Method for improving purity of ammonium chloride in resource utilization of sodium chloride

Abstract

The application discloses a method for improving the purity of ammonium chloride in the resource utilization of sodium chloride, which comprises the following steps: (1) performing cold separation treatment on a deacidification mother liquor, and obtaining a cold separation mother liquor and first ammonium chloride solid after solid-liquid separation; (2) adding sodium chloride solid into the cold separation mother liquor to perform salting-out treatment, and obtaining second ammonium chloride solid and salting-out mother liquor after solid-liquid separation; and (3) adding the obtained second ammonium chloride solid into the deacidification mother liquor in the step (1) to continue the cold separation treatment. The deacidification mother liquor is first subjected to cold separation crystallization to obtain the first ammonium chloride solid, then subjected to salting-out crystallization to obtain the second ammonium chloride solid, and finally the second ammonium chloride solid obtained through the salting-out crystallization is returned to the deacidification mother liquor, so that the first ammonium chloride solid with high purity is obtained.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of sodium chloride recycling. Specifically, it is a method for improving the purity of ammonium chloride during the resource utilization of sodium chloride. 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. The preparation of sodium bicarbonate / sodium carbonate products from sodium chloride as raw material and the byproduct of ammonium chloride fertilizer makes good use of 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] Compared with agricultural ammonium chloride, industrial ammonium chloride has high purity, low sodium ion content, wide range of use and high economic value. The preparation methods of industrial ammonium chloride mainly include neutralization method, double decomposition method and combined alkali production method. In the existing industrial process, the ammonium chloride obtained by the neutralization method can be directly used as industrial products, but the raw material cost of the neutralization method is relatively high. The other two methods are mainly used for agricultural purposes, such as industrial products, which need to be refined through sublimation, recrystallization (Chinese invention patent 202110355387.2) and other processes.

[0004] In the process of preparing sodium bicarbonate from sodium chloride and ammonium bicarbonate and byproduct ammonium chloride, sodium chloride needs to be added to promote the precipitation of ammonium chloride. Too small amount of sodium chloride is not conducive to the precipitation of ammonium chloride. If the amount of sodium chloride is too large, it will cause the precipitation of ammonium chloride to be mixed with a large amount of impurities such as sodium chloride, thereby limiting the use range of the byproduct ammonium chloride. SUMMARY

[0005] Therefore, the technical problem to be solved by the present application is to provide a method for improving the purity of ammonium chloride 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 ammonium chloride during the resource utilization of sodium chloride, comprising the following steps:

[0008] (1) The deacidification mother liquor is subjected to cold precipitation treatment, and after solid-liquid separation, a cold precipitation mother liquor and a first ammonium chloride solid are obtained. The content of each chemical component in the deacidification mother liquor is: 200-240 g / L of ammonium chloride, 60-85 g / L of sodium chloride, 40-60 g / L of carbonate, and 24-36 g / L of ammonium ion;

[0009] (2) adding sodium chloride solid to the cold separation mother liquor to carry out salting-out treatment, and then separating the solid and the liquid to obtain second ammonium chloride solid and a salting-out mother liquor;

[0010] (3) dissolving the obtained second ammonium chloride solid in the deacidification mother liquor in step (1) and then carrying out cold separation treatment.

[0011] In the method for improving the purity of ammonium chloride in the resource utilization of sodium chloride, in step (1), the deacidification mother liquor is first rapidly cooled, and then the first sodium chloride solid is continuously added to the deacidification mother liquor while slowly cooling.

[0012] In the method for improving the purity of ammonium chloride in the resource utilization of sodium chloride, in step (1), the deacidification mother liquor is first rapidly cooled to 10-20℃, and then the first sodium chloride solid is added to the deacidification mother liquor while slowly cooling to 5-10℃.

[0013] In the method for improving the purity of ammonium chloride in the resource utilization of sodium chloride, in step (1), the first-stage cooling rate is 50-60℃ / h, and the second-stage cooling rate is 5-15℃ / h.

[0014] In the method for improving the purity of ammonium chloride in the resource utilization of sodium chloride, in step (1), the first-stage cooling time is 0.5-1h, and the second-stage cooling time is 1-2h.

[0015] In the method for improving the purity of ammonium chloride in the resource utilization of sodium chloride, in step (1), the first sodium chloride solid is added to the deacidification mother liquor so that the mass fraction of sodium chloride in the solution after the end of the cold separation is 1.1-1.2 times that of the mass fraction of ammonium carbonate.

[0016] In the method for improving the purity of ammonium chloride in the resource utilization of sodium chloride, in step (1), the rate of adding the first sodium chloride solid is kept unchanged.

[0017] In the method for improving the purity of ammonium chloride in the resource utilization of sodium chloride, in step (2), the second sodium chloride solid is added to the cold separation mother liquor so that the mass fraction of sodium chloride in the solution after the end of the salting-out is 2.5-3 times that of the mass fraction of ammonium carbonate.

[0018] In the method for improving the purity of ammonium chloride in the resource utilization of sodium chloride, in step (2), the salting-out time is 2-4h, and the temperature is 5-10℃.

[0019] In the method for improving the purity of ammonium chloride in the resource utilization of sodium chloride, in step (2), the rate of adding the second sodium chloride solid during the salting-out process is kept unchanged.

[0020] The technical scheme of the present application has the following beneficial technical effects:

[0021] 1. The first ammonium chloride solid is obtained by cold crystallization of the deacidification mother liquor, and the second ammonium chloride solid is obtained by salting-out crystallization, and the second ammonium chloride solid obtained by salting-out crystallization is returned to the deacidification mother liquor, the first ammonium chloride solid obtained has high purity (purity 99.0-99.5%) and sodium content less than 0.45wt%.

[0022] 2. In the cold crystallization process, the temperature is rapidly reduced and no sodium chloride is added, so that a large amount of fine and high-purity ammonium chloride crystals can be precipitated, and the purity can be improved by avoiding the entrainment of liquid in the initial stage of ammonium chloride precipitation; sodium chloride is gradually added during the slow cooling process, and since the concentration of ammonium chloride in the solution has been reduced, the precipitated ammonium chloride crystals will not be entrained with liquid, and these fine ammonium chloride crystals can grow rapidly, so that the solid-liquid separation is easy after the cold crystallization is completed, not only the yield of the first ammonium chloride relative to the second ammonium chloride is improved, but also the ammonium chloride crystals with high purity (purity 99.0-99.5%, sodium content less than 0.45wt%) and large particles (particle size 2.00-4.75mm accounting for more than 90%) can be obtained. BRIEF DESCRIPTION OF DRAWINGS

[0023] Figure 1 The flowchart of the method for improving the purity of ammonium chloride in the resource utilization of sodium chloride according to the present application;

[0024] Figure 2 The particle size distribution graph of the first ammonium chloride solid after the cold crystallization process of Example 1;

[0025] Figure 3 The morphology graph of the first ammonium chloride solid after the cold crystallization process of Example 1;

[0026] Figure 4 The particle size distribution graph of the first ammonium chloride solid after the cold crystallization process of Example 2;

[0027] Figure 5 The morphology graph of the first ammonium chloride solid after the cold crystallization process of Example 2;

[0028] Figure 6 The particle size distribution graph of the first ammonium chloride solid after the cold crystallization process of Example 3;

[0029] Figure 7 The morphology graph of the first ammonium chloride solid after the cold crystallization process of Example 3. DETAILED DESCRIPTION

[0030] The technical solutions in the embodiments of the present application will be described clearly and completely below with reference to the drawings in the embodiments of the present application.

[0031] Example 1

[0032] The method for improving the purity of ammonium chloride in the resource utilization of sodium chloride in the embodiment comprises the following steps:

[0033] (1) Cold analysis: the deacidification mother liquor with a temperature of 70°C is subjected to cold analysis treatment, and is rapidly cooled to 10°C in 1 h; then first sodium chloride solids are uniformly added to the deacidification mother liquor so that the mass fraction of sodium chloride in the solution after the cold analysis is 1.1-1.2 times that of the mass fraction of ammonium carbonate, and the solution is slowly cooled to 5°C in 1 h; after solid-liquid separation, a cold analysis mother liquor and first ammonium chloride solids are obtained, and the morphology and particle size distribution of the first ammonium chloride solids are as shown in Figure 2 、 Figure 3 The sodium content in the obtained first ammonium chloride solids is 0.2 wt%, and the particle size distribution of the first ammonium chloride solids is as follows: the proportion of the particle size of 2.00-4.75 mm is 93%.

[0034] (2) Salting-out: second sodium chloride solids are uniformly added to the cold analysis mother liquor so that the mass fraction of sodium chloride in the solution after the salting-out is 3 times that of the mass fraction of ammonium carbonate, and the salting-out treatment is performed for 2 h; the solution temperature is maintained at 5°C during the salting-out process; after solid-liquid separation, second ammonium chloride solids and a salting-out mother liquor are obtained, and the mass ratio of the first ammonium chloride solids to the second ammonium chloride solids is 1.5:1; sodium chloride solids are uniformly added to the cold analysis mother liquor.

[0035] (3) The obtained second ammonium chloride solids are added to the deacidification mother liquor in step (1) to continue the cold analysis treatment.

[0036] Example 2

[0037] The method for improving the purity of ammonium chloride in the resource utilization of sodium chloride in the embodiment comprises the following steps:

[0038] (1) Cold analysis: the deacidification mother liquor with a temperature of 70°C is subjected to cold analysis treatment, and is cooled to 5°C in 1 h 5 min and maintained for 55 min; after solid-liquid separation, a cold analysis mother liquor and first ammonium chloride solids are obtained, and the morphology and particle size distribution of the first ammonium chloride solids are as shown in Figure 4 、 Figure 5 The sodium content in the obtained first ammonium chloride solids is 1.2 wt%, and the particle size distribution is as follows: the proportion of the particle size of 2.00-4.75 mm is 46%;

[0039] (2) Salting-out: sodium chloride solids are uniformly added to the cold analysis mother liquor to perform salting-out treatment, and the salting-out time is 2 h; the solution temperature is maintained at 5°C during the salting-out process; after solid-liquid separation, second ammonium chloride solids and a salting-out mother liquor are obtained, and the mass ratio of the first ammonium chloride solids to the second ammonium chloride solids is 1:1; sodium chloride solids are added to the cold analysis mother liquor so that the mass fraction of sodium chloride in the solution after the salting-out is 3 times that of the mass fraction of ammonium carbonate.

[0040] (3) The obtained second ammonium chloride solids are added to the deacidification mother liquor in step (1) to continue the cold analysis treatment.

[0041] Embodiment 3

[0042] The method for improving the purity of ammonium chloride in the resource utilization of sodium chloride includes the following steps:

[0043] (1) Cold separation: The deacidification mother liquor with a temperature of 70℃ is subjected to cold separation treatment, and is rapidly cooled to 10℃ in 1h, and then is slowly cooled to 5℃ in 1h. After solid-liquid separation, a cold separation mother liquor and a first ammonium chloride solid are obtained. The morphology and particle size distribution of the first ammonium chloride solid are shown in Figs. 1 and 2, respectively. The sodium content in the obtained first ammonium chloride solid is 0.9wt%, and the particle size distribution is as follows: the proportion of the particle size of 2.00-4.75mm is 60%. Figure 6 、 Figure 7

[0044] (2) Salting-out: Sodium chloride solid is uniformly added into the cold separation mother liquor to perform salting-out treatment. The salting-out time is 2h, and the solution temperature is maintained at 5℃ during the salting-out process. After solid-liquid separation, a second ammonium chloride solid and a salting-out mother liquor are obtained. The mass ratio of the first ammonium chloride solid to the second ammonium chloride solid is 1:1. Sodium chloride solid is added into the cold separation mother liquor so that the mass fraction of sodium chloride in the solution after salting-out is 3 times the mass fraction of ammonium carbonate.

[0045] (3) The obtained second ammonium chloride solid is added into the deacidification mother liquor in step (1) to continue the cold separation treatment.

[0046] Obviously, the above embodiments are merely examples for clearly illustrating, but not limitation on the embodiments. For those skilled in the art, other different forms of changes or variations can be made on the basis of the above description. 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 ammonium chloride during resource utilization of sodium chloride, characterized in that: The steps include: (1) subjecting the deacidification mother liquor to cold precipitation treatment, and obtaining the cold precipitation mother liquor and the first ammonium chloride solid after solid-liquid separation; the chemical component contents of the deacidification mother liquor are: ammonium chloride 200-240 g / L, sodium chloride 60-85 g / L, carbonate 40-60 g / L, and ammonium ion 24-36 g / L; (2) adding sodium chloride solid to the cold precipitation mother liquor to perform salting-out treatment, and obtaining a second ammonium chloride solid and a salting-out mother liquor after solid-liquid separation; (3) adding the obtained second ammonium chloride solid to the deacidification mother liquor in step (1) to dissolve the solid and then perform cold precipitation treatment; In step (1): first, the deacidification mother liquor is rapidly cooled to 10-20° C., and then slowly cooled to 5-10° C. while adding the first sodium chloride solid to the deacidification mother liquor; the cooling rate in the first stage is 50-60° C. / h, and the cooling rate in the second stage is 5-15° C. / h; the cooling time in the first stage is 0.5-1h, and the cooling time in the second stage is 1-2h.

2. The method for improving ammonium chloride purity during sodium chloride resource utilization according to claim 1, wherein In step (1): a first sodium chloride solid is added to the deacidification mother liquor so that the mass fraction of sodium chloride in the solution after the cold precipitation is 1.1-1.2 times the mass fraction of ammonium carbonate.

3. The method for improving ammonium chloride purity during sodium chloride resource utilization according to claim 1, wherein In step (1): the rate of adding the first sodium chloride solid remains unchanged.

4. The method for improving ammonium chloride purity during sodium chloride resource utilization according to claim 1, wherein In step (2): a second sodium chloride solid is added to the cold precipitation mother liquor so that the mass fraction of sodium chloride in the solution after the salting out is 2.5-3 times the mass fraction of ammonium carbonate.

5. The method for improving ammonium chloride purity during sodium chloride resource utilization according to claim 1, wherein In step (2): the salting-out time is 2-4 hours and the temperature is 5-10°C.

6. The method for improving the purity of ammonium chloride during the resource utilization of sodium chloride according to claim 1, wherein In step (2): the rate of adding the second sodium chloride solid during the salting-out process remains constant.

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