Large-particle spherical salt and preparation method thereof

Abstract

A large-particle spherical salt with a particle size of 400-950 μm and a sphericity of 0.5-1.0 is disclosed, which overcomes the existing difficulty in this field for larger particle size as well as higher sphericity. A preparation method of the large-particle spherical salt is also disclosed, wherein in one preparation process, 2% of gum arabic (based on the mass percentage of solute sodium chloride in a sodium chloride saturated solution) is added, and under conditions of an evaporating temperature of 60° C. a stirring rate of 350 rpm, and an evaporating time of 8 hours, a large-particle spherical salt with a particle size of 921.593 μm and an average sphericity of 0.904 is successfully prepared. The large-particle spherical salt prepared by the method has a uniform particle size distribution and good appearance, can be combined with other substances, adding some extra value to the salt. Meanwhile, the large-particle spherical salt prepared by the method has a high safety grade (e.g.: food grade) and can be used as edible salt, nutrient salt or foot bath salt.

Claims

1. A method for preparing sodium chloride crystals, comprising: (1) preparing a saturated solution of sodium chloride in a crystallizer, adding gum arabic into the saturated solution in a mass percentage of 0.5-5% of a mass of the sodium chloride in the saturated solution, then heating the saturated solution at a temperature of 55-75° C., stirring at a rate of 300-400 rpm, and evaporating the saturated solution for a time of 4-12 hours to form the sodium chloride crystals; and (2) filtering and drying the sodium chloride crystals, wherein the sodium chloride crystals have a particle size of 400-950 μm and a sphericity of 0.5-1.0 after filtering and drying.

2. The method of claim 1, wherein the mass percentage of the gum arabic is 2% of the sodium chloride in the saturated solution, the temperature is 60° C., the rate is 350 rpm, and the evaporation time is 8 hours.

3. The method of claim 1, wherein the crystals are dried at a temperature of 60° C. for a time of 2 hours.

4. The method of claim 1, wherein the mass percentage of the gum arabic is 2% of the sodium chloride in the saturated solution.

5. The method of claim 1, wherein the temperature is 60° C.

6. The method of claim 1, wherein the rate is 350 rpm.

7. The method of claim 1, wherein the evaporation time is 8 hours.

8. The method of claim 1, wherein the crystals are dried at a temperature of 60° C.

9. The method of claim 1, wherein the crystals are dried for a time of 2 hours.

10. The method of claim 1, wherein the time for evaporating the saturated solution is calculated from a moment when the sodium chloride crystals begin to form a crystal nucleus to a moment when evaporating the saturated solution is terminated.

11. The method of claim 1, wherein the saturated solution of sodium chloride is prepared at 55-75° C.

12. The method of claim 1, wherein the saturated solution of sodium chloride contains the sodium chloride and distilled water.

13. The method of claim 12, wherein the sodium chloride and the distilled water are present in a ratio of about 37-38 g of the sodium chloride per 100 mL of the distilled water.

14. The method of claim 1, wherein the particle size is 600-925 μm and the sphericity is 0.52-0.95.

15. The method of claim 14, wherein the particle size is 684-922 μm and the sphericity is 0.685-0.904.

16. The method of claim 15, wherein the particle size is 739.388-921.593 μm and the sphericity is 0.721-0.904.

17. The method of claim 1, further comprising determining the particle size and a particle size distribution of the sodium chloride crystals using a particle size analyzer.

18. The method of claim 17, further comprising measuring the sphericity of the sodium chloride crystals using a particle shape meter.

Description

DRAWINGS

(1) FIG. 1 is an EMS map of the surface of the particulate salt prepared in comparative example 1;

(2) FIG. 2 is an EMS map of the surface of the particulate salt prepared in comparative example 2;

(3) FIG. 3 is an EMS map of the surface of the large particle spherical salt prepared in exemplary embodiment 1;

(4) FIG. 4 is an EMS map of the surface of the large particle spherical salt prepared in exemplary embodiment 2;

(5) FIG. 5 is an EMS map of the surface of the large particle spherical salt prepared in exemplary embodiment 3;

(6) FIG. 6 is an EMS map of the surface of the large particle spherical salt prepared in exemplary embodiment 4;

(7) FIG. 7 is an EMS map of the surface of the large particle spherical salt prepared in exemplary embodiment 5;

(8) FIG. 8 is an EMS map of the surface of the large particle spherical salt prepared in exemplary embodiment 6;

(9) FIG. 9 is an EMS map of the surface of the large particle spherical salt prepared in exemplary embodiment 7;

(10) FIG. 10 is an EMS map of the surface of the large particle spherical salt prepared in exemplary embodiment 8;

(11) FIG. 11 is an EMS map of the surface of the large particle spherical salt prepared in exemplary embodiment 9;

(12) FIG. 12 is an EMS map of the surface of the large particle spherical salt prepared in exemplary embodiment 10

(13) FIG. 13 is an EMS map of the surface of the large particle spherical salt prepared in exemplary embodiment 11;

(14) FIG. 14 is an EMS map of the surface of the large particle spherical salt prepared in exemplary embodiment 12; and

(15) FIG. 15 is an EMS map of the surface of the large particle spherical salt prepared in exemplary embodiment 2.

(16) The magnification of FIGS. 1-14 is 40, and the magnification of FIG. 15 is 4.

DETAILED DESCRIPTION

(17) The present invention will be described below with reference to specific examples, but the embodiments of the present invention are not limited thereto.

(18) The morphology of the large-particle spherical salt was observed under a polarization microscope (EMS) in the following comparative examples and exemplary embodiments. The particle size and particle size distribution of the large-particle spherical salt were measured by a particle size analyzer, and the sphericity of the large-particle spherical salt was measured by a particle shape meter.

Comparative Example 1

(19) 300 mL of a saturated solution of sodium chloride was prepared, the saturated solution was placed in a crystallizer, heated at a constant temperature in a water bath, and evaporated at a temperature of 60° C. for 8 hours with stirring at a stirring speed of 350 rpm, until a large number of crystals were formed. The saturated solution was filtered and the crystals were dried in an oven at a temperature of 60° C. for 2 hours to obtain a granular salt reference sample 1. The crystal shape was observed under a polarizing microscope (see FIG. 1). The particle size of the crystal was 382.744 in as measured by a particle size analyzer, and the sphericity of the crystal was 0.136 as measured by a particle shape meter.

Comparative Example 2

(20) 300 mL of a saturated solution of sodium chloride was prepared in a crystallizer. 2% glycine by mass of the sodium chloride in the saturated solution was added, heated at a constant temperature in a water bath, and evaporated at 60° C. for 8 hours with stirring the solution at a stirring speed of 350 rpm to form a large number of crystals. The solution was filtered and the crystals were dried in an oven at 60° C. for 2 hours to obtain a granular salt reference sample 2. The shape of the crystal was observed under a microscope (see FIG. 2). The particle size of the crystal was 391.628 μm as measured by a particle size analyzer, and the sphericity of the crystal was 0.426 as measured by a particle shape meter.

Examples 1 to 12

(21) In examples 1-12, large particle spherical salt samples 1-12 were prepared, respectively, using substantially the same procedure as in comparative example 2, except that the additive, the amount of additive added (relative to the mass of the sodium chloride in the saturated solution), the evaporation temperature, the stirring rate during evaporation, and the evaporation time were varied, as shown in table 1. The particle size and particle size distribution of the large-particle spherical salt samples 1 to 12 were measured by a particle size analyzer, and the sphericity of the large-particle spherical salt samples 1 to 12 was measured by a particle shape meter. The results are shown in Table 1.

(22) TABLE-US-00001 TABLE 1 Preparation conditions for large particle spherical salt samples 1-12 and their particle sizes and sphericities Additive Evaporation Stirring Evaporation Particle Embodiment Sample Additive percentage (%) Temp (° C.) rate (rpm) duration (h) size (μm) Sphericity Comparative Particle salt N/A N/A 60 350 8 382.744 0.136 example 1 comparative example 1 Comparative Particle salt Glycine 2 60 350 8 391.628 0.426 example 2 comparative example 2 Embodiment Large particle gum 0.5 60 350 8 403.597 0.596 1 spherical salt arabic sample 1 Embodiment Large particle gum 2 60 350 8 921.593 0.904 2 spherical salt arabic sample 2 Embodiment Large particle gum 5 60 350 8 748.625 0.685 3 spherical salt arabic sample 3 Embodiment Large particle gum 2 60 250 8 388.942 0.316 4 spherical salt arabic sample 4 Embodiment Large particle gum 2 60 300 8 789.642 0.721 5 spherical salt arabic sample 5 Embodiment Large particle gum 2 60 400 8 414.051 0.532 6 spherical salt arabic sample 6 Embodiment Large particle gum 2 60 350 2 486.354 0.236 7 spherical salt arabic sample 7 Embodiment Large particle gum 2 60 350 4 739.388 0.831 8 spherical salt arabic sample 8 Embodiment Large particle gum 2 60 350 12 684.592 0.774 9 spherical salt arabic sample 9 Embodiment Large particle gum 2 45 350 8 604.715 0.154 10  spherical salt arabic  sample 10 Embodiment Large particle gum 2 55 350 8 893.569 0.892 11  spherical salt arabic  sample 11 Embodiment Large particle gum 2 75 350 8 628.939 0.528 12  spherical salt arabic  sample 12

(23) As can be seen from Table 1, compared with the granular salt in comparative samples 1-2, the particle sizes of the large-particle spherical salt samples 1-12 are significantly increased, and the sphericities are also significantly improved under the conditions of well-controlled stirring rate, temperature, evaporation duration and the like.

(24) Comparing the large particle spherical salt samples 1 to 3, it can be seen that adding more gum arabic increases the particle size and sphericity of the large particle spherical salt, but when the amount of gum arabic increases beyond a certain amount, the particle size and sphericity are reduced. Comparing the large particle spherical salt samples 2 and 4-6, it can be seen that the particle size and sphericity of the large particle spherical salt can be increased by properly increasing the stirring rate during the evaporation process, but the particle size and sphericity can decrease when the stirring rate increases beyond a certain rate. Comparing the large-particle spherical salt samples 2 and 7-9, it can be seen that when the evaporation time is less than the ideal length, the crystals are not completely formed, and the particle size and the sphericity of the crystals are relatively low. When the evaporation time is longer than ideal, a large number of crystals collide and wear, and the particle size and the sphericity of the crystals are relatively low. When the evaporation duration is 8 hours, the sphericity of the crystals is the best, and the particle size is the largest. Comparing the large-particle spherical salt samples 2 and 10-12, it can be seen that the evaporation temperature has a great influence on the particle size and sphericity of the large-particle spherical salt, when the temperature is less than ideal, the nucleation and growth of the crystal is relatively difficult, leading to relatively small particle size and sphericity of the crystal, a relatively low yield and relative difficulty for actual production. When the temperature is relatively high, the particle size and sphericity are relatively low due to over-evaporation Under ideal temperature conditions, the sphericity of the salt reached as high as 0.904 at an evaporation temperature of 60° C., and when the evaporation temperature was slightly decreased to 55° C., the sphericity still reached 0.892.

Embodiment 13

(25) The granular salt reference sample 1, the granular salt reference sample 2, the large-particle spherical salt sample 2 and the large-particle spherical salt sample 6 were respectively stored at an ambient temperature of 23° C. and an ambient humidity of 15% for 30 days, and each sample was observed. The granular salt reference sample 1 and the granular salt reference sample 2 showed caking phenomena of different degrees, but the large-particle spherical salt sample 2 and the large-particle spherical salt sample 6 had no obvious caking phenomenon. In particular, the large-particle spherical salt sample 2 shows almost no caking phenomenon and has good fluidity, and the reason for the phenomenon is that the spherical salt has a smaller contact area and better fluidity than a cubic salt crystal. Also, the spherical salt prepared by this invention has larger particle size, which does not easily aggregate and agglomerate