JPH06178902A - Defoaming method - Google Patents

Abstract

PURPOSE:To effectively add a small addition amt. of a defoaming agent having a high function and to effectively execute replacement washing of a blow black liquid so as to obtain a clean pipe by injecting and dispersing a silicon-based defoaming agent into mixing machine at the time of circulating the filtrate separated in a vacuum drum washer to a vat and repulper. CONSTITUTION:The defoaming agent consisting of a silicone oil or silicon compd., such as hydrophobic silica, is injected and dispersed into the filtrate circulating in the pipeline of a piping (d) which circulates the filtrate from a filtrate storage tank (h) storing the filtrate from the vacuum drum washer to the vat (f) and the repulper. The foam formed within the vat (f), repulper (g) and liquid discharge piping (c) of the vacuum drum washer combined in multiple stages in counter current is ruptured. Then, the blow black liquid varying in characteristics according to tree kinds is efficiently subjected to replacement washing and the clean pipe is obtd.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a vat or a repulsor of a vacuum drum washer or a vacuum of a vacuum drum washer when the produced pulp is washed in a multistage countercurrent of 2 to 5 stages by a so-called vacuum drum washer in a pulp washing process. The foaming phenomenon that occurs in the atmosphere leg is particularly suppressed by a defoaming agent mainly composed of silicon oil, a silicon compound such as hydrophobic silica or the like, which has excellent foam retention durability, or as a defoaming component.
%, The antifoaming agent containing a high concentration of 10 to 40% of antifoaming agent can be more effectively maintained in various situations, such as when the amount used is changed due to differences in tree species. The present invention relates to a method of adding an antifoaming agent for the purpose.

[0002]

2. Description of the Related Art Pulp is made from wood such as conifers and hardwoods, bagasse, hemp, and other various types of lignocellulosic materials as raw materials, and alkali cooking such as soda (AP) and kraft (KP) and sulfite using sulfite. Salt cooking (NSS
P), and various other cooking processes. The purpose of the pulp washing step here is to separate the solution (black liquor) containing the chemicals used for cooking and the dissolved lignin discharged from the so-called digester (daidester) and the pulp suspended in it. And take out the clean pulp.

There are many types of so-called washers (washers) used in this pulp washing process, such as a vacuum drum washer, a diffuser washer used before, and a pressure type drum washer corresponding to vacuum. The most popular of these is
A vacuum drum washer, which is usually connected to a series of 2 to 5 stages and is washed with hot water in multi-stage countercurrent. Here, the pulp is separated on the wire mesh screen of the drum and washed with countercurrently flowing wash water, and finally washed with clean water and then separated.

These devices are designed to efficiently collect black liquor in which lignin and cooking chemicals are dissolved, minimize dilution with wash water, and separate clean pulp. That is, the vacuum drum washer excels in uniform and continuous effective cleaning, but the foaming property of the liquid to be filtered affects the cleaning effect (number of stages). For example, a liquid having a relatively low foaming property from a hardwood is usually washed with a vacuum drum washer having three stages, and a softwood having a large foaming property is designed to require four stages.
The vacuum drum washer of the stage compensates for the fluctuation of the throughput and quality depending on the tree species by other means, for example, by adding a chemical such as an antifoaming agent.

The foamed liquid hinders the adhesion of the pulp onto the wire mesh screen of the drum, and also hinders the liquid flow in the atmospheric leg, thereby lowering the vacuum degree of the vacuum drum washer. The bubbles adhering to the screen surface, without flowing down, are brought to the next washing stage while adhering to the pulp sheet formed on the screen surface, and become a cause of hindering effective displacement washing of lignin, cooking chemicals and the like.

Examples of the defoaming agent used as an auxiliary agent include, for example, mineral oils such as kerosene and liquid paraffin, fatty acid such as oleic acid and stearic acid, and generally diethylene glycol laurate. Glycerin monoricinoleate, alkenyl succinic acid derivative, sorbitol trioleate, alcohol-based such as polyoxyethylene sorbitol monolaurate, amide-based such as polyoxyalkylenamide, acrylate polyamine, and tributyl phosphate, octyl aluminum phosphate,
Metal soap system such as calcium oleate is used,
Recently, a silicone-based base agent having high foam breaking and suppressing properties such as dimethyl silicone oil has been used.

These defoaming agents are either self-emulsifying liquid (emulsion type), oily liquid (oil base type), or a form in which this is emulated (water base type). It has been used and is now stable in handling blow black liquor (effluent) from the Daize Star, which fluctuates due to diversifying tree species or cooking conditions, etc., is effectively washed, is efficiently collected, and maintains a certain quality. In order to be an essential drug. However, when this useful chemical is added in a large amount, it becomes a main cause of pitch formation in the pulp, and unfavorable points such as affecting the water balance in the system surface. In addition, recently, the development and improved design of antifoaming agents have advanced further, and there are excellent defoaming and foam suppressing properties that show the maximum effect with a small addition amount of about 1/10 to 1/20 of the conventional one. It has been prepared.

In particular, a silicone oil compound type defoaming agent in which silicone oil such as dimethylpolysiloxane, methylphenylpolysiloxane and methylvinylpolysiloxane is mixed with fine powder silica, and silicone oil compound are dispersed in water together with a surfactant. Emulsion type defoaming agent or defoaming agent mainly composed of hydrocarbon oil, dispersant, silicone oil and water and bisamide and / or hydrophobic silica has excellent defoaming property and defoaming property with a small addition amount. Is an antifoaming agent. However, these antifoam agents
Due to its high functionality, the amount added is small, so it is possible to spread it over a large area of the vat, and dilute it again with water in order to achieve the maximum foam breaking and foam suppressing effect. Need to take action.

The combination of a vacuum drum washer and a repulsor in a three-stage countercurrent will be described in more detail with reference to FIG. 1. The blow black liquor containing pulp sent from the blow tank is knot screen. As is, the raw black liquor supply pipe (a) 1 and the butt (f) 1 of the first stage vacuum drum washer. The lower part of the drum rotating clockwise is submerged below the liquid surface of the vat, and the internal pressure reduction is started at that position. The pulp sent from the blow tank is adsorbed in a sheet form on the wire mesh screen on the outer surface of the drum and carried, and after being washed by the shower from the nozzle of the washing water spray pipe (b) 1 installed on the drum, , Released from the vacuum, carried on the wire mesh screen, charged into the first-stage repulsor (g) 1, and sent through the pipe (a) 2 circulating through the first-stage repulsor (g) 1 by the filtrate. It becomes the first-stage washed repulp liquid and enters the vat (f) 2 of the second-stage vacuum drum washer. The black liquor is sucked into the drum through the wire mesh screen of the first-stage vacuum drum washer (e) 1 and passes through the filtrate discharge pipe (c) 1 (atmosphere leg) from the vacuum drum washer to the first stage. It is stored in the filtrate receiving tank (h) 1. The black liquor stored in the first-stage filtrate receiving tank (h) 1 is sent to the blow tank and the concentrating step as the circulating black liquor (d) 1. Also in the second and third stages, that is, the black liquor stored in the second-stage filtrate receiving tank (h) 2 passes through the pipe (a) 2 and the washing water spray pipe (b) 1 and the first stage. Of the black liquor sent to the re-pulper (g) 1 and stored in the filtrate receiving tank (h) 3 of the third stage is pipe (a) 3
After that, the washing water is sent to the spray pipe (b) 2 and the second stage repulsor (g) 2 and the countercurrent washing operation is repeated.

In the example of the combination of the three-stage countercurrent vacuum drum washer and the repulsor described above, normally, the stock solution inlet side of the vat (f) 1 of the first-stage vacuum drum washer and the second-stage vacuum drum washer are used. Bat (f) 2
Of the first-stage cleaning repulp liquid inlet side, the second-stage cleaning repulp liquid inlet side of the vat (f) 3 of the three-stage vacuum drum washer, and the first-stage filtrate receiving tank (h) 1, 2 Significant foaming is observed in the filtrate receiving tank (h) 2 of the third stage and the filtrate receiving tank (h) 3 of the third stage, and the washing efficiency is often lowered.

Therefore, in a place where foaming is likely to occur, a defoaming agent spraying pipe is provided so that the defoaming agent can be continuously added by using a metering pump or the like. This defoamer spraying pipe is generally used for the first-stage cleaning repulp liquid inlet side E of the bat (f) 2 of the second-stage vacuum drum washer where foaming is most likely to occur, and for the three-stage vacuum drum washer. Second-stage cleaning repulp liquid inlet side F of vat (f) 3
Etc. are permanently installed. In general, the amount of the defoaming agent to be added is 1500 ppm / air-dry pulp ton for softwood and 500 ppm / air-dry pulp ton for hardwood. However, in order to be aware of the stability of the operation, the added amount often tends to be excessive, so the added defoamer component is combined with the resin component of the pulp to cause a problem such as pitch formation. This is a factor of increasing the degree of similarity and increasing the disadvantages such as the increase in the cost of the antifoaming agent.

[0012]

The problem to be solved is that, in a pulp washing process involving a combination of a multi-stage countercurrent vacuum drum washer and a re-pulper, the vacuum drum washer with the number of stages installed causes the property to vary depending on the tree species. Differently blown black liquor is effectively replaced and washed, and in order to obtain clean pulp, a high-performance, small amount of antifoaming agent is effectively added in an appropriate amount to aid its diffusion and dispersion. To maximize the effect of defoaming and suppressing bubbles.

[0013]

According to the present invention, the stock solution inlet side D of the vat (f) 1 of the first-stage vacuum drum washer, the vat (f) of the second-stage vacuum drum washer, which reduces the cleaning efficiency, is provided. 2, the first-stage cleaning repulp liquid inlet side E, the third-stage vacuum drum washer vat (f) 3 second-stage cleaning repulp liquid inlet side F, and the first-stage filtrate receiving tank (h) 1 Permanently installed to break and suppress foaming in the atmosphere leg, in the second-stage filtrate receiving tank (h) 2 in the atmosphere leg, and in the third-stage filtrate receiving tank (h) 3 atmosphere leg. Of the anti-foaming agent spraying pipe, the method of spraying on a large area of the vat and / or its dilution, the effect of the addition place, etc. were compared and examined. From the filtrate storage tank (h) containing the filtrate from the washer to the vacuum drum washer A defoaming agent containing a silicon compound such as silicon oil or hydrophobic silica as a main component may be directly or in the filtrate circulating in the pipeline of the piping (a) circulating in the cloth piping (b) and the repulsor (g). Possessing proper amount without excess or deficiency through a mechanical mixer, and evenly and quickly dispersing, there is no trouble such as pitch generation, and high concentration of defoaming component is kept at the same concentration. It was realized that the bubbles generated in the vat (f), the repulsor (g) and the liquid discharge pipe (c) of the vacuum drum washer combined in a multi-stage countercurrent were broken or suppressed.

[0014]

EXAMPLES The present invention will now be described in more detail with reference to examples. <Defoaming agent used> Defoaming agent X Emulsion type silicone defoaming agent, defoaming agent Y Oil base type (silicon preparation) defoaming agent, defoaming agent Z Water base type (silicon preparation) defoaming agent is there.

<Example of addition place> Addition place A Raw black liquor supply pipe (a) 1 passing through the knot screen, addition place B
Suction-side piping of the liquid feed pump of the second-stage filtrate storage tank (h) 2 that circulates the filtrate through the first-stage re-pulper (g) 1, the addition location C, the filtrate to the second-stage re-pulper (g) 2 Suction-side piping of the liquid feed pump of the third-stage filtrate storage tank (h) 3 that circulates.

<Comparative Example Addition Place> Addition Place D Liquid surface of undiluted solution at inlet opening of knot screen, addition place E Second
Upper surface of the first-stage cleaning repulp liquid inlet side of the vat (f) 2 of the single-stage vacuum drum washer and addition site F: Upper surface of the second-stage cleaning repulp liquid inlet side of the vat (f) 3 of the third-stage vacuum drum washer.

<Method of comparing effects> First stage, second stage, third stage
The vacuum degree of the vacuum drum washer of the third stage is maintained at the same vacuum degree, the water content of the pulp released from the vacuum on the third stage drum and carried on the wire mesh screen, and the attached water contained in the pulp. The amount of defoamer required to maintain equivalent electrical conductivity was compared. An example in which the added amount is small is superior and effective.

[Examples 1 to 3] Defoaming agent used X (emulsion type), Y (oil base type) Same as above Component content rate Silicon compound content rate in defoaming agent 2
0, 10 and 4% Applicable tree species Softwood Equipment capacity 75 tons / day, but Kappa number 30
Bleached pulp Implementation conditions Vacuum degree of vacuum drum washer maintained 1st stage Vacuum drum 80 (+ -10) mmHg 2nd stage Vacuum drum 100 (+ -15) mmHg 3rd stage vacuum drum 110 (+ -20) mmHg Separation Moisture content of pulp 80 (+-2)% Electric conductivity of separated pulp adhered water 1.5 (+-0.3)
ms / cm

Implementation Results “Examples 1 to 3”

[Table 01]

"Comparative Examples 1 to 3"

[Table 02]

[Examples 4 to 6] Antifoaming agent used X (emulsion type), Z (water-based type) Same as above Component content rate Silicon compound content rate in defoaming agent 2
0, 10 and 3% Applicable tree species Hardwood Equipment capacity 75 tons / day, but Kappa number 20
Bleached pulp Implementation conditions Vacuum degree of vacuum drum washer maintained 1st stage Vacuum drum 90 (+ -10) mmHg 2nd stage Vacuum drum 100 (+ -10) mmHg 3rd stage Vacuum drum 120 (+ -10) mmHg Separation Moisture content of pulp 82 (+ -2)% Electric conductivity of separated pulp adhered water 1.0 (+ -0.2)
ms / cm

Implementation Results "Examples 4-6"

[Table 03]

"Comparative Examples 4 to 6"

[Table 04]

[0024]

As described above, according to the present invention,
In the washing process of pulp related to the combination of multi-stage countercurrent vacuum drum washer and re-pulper, the vacuum drum washer with the number of stages installed effectively replaces blown black liquor, which has different properties depending on the tree species, to clean the pulp. In order to obtain the above, it is possible to effectively add a proper amount of a defoaming agent having a high function and a small amount, and the excellent function of each defoaming agent is sufficiently applied to the application in which its dispersion and diffusion are indispensable. Can be demonstrated.

[0025]

[Brief description of drawings]

FIG. 01 is an explanatory diagram showing an example in which a vacuum drum washer and a repulsor are combined in a three-stage counterflow.

[0026]

[Explanation of symbols]

A Place of addition of Example Supply pipe for raw black liquor passing through the knot screen (a) 1 B Place of addition of Example Filtrate storage tank (h) Pipe for suction side of 2 C Pipe of addition side of Example C Filtration tank ( h) Liquid delivery pump suction side piping of 3 D Place of addition of comparative example Liquid surface of undiluted solution at knot screen inlet opening E Place of addition of comparative example 1st stage washing repulp liquid inlet side upper surface of vat (f) 2 F Comparative example Place of addition of bat (f) 3 upper surface on the inlet side of the second stage washing repulp liquid (a) Pipe for circulating raw black liquor passing through the knot screen or repulsor (g) (b) Installed on the upper part of the drum of each stage Cleaning water spray pipe (c) Filtrate discharge pipe from each stage vacuum drum washer (d) Circulating black liquor supply pipe (e) Wire drum screen of each stage vacuum drum washer (f) Each stage vacuum Do Beam Washer bat (g) filtrate receiving tank subscript repulper (h) each stage of each stage shows the apparatus of the first stage to third stage.

Claims (4)

[Claims] 1. A raw black liquor supply pipe (a), a washing water spray pipe (b), a filtrate discharge pipe (c) from a vacuum drum washer, and a filtrate is circulated to a vat and a repulsor of a vacuum drum washer. In the process of washing the pulp in a multi-stage countercurrent by the combination of the vacuum drum washer (e) equipped with the pipe (d) and the repulsor (g), from the filtrate storage tank (h) storing the filtrate from the vacuum drum washer. In the filtrate circulating in the pipe (d) circulating in the vat (f) of the vacuum drum washer and the repulsor,
Vat (f) of a vacuum drum washer in which a defoaming agent containing a silicon compound such as silicone oil or hydrophobic silica as a main component is injected or dispersed directly or through a mechanical mixer, and combined in a countercurrent multistage manner. , Rupture bubbles generated in the repulsor (g) and the liquid discharge pipe (c) and the filtrate storage tank (h),
Alternatively, a defoaming method characterized by suppressing bubbles. 2. An antifoaming agent containing a silicon compound such as silicone oil or hydrophobic silica as a main component, wherein the silicone oil such as dimethylpolysiloxane, methylphenylpolysiloxane or methylvinylpolysiloxane is mixed with fine powder silica. Compound type antifoaming agent, or emulsion type antifoaming agent in which silicone oil compound is dispersed in water together with surfactant, or oil base mainly containing hydrocarbon oil, dispersant and bisamide and / or hydrophobic silica Type defoamer or hydrocarbon oil,
The defoaming method according to claim 1, which is a water-based defoaming agent containing a dispersant and water, bisamide and / or hydrophobic silica as main components. 3. A static mixer, an injector or a liquid transfer device provided directly or in a pipe line in which the filtrate transported in the circulating pipe (d) becomes turbulent diffusion (Reynolds number of 2,100 or more). The defoaming method according to claim 1, wherein the defoaming is performed via a mechanical mixer such as a pump. 4. An antifoaming agent, which is a main component, as an antifoaming component,
The antifoaming method according to claim 1, wherein the antifoaming agent is a defoaming agent containing a high concentration of 10 to 40% of an antifoaming component, as compared to usual 2 to 10%.