A method for removing chloride ions from coking circulating water

Abstract

The present invention provides a method for removing chloride ions in coking circulating water, and relates to the technical field of chloride ion removal in water. The method for removing chloride ions in coking circulating water is to adjust the pH of coking circulating water to be neutral or weakly alkaline, add CaO and aluminum salt to control the molar ratio of Ca / Al / Cl in water to be 8-10:3-4:1, and remove chloride ions by coprecipitation reaction in the form of early stirring, mid-term intermittent ultrasonic treatment and subsequent pressure-boosting stirring. The present invention overcomes the shortcomings of the prior art, can effectively reduce or eliminate the interference of other anions on the dechlorination effect, improve the removal effect of chloride ions in circulating water, and is easy to control as a whole, with low processing cost.

Description

Technical Field

[0001] The invention relates to the technical field of chloride ion removal in water, and in particular to a method for removing chloride ions in coking circulating water. Background Art

[0002] The recycling and reuse of water resources provides us with more available water resources and enhances the safety of water ecology; however, for the recycling of water, risk management and ensuring the safety of water resources are particularly critical. In recent years, the hidden dangers caused by organic pollutants and microorganisms have received widespread attention. However, the risks caused by inorganic salts have not received enough attention. Although inorganic salts are less directly harmful to human health than organic pollutants and microorganisms, they may cause scale formation, corrosion of pipes, and have adverse effects on water recycling and final application.

[0003] Chloride, as the main inorganic substance in recycled water, has a variety of negative effects on water reuse. Chloride is considered to be one of the most common anions in nature, and it plays a vital role in physiological and industrial processes. Wastewater discharged from both daily life and industry contains a large amount of chloride ions, with a concentration greater than 200 mg / L. However, chloride ions are generally not considered as a mandatory control standard in wastewater treatment processes; therefore, wastewater treatment plants (WWTPs) are not designed to remove chlorides, but are often discharged to water recovery plants (WRPs). Chloride ions are different from sulfate ions because they have better solubility, smaller ionic radius, lower charge, and limited bioavailability. Therefore, wastewater containing chloride is more corrosive to pipes or related facilities. Chloride ions have the potential to negatively affect the end use of recycled water for agricultural irrigation and industrial applications, such as reducing crop yields, soil salinization, and corrosion of equipment. In addition, observational data show that the concentration of chloride in global freshwater environments has increased at a rate of approximately 2% over the past few decades.

[0004] Existing chloride ion treatment technologies mainly include non-selective treatment technologies and selective treatment technologies. Among them, non-selective treatment technologies include distillation, electrodialysis, ion exchange, membrane technology, electrochemical technology, advanced oxidation process, etc. The overall equipment investment is large and the loss is high. It may also cause secondary pollution and has a small application prospect. Selective treatment technologies mainly include AgCl precipitation method, CuCl precipitation method, Bi2O3 precipitation method, and Friedel salt precipitation method. Among them, Friedel salt precipitation method has a better overall development. The ultra-high lime aluminum process (UHLA) using calcium oxide (CaO) and sodium aluminate (NaAlO2) as calcium aluminum salts is used to remove Cl from circulating cooling water. -The process has a good overall effect and is easy to control the cost, but the overall removal rate is generally around 75% under more appropriate conditions. On this basis, further improving the efficiency of chloride ion removal is an important direction for coking circulating water treatment at this stage. Summary of the invention

[0005] In view of the shortcomings of the prior art, the present invention provides a method for removing chloride ions in coking circulating water, which can effectively reduce or eliminate the interference of other anions on the dechlorination effect, improve the removal effect of chloride ions in circulating water, and is easy to control as a whole with low processing cost.

[0006] To achieve the above objectives, the technical solution of the present invention is implemented through the following technical solutions:

[0007] A method for removing chloride ions from coking circulating water, the removal method comprising the following steps:

[0008] S1. Pretreatment of coking circulating water: adjusting the pH of the coking circulating water to 7-9 to obtain pretreated coking circulating water for standby use;

[0009] S2, raw material addition: add CaO and aluminum salt to the above-mentioned pre-treated coking circulating water, and control the molar ratio of Ca, Al in CaO and aluminum salt and Cl in pre-treated coking circulating water to be Ca / Al / Cl=8-10:3-4:1;

[0010] S3. Reaction treatment: adjust and control the temperature of the reaction system to 25-30°C, stir and treat for 8-10 minutes, then intermittently perform ultrasonic treatment, and then increase the pressure to 0.4-0.6 MPa and stir and treat for 10-15 minutes.

[0011] Preferably, the aluminum salt in step S2 is any one of NaAlO2, Al(NO3)3, and Al(OH)3.

[0012] Preferably, the aluminum salt in step S2 is NaAlO2.

[0013] Preferably, in step S2, the molar ratio of Ca / Al is controlled to be 2.5.

[0014] Preferably, the stirring speed of the stirring process in step S3 is 400-500 r / min.

[0015] Preferably, the intermittent ultrasonic treatment in step S3 is carried out by ultrasonic treatment for 1-2 minutes and then standing for 1-2 minutes, and the ultrasonic standing treatment is cyclically repeated 3-5 times.

[0016] Preferably, the frequency of the ultrasonic treatment is 20-40 kHz and the power is 300-400W.

[0017] The present invention provides a method for removing chloride ions in coking circulating water, which has the following advantages compared with the prior art:

[0018] The present invention adopts aluminum salt combined with CaO to remove chloride ions in circulating water, sets a suitable temperature, promotes the occurrence of chloride ion coprecipitation reaction by stirring in the early stage, ultrasonic intermittent treatment in the middle stage and pressure-boosting stirring in the late stage, and the chloride ions are efficiently precipitated, and the F - 、SO4 2- In the coprecipitation reaction, Cl - Remove the different degrees of inhibition shown to achieve F - 、SO4 2- The method of the present application can generate Ca4Al2O6Cl2·10H2O and Ca2Al (OH)6Cl·2H2O with more uniform and fine particle size distribution, thus enhancing the Cl - The removal effect makes the particles contact quickly and improves the Cl - removal efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 A schematic diagram of the microscopic morphology of the precipitate generated by using NaAlO2 as the aluminum salt in Example 2 of the present invention;

[0020] Figure 2 A schematic diagram of the microscopic morphology of the precipitate generated by using Al(NO3)3 as the aluminum salt in Example 2 of the present invention;

[0021] Figure 3 A schematic diagram of the microscopic morphology of the precipitate generated by using Al(OH)3 as the aluminum salt in Example 2 of the present invention;

[0022] Figure 4 The SEM images (ad) and TEM images (eh) of the precipitates obtained in Example 2 of the present invention and Comparative Example 1, wherein ab and ef are the SEM images and TEM images of the precipitate in Comparative Example 1; cd and gh are the SEM images and TEM images of the precipitate in Example 2;

[0023] Figure 5 This is an EDS image of the precipitate of Example 2 of the present invention;

[0024] Figure 6 This is the EDS graph of the precipitate of Comparative Example 2 of the present invention. DETAILED DESCRIPTION

[0025] In order to make the purpose, technical solution and advantages of the embodiments of the present invention clearer, the technical solution in the embodiments of the present invention is clearly and completely described below in combination with the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0026] Embodiment 1:

[0027] Removal of chloride ions in coking circulating water:

[0028] (1) Adjust the pH of the coking circulating water to 7 to obtain pre-treated coking circulating water for standby use;

[0029] (2) adding CaO and NaAlO2 to the above-mentioned pretreated coking circulating water, and controlling the molar ratio of Ca and Al in CaO and NaAlO2 and Cl in the pretreated coking circulating water to be Ca / Al / Cl=8:3.2:1;

[0030] (3) The temperature of the reaction system was adjusted to 25°C, and the mixture was stirred at 400 r / min for 8 min. Ultrasonic treatment was then performed at a frequency of 20 kHz and a power of 300 W for 2 min, followed by standing for 2 min. The ultrasonic standing treatment was repeated 3 times, and the pressure was increased to 0.4 MPa, and the mixture was stirred at 400 r / min for 15 min. The mixture was then filtered to obtain circulating water from which chloride ions had been removed.

[0031] Embodiment 2:

[0032] Removal of chloride ions in coking circulating water:

[0033] (1) Adjust the pH of the coking circulating water to 9 to obtain pre-treated coking circulating water for standby use;

[0034] (2) adding CaO and NaAlO2 to the above-mentioned pretreated coking circulating water, and controlling the molar ratio of Ca and Al in CaO and NaAlO2 and Cl in the pretreated coking circulating water to be Ca / Al / Cl=10:4:1;

[0035] (3) The temperature of the reaction system was adjusted to 30°C, and the mixture was stirred at 500 r / min for 10 min. The mixture was then ultrasonically treated at a frequency of 40 kHz and a power of 400 W for 1 min and allowed to stand for 1 min. The ultrasonic treatment was repeated 5 times, and the pressure was increased to 0.6 MPa and stirred at 500 r / min for 10 min. The mixture was then filtered to obtain circulating water from which chloride ions had been removed.

[0036] Comparative Example 1:

[0037] Removal of chloride ions in coking circulating water:

[0038] (1) Adjust the pH of the coking circulating water to 9 to obtain pre-treated coking circulating water for standby use;

[0039] (2) adding CaO and NaAlO2 to the above-mentioned pretreated coking circulating water, and controlling the molar ratio of Ca and Al in CaO and NaAlO2 and Cl in the pretreated coking circulating water to be Ca / Al / Cl=10:4:1;

[0040] (3) The temperature of the reaction system was adjusted to 30°C, and the mixture was stirred at 500 r / min for 30 min. The mixture was then filtered to obtain circulating water from which chloride ions had been removed.

[0041] Comparative Example 2:

[0042] Removal of chloride ions in coking circulating water:

[0043] (1) Adjust the pH of the coking circulating water to 9 to obtain pre-treated coking circulating water for standby use;

[0044] (2) adding CaO and NaAlO2 to the above-mentioned pretreated coking circulating water, and controlling the molar ratio of Ca and Al in CaO and NaAlO2 and Cl in the pretreated coking circulating water to be Ca / Al / Cl=10:4:1;

[0045] (3) The temperature of the reaction system was adjusted to 30°C, and ultrasonic treatment was performed for 30 min at a frequency of 40 kHz and a power of 400 W. The water was then filtered to obtain circulating water from which chloride ions were removed.

[0046] Comparative Example 3:

[0047] Removal of chloride ions in coking circulating water:

[0048] (1) Adjust the pH of the coking circulating water to 9 to obtain pre-treated coking circulating water for standby use;

[0049] (2) adding CaO and NaAlO2 to the above-mentioned pretreated coking circulating water, and controlling the molar ratio of Ca and Al in CaO and NaAlO2 and Cl in the pretreated coking circulating water to be Ca / Al / Cl=10:4:1;

[0050] (3) The temperature of the reaction system was adjusted to 30°C, and the mixture was stirred at 500 r / min for 10 min. The mixture was then ultrasonically treated at a frequency of 40 kHz and a power of 400 W for 1 min and allowed to stand for 1 min. The ultrasonic treatment was repeated 5 times, and the mixture was stirred at 500 r / min for 10 min. The mixture was then filtered to obtain circulating water from which chloride ions had been removed.

[0051] Comparative Example 4:

[0052] Removal of chloride ions in coking circulating water:

[0053] (1) Adjust the pH of the coking circulating water to 9 to obtain pre-treated coking circulating water for standby use;

[0054] (2) adding CaO and NaAlO2 to the above-mentioned pretreated coking circulating water, and controlling the molar ratio of Ca and Al in CaO and NaAlO2 and Cl in the pretreated coking circulating water to be Ca / Al / Cl=10:4:1;

[0055] (3) The temperature of the reaction system was adjusted to 25°C, and the mixture was stirred at 500 r / min for 10 min. Ultrasonic treatment was then performed at a frequency of 40 kHz and a power of 400 W for 10 min. The pressure was then increased to 0.6 MPa and stirred at 500 r / min for 10 min. The mixture was then filtered to obtain circulating water from which chloride ions had been removed.

[0056] Detection:

[0057] The same batch of coking circulating water from Huaibei Linhuan Coking Plant was selected as the experimental sample, and the chloride ion content was 108.40 mg / L, SO4 2- The content is 32.62mg / L.

[0058] 1. Detect the chloride ion content and SO4 content in the final circulating water of the above-mentioned Examples 1-2 and Comparative Examples 1-4. 2- The specific results are shown in Table 1 below:

[0059] Table 1

[0060]

[0061] From the above test, it can be seen that the method of Example 1-2 can significantly improve Cl - removal rate.

[0062] 2. Detect the influence of different aluminum salts on circulating water treatment:

[0063] Referring to the treatment method of Example 2, three aluminum salts, NaAlO2, Al(NO3)3, and Al(OH)3, were selected for detection to detect the effects of different aluminum salt co-precipitations on chloride ions and SO4 in circulating water. 2- The removal rate of , the specific results are shown in Table 2 below:

[0064] Table 2

[0065]

[0066] It can be seen from the above table that NaAlO2, Al(NO3)3, and Al(OH)3 can all remove chloride ions in circulating water, among which NaAlO2 has the best effect.

[0067] 3. Detect the influence of different Ca / Al / Cl molar ratios on circulating water treatment:

[0068] Referring to the treatment method and aluminum salt of Example 2, the effects of different Ca / Al / Cl molar ratios on chloride ions and SO4 in circulating water were detected. 2- The removal rate of , the specific results are shown in Table 3 below:

[0069] Table 3

[0070]

[0071] 4. The precipitates after filtering of Example 1-2 and Comparative Example 1-4 were analyzed to detect the particle size range of the precipitates. The specific results are shown in Table 4 below:

[0072] Table 4

[0073]

[0074] It can be seen from the above table that the precipitate obtained in Example 1-2 has a finer and more uniform particle size distribution.

[0075] The above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit the same. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that the technical solutions described in the aforementioned embodiments may still be modified, or some of the technical features may be replaced by equivalents. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for removing chloride ions from coking circulating water, characterized in that: The removal method comprises the following steps: S1. Pretreatment of coking circulating water: adjusting the pH of the coking circulating water to 7-9 to obtain pretreated coking circulating water for standby use; S2, raw material addition: add CaO and aluminum salt to the above-mentioned pre-treated coking circulating water, and control the molar ratio of Ca, Al in CaO and aluminum salt and Cl in pre-treated coking circulating water to be Ca / Al / Cl=8-10:3-4:1; the aluminum salt in step S2 is any one of NaAlO2, Al(NO3)3, and Al(OH)3; S3, reaction treatment: adjust and control the temperature of the reaction system to 25-30°C, stir for 8-10min, and stir at a speed of 400-500r / min, then intermittently ultrasonicate, and then increase the pressure to 0.4-0.6MPa and stir for 10-15min; the intermittent ultrasonicate is ultrasonicate for 1-2min and then allowed to stand for 1-2min, and the ultrasonicate is cycled for 3-5 times, and the frequency of the ultrasonicate is 20-40kHz, and the power is 300-400W.

2. The method for removing chloride ions from coking circulating water according to claim 1, characterized in that: The aluminum salt in step S2 is NaAlO2.

3. The method for removing chloride ions from coking circulating water according to claim 1, characterized in that: In step S2, the molar ratio of Ca / Al is controlled to be 2.5.

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