JPH07313999A - Dehydration of sludge - Google Patents

Abstract

PURPOSE:To dehydrate org. sludge whose negative charge is lowered by the addition of a metal salt. CONSTITUTION:A cationic vinyl polymer is added to org. sludge whose negative charge is lowered by the addition of a metal salt to form floc which is, in turn, dehydrated. The polymer is obtained by polymerizing a vinyl monomer containing 0.0005-0.003wt.% of a polyfunctional monomer.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for coagulating and dehydrating sludge containing a large amount of metal salts.

[0002]

2. Description of the Related Art As shown in FIG. 1, in order to reduce the negative charge of sludge and neutralize it for the purpose of improving dehydration, a cationic coagulant is added to sludge to which a metal salt has been added to coagulate and dehydrate. The method is known.

Further, (1) a method of adding a cationic coagulant and an anionic coagulant in two steps to coagulate and dehydrate,
(2) A method has been proposed in which a mixed amphoteric polymer flocculant containing a cationic flocculant and an anionic flocculant or an intramolecular amphoteric polymer flocculant is added to perform coagulation dehydration.

[0004]

However, if the addition amount of the metal salt agent is increased in order to sufficiently reduce the negative charge of sludge, the conventional cationic flocculant loses sufficient cohesive force, or Even if flock is made, it is weak and the drainage and water content are not improved.

Further, the two-step addition method requires complicated processing,
Increase processing costs. The amphoteric polymer flocculant has a limited dissolution pH or a suitable sludge system pH in order to exhibit sufficient performance, and a metal salt is used in order to sufficiently reduce the water content of the dehydrated cake. Need more,
It is not always sufficient treatment.

The inventors of the present invention have arrived at the present invention as a result of intensive research in order to solve such problems.

[0007]

According to the present invention, a polyfunctional monomer is used in an amount of 0.0005 wt.
A sludge characterized in that a cationic vinyl-based polymer obtained by adding and polymerizing in the range of 003 wt% is added to a sludge in which a negative charge of sludge is reduced by adding a metal salt to form flocs to dehydrate the sludge. It is a dehydration method.

[0008]

[Function] When a conventional polymer flocculant is added to sludge containing a metal salt for the purpose of improving the water content, it is considered that the polymer is threaded due to the influence of the inorganic metal salt in the sludge. It is considered that the aggregation performance does not appear.

[0009] However, in the case of a vinyl polymer obtained by polymerizing by adding a polyfunctional monomer, even if it is added to sludge containing a metal salt, it will prevent or reduce the formation of yarn bran, and it is suitable for coagulating sedimentation and dehydration treatment. It is believed that it is possible to form a sufficiently firm floc and reduce the water content of the dehydrated cake.

The present invention will be described in detail below.

As the cationic vinyl polymer used in the present invention, one or two nonionic vinyl monomers are used.
Copolymers obtained by polymerizing one or more and one or more cationic vinyl monomers with one or more polyfunctional monomers, and a cationic vinyl monomer 1.
There are copolymers obtained by polymerizing one or more polyfunctional monomers by adding one or more polyfunctional monomers.

Further, one or more kinds of nonionic monomers are added to one or more kinds of polyfunctional monomers to form a copolymer obtained by polymerization, and then the functional groups are modified. A method of finally using a cationic polymer may be used.

For example, a method in which methylenebisacrylamide is added in advance to polymerize acrylamide to form polyacrylamide, which is then converted into a cationic polymer by a Mannich reaction, a Hoffmann decomposition reaction, and the like are included.

The vinyl monomer used in the present invention is (a) nonionic, (b) cationic and water-soluble. Specific examples are as follows.

(A) Nonionic vinyl monomer (meth) acrylamide, vinyl methyl ether, vinyl ethyl ether and the like.

(B) Cationic vinyl monomer The following (1-A), (2-A), (3-A), (4
-A) selected from the group.

(1-A) Quaternary nitrogen-containing (meth) acrylate [(meth) acrylate refers to acrylate or methacrylate. The same applies below. ]

(I) (meth) acryloyloxyalkyltrialkylammonium salt such as 2- (meth) acryloyloxyethyltrimethylammonium chloride,
2- (meth) acryloyloxyethyltrimethylammonium methosulfate, 2- (meth) acryloyloxyethyltriethylammonium ethosulfate, 3
-(Meth) acryloyloxypropyldimethylethylammonium methosulfate and the like.

(Ii) (meth) acryloyloxyhydroxyalkyltrialkylammonium salt, eg 3-
Methacryloyloxy-2-hydroxypropyltrimethylammonium chloride, 3-methacryloyloxy-2
-Hydroxypropylmethyldiethylammonium chloride, 3-methacryloyloxy-2-hydroxypropyltrimethylammonium methosulfate and the like.

(2-A) Salt of tertiary nitrogen-containing (meth) acrylate and acid

(I) Dialkylaminoalkyl (meth)
Acrylate salts such as 2-dimethylaminoethyl (meth) acrylate sulfate and 2-diethylaminoethyl (meth) acrylate hydrochloride.

(Ii) Dialkylaminohydroxyalkyl (meth) acrylate salts such as 3-dimethylamino-2-hydroxypropyl (meth) acrylate hydrochloride, 3-diethylamino-2-hydroxypropyl (meth) acrylate sulfate and the like.

(3-A) quaternary nitrogen-containing (meth) acrylamide

(I) (Meth) acrylamidoalkyltrialkylammonium salt such as 3-acrylamidopropyltrimethylammonium chloride, 2- (meth) acryloylaminoethyltrimethylammonium methosulfate.

(Ii) (meth) acrylamidohydroxyalkyltrialkylammonium salt, eg 3-
(Meth) acryloylamino-2-hydroxypropyltrimethylammonium chloride, 3- (meth) acryloylaminoethyltrimethylammonium methosulfate and the like.

(4-A) Salt of tertiary nitrogen-containing (meth) acrylamide and acid

(I) Dialkylaminoalkyl (meth)
Acrylamide salts such as 2-dimethylaminoethyl (meth) acrylamide hydrochloride and 2-diethylaminopropyl (meth) acrylamide sulfate.

(Ii) Dialkylaminohydroxyalkyl (meth) acrylamide salts such as 3-dimethylamino-2-hydroxypropyl (meth) acrylamide acetate, 3-diethylamino-2-hydroxypropyl (meth) acrylamide sulfate and the like.

As the polyfunctional monomer, N,
N'-methylenebisacrylamide, N, N'-methylenebismethacryamide, polyethylene glycol di (meth) acrylate, polypropylene glycol di (meth) acrylate, divinyl compound such as divinylbenzene, vinyl methylol compound such as methylol methacrylamide , Vinyl aldehyde compounds such as acrolein, and vinyl compounds such as methyl acrylamide glycolate methyl ether.

The polyfunctional monomer of the polymer used in the present invention is 0.000 based on the total amount of the water-soluble vinyl monomer.
It is a mixture of 5 to 0.003 wt% and copolymerization.

If the amount of the polyfunctional monomer is less than 0.0005 wt%, only the effect equivalent to that of the commonly used polymer flocculant can be obtained, and if it exceeds 0.003 wt%, the amount added to sludge becomes too large. The effect cannot be recognized within a realistic range of addition amount.

The cationic degree of the cationic vinyl polymer used in the present invention (cationic polymer flocculant physical property display method and analytical method-3, Polymer Coagulant Industry Association) is 1 meq.
/ G or more, preferably 1.5 meq / g or more is particularly effective.

The metal salt added to or contained in the sludge includes polyaluminum chloride, a sulfuric acid band, and a second chloride.
Examples include iron, ferrous sulfate, ferric sulfate, polyiron, and sodium aluminate. The sludge may contain one kind or two or more kinds of these metal salts.

The addition amount and content of these metal salts vary depending on the properties of the sludge to be treated.
1500 to 4000 ppm is a generally preferable range from the economical aspect with respect to sludge.

The polymer used in the present invention can be copolymerized by a commonly used known polymerization method.

Particularly preferred is a method of copolymerizing the water-soluble vinyl monomer and a small amount of a polyfunctional monomer in a hydrophobic surfactant and an organic solvent.

Further, a chain transfer agent, a chelating agent or the like can be used if necessary. Further, the polyfunctional monomer may be added at any time before, during or after the polymerization.

For example, an aqueous solution containing a water-soluble vinyl monomer and a polyfunctional monomer and an organic dispersion medium containing a hydrophobic surfactant having an HLB of 3 to 6 are mixed and emulsified, and then a radical polymerization catalyst is present. There is a method of producing a water-in-oil type cationic polymer emulsion by polymerizing at a temperature of 30 to 80 ° C. (Japanese Patent Application No. 61-236250).

To this water-in-oil emulsion, a hydrophilic surfactant is added and mixed with water, and the emulsion is converted into an oil-in-water emulsion for use.

The method for obtaining the cationic polymer of the present invention is as follows:
A method in which a cationic polymer is finally obtained by modifying the functional group may be used.

For example, a method in which acrylamide is preliminarily polymerized to form polyacrylamide, which is then converted into a cationic polymer by a Mannich reaction, a Hoffmann decomposition reaction, or the like is included.

The polymer used in the present invention may be in the form of powder or liquid such as emulsion and suspension, but emulsion having good water dispersibility is preferable.

When such a polymer is added to a sludge to which a metal salt is added or contained and stirred and mixed, a firm and hard floc is obtained.

The metal salt may be added either before the polymer is added and mixed and stirred, or when it is added together with the polymer.

The method of adding the polymer to the sludge, stirring, and mixing is not specified because it varies depending on the conditions of the sludge to be treated. 0.1 wt% or more and 5 wt% or less, preferably about 2 to 0.3 wt% of a polymer active ingredient is added to a product (according to the sewer test method), and rapid stirring is performed for a short time to form flocs, which are dehydrated. The method of doing is mentioned.

Hereinafter, the present invention will be described more specifically with reference to examples.

[0047]

Examples and Comparative Examples 240.0 g of dimethylaminoethyl acrylate methyl chloride quaternary compound (DMAEA),
And 160.0 g of acrylamide (AMD) and 0 g of methylenebisacrylamide (MBA) (Sample
A, 0 wt%), 0.004 g (Sample B,
0.001 wt%), 0.01 g (Sample C,
0.0025 wt%), 0.02 g (Sample
D, 0.005 wt%) was dissolved in 307 g of distilled water to prepare an aqueous solution of 15.4 g of nonionic surfactant of HLB4.2.
Was poured into 204.7 g of paraffin oil and emulsified with a homogenizer.

This was degassed with nitrogen gas and a water-soluble azo catalyst was added to polymerize the cationic vinyl polymer.

An aqueous solution prepared by dissolving 233.1 g of methyl quaternary dimethylaminoethyl acrylate (DMAEA), 32.3 g of sodium acrylate (NaAc) and 134.5 g of acrylamide (AMD) in 307 g of distilled water was used to obtain HLB4.2. Nonionic surfactant of 15.
4 g was poured into 204.7 g of paraffin oil and emulsified with a homogenizer.

This was degassed with nitrogen gas, and a water-soluble azo catalyst was added to polymerize the amphoteric vinyl polymer (Sampl).
e E).

Sludge collected from a food factory from these polymers (TS (evaporation residue) 0.64%, SS (suspended matter))
0.58%, VTS (loss on ignition of evaporation residue) 78.4
4%, VSS (Ignition loss of suspended solids) 85.25%) 1
Collect 50 ml and use polyiron (Fe ³⁺ 11
Poly iron stock solution containing more than 50% of total sludge is 1500
After adding ppm and stirring, 0.6% of each cationic vinyl polymer and amphoteric vinyl polymer polymerized as described above with respect to sludge TS was added, and after stirring with a CST mixer at 1000 rpm for 30 seconds Then, the floc size was visually determined, then poured on a 60 mesh screen, and the amount of drainage after 10 seconds was measured with a graduated cylinder.

Further, the water content was measured by dewatering the sludge remaining on the screen at 2000 rpm for 5 minutes with a circular sedimentation tube type centrifugal separator.

Table 1 shows these results and the results when polyiron was not added.

From Table 1, according to the method of the present invention, sludge can be efficiently dehydrated.

300.0 g of methyl chloride quaternary product of dimethylaminoethyl acrylate (DMAEA), and 100.0 g of acrylamide (AMD), and 0 g of methylenebisacrylamide (MBA) (Sample F, 0).
wt%), 0.004 g (Sample G, 0.00
1 wt%), 0.01 g (Sample H, 0.00
25 wt%), 0.02 g (Sample I, 0.0
(05 wt%) dissolved in 307 g of distilled water
The nonionic surfactant of B4.2 (15.4 g) was poured into paraffin oil (204.7 g) and emulsified with a homogenizer.

This was degassed with nitrogen gas, and a water-soluble azo catalyst was added to polymerize the cationic vinyl polymer.

A solution of 235.5 g of methyl quaternary dimethylaminoethyl acrylate (DMAEA), 16.3 g of sodium acrylate (NaAc) and 148.10 g of acrylamide (AMD) dissolved in 307 g of distilled water was prepared as HLB4.2. Nonionic surfactant 1
5.4 g was poured into 204.7 g of paraffin oil and emulsified with a homogenizer.

This was degassed with nitrogen gas, and a water-soluble azo catalyst was added to polymerize the amphoteric vinyl polymer (Sampl).
e J).

Mixed sludge (TS 1.85%, SS 1.68%, VTS
(65.45%, VSS 65.29%) 300 ml was placed in a beaker, and 2000 ppm of polyaluminum chloride (polyaluminum chloride stock solution containing 10% of Al ₂ O ₃ as a metal salt) was added as a metal salt, and the mixture was stirred, Then, each cationic vinyl polymer and amphoteric vinyl polymer polymerized as described above were added to sludge TS in an amount of 0.6.
%, And after stirring for 30 seconds at 400 rpm with a three-blade mixer, the floc size was visually determined, then 60
The amount of drainage after 10 seconds of pouring on a mesh screen was measured with a graduated cylinder.

Further, the sludge remaining on the screen was 0.05, 0.10, 0.15, 0.20 by a pressure type dehydration tester.
The water content was measured by pressure dehydration for 1 minute at each surface pressure of kg / cm ² . Table 2 shows these results and the results when the polyaluminum chloride stock solution containing 10% of Al ₂ O ₃ was not added.

[0061]

[Table 1]

[0062]

[Table 2]

[0063]

According to the method of the present invention, sludge can be efficiently dehydrated.

[Brief description of drawings]

FIG. 1 is a general process flow diagram.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Masuzou Machida 1190 Kasama-cho, Sakae-ku, Yokohama Mitsui Cytec Co., Ltd. Ofuna Technical Research Institute

Claims (1)

[Claims] 1. A negative charge of sludge obtained by adding a metal salt selected from polyaluminum chloride, sulfuric acid band, ferric chloride, ferrous sulfate, ferric sulfate, polyiron, and sodium aluminate to organic sludge. Of polyfunctional monomer from 0.0005 wt% to 0.003 wt% based on all monomers
The sludge dewatering method is characterized in that a cationic vinyl polymer obtained by adding and polymerizing within the range is added to form flocs for dehydration.