Method for preparing borax pentahydrate by using boron concentrated solution

Abstract

The invention belongs to the technical field of inorganic salt chemical industry. The invention provides a method for preparing borax pentahydrate by using a boron concentrated solution, which comprises the following steps: adding an acid into the boron concentrated solution to adjust the pH value to 9-10, continuing to evaporate and concentrate, and then carrying out heat-preservation crystallization and heat-preservation separation to obtain crude borax pentahydrate and a crystallized filtrate; leaching the crude borax pentahydrate by adopting a borax solution to obtain borax pentahydrate and leacheate; drying the borax pentahydrate to obtain a finished product borax pentahydrate; mixing the crystallization filtrate with the leacheate, cooling and crystallizing the mixed solution, and separating at normal temperature to obtain crude borax decahydrate and filtrate 1; evaporating and concentrating the filtrate 1, and separating at high temperature to obtain crude sodium chloride and filtrate 2; according to the method, the borax pentahydrate is prepared from the boron concentrated solution through high-temperature crystallization and high-temperature washing, meanwhile, sodium chloride is only discharged at the tail end in the whole process, and the overall yield of boron reaches 95% or above. In addition, the purity of the borax pentahydrate product is high, and industrial production is easy to realize.

Description

Technical Field

[0001] This invention relates to the field of inorganic salt chemical technology, and in particular to a method for preparing pentahydrate borax using boron concentrate. Background Technology

[0002] Borax pentahydrate (Na₂B₄O₇·5H₂O), as an important basic boron chemical product, holds an irreplaceable position in the national economy and modern industrial system. It is widely used in glass manufacturing (especially high borosilicate specialty glass), enamel glazes, metal smelting, new boron fertilizers, and nuclear industry shielding materials, serving as a fundamental chemical raw material supporting several key industries. my country's boron resource supply has long faced severe challenges. Traditional solid boron ore production bases, mainly in Liaoning and Jilin provinces, are unable to meet domestic demand due to resource depletion, resulting in the current import of over 70% of borax.

[0003] It is noteworthy that against the backdrop of the rapid development of the new energy industry, the lithium extraction industry from salt lakes has expanded rapidly, creating new opportunities for the synergistic extraction of boron resources. The boron-containing wastewater (containing 1.0–2.5 g / L of boron) and boron elements (B2O3 between 3 and 35 g / L) generated during the lithium extraction process from salt lakes, if not effectively utilized, will not only lead to resource waste but also cause environmental problems. Therefore, developing efficient and environmentally friendly pentahydrate borax extraction technology from salt lakes has become a strategic task urgently needing breakthroughs in my country's salt lake chemical industry. Summary of the Invention

[0004] The purpose of this invention is to address the shortcomings of existing technologies and fill the gap in pentahydrate borax production technology in the field of efficient and comprehensive utilization of salt lake resources, by providing a method for preparing pentahydrate borax using boron concentrate.

[0005] To achieve the above-mentioned objectives, the present invention provides the following technical solution:

[0006] This invention provides a method for preparing pentahydrate borax using boron concentrate, comprising the following steps:

[0007] 1) Add acid to boron concentrate 1 to adjust the pH to 9-10 to obtain the adjusted boron concentrate;

[0008] The mass concentration of B2O3 in the boron concentrate 1 is 90-120 g / L;

[0009] 2) Continue to evaporate and concentrate the adjusted boron concentrate to obtain boron concentrate 2;

[0010] The mass concentration of B2O3 in the boron concentrate 2 is ≥200g / L;

[0011] 3) The boron concentrate 2 was subjected to heat preservation and crystallization, and then separated to obtain crude pentahydrate borax and crystallization filtrate;

[0012] 4) The crude pentahydrate borax was leached with borax solution to obtain pentahydrate borax and leaching solution;

[0013] 5) Dry the pentahydrate borax to obtain the finished pentahydrate borax;

[0014] 6) Mix the crystallization filtrate with the eluent, and then cool the resulting mixed solution to crystallize it. Separate it at room temperature to obtain crude borax decahydrate and filtrate 1. Return the crude borax decahydrate to the boron concentrate 2 obtained in step 2).

[0015] 7) Evaporate and concentrate filtrate 1 to a B2O3 mass concentration of 90-120 g / L, and separate it at high temperature to obtain crude sodium chloride and filtrate 2. Filtrate 2 is returned to the mixed solution in step 6), and crude sodium chloride is used as a raw material for the preparation of refined salt.

[0016] Preferably, the acid in step 1) is hydrochloric acid, and the mass fraction of hydrochloric acid is 28-32%.

[0017] Preferably, the evaporation and concentration temperature in step 2) is 90–100°C.

[0018] Preferably, the temperature for heat preservation and crystallization in step 3) is 60-90°C, and the time for heat preservation and crystallization is 60-120 min.

[0019] Preferably, the temperature for heat preservation and separation in step 3) is 60–90°C.

[0020] Preferably, the borax solution in step 4) is a borax decahydrate solution with a mass fraction of 20-30% and a temperature of 50-70°C.

[0021] Preferably, the drying temperature in step 5) is 60–100°C and the drying time is 30–120 min.

[0022] Preferably, the cooling rate of the cooling crystallization in step 6) is 0.5 to 1.0 °C / min, and the final temperature is ≤30 °C.

[0023] Preferably, the evaporation and concentration temperature in step 7) is 100–110°C.

[0024] Preferably, the temperature of the high-temperature separation in step 7) is ≥60℃.

[0025] The beneficial effects of this invention include the following:

[0026] 1) This invention provides a method for preparing pentahydrate borax using boron concentrate. This method directly produces pentahydrate borax by re-concentrating and high-temperature crystallizing the MVR boron concentrate. This fills the gap in the current process where boron concentrate can only be used to prepare decahydrate borax and boric acid. It effectively utilizes salt lake resources and has broad market prospects.

[0027] 2) This invention uses a 25% decahydrate borax solution at 65°C to rinse the coarse pentahydrate borax, thereby displacing the sodium chloride entrained in the coarse pentahydrate borax. This significantly removes chlorate from the coarse pentahydrate borax, while ensuring that the resulting pentahydrate borax does not absorb water and turn into decahydrate borax, thus improving the purity of the finished pentahydrate borax.

[0028] 3) This invention recovers boron from filtrate 1, filtrate 2 and washing liquid. The entire process only removes <5% of boron by discharging sodium chloride at the tail end, achieving a boron recovery rate of over 95% in the MVR boron concentrate, which greatly improves the utilization rate of boron in salt lake brine. Attached Figure Description

[0029] Figure 1 This is a process flow diagram of preparing pentahydrate borax using boron concentrate as described in this invention;

[0030] Figure 2 The phase analysis results for Example 1 are shown in the image.

[0031] Figure 3 The phase analysis results for Comparative Example 1 are shown in the image.

[0032] Figure 4 The phase analysis results for Example 2 are shown in the image.

[0033] Figure 5 For the phase analysis of Comparative Example 2;

[0034] Figure 6 The phase analysis results are for Example 3. Detailed Implementation

[0035] This invention provides a method for preparing pentahydrate borax using boron concentrate, comprising the following steps:

[0036] 1) Add acid to boron concentrate 1 to adjust the pH to 9-10 to obtain the adjusted boron concentrate;

[0037] The mass concentration of B2O3 in the boron concentrate 1 is 90-120 g / L;

[0038] 2) Continue to evaporate and concentrate the adjusted boron concentrate to obtain boron concentrate 2;

[0039] The mass concentration of B2O3 in the boron concentrate 2 is ≥200g / L;

[0040] 3) The boron concentrate 2 was subjected to heat preservation and crystallization, and then separated to obtain crude pentahydrate borax and crystallization filtrate;

[0041] 4) The crude pentahydrate borax was leached with borax solution to obtain pentahydrate borax and leaching solution;

[0042] 5) Dry the pentahydrate borax to obtain the finished pentahydrate borax;

[0043] 6) Mix the crystallization filtrate with the eluent, and then cool the resulting mixed solution to crystallize it. Separate it at room temperature to obtain crude borax decahydrate and filtrate 1. Return the crude borax decahydrate to the boron concentrate 2 obtained in step 2).

[0044] 7) Evaporate and concentrate filtrate 1 to a B2O3 mass concentration of 90-120 g / L, and separate it at high temperature to obtain crude sodium chloride and filtrate 2. Filtrate 2 is returned to the mixed solution in step 6), and crude sodium chloride is used as a raw material for the preparation of refined salt.

[0045] In this invention, the acid in step 1) is preferably hydrochloric acid, and the mass fraction of hydrochloric acid is preferably 28-32%, more preferably 31%.

[0046] In this invention, the preparation method of boron concentrate 1 in step 1) is as follows: The pH of old brine from a salt lake is adjusted to 7.0–7.5, and the solution is passed into a membrane separation device at room temperature (20–30°C) under an operating pressure of 0.5–1.0 MPa to obtain a boron-rich solution after removing lithium and magnesium. The boron-rich solution is diluted to a borate ion concentration of 3–5 g / L, and then fed into a reverse osmosis membrane separation device under an operating pressure of 1.5–2.5 MPa to remove some impurities and achieve preliminary separation of boron, obtaining a boron-containing permeate. A 1 mol / L sodium hydroxide solution is slowly added to the boron-containing permeate to adjust the pH of the solution to 10.0–11.0, thereby changing the form of boron (from neutral H3BO3 to charged B(OH)4). - The solution, after being adjusted with alkali, is then fed into a reverse osmosis membrane unit for secondary concentration. The operating pressure is controlled at 2.0–3.0 MPa and the temperature at 25–35 °C, until the mass concentration of B2O3 in the solution reaches 15–20 g / L, yielding a boron concentrate. Finally, the boron concentrate is fed into an MVR evaporator and subjected to forced evaporation at 70–90 °C and -0.05–0.08 MPa, with the evaporation ratio controlled at 2–4 times, to further concentrate the solution and obtain the boron concentrate 1.

[0047] In this invention, the evaporation and concentration temperature in step 2) is preferably 90-100°C, and more preferably 95°C.

[0048] In this invention, the temperature for heat preservation and crystallization in step 3) is preferably 60-90°C, more preferably 70-80°C, and even more preferably 75°C; the time for heat preservation and crystallization is preferably 60-120 min, more preferably 70-100 min, and even more preferably 80 min.

[0049] In this invention, the temperature for heat preservation and separation in step 3) is preferably 60-90°C, more preferably 70-80°C, and even more preferably 75°C.

[0050] In this invention, the borax solution in step 4) is preferably a borax decahydrate solution, the mass fraction of the borax decahydrate solution is preferably 20-30%, more preferably 25%, and the temperature of the borax decahydrate solution is preferably 50-70°C, more preferably 60°C.

[0051] In this invention, the drying temperature in step 5) is preferably 60-100°C, more preferably 70-90°C, and even more preferably 80°C, and the drying time is preferably 30-120 min, more preferably 60-90 min, and even more preferably 70-80 min.

[0052] In this invention, the cooling rate of the cooling crystallization in step 6) is preferably 0.5-1.0℃ / min, more preferably 0.6-0.8℃ / min, and even more preferably 0.7℃ / min, and the endpoint temperature is preferably ≤30℃, and even more preferably ≤25℃.

[0053] In this invention, the evaporation and concentration temperature in step 7) is preferably 100-110°C, more preferably 104-106°C, and even more preferably 105°C.

[0054] In this invention, the temperature for high-temperature separation in step 7) is preferably ≥60℃, and more preferably ≥70℃.

[0055] The technical solutions provided by the present invention will be described in detail below with reference to the embodiments, but they should not be construed as limiting the scope of protection of the present invention.

[0056] Example 1

[0057] 1) Take 3LB2O3 with a mass concentration of 105.3 g / L boron concentrate 1, and adjust the pH to 9.5 with 31% hydrochloric acid to obtain the adjusted boron concentrate;

[0058] 2) The adjusted boron concentrate was further evaporated and concentrated at 90°C until crystals appeared in the solution, to obtain boron concentrate 2, in which the mass concentration of B2O3 was 205.5 g / L;

[0059] 3) The boron concentrate 2 was kept at 80℃ for 120 min to crystallize, and then the solid and liquid were separated at 80℃ to obtain 211.2 g of crude pentahydrate borax and crystallization filtrate;

[0060] 4) The crude pentahydrate borax was rinsed with a borax decahydrate solution at 65℃ and a mass fraction of 25% to obtain pentahydrate borax and rinsing solution.

[0061] 5) Dry the pentahydrate borax at 80℃ for 30 minutes to obtain the finished pentahydrate borax;

[0062] 6) Mix the crystallization filtrate with the eluent, and then perform cooling crystallization on the resulting mixed solution. The cooling rate of the cooling crystallization is 0.5℃ / min, and the final temperature is 30℃. Then separate at room temperature to obtain crude borax decahydrate and filtrate 1. The crude borax decahydrate is returned to the boron concentrate 2 in step 2).

[0063] 7) Evaporate and concentrate filtrate 1 at 100℃ to a B2O3 mass concentration of 100g / L, and separate it at high temperature (60℃) to obtain crude sodium chloride and filtrate 2. Filtrate 2 is returned to the mixed solution in step 6), and crude sodium chloride is used as a raw material for the preparation of refined salt.

[0064] The chemical composition data of some materials involved in this embodiment are shown in Table 1, and the phase analysis results are shown in... Figure 2 As shown.

[0065] Table 1. Chemical composition of some materials involved in Example 1

[0066]

[0067] Comparative Example 1

[0068] The process is basically the same as in Example 1, except that the mass concentration of B2O3 in the boron concentrate 2 obtained in step 2) is 199.03 g / L, the temperature of the crystallization in step 3) is changed to 55°C, and the temperature of the separation is changed to 55°C, resulting in 321.2 g of crude pentahydrate borax and crystallization filtrate.

[0069] The chemical composition data of some materials involved in this comparative example are shown in Table 2, and the phase analysis results are shown in the figure. Figure 3 As shown.

[0070] Table 2 shows the chemical composition of some of the materials involved in Comparative Example 1.

[0071]

[0072] By comparing the data in Tables 1 and 2 (B2O3 in coarse pentahydrate borax of Example 1 and Comparative Example 1), the B2O3 content in crude pentahydrate borax was determined. 2-According to the content, when the crystallization temperature is below 60℃, the crude pentahydrate borax contains decahydrate borax. Therefore, the crystallization temperature and separation temperature of pentahydrate borax should be kept above 60℃.

[0073] Example 2

[0074] 1) Take 3LB2O3 with a mass concentration of 104.9 g / L boron concentrate 1, and adjust the pH to 9.5 with 31% hydrochloric acid to obtain the adjusted boron concentrate;

[0075] 2) The adjusted boron concentrate was further evaporated and concentrated at 100℃ until crystals appeared in the solution, to obtain boron concentrate 2, in which the mass concentration of B2O3 was 198.15 g / L;

[0076] 3) The boron concentrate 2 was kept at 65℃ for 120 min to crystallize, and then the solid and liquid were separated at 65℃ to obtain crude pentahydrate borax and crystallization filtrate;

[0077] 4) The crude pentahydrate borax was rinsed twice with a borax decahydrate solution at 65℃ and a mass fraction of 25% to obtain 293.1g of pentahydrate borax and the rinsing solution.

[0078] 5) Dry the pentahydrate borax at 60℃ for 120 min to obtain the finished pentahydrate borax;

[0079] 6) Mix the crystallization filtrate with the eluent, and then perform cooling crystallization on the resulting mixed solution. The cooling rate of the cooling crystallization is 1.0℃ / min, and the final temperature is 30℃. Then separate at room temperature to obtain crude borax decahydrate and filtrate 1. The crude borax decahydrate is returned to the boron concentrate 2 in step 2).

[0080] 7) Evaporate and concentrate filtrate 1 at 110℃ to a B2O3 mass concentration of 100g / L, and separate it at high temperature (80℃) to obtain crude sodium chloride and filtrate 2. Filtrate 2 is returned to the mixed solution in step 6), and crude sodium chloride is used as raw material for the preparation of refined salt.

[0081] The chemical composition data of some materials involved in this embodiment are shown in Table 3, and the phase analysis results are shown in... Figure 4 As shown.

[0082] Table 3 Chemical composition of some materials involved in Example 2

[0083]

[0084] Comparative Example 2

[0085] The process is basically the same as in Example 2, except that in step 4), the coarse pentahydrate borax is rinsed twice with hot water at a temperature of 65°C to obtain 211.2g of pentahydrate borax and the rinsing solution.

[0086] The chemical composition data of some materials involved in this comparative example are shown in Table 4, and the phase analysis results are shown in the figure. Figure 5 As shown.

[0087] Table 4 shows the chemical composition of some materials involved in Comparative Example 2.

[0088]

[0089] By comparing the data in Tables 3 and 4 (B2O3 content in the rinsing solutions of Example 2 and Comparative Example 2), it can be seen that the B2O3 concentration in the rinsing solution of Comparative Example 2 is less than 90 g / L, and it cannot be directly used as a raw material for the preparation of decahydrate borax by cooling crystallization. The rinsing solution of this process should be a decahydrate borax solution with a mass fraction of 25%.

[0090] Example 3

[0091] 1) Take 2L of boron concentrate 1 with a mass concentration of 112.8g / L of B2O3, and adjust the pH to 9.5 with 31% hydrochloric acid to obtain the adjusted boron concentrate;

[0092] 2) The adjusted boron concentrate was further evaporated and concentrated at 90°C until crystals appeared in the solution, to obtain boron concentrate 2, in which the mass concentration of B2O3 was 246.5 g / L;

[0093] 3) The boron concentrate 2 was kept at 65℃ for 120 min to crystallize, and then the solid and liquid were separated at 65℃ to obtain crude pentahydrate borax and crystallization filtrate;

[0094] 4) The crude pentahydrate borax was rinsed twice with a borax decahydrate solution at 65℃ and a mass fraction of 25% to obtain 460.5g of pentahydrate borax and the rinsing solution.

[0095] 5) Dry the pentahydrate borax at 80℃ for 30 minutes to obtain the finished pentahydrate borax;

[0096] 6) Mix the crystallization filtrate with the eluent, and then perform cooling crystallization on the resulting mixed solution. The cooling rate of the cooling crystallization is 0.8℃ / min, and the final temperature is 25℃. Then separate at room temperature to obtain 297.3g of crude borax decahydrate and filtrate 1. The crude borax decahydrate is returned to the boron concentrate 2 in step 2).

[0097] 7) Evaporate and concentrate filtrate 1 at 100℃ to a B2O3 mass concentration of 100g / L, and separate it at high temperature (60℃) to obtain crude sodium chloride and filtrate 2. Filtrate 2 is returned to the mixed solution in step 6), and crude sodium chloride is used as a raw material for the preparation of refined salt.

[0098] The chemical composition data of some materials involved in this embodiment are shown in Table 5, and the phase analysis results are shown in... Figure 6 As shown.

[0099] Table 5 Chemical composition of some materials involved in Example 3

[0100]

[0101] As can be seen from Table 5, the B2O3 content in the pentahydrate borax of step 5) is 47.06%, which meets the requirement for B2O3 content in pentahydrate borax.

[0102] Example 4

[0103] 1) Take 10 L of boron concentrate 1 with a mass concentration of 104.9 g / L and adjust the pH to 9.5 with 31% hydrochloric acid to obtain the adjusted boron concentrate;

[0104] 2) Continue to evaporate and concentrate the adjusted boron concentrate at 90°C until crystals appear in the solution, to obtain 5L of boron concentrate 2;

[0105] 3) The boron concentrate 2 was kept at 65℃ for 120 min to crystallize, and then the solid and liquid were separated at 65℃ to obtain crude pentahydrate borax and crystallization filtrate;

[0106] 4) The crude pentahydrate borax was rinsed twice with a borax decahydrate solution at 65℃ and a mass fraction of 25% to obtain 1529.6g of pentahydrate borax and the rinsing solution.

[0107] 5) Dry the pentahydrate borax at 80℃ for 30 minutes to obtain the finished pentahydrate borax;

[0108] 6) Mix the crystallization filtrate with the eluent, and then perform cooling crystallization on the resulting mixed solution. The cooling rate of the cooling crystallization is 0.8℃ / min, and the final temperature is 25℃. Then separate at room temperature to obtain 1280.3g of crude borax decahydrate and 3270mL of filtrate 1. Return the crude borax decahydrate to the boron concentrate 2 in step 2).

[0109] 7) Evaporate and concentrate filtrate 1 to 500 mL at 100 °C, and separate it at high temperature (60 °C) to obtain 230 g of crude sodium chloride and 390 mL of filtrate 2. Filtrate 2 is returned to the mixed solution in step 6), and crude sodium chloride is used as raw material for the preparation of refined salt.

[0110] The chemical composition data of some of the materials involved in this embodiment are shown in Table 6.

[0111] Table 6 Chemical composition of some materials involved in Example 4

[0112]

[0113]

[0114] As shown in Table 6, the boron yield in the pentahydrate borax crystallization section was 63.3%, the boron yield in the cooling crystallization section was 32.18%, and the boron yield in the concentration and impurity removal section was 1.86%, with the overall boron yield reaching over 95%.

[0115] The method for preparing pentahydrate borax using boron concentrate described in this invention involves first forcibly evaporating boron concentrate in an MVR evaporator, adjusting the pH with acid, then further concentrating, followed by high-temperature crystallization, washing, separation, and drying to obtain the finished pentahydrate borax. Its quality meets the national standards and can fill the gap in pentahydrate borax production technology in the field of efficient and comprehensive utilization of salt lake resources.

[0116] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for preparing pentahydrate borax using boron concentrate, characterized in that, It includes the following steps: 1) Add acid to boron concentrate 1 to adjust the pH to 9-10 to obtain the adjusted boron concentrate; The mass concentration of B2O3 in the boron concentrate 1 is 90-120 g / L; 2) Continue to evaporate and concentrate the adjusted boron concentrate to obtain boron concentrate 2; The mass concentration of B2O3 in the boron concentrate 2 is ≥200g / L; 3) The boron concentrate 2 was subjected to heat preservation and crystallization, and then separated to obtain crude pentahydrate borax and crystallization filtrate; 4) The crude pentahydrate borax was leached with borax solution to obtain pentahydrate borax and leaching solution; 5) Dry the pentahydrate borax to obtain the finished pentahydrate borax; 6) Mix the crystallization filtrate with the eluent, and then cool the resulting mixed solution to crystallize it. Separate it at room temperature to obtain crude borax decahydrate and filtrate 1. Return the crude borax decahydrate to the boron concentrate 2 obtained in step 2). 7) Evaporate and concentrate filtrate 1 to a B2O3 mass concentration of 90-120 g / L, and separate it at high temperature to obtain crude sodium chloride and filtrate 2. Filtrate 2 is returned to the mixed solution in step 6), and crude sodium chloride is used as a raw material for the preparation of refined salt.

2. The method for preparing pentahydrate borax using boron concentrate according to claim 1, characterized in that, The acid mentioned in step 1) is hydrochloric acid, with a mass fraction of 28-32%.

3. The method for preparing pentahydrate borax using boron concentrate according to claim 1 or 2, characterized in that, The evaporation and concentration temperature in step 2) is 90–100°C.

4. The method for preparing pentahydrate borax using boron concentrate according to claim 3, characterized in that, Step 3) The temperature for heat preservation and crystallization is 60-90℃, and the time for heat preservation and crystallization is 60-120 min.

5. The method for preparing pentahydrate borax using boron concentrate according to claim 4, characterized in that, Step 3) The temperature for heat preservation and separation is 60-90℃.

6. The method for preparing pentahydrate borax using boron concentrate according to claim 4 or 5, characterized in that, Step 4) The borax solution is a decahydrate borax solution with a mass fraction of 20-30% and a temperature of 50-70°C.

7. The method for preparing pentahydrate borax using boron concentrate according to claim 6, characterized in that, Step 5) The drying temperature is 60-100℃ and the drying time is 30-120 min.

8. The method for preparing pentahydrate borax using boron concentrate according to claim 7, characterized in that, The cooling rate of the cooling crystallization in step 6) is 0.5 to 1.0 °C / min, and the final temperature is ≤30 °C.

9. The method for preparing pentahydrate borax using boron concentrate according to claim 7 or 8, characterized in that, The evaporation and concentration temperature in step 7) is 100-110℃.

10. The method for preparing pentahydrate borax using boron concentrate according to claim 9, characterized in that, Step 7) The high-temperature separation temperature is ≥60℃.

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