JP2022012848A - Green liquor treatment liquid - Google Patents

Abstract

To provide a technique for treatment of a green liquor more properly.SOLUTION: A green liquor treatment liquid employs a cationic polymer free from ester-bonded cationic group as an active substance. A green liquor treatment method involves a step of adding a cationic polymer free from ester-bonded cationic group to a coarse green liquor. A manufacturing method of calcium carbonate involves a step of slaking and caustification for producing calcium carbonate by using a green liquor which has been clarified by adding a cationic polymer free from ester-bonded cationic group to a coarse green liquor.SELECTED DRAWING: Figure 1

Description

The present invention relates to a green liquor treatment agent, a green liquor treatment method, a calcium carbonate production method, and the like.

Pulp is produced by adding treated water containing sodium hydroxide to wood chips and steaming them. Then, in the cooking step, the chips are steamed with an alkali (white liquid) to obtain pulp, and the cooking agent and heat energy are recovered from the pulp waste liquid (black liquid). Specifically, the chemicals are recovered by a recovery step including a cooking step, a pulp washing step, a black liquor concentration step, a black liquor burning step, a green liquor manufacturing step, a white liquor manufacturing step, and a lime firing step.

The smelt generated by burning black liquor contains insoluble impurities (dregs) such as unburned carbon, calcium carbonate, aluminum hydroxide, iron oxide, and silicon dioxide. Further, the wood chips are rich in calcium salt, barium salt, phosphate, cellulose, lignin and the like, which are the sources of the insoluble impurities, and insoluble impurities are likely to occur.
This insoluble impurity called dregs adversely affects the production of calcium carbonate in the white liquor production process. Therefore, in the green liquor production process, the dregs in the crude green liquor are removed as much as possible to better clarify the green liquor.

For example, in Patent Document 1, 0.5 to 10%, preferably 1 to 5% of the amount of quicklime required for completely causticizing the green liquid is added to the unclarified green liquid being stirred. After that, a method for clarifying the green liquor has been proposed, which comprises removing solid particles from the green liquor.

Special Table 1-502207 Gazette

An object of the present invention is to provide a technique for treating green liquor better.

As a result of diligent studies on a technique for better treating green liquor, the present inventor has found that the green liquor can be treated better by using a cationic polymer having no ester-bonded cationic group. , The present invention has been completed.

The present invention provides a green liquor treatment agent containing a cationic polymer having no ester-bonded cationic group.
The present invention provides a green liquor treatment method in which a cationic polymer having no ester-bonded cationic group is added to a crude green liquor.
The present invention comprises a calcium carbonate step of producing calcium carbonate using a green liquor clarified by adding an ester-bonded cationic polymer having no cationic group to the crude green liquor. It provides a manufacturing method.
The present invention comprises a green liquor clarification step of clarifying a green liquor by adding an ester-bonded cationic polymer having no cationic group to the crude green liquor.
The present invention provides a method for producing calcium carbonate, which comprises a soothing / causticizing step of producing calcium carbonate in a soothing reaction and a causticizing reaction using the green liquid.

The cationic polymer is a polymer having at least a structural unit derived from a cationic monomer having no ester bond.
The cation monomer having no ester bond may be an amine monomer having no ester bond and / or a quaternary ammonium salt monomer having no ester bond.
The cationic polymer is a polydiallyldimethylammonium salt and / or a copolymer thereof; an acrylamide / 3-acrylamidepropyl (trimethyl) ammonium salt copolymer, an acrylamide / diallyldimethylammonium salt copolymer, an alkylamine / epichlorohydrin. It may be one kind or two or more kinds selected from the polycondensate.
The green liquor treatment may be green liquor clarification.

According to the present invention, it is possible to provide a technique for treating green liquor better. The effects described here are not necessarily limited, and may be any of the effects described in the present specification.

It is a schematic block diagram of the pulp production system provided with the green liquid production system which concerns on one Embodiment of this invention, but this invention is not limited to this. It is a figure which shows the tendency of the color tone (a ^* value and b ^* value) of the green liquid of each drug treatment in Experimental Example 1. ● indicates a change in the color tone of the green liquor after treatment with each agent of cation + anion or one cation agent, and ◯ indicates a change in color tone of the green liquor treated with each reagent of one anion / amphoteric agent. It is a figure which shows the tendency of the color tone (a ^* value and b ^* value) of the green liquid of each drug treatment in Experimental Example 2. ● indicates a change in the color tone of the green liquor after treatment with each agent of cation + anion or one cation agent, and ◯ indicates a change in color tone of the green liquor after treatment with each reagent of one anion / amphoteric agent. It is a figure which shows the addition amount of the crosslinked cationic polymer which does not have an ester-bonded cationic group but has a quaternary ammonium base, and the change in the color tone (green direction) of the clarified green liquid.

Hereinafter, embodiments for carrying out the present invention will be described. It should be noted that the embodiments described below show an example of a typical embodiment of the present invention, and the scope of the present invention is not limited and interpreted by this. The upper limit value and the lower limit value in the numerical value can be arbitrarily combined as desired.

An embodiment of the green liquor treatment according to the present invention will be described with reference to FIG. 1, but the present invention is not limited thereto.

<1. Pulp production system and green liquid treatment system in this embodiment>
<1-1. Overview of pulp manufacturing system>
FIG. 1 is a schematic configuration diagram of a pulp production system 1 provided with a green liquid treatment system according to an embodiment of the present invention, and the present invention is not limited thereto.
The pulp production system 1 can include a cooking system 10, a black liquor treatment system 20, a green liquor clarification system 30, and a scavenging / caustic system 40. These systems may be communicated with each other by a pipe shown by a solid line in FIG. 1 to form a circulation path as a whole.
Hereinafter, each component will be described in detail.

<1-1-1. Cooking system ＞
The cooking system 10 has a cooking pot 11, and a pulp refining section may be provided downstream of the cooking pot 11. Wood chips, which are raw materials for pulp, and white liquor containing sodium hydroxide are put into the cooking pot 11, and the wood chips are steamed.
The resulting pulp is transferred to the pulp refining section, where it undergoes bleaching and papermaking processes in sequence to produce paper. On the other hand, the black liquor, which is a waste liquid, is transferred to the evaporator 21, which will be described later, for the purpose of recovering sodium hydroxide and the like.

<1-1-2. Black liquor treatment system>
The black liquor treatment system 20 may have an evaporator 21 and a boiler 22 in order from the upstream. The black liquor is concentrated by the evaporator 21 and then transferred to the boiler 22 and burned in the boiler 22. As a result, the inorganic sodium salts contained in the black liquor are melted and discharged as smelt from the bottom of the boiler 22. The discharged smelt is transferred to the melting tank 31.

The boiler 22 may be provided with a heat recovery system for recovering heat energy. As such a heat recovery system, a conventionally known one can be used (see, for example, Japanese Patent Application Laid-Open No. 6-212586).

<1-1-3. Green liquid clarification system ＞
The green liquid clarification system 30 may have a dissolution tank 31, a green liquid clarifier 32, and a green liquid tank 33 in this order from the upstream. The smelt is stirred in water in the dissolution tank 31 to dissolve or disperse. This produces a green liquor (also referred to as "crude green liquor") that is rich in sodium carbonate in addition to sodium hydroxide. The melting tank 31 is provided with a liquid feeding pump (not shown), and the crude green liquid is sucked by the liquid feeding pump and transferred to the green liquid clarifier 32. In the crude green liquor, the remaining undissolved components are removed by the green liquor clarifier 32. After that, it is transferred to the green liquid tank 33 and stored, and then transferred to the caustic system 41.

Examples of the apparatus used for clarification of the green liquid in the present embodiment include, but are not limited to, a gravity sedimentation type apparatus and a forced filtration type apparatus. A typical green liquid clarifier of the gravity settling method is preferable.
The green liquid clarifier is not particularly limited, and examples thereof include a multi-stage clarifier, a unit clarifier, a storage tank combined type clarifier, and a sedimentation concentration type clarifier, and among these, the storage tank combined type is preferable.

<1-1-4. Caustic / caustic system ＞
The caustic / caustic system 40 may have a caustic system 41, a white liquor clarifier 42, and a white liquor tank 43. The caustic / caustic system 40 may further have a lime mud filter 45 and a kiln 44 located downstream of the white liquor clarifier 42. The caustic system 41, the white liquor clarifier 42, and the white liquor tank 43 communicate with each other to form a circulation path as a whole.

The green liquor transferred to the caustic system 41 is mixed with the calcium oxide supplied from the kiln 44 in the caustic system 41. This mixing will be described in more detail.

The caustic system 41 may have a slaker 411 and a plurality of caustic reaction tanks 412 located downstream of the slaker 411. The green liquor (usually 90-100 ° C., pH 13-14) transferred to the slaker 411 is mixed with calcium oxide also supplied to the slaker 411. As a result, calcium oxide is dissolved with water to produce calcium hydroxide. Then, when it is transferred to the caustic reaction tank 412, sodium carbonate in the green liquor reacts with calcium hydroxide to produce sodium hydroxide and calcium carbonate.

The white liquor thus obtained is transferred to the white liquor clarifier 42. In the white liquor clarifier 42, after the insoluble calcium carbonate is settled and separated, the white liquor is stored in the white liquor tank 43 and eventually circulated to the cooking pot 11 for reuse. On the other hand, the separated calcium carbonate is recovered in the kiln 44, roasted and returned to calcium oxide, and reused in the caustic system 41.

<2. Green liquid treatment in this embodiment>
The present embodiment can provide a green liquor treatment agent containing a cationic polymer having no ester-bonded cationic group as an active ingredient.
Further, the present embodiment can provide a green liquid treatment method in which a cationic polymer having no ester-bonded cationic group or a green liquid treatment agent containing the polymer is added to the crude green liquid.

Further, in the present embodiment, a green liquor clarified by adding a cationic polymer having no ester-bonded cationic group (hereinafter, also referred to as “cationic polymer of the present embodiment”) to a crude green liquor is used. It is possible to provide a method for producing calcium carbonate, which comprises a calming / cauterizing step of producing calcium carbonate.

The "green liquid treatment" in the present embodiment is a green liquid treatment in the green liquid clarification step and / or the deconversion / causticization step in pulp production, and has a broad meaning.
In the green liquor clarification step according to the present embodiment, the color tone (a ^* value: green (-60) direction) of the green liquor can be further improved by using the cationic polymer of the present embodiment. By this green liquid clarification, the dregs can be satisfactorily separated from the crude green liquid (water to be treated) containing the dregs, and a green liquid having an excellent color tone according to the present embodiment can be produced.
Furthermore, by using a green liquor having an excellent color tone (a ^* value: (-60) green direction) according to the present embodiment, calcium carbonate according to the present embodiment can be more stably and better in the reconciliation / cauterization step. Can be manufactured.

The present inventor has used a cationic polymer having a cationic group having an ester bond (for example, a carboxylic acid ester (R-OOC-R')) (for example, a cationic moiety-OOC-polymer) for a clarification treatment of a crude green liquid. The behavior when used was examined. According to the present inventor, under a high pH crude green liquor, a cationic polymer having a cationic group having an ester bond undergoes hydrolysis at the ester bond portion, the cationic group is cleaved, and an anionic group is generated. , Focused on the formation of polymers with anionic groups (eg, HOOC-polymers). The present inventor considered that the longer the polymer is used in the crude green liquor, the more the ester-bonded portion of the polymer is hydrolyzed, which increases the proportion of the polymer having an anionic group. Then, the present inventor causes a reaction between the anionic group generated by hydrolysis and the unhydrolyzed cationic group, and as a result, an agglomerate is formed, and the agglomerate causes clogging of the dregs filter, etc. I thought that it would be easy to cause troubles.

In addition, the present inventor found that on the high pH side of the crude green liquor, the cationicity of the polymer having a cationic group having an ester bond is further reduced by hydrolysis, and the hydroxide ion OH ⁻ is abundant. It was estimated that the cationic groups would be charge-neutralized, the charge repulsion within the polymer molecule would disappear, the polymer molecule would shrink, and the polymer-specific effects would be less and less exerted.

Therefore, as a result of diligent studies, the present inventor has found that a cationic polymer having no ester-bonded cationic group has an excellent green liquid treatment ability.
The cationic polymer of the present embodiment tends to be less likely to cause hydrolysis even when the green liquid is in a high pH condition, and tends to have a good coagulating action even if the amount of hydroxide ion OH ⁻ is large. Therefore, by using the cationic polymer of the present embodiment, it is possible to stabilize the green liquid clarification step and produce a green liquid having an excellent color tone.

Furthermore, by producing calcium carbonate using the green liquor produced by the cationic polymer of the present embodiment, the particle size can be further increased by secondary aggregation after calcium carbonate production.
When the particle size of the generated calcium carbonate is large, the washing and dehydration with the lime mud filter is improved, and the water content of the calcium carbonate can be reduced. By using calcium carbonate having a reduced water content, the amount of heavy oil in the kiln after that can be reduced, and the firing rate (CaO / (CaO + CaCO ₃ ) × 100 (%)) can also be improved.
Therefore, the green liquor treatment according to the present embodiment can secure a larger amount of reusable calcium oxide (quicklime), and thus can reduce the amount of quicklime that is normally purchased.

<2-1. Cationic polymer used in this embodiment>
The cationic polymer used in this embodiment is a cationic polymer having no ester-bonded cationic group. Unless otherwise specified, the polymer is meant to include homopolymers and copolymers with acrylamide and the like.
It is preferable that the cationic polymer of the present embodiment has at least a structural unit derived from a cationic monomer having no ester bond. The cationic polymer may contain a small amount of a structural unit derived from an ester-bonded cationic monomer as long as the effect of the present invention is not impaired.
The cation polymer may be a homopolymer having a structural unit derived from a cation monomer having no ester bond, a structural unit derived from a cation monomer having no ester bond, and another single amount. It may be a copolymer having a constituent unit derived from the body. In general, as the copolymer, a random copolymer (for example, -ABABBA-), an alternate copolymer (for example, -ABABAB-), a periodic copolymer (for example, -ABBABB-), and a block copolymer (for example, -ABBABB-) are used. For example, there are four types of structures, -AAABBBBB-), and one of the block copolymers is called a graft copolymer.

The cationic polymer used in the present embodiment is not particularly limited as long as it is a cationic polymer containing a cationic group having no ester bond, and for example, a homopolymer or a copolymer that can be used for clarification of green liquor has an ester bond. A cation polymer introduced with a cation group (preferably a quaternary ammonium base); a homopolymer having a cation monomer having no ester bond as a constituent unit; a cation monomer having no ester bond, It may be a copolymer having another monomer (which may be an oligomer) as a constituent unit; or the like.

Unless otherwise specified, the "copolymer" in the present embodiment broadly includes a copolymer obtained by polymerizing one or more selected from the same or different monomers, oligomers and polymers as a raw material. Means. Examples of the "copolymer" include "a copolymer in which a monomer or an oligomer (preferably a monomer) and another crosslinkable monomer are crosslinked" and "a copolymer obtained by polymerizing a monomer and another monomer". Examples thereof include, but the copolymer is not limited thereto.

The colloidal equivalent (meq / g) of the cationic polymer used in the present embodiment is not particularly limited as long as it is cationic, but as a suitable lower limit thereof, it is preferably 0.1 meq / g or more, more preferably 0.2 meq / g. It is g or more, more preferably 1 meq / g or more, more preferably 3 meq / g or more, still more preferably 4 meq / g or more, still more preferably 5 meq / g or more, and the suitable upper limit thereof is not particularly limited, but for example. Examples thereof include 15 meq / g, 10 meq / g, 8 meq / g, and the like, preferably 8 meq / g or less. The suitable numerical range is preferably 0.1 to 15 meq / g, more preferably 0.2 to 8 meq / g. As a result, better green liquor treatment (for example, even when the composition of the green liquor fluctuates, the green clarification is maintained, the amount of drawn legs is stabilized, the calcium carbonate production is stabilized, etc.) can be performed. The method for measuring the colloid equivalent is as described in [Example] described later.

The intrinsic viscosity ([η]) of the cationic polymer used in the present embodiment is not particularly limited, but as a suitable lower limit value thereof, it is preferably 0.001 or more, more preferably 0.01 or more, still more preferably 0.05. The above is more preferably 0.1 or more, still more preferably 0.2 or more, and the preferred upper limit thereof is preferably 50 or less, more preferably 25 or less, still more preferably 10 or less, and more preferably 5. Below, it is more preferably 3 or less, and more preferably 1 or less. The suitable numerical range is preferably 0.2 to 5. As a result, better green liquor treatment (for example, even when the composition of the green liquor fluctuates, the green clarification is maintained, the amount of drawn legs is stabilized, the calcium carbonate production is stabilized, etc.) can be performed. The method for measuring the intrinsic viscosity is as described in [Example] described later.

The "cationic group having no ester bond" is not particularly limited, and examples thereof include primary to tertiary amines having no ester bond, and quaternary ammonium salts having no ester bond. One or more selected from the group consisting of these cationic groups can be used.

Further, the cation monomer having no ester bond is not particularly limited, but the cation monomer having no ester bond has an amine monomer having no ester bond and / or an ester bond. It is preferable that the quaternary ammonium salt monomer having no quaternary ammonium salt monomer is contained at least as a constituent unit of the cationic polymer, and among these monomers, the quaternary ammonium salt monomer having no ester bond is preferable. ..

<2-1-1. Amine monomer>
The amine monomer having no ester bond is not particularly limited, and is, for example, ammonia, monomethylamine, dimethylamine, trimethylamine, monoethylamine, diethylamine, triethylamine, monoisopropylamine, diisopropylamine, triisopropylamine, monobutylamine. , Primary, secondary to tertiary alkylamines such as dibutylamine; alkanolamines such as monoisopropanolamine, dimethylaminoethanol and diethylaminoethanol, methyldiethanolamine; ethylenediamine, propylenediamine, tetramethylenediamine, hexa Diamines such as methylenediamine; alkyleneimines such as ethyleneimine and propyleneimine; saturated or unsaturated nitrogen-containing monocyclic systems such as saturated heteromonocycles such as piperazine and morpholine and unsaturated heteromonocycles such as pyrazine and pyridine; and Examples thereof include these oligomers.
The number of carbon atoms in the hydrocarbon moiety such as alkyl, alkylene, alkanol, and monocycle in the amine group-containing monomer is not particularly limited, but is preferably 1 to 10 carbon atoms, and more preferably 1 to 6 carbon atoms. Is.

One or more selected from the group consisting of the amine monomers can be used.
Among these, as the amine monomer having no ester bond, alkylamines, alkanolamines and diamines are preferable, and alkylamines are more preferable.

Further, for example, the monomer of the alkylamines includes ethyleneamines having an alkyl having 2 carbon atoms. Examples of the monomer of the ethyleneamines include ethylenediamine. Examples of the oligomer include polyethylene polyamines such as diethylenetriamine, triethylenetetraamine, tetraethylenepantaamine, pentaethylenehexamine, piperazine, and N-aminoethylpiperazine, and one or two selected from the group consisting of these. The above can be used.

<2-1-2. Quaternary ammonium salt monomer>
The quaternary ammonium salt monomer is not particularly limited as long as it exhibits the effects of the present embodiment, and examples thereof include di (meth) acrylic quaternary ammonium salt monomers and vinyl alkylammonium salt monomers. One or more of these groups may be used.

The "quaternary ammonium salt" is not particularly limited as long as it exhibits the effects of the present embodiment, but for example, diallylmethylethylammonium ethylsulfate, diallyldimethylammonium chloride, dimethacryldimethylammonium chloride, and diallyldiethylammonium iodide. , N, N-dialkyl-N, N-di (meth) acrylic quaternary ammonium salts such as diallylmethylpropylammonium iodide; 3-acrylamidepropyl (trimethyl) ammonium chloride, 3-methacrylamidopropyl (trimethyl) ammonium chloride Examples thereof include N, N, N-trialkyl quaternary ammonium salt-alkyl (meth) acrylamide, and one or more of these may be used. The salt is not particularly limited, and examples thereof include halides such as bromide and chloride.

Among the quaternary ammonium salt monomers, N, N-dialkyl-N, N-di (meth) acrylic quaternary ammonium salt is more preferable, and diallyldimethylammonium salt is more preferable. preferable.
The "alkyl group" in the "N, N-dialkyl" moiety may be the same or different, and is preferably the same, and the number of carbon atoms of the alkyl group is preferably 1 to 10, more preferably. Is preferably 1 to 3 carbon atoms such as methyl, ethyl and n-propyl.

<2-1-3. Acrylamide monomer>
The acrylamide monomer is not particularly limited, and examples thereof include acrylamide, dimethylacrylamide, isopropylacrylamide, diacetoneacrylamide, N, N'-methylenebis (meth) acrylamide, and one or more of these. Can be used.

<2-1-4. Example of cationic polymer used in this embodiment>
The cationic polymer used in the present embodiment is not particularly limited, and is, for example, a partially methylolated partially tertiary amine lower alkylated modified product of polyacrylamide, a diallyldimethylammonium salt polymer and / or a copolymer thereof, acrylamide 3-. One or more selected from an acrylamide propyl (trimethyl) ammonium salt copolymer, an acrylamide / diallyldimethylammonium salt copolymer, and an alkylamine / epichlorohydrin polycondensate is preferable. Since these do not have an ester-bonded cationic group and are not easily hydrolyzed, the effects of the present invention can be exhibited more satisfactorily.

Of these, polydiallyldimethylammonium chloride and / or a copolymer thereof, acrylamide / 3-acrylamidepropyl (trimethyl) ammonium chloride copolymer, acrylamide / diallyldimethylammonium chloride copolymer, alkylamine / epichlorohydrin polycondensation. The thing is preferable.
Further, an acrylamide / 3-acrylamidepropyl (trimethyl) ammonium chloride copolymer crosslinked with N, N'-methylenebisacrylamide and / or an acrylamide / diallyldimethylammonium crosslinked with N, N'-methylenebisacrylamide. Chloride copolymers are preferred.

Examples of the copolymer of the diallyldimethylammonium salt (chloride as a suitable salt) include a copolymer of a diallyldimethylammonium salt and a monomer copolymerizable with the diallyldimethylammonium salt.
Examples of the monomer copolymerizable with the diallyldimethylammonium salt include acrylamide, allylamine, diallylamine, methyldiallylamine, acrylic acid, epichlorohydrin, dimethylamine and the like, and one or more of these are used. be able to.
Of these, acrylamide, allylamine, and diallylamine are preferable, and acrylamide is more preferable.

<2-2. Method for producing cationic polymer used in this embodiment>
The method for producing the cationic polymer used in the present embodiment is not particularly limited, and a known method for producing the cationic polymer can be adopted. The method for producing a cationic polymer is not particularly limited, and examples thereof include a radical polymerization method, an emulsion polymerization method, a suspension polymerization method, a solution polymerization method, and a bulk polymerization method.

As a method for producing a cationic polymer in the present embodiment, for example, a cationic monomer having no ester bond (preferably a quaternary ammonium salt monomer) is added to water and mixed. If necessary, other monomers (preferably crosslinkable monomers) are further added to the water. A water-soluble polymerization initiator is added to an aqueous solution containing at least a cationic monomer having no ester bond, the atmosphere is replaced with an inert gas, and the mixture is heated to polymerize the ester-bonded cationic group. A cationic polymer that does not exist can be obtained. Further, when synthesizing the cationic polymer of the present embodiment, the oligomer can also be used as a raw material for the monomer.

As the other monomer (preferably a crosslinkable monomer), it is preferable to use 0.05 to 500 ppm (weight ratio) with respect to the “cationic monomer having no ester bond”. If the amount of the other monomer (preferably a crosslinkable monomer) is used, the degree of crosslinkability will be better, and the performance of the obtained cationic polymer of the present embodiment as a green liquid treatment agent will be better exhibited. can.

The polymerization initiator used is not particularly limited, and for example, 2,2'-azobis (2-amidinopropane) dihydrochloride, 4,4'-azobis (4-cyanovaleric acid), 2,2'-azobis [ 2- (2-imidazolin-2-yl) propane] dihydrochloride, 2,2'-azobisisobutyramid dihydrate, azobisisobutyronitrile, 2,2'-azobis (2,4-dimethyl) Examples thereof include an azo-based initiator such as valeronitrile), a redox initiator system in which a peroxide such as a persulfate or an alkyl peroxide compound is combined with a sulfite, a ferrous salt, an amine compound and the like.
Further, it can be polymerized by irradiating with light in the presence of a photosensitizer such as benzophenone or benzoin ethyl ether. Among these, a water-soluble azo-based initiator can be preferably used.

According to the production method of the present embodiment, the cationic polymer having no ester-bonded cationic group used in the present embodiment can be produced. Further, it is preferable that the cationic polymer is a polymer having at least a structural unit derived from a cationic monomer having no ester bond, and a crosslinked polymer is more preferable.

<2-2-1. An example of a method for producing a cationic polymer used in this embodiment>
As an example of the method for producing the cationic polymer used in the present embodiment, a method for producing a diallyldimethylammonium salt polymer, an acrylamide / diallyldimethylammonium salt copolymer, or an acrylamide / 3-acrylamidepropyl (trimethyl) ammonium salt copolymer. Will be described below.

There are no particular restrictions on the method for producing the diallyldimethylammonium salt polymer (homopolymer) or copolymer (copolymer), or the acrylamide / 3-acrylamidepropyl (trimethyl) ammonium salt copolymer in the present embodiment. The salt is preferably chloride.
For example, a diallyldimethylammonium salt monomer or a 3-acrylamidepropyl (trimethyl) ammonium salt monomer and, if necessary, another monomer (preferably a polyfunctional crosslinkable monomer) are mixed with water. A water-soluble polymerization initiator is added to the solution. After the addition, the atmosphere is replaced with an inert gas and heated to obtain a crosslinked diallyldimethylammonium salt polymer or copolymer, or a crosslinked acrylamide / 3-acrylamidepropyl (trimethyl) ammonium salt copolymer. can.

The other monomer used in the present embodiment is not particularly limited, and is, for example, ethylene glycol di (meth) acrylate, diethylene glycol di (meth) acrylate, polyethylene glycol di (meth) acrylate, propylene glycol di (meth) acrylate. , Dipropylene glycol di (meth) acrylate, polypropylene glycol di (meth) acrylate, N, N'-methylenebis (meth) acrylamide, glycerintri (meth) acrylate, diallyl phthalate, diallyl maleate, diallylamine, ethylene glycol diallyl ether, Triallylamine, Triallyl trimerite, Triallyl isocyanurate, Triallyl phosphate, Divinylbenzene, Ethylene glycol diglycidyl ether, Polyethylene glycol diglycidyl ether, Di or polyglycidyl ether of aliphatic polyhydric alcohols, N-methylol acrylamide. , Glycidyl methacrylate and the like, and one or more of these groups can be used. The other monomer can be used as a polyfunctional crosslinkable monomer. A monomer other than the polyfunctional crosslinkable monomer may be further used as long as the effect of the present invention is not impaired, and a monomer other than the polyfunctional crosslinkable monomer may be used. For example, the ester-bonded cation monomer is substantially not contained (for example, 1.0% or less or 0.5% or less, 0 in 100% by mass of all the monomer units constituting the polymer. .1% or less, etc.).
Of these, N, N'-methylenebis (meth) acrylamide can be preferably used.

As the other monomer, it is preferable to use 0.05 to 500 ppm (weight ratio) with respect to the diallyldimethylammonium salt monomer or the 3-acrylamidepropyl (trimethyl) ammonium salt monomer. With the amount of the crosslinkable monomer, the degree of crosslinkability does not decrease or become too high, and the performance as a green liquid treatment agent can be sufficiently exhibited.

The structural unit of the diallyldimethylammonium salt polymer used in this embodiment is not particularly limited. For example, a cyclic structure such as a 6-membered piperidinium ring or a 5-membered pyrrolidinium ring may be contained, or a polymer in which these two types of structures coexist may be used. Of these, it is preferable to use a linear or branched (preferably linear) of diallyldimethylammonium salt as a constituent unit.
Further, the diallyldimethylammonium salt copolymer may be a cationic polymer having only a cationic constituent unit, or as long as the effect of the present invention is not impaired, the cationic constituent unit and the anionic constituent unit may be copolymerized. It may be an amphoteric polymer having.

Examples of the copolymer of diallyldimethylammonium chloride include a copolymer of diallyldimethylammonium chloride and a monomer copolymerizable with the diallyldimethylammonium chloride. Examples of the monomer copolymerizable with diallyldimethylammonium chloride include acrylamide, allylamine, diallylamine, methyldiallylamine, acrylic acid, epichlorohydrin, dimethylamine and the like, and one or two selected from the group consisting of these. More than a seed can be used. Of the copolymers, the crosslinked polymer is more preferable.
Among them, one or more selected from acrylamide, allylamine, and diallylamine are preferable.

<3. Green liquid treatment agent of this embodiment>
The green liquid treatment agent of the present embodiment contains the above-mentioned cationic polymer of the present embodiment as an active ingredient. The above <1. > And <2. The configuration that overlaps with> is omitted as appropriate.
The green liquor treatment agent of the present embodiment can be used in an aqueous solution in which the ester-bonded cationic polymer having no cationic group is dissolved or suspended in water, but the present invention is not particularly limited thereto, for example. , Slurry or powder can also be used.

Further, the cationic polymer having no ester-bonded cationic group of the present embodiment can be satisfactorily treated with a green liquor as an active ingredient. Further, by using the cationic polymer having no ester-bonded cationic group of the present embodiment for the green liquor treatment, the green liquor can be clarified better, and the clarified green liquor can be used to calcium carbonate. Can be produced better.
Therefore, the cationic polymer having no ester-bonded cationic group of the present embodiment can be contained in the green liquor treatment agent and can be used for producing the green liquor treatment agent.
The present embodiment can also provide the above-mentioned cationic polymer having no ester-bonded cationic group, or the use thereof, for improving the green liquor treatment. Further, the present embodiment can also provide a green liquor treatment method, a clarified green liquor production method, and a calcium carbonate production method.

<3-1. Optional ingredient>
The green liquor treatment agent of the present embodiment may contain or mix any agent as an optional component as long as the effect of the present invention is not impaired.
Optional agents include, for example, anticorrosive agents (corrosion inhibitors), antiscale agents, slime control agents, solvents or dispersion media such as water, dispersant enzymes, bactericides and defoamers, anionic polymers, other than the present embodiment. Examples thereof include, but are not limited to, a cationic polymer, an amphoteric polymer, and a nonionic polymer, and various chemicals that can be generally used for green liquor treatment may be used. One or more selected from the group consisting of these can be used.

At this time, the green liquid treatment agent of the present embodiment may be a one-component type agent containing the cationic polymer of the present embodiment, or a multi-component type such as a two-component type or a three-component type composed of a combination with a selected component. It can also be used as (for example, a drug kit). Further, when the cationic polymer of the present embodiment is used, the selected components may be added to the water to be treated with other chemicals at the same time or separately, and the order of addition may be appropriately set. Can be done. Further, it is preferable to add any of the selected agents to the same place as the place where the cationic polymer of the present embodiment is added, or to a place upstream or downstream of the place where the cationic polymer is added, which is similar to the place where the cationic polymer is added.

It is preferable that the green liquor treatment agent of the present embodiment further contains an anionic polymer from the viewpoint of treatment of the green liquor and cost. At this time, the green liquid treatment agent of the present embodiment may be a one-component type drug containing the cationic polymer of the present embodiment, or may be used as a two-component type (for example, a drug kit) composed of a combination thereof. be. Further, when the anionic polymer is used, it may be added to the cationic polymer of the present embodiment and the water to be treated at the same time or separately. The addition of the anionic polymer can be carried out at a location close to the location of addition of the cationic polymer of the present embodiment after or before the addition of the cationic polymer of the present embodiment. Further, it is more preferable to carry out after the addition.

The colloidal equivalent (meq / g) of the anionic polymer is not particularly limited as long as it is anionic, but as a suitable upper limit thereof, it is preferably −1.0 meq / g or less, more preferably −2.0 meq / g or less. It is more preferably -2.5 meq / g or less, and its preferred lower limit is preferably -8.0 meq / g or more, more preferably -5.0 meq / g or more, still more preferably -4.5 meq / g. It is g or more. The suitable numerical range is preferably −8.0 to −0.5 meq / g, and more preferably −4.5 to −2.5 meq / g. By using in combination with the cationic polymer of the present embodiment, better green liquid treatment (for example, maintaining green clarity even when the composition of green liquid fluctuates, stabilizing the amount of drawn legs, stabilizing calcium carbonate production, etc.) can be achieved. It can be carried out. The method for measuring the colloid equivalent is as described in [Example] described later.

The intrinsic viscosity ([η]) of the anionic polymer is not particularly limited, but is preferably 1 or more, more preferably 5 or more, still more preferably 10 or more, and more preferably 15 or more as a suitable lower limit value. The preferred upper limit thereof is preferably 100 or less, more preferably 80 or less, still more preferably 50 or less, and even more preferably 40 or less. The suitable numerical range is preferably 5 to 50, more preferably 15 to 40. By using in combination with the cationic polymer of the present embodiment, better green liquid treatment (for example, maintaining green clarity even when the composition of green liquid fluctuates, stabilizing the amount of drawn legs, stabilizing calcium carbonate production, etc.) can be achieved. It can be carried out. The method for measuring the intrinsic viscosity is as described in [Example] described later.

The anionic polymer is not particularly limited, but it is preferable to use one that can be used as a polymer flocculant, and more preferably one that is used for the clarification treatment of green liquor.
Examples of the anion polymer include poly (meth) acrylate-based polymers or copolymers, anionic poly (meth) acrylamide-based polymers, (meth) acrylate-based / (meth) acrylamide copolymers, and the like. One or more selected from the group consisting of these can be used. Examples of the salt include alkali metal salts (for example, sodium, potassium, etc.), but the salt is not particularly limited thereto.
Of these, a poly (meth) acrylate-based polymer or a copolymer is preferable, and a (meth) acrylate / (meth) acrylamide copolymer is more preferable.

<4. Green liquid treatment method using the cationic polymer of the present embodiment>
<4-1. Green liquid treatment method of this embodiment>
The cationic polymer of the present embodiment or the green liquid treatment agent containing the polymer (hereinafter, also referred to as “the agent of the present embodiment”) is added to the water to be treated of the green liquid treatment system to treat the green liquid. be able to. For example, the green liquor can be clarified better, and calcium carbonate having a larger particle size and a lower water content can be efficiently produced from the green liquor. In addition, the above-mentioned <1. ＞ ～ ＜ 3. The configuration that overlaps with> is omitted as appropriate.

<4-1-1. Water to be treated>
Examples of the water to be treated for clarifying the green liquid in the present embodiment include crude green liquid.
The pH of the water to be treated (20 ° C. at the time of measurement) in the present embodiment is highly alkaline, but for example, it is preferably 9 or more, more preferably 10 or more, more preferably 11 or more, still more preferably 12 or more, and more preferably. 13 or more.

The suspended solid substance (SS) in the water to be treated in the present embodiment is not particularly limited, but as a suitable lower limit value thereof, it is preferably 100 mg / L or more, more preferably 200 mg / L or more, still more preferably 300 mg / L. The above is more preferably 400 mg / L or more, and the preferred upper limit thereof is preferably 1500 mg / L or less, more preferably 1000 mg / L or less, still more preferably 900 mg / L or less, and more preferably 800 mg / L or less. be.

The total iron in the water to be treated in the present embodiment is not particularly limited, but as a suitable lower limit value thereof, it is preferably 1 mg / L or more, more preferably 2 mg / L or more, still more preferably 5 mg / L or more. As a suitable upper limit value, it is preferably 100 mg / L or less, more preferably 80 mg / L or less, and further preferably 50 mg / L or less.
The ionic iron in the water to be treated in the present embodiment is not particularly limited, but as a suitable lower limit value thereof, it is preferably 0.01 mg / L or more, more preferably 0.05 mg / L or more, still more preferably 0.1 mg. It is / L or more, and the suitable upper limit thereof is preferably 10 mg / L or less, more preferably 5 mg / L or less, and further preferably 3 mg / L or less.

The total organic carbon (TOC) in the water to be treated in the present embodiment is not particularly limited, but as a suitable lower limit value thereof, it is preferably 5 mg / L or more, more preferably 10 mg / L or more, still more preferably 50 mg / L. As described above, the preferred upper limit thereof is preferably 2000 mg / L or less, more preferably 1500 mg / L or less, and further preferably 1000 mg / L or less.

The water quality of the water to be treated in this embodiment is not particularly limited, but it is preferable to consider one or more water quality conditions selected from pH, SS, total iron, ionic iron, and TOC. When the water quality condition is within a suitable range, better green liquid treatment can be performed, and when the water to be treated falls within the numerical range, the cationic polymer of the present embodiment is appropriately used. This is preferable from the viewpoint of clarification of the green liquid and work efficiency.

<4-1-2. Place of addition of the drug of this embodiment>
The agent of this embodiment can be added to an appropriate place in the green liquid treatment system. The place is not particularly limited, and examples thereof include each processing device, processing system, piping, and flow path system. For example, the addition of the agent of the present embodiment is preferably at a place where green liquor treatment is required or upstream thereof. At this time, it is desirable that a stirrer or a mixer is provided at the place or upstream so that the water to be treated and the chemical of the present embodiment can be easily mixed.

Further, in the present embodiment, it is possible to provide a drug addition device for introducing the drug of the present embodiment into the green liquid treatment system, and a flow path and piping for introducing the drug of the present embodiment into the green liquid treatment system. preferable. For example, the agent of the present embodiment can be added to the dissolution tank 31 or the green liquid clarifier 32, or can be added to water for dissolving the smelt.
The chemicals of the present embodiment are preferably added between the dissolution tank 31 and the green liquid clarifier 32, and it is more preferable to add the chemicals to the flow paths, pipes, equipment, etc. provided between them from the viewpoint of work efficiency. preferable.
When the cationic polymer of the present embodiment and the anionic polymer are added in combination, it is preferable to add both of them at the same time or separately between the dissolution tank 31 and the green liquid clarifier 32, and green. From the viewpoint of liquid treatment and cost, it is preferable to add the cationic polymer of the present embodiment and then the anionic polymer to the water to be treated in this order.

<4-1-3. Amount of chemical added to the water to be treated according to this embodiment>
The addition amount and addition period of the cationic polymer of the present embodiment may be appropriately set according to the state of the water to be treated, the amount of flowing fluid, and the like. The amount to be added is not particularly limited, but is preferably 0.1 mg / L or more as a suitable lower limit value for a fluid (for example, crude green liquid) from the viewpoint of treatment of green liquid and cost. It is preferably 0.5 mg / L or more, more preferably 1 mg / L or more, more preferably 2 mg / L or more, still more preferably 3 mg / L or more, and as a suitable upper limit thereof, 1000 mg / L or less, more preferably. It is 500 mg / L or less, more preferably 100 mg / L or less, more preferably 50 mg / L or less, still more preferably 30 mg / L or less, still more preferably 20 mg / L or less, and the suitable numerical range is preferably 0. .1 to 1000 mg / L, more preferably 1 to 50 mg / L.
The volume of the flowing fluid can be calculated, for example, by arranging a flow meter at an appropriate position in the fluid flow path and based on the measured value.

The addition period of the cationic polymer of the present embodiment is not particularly limited, but the color tone of the green liquor in the green liquor clarifier or the green liquor tank green liquor can be confirmed and set to a desired color tone. For example, it is also possible to set so that the effect of the present embodiment can be exhibited after addition for 1 to 24 hours (preferably 6 to 20 hours). The cationic polymer of the present embodiment may be added continuously or discontinuously (ON / OFF of addition at regular intervals, etc.).

When the cationic polymer of the present embodiment and the anionic polymer are used in combination, the amount of the anionic polymer added may be appropriately set according to the state of the water to be treated, the amount of flowing fluid, and the like.
Further, from the viewpoint of treatment of green liquor and cost, it is preferable to use 0.01 to 1 part by mass of the anionic polymer with respect to 1 part by mass of the cationic polymer of the present embodiment, and more preferably 0 of the anionic polymer. It is 0.05 to 0.5 parts by mass.

The amount of the anion polymer added when used in combination is not particularly limited, but is preferably set as a suitable lower limit value for a fluid (for example, crude green liquid) from the viewpoint of treatment of green liquid and cost. It is 0.01 mg / L or more, more preferably 0.05 mg / L or more, still more preferably 0.11 mg / L or more, and suitable upper limit values thereof are 100 mg / L or less, more preferably 50 mg / L or less, and further. It is preferably 10 mg / L or less, more preferably 5 mg / L or less, and the suitable numerical range is preferably 0.01 to 100 mg / L, more preferably 0.01 to 10 mg / L.

The green liquor treatment method of the present embodiment is excellent in clarification by adding the agent of the present embodiment to the water to be treated (for example, crude green liquor) and performing a green liquor clarification step and a scavenging / cauterizing step. The next best calcium carbonate can be obtained.

<4-1-4. Clarified green liquor and calcium carbonate in this embodiment>
The green liquor clarified by the green liquor clarification treatment of the present embodiment preferably has a weak red color and a strong green color (a ^* value -60 direction). The range of the numerical values of a ^* value and b ^* value is ± 60.
Further, in the L ^* a ^* b ^* color system, the a ^* value of the clarified green liquid is not particularly limited, but is preferably 1.5 or less, more preferably 1.0 or less, more preferably 0 or less, and further. It is preferably −0.5 or less, more preferably −1.0 or less, still more preferably −1.5 or less. In addition, "less than or equal to" of a ^* value means approaching -60.

The calcium carbonate produced by the calcium carbonate production treatment of the present embodiment has a lower limit of the particle size of preferably 5 μm or more, more preferably 10 μm or more, and the upper limit thereof is not particularly limited, but is, for example, 150 μm or less. , 100 μm or less. The larger the particle size, the more preferable from the viewpoint of work efficiency and reuse.
(Measuring method of particle size)
Calcium carbonate is dispersed in water, and the particle size of calcium carbonate (median) is measured by a laser diffraction / scattering particle size distribution measurement method (example: laser diffraction / scattering particle size distribution measuring device LA-300 manufactured by Horiba Seisakusho Co., Ltd.). Diameter) is measured.

The water content of the produced calcium carbonate is preferably 25% or less, more preferably 20% or less. The lower the water content, the more preferable from the viewpoint of work efficiency and reuse.

(Measurement method of water content)
Examples include a method using a dryer, a method of heating and drying with infrared rays, and a method using near infrared rays.
The method using a dryer is carried out according to JIS P8202 for testing the absolute drying rate of pulp, and a sample is taken and left to dry overnight in a constant temperature heating dryer at 105 ° C., and then a desiccator. It is measured by returning to room temperature and determining the water content from the difference in weight of the sample before and after drying.
The method of heating and drying with infrared rays can quickly measure the moisture content. The sample is placed in "Kurigansui" (trade name) manufactured by Kurita Water Industries, Ltd., irradiated with infrared rays, and the water content is measured from the mass change due to evaporation of water.
The near-infrared method is performed using a near-infrared moisture meter "KJT-130" (trade name) manufactured by Kett Science Institute Co., Ltd. Near-infrared light is invisible light that has a longer wavelength than visible light and is outside the red color. Since it absorbs moisture well, it irradiates light containing near-infrared light and measures its reflectance to measure the water content. To measure.
In the examples shown in Table 7, it was determined by the method using a dryer.

<4-2. Method for producing clarified green liquid and calcium carbonate according to this embodiment>
By using the agent of this embodiment, a better clarified green liquor and a better calcium carbonate can be produced. In addition, the above-mentioned <1. ＞ ～ ＜ 3. ＞ ＜ 4-1. The configuration that overlaps with> is omitted as appropriate.

The green liquor treatment method of the present embodiment uses (A) a green liquor clarification step of adding the agent of the present embodiment to the crude green liquor to clarify the green liquor, and (B) a caustic using the green liquor. It is preferable to include a calcining / causticizing step of producing calcium carbonate in the reaction and the causticizing reaction.
Further, by the green liquor treatment of the present embodiment, the agent of the present embodiment may be added to the crude green liquor to produce a clarified green liquor, and calcium carbonate may be produced using the green liquor. can.

In the green liquor clarification method of the present embodiment, it is preferable to add the agent of the present embodiment to the crude green liquor to clarify the green liquor.
As the method for scavenging and causticizing the present embodiment, it is preferable to generate calcium carbonate using the green liquor obtained by the green liquor clarification method.

The method for producing calcium carbonate of the present embodiment is a calming / cauterizing step of producing calcium carbonate using a green liquor clarified by adding a cationic polymer having no cation group bonded with an ester to a crude green liquor. It is preferable to include.
The calcium carbonate production method of the present embodiment includes (A) a green liquor clarification step of adding a cationic polymer having substantially no ester-bonded cationic group to the crude green liquor to clarify the green liquor, and (B). ) It is preferable to include a soothing / causticizing step of producing calcium carbonate in a soothing reaction and a causticizing reaction using the green liquid.
This makes it possible to produce excellent calcium carbonate.

It should be noted that the processing method of the present invention can also be realized by a control unit including a CPU in an apparatus for managing the above-mentioned green liquid processing (for example, a computer, PLC, server, cloud service, etc.). Further, the processing method of the present invention may be stored as a program in a hardware resource including a recording medium (nonvolatile memory (USB memory, etc.), HDD, CD, DVD, Blu-ray, etc.) and realized by the control unit. It is possible. It is also possible to provide the control unit or a device including the system, such as a green liquid treatment system that controls the addition of a chemical to the water to be treated (for example, for adjusting the color tone of the green liquid) by the control unit. .. Further, the management device may be provided with an input unit such as a keyboard, a communication unit such as a network, a display unit such as a display, and the like.

The present invention can also adopt the following configurations.
[1]
A green liquor treatment agent containing a cationic polymer having no ester-bonded cationic group.
[2]
Use of a cationic polymer having no ester-bonded cationic group or a cationic polymer thereof for producing a green liquid treatment agent.
[3]
Cation polymers without ester-bonded cationic groups or their use for green liquor treatment.
[4]
A green liquor treatment method in which a cationic polymer having no ester-bonded cationic group or a treatment agent containing the same is added to the crude green liquor. It is preferable that the green liquor treatment is clarification of the green liquor and / or scavenging / causticization or calcium carbonate production. A suitable place of addition is between the dissolution tank and the green liquor clarifier.
[5]
Calcium carbonate, which comprises a calming / cauterizing step of producing calcium carbonate using a cation polymer having no ester-bonded cation group or a green liquor clarified by adding the containing treatment agent to the crude green liquor. Production method.
[6]
A green liquor clarification step of adding an ester-bonded cationic polymer having no cationic group or the containing treatment agent to the crude green liquor to clarify the green liquor.
A method for producing calcium carbonate, which comprises a soothing / causticizing step of producing calcium carbonate in a soothing reaction and a causticizing reaction using the green liquid.

[7]
It is preferable that the cationic polymer according to any one of [1] to [6] is a polymer having at least a structural unit derived from a cationic monomer having no ester bond.
More preferably, the cation monomer having no ester bond is an amine monomer having no ester bond and / or a quaternary ammonium salt monomer having no ester bond.
More preferably, when the polymer is a copolymer, the crosslinked copolymer has a structural unit derived from the cation monomer having no ester bond and a structural unit derived from another crosslinkable monomer. It is a coalescence.
[8]
The colloidal equivalent (meq / g) of any one of the above [1] to [7] is 0.1 to 15 meq / g, and / or the intrinsic viscosity of the cationic polymer ([η]). Is preferably 0.2 to 5.
[9]
It is preferable that the cation monomer having no ester bond of any one of [1] to [8] is a quaternary ammonium salt monomer, and more preferably N, N-. Dialkyl-N, N-di (meth) acrylic quaternary ammonium salt.
[10]
The cationic polymer according to any one of [1] to [9] is a polydiallyldimethylammonium salt and / or a copolymer thereof; an acrylamide / 3-acrylamidepropyl (trimethyl) ammonium salt copolymer, an acrylamide / diallyldimethylammonium. It is preferably one or more selected from a salt copolymer and an alkylamine / epichlorohydrin polycondensate. Chloride or bromide is suitable as the salt.
[11]
It is preferable that the amount of the cationic polymer added to any one of [1] to [10] is 0.1 to 1000 mg / L with respect to the water to be treated.
[12]
It is preferable to use any one of the above [1] to [11] in combination with an anionic polymer.
As the anionic polymer, a poly (meth) acrylate-based polymer or a copolymer is suitable.
The order of addition of the cationic polymer and the anionic polymer is not particularly limited, but it is preferable to add the cationic polymer to the water to be treated in the order of the cationic polymer and then the anionic polymer.
Preferably, 0.01 to 1 part by mass of the anionic polymer is used with respect to 1 part by mass of the cationic polymer.

An embodiment of the present invention will be described with reference to the following experimental examples and test examples. The scope of the present invention is not limited to experimental examples, test examples, and the like.

[Experimental Example 1: Drugs 1 to 13 / Experimental Example 2: Drugs 14 to 19]
In Test Examples (No.) 1 to 13 in Experimental Example 1, crude green liquid 1 (Table 1) and each drug 1 to 13 (Table 3) were used.
In Test Examples (No.) 14 to 19 in Experimental Example 2, crude green liquid 2 (Table 1) and each drug 14 to 19 (Table 5) were used.
The crude green liquor used in this experimental example is a smelt-containing crude green liquor produced during pulp production in a paper mill.
Further, in the case of the cationic polymer copolymer, the crosslinkable monomer is in the range of 0.1 to 100 ppm with respect to the cationic group-containing monomer in terms of weight ratio.
The experimental conditions of Experimental Example 1 and Experimental Example 2 are as follows.

Table 1 shows the water qualities of the crude green liquor 1 and the crude green liquor 2 used in the desktop test. A crude green liquor having a high TOC and a high Fe content was used.

<Experimental conditions>
The green liquid clarifier treatment was evaluated by a desk test in a jar test.
Agent I was added and mixed with the water to be treated, and then Agent II was added and mixed. It was confirmed that the water quality of the treated water was improved by using the agent I as compared with the green liquid treatment using only the anionic polymer.
500 mL of green liquid was taken and measured by running a jar tester.
Stirring conditions 150 rpm x 30 seconds → 60 rpm x 90 seconds Take a picture of the supernatant 3 minutes after stopping stirring, and apply a color sensor (ColorTouch 2 Model ISO manufactured by Technidiyne) to the L ^* a ^* b ^* color space (JIS). The a ^* value and b ^* value of Z 8781-4) were obtained. When the green liquor treatment is improved, the reddish green liquor turns green, so the lower the a ^* value is, the better the treatment is (Reference Material 1: Norio Ishikawa, Journal of the Imaging Society of Japan 2005, Volume 44, No. 6, p.489-498)

<Measurement method of intrinsic viscosity>
The method for measuring the intrinsic viscosity of a polymer in the present specification shall be based on JIS K 7367-1: 2002 "Plastic-How to determine the viscosity of a polymer diluted solution using a capillary viscometer-Part 1: General rules". Can be done.
In the present specification, the intrinsic viscosities of the cationic polymer and the amphoteric polymer are 1.0 N nitrate so as to have concentrations of 0.1%, 0.08%, 0.06%, 0.04% and 0.02%. Dissolve in a solvent of aqueous sodium solution, measure at 30 ° C with a Canon Fenceke type viscosity meter (eg, manufactured by Kusano Kagaku), plot each value with the concentration on the horizontal axis and the reduced viscosity on the vertical axis, and set the straight line to zero. Externalize to the concentration to determine the intrinsic viscosity.

As used herein, the solvent of a 1.0 N NaCl aqueous solution is such that the intrinsic viscosity of the anionic polymer is 0.08%, 0.06%, 0.05%, 0.04%, 0.02%. Measured at 30 ° C with a Canon Fenceke type viscosity meter (eg, manufactured by Kusano Kagaku), plot each value with the concentration on the horizontal axis and the reduced viscosity on the vertical axis, and extrapolate the straight line to zero concentration. To obtain the intrinsic viscosity.

<Measurement method of ionicity (colloidal equivalent)>
The ionicity of polymers herein is calculated as colloidal equivalents. The measurement of "colloidal equivalent (meq / g)" in the present specification is performed based on "colloidal titration method" (Reference Material 2; by Ryoichi Sente, Nankodo Co., Ltd. (issued in November 1944)).

<Measurement method of pH, SS, total iron, ionic iron, TOC of water to be treated>
The pH is measured based on JIS Z 8802 "pH measuring method". The device was a pH meter (model number D-52 manufactured by HORIBA, Ltd.) (20 ° C.).
The TOC is measured based on JIS K 102 22.1 “Factory Wastewater Test Method Organic Carbon (TOC)”. The equipment was TOC-L (manufactured by Shimadzu Corporation).
The measurement of SS is carried out based on JIS K 102 14.1 “Factory wastewater test method, turbid substance)”. Suction filtration was performed with a filter, and the weight was determined after drying.
The total iron is measured based on JIS K 102 57.4 “Factory Wastewater Test Method Iron (Fe) ICP Emission Spectroscopy)”. The device was 720ICP-OES (manufactured by Agilent Technologies, Inc.).
The measurement of ionic iron is carried out based on JIS K 102 57.4 Remark 14 “Factory effluent test method Iron (Fe) ICP emission spectroscopic analysis) When quantifying dissolved iron”. The device was a 5110VDVICP-OES system (manufactured by Agilent Technologies, Inc.). The measurement was performed using a sample filtered through 5 types of filter paper C.

[Experimental Example 1]
The contents of each drug used in Experimental Example 1 are shown in Tables 2 and 3. The term "special" in the table means "a copolymer crosslinked using a crosslinkable monomer".
The drug cation 7 of Test Example 12 and the drug cation 8 of Test Example 13 are copolymers crosslinked with N, N'-methylenebisacrylamide, respectively. Table 2 shows the results of desk evaluation using the crude green liquid 1 and each of the agents 1 to 13, and the presence or absence of an ester-bonded cation group, the class of the cation group, and the presence or absence of a crosslinked structure for the drug cations 1 to 8. Table 3 shows the physical characteristics of the drugs used.

In Test Examples 1 to 4, various anion polymers (drug anions 1 to 4) were treated with water to be treated (crude green liquid) alone. In Test Example 5, the water to be treated (crude green liquid) was treated with an amphoteric polymer (drug amphoteric 1 having an ester-bonded cation group alone). In Test Example 6, a cation having an ester-bonded cation group was performed. The water to be treated (crude green liquid) was treated with the polymer (drug cation 1) alone.
In Test Examples 7 and 8, the water to be treated (crude green liquid) was treated with the chemical cations 2 and 3 using the cationic polymer having an ester-bonded cationic group.
In Test Examples 9 to 13, water to be treated (crude green liquid) was treated with chemical cations 4 to 8 using a cationic polymer having no ester-bonded cationic group.
In Test Examples 7 to 13, various cationic polymers (drug cations 2 to 8) were additionally added to the drug anion 2.

As a result of Test Examples 1 to 4, in the treatment of the crude green liquid using the anionic polymer (anions 1 to 4), the color tone a ^* value tended to be high (+60 direction). The drug anion 2 had a lower a ^* value among the drug anions 1 to 4.
The color tone was worse in the treatment with one amphoteric agent (Test Example 5) than in the treatment with one anion agent (drug anions 1 to 4) (Test Examples 1 to 4).
Treatment with the drug cation 1 having an ester-bonded cation group (Test Example 6) did not show a significant improvement in the a ^* value.
Further, in the treatment with the drug cations 2 and 3 having an ester-bonded cation group and the drug anion 2 in combination (Test Examples 7 and 8), the improvement effect of lowering the color tone a ^* value of the green liquid was small.
Agents 10 to 13 (drug cations 4 to 8), which do not have an ester-bonded cation group and whose cation group is a quaternary salt, have a better effect of lowering the color tone a ^* value of the green liquor, and particularly have a crosslinked structure. Drugs 12.13 (drug cations 7.8) showed excellent effects.
FIG. 2 is a plot of the results of the color tone (a ^* b ^* ) of the green liquor for each drug in Table 2. It can be seen that in the treatment with one anion agent, the a ^* value on the right shifts to the left, which is the color tone of the green liquor, in the treatment using the cations 2 to 8 of the present invention ^.

From the above, from the results of Test Examples 9 to 13, the color tone a ^* value tends to be low in the crude green liquid treatment using the drug cations 4 to 8 (-60 direction). In particular, from the results of Test Examples 7 to 13, the color tone a ^* value of the green liquor was improved in the (-60 direction) by the crude green liquor treatment using the polymer having the quaternary salt as a constituent. By using the chemical cations 4 to 8, a better clarified green liquor could be obtained, impurities were significantly reduced, and a better quality green liquor could be obtained.

[Experimental Example 2]
The contents of each drug used in Experimental Example 2 are shown in Tables 4 and 5. The term "special" in the table means "a copolymer crosslinked using a crosslinkable monomer". The drug cation 9 of Test Example 16 is a copolymer crosslinked with N, N'-methylenebisacrylamide. Results of desk evaluation using crude green liquor 2 and each drug 14 to 19 (anions 2, 6, cations 9 to 12), presence or absence of ester-bonded cation groups, and cation group class for drug cations 16 to 19. The presence or absence of a crosslinked structure is shown in Table 5. Table 5 shows the physical characteristics of the drugs used.
In Test Examples 14 and 15, only the drug anion was treated alone, and in Test Examples 16 to 19, various cationic polymers (drug cations 9 to 12) were additionally added to the drug anion 6.

In Test Examples 16 to 19 using agents (cations 9 to 12) having no ester-bonded cation group and having a quaternary cation group, the cations 9 to 12 have an effect of lowering the color tone a ^* value of the green liquor. It is possible to obtain an excellent quality green liquor by showing an excellent clarification effect of the green liquor. Further, among these, the crosslinked drug, cation 9, was able to obtain a more excellent clarified green liquor, and the impurities were significantly reduced, so that a green liquor of better quality could be obtained.

[Experimental Example 3: Test Example 20 to Test Example 21]
In the green liquor clarifier, the particles of CaCO ₃ produced when the conventional treated agent (Test Example 20) or the present-executed agent (Test Example 21) was added at the time of the water quality of the crude green liquor 3 shown in Table 6. Table 7 shows the results of the diameter and the water content of the lime mud filter. The measurement was carried out by the above-mentioned (method for measuring particle size) and (method for measuring water content).
In Test Example 21, which is the present product, the improvement in the green liquor treatment resulted in the improvement in the production of CaCO ₃ in the subsequent step and the dehydration step of CaCO ₃ .

[Experimental Example 4: Test Example 22]
As shown in FIGS. 4 and 8, in the green liquid clarifier, when an anionic polymer (manufactured by Kurita Water Industries, Ltd.) is used in combination, the green liquid clarifier does not have an ester-bonded cationic group but has a cation group of a quaternary salt. Changes in the a ^* value of the clarified green liquor were shown when the amount of the crosslinked cationic polymer (drug cation 9) added was changed. The target value of the a * value cannot be shown as an absolute value because it depends on the operating conditions of each factory, but at this site, it was judged that the red color turned green when the a * value became almost 0, and the drug cation 9 was added. The amount is estimated to be 8 mg / L from FIG.
As the amount of the crosslinked cation polymer having no cation group of the ester bond increased, the a ^* value decreased, the color tone of the treated green liquor moved toward -60 green, and the clarification of the excellent green liquor was excellent. It was found that there was a chemical effect and the quality of the obtained green liquor was excellent, which is in agreement with the results of the above-mentioned actual machine test.

Therefore, when the crude green liquor is treated with a cross-linked cation polymer agent having no ester-bonded cation group, the color tone a ^* is improved more (-60 direction), and the clarified green liquor is more excellent. In addition, impurities were significantly reduced, and a green liquor of superior quality could be obtained. Furthermore, by using the green liquid, more excellent calcium carbonate could be produced.

1 Pulp production system; 10 Cooking system; 11 Cooking kettle; 20 Black liquor treatment system; 21 Evaporator; 22 Boiler; 30 Green liquid clarification (treatment of crude green liquid) system; 31 Dissolution tank (dispersion); 32 Green liquid clarifier (Clear); 33 Green liquor tank; 40 Caustic / caustic system ;; 41 Caustic system; 42 White liquor clarifier; 43 White liquor tank; 44 Kiln; 411 Slaker; 412 Caustic reaction tank; 45 Lime mud filter

<2-1. Cationic polymer used in this embodiment>
The cationic polymer used in this embodiment is a cationic polymer having no ester-bonded cationic group. Unless otherwise specified, the polymer is meant to include homopolymers and copolymers with acrylamide and the like.
It is preferable that the cationic polymer of the present embodiment has at least a structural unit derived from a cationic monomer having no ester bond . The cation polymer may be a homopolymer having a structural unit derived from a cation monomer having no ester bond, a structural unit derived from a cation monomer having no ester bond, and another single amount. It may be a copolymer having a constituent unit derived from the body. In general, as the copolymer, a random copolymer (for example, -ABABBA-), an alternate copolymer (for example, -ABABAB-), a periodic copolymer (for example, -ABBABB-), and a block copolymer (for example, -ABBABB-) are used. For example, there are four types of structures, -AAABBBBB-), and one of the block copolymers is called a graft copolymer.

It is a schematic block diagram of the pulp production system provided with the green liquid production system which concerns on one Embodiment of this invention, but this invention is not limited to this. It is a figure which shows the tendency of the color tone (a ^* value and b ^* value) of the green liquid of each drug treatment in Experimental Example 1. ● indicates a change in the color tone of the green liquor after treatment with each agent of cation + anion or one cation agent, and ◯ indicates a change in color tone of the green liquor after treatment with each reagent of one anion / amphoteric agent. It is a figure which shows the tendency of the color tone (a ^* value and b ^* value) of the green liquid of each drug treatment in Experimental Example 2. ● indicates a change in the color tone of the green liquor after treatment with each agent of cation + anion or one cation agent, and ◯ indicates a change in color tone of the green liquor after treatment with each reagent of one anion / amphoteric agent. It is a figure which shows the addition amount of the crosslinked cationic polymer which does not have an ester-bonded cationic group but has a quaternary ammonium base, and the change in the color tone (green direction) of the clarified green liquid.

Further, for example, the monomer of the alkylamines includes ethyleneamines having an alkyl having 2 carbon atoms. Examples of the monomer of the ethyleneamines include ethylenediamine. Examples of the oligomer include polyethylene polyamines such as diethylenetriamine, triethylenetetraamine, tetraethylenepentamine, pentaethylenehexamine , piperazine, and N-aminoethylpiperazine, and one selected from the group consisting of these. Two or more types can be used.

The addition period of the cationic polymer of the present embodiment is not particularly limited, but the color tone of the green liquid in the green liquid clarifier or the green liquid tank can be confirmed and set to a desired color tone. For example, it is also possible to set so that the effect of the present embodiment can be exhibited after addition for 1 to 24 hours (preferably 6 to 20 hours). The cationic polymer of the present embodiment may be added continuously or discontinuously (ON / OFF of addition at regular intervals, etc.).

1 Pulp production system; 10 Cooking system; 11 Cooking kettle; 20 Black liquor treatment system; 21 Evaporator; 22 Boiler; 30 Green liquid clarification (treatment of crude green liquid) system; 31 Dissolution tank (dispersion); 32 Green liquid clari Fire (clarification); 33 Green liquor tank; 40 Caustic / caustic system ;; 41 Caustic system; 42 White liquor clarifier; 43 White liquor tank; 44 Kiln; 411 Slaker; 412 Caustic reaction tank; 45 Lime mud filter

Claims (7)

A green liquor treatment agent containing a cationic polymer having no ester-bonded cationic group. The cationic polymer is a polymer having at least a structural unit derived from a cationic monomer having no ester bond.
The green according to claim 1, wherein the cation monomer having no ester bond is an amine monomer having no ester bond and / or a quaternary ammonium salt monomer having no ester bond. Liquid treatment agent. The cationic polymer is a polydiallyldimethylammonium salt and / or a copolymer thereof; an acrylamide / 3-acrylamidepropyl (trimethyl) ammonium salt copolymer, an acrylamide / diallyldimethylammonium salt copolymer, an alkylamine / epichlorohydrin. The green liquid treatment agent according to claim 1 or 2, which is one or more selected from the polycondensate. A green liquor treatment method in which a cationic polymer having no ester-bonded cationic group is added to a crude green liquor. The green liquid treatment method according to claim 4, wherein the green liquid treatment is green liquid clarification. A method for producing calcium carbonate, which comprises a calming / cauterizing step of producing calcium carbonate using a green liquor clarified by adding an ester-bonded cation polymer having no cation group to the crude green liquor. A green liquor clarification step for clarifying the green liquor by adding an ester-bonded cationic polymer having no cationic group to the crude green liquor.
A method for producing calcium carbonate, which comprises a soothing / cauterizing step of producing calcium carbonate in a soothing reaction and a causticizing reaction using the green liquid.

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