Method for improving sodium bicarbonate purity and improving filtration efficiency during sodium chloride resource utilization

Abstract

The application discloses a method for improving the purity of sodium bicarbonate and the filtering efficiency during the resource utilization of sodium chloride, and comprises the following steps: (1) carbonization; (2) separation and washing of sodium bicarbonate solid, and obtaining carbonization mother liquor; (3) deacidification: adding ammonium bicarbonate into the carbonization mother liquor during the deacidification, and making the added ammonium bicarbonate all be converted into ammonium carbonate, obtaining deacidification mother liquor, and returning the gas generated during the deacidification to the carbonization reaction solution in the step (1); (4) crystallization; (5) separation of ammonium chloride, and returning the obtained crystallization mother liquor to the carbonization reaction solution in the step (1).

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of sodium chloride resource utilization. Specifically, it is a method for improving the purity of sodium bicarbonate and the filtration efficiency during sodium chloride resource utilization. BACKGROUND

[0002] Chemical processes produce a large amount of sodium chloride byproducts or waste salts containing sodium chloride as the main component every year. The resource recycling of sodium chloride is of great significance for reducing enterprise operating costs and environmental protection. Using sodium chloride as raw material to prepare sodium bicarbonate / sodium carbonate products and byproduct ammonium chloride fertilizer can better utilize Na and Cl components. The generated sodium bicarbonate / sodium carbonate products are relatively easy to recycle within the enterprise, and compared with landfilling, high-temperature treatment and other methods, it is environmentally friendly, has strong industrial operability, relatively mature technology, and is simple. It has gradually become one of the important ways for the resource recycling of sodium chloride.

[0003] In the existing technology, a recycling system for preparing sodium bicarbonate by using ammonia / carbon dioxide and sodium chloride for double decomposition reaction exists. Because the solubility of sodium bicarbonate is relatively small and changes greatly with temperature, when ammonium chloride is precipitated by cold separation and salting-out crystallization in the crystallization process, sodium bicarbonate will be precipitated with ammonium chloride. Na ions cannot be removed during the drying process of ammonium chloride, which affects the quality of ammonium chloride. And because the concentration of NH4 + + in the solution is low, only the chloride ions in the added sodium chloride can produce a common ion effect when ammonium chloride is generated by cold separation and salting-out, so the conversion rate of chloride ions when sodium chloride is used to produce alkali with ammonia / carbon dioxide is low.

[0004] In addition, when ammonium bicarbonate and sodium chloride are used for double decomposition reaction to prepare sodium bicarbonate, the reaction speed is fast, the crystal grains are small, and the ammonium bicarbonate will be wrapped by the newly generated sodium bicarbonate and cannot participate in the reaction, thereby increasing the amount of ammonium bicarbonate or reducing the conversion rate of sodium chloride, the filtration efficiency is low, and the generated sodium bicarbonate will entrain impurities such as ammonium bicarbonate, ammonium chloride and sodium chloride. SUMMARY

[0005] Therefore, the technical problem to be solved by the present application is to provide a method for improving the purity of sodium bicarbonate, the single conversion rate of chloride ions and the filtration efficiency during the resource utilization of sodium chloride.

[0006] To solve the above technical problems, the present application provides the following technical solutions:

[0007] A method for improving the purity of sodium bicarbonate and the filtration efficiency during the resource utilization of sodium chloride, comprising the following steps:

[0008] (1) carbonization;

[0009] (2) solid separation and washing of sodium bicarbonate, and obtaining carbonation mother liquor;

[0010] (3) deacidification: adding ammonium bicarbonate to the carbonation mother liquor, and making the added ammonium bicarbonate all convert into ammonium carbonate to obtain a deacidification mother liquor, and returning the gas generated in the deacidification process to the carbonation reaction solution in step (1);

[0011] (4) crystallization;

[0012] (5) separation of ammonium chloride, and returning the obtained crystallization mother liquor to the carbonation reaction solution in step (1).

[0013] The deacidification treatment method in step (3) of the method for improving the purity of sodium bicarbonate and the filtration efficiency in the resource utilization of sodium chloride is as follows: heating and warming the carbonation mother liquor, then flash cooling, cooling the overflow gas or spraying the carbonation mother liquor or first spraying the carbonation mother liquor and then cooling and returning to the carbonation reaction solution in step (1).

[0014] In step (3) of the method for improving the purity of sodium bicarbonate and the filtration efficiency in the resource utilization of sodium chloride, the heating and warming temperature during deacidification is 65-75℃, and the flash cooling temperature is 50-70℃.

[0015] In step (3) of the method for improving the purity of sodium bicarbonate and the filtration efficiency in the resource utilization of sodium chloride, the heating and warming rate during deacidification is 2-5℃ / s, and the flash cooling time is 0.1-5min.

[0016] In step (3) of the method for improving the purity of sodium bicarbonate and the filtration efficiency in the resource utilization of sodium chloride, the ammonium bicarbonate is added to the carbonation mother liquor at a uniform speed.

[0017] In step (3) of the method for improving the purity of sodium bicarbonate and the filtration efficiency in the resource utilization of sodium chloride, the mass of the ammonium bicarbonate added per cubic carbonation mother liquor is 170-230Kg.

[0018] In step (3) of the method for improving the purity of sodium bicarbonate and the filtration efficiency in the resource utilization of sodium chloride, the particle size of the added ammonium bicarbonate is 200-300um.

[0019] In the method for improving the purity of sodium bicarbonate and the filtration efficiency in the resource utilization of sodium chloride, sodium chloride is added in the carbonation process of step (1) and / or the crystallization process of step (4), the total amount of sodium chloride added in steps (1) and (4) is greater than or equal to the amount of sodium bicarbonate obtained in step (2), and the amount of ammonium bicarbonate added in step (3) is greater than or equal to the amount of sodium bicarbonate obtained in step (2).

[0020] The method for improving the purity of sodium bicarbonate and the filtering efficiency during the resource utilization of sodium chloride, in step (4), adopts the method of cold separation and / or salting-out to crystallize and precipitate the solid ammonium chloride.

[0021] The method for improving the purity of sodium bicarbonate and the filtering efficiency during the resource utilization of sodium chloride, in step (1), the carbonization reaction temperature is 30-55 DEG C, and the reaction time is 0.5-2.5 h.

[0022] The technical scheme of the present application has the following beneficial technical effects:

[0023] In the present application, ammonium bicarbonate is added in the deacidification step, and then the temperature is raised to a certain temperature and flash evaporation is carried out, so that the added ammonium bicarbonate is completely converted into ammonium carbonate, and there is no ammonium bicarbonate in the circulating system but only ammonium carbonate, thereby having the following advantages:

[0024] (1) There is no bicarbonate ion in the solution, so there is no sodium bicarbonate precipitated with ammonium chloride in the crystallization step, and the purity of ammonium chloride can be improved.

[0025] (2) Slow liquid-gas reaction (slow carbonation reaction): there is only ammonium carbonate in the crystallization mother liquor, and there is no ammonium bicarbonate, so ammonium carbonate, water and carbon dioxide first react to form ammonium bicarbonate, and carbon dioxide is continuously introduced to complete the carbonation of the crystallization mother liquor.

[0026] (3) Slow double decomposition reaction: due to the reasons described in (2) above, ammonium carbonate first reacts with water and carbon dioxide to form ammonium bicarbonate, and after the solution is carbonated, the generated ammonium bicarbonate can only react with sodium chloride to form sodium bicarbonate; ammonium bicarbonate can only be generated through gas-liquid reaction, so the generation rate of ammonium bicarbonate is slow, it is not easy to be wrapped or entrained, and finally the double decomposition reaction generates coarse sodium bicarbonate crystals, which have high purity (few impurities such as ammonium bicarbonate, ammonium chloride and sodium chloride are entrained), are easy to filter, save energy, have low moisture content of filter cake, require less washing water, and are easy to dry.

[0027] (4) In the deacidification process, the ammonium bicarbonate in the carbonation mother liquor decomposes to generate carbon dioxide, and in the overflow process, the carbonation mother liquor can be uniformly stirred, so that the ammonium bicarbonate added into the carbonation mother liquor is quickly dispersed in the carbonation mother liquor, which is beneficial to the complete and rapid decomposition of ammonium bicarbonate, and a small amount of undissolved ammonium bicarbonate can provide enough gasification core during flash evaporation to prevent explosive boiling and carryover. The overflow gas in the carbonation mother liquor is first sprayed and then cooled, which can recover a small amount of ammonia gas generated by excessive decomposition in the overflow gas, control the thermal decomposition process of ammonium bicarbonate in the carbonation mother liquor, thereby shortening the deacidification time, and on the other hand, the carbonation mother liquor sprayed from top to bottom strengthens the heat and mass transfer process of gas-liquid-solid three-phase, promotes the dissolution of ammonium bicarbonate powder, and further accelerates the complete conversion of ammonium bicarbonate to ammonium carbonate. BRIEF DESCRIPTION OF DRAWINGS

[0028] Figure 1 The morphology of sodium bicarbonate obtained in Example 1;

[0029] Figure 2 The particle size distribution of sodium bicarbonate obtained in Example 1;

[0030] Figure 3 The morphology of sodium bicarbonate obtained in Example 2;

[0031] Figure 4 The particle size distribution of sodium bicarbonate obtained in Example 2;

[0032] Figure 5 The morphology of sodium bicarbonate obtained in Example 3;

[0033] Figure 6 The particle size distribution of sodium bicarbonate obtained in Example 3;

[0034] Figure 7 The flowchart of the method for improving the purity of sodium bicarbonate and improving the filtration efficiency in the resource utilization of sodium chloride. DETAILED DESCRIPTION

[0035] The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application.

[0036] Example 1

[0037] A method for improving the purity of sodium bicarbonate and improving the filtration efficiency in the resource utilization of sodium chloride, comprising the following steps:

[0038] (1) Carbonation: the carbonation reaction temperature is 35℃, and the reaction time is 1h.

[0039] (2) Separation and washing of sodium bicarbonate solid, and obtaining carbonation mother liquor.

[0040] (3) Deacidification: ammonium bicarbonate is added to the carbonation mother liquor during deacidification, and the added ammonium bicarbonate is completely converted into ammonium carbonate to obtain a deacidification mother liquor, and the gas generated during the deacidification process is returned to the carbonation reaction solution in step (1).

[0041] The deacidification treatment method is as follows: the carbonation mother liquor is heated at a rate of 2 ℃ / s to 65 ℃, and then flash-cooled to 60 ℃, and the flash-cooling time is 0.1 min; ammonium bicarbonate is added at a uniform rate during the heating of the carbonation mother liquor, and the mass of the ammonium bicarbonate added per cubic carbonation mother liquor is 170 Kg, and the particle size of the added ammonium bicarbonate is 200-300 um. During the heating of the carbonation mother liquor, the gas overflowing from the carbonation mother liquor is first sprayed with carbonation mother liquor and then cooled before being returned to the carbonation reaction solution in step (1).

[0042] (4) Crystallization: crystallization is performed by the method of first cold separation and then salt separation to precipitate ammonium chloride solids.

[0043] (5) Ammonium chloride separation, and the obtained crystallization mother liquor is returned to the carbonation reaction solution in step (1).

[0044] Sodium chloride is added during the carbonation process in step (1) and / or the crystallization process in step (4), and the total amount of sodium chloride added in steps (1) and (4) is equal to the amount of sodium bicarbonate obtained in step (2), and the amount of ammonium bicarbonate added in step (3) is equal to the amount of sodium bicarbonate obtained in step (2).

[0045] After the deacidification mother liquor obtained in this example is separated by crystallization to obtain ammonium chloride solids, the sodium chloride is supplemented and recycled for carbonation reaction, and the purity of the obtained sodium bicarbonate is 99.20%, and the morphology and particle size distribution are as shown in Figure 1 、 Figure 2 The sodium bicarbonate obtained in this example has a large particle size and is easy to filter, and the single conversion rate of chloride ions is 63.5%.

[0046] Example 2

[0047] A method for improving the purity of sodium bicarbonate and improving the filtration efficiency during the resource utilization of sodium chloride, comprising the following steps:

[0048] (1) Carbonation: the carbonation reaction temperature is 55 ℃, and the reaction time is 2.5 h.

[0049] (2) Sodium bicarbonate solid separation and washing, and obtaining a carbonation mother liquor.

[0050] (3) Deacidification: ammonium bicarbonate is added to the carbonation mother liquor during deacidification, and the added ammonium bicarbonate is completely converted into ammonium carbonate to obtain a deacidification mother liquor, and the gas generated during the deacidification process is returned to the carbonation reaction solution in step (1).

[0051] The deacidification treatment method is: heating the carbonization mother liquor to 75℃ at a rate of 5℃ / s, and then flash cooling to 70℃, the flash cooling time is 5min; adding ammonium bicarbonate at a uniform speed during the heating process of the carbonization mother liquor, the mass of the ammonium bicarbonate added per cubic carbonization mother liquor is 230Kg, and the particle size of the added ammonium bicarbonate is 200-300um. During the heating process of the carbonization mother liquor, the overflow gas is first sprayed with the carbonization mother liquor and then cooled before being returned to the carbonization reaction solution in step (1).

[0052] (4) Crystallization: crystallization is carried out by the method of first cold separation and then salt separation to precipitate ammonium chloride solid.

[0053] (5) Ammonium chloride separation, and the obtained crystallization mother liquor is returned to the carbonization reaction solution in step (1).

[0054] Sodium chloride is added during the carbonization process of step (1) and / or the crystallization process of step (4), the total amount of sodium chloride added in steps (1) and (4) is equal to the amount of sodium bicarbonate obtained in step (2), and the amount of ammonium bicarbonate added in step (3) is equal to the amount of sodium bicarbonate obtained in step (2).

[0055] After the deacidification mother liquor obtained in this example is separated by crystallization to obtain ammonium chloride solid, a circulating amount of sodium chloride is supplemented and a carbonization reaction is carried out, the obtained sodium bicarbonate has a purity of 99.3%, and its morphology and particle size distribution are shown in Figure 3 、 Figure 4 The sodium bicarbonate obtained in this example has a large particle size and is easy to filter, and the single conversion rate of chloride ions is 45.8%.

[0056] Example 3

[0057] A method for improving the purity of sodium bicarbonate and improving the filtration efficiency during the resource utilization of sodium chloride, comprising the following steps:

[0058] (1) Carbonization: the carbonization reaction temperature is 35℃, and the reaction time is 1h.

[0059] (2) Sodium bicarbonate solid separation and washing, and obtaining carbonization mother liquor.

[0060] (3) Deacidification: adding ammonium bicarbonate to the carbonization mother liquor during deacidification, and making the added ammonium bicarbonate all converted into ammonium carbonate to obtain a deacidification mother liquor, and returning the gas generated during the deacidification process to the carbonization reaction solution in step (1).

[0061] The deacidification treatment method is as follows: heating the carbonization mother liquor to 65°C at a rate of 2°C / s, then flash cooling to 60°C, the flash cooling time is 0.1 min; adding ammonium bicarbonate at a uniform rate during the heating process of the carbonization mother liquor, the mass of the ammonium bicarbonate added per cubic carbonization mother liquor is 170 Kg, the particle size of the added ammonium bicarbonate is 200-300 um. During the heating process of the carbonization mother liquor, the overflow gas is cooled and returned to the carbonization reaction solution in step (1).

[0062] (4) Crystallization: crystallizing and precipitating ammonium chloride solid by the method of first cold separation and then salt separation.

[0063] (5) Separating ammonium chloride, and returning the obtained crystallization mother liquor to the carbonization reaction solution in step (1).

[0064] Sodium chloride is added during the carbonization process in step (1) and / or the crystallization process in step (4), the total amount of sodium chloride added in step (1) and step (4) is equal to the amount of sodium bicarbonate obtained in step (2), and the amount of ammonium bicarbonate added in step (3) is equal to the amount of sodium bicarbonate obtained in step (2).

[0065] After the deacidification mother liquor obtained in the example is separated to obtain ammonium chloride solid, the sodium chloride is supplemented and recycled, and then the carbonization reaction is carried out, the obtained sodium bicarbonate has a purity of 97.60%, and the morphology and particle size distribution are as shown in Figure 5 、 Figure 6 The sodium bicarbonate obtained in the example has smaller particle size and slower filtration, and the single conversion rate of chloride ion is 63.9%.

[0066] As can be seen from example 1 and example 3, under the same process conditions, because the overflow gas is not sprayed during the deacidification process, the ammonia content in the carbonization mother liquor is low, and the conversion of ammonium bicarbonate to ammonium carbonate is not complete, so the sodium bicarbonate obtained in the carbonization reaction has low purity and small particle size.

[0067] Obviously, the above examples are only examples for clearly illustrating, but not limiting the embodiments. Based on the above description, other different forms of changes or variations can be made by those skilled in the art. Here, it is not necessary and impossible to enumerate all the embodiments. The obvious changes or variations derived therefrom are still within the protection scope of the patent application claims.

Claims

1. A method for improving the purity of sodium bicarbonate and improving filtration efficiency during the resource utilization of sodium chloride, characterized in that: The steps include: (1) Carbonization; (2) Separating and washing the sodium bicarbonate solid to obtain the carbonized mother liquor; (3) Deacidification: During deacidification, ammonium bicarbonate is added to the carbonization mother liquor, and the added ammonium bicarbonate is completely converted into ammonium carbonate to obtain a deacidification mother liquor, and the gas generated during the deacidification process is returned to the carbonization reaction solution in step (1); (4) crystallization; (5) separating ammonium chloride and returning the resulting crystallization mother liquor to the carbonization reaction solution in step (1); The deacidification treatment method in step (3) is: heating the carbonization mother liquor to increase its temperature, then flash evaporating the temperature, cooling the overflowed gas or spraying it with the carbonization mother liquor or first spraying it with the carbonization mother liquor and then cooling it before returning it to the carbonization reaction solution in step (1); During deacidification, the temperature is heated to 65-75°C and then flash-cooled to 50-70°C. The heating rate during deacidification is 2-5°C / s and the flash-cooling time is 0.1-5 min. Sodium chloride is added during the carbonization process of step (1) and / or the crystallization process of step (4), the total amount of sodium chloride added in step (1) and step (4) is greater than or equal to the amount of sodium bicarbonate obtained in step (2), and the amount of ammonium bicarbonate added in step (3) is greater than or equal to the amount of sodium bicarbonate obtained in step (2).

2. A method for improving the purity of sodium bicarbonate and improving filtration efficiency during the resource utilization of sodium chloride according to claim 1, characterized in that, In step (3): ammonium bicarbonate is added to the carbonization mother liquor at a uniform rate.

3. A method for improving the purity of sodium bicarbonate and improving filtration efficiency during the resource utilization of sodium chloride according to claim 1, characterized in that, In step (3): the mass of ammonium bicarbonate added to each cubic meter of carbonization mother liquor is 170-230 kg.

4. A method for improving the purity of sodium bicarbonate and improving filtration efficiency during the resource utilization of sodium chloride according to claim 1, characterized in that, In step (3): the particle size of the added ammonium bicarbonate is 200-300 μm.

5. A method for improving the purity of sodium bicarbonate and improving filtration efficiency during the resource utilization of sodium chloride according to claim 1, characterized in that, In step (4), the ammonium chloride solid is crystallized by cold precipitation and / or salting out.

6. A method for improving the purity of sodium bicarbonate and improving filtration efficiency during the resource utilization of sodium chloride according to claim 1, characterized in that: In step (1), the carbonization reaction temperature is 30-55° C. and the reaction time is 0.5-2.5 h.

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