CN113683249B - Method for removing chloride ions in desulfurization wastewater - Google Patents
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Abstract
The invention discloses a method for removing chloride ions in desulfurization wastewater, which comprises the steps of adding calcium aluminate into the desulfurization wastewater for pretreatment, removing primary precipitate after pretreatment, adding calcium hydroxide and aluminum powder, adjusting the pH value to be alkaline, carrying out ultrasonic treatment, heating to generate secondary precipitate, and removing the secondary precipitate. The method is not only suitable for removing the chloride ions in a large amount of wastewater, but also can effectively reduce the dechlorination cost.
Description
Technical Field
The invention belongs to the technical field of wastewater treatment and recycling, and relates to a method for removing chloride ions in desulfurization wastewater.
Background
The information in this background section is only for enhancement of understanding of the general background of the invention and is not necessarily to be construed as an admission or any form of suggestion that this information forms the prior art that is already known to a person of ordinary skill in the art.
The water used by power plants and steel plants belongs to industrial water, the water consumption is large, and the unreasonable utilization easily causes water resource waste, so that the water using mode of zero discharge of waste water of the power plants and the steel plants is imperative. Under the urgent requirement of zero discharge of wastewater of power plants and steel plants, the content of chloride ions is taken as an important index for recycling wastewater of the power plants and the steel plants, and the high content of chloride ions in the wastewater seriously harms equipment and production, so the detection of the high content of chloride ions in the wastewater of the power plants and the steel plants is necessary. The method is characterized by comprising the following steps of considering the complex conditions of the waste water composition, turbidity, color and the like of a power plant and a steel plant, wherein the high-salinity waste water composition is complex and has extremely high pollution, the most difficult-to-treat component is the overhigh content of chloride ions, the concentration of the chloride ions in the high-salinity waste water of a common enterprise is 1000-50000 mg/L, the high concentration of the chloride ions can cause serious damage to equipment and facilities of the power plant and the steel plant and cause serious corrosion, so far, no process for efficiently treating the chloride ions in the waste water at low cost exists, and the removal of the chloride ions is the most important problem in the high-salinity waste water treatment and is also a worldwide problem; and has the functions of removing phosphorus, heavy metals and the like.
According to the knowledge of the inventor, the current removing principle of the chloride ions in the desulfurization wastewater mainly comprises two principles: the first is replacement by other anions; the second is removal with other cations. According to different properties, the method can be divided into: precipitation, evaporative concentration, electro-adsorption, ion-exchange and electrochemical methods.
The precipitation method adopts Ag or Hg and the like to react with Cl to generate AgCl or HgCl precipitate so as to remove Cl, the removal rate of chloride ions reaches more than 90 percent, and the method has the characteristics of simple operation, small pollution, high removal rate and the like. The chemical precipitation method has high industrial cost due to the addition of high-price precipitation reagents such as silver nitrate, mercury nitrate and the like, and cannot be widely applied.
The evaporation concentration method heats the waste water due to the relatively low boiling point of the hydrogen chloride, removes the waste water together with volatile substances such as water vapor and the like, and finally concentrates and crystallizes the inorganic salt chloride which has a boiling point higher than that of water, thereby realizing the separation of chloride ions and the waste water. The evaporation concentration method is suitable for small-volume high-concentration wastewater, is simple to operate and has obvious effect, but the industrial wastewater has larger water volume and higher treatment cost, and is not practical compared with other treatment methods.
The electro-adsorption method and the electro-adsorption separation technology combine an electrochemical theory and an adsorption separation technology, and apply an electrostatic field effect on an aqueous solution, and apply direct current voltage on an electrode end to form an electric double layer on the surface of two electrode levels. Ions in the solution are adsorbed during charging, and energy and ions are released during discharging, so that the double electric layers are regenerated. The main problems are as follows: (1) the system has low salt removal rate, generally 60-75%, and high removal efficiency, generally speaking, the removal rate of chloride ions. And the salt rejection rate is obviously influenced by the hardness. The efficiency of treating high-hardness water is reduced; (2) the regeneration time is long, the concentrated water discharge amount is large, generally speaking, the system regeneration time is 36-42min, and the influence of the subsequent process is serious; (3) the internal electrode plate is not easy to be uniformly contacted with water. The method has no engineering application basically except the limitation of the technology, and the general customers cannot accept the method because the material price is too high.
The ion exchange method adopts ion exchanger to exchange with chloride ion, and the ion exchange resin has different adsorption capacities on different ions, so that the ions in the medium can be selectively removed. Dilute sulfuric acid is used as a transformation agent and a resolving agent, and macroporous anion resin is used for removing chloride ions in the zinc sulfate solution. The resin can form internal salt when contacting with external strong salt solution, which is not good for removing chloride ions, but the tendency of forming internal salt is weakened when distilled water is introduced, and the strong base weak acid type amphoteric resin self-made in a laboratory is used for removing Cl in the soda ash water by an ion exchange method, and the Cl removal rate is 85% under the best application condition. The treatment cost is very high and is not suitable for industrial application with large water amount.
The chemical redox method mainly includes electrolysis, electrodialysis, and the like. The electrolysis is that when the sewage in the electrolytic cell is electrified, the negative and positive levels generate potential difference, and pollutants in the sewage are oxidized at the anode and reduced at the cathode or reacted with polar reaction products to be converted into harmless components to be separated and removed. However, the electrolysis method has low efficiency of removing chloride ions, and is not suitable for practical application. The electrodialysis method takes an ion exchange membrane as a dialysis membrane and takes electric energy as power, and the process is the combination of electrolysis and dialysis diffusion; under the action of an external direct current electric field, the anions and the cations move towards the anode and the cathode respectively, and because the cation membrane theoretically only allows the cations to pass through and the anion membrane only allows the anions to pass through, the removal of the chloride ions is realized. The electrodialysis method is suitable for treating chlorine-containing wastewater with small water volume and low concentration, has larger water consumption and power consumption and higher cost, and a dialysis membrane is easy to block.
In conclusion, the existing method for removing chloride ions has high cost, so that the development of removing chloride ions in wastewater is hindered.
Disclosure of Invention
In order to solve the defects of the prior art, the invention aims to provide a method for removing chloride ions in desulfurization wastewater, which is not only suitable for removing chloride ions in a large amount of wastewater, but also can effectively reduce the cost of chlorine removal.
In order to achieve the purpose, the technical scheme of the invention is as follows:
on the one hand, the method for removing chloride ions in the desulfurization wastewater comprises the steps of adding calcium aluminate into the desulfurization wastewater for pretreatment, removing primary precipitate after pretreatment, adding calcium hydroxide and aluminum powder, adjusting the pH value to be alkaline, carrying out ultrasonic treatment, carrying out heating treatment to generate secondary precipitate, and removing the secondary precipitate.
The object of the present invention is to remove chloride ions from waste water in the form of a precipitate of hydrated calcium chloroaluminate. The hydrated calcium chloroaluminate is divided into low-chlorine type and high-chlorine type according to the amount of bound chlorine, and the chemical formula of the low-chlorine hydrated calcium chloroaluminate is 3 CaO. Al2O3·CaCl2·10H2O, high-chlorine hydrated calcium chloroaluminate with the chemical formula of 3CaO & Al2O3·3CaCl2·30H2And O, wherein more chloride ions can be combined in the high-chlorine hydrated calcium chloroaluminate, so that the removal efficiency of the chloride ions in the wastewater can be greatly improved, however, the high-chlorine hydrated calcium chloroaluminate is difficult to form, and is particularly difficult to form in the desulfurization wastewater. Therefore, in the technical scheme provided by the invention, firstly, the calcium aluminate is adopted to treat the desulfurization wastewater, and the desulfurization wastewater contains a large amount of sulfate radicals, but the inventor researches and discovers that the existence of the sulfate radicals can influence the formation of hydrated calcium chloroaluminate (especially high-chloride type hydrated calcium chloroaluminate), so that calcium aluminate forms ettringite precipitate with the sulfate radicals and calcium in the desulfurization wastewater, sulfate ions in the desulfurization wastewater are removed, and the formation of the hydrated calcium chloroaluminate (especially high-chloride type hydrated calcium chloroaluminate) is ensured. To form stable high-chlorine hydrated calcium chloroaluminate in desulfurization for removing sulfate radicalAccording to the invention, calcium hydroxide and aluminum powder are added, the pH is adjusted, so that ions in the wastewater are fully combined to form hydrated calcium chloroaluminate, and then ultrasonic and heating treatment is performed in sequence, so that stable high-chlorine hydrated calcium chloroaluminate is formed. By forming the high-chlorine type hydrated calcium chloroaluminate, chloride ions in the desulfurization wastewater are fixed, the cost of the adopted raw materials is low, the fixed amount of the high-chlorine type hydrated calcium chloroaluminate to the chloride ions is large, the usage amount of the raw materials is further reduced, and the treatment cost of the desulfurization wastewater is greatly reduced.
Meanwhile, the hydrated calcium chloroaluminate is an intercalation compound and has peculiar adsorption exchange effect, so that after the high-chlorine hydrated calcium chloroaluminate is formed, other impurities and ions in the desulfurization wastewater can be adsorbed, and the treatment effect of the desulfurization wastewater is improved.
As the hydrated calcium chloroaluminate belongs to inorganic and non-hazardous articles and is widely applied, on the other hand, the method for removing the chloride ions in the desulfurization wastewater is applied to the preparation of the high-chlorine hydrated calcium chloroaluminate.
Since the hydrated calcium chloroaluminate can be used for water treatment, soil remediation and pesticide or fertilizer slow release agents, the high-chlorine hydrated calcium chloroaluminate formed in the removal method can be used for preparing water treatment agents, soil remediation agents, slow release pesticides and/or slow release fertilizers. Therefore, in the third aspect of the invention, the application of the method for removing chloride ions in the desulfurization wastewater in the preparation of water treatment agents, soil remediation agents, slow-release pesticides and/or slow-release fertilizers is provided.
Compared with the existing preparation method of hydrated calcium chloroaluminate, the method for removing chloride ions in the desulfurization wastewater is applied to the preparation of high-chlorine hydrated calcium chloroaluminate, so that the raw material cost is reduced, the utilization value of the hydrated calcium chloroaluminate is high, and low-value desulfurization wastewater can be converted into high-value hydrated calcium chloroaluminate, so that the enterprise benefit is increased.
The invention has the beneficial effects that:
1. according to the method, the calcium aluminate is adopted to pretreat the desulfurization wastewater, the calcium aluminate adsorbs sulfate radicals to be converted into ettringite precipitate, the sulfate radicals in the desulfurization wastewater are removed through pretreatment, and the formation of hydrated calcium chloroaluminate is prevented from being influenced by the existence of the sulfate radicals.
2. According to the method, calcium hydroxide and aluminum powder are added, the pH value is adjusted, ions in the wastewater are fully combined to form hydrated calcium chloroaluminate, then ultrasonic treatment and heating treatment are sequentially carried out, so that stable high-chlorine hydrated calcium chloroaluminate is formed, and the removal efficiency of chloride ions in the wastewater is greatly improved by forming the high-chlorine hydrated calcium chloroaluminate, so that the dechlorination efficiency of the desulfurization wastewater treated by the method disclosed by the invention can be up to more than 90%.
3. The method provided by the invention forms high-chlorine hydrated calcium chloroaluminate, and removes heavy metals, phosphorus and other substances while removing chlorine.
4. According to the method provided by the invention, a small amount of calcium hydroxide and aluminum powder are added to form high-chlorine hydrated calcium chloroaluminate, less raw materials are combined with more chloride ions, the wastewater dechlorination cost is low, and the method is suitable for large-water-volume industrial wastewater treatment; meanwhile, the method is simple to operate and does not need maintenance.
Detailed Description
It is to be understood that the following detailed description is exemplary and is intended to provide further explanation of the invention as claimed. Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs.
It is noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of exemplary embodiments according to the invention. As used herein, the singular forms "a", "an" and "the" are intended to include the plural forms as well, and it should be understood that when the terms "comprises" and/or "comprising" are used in this specification, they specify the presence of stated features, steps, operations, devices, components, and/or combinations thereof, unless the context clearly indicates otherwise.
In view of the fact that the method for removing chloride ions in the prior art is high in cost, the invention provides a method for removing chloride ions in desulfurization wastewater.
The invention provides a method for removing chloride ions in desulfurization wastewater, which comprises the steps of adding calcium aluminate into the desulfurization wastewater for pretreatment, removing primary precipitate after pretreatment, adding calcium hydroxide and aluminum powder, adjusting the pH value to be alkaline, carrying out ultrasonic treatment, heating to generate secondary precipitate, and removing the secondary precipitate.
According to the method, the calcium aluminate is firstly adopted to treat the desulfurization wastewater, ettringite precipitate is formed by the calcium aluminate and sulfate radicals and calcium in the desulfurization wastewater, and sulfate radical ions in the desulfurization wastewater are separated, so that formation of hydrated calcium chloroaluminate (especially high-chlorine type hydrated calcium chloroaluminate) is guaranteed. Secondly, calcium hydroxide and aluminum powder are added, the pH value is adjusted, ions in the wastewater are fully combined to form hydrated calcium chloroaluminate, and then ultrasonic and heating treatment is sequentially carried out, so that stable high-chlorine hydrated calcium chloroaluminate is formed. By forming the high-chlorine type hydrated calcium chloroaluminate, chloride ions in the desulfurization wastewater are fixed, the cost of the adopted raw materials is low, the fixed amount of the high-chlorine type hydrated calcium chloroaluminate to the chloride ions is large, the usage amount of the raw materials is further reduced, and the treatment cost of the desulfurization wastewater is greatly reduced. After the high-chlorine hydrated calcium chloroaluminate is formed, other impurities and ions in the desulfurization wastewater can be adsorbed, and the treatment effect of the desulfurization wastewater is improved.
The desulfurization wastewater of the present invention is wastewater generated in a conventional flue gas desulfurization process, in which wet desulfurization based on a limestone/gypsum method is generally adopted.
The pretreatment of the invention mainly means that after calcium aluminate is added, the calcium aluminate is combined with calcium ions and sulfate radicals to generate ettringite (3 CaO. Al)2O3·3CaSO4·32H2O), in order to promote the binding of calcium aluminate to calcium ions, sulfate, in some embodiments of this embodiment, the pretreatment is performed under agitation conditions. The calcium aluminate is insoluble in water, the calcium aluminate is difficult to be uniformly distributed in the water, the efficiency of combining calcium ions and sulfate radicals is lower, the uniform distribution of the calcium aluminate in the water is improved, the efficiency of the calcium ions and the sulfate radicals can be greatly improved, and the uniform distribution of the calcium aluminate in the water is improvedThe method comprises the steps of ultrasound, stirring, oscillation and the like, the ultrasound dispersion has higher requirement on the particle size of the calcium aluminate, and the oscillation dispersion has higher energy consumption for the treatment of large water amount, so that the stirring is adopted, the requirement on the particle size of the raw material is lower, the energy consumption is lower, and the cost is favorably reduced.
In some examples of this embodiment, the pretreatment time is 25 to 35 min. Under the condition, most of sulfate radicals can be completely converted into ettringite, the treatment efficiency is high, and especially, the sulfate radicals in the desulfurization wastewater can be completely converted into ettringite under the stirring condition.
In some examples of the embodiment, the ratio of the addition amount of the aluminum powder to the desulfurization wastewater after primary precipitation removal is 0.30-0.50: 1, g: and L.
In some examples of this embodiment, the mass ratio of the calcium hydroxide to the aluminum powder is 4.6-5.4: 3.6-4.4. The addition variety of chemical reagents is reduced, and the formation of hydrated calcium chloroaluminate is ensured.
In some examples of this embodiment, the pH is adjusted by the addition of calcium hydroxide and aluminum powder.
In some embodiments of this embodiment, the pH is adjusted to between 8.6 and 9.4. Under the condition, the forming efficiency of the hydrated calcium chloroaluminate can be ensured.
In some examples of this embodiment, the sonication time is 25 to 35 min. Ensures the formation of high-chlorine hydrated calcium chloroaluminate and reduces energy consumption.
In some examples of this embodiment, the heating is to 55-65 ℃. Ensures the formation of high-chlorine hydrated calcium chloroaluminate and reduces energy consumption.
In some examples of this embodiment, the heat treatment time is 45 to 50 hours.
In some examples of this embodiment, the heat treatment is performed with shaking. Ensuring the formation efficiency of the high-chlorine hydrated calcium chloroaluminate.
The invention also provides an application of the method for removing chloride ions in the desulfurization wastewater in preparation of high-chlorine hydrated calcium chloroaluminate.
In a third embodiment of the invention, the application of the method for removing chloride ions in the desulfurization wastewater in the preparation of a water treatment agent, a soil remediation agent, a slow-release pesticide and/or a slow-release fertilizer is provided.
In order to make the technical solutions of the present invention more clearly understood by those skilled in the art, the technical solutions of the present invention will be described in detail below with reference to specific embodiments.
Example 1
A method for removing chloride ions in desulfurization wastewater comprises the following steps:
1. adding 3CaO & Al into the desulfurization waste water2O3Until the pH value of the desulfurization wastewater is 7, mixing and stirring for 30min to remove sulfate radicals to form an ettringite precipitate 3 CaO. Al2O3·3CaSO4·32H2And O, filtering and separating the ettringite and the desulfurization wastewater.
2. Calcium hydroxide Ca (OH)2And adding aluminum powder Al into the desulfurization wastewater filtered in the step 1 according to the mass ratio of 5:4, mixing, and adjusting the pH value to 9, wherein the addition amount of the aluminum powder in each liter of the desulfurization wastewater is 0.4 g/L.
3. And (3) fully mixing for 30min by adopting an ultrasonic vibration rod to promote chemical reaction.
4. Regulating the water temperature to 60 ℃, keeping the temperature for 48 hours and shaking to form white hydrated calcium chloroaluminate 3CaO & Al2O3·3CaCl2·30H2The chloride ions are removed simultaneously with the precipitation of O.
5. The chloride ions and the additives in the water form hydrated calcium chloroaluminate 3CaO & Al2O3·3CaCl2·30H2White precipitate of O.
6. The white particle precipitate is filtered, and finally the chlorine ions in the wastewater are removed (the removal efficiency is 80 percent) and the hydrated calcium chloroaluminate with economic value is formed.
Example 2
A method for removing chloride ions in desulfurization wastewater comprises the following steps:
1. adding 3CaO & Al into the desulfurization waste water2O3Until the pH value of the desulfurization wastewater is 7, mixing and stirring for 30min to remove sulfate radicals to form an ettringite precipitate 3 CaO. Al2O3·3CaSO4·32H2And O, filtering and separating the ettringite and the desulfurization wastewater.
2. Calcium hydroxide Ca (OH)2And adding aluminum powder Al to the desulfurization wastewater filtered in the step 1 according to the mass ratio of 5:4, and mixing to adjust the pH value to 8.
3. And (3) fully mixing for 30min by adopting an ultrasonic vibration rod to promote chemical reaction.
4. Regulating the water temperature to 60 ℃, keeping the temperature for 48 hours and shaking to form white hydrated calcium chloroaluminate 3CaO & Al2O3·3CaCl2·30H2The chloride ions are removed simultaneously with the precipitation of O.
5. The chloride ions and the additives in the water form hydrated calcium chloroaluminate 3CaO & Al2O3·3CaCl2·30H2White precipitate of O.
6. The white particulate precipitate was filtered to finally remove chloride ions from the wastewater (removal efficiency of 68%) and form economically valuable hydrated calcium chloroaluminate.
Example 3
A method for removing chloride ions in desulfurization wastewater comprises the following steps:
1. adding 3CaO & Al into the desulfurization waste water2O3Until the pH value of the desulfurization wastewater is 7, mixing and stirring for 30min to remove sulfate radicals to form an ettringite precipitate 3 CaO. Al2O3·3CaSO4·32H2And O, filtering and separating the ettringite and the desulfurization wastewater.
2. Mixing calcium hydroxide Ca (OH)2And adding aluminum powder Al to the desulfurization wastewater filtered in the step 1 according to the mass ratio of 5:4, and mixing to adjust the pH value to 10.
3. And (3) fully mixing for 30min by adopting an ultrasonic vibration rod to promote chemical reaction.
4. Regulating the water temperature to 60 ℃, keeping the temperature for 48 hours and shaking to form white hydrated calcium chloroaluminate 3CaO & Al2O3·3CaCl2·30H2The chloride ions are removed simultaneously with the precipitation of O.
5. The chloride ions and the additives in the water form hydrated calcium chloroaluminate 3CaO & Al2O3·3CaCl2·30H2White precipitate of O.
6. The white particulate precipitate was filtered to finally remove chloride ions from the wastewater (removal efficiency of 74%) and form hydrated calcium chloroaluminate of economic value.
Comparative example 1
1. Proportionally mixing Ca (OH) hydroxide2And mixing the aluminum powder Al with the desulfurization wastewater filtered in the step 1 according to a certain proportion, and adjusting the pH value to 9.
2. And (3) fully mixing for 30min by adopting an ultrasonic vibration rod to promote chemical reaction.
3. The water temperature is adjusted to 60 ℃, the temperature is kept constant for 48 hours, and the shaking is carried out, so that white precipitates cannot be generated.
The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention, and various modifications and changes may be made by those skilled in the art. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.
Claims (9)
1. A method for removing chloride ions in desulfurization wastewater is characterized in that calcium aluminate is added into the desulfurization wastewater for pretreatment, calcium hydroxide and aluminum powder are added after primary precipitation after pretreatment is removed, the pH value is adjusted to be alkaline, ultrasonic treatment is carried out, then secondary precipitation is generated by heating treatment, and the secondary precipitation is removed;
the pretreatment comprises the steps of adding calcium aluminate into the desulfurization wastewater until the pH value of the desulfurization wastewater is 7, mixing and stirring, removing sulfate radicals to form ettringite precipitate, and filtering and separating the ettringite and the desulfurization wastewater; the pretreatment is carried out under the condition of stirring;
the secondary precipitation is high-chlorine hydrated calcium chloroaluminate.
2. The method for removing chloride ions from desulfurization waste water according to claim 1, wherein the pretreatment time is 25 to 35 min.
3. The method for removing chloride ions from desulfurization waste water according to claim 1, wherein the ratio of the addition amount of aluminum powder to the desulfurization waste water from which the primary precipitate is removed is 0.30 to 0.50:1, g: and L.
4. The method for removing chloride ions from desulfurization waste water according to claim 1, wherein the mass ratio of the calcium hydroxide to the aluminum powder is 4.6 to 5.4:3.6 to 4.4,
adjusting the pH value through the addition amount of calcium hydroxide and aluminum powder;
or, adjusting the pH value to 8.6-9.4.
5. The method for removing chloride ions from desulfurization waste water according to claim 1, wherein the ultrasonic treatment time is 25 to 35 min.
6. The method for removing chloride ions from desulfurization waste water according to claim 1, wherein the heating is carried out to 55 to 65 ℃;
or the time of the heating treatment is 45-50 h.
7. The method for removing chloride ions from desulfurization waste water according to claim 1, wherein the heating treatment is performed with shaking.
8. An application of the method for removing chloride ions in desulfurization wastewater according to any one of claims 1 to 7 in preparation of high-chlorine hydrated calcium chloroaluminate.
9. An application of the method for removing chloride ions in desulfurization wastewater according to any one of claims 1 to 7 in preparation of water treatment agents, soil remediation agents, slow-release pesticides and/or slow-release fertilizers.
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