Washing salt manufacturing method and washing salt manufacturing equipment

Abstract

To provide a method and equipment for producing washing salt, capable of producing high-quality washing salt with high cleanliness by effectively removing foreign matter adhering to solar salt. [Solution] Raw salt, which is solar salt, is ultrasonically cleaned in a liquid.

Description

[Technical Field]

[0001] The present invention relates to a method and equipment for producing washed salt from raw salt, i.e., solar salt. [Background technology]

[0002] Washed salt is a product made by, for example, washing imported solar salt with saturated brine to separate and remove foreign matter such as sand that has adhered to the crystal surface, with an average particle size of about 3 mm, and then dehydrating, drying, crushing (some salt is uncrushed), and packaging it (see, for example, Patent Document 1). This washed salt is distributed as a general-purpose product for the primary processing of soy sauce, marine products, etc., and as a highly cleaned refined product for direct use in food. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent No. 6859476 Summary of the Invention [Problem to be solved by the invention]

[0004] In the production of washed salt, as described above, solar salt is washed to remove foreign matter adhering to the crystal surface, but the degree of cleanliness is not necessarily sufficient.

[0005] The object of the present invention is to provide a method and equipment for producing washing salt that can effectively remove foreign matter adhering to solar salt and produce high-quality washing salt with high cleanliness. [Means for solving the problem]

[0006] The inventors discovered that ultrasonic cleaning can be used to effectively remove foreign matter adhering to solar salt, thereby producing high-quality washed salt with a high level of cleanliness, and thus completed the present invention.

[0007] That is, the present invention is as follows. [1] A method for producing washed salt, characterized by ultrasonically cleaning raw salt, which is solar salt, in a liquid.

[0008] [2] The method for producing washing salt according to [1] above, characterized in that raw salt is ultrasonically washed while being flowed.

[0009] [3] A method for producing washed salt according to [1] or [2] above, characterized in that raw salt is charged into a tank and ultrasonically cleaned while being continuously transported by a conveyor equipped with a sunshade placed in the tank.

[0010] [4] A method for producing washed salt according to [3] above, characterized in that the raw salt is ultrasonically cleaned using a plurality of ultrasonic generators arranged on the outside of the bottom of the tank along the direction in which the raw salt is transported.

[0011] [5] The method for producing washing salt according to any one of the above [1] to [4], wherein the liquid is water. [6] The method for producing washing salt according to any one of the above [1] to [4], wherein the liquid is brine. [7] The method for producing washing salt according to any one of [1] to [4] above, wherein the liquid is warm brine obtained by heating brine. [8] The method for producing washing salt according to [7] above, wherein the temperature of the warm brine is 35 to 45°C.

[0012] [9] A method for producing table salt, characterized in that the cleaning solution used in ultrasonic cleaning in the method for producing washed salt according to any one of [1] to [8] above is used as part of the raw material for salt production using seawater as the raw material.

[0013]

[10] a tank into which raw salt, which is sun-dried salt, is introduced at one end and discharged at the other end; a conveyor with a sunshade disposed in the tank and transporting raw salt introduced into the tank from one side to the other side; a plurality of ultrasonic generators arranged on the outside of the bottom of the tank from one side to the other side of the tank; A washed salt manufacturing facility characterized in that raw salt placed in the tank is ultrasonically cleaned while being continuously transported by the conveyor. [Effects of the Invention]

[0014] According to the present invention, it is possible to provide a method and equipment for producing washing salt that can effectively remove foreign matter adhering to solar salt and produce high-quality washing salt with high cleanliness. [Brief explanation of the drawings]

[0015] [Figure 1] 1 is an explanatory diagram of a washing salt manufacturing equipment according to a first embodiment of the present invention. FIG. [Figure 2] FIG. 2 is a partially enlarged explanatory view showing the washing salt manufacturing equipment in use. [Figure 3] The results show the degree of contamination of filter paper after dissolution and filtration tests of various salts. (a) is Mexican solar salt, (b) is Australian solar salt, (c) is Company A's washed salt, and (d) is Company B's washed salt after dissolution and filtration tests. [Figure 4] The results show the degree of contamination of filter paper after dissolution and filtration tests of various salts. (a) is filter paper washed with saturated brine at 8°C, (b) is ultrasonically cleaned with saturated brine at 8°C, and (c) is filter paper after ultrasonically cleaned with saturated brine at 40°C. DETAILED DESCRIPTION OF THE INVENTION

[0016] The method for producing washed salt of the present invention is characterized by ultrasonically washing raw salt, which is solar salt, in a liquid.

[0017] The raw salt (raw material salt) of the present invention is solar salt, which is obtained, for example, by drawing seawater into salt fields and evaporating the water with solar heat and wind to crystallize the salt. Most solar salt is imported from overseas, and foreign matter such as sand adheres to the crystal surface.

[0018] Examples of the liquid used in the present invention include water, brine, and warm brine obtained by heating brine. To effectively remove foreign matter adhering to raw salt, it is preferable to use warm brine. The temperature of the warm brine is preferably 35 to 45°C, and more preferably 38 to 45°C. The brine preferably has a salt concentration of 300 g / L or more, and more preferably 310 g / L or more. Specifically, for example, ion brine (salt concentration of about 180 g / L) or saturated brine (salt concentration of about 320 g / L) produced using an ion exchange membrane (in an existing salt production plant) when producing salt from seawater as a raw material can be used.

[0019] The mass ratio (addition ratio) of raw salt to liquid during washing depends on the salt concentration of the liquid, but is preferably about 1:0.5 to 5.0, and more preferably about 1:0.8 to 2.0.

[0020] The method for producing washing salt of the present invention can effectively remove foreign matter adhering to raw salt by the disruptive force (cavitation) of bubbles generated by ultrasonic waves, thereby producing high-quality washing salt with high cleanliness.

[0021] Here, the ultrasonic cleaning is preferably carried out while the raw salt is flowing. The raw salt may be stirred with a stirring blade or moved in one direction in any manner as long as it moves through the liquid without being fixed in a specific position. By subjecting the raw salt to ultrasonic cleaning in such a manner, foreign matter adhering to the raw salt can be removed more effectively.

[0022] The raw salt can be washed in a continuous or batch manner, but the continuous manner is preferred from the viewpoint of production efficiency. Examples of continuous cleaning methods include a method in which raw salt is continuously (including intermittently; the same applies below) loaded into a long, horizontal tank, and the loaded raw salt is ultrasonically cleaned while being continuously transported by a conveyor (conveyor with fins) with fins (slats) placed inside the tank, and then continuously discharged. Another method involves continuously loading raw salt into a long, vertical tank, and ultrasonically cleaning the loaded raw salt while stirring it with stirring blades placed inside the tank, and then continuously discharged. The raw salt may be loaded into the tank independently of the liquid, or together with the liquid. When using equipment equipped with a conveyor with fins, the raw salt is stirred and mixed, i.e., flows, in a vortex between adjacent fins on the conveyor due to the propulsion force of the fins and the frictional force with the bottom of the tank, allowing for efficient ultrasonic cleaning (see Figures 1 and 2).

[0023] Furthermore, as a batch-type cleaning method, there can be mentioned an embodiment in which the raw salt is not discharged in the same manner as in the continuous cleaning method described above. Although the foreign matter removed from the raw salt remains in the cleaning solution, it is unlikely to reattach to the raw salt, so there is no need to replace the cleaning solution every time.

[0024] The cleaning solution used in the ultrasonic cleaning in the above-mentioned method for producing washed salt can be used as part of the raw material for salt production, for example, by using seawater as the raw material, thereby achieving effective use of resources. Examples of salt production methods include the conventionally known ion exchange membrane salt production method and the dissolution and recycling method, with the ion exchange membrane salt production method being preferred from the standpoint of safety. Examples of this ion exchange membrane salt production method include taking seawater, concentrating it using an ion exchange membrane, treating the resulting ion brine in an evaporator, and evaporating the water to produce salt crystals.

[0025] An example of a manufacturing facility for washed salt of the present invention to which the above-mentioned manufacturing method for washed salt can be applied is a facility that includes a tank into which raw salt, which is solar salt, is fed into one side and discharged from the other side, a conveyor with a sun that is placed inside the tank and transports the raw salt fed into the tank from one side to the other, and a plurality of ultrasonic generators that are placed on the outside bottom of the tank from one side to the other, and ultrasonically cleans the raw salt fed into the tank while continuously transporting it on the conveyor.

[0026] Hereinafter, a washing salt manufacturing facility according to one embodiment of the present invention will be described with reference to the drawings, in which Fig. 1 is an explanatory diagram of the washing salt manufacturing facility according to one embodiment of the present invention, and Fig. 2 is an enlarged explanatory diagram of a part of the washing salt manufacturing facility. As shown in Figure 1, the washed salt manufacturing equipment 10 includes a tank 11 into which raw salt, which is solar salt, is placed, a conveyor 12 placed inside the tank 11, and a plurality of ultrasonic generators 13 placed on the outside bottom of the tank 11.The raw salt placed in the tank 11 is ultrasonically cleaned while being continuously transported by the conveyor 12. A detailed explanation is provided below.

[0027] Tank 11 is long in the direction of transport of the raw salt (horizontal direction), with a raw salt inlet chute 14 provided at the top of one side (left side in Figure 1: upstream side) and a slurry outlet 15 facing downward on the other side (right side in Figure 1: downstream side), so that raw salt is continuously introduced into one side and washed raw salt is continuously discharged from the other side. Note that raw salt can be introduced into tank 11 together with liquid from inlet chute 14, but the raw salt and liquid can also be introduced into tank 11 from different locations.

[0028] The length of the tank is not particularly limited and can be set depending on, for example, the amount of raw salt to be processed and the required cleanliness of the washed salt, and is, for example, about 1 to 5 m, preferably about 1 to 3 m. The inner width of the tank is, for example, about 20 to 100 cm, preferably about 20 to 50 cm. The depth of the tank is, for example, about 10 to 50 cm, preferably about 10 to 20 cm. The material of the tank may be any material that can prevent corrosion due to salt, and for example, SUS316L is preferable.

[0029] As shown in Figures 1 and 2, the conveyor 12 has a belt 17 with a sun 16 attached, and is a device that sends raw salt accumulated at the bottom of the tank 11 from one side to the other while scraping it with the sun 16. Specifically, the conveyor 12 has a base (not shown), pulleys 18 and 19 rotatably mounted on both ends of the base, and a belt 17 stretched around the pulley 18 and the pulley 19, with multiple suns 16 mounted at regular intervals on the outer periphery. The suns 16 are mounted on the outer periphery of the belt 17 so as to protrude vertically outward, but may also be inclined toward the front or rear of the conveying direction. Furthermore, although the tip of the sun 16 may contact the bottom surface of the tank 11, it is preferable that a gap be formed between the tip of the sun 16 and the bottom surface of the tank 11 (non-contact) in consideration of damage to the sun 16.

[0030] The ultrasonic generator 13 has a vibrator (not shown) and generates ultrasonic waves by vibrating the vibrator. Note that, although a frequency of, for example, 15 kHz to 3 MHz can be used, it is preferable to use a low frequency of about 15 to 50 kHz, which enables relatively powerful cleaning.

[0031] A plurality of ultrasonic generators 13 are arranged along the direction of conveyance of the raw salt in a water tank 20 filled with water and provided outside the bottom of tank 11. In order to efficiently transmit the ultrasonic waves generated by ultrasonic generators 13 to the raw salt in tank 11, it is preferable that the thickness of the bottom of tank 11 is thin, for example, about 2 mm or less. As a result, the raw salt put into the tank 11 can be ultrasonically cleaned while being continuously transported and flowed by the conveyor 12 arranged inside the tank 11.

[0032] Although the cleaning solution used in ultrasonic cleaning can be disposed of as waste, as mentioned above, from the viewpoint of effective resource utilization and environmental conservation, it is preferable to use it as part of the raw material for salt production, which produces table salt from seawater. For example, when ionized brine is used as the liquid for producing wash salt, a dissolution loss of, for example, about 5 to 10 mass% of the salt occurs during the washing of the raw salt, and it is preferable to send this liquid to a salt production facility where the salt is recrystallized to produce a product. [Example]

[0033] Next, examples carried out to confirm the effects of the present invention will be described.

[0034] [Reference exam] 1. Test Method Dissolution and filtration tests were conducted using solar salt and commercially available washed salt to confirm the degree of contamination. Here, solar salt from Mexico and Australia was used as the solar salt, and washed salt from companies A and B was used as the washed salt. 100 g of each of the solar salt and washed salt was dissolved in purified water, filtered through a glass fiber filter, and evaluated by measuring the color difference (ΔE) using a colorimeter. The larger the ΔE value, the greater the degree of contamination (the same applies below).

[0035] 2. Test Results For solar salt produced in Mexico, ΔE was 39.1 (see Figure 3(a)), and for solar salt produced in Australia, ΔE was 30.8 (see Figure 3(b)), confirming that unwashed solar salt is highly polluted. On the other hand, the cleaning salts available on the market had ΔE = 4.3 (see Figure 3(c)) from Company A and ΔE = 18.5 (see Figure 3(d)) from Company B, confirming that the degree of contamination was reduced to a certain extent compared to solar salt.

[0036] [Actual exam] 1. Test Method 1-1. Cleaning (a) Washing with saturated brine at 8°C (reference example) 100g of Mexican solar salt was placed in a 500cc beaker, and 100cc of saturated brine with a salt concentration of 26% by mass and a temperature of 8°C was added. The mixture was stirred for 1 minute with a Teflon (registered trademark) stirring rod, after which the supernatant liquid was discarded and 100cc of clean saturated brine was added again. This washing procedure was repeated 10 times.

[0037] (b) Washing using saturated warm brine at a temperature of 8°C and ultrasound (Example 1) A 500cc beaker containing 100g of Mexican solar salt and 100cc of saturated warm brine at 8°C with a salt concentration of 26% by mass was immersed in water in the bath of an ultrasonic cleaning device and stirred with a Teflon (registered trademark) stirring rod for 3 minutes. This cleaning operation was performed once. The ultrasonic cleaning device used was a Phoenix III manufactured by Kaijo Co., Ltd. This ultrasonic cleaning device has a low frequency of 27kHz and a 10-level output adjustment function, and this cleaning was performed at output level 9.

[0038] (c) Washing using saturated warm brine at 40°C and ultrasound (Example 2) A 500cc beaker containing 100g of Mexican solar salt and 100cc of saturated warm brine adjusted to a salt concentration of 26% by mass and heated to 40°C was immersed in water in the bath of an ultrasonic cleaning device and stirred with a Teflon (registered trademark) stirring rod for 3 minutes. This cleaning operation was carried out once. The ultrasonic cleaning device used was the same as above, and the main cleaning was carried out at output level 9.

[0039] 1-2. Measuring the degree of dirt (common) After the above-mentioned washing operation was completed, the salts were transferred to a 1000 μm sieve to separate the solid and liquid. 100 g of each washed salt on the sieve was dissolved in purified water and filtered through a glass fiber filter. The color difference (ΔE) was measured and evaluated using a colorimeter.

[0040] 2. Test Results When cleaning was performed using saturated brine at 8°C without ultrasonic cleaning, the result was ΔE = 5.9 (see Figure 4(a)), which was worse than the result using Company A's cleaning salt. However, by performing ultrasonic cleaning using saturated warm brine at 8°C, the effect of removing attached foreign matter improved, resulting in ΔE = 3.9 (see Figure 4(b)), which was better than the result using Company A's cleaning salt.

[0041] Furthermore, by using saturated warm brine heated to 40°C for ultrasonic cleaning, the value of ΔE was reduced to an extremely low value of 1.8 (see Figure 4(c)), demonstrating a significant improvement in the effectiveness of removing adhering foreign matter. [Industrial Applicability]

[0042] The present invention is industrially useful because it can effectively remove foreign matter adhering to solar salt and produce high-quality washed salt with high purity. [Explanation of symbols]

[0043] 10. Washing salt manufacturing facility 11 tanks 12 Conveyor 13 Ultrasonic generator 14 Throw-in shots 15 Outlet 16 Sun 17 Belt 18 Pulley 19 Pulley 20 aquarium

Claims

1. This method for producing washed salt is characterized by charging raw salt, which is solar salt, into a tank, and then ultrasonically cleaning the charged raw salt at 15 to 50 kHz in brine or warm brine having a salt concentration of 300 g / L or more while continuously transporting the raw salt on a conveyor equipped with a sun located in the tank.

2. 2. The method for producing washing salt according to claim 1, wherein the raw salt is ultrasonically washed while being flowed.

3. 2. A method for producing washed salt according to claim 1, wherein the raw salt is ultrasonically cleaned by a plurality of ultrasonic generators arranged on the outside of the bottom of the tank along the direction in which the raw salt is transported.

4. 2. The method for producing washing salt according to claim 1, wherein the temperature of the warm brine is 35 to 45°C.

5. 3. The method for producing salt according to claim 1, wherein the cleaning solution used in the ultrasonic cleaning is used as part of the raw material for salt production using seawater as the raw material.

6. A tank into which raw salt, which is sun-dried salt, is put in one side and discharged from the other side; a conveyor with a sunshade disposed in the tank and transporting raw salt introduced into the tank from one side to the other side; a plurality of ultrasonic generators arranged on the outside of the bottom of the tank from one side to the other side of the tank, each generating ultrasonic waves of 15 to 50 kHz; A washed salt manufacturing facility characterized in that raw salt placed in the tank is ultrasonically cleaned while being continuously transported by the conveyor.

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