Process for extracting calcium chloride from circulating water for producing titanium tetrachloride

Abstract

The invention provides a process for extracting calcium chloride from circulating water for producing titanium tetrachloride, the titanium tetrachloride is obtained from boiling chlorination production, and the process comprises the following steps: S1, conveying working wastewater generated in the production of the circulating water from the titanium tetrachloride to an industrial wastewater collection pool; s2, performing filtration treatment on the wastewater in the industrial wastewater collection pool; s3, purifying the filtered wastewater to obtain a calcium chloride solution; s4, feeding the calcium chloride solution into a calcium chloride collecting tank; s5, evaporating, concentrating and drying the solution in the calcium chloride collecting tank to obtain anhydrous calcium chloride. The prepared high-purity calcium chloride solution can supplement raw materials for a frozen brine system, purification of calcium chloride can be achieved through one-time evaporation concentration and drying, the purification process is simple, the purification efficiency is high, and most importantly, the purified calcium chloride is low in water content and meets the national standard.

Description

Technical Field

[0001] The invention relates to the field of recycling of solid wastes, and in particular to a process for extracting calcium chloride from circulating water for producing titanium tetrachloride. Background Art

[0002] During the use of the production circulating water in the process of boiling chlorination to produce titanium tetrachloride, a lot of wastewater will be generated which is difficult to treat, unusable and has environmental safety risks.

[0003] In the process of producing titanium tetrachloride by boiling chlorination, the production circulating water will be enriched with a lot of solid particles, chloride ions, oil substances, other metal ions and other substances brought in by chemical reactions in the chlorination furnace, equipment cleaning and tail gas absorption. Dilute hydrochloric acid water with a concentration of 10%-20% containing heavy metal ions, oil, and solid particles is formed. This hydrochloric acid water has too many impurities and is difficult to use, even if the amount used in industrial applications is very limited, and the substance is a hazardous chemical with great difficulty and risk in transportation. Only caustic soda or lime can be added for neutralization. A calcium chloride solution with a concentration of 30%-50% containing heavy metal ions, oil, and solid particles is formed. This calcium chloride solution contains high chloride ions, heavy metal ions, and oil, and cannot be used or discharged. It also cannot meet the acceptance requirements of the sewage treatment company's pipeline network due to its high salt content, COD higher than the national standard of 1000 mg / L, and ammonia nitrogen higher than the national standard of 150 mg / L. It can only be diluted with water when treated by itself. The water addition ratio is about 200 to 500 times the weight of the industrial sewage to be treated, which is extremely costly, cumbersome to operate and greatly wastes water resources.

[0004] The prior art with publication number CN105836862B discloses a comprehensive treatment method for dust ash collected during the production of titanium tetrachloride by boiling chlorination method, which method comprises the following steps: 1) the dust ash is absorbed by water, and solid-liquid separation is performed to obtain solid slag and mixed solution; 2) excessive Fe is added to the mixed solution, heavy metal ions are removed by replacement reaction, and filtered to obtain a pre-heavy metal removal filtrate; 3) the pre-heavy metal removal filtrate is subjected to extraction to remove vanadium and manganese to obtain an extraction tail liquid; 4) the extraction tail liquid is added with an oxidant for oxidation, and then evaporated and concentrated, cooled and crystallized to obtain a composite flocculant polyaluminum ferric chloride. This prior art is only suitable for collecting aluminum ferric chloride, and is not suitable for extracting calcium chloride; moreover, the method is relatively complicated, and the chloride content is low in one-time purification, and the efficiency is low. Summary of the invention

[0005] In view of this, the present invention aims to propose a process for extracting calcium chloride from circulating water in the production of titanium tetrachloride, so as to solve the problem that the prior art is only suitable for collecting aluminum ferric chloride but not for extracting calcium chloride; moreover, the purification method is relatively complicated, the chloride content is small in one purification, and the efficiency is low.

[0006] To achieve the above object, the technical solution of the present invention is achieved as follows:

[0007] A process for extracting calcium chloride from circulating water for producing titanium tetrachloride comprises the following steps:

[0008] S1. Transporting the working wastewater generated by the circulating water of titanium tetrachloride production to the industrial wastewater collection pool;

[0009] S2, filtering and treating the wastewater in the industrial wastewater collection pool;

[0010] S3, purifying the filtered wastewater to obtain a calcium chloride solution;

[0011] S4, the calcium chloride solution enters the calcium chloride collection tank;

[0012] S5. Evaporating and concentrating the solution in the calcium chloride collection tank and drying it to obtain anhydrous calcium chloride.

[0013] This setting can prepare high-purity calcium chloride solution by treating industrial wastewater generated by circulating water in titanium tetrachloride production. It can not only replenish raw materials for the frozen brine system, but also purify calcium chloride through one-time evaporation concentration and drying. Not only is the purification process simple, but the purification efficiency is high. Most importantly, the purified calcium chloride has a low water content and meets national standards. Anhydrous calcium chloride can be used as electrolyte for electrolysis of magnesium chloride in subsequent sponge titanium production, avoiding high direct wastewater discharge indicators, and the recovered calcium chloride can be reused to avoid waste.

[0014] Furthermore, in step S5, the following steps are also included:

[0015] S51, conveying the calcium chloride solution to a drum dryer for evaporation and concentration to obtain a calcium chloride concentrate;

[0016] S52, placing the calcium chloride concentrate in a vibrating shaker for drying to obtain anhydrous calcium chloride.

[0017] Furthermore, in step S51, during the evaporation and concentration process, the negative pressure of the drum dryer is maintained at 0.2-0.4 MPa, the rotation speed is 50-70 rpm, and saturated steam is introduced into the drum dryer as a heat source, and 4.5-5.5 t of calcium chloride solution is concentrated under negative pressure per hour.

[0018] In this setting, evaporation concentration is carried out in a drum dryer. Since the drum dryer is constantly rotating, the material is not easy to scale, and the heating is uniform, the heating surface is large, the concentration effect is more stable, and more calcium chloride solution can be concentrated, with higher efficiency.

[0019] Further, in step S52, a hot air inlet and a hot air outlet are provided on the vibrating table, and the hot air inlet is connected to the waste heat hot air duct of the magnesium electrolysis workshop. During the drying process, waste heat hot air is introduced at the same time, and the hot air speed is maintained at 1-3 m / s into the drum dryer. The hot air temperature is 330-360°C, and the vibrating table vibrates continuously.

[0020] In this setting, drying is performed in a vibrating shaker, and the waste heat hot air duct of the magnesium electrolysis workshop is connected to assist in connecting the hot air. During the hot air drying process, the vibrating shaker is constantly vibrated to prepare anhydrous calcium chloride. This setting completely uses the high-temperature hot air generated by the plant itself, which can completely utilize waste and save energy. Drying and molding are carried out simultaneously, which greatly increases production efficiency.

[0021] Furthermore, in step S52, the vibrating shaker includes a drying tank, and the drying tank is provided with multiple layers, and each layer of the drying tank can hold 230-260 kg of calcium chloride concentrate.

[0022] This setting can significantly improve the drying efficiency of calcium chloride.

[0023] Furthermore, in step S51, the concentration of the calcium chloride solution after evaporation and concentration is 50-70%.

[0024] Furthermore, in step S3, the concentration of the purified calcium chloride solution is 30-50%.

[0025] Further, in step S3, the purification is specifically:

[0026] S31, adding a demulsifier to the wastewater in the calcium chloride solution collection tank to decompose the upper oily matter to form solid sediments that are separated from the circulating water;

[0027] S32. The separated liquid is filtered and cleaned by a filter press to remove suspended matter on the surface to obtain a calcium chloride solution.

[0028] This setting can improve the clarity of the calcium chloride solution, which not only meets the national standards, but also is more conducive to the subsequent evaporation concentration and drying, thereby improving the production efficiency of the entire anhydrous calcium chloride preparation.

[0029] Furthermore, in step S31, the demulsifier used is polydimethyl ether.

[0030] Further, in step S31, the mass ratio of the demulsifier to the wastewater is 1:1500 to 2500. Preferably, the mass ratio of the demulsifier to the wastewater is 1:2000.

[0031] Further, in step S2, the filtration treatment adopts filter press filtration and activated carbon adsorption.

[0032] Furthermore, the method further comprises step S6, wherein the steam generated in step S5 is condensed and recycled, and the condensed liquid is returned to the titanium tetrachloride production circulating water for continued use.

[0033] Furthermore, in step S5, the water content of the dried calcium chloride is below 0.01%.

[0034] Furthermore, in step S32, 8-20% sodium hypochlorite and an adsorbent are added to the solution of step S31. The sodium hypochlorite removes organic matter and color substances in the wastewater to make the calcium chloride solution clearer. The adsorbent is wooden tubular activated carbon. The adsorbent can remove heavy metal ions to ensure that the calcium chloride solution meets national standards. The mass ratio of sodium hypochlorite, adsorbent and calcium chloride solution is (1-3): (10-20): 1000.

[0035] Compared with the prior art, the process for extracting calcium chloride from circulating water for producing titanium tetrachloride described in the present invention has the following advantages:

[0036] (1) The present invention can prepare a high-purity calcium chloride solution by treating the industrial wastewater generated by the circulating water of titanium tetrachloride production, which can not only supplement the raw materials for the frozen brine system, but also concentrate and dry the calcium chloride solution to prepare anhydrous calcium chloride that meets the national standard. The anhydrous calcium chloride can be used as an electrolyte for the subsequent electrolysis of magnesium chloride in the production of sponge titanium, thereby avoiding the high direct discharge index of wastewater, and the recovered calcium chloride can be reused to avoid waste;

[0037] (2) The calcium chloride purification process of the present invention can achieve the purification of calcium chloride by evaporation concentration and drying once, which not only has a simple purification process but also high purification efficiency, and most importantly, the purified calcium chloride has a low water content;

[0038] (3) The present invention performs evaporation concentration in a drum dryer. Since the drum dryer rotates continuously, the material is not easy to scale, and the heating is uniform, the heating surface is large, the concentration effect is more stable, and more calcium chloride solution can be concentrated, with higher efficiency.

[0039] (4) The present invention uses a vibrating shaker to dry the waste heat hot air duct of the magnesium electrolysis workshop, which is used to connect the hot air. During the hot air drying process, the vibrating shaker vibrates continuously to prepare anhydrous calcium chloride. This setting completely uses the high-temperature hot air generated by the factory itself, which can completely utilize waste and save energy. Drying and molding are carried out simultaneously, which greatly increases production efficiency.

[0040] (5) The present invention repeatedly recycles the wastewater generated by the circulating water in the production of titanium tetrachloride, so that the wastewater does not need to be discharged or outsourced for treatment. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] Figure 1 A process for extracting calcium chloride from circulating water for producing titanium tetrachloride according to the present invention Figure 1 ;

[0042] Figure 2 A process for extracting calcium chloride from circulating water for producing titanium tetrachloride according to the present invention Figure 2 ;

[0043] Figure 3 A simplified diagram of a drum drying machine of the present invention;

[0044] Figure 4 It is a simplified diagram of a vibrating shaker of the present invention.

[0045] Description of reference numerals:

[0046] 1-drum dryer, 11-material inlet, 12-material outlet, 13-steam inlet, 14-steam outlet, 2-vibrating shaker, 21-bed, 211-hot air inlet, 212-hot air outlet, 213-nitrogen purge inlet, 214-material inlet, 215-dry material collection box, 216-drying trough, 22-base. DETAILED DESCRIPTION

[0047] In order to make the above-mentioned objects, features and advantages of the present invention more clearly understood, the specific embodiments of the present invention are described in detail below in conjunction with the accompanying drawings. In addition, the directions involved in the following specific embodiments are briefly described: the directions or positional relationships indicated by "up", "down", "left" and "right" mentioned in the embodiments refer to the directions or positional relationships shown in the accompanying drawings.

[0048] like Figures 1 to 4 The present invention relates to a process for extracting calcium chloride from circulating water for producing titanium tetrachloride, wherein the titanium tetrachloride is produced by boiling chlorination, comprising the following steps:

[0049] S1. Transporting the working wastewater generated by the circulating water of titanium tetrachloride production to the industrial wastewater collection pool;

[0050] S2, filtering and treating the wastewater in the industrial wastewater collection pool;

[0051] Specifically, in step S2, the filtration treatment adopts filter press filtration and activated carbon adsorption, which is set up to prepare a clear calcium chloride solution that meets the standards.

[0052] Specifically, in step S2, the filtered waste residue is collected through a filter residue pressing process to form a filter cake for sale, and the carbon mass fraction in the filter cake is 15-20%, and the combustion calorific value is 800-1000 J / Kg, which can be sold to power plants or brick factories for combustion to provide heat source.

[0053] S3, purifying the filtered wastewater to obtain a calcium chloride solution;

[0054] Specifically, in step S3, the purification is specifically:

[0055] S31. Add a demulsifier to the wastewater in the calcium chloride solution collection pool to decompose the upper oily matter to form solid sediment and separate it from the circulating water; the demulsifier used is a polydioxane; the mass ratio of the demulsifier to the wastewater is 1:2000.

[0056] S32, filtering and removing the separated liquid by a filter press to remove the suspended matter on the surface, and obtaining a calcium chloride solution. The calcium chloride solution can be used in a frozen brine system.

[0057] S4, the calcium chloride solution is put into the calcium chloride collection pool; determine whether there are solid particles and color (iron compound) in the calcium chloride solution; if not, proceed to step S5, if there are solid particles, proceed to step S32; if there is color, proceed to step S41, step S41 specifically includes adding 8-20% sodium hypochlorite and adsorbent to the solution in step S32, sodium hypochlorite removes organic matter and color substances in wastewater, so that the calcium chloride solution is clearer, the adsorbent is wooden tubular activated carbon, the adsorbent can remove heavy metal ions, and ensure that the calcium chloride solution meets national standards, wherein the mass ratio of sodium hypochlorite, adsorbent and calcium chloride solution is 2:15:1000.

[0058] In this setting, the concentration of calcium chloride is guaranteed to be 30-50%, COD <1000, ammonia nitrogen <150, chroma <3, and other metal compounds <1% of high-purity calcium chloride solution. This concentration limit prevents the calcium chloride solution from being too concentrated and evaporated and concentrated in the negative pressure drum dryer. The calcium chloride solution has a large viscosity and is very easy to crystallize when encountering crystal nuclei. The calcium chloride after evaporation and concentration must also be a saturated calcium chloride solution of 50-70%; the concentration of other metal solutions is guaranteed to meet national standards.

[0059] Specifically, a portion of the calcium chloride solution in step S41 can be selectively recycled into a calcium chloride solution to supplement the frozen brine process to supplement the frozen brine station, and the remaining calcium chloride solution enters step S5.

[0060] S5. Evaporating and concentrating the solution in the calcium chloride collection tank and drying it to obtain anhydrous calcium chloride.

[0061] Specifically, in step S5, the following steps are also included:

[0062] S51, conveying the calcium chloride solution to a drum dryer for evaporation and concentration to obtain a calcium chloride concentrate;

[0063] Specifically, in step S51, the drum dryer 1 includes a material inlet 11, a material outlet 12, a steam inlet 13, and a steam outlet 14, wherein the material inlet is located at the upper end of the drum dryer, the material outlet is located at the lower end of the material inlet, and the two are staggered up and down, the steam inlet is located at the side end of the drum dryer, and the steam outlet is located at the side end of the drum dryer away from the steam inlet; before evaporation and concentration, according to the drum dryer and in conjunction with the Venturi principle, the inside of the drum dryer is evacuated to maintain a negative pressure of 0.3 MPa. During the evaporation and concentration process, the negative pressure of the drum dryer is maintained at 0.3 MPa, and the rotation speed is 60 rpm, under the negative pressure of 0.3 MPa, the liquid in the drum dryer keeps rolling so that the internal materials are evenly heated. The outer wall of the drum uses 4 kg of saturated steam produced in the factory to provide a heat source to evaporate the moisture of the materials in the drum and concentrate them once. 4.5-5.5t of calcium chloride solution can be concentrated under negative pressure per hour; at the same time, the calcium chloride solution with a concentration of 30-50% can be concentrated to 50-70%, preferably 60%. Compared with the traditional evaporator, this setting is not easy to scale the material because the drum dryer keeps rotating; and it has the advantages of uniform heating and a large heating surface. Under the same energy conditions, more materials can be concentrated and the effect is more stable.

[0064] S52, placing the calcium chloride concentrate in a vibrating shaker for drying to obtain anhydrous calcium chloride, which can be used for electrolysis of calcium chloride.

[0065] Specifically, the concentrated 60% calcium chloride solution is transported to the hot air vibrating shaker. A forced circulation method is used during the transportation process, that is, a reflux pipe is set in the transportation pipe. Even after the hot air vibrating shaker finishes feeding, a large amount of calcium chloride solution is still circulated to prevent the crystallization of the highly viscous calcium chloride concentrated solution from clogging the pipe.

[0066] Specifically, in step S52, the vibrating shaking table 2 includes a bed 21 and a base 22, the bed is located on the base, the bed 21 includes a hot air inlet 211, a hot air outlet 212, a nitrogen purge inlet 213, a material inlet 214, a dry material collection box 215, and a drying trough 216, the hot air inlet is located at the upper end of the bed, the hot air inlet is located at the side end of the bed and close to the lower end of the bed, the hot air inlet is connected to the waste heat hot air pipeline of the magnesium electrolysis workshop, the material inlet is located at the side end of the bed and at the upper end of the hot air outlet, the dry material collection box is located at the side end of the bed and away from the material inlet, and the drying trough is arranged in 7 layers, and each layer of the drying trough can hold 230-260 kg of calcium chloride concentrate.

[0067] Specifically, before drying, the calcium chloride solution is first introduced from the material inlet and filled in the drying tank. Then, nitrogen is filled in through the nitrogen purge inlet to drive away the air to avoid oxidation and decomposition of calcium chloride during high-temperature drying. During drying, only residual hot air is introduced, and the hot air speed is maintained at 1-3m / s to enter the drum dryer. The hot air temperature is 330-360°C, and the vibrating shaker is constantly vibrating; after drying, nitrogen needs to be introduced to prevent the generation of harmful gases. The hot air is continuously dried from top to bottom, and 35 kg of 60% calcium chloride solution can be concentrated to a water content of less than 0.01% in 20 minutes in conjunction with the gas flow. The evaporated water vapor will follow the hot air into the condenser for collection and reuse. The hot air can also oxidize the residual carbon element in the calcium chloride solution and take it away, making the calcium chloride solution purer. During the hot air drying process, the vibrating shaker vibrates continuously, and the gradually dried calcium chloride solution gradually forms spherical crystals as the water content decreases, and finally forms spherical anhydrous calcium chloride, which can be collected and bagged for use or sale. Compared with traditional evaporators or vibrating shakers, this equipment does not require high-pressure steam or high-power electric heaters, and completely uses the high-temperature hot air generated by the factory itself, which can completely utilize waste and save energy. Drying and molding are carried out simultaneously, which greatly increases production efficiency.

[0068] S6. Condensing the steam generated by evaporation, concentration and drying, the obtained distilled water is returned to the circulating water system for use. This setting can improve the utilization rate of condensed water and save water resources.

[0069] In conclusion, the present invention recovers all the waste heat steam and hot air in production as energy for treatment, and the recovered steam can also be returned to the circulating water system for reuse, thus avoiding unnecessary waste.

[0070] Example 1

[0071] The calcium chloride solution obtained in steps S1, S2, S3 and S4 has a concentration of 40%. 1 t of the calcium chloride solution is taken and evaporated, concentrated and dried in step S5. The time required is 9 hours. The water content of the dried calcium chloride is less than 0.01%.

[0072] Comparative Example 1

[0073] The calcium chloride solution obtained in steps S1, S2, S3, and S4 has a concentration of 40%. 1 t of the calcium chloride solution is taken and, when entering step S5, the production process for extracting anhydrous calcium chloride from the calcium chloride solution disclosed in publication number CN 106976899 A is adopted. The calcium chloride solution needs to be preheated - several cascaded evaporators - dried during drying, and the required time is 24.5 hours.

[0074] It can be seen from Example 1 and Comparative Example 1 that the purification process of calcium chloride of the present invention is more simplified and the required time is short.

[0075] Although the present invention is disclosed as above, the present invention is not limited thereto. Any person skilled in the art can make various changes and modifications without departing from the spirit and scope of the present invention. Therefore, the protection scope of the present invention shall be subject to the scope defined by the claims.

Claims

1. A process for extracting calcium chloride from circulating water for producing titanium tetrachloride, characterized in that: The steps include: S1. Transporting the working wastewater generated by the circulating water of titanium tetrachloride production to the industrial wastewater collection pool; S2, filtering and treating the wastewater in the industrial wastewater collection pool; S3, purifying the filtered wastewater to obtain a calcium chloride solution; S4, the calcium chloride solution enters the calcium chloride collection tank; S5. Evaporating and concentrating the solution in the calcium chloride collection tank and drying it to obtain anhydrous calcium chloride.

2. The process according to claim 1, characterized in that In step S5, the following steps are also included: S51, conveying the calcium chloride solution to a drum dryer for evaporation and concentration to obtain a calcium chloride concentrate; S52, placing the calcium chloride concentrate in a vibrating shaker for drying to obtain anhydrous calcium chloride.

3. The process according to claim 2, characterized in that In step S51, during the evaporation and concentration process, the negative pressure of the drum dryer is maintained at 0.2-0.4 MPa, the rotation speed is 50-70 rpm, and saturated steam is introduced into the drum dryer as a heat source, and 4.5-5.5 tons of calcium chloride solution are concentrated under negative pressure per hour.

4. The process according to claim 2, characterized in that In step S52, a hot air inlet and a hot air outlet are provided on the vibrating table, and the hot air inlet is connected to the waste heat hot air duct of the magnesium electrolysis workshop. During the drying process, waste heat hot air is introduced at the same time, and the hot air speed is maintained at 1-3m / s into the dryer. The hot air temperature is 330-360°C, and the vibrating table vibrates continuously.

5. The process according to claim 2, characterized in that In step S52, the vibrating shaker includes a drying tank, and the drying tank is arranged in multiple layers, and each layer of the drying tank can hold 230-260 kg of calcium chloride concentrate.

6. The process according to claim 2, characterized in that In step S51, the concentration of the calcium chloride solution after evaporation and concentration is 50-70%.

7. The process according to claim 1, characterized in that In step S3, the concentration of the purified calcium chloride solution is 30-50%.

8. The process according to claim 1, characterized in that In step S3, the purification is specifically: S31, adding a demulsifier to the wastewater in the industrial wastewater collection tank to decompose the upper oily matter to form solid sediments that are separated from the circulating water; S32. The separated liquid is filtered and cleaned by a filter press to remove suspended matter on the surface to obtain a calcium chloride solution.

9. The process according to claim 8, characterized in that In step S31, the demulsifier used is polydimethyl ether.

10. The process according to claim 9, characterized in that In step S31, the mass ratio of the demulsifier to the wastewater is 1:1500-2500.

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