CN112794493B - System and method for reducing scaling in softening treatment of reverse osmosis concentrated brine caustic soda/lime soda ash - Google Patents
System and method for reducing scaling in softening treatment of reverse osmosis concentrated brine caustic soda/lime soda ash Download PDFInfo
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- CN112794493B CN112794493B CN202011531606.XA CN202011531606A CN112794493B CN 112794493 B CN112794493 B CN 112794493B CN 202011531606 A CN202011531606 A CN 202011531606A CN 112794493 B CN112794493 B CN 112794493B
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- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F9/00—Multistage treatment of water, waste water or sewage
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- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F1/00—Treatment of water, waste water, or sewage
- C02F1/44—Treatment of water, waste water, or sewage by dialysis, osmosis or reverse osmosis
- C02F1/441—Treatment of water, waste water, or sewage by dialysis, osmosis or reverse osmosis by reverse osmosis
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- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F5/00—Softening water; Preventing scale; Adding scale preventatives or scale removers to water, e.g. adding sequestering agents
- C02F5/02—Softening water by precipitation of the hardness
- C02F5/06—Softening water by precipitation of the hardness using calcium compounds
Abstract
The invention relates to a system and a method for reducing scaling in softening treatment of reverse osmosis strong brine lime/caustic soda and belongs to the technical field of industrial wastewater treatment. According to the system and the method for reducing scaling in the softening treatment of Reverse Osmosis (RO) concentrated brine lime/caustic soda, light sludge is introduced and added into an RO concentrated brine multistage chemical softening reaction tank to increase suspended matters in water, so that a carrier and a balance weight are provided for calcium carbonate crystallization, hardness in water is removed, and if lime is added at the front end for hardness removal, on one hand, the lime adding amount of RO concentrated brine concentration or evaporative crystallization pretreatment can be reduced, and meanwhile, the problems of low suspended matters, poor precipitation effect and the like in lime soda hardness removal are solved; on the other hand, the problem of scaling of the tank wall and the pipeline equipment is mainly delayed and solved.
Description
Technical Field
The invention relates to a system and a method for reducing scaling in softening treatment of reverse osmosis concentrated brine caustic soda/lime soda ash, belonging to the technical field of environment-friendly water treatment.
Background
The industrial sewage and wastewater has complex components, and besides the conventional chemical pollutants, various trace toxic and harmful chemical pollutants and color and odor causing substances exist. The reverse osmosis system has good removal effect on organic matters, pathogenic microorganisms, nitrate nitrogen and refractory organic matters in the sewage, and is gradually popularized and utilized in the field of sewage recycling. The reverse osmosis system can produce high-quality regenerated water and simultaneously produce a byproduct RO concentrated water. The water amount of the RO concentrated water usually accounts for 25-50% of the water inflow, and is determined by the recovery rate of the RO system.
Some sewage treatment projects adopt reverse osmosis concentrated water to further concentrate RO concentrated water through seawater desalination reverse osmosis and brackish water desalination reverse osmosis, so that the reuse rate of sewage is improved, the discharge of concentrated brine is reduced, the concentrated brine subjected to concentration is subjected to evaporation crystallization to realize resource utilization, however, substances such as calcium, magnesium and the like in the concentrated brine can cause scaling of reverse osmosis, an evaporator and the like, and therefore, before RO concentrated water is further concentrated, softening is needed to remove hardness in water.
Hardness is an important water quality indicator and has attracted considerable attention in drinking water and industrial water. Generally, calcium ions and magnesium ions are the main reasons for generating hardness, and the water can be soft water, light hard water, medium hard water and hard water, and the corresponding mass concentration of the calcium ions is 0-17, 17-60, 60-120 and 120-180 mg/L respectively. Excessive hardness in water can cause problems in municipal and industrial water processes.
Common softening and hardness removal methods include a scale inhibitor method, a lime softening method, a lime soda softening method, a coagulating sedimentation method, a zeolite method and an alumina method; for strong brines with high hardness (especially those with high permanent hardness), the caustic/lime-soda softening process is the most economical and has many engineering cases in industrial applications.
The basic principle of removing water by softening caustic soda/lime-soda ash is to generate calcium carbonate and magnesium hydroxide precipitates through chemical reaction, and remove the total hardness of calcium and magnesium in water through precipitation.
MgSO 4 +2NaOH＝Mg(OH) 2 ↓+Na 2 SO 4
CaCl 2 +Na 2 CO 3 ＝CaCO 3 ↓+2NaCl
In recent years, a reverse osmosis strong brine softening treatment process is widely applied in the industry, and a published granted patent CN10592815A discloses a method for crystallizing reverse osmosis membrane strong brine and the like to recycle the strong brine and sulfate, wherein the strong brine is softened.
The CN106186550A patent discloses a sewage zero discharge device and method, pretreating and softening reverse osmosis strong brine, finally evaporating and crystallizing to obtain sulfate, and simultaneously recycling the strong brine to realize zero discharge, wherein the softening part also adopts a caustic soda/lime-soda softening process.
However, in the RO concentrated water further reduction treatment or concentrated water zero discharge process, when the caustic soda/lime-soda softening method is used for hardness removal, although the method is economical, has good effect and wide application, the biggest problem is that the scale formation of the tank wall, the pipeline, the stirrer and the like is serious, the equipment is damaged, the operation is influenced, meanwhile, a sludge deposition pipeline is formed, the manual cleaning is required at regular intervals (1-3 months), the adverse effect is brought to the operation and maintenance, and the maintenance cost is greatly increased.
Therefore, the technical method and the system for reducing the scale formation in the softening process of the caustic soda/lime-soda ash are provided, so that the RO concentrated water softening and hardness removal operation is safer and more stable, and the technical problem which needs to be solved urgently in the technical field is solved.
Disclosure of Invention
One of the purposes of the invention is to provide a system for reducing scaling in softening treatment of Reverse Osmosis (RO) concentrated brine lime soda ash, which is characterized in that light sludge is introduced and added into an RO concentrated brine multistage chemical softening reaction tank, suspended matters in water are increased, a carrier and a balance weight are provided for calcium carbonate crystallization, hardness in water is removed, and if lime is added at the front end for hardness removal, on one hand, the invention can also reduce lime adding amount in pretreatment of RO concentrated brine concentration or evaporative crystallization, and simultaneously solve the problems of low suspended matters, poor precipitation effect and the like in the process of hardness removal of the lime soda ash; on the other hand, the problem of scaling of the tank wall and the pipeline equipment is mainly delayed and solved.
The above object of the present invention is achieved by the following technical solutions:
a system for reducing scale formation in softening treatment of reverse osmosis strong brine caustic soda/lime soda ash comprises a dissolving and dispensing device, a dosing pump, an RO (reverse osmosis) concentrated water device, a sludge dosing pump, a primary reaction tank, a secondary reaction tank, a tertiary reaction tank, a pre-settling tank, a sedimentation tank, a sludge discharge pump, an air compressor, a storage tank, a valve, a soda feeding pump, a soda feeding device and a PAM (polyacrylamide) dosing device; the device comprises a dissolving and dispensing device, a first-stage reaction tank, a RO concentrated water device, a sludge feeding device, a first-stage reaction tank, a second-stage reaction tank, a sedimentation tank, a second-stage reaction tank, a third-stage reaction tank, a pre-sedimentation tank, a sedimentation tank and a control device, wherein the dissolving and dispensing device is connected with the first-stage reaction tank through a chemical feeding pump and a chemical distributing pipeline; the soda feeding device is connected with the secondary reaction tank through a soda feeding pump and a pipeline, the PAM feeding device is connected with the tertiary reaction tank through a pump and a pipeline, the air compressor is connected with the storage tank, and the storage tank is respectively connected with the secondary reaction tank, the tertiary reaction tank and the pre-settling tank through a valve and a gas distribution pipeline.
Preferably, the dissolving and dispensing device comprises a dissolving and dispensing pool, wherein a stirrer is arranged in the dissolving and dispensing pool.
Preferably, the primary reaction tank is provided with a stirrer.
Preferably, the secondary reaction tank is provided with a stirrer.
Preferably, the third-stage reaction tank is provided with a stirrer.
Preferably, the secondary reaction tank is provided with openings at intervals of 10-15cm on the cover, and the openings are uniformly added on the stirring diameter of the stirrer.
Preferably, the feeding pipes of the dissolving and dispensing device are all transversely suspended on the water surface of the reaction tank of the primary reaction tank.
Preferably, the feeding pipes of the soda feeding device are transversely suspended on the water surface of the reaction tank of the secondary reaction tank.
Preferably, the feeding pipes for feeding PAM are all transversely suspended on the water surface of the reaction tank of the third-stage reaction tank.
Preferably, the feeding pipes of the compressed air fed into the second-stage reaction tank, the third-stage reaction tank and the pre-settling tank are stainless steel pipes with the diameter DN 8.
Preferably, the aeration feeding point is positioned 10-20cm away from the bottom of the secondary reaction tank, the tertiary reaction tank and the preliminary sedimentation tank.
Preferably, the gas distribution pipeline is provided with 1 feeding point at the interval of 0.3-0.5m in the pre-settling tank, and aeration plug flow is carried out to avoid sludge deposition.
One of the other objects of the invention is to provide a method for reducing scaling in the softening treatment of Reverse Osmosis (RO) strong brine lime/caustic soda, which adds suspended matters in water by introducing light sludge and adding the light sludge into an RO strong brine multistage chemical softening reaction tank to increase the suspended matters in the water, provides a carrier and a counterweight for calcium carbonate crystallization and removes hardness in the water, and if lime is added to the front end for hardness removal, the method can reduce the lime adding amount in the pretreatment of RO strong brine concentration or evaporative crystallization on one hand, and simultaneously solve the problems of low suspended matters, poor precipitation effect and the like in the softening and hardness removal of RO strong brine; on the other hand, the problem of scaling of the tank wall and the pipeline equipment is mainly delayed and solved.
The above object of the present invention is achieved by the following technical solutions:
a method for reducing scaling in softening treatment of reverse osmosis concentrated brine caustic soda/lime soda ash comprises the following steps:
(1) preparing a hydrated lime solution with the concentration of 1-5% or a caustic soda solution with the concentration of 1-10%, adding the hydrated lime solution or the caustic soda solution into a first-stage softening tank (a first-stage reaction tank) through a dosing pump, and raising the pH value of RO concentrated water to 9.5-11, wherein the optimal pH range is usually 10-10.5;
(2) preparing a soda solution with the concentration of 3-10%, adding a proper amount of soda solution, and feeding the soda solution into a second-stage reaction tank (a reaction tank of the second-stage reaction tank), wherein the specific adding amount is calculated by the calcium hardness of the RO concentrated water to be removed, and usually 0.5-1.2 times of the calcium hardness (in molar weight) is taken;
(3) preparing 0.1-0.4% Polyacrylamide (PAM), and adding into a reaction tank of a third-stage reaction tank;
(4) adding returned light sludge into a reaction tank of a primary reaction tank through a sludge adding device, wherein the concentration of the returned light sludge is 1-2% (the water content is 98-99%);
(5) aeration pipes are added in the overflow area (the second-stage reaction tank), the stirring dead area (the third-stage reaction tank) and the pre-settling tank for aeration, so as to prevent sludge deposition.
Preferably, in the steps (1) and (2), the caustic soda/lime-soda ash is added at multiple points, so that the uniform and rapid mixing of the added chemicals is ensured.
Preferably, in the step (1), the lime/caustic soda is added in a multipoint way and is uniformly added on the water inlet section of the first-stage reaction zone (first-stage reaction tank).
Preferably, in the step (2), the soda ash is added by a tubular drilling way, and the soda ash is uniformly added on the stirring diameter of the stirrer at the intervals of 10-15cm of openings.
Preferably, in the step (1), the step (2) and the step (3), the adding pipes are respectively suspended on the water surfaces of the reaction tanks of the first-stage reaction tank, the second-stage reaction tank and the third-stage reaction tank in a transversely-arranged mode and are not in direct contact with the RO concentrated water during adding.
Preferably, in the step (5), the compressed air is added into the secondary reaction tank, the tertiary reaction tank and the pre-settling tank through storage tanks, and the adding pipes of the secondary reaction tank, the tertiary reaction tank and the pre-settling tank are stainless steel pipes with the diameter DN 8.
Preferably, in the step (5), the aeration feeding point is positioned 10-20cm away from the bottom of the secondary reaction tank, the tertiary reaction tank and the pre-settling tank.
Preferably, in the step (5), 1 feeding point is arranged on the compressed air pipe at the interval of 0.3-0.5m in the pre-sedimentation tank, and the sludge sedimentation is avoided by aeration plug flow.
Preferably, in the step (1), the TDS of the RO concentrated water in the RO concentrated water device is 2000-12000mg/L, the total hardness is 1000-4000mg/L, and the calcium hardness is 500-2000 mg/L.
Has the advantages that:
according to the system and the method for reducing scaling in the softening treatment of Reverse Osmosis (RO) concentrated brine lime/caustic soda ash, light sludge is introduced and added into an RO concentrated brine multistage chemical softening reaction tank to increase suspended matters in water, so that a carrier and a balance weight are provided for calcium carbonate crystallization, hardness in water is removed, and if lime is added at the front end for hardness removal, on one hand, the lime adding amount of RO concentrated brine concentration or evaporative crystallization pretreatment can be reduced, and meanwhile, the problems of low suspended matters, poor precipitation effect and the like in lime soda ash hardness removal are solved; on the other hand, the problem of scaling of the tank wall and the pipeline equipment is mainly delayed and solved.
The invention is further illustrated by the following figures and detailed description of the invention, which are not meant to limit the scope of the invention.
Drawings
FIG. 1 is a schematic diagram of the structure of a system for reducing scaling in the softening treatment of reverse osmosis concentrated brine caustic soda/limemite.
Description of the main reference numbers:
1 dissolve dispensing device 2 dosing pumps
3 RO dense water device 4 sludge feeding device
5 sludge feeding pump 6 first-stage reaction tank
7 soda adding device 8 second-stage reaction tank
9 three-stage reaction tank 10 pre-settling tank
11 sedimentation tank 12 sludge discharge pump
13 air compressor 14 storage tank
15 valve 16 soda adding pump
17 PAM charge device
Detailed Description
The components and the like in the following embodiments are, unless otherwise specified, conventional ones, and unless otherwise specified, all of the components and the like used in the present invention are commercially available. Unless otherwise specified, the concentrations in the following examples are given in weight percent.
Example 1
FIG. 1 is a schematic diagram of a system for reducing scaling in the softening treatment of reverse osmosis concentrated brine caustic soda/limemite according to the present invention; the system comprises a dissolving and dispensing device 1, a dosing pump 2, an RO (reverse osmosis) concentrated water device 3, a sludge feeding device 4, a sludge feeding pump 5, a primary reaction tank 6, a soda feeding device 7, a secondary reaction tank 8, a tertiary reaction tank 9, a preliminary sedimentation tank 10, a sedimentation tank 11, a sludge discharge pump 12, an air compressor 13, a storage tank 14, a valve 15, a soda feeding pump 16 and a PAM (polyacrylamide) dosing device 17, wherein the dissolving and dispensing device is used for dissolving and dispensing the raw materials; the system for reducing scale formation in softening treatment of Reverse Osmosis (RO) strong brine lime and soda ash comprises a dissolving and dispensing device 1, a dosing pump 2, an RO concentrated water device 3, a sludge dosing device 4, a sludge dosing pump 5, a primary reaction tank 6, a soda dosing device 7, a secondary reaction tank 8, a tertiary reaction tank 9, a pre-settling tank 10, a settling tank 11, a sludge discharge pump 12, an air compressor 13, a storage tank 14, a valve 15, a soda dosing pump 16 and a PAM dosing device 17; the device for dissolving and dispensing the drug 1 is connected with a first-stage reaction tank 6 through a drug pump 2 and a drug distribution pipeline, an RO concentrated water device 3 is connected with the first-stage reaction tank 6 through a water inlet pump (not marked in the figure) and a water distribution pipeline, a sludge feeding device 4 is connected with the first-stage reaction tank 6 through a sludge feeding pump 5 and a sludge distribution pipeline, the first-stage reaction tank 6 is connected with a second-stage reaction tank 8 through a tank top overflow, the second-stage reaction tank 8 is adjacent to the third-stage reaction tank 9 and is communicated through an adjacent wall middle pipeline, a PAM drug feeding device 17 is positioned above the third-stage reaction tank 9, the third-stage reaction tank 9 is communicated with a pre-settling tank 10 through an opening in the middle of the adjacent wall, the pre-settling tank 10 is adjacent to a settling tank 11, an overflow weir is arranged in the middle, the settling tank 11 discharges sludge outwards through a sludge discharge pump 12, and the sludge is concentrated and filter-pressed; the soda adding device 7 is connected with the secondary reaction tank 8 through a soda adding pump 16 and a pipeline, the air compressor 13 is connected with the storage tank 14, and the storage tank 14 is respectively connected with the secondary reaction tank 8, the tertiary reaction tank 9 and the pre-settling tank 10 through a valve 15 and a gas distribution pipeline; dissolve dispensing device 1 including dissolving the dispensing pond, wherein be equipped with the agitator, one-level reaction tank 6 includes one-level chemical reaction pond, wherein is equipped with the agitator, and second grade reaction tank 8 includes second grade chemical reaction pond, wherein is equipped with the agitator, and tertiary reaction tank 9 includes tertiary chemical reaction pond, wherein is equipped with the agitator.
Wherein, the adding pipes of the dissolving and dispensing device 1 and the soda adding device 7 are transversely suspended on the water surfaces of the reaction tanks of the first-stage reaction tank 6 and the second-stage reaction tank 8; and the feeding pipe of the PAM feeding device 17 is suspended on the water surface of the reaction tank of the third-stage reaction tank 9.
Wherein, the feeding pipes of the storage tank 14, the second-stage reaction tank 8, the third-stage reaction tank 9 and the pre-settling tank 10 are stainless steel pipes with the diameter DN 8; the aeration feeding point (namely an air distribution pipeline or an aeration pipe) is positioned 10-20cm away from the bottom of the secondary reaction tank 8, the tertiary reaction tank 9 and the pre-settling tank 10.
The invention discloses a system for reducing scale formation in softening treatment of Reverse Osmosis (RO) strong brine lime and soda ash: RO concentrated water is connected with the multistage reaction tank through pipelines such as a sludge feeding pump, a dispensing tank, a lime dosing pump and the like through a water pump and a sludge tank, valves are arranged on the pipelines, the water regulating quantity, the sludge quantity, the dosing quantity and the like can be controlled, the sludge after reaction is discharged to the concentration tank through a sludge discharge pump, and part of the sludge can also flow back to the first stage reaction tank for recycling.
The sludge feeding device adopts newly precipitated light sludge which can be provided by a front end regulating tank or a sedimentation tank, and sludge with the concentration of 1-2% is stirred and uniformly mixed by a stirrer and then pumped into the front end of a first-stage reaction area of the multistage reaction tank to be mixed and reacted with RO concentrated water and lime/caustic soda liquid medicine; the total solid concentration of the first-stage reaction zone after lime and sludge are added is 1-1.5 g/L.
The amount of sludge added into the first reaction tank is about 8-15% of the total water inlet flow, a valve is arranged on the pipeline to adjust and control the flow, and a cleaning water gap is reserved for flushing the pipeline.
And blowing air to the second and third reaction tanks and the preliminary sedimentation tank of the multistage reaction tank through a compressed air branch pipe by using 0.2-0.5MPa of compressed air, wherein the aeration flow rate is 0.5-2 m/s.
And finally, the sludge is precipitated in a sedimentation tank and discharged through a sludge discharge pump, and the turbidity of the discharged water is less than 5 NTU.
The system for reducing scaling in the softening treatment of Reverse Osmosis (RO) concentrated brine lime/caustic soda ash is characterized by comprising the following components in parts by weight: the multistage reaction tank and the dispensing tank are both provided with stirring equipment; the sludge feeding device adopts a screw pump or a slurry centrifugal pump, the sludge is pumped into the first reaction tank, and the feeding point is positioned below the water surface at the front end of the first reaction tank; lime is added at multiple points through a medicine distribution pipeline after being dissolved.
The invention discloses a method for reducing scale formation in softening treatment of Reverse Osmosis (RO) concentrated brine lime/caustic soda ash, which comprises the following steps:
(1) preparing a hydrated lime solution with the concentration of 1-5% or a caustic soda solution with the concentration of 1-10%, adding the hydrated lime solution or the caustic soda solution into a first-stage softening tank (a first-stage reaction tank 6) through a dosing pump, and raising the pH value of RO concentrated water to 9.5-11, wherein the optimal pH range is usually 10-10.5;
(2) preparing a soda solution with the concentration of 3-10%, adding a proper amount of soda solution into a second-stage reaction tank (a second-stage reaction tank 8) through a soda adding device 7, wherein the specific adding amount is calculated according to the calcium hardness of the RO concentrated water to be removed, and is usually calculated according to the calcium hardness (in molar quantity) of 0.5-1.2 times;
(3) preparing 0.1-0.4% Polyacrylamide (PAM), and adding into a third-stage reaction tank (a third-stage reaction tank 9) through a PAM dosing device 17;
(4) adding returned light sludge into a reaction tank of a primary reaction tank 6 through a sludge adding device 4, wherein the concentration is 1-2% (the water content is 98-99%);
(5) the caustic soda/lime-soda ash are added at multiple points, so that the uniform and rapid mixing of the added chemicals is ensured;
(6) aeration pipes are added in the overflowing area (the second-stage reaction tank 8), the stirring dead area (the third-stage reaction tank 9) and the pre-settling tank for aeration, so that sludge deposition is prevented.
Wherein, the soda is added by a tubular drilling, openings are arranged at intervals of 10-15cm (the openings are arranged on the cover of the secondary reaction tank 8 at intervals), and are uniformly added on the stirring diameter of the stirrer; the lime/caustic soda is added in a multipoint way and is uniformly added on the water inlet section of a first-stage reaction zone (a first-stage reaction tank 6); the adding pipes (dosing pipes) are horizontally suspended on the water surfaces of the reaction tanks of the first-stage reaction tank 6, the second-stage reaction tank 8 and the third-stage reaction tank 9 and are not in direct contact with RO concentrated water during dosing; compressed air is fed into the feeding pipes of the second-stage reaction tank 8, the third-stage reaction tank 9 and the pre-settling tank 10 through the storage tank 14, the feeding pipes are stainless steel pipes with the diameter DN8, and the aeration feeding points are positioned at the positions 10-20cm away from the bottoms of the second-stage reaction tank 8, the third-stage reaction tank 9 and the pre-settling tank 10; 1 feeding point is arranged on the compressed air pipe at intervals of 0.3-0.5m in the pre-settling tank 10, and sludge sedimentation is avoided by aeration plug flow; the TDS of the RO concentrated water in the RO concentrated water device 3 is 2000-12000mg/L, and the total hardness is 1000-4000 mg/L; the calcium hardness is 500-2000 mg/l.
According to the invention, by introducing the light sludge, the suspended matters of the RO concentrated water are increased, a carrier and a balance weight are provided for calcium carbonate crystallization, and scaling precipitation, pipeline blockage, damage to stirring equipment and the like at overflowing positions of pipelines, stirrers and the like are avoided.
Application example 1
A certain iron and steel plant, it carries out furthest's processing retrieval and utilization to synthesize waste water of sewage treatment plant in to the factory, divide into the preliminary treatment unit (high-efficient sedimentation tank + V type filtering pond), advanced treatment unit (ultrafiltration reverse osmosis) to and strong brine unit, wherein strong brine unit carries out further concentrated decrement to the thick water of RO, adopts traditional lime-soda softening process to soften the thick water of RO and removes hard, the following problem appears in the operation process: the scale formation is serious, the sedimentation tank is often blocked, and the stirrer is damaged due to scale formation, so that the tank body needs to be cleaned after about 1 month of operation.
Specific data are shown in table 1 below:
TABLE 1 conventional apparatus and Process
The problems are as follows: the whole winter operation condition is that the first reaction tank and the soda addition reaction tank are seriously scaled, the blade of the stirrer is seriously scaled (the thickness is about 10cm), the eccentric swing is large during the operation, the variable speed motor leaks oil, the aeration stirring is used instead of the stirring when the stirring is stopped, the operation lasts for about 1 month, the tank wall is about 15-20cm scaled, the overflow pipe is also scaled and blocked, the multistage reaction tank cannot operate, and a large amount of sludge is deposited in a pre-precipitation area and a flocculation area during drainage inspection.
The system and the method for reducing scale formation in the softening treatment of Reverse Osmosis (RO) concentrated brine lime soda ash are adopted to carry out production operation after the process is modified, and the results are shown in the following table 2:
TABLE 2 systems and methods of the present invention
After the sludge in the front-end efficient sedimentation tank is introduced, the operation lasts for about 3 months, only a thin layer of scale is formed on the wall of the tank, and only a thin layer (1-3mm) of scale is formed on the hanging piece of the soda tank after 3 months. The method has the advantages that the sludge of the efficient sedimentation tank with the pretreated front end is introduced, the pH value of the lime tank is increased by 10.0-10.5, and the ideal effect is obtained after the chemical addition of the soda ash is improved, the scaling of the multistage reaction tank is greatly delayed, the effluent quality is also guaranteed, the sludge deposition problem is solved by introducing aeration, the sedimentation tank is changed from the original 1-month shutdown cleaning and maintenance into 1-year 1 maintenance, the operation period is prolonged, and the stability of production operation is guaranteed.
Application example 2
Certain industry garden sewage treatment plant, adopt high-efficient sedimentation tank + V type filtering pond + ultrafiltration + reverse osmosis process to carry out the advanced treatment retrieval and utilization to the interior waste water of garden, the thick water of RO gets into the strong brine unit and carries out further concentration decrement, adopt traditional caustic soda-soda softening process to soften the unhardened to the thick water of RO, the pencil that adds appears in the operation process, the agitator, the pool wall scale deposit is serious, soda reaction tank is often stifled, the agitator damages scheduling problem because of the scale deposit, about 30 ~ 50 days of continuous operation need clear up the cell body promptly, sedimentation zone effect is not good simultaneously, the floc is lighter.
Specific data are shown in table 3 below:
TABLE 3 conventional apparatus and Process
The problems are as follows: the operation condition in the whole autumn and winter is that the scale of the soda feeding reaction tank is serious, the operation lasts for about 40 days, the wall of the tank has about 15-20cm scale, the overflow pipe is also scaled and blocked, the strong brine softening reaction tank cannot operate, and simultaneously the effluent turbidity
The system and the method for reducing scale formation in the softening treatment of Reverse Osmosis (RO) concentrated brine lime/caustic soda ash are adopted to carry out production operation after the process is modified, and the results are shown in the following table 4:
table 4 systems and methods of the present invention
After the method is adopted, the operation is about 3 months after the sludge of the front-end efficient sedimentation tank is introduced, the tank wall only has a thin layer of scale, and the sodium carbonate tank hanging piece only has a thin layer of scale (1-3mm) after 3 months. The efficient sedimentation tank sludge pre-treated at the front end is introduced, the pH value of the first reaction tank is increased to 10.5, the good effect is obtained after the chemical addition of the soda ash is improved, the scaling of the soda ash softening reaction tank is delayed, the problem of poor sedimentation effect of the sedimentation tank is solved, the aeration (deposition prevention) is introduced into the flocculation area, the sedimentation tank is stopped for cleaning and maintenance within 30-40 days, the maintenance is changed into the maintenance within 8-10 months, and the stable production of the system is ensured.
The device for reducing scale formation in the softening treatment of Reverse Osmosis (RO) concentrated brine lime/caustic soda comprises a sludge feeding device, a multistage reaction tank, a chemical feeding device, an aeration device and the like. The invention has good effect of reducing scaling tendency for water treatment process facilities with longer running time and serious influence of scaling on pool wall pipelines, stirrers and the like.
According to the system and the method for reducing scaling in the softening treatment of the Reverse Osmosis (RO) strong brine lime/caustic soda, the front-end light sludge can be added into the RO strong brine multistage chemical softening reaction tank for hardness removal, if lime is added to the front end for hardness removal, on one hand, the addition amount of lime for the pretreatment of RO strong brine concentration or evaporative crystallization can be reduced, and meanwhile, the problems that suspended matters are low and the precipitation effect is poor when the RO strong brine is softened and hardness is removed are solved; on the other hand, the problem of scaling of the tank wall and the pipeline equipment is mainly delayed and solved.
The above description is only for the preferred embodiment of the present invention, but the scope of the present invention is not limited thereto, and any person skilled in the art should be able to cover the technical solutions and the inventive concepts of the present invention within the technical scope of the present invention.
Claims (7)
1. The utility model provides a reduce reverse osmosis strong brine lime/caustic soda ash and soften processing scale deposit system which characterized in that: comprises a dissolving and dispensing device, a dosing pump, an RO concentrated water device, a sludge dosing pump, a primary reaction tank, a secondary reaction tank, a tertiary reaction tank, a pre-settling tank, a sedimentation tank, a sludge discharge pump, an air compressor, a storage tank, a valve, a soda dosing pump, a soda dosing device and a PAM dosing device; the device comprises a dissolving and dispensing device, a first-stage reaction tank, a RO concentrated water device, a sludge feeding device, a sludge distribution pipeline, a second-stage reaction tank, a sedimentation tank, a first-stage reaction tank, a second-stage reaction tank, a third-stage reaction tank, a second-stage sedimentation tank, a third-stage sedimentation tank, a second-stage reaction tank and a third-stage sedimentation tank, wherein the dissolving and dispensing device is connected with the first-stage reaction tank through a chemical feeding pump and a chemical distribution pipeline; the sodium carbonate feeding device is connected with the secondary reaction tank through a sodium carbonate feeding pump and a pipeline, the PAM feeding device is connected with the tertiary reaction tank through a pump and a pipeline, the air compressor is connected with the storage tank, and the storage tank is respectively connected with the secondary reaction tank, the tertiary reaction tank and the preliminary sedimentation tank through a valve and an air distribution pipeline.
2. The system for reducing scaling in a reverse osmosis concentrated brine lime/caustic soda softening process of claim 1, wherein: the dissolving and dispensing device comprises a dissolving and dispensing pool, wherein a stirrer is arranged in the dissolving and dispensing pool.
3. The method of reducing scaling in a reverse osmosis concentrated brine lime/caustic soda softening process system as claimed in any one of claims 1 to 2, comprising the steps of:
(1) preparing a hydrated lime solution with the concentration of 1-5% or a caustic soda solution with the concentration of 1-10%, adding the hydrated lime solution or the caustic soda solution into a first-stage reaction tank through a dissolving and dispensing device and a dosing pump, and raising the pH value of RO concentrated water to 9.5-11;
(2) preparing a soda ash solution with the concentration of 3-10%, and adding a proper amount of soda ash into a secondary reaction tank through a soda ash adding device, wherein the specific adding amount is calculated by the calcium hardness in the RO concentrated water to be removed, and 0.5-1.2 times of the calcium hardness is taken according to the molar weight;
(3) preparing 0.1-0.4% polyacrylamide, and adding into a reaction tank of a three-stage reaction tank through a PAM dosing device;
(4) adding returned light sludge into the primary reaction tank through a sludge adding device, wherein the concentration of the returned light sludge is 1-2%, and the water content of the returned light sludge is 98-99%;
(5) aeration pipes are added in the second-stage reaction tank, the third-stage reaction tank and the pre-settling tank for aeration, so that sludge deposition is prevented.
4. The method of claim 3 for reducing scaling in a reverse osmosis concentrated brine lime/caustic soda softening process system, wherein the method comprises the steps of: in the step (1), the lime/caustic soda is added in a multi-point way and is uniformly added on the water inlet section of the primary reaction tank; in the step (1), the TDS of the RO concentrated water in the RO concentrated water device is 12000mg/L at 2000-.
5. The method of claim 4 for reducing scaling in a reverse osmosis concentrated brine lime/caustic soda softening process system, wherein the method comprises the steps of: in the step (2), the soda ash is added into a tubular drilled hole, and holes are uniformly added on the stirring diameter of the stirrer at intervals of 10-15 cm.
6. The method of claim 5 for reducing scaling in a reverse osmosis concentrated brine lime/caustic soda softening process system, wherein the method comprises the steps of: in the step (1), the step (2) and the step (3), the adding pipes are respectively suspended on the water surfaces of the reaction tanks of the first-stage reaction tank, the second-stage reaction tank and the third-stage reaction tank in a transversely-arranged mode and are not in direct contact with RO concentrated water during adding.
7. The method of claim 6 for reducing scaling in a reverse osmosis concentrated brine lime/caustic soda softening process system, wherein the method comprises the steps of: in the step (5), compressed air is added into the second-stage reaction tank, the third-stage reaction tank and the pre-settling tank through a storage tank, and the adding pipes of the two-stage reaction tank, the third-stage reaction tank and the pre-settling tank are stainless steel pipes with the diameter DN 8; the aeration pipe is positioned 10-20cm away from the bottom of the secondary reaction tank, the tertiary reaction tank and the preliminary sedimentation tank; the aeration pipe is provided with 1 feeding point at the interval of 0.3-0.5m in the preliminary sedimentation tank.
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