more attention to the zero discharge of desulfurization wastewater, but the operating cost is the main problem at present. Therefore, developing a new type of dechlorination technology with safety, environmental protection, economy and high efficiency is of great significance for achieving the goal of zero discharge of desulfurization wastewater in power plants. Summary of the Invention

[0004] [[ID=1ó]]The purpose of the present invention is to provide a system and method for realizing zero discharge of desulfurization wastewater by dechlorinating flue gas, which can absorb HCl in the flue gas, thereby reducing the concentration of HCl entering the desulfurization tower, reducing the amount of desulfurization wastewater, and recycling the reacted desulfurization wastewater to the flue for treatment, ultimately achieving the goal of zero discharge of desulfurization wastewater.

[0005] The technical solution for realizing the purpose of the present invention is: A system for realizing zero discharge of flue gas desulfurization wastewater, comprising:

[0006] An adsorbent injection device: used for injecting a dechlorination adsorbent into the flue;

[0007] An exhaust gas treatment device: including an electrostatic precipitator, a desulfurization tower, a wastewater treatment system, and a chimney. The electrostatic precipitator is connected to the end of the flue, and the rear end of the electrostatic precipitator is connected to the desulfurization tower;

[0008] A desulfurization wastewater recovery device: including a sedimentation tank, a nozzle, and a pH control system. The pH value of the desulfurization wastewater in the sedimentation tank is controlled by the pH control system, and the supernatant of the sedimentation tank is sprayed into the flue through the nozzle.

[0009] Further, the adsorbent injection device includes a fan, a storage bin, and an injector connected in sequence, and the dechlorination adsorbent in the storage bin is injected into the flue by the fan.

[0010] Further, the dechlorination adsorbent in the storage bin is calcium oxide or calcium hydroxide.

[0011] Further, a desulfurizing agent is provided in the desulfurization tower, and the desulfurizing agent is limestone slurry or ammonia water.

[0012] Further, the desulfurized wastewater recovery device further includes a water pump I, a water pump II, a feeding tank, and a water pump III.

[0013] The desulfurized wastewater generated by the desulfurization tower enters the sedimentation tank under the action of the water pump I. There is lime milk in the feeding tank, and the lime milk is added into the sedimentation tank through the water pump III, and the addition amount of the lime milk is controlled by a pH control system. The supernatant of the sedimentation tank is sprayed into the flue through a nozzle under the action of the water pump II.

[0014] A method for realizing zero discharge of flue gas desulfurized wastewater, based on the above system, includes the following steps:

[0015] Step (1): The storage bin is filled with a dechlorination adsorbent. After the fan is started, the ejector evenly sprays the dechlorination adsorbent into the flue to absorb HCl.

[0016] Step (2): The electrostatic precipitator is connected to the end of the flue, and uses an electric field to capture the fly ash attached with HCl in the flue gas and the adsorbent after HCl is removed.

[0017] Step (3): One end of the electrostatic precipitator is connected to a desulfurization tower, which is filled with a desulfurization agent to remove SO2 in the flue gas. Part of the generated desulfurized wastewater enters the wastewater treatment system, and the other part enters the sedimentation tank under the action of the water pump I.

[0018] Step (4): The feeding tank is filled with lime milk, enters the sedimentation tank through the water pump III, and the flow rate is adjusted through a pH control system to react with the desulfurized wastewater to generate precipitation.

[0019] Step (5): After the desulfurized wastewater in the sedimentation tank is precipitated, the upper alkaline supernatant is sprayed into the flue through a nozzle under the action of the water pump II to generate droplets, which are neutralized with the acidic gas in the flue gas to realize zero discharge of the desulfurized wastewater.

[0020] Further, in step (4), the pH of the desulfurized wastewater in the sedimentation tank is adjusted to 8.5 - 9.5 through the pH control system.

[0021] Further, for flue gas treatment in coal-fired power plants

[0022] Compared with the prior art, the significant advantages of the present invention are as follows:

[0023] 1. The present invention sprays an adsorbent into the flue to absorb HCl, thereby effectively removing the target pollutants.

[0024] 2. The present invention absorbs the fly ash attached with HCl in the flue gas and the adsorbent after HCl is removed through the electrostatic precipitator, effectively reducing the chloride ion concentration in the desulfurization tower, thereby reducing the amount of desulfurized wastewater and ensuring the stability and desulfurization efficiency of the desulfurization tower.

[0025] 3. The present invention adds chemicals into the sedimentation tank through a feeding tank to adjust the pH of the desulfurized wastewater, causing a precipitation reaction. The upper alkaline clear liquid is sprayed into the flue for recovery treatment, achieving zero discharge of the desulfurized wastewater. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 It is a schematic diagram of the system for zero discharge of wastewater in the present invention.

[0027] DESCRIPTION OF THE REFERENCE NUMERALS:

[0028] 1 - sedimentation tank, 2 - storage bin, 3 - nozzle, 4 - flue, 5 - electrostatic precipitator, 6 - desulfurization tower, 7 - water pump I, 8 - water pump II, 9 - fan, 10 - HCl, 11 - fly ash, 12 - droplet, 13 - feeding tank, 14 - water pump III, 15 - ejector, 16 - wastewater treatment system, 17 - chimney, 18 - pH control system. DETAILED DESCRIPTION OF THE INVENTION

[0029] The present invention will be further described in detail below with reference to the drawings.

[0030] As Figure 1 shown, a system for realizing zero discharge of desulfurized wastewater by flue gas dechlorination includes

[0031] Adsorbent injection device: including a fan 9, a storage bin 2, and an ejector 15 connected in sequence; the fan 9 is used to inject the adsorbent in the storage bin 2 into the flue 4.

[0032] Tail gas treatment device: including an electrostatic precipitator 5, a desulfurization tower 6, a wastewater treatment system 16, and a chimney ١٧; the electrostatic precipitator 5 is connected to the end of the flue 4 and then connected to the desulfurization tower 6.

[0033] Desulfurized wastewater recovery device: including a sedimentation tank 1, a pH control system 18, a feeding tank 13, and a nozzle 3 at the end of the connecting pipeline. The sedimentation tank 1 is respectively connected to the desulfurization tower 6 and the feeding tank 13. A part of the desulfurized wastewater from the desulfurization tower 6 enters the wastewater treatment system 16, and the other part enters the sedimentation tank 1. The nozzle (3) sprays the clear liquid on the upper layer of the sedimentation tank 1 into the flue 4 for treatment.

[0034] The ejector 15 is placed inside the flue 4 and can adjust the adsorbent injection rate to evenly inject the adsorbent in the storage bin 2 into the flue 4.

[0035] The adsorbent in the storage bin 2 is a dechlorination adsorbent, which can be calcium oxide or calcium hydroxide, etc. Its function is to absorb HCl in the flue gas and reduce the Cl - concentration.

[0036] The electrostatic precipitator 5 uses an electric field to capture the fly ash 11 attached with HCl in the flue gas and the adsorbent after HCl is removed.

[0037] The desulfurization agent in the desulfurization tower 6 can be an alkaline solution such as limestone slurry or ammonia water, which is used to remove gases such as SO2 in the flue gas, and then the desulfurized wastewater is produced and enters the sedimentation tank 1.

[0038] The feeding tank 13 contains lime milk, which enters the sedimentation tank 1 under the action of the water pump Ⅲ14.

[0039] The lime milk can adjust the pH of the desulfurized wastewater to 8.5 - 9.5, so that some heavy metal ions such as Fe 3+ 、Cu 2+ etc. generate hydroxide precipitates.

[0040] The pH control system 18 can detect the pH of the sedimentation tank 1 in real time and flexibly control the delivery volume of the feeding tank 13.

[0041] After the reaction in the sedimentation tank 1, the upper layer is alkaline clear liquid, which is sprayed into the flue duct 4 through the nozzle 3 at the end of the pipeline under the action of the water pump Ⅱ8.

[0042] The nozzle 3 is placed in the flue duct 4. Its function is to atomize the alkaline clear liquid on the upper layer of the sedimentation tank, generate a large number of liquid droplets 12, and distribute them evenly in the flue duct 4.

[0043] The atomization of the alkaline clear liquid specifically means spraying the desulfurized wastewater after the reaction into the flue duct 4 for recovery treatment, neutralizing with acidic gases such as HCl in the flue gas, and realizing zero discharge of the desulfurized wastewater.

[0044] The method provided by the present invention includes the following steps:

[0045] Step 1. The storage bin 2 is filled with a dechlorination adsorbent. After the fan 9 is started, the ejector 15 evenly sprays the dechlorination adsorbent into the flue duct 4 to absorb HCl and reduce the Cl - concentration.

[0046] Step 2. The electrostatic precipitator 5 is connected to the end of the flue duct 4, and uses an electric field to capture the fly ash 11 attached with HCl in the flue gas and the adsorbent after removing HCl.

[0047] Step 3. One end of the electrostatic precipitator 5 is connected to the desulfurization tower 6, which is filled with a desulfurization agent (such as an alkaline solution like limestone slurry or ammonia water) to remove gases such as SO2 in the flue gas. A part of the generated desulfurized wastewater enters the wastewater treatment system, and the other part enters the sedimentation tank 1 under the action of the water pump Ⅰ7.

[0048] Step 4. The feeding tank 13 is filled with a lime milk solution, which enters the sedimentation tank 1 through the water pump Ⅲ14. The flow rate is adjusted through the pH control system 18, and a reaction occurs with the desulfurized wastewater to generate a precipitate.

[0049] Step 5. After the desulfurized wastewater in the sedimentation tank 1 is precipitated, the upper alkaline clear liquid is sprayed into the flue 4 through the nozzle 3 under the action of the water pump II 8, generating a large number of droplets 12, which neutralize acidic gases such as HCl in the flue gas, achieving zero discharge of desulfurized wastewater.

Claims

1. A system for realizing zero discharge of flue gas desulfurization wastewater, characterized in that, including an adsorbent injection device: for injecting a dechlorination adsorbent into the flue; an exhaust gas treatment device: including an electrostatic precipitator (5), a desulfurization tower (6), a waste water treatment system (16) and a chimney (17), the electrostatic precipitator (5) is connected to the end of the flue (4), and the rear end of the electrostatic precipitator (5) is connected to the desulfurization tower (6); a desulfurized waste water recovery device: including a sedimentation tank (1), a nozzle (3) and a pH control system (18), the pH value of the desulfurized waste water in the sedimentation tank (1) is controlled by the pH control system (18), and the supernatant of the sedimentation tank (1) is sprayed into the flue (4) through the nozzle (3).

2. The system according to claim 1, characterized in that, The adsorbent injection device includes a blower (9), a storage bin (2) and an injector (15) connected in sequence, and the dechlorination adsorbent in the storage bin (2) is sprayed into the flue (4) by the blower (9).

3. The system according to claim 2, wherein The dechlorination adsorbent in the storage bin (2) is calcium oxide or calcium hydroxide.

4. The system according to claim 3, wherein A desulfurizing agent is provided in the desulfurization tower (6), and the desulfurizing agent is limestone slurry or ammonia water.

5. The system according to claim 4, characterized in that The desulfurized waste water recovery device further includes a water pump I (7), a water pump II (8), a feeding tank (13) and a water pump III (14), the desulfurized waste water generated by the desulfurization tower (6) enters the sedimentation tank (1) under the action of the water pump I (7), lime milk is provided in the feeding tank (13), the lime milk is added into the sedimentation tank (1) through the water pump III (14), and the addition amount of the lime milk is controlled by the pH control system (18), and the supernatant of the sedimentation tank (1) is sprayed into the flue (4) through the nozzle (3) under the action of the water pump II (8).

6. A method for realizing zero discharge of flue gas desulfurization wastewater, characterized in that The system according to any one of claims 1-5 includes the following steps: Step (1): The storage bin (2) is filled with a dechlorination adsorbent. After the blower (9) is started, the injector (15) evenly sprays the dechlorination adsorbent into the flue (4) to absorb HCl; Step (2): The electrostatic precipitator (5) is connected to the end of the flue (4), and the fly ash (11) attached with HCl in the flue gas and the adsorbent after HCl is removed are captured by the electric field; Step (3): One end of the electrostatic precipitator (5) is connected to a desulfurization tower (6), which is filled with a desulfurizing agent for removing SO2 in the flue gas. A part of the generated desulfurized waste water enters the waste water treatment system, and the other part enters the sedimentation tank (1) under the action of the water pump I (7); Step (4): The feeding tank (13) is filled with lime milk, which enters the sedimentation tank (1) through the water pump III (14), and the flow rate is adjusted by the pH control system (18) to react with the desulfurized waste water to generate precipitation; Step (5): After the desulfurized waste water in the sedimentation tank (1) is precipitated, the upper alkaline supernatant is sprayed into the flue (4) through the nozzle (3) under the action of the water pump II (8) to generate droplets (12), which are neutralized with the acidic gas in the flue gas to achieve zero discharge of desulfurized waste water.

7. The method according to claim 6, wherein In step (4), the pH of the desulfurized waste water in the sedimentation tank is adjusted to 8.5-9.5 by the pH control system (18).

8. The method according to claim 6 or 7, characterized in that, It is used for flue gas treatment in coal-fired power plants.

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