JP2016140856A - Sludge dewatering agent and sludge dewatering method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce cost in a dewatering treatment for organic sludge by reducing consumption of an expensive amidine-based cationic polymer.SOLUTION: A sludge dewatering agent comprises: a cationic polymer A having a benzyl-based cationic unit represented by a specific structural formula as a repeating unit; a diallyl dialkyl ammonium salt-based cationic polymer B; and a cationic polymer C having an amidine unit represented by a specific structural formula as a repeating unit. On the basis of 100 wt.% of the total of the cationic polymer A, the cationic polymer B and the cationic polymer C, a content of the cationic polymer A is 50 to 90 wt.%, a content of the cationic polymer B is 5 to 40 wt.%, and a content of the cationic polymer C is 2 to 30 wt.%. A method for dewatering sludge comprises adding the sludge dewatering agent to a sludge to dewater the sludge.SELECTED DRAWING: None

Description

  The present invention relates to a sludge dewatering agent and a sludge dewatering method, and in particular, the amount of expensive cationic polymer used can be reduced, and organic sludge has a high salt concentration, particularly unwashed digested sludge. The present invention relates to a sludge dewatering agent that can efficiently dehydrate organic sludge at low cost, and a sludge dewatering method using the sludge dewatering agent.

  Organic sludge mainly composed of excess sludge generated in food factories, chemical factories, sewage treatment plants, etc. is generally added with cationic polymer (cationic polymer flocculant), screw press, centrifugal dehydrator, belt press After being dehydrated with a dehydrator such as a dehydrated cake, it is disposed of as industrial waste or incinerated. Therefore, if the moisture content of the dewatered cake obtained by dewatering the coagulated sludge can be reduced, the cost for disposal can be reduced and the burden on the environment can be reduced.

For this reason, it is desired to reduce the moisture content of the dehydrated cake as much as possible. Conventionally, the following proposals have been made in place of using a cationic polymer alone for the purpose of reducing the moisture content of the dehydrated cake. .
(1) A method of adding an amphoteric organic polymer agent after adding an inorganic flocculant (Japanese Patent Laid-Open No. 63-158200)
(2) A method in which an amidine-based cationic polymer and two kinds of cationic polymers are used in combination (JP 2011-224420 A).
(3) A method in which an amidine cationic polymer and a benzylic cationic polymer are used in combination (JP 2012-96199 A).
(4) A method in which polyvinylamidine and a crosslinkable ionic water-soluble polymer (methacrylic acid ester-based or diallyldimethylammonium chloride-based cationic polymer) are used in combination (Japanese Patent Laid-Open No. 2004-25095)

JP 63-158200 A JP 2011-224420 A JP 2012-96199 A JP 2004-25095 A

Among the above-mentioned conventional techniques, the method of using an inorganic flocculant and an amphoteric organic polymer agent together has drawbacks such as complicated adjustment of the addition ratio of two types of drugs.
When the amidine polymer and the cationic polymer are used in combination, there are disadvantages in that they do not agglomerate, the flocs are small, and the moisture content of the dehydrated cake is difficult to decrease.
Moreover, the spray-dried product of the crosslinkable ionic water-soluble polymer used in JP-A No. 2004-25095 has drawbacks in handling that it takes a long time to dissolve and an undissolved product is easily generated.

In addition, although a dehydrating agent using an amidine-based cationic polymer has a high dehydrating effect, the amidine-based cationic polymer is expensive, so there is a problem that the cost is high, and an inexpensive alternative technique is required.
For example, JP 2012-96199 describes the combined use of the cationic polymer A (cationic polymer B in JP 2012-96199) and the cationic polymer C (cationic polymer A in JP 2012-96199) used in the present invention. The amount of the cationic polymer A disclosed in Japanese Patent Application Laid-Open No. 2012-96199 corresponding to the amidine-based cationic polymer is 30 to 70% by weight, so that the amount of the amidine-based cationic polymer is large. It is the cause that pushes up the cost.

  For these reasons, it is desired to develop a sludge dehydrating agent that can obtain the same or higher effect while reducing the amount of the amidine-based cationic polymer.

  The present invention solves the above-mentioned conventional problems, reduces the amount of expensive amidine-based cationic polymer used compared to conventional products, has a fast dissolution rate, and is amidine-based cationic polymer in terms of filterability and dehydration. An object is to provide a sludge dewatering agent that exhibits an effect higher than that of a single product or a conventional product containing an amidine-based cationic polymer, and a sludge dewatering method using this sludge dewatering agent.

As a result of intensive studies to solve the above-mentioned problems, the present inventors made a combination of three kinds of cationic polymers by using a combination of two specific kinds of cationic polymers with amidine-based cationic polymers. Thus, it has been found that the above problems can be solved.
That is, the gist of the present invention is as follows.

[1] Polymerization or copolymerization of a cationic polymer A having a benzylic cation unit represented by the following general formula (1) as a repeating unit and a monomer component containing at least an ammonium salt represented by the following general formula (2) A cationic polymer B obtained by the following process, and a cationic polymer C having the amidine unit represented by the following general formula (3) or (4) as a repeating unit, the cationic polymer A, the cationic polymer B, and the cation The proportion of the cationic polymer A in the total 100% by weight with the cationic polymer C is 50 to 90% by weight, the proportion of the cationic polymer B is 5 to 40% by weight, and the proportion of the cationic polymer C is 2 to 30% by weight. A sludge dehydrating agent characterized by that.

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

(In General Formula (2), R ⁵ represents a hydrogen atom or a methyl group, and R ^6a and R ^6b each independently represents an alkyl group having 1 to 3 carbon atoms, an alkoxy group having 1 to 3 carbon atoms, or a benzyl group. , Q ^- represents a salt-forming anion).

(In the general formulas (3) and (4), R ¹¹ and R ¹² each independently represents a hydrogen atom or a methyl group, and X ⁻ represents a salt-forming anion.)

[2] In [1], the proportion of the cationic polymer A in the total of 100 wt% of the cationic polymer A, the cationic polymer B, and the cationic polymer C is 60 to 80 wt%, and the proportion of the cationic polymer B is 15 A sludge dewatering agent characterized in that the proportion of the cationic polymer C is 35 wt% and 2 wt% is 30 wt%.

[3] In [1] or [2], the cationic polymer A is a homopolymer consisting only of the benzylic cation unit represented by the general formula (1), or the benzylic cation unit and A sludge dehydrating agent, which is a copolymer having other repeating units, the copolymer containing 70 mol% or more of the benzylic cation units in all repeating units.

[4] The sludge dewatering agent according to any one of [1] to [3], wherein the cationic polymer B is a homopolymer of an ammonium salt represented by the general formula (2).

[5] In any one of [1] to [4], the cationic polymer C is a copolymer having an amidine unit represented by the general formula (3) or (4) and another repeating unit. A sludge dehydrating agent characterized in that it is a copolymer containing 20 to 90 mol% of the amidine unit in all repeating units.

[6] A sludge dewatering method comprising adding the sludge dewatering agent according to any one of [1] to [5] to sludge for dewatering.

[7] The sludge dehydrating agent is added so that the total amount of addition of the cationic polymer A, the cationic polymer B, and the cationic polymer C is 0.4 to 4.0% by weight with respect to SS of the sludge. The sludge dewatering method according to [6], wherein:

[8] The sludge dewatering method according to [6] or [7], wherein the sludge is an organic sludge having a conductivity of 250 mS / m or more.

[9] The sludge dewatering method according to any one of [6] to [8], wherein dewatering is performed using a multiple disk dehydrator, a screw press dehydrator, or a rotary pressure dehydrator.

According to the present invention, the following excellent effects can be obtained.
(1) Filtration of sludge that could not be agglomerated with conventional dimethylaminoethyl methacrylate (DAM) cationic polymer or dimethylaminoethyl acrylate (DAA) cationic polymer, etc. Agglomerates having excellent properties and dehydration properties can be obtained.
(2) It is possible to obtain a good agglomeration effect and an improvement effect of filterability and dehydrability after greatly reducing the blending ratio of the cationic polymer C, which is an amidine-based cationic polymer, as compared with the conventional product.
(3) It can be easily made into one agent by mixing three kinds of cationic polymers in a powder state, and can be easily controlled as an aqueous solution in which it is dissolved in water. In this case, the solubility is fast and the handling and workability are excellent.

  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 repeating units represented by the same general formula.
Further, “(meth) acryl” means “acryl” and / or “methacryl (methacryl)”, and the same applies to “(meth) acrylate” and “(meth) acrylo”.

[Action mechanism]
In the present invention, the details of the interaction between each of the specific cationic polymer A, the cationic polymer B, and the cationic polymer C are not clear, but the effects of the present invention are achieved by the synergistic effect of the following mechanism of action. Is presumed to be expressed.
(1) Due to the high hydrophobicity derived from the benzyl group of the benzyl quaternized salt contained in the cationic polymer A, the water affinity of the aggregated floc obtained by adding the sludge dehydrating agent of the present invention decreases, Agglomerated flocs having excellent dewatering properties that tend to lower the water content are formed.
(2) The ammonium salt of the cationic polymer B has a cationic degree as high as that of the cationic polymer C, which is an amidine-based cationic polymer, and contributes to further reduction of the moisture content of the dehydrated cake. In combination, the required amount of the cationic polymer C can be reduced.
(3) Cationic polymer C, which is an amidine-based cationic polymer, contributes to increase the floc strength by its characteristic flock-forming ability and to obtain a floc strength against the pressing pressure of the dehydrator.

[Cationic polymer A]
The cationic polymer A used in the present invention contains a benzylic cation unit (1) represented by the following general formula (1) (hereinafter sometimes referred to as “benzylic cation unit (1)”) as a repeating unit. It is a waste.

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

In the general formula (1), 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 a propylene group and a butylene group. 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 A having a repeating unit represented by the general formula (1) is produced using a benzylic cationic monomer represented by the following general formula (1A).

(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 (1), and specific examples thereof are also the same).

  Examples of the benzylic cationic monomer represented by the general formula (1A) 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 methacrylamide, 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) acrylamide or methacrylamide, diisobutylamino (methyl, ethyl, propyl or butyl) acrylamide or methacrylate Such as amides, quaternized by benzyl halide can be mentioned. Examples of the benzyl halide include benzyl chloride and benzyl bromide.

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

  As the cationic polymer A used in the present invention, a homopolymer of the above-mentioned benzylic cationic monomer can be preferably used, but other monomers copolymerizable with the benzylic cationic monomer (hereinafter referred to as “copolymerizable”). May be referred to as a “monomer.”) Or a copolymer of two or more. The homopolymer of the benzylic cationic monomer includes one containing two or more benzylic cationic units (1).

  When the cationic polymer A 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 A is the above-mentioned copolymer, the effect of the present invention cannot be sufficiently obtained if the proportion of the benzylic cation unit (1) in the copolymer is excessively small. Therefore, the cationic polymer A preferably has a benzylic cationic unit (1) ratio of 70 to 100 mol% in all repeating units and 0 to 30 mol% of repeating units derived from a nonionic vinyl monomer, In particular, the proportion of the benzylic cation unit (1) in all repeating units is preferably 80 to 100 mol%, particularly 90 to 100 mol%.

  In addition, the cationic polymer A 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 chloride 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 A used in the present invention is preferably 2.8 to 3.7 meq / g. If the colloid equivalent is too small, it is difficult to obtain the hydrophobic effect of the benzyl group, which is not 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)).

  There is no restriction | limiting in particular in the manufacturing method of the cationic polymer A 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, and the temperature is raised to the polymerization temperature. As a polymerization initiator, ammonium persulfate, potassium persulfate, 2,2′-azobis (2- Polymerization can be carried out by adding a water-soluble polymerization initiator such as amidinopropane) dihydrochloride.

[Cationic polymer B]
The cationic polymer B used in the present invention is obtained by polymerizing or copolymerizing a monomer component containing at least an ammonium salt represented by the following general formula (2) (hereinafter sometimes referred to as “ammonium salt (2)”). It is obtained.

(In General Formula (2), R ⁵ represents a hydrogen atom or a methyl group, and R ^6a and R ^6b each independently represents an alkyl group having 1 to 3 carbon atoms, an alkoxy group having 1 to 3 carbon atoms, or a benzyl group. , Q ^- represents a salt-forming anion).

In the general formula (2), Q ⁻ 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 ^{— and the} like can be mentioned, and R ⁵ is preferably a hydrogen atom.

  Examples of the ammonium salt (2) represented by the general formula (2) include diallyldimethylammonium chloride (DADMAC) and diallylmethylbenzylammonium chloride.

  Cationic polymer B may be a homopolymer obtained by polymerization using only ammonium salt (2), and may be another monomer copolymerizable with ammonium salt (2) (hereinafter referred to as “copolymerizable monomer”). A copolymer obtained by copolymerizing one or more of nonionic vinyl monomers as a copolymerizable monomer used for the production of the above-mentioned cationic polymer A, such as acrylamide, for example. Generally, it is used as a homopolymer of an ammonium salt (2) represented by the following general formula (2A). In addition, this homopolymer shall include what contains the structural unit derived from 2 or more types of ammonium salt (2).

(In the general formula (2A), R ⁵ , R ^6a , R ^6b and Q ⁻ have the same ^meaning as in the general formula (2).)

  In addition, when the cationic polymer B is a copolymer of an ammonium salt (2) and another copolymerizable monomer, if the number of structural units derived from the ammonium salt (2) in the copolymer is excessively small, the effect of the present invention can be obtained. I can't get enough. Therefore, in the cationic polymer B, the proportion of the structural unit derived from the ammonium salt (2) in all repeating units is preferably 70 to 100 mol%, particularly 80 to 100 mol%, particularly 90 to 100 mol%. .

  Further, the cationic polymer B used in the present invention preferably has an intrinsic viscosity of 0.2 dl / g or more, particularly 0.5 dl / g or more, measured at 30 ° C. using a 1.0 N sodium nitrate aqueous solution as a solvent. If the intrinsic viscosity is less than 0.2 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 7.0 dl / g or less.

  The colloidal equivalent of the cationic polymer B is preferably 5.0 to 6.2 meq / g, particularly preferably 5.5 to 6.1 meq / g. When the colloid equivalent of the cationic polymer B is within this range, high cohesiveness can be obtained, which is preferable. 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.

[Cationic polymer C]
The cationic polymer C used in the present invention is an amidine unit represented by the following general formula (3) (hereinafter sometimes referred to as “amidine unit (3)”) or an amidine represented by the following general formula (4). It has a unit (hereinafter sometimes referred to as “amidine unit (4)”) as a repeating unit.

(In the general formulas (3) and (4), 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 general formulas (3) and (4), X ⁻ represents 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 C (which may include both the amidine unit (3) and the amidine unit (4)) containing the amidine unit (3) or the amidine unit (4) 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 suspension polymerization, a polymer can be obtained by heating water, a monomer, an emulsifier, a water-soluble polymerization initiator, a hydrocarbon dispersion medium and the like 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, an aqueous solution or suspension of the above polymer is heated in the presence of an acid or an alkali to hydrolyze the acid amide unit in the polymer to an amine unit, and further to the nitrile unit adjacent to the amine unit. An amidine reaction is carried out to produce amidine units (3) and / or (4) by the reaction.
Amidine units (3) and (4) 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 suspension 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.

  The proportion of the amidine units (3) and (4) in the total repeating units constituting the cationic polymer C having the amidine units (3) and (4) is preferably 20 to 90 mol%, and 50 to 90 More preferably, it is mol%. If the amount of the amidine units (3) and (4) in the cationic polymer A is too small, the water content reduction effect due to the inclusion of the amidine units (3) and (4) is lowered. A polymer containing more than 90 mol% of amidine units (3) and (4) in all repeating units is not easy to produce.

  The cationic polymer C having amidine units (3) and (4) 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.

  The colloidal equivalent of the cationic polymer C 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 C is within this range, high cohesiveness can be obtained, which is preferable. The colloidal equivalent of the cationic polymer C is measured by the same method as that for the cationic polymer A.

  In the present invention, the cationic polymer C can be used as a sludge dewatering agent as an aqueous solution after completion of the above-mentioned amidation reaction, or as a concentrated or diluted aqueous solution. Alternatively, an aqueous solution or suspension of the cationic polymer C can be separated and dried by a known method to be used as a powder.

[Proportion of cationic polymer A, cationic polymer B, and cationic polymer C]
The ratio of the cationic polymer A, the cationic polymer B, and the cationic polymer C in the sludge dehydrating agent of the present invention is such that the ratio of the cationic polymer A in the total 100% by weight is 50 to 90% by weight. The proportion of B is 5 to 40% by weight, the proportion of the cationic polymer C is 2 to 30% by weight, and particularly the proportion of the cationic polymer C is preferably less than 30% by weight, particularly preferably 25% by weight or less. Preferably, the proportion of the cationic polymer A is 60 to 80% by weight, the proportion of the cationic polymer B is 15 to 35% by weight, and the proportion of the cationic polymer C is 2 to 30% by weight.
When the ratio of each cationic polymer is out of the above range, the effect of the present invention cannot be obtained by using these three kinds of cationic polymers in combination.

[Form of sludge dehydrating agent]
The sludge dewatering agent of the present invention is only required to contain the above-mentioned cationic polymer A, cationic polymer B, and cationic polymer C, and the cationic polymer A, the cationic polymer B, and the cationic polymer C are separated. Even if these are provided, they may be premixed into a single agent.

If the cationic polymer A, the cationic polymer B, and the cationic polymer C 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.
For example, when a cationic polymer A, a cationic polymer B, and a cationic polymer C are formulated as a powder composition obtained by mixing in a predetermined state in a powder state and used, an aqueous solution of about 0.1 to 0.5% by weight is used. As can be added to the sludge.
Alternatively, the same effect can be obtained by dissolving each cationic polymer separately and adding each aqueous solution to the sludge.

  In addition, the sludge dehydrating agent of the present invention is one or more kinds of agents other than the cationic polymer A, the cationic polymer B, and the cationic polymer C, for example, powdered acid such as sulfamic acid and salts such as sodium sulfate. May be contained.

[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 or may be performed in a coagulation reaction tank provided separately. Moreover, if it is a dehydrator which has a mixing mechanism like a centrifugal dehydrator, the mixing process before dehydration can be omitted.

  The amount of the sludge dehydrating agent added to the sludge is not limited as long as high dewaterability can be obtained with a sufficient coagulation effect, and is appropriately determined depending on the sludge properties, the type of polymer used, etc. The total addition amount of the cationic polymer A, the cationic polymer B and the cationic polymer C is about 20 to 1600 mg / L, particularly about 60 to 1200 mg / L with respect to about 4.0% by weight of sludge. The addition amount is preferably 0.5 to 4.0% by weight, particularly about 1.5 to 3.0% by weight with respect to SS.

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

  As the agglomeration reaction tank, a vertical general agglomeration reaction tank with stirring blades can be used, and no special reaction apparatus is required. Also, there are no particular restrictions on applicable dehydrators, and various dehydrators such as multiple disk dehydrators, screw press dehydrators, rotary press dehydrators, filter press dehydrators, belt press dehydrators, centrifugal dehydrators, etc. However, in the sludge dewatering method using the sludge dewatering agent of the present invention, since floc strength is particularly strong and floc excellent in drainage can be formed, from a metal mesh, metal slit or wire A multi-disk dehydrator, a screw press dehydrator, and a rotary pressure dehydrator, which are dehydrators having a filtration zone and a compaction pressing process, are preferably used.

  According to the present invention, by such dehydration treatment, a dehydrated cake having a low water content of 1 to 2 points can be obtained as compared with conventional sludge dewatering agents and sludge dewatering methods. The obtained dehydrated cake is used for incineration or landfill disposal.

The sludge to be dehydrated in the present invention is not particularly limited. For example, organic sludge generated in sewage, human waste, general industrial wastewater treatment, etc., and discharged from food factories, fish processing factories, meat processing factories, livestock industries, etc. Surplus sludge or mixed sludge containing these sludges.
In particular, since the effect of the present invention is a synergistic effect of the high aggregation ability of polymer A at a high salt concentration and the high charge neutralization ability of polymer B and polymer C, like unwashed digested sludge, Since a good dehydration effect is obtained for organic sludge having a high salt concentration of 250 mS / m or more, for example, 300 to 3000 mS / m, it is suitable for such sludge dehydration treatment. Usually, these organic sludges have a VSS / SS ratio of 60 to 90, and fibrous materials measured with a 100 mesh sieve are 0 to 15% by weight 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”.

[Cationic polymer]
The cationic polymers used in the following examples and comparative examples are as follows.

<Production Example 1: Production of cationic polymer A-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 sodium chloride aqueous 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 A-1.

<Production Example 2: Production of Cationic Polymer B-1>
300 mL of a 20 mol / L solution of diallyldimethylammonium chloride was placed in a 500 mL flask equipped with a stirrer, a reflux condenser, a thermometer, and a nitrogen introduction tube, and the atmosphere was replaced with nitrogen gas. To this, 1.3 × 10 ⁻³ mol / L of 2,2′-azobis (2-amidinopropane) dihydrochloride was added, and the temperature was raised to 40 ° C. for polymerization for 20 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 1.0 N sodium nitrate aqueous solution as a solvent was 0.7 dl / g. Moreover, the colloid equivalent of this cationic polymer was 5.9 meq / g in pH = 4. This cationic polymer is designated as polymer B-1.

<Production Example 3: Production of Cationic Polymer C-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 5.8 meq / g in pH = 4. This cationic polymer is designated as polymer C-1.

<Production Example 4: Production of Cationic Polymer X-1>
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 is 80:20 mol% and the total monomer concentration is 2.0 mol / L. 300 mL of the monomer solution prepared so as to become was put, 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 1.0 N sodium nitrate aqueous solution as a solvent was 6.5 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 5: Production of cationic polymer X-2>
In a 500 mL flask equipped with a stirrer, a reflux condenser, a thermometer, and a nitrogen introducing 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 1.0 N sodium nitrate aqueous solution as a solvent was 6.2 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.

[Sludge properties]
In the following Examples and Comparative Examples, the properties of sludges I to III subjected to the dehydration test in the desktop test are as shown in Tables 2 to 4 below, and the properties of sludge IV subjected to the actual machine test are listed in Table 5 below. As shown.

[Test method]
The desktop tests and actual machine tests in the following examples and comparative examples were performed by the following methods.

<Desktop test>
200 mL of sludge was collected in a 300 mL beaker, various dehydrating agents were added, and the mixture was reacted at 180 rpm for 30 seconds for aggregation. For Example 7 and Comparative Examples 11 and 12, which are combined treatments of a cationic polymer and an anionic polymer (PA-923), the mixture was stirred at 180 rpm after the addition of the cationic polymer, and after 5 seconds, the anionic polymer (PA- 923) was added, followed by agitation for 25 seconds to agglomerate. 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, the floc diameter of the collected aggregate and the amount of SS leakage (SV) to the filtrate were measured. It is preferable that the amount of filtration is larger, the floc diameter is larger, and the SV is smaller.
Moreover, evaluation of the aggregation floc strength and measurement of the moisture content of the dehydrated cake were performed by the following methods.

<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.
○: A solid substance that is easily squeezed in one time and has no fluidity is obtained, and there is no leakage of SS during the squeezing process.
Δ ○: Between the above ○ and the following Δ.
Δ: Slowly squeezed 4 to 5 times to form a solid, but in the meantime leakage of floc from the finger is observed.
X: The flock comes off between the fingers even when gently squeezed.
With the above evaluation, it is possible to relatively evaluate the floc resistance in the compaction squeezing process in the latter half of the dewatering process in the multiple disk dewatering machine, screw press dewatering machine, rotary pressure dehydrating machine, and the evaluation is “Δ ○” or “ "" Is preferable.

<Cake moisture content>
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. The water content of the dehydrated cake was measured.

<Real machine test>
The floc diameter of agglomerated floc is obtained by observation of the appearance when various dehydrating agents are added to the agglomeration tank of a dewatering facility for anaerobic digested sludge with a sludge treatment amount of 75 m ³ / day. The moisture content of was measured.

  The moisture content of the dehydrated cake was calculated from the weight of the dehydrated cake before drying and the weight of the dehydrated cake after drying after drying the dehydrated cake at 105 ° C. for 1 day.

[Examples 1 and 2 and Comparative Examples 1 to 6]
The cationic polymers shown in Table 6 below are used as dehydrating agents, and each dehydrating agent is added to sludge I (in the case of a desktop test) or sludge IV (in the case of an actual machine test) in the addition amount shown in Tables 7 and 8. The above-mentioned desk test and actual machine test were conducted, and the results are shown in Tables 7 and 8.
The dehydrating agent was added as a 0.2% by weight aqueous solution. The dehydrating agent addition amount shown in Tables 7 and 8 indicates the addition amount as an active ingredient (cationic polymer).

<Discussion>
The following can be understood from the above results.

(Desktop test)
In Comparative Example 1 using the polymer A-1 alone, the SS leak is small, but the floc strength is weak, and the cake moisture content is also high. Moreover, in the comparative example 2 of polymer C-1 single, although a cake moisture content is low, there are many leaks (SV) of SS to a filtrate.
In Comparative Examples 3 and 4 in which the polymer A-1 and the polymer C-1 are used in combination, the blending ratio of the polymer C-1 which is an expensive amidine-based cationic polymer is increased (Comparative Example 3) or the blending ratio is small. In this case, unless the addition amount is increased (Comparative Example 4), sufficient effects cannot be exhibited, and in any case, the amount of the polymer C-1 used is increased and the processing cost is increased. Comparative Examples 5 and 6 were not in a dewaterable state.
On the other hand, in Examples 1 and 2 in which the polymer B-1 was further blended with the polymer A-1 and the polymer C-1, the cake moisture content was high as compared with the comparative example 2 of the polymer C-1 alone. However, the filtrate amount and SS leak were good, and the results were better than any of the comparative examples when viewed comprehensively. Furthermore, since the processing cost is lower than that of the polymer C-1 alone, the merit of application is considered to be great.

(Real machine test)
In Example 1 in which Polymer A-1, Polymer B-1 and Polymer C-1 were used in combination, the moisture content of the cake could be reduced as compared with Comparative Example 2 using only Polymer C-1. From this, it can be seen that the sludge dewatering agent of the present invention has characteristics suitable for filtration and compression type screw presses using metal mesh, multiple disk dewatering machines, and the like.

[Examples 3-6, Comparative Examples 7-10]
The cationic polymer shown in the following Table 9 was used as a dehydrating agent, and each dehydrating agent was added to the sludge II in the addition amount shown in Table 10, and the above-mentioned desktop test was conducted. The results are shown in Table 10.
The dehydrating agent was added as a 0.2% by weight aqueous solution. The dehydrating agent addition amount shown in Table 10 indicates the addition amount as an active ingredient (cationic polymer).

<Discussion>
Sludge II is a sludge that is difficult to treat due to the fact that it is difficult for flocs to increase as a whole and the moisture content does not decrease. As a factor resulting in the above results, it is considered that the amount of SS in the sludge is large and the amount of the dehydrating agent added per SS is insufficient.
Although it was difficult, all the examples were sufficiently put on the dehydrator, and better results were obtained than any of the comparative examples.

[Example 7, Comparative Examples 11 and 12]
Each of the cationic polymer-based dehydrating agents shown in Table 11 below and an anionic polymer flocculant “Kurifama PA-923” (described as “PA-923”) manufactured by Kurita Kogyo Co., Ltd. was used as the dehydrating agent. A dehydrating agent was added to the sludge III in the addition amount shown in Table 12, the above-mentioned desktop test was conducted, and the results are shown in Table 12.
The cationic polymer-based dehydrating agent was added as a 0.2% by weight aqueous solution. The addition amount of the cationic polymer-based dehydrating agent shown in Table 12 indicates the addition amount as an active ingredient (cationic polymer).

  From the above results, in the present invention, it is predicted that the moisture content of the cake will be the same as or slightly inferior to the conventional treatment depending on the sludge properties, but considering the small proportion of amidine-based cationic polymer, It can be seen that it can be processed inexpensively.

Claims (9)

Obtained by polymerizing or copolymerizing a cationic polymer A having a benzylic cation unit represented by the following general formula (1) as a repeating unit and a monomer component containing at least an ammonium salt represented by the following general formula (2) A cationic polymer B, and a cationic polymer C having an amidine unit represented by the following general formula (3) or (4) as a repeating unit, the cationic polymer A, the cationic polymer B, and the cationic polymer C The proportion of the cationic polymer A is 50 to 90% by weight, the proportion of the cationic polymer B is 5 to 40% by weight, and the proportion of the cationic polymer C is 2 to 30% by weight. Sludge dewatering agent.

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

(In General Formula (2), R ⁵ represents a hydrogen atom or a methyl group, and R ^6a and R ^6b each independently represents an alkyl group having 1 to 3 carbon atoms, an alkoxy group having 1 to 3 carbon atoms, or a benzyl group. , Q ^- represents a salt-forming anion).

(In the general formulas (3) and (4), R ¹¹ and R ¹² each independently represents a hydrogen atom or a methyl group, and X ⁻ represents a salt-forming anion.)   In Claim 1, the ratio of the cationic polymer A in the total of 100 weight% of the cationic polymer A, the cationic polymer B, and the cationic polymer C is 60 to 80 weight%, and the ratio of the cationic polymer B is 15 to 35 weight%. %, And the ratio of the cationic polymer C is 2 to 30% by weight.   In Claim 1 or 2, the said cationic polymer A is a homopolymer which consists only of the benzylic cation unit represented by the said General formula (1), or this benzylic cation unit and another repeating unit, A sludge dehydrating agent characterized in that it is a copolymer containing 70 mol% or more of the benzylic cation unit in all repeating units.   The sludge dehydrating agent according to any one of claims 1 to 3, wherein the cationic polymer B is a homopolymer of an ammonium salt represented by the general formula (2).   5. The copolymer according to claim 1, wherein the cationic polymer C is a copolymer having the amidine unit represented by the general formula (3) or (4) and another repeating unit. A sludge dewatering agent characterized in that it is a copolymer containing 20 to 90 mol% of all repeating units.   A sludge dewatering method, wherein the sludge dewatering agent according to any one of claims 1 to 5 is added to the sludge and dehydrated.   The sludge dehydrating agent is added so that the total addition amount of the cationic polymer A, the cationic polymer B, and the cationic polymer C is 0.4 to 4.0% by weight with respect to SS of the sludge. The sludge dewatering method according to claim 6, wherein the sludge is dehydrated.   The sludge dewatering method according to claim 6 or 7, wherein the sludge is an organic sludge having a conductivity of 250 mS / m or more.   The sludge dewatering method according to any one of claims 6 to 8, wherein the dewatering is performed by a multiple disk dehydrator, a screw press dehydrator or a rotary pressure dehydrator.