Production method of high-purity ammonium chloride

Abstract

The invention discloses a production method of high-purity ammonium chloride, which comprises the following steps: (1) adding sodium chloride into a solution containing ammonium chloride, sodium bicarbonate and sodium chloride at the temperature of 35-40 DEG C to adjust the molar concentration relationship between sodium ions and bicarbonate ions, and then introducing ammonia gas for reaction to form a solution containing ammonia water, ammonium chloride and sodium carbonate; and (2) adding an adsorbent and a flocculant into the solution of ammonia water, ammonium chloride and sodium carbonate, filtering to remove flocculent precipitate, concentrating and crystallizing filtrate, cooling and crystallizing, and carrying out solid-liquid separation to obtain an ammonium chloride product and cooled ammonium chloride mother liquor. According to the production method, the purity of ammonium chloride can be improved, the ammonium chloride product achieves the technical effect of a high-quality pure ammonium chloride crystal, the application range of the ammonium chloride product is expanded, and the ammonium chloride product can be applied to industrial use and even medicinal use.

Description

Technical Field

[0001] The invention relates to a production method of high-purity ammonium chloride and belongs to the technical field of chemical processes. Background Art

[0002] Sodium chloride alkali production is considered to be an effective method. In the traditional sodium chloride alkali production method, after sodium bicarbonate is separated by double decomposition reaction, the unreacted ammonium bicarbonate in the mother liquor needs to be decomposed by high temperature, and then recovered by processes such as ammoniation and carbonation. However, the process is complicated and costly, and there is a risk of ammonia leakage in liquid ammonia and ammonia evaporation. The double decomposition reaction of sodium chloride and ammonium bicarbonate can greatly simplify the process and avoid processes such as ammonia evaporation, ammoniation and carbonation in traditional methods. It is an ideal method for high-value conversion of sodium chloride to produce soda ash. However, during the double decomposition reaction of sodium chloride and ammonium bicarbonate, ammonium bicarbonate exists in the mother liquor after conversion, and mixed crystals of sodium bicarbonate and ammonium chloride will be produced during the salting out process. It is impossible to obtain pure ammonium chloride in physical phase, and the purity is low. It is mainly used for agricultural purposes, which limits the scope of use of by-product ammonium chloride. Summary of the invention

[0003] In view of at least one problem existing in the above-mentioned prior art, the present invention provides a method for producing high-purity ammonium chloride, which can solve the problem of mixed crystals of sodium bicarbonate and ammonium chloride being generated during the salting-out process in the prior art, improve the purity of ammonium chloride, and expand the application scope of ammonium chloride products, so as to achieve industrial use and even medicinal use.

[0004] In order to achieve the above object, the present invention adopts the following technical scheme: a method for producing high-purity ammonium chloride, comprising the following steps: (1) adding sodium chloride to a solution containing ammonium chloride, sodium bicarbonate and sodium chloride at a temperature of 35-40° C. to adjust the molar concentration relationship between sodium ions and bicarbonate ions, and then introducing ammonia gas to react to form a solution containing ammonia water, ammonium chloride and sodium carbonate; wherein, at room temperature, the sodium bicarbonate in the solution containing ammonium chloride, sodium bicarbonate and sodium chloride is in a saturated state; (2) Add an adsorbent and a flocculant to the above-mentioned solution of ammonia water, ammonium chloride and sodium carbonate, filter to remove the flocculated precipitate, concentrate the filtrate for crystallization, cool the crystallization, separate the solid and the liquid, and obtain an ammonium chloride product and a cooled ammonium chloride mother liquor.

[0005] Preferably, in step (1), the molar concentration relationship between the sodium ions and the bicarbonate ions is: the ratio of the molar concentration of the sodium ions to the molar concentration of the bicarbonate ions is 1.4-1.8:1. If the concentration is too high, more sodium chloride is required. On the one hand, the ratio of the molar concentration of the sodium ions to the molar concentration of the bicarbonate ions exceeds 1.8:1, and there are too many carbonate ions, and more carbon dioxide is consumed subsequently. On the other hand, if the ratio of the molar concentration of the sodium ions to the molar concentration of the bicarbonate ions exceeds 2:1, sodium chloride will remain in the solution, which will affect the precipitation quality of ammonium chloride. If the concentration is too low, the existing sodium bicarbonate will precipitate with the ammonium chloride, which will also affect the precipitation quality of the ammonium chloride, and the ammonium chloride yield will also be low.

[0006] Preferably, in step (2), the filtrate is concentrated and crystallized, and the liquid is concentrated to 35-40% of the original volume. If too much water evaporates from the liquid, sodium carbonate will precipitate along with the ammonium chloride, affecting the precipitation quality of the ammonium chloride. If too little water evaporates from the liquid, too much ammonium chloride will remain in the water, affecting the yield of ammonium chloride.

[0007] Preferably, in step (1), the concentration of hydroxide ions in the solution containing ammonia water, ammonium chloride and sodium carbonate is 2.5-3.5 g / L. If the concentration is too high, more ammonia gas is required, and more ammonia gas is produced after the concentration; if the concentration is too low, the soluble impurity ions cannot be removed completely, and both too high and too low concentrations affect the quality of the ammonium chloride product.

[0008] Preferably, in step (2), the temperature of concentrated crystallization is 55-60°C.

[0009] Preferably, in step (2), the cooling crystallization temperature is 30-35° C., which can effectively avoid the precipitation of sodium carbonate with ammonium chloride and improve the purity and yield of ammonium chloride.

[0010] Preferably, in step (2), the amount of the adsorbent used is 0.0025-0.0035% by weight of the solution containing ammonium chloride, sodium bicarbonate and sodium chloride.

[0011] Preferably, in step (2), the adsorbent is one of polyaluminium chloride and polyaluminium ferric chloride sulfate.

[0012] Preferably, in step (2), the amount of flocculant used is 0.004-0.006% by weight of the solution containing ammonium chloride, sodium bicarbonate and sodium chloride.

[0013] Preferably, in step (2), the flocculant is polyacrylamide.

[0014] Preferably, in step (2), the pore size of the filter screen is 0.1-0.2 μm.

[0015] Preferably, the method further comprises step (3) of introducing carbon dioxide into the cooled ammonium chloride mother liquor to react and form a solution of ammonium chloride and sodium bicarbonate, and then cooling and crystallizing the solution and performing solid-liquid separation to obtain a sodium bicarbonate product and a mixed waste liquid containing sodium bicarbonate and ammonium chloride.

[0016] Preferably, in step (3), the cooling crystallization is at 35-40°C.

[0017] Preferably, the mixed waste liquid containing sodium bicarbonate and ammonium chloride in step (3) is recycled into the solution containing ammonium chloride, sodium bicarbonate and sodium chloride in step (1).

[0018] The invention has the beneficial effects as follows: the invention controls the molar concentration relationship between sodium ions and bicarbonate ions in a solution containing ammonium chloride, sodium bicarbonate and sodium chloride, performs ammoniation treatment to convert bicarbonate into carbonate, performs adsorption flocculation to reduce the content of insoluble substances and soluble impurity ions in the solution, and then performs concentration crystallization and cooling crystallization, thereby solving the problem that mixed crystals of sodium bicarbonate and ammonium chloride are generated in the salting-out process of the prior art, which limits the agricultural use; the production method of the invention improves the purity of ammonium chloride, realizes the technical effect of using the ammonium chloride product as high-grade pure ammonium chloride crystals, expands the use range of the ammonium chloride product, and can achieve industrial use and even medicinal use; the production method of the invention can also recover the sodium bicarbonate in the solution containing ammonium chloride, sodium bicarbonate and sodium chloride, and the mixed waste liquid finally generated can be circulated, thereby improving the yield of ammonium chloride. DETAILED DESCRIPTION

[0019] The following is a clear and complete description of the technical solutions in the implementation of the present invention. The described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in the field without making creative work are within the scope of protection of the present invention. If the specific conditions are not specified in the embodiments, they are carried out according to the normal conditions or the conditions recommended by the manufacturer. If the manufacturer is not specified for the reagents, instruments, and components used, they are all conventional products that can be purchased commercially.

[0020] The present invention provides a method for producing high-purity ammonium chloride, comprising the following steps: (1) adding sodium chloride to a solution containing ammonium chloride, sodium bicarbonate and sodium chloride at a temperature of 35-40° C. to adjust the molar concentration relationship between sodium ions and bicarbonate ions: the ratio of the molar concentration of sodium ions to the molar concentration of bicarbonate ions is 1.2-1.5:1, and then introducing ammonia gas to react so that the concentration of hydroxide ions is 2.5-3.5 g / L, and the solution contains ammonia water, ammonium chloride and sodium carbonate; wherein, at room temperature, the solution containing ammonium chloride, sodium bicarbonate and sodium chloride is in a saturated state of sodium bicarbonate; (2) Add polyaluminium chloride or polyaluminium ferric chloride sulfate adsorbent and polyacrylamide flocculant to the above-mentioned solution of ammonia water, ammonium chloride and sodium carbonate, the amount of adsorbent is 0.0025-0.0035% by weight of the solution containing ammonium chloride, sodium bicarbonate and sodium chloride; the amount of flocculant is 0.004-0.006% by weight of the solution containing ammonium chloride, sodium bicarbonate and sodium chloride, filter with a mesh with a pore size of 0.1-0.2 μm to remove flocculated precipitates, and then concentrate and crystallize the filtrate at a temperature of 55-60°C until the liquid is concentrated to 35-40% of the original volume, that is, the amount of water evaporated by concentration is 60-65% of the original volume of the liquid, and then cool and crystallize at a temperature of 30-35°C, separate the solid and liquid, and obtain ammonium chloride product and cooled ammonium chloride mother liquor.

[0021] The method for producing high-purity ammonium chloride of the present invention further comprises step (3): introducing carbon dioxide into the cooled ammonium chloride mother liquor for reaction to form a solution of ammonium chloride and sodium bicarbonate, and then cooling and crystallizing at a temperature of 35-40° C., and performing solid-liquid separation to obtain a sodium bicarbonate product and a mixed waste liquid containing sodium bicarbonate and ammonium chloride; wherein the mixed waste liquid containing sodium bicarbonate and ammonium chloride is recycled into the solution containing ammonium chloride, sodium bicarbonate and sodium chloride in step (1).

[0022] Example 1 A method for producing high-purity ammonium chloride provided in this embodiment comprises the following steps: (1) A solution containing ammonium chloride, sodium bicarbonate and sodium chloride (10 L). After testing, the ammonium chloride content was 362.5 g / L, the sodium bicarbonate content was 103.5 g / L and the sodium chloride content was 10.2 g / L. The solution was heated to 40°C, and sodium chloride was added to adjust the molar concentration relationship between sodium ions and bicarbonate ions so that the sodium ion concentration reached 51.0 g / L. Ammonia gas was then introduced to react so that the hydroxide ion concentration reached 2.5 g / L, thereby forming a solution containing aqueous ammonia, ammonium chloride and sodium carbonate. (2) Add 3.7 g of polyaluminium chloride adsorbent 6.8 g and 6 g of polyacrylamide flocculant to the above solution of ammonia water, ammonium chloride and sodium carbonate, filter with a sieve with a pore size of 0.1 μm to remove the flocculated precipitate, concentrate and crystallize the filtrate at a temperature of 55°C, remove 6 L of liquid by concentrated evaporation, cool and crystallize at a temperature of 30°C, separate the solid and liquid, and obtain ammonium chloride and cooled ammonium chloride mother liquor. The ammonium chloride is then dried to obtain 2.49 kg of ammonium chloride product, and the yield of ammonium chloride product is 68.66% (the initial mass of ammonium chloride is calculated based on the concentration of ammonium chloride in the solution of step (1), and the ammonium chloride product of step (2) is the recovered mass, and the yield = recovered mass / initial mass*100%).

[0023] Example 2 A method for producing high-purity ammonium chloride provided in this embodiment comprises the following steps: (1) A solution similar to that in Example 1, containing 15 L of ammonium chloride, sodium bicarbonate and sodium chloride, was selected and heated to 38° C. Sodium chloride was added to adjust the molar concentration relationship between sodium ions and bicarbonate ions so that the sodium ion concentration reached 36.8 g / L, and then ammonia gas was introduced to react so that the hydroxide ion concentration reached 3 g / L, thereby forming a solution containing aqueous ammonia, ammonium chloride and sodium carbonate; (2) Add 5.9 g of polyaluminium chloride adsorbent and 9.9 g of polyacrylamide flocculant to the above-mentioned solution of ammonia water, ammonium chloride and sodium carbonate, filter with a sieve with a pore size of 0.2 μm to remove the flocculated precipitate, concentrate and crystallize the filtrate at a temperature of 58° C., remove 9.75 L of liquid by concentrated evaporation, cool and crystallize at a temperature of 38° C., separate the solid and liquid, and obtain ammonium chloride and cooled ammonium chloride mother liquor. The ammonium chloride is then dried to obtain 3.50 kg of ammonium chloride product, and the yield of ammonium chloride product is 64.40% (the initial mass of ammonium chloride is calculated based on the concentration of ammonium chloride in the solution of step (1), and the ammonium chloride product of step (2) is the recovered mass, and the yield = recovered mass / initial mass*100%).

[0024] Example 3 A method for producing high-purity ammonium chloride provided in this embodiment comprises the following steps: (1) A solution of 12 L containing ammonium chloride, sodium bicarbonate and sodium chloride was selected as the same solution as in Example 1, and the solution was heated to 40° C. Sodium chloride was added to adjust the molar concentration relationship between sodium ions and bicarbonate ions so that the sodium ion concentration reached 45.3 g / L, and then ammonia gas was introduced to react so that the hydroxide ion concentration reached 3.5 g / L, thereby forming a solution containing aqueous ammonia, ammonium chloride and sodium carbonate; (2) Add 5.8 g of polyaluminium chloride adsorbent and 10 g of polyacrylamide flocculant to the above-mentioned solution of ammonia water, ammonium chloride and sodium carbonate, filter with a sieve with a pore size of 0.2 μm to remove the flocculated precipitate, concentrate and crystallize the filtrate at a temperature of 60° C., remove 7.56 L of liquid by concentrated evaporation, cool and crystallize at a temperature of 35° C., separate the solid and liquid, obtain ammonium chloride and cooled ammonium chloride mother liquor, and dry the ammonium chloride to obtain 2.74 kg of ammonium chloride product, with an ammonium chloride product yield of 62.94% (the initial mass of ammonium chloride is calculated based on the ammonium chloride concentration in the solution of step (1), and the ammonium chloride product of step (2) is the recovered mass, and the yield = recovered mass / initial mass*100%); (3) The above-mentioned cooled ammonium chloride mother liquor was mixed with the cooled ammonium chloride mother liquor produced in Example 1 and Example 2, and the total volume of the cooled ammonium chloride mother liquor was 13.62L. After testing, the ammonium chloride was 422.9g / L, the sodium bicarbonate was 59.7g / L, and the sodium bicarbonate was 277.6g / L. Carbon dioxide was introduced into the cooled ammonium chloride mother liquor to react to form a solution of ammonium chloride and sodium bicarbonate. The carbonate ion concentration was controlled to be 195g / L, and then cooled and crystallized at a temperature of 35°C, and solid-liquid separation was performed to obtain a sodium bicarbonate product and a mixed waste liquid containing sodium bicarbonate and ammonium chloride. The sodium bicarbonate was then dried to obtain 2.01kg of sodium bicarbonate product, and the sodium bicarbonate yield was 52.49% (the initial mass of sodium bicarbonate was calculated based on the sum of the sodium bicarbonate concentrations in the solutions of Examples 1 to 3, and the sodium bicarbonate product in step (3) was taken as the recovered mass, and the yield = recovered mass / initial mass*100%).

[0025] Example 4 A method for producing high-purity ammonium chloride provided in this embodiment comprises the following steps: (1) The same solution as in Example 1 was selected, containing 6.4 L of a solution of ammonium chloride, sodium bicarbonate and sodium chloride, and heated to 35° C. The solution was mixed with 13.6 L of a mixed waste liquid containing sodium bicarbonate and ammonium chloride produced in Example 3. After testing, the ammonium chloride content was 409.5 g / L, the sodium bicarbonate content was 115.7 g / L and the sodium chloride content was 6.5 g / L. Sodium chloride was added to adjust the molar concentration relationship between sodium ions and bicarbonate ions so that the sodium ion concentration reached 43.5 g / L. Ammonia gas was then introduced to react so that the hydroxide ion concentration reached 3.3 g / L, thereby forming a solution containing aqueous ammonia, ammonium chloride and sodium carbonate. (2) Add 3 g of polyaluminium chloride adsorbent and 5 g of polyacrylamide flocculant to the above-mentioned solution of ammonia water, ammonium chloride and sodium carbonate, filter with a sieve with a pore size of 0.2 μm to remove the flocculated precipitate, concentrate and crystallize the filtrate at a temperature of 60° C., remove 12.6 L of liquid by concentrated evaporation, cool and crystallize at a temperature of 35° C., separate the solid and liquid, and obtain ammonium chloride and cooled ammonium chloride mother liquor. The ammonium chloride is then dried to obtain 5.34 kg of ammonium chloride product, and the yield of the ammonium chloride product is 67.39% (the initial mass of ammonium chloride is calculated based on the concentration of ammonium chloride in the mixed solution in step (1), and the ammonium chloride product in step (2) is the recovered mass, and the yield = recovered mass / initial mass*100%); (3) The above-mentioned cooled ammonium chloride mother liquor, the total volume of the cooled ammonium chloride mother liquor is 7.2L, and after testing, the ammonium chloride is 433.1g / L, the sodium bicarbonate is 270.7g / L, and the sodium bicarbonate is 91.9g / L. Carbon dioxide is introduced into the cooled ammonium chloride mother liquor to react to form a solution of ammonium chloride and sodium bicarbonate, and the carbonate ion concentration is controlled to be 171.2g / L. Then, the solution is cooled and crystallized at a temperature of 40°C, and the solid-liquid separation is performed to obtain a sodium bicarbonate product and a mixed waste liquid containing sodium bicarbonate and ammonium chloride. The sodium bicarbonate is then dried to obtain 1.19kg of sodium bicarbonate product, and the sodium bicarbonate yield is 51.92% (the initial mass of sodium bicarbonate is calculated based on the sodium bicarbonate concentration in the solution of Example 4, and the sodium bicarbonate product in step (3) is the recovered mass, and the yield = recovered mass / initial mass*100%).

[0026] Comparative Example 1 This embodiment provides a method for producing high-purity ammonium chloride, which is partially the same as that of embodiment 1, except that: the solution containing ammonia water, ammonium chloride and sodium carbonate is directly passed through a sieve with a pore size of 0.1 μm, and then concentrated and crystallized; the remaining steps are the same; Ammonium chloride is obtained and the ammonium chloride mother liquor is cooled. The ammonium chloride is then dried to obtain 2.51 kg of ammonium chloride product, and the yield of the ammonium chloride product is 69.24%.

[0027] Comparative Example 2 The present embodiment provides a method for producing high-purity ammonium chloride, which is partially the same as that of embodiment 1, except that: the hydroxide ion concentration is set to 2 g / L; the remaining steps are the same; Ammonium chloride is obtained and the ammonium chloride mother liquor is cooled. The ammonium chloride is then dried to obtain 2.49 kg of ammonium chloride product, and the yield of the ammonium chloride product is 68.72%.

[0028] Comparative Example 3 The present embodiment provides a method for producing high-purity ammonium chloride, which is partially the same as that of embodiment 1, except that: step (1) sodium chloride is added to adjust the molar concentration relationship between sodium ions and bicarbonate ions so that the sodium ion concentration reaches 36.8 g / L, and step (2) 6.5 L of liquid is removed by concentrating and evaporating; the remaining steps are the same; Ammonium chloride is obtained and the ammonium chloride mother liquor is cooled. The ammonium chloride is then dried to obtain 2.3 kg of ammonium chloride product, and the yield of the ammonium chloride product is 63.45%.

[0029] Comparative Example 4 The present embodiment provides a method for producing high-purity ammonium chloride, which is partially the same as that of embodiment 1, except that: in step (2), the cooling crystallization temperature is 25° C., and the remaining steps are the same; Ammonium chloride is obtained and the ammonium chloride mother liquor is cooled. The ammonium chloride is then dried to obtain 2.03 kg of ammonium chloride product, and the yield of the ammonium chloride product is 56.06%.

[0030] Comparative Example 5 The present embodiment provides a method for producing high-purity ammonium chloride, which is partially the same as that of embodiment 1, except that: step (1) sodium chloride is added to adjust the molar concentration relationship between sodium ions and bicarbonate ions so that the sodium ion concentration reaches 39.6 g / L, step (2) 7 L of liquid is removed by concentrating and evaporating, and the remaining steps are the same; Ammonium chloride is obtained and the ammonium chloride mother liquor is cooled. The ammonium chloride is then dried to obtain 2.64 kg of ammonium chloride product, and the yield of the ammonium chloride product is 72.83%.

[0031] Comparative Example 6 The present embodiment provides a method for producing high-purity ammonium chloride, which is partially the same as that of embodiment 1, except that: in step (1), sodium chloride is added to adjust the molar concentration relationship between sodium ions and bicarbonate ions so that the sodium ion concentration reaches 65.2 g / L, and the remaining steps are the same; Ammonium chloride is obtained and the ammonium chloride mother liquor is cooled. The ammonium chloride is then dried to obtain 2.84 kg of ammonium chloride product, and the yield of the ammonium chloride product is 78.3%.

[0032] The ammonium chloride products prepared in Examples 1 to 4 and Comparative Examples 1 to 5 were tested for performance according to GB / T658-2006 and the Pharmacopoeia. The results are shown in Table 1 below.

[0033] Table 1

[0034] As can be seen from Table 1 above, the production method of the present invention is used to control the sodium ion concentration of a solution containing ammonium chloride, sodium bicarbonate and sodium chloride, perform an amination reaction to generate part of bicarbonate into carbonate, and then perform adsorption flocculation, concentration and cooling crystallization, thereby effectively increasing the content of ammonium chloride and effectively reducing the content of insoluble substances and soluble impurity ions in the solution; the production method of the present invention can improve the purity of ammonium chloride, achieve the technical effect of superior pure ammonium chloride crystals for ammonium chloride products, expand the scope of use of ammonium chloride products, and achieve industrial use or even medicinal use.

[0035] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the present invention can be implemented in other specific forms without departing from the spirit and essential features of the present invention. Therefore, the embodiments should be considered exemplary and non-restrictive in all respects, and the scope of the present invention is defined by the appended claims rather than the above description, and it is intended that all changes falling within the meaning and scope of the equivalent elements of the claims be included in the present invention.

[0036] In addition, it should be understood that although the present specification is described according to implementation modes, not every implementation mode contains only one independent technical solution. This description of the specification is only for the sake of clarity. Those skilled in the art should regard the specification as a whole. The technical solutions in each embodiment may also be appropriately combined to form other implementation modes that can be understood by those skilled in the art.

Claims

1. A method for producing high-purity ammonium chloride, characterized in that: The following steps are involved: (1) adding sodium chloride to a solution containing ammonium chloride, sodium bicarbonate and sodium chloride at a temperature of 35-40° C. to adjust the molar concentration relationship between sodium ions and bicarbonate ions, and then introducing ammonia gas to react to form a solution containing ammonia water, ammonium chloride and sodium carbonate; wherein, at room temperature, the sodium bicarbonate in the solution containing ammonium chloride, sodium bicarbonate and sodium chloride is in a saturated state; (2) Add an adsorbent and a flocculant to the above-mentioned solution of ammonia water, ammonium chloride and sodium carbonate, filter to remove the flocculated precipitate, concentrate the filtrate for crystallization, cool the crystallization, separate the solid and the liquid, and obtain an ammonium chloride product and a cooled ammonium chloride mother liquor.

2. A method for producing high-purity ammonium chloride according to claim 1, characterized in that: In step (1), the molar concentration relationship between the sodium ions and the bicarbonate ions is: the ratio of the molar concentration of the sodium ions to the molar concentration of the bicarbonate ions is 1.4-1.8:

1.

3. A method for producing high-purity ammonium chloride according to claim 1, characterized in that: In step (2), the filtrate is concentrated and crystallized, and the liquid is concentrated to 35-40% of the original volume.

4. The method for producing high-purity ammonium chloride according to claim 1, wherein: In step (1), the concentration of hydroxide ions in the solution containing ammonia water, ammonium chloride and sodium carbonate is 2.5-3.5 g / L.

5. A method for producing high-purity ammonium chloride according to claim 1, characterized in that: In step (2), the temperature of the concentrated crystallization is 55-60°C.

6. The method for producing high-purity ammonium chloride according to claim 1, characterized in that: In step (2), the temperature of the cooling crystallization is 30-35°C.

7. The method for producing high-purity ammonium chloride according to claim 1, characterized in that: In step (2), the amount of the adsorbent is 0.0025-0.0035% by weight of the solution containing ammonium chloride, sodium bicarbonate and sodium chloride; the adsorbent is one of polyaluminium chloride or polyaluminium ferric chloride sulfate.

8. The method for producing high-purity ammonium chloride according to claim 1, characterized in that: The dosage of the flocculant is 0.004-0.006% of the weight of the solution containing ammonium chloride, sodium bicarbonate and sodium chloride; the flocculant is polyacrylamide.

9. The method for producing high-purity ammonium chloride according to claim 1, wherein: The method further comprises the step (3) of introducing carbon dioxide into the cooled ammonium chloride mother liquor to react and form a solution of ammonium chloride and sodium bicarbonate, and then cooling and crystallizing the solution and performing solid-liquid separation to obtain a sodium bicarbonate product and a mixed waste liquid containing sodium bicarbonate and ammonium chloride; and the mixed waste liquid containing sodium bicarbonate and ammonium chloride is recycled into the solution containing ammonium chloride, sodium bicarbonate and sodium chloride in step (1).

10. The method for producing high-purity ammonium chloride according to claim 1, characterized in that: In step (3), the cooling crystallization is 35-40°C.

Images