Method for flotational separation of industrial waste salts using calcium chloride solution

Abstract

The present invention relates to a method for flotation separation of industrial waste salt with calcium chloride solution, comprising: (1) preparing the mother liquor for flotation: the proportion of calcium chloride in the salts in the mother liquor is 85% - 95%, and the salt content rate of the mother liquor is 30% - 45%; (2) ball-milling and flotation of the salt: mixing the salt and the mother liquor at a weight ratio of 0.9 - 1.1 to form a grinding concentration of 45 - 55 wt% and then ball-milling; (3) preparing the flotation slurry: mixing the ball-milled slurry with the mother liquor, adding 200 L of the mother liquor for flotation per 100 kg of the ball-milled slurry, and obtaining a flotation slurry concentration of 180 - 240 g / L; (4) flotation separation of the ball-milled salt: adjusting the pH of the flotation system to 5.5 - 6.5, adding a potassium salt collector and a foaming agent, and then performing flotation on the flotation slurry to separate a foam product and a tailing pulp; (5) separating the solid and liquid phases: separating the solid and liquid phases of the foam product and the tailing pulp to obtain a crude concentrate product and a crude tailing product; (6) purifying the crude product: washing and drying the crude concentrate product and the crude tailing product to obtain an industrial-grade finished salt.

Description

Technical Field

[0001] The present invention belongs to the technical field of environmental protection and industrial waste treatment, and particularly relates to a method for flotation separation of industrial waste salts from calcium chloride solution used for treating soluble chloride industrial waste salts. Background Art

[0002] Due to the pollution of industrial waste salts to soil and water resources, the disposal method mainly by landfill is not sustainable. In the long run, it is necessary to find a way for the resource utilization of industrial waste salts.

[0003] Existing industrial waste salt resource utilization methods include recrystallization, salt washing method, extraction method, advanced oxidation method, carbonization method, etc. These methods generally have problems such as high comprehensive utilization cost, complex process, and low resource utilization degree, which hinder large-scale market application. Therefore, there is an urgent need for a process for industrial waste salt resource utilization with low cost, simple process, and high resource utilization degree.

[0004] The flotation method is a widely used, mature process, and low-cost separation technology. Applying it to the field of treating industrial waste salts will greatly reduce its comprehensive utilization cost and improve its resource utilization degree. The difficulty lies in that when using the flotation method for separation, a mother liquor for flotation needs to be provided so that the target components to be separated are in the solid phase of the flotation system to be separated under the action of flotation reagents.

[0005] The components of soluble chloride industrial waste salts include potassium chloride, sodium chloride, and a small amount of calcium chloride, etc. If this kind of industrial waste salt is separated by the flotation method, a co-saturated solution of sodium chloride and potassium chloride is usually used as the mother liquor for flotation. Using this co-saturated solution as the mother liquor for flotation, although it is feasible in principle, the following problems will occur when used on a large scale:

[0006] Problem 1: Unstable flotation effect

[0007] The component ratio and salt content rate of the co-saturated solution composed of sodium chloride and potassium chloride are affected by factors such as temperature and change, breaking the balance of the brine mixing system, resulting in poor separation effect of the mixed salts, the amount of separated salts being uncontrollable, and further affecting the setting of the dosage of flotation reagents and the selection of flotation equipment.

[0008] Problem 2: Easy crystallization of the mother liquor for flotation

[0009] The co-saturated solution is easy to precipitate crystals. Especially, salt cheeks will form at the scraper of the flotation machine and the discharge port of the ball mill. These salt cheeks will accumulate with the increase of the flotation separation time, resulting in a decrease in the processing capacity of the equipment, an increase in the operating load of the equipment, a reduction in the service life of the equipment, and an increase in the maintenance workload of the equipment.

[0010] Problem 3: Frequent preparation of the mother liquor for flotation

[0011] This co-saturated solution system has poor stability and requires frequent adjustment of the sodium chloride and potassium chloride components or replacement of the mother liquor. According to actual engineering experience, it generally takes 24 hours for the co-saturated solution to reach equilibrium and stability, which increases the process workload and corresponding equipment to a certain extent. Summary of the Invention

[0012] The purpose of the present invention is to overcome the deficiencies in the above-mentioned prior art, and provide a mother liquor for the flotation separation of industrial waste salts of soluble chlorides with a solution mainly composed of calcium chloride, which meets the requirements of low comprehensive utilization cost, simple process, high degree of resource utilization, etc. in the resource utilization and harmless treatment of waste salts, and further improves the stability of the mother liquor for flotation, and a method for flotation separation of industrial waste salts with a calcium chloride solution.

[0013] The technical solution of the present invention for the method of flotation separation of industrial waste salts with a calcium chloride solution is characterized in that it includes the following steps:

[0014] (1) Preparation of the mother liquor for flotation: The proportion of calcium chloride in the prepared mother liquor for flotation is 85% - 95%, and the salt content rate of the mother liquor is 30% - 45%;

[0015] (2) Ball milling of the flotation salt: The salt to be flotation separated is mixed with the mother liquor for flotation described in step (1) at a weight ratio of 0.9 - 1.1 to form a grinding concentration of 45 - 55 wt%, and then ball milling is carried out;

[0016] (3) Preparation of the flotation slurry: The ball mill slurry in step (2) is mixed with the mother liquor for flotation in step (1). For every 100 kg of the ball mill slurry, 200 L of the mother liquor for flotation is added, and the flotation slurry concentration of 180 - 240 g / L is obtained;

[0017] (4) Flotation separation of the ball milled salt: The pH of the flotation system is adjusted to 5.5 - 6.5. After adding a potassium salt collector and a foaming agent, the flotation slurry is fed into the flotation machine of the flotation cell at a flow rate of 250 L / h for flotation to separate the foam product and the tailing slurry;

[0018] (5) Separation of the solid and liquid phases: The foam product and the tailing slurry obtained in step (4) are separated into the solid and liquid phases to obtain the concentrate crude product and the tailing crude product;

[0019] (6) Purification of the crude product: The concentrate crude product and the tailing crude product obtained in step (5) are washed and dried to obtain the industrial grade finished salt.

[0020] Preferably: In step (2), the particle size of the salt to be flotation separated after ball milling is such that the proportion of -100 mesh is 90 - 95 wt%, and the proportion of -325 mesh is less than 30 wt%.

[0021] Preferably: In step (4), the flotation adopts a flotation separation process of one-stage roughing, two-stage cleaning, and two-stage scavenging.

[0022] Preferably, in step (4), the pH of the flotation slurry system is adjusted to 5.5 - 6.5 with hydrochloric acid. After adding the potassium salt collector octadecyl primary amine and the foaming agent No. 2 oil, the flotation slurry is fed into the flotation machine at a constant flow rate for flotation.

[0023] Preferably, in step (6), when purifying the crude product, its saturated solution is used for washing and purification, and the washing concentration is 600 - 750 g / L.

[0024] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0025] (1) The present invention has low comprehensive utilization cost, simple process and high resource utilization degree. Specifically, in the flotation separation of industrial waste salts containing soluble chlorides, compared with common physical and chemical methods and high-temperature treatment methods, the comprehensive utilization cost of industrial waste salts will be significantly reduced. The flotation separation process is relatively simple. As a widely used separation process for producing industrial salts, its resource utilization degree is high. Compared with the saturated solutions of potassium chloride and sodium chloride as the mother liquor for flotation, calcium chloride has a lower price and does not need to be frequently prepared, with better economy.

[0026] (2) The flotation effect of the present invention is good and the operation is stable. Specifically, compared with using the saturated solutions of potassium chloride and sodium chloride as the mother liquor for flotation, according to the phase diagram of the water-salt system and actual applications, it is found that even when the salt content rate of the calcium chloride solution fluctuates within a large range, the solubility of potassium chloride and sodium chloride in the brine system is relatively small, indicating that the calcium chloride solution is less affected by factors such as temperature. When actually using the calcium chloride solution as the mother liquor for flotation, the separation effect is good and the operation is stable. The product purity and recovery rate of the concentrate and tailings are better than those when using the co-saturated solution of potassium chloride and sodium chloride as the mother liquor.

[0027] (3) The present invention solves the problem of crystallization precipitation of the mother liquor for flotation on the equipment wall. Specifically, due to its own properties, the calcium chloride solution is not easy to lose water and calcium chloride salt has strong water absorption, so there is basically no crystallization precipitation in an open environment, and thus no salt scale will be generated on the equipment wall. Compared with the process of using a saturated solution as the mother liquor for flotation, it avoids problems such as increased equipment operation load, reduced equipment service life, and unfavorable equipment maintenance.

[0028] (4) The present invention solves to a certain extent the problem of the need to prepare the mother liquor for flotation. Specifically, compared with using a saturated solution as the mother liquor for flotation, when treating industrial waste salts such as municipal solid waste incineration fly ash that contain more calcium chloride itself, calcium chloride solution that meets the requirements of the flotation process production can be obtained during the treatment process, and there is no need to prepare the mother liquor for flotation. When treating industrial waste salts with little or no calcium chloride, because the calcium chloride solution has a large applicable range of salt content rate in the flotation process, a long stabilization time is not required when preparing the calcium chloride solution.

[0029] ⑸ The present invention improves the overall recovery rate of the product. Specifically, since the calcium chloride solution with a salt content of 30-44% has an obvious salting-out effect on potassium chloride, potassium chloride and sodium chloride in the saturated solution with a decreased washing effect can be recovered, thus improving the overall recovery rate of the product.

[0030] ⑹ The present invention can float industrial waste salts with a relatively high content of calcium chloride. Specifically, since the calcium chloride solution is used as the mother liquor for flotation, calcium chloride and other water-soluble salts in the industrial waste salts can be dissolved to a certain extent, reducing the content control requirements for water-soluble salts such as calcium chloride in the mixed salts to be floated. Brief Description of the Drawings

[0031] Figure 1 is the equipment flow chart for floating and separating industrial waste salts using a calcium chloride solution in the present invention;

[0032] Figure 2 is the process flow chart for floating and separating industrial waste salts using a calcium chloride solution in the present invention;

[0033] Figure 3 is the process flow chart for floating and separating ball-milled salts in the present invention;

[0034] Figure 4 is the process flow chart for purifying the crude product in the present invention. Detailed Embodiments

[0035] The present invention will be further described in detail below in conjunction with embodiments:

[0036] Example 1:

[0037] Please refer to Figure 2 As shown, for the process of floating and separating industrial waste salts using a calcium chloride solution, 300 kg of industrial waste salts generated in the resource treatment of fly ash from a waste incineration power plant in Guangdong Province are processed each time; during the fly ash resource treatment process, a large amount of high-concentration calcium chloride mother liquor is generated. The process steps for the industrial waste salts with 31.01% potassium chloride, 62.03% sodium chloride, and 6.96% calcium chloride are as follows:

[0038] ⑴ Prepare the mother liquor for flotation: Adjust the high-concentration calcium chloride mother liquor with water to a calcium chloride solution with a salt content of 33.0%, in which calcium chloride accounts for 90.97% of the total salts, and a total of about 2000 L of mother liquor for flotation is prepared; the specific implementation methods include that the proportion of calcium chloride in the prepared mother liquor for flotation is implemented in the ways of 85%, 90%, 95%, as well as 85%-90%, 90%-95%, 86%-90%, 90%-94% respectively in different embodiments; the salt content of the mother liquor is implemented in the ways of 30%, 40%, 45%, 30%-40%, 40%-45%, 35%-45%, 30%-40% respectively in different embodiments;

[0039] ⑵ Ball-milling and flotation of salts: Mix 50 kg of industrial waste salts with the mother liquor for flotation in step ⑴ to a grinding concentration of 50 wt%, and put it into an intermittent ball mill with a processing capacity of 50 kg per time. The ball mill contains 200 kg of alumina balls, and the alumina balls are distributed as follows: diameter = 7.4 mm, φ = 4.4 mm: small φ = 1.8 mm, mass ratio = 1:1:1. After ball-milling for 1 h, the particle size distribution of the industrial waste salts is 95.0 wt% -100 mesh, of which 25.0 wt% is -325 mesh. Temporarily store the ball-milled slurry until 300 kg of industrial waste salts are ball-milled. The specific implementation method includes mixing the salts to be separated by flotation with the mother liquor for flotation at a weight ratio of 0.9 - 1.1 to a grinding concentration of 45 - 55 wt%, and then performing ball-milling. The weight ratio of the salts to the mother liquor is implemented in different embodiments in the ways of 0.9, 1.0, 1.1, as well as 0.9 - 1.0, 1.0 - 1.1 respectively. The grinding concentration is implemented in different embodiments in the ways of 45 wt%, 50 wt%, 55 wt%, as well as 45 - 50 wt%, 50 - 55 wt%, 46 - 50 wt%, 50 - 54 wt% respectively.

[0040] ⑶ Prepare the flotation slurry: Adjust the ball-milled slurry in step ⑵ and the mother liquor for flotation in step ⑴ to a volume of 1500 L, so that the concentration of the flotation slurry is 200 g / L. Mix the ball-milled slurry in step ⑵ and the mother liquor for flotation in step ⑴. Add 200 L of the mother liquor for flotation per 100 kg of the ball-milled slurry to obtain the flotation slurry. The concentration of the flotation slurry is implemented in different embodiments in the ways of 180 g / L; 200 g / L; 220 g / L; 240 g / L; as well as 180 - 200 g / L; 200 - 220 g / L; 220 - 240 g / L; 200 - 230 g / L; 190 - 200 g / L respectively.

[0041] ⑷ Flotation separation of the ball-milled salts: Adjust the pH of the flotation system to 5.5 - 6.5. After adding a potassium salt collector and a foaming agent, feed the flotation slurry into a flotation machine with a total of 8 flotation cells of 39 L each at a flow rate of 250 L / h for flotation. The flotation process is one-stage roughing, two-stage cleaning, and two-stage scavenging to collect the foam product and the tailing slurry. The adjustment of the pH of the flotation system is implemented in different embodiments in the ways of 5.5, 6.0, 6.5, as well as 5.5 - 6.0, 6.0 - 6.5 respectively.

[0042] ⑸ Separate the solid and liquid phases: Centrifugally separate the foam product and the tailing slurry obtained in ⑷ in a centrifuge to obtain a crude potassium chloride product and a crude sodium chloride product. The purity of the obtained crude potassium chloride product is 85.25%, and the purity of the obtained crude sodium chloride product is 98.60%.

[0043] ⑹ Purify the crude products; Wash the crude potassium chloride products and the tailing crude sodium chloride products obtained in ⑸ respectively in saturated potassium chloride solution and sodium chloride solution at a washing concentration of 700 g / L for 20 minutes. Then perform centrifugal separation in a centrifuge. After testing the products, the purity of potassium chloride is 96.5% and the purity of sodium chloride is 99.2%. Dry the obtained products by blowing air. Thus, industrial-grade potassium chloride and sodium chloride are obtained. When purifying the crude products, their saturated solutions are used for washing and purification. In different embodiments, they are respectively implemented in the ways of washing concentrations of 600 g / L, 650 g / L, 700 g / L, 750 g / L, as well as 600 - 650 g / L, 650 - 700 g / L, 700 - 750 g / L, 600 - 700 g / L, 700 - 750 g / L, 600 - 750 g / L;

[0044] Taking the industrial waste salt generated in the resource treatment of fly ash from a waste incineration power plant in a certain area of Guangdong Province as an example, in which the proportion of potassium chloride in the industrial waste salt is 28.5%, the proportion of sodium chloride is 65.3%, and the proportion of calcium chloride is 6.2%, and a large amount of high-concentration calcium chloride mother liquor is obtained during the generation of industrial waste salt, the process of the present invention will be described step by step.

[0045] Example 2:

[0046] Prepare the mother liquor for flotation; Take a sample of the high-concentration calcium chloride mother liquor for analysis and detect its salt content rate in the mother liquor and the content of calcium chloride in its total salt. By calculating the dosing ratio of water and the mother liquor, add water for dilution to obtain a calcium chloride solution with a salt content rate of 33.0%, in which calcium chloride accounts for 91.97% of the total salt content. It should be noted that if directly preparing the mother liquor for flotation with industrial calcium chloride, in addition to the prepared solution needing to meet the requirement that the proportion of calcium chloride in the salt is 85% - 95% and the salt content rate of the mother liquor is 30% - 45%; the prepared mother liquor for flotation should also be placed open and naturally until the temperature does not exceed 30 °C to avoid affecting the measurement result of the pH meter when adjusting the pH value of the system during flotation.

[0047] In different embodiments, the proportion of calcium chloride in the salt is respectively implemented in the ways of 85%, 90%, 95%, as well as 85% - 90%, 90% - 95%, 86% - 90%, 90% - 94%; the salt content rate of the mother liquor is respectively implemented in the ways of 30%, 40%, 45%, 30% - 40%, 40% - 45%, 35% - 45%, 30% - 40%;

[0048] Example 3:

[0049] Ball-milled flotation salt: After adjusting the industrial waste salt to a concentration of 50 wt% with the mother liquor for flotation obtained in Example 1, it is put into a ball mill. The mass of alumina balls in the ball mill is 4 times the mass of the ball-milled salt (in dry weight). The distribution of alumina balls is diameter = 7.4 mm, φ = 4.4 mm: small φ = 1.8 mm, mass ratio = 1:1:1. After ball-milling for 1 h, sampling and testing show that the particle size distribution of the industrial waste salt is -100 mesh accounting for 95.0 wt%, among which -325 mesh accounts for 25.0 wt%.

[0050] Example 4:

[0051] Prepare the flotation slurry: Adjust the ball-milled slurry in Example 2 with the mother liquor for flotation in Example 1 to a flotation slurry concentration of 200 g / L at a stirring speed of 300 r / min.

[0052] Example 5:

[0053] Floatation separation of ball-milled salt: As Figure 3 shown, adjust the pH of the flotation slurry system in Example 4 to 5.5 - 6.5 with hydrochloric acid. After adding the potassium salt collector octadecyl primary amine and the foaming agent No. 2 oil, feed the flotation slurry into the flotation machine at a constant flow rate for flotation. The flotation process is one-stage roughing, two-stage cleaning, and two-stage scavenging to collect the foam product and the tailing slurry.

[0054] When calcium chloride solution is used as the mother liquor for flotation and the flotation separation is recycled 10 times, the flotation effect remains stable. When the salt content of the mother liquor for flotation exceeds 45% during recycling, the flotation effect decreases significantly, manifested as the floatability of potassium chloride decreasing under the action of the reagent and the foam layer thickness becoming significantly thinner.

[0055] Example 6:

[0056] Separate the solid and liquid phases: Centrifuge the foam product and the tailing slurry obtained in Example 5 in a centrifuge to make the moisture content of the crude potassium chloride product and the crude sodium chloride product less than 5%. Collect the centrifugal mother liquor of the concentrate and the centrifugal mother liquor of the tailings for recycling; Detection and analysis show that the purity of the crude potassium chloride product is 85.25%, and the purity of the obtained crude sodium chloride product is 98.50%.

[0057] Example 7:

[0058] Purify the crude product: As Figure 4:The crude potassium chloride product and the crude tailing sodium chloride product obtained in Example 6 are washed in a stirring tank at a washing concentration of 700 g / L in a saturated potassium chloride solution and a saturated sodium chloride solution respectively at a stirring speed of 250 r / min for 20 min. Then, centrifugal separation is carried out in a centrifuge, and the purity of the washed products is detected. It is required that the purity of potassium chloride is not less than 95.0%, and the purity of sodium chloride is not less than 99.0%. The obtained products are dried by blowing air. Thus, industrial-grade potassium chloride and sodium chloride are obtained.

[0059] When the washing effect of the saturated solution for washing significantly decreases, saturated sodium chloride is mixed with the mother liquor for flotation at a volume ratio of 1:2, and saturated potassium chloride brine is mixed with the mother liquor for flotation at a volume ratio of 1:3. After stirring for 10 min and standing for 30 min, separation is carried out in a centrifuge; the precipitated salt obtained is mixed with industrial waste salt and awaits treatment by the flotation separation process, and the salt solution is mixed with the mother liquor for flotation and used as the mother liquor for flotation.

[0060] The above are only the preferred embodiments of the present invention. All equivalent changes and modifications made within the scope of the claims of the present invention shall fall within the scope covered by the claims of the present invention.

Claims

1. A method for flotation separation of industrial waste salts with calcium chloride solution, characterized in that, Including the steps: ⑴ Prepare the mother liquor for flotation: In the prepared mother liquor for flotation, calcium chloride in the salt accounts for 85% - 95%, and the salt content rate of the mother liquor is 30% - 45%; ⑵ Ball-mill the flotation salt: Mix the salt to be separated by flotation with the mother liquor for flotation described in step ⑴ at a weight ratio of 0.9 - 1.1 to form a grinding concentration of 45 - 55 wt%, and then carry out ball-milling; ⑶ Configure the flotation slurry: Mix the ball-milled slurry in step ⑵ with the mother liquor for flotation in step ⑴. Add 200 L of the mother liquor for flotation per 100 kg of the ball-milled slurry, and the concentration of the flotation slurry obtained is 180 - 240 g / L; ⑷ Flotation-separate the ball-milled salt: Adjust the pH of the flotation system to 5.5 - 6.

5. After adding a potassium salt collector and a foaming agent, feed the flotation slurry into the flotation machine in the flotation cell at a flow rate of 250 L / h for flotation to separate the foam product and the tailing slurry; ⑸ Separate the solid and liquid phases: Separate the solid and liquid phases of the foam product and the tailing slurry obtained in step ⑷ to obtain the crude concentrate product and the crude tailing product; ⑹ Purify the crude product: Wash and dry the crude concentrate product and the crude tailing product obtained in step ⑸ to obtain the industrial-grade finished salt.

2. The method for flotation separation of industrial waste salt using calcium chloride solution according to claim 1, wherein In step ⑵, the particle size of the salt to be separated by flotation after ball-milling is -100 mesh, accounting for 90 - 95 wt%, and the proportion of -325 mesh is less than 30 wt%.

3. The method for flotation separation of industrial waste salts using a calcium chloride solution according to claim 1, characterized in that, In step ⑷, the flotation separation process of one-stage roughing, two-stage cleaning, and two-stage scavenging is adopted for flotation.

4. The method for flotational separation of industrial waste salts using a calcium chloride solution according to claim 1, wherein In step ⑷, adjust the pH of the flotation slurry system to 5.5 - 6.5 with hydrochloric acid. After adding the potassium salt collector octadecyl primary amine and the foaming agent no. 2 oil, feed the flotation slurry into the flotation machine at a constant flow rate for flotation.

5. The method for flotation separation of industrial waste salt using calcium chloride solution according to claim 1, characterized in that, In step ⑹, when purifying the crude product, its saturated solution is used for washing and purification, and the washing concentration is 600 - 750 g / L.

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