JPS6012191A - Fluidized bed type dephosphorization apparatus - Google Patents

Abstract

PURPOSE:To perform dephosphorization in good efficiency and to enhance operation efficiency, by withdrawing a grown crystal seed with low wet specific gravity mainly floating in an agitated state above the upper surface level of a fluidized bed out of a tower through a downcomer. CONSTITUTION:A fluidized bed type dephosphorization apparatus is constituted of a treating tower 1, a fluidized bed 3 containing a crystal seed provided in the tower 1, a supply pipe 4 for supplying the seed crystal to the fluidized bed 3, a supply pipe 5 for supplying raw water to the fluidized bed 3 in an upward stream and a withdrawing pipe 8 for withdrawing water and the crystal seed in the fluidized bed 3 from the lower end of said tower 3. To this fluidized bed type dephosphorization apparatus, downcomers 9, of which the upper ends are opened in the vicinity of the upper surface of the fluidized bed 3 in the tower 1 and the lower ends are communicated with the outside of the fluidized bed 3, are provided.

Description

DETAILED DESCRIPTION OF THE INVENTION This invention provides a dephosphorizing agent (
A contact layer is formed in the treatment tower with crystals of phosphate rock, bone char, calcium phosphate crystals, calcium carbonate, calcium phosphate precipitated on the surface of coral fossils, etc., and raw water containing phosphates is removed. This invention relates to a fluidized bed crystallization dephosphorization device that fluidizes a contact layer by passing water through a treatment tower in an upward flow to crystallize and remove phosphate ions in the water.

The applicant of this patent filed a patent application for such a dephosphorization device in 1982-10.
No. 3895 (Japanese Unexamined Patent Application Publication No. 58-1988), Patent Application No. 198-30
This was proposed in No. 889 (Japanese Unexamined Patent Publication No. A859-). Japanese Patent Application No. 57-103895 solves the conventional problem of passing raw water through the contact layer in a downward flow and treating the contact layer as a fixed bed. This is an improved version of the patent application 1983-3, which was improved so that the treatment could be carried out as a fluidized bed.
No. 0889 states that when processing in a fluidized bed type, the crystal seeds become enlarged over time, causing the fluidized bed to expand, causing the crystal seeds to mix into the treated water and also deteriorating the water quality. The amount of expansion of the fluidized bed is sensed by detection and measurement of pressure loss in the fluidized bed, and the amount of extracted crystal seeds is controlled to keep the amount of fluidized seed crystal particles below a certain level and prevent deterioration of water quality. It was designed to do so.

A detailed study of calcium phosphate, which precipitates on the surface of crystal seeds through a crystallization reaction and enlarges them, reveals that
Since calcium phosphate crystals grow porous, the apparent specific gravity (wet specific gravity) of the crystal seeds in the liquid decreases,
When the raw water flows vertically through the upward flow ``'C'', the sedimentation rate increases due to enlargement and increase in particle size, but the effect of lowering the wet specific gravity is large, and the sedimentation rate of brushing decreases. , it was found that it becomes easier to migrate to the upper part of the fluidized bed.

This means that the harmonic mean grain size of the crystal seeds is 0.32 m (grain size 0.
Using phosphate rock (25 to 0.45 mm), the raw water was prepared by adding phosphoric acid = sodium hydrogen, sodium bicarbonate, and calcium chloride solution to city water, P = 2WVt, M - alkalinity =
100 W9/L N Cm = 45 ” I/L tonal 'ijA - Adjust to this by adding NaOH solution and p
Using synthetic water with H=9, a transparent acrylic column with a diameter of 3011111% and a height of 1000 tan was filled with about 200 of the above crystal seeds, and the synthetic raw water was passed at a power of 2 m at a water flow rate of about 10%/hr. After 60 days of upward flow, the particle size of the crystal seeds,
This is also clear from the results of wet specific gravity measurements shown in the table below.

Before use After 60 days Harmonic mean particle diameter (mm) 0.32 0.369 True ratio
Weight 3.00 3.03 Wet specific gravity 2.48 2.07 Terminal velocity -) 0.083 0.075 Furthermore, terminal velocity U
t is the Stokes sedimentation rate formula, where ρ2 = particle density (V
-) C = particle diameter (m) ρ = original fluid density (V-) μ = viscosity (Klm-s).

That is, after 60 days, the particle size increases, the true specific gravity increases, and the wet specific gravity decreases, and as a result, the total image speed also decreases. Since the contact area of the enlarged crystal seeds with the liquid is smaller than the total contact area of a plurality of small crystal seeds that become the same size when aggregated, the dephosphorization efficiency is low.

No.
~0.35mm has a good phosphorus rate, especially 0.2
11III is the highest. Therefore, the diameter of the dephosphorizing agent supplied to the fluidized bed should be within this range. If the harmonic mean diameter is larger than that, the phosphorus removal rate is lower because the contact area with the liquid is reduced. For details regarding FIG. 1 and the mechanism by which the crystal seeds enlarge due to use, please refer to the description in the Japanese Patent Application No. 1983 (filed on June 29, 1988). In order to eliminate the expansion of the crystal seeds used in the treatment tower and to replace them, the upward flow of raw water is stopped and the water in the tower is extracted from the lower end of the treatment tower to form a contact layer. In the case of a multi-stage system, part of the crystal seeds in the system are moved from the upper stage to the lower stage, and a part of the lower stage is taken out, activated, and supplied to the upper stage.
In this case, the wet specific gravity decreases, the enlarged crystal seeds mainly present in the upper layer of the contact layer are difficult to take out, and the number of enlarged crystal seeds in the contact layer at each stage gradually increases.

Therefore, the present invention aims at extracting the enlarged crystal seeds, which mainly have a reduced wet specific gravity, which are scattered on the upper surface level of the fluidized bed during operation with raw water flowing upward, to the outside of the column using a down conveyor manifold. The present invention has been solved, and the present invention will be described below with reference to an embodiment shown in the drawings.

Figure 2 shows the aforementioned prior patent application (Japanese Patent Application No. 57-10389).
This is an embodiment of the present invention implemented in a multi-stage fluidized bed dephosphorization apparatus similar to 5, 58-308'89), in which the angle of repose is Support plates to which nozzles and non-repose angle nozzles are attached are provided in multiple stages, only the angle of repose nozzle is attached to the lowest support plate -', and a contact layer 3 of crystal seeds of the dephosphorizing agent is provided on each support plate. Configure.

To operate, new or regenerated crystal seeds are continuously or intermittently supplied to the uppermost contact layer 3 through a supply pipe, and raw water is supplied under the lowermost support plate -' through a water supply pipe. The treated water, from which phosphate ions in the water have been removed by a crystallization reaction, is passed through the nozzles of each support plate and flowed upward in the column, causing the crystal seeds that make up the contact layer at each stage to flow in a turbulent state. Get to the overflow weir at the upper end of the dam. During operation, calcium agents, alkaline agents, and crystallization accelerators (e.g., chlorine agents, fluorides, etc.) are injected into the raw water flowing through the water supply pipe S using a chemical dosing device. Note: A calcium agent, an alkaline agent, and a crystallization accelerator are also injected into the fluidized bed at each stage using device 7.

As the operation continues in this way, the crystal seeds in the contact layer of each stage enlarge, and the contact layer expands as fine particles of calcium phosphate precipitated on the surface become mixed.Especially, the contact layer of the uppermost stage expands. Since new or regenerated crystal seeds are continuously or intermittently replenished, the crystal expands the most.

For this reason, the flowing upper surface of the contact layer at the top stage is detected using a level switch or pressure increase, and when the value exceeds a certain level, the supply of raw water is stopped, and the valve of the extraction pipe g at the bottom of the tower is opened. 1. The water in the tower is caused to flow downward through the holes of the angle of repose nozzle and the non-repose nozzle of each membrane support plate, and the water is accompanied by this water to mutually move a part of the contact layer on the upper stage to the lower stage. A portion of the crystal seeds in the lower contact layer is extracted out of the column through the hole of the angle of repose nozzle in the lowermost support plate. As a result, when the amount of crystal seeds on the support plates of each stage is reduced to a certain extent, the downward flow of water in the column is stopped and the column is allowed to stand still.

Then, except for the lowest support plate, a part of the crystal seeds in the upper layer near the non-repose angle nozzle falls to the lower layer through the non-repose angle nozzles attached to each support plate above it. Since the amount of crystal seeds in the contact layer at the top level is often equal to the amount of crystal seeds in the contact layers in the other layers, operation is restarted.

The details of the above-mentioned operation are particularly detailed in the earlier patent application, especially in the patent application filed in 1973.
7-103895, so please refer to that for details.

Now, as mentioned above, the supply of raw water is stopped, the water in the tower is drained from the extraction pipe, and some of the crystal seeds in the upper contact layer are transferred to the lower layer. Even if a part of the crystals is taken out of the column, the enlarged crystal seeds whose wet specific gravity has decreased are present in the upper part of the contact layer, so they are unlikely to move to the lower stage or be taken out of the column. For this reason, the present invention allows the raw water to flow upwardly 1.
□ When the contact layer is fluidized by passing water in step 11, a downcomer (sampling pipe) q is installed through the side wall of the column with its upper end positioned at or slightly above the planned upper surface of the fluidized bed. It was.

When there are multiple contact layers, it is most preferable to provide a downcomer for each contact layer as in this example, but it is not always necessary, and downcomers may be provided for some contact layers, such as every other contact layer. You can just set it up.

Each downcomer is provided with an opening/closing means 9' such as a manually operated or automatically operated valve.

Therefore, during operation, the opening/closing means of the downcomer is periodically opened for a certain period of time using a timer, etc., and an interface detection sensor is installed above the top of the downcomer or inside the tower, and the sensor detects the crystal seeds. The downcomer's opening/closing means can be opened using a signal emitted from time to time, or a viewing window can be installed in the tower wall to see through the inside of the tower. By opening the opening/closing means, some of the flowing crystal seeds can be drawn out of the column. This prevents the phenomenon that the number of enlarged crystal seeds in the contact layer gradually increases, and allows effective dephosphorization.

□Also, in this way, the crystal seeds at the top or upper part of the fluidized bed are taken out of the column using the downcomer, and the expansion is somewhat reduced, so depending on the amount of new and recycled crystal seeds supplied to the top stage,
The interval at which the operation is interrupted in order to replace some of the crystal seeds in the column and to restore the expanded column to its original state can be made longer than in the past, and the operation efficiency can be improved.

In this embodiment, the crystal seeds and liquid extracted by the downcomer are received in a common storage tank 10 which also contains the crystal seeds extracted from the lowermost contact layer for replacement, and the liquid is used as raw water from the water supply pipe. The crystal seeds are then passed through a refining process that involves mechanical crushing, surface peeling, etc., or chemical acid treatment to dissolve the surface, and then passed through a classifier 12, such as a hydrocyclone or screen. The wet sieve fraction is processed into a mechanical sedimentation separation tank with a harmonic mean diameter of 0.1 to 0.35 M, which has a high phosphorus removal rate.
% Preferably, those with the highest harmonic mean diameter of 0.2 mm are classified, and this is preferably subjected to one or a combination of two or more of alkali treatment, acid treatment, sodium hypochlorite treatment, and heating treatment. Chemical tank/3. After being supplied and activated, it is supplied to the uppermost contact layer at the supply pipe. In addition, those with a harmonic mean diameter or less generated in the classifier are collected.

In this way, according to the present invention, by focusing on the fact that the crystal seeds enlarged due to use lower the wet specific gravity and flow above the fluidized bed, the expansion of the contact layer is suppressed by mainly extracting them to the outside of the column using a downcomer. However, dephosphorization can be carried out efficiently by using crystal seeds having a particle size with high dephosphorization efficiency, and the operation interruption interval for replacing the crystal seeds in the column can be extended, thereby increasing the operating efficiency of the apparatus.

Although the illustrated embodiment is of a multi-stage type, it goes without saying that the present invention can also be applied to a single-stage type with a single contact layer.

[Brief explanation of the drawing]

Fig. 1 is a chart showing the dephosphorization rate on the grain size side of crystal seeds, and Fig. 2 is a flow sheet showing an example of the present invention. layer, Hiro is the crystal seed supply pipe, Yu is the raw water supply pipe, g is the crystal seed and water extraction pipe,
9 indicates a downcomer. Patent applicant Kurita Industries Co., Ltd.

Claims (1)

[Claims] A treatment tower, a fluidized bed containing crystal seeds provided in the tower, means for supplying crystal seeds to the fluidized bed, means for supplying raw water to the fluidized bed in an upward flow, and water and crystals in the fluidized bed. A fluidized bed dephosphorization apparatus having a means for extracting seeds from the lower end of the treatment tower, characterized by having a downcomer whose upper end opens near the upper surface of the fluidized bed in the tower and whose lower end communicates with the outside of the fluidized bed. Fluidized bed dephosphorization equipment.