JP2002294577A - Dehydration promoting agent for lime mud - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a dehydration promoting agent for lime mud formed in the causticizing step in the production of kraft pulp, having low foaming property and capable of stably reducing the water content of the lime mud even by the fluctuation of the production conditions. SOLUTION: The objective dehydration promoting agent contains a polyoxyethylene alkyl ether and/or a polyoxyethylene alkenyl ether expressed by general formula (1) R-O-(CH2 CH2 O)n -H...(1) (R is a 16-36C branched alkyl and/or a 16-36C branched alkenyl; and (n) is an integer of 3-7) as an active component.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a lime mud dehydration accelerator, and more particularly, to a lime mud cake obtained by dehydrating lime mud mainly composed of calcium carbonate produced in a causticizing step in kraft pulp production. The present invention relates to a lime mud dehydration accelerator for reducing the water content of lime.

[0002]

2. Description of the Related Art In a causticizing step in the production of kraft pulp, a smelt obtained by burning a recovered black liquor in a boiler is dissolved, and quicklime is poured into a green liquor as a supernatant liquid.
Convert sodium carbonate in green liquor to sodium hydroxide,
In this step, the generated calcium carbonate is removed to prepare a white liquor which is used as a cooking liquid for wood chips. Green liquor is usually a strongly alkaline aqueous solution mainly composed of sodium carbonate and sodium sulfide. When quicklime is added to this green liquor, quicklime reacts with water to form calcium hydroxide, and sodium carbonate in the green liquor Exchange reaction with water to produce water-insoluble calcium carbonate. As a result, the green liquor becomes a lime mud slurry containing water-soluble sodium hydroxide, sodium sulfide and water-insoluble calcium carbonate. This lime mud slurry is solid-liquid separated by a drum type vacuum dewatering lime mud filter. Commonly used lime mud filters include Oliver filters, Young filters, and pre-coated filters. For example, in the Oliver filter, the filtrate is sent to the pulp digestion process as a white liquor containing sodium hydroxide and sodium sulfide, and the lime mud cake separated on the filter surface is peeled off, burned in a kiln and regenerated into quick lime. , Again used in the causticizing process. The moisture content of the lime mud cake is usually 30% by weight to 40% by weight. However, if the properties of the lime mud change due to fluctuations in the causticizing process, the dehydration property decreases, or the Oliver filter becomes clogged, the lime mud cake Not only hinders the dewatering process, but also requires more fuel when firing in a kiln.

[0003] Therefore, the operation of the apparatus is stopped to wash the filter cloth surface. However, if the washing frequency is high, operation is hindered. In addition, the pre-coat filter first covers the filter surface with a thin layer of lime mud (pre-coat), performs dehydration filtration using this as a filter medium, and scrapes off the lime mud accumulated on the surface to a certain depth to solidify. If liquid separation occurs and clogging of the precoat layer occurs, the precoat layer is rebuilt (renewal of the precoat layer) and the operation is continued again. If the lime mud dewatering property is poor, the water content of the lime mud cake will only increase. Or, it takes time to update the pre-coat layer, which hinders the operation.

[0004] Therefore, in order to improve the dewaterability of the lime mud slurry, application of various dehydration accelerators has been proposed. For example, a method using a cationic polymer (Japanese Unexamined Patent Publication No.
No. 48340), a method using a combination of polyoxyethylene alkylphenyl ether and polyoxyethylene polyoxypropylene alkyl ether (Japanese Patent Laid-Open No. 62-1).
No. 21700), a method in which a nonionic surfactant such as polyoxyethylene alkyl phenyl ether and a polyoxyethylene polyoxypropylene condensate are used in combination (Japanese Patent Application Laid-Open No. 7-48793), a method of using a linear alcohol having 10 to 14 carbon atoms. There has been proposed a method in which a method using an ethylene oxide 3 to 4 mol adduct (JP-A-2000-344518) or the like is used as a dehydration accelerator.

However, in the method using the cationic polymer, the lime mud slurry is aggregated, but the dewatering effect is not increased, and conversely, water is entrapped in the aggregate, and the dewatering rate may be reduced. In addition, a method using a combination of polyoxyethylene alkylphenyl ether and polyoxyethylene polyoxypropylene alkyl ether, a method using a nonionic surfactant such as polyoxyethylene alkylphenyl ether and polyoxyethylene polyoxypropylene condensate, In the method using 10 to 14 linear alcohol adducts of 3 to 4 moles of ethylene oxide, these have surface activity and thus promote the foaming of the lime mud slurry, and impede lime mud sedimentation due to the bubbles that enter. And the dewatering of the lime mud slurry is hindered, the water content of the lime mud cake does not decrease, and the effect of adding a dehydration accelerator cannot be obtained. Further, due to the fluctuation of the causticizing process, the physical properties of the generated calcium carbonate change, the water content of the lime mud cake in the dehydrator fluctuates, and the water content of the lime mud cake is stable even when the dehydration accelerator is added. In some cases could not be obtained. Therefore, a lime mud dehydration accelerator capable of stably reducing the dehydration rate is strongly desired.

[0006]

DISCLOSURE OF THE INVENTION The present invention has a low foaming property with respect to lime mud in the causticizing step of kraft pulp production, and has a stable lime mud cake moisture content even when the causticizing step conditions fluctuate. An object of the present invention is to provide a lime mud dehydration accelerator capable of achieving reduction.

[0007]

Means for Solving the Problems The present inventors have conducted intensive studies on a dehydration accelerator for lime mud generated in the causticizing step of kraft pulp production. As a result, the ethylene oxide adduct of a specific branched higher alcohol was found to have low foaming. The present inventors have found that the lime mud cake significantly improves the dewatering property of the lime mud cake, and completed the present invention.

That is, the present invention relates to a compound represented by the general formula (1) R--O-(CH ₂ CH ₂ O) _n --H (1) wherein R is a branched alkyl group having 16 to 36 carbon atoms and / or 16-36 branched alkenyl groups;
n is an integer of 3 to 7), and is a lime mud dehydration accelerator containing a polyoxyethylene alkyl ether and / or a polyoxyethylene alkenyl ether as an active ingredient.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail.
The polyoxyethylene alkyl ethers or polyoxyethylene alkenyl ethers used as a lime mud dehydration accelerator in the present invention are obtained by adding ethylene oxide to a saturated or unsaturated higher alcohol having a branched chain. Higher alcohols with branched chains
These are primary alcohols and secondary alcohols having a branched chain, and any of them may be used, and any of natural alcohol and synthetic alcohol may be used. The higher alcohol having a branched chain has 16 to 36 carbon atoms, preferably 1 carbon atom.
6 to 26.

Specifically, isopalmityl alcohol,
Isostearyl alcohol, isooleyl alcohol,
Isobehenyl alcohol is an oxo alcohol having 16 to 26 carbon atoms produced by the oxo method. Examples of oxo alcohols having 16 to 26 carbon atoms produced by the oxo method include "Fine oxo coal 160" (trade name, oxo alcohol having 16 carbon atoms, manufactured by Nissan Chemical Industries, Ltd.), "Fine oxo coal" 180 "(trade name, oxo alcohol having 18 carbon atoms, manufactured by Nissan Chemical Industry Co., Ltd.)," FINE oxo call 22 "(trade name,
22-carbon oxo alcohol, Nissan Chemical Industries, Ltd.
), "Dovanol 246" (trade name, carbon number 24 to 2)
No. 6 oxo alcohol, manufactured by Mitsubishi Chemical Corporation) and the like are commercially available, and these can be used. In the present invention, one or more of these higher alcohols are selected. If the carbon number of the higher alcohol having a branched chain is 15 or less, the dehydration effect aimed at by the present invention may not be sufficiently exhibited, and if the carbon number exceeds 36, it becomes difficult to obtain and may not be practical.

In the present invention, those obtained by adding 3 to 7 mol of ethylene oxide to the above higher alcohols are used.
If the number of moles of ethylene oxide added is less than 3 moles, a favorable dehydration effect may not be obtained, and if the number of moles of ethylene oxide exceeds 7 moles, the foaming property becomes high and the dewatering effect may be small. However, it is well known that the ethylene oxide addition number shown here is only a statistical average value, and actually includes numbers before and after this average value.

It is to be noted that straight-chain saturated or unsaturated higher alcohols having 16 or more carbon atoms, such as stearyl alcohol and oleyl alcohol, ethylene oxide 3
As shown in Comparative Examples below, the adduct of 7 to 7 mol has a lower dehydration promoting effect than the adduct of 3 to 7 mol of ethylene oxide of a higher alcohol having a branched chain according to the present invention, and has a strong foaming property. In some cases, the foaming of the slurry is promoted, resulting in poor lime mud sedimentation and dehydration inhibition due to the inclusion of air bubbles, and the intended effects of the present invention cannot be achieved.

The production of the polyoxyethylene alkyl ethers and polyoxyethylene alkenyl ethers according to the present invention is not particularly limited, and is produced by a general method. Higher alcohols having a weight of about 0.3% by weight of an alkali metal hydroxide such as sodium hydroxide as a catalyst
(Vs. higher alcohol) Add and dissolve, temperature: about 150 ~
A predetermined amount of ethylene oxide is gradually blown in while stirring at 160 ° C. and pressure: about 3 kg / cm ² , and an addition reaction is performed for 30 to 60 minutes while observing the reaction amount of ethylene oxide,
It can be obtained by cooling, neutralizing with a mineral acid such as sulfuric acid, and then filtering.

To add the polyoxyethylene alkyl ethers and / or polyoxyethylene alkenyl ethers according to the present invention to the process as a dehydration accelerator,
This can be added directly using a chemical pump, or added as an aqueous solution, or a suitable organic solvent,
For example, it may be added by dissolving in methanol, ethanol, propyl alcohol, isopropyl alcohol, ethylene glycol, diethylene glycol, propylene glycol, ethylene glycol dimethyl ether, alcohols such as methylcellosolve and butylcellosolve, dioxane, ethylene carbonate and the like. The addition may be carried out either continuously or intermittently.

The location of addition is not particularly limited, and is appropriately selected depending on the cake moisture content of the lime mud and the operating condition of the vacuum dehydrator. In general, a vacuum for dehydrating the lime mud is generally used. It is appropriately added to a dewatering machine vat, a washing machine vat, a lime mud slurry storage tank, or a piping line connected to these.

The amount of addition varies depending on the solid content of the lime mud slurry, but as a guide, it is 10 to 1,000 ppm, preferably 50 to 50 ppm, based on the solid content of the lime mud slurry.
0 ppm. In practice, it is common to adjust the amount of addition based on the moisture content of the lime mud cake.

In applying the polyoxyethylene alkyl ethers and / or polyoxyethylene alkenyl ethers which are the dehydration accelerators of the present invention, the dehydration accelerators conventionally used are not impaired as long as the effects of the present invention are not impaired. Accelerators such as cationic polymers, polyoxyethylene alkylphenyl ethers, polyoxyethylene polyoxypropylene condensates, and ethylene oxide adducts of linear alcohols may be used in combination.

[0018]

The present invention will be described below in more detail with reference to examples, but the present invention is not limited thereto.

[Compounds used in the test] A-1: "Fine oxocol 160" (trade name, oxo alcohol having 16 carbon atoms, manufactured by Nissan Chemical Industries, Ltd.)
A-2: "Fine oxocol 180" (trade name, oxo alcohol having 18 carbon atoms, manufactured by Nissan Chemical Industries, Ltd.)
A-3: Octadecane-9-ol (reagent, manufactured by Tokyo Chemical Industry Co., Ltd.) Ethylene oxide 5 mol adduct A-4: "Spectiol 935U" (trade name, isooleyl alcohol, Cognis Japan Co., Ltd.) A): Fine Oxocol 200 (trade name, oxo alcohol having 20 carbon atoms, manufactured by Nissan Chemical Industries, Ltd.)
A-6: "Dovanol 246" (trade name, having 24 to 24 carbon atoms)
26-oxo alcohol, 7 mol ethylene oxide adduct of Mitsubishi Chemical Co., Ltd. A-7: 5 mol ethylene oxide adduct of "ISOFOL36" (trade name, branched alcohol having 36 carbon atoms, manufactured by Condea)

[Polyoxyethylene alkyl ethers used in Comparative Examples] B-1: "ISOFOL12" (trade name), carbon number 12
B-2: "Nikkor BL-4" (trade name, ethylene oxide 4 mol adduct of lauryl alcohol, manufactured by Nikko Chemicals Co., Ltd.) B-3: "Nikkol BL-4" Nikkor BS-4 (trade name, 4 mol of ethylene oxide adduct of stearyl alcohol, manufactured by Nikko Chemicals Co., Ltd.) B-4: "Nikkor BO-7" (trade name, 7 mol of ethylene oxide adduct of oleyl alcohol, Nikko Chemicals) B-5: "Nikkor NP-7.5" (trade name, 7.5 mol addition product of ethylene oxide of nonylphenol ether, manufactured by Nikko Chemicals Co., Ltd.) B-6: "Pluronic L-61" ( Trade name, ethylene oxide (10 mol%)-propylene oxide (90 mol%) copolymer (molecular weight about , 950), Asahi Denka Kogyo Co., Ltd.)

[Dehydration Test-1] In the causticizing process of the paper company A, the lime mud slurry is operated at a solid concentration of about 25% by weight, and the water content of the lime mud cake in the Oliver filter is about 30% by weight or more. It varied between about 42% by weight. Lime mud (solid content 25%) when the lime mud cake moisture content during operation was about 42% by weight was sampled and subjected to a test.

500 g of the lime mud slurry was placed in a 1-liter beaker and heated to 60 to 70 ° C. while stirring with a stirrer equipped with propeller blades. A dehydration accelerator having the composition shown in Table 1 was converted into an aqueous solution, and a predetermined amount (mg / lime slurry slurry solid content) was added thereto using a microsyringe.
for 1 minute. No. 2 filter paper was spread on a mesh plate of a Buchner funnel having a diameter of 9 cm, this lime mud slurry was poured at a stretch, and suction-filtered at a degree of vacuum of 650 mmHg using a leaf tester (manufactured by Miyamoto Seisakusho). After performing suction for 30 seconds, the suction was stopped, the weight (W1) of the filtered lime mud cake was measured, and the cake was dried in a dryer at 105 ° C. for 6 hours. After cooling, the weight (W2) of the lime mud cake was measured, and the water content (%) of the lime mud cake was determined by the following equation. Moisture content (%) of lime mud cake = ｛(W1-W2) / W
1｝ × 100

The foaming property of the lime mud during the dehydration test was evaluated as follows. 300 mL of the heated lime mud slurry was placed in a 500-mL stoppered test tube, 100 ppm of a dehydration accelerator was added with a microsyringe, the tube was slowly turned upside down 5 times, and then allowed to stand. The height of the foam from the liquid level was measured. If the foaming property is high, the operation of the lime mud filter is not only hindered, but also the dewatering property decreases, and the water content of the lime mud cake tends to increase, which is not preferable. Table 1 shows the test results.

[0024]

[Table 1]

When the dewatering property of the lime mud is insufficient and the water content of the lime mud cake is high, the dehydration accelerator of the present invention is used in an amount of 100 to 200.
ppm (based on lime mud slurry solids), the water content of the lime mud cake is reduced by about 11 to 13% by weight,
Conventional polyoxyethylene alkyl phenyl ether,
Polyoxyethylene polyoxypropylene condensate, C _{1
2 When} the ethylene oxide adduct of a linear alcohol is used, and when the ethylene oxide adduct of a _C18 linear alcohol (stearyl alcohol, oleyl alcohol) is used, the reduction of the water content of the lime mud cake is about 2 to 6% by weight. In comparison with the above, a remarkable dehydration promoting property was shown.
In addition, when a conventional polyoxyethylene alkylphenyl ether, polyoxyethylene polyoxypropylene condensate, or ethylene oxide adduct of a linear alcohol was used, a large number of bubbles were generated in the lime slurry, resulting in insufficient dewatering. On the other hand, with the dehydration accelerator of the present invention, a lime mud cake having less foam of the lime mud slurry and a lower moisture content was obtained.

[Dehydration test-2] In the same causticizing step as in the dehydration test-1, lime mud (solid content 25%) was collected when the water content of the lime mud cake was about 33% by weight.
A dehydration test was performed in the same manner as the dehydration test-1. A foaming test was also performed. The results are shown in Table 2.

[0027]

[Table 2]

In a situation where the water content of the cake is low and the dewatering property is good
Even if the dehydration accelerator of the present invention is 100 to 200 ppm
(With respect to lime mud slurry solids)
The water content of the mud cake was further reduced by about 4-6% by weight. one
On the other hand, conventional polyoxyethylene alkylphenyl ether
, Polyoxyethylene polyoxypropylene condensate,
C ₁₂Using ethylene oxide adduct of linear alcohol
And if C₁₈Linear alcohol (stearyl urea)
Alcohol, oleyl alcohol) with ethylene oxide
When the additive is used, the water content of the lime mud cake is reduced by about 1 to
3% by weight, the dehydration accelerator of the present invention has excellent dehydration
Showed progressiveness.

[Dehydration Test-3] In the causticizing step (lime sludge slurry solids concentration of about 25% by weight) of the paper company B, the water content of the lime mud cake by the Oliver filter is about 3
It was operating between 0% and about 40% by weight. In this plant, the pulp species used in kraft cooking is softwood (N
) And hardwood (L), the operating conditions of the causticizing process fluctuated, the operations with a high water content of lime mud cake increased, and the amount of heavy fuel oil used in the kiln increased. . Therefore, the operation was performed by adding 300 to 500 ppm (based on lime mud solids) of a 3 mol adduct of lauryl alcohol with ethylene oxide to the vat of the Oliver filter for the purpose of accelerating dehydration, but the operation was not sufficiently improved.

The causticizing process of the plant and the operating conditions of the kiln are as follows. Oliver filter operation vacuum degree: 430 to 510 mmHg Oven filter rotation speed: 0.8 to 2.4 rpm Lime mud slurry temperature: 50 to 60 ° C Cyclone outlet exhaust gas temperature after firing kiln: 150 to 170 ° C : 1,300 (L / h)

Therefore, the dehydration accelerator of the present invention is used at 300 pp.
m (mg / lime mud slurry solids-kg) was added to increase the dehydration effect. Was evaluated based on the temperature of the exhaust gas from the cyclone outlet and the amount of calcined kiln heavy oil used (L / h). Table 3 shows the results.

[0032]

[Table 3]

As is clear from the above test results, the lime mud cake water content without addition of the dehydration accelerator was about 39%, and the water content of the lime mud cake was reduced from 30 to 33% from the time of poor dewatering. Lauryl alcohol ethylene oxide 3 ~
Since a remarkable dewatering effect is obtained and foaming of the lime mud slurry is less than that of a dehydration accelerator using a 4-mol adduct and a dehydration accelerator using a polyoxyethylene alkylphenol ether and an ethylene oxide propylene oxide polymer in combination, lime There was no poor sedimentation of the mud and no poor dewatering of the lime mud slurry, and the amount of heavy oil used for the firing kiln was reduced, resulting in cost reduction.

[0034]

By using the polyoxyethylene alkyl ethers and polyoxyethylene alkenyl ethers according to the present invention as a lime mud dehydration accelerator, the water content of lime mud cake is reduced and the productivity is improved. , The amount of heavy oil used in firing the kiln is reduced, the cost is reduced, and great advantages can be obtained.

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Claims (1)

[Claims] 1. A compound represented by the general formula (1): R—O— (CH ₂ CH ₂ O) _n —H (1) wherein R is a branched alkyl group having 16 to 36 carbon atoms and / or 16 to 36 carbon atoms. Is a branched alkenyl group of
n is an integer of 3 to 7), wherein the polyoxyethylene alkyl ethers and / or polyoxyethylene alkenyl ethers represented by the formula (I) are contained as active ingredients.