JPH0158121B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Field of Application) The present invention relates to a two-layer separation type iodine adsorption method.

(Prior Art) Conventionally, various fluidized bed adsorption devices have been proposed as iodine adsorption devices used for ion exchange resins.

Invention filed earlier by the applicant, patent application filed in 1977-
No. 52025 (Special Publication No. 54-2625), Patent Application No. 130271-1971
No. 55779/1983 (Japanese Unexamined Patent Publication No. 51-55779), Japanese Patent Application No. 77741/1977 (Japanese Patent Application No. 3869/1983), etc. also relate to fluidized bed adsorption devices, and these are already in operation as large-scale devices.

However, in the above-mentioned fluidized bed adsorption tower, if all the supplied ion exchange resins have uniform high performance, adsorption efficiency similar to that of a fixed bed is maintained, but as time passes after the start of use, The performance of the ion exchange resin gradually deteriorates, and the particles are physically worn away, resulting in differences in particle size and performance.

These differences in particle size and performance are sieved out by the upward flow, and the small ion exchange resin with poor performance is concentrated in the upper part of the adsorption tower, while the large particles with good performance are concentrated in the lower part. It becomes like this.

The reason for this is that resin particles with high ion exchange performance have a fast iodine adsorption rate and increase the amount of iodine adsorption.
Correspondingly, the true specific gravity of the resin particles increases, the sedimentation speed increases, and the resin particles tend to settle to the bottom. On the other hand, resin particles with low ion exchange performance have a slow iodine adsorption rate, and the amount of iodine adsorbed does not easily increase, so the sedimentation rate is also slow and the particles stagnate at the top.

Therefore, resin particles with better adsorption performance settle to the bottom, and they are intermittently taken out, regenerated, and supplied from the top, so that the cycle of adsorption and regeneration becomes faster. On the other hand, resin particles with poor adsorption performance have a slow iodine adsorption rate and do not easily increase the amount of iodine adsorbed, so they remain in the column for a long time, slowing down the adsorption and regeneration cycle.

According to the findings of the present inventors, the iodine adsorption efficiency of the adsorption tower is not due to the average adsorption performance of the anion exchange resin in the tower, but rather to the performance of the anion exchange resin present in the upper part of the adsorption tower. I found out that a lot depends on whether it's good or bad.

This is because as the liquid containing free iodine rises to the top of the adsorption tower, iodine is adsorbed by the anion exchange resin, so the iodine content is the most dilute in the uppermost layer, and the anion exchange resin has good adsorption performance. This is because unless it is a resin, it will be difficult to effectively adsorb iodine.

However, as mentioned above, anion exchange resins with good adsorption performance adsorb iodine quickly and increase true specific gravity, so that they settle faster than other particles with low adsorption performance. For this reason, particles of anion exchange resin with relatively low performance are left behind in the upper layer of the adsorption tower, and generally the adsorption efficiency of the fluidized bed gradually decreases.

In order to maintain good adsorption efficiency of the entire fluidized bed, it is most important to form a layer of ion exchange resin particles with good adsorption performance in the upper part of the adsorption tower.

Japanese Patent Publication No. 53-28038 has been known as a proposal to improve the problems of fluidized bed adsorption towers as described above.

This is done by dividing the fluidized bed into many spaces in the vertical direction using a large number of porous partition plates, thereby maintaining the effect of natural classification in which the anion exchange resin in the column adsorbs iodine and sediments while increasing its true specific gravity. At the same time, the presence of the partition plate suppresses as much as possible the phenomenon of so-called back mixing, in which the lower resin mixes with the upper resin.

However, in order to implement this method efficiently,
It is necessary that the adsorption performance of the anion exchange resin be maintained generally uniformly. This is explained in the above-mentioned conventional publication as ``In order to obtain a uniform flow of the resin and classification according to the amount of adsorption, the particle size distribution of the resin must be limited within a certain range.'' It can also be seen from Furthermore, as pointed out above by the present applicant, it can be seen from the fact that the flow of resin with poor adsorption performance and resin with good adsorption performance is different.

By the way, there are various factors that affect the classification of resin, including not only the particle size of the resin but also the deterioration of adsorption performance due to repeated use. Since it is practically impossible to avoid using resins with uniform performance, even with conventional methods, problems with the above-mentioned fluidized bed iodine adsorption method, such as deterioration of adsorption performance, result in a resin with a small amount of iodine being adsorbed in the upper layer. The problem of being left behind forever remains unsolved.

(Problem to be Solved by the Invention) Therefore, the present inventor changed the idea from the conventional fluidized bed method of utilizing the natural classification effect of the anion exchange resin, and realized that mutual classification within the adsorption column cannot be performed at all. The upper and lower regions are defined, and the resins in each of the divided upper and lower layers are considered as a group whose adsorption performance can be understood on average, and the resin in the upper layer is used to efficiently absorb the relatively dilute concentration of iodine that passes through this region. A regenerated or new anion exchange resin with sufficient average iodine adsorption margin (i.e. high quantitative adsorption capacity) is always present to allow adsorption, while the lower group of resins Because a liquid with a high iodine concentration passes through, even anion exchange resins with low quantitative adsorption capacity can adsorb iodine. , developed the method of the present invention for use in the next cycle of adsorption operation.

(Means for Solving the Problems) Specifically, the method of the present invention is characterized by supplying a liquid containing free iodine in an upward flow from the bottom, and supplying an anion exchange resin that adsorbs iodine from the top, so that both are in a fluidized state. In a fluidized bed iodine adsorption method in which iodine is adsorbed through countercurrent contact with the adsorption tower, a narrow space is provided in the middle of the adsorption tower to speed up the upward flow, and the anion exchange resin above that location is The process involves performing an iodine adsorption operation while keeping the anion exchange resin substantially separated into two layers, the upper and lower layers, by preventing the anion exchange resin from settling below that point, and removing the lower layer of the anion exchange resin from the outside. The steps of extracting the anion exchange resin from the upper layer, transferring all the anion exchange resin from the upper layer to the lower layer, and supplying regenerated or new anion exchange resin to the upper layer are alternately repeated.

According to this method, every time one cycle of adsorption operation is completed, all the resins in the upper layer are transferred from the upper layer to the lower layer, and some or all of the resins in the lower layer are extracted from the tower, and are then recycled or new. Since a group of resins is supplied to the upper layer, both the upper and lower layers contain a mixture of resins with good adsorption performance and resins with degraded performance, but in particular, the upper layer is constantly supplied with new resin, so the adsorption performance is lower than that of the lower layer. There will be a resin with a high margin of iodine adsorption on average, and at the end of each cycle of adsorption operation, all of the resin in this upper layer will be transferred to the lower layer, leaving only the resin with degraded performance left behind in the upper layer. This eliminates problems that occur in conventional fluidized bed adsorption towers, such as differences in residence time due to differences in adsorption performance of resins.

By adopting such a method, the iodine concentration in wastewater is significantly lower than that of the conventional fluidized bed method (or the method described in Japanese Patent Publication No. 53-28038), as described below. It was confirmed that an extremely excellent effect of reducing the amount of water was obtained.

The flow rate of the upward flow of the liquid in the adsorption tower of the present invention is such as to give a flow rate of 225 m/hour or more in the narrow area (hereinafter referred to as the narrow area).
This is significantly different from the flow velocity of conventional fluidized beds, which is usually 10 to 50 m/hour. This prevents the anion exchange resin from descending and separates the anion exchange resin into two layers, upper and lower.

The narrow sections according to the present invention are as shown in FIG. 1, and they are provided in the middle of the adsorption tower as follows (first
(see figure).

(A) Fix the perforated plate in the middle of the adsorption tower. In this case, the position and size of the holes are selected to be appropriate in terms of fluid dynamics. Usually the hole diameter is
20 to 50 mm is appropriate (perforated plate type).

(B) Narrow the flow path by providing a mountain-shaped protrusion in the middle of the adsorption tower and a buffer at the top (ventilary type).

(C) Narrow the opening from both sides of the middle part of the adsorption tower and provide a buffer above the opening (orifice type).

Further, to explain one embodiment of the method of the present invention with reference to drawings of an embodiment, FIG. 2 shows an adsorption tower, which is cylindrical or square in shape, and has doglegged inclined plates 4 and 7 inside. Many are arranged. A perforated plate 5 is arranged in the middle of the adsorption tower, and the tower has an upper part 6 and a lower part 3.
The regenerated or new anion exchange resin is supplied from the upper supply port 9 and comes into fluid countercurrent contact with the iodine-containing liquid rising in the column.

However, in this case, the anion exchange resin does not descend to the lower layer due to the perforated plate 5. Also in the lower layer, the anion exchange resin comes into fluid countercurrent contact with the ascending flow and adsorbs iodine. After performing such an adsorption operation for a certain period of time, a certain amount of anion exchange resin that has adsorbed iodine is extracted from the lower layer through the outlet 10.
At this time, the upward flow rate in the column is reduced to make the upward flow at the perforated plate 5 200 m/hour or less, and all the anion exchange resin present above the perforated plate 5 is allowed to settle to the lower layer. Next, the iodine-containing liquid is returned to its normal upward flow and passed through, and the regenerated or new anion exchange resin is supplied to the upper layer again to start the adsorption operation.

By repeating the above operations, iodine is adsorbed and collected from a liquid containing iodine.

Through the above operations, adsorption is always carried out in the upper layer of the adsorption tower using a resin that has an averagely high quantitative adsorption performance, so the amount of iodine discharged from the adsorption tower is much lower than in conventional methods, and is normally discharged. While the iodine content of the liquid is 15 to 20 ppm, when the method of the present invention is used, the iodine content is 7 to 10 ppm, and the adsorption yield is about 8.
%, which is an extremely excellent effect.

In addition, when the method of the present invention is used, the cycle of adsorption and regeneration is accelerated, which has a favorable effect on the efficiency of iodine production.

(Example) The present invention will be explained below by way of an example.

Example The adsorption tower used in the experimental apparatus of the present invention is as shown in Fig. 2. The tower is a square shape made of vinyl chloride, and the horizontal cross-sectional area of the lower layer is 17.5 cm x 17.5 cm = 306.25 cm ² . The height of the tower is 570cm.

A large number of inclined plates are arranged inside this. The inclined plate has a dogleg shape with an inclination angle of 60 degrees and an included angle of 120 degrees.
The length of the sloped surface is 11.2cm, the width is 17.5cm, and the horizontal and parallel intervals between the sloped plates are 3cm, and they are arranged squarely in parallel.The sloped plates are installed between 40cm and 220cm from the bottom edge. The upper 40cm is a void. In this tower, the perforated plate according to the invention was provided at a position 260 cm from the lower end and had eight holes with a diameter of 25 cm. Therefore, its aperture area is 39.25 cm ² .

The upper part of this adsorption tower has a horizontal cross-sectional area of 23.5cm x 23.5cm.
= 552.25cm ² and the height is 70cm. The height of the tapered part is 66cm, and the bottom 30cm of the tapered part is a void.
In other cases, the inclined plate is inserted.

The anion exchange resin used in the experiment was Amberlite IRA-400 (trade name) 138, which had a neutral salt decomposition capacity of 0.5meq/ml-R48,
0.75meq/ml-R 60, 0.85meq/ml-R
Consists of 30 pieces.

These three types of used ion exchange resins were mixed and supplied to the column for use. In the conventional method for comparison, the same adsorption tower was used except that it did not have a perforated plate in the middle of the adsorption tower.

The amount of ion exchange resin packed into each adsorption tower was 60,
In the case of the present invention, 9 of them were supplied from the supply port at the upper part of the perforated plate, and 51 was supplied to the lower part of the perforated plate.
The ion exchange resin in step 9 to be replenished is stored outside the tower.
Used for cycling.

The natural gas brine used in the above adsorption towers had an iodine content of 90 ppm, which was adjusted to contain free iodine at an average of 67 ppm, and was passed through each adsorption tower in an upward flow. The flow rate of liquid was 1260/hour, the upward flow rate in the lower layer was 40 meters/hour, and the upward flow rate in the perforated plate was 500 meters/hour.

Every 24 hours of the above-mentioned liquid passage, nine portions of anion exchange resin were extracted from the lower portion, and nine portions of the regenerated anion exchange resin were supplied to the upper portion.

Note that a sulfite solution and 10% sulfuric acid were used for the above regeneration. The anion exchange resin in the tower shows a resin distribution similar to that in a normal adsorption tower after one cycle of about 8 days, and when comparing the average iodine content in the wastewater after 24 hours, it is found that the average iodine content in the wastewater after 24 hours is similar to that in the conventional adsorption tower. The average was 16 ppm, and the adsorption yield was 82.2%, whereas in the case of the present invention, it was 9 ppm, and the adsorption yield was 90.0%.

In addition, when using the new Amberlite IRA-400 resin with a neutral salt decomposition capacity of 1.2 meq/ml-R, the average content of wastewater is 6 to 8 ppm in the conventional case, so the performance of the anion exchange resin deteriorates considerably. It was demonstrated that a good adsorption yield could be maintained even under such conditions, and the effects of the present invention were made clear.

Comparative Example The three types of used ion exchange resins used in the above examples were used in an apparatus having the same structure as the present invention except that it was partitioned into five upper and lower stages using perforated plates according to the description in the above-mentioned Japanese Patent Publication No. 53-28038. Using this method, iodine adsorption was carried out over three cycles in accordance with the description in Japanese Patent Publication No. 53-28038.

As a result, the average iodine content in wastewater was 15 ppm,
The adsorption recovery rate was 83%, confirming the excellent effects of the present invention.

[Brief explanation of drawings]

Figure 1 shows the configuration of the narrow part of the present invention (A)
indicates a perforated plate type, (B) a ventilate type, and (C) an orifice type. FIG. 2 is an explanatory diagram of an adsorption tower according to the present invention. DESCRIPTION OF SYMBOLS 1... Rising liquid inlet, 2... Straightening plate, 3... Lower layer part, 4... Inclined plate, 5... Perforated plate, 6... Upper layer part, 7... Inclined plate, 8... Outlet, 9...Ion exchange resin supply port, 10...Ion exchange resin outlet.

Claims (1)

[Claims] 1. In a fluidized bed iodine adsorption method in which a liquid containing free iodine is supplied in an upward flow from the bottom, an anion exchange resin that adsorbs iodine is supplied from the top, and the two are brought into countercurrent contact in a fluidized state to adsorb iodine.
A narrow space is provided in the middle of the adsorption tower to speed up the upward flow and prevent the anion exchange resin located above that location from settling below that location. A process of performing an iodine adsorption operation while maintaining the anion exchange resin substantially separated into upper and lower layers, extracting at least a part of the anion exchange resin in the lower layer to the outside, and transferring all the anion exchange resin in the upper layer to the lower layer. A two-layer separation type iodine adsorption method characterized by alternately repeating the steps of , , and the steps of supplying regenerated or new anion exchange resin to the upper layer.