A method for removing impurities from a crude brine based on molten salt chlorination slag

Abstract

The present application relates to the technical field of resource processing of waste residue, and particularly relates to a method for removing impurities based on coarse salt water prepared from molten salt chlorination residue. The method comprises the following steps: S1, adding lime milk into the molten salt chlorination residue to obtain saturated coarse salt water with pH of 5.8-6.2, and after the saturated coarse salt water is fully mixed and reacted, qualified coarse salt water is obtained; S2, adding waste lye into the qualified coarse salt water, wherein the waste lye is added in an amount according to the molar ratio of effective chlorine to ferrous ions of 0.18-0.24, after the addition is completed, reaction and standing are performed, and then filtration treatment is performed to obtain mixed salt water and iron-containing sludge; S3, under the action of stirring, adding calcium removal agent into the mixed salt water, adjusting pH to 8.0-8.5, and then standing and filtering to separate to obtain magnesium removal salt water and Ca-containing residue; S4, heating the magnesium removal salt water to 90-95 DEG C, adding sodium carbonate solution, fully reacting, standing and filtering to separate to obtain qualified salt water after purification and basic magnesium carbonate; and S5, configuring the qualified salt water and hydrochloric acid into qualified NaCl salt water with pH of 4.6-4.9 in a volume ratio of 1:1.

Description

Technical Field

[0001] This invention relates to the field of resource utilization technology for waste residue, and in particular to a method for removing impurities from crude brine prepared from molten salt chlorination slag. Background Technology

[0002] Crude brine prepared from molten salt chlorination waste contains high concentrations of Fe (0–40 g / L), Mn (0–4 g / L), Ca (0–5 g / L), and Mg (0–22 g / L) and low concentrations of Cr (0–30 mg / L), Ti (0–1 mg / L), and V (0–12 mg / L). Currently, the relevant patent ZL2016 10213027.8 describes a sodium-based treatment process, which suffers from problems such as low iron content in the iron-manganese slag, unstable quality of basic magnesium carbonate, and lack of Cr and V removal. This leads to difficulties in reusing byproducts, resulting in high process costs and hindering the widespread adoption of molten salt chlorination technology. To address this technical problem, a method for removing impurities from crude brine prepared from molten salt chlorination slag is proposed. Summary of the Invention

[0003] In order to solve the technical problems existing in the prior art, the present invention provides a method for removing impurities from crude brine prepared by molten salt chlorination slag.

[0004] To achieve the above objectives, the embodiments of the present invention provide the following technical solutions:

[0005] In a first aspect, in one embodiment of the present invention, a method for removing impurities from crude brine prepared from molten salt chlorination slag is provided, the method comprising the following steps:

[0006] S1. Add lime milk to molten salt chlorination slag to prepare saturated crude brine with a pH of 5.8 to 6.2. After the saturated crude brine is fully mixed and reacted, qualified crude brine is obtained.

[0007] S2. Add the waste alkaline solution to the qualified crude brine, wherein the amount of waste alkaline solution added is based on the molar ratio of available chlorine to ferrous ions of 0.18 to 0.24. After the reaction is completed and the mixture is allowed to stand, it is filtered to obtain mixed brine and iron-containing sludge.

[0008] S3. Under stirring, add the calcium removal agent to the mixed brine, adjust the pH to 8.0-8.5, then let it stand and filter to separate, and obtain magnesium-removed brine and Ca-containing residue.

[0009] S4. Heat the magnesium-removed brine to 90-95℃, add a 30% sodium carbonate solution at a sodium carbonate to magnesium ion molar ratio of 1.02-1.05, allow it to react fully, let it stand, filter and separate to obtain purified qualified brine and basic magnesium carbonate.

[0010] Step S5: Prepare qualified NaCl saline solution with a pH of 4.6 to 4.9 by mixing qualified saline solution and hydrochloric acid at a volume ratio of 1:1.

[0011] As a further embodiment of the present invention, the lime milk is prepared by mixing lime and refined brine at a mass ratio of 1:5.5.

[0012] As a further embodiment of the present invention, the mixture of lime and refined salt water is stirred at 50°C for 30 minutes and then allowed to stand for 2 hours to obtain lime milk.

[0013] As a further aspect of the present invention, in step S2, the waste alkaline solution is added to qualified crude brine, wherein the amount of waste alkaline solution added is based on an effective chloride to ferrous ion molar ratio of 0.18 to 0.24. After the reaction is completed and the mixture is allowed to stand, it is filtered to obtain a mixed brine and iron-containing sludge, comprising:

[0014] Waste alkaline solution is added to qualified crude brine, with the amount of waste alkaline solution added being 0.18 to 0.24 molar ratio of available chlorine to ferrous ions. After the addition is complete, the mixture is reacted for 30 to 40 minutes, allowed to stand for 18 to 24 hours, and then filtered to obtain mixed brine and iron-containing sludge.

[0015] As a further aspect of the present invention, in step S2, the waste alkaline solution is added to qualified crude brine, wherein the amount of waste alkaline solution added is based on an effective chlorine to ferrous ion molar ratio of 0.18 to 0.24. After the reaction is completed and the mixture is allowed to stand, it is filtered to obtain a mixed brine and iron-containing sludge. The filtration process includes: using a flat-plate silicon carbide ceramic membrane method; the filtration pore size is 0.5 to 1.0 μm, and the filtration pressure is 0.5 to 0.1 MPa.

[0016] As a further aspect of the present invention, in step S3, a calcium removal agent is added to the mixed brine under stirring, the pH is adjusted to 8.0-8.5, and then the mixture is allowed to stand and filtered to separate, yielding magnesium-removed brine and Ca-containing slag, comprising:

[0017] The calcium removal agent is added to the mixed brine under stirring, with the amount of calcium removal agent added according to the ratio of Ca:SO4. 2～ The molar ratio was 1:0.95, the reaction time was 30 min, the pH was adjusted to 8.0-8.5, the mixture was allowed to stand for 18-20 h, and then filtered to separate the magnesium-free brine and the Ca-containing residue.

[0018] As a further embodiment of the present invention, in step S3, the calcium removal agent is added to the mixed brine under stirring, the pH is adjusted to 8.0-8.5, and then the mixture is allowed to stand and filtered to separate the magnesium-free brine and the Ca-containing slag. The process includes: the filtration treatment is carried out using a flat silicon carbide ceramic membrane method; the filtration pore size is 0.5-1.0 μm, and the filtration pressure is 0.5-0.1 MPa.

[0019] As a further aspect of the present invention, in step S3, a calcium removal agent is added to the mixed brine under stirring, the pH is adjusted to 8.0-8.5, and then the mixture is allowed to stand and filtered to separate, yielding magnesium-removed brine and Ca-containing slag, comprising:

[0020] The calcium removal agent is added to the mixed brine under stirring, with the amount of calcium removal agent added according to the ratio of Ca:SO4. 2～ The molar ratio was 1:0.95, the reaction time was 30 min, the pH was adjusted to 8.0-8.5, the mixture was allowed to stand for 18-20 h, and then filtered to separate the magnesium-free brine and the Ca-containing residue.

[0021] As a further embodiment of the present invention, in step S3, the calcium removal agent is added to the mixed brine under stirring, the pH is adjusted to 8.0-8.5, and then the mixture is allowed to stand and filtered to obtain magnesium-free brine and Ca-containing slag. The filtration separation is carried out using a fully automatic plate and frame filter method with a filtration pore size of 0.1-1.0 μm and a filtration pressure of ≤1.0 MPa.

[0022] As a further aspect of the present invention, the calcium removal agent is a mixture of sodium sulfate, sodium carbonate, and sodium sulfite.

[0023] The technical solution provided by this invention has the following beneficial effects:

[0024] The present invention provides a method for removing impurities from crude brine prepared from molten salt chlorination slag, comprising the following steps: S1, adding lime slurry to molten salt chlorination slag to prepare saturated crude brine with a pH of 5.8-6.2, and obtaining qualified crude brine after the saturated crude brine has fully mixed and reacted; S2, adding waste alkali solution to the qualified crude brine, wherein the amount of waste alkali solution added is based on an effective chloride to ferrous ion molar ratio of 0.18-0.24, and after the reaction is completed and the mixture has settled, it is filtered to obtain mixed brine and iron-containing sludge; S3, under stirring... Add the calcium removal agent to the mixed brine, adjust the pH to 8.0-8.5, then let it stand and filter to separate, obtaining magnesium-removed brine and Ca-containing residue; S4, heat the magnesium-removed brine to 90-95℃, add a 30% sodium carbonate solution at a sodium carbonate to magnesium ion molar ratio of 1.02-1.05, after sufficient reaction, let it stand and filter to separate, obtaining purified qualified brine and basic magnesium carbonate; Step S5, mix the qualified brine and hydrochloric acid at a volume ratio of 1:1 to prepare qualified NaCl brine with a pH of 4.6-4.9.

[0025] This invention employs the synergistic treatment of pollutants such as waste alkaline solution and SDS desulfurization ash, with low-cost and precise raw material adjustment, to efficiently solve the problems of crude brine treatment and effective resource utilization, thereby achieving waste-to-waste treatment and resource recycling, and greatly reducing the cost of resource-based treatment of molten salt chlorination waste salt.

[0026] These or other aspects of the invention will become more apparent from the following description of embodiments. It should be understood that the foregoing general description and the following detailed description are exemplary and explanatory only, and are not intended to limit the invention. Attached Figure Description

[0027] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other embodiments can be obtained based on these drawings without creative effort.

[0028] Figure 1 This is a flowchart illustrating a method for removing impurities from crude brine prepared from molten salt chlorination slag, according to an embodiment of the present invention. Detailed Implementation

[0029] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0030] The flowchart shown in the attached diagram is for illustrative purposes only and does not necessarily include all content and operations / steps, nor does it necessarily have to be performed in the described order. For example, some operations / steps can be broken down, combined, or partially merged, so the actual execution order may change depending on the actual situation.

[0031] This invention provides a method for removing impurities from crude brine prepared from molten salt chlorination slag. The method includes the following steps:

[0032] S1. Add lime milk to molten salt chlorination slag to prepare saturated crude brine with a pH of 5.8 to 6.2. After the saturated crude brine is fully mixed and reacted, qualified crude brine is obtained.

[0033] S1 involves adding lime slurry to molten salt chlorination slag to prepare saturated crude brine with a pH of 5.8–6.2. After the saturated crude brine has fully mixed and reacted, qualified crude brine is obtained; comprising:

[0034] A saturated crude brine solution with a mass concentration of 15-16% was added to the molten salt chlorination slag under stirring at 300-350 rpm. The mixture was then thoroughly mixed and reacted for 10-15 minutes to obtain qualified crude brine.

[0035] The lime milk is prepared by mixing lime and refined salt water at a mass ratio of 1:5.5.

[0036] In this embodiment of the invention, the mixture of lime and refined salt water is stirred at 50°C for 30 minutes and then allowed to stand for 2 hours to obtain lime milk.

[0037] The qualified crude brine composition is as follows: NaCl: 125–140 g / L, FeCl2: 75–80 g / L, FeCl3: 7.0–10.0 g / L, MgCl2: 95–102 g / L, MnCl2: 5.0–6.0 g / L, CaCl2: 6.0–6.5 g / L, and a small amount of SO4. 2～ Trace amounts of Cr, V, and Ti; pH 0.7–1.1; temperature 40–55℃.

[0038] S2. Add the waste alkaline solution to qualified crude brine, wherein the amount of waste alkaline solution added is based on an effective chloride to ferrous ion molar ratio of 0.18 to 0.24. After the reaction is complete and the mixture is allowed to stand, it is filtered to obtain a mixed brine and iron-containing sludge. The filtration process uses a flat-plate silicon carbide ceramic membrane method; the filtration pore size is 0.5 to 1.0 μm, and the filtration pressure is 0.5 to 0.1 MPa.

[0039] In step S2, the waste alkaline solution is added to qualified crude brine, wherein the amount of waste alkaline solution added is based on an effective chloride to ferrous ion molar ratio of 0.18 to 0.24. After the reaction is completed and the mixture is allowed to stand, it is filtered to obtain a mixed brine and iron-containing sludge, comprising:

[0040] Waste alkaline solution is added to qualified crude brine, with the amount of waste alkaline solution added being 0.18 to 0.24 molar ratio of available chlorine to ferrous ions. After the addition is complete, the mixture is reacted for 30 to 40 minutes, allowed to stand for 18 to 24 hours, and then filtered to obtain mixed brine and iron-containing sludge.

[0041] The waste alkaline solution is prepared by absorbing the waste liquid discharged from the chlorination tail gas with 32% alkaline solution.

[0042] The waste alkaline solution has the following composition: NaCO3: 6-20 g / L, NaCl: 15-16 g / L, NaClO: 1.5-5.0 g / L, pH 8.0-9.5, and temperature 25-30℃.

[0043] The mixed brine contains Fe≦1mg / L, Mn≦100mg / L, SS≦1mg / L, and Mg≦1mg / L. 2+ 18~20g / L, Ca 2+ : 1~2g / L, Ti≦0.01mg / L, V≦0.1mg / L, Cr≦1mg / L, pH 6.8~7.0; iron-containing sludge with Fe grade of 42~45%, used for sintering feedstock.

[0044] S3. Under stirring, add the calcium removal agent to the mixed brine, adjust the pH to 8.0-8.5, then let it stand and filter to separate, obtaining magnesium-removed brine and Ca-containing slag.

[0045] In step S3, the calcium removal agent is added to the mixed brine under stirring, the pH is adjusted to 8.0-8.5, and then the mixture is allowed to stand and filtered to separate, yielding magnesium-removed brine and Ca-containing slag, comprising:

[0046] The calcium removal agent is added to the mixed brine under stirring, with the amount of calcium removal agent added according to the ratio of Ca:SO4. 2～ The molar ratio was 1:0.95, the reaction time was 30 min, the pH was adjusted to 8.0-8.5, the mixture was allowed to stand for 18-20 h, and then filtered to separate the magnesium-free brine and the Ca-containing residue.

[0047] The filtration and separation process employs a fully automated plate and frame filter method with a filtration pore size of 0.1–1.0 μm, a filtration pressure of ≤1.0 MPa, and a countercurrent washing filter cake preparation.

[0048] The calcium removal agent is a mixture of sodium sulfate, sodium carbonate, and sodium sulfite, wherein the ratio of sodium sulfate to sodium carbonate is 3 to 5:1.

[0049] The preferred calcium removal agent is SDS desulfurization solid waste, containing NaSO4: 65-70%, NaCO3: 15-20%, C: 0-9.8%, NaSO3: 0-0.3%, and NaCl: 0-5%. Sodium sulfite primarily reduces Cr. 6+ For Cr 3+ V 5+ For V 4+ After reduction, it is removed as the pH increases, and sodium carbonate synergistically removes Mn.

[0050] Except for magnesium-containing salts containing Fe≦1mg / L, Mn≦1mg / L, and Mg≦1mg / L, 2+ 17.2~17.8g / L, Ca 2+ 0.18~0.2g / L, Ti≦0.01mg / L, V≦0.1mg / L, Cr≦0.1mg / L; After being washed and qualified, the decalcified slag is sent to a cement plant or further processed for use as building gypsum.

[0051] S4. Heat the magnesium-free brine to 90-95℃, add a 30% sodium carbonate solution at a sodium carbonate to magnesium ion molar ratio of 1.02-1.05, allow it to react fully, let it stand, filter and separate to obtain purified qualified brine and basic magnesium carbonate.

[0052] In step S4, the magnesium-removed brine is heated to 90-95°C, and a 30% sodium carbonate solution is added at a sodium carbonate to magnesium ion molar ratio of 1.02-1.05. After the reaction is complete, the solution is allowed to stand and filtered to separate, yielding purified qualified brine and basic magnesium carbonate, comprising:

[0053] The magnesium-free brine is heated to 90-95℃, and a 30% sodium carbonate solution is added at a sodium carbonate to magnesium ion molar ratio of 1.02-1.05. The feeding rate is controlled at 450-500 ml / min. After the reaction is complete, the brine is allowed to stand for 2 hours, and then filtered to separate the brine and basic magnesium carbonate products.

[0054] Among them, the method of filtering and separating flat silicon carbide ceramic membranes; the filter pore size is 40-100nm, the filtration pressure is ~0.25-0.04Mpa, and it is equipped with multi-stage washing. The alkaline magnesium carbonate washing is qualified, that is, Cl≦0.1% and Fe≦0.02%, and the first-grade product standard is stably controlled.

[0055] The qualified brine after purification has the following specifications: NaCl: 18-20%, Fe≦1mg / L, Mn≦1mg / L, Mg 2+ ≤20mg / L, Ca 2+ ≦30mg / L, Ti≦0.01mg / L, V≦0.01mg / L, Cr≦0.1mg / L.

[0056] Step S5: Prepare qualified brine and hydrochloric acid at a volume ratio of 1:1 to form qualified NaCl brine with a pH of 4.6 to 4.9, which will be used as raw material in the primary brine production tank of chlor-alkali chemical plant.

[0057] Example 1

[0058] A method for removing impurities from crude brine prepared from molten salt chlorination slag includes the following steps:

[0059] S1. Add lime milk to molten salt chlorination slag to prepare saturated crude brine with a pH of 5.8. After the saturated crude brine is fully mixed and reacted, qualified crude brine is obtained.

[0060] The lime slurry is prepared by mixing lime and refined salt water at a mass ratio of 1:5.5.

[0061] In this embodiment of the invention, the mixture of lime and refined salt water is stirred at 40-60°C for 25 minutes and then allowed to stand for 1.5 hours to obtain lime milk.

[0062] S1 involves adding lime slurry to molten salt chlorination slag to prepare saturated crude brine with a pH of 5.8. After the saturated crude brine has fully mixed and reacted, qualified crude brine is obtained; including:

[0063] A 15% lime slurry was added to the molten salt chlorination slag under stirring at 300 rpm to prepare saturated crude brine. The mixture was then thoroughly mixed and reacted for 10 minutes to obtain qualified crude brine.

[0064] S2. Add the waste alkaline solution to qualified crude brine, wherein the amount of waste alkaline solution added is based on an effective chloride to ferrous ion molar ratio of 0.18. After the reaction is complete and the mixture is allowed to stand, it is then filtered to obtain a mixed brine and iron-containing sludge. The filtration process uses a flat-plate silicon carbide ceramic membrane method; the filtration pore size is 0.5–1.0 μm, and the filtration pressure is 0.5–0.1 MPa.

[0065] In step S2, the waste alkaline solution is added to qualified crude brine, wherein the amount of waste alkaline solution added is based on a molar ratio of available chloride to ferrous ions of 0.18. After the reaction is completed and the mixture is allowed to stand, it is filtered to obtain a mixed brine and iron-containing sludge, comprising:

[0066] Waste alkaline solution is added to qualified crude brine, with the amount of waste alkaline solution added being based on a molar ratio of available chlorine to ferrous ions of 0.18. After the addition is complete, the mixture is reacted for 30 minutes, allowed to stand for 18 hours, and then filtered to obtain mixed brine and iron-containing sludge.

[0067] The waste alkaline solution is prepared by absorbing the waste liquid discharged from the chlorination tail gas with 32% alkaline solution.

[0068] The mixed brine contains Fe≦1mg / L, Mn≦100mg / L, SS≦1mg / L, and Mg≦1mg / L. 2+ 18~20g / L, Ca 2+ : 1~2g / L, Ti≦0.01mg / L, V≦0.1mg / L, Cr≦1mg / L, pH 6.8~7.0; iron-containing sludge with Fe grade of 42~45%, used for sintering feedstock.

[0069] S3. Under stirring, add the calcium removal agent to the mixed brine, adjust the pH to 8.0, and then let it stand and filter to separate, obtaining magnesium-removed brine and Ca-containing residue.

[0070] In step S3, the calcium removal agent is added to the mixed brine under stirring, the pH is adjusted to 8.0, and then the mixture is allowed to stand and filtered to separate, yielding magnesium-removed brine and Ca-containing slag, comprising:

[0071] The calcium removal agent is added to the mixed brine under stirring, with the amount of calcium removal agent added according to the ratio of Ca:SO4. 2～ The molar ratio was 1:0.95, the reaction time was 30 min, the pH was adjusted to 8.0, the mixture was allowed to stand for 18-20 h, and then filtered to separate the magnesium-free brine and the Ca-containing residue.

[0072] The filtration and separation process employs a fully automated plate and frame filter method with a filtration pore size of 0.1–1.0 μm, a filtration pressure of ≤1.0 MPa, and a countercurrent washing filter cake preparation.

[0073] The calcium removal agent is a mixture of sodium sulfate, sodium carbonate, and sodium sulfite, wherein the ratio of sodium sulfate to sodium carbonate is 3 to 5:1.

[0074] The preferred calcium removal agent is SDS desulfurization solid waste, containing NaSO4: 65-70%, NaCO3: 15-20%, C: 0-9.8%, NaSO3: 0-0.3%, and NaCl: 0-5%. Sodium sulfite primarily reduces Cr. 6+ For Cr 3+ V 5+ For V 4+ After reduction, it is removed as the pH increases, and sodium carbonate synergistically removes Mn.

[0075] S4. Heat the magnesium-free brine to 90°C, add a 30% sodium carbonate solution at a sodium carbonate to magnesium ion molar ratio of 1.02, allow it to react fully, let it stand, filter and separate to obtain purified qualified brine and basic magnesium carbonate.

[0076] In step S4, the magnesium-removed brine is heated to 90°C, and a 30% sodium carbonate solution is added at a sodium carbonate to magnesium ion molar ratio of 1.02. After the reaction is complete, the solution is allowed to stand and filtered to separate, yielding purified qualified brine and basic magnesium carbonate, comprising:

[0077] The magnesium-free brine is heated to 90°C, and a 30% sodium carbonate solution is added at a sodium carbonate to magnesium ion molar ratio of 1.02. The feeding rate is controlled at 450-500 ml / min. After the reaction is complete, the brine is allowed to stand for 2 hours, and then filtered to separate the brine and basic magnesium carbonate products.

[0078] Among them, the method of filtering and separating flat silicon carbide ceramic membranes; the filter pore size is 40-100nm, the filtration pressure is ~0.25-0.04Mpa, and it is equipped with multi-stage washing. The alkaline magnesium carbonate washing is qualified, that is, Cl≦0.1% and Fe≦0.02%, and the first-grade product standard is stably controlled.

[0079] Step S5: Prepare qualified brine and hydrochloric acid at a volume ratio of 1:1 to form qualified NaCl brine with a pH of 4.6 to 4.9, which will be used as raw material in the primary brine production tank of chlor-alkali chemical plant.

[0080] Example 2

[0081] A method for removing impurities from crude brine prepared from molten salt chlorination slag includes the following steps:

[0082] S1. Add lime milk to molten salt chlorination slag to prepare saturated crude brine with a pH of 6.2. After the saturated crude brine is fully mixed and reacted, qualified crude brine is obtained.

[0083] The lime slurry is prepared by mixing lime and refined salt water at a mass ratio of 1:5.5.

[0084] In this embodiment of the invention, the mixture of lime and refined salt water is stirred at 40-60°C for 25-35 minutes and then allowed to stand for 1.5-2.5 hours to obtain lime milk.

[0085] S1 involves adding lime slurry to molten salt chlorination slag to prepare saturated crude brine with a pH of 6.2. After the saturated crude brine has fully mixed and reacted, qualified crude brine is obtained; including:

[0086] A saturated crude brine solution with a mass concentration of 15-16% was added to the molten salt chlorination slag under stirring at 350 rpm. The mixture was then thoroughly mixed and reacted for 15 minutes to obtain qualified crude brine.

[0087] S2. Add the waste alkaline solution to qualified crude brine, with the amount of waste alkaline solution added at a molar ratio of available chloride to ferrous ions of 0.24. After the reaction is complete and the mixture is allowed to stand, filter it to obtain a mixed brine and iron-containing sludge. The filtration process uses a flat-plate silicon carbide ceramic membrane method; the filtration pore size is 0.5–1.0 μm, and the filtration pressure is 0.5–0.1 MPa.

[0088] In step S2, the waste alkaline solution is added to qualified crude brine, wherein the amount of waste alkaline solution added is based on a molar ratio of available chloride to ferrous ions of 0.24. After the reaction is completed and the mixture is allowed to stand, it is filtered to obtain a mixed brine and iron-containing sludge, comprising:

[0089] Waste alkaline solution was added to qualified crude brine, with the amount of waste alkaline solution added being based on a molar ratio of available chlorine to ferrous ions of 0.24. After the addition was complete, the mixture was reacted for 40 minutes, allowed to stand for 24 hours, and then filtered to obtain a mixed brine and iron-containing sludge.

[0090] The waste alkaline solution is prepared by absorbing the waste liquid discharged from the chlorination tail gas with 32% alkaline solution.

[0091] The mixed brine contains Fe≦1mg / L, Mn≦100mg / L, SS≦1mg / L, and Mg≦1mg / L. 2+ 18~20g / L, Ca 2+ : 1~2g / L, Ti≦0.01mg / L, V≦0.1mg / L, Cr≦1mg / L, pH 6.8~7.0; iron-containing sludge with Fe grade of 42~45%, used for sintering feedstock.

[0092] S3. Under stirring, add the calcium removal agent to the mixed brine, adjust the pH to 8.5, and then let it stand and filter to separate, obtaining magnesium-removed brine and Ca-containing residue.

[0093] In step S3, the calcium removal agent is added to the mixed brine under stirring, the pH is adjusted to 8.5, and then the mixture is allowed to stand and filtered to separate, yielding magnesium-removed brine and Ca-containing slag, comprising:

[0094] The calcium removal agent is added to the mixed brine under stirring, with the amount of calcium removal agent added according to the ratio of Ca:SO4. 2～ The molar ratio was 1:0.95, the reaction time was 30 min, the pH was adjusted to 8.5, the mixture was allowed to stand for 18–20 h, and then filtered to separate the magnesium-free brine and the Ca-containing residue.

[0095] The filtration and separation process employs a fully automated plate and frame filter method with a filtration pore size of 0.1–1.0 μm, a filtration pressure of ≤1.0 MPa, and a countercurrent washing filter cake preparation.

[0096] The calcium removal agent is a mixture of sodium sulfate, sodium carbonate, and sodium sulfite, wherein the ratio of sodium sulfate to sodium carbonate is 3 to 5:1.

[0097] The preferred calcium removal agent is SDS desulfurization solid waste, containing NaSO4: 65-70%, NaCO3: 15-20%, C: 0-9.8%, NaSO3: 0-0.3%, and NaCl: 0-5%. Sodium sulfite primarily reduces Cr. 6+ For Cr 3+ V 5+ For V 4+ After reduction, it is removed as the pH increases, and sodium carbonate synergistically removes Mn.

[0098] S4. Heat the magnesium-free brine to 95°C, add a 30% sodium carbonate solution at a sodium carbonate to magnesium ion molar ratio of 1.05, allow it to react fully, let it stand, filter and separate to obtain purified qualified brine and basic magnesium carbonate.

[0099] In step S4, the magnesium-removed brine is heated to 95°C, and a 30% sodium carbonate solution is added at a sodium carbonate to magnesium ion molar ratio of 1.05. After the reaction is complete, the solution is allowed to stand and filtered to separate, yielding purified qualified brine and basic magnesium carbonate, comprising:

[0100] The magnesium-free brine is heated to 95°C, and a 30% sodium carbonate solution is added at a sodium carbonate to magnesium ion molar ratio of 1.05. The feeding rate is controlled at 450-500 ml / min. After the reaction is complete, the brine is allowed to stand for 2 hours, and then filtered to separate the brine and basic magnesium carbonate products.

[0101] Among them, the method of filtering and separating flat silicon carbide ceramic membranes; the filter pore size is 40-100nm, the filtration pressure is ~0.25-0.04Mpa, and it is equipped with multi-stage washing. The alkaline magnesium carbonate washing is qualified, that is, Cl≦0.1% and Fe≦0.02%, and the first-grade product standard is stably controlled.

[0102] Step S5: Prepare qualified brine and hydrochloric acid at a volume ratio of 1:1 to form qualified NaCl brine with a pH of 4.6 to 4.9, which will be used as raw material in the primary brine production tank of chlor-alkali chemical plant.

[0103] Example 3

[0104] A method for removing impurities from crude brine prepared from molten salt chlorination slag includes the following steps:

[0105] S1. Add lime milk to molten salt chlorination slag to prepare saturated crude brine with a pH of 6.1. After the saturated crude brine is fully mixed and reacted, qualified crude brine is obtained.

[0106] The lime slurry is prepared by mixing lime and refined salt water at a mass ratio of 1:5.5.

[0107] In this embodiment of the invention, the mixture of lime and refined salt water is stirred at 55°C for 32 minutes and then allowed to stand for 2.2 hours to obtain lime milk.

[0108] S2. Add the waste alkaline solution to qualified crude brine, with the amount of waste alkaline solution added being based on a molar ratio of available chlorine to ferrous ions of 0.23. After the reaction is complete and the mixture is allowed to stand, it is then filtered to obtain a mixed brine and iron-containing sludge. The filtration process uses a flat-plate silicon carbide ceramic membrane method; the filtration pore size is 0.5–1.0 μm, and the filtration pressure is 0.5–0.1 MPa.

[0109] In step S2, the waste alkaline solution is added to qualified crude brine, wherein the amount of waste alkaline solution added is based on a molar ratio of available chloride to ferrous ions of 0.23. After the reaction is completed and the mixture is allowed to stand, it is filtered to obtain a mixed brine and iron-containing sludge, comprising:

[0110] Waste alkaline solution was added to qualified crude brine, with the amount of waste alkaline solution added being based on a molar ratio of available chlorine to ferrous ions of 0.23. After the addition was complete, the mixture was reacted for 37 minutes, allowed to stand for 23 hours, and then filtered to obtain a mixed brine and iron-containing sludge.

[0111] The waste alkaline solution is prepared by absorbing the waste liquid discharged from the chlorination tail gas with 32% alkaline solution.

[0112] The mixed brine contains Fe≦1mg / L, Mn≦100mg / L, SS≦1mg / L, and Mg≦1mg / L. 2+ 18~20g / L, Ca 2+ : 1~2g / L, Ti≦0.01mg / L, V≦0.1mg / L, Cr≦1mg / L, pH 6.8~7.0; iron-containing sludge with Fe grade of 42~45%, used for sintering feedstock.

[0113] S3. Under stirring, add the calcium removal agent to the mixed brine, adjust the pH to 8.4, and then let it stand and filter to separate, obtaining magnesium-removed brine and Ca-containing residue.

[0114] In step S3, the calcium removal agent is added to the mixed brine under stirring, the pH is adjusted to 8.4, and then the mixture is allowed to stand and filtered to separate, yielding magnesium-removed brine and Ca-containing slag, comprising:

[0115] The calcium removal agent is added to the mixed brine under stirring, with the amount of calcium removal agent added according to the ratio of Ca:SO4. 2～ The molar ratio was 1:0.95, the reaction time was 30 min, the pH was adjusted to 8.4, the mixture was allowed to stand for 18-20 h, and then filtered to separate the magnesium-free brine and the Ca-containing residue.

[0116] The filtration and separation process employs a fully automated plate and frame filter method with a filtration pore size of 0.1–1.0 μm, a filtration pressure of ≤1.0 MPa, and a countercurrent washing filter cake preparation.

[0117] The calcium removal agent is a mixture of sodium sulfate, sodium carbonate, and sodium sulfite, wherein the ratio of sodium sulfate to sodium carbonate is 3 to 5:1.

[0118] The preferred calcium removal agent is SDS desulfurization solid waste, containing NaSO4: 65-70%, NaCO3: 15-20%, C: 0-9.8%, NaSO3: 0-0.3%, and NaCl: 0-5%. Sodium sulfite primarily reduces Cr. 6+ For Cr 3+ V 5+ For V 4+ After reduction, it is removed as the pH increases, and sodium carbonate synergistically removes Mn.

[0119] S4. Heat the magnesium-free brine to 94°C, add a 30% sodium carbonate solution at a sodium carbonate to magnesium ion molar ratio of 1.04, allow it to react fully, let it stand, filter and separate to obtain purified qualified brine and basic magnesium carbonate.

[0120] In step S4, the magnesium-removed brine is heated to 94°C, and a 30% sodium carbonate solution is added at a sodium carbonate to magnesium ion molar ratio of 1.04. After the reaction is complete, the solution is allowed to stand and filtered to separate, yielding purified qualified brine and basic magnesium carbonate, comprising:

[0121] The magnesium-free brine was heated to 94°C, and a 30% sodium carbonate solution was added at a sodium carbonate to magnesium ion molar ratio of 1.04. The feeding rate was controlled at 500 ml / min. After the reaction was complete, the brine was allowed to stand for 2 hours, and then filtered to separate the brine and basic magnesium carbonate products.

[0122] Among them, the method of filtering and separating flat silicon carbide ceramic membranes; the filter pore size is 40-100nm, the filtration pressure is ~0.25-0.04Mpa, and it is equipped with multi-stage washing. The alkaline magnesium carbonate washing is qualified, that is, Cl≦0.1% and Fe≦0.02%, and the first-grade product standard is stably controlled.

[0123] Step S5: Prepare qualified NaCl brine with pH 4.6-4.9 by mixing qualified brine and hydrochloric acid at a volume ratio of 1:1. This qualified NaCl brine is then used as a raw material in the primary brine production tank of the chlor-alkali chemical plant.

[0124] Example 4

[0125] A method for removing impurities from crude brine prepared from molten salt chlorination slag includes the following steps:

[0126] S1. Add lime milk to molten salt chlorination slag to prepare saturated crude brine with a pH of 5.9. After the saturated crude brine is fully mixed and reacted, qualified crude brine is obtained.

[0127] The lime slurry is prepared by mixing lime and refined salt water at a mass ratio of 1:5.5.

[0128] In this embodiment of the invention, the mixture of lime and refined salt water is stirred at 45-55°C for 28 minutes and then allowed to stand for 1.8 hours to obtain lime milk.

[0129] S2. Add the waste alkaline solution to qualified crude brine, with the amount of waste alkaline solution added being based on a molar ratio of available chloride to ferrous ions of 0.19. After the reaction is complete and the mixture is allowed to stand, it is then filtered to obtain a mixed brine and iron-containing sludge. The filtration process uses a flat-plate silicon carbide ceramic membrane method; the filtration pore size is 0.5–1.0 μm, and the filtration pressure is 0.5–0.1 MPa.

[0130] In step S2, the waste alkaline solution is added to qualified crude brine, wherein the amount of waste alkaline solution added is based on a molar ratio of available chloride to ferrous ions of 0.19. After the reaction is completed and the mixture is allowed to stand, it is filtered to obtain a mixed brine and iron-containing sludge, comprising:

[0131] Waste alkaline solution is added to qualified crude brine, with the amount of waste alkaline solution added being 0.19 to 0.23 molar ratio of available chlorine to ferrous ions. After the addition is complete, the reaction is allowed to proceed for 33 to 37 minutes, followed by standing for 19 to 23 hours, and then filtered to obtain mixed brine and iron-containing sludge.

[0132] The waste alkaline solution is prepared by absorbing the waste liquid discharged from the chlorination tail gas with 32% alkaline solution.

[0133] The mixed brine contains Fe≦1mg / L, Mn≦100mg / L, SS≦1mg / L, and Mg≦1mg / L. 2+ 18~20g / L, Ca 2+ : 1~2g / L, Ti≦0.01mg / L, V≦0.1mg / L, Cr≦1mg / L, pH 6.8~7.0; iron-containing sludge with Fe grade of 42~45%, used for sintering feedstock.

[0134] S3. Under stirring, add the calcium removal agent to the mixed brine, adjust the pH to 8.1, and then let it stand and filter to separate, obtaining magnesium-removed brine and Ca-containing residue.

[0135] In step S3, the calcium removal agent is added to the mixed brine under stirring, the pH is adjusted to 8.1, and then the mixture is allowed to stand and filtered to separate, yielding magnesium-removed brine and Ca-containing slag, comprising:

[0136] The calcium removal agent is added to the mixed brine under stirring, with the amount of calcium removal agent added according to the ratio of Ca:SO4. 2～ The molar ratio was 1:0.95, the reaction time was 30 min, the pH was adjusted to 8.1, the mixture was allowed to stand for 18 h, and then filtered to separate the magnesium-free brine and the Ca-containing residue.

[0137] The filtration and separation process employs a fully automated plate and frame filter method with a filtration pore size of 0.1–1.0 μm, a filtration pressure of ≤1.0 MPa, and a countercurrent washing filter cake preparation.

[0138] The calcium removal agent is a mixture of sodium sulfate, sodium carbonate, and sodium sulfite, wherein the ratio of sodium sulfate to sodium carbonate is 3 to 5:1.

[0139] The preferred calcium removal agent is SDS desulfurization solid waste, containing NaSO4: 65-70%, NaCO3: 15-20%, C: 0-9.8%, NaSO3: 0-0.3%, and NaCl: 0-5%. Sodium sulfite primarily reduces Cr. 6+ For Cr 3+ V 5+ For V 4+ After reduction, it is removed as the pH increases, and sodium carbonate synergistically removes Mn.

[0140] S4. Heat the magnesium-free brine to 91°C, add a 30% sodium carbonate solution at a sodium carbonate to magnesium ion molar ratio of 1.03, allow it to react fully, let it stand, filter and separate to obtain purified qualified brine and basic magnesium carbonate.

[0141] In step S4, the magnesium-removed brine is heated to 91°C, and a 30% sodium carbonate solution is added at a sodium carbonate to magnesium ion molar ratio of 1.03. After the reaction is complete, the solution is allowed to stand and filtered to separate, yielding purified qualified brine and basic magnesium carbonate, comprising:

[0142] The magnesium-free brine was heated to 91°C, and a 30% sodium carbonate solution was added at a sodium carbonate to magnesium ion molar ratio of 1.03. The feeding rate was controlled at 450-500 ml / min. After the reaction was complete, the brine was allowed to stand for 2 hours, and then filtered to separate the brine and basic magnesium carbonate products.

[0143] Among them, the method of filtering and separating flat silicon carbide ceramic membranes; the filter pore size is 40-100nm, the filtration pressure is ~0.25-0.04Mpa, and it is equipped with multi-stage washing. The alkaline magnesium carbonate washing is qualified, that is, Cl≦0.1% and Fe≦0.02%, and the first-grade product standard is stably controlled.

[0144] Step S5: Prepare qualified NaCl brine with pH 4.6-4.9 by mixing qualified brine and hydrochloric acid at a volume ratio of 1:1. This qualified NaCl brine is then used as a raw material in the primary brine production tank of the chlor-alkali chemical plant.

[0145] Example 5

[0146] A method for removing impurities from crude brine prepared from molten salt chlorination slag includes the following steps:

[0147] S1. Add lime milk to molten salt chlorination slag to prepare saturated crude brine with pH 6. After the saturated crude brine is fully mixed and reacted, qualified crude brine is obtained.

[0148] The lime slurry is prepared by mixing lime and refined salt water at a mass ratio of 1:5.5.

[0149] In this embodiment of the invention, the mixture of lime and refined salt water is stirred at 50°C for 30 minutes and then allowed to stand for 2 hours to obtain lime milk.

[0150] S2. Add the waste alkaline solution to the qualified crude brine, wherein the amount of waste alkaline solution added is based on an effective chloride to ferrous ion molar ratio of 0.21. After the reaction is complete and the mixture is allowed to stand, it is then filtered to obtain a mixed brine and iron-containing sludge. The filtration process uses a flat-plate silicon carbide ceramic membrane method; the filtration pore size is 0.5–1.0 μm, and the filtration pressure is 0.5–0.1 MPa.

[0151] In step S2, the waste alkaline solution is added to qualified crude brine, wherein the amount of waste alkaline solution added is based on a molar ratio of available chloride to ferrous ions of 0.21. After the reaction is completed and the mixture is allowed to stand, it is filtered to obtain a mixed brine and iron-containing sludge, comprising:

[0152] Waste alkaline solution was added to qualified crude brine, with the amount of waste alkaline solution added being based on a molar ratio of available chlorine to ferrous ions of 0.21. After the addition was complete, the mixture was reacted for 35 minutes, allowed to stand for 21 hours, and then filtered to obtain a mixed brine and iron-containing sludge.

[0153] The waste alkaline solution is prepared by absorbing the waste liquid discharged from the chlorination tail gas with 32% alkaline solution.

[0154] The mixed brine contains Fe≦1mg / L, Mn≦100mg / L, SS≦1mg / L, and Mg≦1mg / L. 2+ 18~20g / L, Ca 2+: 1~2g / L, Ti≦0.01mg / L, V≦0.1mg / L, Cr≦1mg / L, pH 6.8~7.0; iron-containing sludge with Fe grade of 42~45%, used for sintering feedstock.

[0155] S3. Under stirring, add the calcium removal agent to the mixed brine, adjust the pH to 8.3, and then let it stand and filter to separate, obtaining magnesium-removed brine and Ca-containing residue.

[0156] In step S3, the calcium removal agent is added to the mixed brine under stirring, the pH is adjusted to 8.3, and then the mixture is allowed to stand and filtered to separate, yielding magnesium-removed brine and Ca-containing slag, comprising:

[0157] The calcium removal agent is added to the mixed brine under stirring, with the amount of calcium removal agent added according to the ratio of Ca:SO4. 2～ The molar ratio was 1:0.95, the reaction time was 30 min, the pH was adjusted to 8.3, the mixture was allowed to stand for 19 h, and then filtered to separate the magnesium-free brine and the Ca-containing residue.

[0158] The filtration and separation process employs a fully automated plate and frame filter method with a filtration pore size of 0.1–1.0 μm, a filtration pressure of ≤1.0 MPa, and a countercurrent washing filter cake preparation.

[0159] The calcium removal agent is a mixture of sodium sulfate, sodium carbonate, and sodium sulfite, wherein the ratio of sodium sulfate to sodium carbonate is 3 to 5:1.

[0160] The preferred calcium removal agent is SDS desulfurization solid waste, containing NaSO4: 65-70%, NaCO3: 15-20%, C: 0-9.8%, NaSO3: 0-0.3%, and NaCl: 0-5%. Sodium sulfite primarily reduces Cr. 6+ For Cr 3+ V 5+ For V 4+ After reduction, it is removed as the pH increases, and sodium carbonate synergistically removes Mn.

[0161] S4. Heat the magnesium-free brine to 92°C, add a 30% sodium carbonate solution at a sodium carbonate to magnesium ion molar ratio of 1.35, allow it to react fully, let it stand, filter and separate to obtain purified qualified brine and basic magnesium carbonate.

[0162] In step S4, the magnesium-removed brine is heated to 92°C, and a 30% sodium carbonate solution is added at a sodium carbonate to magnesium ion molar ratio of 1.35. After the reaction is complete, the solution is allowed to stand and filtered to separate, yielding purified qualified brine and basic magnesium carbonate, comprising:

[0163] The magnesium-free brine was heated to 92°C, and a 30% sodium carbonate solution was added at a sodium carbonate to magnesium ion molar ratio of 1.35. The feeding rate was controlled at 475 ml / min. After the reaction was complete, the brine was allowed to stand for 2 hours, and then filtered to separate the brine and basic magnesium carbonate products.

[0164] Among them, the method of filtering and separating flat silicon carbide ceramic membranes; the filter pore size is 40-100nm, the filtration pressure is ~0.25-0.04Mpa, and it is equipped with multi-stage washing. The alkaline magnesium carbonate washing is qualified, that is, Cl≦0.1% and Fe≦0.02%, and the first-grade product standard is stably controlled.

[0165] Step S5: Prepare qualified brine and hydrochloric acid at a volume ratio of 1:1 to form qualified NaCl brine with a pH of 4.6 to 4.9, which will be used as raw material in the primary brine production tank of chlor-alkali chemical plant.

[0166] Example 6

[0167] At a stirring speed of 300 rpm, 15.4% lime slurry was added to crude brine (NaCl: 126 g / L, FeCl2: 78 g / L, FeCl3: 7.8 g / L, MgCl2: 96 g / L, MnCl2: 5.4 g / L, CaCl2: 6.2 g / L, Cr: 7 mg / L, V < 0.1 mg / L, Ti < 0.1 mg / L, pH 0.84, temperature 45℃). The pH was adjusted to 5.8, and after reacting for 15 min, waste alkali solution was gradually added (the amount added was based on an effective chloride to ferrous ion molar ratio of 0.22). After the addition was complete, the reaction was allowed to proceed for 40 min, and the mixture was allowed to stand for 24 h. The solution was then filtered through a flat plate membrane (filtration pore size 1.0 μm, pressure 0–0.45 MPa) to obtain the filtrate, which contained Fe≦1 mg / L, Mn 91 mg / L, SS≦1 mg / L, and Mg 2+ 18.6 g / L, Ca 2+ 1.86 g / L, Ti ≤ 0.01 mg / L, V ≤ 0.01 mg / L, Cr ≤ 1 mg / L, pH 6.8, under stirring, Ca:SO4 2～ Add calcium removal agent at a molar ratio of 1:0.95, react for 30 min, adjust pH to 8.5 with 32% alkali solution, let stand for 20 h, and then filter through a fully automatic plate and frame filter. The filtrate contains Fe≦1 mg / L, Mn≦2 mg / L, and Mg≦1 mg / L. 2+ 17.6 g / L, Ca 2+0.18 g / L, Ti ≤ 0.01 mg / L, V ≤ 0.1 mg / L, Cr ≤ 0.1 mg / L; The filtrate was heated to 92℃, and a 30% (mass concentration) sodium carbonate solution was slowly added at 480 ml / min according to a sodium carbonate to magnesium ion molar ratio of 1.03. After the addition was complete, the mixture was reacted for 30 min, then allowed to stand for 2 h. The solution was filtered through a flat ceramic membrane, and the pH of the filtrate was adjusted to 4.9 with hydrochloric acid. At this point, the salt solution concentration was NaCl: 18.8%, Fe ≤ 1 mg / L, Mn ≤ 1 mg / L, Mg ≤ 0.18 g / L, Ti ≤ 0.01 mg / L, V ≤ 0.1 mg / L, Cr ≤ 0.1 mg / L; 2+ 16 mg / L, Ca 2+ 24 mg / L, Ti≦0.01 mg / L, V≦0.01 mg / L, Cr≦0.05 mg / L, were sent to the primary brine tank of the ion-exchange membrane caustic soda.

[0168] The Fe-containing slag obtained from filtration, after 7 water washings, had a Cl content of 0.21% and an Fe content of 44.1%; the Ca-containing slag, after 3 water washings, had a Cl content of 0.06% and a calcium sulfate content of 90.1%; the basic magnesium carbonate, after 3 water washings, had a Cl content of 0.03%. The drying index analysis showed that the MgO content was 42.07%, the CaO content was 0.5%, the Fe content was 0.018%, and the Mn content was 0.003%, meeting the requirements for first-class products.

[0169] Example 7

[0170] At a stirring speed of 350 rpm, 16% lime slurry was added to crude brine (NaCl: 138 g / L, FeCl2: 75 g / L, FeCl3: 9.2 g / L, MgCl2: 101 g / L, MnCl2: 5.1 g / L, CaCl2: 6.4 g / L, Cr: 1 mg / L, V < 1 mg / L, Ti < 0.01 mg / L, pH 1.08, temperature 40℃). The pH was adjusted to 6.2, and after reacting for 15 min, waste alkali solution was gradually added (the amount added was based on an effective chloride to ferrous ion molar ratio of 0.18). After the addition was complete, the reaction was allowed to proceed for 40 min, and the mixture was allowed to stand for 24 h. The solution was then filtered through a flat plate membrane (filter pore size 1.0 μm, pressure ~0.40 MPa) to obtain the filtrate, which contained Fe≦1 mg / L, Mn 71 mg / L, SS≦1 mg / L, and Mg 2+ 19.2 g / L, Ca 2+ 1.96 g / L, Ti ≤ 0.01 mg / L, V ≤ 0.01 mg / L, Cr ≤ 0.5 mg / L, pH 7.0, prepared by stirring according to Ca:SO4 2 ～ Add calcium removal agent at a molar ratio of 1:0.95, react for 30 min, adjust pH to 9.0 with 32% alkali solution, let stand for 18 h, and then filter through a fully automatic plate and frame filter. The filtrate contains Fe≦1 mg / L, Mn≦1 mg / L, and Mg≦1 mg / L.2+ 18.2 g / L, Ca 2+ The concentrations of the sodium carbonate solution were: 0.186 g / L, Ti ≤ 0.01 mg / L, V ≤ 0.01 mg / L, Cr ≤ 0.03 mg / L. The filtrate was heated to 92℃, and a 30% (mass concentration) sodium carbonate solution was slowly added at a rate of 460 ml / min according to a sodium carbonate to magnesium ion molar ratio of 1.05. After the addition was complete, the solution was reacted for 30 min, allowed to stand for 2 h, and then filtered through a flat ceramic membrane. The pH of the filtrate was adjusted to 4.6 with hydrochloric acid. At this point, the salt solution concentration was: NaCl: 19.6%, Fe ≤ 1 mg / L, Mn ≤ 1 mg / L, Mg ≤ 0.186 g / L, Ti ≤ 0.01 mg / L, V ≤ 0.01 mg / L, Cr ≤ 0.03 mg / L. 2+ 15mg / L, Ca 2+ 21 mg / L, Ti≦0.01 mg / L, V≦0.01 mg / L, Cr≦0.03 mg / L, were sent to the primary brine tank of the ion-exchange membrane caustic soda.

[0171] The Fe-containing slag obtained from filtration, after 6 water washings, had a Cl content of 0.28% and an Fe content of 42.1%; the Ca-containing slag, after 3 water washings, had a Cl content of 0.05% and a calcium sulfate content of 90.7%; the basic magnesium carbonate, after 3 water washings, had a Cl content of 0.02%. The drying index analysis showed that the MgO content was 42.97%, the CaO content was 0.42%, the Fe content was 0.01%, and the Mn content was 0.004%, meeting the requirements for first-class products.

[0172] The preferred embodiments of the present invention have been described in detail above. However, the present invention is not limited to the above embodiments. Within the scope of knowledge possessed by those skilled in the art, various changes can be made without departing from the spirit of the present invention.

Claims

1. A method for removing impurities from crude brine prepared from molten salt chlorination slag, characterized in that, The method includes the following steps: S1. Lime slurry is added to molten salt chlorination slag to prepare saturated crude brine with a pH of 5.8–6.

2. After the saturated crude brine is fully mixed and reacted, qualified crude brine is obtained. The lime slurry is prepared by mixing lime and refined brine at a mass ratio of 1:5.

5. The qualified crude brine has the following components: NaCl: 125–140 g / L, FeCl2: 75–80 g / L, FeCl3: 7.0–10.0 g / L, MgCl2: 95–102 g / L, MnCl2: 5.0–6.0 g / L, CaCl2: 6.0–6.5 g / L, and a small amount of SO4. 2- Trace amounts of Cr, V, and Ti; pH 0.7–1.1; temperature 40–55℃; S2. Add the waste alkaline solution to qualified crude brine, wherein the amount of waste alkaline solution added is based on an effective chloride to ferrous ion molar ratio of 0.18 to 0.

24. After the reaction is completed and the mixture is allowed to stand, it is filtered to obtain a mixed brine and iron-containing sludge. The waste alkaline solution has the following composition: NaCO3: 6-20 g / L, NaCl: 15-16 g / L, NaClO: 1.5-5.0 g / L, pH 8.0-9.5, and temperature 25-30℃. S3. Under stirring, the calcium removal agent is added to the mixed brine, the pH is adjusted to 8.0-8.5, and then the mixture is allowed to stand and filtered to separate, yielding magnesium-removed brine and Ca-containing slag. The calcium removal agent is SDS desulfurization solid waste, with the following composition: NaSO4: 65-70%, NaCO3: 15-20%, C: 0-9.8%, NaSO3: 0-0.3%, NaCl: 0-5%, where NaSO3 is not zero. The magnesium-removed brine contains Fe≦1mg / L, Mn≦1mg / L, and Mg≦1mg / L. 2+ 17.2~17.8g / L, Ca 2+ :0.18~0.2g / L, Ti≦0.01mg / L, V≦0.1mg / L, Cr≦0.1mg / L; S4. Heat the magnesium-removed brine to 90-95℃, add a 30% sodium carbonate solution at a sodium carbonate to magnesium ion molar ratio of 1.02-1.05, allow to react completely, then let stand and filter to separate, obtaining purified qualified brine and basic magnesium carbonate. The purified qualified brine has the following composition: NaCl: 18-20%, Fe≦1mg / L, Mn≦1mg / L, Mg≦1mg / L. 2+ ≤20mg / L, Ca 2+ ≦30mg / L, Ti≦0.01mg / L, V≦0.01mg / L, Cr≦0.1mg / L; S5. Prepare qualified NaCl brine with a pH of 4.6 to 4.9 by mixing the purified qualified brine with hydrochloric acid at a volume ratio of 1:

1.

2. The method for removing impurities from crude brine prepared from molten salt chlorination slag as described in claim 1, characterized in that, The mixture of lime and refined salt water was stirred at 50°C for 30 minutes and then allowed to stand for 2 hours to obtain lime milk.

3. The method for removing impurities from crude brine prepared from molten salt chlorination slag as described in claim 1, characterized in that, In step S2, the waste alkaline solution is added to qualified crude brine, wherein the amount of waste alkaline solution added is based on an effective chloride to ferrous ion molar ratio of 0.18 to 0.

24. After the reaction is completed and the mixture is allowed to stand, it is filtered to obtain a mixed brine and iron-containing sludge, comprising: Waste alkaline solution is added to qualified crude brine, with the amount of waste alkaline solution added being 0.18 to 0.24 molar ratio of available chlorine to ferrous ions. After the addition is complete, the mixture is reacted for 30 to 40 minutes, allowed to stand for 18 to 24 hours, and then filtered to obtain mixed brine and iron-containing sludge.

4. The method for removing impurities from crude brine prepared from molten salt chlorination slag as described in claim 3, characterized in that, In step S2, the waste alkaline solution is added to qualified crude brine, wherein the amount of waste alkaline solution added is based on an effective chlorine to ferrous ion molar ratio of 0.18 to 0.

24. After the reaction is completed and the mixture is allowed to stand, it is filtered to obtain a mixed brine and iron-containing sludge. The filtration process includes using a flat-plate silicon carbide ceramic membrane method with a pore size of 0.5 to 1.0 μm and a filtration pressure of 0.5 to 0.1 MPa.

5. The method for removing impurities from crude brine prepared from molten salt chlorination slag as described in claim 1, characterized in that, In step S3, the calcium removal agent is added to the mixed brine under stirring, the pH is adjusted to 8.0-8.5, and then the mixture is allowed to stand and filtered to separate, yielding magnesium-removed brine and Ca-containing slag, comprising: The calcium removal agent was added to the mixed brine under stirring, with the amount of calcium removal agent added according to the ratio of Ca:SO4. 2～ The molar ratio was 1:0.95, the reaction time was 30 min, the pH was adjusted to 8.0-8.5, the mixture was allowed to stand for 18-20 h, and then filtered to separate the magnesium-free brine and the Ca-containing residue.

6. The method for removing impurities from crude brine prepared from molten salt chlorination slag as described in claim 5, characterized in that, In step S3, the calcium removal agent is added to the mixed brine under stirring, the pH is adjusted to 8.0-8.5, and then the mixture is allowed to stand and filtered to separate the magnesium-free brine and Ca-containing slag. The process includes: the filtration treatment is carried out using a flat silicon carbide ceramic membrane method; the filtration pore size is 0.5-1.0 μm, and the filtration pressure is 0.5-0.1 MPa.

7. The method for removing impurities from crude brine prepared from molten salt chlorination slag as described in claim 1, characterized in that, In step S3, the calcium removal agent is added to the mixed brine under stirring, the pH is adjusted to 8.0-8.5, and then the mixture is allowed to stand and filtered to obtain magnesium-free brine and Ca-containing slag. The filtration separation is carried out using a fully automatic plate and frame filter method with a filtration pore size of 0.1-1.0 μm and a filtration pressure of ≤1.0 MPa.

Images