JP2003174855A - Method for producing salt from seawater - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for producing salt from seawater intended for extremely easily and economically preventing a condition that calcium carbonate and calcium sulphate are separated from salt and firmly stick to the outer surface of a drum when bringing the salt to burnt salt. <P>SOLUTION: This method for producing the salt comprises scattering salt powder from a salt scattering nozzle 30 to the outer surface of a rotating drum 2 before spraying seawater from a nozzle 14. Scatter of the powder salt is done in a place just before the place to be sprayed with seawater. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing high-quality salt from seawater with good productivity using a rotary drum dryer.

[0002]

2. Description of the Related Art As a salt production method of this kind, the present applicant has already provided a method as disclosed in Japanese Patent No. 3077062. In this method, the inside of a first rotary drum dryer having a double-cylinder structure and a second rotary drum dryer having a similar double-cylinder structure are communicated with each other so that the flame from the burner is discharged. The outer cylinder of the first rotary drum dryer is blown into the space between the outer cylinder and the inner cylinder to heat the outer cylinder from the inside, and the outer cylinder of the second rotary drum dryer is also heated from the inside. Meanwhile, seawater is sprayed onto the outer surface of the rotating outer cylinder of the first rotary drum type dryer to evaporate and condense water, and the concentrated salt water is recovered to rotate the second rotary drum type dryer. The water is evaporated by spraying on the outer surface of the outer cylinder, and the salt content adhering to the outer surface of the outer cylinder is peeled off and collected.

In this method, seawater is first concentrated in the first rotary drum dryer and then converted into so-called roasted salt in the second rotary drum dryer having the same structure, so that productivity is improved and thermal efficiency is improved. Is also good.

[0004]

However, in this case, since the seawater recovered from the first rotary drum type dryer is concentrated, it is heated by the second rotary drum type dryer when the salt is roasted. Causes calcium carbonate, calcium sulfate, etc. to separate and firmly adhere to the outer surface of the drum (outer surface of the outer cylinder),
There is a problem in that not only the layer cannot be peeled off from the outer surface of the drum, but the layer is gradually thickened with the lapse of time to reduce the productivity, and also the quality of the salt as a product is reduced.

Therefore, an object of the present invention is to make it possible to economically prevent a situation in which calcium carbonate, calcium sulfate, etc. are separated and firmly fixed to the outer surface of the drum when the salt is roasted, by a very simple method. Is to

[0006]

The present invention relates to a method for producing salt by spraying seawater onto the outer surface of a rotating drum which is heated from the inside to evaporate the salt, and collecting the salt adhering to the outer surface to produce salt. It is characterized in that the outer surface of the rotating drum is sprinkled with powdered salt before spraying seawater.

According to the present invention, seawater is directly sucked onto the outer surface of the rotary drum because the powder salt sprinkled on the outer surface of the rotary drum is heated and dried. Therefore, calcium carbonate and calcium sulfate will not stick to the outer surface of the drum.

It is effective to spray the powdered salt at a position immediately before spraying seawater. As for the powdered salt to be sprinkled, if the salt that has adhered to the outer surface of the rotary drum is recovered, the quality uniformity can be maintained. Seawater sprayed onto the outer surface of the rotary drum when sprinkling the powdered salt is effectively concentrated in the previous step, but even in the case of unconcentrated seawater, the fixation of calcium carbonate, calcium sulfate, etc. can be prevented.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, embodiments of the present invention will be described in detail with reference to the drawings.

1, 2 and 3 show the schematic construction of an embodiment of the present invention. In FIG. 1, a first rotary drum type dryer 1 and a second rotary drum type dryer 2 are installed side by side in series.

Each of the dryers 1 and 2 rotatably supports a horizontally elongated cylindrical metal rotary drum (drum body) 3 by bearings 4 at both ends thereof, and is provided on the outer periphery of one end of each rotary drum 3. The rotating drum 3 is driven to rotate in the arrow direction by the motor 6 by winding the chain 8 between the sprocket wheel 5 and the sprocket wheel 7 on the motor 6 side.

As shown in FIGS. 2 and 3, each rotary drum 3 has a double cylindrical structure composed of an outer cylinder 3a and an inner cylinder 3b. Both ends of the inner cylinder 3b are closed, but the outer cylinder 3a Both ends are open. One end of the first dryer 1 is connected to the heat source 10 by the horn 9, and the rotary drum 3 of the first dryer 1 is connected.
The heating medium (water vapor, flame, heating gas, etc.) from the heat source 10 is directly blown into the space between the outer cylinder 3a and the inner cylinder 3b.

Further, the first dryer 1 and the second dryer 2 are connected to each other at the intermediate portion between the outer cylinder 3a and the inner cylinder 3b by a connection horn 11, and the second dryer 2 has A chimney 12 for exhaust is connected to the opposite side.

A horizontally long seawater spray nozzle 13 for spraying seawater in a spray form is installed parallel to the axis of the rotary drum 3 at a position facing the upper outer periphery of the rotary drum 3 of the first dryer 1. Further, a horizontally long nozzle 14 for spraying salt water is also provided at a position facing the upper outer periphery of the rotary drum 3 of the second dryer 2 so as to spray the salt water after seawater concentration by the first dryer 1 in the same manner. , Is installed parallel to the axis of the rotary drum 3. The nozzles 13 and 14 have a large number of injection holes arranged horizontally.

Further, in the second dryer 2, a horizontally long nozzle for spraying the powder to the outer surface of the rotary drum 3 immediately before spraying the salt water after concentration of the seawater from the salt spray nozzle 14. 30 are arranged. That is,
The salt spraying nozzle 30 is installed closer to the salt spray nozzle 14 in a direction opposite to the rotation direction of the rotary drum 3 than that. Further, a horizontally long stripping device 15 is disposed on the rotation direction side of the rotary drum 3 with respect to the salt spray nozzle 14 in order to strip salt that has adhered to the outer surface of the rotary drum 3. Since the stripper 15 strips salt in a state where water is evaporated as much as possible, it is preferable to dispose the stripper 15 as far as possible from the position of spraying salt water by the nozzle 14 in the rotating direction of the rotary drum 3.

Seawater taken from the sea is temporarily stored in a seawater tank 16 in a seawater spray nozzle 13 of the first dryer 1, filtered by a filtration tank 17, and then supplied by a water pump 18. . Since the amount of seawater sprayed by the nozzle 13 is automatically adjusted according to the surface temperature of the rotary drum 3 of the first dryer 1, the temperature sensor 1 is provided on the heating medium blowing side.
9 is arranged, and the water feed pump 18 (or electromagnetic valve) is automatically controlled by the signal of the temperature sensor 19. A salt water recovery tray 20 is arranged below the first dryer 1.

In the first dryer 1, seawater is sprayed from the seawater spray nozzle 13 onto the outer surface of the rotating rotary drum 3, and the seawater is rapidly heated by the rotary drum 3. The water content is evaporated and becomes concentrated salt water, which flows down to the salt water recovery tray 20 through the hopper 20a.

The salt water spraying nozzle 21 supplies the salt water spray nozzle 21 of the second dryer 2 with the salt water recovered in the salt water recovery tray 20. In order to automatically adjust the amount of salt water sprayed by the nozzle 14 according to the surface temperature of the rotary drum 3 of the second dryer 2, a temperature sensor 22 is arranged on the heating medium blowing side, and water is sent by a signal from the temperature sensor 22. The pump 21 (or solenoid valve) is automatically controlled. Second
A screw conveyor 23 is arranged below the dryer 2.

In the second dryer 2, salt water is sprayed from the seawater spray nozzle 14 onto the outer surface of the rotating rotary drum 3, and immediately before that, the salt spray nozzle 3 is sprayed.
Since the powder salt is sprinkled on the outer surface of the rotary drum 3 from 0, the salt water sprayed from the seawater spray nozzle 14 is absorbed by the powder salt sprinkled on the outer surface of the rotary drum 3, and at the same time, the rotary drum 3 The metal surface is rapidly heated to evaporate water, and become salted to adhere to the outer surface of the rotating drum 3. Then, after being dried on the rotary drum 3, it is peeled off by the peeling device 15 and dropped into the screw conveyor 23 through the hopper 23a to be collected. A part of the recovered salt content is reused as powdered salt sprayed from the salt spraying nozzle 30, but most of the remaining salt is purified as salt in a purification processing unit (not shown).

Above the first dryer 1 and the second dryer 2, a steam recovery unit 2 for recovering exhaust steam generated by evaporation of seawater.
4 ・ 25 are arranged.

In the above-mentioned equipment, the seawater taken from the sea and stored in the seawater tank 16 is filtered by the filtration tank 17
The first dryer while automatically adjusting the flow rate in accordance with the temperature of the first dryer 1 (the flow rate is reduced when the temperature is low, and the flow rate is increased when the temperature is high) after being filtered by The outer surface of the rotating rotating drum 3 of No. 1 is sprayed from the nozzle 13. A large amount of water evaporates on the rotary drum 3 and is recovered by the steam recovery device 24, whereby the seawater is concentrated and flows down to the salt water recovery tray 20.

The salt water concentrated and collected in the salt water recovery tray 20 is automatically adjusted in flow rate according to the temperature of the second dryer 2 while the outer surface of the rotating drum 3 of the second dryer 1 is rotated. Is sprayed from the nozzle 14. Since the sprayed salt water soaks into the powdered salt sprinkled on the outer surface of the rotary drum 3 immediately before, separation and fixation of calcium carbonate, calcium sulfate, etc. due to rapid heating is prevented. The salt water soaked in the powdered salt is heated together with the powdered salt on the metal surface of the rotating drum 3 at a temperature of 100 ° C. or higher, and the water content evaporates at once, and the salt content becomes a baked salt and adheres to the metal surface. The deposited salt is dried on the metal surface, and then the stripper 15
Is peeled off, dropped into the screw conveyor 23, and conveyed to the refining processing section. The exhaust steam recovered by the steam recoverers 24 and 25 is cooled and recovered as fresh water.

In the above-described embodiment, the two rotary drum dryers 1 and 2 were used to once concentrate the seawater and then produce the roasted salt, but the concentration step may be omitted. Another embodiment of the present invention shown in FIG. 4 is an example thereof.
The dryer 1 is omitted.

That is, the seawater tank 16 which takes water from the sea
After filtering the seawater stored in
While automatically adjusting the flow rate according to the temperature of the dryer 2 (the flow rate is decreased when the temperature is low, the flow rate is increased when the temperature is high), the nozzle 1 is formed on the metal surface of the rotating rotary drum 3.
While spraying seawater from 4, the powdered salt was sprinkled on the metal surface of the rotating drum 3 immediately before that, and seawater was allowed to soak into the salt, and the baked salt produced on the metal surface of the rotating drum 3 was peeled off by the peeling device 15. Then, it is conveyed to the refining processing section by the screw conveyor 23.

[0025]

As described above, according to the present invention, seawater is sucked into the powder salt sprinkled on the outer surface of the rotary drum, and the seawater is heated and dried.
A situation in which seawater does not come into direct contact with the outer surface of the rotating drum and therefore calcium carbonate, calcium sulfate, etc. are separated and firmly fixed to the outer surface of the drum can be economically prevented by a very simple method.

As the powdered salt to be sprinkled, it is possible to maintain the uniformity of quality by using the salt collected from the outer surface of the rotary drum.

[Brief description of drawings]

FIG. 1 is a system configuration diagram of an embodiment of the present invention.

FIG. 2 is a schematic sectional view of a first dryer in the above.

FIG. 3 is a schematic sectional view of a second dryer.

FIG. 4 is a system configuration diagram of another embodiment of the present invention.

[Explanation of symbols]

1 First rotary drum dryer 2 Second rotary drum dryer 3 rotating drums 3a Outer cylinder 3b inner cylinder 4 bearings 5 sprocket wheels 6 motor 7 sprocket wheel 8 chains 9 horns 10 burners 11 connection horn 12 chimney 13 Seawater spray nozzle 14 Salt spray nozzle 15 Peeler 16 Seawater tank 17 Filtration tank 18 Water pump 19 Temperature sensor 20 Salt water recovery tray 21 Water pump 22 Temperature sensor 23 Screw conveyor 24 ・ 25 Steam collector 30 salt spray nozzle

Claims (4)

[Claims] 1. A method for producing salt by spraying seawater onto an outer surface of a rotating drum, which is heated from the inside to evaporate the salt, to collect salt, thereby producing salt. A method for producing salt from seawater, which comprises spraying powdered salt before spraying seawater. 2. The method for producing salt from seawater according to claim 1, wherein the powdered salt is sprinkled at a position immediately before the spraying of seawater. 3. The method for producing salt from seawater according to claim 1 or 2, characterized in that, as the powdered salt to be sprinkled, the salt collected from the outer surface of the rotating drum is used. 4. The seawater sprayed on the outer surface of the rotating drum is
The method for producing salt from seawater according to claim 1, 2 or 3, wherein the salt is concentrated.