System and method for efficient discharge of wet desulfurization wastewater

Abstract

The application discloses a system and method for efficient discharge of wet desulfurization wastewater, which comprises a desulfurization tower, a slurry temporary storage tank, a slurry discharge pump, a desulfurization wastewater discharge outlet and a gypsum dehydration system, a liquid outlet at the bottom of the desulfurization tower is connected with the slurry temporary storage tank by a pipeline through a 1# valve, a stirrer is arranged on the slurry temporary storage tank, two liquid outlets are arranged on the side of the slurry temporary storage tank, and the two liquid outlets are connected with the inlet of the slurry discharge pump by pipelines through 2# and 3# valves respectively, the installation height of the 2# valve is close to the bottom of the slurry temporary storage tank, and the installation height of the 3# valve is greater than the height of the sediment layer after the slurry in the slurry temporary storage tank is fully deposited; the outlet of the slurry discharge pump is divided into two paths, and the two paths are connected with the desulfurization wastewater discharge outlet and the gypsum dehydration system by pipelines. The application can realize efficient grading discharge of chloride ions and fine particles in the desulfurization slurry, and can be independent of the gypsum dehydration system when the desulfurization slurry is poisoned or foamed and needs to be replaced in large quantities in an emergency, so that efficient slurry replacement and discharge can be maintained.

Description

TECHNICAL FIELD

[0001] The present application relates to a system and method for efficient discharge of wet desulfurization wastewater. BACKGROUND

[0002] The limestone-gypsum wet desulfurization process for flue gas is widely used in large coal-fired power generating units and steel enterprises, etc., and has the main advantages of mature technology, strong adaptability to coal types and load, and deep desulfurization potential. Due to the large deviation of the coal delivered to the plant from the design coal type, insufficient combustion of the boiler, and untimely discharge of the desulfurization wastewater, etc., the enrichment of chloride ions and impurities in the desulfurization slurry occurs in some desulfurization systems, which leads to the limestone entering the reaction blind area, the desulfurization slurry foaming, and the corrosion of the equipment in the tower intensifying, etc. When the limestone enters the reaction blind area, the dissolution reaction of the limestone (CaCO3) in the desulfurization slurry is blocked, the activity decreases, and the pH value cannot quickly rise when the slurry supply is increased, which leads to a decrease in the desulfurization efficiency. After the desulfurization slurry foams, the liquid level in the tower is inaccurate, which causes the slurry to flow backward and affects the safe operation of the fan, and the decrease in the circulating slurry volume also causes the desulfurization efficiency to decrease. At the same time, the enrichment of chloride ions and impurities also causes the abnormality of the gypsum index, the increase in the water content of the gypsum, the excessive chloride ion content, the low content of CaSO4·2H2O, etc., which affects the sale of the gypsum.

[0003] The existing desulfurization wastewater is completed by relying on the operation of the gypsum dewatering system, and the desulfurization wastewater discharge system cannot be operated during the discharge of the gypsum, which cannot meet the emergency replacement demand during the system entering the blind area or the slurry foaming, and the desulfurization wastewater discharge has the disadvantages of low discharge efficiency, high solid content in the discharged wastewater, and increased discharge volume, which seriously affects the disposal efficiency and operation rate of the later-stage desulfurization wastewater treatment system. The existing technology desulfurization wastewater discharge process is shown in Figure 1 , the desulfurization slurry is fed into the gypsum dewatering system by the gypsum discharge pump, and the solid gypsum is discharged after being dewatered by the first-stage gypsum cyclone station and the second-stage vacuum belt machine, while the overflow from the first-stage dewatering and the filtrate from the second-stage dewatering are partly fed back to the absorption tower and partly used for discharging the desulfurization wastewater. The desulfurization wastewater discharge port 1 is the overflow water from the gypsum cyclone station (after the overflow water from the desulfurization wastewater discharge port 1 is fed into the desulfurization wastewater treatment system, the sludge and the clear water are respectively discharged after being separated by the plate and frame filter pressing). The desulfurization wastewater treatment system currently widely uses the triple box treatment technology, and the process flow of the wastewater treatment is shown in Figure 4 , and the technical feature is that the treatment is greatly affected by the desulfurization wastewater volume and the solid content in the wastewater), when the gypsum slurry particle size is low or the separation effect of the cyclone station is poor, the solid content in the wastewater from this discharge port may increase from the designed 2% to 8%, which leads to the decrease in the operation reliability of the plate and frame filter pressing system in the later-stage desulfurization wastewater treatment system; the desulfurization wastewater discharge port 2 is the suction filtrate from the belt dewatering machine, and the process water such as the flushing water and the sealing water during the gypsum dewatering is mixed into the wastewater, which leads to the chloride ion concentration in the wastewater decreasing to half of that in the desulfurization slurry, which leads to the discharge volume of the desulfurization wastewater doubling, which limits the treatment of the later-stage desulfurization wastewater disposal system.

[0004] In view of the low desulfurization wastewater discharge efficiency, the low disposal efficiency and the low operation rate of the desulfurization wastewater treatment system, the present application provides a system and method for efficient discharge of wet desulfurization wastewater, which can efficiently discharge chloride ions and fine particles in the desulfurization slurry, and reduce the sludge load and wastewater treatment capacity of the later-stage desulfurization wastewater treatment system. The present application has the following advantages: 1. The chloride ions and fine particles in the desulfurization slurry can be selectively discharged, thereby reducing the production pressure of the later-stage desulfurization wastewater treatment system; 2. The concentration of chloride ions in the discharged desulfurization wastewater is not reduced compared with that in the desulfurization slurry, and more chloride ions can be discharged under the same wastewater discharge capacity; 3. The desulfurization wastewater discharge system is independent of the gypsum dehydration system, thereby greatly improving the wastewater discharge efficiency during emergency replacement. That is, the desulfurization tower is equipped with two independent discharge systems during production, one of which is the device system of the present application, which is used as a normal channel for discharging desulfurization wastewater, and the purpose is to discharge desulfurization wastewater to reduce the Cl ions and fine particles in the desulfurization tower; the other is the existing conventional gypsum dehydration system, which is used to discharge solid gypsum to reduce the solid content in the desulfurization tower. SUMMARY

[0005] In order to solve the problems that the current desulfurization wastewater discharge can only rely on the operation of the gypsum dehydration system, and the solid content of the discharged wastewater is large and the discharge amount of the diluted desulfurization wastewater is greatly increased, the present application provides a system and method for efficient discharge of wet desulfurization wastewater, which can realize the efficient discharge of chloride ions and fine particles in the desulfurization slurry, and can be independent of the gypsum dehydration system when the desulfurization slurry is poisoned or foamed and needs to be replaced in large quantities, thereby maintaining efficient slurry replacement discharge.

[0006] The present application provides a system for efficient discharge of wet desulfurization wastewater, which adds an independent wastewater efficient discharge device compared with the original system, and the main system equipment is shown in Figure 2 .

[0007] The technical scheme adopted by the present application is as follows:

[0008] A system for efficient discharge of wet desulfurization wastewater, comprising a desulfurization tower, a slurry temporary storage tank, a slurry discharge pump, a desulfurization wastewater discharge outlet and a gypsum dehydration system, a liquid outlet at the bottom of the desulfurization tower is connected by a pipeline with the slurry temporary storage tank through a 1# valve, so that the desulfurization slurry at the bottom of the desulfurization tower is discharged into the slurry temporary storage tank, the desulfurization slurry is fully settled and is divided into a sediment layer and a desulfurization clear water layer from bottom to top, and the sediment layer comprises a lower gypsum crystal particle layer and an upper fine particle impurity layer.

[0009] A stirrer is arranged on the slurry temporary storage tank, and the gypsum crystal particle layer in the slurry temporary storage tank can be fully disturbed under the stirring action of the stirrer, and the stirring blade of the stirrer is located above the gypsum crystal particle layer.

[0010] Two liquid outlets are arranged on the side of the slurry temporary storage tank, and are connected by pipelines with the inlets of the slurry discharge pump through 2# valve and 3# valve respectively. The installation height of 2# valve is close to the bottom of the slurry temporary storage tank, and is used for emptying the gypsum slurry in the slurry temporary storage tank. The installation height of 3# valve is greater than the height of the sediment layer after the slurry in the slurry temporary storage tank is fully deposited. The outlet of the slurry discharge pump is divided into two routes, and is connected with the desulfurization wastewater outlet and the gypsum dehydration system by pipelines respectively. The desulfurization wastewater outlet is further connected with the desulfurization wastewater treatment system by a pipeline. The desulfurization wastewater treatment system is a conventional technology, and the process of treating the desulfurization wastewater is shown in Figure 4

[0011] Further, the slurry temporary storage tank in the present application is used for temporarily storing the desulfurization slurry and separating the water, fine particles and gypsum sediment in the slurry. The slurry temporary storage tank has the following characteristics: 1, the inner wall of the slurry temporary storage tank is provided with necessary corrosion protection measures such as glass flake coating; 2, the height of the slurry temporary storage tank is greater than the height of the overflow port of the desulfurization tower; 3, the top of the slurry temporary storage tank is provided with a vent hole to balance the atmospheric pressure in the slurry temporary storage tank; and 4, the slurry temporary storage tank is provided with a liquid level meter to facilitate monitoring the liquid level in the tank and the amount of wastewater discharge.

[0012] Further, the agitator of the slurry temporary storage tank is used for stirring and disturbing the fine particles and gypsum sediment in the slurry temporary storage tank. The agitator has the following characteristics: 1, the blade of the agitator is made of corrosion-resistant and wear-resistant stainless steel; 2, the height and diameter length of the blade from the bottom of the tank can meet the requirement that the gypsum in the slurry temporary storage tank is fully disturbed and there is no dead zone during the operation of the agitator. Therefore, the height of the blade from the bottom of the tank needs to be greater than the height of the surface of the gypsum crystal particle layer from the bottom of the tank, so as to prevent the blade of the agitator from being buried by the gypsum crystal particles and affect the stirring of the gypsum crystal particles. 3, the control motor of the agitator is a variable frequency motor, which can adjust the stirring speed.

[0013] Further, the water outlet of the gypsum dehydration system is divided into two routes, one of which is connected with the upper part of the slurry temporary storage tank by a pipeline through 4# valve, and the other of which is connected with the upper part of the desulfurization tower by a pipeline through 4# valve.

[0014] Further, the slurry discharge pump is used for quickly discharging the water and fine particles in the slurry temporary storage tank and emptying the slurry in the slurry temporary storage tank. The slurry discharge pump has the following characteristics: 1, when 3# valve is opened and 2# valve is closed, the desulfurization water or the mixed water of desulfurization water and fine particles is discharged to the desulfurization wastewater outlet for disposal; 2, when 2# valve is opened and 3# valve is closed, the gypsum slurry in the slurry temporary storage tank is discharged to the gypsum dehydration system; and 3, the slurry discharge pump and the inlet and outlet pipelines thereof are provided with a blow-off and flushing pipeline to prevent the pipelines from accumulating slurry.

[0015] ​The five valves mainly play the following roles: the 1# valve is connected with the desulfurization tower, and when opened, the gypsum slurry in the desulfurization tower enters the temporary storage tank; the 2# valve is installed at a height close to the bottom of the slurry temporary storage tank (for example, at a height of 0.5 m close to the bottom of the slurry temporary storage tank), and is used to empty the gypsum slurry in the slurry temporary storage tank; the 3# valve is installed at a height greater than the bottom sediment of the slurry in the slurry temporary storage tank after full sedimentation, and is used to discharge desulfurization clean water and fine particles in the desulfurization slurry; the 4# valve and the 5# valve are respectively the water recycling valve and the desulfurization tower water supply valve of the gypsum dehydration system, and when the 4# valve is opened and the 5# valve is closed, the recycled water is supplied to the slurry temporary storage tank, and the mixed gypsum sediment is stirred and discharged; and when the 4# valve is closed and the 5# valve is opened, the recycled water is supplied to the desulfurization tower.

[0016] The 3# valve is discharged at a high speed by the slurry discharge pump, or can be manually discharged to the desulfurization wastewater pool through the 3# valve, and the discharge speed is slightly slower, but the purpose of energy saving is achieved.

[0017] The application further provides a method for efficient discharge of wet desulfurization wastewater, comprising the following steps:

[0018] S1: slurry enters the slurry temporary storage tank: close the 2# valve and the 3# valve, stop the operation of the agitator of the slurry temporary storage tank, open the 1# valve, and then the slurry enters the slurry temporary storage tank, and after the liquid level of the slurry temporary storage tank is stable, close the 1# valve;

[0019] S2: discharge desulfurization clean water or fine particles in the slurry: after the slurry in the slurry temporary storage tank is fully sedimented, open the 3# valve and the slurry discharge pump, discharge the desulfurization clean water to the desulfurization wastewater discharge port through the slurry discharge pump, or simultaneously discharge the desulfurization clean water and the fine particle impurity slurry, wherein when the desulfurization clean water is discharged, the agitator of the slurry temporary storage tank is stopped; when the desulfurization clean water and the fine particle impurity slurry are discharged, the agitator of the slurry temporary storage tank is stirred at a low speed, after the discharge is completed, the 3# valve is closed, and the slurry discharge pump and the inlet and outlet pipelines thereof are flushed to prevent the pipelines from accumulating slurry;

[0020] S3: discharge gypsum slurry: close the 1# valve, the 2# valve and the 3# valve, supplement the recycled water from the gypsum dehydration system to the slurry temporary storage tank, the agitator of the slurry temporary storage tank is stirred at a high speed to fully stir the gypsum deposited at the bottom, open the 2# valve and the slurry discharge pump, and then start to discharge the gypsum slurry to the gypsum dehydration system, after the discharge is completed, close the 2# valve, and flush the slurry discharge pump and the inlet and outlet pipelines thereof to prevent the pipelines from accumulating slurry.

[0021] Further, in step S2, the low-speed stirring speed is 100-300 rpm. In step S3, the high-speed stirring speed is 400-500 rpm.

[0022] The step S2 fully precipitates the slurry in the slurry temporary storage tank by using gravity to separate the particulate matters and clear water in the desulfurization slurry, and the fully precipitation time of the desulfurization slurry is generally within 30-45 minutes according to the characteristics of the gypsum slurry; the desulfurization clear water or the fine particulate matters in the slurry can be flexibly selected according to the operation of the desulfurization waste water treatment system, and the desulfurization clear water is selected when the sludge load of the desulfurization waste water treatment system is too high; the clear water or the fine particulate matters is selected by adjusting the rotating speed of the agitator of the slurry temporary storage tank, the clear water is selected when the agitator is stopped, and the fine particulate matters is selected when the agitator rotates and the rotating speed is lower than the disturbing speed of the deposited gypsum.

[0023] In the step S3, the rotating speed of the agitator of the slurry temporary storage tank is adjusted to be greater than the disturbing speed of the deposited gypsum, so that the deposited gypsum in the tank can be fully agitated.

[0024] Compared with the prior art, the present application has the following beneficial effects:

[0025] 1) The desulfurization gypsum slurry has good natural sedimentation characteristics, and is fully precipitated within 30-45 minutes, and is mainly divided into a gypsum crystal particle layer, a fine particulate matter impurity layer and a desulfurization clear water layer from bottom to top. By adjusting the rotating speed of the agitator from 0 to low speed to high speed, the desulfurization clear water is discharged when the agitator is stopped, the water and the fine particulate matter impurity layer are disturbed and discharged at low speed, and the water and the gypsum crystal particle layer are disturbed and discharged at high speed.

[0026] The present application separates the desulfurization clear water, the fine particulate matter and the gypsum crystal by using the gravity sedimentation of the desulfurization gypsum slurry in the temporary storage tank and the hierarchical disturbing effect of the agitator, and realizes hierarchical selection and discharge.

[0027] The present application realizes hierarchical and efficient discharge of the chloride ions and the fine particulate matter in the desulfurization slurry, retains normal gypsum crystals, improves the particle size of the desulfurization slurry, promotes gypsum dewatering, and reduces the production pressure of the later-stage desulfurization waste water treatment system.

[0028] 2) The present application establishes an efficient desulfurization waste water discharge system independent of the gypsum dewatering system, realizes continuous discharge of the desulfurization waste water, improves the replacement efficiency in abnormal replacement, reduces the energy consumption of the gypsum dewatering, and reduces the water quantity of the later-stage desulfurization waste water treatment. In addition, when the desulfurization slurry is abnormal in poisoning or foaming, the continuous discharge of the desulfurization waste water can be realized without discharging the gypsum, and the replacement efficiency of the slurry is improved; the chloride ions in the discharged waste water are not diluted by various sealing water and flushing water in the dewatering system, and the water quantity of the later-stage desulfurization waste water treatment is reduced. BRIEF DESCRIPTION OF DRAWINGS

[0029] Figure 1 It is the treatment process flow of the desulfurization waste water discharge in the prior art.

[0030] Figure 2 The structural schematic diagram of the system for efficient discharge of wet desulfurization wastewater of the present application;

[0031] Figure 3 The state performance of slurry sample 1 in example 1 of the present application under different stirring speeds;

[0032] Figure 4 The process flow of the existing conventional desulfurization wastewater treatment system for treating wastewater. DETAILED DESCRIPTION

[0033] The present application will be further described in conjunction with specific examples, but the scope of protection of the present application is not limited thereto.

[0034] Example: Control Figure 2

[0035] A system for efficient discharge of wet desulfurization wastewater, comprising a desulfurization tower 6, a slurry temporary storage tank 7, a slurry discharge pump 8, a desulfurization wastewater discharge outlet and a gypsum dehydration system 9, the bottom liquid outlet of the desulfurization tower 6 is connected by a pipeline with the slurry temporary storage tank 7 through a 1# valve 1, so that the desulfurization slurry at the bottom of the desulfurization tower 6 is discharged into the slurry temporary storage tank 7, and after the desulfurization slurry in the slurry temporary storage tank 7 is fully settled, it is divided into a sediment layer and a desulfurization clear water layer from bottom to top, the sediment layer comprises a lower gypsum crystal particle layer and an upper fine particle impurity layer.

[0036] A stirrer is arranged on the slurry temporary storage tank 7, which can fully disturb the gypsum crystal particle layer in the slurry temporary storage tank 7 under the stirring action of the stirrer; the stirring paddle of the stirrer should be located above the settled gypsum crystal particle layer in the slurry temporary storage tank 7.

[0037] Two liquid outlets are arranged on the side of the slurry temporary storage tank 7, which are respectively connected by a pipeline with the inlet of the slurry discharge pump 8 through a 2# valve 2 and a 3# valve 3, the installation height of the 2# valve 2 is close to the bottom of the slurry temporary storage tank 7, which is used for emptying the gypsum slurry in the slurry temporary storage tank 7; the installation height of the 3# valve 3 is greater than the height of the sediment layer after the slurry in the slurry temporary storage tank 7 is fully settled; the outlet of the slurry discharge pump 8 is divided into two routes, which are respectively connected by a pipeline with the desulfurization wastewater discharge outlet and the gypsum dehydration system 9, and the desulfurization wastewater discharge outlet is further connected by a pipeline with a desulfurization wastewater treatment system.

[0038] The inner wall of the slurry temporary storage tank 7 is provided with a glass flake coating for corrosion prevention, and the height of the slurry temporary storage tank 7 is greater than the height of the overflow port of the desulfurization tower 6. The top of the slurry temporary storage tank 7 is provided with a gas permeable hole to balance the atmospheric pressure in the slurry temporary storage tank, and the slurry temporary storage tank 7 is provided with a liquid level meter to facilitate monitoring of the liquid level in the tank and the wastewater discharge amount.

[0039] The water outlet of the gypsum dehydration system 9 discharges the recycled water, which is divided into two routes, one of which is connected to the upper part of the slurry temporary storage tank 7 through a 4# valve 4, and the other of which is connected to the upper part of the desulfurization tower 6 through a 5# valve 5.

[0040] The slurry discharge pump 8 and its inlet and outlet pipelines are matched with a drainage and flushing pipeline to prevent the pipeline from accumulating slurry.

[0041] The discharge mode of the 3# valve 3 opening of the present application has the following two working conditions:

[0042] 1) The first working mode is to discharge only clean water, which has two main purposes: 1) Cl- in the desulfurization tower exists in clean water, and only discharging clean water can reduce Cl- in the desulfurization tower; 2) Since the desulfurization wastewater treatment system is greatly affected by the solid content of the discharged wastewater, the greater the solid content, the smaller the amount of wastewater that can be disposed of by the wastewater treatment system, and only discharging clean water can ensure the normal treatment of the later-stage wastewater treatment system.

[0043] 2) Directly stirring and mixing the clean water with the fine particle impurities to discharge the fine particle slurry

[0044] The second working mode is to discharge the mixture of clean water and fine particle impurities, which is the normal working mode, and the main purpose of this mode is to reduce the fine particles and impurities in the desulfurization tower to prevent the decrease of the particle size of the gypsum crystals in the tower and the enrichment of impurities affecting the desulfurization reaction. As much fine particle slurry as possible is discharged, and then the recycled water from the gypsum dehydration system is added to discharge the gypsum, and the purpose of adding the recycled water instead of clean water is to reduce the influence of the incoming clean water on the water balance of the desulfurization system.

[0045] Example 1:

[0046] In order to verify the different stirring effects of different stirring speeds of the stirrer on the fine particle layer and the gypsum crystal layer in the slurry, two portions of desulfurization slurry were taken and placed in two transparent glass cylinders to observe the settling and stirring conditions of the gypsum slurry. The diameter of the bottom of the transparent glass cylinder is 5 cm, the internal liquid level is 8 cm, the stirring speed of the stirrer is adjustable, the diameter of the stirring blade is 2 cm, and the installation height of the stirring blade is 5 cm from the bottom of the transparent glass cylinder. After 45 minutes of full precipitation, the desulfurization slurry is naturally divided into three layers from bottom to top, mainly into a gypsum crystal particle layer, a fine particle impurity layer and a desulfurization clean water layer, and the heights of the layers in the two portions of desulfurization slurry are shown in Table 1. The main reason for the difference in height between different layers is that the solid content and fine particle impurity content in the slurry are different.

[0047] Table 1

[0048] Slurry sample Layer of gypsum crystal particles Layer of fine particulate impurities Layer of desulphurised water Slurry sample 1 0.8 cm 0.2 cm 7 cm Slurry sample 2 1 cm 2 cm 5 cm

[0049] The state of the slurry sample 1 under different stirring speeds is shown in Table 2. Figure 3rpm, the fine particle impurity layer began to be disturbed under the driving of the supernatant; when the rotation speed was set to 300 rpm, the fine particle impurity layer was completely stirred up, while the gypsum crystal particle layer had no change; when the rotation speed was set to 500 rpm, the gypsum crystal particle layer began to be stirred and affected, and the slurry returned to the mixed state before precipitation. The stirring effects of the two slurry samples were basically the same, although the solid content and fine particle impurity content were different: after sufficient precipitation, the two samples were naturally stratified according to the particle size, the fine particle layer was completely suspended at 300 rpm, and the gypsum crystal particle layer began to be affected by stirring at 500 rpm, forming a completely desulfurized slurry suspension.

[0050] From the experiment, it can be seen that: by using the natural sedimentation characteristics of the desulfurized gypsum slurry, the supernatant containing chloride ions, the fine particle impurity layer, and the gypsum crystal particle layer in the desulfurized slurry can be separated under different stirring speeds, so that the desulfurized slurry can be classified and discharged.

[0051] Example 2:

[0052] A 660 MW unit boiler is a subcritical intermediate once-reheat natural circulation drum boiler, the evaporation capacity under BMCR condition is 2019 t / h, the design sulfur content for desulfurization is 0.9%, the diameter of the desulfurization absorption tower is 16 m, the operating liquid level is 8.5 m, the design desulfurization wastewater discharge capacity is 6.5 t / h, the diameter of the slurry temporary storage tank is 5.6 m, the height is 10 m, the rotation speed adjustment range of the agitator of the slurry temporary storage tank is 0-400 rpm, the design flow of the slurry discharge pump is 145 m 3 / h, the distance from the bottom surface of the 2# valve 2 of the slurry temporary storage tank is 1 m, and the distance from the bottom surface of the 3# valve 3 is 2 m. The main steps of the high-efficiency desulfurization wastewater discharge are as follows:

[0053] Step 1: open the slurry inlet valve 1 of the slurry temporary storage tank, start the slurry into the temporary storage tank, and close the slurry inlet valve 1 after the liquid level of the temporary storage tank is stable near 8.5 m;

[0054] Step 2: after the slurry in the slurry temporary storage tank is fully precipitated for 45 min, the height of the precipitated gypsum layer is about 1 m, and the deposition depth of the fine particle layer is about 0.25-0.3 m, the rotation speed of the agitator of the temporary storage tank is adjusted to 150 rpm, at this time, the fine particle layer in the desulfurized gypsum slurry is fully suspended in the desulfurized supernatant under the action of the agitator, the 3# valve 3 and the slurry discharge pump are opened, and the desulfurization wastewater containing fine particles is discharged to the desulfurization wastewater discharge port for disposal by the desulfurization wastewater treatment system, the 3# valve 3 is closed when the liquid level of the slurry temporary storage tank is discharged to 2.5 m, and the slurry discharge pump and the pipeline are flushed.

[0055] Step 3: Close valve 5 and open valve 4 to replenish the slurry storage tank with recycled water from the gypsum dewatering system 9. After replenishment, close valve 4 (the liquid level stabilizes at around 8.5m after replenishment). Start the agitator in the slurry storage tank and adjust the agitator speed to 400rpm to fully agitate the deposited gypsum. Open valve 2 and the slurry discharge pump to start discharging gypsum slurry into the gypsum dewatering system. When the liquid level in the slurry storage tank reaches 1m, close valve 2 and flush the slurry discharge pump and pipeline.

[0056] Analysis of the energy-saving effect of efficient wastewater discharge: Figure 1 Taking the discharge of desulfurization wastewater from outlet 2 as an example, when the measured chloride ion concentration in the desulfurization slurry was 15000 mg / L, the chloride ion concentration in the discharged desulfurization wastewater was between 6000-8000 mg / L due to the dilution effect of the sealing water and flushing water of the vacuum conveyor during the dewatering process. Therefore, under the condition of discharging the same amount of chloride ions in the tower, after the implementation of Example 2, the chloride ion concentration in the directly discharged desulfurization water was twice as high, so the discharge volume of desulfurization wastewater was reduced by about 50%. The gypsum dewatering and desulfurization wastewater treatment system can reduce the operating time by about 50%, which corresponds to a 50% energy saving compared to direct treatment to the gypsum dewatering system.

[0057] Analysis of the efficiency improvement of wastewater discharge: 1. The efficiency of desulfurization wastewater discharge is greatly improved. It only takes 3 hours to discharge 147.7t of desulfurization wastewater at one time, which can meet the daily wastewater discharge requirements of the unit. In case of emergency, the entire slurry replacement can be completed in one day; 2. The solid content of desulfurization wastewater is greatly reduced. After sedimentation, the solid content of desulfurization wastewater is less than 1%. In step 2, it is possible to choose not to run the agitator in the temporary storage tank and only discharge the chloride ions in the desulfurization supernatant. There will be no problem of excessive sludge load in the downstream desulfurization wastewater treatment system, which would restrict the discharge of desulfurization wastewater.

[0058] The contents described in this specification are merely an enumeration of the implementation forms of the inventive concept, and the scope of protection of this invention should not be regarded as limited to the specific forms described in the embodiments.

Claims

1. A method for efficient discharge of wet desulfurization wastewater of a system for efficient discharge of wet desulfurization wastewater, characterized by The system comprises a desulfurization tower (6), a slurry temporary storage tank (7), a slurry discharge pump (8), a desulfurization wastewater discharge port and a gypsum dehydration system (9), a liquid outlet at the bottom of the desulfurization tower (6) is connected to the slurry temporary storage tank (7) by a pipeline through a 1# valve (1), so that the desulfurization slurry at the bottom of the desulfurization tower (6) is discharged into the slurry temporary storage tank (7), and after the desulfurization slurry in the slurry temporary storage tank (7) is fully settled, the desulfurization slurry is divided into a sediment layer and a desulfurization clear water layer from bottom to top, the sediment layer comprises a lower gypsum crystal particle layer and an upper fine particle impurity layer; A stirrer is arranged on the slurry temporary storage tank (7), and the gypsum crystal particle layer in the slurry temporary storage tank (7) can be fully disturbed under the stirring action of the stirrer; Two liquid outlets are arranged on the side of the slurry temporary storage tank (7), and the two liquid outlets are connected to the inlet of the slurry discharge pump (8) by pipelines through a 2# valve (2) and a 3# valve (3), the 2# valve (2) is installed at a height close to the bottom of the slurry temporary storage tank (7) and is used for discharging the gypsum slurry in the slurry temporary storage tank (7), and the 3# valve (3) is installed at a height greater than the height of the sediment layer after the slurry in the slurry temporary storage tank (7) is fully settled; The outlet of the slurry discharge pump (8) is divided into two paths, and the two paths are connected to the desulfurization wastewater discharge port and the gypsum dehydration system (9) by pipelines, and the desulfurization wastewater discharge port is further connected to a desulfurization wastewater treatment system by a pipeline; The control motor of the stirrer is a variable frequency speed regulation motor, so that the stirring speed can be adjusted; The water outlet of the gypsum dehydration system (9) discharges recycled water, and the water outlet is divided into two paths, one path is connected to the upper part of the slurry temporary storage tank (7) by a pipeline through a 4# valve (4), and the other path is connected to the upper part of the desulfurization tower (6) by a pipeline through a 5# valve (5); The method for efficiently discharging wet desulfurization wastewater comprises the following steps: S1: slurry is fed into the slurry temporary storage tank, the 2# valve (2) and the 3# valve (3) are closed, the stirrer of the slurry temporary storage tank (7) is stopped, the 1# valve (1) is opened, and then the slurry is fed into the slurry temporary storage tank (7), and after the liquid level of the slurry temporary storage tank (7) is stable, the 1# valve (1) is closed; S2: desulfurization clear water or fine particle impurities in the slurry are discharged, after the slurry in the slurry temporary storage tank (7) is fully settled, the 3# valve (3) and the slurry discharge pump (8) are opened, the desulfurization clear water is discharged to the desulfurization wastewater discharge port through the slurry discharge pump (8), or the desulfurization clear water and the fine particle impurity slurry are simultaneously discharged, wherein the stirrer of the slurry temporary storage tank (7) is stopped when the desulfurization clear water is discharged, and the stirrer of the slurry temporary storage tank (7) is stirred at a low speed when the desulfurization clear water and the fine particle impurity slurry are simultaneously discharged, the 3# valve (3) is closed after the discharge is completed, and the slurry discharge pump (8) and the pipeline connected to the inlet and outlet of the slurry discharge pump (8) are flushed to prevent the pipeline from being filled with slurry; S3: Discharge the gypsum slurry: close the 1# valve (1), 2# valve (2) and 3# valve (3), add the recycled water from the gypsum dewatering system (9) to the slurry temporary storage tank (7), the agitator in the slurry temporary storage tank (7) is running at high speed to fully stir the deposited gypsum at the bottom, open the 2# valve (2) and the slurry discharge pump (8), start to discharge the gypsum slurry to the gypsum dewatering system (9), close the 2# valve (2) after the discharge is completed, and flush the slurry discharge pump (8) and its inlet and outlet pipelines to prevent the pipelines from being filled with the slurry.

2. The method of claim 1, wherein The inner wall of the slurry temporary storage tank (7) is coated with glass flake to prevent corrosion, and the height of the slurry temporary storage tank (7) is greater than the height of the overflow port of the desulfurization tower (6).

3. The method of claim 1, wherein The top of the slurry temporary storage tank (7) is provided with a vent hole to balance the atmospheric pressure in the slurry temporary storage tank, and the slurry temporary storage tank (7) is provided with a liquid level meter to monitor the liquid level in the tank and the amount of wastewater discharged.

4. The method of claim 1, wherein The stirring paddle of the agitator is located above the gypsum crystal particle layer.

5. The method of claim 1, wherein The slurry discharge pump (8) and its inlet and outlet pipelines are equipped with a flushing pipeline to prevent the pipelines from being filled with the slurry.

6. The method of claim 1, wherein In step S2, the low-speed stirring speed is 100-300 rpm.

7. The method of claim 1, wherein In step S3, the high-speed stirring speed is 400-500 rpm.

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