JP5732818B2 - Sludge dewatering agent and sludge dewatering method - Google Patents

Description

  The present invention relates to a sludge dewatering agent capable of efficiently dewatering hardly dewatering organic sludge and a sludge dewatering method using the sludge dewatering agent.

Organic sludge mainly composed of surplus sludge generated in food factories, chemical factories, sewage treatment plants, etc. is generally dehydrated with a dehydrator after adding a sludge dehydrating agent.
Conventionally, as a sludge dehydrating agent to be added to the treated sludge, a vinyl cationic polymer, particularly dimethylaminoethyl methacrylate (DAM) or its methyl chloride quaternized product (DAM · MeCl ₄ ), dimethylaminoethyl acrylate (DAA) Alternatively, a cationic polymer dehydrating agent such as methyl chloride quaternized product (DAA · MeCl ₄ ) is mainly used, but with the aim of further reducing the water content of the dehydrated cake obtained, A method of adding an amphoteric polymer dehydrating agent after adding an inorganic flocculant instead of using alone is also proposed (for example, Patent Document 1).

  However, the method using an inorganic flocculant has drawbacks such as an increase in the amount of sludge due to the inorganic flocculant and a complicated adjustment of the addition rate balance of the two kinds of chemicals, the inorganic flocculant and the polymer dehydrating agent. For this reason, it is desired to dehydrate organic sludge only with a polymer dehydrating agent.

As sludge dewatering methods using a polymer dehydrating agent, combined use of polyvinylamine or polyamidine and a vinyl cationic polymer (Patent Documents 2 and 3), and combined use of polyamidine and a crosslinkable vinyl cationic polymer (Patent Document 4) ) Etc. have been proposed. In addition, Patent Documents 2 to 4 also describe benzyl-based polymers as vinyl-based cationic polymers, but only examples are given as one of many vinyl-based cationic polymers. There is no. Conventionally, the above-mentioned DAA, DAM, DAA · MeCl ₄ , DAM · MeCl _{4 and the} like are usually used as the vinyl cationic polymer.

  Patent Document 5 proposes a sludge dewatering agent comprising a copolymer of a benzylic cationic monomer and a non-benzylic cationic monomer. Patent Document 5 discloses a benzylic cationic polymer ( Methacryloyloxyethyldimethylbenzylammonium chloride homopolymer or copolymer) shows a good effect on sludge containing a large amount of inorganic salt, but it is described that a sufficient effect cannot be obtained on other sludges. Yes.

JP 63-158200 A JP-A-4-293600 JP-A-6-218400 JP 2004-25095 A Japanese Patent Publication No. 7-71678

  Many organic sludges are difficult to dehydrate, and the moisture content of the dehydrated cake obtained by adding a sludge dehydrating agent to such organic sludge is usually as high as 80% or more, and this is incinerated. Further reduction of the moisture content of the resulting dehydrated cake is desired from the viewpoint of disposal costs and environmental impact, such as an increase in incinerated fuel and an increase in final disposal amount. In addition, surplus sludge does not have sufficient strength of agglomeration floc obtained by adding a dehydrating agent. Especially, it is consolidated with metal slits such as multiple disk dehydrators, screw press dehydrators, rotary press dehydrators and metal mesh filtration parts. When a dehydrator having a dewatering unit is used, a decrease in dewatering efficiency (decrease in cake yield) due to SS leakage from the filtration unit is also a problem.

For such problems, none of the conventional sludge dewatering agents can be said to be sufficiently satisfactory. For example, polyvinylamine described in Patent Documents 2 and 3, or polyvinylamine and a vinyl cationic polymer. In combination, the water content of the dehydrated cake obtained cannot be lowered sufficiently. In addition, the crosslinkable vinyl cationic polymer described in Patent Document 4 has problems such as poor handling in addition due to poor solubility in water; easy deterioration due to moisture absorption and poor temporal stability. .
The present invention provides a sludge dewatering agent and a sludge dewatering method capable of solving the above-mentioned conventional problems and efficiently obtaining a dehydrated cake having a low water content by efficiently dewatering hardly dewaterable organic sludge. This is the issue.

  As a result of intensive studies to solve the above-mentioned problems, the present inventor efficiently dehydrated difficult-to-dehydrate organic sludge by using a combination of polyvinylamidine or polyvinylamine and a benzylic vinyl cation polymer. It has been found that a dehydrated cake having a low water content can be obtained.

  The present invention has been achieved on the basis of such findings, and the gist thereof is as follows.

[1] Cationic polymer A having an amidine unit represented by the following general formula (1) or (2) or a vinylamine unit represented by the following general formula (3) as a repeating unit, and the following general formula (4) And a cationic polymer B having a benzylic cationic unit as a repeating unit, wherein the cationic polymer A and the cationic polymer B are in a weight ratio of 30 to 70:70 to 30. The cationic polymer A is a copolymer having an amidine unit represented by the following general formula (1) or (2) and another repeating unit, and the amidine unit is contained in all repeating units. A copolymer containing 20 to 90 mol%, or a homopolymer consisting only of vinylamine units represented by the following general formula (3), or A copolymer having a nilamine unit and another repeating unit, wherein the vinylamine unit is contained in an amount of 35 mol% or more in all repeating units, and the cationic polymer B is represented by the general formula (4). Or a copolymer having the benzylic cation unit and another repeating unit, the benzylic cation unit being contained in 70% by mole or more in all the repeating units. A sludge dehydrating agent characterized by being a copolymer.

(In the above formula, R ¹¹ and R ¹² each independently represents a hydrogen atom or a methyl group, and X ⁻ represents a salt-forming anion.)

(In the above formula, Y ⁻ represents a salt-forming anion.)

(In the above formula, R ¹ represents a hydrogen atom or a methyl group, R ² represents an alkylene group having 1 to 4 carbon atoms, R ^3a and R ^3b each independently represents an alkyl group having 1 to 4 carbon atoms, R ⁴ is -NH- .A is -O- or where a benzyl group, Z ^- represents a salt-forming anion).

[2] The sludge dehydrating agent according to [1], comprising the cationic polymer A and the cationic polymer B in a weight ratio of 30 to 70:70 to 30.

[ 2 ] A sludge dewatering method, wherein the sludge dewatering agent according to [1 ] is added to the sludge for dehydration.

[ 3 ] The sludge dewatering method according to [ 2 ], wherein the sludge dewatering agent is added at a ratio of 0.4 to 2.0% by weight with respect to SS of the sludge.

[ 4 ] The sludge dewatering method according to [ 2 ] or [ 3 ], wherein the sludge is an organic sludge having a VSS / SS ratio of 0.68 or more.

[ 5 ] The sludge dewatering method according to any one of [ 2 ] to [ 4 ], wherein the dewatering is performed by a multiple disk dehydrator, a screw press dehydrator, or a rotary pressure dehydrator.

  By adding the sludge dehydrating agent of the present invention to sludge and agglomerating it, it is possible to obtain a coagulated floc having excellent filtration and dewatering properties and high strength.

  This agglomerated floc has sufficient strength and is easy to handle. For example, a dehydrator having a filtration part and a consolidation dehydration part made of a metal slit or metal mesh, for example, a screw press dehydrator or a rotary press filter dehydrator was used. Even if it is a case, the leakage of SS from a filtration part is prevented, and a cake yield (SS collection | recovery efficiency) can be improved. Moreover, since it is excellent in filtration and dehydrating property, it can be dehydrated to obtain a dehydrated cake having a low water content.

  The dehydrated cake obtained by the present invention has a low water content compared to the dehydrated cake obtained by the conventional method, and thus has a small capacity, and can reduce the incinerated fuel when incinerated. Because of its small capacity, it can reduce transportation costs, sludge disposal costs, and environmental impact.

  Hereinafter, embodiments of the present invention will be described in detail.

In this specification, “polymer” is a general term for polymers or polymers including “homopolymer (homopolymer)” and “copolymer (copolymer)”. However, homopolymers include those having one type of repeating unit and those containing the same type of repeating unit, that is, two or more types of amidine units, vinylamine units and benzylic cation units represented by the same general formula. Shall.
Further, “(meth) acryl” means “acryl” and / or “methacryl (methacryl)”, and the same applies to “(meth) acrylate” and “(meth) acrylo”.

[Action mechanism]
Although the details of the action mechanism of the effect of improving the dehydration efficiency of the present invention using the specific cationic polymer A and the cationic polymer B in combination are not clear, the benzyl group of the benzyl quaternized salt contained in the cationic polymer B Due to the high hydrophobicity derived, the water affinity of the aggregated floc obtained by adding the sludge dehydrating agent of the present invention is reduced, and the aggregated floc excellent in dehydrating property is easily formed and the water content is easily lowered. In combination with the cohesive strength of the conductive polymer A, it is presumed that the high dehydration efficiency that cannot be obtained by the combination with the conventional non-benzyl vinyl cationic polymer is obtained.

[Cationic polymer A]
The cationic polymer A used in the present invention is an amidine unit represented by the following general formula (1) (hereinafter sometimes referred to as “amidine unit (1)”) or an amidine represented by the following general formula (2). A unit (hereinafter sometimes referred to as “amidine unit (2)”) or a vinylamine unit represented by the following general formula (3) (hereinafter sometimes referred to as “vinylamine unit (3)”). It has as a repeating unit.

(In the above formula, R ¹¹ and R ¹² each independently represents a hydrogen atom or a methyl group, and X ⁻ represents a salt-forming anion.)

(In the above formula, Y ⁻ represents a salt-forming anion.)

In the above general formulas (1) to (3), X ⁻ and Y ⁻ are a halogen ion such as chlorine ion, bromine ion or iodine ion, 1 / 2SO ₄ ²⁻ , NO ₃ ⁻ , CH ₃ COO ⁻ , CH ₃ SO ₄ ⁻ , C ₂ H ₅ SO ₄ ^{— and the} like.

  The cationic polymer A (which may contain both the amidine unit (1) and the amidine unit (2)) containing the amidine unit (1) or the amidine unit (2) as a repeating unit used in the present invention may be used. N-vinylcarboxylic acid amide or N-isopropenylcarboxylic acid amide represented by the following general formula (5), (meth) acrylonitrile represented by the following general formula (6), and those used as necessary It can be obtained by copolymerizing a copolymerizable monomer (hereinafter sometimes referred to as “copolymerizable monomer”), and hydrolyzing and amidating the resulting copolymer.

(In the formula, R ¹¹ is a hydrogen atom or a methyl group, and R ¹³ is a hydrogen atom or an alkyl group having 1 to 4 carbon atoms.)

CH ₂ = CR ¹² -CN (6)

(In the formula, R ¹² is a hydrogen atom or a methyl group.)

  Examples of the N-vinylcarboxylic acid amide include N-vinylformamide, N-vinylacetamide, N-vinylpropionamide, N-vinylbutyramide, N-vinyl barrelamide, and the like. Examples of N-isopropenylcarboxylic acid amide include N-isopropenylformamide, N-isopropenylacetamide, N-isopropenylpropionamide, N-isopropenylbutyramide, N-isopropenylvaleramide and the like. .

  N-vinyl succinimide, N-vinyl glutarimide, N-isopropenyl succinimide, N-isopropenyl glutarimide, etc. instead of N-vinyl carboxylic amide or N-isopropenyl carboxylic amide as required N-vinylcarboxylic acid imide or N-isopropenylcarboxylic acid imide can be used.

  As the copolymerizable monomer, any monomer having an appropriate monomer reactivity ratio can be used without limitation. For example, (meth) acrylamide, styrene, methyl (meth) acrylate, ethyl (meth) acrylate, vinyl acetate Nonionic monomers such as N-vinylpyrrolidone, (meth) acrylic acid or alkali metal salts thereof, monomers having a sulfone group such as vinylsulfonic acid, 2-acrylamido-2-methylpropanesulfonic acid, styrenesulfonic acid, or alkalis thereof Examples thereof include one or more anionic monomers such as metal salts, cationic monomers such as tertiary salts or quaternary ammonium salts such as dimethylaminoethyl (meth) acrylate and dimethylaminopropyl (meth) acrylamide. it can.

  The polymerization method is not particularly limited, and solution polymerization, suspension polymerization, emulsion polymerization, and the like can be selected according to the monomer used and the solubility of the polymer to be formed. For example, if the monomer to be used and the polymer to be produced are both water-soluble, aqueous solution polymerization is possible. The monomer is dissolved in water, an inert gas is bubbled, the temperature is raised to a predetermined temperature, and then a water-soluble polymerization initiator is used. The polymer can be obtained by adding. The polymer obtained by aqueous solution polymerization can be subjected to hydrolysis and amidine reaction as it is or after isolation. Moreover, when the solubility of the monomer used in water is small, suspension polymerization, emulsion polymerization, or the like can be used.

  In emulsion polymerization, a polymer can be obtained by adding a monomer, an emulsifier, a water-soluble polymerization initiator and the like to water and heating in an inert gas atmosphere with stirring.

  As the polymerization initiator, general initiators such as ammonium persulfate, potassium persulfate, and 2,2′-azobis (2-amidinopropane) dihydrochloride can be used, and azo compounds are particularly preferable.

In the present invention, by heating an aqueous solution of the above polymer in the presence of an acid or alkali, the acid amide unit in the polymer is hydrolyzed to an amine unit, and the amidine unit is further reacted by the reaction of the nitrile unit adjacent to the amine unit. An amidation reaction to produce (1) and / or (2) is performed.
Amidine units (1) and (2) are determined by the isomers of the monomers to be reacted. This isomer usually coexists.

  The hydrolysis and amidination reaction can be carried out in two stages, but usually it is preferably carried out in one stage. The reaction conditions can be selected depending on the structure of the polymer and the desired hydrolysis rate and amidation rate. Usually, the above polymer is made into an aqueous solution or water dispersion of 5 to 80% by weight, 1 to 5 equivalents of acid to acid amide units, or 1 to 5 equivalents of alkali to acid amide units is added, and 40 to By heating to 100 ° C., hydrolysis and amidine reaction can be performed. In the case of hydrolysis and amidation reaction with an acid, the amino group of the resulting cationic polymer A forms an ammonium salt.

  Among the copolymerizable monomers, a part of the structural units in the polymer derived from (meth) acrylamides and (meth) acrylates are changed to (meth) acrylic acid units by hydrolysis.

Amidine units (1), (2) the amidine units in the total repeating units constituting the cationic polymer A having a (1), the ratio of (2) is Ri 20-90 mol% der, 50-90 mol% it is good Masui is. If the amount of the amidine units (1) and (2) in the cationic polymer A is too small, the water content reduction effect due to the inclusion of the amidine units (1) and (2) is lowered. A polymer containing more than 90 mol% of amidine units (1) and (2) in all repeating units is not easy to produce.

  The cationic polymer A having amidine units (1) and (2) preferably has a high molecular weight, and has an intrinsic viscosity of 1 dl / g or more measured at 30 ° C. using a 1N sodium chloride aqueous solution serving as a molecular weight index as a solvent. It is preferable that it is 3 dl / g or more. The upper limit of this intrinsic viscosity is usually 10 dl / g or less.

  In the present invention, the cationic polymer A having a vinylamine unit (3) is an N-vinyl carboxylic acid amide or N-isopropenyl carboxylic acid amide represented by the general formula (5) and, if necessary, other It can be obtained by polymerizing or copolymerizing a copolymerizable monomer and hydrolyzing the resulting polymer.

  As N-vinylcarboxylic acid amide or N-isopropenylcarboxylic acid amide, those exemplified for use in the production of cationic polymer A having amidine units (1) and (2) can be used. N-vinylformamide, N-vinylacetamide, N-vinylpropionamide, N-vinylbutyramide, N-vinylvaleramide, N-isopropenylformamide, N-isopropenylacetamide, N-isopropenylpropionamide, N-iso Propenylbutyramide, N-isopropenylvaleramide and the like can be used. Moreover, N-vinyl carboxylic imide or N-isopropenyl carboxylic imide can be used instead of N-vinyl carboxylic amide or N-isopropenyl carboxylic amide as needed.

  As the copolymerizable monomer, any monomer having an appropriate monomer reactivity ratio can be used without limitation. For example, (meth) acrylamide, styrene, methyl (meth) acrylate, ethyl (meth) acrylate, vinyl acetate , A nonionic monomer such as acrylonitrile, N-vinylpyrrolidone, a monomer having a sulfone group such as (meth) acrylic acid or an alkali metal salt thereof, vinylsulfonic acid, 2-acrylamido-2-methylpropanesulfonic acid, styrenesulfonic acid, or the like One or more of anionic monomers such as alkali metal salts, cationic monomers such as tertiary salts or quaternary ammonium salts such as dimethylaminoethyl (meth) acrylate and dimethylaminopropyl (meth) acrylamide are listed. It is possible .

  In the present invention, the method for polymerizing the above monomers is not particularly limited, and solution polymerization, suspension polymerization, emulsion polymerization, and the like can be selected according to the monomers used and the solubility of the produced polymer. By heating an aqueous solution of the obtained polymer in the presence of an acid or an alkali, the acid amide unit in the polymer is hydrolyzed to produce a vinylamine unit (3).

  In the present invention, reaction conditions can be selected according to the polymer structure and the desired hydrolysis rate. Usually, the above polymer is made into an aqueous solution or water dispersion of 5 to 80% by weight, 1 to 5 equivalents of acid to acid amide units, or 1 to 5 equivalents of alkali to acid amide units is added, and 40 to Hydrolysis can be performed by heating to 100 ° C. In the case of hydrolysis with an acid, the amino group of the resulting cationic polymer A forms an ammonium salt, and in the case of hydrolysis with an alkali, the amino group of the resulting cationic polymer A is free. It becomes a form.

  Among the copolymerizable monomers, a part of the structural unit in the polymer derived from (meth) acrylamides and (meth) acrylates is changed to a (meth) acrylic acid unit by hydrolysis.

Ratio of vinylamine the total repeating units units (3) constituting the cationic polymer A having a vinylamine unit (3) is 35 to 100 mol% der is, it is favorable preferable 60 to 80 mol%. When there are too few vinylamine units (3) in the cationic polymer A, the aggregation performance as a sludge dewatering agent will fall.

  The cationic polymer A having a vinylamine unit (3) preferably has a high molecular weight, and preferably has an intrinsic viscosity of 4 dl / g or more measured at 30 ° C. using a 1N sodium chloride aqueous solution serving as a molecular weight index as a solvent. More preferably, it is 5 dl / g or more. The upper limit of this intrinsic viscosity is usually 10 dl / g or less.

  Further, the colloid equivalent of the cationic polymer A is preferably 5.0 to 6.4 meq / g, particularly preferably 5.5 to 6.4 meq / g. When the colloid equivalent of the cationic polymer A is within this range, high cohesiveness can be obtained, which is preferable. The colloidal equivalent of the cationic polymer A is measured by “colloidal titration method” (by Soichi Sente, Nankodo Co., Ltd. (issued in November, S44)).

  In the present invention, the cationic polymer A can be used as a sludge dewatering agent as an aqueous solution that has been subjected to the amidation reaction or hydrolysis, or as a concentrated or diluted aqueous solution. Alternatively, an aqueous solution of the cationic polymer A can be mixed with an organic solvent such as acetone to precipitate the cationic polymer A, and then separated, dried, powdered, or used as an emulsion.

[Cationic polymer B]
The cationic polymer B used in the present invention contains a benzylic cation unit (4) represented by the following general formula (4) (hereinafter sometimes referred to as “benzylic cation unit (4)”) as a repeating unit. It is a waste.

(In the above formula, R ¹ represents a hydrogen atom or a methyl group, R ² represents an alkylene group having 1 to 4 carbon atoms, R ^3a and R ^3b each independently represents an alkyl group having 1 to 4 carbon atoms, R ⁴ is -NH- .A is -O- or where a benzyl group, Z ^- represents a salt-forming anion).

In the general formula (4), R ¹ is a hydrogen atom or a methyl group, R ² is an alkylene group having 1 to 4 carbon atoms such as a methylene group, an ethylene group, a propylene group, or a butylene group, and the propylene group and butylene. The group may be linear or have a side chain. R ^3a and R ^3b are each independently an alkyl group having 1 to 4 carbon atoms such as methyl group, ethyl group, n-propyl group, isopropyl group, n-butyl group, isobutyl group, sec-butyl group, and tert-butyl group. And R ⁴ is a benzyl group. A is —O— or —NH—, and Z ⁻ is a halogen ion such as chlorine ion, bromine ion, iodine ion, 1 / 2SO ₄ ²⁻ , NO ₃ ⁻ , CH ₃ COO ⁻ , CH ₃ SO _{4. ^{-, C 2 H 5 SO 4}} - is a salt-forming anion such as.

  The cationic polymer B having a repeating unit represented by the general formula (4) is produced using a benzylic cationic monomer represented by the following general formula (4A).

(In the above formula, R ¹ , R ² , R ^3a , R ^3b , R ⁴ , A and Z ⁻ have the same meaning as in general formula (4), and specific examples thereof are also the same).

  Examples of the benzylic cationic monomer represented by the general formula (4A) include dimethylamino (methyl, ethyl, propyl or butyl) acrylate or methacrylate, diethylamino (methyl, ethyl, propyl or butyl) acrylate or methacrylate, di- n-propylamino (methyl, ethyl, propyl or butyl) acrylate or methacrylate, diisopropylamino (methyl, ethyl, propyl or butyl) acrylate or methacrylate, di-n-butylamino (methyl, ethyl, propyl or butyl) acrylate or methacrylate , Di-sec-butylamino (methyl, ethyl, propyl or butyl) acrylate or methacrylate, diisobutylamino (methyl, ethyl, propyl or butyl) acrylate or methacrylate Dimethylamino (methyl, ethyl, propyl or butyl) acrylamide or methacrylamide, diethylamino (methyl, ethyl, propyl or butyl) acrylamide or methacrylamide, di-n-propylamino (methyl, ethyl, propyl or butyl) acrylamide or methacryl Amide, diisopropylamino (methyl, ethyl, propyl or butyl) acrylamide or methacrylamide, di-n-butylamino (methyl, ethyl, propyl or butyl) acrylamide or methacrylamide, di-sec-butylamino (methyl, ethyl, propyl) Or butyl) quaternization with benzyl halides such as acrylamide or methacrylamide, diisobutylamino (methyl, ethyl, propyl or butyl) acrylamide or methacrylamide. And the like. Examples of the benzyl halide include benzyl chloride and benzyl bromide.

  In the production of the cationic polymer B, these benzylic cationic monomers can be used alone or in combination of two or more.

  The cationic polymer B used in the present invention may be a homopolymer of the above-mentioned benzylic cationic monomer, but may be another monomer copolymerizable with this benzylic cationic monomer (hereinafter referred to as “copolymerizable monomer”). 1) or a copolymer with two or more thereof.

  When the cationic polymer B is a copolymer of a benzylic cationic monomer and a copolymerizable monomer, the copolymerizable monomer used is not particularly limited.

  Examples of the nonionic vinyl monomer as the copolymerizable monomer include amides such as acrylamide, methacrylamide, N, N-dimethylacrylamide and N, N-dimethylmethacrylamide, and vinyl cyanide such as acrylonitrile and methacrylonitrile. Compounds, alkyl esters of (meth) acrylic acid such as methyl acrylate, ethyl acrylate, methyl methacrylate, ethyl methacrylate, vinyl esters such as vinyl acetate, styrene, α-methyl styrene, p-methyl styrene, etc. And aromatic vinyl compounds. These nonionic vinyl monomers can be used individually by 1 type, and can also be used in combination of 2 or more type.

In the present invention, when the cationic polymer B is the above-mentioned copolymer, the effect of the present invention cannot be sufficiently obtained if the proportion of the benzylic cation unit (4) in the copolymer is excessively small. Thus, the cationic polymer B, and the ratio is 70 to 100 mol% of benzylic cation units in all repeating units (4), Ri repeating units from 0 to 30 mol% der from nonionic vinyl monomer, in particular, The proportion of the benzylic cationic unit (4) in all repeating units is 80 to 100 mol%, particularly 90 to 100 mol%, and the cationic polymer B is a homopolymer consisting only of the benzylic cationic monomer (4). Is preferred. The homopolymer includes those containing two or more benzylic cation units (4).

  Further, the cationic polymer B used in the present invention preferably has an intrinsic viscosity of 4 dl / g or more, particularly 6 dl / g or more, measured at 30 ° C. using a 0.1N sodium nitrate aqueous solution as a solvent. If the intrinsic viscosity is less than 4 dl / g, the cohesive force is weak and the amount of sludge treated may be reduced. The upper limit of this intrinsic viscosity is usually 12 dl / g or less.

  The colloid equivalent of the cationic polymer B used in the present invention is preferably 2.8 to 3.5 meq / g. If it is too small, it is difficult to obtain the hydrophobic effect of the benzyl group. The colloid equivalent of the cationic polymer B is measured by the same method as that for the cationic polymer A.

  There is no restriction | limiting in particular in the manufacturing method of the cationic polymer B used for this invention, Any methods, such as solution polymerization, suspension polymerization, and emulsion polymerization which are conventional methods, can be used. In aqueous solution polymerization, the monomer is dissolved in water, the atmosphere is replaced with an inert gas, the temperature is raised to the polymerization temperature, and ammonium persulfate, potassium persulfate, 2,2′-azobis (2- Polymerization can be carried out by adding a water-soluble polymerization initiator such as amidinopropane) dihydrochloride.

[Proportion of cationic polymer A and cationic polymer B]
When the ratio of the cationic polymer A and the cationic polymer B in the sludge dehydrating agent of the present invention is excessively large and excessively small, the effect of the present invention by using these two types of polymers in combination. Can't get enough.

Thus, the proportion of the cationic polymer A and the cationic polymer B in the sludge dehydrating agent of the present invention, 30 to 70 by weight ratio: ranges der of 70-30 is, in particular 40 to 60: in the range of 60 to 40 Preferably there is.

[Form of sludge dehydrating agent]
The sludge dehydrating agent of the present invention is only required to contain the above-mentioned cationic polymer A and cationic polymer B, and even if the cationic polymer A and the cationic polymer B are provided separately, These may be mixed in advance to form a single agent.
If the cationic polymer A and the cationic polymer B are previously mixed at a predetermined ratio into a single agent, the addition control of the dehydrating agent to the sludge is simplified, which is preferable.

  In addition, the sludge dehydrating agent of the present invention contains one or more kinds of agents other than the cationic polymer A and the cationic polymer B, such as powder acids such as sulfamic acid and salts such as sodium sulfate. Also good.

[Dehydration method]
In order to add the sludge dehydrating agent of the present invention to sludge and dehydrate it, the sludge dehydrating agent of the present invention may be added to the sludge and mixed for about 20 seconds to 5 minutes, and then charged into a dehydrator for dehydration.
The mixing of the sludge dewatering agent and the sludge may be performed in a transfer pipe. If the dehydrator has a mixing mechanism such as a centrifugal dehydrator, the mixing step before dehydration may be omitted. it can.

  The amount of the sludge dehydrating agent added to the sludge is not limited as long as high dewaterability is obtained with a sufficient coagulation effect, and is appropriately determined depending on the sludge properties and the type of polymer used. The total addition amount of the cationic polymer A and the cationic polymer B is about 20 to 400 mg / L, particularly about 50 to 300 mg / L with respect to about 2% by weight of sludge, that is, 0.4 with respect to the sludge SS. It is preferable to set the amount to be about 2.0 to 2.0% by weight, particularly about 1.0 to 1.5% by weight.

  The cationic polymer A and the cationic polymer B may be added to the sludge at the same time, may be added in advance, or may be added separately.

  The dehydrator to be used is not particularly limited, and various dehydrators such as a multiple disk dehydrator, a screw press dehydrator, a rotary pressure dehydrator, a filter press dehydrator, a belt press dehydrator, a centrifugal dehydrator, etc. can be applied. However, in the sludge dewatering method using the sludge dewatering agent of the present invention, a multi-disk dewatering machine, a screw press dewatering machine, and a rotary pressure dewatering machine are preferably used because of particularly strong floc strength and excellent drainage.

  According to the present invention, by such a dehydration treatment, a dehydrated cake having a low water content of 80% by weight or less can be obtained. The obtained dehydrated cake is used for incineration or landfill disposal.

The sludge to be dehydrated in the present invention is not particularly limited, and is discharged from, for example, organic sludge generated in sewage, human waste, general industrial wastewater treatment, food factories, fish processing factories, meat processing factories, livestock industries, etc. Surplus sludge or mixed sludge containing these sludges.
In particular, the present invention has a VSS / SS ratio of 0.68 or more and a 100 mesh sieve such as surplus sludge discharged from food factories, fishery processing factories, meat processing factories, livestock industries, etc. due to its excellent dehydration effect. It is effective for the dehydration treatment of hardly dewatering organic sludge in which the fibrous material measured in (1) is 10% by weight or less of the SS weight.

  Hereinafter, the present invention will be described more specifically with reference to production examples, examples, and comparative examples. However, the present invention is not limited to the following examples unless it exceeds the gist. In the following, “%” means “% by weight”.

  The polymers used in the following examples and comparative examples are as follows.

[Production Example 1: Production of cationic polymer A-1]
N-vinylformamide 35.5 g (0.5 mol), acrylonitrile 26.5 g (0.5 mol) and water 310 g were placed in a 500 ml flask equipped with a stirrer, reflux condenser, thermometer and nitrogen inlet tube. The atmosphere was replaced with nitrogen. The temperature was raised to 60 ° C. with stirring, 1.0 g of a 10% aqueous solution of 2,2′-azobis (2-amidinopropane) dihydrochloride was added, and polymerization was continued for 5 hours while maintaining 60 ° C. Concentrated hydrochloric acid 98.1 g (1.0 mol as hydrogen chloride) was added to the suspension in which the polymer was precipitated in water, and the mixture was reacted for 4 hours while heating to reflux to amidine the polymer. The obtained polymer solution was added to acetone, and the precipitated polymer was vacuum-dried.
The intrinsic viscosity of this cationic polymer measured at 30 ° C. using a 1N sodium chloride aqueous solution as a solvent was 4.0 dl / g. Moreover, the colloid equivalent of this cationic polymer was 7.5 meq / g in pH = 4. This cationic polymer is designated as polymer A-1.

[Production Example 2: Production of cationic polymer A-2]
In a 500 ml flask equipped with a stirrer, a reflux condenser, a thermometer, and a nitrogen inlet tube, 71.0 g (1.0 mol) of N-vinylformamide and 310 g of water were placed, and the atmosphere was replaced with nitrogen. The temperature was raised to 60 ° C. with stirring, 1.0 g of a 10% aqueous solution of 2,2′-azobis (2-amidinopropane) dihydrochloride was added, and polymerization was continued for 5 hours while maintaining 60 ° C. Concentrated hydrochloric acid 147 g (1.5 mol as hydrogen chloride) was added to the polymer solution, and the mixture was heated and refluxed for 4 hours to hydrolyze the polymer. The obtained polymer solution was added to acetone, and the precipitated polymer was vacuum-dried. The intrinsic viscosity of this cationic polymer measured at 30 ° C. using a 1N sodium chloride aqueous solution as a solvent was 5.4 dl / g. Further, the colloid equivalent of this cationic polymer was 6.2 meq / g at pH = 4. This cationic polymer is designated as polymer A-2.

[Production Example 3: Production of Cationic Polymer X-1]
In a 500 mL flask equipped with a stirrer, a reflux condenser, a thermometer, and a nitrogen introduction tube, 300 mL of a 2.0 mol / L solution of dimethylaminoethyl methacrylate in methyl chloride quaternized product was placed, and the atmosphere was replaced with nitrogen gas. . To this, 2,2′-azobis (2-amidinopropane) dihydrochloride (5.0 × 10 ⁻⁴ mol / L) was added, and the temperature was raised to 40 ° C. for polymerization for 10 hours. The obtained polymer gel was cut in acetone, filtered, and then vacuum dried to obtain a powder polymer.
The intrinsic viscosity of this cationic polymer measured at 30 ° C. using a 0.1N sodium nitrate aqueous solution as a solvent was 6.4 dl / g. Moreover, the colloid equivalent of this cationic polymer was 4.8 meq / g in pH = 4. This cationic polymer is referred to as polymer X-1.

[Production Example 4: Production of cationic polymer X-2]
In a 500 mL flask equipped with a stirrer, reflux condenser, thermometer and nitrogen inlet tube, the ratio of methyl chloride quaternized dimethylaminoethyl acrylate to acrylamide was 80:20 mol% and the total monomer concentration was 2.0 mol / 300 mL of the monomer solution adjusted to L was added, and the atmosphere was replaced with nitrogen gas. To this was added potassium persulfate (5.0 × 10 ⁻³ mol / L), the temperature was raised to 40 ° C., and polymerization was carried out for 10 hours. The obtained polymer gel was cut in acetone, filtered, and then vacuum dried to obtain a powder polymer.
The intrinsic viscosity of this cationic polymer measured at 30 ° C. using a 0.1N aqueous sodium nitrate solution as a solvent was 6.8 dl / g. Moreover, the colloid equivalent of this cationic polymer was 4.8 meq / g in pH = 4. This cationic polymer is referred to as a polymer X-2.

[Production Example 5: Production of cationic polymer B-1]
A 500 mL flask equipped with a stirrer, a reflux condenser, a thermometer, and a nitrogen inlet tube was charged with 300 mL of a 2.0 mol / L solution of benzyl chloride quaternized dimethylaminoethyl methacrylate, and the atmosphere was replaced with nitrogen gas. . To this, 2,2′-azobis (2-amidinopropane) dihydrochloride (5.0 × 10 ⁻⁴ mol / L) was added, and the temperature was raised to 40 ° C. for polymerization for 10 hours. The obtained polymer gel was cut in acetone, filtered, and then vacuum dried to obtain a powder polymer.
The intrinsic viscosity of this cationic polymer measured at 30 ° C. using a 0.1N aqueous sodium nitrate solution as a solvent was 6.6 dl / g. Further, the colloid equivalent of this cationic polymer was 3.6 meq / g at pH = 4. This cationic polymer is designated as polymer B-1.

[Production Example 6: Production of cationic polymer B-2]
In a 500 mL flask equipped with a stirrer, a reflux condenser, a thermometer, and a nitrogen introduction tube, the ratio of benzyl chloride quaternized dimethylaminoethyl acrylate to acrylamide was 80:20 mol%, and the total monomer concentration was 2.0 mol / 300 mL of the monomer solution adjusted to L was added, and the atmosphere was replaced with nitrogen gas. To this was added potassium persulfate at 5.0 × 10 ⁻⁴ mol / L, the temperature was raised to 40 ° C., and polymerization was carried out for 10 hours. The obtained polymer gel was cut in acetone, filtered, and then vacuum dried to obtain a powder polymer.
The intrinsic viscosity of this cationic polymer measured at 30 ° C. using a 0.1N sodium nitrate aqueous solution as a solvent was 6.2 dl / g. Moreover, the colloid equivalent of this cationic polymer was 4.0 meq / g in pH = 4. This cationic polymer is designated as polymer B-2.

[Examples 1-3, Comparative Examples 1-3]
A coagulation dehydration test was conducted using surplus sludge (SS: 1.15%, VSS / SS: 0.726, pH: 6.3, conductivity: 600 mS / m) of a food processing plant mainly made from soybeans. .
200 mL of sludge was collected in a 300 mL beaker, a dehydrating agent was added, and the mixture was reacted at 180 rpm for 30 seconds for aggregation. Table 2 shows the types and addition amounts of the polymers used as the dehydrating agent. Next, a tube having a diameter of 50 mm was set on the Buchner funnel, and the coagulated sludge was poured therein, and the amount of filtration after 20 seconds was measured.
In addition, evaluation of the aggregate floc strength and measurement of the moisture content and cake yield of the dehydrated cake were carried out by the following methods, and the results are shown in Table 2.

<Flock strength>
Aggregates on the Buchner funnel after filtration were picked up and gradually squeezed, and the strength at that time was determined as the flock strength according to the following criteria.
Strength 5: Squeeze once to easily drain water and become a solid substance.
Aggregates do not come off.
Strength 4: Intermediate strength between the above strength 5 and the following strength 3.
Strength 3: A solid material is obtained by gently squeezing 4 to 5 times, but aggregates leak from between fingers.
Strength 2: An intermediate strength between the above strength 3 and the following strength 1.
Strength 1: Flock can easily come out from between fingers even if it is gently squeezed, and it can be squeezed to a solid state.
do not come.
In the range of strength 5 to strength 1, floc resistance in the compaction squeezing process in the latter half of the dehydration process in the multiple disk dehydrator, screw press dehydrator, and rotary pressure dehydrator can be relatively evaluated. Or 5 is preferred.

<Moisture content / cake yield>
The aggregate on the Buchner funnel after filtration was packed in a column with a diameter of 30 mm and a height of 17.5 mm, and pressed at 0.1 MPa for 60 seconds to obtain a dehydrated cake. While measuring the moisture content of this dehydrated cake, the amount of solids per unit cake area (mg / cm ² ) was measured.
The cake yield indicates the compactness of the cake, and the larger the value, the better the effect of the dehydrating agent.

  As apparent from Table 2, in Examples 1 to 3, the floc strength is higher and the cake moisture content is lower by about 1% than in Comparative Examples 1 to 3. In addition, the cake yield was 20% higher, showing good effects in all items.

[Examples 4 and 5, Comparative Examples 4 to 7]
Excess sludge from a dairy factory (SS: 0.95%, VSS / SS: 0.916, pH: 6.8, conductivity: 190 mS / m) is used as the sludge to be treated. The aggregation dehydration test was conducted in the same manner as in Examples 1 to 3 except that the polymer was used in the proportions and addition amounts shown in Table 3, and the results are shown in Table 3.

As is apparent from Table 3, in Examples 4 and 5, the filterability is excellent and the floc strength is high as compared with Comparative Examples 4 and 5. Further, the moisture content of the cake is 0.8 to 1.2% lower, and the cake yield is about 20% higher.
As shown in Comparative Examples 6 and 7, when the DAM · BzCL ₄ homopolymer and the polymer of DAM · MeCL ₄ were used alone, the DAM · MeCL ₄ homopolymer was superior, but Example 4 and Comparative Example 7. As is clear from the comparison between Comparative Example 4 and Comparative Example 6, DAM · BzCL ₄ has a particularly excellent effect when combined with polyamidine.

Claims (5)

The cationic polymer A having the amidine unit represented by the following general formula (1) or (2) or the vinylamine unit represented by the following general formula (3) as a repeating unit, and the following general formula (4) A sludge dehydrating agent comprising a cationic polymer B having a benzylic cationic unit as a repeating unit,
The cationic polymer A and the cationic polymer B are included in a weight ratio in the range of 30 to 70:70 to 30,
The cationic polymer A is a copolymer having an amidine unit represented by the following general formula (1) or (2) and another repeating unit, and the amidine unit is contained in an amount of 20 to 90 mol% in all repeating units. A copolymer containing only a vinylamine unit represented by the following general formula (3), or a copolymer having the vinylamine unit and another repeating unit, A copolymer containing at least 35 mol% of all repeating units,
The cationic polymer B is a homopolymer consisting only of the benzylic cation unit represented by the general formula (4), or a copolymer having the benzylic cation unit and another repeating unit, A sludge dewatering agent, which is a copolymer containing 70 mol% or more of the benzylic cationic unit in all repeating units.

(In the above formula, R ¹¹ and R ¹² each independently represents a hydrogen atom or a methyl group, and X ⁻ represents a salt-forming anion.)

(In the above formula, Y ⁻ represents a salt-forming anion.)

(In the above formula, R ¹ represents a hydrogen atom or a methyl group, R ² represents an alkylene group having 1 to 4 carbon atoms, R ^3a and R ^3b each independently represents an alkyl group having 1 to 4 carbon atoms, R ⁴ is -NH- .A is -O- or where a benzyl group, Z ^- represents a salt-forming anion). A sludge dewatering method comprising adding the sludge dewatering agent according to claim 1 to sludge for dewatering. The sludge dewatering method according to claim 2 , wherein the sludge dewatering agent is added at a ratio of 0.4 to 2.0 wt% with respect to SS of the sludge. The sludge dewatering method according to claim 2 or 3 , wherein the sludge is an organic sludge having a VSS / SS ratio of 0.68 or more. The sludge dewatering method according to any one of claims 2 to 4 , wherein the dewatering is performed by a multiple disk dehydrator, a screw press dehydrator or a rotary pressure dehydrator.