CN111847745A - Method for preventing scaling in evaporation process - Google Patents
Method for preventing scaling in evaporation process Download PDFInfo
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- CN111847745A CN111847745A CN202010665699.9A CN202010665699A CN111847745A CN 111847745 A CN111847745 A CN 111847745A CN 202010665699 A CN202010665699 A CN 202010665699A CN 111847745 A CN111847745 A CN 111847745A
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- scaling
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- 238000000034 method Methods 0.000 title claims abstract description 59
- 238000001704 evaporation Methods 0.000 title claims abstract description 41
- 230000008020 evaporation Effects 0.000 title claims abstract description 38
- 230000008569 process Effects 0.000 title claims abstract description 37
- 239000002351 wastewater Substances 0.000 claims abstract description 32
- 239000000126 substance Substances 0.000 claims abstract description 23
- 239000007787 solid Substances 0.000 claims abstract description 21
- 239000002245 particle Substances 0.000 claims abstract description 11
- 239000003795 chemical substances by application Substances 0.000 claims description 33
- HEMHJVSKTPXQMS-UHFFFAOYSA-M Sodium hydroxide Chemical compound [OH-].[Na+] HEMHJVSKTPXQMS-UHFFFAOYSA-M 0.000 claims description 27
- 238000002425 crystallisation Methods 0.000 claims description 17
- 230000008025 crystallization Effects 0.000 claims description 15
- CDBYLPFSWZWCQE-UHFFFAOYSA-L sodium carbonate Substances [Na+].[Na+].[O-]C([O-])=O CDBYLPFSWZWCQE-UHFFFAOYSA-L 0.000 claims description 12
- 239000007788 liquid Substances 0.000 claims description 10
- 239000000243 solution Substances 0.000 claims description 10
- 229910000029 sodium carbonate Inorganic materials 0.000 claims description 6
- 230000001105 regulatory effect Effects 0.000 claims description 5
- 239000012047 saturated solution Substances 0.000 claims description 4
- 239000002253 acid Substances 0.000 claims description 2
- 239000003814 drug Substances 0.000 claims description 2
- 230000003750 conditioning effect Effects 0.000 claims 1
- 238000004140 cleaning Methods 0.000 abstract description 3
- 230000002035 prolonged effect Effects 0.000 abstract 1
- 239000012452 mother liquor Substances 0.000 description 19
- 229910001424 calcium ion Inorganic materials 0.000 description 18
- OSGAYBCDTDRGGQ-UHFFFAOYSA-L calcium sulfate Chemical compound [Ca+2].[O-]S([O-])(=O)=O OSGAYBCDTDRGGQ-UHFFFAOYSA-L 0.000 description 16
- BHPQYMZQTOCNFJ-UHFFFAOYSA-N Calcium cation Chemical compound [Ca+2] BHPQYMZQTOCNFJ-UHFFFAOYSA-N 0.000 description 14
- VTYYLEPIZMXCLO-UHFFFAOYSA-L Calcium carbonate Chemical compound [Ca+2].[O-]C([O-])=O VTYYLEPIZMXCLO-UHFFFAOYSA-L 0.000 description 13
- 238000006243 chemical reaction Methods 0.000 description 13
- 239000013078 crystal Substances 0.000 description 12
- BVKZGUZCCUSVTD-UHFFFAOYSA-L Carbonate Chemical compound [O-]C([O-])=O BVKZGUZCCUSVTD-UHFFFAOYSA-L 0.000 description 7
- 235000011132 calcium sulphate Nutrition 0.000 description 7
- 230000004224 protection Effects 0.000 description 7
- 238000000926 separation method Methods 0.000 description 7
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 7
- OYPRJOBELJOOCE-UHFFFAOYSA-N Calcium Chemical compound [Ca] OYPRJOBELJOOCE-UHFFFAOYSA-N 0.000 description 6
- VEXZGXHMUGYJMC-UHFFFAOYSA-N Hydrochloric acid Chemical compound Cl VEXZGXHMUGYJMC-UHFFFAOYSA-N 0.000 description 6
- JLVVSXFLKOJNIY-UHFFFAOYSA-N Magnesium ion Chemical compound [Mg+2] JLVVSXFLKOJNIY-UHFFFAOYSA-N 0.000 description 6
- 239000011575 calcium Substances 0.000 description 6
- 229910000019 calcium carbonate Inorganic materials 0.000 description 6
- 239000013043 chemical agent Substances 0.000 description 6
- 229910001425 magnesium ion Inorganic materials 0.000 description 6
- 150000003839 salts Chemical class 0.000 description 6
- BVKZGUZCCUSVTD-UHFFFAOYSA-M Bicarbonate Chemical compound OC([O-])=O BVKZGUZCCUSVTD-UHFFFAOYSA-M 0.000 description 5
- 239000000047 product Substances 0.000 description 5
- CURLTUGMZLYLDI-UHFFFAOYSA-N Carbon dioxide Chemical compound O=C=O CURLTUGMZLYLDI-UHFFFAOYSA-N 0.000 description 4
- FAPWRFPIFSIZLT-UHFFFAOYSA-M Sodium chloride Chemical compound [Na+].[Cl-] FAPWRFPIFSIZLT-UHFFFAOYSA-M 0.000 description 4
- 230000002265 prevention Effects 0.000 description 4
- 238000010586 diagram Methods 0.000 description 3
- 239000002244 precipitate Substances 0.000 description 3
- QAOWNCQODCNURD-UHFFFAOYSA-L Sulfate Chemical compound [O-]S([O-])(=O)=O QAOWNCQODCNURD-UHFFFAOYSA-L 0.000 description 2
- 230000015572 biosynthetic process Effects 0.000 description 2
- 239000001569 carbon dioxide Substances 0.000 description 2
- 229910002092 carbon dioxide Inorganic materials 0.000 description 2
- 125000005587 carbonate group Chemical group 0.000 description 2
- 230000006835 compression Effects 0.000 description 2
- 238000007906 compression Methods 0.000 description 2
- 230000009977 dual effect Effects 0.000 description 2
- 230000000694 effects Effects 0.000 description 2
- 230000009467 reduction Effects 0.000 description 2
- 239000002455 scale inhibitor Substances 0.000 description 2
- 239000011780 sodium chloride Substances 0.000 description 2
- FYYHWMGAXLPEAU-UHFFFAOYSA-N Magnesium Chemical compound [Mg] FYYHWMGAXLPEAU-UHFFFAOYSA-N 0.000 description 1
- BPQQTUXANYXVAA-UHFFFAOYSA-N Orthosilicate Chemical compound [O-][Si]([O-])([O-])[O-] BPQQTUXANYXVAA-UHFFFAOYSA-N 0.000 description 1
- 229910019142 PO4 Inorganic materials 0.000 description 1
- 238000009825 accumulation Methods 0.000 description 1
- 150000001450 anions Chemical class 0.000 description 1
- 238000010923 batch production Methods 0.000 description 1
- 229910052791 calcium Inorganic materials 0.000 description 1
- 239000001175 calcium sulphate Substances 0.000 description 1
- 150000001768 cations Chemical class 0.000 description 1
- 238000005119 centrifugation Methods 0.000 description 1
- 239000002738 chelating agent Substances 0.000 description 1
- 238000010924 continuous production Methods 0.000 description 1
- 230000007547 defect Effects 0.000 description 1
- 230000003111 delayed effect Effects 0.000 description 1
- 230000003467 diminishing effect Effects 0.000 description 1
- 230000003631 expected effect Effects 0.000 description 1
- 239000006260 foam Substances 0.000 description 1
- 239000010440 gypsum Substances 0.000 description 1
- 229910052602 gypsum Inorganic materials 0.000 description 1
- 230000006872 improvement Effects 0.000 description 1
- 150000002500 ions Chemical class 0.000 description 1
- 230000007774 longterm Effects 0.000 description 1
- 239000011777 magnesium Substances 0.000 description 1
- 229910052749 magnesium Inorganic materials 0.000 description 1
- 159000000003 magnesium salts Chemical class 0.000 description 1
- 238000012423 maintenance Methods 0.000 description 1
- 229910052751 metal Inorganic materials 0.000 description 1
- 239000002184 metal Substances 0.000 description 1
- 239000000203 mixture Substances 0.000 description 1
- 239000010452 phosphate Substances 0.000 description 1
- 229940088417 precipitated calcium carbonate Drugs 0.000 description 1
- 238000001556 precipitation Methods 0.000 description 1
- 238000002203 pretreatment Methods 0.000 description 1
- 238000004886 process control Methods 0.000 description 1
- 235000012239 silicon dioxide Nutrition 0.000 description 1
- 239000002904 solvent Substances 0.000 description 1
- 238000003756 stirring Methods 0.000 description 1
- 239000002562 thickening agent Substances 0.000 description 1
- 238000004065 wastewater treatment Methods 0.000 description 1
Images
Classifications
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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
-
- 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
- C02F5/08—Treatment of water with complexing chemicals or other solubilising agents for softening, scale prevention or scale removal, e.g. adding sequestering agents
-
- 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
- C02F1/02—Treatment of water, waste water, or sewage by heating
- C02F1/04—Treatment of water, waste water, or sewage by heating by distillation or evaporation
-
- 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
- C02F1/02—Treatment of water, waste water, or sewage by heating
- C02F1/04—Treatment of water, waste water, or sewage by heating by distillation or evaporation
- C02F1/042—Prevention of deposits
-
- 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
- C02F1/38—Treatment of water, waste water, or sewage by centrifugal separation
- C02F1/385—Treatment of water, waste water, or sewage by centrifugal separation by centrifuging suspensions
-
- 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
- C02F1/52—Treatment of water, waste water, or sewage by flocculation or precipitation of suspended impurities
- C02F1/5236—Treatment of water, waste water, or sewage by flocculation or precipitation of suspended impurities using inorganic agents
-
- 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
- C02F1/52—Treatment of water, waste water, or sewage by flocculation or precipitation of suspended impurities
- C02F1/5236—Treatment of water, waste water, or sewage by flocculation or precipitation of suspended impurities using inorganic agents
- C02F1/5245—Treatment of water, waste water, or sewage by flocculation or precipitation of suspended impurities using inorganic agents using basic salts, e.g. of aluminium and iron
-
- 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
- C02F1/52—Treatment of water, waste water, or sewage by flocculation or precipitation of suspended impurities
- C02F2001/5218—Crystallization
-
- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F2301/00—General aspects of water treatment
- C02F2301/08—Multistage treatments, e.g. repetition of the same process step under different conditions
Landscapes
- Chemical & Material Sciences (AREA)
- Life Sciences & Earth Sciences (AREA)
- Hydrology & Water Resources (AREA)
- Engineering & Computer Science (AREA)
- Environmental & Geological Engineering (AREA)
- Water Supply & Treatment (AREA)
- Organic Chemistry (AREA)
- Chemical Kinetics & Catalysis (AREA)
- General Chemical & Material Sciences (AREA)
- Heat Treatment Of Water, Waste Water Or Sewage (AREA)
- Vaporization, Distillation, Condensation, Sublimation, And Cold Traps (AREA)
Abstract
In the process of evaporating the wastewater in the evaporation process equipment, a chemical descaling agent is added to separate solid particles formed by easily-scaling components from the wastewater in an insoluble form, so that the evaporator can be effectively prevented from scaling, the occupied area is small, the investment is small, the effective working time of the evaporator can be prolonged, the cleaning frequency of the evaporator can be reduced, the control is simple, and the management is simple.
Description
Technical Field
The invention relates to a method for preventing scaling in an evaporation process, in particular to an evaporation process in a wastewater treatment process.
Background
The components in the wastewater include water as a solvent and solutes such as various salts and organic substances. The evaporation process is commonly used for evaporation of high salinity wastewater for removing water and reducing the weight of residual wastewater, and is sometimes used for evaporation and crystallization to reduce the salinity of wastewater. Commonly used evaporators include single-effect evaporators, double-effect evaporators, multiple-effect evaporators, mechanical compression re-evaporation (MVR) evaporators, heat pump type evaporators and the like. A component in wastewater has a tendency to precipitate out of solution if reaching the crystallization point, i.e., the crystallization threshold, such that the product of the concentrations of such component in solution is greater than the solubility product of the component, e.g., a solution of sodium chloride may undergo repeated evaporation to cause precipitation of sodium chloride solids. Some components are easy to separate out from the waste water solution in the evaporation process, and deposit and attach on the surface of a waste water flow channel to form scale, such as the positions in a flow channel of a heat exchanger, the inner wall of a pipeline and the like. Especially, calcium ions, magnesium ions, other high valence metal cations and anions such as carbonate, sulfate radicals, silicic acid radicals, phosphate radicals and the like are combined to form dirt with strong adhesion and high hardness, and long-term accumulation easily causes the reduction of the inner diameter of a pipeline, the reduction of heat transfer performance and the like, and even leads to the unsmooth operation of an evaporation process.
There are three methods commonly used to prevent evaporative fouling. Firstly, the softening process is used as pretreatment, and the concentration of calcium and magnesium ions is reduced to reduce the risk of scaling. However, even through the softening process in the pretreatment, the concentration of scaling ions caused in the evaporation process is gradually increased, crystals are separated out after the concentration is higher than the critical value of scaling, or a supersaturated solution is formed, and the supersaturated solution is easily attached to a pipeline and equipment to form scaling, so that the equipment and the pipeline of the evaporation process are scaled in different degrees; secondly, a gypsum crystal seed method is adopted, a large amount of fine calcium sulfate crystals are used as crystal seeds to enable scaling to be carried out on the surfaces of the crystal seeds, scaling in evaporation equipment and pipelines is delayed, but the crystal seed method is easy to generate foam during evaporation, low in heat efficiency, low in cost performance and high in management level; thirdly, a method of adding a scale inhibitor is adopted, and the scale inhibitor or a chelating agent is added into the wastewater to prevent scale formation, but with the increase of the salt content of the evaporation mother liquor, the expected effect is difficult to achieve.
In order to overcome the defects of the evaporation and scaling prevention method, the invention provides the method which has simple and reliable working principle, convenient implementation and simple management and can effectively prevent the scaling of equipment and pipelines in the evaporation process for a long time.
Disclosure of Invention
The technical scheme for solving the problems is as follows: in the process of evaporating the wastewater in the evaporation process equipment, the method comprises the step of adding a chemical descaling agent to enable the easily-scaling components to form solid particles, so that the easily-scaling components are separated from the wastewater in a specific process equipment in an insoluble matter mode and are discharged out of an evaporation system, and the separated wastewater is continuously evaporated or is discharged out of the evaporation system.
The general evaporation equipment is mainly composed of a heat exchanger, an evaporator (also called separator, separation chamber, etc.), a vacuum pump, a circulating pump, a connecting pipeline, etc., and equipment such as a crystallizer (also called thickener, etc.), a mother liquor tank, a mother liquor pump, a centrifuge, etc. is possible for the technological process with crystallization requirements; MBR equipment also has equipment such as vapor compressor. The process equipment illustrated in this patent is only for the purpose of illustrating the patent principles and may not be necessary or alternative to the specific implementation, as desired, without diminishing the scope of protection of this patent.
The chemical agent is added in the patent, so that the added agent in the process of forming solid particles by the easily-scaling components is temporarily called as a chemical descaling agent, the specific type needs to be determined according to the water quality characteristics, if the agent which is possibly added for calcium and magnesium ions is a combined agent similar to sodium carbonate and sodium hydroxide liquid, magnesium salt is probably added for preventing silicate scaling, then agents such as sodium hydroxide and the like or similar agents are added, the possible reaction and separation processes are at least once, and the continuous process or the batch process can be carried out. The description of the patent only takes the calcium and magnesium ion scale prevention as an example for illustration, and the types of chemical agents and reaction modes which need to be added are only used for illustrating the working principle of the invention, so that the protection scope of the patent is not reduced.
Adding chemical descaling agent to make the waste water after the easy-scaling component forms solid particles, namely the evaporation mother liquor, return to the evaporation system for continuous evaporation. The evaporation system may also be vented. As a further improvement of the invention, a chemical descaling agent is added to enable the solid particles in the wastewater after the solid particles are formed by the easily-scaling components to be separated from the mother liquor, and a suitable chemical agent is added to enable the mother liquor to be changed from a saturated solution of a certain scaling substance to an unsaturated solution. If sodium carbonate and sodium hydroxide liquid are used as chemical descaling agents to enable calcium and magnesium ions to form solids, a proper amount of chemical agents are added into mother liquor of calcium and magnesium precipitates separated by a centrifuge, the chemical agents are tentatively named as 'post-crystallization regulating agents', if sodium hydroxide and sodium carbonate are added to remove calcium and magnesium ions, a proper amount of hydrochloric acid is added to serve as post-crystallization regulating agents, firstly, the PH value of the mother liquor can be reduced, and secondly, the mother liquor is changed into unsaturated solution and is far away from a crystallization point.
The invention adds simple procedures in the conventional evaporation process to prevent scaling, has simpler process and particularly simplifies the upgrading and reconstruction of the existing evaporation equipment.
The chemical descaling agent is added, particularly the chemical descaling agent is added into a crystallizer, and the agent is adjusted after crystallization is added into a mother liquor tank, so that equipment is not specially added, and dirt solids and other solid salts to be crystallized can be discharged together. This is also one of the important protections of this patent. Even if a method of adding chemical descaling agents to other parts of the evaporator for scale prevention is adopted, the consumption of the agents is greatly reduced because the concentrated wastewater is treated and the water quantity is reduced, and the volume required by the reaction is reduced because the reaction is accelerated due to higher reaction temperature, so that the total occupied area is smaller than that of a softening pretreatment method and a crystal seed method.
The invention effectively prevents scaling and reduces the downtime loss and maintenance cost of cleaning. Because the solubility product of the crystals formed by the specific scaling substances under the specific reaction conditions is unchanged, the scale prevention effect of the invention is stable, and the controllability of the technological process is good.
The main process method of the invention is adding medicament and simple separation, the adding and reaction processes can be controlled by metering equipment and a process control instrument, the control is simple, and the management is simpler.
The invention has the advantages of effectively preventing scaling, small occupied area, less investment, simple control and simple management, can improve the effective working time of the evaporator, and can reduce the cleaning times of the evaporator.
Drawings
The invention is further illustrated with reference to the figures and examples and is described in principle in order to prevent calcium ions from forming calcium sulphate scale.
FIG. 1 is a process flow diagram of the present invention, an embodiment of a mechanical compression re-evaporator.
FIG. 2 is another process flow diagram of the present invention, which is one embodiment of a dual effect evaporator.
FIG. 3 is a flow diagram of another process of the present invention for a dual effect evaporator.
In the above drawings: 1. the system comprises a heat exchanger, 2 a circulating pump, 3 an evaporator, 4 a vacuum pump, 5 a crystallizer, 6 a centrifuge, 7 a mother liquor tank, 8 a discharge pump, 9 a mother liquor pump, 10 a steam compressor, 11 a chemical descaling agent reaction tank, 12 a solid scale separator, 13 a steam-water separator and 14 a secondary steam condensate pump.
Detailed Description
The wastewater in figure 1 and figure 2 is continuously heated by the heat exchanger and evaporated by the evaporator, and as the water is evaporated, the concentration of calcium ions and sulfate ions in the wastewater is higher and higher, and the crystallization point is approached, and in the wastewater is assumed to contain a small amount of bicarbonate. In the figure 1 and the figure 2, the chemical descaling agents are added into the crystallizer (5), the agents are sodium hydroxide and sodium carbonate, the sodium hydroxide enables the original bicarbonate in the wastewater to form carbonate, the added and newly formed carbonate ions and calcium ions can form calcium carbonate precipitates, the calcium ions dissolved in the liquid are greatly reduced, the concentration of the calcium ions is low, and the scaling of calcium sulfate is prevented. The precipitated calcium carbonate crystals formed in the crystallizer are more easily attached to the existing crystal nuclei, namely small suspended particles, in the crystallizer, so that the small suspended particles form large suspended particles, the subsequent solid-liquid separation is more facilitated, and even if small dirt is formed on the wall of the crystallizer, the dirt can quickly fall off from the wall of the crystallizer due to stirring disturbance in the crystallizer to form new crystal nuclei. The mother liquor mixture containing a large number of large-particle crystals enters a centrifuge (6) for solid-liquid separation, the centrifugate enters a mother liquor tank (7), and the centrifuged solid salt is collected and then is separately disposed. The waste water after centrifugation is saturated solution of calcium carbonate, acid is added into the mother liquor tank, for example, hydrochloric acid is used as regulating agent after crystallization, carbonate forms bicarbonate or forms carbon dioxide gas to be released out of liquid, the solubility product of calcium ions and sulfate radicals or carbonate in the waste water mother liquor is far less than the concentration required by crystallization of calcium sulfate and calcium carbonate, and thus the scaling tendency of calcium sulfate and calcium carbonate of calcium ions in the system can not be increased after the mother liquor flows back to the system. All the feeding parts described in this embodiment are generally indicated, and as shown in fig. 1 and fig. 2, the feeding parts are fed into the crystallizer and are fed into the upper part of the crystallizer, and actually, the feeding parts can also be fed into any pipeline connected with the crystallizer and any part of the crystallizer, which does not reduce the protection scope of the present invention.
The method for adding chemical agents to prevent scale is indicated in the attached figure 3, waste water is heated by a first-stage heat exchanger and evaporated by a first-stage evaporator, the concentrations of calcium ions and sulfate ions in the waste water are higher and are close to a crystallization point, a chemical scale removal agent reaction tank (11) and a solid scale separator (12) are arranged at the outlet of a circulating pump of the evaporator, sodium hydroxide and sodium carbonate are added into the chemical scale removal agent reaction tank (11), the sodium hydroxide enables original bicarbonate in the waste water to form carbonate, the added and newly formed carbonate ions and the calcium ions form calcium carbonate precipitate and are separated out in the solid scale separator, so that the calcium ions dissolved in the liquid are greatly reduced, the concentration of the calcium ions is low, and the scale formation of calcium sulfate of a subsequent system is prevented. The waste water after solid scale separation is saturated solution of calcium carbonate, hydrochloric acid is added into a water outlet pipeline of the solid scale separator to be used as a regulating agent after crystallization, carbonate forms bicarbonate or forms carbon dioxide gas to be released out of liquid, the solubility product of calcium ions and sulfate radicals or carbonate in the waste water mother liquor is far less than the concentration required by crystallization, and therefore the calcium sulfate scaling tendency of the calcium ions in the system can not be increased after the mother liquor flows back to the system. All the adding parts described in the embodiment are general terms, and as shown in the attached drawing 3, the adding parts can be added into any pipeline and any part of a chemical descaling agent reaction tank, so that the protection range of the invention is not reduced. And as shown in the attached figure 3, the part which is reasonably added in the solid scale separator can also be added in the outlet pipeline of the solid scale separator to achieve the same effect, so that the protection scope of the invention is not reduced. The first stage of the secondary evaporator at the anti-scale agent adding part in the attached figure 3 is only an illustration of the method, and the practical implementation can be applied to any one stage or a plurality of parts of the evaporator for simultaneous use.
The attached fig. 3 needs to additionally add a chemical descaling agent reaction tank (11) and a solid scale separator (12), while the crystallizer in the embodiment of the attached fig. 1 and 2 functions as both a crystallization device for other salts and a chemical descaling agent reaction tank, and the centrifuge in the embodiment of the attached fig. 1 and 2 functions as both a solid-liquid separation device for other salts and a solid scale separator. This is also one of the important protections of this patent.
The above-described embodiments merely provide one solution to the objects of the invention, and any other variations and combinations may be adopted according to the principles of the invention without departing from the scope of the invention.
Claims (6)
1. A method for preventing scaling in an evaporation process, wherein waste water is evaporated in evaporation process equipment, is characterized in that: the evaporation process comprises a process of adding a chemical descaling agent to enable the easily-scaling components to form solid particles, so that the easily-scaling components are separated from the wastewater in an insoluble form and are discharged out of an evaporation system, and the separated wastewater is continuously evaporated or discharged out of the evaporation system.
2. The method of preventing fouling in an evaporation process according to claim 1, wherein: adding the separated wastewater into a regulating agent after crystallization so as to change the separated wastewater from a saturated solution of the scaling substances into an unsaturated solution.
3. The method of preventing fouling in an evaporation process according to claim 1, wherein: the part where the chemical descaling agent is added is in the crystallizer.
4. The method of preventing fouling in an evaporation process according to claim 2, wherein: the part for adjusting the medicament after adding and crystallizing is in a mother liquid tank.
5. The method of preventing fouling in an evaporation process according to claim 1, wherein: the class of chemical descaling agents is similar to the combination of sodium hydroxide and sodium carbonate.
6. The method of preventing fouling in an evaporation process according to claim 2, wherein: the type of conditioning agent after crystallization is an acid.
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Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN115259474A (en) * | 2022-08-23 | 2022-11-01 | 嘉戎技术(北京)有限公司 | Medical wastewater softening and hardness removing unit, treatment system and treatment method |
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