JP2565613B2 - Method and apparatus for producing slaked lime aqueous solution - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and an apparatus for producing an aqueous slaked lime solution. The slaked lime aqueous solution is used to improve tap water.

[0002]

2. Description of the Related Art Conventionally, caustic soda injection, soda ash injection, slaked lime injection, and the like have been known as techniques for preventing red water from tap water. Recently, however, slaked lime injection has attracted attention. Not only does slaked lime not only raise the pH of water, it is said that calcium as the main component is good for health, and the technology to inject slaked lime not as powder but as an aqueous solution has been developed. It has been widely adopted by water purification plants of business entities.

Regarding the continuous production of slaked lime aqueous solution, a method using an apparatus as described in, for example, Japanese Patent Publication No. 63-2890 is known. Japanese Examined Japanese Patent Sho 63-28
In the method described in No. 90, the upper part is a cylindrical type or a rectangular tube type, and the lower part is a water pipe and an insoluble matter take-out port at the bottom part of the inverted truncated pyramid type, which rotates horizontally just above the water pipe. Using a device equipped with a stirring blade and an overflow liquid receiving part with a slaked lime aqueous solution take-out pipe at the upper end of the tank, a slaked lime deposit layer was formed in this tank, and water was stirred at a constant speed from the bottom while stirring at a low speed. It is a method in which the slaked lime aqueous solution is taken out from the upper part by supplying with.

[0004]

However, in a tank such as this device in which only a stirrer is provided in the slaked lime dissolution tank, the rising velocity of water rises in the upper portion of the dissolution tank due to the possibility of carryover of the slaked lime slurry blanket. Water can be supplied only when the flow velocity is at most 0.2 mm / sec. Therefore, for large-scale water purification plants, the rising speed is too low for practical use, and the size of the device must be increased or a large number of devices must be installed, resulting in a large installation area and an excessively high construction cost.

The present invention increases the production rate of the slaked lime aqueous solution per unit time and unit volume by increasing the rising speed of water in the slaked lime dissolution tank while avoiding the loss of the slaked lime fine particles in the tank. The challenge is to achieve miniaturization.

[0006]

In order to solve such a problem, the inventors of the present invention have made earnest studies and, as a result, arrived at the present invention in which a slaked lime fluidized bed height suppressing device is provided inside a slaked lime dissolution tank.

That is, the method for producing a slaked lime aqueous solution according to the present invention has a cylindrical or square tube type dissolution tank, a water supply pipe at the bottom of the tank, a stirring blade at the bottom of the tank and a slaked lime aqueous solution take-out tube at the top of the tank. And, in the slaked lime dissolution device in which the slaked lime fluidized bed height suppressing device is installed above the stirring blades in the tank, after pouring water, a predetermined amount of slaked lime is charged in advance, and while stirring at low speed, from the water supply pipe This is to supply water in an amount so that the rising rate of water in the cylindrical or prismatic portion in the upper part of the tank is 0.25 to 1.2 mm / sec and to take out the slaked lime aqueous solution from the slaked lime aqueous solution extraction pipe.

The apparatus for producing a slaked lime aqueous solution according to the present invention has a cylindrical or prismatic dissolution tank, a water supply pipe at the bottom of the tank, a stirring blade at the bottom of the tank and a slaked lime aqueous solution take-out tube at the top of the tank, and A slaked lime fluidized bed height suppressing device is installed above the stirring blade in the tank.

The present invention will be described in detail below.

The slaked lime aqueous solution manufacturing apparatus used in the present invention is
It has a cylindrical or prismatic dissolution tank, a water supply pipe attached to the bottom of this tank, a slaked lime aqueous solution take-out pipe provided at the top of the tank, and inside this tank, a stirring blade is provided at the bottom and a stirring blade. A slaked lime fluidized bed height suppressing device is attached to the upper part.

When slaked lime is filled in the dissolution tank in advance and filled with water, and then water is supplied from the lower portion of the dissolution tank while stirring, the slaked lime particles are dissolved in the lower portion of the dissolution tank while forming a fluidized bed. The height of the water increases as the water supply speed (the rising speed of water in the tank) increases, and undissolved slaked lime particles may mix into the slaked lime aqueous solution and flow out from the upper part of the tank.
Providing a resistance against the rising water flow in the dissolution tank suppresses the rise of slaked lime particles accompanying the rising water flow. Therefore, by providing such a resistor in the slaked lime dissolution tank, the slaked lime fluidized bed can be kept relatively low even if the rising water flow velocity is increased to some extent, and slaked lime particles can be prevented from flowing out undissolved. . In the present invention, such a resistor is called a fluidized bed height suppressing device.

The fluidized bed height suppressing device provided in the dissolution tank may have any structure as long as it can keep the slaked lime fluidized bed low and prevent outflow of undissolved slaked lime particles. As a preferable suppressing device, two or more inclined plates or one having a structure as shown in FIGS. 3 to 9 is used.

As a typical slaked lime fluidized bed height suppressing apparatus, a slaked lime aqueous solution manufacturing apparatus shown in FIG. 1 in which two or more inclined plates are mounted in a dissolution tank will be described.

In FIG. 1, reference numeral 1 denotes a melting tank having a cylindrical shape or a rectangular tube shape. Preferably, the upper portion is a cylindrical shape and the lower portion is a reverse truncated pyramid shape. Reference numeral 2 is a water supply pipe, 3 is a stirring blade, 4 is a partition plate for forming a charging portion of the slaked lime powder in one corner of the cylindrical portion of the tank 1, and 5 is an inclined plate as a slaked lime fluidized bed height suppressing device, It is provided so as to be inclined between the partition plate 4 and the other end of the tank. Reference numeral 6 is a slaked lime aqueous solution extraction pipe.

The partition plate 4 is provided for providing a zone where there is no inclined plate (fluidized bed height suppressing device) for supplying slaked lime from the upper side of the tank. The partition plate 4 is located near the wall of the tank above the stirring blades provided above the water surface in the tank to below the water surface of the tank so as to form a zone that does not hinder the supply of slaked lime, and as deep as possible. It is provided to reach. When the lower part of the melting tank is of an inverted pyramid type, it is preferably provided so as to reach the inverted cone type part.

At least two inclined plates 5 are provided, preferably at equal intervals between the partition plate 4 and the tank wall with an inclination such that the slaked lime aqueous solution take-out pipe 6 is on the back. The lowermost inclined plate 5a is provided so that the upper end is in contact with the partition plate 4 and the lower end is preferably located on the tank wall side from the rotation axis of the stirring blade 3. Other inclined plates are 5a above 5a
Are provided in parallel with each other, preferably at intervals of 5 to 50 mm.
The upper ends of these inclined plates are located 20 to 100 cm below the water surface, and the lower ends are located 10 to 30 cm away from the wall surface of the tank. Only, the lower end of the uppermost inclined plate 5b is provided so that there is no gap on the wall surface of the tank to prevent the slaked lime slurry from short-passing. In FIG. 1, 7 is a slaked lime charging hopper, 8 is an insoluble matter extraction pipe, and 9 is a level controller. 2 is a sectional view taken along line AA of FIG.

The production of a slaked lime aqueous solution using the apparatus shown in FIG. 1 will be described.

After about 2/3 of water was poured into the dissolution tank 1, slaked lime was powdered or 10 to 30% with stirring by the stirring blade 3.
Supply as a slurry. When supplying slaked lime in powder form, a slaked lime charging hopper 7 is provided and the rotary valve 1
A predetermined amount is input through 0. At this time, in order to prevent the slaked lime powder from scattering to the outside, a water spray nozzle 1
The slaked lime powder collector 12 having No. 1 is provided, and water is sprayed at the time of charging the slaked lime powder to prevent scattering of the slaked lime powder.

When the supply of slaked lime is completed, when the water is supplied from the water supply pipe 2 and the water level reaches a predetermined position slightly below the slaked lime aqueous solution extraction pipe 6, the water supply is stopped by the signal from the level controller 9. After the water supply is stopped, stirring and sedimentation are carried out for about 1 hour to homogenize the slaked lime slurry in the lower part of the tank. Subsequently, water is supplied to the tank 1 from the water supply pipe 2 at a predetermined flow rate while stirring. The supplied water passes through the slaked lime slurry layer in the tank while stirring at a low speed, and a slaked lime aqueous solution take-out pipe 6
During the period, the solution becomes a slaked lime aqueous solution of about 1600 ppm and is taken out of the tank through the take-out pipe 6. The rotational peripheral speed of the stirring blade is 1 m / sec or less, preferably 0.5 m / sec or less.

If there is no slaked lime fluidized bed height suppressing device in this dissolution tank, the supplied water rises substantially straight up in the tank, and the amount of supplied water is extremely limited in order to avoid entrainment of slaked lime fine particles. However, in the case of using the melting tank equipped with the inclined plate 5 as the slaked lime fluidized bed height suppressing device as described above,
The slaked lime supplied into the tank forms a thick slurry at the bottom of the tank and rises in the tank, but the inclined plate 5a prevents the slurry from rising directly above. The portion of the slaked lime slurry surrounded by the stirring blade 3, the inclined plate 5a, the partition plate 4 and the tank wall forms a water flow buffer chamber, and the slaked lime slurry circulates here to suppress the rise of the slaked lime slurry while suppressing the rise of the inclined plate. Ascend between the inclined plates from the lower end. Here again, the slaked lime slurry is prevented from rising by the upper sloping plate and falls along the sloping plate. In order for the inclined plate to exert the function as such a slaked lime fluidized bed height suppressing device, the mounting angle thereof is 45 ° to 75 ° with respect to the water surface, preferably 55 ° to 6 °.
It is 5 °, and it becomes difficult to fulfill a sufficient function as a slaked lime fluidized bed height suppressing device regardless of whether the mounting angle is larger or smaller than this. The narrower the distance between the inclined plates, the more preferable it is, and it is preferably 50 mm or less, more preferably 30 mm or less. However, when the interval is made too narrow and the number of inclined plates is increased, the actual volume of the melting tank becomes small, and scale may be generated and clogged. Therefore, the distance is 5 mm or more, preferably 15 mm or more. The water supplied from the lower part rises between such inclined plates (slaked lime fluidized bed height suppressing device), so that the rising flow velocity of water in the cylindrical or rectangular tube part above the water supply pipe is 0.25 to 1 Water can be supplied even at high speeds such as 0.2 mm / sec. Even if water is supplied at a speed several times higher than that without a tilted plate, for example, about 4 times, the water that reaches the slaked lime aqueous solution extraction pipe is slaked lime. It is taken out as an approximately 1600 ppm slaked lime aqueous solution containing almost no fine particles and can be used for modifying tap water.

As the slaked lime fluidized bed height suppressing device, various devices can be used in place of the above-mentioned inclined plate. For example, as shown in FIGS. 3 to 5, the back surface (lower side) of the aforementioned inclined plate.
Further, the effect of suppressing the slaked lime fluidized bed height can be increased by mounting the projection plate in the vertical direction, the horizontal direction or the diagonal direction. In the case of an inclined plate with a protruding plate on the back side,
It is possible to make the gap larger than in the case of the above-mentioned inclined plate,
20 to 100 mm, preferably 30 to 70 mm, 4
Mount at an angle of 5 ° to 75 °.

Further, as shown in FIGS. 6 to 9, a structure in which a large number of cylinders or rectangular cylinders are combined may be mounted in the tank with a similar inclination. The inner side of these cylinders (the maximum inner side in a square cylinder) is 10 to 50 mm, preferably 20 to 40 mm, and is attached at an angle of 45 ° to 75 ° for the same reason as the interval of the inclined plates described above. , Suppress the height of slaked lime fluidized bed.

When installing these slaked lime fluidized bed height suppressing devices in the melting tank, the individual inclined plates or cylinders may be directly fixed to the inner wall of the melting tank, but preferably the inclined plates or cylinders are previously prepared. Are integrated and fixed by being fixed in the dissolution tank to form a slaked lime fluidized bed height suppressing device. Of course, in this case, the slaked lime fluidized bed height suppressing device is provided with holes therefor at the portion where the stirring shaft 3a passes.

[0024]

[Example] In FIG. 1, 12 plates were installed at an interval of 10 mm at an angle of 60 ° with respect to the water surface in a dissolution tank having a cylindrical shape in the upper part and an inverted truncated cone shape in the lower part with an inner diameter of 300 mm and a height of 2 m. A slaked lime aqueous solution was manufactured using the slaked lime aqueous solution manufacturing apparatus as shown.

After pouring about 2/3 of water into the dissolution tank, 8 kg of slaked lime powder was charged, and the stirring blade was rotated at 18 rpm (rotational peripheral speed of the stirring blade was 0.19 m / sec) from the bottom of the tank. Water was supplied, and when the water level reached 20 cm below the slaked lime aqueous solution take-out pipe, water supply was stopped, and stirring and sedimentation were performed for about 1 hour.
The height of the slaked lime fluidized bed when the water supply was stopped and stirring was 50 cm from the bottom.

Next, while stirring at the same speed, water was supplied from the lower part of the dissolution tank at a rate of 144 liters / hr (water rising rate in the dissolution tank cylinder portion was 0.56 mm / sec), and the pH was adjusted to 12.8 from the slaked lime aqueous solution extraction pipe. An aqueous slaked lime solution containing a slaked lime concentration of 1780 ppm and suspended solids of 50 ppm was obtained.

Comparative Example The same apparatus as that used in the example was used and operated under the same conditions as the example, except that the inclined plate was not installed. The height of the slaked lime fluidized bed at the time of stirring with the water supply stopped is 120 from the bottom.
It was cm. When water was supplied at 144 liters / hr from the lower part of the dissolution tank while stirring, the fluidized bed reached the water surface after 30 minutes, and the slaked lime slurry began to flow out from the slaked lime aqueous solution take-out pipe.

An experiment was conducted by changing the amount of water supplied so that the slaked lime slurry would not be washed away. As a result, the amount of water supplied to obtain an aqueous slaked lime solution having a suspended solid content of 60 ppm was 36 liters /
It was hr (water rising rate in the tubular portion of the dissolution tank: 0.14 mm / sec).

[0029]

EFFECTS OF THE INVENTION By providing a slaked lime fluidized bed height suppressing device in the slaked lime dissolution tank as in the present invention, almost no undissolved slaked lime is entrained even if the amount of water supplied to the dissolution tank is several times that of the conventional case. It has become possible to produce a substantially saturated aqueous solution of slaked lime. Therefore, the production amount of slaked lime aqueous solution per unit volume and unit time is increased, the device can be downsized, and the installation area of the device can be reduced, which is very easy to apply to improve the water quality of a large-scale water purification plant. became.

[Brief description of drawings]

FIG. 1 is a schematic sectional view showing an example of an apparatus according to the present invention.

FIG. 2 is a sectional view taken along line AA of FIG.

FIG. 3 is a perspective view showing another example of a slaked lime fluidized bed height suppressing device.

FIG. 4 is a perspective view showing another example of a slaked lime fluidized bed height suppressing device.

FIG. 5 is a perspective view showing another example of a slaked lime fluidized bed height suppressing device.

FIG. 6 is a perspective view showing another example of a slaked lime fluidized bed height suppressing device.

FIG. 7 is a perspective view showing another example of a slaked lime fluidized bed height suppressing device.

FIG. 8 is a perspective view showing another example of a slaked lime fluidized bed height suppressing device.

FIG. 9 is a perspective view showing another example of a slaked lime fluidized bed height suppressing device.

[Explanation of symbols]

 1 Dissolution tank 2 Water supply pipe 3 Stirring blade 3a Stirring shaft 4 Partition plate 5 Slaked lime fluidized bed height suppression device 6 Slaked lime aqueous solution take-out pipe 7 Slaked lime charging hopper

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁶ Identification code Office reference number FI Technical display location B01F 5/00 B01F 5/00 B C01F 11/02 C01F 11/02 A C04B 2/04 C04B 2 / 04 (56) References: Kaihei 2-95539 (JP, U) JP 63-2890 (JP, B2)

Claims (3)

(57) [Claims] 1. A cylindrical or prismatic dissolution tank, a water supply pipe at the bottom of the tank, a stirring blade at the bottom of the tank, and a slaked lime aqueous solution take-out tube at the top of the tank, and a stirring blade in the tank. On top
After pouring water into a slaked lime dissolution device equipped with a slaked lime fluidized bed height suppressing device consisting of a sloping plate or a sloping member such as a sloping pipe , a predetermined amount of slaked lime is filled in advance, and a tank is supplied from the water supply pipe while stirring at low speed A slaked lime aqueous solution characterized in that the slaked lime aqueous solution is taken out from the slaked lime aqueous solution taking-out pipe by supplying water in an amount such that the water rising velocity in the upper cylindrical or square tubular portion is a rate of 0.25 to 1.2 mm / sec. Manufacturing method. 2. A cylindrical or prismatic dissolution tank, a water supply pipe at the bottom of the tank, a stirring blade at the bottom of the tank, and a slaked lime aqueous solution take-out tube at the top of the tank, and the stirring blade in the tank. On top
An apparatus for producing a slaked lime aqueous solution, which is equipped with a slaked lime fluidized bed height suppressing device including an inclined member such as an inclined plate or an inclined pipe . 3. The slaked lime fluidized bed height suppressing device is composed of two or more inclined plates, and the inclined plates are attached at an interval of 5 to 50 mm and at an angle of 45 to 75 °.
The apparatus for producing a slaked lime aqueous solution according to.