Papermaking black liquor defoaming agent

Abstract

The polyether, the wax substance and the white carbon black are matched to replace fatty acid soap defoaming particles in a traditional mineral oil defoaming agent, the main defoaming particles are dispersed in the mineral oil, and the main defoaming particles are combined with the ester modified organic silicon, the polyether modified organic silicon and the ester substance to prepare the defoaming agent taking the mineral oil as a main body. The obtained defoaming agent has the advantages of good effect of removing the taros oil soap, good water filtering property, solving of the problem of organic silicon deposition, good effect of removing the taros oil soap, and strong foam removing and inhibiting effects and storage stability.

Description

Technical Field

[0001] This patent relates to a defoamer. More precisely, it relates to a defoamer used in papermaking black liquor. Defoamers are fine chemical additives, and therefore, the invention belongs to the technical field of fine chemical preparations. Technical Background

[0002] Due to the diversity of foaming substances, defoamers, as chemical additives, are not universal but rather targeted. The presence of large amounts of surfactants in papermaking black liquor can easily generate foam, severely impacting normal production and operation. Adding an appropriate amount of defoamer is a promising solution. Wood tall oil soap is a byproduct recovered during the cooking process of kraft pulp mills using high-quality pine wood as raw material. It can be processed through distillation to produce rosin, which can be reused as a water-repellent in papermaking. Currently, rosin derived from wood tall oil soap is replacing gum rosin as an alternative source of rosin production abroad. Therefore, paper mills are prioritizing the recovery of wood tall oil soap as a key means of improving economic efficiency. Recovering tall oil soap from pulp wastewater is a crucial unit operation in the pulping process. Besides its value for recycling, tall oil can also cause evaporator fouling and scaling, asphalt formation, the need for bleaching chemicals, paper machine foaming, and blackening of the recovery furnace during the kraft recovery process and subsequent papermaking.

[0003] CN102489049B discloses a mineral oil-based defoamer and its preparation method. By modifying the method of adding materials to the mineral oil system, this defoamer provides a low viscosity and reduced cratering. The preparation method involves separating the carrier into two parts: mineral oil and solvent. First, white carbon black is dispersed in the mineral oil, then a fatty acid metal soap is dissolved in the solvent. Finally, the two parts are mixed and an emulsifier is added. While this method improves the dispersibility of the defoamer, it is less effective in removing tall oil soap.

[0004] CN104771939B discloses a mineral oil defoamer for papermaking black liquor and its preparation method. This method improves the removal rate of tall oil from papermaking black liquor and reduces tall oil adhesion to equipment and mesh by gradually introducing different types of blocked polyethers into a carrier. However, the defoamer's stability in high-temperature, highly alkaline environments still needs to be improved, and stratification may occur during long-term use.

[0005] CN100531850C discloses a universal non-silicone defoamer composition and its preparation method. The defoamer comprises an organic hydrocarbon substance, a primary defoaming substance, a defoaming synergist, and an emulsifier. The addition of a polymer defoaming synergist improves the defoaming and anti-foaming properties. However, the defoamer is less than ideal when treating papermaking black liquor containing large amounts of tall oil soap, and its water filtration performance needs to be improved.

[0006] CN1903951B proposes an improved non-silicone coating defoamer and its preparation method. By adding a small amount of a modified polyether with a special structure to a high-mineral oil defoamer, the product's foam removal and suppression performance are enhanced. While this defoamer avoids the shortcomings of silicone, its defoaming durability and effectiveness in removing tall oil soap in the unique environment of papermaking black liquor remain insufficient.

[0007] CN101991975B discloses a mineral oil-based defoamer and its preparation method. The defoaming agents include fatty acid metal soap, fatty acid amide, and white carbon black. The method of mixing the defoaming agents into the mineral oil is modified, thereby improving the stability and foam removal performance of the mineral oil defoamer. However, the defoamer's stability in high-temperature, strong-alkaline environments and its effectiveness in removing tall oil soap still need to be improved.

[0008] In summary, existing defoamers present the following challenges when treating papermaking black liquor: First, they are less than ideal at removing tall oil soap, resulting in tall oil soap residue remaining in the system and impacting equipment efficiency; second, they suffer from poor water filtration, impacting paper quality; third, while silicone-based defoamers offer excellent defoaming effects, they are prone to depositing in the system, causing equipment and paper quality issues; and fourth, they are insufficiently stable in high-temperature, high-alkaline environments, resulting in a short service life. Therefore, developing a defoamer that effectively removes tall oil soap, exhibits excellent water filtration performance, is free of silicone deposition, and is stable in high-temperature, high-alkaline environments is crucial for improving production efficiency and product quality in the papermaking industry. Summary of the Invention

[0009] The present invention adopts polyether and wax substances combined with white carbon black to replace fatty acid soap defoaming particles in traditional mineral oil defoaming agents, disperses the main defoaming particles in mineral oil, and combines them with ester-modified silicone, polyether-modified silicone and ester substances to prepare a defoaming agent with mineral oil as the main component. The obtained defoaming agent has good effect of removing tall oil soap and good water filterability, solves the problem of silicone deposition, has good effect of removing tall oil soap, strong defoaming and suppression effect and storage stability.

[0010] The defoamer used in the papermaking black liquor is composed of the following components:

[0011] A. Mineral oil

[0012] The mineral oil is a compound composed of carbon and hydrogen atoms. It can be selected from kerosene, diesel, engine oil, machine oil, white oil, liquid paraffin, alkylbenzene, naphthenic oil, and heavy alkylbenzene, and can be used alone or in combination. The amount of mineral oil used is 75-90% of the total mass of the defoamer.

[0013] B. Polyether

[0014] The polyether is obtained by the addition reaction of higher fatty alcohols with ethylene oxide (EO) and propylene oxide (PO) in the presence of a catalyst. The general structural formula is as follows:

[0015] RO(EO) x (PO) y H

[0016] Wherein the subscripts x and y represent the degrees of polymerization of EO and PO, respectively; x is an integer from 0 to 100, and y is an integer from 1 to 200, preferably an integer from 20 to 80, and y is an integer from 1 to 20. R is a hydrocarbon group having 3 to 22 carbon atoms, including an alkyl group, an aryl group, or an olefin group. The alkyl group includes propyl, isopropyl, butyl, isobutyl, pentyl, hexyl, octyl, isooctyl, decyl, dodecyl, tetradecyl, hexadecyl, and octadecyl; the aryl group includes phenyl, tolyl, and benzyl; and the olefin group includes propyl and olefin groups. Preferably, R is a linear alkyl group having 8 to 22 carbon atoms. The amount of polyether used is 0.1 to 10% of the total mass of the defoamer.

[0017] C. Wax

[0018] The wax material is selected from waxes with a melting point of 30 to 120°C, including natural wax, synthetic wax, mineral wax, and petroleum wax, and the amount used accounts for 0.1 to 5% of the total mass of the defoamer, preferably 0.1 to 3%;

[0019] D. Silica

[0020] The white carbon black is preferably hydrophobic white carbon black, and its specific surface area is 30 to 500 m2 / g; and its usage is 0.5 to 5% of the total mass of the defoaming agent.

[0021] E. Emulsifier

[0022] The emulsifier is a surfactant, which includes three categories: anionic surfactants, cationic surfactants, and nonionic surfactants. Nonionic surfactants are preferred, with a hydrophilic-lipophilic balance (HLB) of 1 to 10. Nonionic emulsifiers mainly include fatty alcohol polyoxyethylene ethers, oleic acid polyoxyethylene ethers, alkylphenol polyoxyethylene ethers, and castor oil polyoxyethylene ethers. The emulsifier dosage is 0.1 to 10% of the total mass of the defoamer.

[0023] F. Polyether modified silicone

[0024] The polyether-modified silicone is referred to as "silicon polyether". Its structural formula is as follows:

[0025] (CH3)3SiO{(CH3)2SiO) x (CH3GSiO) y}(CH3)3, G is a polyether group, the structural formula is: -(CH2) z (EO)g (PO) h R, wherein R is -H or -CH3 or -COCH3; the subscripts x, y, z, g, and h represent the degree of polymerization, where x is an integer of 10 to 500; y is an integer of 1 to 50; z is an integer of 2 to 6; g is an integer of 1 to 40; and h is an integer of 1 to 60.

[0026] Silicone polyethers are prepared by the addition reaction of hydrogenated polysiloxanes and unsaturated polyethers in the presence of an acidic catalyst. The specific preparation method can be found in existing professional literature. The silicone polyethers have a dynamic viscosity of 10 to 30,000 mPa·s at 25°C, preferably 60 to 5,000 mPa·s at 25°C. The dosage is 1% to 10% of the total defoamer.

[0027] G. Ester modified silicone

[0028] The ester-modified silicone is an acrylate-modified silicone, which is based on polysiloxane (-Si-O- main chain) and introduces acrylate groups through chemical bonds. Its structural formula is:

[0029] [Si(CH3)2O] a −[Si(CH3)(R)O] b −[Si(CH3)2O] c

[0030] Among them, R is the acrylate functional side chain, a, b, and c represent the number of repetitions of different units, and the ratio affects the degree of modification.

[0031] Preferably, the molecular weight of the ester-modified silicone is 2000 to 20000 g / mol, and the ester-modified silicone accounts for 5 to 15% of the total mass of the defoamer.

[0032] H. Ester

[0033] The ester is selected from tributyl phosphate, tributyl citrate, triethyl citrate, epoxy fatty acid methyl ester, polypropylene adipate, polysebacate, etc., and the amount used is 1-8% of the total amount of the defoamer.

[0034] The preparation method of the black liquor defoamer is as follows:

[0035] (1) Add mineral oil to a reaction vessel, then add wax and white carbon black thereto, stir and heat to 80-150°C, and keep warm for 0.5-3 hours to obtain a mixture M1;

[0036] (2) After the insulation is completed, maintain low-speed stirring (500-800 rpm) and cool to 50-30°C; during the cooling process, add polyether to M1 twice to obtain mixture M2;

[0037] (3) Add the ester-modified silicone, the polyether-modified silicone, and the first part of the emulsifier to the mixture M2 and stir (800-1200 rpm) for 15-30 min to obtain a mixture M3;

[0038] (4) Add the ester substance to the mixture M3 and mix evenly. Then add the second part of the emulsifier and use a high shear emulsifier (12000-15000 rpm) to shear for 30 to 60 minutes to obtain the papermaking black liquor defoamer of the present invention. DETAILED DESCRIPTION

[0039] Polyether Examples

[0040]

[0041] Polyether modified silicone embodiment

[0042]

[0043] Example values ​​of ester modified silicone

[0044]

[0045] Example 1

[0046] (1) 75 parts of kerosene were added to a reaction vessel, followed by 5 parts of natural wax and 2 parts of hydrophobic white carbon black (specific surface area 30 m 2 / g), after addition, stirring and heating to 80 ° C, and keeping warm for 3 h to obtain mixture M1-1;

[0047] (2) After the insulation is completed, the mixture is cooled to 35°C while stirring at a low speed (500 rpm). During the cooling process, 5 parts of polyether B1 are added to M1-1 in two portions to obtain a mixture M2-1.

[0048] (3) 7 parts of ester-modified silicone F1, 1 part of polyether-modified silicone G1, and 1.5 parts of fatty alcohol polyoxyethylene ether were added to the mixture M2-1 and stirred (800 rpm) for 30 minutes to obtain a mixture M3-1;

[0049] (4) 2 parts of tributyl phosphate were added to the mixture M3-1 and mixed evenly. Then, 1.5 parts of fatty alcohol polyoxyethylene ether were added and sheared for 60 minutes using a high shear emulsifier (12000 rpm) to obtain the papermaking black liquor defoamer N1 of the present invention.

[0050] Example 2

[0051] (1) 80 parts of diesel were added to a reaction vessel, followed by 3 parts of synthetic wax and 5 parts of hydrophobic silica (specific surface area 50 m2 / g), after addition, stirring and heating to 100 ° C, keeping warm for 2 h to obtain mixture M1-2;

[0052] (2) After the insulation is completed, the mixture is stirred at a low speed (600 rpm) and cooled to 30°C. During the cooling process, 2 parts of polyether B2 are added to M1-2 in two portions to obtain a mixture M2-2.

[0053] (3) 7 parts of ester-modified silicone F2, 1 part of polyether-modified silicone G2, and 0.5 parts of oleic acid polyoxyethylene ether were added to the mixture M2-2 and stirred (900 rpm) for 25 minutes to obtain a mixture M3-2;

[0054] (4) Add 1 part of tributyl citrate to the mixture M3-2 and mix well. Then add 0.5 parts of oleic acid polyoxyethylene ether and shear for 50 minutes using a high shear emulsifier (13000 rpm) to obtain the papermaking black liquor defoamer N2 of the present invention.

[0055] Example 3

[0056] (1) 83 parts of white oil were added to a reaction vessel, and then 0.5 parts of mineral wax and 0.5 parts of hydrophobic white carbon black (specific surface area 100 m 2 / g), after addition, stirring and heating to 120 ° C, keeping warm for 1.5 h to obtain mixture M1-3;

[0057] (2) After the insulation is completed, the mixture is stirred at a low speed (700 rpm) and cooled to 40°C. During the cooling process, 0.5 parts of polyether B3 are added to M1-3 in two portions to obtain a mixture M2-3.

[0058] (3) 6 parts of ester-modified silicone F3, 5 parts of polyether-modified silicone G3, and 0.2 parts of alkylphenol polyoxyethylene ether were added to the mixture M2-3 and stirred (1000 rpm) for 20 minutes to obtain a mixture M3-3;

[0059] (4) 4 parts of triethyl citrate were added to the mixture M3-3 and mixed evenly. Then, 0.3 parts of alkylphenol polyoxyethylene ether were added and sheared for 40 minutes using a high shear emulsifier (14000 rpm) to obtain the papermaking black liquor defoamer N3 of the present invention.

[0060] Example 4

[0061] (1) 78 parts of naphthenic oil were added to a reaction vessel, followed by 1 part of petroleum wax and 1 part of hydrophobic silica (specific surface area 300 m 2 / g), after addition, stirring and heating to 130 ° C, keeping warm for 1 hour to obtain mixture M1-4;

[0062] (2) After the insulation is completed, the mixture is stirred at a low speed (750 rpm) and cooled to 45°C. During the cooling process, 1 part of polyether B4 is added to M1-4 in two portions to obtain a mixture M2-4.

[0063] (3) 10 parts of ester-modified silicone F4, 2 parts of polyether-modified silicone G4, and 0.5 parts of castor oil polyoxyethylene ether were added to the mixture M2-4 and stirred (1100 rpm) for 15 minutes to obtain a mixture M3-4;

[0064] (4) 4 parts of epoxy fatty acid methyl ester were added to the mixture M3-4 and mixed evenly. Then, 0.3 parts of castor oil polyoxyethylene ether were added and sheared for 30 minutes using a high shear emulsifier (15000 rpm) to obtain the papermaking black liquor defoamer N4 described in the present invention.

[0065] Example 5

[0066] (1) 76 parts of engine oil were added to a reaction vessel, followed by 0.5 parts of petroleum wax and 3 parts of hydrophobic silica (specific surface area 500 m 2 / g), after addition, stirring and heating to 150 ° C, keeping warm for 0.5 h to obtain mixture M1-5;

[0067] (2) After the insulation is completed, the mixture is cooled to 50°C while stirring at a low speed (800 rpm). During the cooling process, 9 parts of polyether B5 are added to M1-5 in two portions to obtain a mixture M2-5.

[0068] (3) 5 parts of ester-modified silicone F5, 1.5 parts of polyether-modified silicone G5, and 2 parts of oleic acid polyoxyethylene ether were added to the mixture M2-5 and stirred (1200 rpm) for 15 minutes to obtain a mixture M3-5;

[0069] (4) Add 1 part of polypropylene adipate to the mixture M3-5 and mix well. Then add 2 parts of oleic acid polyoxyethylene ether and shear for 45 minutes using a high shear emulsifier (15000 rpm) to obtain the papermaking black liquor defoamer N5 of the present invention.

[0070] Comparative Example 1

[0071] (1) 75 parts of kerosene were added to a reaction vessel, followed by 5 parts of natural wax and 2 parts of hydrophobic white carbon black (specific surface area 30 m 2 / g), after addition, stirring and heating to 80 ° C, and keeping warm for 3 h to obtain mixture M1-6;

[0072] (2) After the insulation is completed, the mixture is cooled to 35°C while stirring at a low speed (500 rpm). During the cooling process, 5 parts of polyether B1 are added to M1-6 to obtain a mixture M2-6.

[0073] (3) 7 parts of ester-modified silicone F1, 1 part of polyether-modified silicone G1, and 3 parts of fatty alcohol polyoxyethylene ether were added to the mixture M2-1 and stirred (800 rpm) for 30 minutes to obtain a mixture M3-6;

[0074] (4) Add 2 parts of tributyl phosphate to the mixture M3-6, mix well, and use a high shear emulsifier (12000 rpm) to shear for 60 minutes to obtain the papermaking black liquor defoamer N6 of the present invention.

[0075] Comparative Example 2

[0076] (1) 85 parts of diesel were added to the reaction vessel, and then 5 parts of hydrophobic silica (specific surface area 50 m 2 / g), after addition, stirring and heating to 100 ° C, keeping warm for 2 h to obtain mixture M1-7;

[0077] (2) After the insulation is completed, the mixture is stirred at a low speed (600 rpm) and cooled to 30°C to obtain a mixture M2-7;

[0078] (3) 7 parts of ester-modified silicone F2, 1 part of polyether-modified silicone G2, and 0.5 parts of oleic acid polyoxyethylene ether were added to the mixture M2-7 and stirred (900 rpm) for 25 minutes to obtain a mixture M3-7;

[0079] (4) 1 part of tributyl citrate was added to the mixture M3-7 and mixed evenly. Then, 0.5 parts of oleic acid polyoxyethylene ether was added and sheared for 50 minutes using a high shear emulsifier (13000 rpm) to obtain the papermaking black liquor defoamer N7 described in the present invention.

[0080] Comparative Example 3

[0081] (1) 83 parts of white oil were added to a reaction vessel, followed by 2 parts of mineral wax and 3 parts of hydrophobic white carbon black (specific surface area 100 m 2 / g), after addition, stirring and heating to 120 ° C, and keeping warm for 1.5 h to obtain mixture M1-8;

[0082] (2) After the insulation is completed, the mixture is cooled to 40°C while stirring at a low speed (700 rpm). During the cooling process, 10 parts of polyether B3 are added to M1-3 in two portions to obtain a mixture M2-8.

[0083] (3) 2 parts of alkylphenol polyoxyethylene ether were added to the mixture M2-8, and sheared for 40 minutes using a high shear emulsifier (14000 rpm) to obtain the papermaking black liquor defoamer N8 of the present invention.

[0084] Comparative Example 4

[0085] (1) 78 parts of naphthenic oil were added to a reaction vessel, followed by 1 part of petroleum wax and 1 part of hydrophobic silica (specific surface area 300 m 2 / g), after addition, stirring and heating to 130 ° C, keeping warm for 1 hour to obtain mixture M1-9;

[0086] (2) After the insulation is completed, the mixture is cooled to 45°C while stirring at a low speed (750 rpm). During the cooling process, 1 part of polyether B4 is added to M1-9 in two portions to obtain a mixture M2-9.

[0087] (3) 10 parts of ester-modified silicone F4, 2 parts of polyether-modified silicone G4, and 0.5 parts of castor oil polyoxyethylene ether were added to the mixture M2-9 and stirred (1100 rpm) for 15 minutes to obtain a mixture M3-9;

[0088] (4) 7 parts of castor oil polyoxyethylene ether were added to the mixture M3-9, and the mixture was sheared for 30 minutes using a high shear emulsifier (15000 rpm) to obtain the papermaking black liquor defoamer N9 of the present invention.

[0089] Comparative Example 5

[0090] (1) 76 parts of engine oil were added to a reaction vessel, followed by 0.5 parts of petroleum wax and 3 parts of hydrophobic silica (specific surface area 500 m 2 / g), after addition, stirring and heating to 150 ° C, keeping warm for 0.5 h to obtain mixture M1-10;

[0091] (2) After the insulation is completed, maintain low-speed stirring (800 rpm) and cool to 50°C; during the cooling process, add 9 parts of polyether B5, 5 parts of ester-modified silicone F5, 1.5 parts of polyether-modified silicone G5, 4 parts of oleic acid polyoxyethylene ether, and 1 part of polypropylene adipate, and use a high-shear emulsifier (15000 rpm) to shear for 45 minutes to obtain the papermaking black liquor defoamer N10 described in the present invention.

[0092] Tarot Oil Extraction Test

[0093] 0.6% of the defoamer sample was added to 100g of black liquor. After desulfurization and acidification, the lignin was dissolved with a methanol-acetone solution, and finally extracted with petroleum ether and evaporated to dryness to obtain tall oil.

[0094] Test results:

[0095] Tarot Oil Extraction Test

[0096]

[0097] From the test results, it can be seen that the efficiency of extracting tall oil using N1-N5 samples is significantly higher than that using N6-N10.

[0098] Performance test of defoaming agent:

[0099] (1) Foam suppression performance test

[0100] First, add 600mL of black liquor to the circulating bubbler, set the temperature to 85°C, and the flow rate to 6L / min. Then, turn on the temperature control switch, heat the foaming liquid to the set temperature, start the circulation pump, and begin impact foaming. When the foam rises to 300mL, add 0.2% defoamer and record the change in foam height over time. The better the defoamer's performance, the lower the minimum scale the foam reaches; the better the defoamer's anti-foaming performance, the longer it takes for the foam to reach 300mL again.

[0101]

Claims

1. A papermaking black liquor defoamer according to the present invention is characterized in that: It is composed of the following components: The amount of mineral oil in component A is 75-90% of the total mass of the black liquor defoamer; The dosage of component B polyether is 0.1-10% of the total mass of the black liquor defoamer; The dosage of component C wax is 0.1-5% of the total mass of the black liquor defoamer; The amount of component D white carbon black is 0.5-5% of the total mass of the black liquor defoamer; The dosage of component E emulsifier is 0.1-10% of the total mass of black liquor defoamer; The dosage of component F polyether modified silicone is 1-10% of the total mass of the black liquor defoamer; The dosage of component G ester modified silicone is 5-15% of the total mass of the black liquor defoamer; The dosage of component H ester is 1-8% of the total mass of the black liquor defoamer; The preparation method of the black liquor defoamer is as follows: (1) Add mineral oil to a reaction vessel, then add wax and white carbon black thereto, stir and heat to 80-150°C, and keep warm for 0.5-3 hours to obtain a mixture M1; (2) After the insulation is completed, maintain low-speed stirring (500-800 rpm) and cool to 50-30°C; during the cooling process, add polyether to M1 twice to obtain mixture M2; (3) Add the ester-modified silicone, the polyether-modified silicone, and the first part of the emulsifier to the mixture M2 and stir (800-1200 rpm) for 15-30 min to obtain a mixture M3; (4) Add the ester substance to the mixture M3 and mix evenly. Then add the second part of the emulsifier and use a high shear emulsifier (12000-15000 rpm) to shear for 30 to 60 minutes to obtain the papermaking black liquor defoamer of the present invention.

2. A black liquor defoamer according to claim 1, characterized in that the mineral oil of component A is a compound composed of carbon atoms and hydrogen atoms; selected from kerosene, diesel, engine oil, machine oil, white oil, liquid paraffin, alkylbenzene, naphthenic oil, heavy alkylbenzene, used alone or in combination.

3. The black liquor defoamer according to claim 1, wherein the polyether of component B is obtained by addition reaction of a higher fatty alcohol with ethylene oxide (EO) and propylene oxide (PO) in the presence of a catalyst; and the general structural formula is as follows: RO(EO) x (SHELF) y H wherein the subscripts x and y represent the polymerization degrees of EO and PO, respectively; x is an integer from 0 to 100, and y is an integer from 1 to 200, preferably an integer from 20 to 80, and y is an integer from 1 to 20. R is a hydrocarbon group having 3 to 22 carbon atoms, including an alkyl group, an aryl group, or an alkene group; the alkyl group includes propyl, isopropyl, butyl, isobutyl, pentyl, hexyl, octyl, isooctyl, decyl, dodecyl, tetradecyl, hexadecyl, and octadecyl; the aryl group includes phenyl, tolyl, and benzyl; the alkene group includes propyl and alkene groups; preferably, R is a straight-chain alkyl group having 8 to 22 carbon atoms.

4. A black liquor defoamer according to claim 1, characterized in that the wax substance of component C is selected from waxes with a melting point of 30 to 120°C, including natural wax, synthetic wax, mineral wax, and petroleum wax.

5. A black liquor defoamer according to claim 1, characterized in that the component D white carbon black is preferably hydrophobic white carbon black with a specific surface area of ​​30 to 500 m 2 / g.

6. A black liquor defoamer according to claim 1, characterized in that the emulsifier of component E is a surfactant, including three categories of anionic surfactants, cationic surfactants, and nonionic surfactants, preferably a nonionic surfactant with a hydrophile-lipophile balance (HLB) of 1 to 10. The nonionic emulsifier mainly includes fatty alcohol polyoxyethylene ether, oleic acid polyoxyethylene ether, alkylphenol polyoxyethylene ether, and castor oil polyoxyethylene ether.

7. The black liquor defoamer according to claim 1, wherein the component F is polyether-modified silicone, referred to as "silicon polyether", and has the following structural formula: (CH3)3SiO{(CH3)2SiO) x (CH3GSiO) y }(CH3)3, G is a polyether group, the structural formula is: -(CH2) z (EO) g (PO) h R, where R is -H or -CH3 or -COCH3; subscripts x, y, z, g, h are the degree of polymerization, x is an integer from 10 to 500; y is an integer from 1 to 50; z is an integer from 2 to 6; g is an integer from 1 to 40; h is an integer from 1 to 60; Silicone polyether is prepared by an addition reaction between hydrogenated polysiloxane and unsaturated polyether in the presence of an acidic catalyst. The specific preparation method can be found in existing professional literature. The silicone polyether has a dynamic viscosity of 10 to 30,000 mPa·s at 25°C, preferably 60 to 5,000 mPa·s at 25°C.

8. The black liquor defoamer according to claim 1, wherein the ester-modified silicone of component G is an acrylate-modified silicone, based on polysiloxane (-Si-O- main chain) with acrylate groups introduced through chemical bonds, and has the structural formula: [Si(CH3)2O] a −[Si(CH3)(R)O] b −[Si(CH3)2O] c in, R is an acrylate functionalized side chain, a, b, and c represent the number of repetitions of different units, and the ratio affects the degree of modification; The molecular weight of ester-modified silicone is 2000-20000 g / mol.

9. A black liquor defoamer according to claim 1, characterized in that the component H ester is selected from tributyl phosphate, tributyl citrate, triethyl citrate, epoxy fatty acid methyl ester, polypropylene adipate, polysebacate, etc.

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