High-solid and low-viscosity magnesium hydroxide concentrated slurry and preparation method thereof

Abstract

The application discloses a high-solid and low-viscosity magnesium hydroxide concentrated slurry and a preparation method thereof. The magnesium hydroxide concentrated slurry is composed of the following raw materials in a weight ratio: dispersant 1-2.2 parts, wetting agent 0.1-0.4 parts, magnesium hydroxide powder 68-71 parts, auxiliary agent 0.5-0.8 parts, defoaming agent 0.06-0.08 parts and pure water 25.25-30.34 parts. The magnesium hydroxide concentrated slurry has the advantages of high solid content (magnesium hydroxide powder content is 68-71%), low viscosity (200-300 cp), average particle size below 800 nm, no precipitation and caking after being placed at room temperature for 3 months, small viscosity change range and very suitable for a spraying operation mode. When the magnesium hydroxide concentrated slurry is applied to an EGC system, the working load of a feed pump and the required storage space are small, the transportation cost is low, long-period transportation and use of products are facilitated, and the magnesium hydroxide concentrated slurry has a wide application prospect in the field of wet-type ship EGC system treatment of tail gas.

Description

Technical Field

[0001] This invention relates to magnesium hydroxide concentrate and its preparation method, specifically to a high-solids, low-viscosity magnesium hydroxide concentrate and its preparation method. The magnesium hydroxide concentrate of this invention can be used as a desulfurizing agent in ship exhaust gas cleaning (EGC) systems. Background Technology

[0002] Marine EGC systems are mainly divided into two types: dry and wet. Dry marine EGC systems use granular quicklime to adsorb SO₂. X The system, which deals with particulate matter, mainly consists of an absorber, a storage tank, a particle supply device, a particle processing device, and a control system. The main process is as follows: fresh granular quicklime is supplied to the storage tank at the top of the absorber to clean SO2 from the waste gas. X After being processed by pipeline, the particulate matter is transported to a particulate treatment unit for further processing, and finally transported externally. Wet marine EGC systems use seawater or freshwater with chemical additives to clean SO2. X The system, which deals with particulate matter, mainly consists of an exhaust gas cleaner, a cleaning water treatment device, a suspended solids separator, a sludge treatment device, a seawater supply and discharge system, and an electrical control system. The main process is as follows: the cleaning water is pumped into the cleaner to wash the engine exhaust gas containing SO2. The purified exhaust gas is discharged through a chimney. The acidic seawater after the exhaust gas is cleaned enters the cleaning water treatment device for neutralization, so that its discharge is friendly to the marine ecological environment.

[0003] Currently, the industry commonly uses wet marine EGC systems to treat exhaust gases. From an operational efficiency perspective, using chemical alkalis, such as sodium hydroxide and magnesium hydroxide, is the best choice. Sodium hydroxide is a hazardous chemical, corrosive to certain metals and to humans, while magnesium hydroxide is non-toxic, harmless, and easy to store and transport. The industry often delivers concentrated magnesium hydroxide slurry (40-65% solids content) for use. Summary of the Invention

[0004] The purpose of this invention is to provide a high-solids, low-viscosity magnesium hydroxide concentrate and its preparation method. This concentrate has a magnesium hydroxide solids content as high as 68-71% and a low viscosity (200-300 cp), making it suitable for common spraying operations in the industry and possessing broad market prospects.

[0005] The technical solution of the present invention is as follows:

[0006] A high-solids, low-viscosity magnesium hydroxide concentrate is composed of the following raw materials in the indicated weight ratios:

[0007] Dispersant 1-2.2 parts, wetting agent 0.1-0.4 parts, magnesium hydroxide powder 68-71 parts, auxiliary agent 0.5-0.8 parts, defoamer 0.06-0.08 parts, purified water 25.25-30.34 parts.

[0008] The wetting agent is one or more of alkyl ammonium salt wetting agents (such as ANTI-TERRA-250, BYK) and acrylic copolymer solution wetting agents (such as DISPERBYK-2012, BYK), with alkyl ammonium salt wetting agent ANTI-TERRA-250 (BYK) being particularly preferred.

[0009] The magnesium hydroxide powder is a commercially available white magnesium hydroxide powder, preferably high-purity magnesium hydroxide for desulfurization.

[0010] The auxiliary agent is one or a mixture of two of urea and formamide in any proportion, preferably urea.

[0011] The defoamer mentioned is a low-alcohol defoamer (such as...) DF 3163, Deqian Company), mineral oil defoamers (such as...) W-074, Deqian Company; W-082, Deqian Company; W-098 (Deqian Company); ADVANTAGE AM-1512 (ASHLAND-AQUALON Company); one or more of the following defoamers: silicone defoamers (such as G308, Milliken Chemical Company, USA), preferably mineral oil defoamers, with particular preference. W-074 (Deqian Company).

[0012] The general structural formula of the dispersant is as follows:

[0013]

[0014] in,

[0015] MMA is a methyl methacrylate monomer unit;

[0016] AA is an acrylic monomer unit;

[0017] Z is a C4-C12 alkylthio, C4-C12 alkyl, phenyl, or benzyl group;

[0018] X is an isopropionic acid group, an acetate group, a 2-cyanoacetic acid group, or a 2-aminoacetic acid group;

[0019] n represents the total degree of polymerization of methyl methacrylate monomer units and acrylic acid monomer units, n = 10-30; methyl methacrylate monomer units and acrylic acid monomer units are polymerized in a random copolymerization manner, wherein the degree of polymerization of methyl methacrylate monomer units is 5-10 and the degree of polymerization of acrylic acid monomer units is 5-20.

[0020] The structural formula of the particularly preferred dispersant is as follows:

[0021] n = 10 - 30.

[0022] In comparison, the present invention also uses a block-structured dispersant in the comparative embodiments, the general formula of which is as follows:

[0023]

[0024] in,

[0025] MMA is a methyl methacrylate monomer unit;

[0026] AA is an acrylic monomer unit;

[0027] Z is a C4-C12 alkylthio, C4-C12 alkyl, phenyl, or benzyl group;

[0028] X is an isopropionic acid group, an acetate group, a 2-cyanoacetic acid group, or a 2-aminoacetic acid group; methyl methacrylate monomer units and acrylic acid monomer units are polymerized in a block copolymerization manner; where n1 is the degree of polymerization of the methyl methacrylate monomer unit, n1 = 5-10; n2 is the degree of polymerization of the acrylic acid monomer unit, n2 = 5-20.

[0029] The method for preparing the dispersant involved in this invention is as follows:

[0030] 1) Preparation of precursors

[0031] Precursors with the following structures were prepared according to the method described in the literature: FERGUSON CJ, HUGHES RJ, NGUYEN D, PHAM BTT, GILBERT RG, SERELIS AK, SUCH CH, HAWKETT B S. Ab initio emulsion polymerization by RAFT-controlled self-assembly[J]. Macromolecules, 2005, 38(6):2191-2204.

[0032]

[0033] in,

[0034] Z is a C4-C12 alkylthio, C4-C12 alkyl, phenyl, or benzyl group;

[0035] X is an isopropionic acid group, an acetate group, a 2-cyanoacetic acid group, or a 2-aminoacetic acid group;

[0036] Z is preferably benzyl and X isopropionic acid group;

[0037] 2) Preparation of polymers (all parts below are by weight)

[0038] Random copolymer: 3 parts of precursor, 0.2 parts of azobisisocyanate valerate V501 initiator, 4.32-17.28 parts of AA, 6-12 parts of MMA and 106 parts of dioxane were mixed, stirred and dissolved, and nitrogen was purged for half an hour to remove oxygen. The mixture was then reacted at 80°C for 2 hours. The system was then cooled to room temperature, and the dispersant was precipitated using cyclohexane as a precipitant. The precipitate was vacuum dried at 45°C to constant weight to obtain a random structure dispersant.

[0039] Block copolymer: 3 parts of precursor, 0.2 parts of azobisisocyanate valerate V501 initiator, 4.32-17.28 parts of AA and 106 parts of dioxane were mixed and stirred to dissolve. After purging with nitrogen for half an hour to remove oxygen, the mixture was reacted at 80°C for 2 hours. 6-12 parts of MMA, 0.2 parts of azobisisocyanate valerate V501 initiator and 32 parts of dioxane were added to the system. After purging with nitrogen for half an hour to remove oxygen, the mixture was reacted at 80°C for 12 hours. The system was then cooled to room temperature, and the dispersant was precipitated using cyclohexane as a precipitant. The resulting precipitate was vacuum dried at 45°C to constant weight to obtain a block-structured dispersant.

[0040] The preparation method of the high-solids, low-viscosity magnesium hydroxide concentrate slurry of the present invention is as follows:

[0041] According to the formula, the dispersant, wetting agent, purified water and magnesium hydroxide powder are mixed and stirred at a speed of 300-600 rpm. The stirring speed is kept constant. Then, the auxiliary agent and defoamer are added in sequence and stirred at a speed of 200-300 rpm until they are mixed evenly. The mixture is then transferred to a horizontal sand mill for grinding 1-3 times until the particle size reaches below 800 nm. The mixture is then filtered to obtain the high-solids and low-viscosity magnesium hydroxide concentrated slurry.

[0042] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0043] 1. The magnesium hydroxide concentrate slurry prepared by this invention has a high solid content (magnesium hydroxide powder content is 68-71%) and low viscosity (200-300cp). When applied to an EGC system, the workload of the feed pump and the required storage space are small, and the transportation cost is low.

[0044] 2. The magnesium hydroxide concentrated slurry prepared by this invention has a finer average particle size, below 800nm, making it very suitable for spraying operations.

[0045] 3. The magnesium hydroxide concentrate prepared by this invention has good storage stability. It does not precipitate or clump after being left at room temperature for 3 months, and the viscosity increases only slightly, which is beneficial for long-term transportation and use of the product. Detailed Implementation

[0046] The present invention is further described below through specific embodiments, but the scope of protection of the present invention is not limited thereto.

[0047] The molecular structure of the dispersant was determined by nuclear magnetic resonance spectroscopy and gel permeation chromatography, using DMSO-d6 as the deuterated reagent and tetrahydrofuran as the mobile phase for gel permeation chromatography.

[0048] The particle size and particle size distribution of magnesium hydroxide concentrate were tested using a Malvern Zetasizer 3000HAS particle size analyzer.

[0049] The solid content of magnesium hydroxide concentrate was measured by thermogravimetric analysis at a drying temperature of 120℃. The measurements were performed twice in parallel, and the average value was taken.

[0050] Viscosity tests of magnesium hydroxide concentrate slurry were performed on a BGD 152S smart touch viscometer.

[0051] The storage stability of magnesium hydroxide concentrate refers to the fact that after being placed at 25°C for 3 months, there is no precipitation and the viscosity increase does not exceed 10% of the initial viscosity, which means that the slurry storage stability is >3 months.

[0052] The dispersant used in Examples 1-4 of this invention is a random copolymer of MMA and AA, with the following structure:

[0053]

[0054] In Example 1, the average number of units in MMA monomers is 5, and the average number of units in AA monomers is 5.

[0055] In Example 2, the average number of units in MMA monomers is 5, and the average number of units in AA monomers is 15.

[0056] In Example 3, the average number of units in the MMA monomer is 8, and the average number of units in the AA monomer is 20.

[0057] In Example 4, the average number of units in the MMA monomer was 10, and the average number of units in the AA monomer was 20.

[0058] The dispersant used in Comparative Examples 1-4 is a block copolymer of MMA and AA, with the following structure:

[0059]

[0060] In Comparative Example 1, the average degree of polymerization of MMA monomers n1 is 5, and the average degree of polymerization of AA monomers n2 is 5.

[0061] In Comparative Example 2, the average degree of polymerization of MMA monomers n1 was 5, and the average degree of polymerization of AA monomers n2 was 15.

[0062] In Comparative Example 3, the average degree of polymerization of MMA monomers n1 was 8, and the average degree of polymerization of AA monomers n2 was 20.

[0063] In Comparative Example 4, the average degree of polymerization of MMA monomers, n1, was 10, and the average degree of polymerization of AA monomers, n2, was 20.

[0064] Example 1

[0065] Methods for preparing dispersants:

[0066] 1) Precursors with the following structures were prepared according to the method described in the literature: FERGUSON CJ, HUGHES RJ, NGUYEN D, PHAM BTT, GILBERT RG, SERELIS AK, SUCH CH, HAWKETT B S. Ab initio emulsion polymerization by RAFT-controlled self-assembly[J]. Macromolecules, 2005, 38(6):2191-2204. (The preparation of precursors in the following examples and comparative examples is the same.)

[0067]

[0068] 2) Random copolymer: First, add 3g of the precursor obtained in 1), 0.2g of azobisisocyanate valerate V501 initiator (Sinopharm Group), 4.32g of AA, 6g of MMA and 106g of dioxane to a three-necked round-bottom flask, stir thoroughly to dissolve, remove oxygen by purging with nitrogen for half an hour, and react at 80℃ for 2 hours; then cool the system to room temperature, and finally use cyclohexane as a precipitant to precipitate the dispersant. The obtained product is vacuum dried at 45℃ to constant weight to obtain a random structure dispersant.

[0069] Mix 1g of dispersant, 0.1g of ANTI-TERRA-250 (BYK), 30.34g of purified water, and 68g of magnesium hydroxide powder (Jiangyin Guangyuan Ultrafine Powder Co., Ltd.). Add the mixture to a mixing tank and stir at 300 rpm, maintaining a constant stirring speed. Then add 0.5g of urea (Jinan Youshengyuan Chemical Co., Ltd.), and finally add 0.06g of... W-074 (Deqian Company) was stirred and mixed evenly at a speed of 200 rpm and then transferred to a horizontal sand mill (TBM-50, Taiyi (Shanghai) Industrial Co., Ltd.) for grinding once until the particle size reached below 800 nm. Then, it was filtered out into the high-solids and low-viscosity magnesium hydroxide concentrated slurry.

[0070] Comparative Example 1

[0071] Methods for preparing dispersants:

[0072] First, add 3g of the precursor obtained in step 1), 0.2g of azobisisocyanate valerate V501 initiator (Sinopharm Group), 4.32g of AA and 106g of dioxane to a three-necked round-bottom flask, stir thoroughly to dissolve, purge with nitrogen for half an hour to remove oxygen, and then react at 80℃ for 2 hours. Then add 6g of MAA, 0.2g of azobisisocyanate valerate V501 initiator (Sinopharm Group) and 32g of dioxane to the flask, purge with nitrogen for half an hour to remove oxygen, and then react at 80℃ for 12 hours. Then cool the system to room temperature, and finally precipitate the dispersant with cyclohexane as a precipitant. The obtained product is vacuum dried at 45℃ to constant weight to obtain a block structure dispersant.

[0073] As described above, the dispersant of the random copolymer of MMA and AA in Example 1 was replaced with the dispersant of the block copolymer of MMA and AA (the polymerization method is different, but the number of monomer units is the same), and the formulation amounts of other components remained unchanged. The magnesium hydroxide concentrated slurry was prepared according to the operation steps of Example 1.

[0074] Example 2

[0075] Methods for preparing dispersants:

[0076] First, add 3g of the precursor obtained in step 1), 0.2g of azobisisocyanate valerate V501 initiator (Sinopharm Group), 12.96g of AA, 6g of MMA, and 106g of dioxane to a three-necked round-bottom flask. Stir thoroughly to dissolve, purge with nitrogen to remove oxygen for half an hour, and then react at 80℃ for 2 hours. Then, cool the system to room temperature, and finally use cyclohexane as a precipitant to precipitate the dispersant. The obtained product is vacuum dried at 45℃ to constant weight to obtain a random structure dispersant.

[0077] Mix 1.2g of dispersant, 0.22g of ANTI-TERRA-250 (BYK), 28.9g of purified water, and 69g of magnesium hydroxide powder (Jiangyin Guangyuan Ultrafine Powder Co., Ltd.). Add the mixture to a mixing tank and stir at 400 rpm, maintaining a constant stirring speed. Then add 0.6g of urea (Jinan Youshengyuan Chemical Co., Ltd.), and finally add 0.08g of... W-074 (Deqian Company) was stirred and mixed evenly at 300 rpm and then transferred to a horizontal sand mill (TBM-50, Taiyi (Shanghai) Industrial Co., Ltd.) for grinding once until the particle size reached below 800 nm. After grinding, the material was filtered out into the high-solids, low-viscosity magnesium hydroxide concentrated slurry.

[0078] Comparative Example 2

[0079] Methods for preparing dispersants:

[0080] First, add 3g of the precursor obtained in step 1), 0.2g of azobisisocyanate valerate V501 initiator (Sinopharm Group), 12.96g of AA and 106g of dioxane to a three-necked round-bottom flask. Stir thoroughly to dissolve, purge with nitrogen for half an hour, and then react at 80℃ for 2 hours. Add 6g of MMA, 0.2g of azobisisocyanate valerate V501 initiator (Sinopharm Group) and 32g of dioxane to the flask. Purge with nitrogen for half an hour, and then react at 80℃ for 12 hours. Then cool the system to room temperature, and finally precipitate the dispersant using cyclohexane as a precipitant. The resulting product is vacuum dried at 45℃ to constant weight to obtain a block structure dispersant.

[0081] As described above, the dispersant of the random copolymer of MMA and AA in Example 2 was replaced with the dispersant of the block copolymer of MMA and AA (the polymerization method is different, but the number of monomer units is the same), and the formulation amounts of other components remained unchanged. The magnesium hydroxide concentrated slurry was prepared according to the operation steps of Example 2.

[0082] Example 3

[0083] Methods for preparing dispersants:

[0084] First, add 3g of the precursor obtained in step 1), 0.2g of azobisisocyanate valerate V501 initiator (Sinopharm Group), 17.28g of AA, 9.6g of MMA, and 106g of dioxane to a three-necked round-bottom flask. Stir thoroughly to dissolve, purge with nitrogen to remove oxygen for half an hour, and then react at 80℃ for 2 hours. Then, cool the system to room temperature, and finally use cyclohexane as a precipitant to precipitate the dispersant. The obtained product is vacuum dried at 45℃ to constant weight to obtain a random structure dispersant.

[0085] Mix 2g of dispersant, 0.3g of ANTI-TERRA-250 (BYK), 26.92g of purified water, and 70g of magnesium hydroxide powder (Jiangyin Guangyuan Ultrafine Powder Co., Ltd.). Add the mixture to a mixing tank and stir at 500 rpm. Maintain this stirring speed. Then add 0.7g of urea (Jinan Youshengyuan Chemical Co., Ltd.), and finally add 0.08g of... W-074 (Deqian Company) was stirred and mixed evenly at 300 rpm and then transferred to a horizontal sand mill (TBM-50, Taiyi (Shanghai) Industrial Co., Ltd.) for grinding twice until the particle size reached below 800 nm. The material was then filtered out to produce the high-solids, low-viscosity magnesium hydroxide concentrated slurry.

[0086] Comparative Example 3

[0087] Methods for preparing dispersants:

[0088] First, add 3g of the precursor obtained in step 1), 0.2g of azobisisocyanate valerate V501 initiator (Sinopharm Group), 17.28g of AA and 106g of dioxane to a three-necked round-bottom flask. Stir thoroughly to dissolve, purge with nitrogen for half an hour to remove oxygen, and then react at 80℃ for 2 hours. Then add 9.6g of MMA, 0.2g of azobisisocyanate valerate V501 initiator (Sinopharm Group) and 32g of dioxane to the flask. Purge with nitrogen for half an hour to remove oxygen, and then react at 80℃ for 12 hours. Then cool the system to room temperature, and finally precipitate the dispersant with cyclohexane as a precipitant. The resulting product is vacuum dried at 45℃ to constant weight to obtain a block structure dispersant.

[0089] As described above, the dispersant of the random copolymer of MMA and AA in Example 3 was replaced with the dispersant of the block copolymer of MMA and AA (the polymerization method is different, but the number of monomer units is the same), and the formulation amounts of other components remained unchanged. The magnesium hydroxide concentrated slurry was prepared according to the operation steps of Example 3.

[0090] Example 4

[0091] Methods for preparing dispersants:

[0092] First, add 3g of the precursor obtained in step 1), 0.2g of azobisisocyanate valerate V501 initiator (Sinopharm Group), 17.28g of AA, 12g of MMA, and 106g of dioxane to a three-necked round-bottom flask. Stir thoroughly to dissolve, purge with nitrogen to remove oxygen for half an hour, and then react at 80℃ for 2 hours. Then, cool the system to room temperature, and finally use cyclohexane as a precipitant to precipitate the dispersant. The obtained product is vacuum dried at 45℃ to constant weight to obtain a random structure dispersant.

[0093] Mix 2.2g of dispersant, 0.4g of ANTI-TERRA-250 (BYK), 25.52g of purified water, and 71g of magnesium hydroxide powder (Jiangyin Guangyuan Ultrafine Powder Co., Ltd.). Add the mixture to a mixing tank and stir at 600 rpm, maintaining a constant stirring speed. Then add 0.8g of urea (Jinan Youshengyuan Chemical Co., Ltd.), and finally add 0.08g of... W-074 (Deqian Company) was stirred and mixed evenly at a speed of 300 rpm and then transferred to a horizontal sand mill (TBM-50, Taiyi (Shanghai) Industrial Co., Ltd.) for grinding three times until the particle size reached below 800 nm. After grinding, the material was filtered out into the high-solids and low-viscosity magnesium hydroxide concentrated slurry.

[0094] Comparative Example 4

[0095] Methods for preparing dispersants:

[0096] First, add 3g of the precursor obtained in step 1), 0.2g of azobisisocyanate valerate V501 initiator (Sinopharm Group), 17.28g of AA and 106g of dioxane to a three-necked round-bottom flask. Stir thoroughly to dissolve, purge with nitrogen for half an hour to remove oxygen, and then react at 80℃ for 2 hours. Then add 12g of MMA, 0.2g of azobisisocyanate valerate V501 initiator (Sinopharm Group) and 32g of dioxane to the flask. Purge with nitrogen for half an hour to remove oxygen, and then react at 80℃ for 12 hours. Then cool the system to room temperature, and finally precipitate the dispersant using cyclohexane as a precipitant. The resulting product is vacuum dried at 45℃ to constant weight to obtain a block structure dispersant.

[0097] As described above, the dispersant of the random copolymer of MMA and AA in Example 4 was replaced with the dispersant of the block copolymer of MMA and AA (the polymerization method is different, but the number of monomer units is the same), and the formulation amounts of other components remained unchanged. The magnesium hydroxide concentrated slurry was prepared according to the operation steps of Example 4.

[0098] Table 1. Characterization results of dispersant in Example 1

[0099] Random copolymer dispersant Block structure dispersants Theoretical molecular weight (g / mol) 1171 671；1171 Actual molecular weight (g / mol) 1200 703；1234 Molecular weight distribution (PDI) 1.05 1.03；1.10

[0100] Note: The two molecular weights of the block structure dispersant are PAA segments with an average of 5 units polymerized on the basis of the precursor (before the addition of MMA monomer), and PMMA segments with an average of 5 units polymerized on the basis of the precursor (after the reaction of the added MMA monomer is complete), forming a dispersant with a PAA5-b-PMMA5 block structure.

[0101] Table 2 Performance Table of Examples 1-4

[0102] Example 1 Example 2 Example 3 Example 4 Solid content 69.21％ 70.31％ 72.41％ 73.77％ Viscosity / cp 203 250 267 299 Particle size 778 797 670 689 Stability (precipitation) No sediment No sediment No sediment No sediment Stability (viscosity) 214 253 265 297

[0103] Table 3 Performance of Comparative Examples 1-4 and Commercially Available Slurry Products

[0104]

[0105] As shown in Table 1, the actual molecular weight of the dispersant prepared by this invention is very close to the theoretical molecular weight, and the molecular weight distribution is low; moreover, the molecular weight of the block copolymer dispersant increases in two stages, proving that this invention has obtained the desired dispersant with the main body of random copolymer of MMA and AA and the dispersant with the main body of block copolymer of MMA and AA.

[0106] As shown in Table 2, the magnesium hydroxide concentrate prepared by this invention has a high solids content (69.21%-73.77% solids, of which magnesium hydroxide powder content is 68-71%) and low viscosity (200-300 cp). When applied to an EGC system, the workload of the feed pump and the required storage space are small, resulting in low transportation costs. The magnesium hydroxide concentrate prepared by this invention has a fine average particle size, below 800 nm, making it very suitable for spraying operations. At the same time, the concentrate has good storage stability, with no precipitation or clumping after 3 months at room temperature, and the viscosity remains stable, which is beneficial for long-term transportation and use of the product.

[0107] As shown in Table 3, the magnesium hydroxide concentrates prepared in Comparative Examples 1-4 using dispersants with MMA and AA block copolymers as the main component had lower initial viscosity and storage stability than those prepared in Examples 1-4 using dispersants with MMA and AA random copolymers as the main component, and also had larger particle sizes. This demonstrates that the self-made dispersant with MMA and AA random copolymers as the main component has unique advantages in preparing high-solids, low-viscosity, well-storage-stable, and fine-particle-size magnesium hydroxide concentrates. Furthermore, the magnesium hydroxide concentrates prepared by this invention are better than commercially available concentrates in terms of solids content, viscosity, stability, and particle size, indicating that the product of this invention has broad application prospects in the field of wet-type marine EGC system exhaust gas treatment.

[0108] The above embodiments are used to explain and illustrate the present invention, but not to limit the present invention. Any equivalent modifications and changes made to the present invention within the spirit and scope of the claims shall fall within the protection scope of the present invention.

Claims

1. A high-solids, low-viscosity magnesium hydroxide concentrate, characterized in that, It is composed of raw materials in the following weight ratio: Dispersant 1-2.2 parts, wetting agent 0.1-0.4 parts, magnesium hydroxide powder 68-71 parts, auxiliary agent 0.5-0.8 parts, defoamer 0.06-0.08 parts, purified water 25.25-30.34 parts; The general structural formula of the dispersant is as follows: in, MMA is a methyl methacrylate monomer unit; AA is an acrylic monomer unit; Z is a C4-C12 alkylthio, C4-C12 alkyl, phenyl, or benzyl group; X is an isopropionic acid group, an acetate group, a 2-cyanoacetic acid group, or a 2-aminoacetic acid group; n represents the total degree of polymerization of methyl methacrylate monomer units and acrylic monomer units, n = 10-30; methyl methacrylate monomer units and acrylic monomer units are polymerized in a random copolymerization manner, wherein the degree of polymerization of methyl methacrylate monomer units is 5-10 and the degree of polymerization of acrylic monomer units is 5-20.

2. The high-solids, low-viscosity magnesium hydroxide concentrate as described in claim 1, characterized in that, The wetting agent is one or more of alkyl ammonium salt wetting agents and acrylic copolymer solution wetting agents.

3. The high-solids, low-viscosity magnesium hydroxide concentrate as described in claim 1, characterized in that, The auxiliary agent is one or a mixture of two of urea and formamide in any proportion.

4. The high-solids, low-viscosity magnesium hydroxide concentrate as described in claim 1, characterized in that, The defoamer is one or more of the following: low alcohol defoamer, mineral oil defoamer, and organosilicon defoamer.

5. The high-solids, low-viscosity magnesium hydroxide concentrate as described in claim 1, characterized in that, The structural formula of the dispersant is as follows: n=10-30。 6. The method for preparing high-solids, low-viscosity magnesium hydroxide concentrated slurry as described in claim 1, characterized in that, The preparation method is as follows: According to the formula, the dispersant, wetting agent, purified water and magnesium hydroxide powder are mixed and stirred at a speed of 300-600 rpm. The stirring speed is kept constant. Then, the auxiliary agent and defoamer are added in sequence and stirred at a speed of 200-300 rpm until they are mixed evenly. The mixture is then transferred to a horizontal sand mill for grinding 1-3 times until the particle size reaches below 800 nm. The mixture is then filtered to obtain the high-solids and low-viscosity magnesium hydroxide concentrated slurry.

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