JPH02174992A - Treatment of suspension containing metal hydroxide - Google Patents

Abstract

PURPOSE:To increase a settling speed, to enhance the efficiency and stability of processing for flocculation and separation, an to form sludge easy to concentrate and dehydrate by adding a granular solid material simultaneously with the addition of an anionic high molecular flocculant, and adding a cationic high molecular flocculant prior to a formation of coarse flocs. CONSTITUTION:An anionic high molecular flocculant 2 and blast furnace granulated slag 3 are added to a suspension 1 (neutralized plating soln.), a cationic high molecular flocculant 4 is then allowed to flow into a solid-liquid separation tank 5 as an upward current. The inflow flocs 7 are dehydrated and rolled in a column to form a pellet-shaped dense floc. Compaction is further caused above an impeller 6. The slurry 9 drawn off from the compaction zone is easy to concentrate and dehydrate, a concentration tank is not needed, and simple press, vacuum filter, etc., are sufficiently used as the dehydrator. Such remarkable effects are produced.

Description

Detailed Description of the Invention [Industrial Field of Application] The present invention is applicable to suspensions containing metal hydroxides, such as waste water discharged from metal surface treatment factories such as Metsuki factories, electrolytic polishing factories, and alumite factories. In order to remove heavy metal ions such as zinc, nickel, aluminum, and tin contained in It relates to a solid-liquid separation process that removes metal hydroxides from liquids.

[Prior Art] Conventionally, precipitation separation methods, flotation separation methods, filtration separation methods, adsorption separation methods, etc. have been known as methods for separating suspended solids from suspensions containing suspended substances. There is.

In particular, when the specific gravity is relatively heavy and the amount of drainage is large, such as metal hydroxide, the precipitation method (for example,
P.9 of “Solid-Liquid Separation Technology” published by Nichigihodo Publishing Co., Ltd.
5 to 98) are the cheapest and can be expected to provide stable processing, and are therefore commonly used.

However, metal hydroxide flocs produced by the reaction of metal ions such as zinc, aluminum, tin, and iron with caustic soda and slaked coal have poor sedimentation properties and are difficult to separate from solid to liquid. A method has been adopted in which the flocs are further increased in size by adding .

However, although the flocs produced by this method have a large apparent particle size, the particles are loosely bonded to each other and contain a large amount of water, so their density is small and the apparent particle size depends on the sedimentation rate. A rise cannot be expected. Also, the concentration and dehydration properties are not good.

[Problems to be Solved by the Invention] The present invention improves the conventional coagulation-sedimentation method by forming dense, highly cohesive, and high-density flocs that have fundamentally different properties from conventional coagulation-sedimentation flocs. In addition to increasing the sedimentation rate several times higher than the sedimentation rate, the processing efficiency and stability of the coagulation separation process are improved to the extent that the filtration step that is conventionally required as a finishing step after coagulation and sedimentation can be omitted, and the process is concentrated. The purpose of this invention is to provide a solid-liquid separation method that simultaneously produces sludge with good properties and dewaterability.

[Means and actions for solving the problem] Generally, metal hydroxides are positively charged, so the addition of an anionic polymer flocculant causes charge neutralization and adsorption crosslinking, which makes the flocs Form.

The inventors added granular solids at the same time as the addition of an anionic polymer flocculant in order to create dense, strong bonding, and high-density flocs with different properties from the conventional 8i flocs shown above. The mixture was rapidly stirred for several tens of seconds, and a cationic polymer flocculant was added before forming coarse flocs.

The granular solids are incorporated into the flocs that are being formed by the action of the anionic polymer flocculant and form a large number of nuclei.

In addition, due to the action of the cationic polymer flocculant, the cationic polymer flocculant and the metal hydroxide/particulate solid are adsorbed and crosslinked, and at the same time form a complex network structure with the anionic polymer flocculant.

Cationic polymer flocculants have many adsorption active sites in their molecules, so they form flocs with strong binding strength.

At this time, since both the metal hydroxide and the cationic polymer flocculant are positively charged, a dispersion phenomenon occurs and the flocs become smaller.

However, this floc is a floc with extremely strong cohesion, and by gentle disturbance, the molecules become entangled, forming a dense, dense floc with strong cohesion.

The liquid consisting of such a group of flocs further flows upward into the solid-liquid separator.

Within the solid-liquid content of 11 ft 41, the stirring blade rotates slowly, and the stirring blade and the flocs collide with each other, and the flocs collide with each other, and the water in the flocs is released. Also, due to the rolling motion, a round, tight flock is formed.

The flocs made in this way have a diameter of 1 mm to 3 mm.
It is a very well-compacted floc, and although the particle size is small, it is a dense floc with granular solids as its core.
Due to its high density, it is possible to increase the sedimentation rate by more than 10 times compared to conventional flocculation method flocs.

In addition, the flocs formed in this solid-liquid branch tank are intermittently or continuously extracted as slurry, and the thickening and dewatering properties of this slurry are considerably better than in conventional methods. Become.

As a granular solid, it can basically be used as long as it forms the core of flocs, but those with high uloid properties, high swelling and water supply properties, such as bentonite, have a low dry volume. The flocs will absorb several times more water, increasing the diameter of the flocs.

Although this floc contains water inside, its flocsif diameter is quite large, so the sedimentation rate is quite high. However, the dewatering properties are not very good, and even if compacted filtration tanks 1 and 2 are formed as described below, the gaps are too large, so unformed flocs flow out, causing instability in the quality of the treated water. Also, like magnetite, it is quite NI with hydroxide.
Those that do not dye are difficult to form a floc and are unsuitable as additives.

Therefore, the inventors repeatedly conducted tests using various granular solids, and found that granulated fine powder with an average particle size of about 50μ was obtained by crushing and classifying granulated slag, which is a byproduct of blast furnaces in the steel industry. found to be the most effective.

When this granulated blast furnace granulated powder having an average particle size of about 50 μm is used as the granular solid, the granulated water is easily incorporated into the metal hydroxide and becomes the core of the floc. This granulated water has a specific gravity of 2~
3, it is effective in increasing the sedimentation rate of formed flocs, and also has good concentration and dewatering properties.

In order to stir and flow the slurry in the slurry zone, the stirring blade is slowly rotated, the blade collides with the flocs, and the flocs collide with each other to drive out the water in the flocs, and a rolling motion is generated to form round flocs. Basically, any method that promotes dehydration can be used.

However, it is difficult to form a dense floc by dehydration in a propeller-type stirrer that causes downward convection movement.

The inventors made stirring blades of various shapes and repeated experiments, and as a result, they arrived at the following stirring blade.

First, we divided the functions into a part that causes turbulent motion and a part that causes rolling motion.

In other words, the part where the blade collides with the flocs and the flocs and dehydration occurs is the part that causes turbulent motion, and the part where regular rotation makes the flocs into a round shape is the part that causes rolling motion. .

Raw water flows upward into the sludge blanket zone from the bottom, and grid-like blades were installed at the bottom to create turbulent flow. A lattice-shaped blade is a combination of flat plates so that the cross section has a lattice shape.

Moreover, a cross feather made of two flat plates arranged in a 1000-character pattern was installed on top of it.

If the depth of the tank becomes deeper, these two types of blades can be separated into upper and lower parts and stacked on top of each other. Also, the two types of blades are fixed to the same shaft and rotated at the same rotational speed. Also, although the length of the blade does not extend to the outer periphery of the tank, it is better to have a certain length.

This treatment method can also have a great effect by providing a consolidation filtration section in the sludge blanket zone above the agitation flow section, that is, the section where turbulence and rolling motion occur.

In other words, in the stirring flow section, the flocs collide with each other, the flocs repeatedly collide with the blades, and the pellet-shaped flocs, which are dense and have a strong bond and have a diameter of 1 to 3,111 m, are formed by the rolling motion and are pushed upward by the upward flow. However, if this group of flocs is further fixed in an area where there is no stirring movement, solid-liquid separation occurs and an interface is formed. The water above the interface is clear and is discharged as treated water.

In addition, the area below the interface becomes a sludge blanket zone, where a consolidation phenomenon occurs where there is no stirring movement. This consolidated layer is a group of dense flocs with a diameter of 1 to 3 l, and has a kind of filtration function, 6 that is, unformed flocs, dissolved heavy metals, SS, etc. are trapped in the gaps between the flocs.

Alternatively, it is adsorbed and taken in by flocs.

Therefore, the treatment is very stable, and processes such as sand filtration, which are normally used as a secondary treatment after coagulation and precipitation, are not necessary.

In addition, the slurry extracted from this compacted zone has a high slurry concentration and good concentrating properties.

In some cases, concentration may also be unnecessary.

In addition, subsequent dehydration is also good. Normally, it is difficult to dehydrate flocs obtained by coagulating and precipitating waste liquids such as plating liquid, and the water content cannot be reduced to 80% or less unless dehydrated using a filter press or the like.

However, the flocs produced by this process are easy to dehydrate, and can be easily dehydrated using a simple belt press, etc.
It is possible to reduce the moisture content to 80% or less.

Therefore, according to the present invention, suspensions containing metal hydroxides can be treated stably and efficiently.

[Actual Example] As shown in Figure 1, zinc ions tiomg#! are generated from an electrogalvanizing factory. , chromium ion 67 mg/
Jl, a waste liquid containing 171 g of iron ions was raised to pH 11 with slaked lime, and neutralized to a suspension containing metal hydroxides, and a polyacrylamide-based anionic polymer flocculant 2 was added.
4 a+g/L 1000mg/F of granulated blast furnace slag 3 with an average particle size of 50μ! After stirring rapidly for 30 seconds, 2 mg/Ll of polyacrylamide-based cationic polymer flocculant 4 was added, and the mixture was allowed to flow into the solid-liquid separation tank 5 in an upward flow.

The solid-liquid fraction l1iff rice cake has a stirring blade 6 consisting of several lattice-shaped blades stacked on the bottom and several cross-shaped blades stacked on the top, and rotates at 40 rpm.

In addition, the solid-liquid fraction m has a column diameter of 100n+m and a height of 400m.
A PVC column of I was used.

The flocs 7 that have flowed into the solid-liquid separation tank undergo a dehydration phenomenon and rolling motion within the column, and become dense pellet-shaped flocs of 1 to 3 mm. Furthermore, at the top of the stirring blade,
Consolidation phenomena also occur, creating a sludge blanket zone.

In this blanket zone, it is possible to obtain an OFR of 10 m/Hr.

Clear water separated from solid and liquid by this column is discharged from the upper part, and contains SS 4 mg/l and iron ions Ill1g#! ,
Zinc ion 1 rag/I, chromium ion 1 mg/l
This results in very good treated water 8.

Furthermore, since the consolidated portion has a filtration function, the processing is stable and unformed flocs do not float.

Further, the slurry 9 drawn out from the consolidation zone can be easily subjected to a leaf test, and the moisture content of the cake is 80%, which allows for highly efficient dewatering.

[Effects of the Invention] According to the present invention, metal hydroxides in the liquid can be efficiently removed from a suspension containing metal hydroxides. That is,
Since the sedimentation rate can be very low, the solid-liquid content 11ilt41 becomes compact.

In addition, a filter that is normally installed as a secondary treatment for coagulation and precipitation becomes unnecessary.

The drawn slurry has good concentration and dewatering properties, and has remarkable effects such as no need for a concentration tank and a simple bell press or vacuum filter can be used as a dehydrator.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram showing an outline of an embodiment of the present invention. 1... Plating liquid after neutralization treatment, 2... Anionic polymer flocculant, 3... Granulated blast furnace slag, 4... Cationic polymer flocculant, 5... Solid-liquid separation Tank, 6... Stirring blade, 7.
...Floc, 8. Treated water, 9. Slurry (exhaust sludge). 4 other people I, $ display 1988 Application No. 3327? Name of No. 10 (Name) Nippon Steel Co., Ltd. Taipei 2-6-2 Marunouchi, Chiyoda-ku, Tokyo To Marunouchi Shigesu Building 330 Date 1 of the amendment order is also amended as per the attached sheet with details of the amendment. We will correct the matters. Note 1: The scope of claims is amended as shown in the attached sheet. 2. On page 2, line 15, "coalstone" is corrected to "limestone." 3゜In the bottom line of page 2, the words "suspended substances" should be corrected to "suspended substances." 4I, page 3, line 11, slaked coal J is corrected to ``slaked lime''. 5. In the first line of page 7, the word "colloid" is corrected to "colloid." 6. On page 7, line 11, "magnetite" is corrected to "magnetite". 7. On page 13, line 1, it says rs84■/Q, iron ion 1■/Q,'' rS
S 3 mg/Q, iron ion 0, 1 mg/
Q,” he corrected. 8゜Page 13, 1st row [Ion 1■/Q, Chromium ion 1■/QJ and F ion 0.2■/Q, Chrome 11 ion O21■/U
I am corrected. 9. On page 13, lines 16 and 18, the words "unnecessary" are corrected to [unnecessary J]. Claim 1: A metal product characterized by adding an anionic polymer flocculant to a suspension containing a metal hydroxide, further adding granular solids and a cationic polymer flocculant, and then stirring with a rotating flow. A method for treating suspensions containing hydroxides. 2. The method for treating 61 items containing metal hydroxides according to claim 1, characterized in that blast furnace granulation is used as the granular solids. 3. As a method of stirring and fluidizing the sludge blanket zone, it is possible to provide a lattice-shaped rotor blade at the bottom of the solid-liquid separation tank to generate turbulent motion, and a cross-shaped rotor blade to generate rolling motion at the top. Characteristic i? lff
A method for treating a suspension of the metal hydroxide according to claim 1. 4 A zone without rotary blades is created above the sludge blanket zone, and the flocs formed in this zone are consolidated to provide the same function as sand filtration.I
A method for treating a suspension containing a metal hydroxide as claimed in claim t.

Claims (1)

[Claims] 1. A sludge that is stirred and fluidized by a rotating flow after adding an anionic polymer flocculant to a suspension containing a metal hydroxide, and further adding granular solids and a cationic polymer flocculant. A method for treating a suspension containing a metal hydroxide, which comprises flowing the suspension into a blanket zone in an upward flow to perform coagulation and separation. 2. The method for treating a suspension containing metal hydroxide according to claim 1, characterized in that blast furnace granules are used as the granular solids. 3. As a method of stirring and fluidizing the sludge blanket zone, it is possible to provide a grid-shaped rotary blade that generates turbulent flow motion at the bottom of the solid-liquid separation tank, and a cross-shaped rotary blade that generates rolling motion at the top. A method for treating a suspension of metal hydroxide according to claim 1. 4. The metallic water according to claim 1, which has a function similar to that of sand filtration by creating a zone without rotary blades above the sludge blanket zone and consolidating the flocs formed within this zone. A method for treating suspensions containing oxides.