Small-grain salt manufacturing method and small-grain salt manufacturing equipment

Abstract

To provide a method and equipment for producing small grain salt, which can economically produce small grain salt and effectively reduce caking. The system has a slurry preparation step in which a slurry is prepared using saltwater as a raw material, and a dehydration and drying step in which the slurry prepared in the slurry preparation step is dehydrated and dried. The slurry preparation step is carried out in a 5-30 m3 tank with a circulation path 16 connecting the upper and lower parts and a heater 17 for heating the circulation path 16. 3 The vessel 15 is used, and a slurry formed from salt water in the vessel 15 is continuously circulated from the bottom to the top of the vessel 15 via a circulation path 16, with the solid content concentration being in the range of 40 to 70% by volume, and then discharged from the vessel 15.

Description

[Technical Field]

[0001] The present invention relates to a method for producing small-grain salt using brine as a raw material, and to an equipment for producing small-grain salt. [Background technology]

[0002] Demand for small-grain salt is increasing for use in the food industry in soups, seasonings, etc. Such small-grain salt is generally produced by crushing and classifying salt, but this has the disadvantage of low yields of around 10 to 20% by mass, which increases production costs, and also tends to caking due to poor crystal shape caused by crushing (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 5-345610 Summary of the Invention [Problem to be solved by the invention]

[0004] The object of the present invention is to provide a method and equipment for producing small-grain salt that can improve yield and produce small-grain salt at low cost, while effectively reducing caking of the small-grain salt. [Means for solving the problem]

[0005] The inventors discovered that by using a special container (device) to circulate brine as a slurry with a predetermined solids concentration to produce small-grain salt, it is possible to improve yield and reduce production costs, as well as to stabilize the crystal shape and effectively mitigate caking, thereby completing the present invention.

[0006] That is, the present invention is as follows. [1] A slurry preparation step of preparing a slurry using salt water as a raw material; A dehydration and drying step of dehydrating and drying the slurry prepared in the slurry preparation step, The slurry preparation step includes: A circulation path connecting the upper and lower parts and a heater for heating the circulation path, with a volume of 5 to 30 m 3 A vessel is used, and a slurry formed from the salt water in the vessel is continuously circulated from the bottom to the top of the vessel through the circulation path at a solid content concentration in the range of 40 to 70% by volume, and then discharged from the vessel. A method for producing small grain salt.

[0007] [2] The circulation path of the container has a branch path, and a pump is provided in the branch path, The method for producing small grain salt described in [1] above, characterized in that the pump takes in slurry from the circulation path into the branch path and discharges it into the circulation path, thereby promoting nucleation of salt.

[0008] [3] The method for producing small-grained salt according to [1] or [2] above, wherein the average particle size of the salt produced is 250 μm or less.

[0009] [4] A slurry is prepared using saltwater as the raw material. The volume is 5 to 30 m. 3 A container of a circulation path that connects the upper and lower parts of the container and circulates a slurry formed from the salt water from the lower part to the upper part of the container; a heater provided in the circulation path and configured to heat the slurry flowing through the circulation path; A branch path provided in the circulation path; a pump provided in the branch channel to take in slurry from the circulation channel into the branch channel and discharge it into the circulation channel; A small grain salt manufacturing facility comprising a slurry preparation device comprising:

[0010] [5] The small-grain salt manufacturing equipment described in [4] above further comprises a tank for storing the slurry discharged from the container, the inner surface of which is lined with glass to prevent the salt in the slurry from adhering.

[0011] [6] A small-grain salt manufacturing facility as described in [5] above, characterized in that a dehydration treatment device for dehydrating the slurry and a drying treatment device for drying the salt treated and recovered by the dehydration treatment device are sequentially provided downstream of the tank. [Effects of the Invention]

[0012] According to the present invention, it is possible to provide a method and equipment for producing small-sized salt particles that can produce small-sized salt particles at low cost and that can effectively reduce caking of the small-sized salt particles. [Brief explanation of the drawings]

[0013] [Figure 1] 1 is an explanatory diagram of a small-grain salt manufacturing facility according to one embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0014] The method for producing small-grained salt of the present invention includes a slurry preparation step in which a slurry is prepared using saltwater as a raw material, and a dehydration and drying step in which the slurry prepared in the slurry preparation step is dehydrated and dried. The slurry preparation step is carried out in a 5 to 30 m3 tank having a circulation path connecting the upper and lower parts and a heater for heating the circulation path. 3 The method is characterized in that a slurry formed from salt water in the container is continuously circulated from the bottom to the top of the container via a circulation path at a solid content concentration in the range of 40 to 70% by volume, and then discharged from the container.

[0015] The average particle size of the small-grain salt produced by the manufacturing method of the present invention is preferably 250 μm or less, more preferably 230 μm or less, and even more preferably 200 μm or less. The average particle size in the present invention is the average particle size on a mass basis determined using a robot sifter (sonic vibration type sieving measuring device) and a Rotap type sieve shaker. It is preferable to remove any large particles that may exceptionally occur using a sieve or the like.

[0016] The method for producing small-sized salt particles of the present invention is a novel technique that uses a special container (apparatus) to circulate a slurry with a predetermined solids concentration generated from brine to produce small-sized salt particles. Because the production method of the present invention can produce salt without crushing it, it is possible to efficiently produce small-sized salt particles with a stable cubic crystal shape. Therefore, small-sized salt particles can be produced at low cost, and caking of the salt can be effectively reduced compared to crushed and classified products.

[0017] The method for producing small-grain salt of the present invention may include other processes before, after, or between the slurry preparation process and the dehydration and drying process. Specifically, for example, a raw material preparation process for adjusting the salinity of seawater to obtain brine may be included before the slurry preparation process. Furthermore, a storage process for temporarily storing the slurry may be included between the slurry preparation process and the dehydration and drying process.

[0018] Each step of the present invention will be described below.

[0019] (Raw material preparation process) The raw material preparation step is a step of preparing salt water as a raw material.

[0020] The brine used in the present invention is not particularly limited as long as it is a solution containing salt, and examples thereof include seawater and processed seawater. For example, a portion of the concentrated brine obtained during the salt production process using seawater as the raw material to produce salt can be extracted and used as the raw material. Specifically, it is preferable to use brine obtained by taking seawater, concentrating it using an ion exchange membrane, and treating it in an evaporator. The salt concentration of this brine is preferably 18% by mass to the saturated concentration, and it is preferable to use multiple brines with different concentrations to control the particle size of the small-particle salt produced.

[0021] (Slurry preparation process) The slurry preparation process is a process in which a slurry is prepared using salt water as the raw material (see Figure 1). Small grains of salt are produced in this slurry.

[0022] In the slurry preparation process, a 5 to 30 m3 tank is provided with a circulation path connecting the upper and lower parts and a heater for heating the circulation path. 3 The vessel is used, and a slurry formed from brine in the vessel is continuously circulated from the bottom to the top of the vessel via a circulation path at a solids concentration in the range of 40 to 70% by volume. This allows for efficient production of small-grain table salt.

[0023] Now, if the volume of the container is 5m 3 If the volume is less than 30m, the volume will be too small, resulting in a decrease in salt productivity. 3 When the temperature exceeds 180°C, the particle size of the salt produced tends to become larger. 3 The volume of the container is 5 to 25 m 3 It is preferable to set the distance between the periphery and the ground plane to 5 to 20 m. 3 It is more preferable to set the distance between the periphery and the ground plane to 7 to 20 m. 3 It is more preferable to set the distance between the first and second electrodes to 7 to 15 m. 3 It is particularly preferable to set the following.

[0024] Furthermore, if the solids concentration of the slurry is less than 40% by volume, the particle size of the salt produced will be large, while if the solids concentration of the slurry is more than 70% by volume, the particle size of the salt produced will be too small, resulting in production losses, for example.To suppress the crystal growth rate and more reliably produce small particles, the solids concentration of the slurry is preferably 45 to 70% by volume, more preferably 45 to 65% by volume, even more preferably 50 to 65% by volume, and particularly preferably 50 to 60% by volume.

[0025] As the heater, for example, a heater, steam, or the like can be used, and it is preferable to use a heater using steam as a heat source.

[0026] In addition, since the water content of the raw material evaporates due to the heating of the heater, it is preferable to supply brine of a predetermined concentration in order to maintain the slurry solids concentration within a predetermined range. Specifically, it is preferable to supply brine such as concentrated brine or saturated brine to the circulation path below the heater.

[0027] Furthermore, it is preferable to provide a shunt passage in the circulation passage of the container and a pump in the shunt passage, and to use this pump to take in the slurry flowing through the circulation passage into the shunt passage and discharge it back into the circulation passage, thereby promoting salt nucleation. Specifically, for example, it is preferable to take in the slurry flowing through the circulation passage from an upper part of the heater (downstream of the heater) into the shunt passage and discharge it back to an upper part of the heater (downstream of the heater). This allows for more efficient production of small-grain salt.

[0028] The degree of supersaturation of the slurry that passes through the heater increases, causing nucleation. Furthermore, by removing the slurry flowing through the circulation path from the upper part of the heater, applying impacts with a pump, and returning it to the upper part of the heater, nucleation can be further promoted, enabling the salt to be made into smaller particles. The operation of this pump can be adjusted according to the desired average particle size of the salt; for example, it can be operated continuously or intermittently.

[0029] The slurry is discharged from the vessel while maintaining the solid content of the slurry at 40 to 70% by volume in the vessel. This discharge of the slurry can be performed either continuously or intermittently. Here, the location for measuring the solid content concentration of the slurry is not particularly limited, but it is preferable to extract a portion of the circulating slurry from the circulation path below the heater and measure the solid content.

[0030] The particle size of the salt is preferably measured, for example, using a particle size measuring device before the slurry discharged from the container is sent to the storage step described below. The particle size of the salt can be adjusted by adjusting the solids concentration of the slurry by adjusting the amount of salt water introduced or the amount of slurry discharged, or by operating a pump provided in the shunt flow path.

[0031] (Storage process) The storage process is a process in which the slurry discharged from the container is temporarily stored in a tank (see Figure 1). This allows the slurry to be sent downstream of the storage process without being affected by the amount of slurry discharged from the container.

[0032] (Dehydration drying process) The dehydration and drying process is a process in which the slurry is dehydrated and then dried (see Figure 1). This dehydration process removes most of the water from the slurry, and the drying process removes the remaining water from the dehydrated and recovered salt. This makes it possible to obtain small grain salt.

[0033] The obtained small-sized salt particles are transported to a packaging process by air transport, for example, and then packed in bags or the like and shipped as a product.

[0034] Next, a description will be given of a manufacturing facility for small-sized table salt of the present invention to which the above-mentioned manufacturing method for small-sized table salt can be applied. The manufacturing facility for small-sized table salt of the present invention may be, for example, a facility with a capacity of 5 to 30 m3 for preparing a slurry using brine as a raw material. 3 an apparatus including a container for preparing slurry, a circulation path connecting the upper and lower parts of the container and circulating a slurry formed from salt water from the lower part to the upper part of the container; a heater provided in the circulation path for heating the salt water flowing through the circulation path; a branch path provided in the circulation path; and a pump provided in the branch path for taking in the slurry from the circulation path into the branch path and discharging it back into the circulation path.

[0035] Hereinafter, a manufacturing system for small-grain salt according to one embodiment of the present invention will be described with reference to the drawings, but the present invention is not limited to these embodiments. Here, Fig. 1 is an explanatory diagram of a manufacturing system for small-grain salt according to one embodiment of the present invention. As shown in FIG. 1, a small grain salt manufacturing facility 10 includes a slurry preparation device 11, a tank 12, a dehydration treatment device 13, and a drying treatment device 14, which are arranged in this order. A detailed explanation is provided below.

[0036] (Slurry preparation equipment) The slurry preparation apparatus 11 includes a container 15 for preparing a slurry using saltwater as a raw material and for holding the slurry, a circulation path 16 connecting the upper and lower parts of the container 15, a heater 17 provided in the circulation path 16, a branch path 18 provided in the circulation path 16, and a pump 19 provided in the branch path 18, and adjusts (maintains) the solids concentration of the slurry to 40 to 70 volume % while circulating the slurry. When the operation of the slurry preparation apparatus 11 is started, the temperature of the saltwater in the container 15 is increased by heat source steam supplied into the circulation path 16 until the water in the saltwater evaporates.

[0037] The container 15 has a volume of 5 to 30 m 3 The vessel 15 is a spindle-shaped evaporator, and with its axis aligned vertically, the upper and lower sides of the vessel 15 are connected by a circulation path 16. A heater 17 is provided in the circulation path 16, and a circulation pump 20 is provided below (upstream of) the heater 17. The slurry is circulated from the bottom to the top of the vessel 15 by the circulation path 16 and the circulation pump 20, and the salt water flowing through the circulation path 16 is heated by the heater 17 to evaporate the water, thereby concentrating the slurry.

[0038] Heater 17 raises the temperature of the supplied brine and the slurry liquid in vessel 15. The vapor generated in vessel 15 by this heating is discharged from the upper end of vessel 15 to the outside. Meanwhile, the slurry with a solids concentration of 40 to 70% by volume is discharged from the lower end of vessel 15 to the outside. The brine is preferably supplied to vessel 15 from the inlet of circulation path 16 between heater 17 and circulation pump 20. For example, concentrated brine with a salinity of approximately 18% by mass or mother liquor with a salinity of approximately 25% by mass is preferably used for the brine supply. In other words, using brines of different concentrations allows for more precise adjustment of the solids concentration of the slurry. For example, if the average particle size of the salt is larger than desired, adding concentrated brine can promote nucleation and reduce the particle size.

[0039] The shunt channel 18 is formed by piping connected to the upper part of the heater 17, and is provided with a pump 19 (nucleation pump). As a result, the heated slurry is taken into the shunt channel 18 from the circulation channel 16, subjected to an impact by the pump 19, and then discharged into the circulation channel 16 above the heater 17, promoting the nucleation of the salt and realizing the reduction of salt particles. The discharge port that discharges the slurry from the shunt channel 18 to the circulation channel 16 is provided above (downstream of) the inlet that takes the slurry from the circulation channel 16 into the shunt channel 18. Here, the amount of slurry taken in from the circulation path 16 into the branch channel 18 is not particularly limited, but is preferably about 1 to 10% by volume of the slurry flowing through the circulation path 16, and more preferably 1 to 5% by volume.

[0040] The pump 19 provided in the branch flow path 18 is not particularly limited as long as it is a pump that can apply an impact to the highly supersaturated, high-temperature brine to promote nucleation. For example, it can include a non-positive displacement pump (turbo pump) that rotates an impeller inside a casing to give energy to the liquid, and a positive displacement pump that applies pressure to a liquid within a certain volume to give energy. Examples of non-positive displacement pumps include centrifugal pumps such as centrifugal pumps and turbine pumps, and propeller pumps such as axial flow pumps and mixed flow pumps. Furthermore, examples of positive displacement pumps include reciprocating pumps such as piston pumps, plunger pumps and diaphragm pumps, and rotary pumps such as gear pumps, screw pumps and vane pumps, with centrifugal pumps being particularly preferred.

[0041] (tank) Tank 12 temporarily stores the slurry discharged from container 15. Reference numeral 21 denotes an extraction pump for discharging the slurry from container 15. A stirring blade 22 is provided in tank 12, and by rotating this stirring blade 22 with a motor 23 to stir the slurry, salt in the slurry can be prevented from settling, adhering to the bottom of tank 12, and solidifying.

[0042] The inner surface and bottom of the tank 12 are preferably provided with a glass lining to prevent salt from adhering to the tank. This glass lining is, for example, a glass material baked onto the metal base of the tank, covering the metal surface with glass. If a stainless steel tank were simply used, crystals would adhere and solidify inside the tank, making it impossible to extract the slurry and significantly reducing productivity. Therefore, by providing a glass lining that is less susceptible to crystal adhesion, productivity can be significantly improved.

[0043] (Dehydration treatment device) The dehydration treatment device 13 is a device that receives the slurry stored in the tank 12 and dehydrates it. Reference numeral 24 denotes a liquid-transport pump that sends the slurry in the tank 12 to the dehydration treatment device 13. The dehydration treatment device is not particularly limited as long as it is configured to recover small-grain salt in a slurry form, and examples thereof include a centrifuge, a vacuum dehydrator, a pressure filter (filter press), and a belt press filter, with a centrifuge being particularly preferred.

[0044] (Drying treatment device) Drying device 14 is a device for drying the salt that has been treated and recovered in the dehydration device. Examples of drying devices include a fluidized bed dryer, a vacuum dryer, and a drum dryer, with a fluidized bed dryer being preferred, which uses a heated air layer to float and dry the salt while stirring it. [Example]

[0045] Using the apparatus shown in Figure 1, the solid content of the slurry was adjusted to 55 to 65% by volume, and small-grain salt was produced. 3 It was. As a result, we were able to produce small cubic salt particles with an average particle size of less than 200 μm, with a yield of about 80%. [Industrial Applicability]

[0046] The present invention is industrially useful because it can produce small-grain salt at low cost and can effectively reduce caking of salt. [Explanation of symbols]

[0047] 10. Small grain salt manufacturing facility 11 Slurry preparation device 12 Tank 13 Dehydration treatment equipment 14 Drying treatment equipment 15 Container 16 Circulation path 17 Heater 18 branch flow path 19 Pump (nuclear generating pump) 20 Circulation pump 21 Extraction pump 22 Mixing blade 23 Motor 24 Liquid delivery pump

Claims

1. a slurry preparation step of preparing a slurry using salt water as a raw material; A dehydration and drying step of dehydrating and drying the slurry prepared in the slurry preparation step, The slurry preparation step includes: A 5-30 m3 tank with a circulation path connecting the upper and lower parts and a heater for heating the circulation path. ３ a vessel is used, a slurry formed from the salt water in the vessel is continuously circulated from the bottom to the top of the vessel through the circulation path in a solid content range of 40 to 70% by volume, and the slurry is then discharged from the vessel; Furthermore, the circulation path of the container is provided with a branch path, and the branch path is provided with a pump, and the pump takes in 1 to 10 volume % of the slurry from the circulation path into the branch path and discharges it into the circulation path, thereby promoting nucleation of salt. A method for producing salt having an average particle size of 250 μm or less.

2. Prepare slurry using saltwater as raw material. Volume: 5-30m ３ A container of a circulation path that connects the upper and lower parts of the container and circulates a slurry formed from the salt water from the lower part to the upper part of the container; a heater provided in the circulation path and configured to heat the slurry flowing through the circulation path; A branch path provided in the circulation path; a pump provided in the branch channel to take in slurry from the circulation channel into the branch channel and discharge it into the circulation channel; A facility for producing salt having an average particle size of 250 μm or less, comprising a slurry preparation device comprising:

3. 3. The equipment for producing salt having an average particle size of 250 μm or less as described in claim 2, further comprising a tank for storing the slurry discharged from the container, the inner surface of the tank being lined with glass to prevent adhesion of salt in the slurry.

4. 4. A salt manufacturing facility having an average particle size of 250 μm or less, as described in claim 3, characterized in that a dehydration treatment device for dehydrating the slurry and a drying treatment device for drying the salt treated and recovered in the dehydration treatment device are sequentially provided downstream of the tank.

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