Method for comprehensively extracting potassium, boron and bromine from chloride type deep well brine

Abstract

The invention provides a method for comprehensively extracting potassium, boron and bromine from chloride type deep well brine, which comprises the following steps: step S1, injecting the brine into a salt pan for solarization evaporation, respectively obtaining rock salt, sylvite mixed salt, carnallite mixed salt and liquid-phase old brine in stages, and measuring the liquid-phase density in the evaporation process as a control index of different salt precipitation stages; s2, carnallite mixed salt is used as a raw material, and a potassium chloride product is prepared through a cold decomposition-direct flotation-washing technology; step S3, taking old brine as a raw material, preparing a liquid bromine product by adopting a process of oxidation, air blowing-out, absorption by an absorbent, oxidation, distillation and rectification, and obtaining a liquid phase after air blowing-out, namely bromine-blown liquid; and S4, taking the bromine-blown liquid as a raw material, and preparing a boric acid product by adopting the processes of extraction, reverse extraction, high-temperature evaporation, low-temperature cooling crystallization, redissolution crystallization and washing. According to the invention, primary separation of potassium and sodium and efficient enrichment and separation of boron and bromine can be realized, the comprehensive utilization value of deep well brine is improved, and the cost is reduced.

Description

Technical Field

[0001] The present invention belongs to the technical field of comprehensive utilization of brine, and specifically relates to a method for comprehensive extraction of potassium, boron and bromine from chloride-type deep well brine. Background Art

[0002] Most of the potassium resources that have been discovered in my country are found in salt lake brines. After years of industrial development and utilization, the surface salt lake resources have been sharply reduced, and in recent years, the dependence on potassium salt has reached more than 50%. Therefore, potassium salt is listed as one of the most scarce mineral resources in my country. Through years of geological exploration and prospecting, large reserves or high-quality deep potassium-containing brines have been discovered in the Qaidam Basin, Sichuan Basin, Jianghan Basin and other places, and they also contain many valuable components such as lithium, boron, bromine, and strontium.

[0003] At present, the utilization mode of brine resources in my country is mostly: selectively extracting simple components or components with high added value, and other valuable components that are not extracted are discharged with the old brine, which not only wastes resources but also pollutes the environment. Compared with surface salt lake brine, deep brine is buried deep and has high mining costs, so it is necessary to take the path of comprehensive utilization. Therefore, how to efficiently and comprehensively extract valuable components from deep brine is a difficult problem that needs to be solved for its sustainable industrial development. If the comprehensive development of deep brine can be achieved, it will alleviate the shortage of resources such as potassium and bromine in my country to a certain extent. Summary of the invention

[0004] A brief overview of the disclosure is given below in order to provide a basic understanding of certain aspects of the disclosure. It should be understood that this overview is not an exhaustive overview of the disclosure. It is not intended to identify key or important parts of the disclosure, nor is it intended to limit the scope of the disclosure. Its purpose is simply to give certain concepts in a simplified form as a prelude to a more detailed description discussed later.

[0005] Deep brine is a multi-component complex brine system, which contains multiple valuable components such as potassium, sodium, bromine, boron, and lithium. However, it is buried deep and has high mining costs, and the existing technology has failed to fully extract its valuable components. To address this problem, the present invention provides a method for comprehensively extracting potassium, boron, and bromine from chloride-type deep well brine, which can separate and extract sodium chloride, potassium chloride, boric acid, and liquid bromine products in a step-by-step, orderly, and efficient manner, thereby realizing the comprehensive utilization of brine resources and enhancing the economic value of brine.

[0006] In order to solve the above technical problems, the technical solution provided by the present disclosure is:

[0007] A method for comprehensively extracting potassium, boron and bromine from chloride-type deep well brine, comprising the following steps:

[0008] Step S1, injecting brine into the salt pan for solar evaporation, obtaining rock salt, sylvite mixed salt, carnallite mixed salt and liquid phase old brine in stages, and measuring the density of the liquid phase during the evaporation process as a control indicator for different salt precipitation stages;

[0009] Step S2, using carnallite mixed salt as raw material, adopting cold decomposition-positive flotation-washing process to prepare potassium chloride product;

[0010] Step S3, using old brine as raw material, adopting oxidation-air blowing-absorbent absorption-oxidation-distillation-rectification process to prepare liquid bromine product, and the liquid phase obtained after air blowing is bromine post-blowing liquid;

[0011] Step S4, using the bromine blown liquid as raw material, adopting extraction-strip extraction-high temperature evaporation-low temperature cooling crystallization-redissolution crystallization-washing process to prepare the boric acid product.

[0012] The above-mentioned method for comprehensive extraction of potassium, boron and bromine from chloride-type deep well brine is a preferred embodiment. In step S1, the "measurement of the density of the liquid phase during the evaporation process as a control index for different salt precipitation stages" means: in the precipitating halite stage, the liquid phase density is controlled at <1.275 g / cm 3 ; Precipitate potassium salt section, liquid phase density is controlled at 1.275-1.285g / cm 3 ; Carnallite segment is precipitated, and the liquid phase density is controlled at 1.285-1.370g / cm 3 .

[0013] The above-mentioned method for comprehensive extraction of potassium, boron and bromine from chloride-type deep well brine is a preferred embodiment, and step S2 specifically comprises: adding water to the carnallite mixed salt for decomposition to obtain a decomposed solid phase; using octadecylamine as a collector, floating the decomposed solid phase in a potassium saturated solution, and obtaining potassium chloride concentrate and sodium chloride tailings after separation; adding water to the potassium chloride concentrate for washing, and obtaining a potassium chloride product and a washing mother liquor after separation; preferably, the potassium saturated solution is recycled in the flotation process; preferably, the washing mother liquor is supplemented with fresh fresh water and recycled in the washing process.

[0014] The above-mentioned method for comprehensive extraction of potassium, boron and bromine from chloride-type deep well brine is a preferred embodiment. In step S2, the water temperature used in the decomposition process is 15-25°C, and the amount of water used is 40%-50% of the mass of the carnallite mixed salt; in the flotation process, the amount of octadecylamine used in the roughing selection is 40-50g / t, and the amount of octadecylamine used in the scavenging selection is 10-15g / t;

[0015] Preferably, in step S2, the detergent in the washing process is a mixed solution of washing mother liquor and fresh fresh water, the amount of fresh fresh water is 20%-30% of the mass of the potassium chloride concentrate, and the amount of detergent is 65%-100% of the mass of the potassium chloride concentrate.

[0016] The above-mentioned method for comprehensive extraction of potassium boron bromine from chloride-type deep well brine is a preferred embodiment, and step S3 specifically comprises: introducing a strong oxidant into the old brine for oxidation, so that the bromide ions are oxidized into bromine elemental substance, introducing air to blow out the bromine elemental substance and carry it into the absorbent solution, reacting with it to form a bromine absorption liquid, and the liquid phase after blowing out is a bromine post-blowing liquid; introducing a strong oxidant into the bromine absorption liquid to oxidize the bromide ions into bromine elemental substance again, and then distilling-condensing to obtain crude bromine, and the crude bromine is subjected to distillation-condensation to obtain a liquid bromine product.

[0017] The above method for comprehensive extraction of potassium, boron and bromine from chloride-type deep well brine is, as a preferred embodiment, in step S3, the pH of the old brine is controlled at 2.5-3.5; the strong oxidant is chlorine or hydrogen peroxide, and the oxidation potential is controlled at 970mV-990mV;

[0018] Preferably, in step S3, the absorbent is at least one of sulfur dioxide, sodium sulfite and sodium hydroxide, and the amount of the absorbent is 5-8 times the theoretical amount.

[0019] The above-mentioned method for comprehensive extraction of potassium, boron and bromine from chloride-type deep well brine is, as a preferred embodiment, in step S3, the distillation temperature is controlled at 100-105°C, the rectification temperature is controlled at 60-65°C, and the condensed water temperature is controlled at 15-30°C.

[0020] The above-mentioned method for comprehensive extraction of potassium boron bromine from chloride-type deep well brine is a preferred embodiment, and step S4 specifically comprises: adjusting the acidity of the bromine-blown liquid, using an extraction system to perform countercurrent extraction, separating to obtain a raffinate and a boron-loaded organic phase, using a stripping agent to perform countercurrent stripping on the boron-loaded organic phase, and the obtained stripping liquid is a boron-containing solution; subjecting the boron-containing solution to high-temperature evaporation-low-temperature cooling and crystallization to obtain crude boric acid; re-dissolving and crystallizing the crude boric acid, separating, washing, and drying to obtain a boric acid product.

[0021] The above-mentioned method for comprehensive extraction of potassium boron bromine from chloride-type deep well brine is, as a preferred embodiment, in step S4, the acidity pH of the bromine blown liquid is controlled at 1.5-3.0; the extraction system is a mixed system of an extractant and sulfonated kerosene, the extractant is at least one of isooctyl alcohol, isopentanol, and isobutanol, and the volume dosage of the extractant is 35%-50% of the total volume of the extraction system; the volume ratio of the extraction system to the bromine blown liquid is 0.5-1:1; preferably, the countercurrent extraction adopts 3-5 stage countercurrent extraction.

[0022] The above-mentioned method for comprehensive extraction of potassium, boron and bromine from chloride-type deep well brine is, as a preferred embodiment, in step S4, the stripping agent is dilute hydrochloric acid, dilute sulfuric acid or distilled water; the volume ratio of the boron-loaded organic phase to the stripping agent is 2-3:1; preferably, the countercurrent stripping adopts 5-7 stage countercurrent stripping.

[0023] Compared with the prior art, the beneficial effects of the present invention include but are not limited to:

[0024] 1. The natural environmental conditions such as solar energy and wind energy in the plateau area were used for solar evaporation of salt fields. Based on the principles of phase equilibrium and phase separation, the main components of potassium and sodium were initially separated, and the trace components of boron and bromine were highly enriched by controlling the liquid phase density.

[0025] 2. The potassium chloride, liquid bromine, boric acid and sodium chloride products jointly produced by the separation and extraction technology provided by the present invention have certain market competitiveness, improve the comprehensive utilization value of deep well brine, reduce costs, and enable the valuable components contained therein to be efficiently utilized. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 This is a flow chart of the steps of a method for comprehensive extraction of potassium, boron and bromine from chloride-type deep well brine according to a preferred embodiment of the present application;

[0027] Figure 2 This is a process flow chart of a method for comprehensive extraction of potassium, boron and bromine from chloride-type deep well brine according to a preferred embodiment of the present application. DETAILED DESCRIPTION

[0028] A method for comprehensive extraction of potassium, boron and bromine from chloride-type deep well brine in the preferred embodiment of the present application, see Figure 1 and Figure 2 , including the following steps:

[0029] Step S1, injecting brine into the salt pan for solar evaporation, and obtaining rock salt, sylvite mixed salt, carnallitite mixed salt and liquid phase old brine in stages; specifically, since the sodium content in the brine just injected into the salt pan is high and close to saturation, as solar evaporation proceeds, rock salt is first precipitated, and during the rock salt precipitation process, potassium in the liquid phase is continuously enriched and saturated, first precipitated in the form of sylvite, and then precipitated in the form of carnallitite, and the liquid phase finally obtained is old brine; during the evaporation process, the density of the liquid phase is measured as a control indicator for the precipitation stages of different salts;

[0030] Step S2, using the carnallite mixed salt ore (containing rock salt mineral impurities) obtained by evaporation as a raw material, and adopting a cold decomposition-positive flotation-washing process to prepare a potassium chloride product;

[0031] Step S3, using old brine as raw material, adopting oxidation-air blowing-absorbent absorption-oxidation-distillation-rectification process to prepare liquid bromine product, and the liquid phase obtained after air blowing is bromine post-blowing liquid;

[0032] Step S4, using the bromine blown liquid as raw material, adopting extraction-strip extraction-high temperature evaporation-low temperature cooling crystallization-redissolution crystallization-washing process to prepare the boric acid product.

[0033] The method adopts a simple and mature process, and realizes the comprehensive extraction of sodium chloride, potassium chloride, liquid bromine and boric acid products in a step-by-step and orderly manner, efficiently utilizes the valuable components in deep well brine, and realizes the comprehensive utilization of brine resources.

[0034] In the above-mentioned method for comprehensive extraction of potassium, boron and bromine from chloride-type deep well brine, in step S1, the brine is injected into the salt pan for solar evaporation. Since the sodium content in the brine is high and close to saturation, rock salt is first precipitated (called the rock salt precipitation section). During the rock salt precipitation process, potassium in the liquid phase is continuously enriched and saturated, first precipitated in the form of sylvite (called the sylvite precipitation section), and then precipitated in the form of carnallite (called the carnallite precipitation section), and the final liquid phase is old brine; the density of the liquid phase is measured during the evaporation process as a control indicator for the precipitation stages of different salts. In the salt pan evaporation process, different types of brine have different mineral types for the solid phase precipitated by evaporation, and the density control range will also be different.

[0035] Preferably, in step S1, the “measurement of the density of the liquid phase during the evaporation process as a control index for different salt precipitation stages” means that in the halite precipitation stage, the density of the liquid phase is controlled to be less than 1.275 g / cm 3 ; Precipitate potassium salt section, liquid phase density is controlled at 1.275-1.285g / cm 3 ; Carnallite segment is precipitated, and the liquid phase density is controlled at 1.285-1.370g / cm 3 The density of the liquid phase is measured regularly, and once the density requirement is reached, solid-liquid separation is performed.

[0036] In the above-mentioned method for comprehensive extraction of potassium, boron and bromine from chloride-type deep well brine, step S2 specifically includes: adding water to the carnallite mixed salt ore (containing rock salt mineral impurities) obtained by evaporation for decomposition, after decomposition, magnesium basically enters the liquid phase, and most of the potassium and sodium remain in the decomposed solid phase; using octadecylamine as a collector, floating the decomposed solid phase in a saturated potassium solution, and obtaining potassium chloride concentrate and sodium chloride tailings after separation, and the saturated potassium solution can be recycled in the flotation process; adding water to the potassium chloride concentrate for washing, and obtaining a potassium chloride product and a washing mother liquor after separation, and the washing mother liquor can be supplemented with fresh fresh water and recycled in the washing process.

[0037] Preferably, in step S2, the water temperature used in the decomposition process is 15-25°C (such as 18°C, 20°C, 22°C, 24°C, etc.), and the water dosage is 40%-50% (such as 42%, 45%, 48%, etc.) of the mass of the carnallite mixed salt ore; in the flotation process, the dosage of octadecylamine in the roughing selection is 40-50g / t (such as 42g / t, 45g / t, 48g / t, etc.), and the dosage of octadecylamine in the scavenging selection is 10-15g / t (such as 12g / t, 14g / t, etc.).

[0038] Preferably, in step S2, the detergent in the washing process is a mixed solution of washing mother liquor and fresh fresh water, the amount of fresh fresh water is 20%-30% (such as 22%, 25%, 28%, etc.) of the mass of the potassium chloride concentrate, and the amount of detergent is 65%-100% (such as 68%, 70%, 75%, 80%, 85%, 90%, 95%, etc.) of the mass of the potassium chloride concentrate.

[0039] In the above-mentioned method for comprehensive extraction of potassium boron bromine from chloride-type deep well brine, step S3 specifically includes: introducing a strong oxidant into the old brine for oxidation, so that the bromide ions are oxidized into bromine elemental substance, introducing air to blow out the bromine elemental substance and take it away, and entering the absorbent solution to react with it to form a bromine absorption liquid, and the liquid phase after blowing out is the bromine post-blowing liquid; introducing a strong oxidant into the bromine absorption liquid (if necessary, the bromine absorption liquid can be appropriately concentrated first) to oxidize the bromide ions into bromine elemental substance again, and then distilling-condensing to obtain crude bromine, and the crude bromine is distilled-condensed to obtain a liquid bromine product.

[0040] Preferably, in step S3, the pH of the old brine is 2.5-3.5 (such as 2.8, 3.0, 3.2, etc.), which can inhibit the hydrolysis reaction of elemental bromine; the strong oxidant is chlorine or hydrogen peroxide, and the oxidation potential is controlled at 970mV-990mV (such as 975mV, 980mV, 985mV, etc.) to avoid excessive strong oxidant, which causes excessive chlorine to react with elemental bromine to generate bromine chloride, thereby causing bromine loss.

[0041] Preferably, in step S3, the absorbent is at least one of sulfur dioxide, sodium sulfite and sodium hydroxide, and the amount of the absorbent is 5-8 times (such as 5.5 times, 6 times, 7 times, 7.5 times, etc.) the theoretical amount.

[0042] Preferably, in step S3, the distillation temperature is controlled at 100-105°C (such as 102°C, 104°C, etc.), the distillation temperature is controlled at 60-65°C (such as 62°C, 64°C, etc.), and the condensed water temperature is controlled at 15-30°C (such as 18°C, 20°C, 22°C, 25°C, 28°C, etc.).

[0043] In the above-mentioned method for comprehensive extraction of potassium boron bromine from chloride-type deep well brine, step S4 specifically includes: adjusting the acidity of the bromine-blown liquid, using an extraction system to perform countercurrent extraction, separating to obtain a raffinate and a boron-loaded organic phase, using a stripping agent to perform countercurrent stripping on the boron-loaded organic phase, and the obtained stripping liquid is a boron-containing solution; subjecting the boron-containing solution to high-temperature evaporation-low-temperature cooling and crystallization to obtain crude boric acid; re-dissolving and crystallizing the crude boric acid, separating, washing, and drying to obtain a boric acid product.

[0044] Preferably, in step S4, the pH value of the bromine-blown liquid is 1.5-3.0 (such as 1.8, 2.0, 2.5, etc.); the extraction system is a mixed system of an extractant and sulfonated kerosene, the extractant is at least one of isooctyl alcohol, isoamyl alcohol, and isobutanol, and the volume amount of the extractant is 35%-50% (such as 38%, 40%, 42%, 45%, 48%, etc.) of the total volume of the extraction system; the volume ratio of the extraction system to the bromine-blown liquid is 0.5-1:1 (such as 0.6:1, 0.8:1, etc.); more preferably, the countercurrent extraction adopts 3-5 level countercurrent extraction.

[0045] Preferably, in step S4, the stripping agent is dilute hydrochloric acid, dilute sulfuric acid or distilled water; the volume ratio of the boron-loaded organic phase to the stripping agent is 2-3:1 (such as 2.2:1, 2.5:1, 2.8:1, etc.); more preferably, the countercurrent stripping adopts 5-7 stage countercurrent stripping.

[0046] The following examples further illustrate the content of the present invention, but should not be construed as limiting the present invention. Without violating the spirit and essence of the present invention, the modification or replacement of the method, steps or conditions of the present invention belongs to the scope of the present invention.

[0047] The technical solution of the present disclosure will be described below in conjunction with exemplary embodiments.

[0048] Unless otherwise specified, the experimental methods used in the following examples are conventional methods.

[0049] Unless otherwise specified, the materials and reagents used in the following examples can be obtained from commercial sources.

[0050] The brine used in the following examples is a deep well brine from Qinghai, and its chemical composition is as follows:

[0051]

[0052] Example 1

[0053] In this embodiment, potassium, boron and bromine are comprehensively extracted from chloride-type deep well brine by the following method:

[0054] Step S1: inject brine into the salt pan for solar evaporation, and the initial density of the brine is 1.19 g / cm 3 The sodium content in the brine is high and close to saturation, and the density of the concentrate is less than 1.275g / cm 3 The main precipitated substance is rock salt, with a purity of 95.06%, which meets the index requirements of solar industrial salt in the industrial salt quality standard GB / T 5462-2015. The sodium recovery rate is about 97.0%. During this process, potassium in the liquid phase is continuously enriched and saturated. When the density of the concentrated liquid is greater than 1.275g / cm 3When the concentration reached 1.285 g / cm 3 , the potassium salt section ends, the potassium and sodium contents in the solid phase are 16.06% and 23.91% respectively, and the potassium recovery rate is 10.6%; when the density of the concentrated liquid is greater than 1.285g / cm 3 When the density is 1.370 g / cm 3 , the carnallite section ends, the contents of potassium, magnesium and sodium in the solid phase are 10.13%, 7.42% and 6.04% respectively, the potassium recovery rate is 75.7%, and the final liquid phase is old brine. During the entire evaporation process, lithium, boron and bromine are always in an enriched state, and the contents in the final old brine are 0.068g / L, 1.58g / L and 0.78g / L respectively.

[0055] Step S2: adding water (water dosage is 40% of the mass of the mixed salt ore, and the water temperature is maintained at 15° C.) to the carnallite mixed salt ore obtained by evaporation for decomposition, wherein after decomposition, 91.7% of magnesium enters the liquid phase, and 74.1%, 83.0% and 8.3% of potassium, sodium and magnesium remain in the decomposed solid phase, respectively, and the contents of the three are 26.43%, 17.65% and 2.17% respectively; taking octadecylamine as a collector, the decomposed solid phase is subjected to positive flotation in a potassium saturated solution, wherein the dosage of octadecylamine during roughing and scavenging is 40 g / t and 15 g / t respectively, and a potassium chloride concentrate with a potassium content of 46.4% is obtained after separation, and the potassium recovery rate of the decomposition-positive flotation process is 65.0%. The potassium chloride concentrate is washed with detergent, which consists of washing mother liquor and fresh fresh water, with fresh fresh water accounting for 20% of the mass of the potassium chloride concentrate and the amount of detergent accounting for 100% of the mass of the potassium chloride concentrate. After washing, solid-liquid separation is performed to obtain a potassium chloride product with a potassium oxide content of 58.45% and an impurity sodium chloride content of 1.53%, meeting the powder crystal type III index in the fertilizer-grade potassium chloride quality standard GB / T37918-2019, and the potassium yield of the washing process is 92.7%.

[0056] Step S3: The pH value of the old brine obtained by solar evaporation is 2.8, which can inhibit the hydrolysis reaction of the oxidized bromine element. Chlorine gas is introduced into the old brine for oxidation, so that the bromide ions are oxidized into bromine element. The oxidation potential is tested to reach 970mV, and the oxidation is terminated; air is introduced into the oxidized old brine (the air flow rate is about 5L / min) to blow out the bromine element and take it away, and it enters into a sodium sulfite solution with a mass concentration of 5.0% (the amount of sodium sulfite is 5 times the theoretical amount), and reacts with it to obtain a bromine absorption liquid with a bromine concentration of 14.0g / L. The bromine recovery rate of the oxidation-air blowing-absorption process is 95.3%. The bromine absorption liquid was concentrated 9 times, chlorine gas was introduced to oxidize the bromide ions into bromine element again (the oxidation potential was controlled to reach 970mV), and the oxidized bromine absorption liquid was placed in a round-bottom flask for distillation-condensation. The distillation temperature was controlled at 105°C and the condensed water temperature was controlled at 15°C. Crude bromine with a bromine purity of 95.0% and a chlorine content of 4.1% was obtained, and the bromine operation recovery rate was 99.0%. The crude bromine was placed in a round-bottom flask for rectification-condensation. The rectification temperature was controlled at 60°C and the condensed water temperature was controlled at 30°C. A liquid bromine product with a purity of 98.6% and an impurity chlorine content of 0.10% was obtained, which met the secondary product index requirements in the industrial bromine quality standard QB / T 2021-2022.

[0057] Step S4: The pH value of the bromine-blown liquid is 1.80, and three-stage countercurrent extraction is carried out under the condition that isooctyl alcohol and sulfonated kerosene are used as the extraction system (wherein the isooctyl alcohol volume concentration is 50%) and the volume ratio of the extraction system to the bromine-blown liquid is 1:1, to obtain a boron-loaded organic phase with a boron content of 1.56 g / L, and a boron extraction rate of 98.80%, and boron is successfully separated from calcium, magnesium, potassium and sodium; under the condition that the stripping agent is 0.01 mol / L dilute hydrochloric acid and the volume ratio of the boron-loaded organic phase to the dilute hydrochloric acid is 2:1, five-stage countercurrent stripping is carried out, to obtain a stripping solution with a boron content of 3.15 g / L, and a boron stripping rate of 100%. The stripping liquid is evaporated at high temperature and cooled and crystallized at low temperature to obtain crude boric acid with a purity of 98.0%. The crude boric acid is added with hot water for redissolution and crystallization. After separation, it is filtered, washed and dried to obtain a boric acid product with a purity of 99.18%, which meets the qualified product index requirements of the industrial boric acid quality standard GB / T 538-2018. The boron recovery rate of the boric acid preparation process is 84.5%.

[0058] Example 2

[0059] In this embodiment, potassium, boron and bromine are comprehensively extracted from chloride-type deep well brine by the following method:

[0060] Step S1: inject brine into the salt pan for solar evaporation, and the initial density of the brine is 1.19 g / cm 3 The sodium content in the brine is high and close to saturation, and the density of the concentrate is less than 1.275g / cm 3The main precipitated substance is rock salt, with a purity of 93.62%, which meets the index requirements of solar industrial salt in the industrial salt quality standard GB / T 5462-2015. The sodium recovery rate is about 95.5%. During this process, potassium in the liquid phase is continuously enriched and saturated. When the density of the concentrated liquid is greater than 1.275g / cm 3 When the concentration reached 1.285 g / cm 3 , the potassium salt section ends, the potassium and sodium contents in the solid phase are 16.20% and 24.50% respectively, and the potassium recovery rate is 11.2%; when the density of the concentrated liquid is greater than 1.285g / cm 3 When the density is 1.375 g / cm 3 , the carnallite section ends, the contents of potassium, magnesium and sodium in the solid phase are 9.91%, 7.90% and 5.01% respectively, the potassium recovery rate is 77.6%, and the final liquid phase is old brine. During the entire evaporation process, lithium, boron and bromine are always in an enriched state, and the contents in the final old brine are 0.057g / L, 1.53g / L and 0.79g / L respectively.

[0061] Step S2: adding water (water dosage is 50% of the mass of the mixed salt ore, and the water temperature is maintained at 25° C.) to the carnallite mixed salt ore obtained by evaporation to decompose it, wherein after decomposition, 96.1% of magnesium enters the liquid phase, and 71.2%, 74.7% and 3.9% of potassium, sodium and magnesium remain in the decomposed solid phase, respectively, and the contents of the three are 27.24%, 14.56% and 1.20% respectively; using octadecylamine as a collector, the decomposed solid phase is subjected to positive flotation in a potassium saturated solution, wherein the dosage of octadecylamine during roughing and scavenging is 50 g / t and 10 g / t respectively, and a potassium chloride concentrate with a potassium content of 46.9% is obtained after separation, and the potassium recovery rate of the decomposition-positive flotation process is 66.3%. The potassium chloride concentrate is washed with detergent, which consists of washing mother liquor and fresh fresh water, with fresh fresh water accounting for 30% of the mass of the potassium chloride concentrate and detergent accounting for 65% of the mass of the potassium chloride concentrate. After washing, solid-liquid separation is performed to obtain a potassium chloride product with a potassium oxide content of 59.17% and an impurity sodium chloride content of 1.01%, meeting the powder crystal type III index in the fertilizer-grade potassium chloride quality standard GB / T37918-2019, and the potassium yield of the washing process is 91.9%.

[0062] Step S3: The pH value of the old brine obtained by solar evaporation is 2.5, which can inhibit the hydrolysis reaction of the oxidized bromine element. Chlorine gas is introduced into the old brine for oxidation, so that the bromide ions are oxidized into bromine element. The oxidation potential is tested to reach 990mV, and the oxidation is terminated; air is introduced into the oxidized old brine (the air flow rate is about 10L / min) to blow out the bromine element and take it away, and it enters into a sodium sulfite solution with a mass concentration of 5.0% (the amount of sodium sulfite is 7 times the theoretical amount), and reacts with it to obtain a bromine absorption liquid with a bromine concentration of 15.2g / L. The bromine recovery rate of the oxidation-air blowing-absorption process is 96.2%. The bromine absorption liquid was concentrated 7 times, chlorine gas was introduced to oxidize the bromide ions into bromine element again (the oxidation potential was controlled to reach 980mV), and the oxidized bromine absorption liquid was placed in a round-bottom flask for distillation-condensation. The distillation temperature was controlled at 100°C and the condensed water temperature was controlled at 30°C. Crude bromine with a bromine purity of 93.0% and a chlorine content of 5.1% was obtained, and the bromine operation recovery rate was 99.2%. The crude bromine was placed in a round-bottom flask for rectification-condensation. The rectification temperature was controlled at 65°C and the condensed water temperature was controlled at 25°C. A liquid bromine product with a purity of 99.0% and an impurity chlorine content of 0.08% was obtained, which met the secondary product index requirements in the industrial bromine quality standard QB / T 2021-2022.

[0063] Step S4: The pH value of the bromine-blown liquid is 1.50, and five-stage countercurrent extraction is carried out under the condition that isooctyl alcohol and sulfonated kerosene are used as the extraction system (isooctanol volume concentration is 50%) and the volume ratio of the extraction system to the bromine-blown liquid is 0.5:1, and a boron-loaded organic phase with a boron content of 3.01 g / L is obtained, and the boron extraction rate is 98.50%, and boron is successfully separated from calcium, magnesium, potassium and sodium; under the condition that the stripping agent is 0.01 mol / L dilute sulfuric acid and the volume ratio of the boron-loaded organic phase to the dilute sulfuric acid is 3:1, seven-stage countercurrent stripping is carried out, and a stripping solution with a boron content of 8.85 g / L is obtained, and the boron stripping rate is 98.0%. The stripping liquid is evaporated at high temperature and cooled and crystallized at low temperature to obtain crude boric acid with a purity of 97.83%. The crude boric acid is added with hot water for redissolution and crystallization. After separation, it is filtered, washed and dried to obtain a boric acid product with a purity of 99.06%, which meets the qualified product index requirements of the industrial boric acid quality standard GB / T 538-2018. The boron recovery rate of the boric acid preparation process is 82.3%.

[0064] Comparative Example 1

[0065] This comparative example comprehensively extracts potassium, boron and bromine from chloride-type deep well brine, and the method is as follows:

[0066] Step S1: inject brine into the salt pan for solar evaporation, and the initial density of the brine is 1.19 g / cm 3 The sodium content in the brine is high and close to saturation, and the density of the concentrate is less than 1.275g / cm 3The main precipitated substance is rock salt, with a purity of 94.32%, which meets the index requirements of solar industrial salt in the industrial salt quality standard GB / T 5462-2015. The sodium recovery rate is about 96.1%. In this process, potassium in the liquid phase is continuously enriched and saturated. When the density of the concentrated liquid is greater than 1.275g / cm 3 When the concentration reached 1.285 g / cm 3 , the potassium salt section ends, the potassium and sodium contents in the solid phase are 17.31% and 24.80% respectively, and the potassium recovery rate is 12.30%; when the density of the concentrated liquid is greater than 1.285g / cm 3 When the density is 1.375 g / cm 3 , the carnallite section ends, the contents of potassium, magnesium and sodium in the solid phase are 9.78%, 7.10% and 4.85% respectively, the potassium recovery rate is 78.9%, and the final liquid phase is old brine. During the entire evaporation process, lithium, boron and bromine are always in an enriched state, and the contents in the final old brine are 0.062g / L, 1.60g / L and 0.75g / L respectively.

[0067] Step S2: adding water (water dosage is 45% of the mass of the mixed salt ore, and the water temperature is maintained at 20° C.) to the carnallite mixed salt ore obtained by evaporation to decompose it, wherein after decomposition, 93.9% of magnesium enters the liquid phase, and 73.2%, 79.9% and 6.1% of potassium, sodium and magnesium remain in the decomposed solid phase, respectively, and the contents of the three are 27.24%, 14.56% and 1.20% respectively; taking octadecylamine as a collector, the decomposed solid phase is subjected to positive flotation in a potassium saturated solution, wherein the dosage of octadecylamine during roughing and scavenging is 45 g / t and 12 g / t respectively, and a potassium chloride concentrate with a potassium content of 46.1% is obtained after separation, and the potassium recovery rate of the decomposition-positive flotation process is 69.0%. The potassium chloride concentrate is washed with detergent, which consists of washing mother liquor and fresh fresh water, with fresh fresh water accounting for 25% of the mass of the potassium chloride concentrate and detergent accounting for 80% of the mass of the potassium chloride concentrate. After washing, solid-liquid separation is performed to obtain a potassium chloride product with a potassium oxide content of 58.93% and an impurity sodium chloride content of 1.27%, meeting the powder crystal type III index in the fertilizer-grade potassium chloride quality standard GB / T37918-2019, and the potassium yield of the washing process is 92.0%.

[0068] Step S3: The pH value of the old brine obtained by solar evaporation is 2.6. Five-stage countercurrent extraction is carried out under the conditions of isooctyl alcohol and sulfonated kerosene as the extraction system (the volume concentration of isooctyl alcohol is 35%) and the volume ratio of the extraction system to the old brine is 1:1, and a boron-loaded organic phase with a boron content of 1.59 g / L is obtained. The boron extraction rate is 99.28%, and boron is successfully separated from calcium, magnesium, potassium and sodium; five-stage countercurrent stripping is carried out under the conditions of 0.01 mol / L dilute hydrochloric acid as the stripping agent and a volume ratio of the boron-loaded organic phase to the dilute hydrochloric acid of 2:1, and a stripping solution with a boron content of 3.18 g / L is obtained, and the boron stripping rate is 100%. The stripping solution was evaporated at high temperature and cooled and crystallized at low temperature to obtain crude boric acid with a purity of 99.05% and an impurity chlorine content of 0.13%. The crude boric acid was added to hot water for redissolution and crystallization. After separation, it was filtered, washed and dried to obtain a boric acid product with a purity of 99.72%, which met the qualified product index requirements of the industrial boric acid quality standard GB / T 538-2018. The boron recovery rate of the boric acid preparation process was 80.6%. The aqueous phase obtained after boron extraction is the raffinate, and its pH is about 4.5.

[0069] Step S4: The pH value of the raffinate is about 4.5, and chlorine is introduced into the raffinate for oxidation, so that the bromide ions are oxidized into bromine elemental substance. The oxidation potential is tested to reach 970mV, and the oxidation is terminated. Since the pH value of the feed liquid is neutral, the ability to inhibit the hydrolysis of bromine elemental substance is reduced, the amount of chlorine introduced is increased, the cost is increased, and the purity of the liquid bromine product is affected; air is introduced into the oxidized raffinate (the air flow rate is about 10L / min) to blow out the bromine elemental substance and take it away, and enter into a sodium sulfite solution with a mass concentration of 5.0% (the amount of sodium sulfite is 7 times the theoretical amount), and react with it to obtain a bromine absorption liquid with a bromine concentration of 13.7g / L, and the bromine recovery rate of the oxidation-air blowing-absorption process is 90.5%. The bromine absorption liquid was concentrated 7 times, chlorine gas was introduced to oxidize the bromide ions into bromine element again (the oxidation potential was controlled to reach 975mV), and the oxidized bromine absorption liquid was placed in a round-bottom flask for distillation-condensation. The distillation temperature was controlled at 103°C, and the condensed water temperature was controlled at 25°C. Crude bromine with a bromine purity of 88.0% and a chlorine content of 9.2% was obtained, and the bromine operation recovery rate was 97.5%. The crude bromine was placed in a round-bottom flask for two distillation-condensation. The first distillation temperature was controlled at 65°C, the second distillation temperature was controlled at 50°C, and the condensed water temperature was 20°C. A liquid bromine product with a purity of 99.2% and an impurity chlorine content of 0.12% was obtained, which met the secondary product index requirements of the industrial bromine quality standard QB / T 2021-2022.

[0070] In this comparative example, although a qualified liquid bromine product can be obtained by first extracting boron and then extracting bromine, the bromine recovery rate is reduced, the bromine extraction efficiency is reduced, and the crude bromine purity is reduced during the bromine extraction process. Compared with the scheme of first extracting bromine and then extracting boron, the production cost of the entire process is increased. If acidification is performed before bromine extraction and then bromide ion oxidation is performed, the subsequent bromine extraction can ensure the bromine extraction efficiency and liquid bromine purity, but the acidification process is added, which still increases the production cost.

[0071] It can be seen from the above examples and comparative examples that it is more reasonable to adopt the scheme of blowing bromine first and then extracting boron. The pH of the old brine is 2.5-3.5 (for example, the pH in Example 1 is 2.8, and the pH in Example 2 is 2.5), in which boron exists in the form of boric acid, and the magnesium chloride concentration is in a saturated state (there is a salting-out effect on the extraction of boron. This old brine is suitable for bromide ion oxidation (under acidic conditions, it can inhibit the hydrolysis reaction of the generated bromine element to generate bromide ions and hypobromite ions, ensuring the extraction efficiency and purity of bromine) and is suitable for efficient extraction of boron from monohydric alcohol. If bromine is blown first, the pH of the bromine liquid after blowing is 1.5-3. 0 (for example, the pH in Example 1 is 1.1.8, and the pH in Example 2 is 1.5), the magnesium chloride concentration is still in a saturated state, and it is still suitable for extracting and separating boron with low-cost monohydric alcohol. If the scheme of extracting boron first and then blowing bromine is adopted, the pH of the raffinate after boron extraction is relatively high (for example, 4.5 in the comparative example), and the bromine blowing operation is performed under this condition, the ability to inhibit the hydrolysis reaction of the bromine element will be reduced due to the raffinate being closer to neutral, thereby affecting the extraction efficiency and purity of bromine and increasing the production cost.

[0072] Finally, it should be noted that, in the present disclosure, if any, relational terms such as first and second, etc., are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "comprises", "comprising" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device. In the absence of further restrictions, an element defined by the statement "comprising a ..." does not exclude the presence of other identical elements in the process, method, article or device including the element.

[0073] Although the present disclosure has been disclosed above through the description of the specific embodiments of the present disclosure, it should be understood that those skilled in the art can design various modifications, improvements or equivalents to the present disclosure within the spirit and scope of the attached scheme. These modifications, improvements or equivalents should also be considered to be included in the scope of protection claimed by the present disclosure.

Claims

1. A method for comprehensive extraction of potassium, boron and bromine from chloride-type deep well brine, characterized in that: The steps include: Step S1, injecting brine into the salt pan for solar evaporation, obtaining rock salt, sylvite mixed salt, carnallite mixed salt and liquid phase old brine in stages, and measuring the density of the liquid phase during the evaporation process as a control indicator for the precipitation stages of different salts; Step S2, using carnallite mixed salt as raw material, adopting cold decomposition-positive flotation-washing process to prepare potassium chloride product; Step S3, using old brine as raw material, adopting oxidation-air blowing-absorbent absorption-oxidation-distillation-rectification process to prepare liquid bromine product, and the liquid phase obtained after air blowing is bromine post-blowing liquid; Step S4, using the bromine-blown liquid as a raw material, adopting an extraction-strip extraction-high-temperature evaporation-low-temperature cooling crystallization-redissolution crystallization-washing process to obtain a boric acid product.

2. The method for comprehensive extraction of potassium, boron and bromine from chloride-type deep well brine according to claim 1, characterized in that: In step S1, the "measurement of the density of the liquid phase during the evaporation process as a control indicator for different salt precipitation stages" means that in the halite precipitation stage, the liquid phase density is controlled at <1.275 g / cm 3 ; Precipitate potassium salt section, liquid phase density is controlled at 1.275-1.285g / cm 3 ; Carnallite segment is precipitated, and the liquid phase density is controlled at 1.285-1.370g / cm 3 .

3. The method for comprehensive extraction of potassium, boron and bromine from chloride-type deep well brine according to claim 1 or 2, characterized in that: Step S2 specifically comprises: adding water to the carnallite mixed salt for decomposition to obtain a decomposed solid phase; using octadecylamine as a collector, floating the decomposed solid phase in a potassium saturated solution, and obtaining potassium chloride concentrate and sodium chloride tailings after separation; adding water to the potassium chloride concentrate for washing, and obtaining a potassium chloride product and a washing mother liquor after separation; preferably, the potassium saturated solution is recycled in the flotation process; preferably, the washing mother liquor is supplemented with fresh fresh water and recycled in the washing process.

4. The method for comprehensive extraction of potassium, boron and bromine from chloride-type deep well brine according to claim 3, characterized in that: In step S2, the water temperature used in the decomposition process is 15-25°C, and the amount of water used is 40%-50% of the mass of the carnallite mixed salt; in the flotation process, the amount of octadecylamine used in the roughing process is 40-50g / t, and the amount of octadecylamine used in the scavenging process is 10-15g / t; Preferably, in step S2, the detergent in the washing process is a mixed solution of washing mother liquor and fresh fresh water, the amount of fresh fresh water is 20%-30% of the mass of the potassium chloride concentrate, and the amount of detergent is 65%-100% of the mass of the potassium chloride concentrate.

5. The method for comprehensive extraction of potassium, boron and bromine from chloride-type deep well brine according to any one of claims 1 to 4, characterized in that: Step S3 specifically includes: introducing a strong oxidant into the old brine for oxidation, so that the bromide ions are oxidized into bromine elemental substance, introducing air to blow out the bromine elemental substance and take it away, and entering the absorbent solution to react with it to form a bromine absorption liquid, and the liquid phase after blowing out is the bromine post-blowing liquid; introducing a strong oxidant into the bromine absorption liquid to oxidize the bromide ions into bromine elemental substance again, and then distilling-condensing to obtain crude bromine, and the crude bromine is distilled-condensed to obtain a liquid bromine product.

6. The method for comprehensive extraction of potassium, boron and bromine from chloride-type deep well brine according to claim 5, characterized in that: In step S3, the pH of the old brine is controlled at 2.5-3.5; the strong oxidant is chlorine or hydrogen peroxide, and the oxidation potential is controlled at 970mV-990mV; Preferably, in step S3, the absorbent is at least one of sulfur dioxide, sodium sulfite and sodium hydroxide, and the amount of the absorbent is 5-8 times the theoretical amount.

7. The method for comprehensive extraction of potassium, boron and bromine from chloride-type deep well brine according to claim 6, characterized in that: In step S3, the distillation temperature is controlled at 100-105°C, the rectification temperature is controlled at 60-65°C, and the condensed water temperature is controlled at 15-30°C.

8. The method for comprehensive extraction of potassium, boron and bromine from chloride-type deep well brine according to any one of claims 1 to 7, characterized in that: Step S4 specifically comprises: adjusting the acidity of the bromine-blown liquid, performing countercurrent extraction using an extraction system, obtaining a raffinate and a boron-loaded organic phase after separation, performing countercurrent stripping on the boron-loaded organic phase using a stripping agent, and obtaining a stripping liquid, which is a boron-containing solution; performing high-temperature evaporation-low-temperature cooling crystallization on the boron-containing solution to obtain crude boric acid; re-dissolving and crystallizing the crude boric acid, and washing and drying after separation to obtain a boric acid product.

9. The method for comprehensive extraction of potassium, boron and bromine from chloride-type deep well brine according to claim 8, characterized in that: In step S4, the pH value of the bromine-blown liquid is controlled at 1.5-3.0; the extraction system is a mixed system of an extractant and sulfonated kerosene, the extractant is at least one of isooctyl alcohol, isoamyl alcohol and isobutyl alcohol, and the volume of the extractant is 35%-50% of the total volume of the extraction system; the volume ratio of the extraction system to the bromine-blown liquid is 0.5-1:1; preferably, the countercurrent extraction adopts 3-5 level countercurrent extraction.

10. The method for comprehensive extraction of potassium, boron and bromine from chloride-type deep well brine according to claim 9, characterized in that: In step S4, the stripping agent is dilute hydrochloric acid, dilute sulfuric acid or distilled water; the volume ratio of the boron-loaded organic phase to the stripping agent is 2-3:1; preferably, the countercurrent stripping adopts 5-7 levels of countercurrent stripping.

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