JPH0469678B2 - - Google Patents

Description

[Detailed description of the invention]

INDUSTRIAL APPLICATION FIELD The present invention relates to a dispersant for coal-water slurry that stably disperses pulverized coal in water at a high concentration. BACKGROUND ART In recent years, efforts have been made to reduce dependence on oil as an energy source due to concerns about oil supplies. To this end, it has become a challenge to develop energy sources other than oil that can be stably supplied, and one of the challenges is to review coal, which has large reserves and is widely available around the world, and how to use it. Various methods are being considered. However, unlike petroleum, coal is a solid, so it is significantly disadvantageous compared to petroleum in terms of transportation, storage, and other handling. Therefore, coal is pulverized, water, methanol,
A method of handling it as a liquid by dispersing it in oil, etc. is being considered. However, a mixture of coal powder dispersed in oil (Coal-Oil-Mixture)
Also, a mixture of coal powder dispersed in methyl alcohol (Methanol-Coal-Mixture) cannot be said to be completely petroleum-free, but a mixture of coal powder dispersed in water, that is, a coal-water slurry (Coal-Water slurry).
-Mixture) is seen as promising. When coal powder is made into a slurry with water, the slurry can be transported, stored, and used as a liquid fuel, making it easier to operate and control the fuel system, simplifying coal lifting and storage, and saving land. Furthermore, as a safe fuel, there is no need to take measures to prevent ignition and dust.
However, since coal is diluted with water, it is unavoidable that the calorific value as a fuel will decrease and transportation costs will increase, so it is preferable to increase the slurry concentration as much as possible to approach close packing. However, when attempting to increase the coal concentration in the water slurry, the slurry rapidly thickens and loses fluidity. Therefore, when dispersing coal in water, for example, naphthalene sulfonic acid formalin condensate, lignin sulfonate, polyoxyethylene alkyl phenyl ether, polyacrylate, etc.
Attempts have been made to prepare coal-water slurries with excellent fluidity using dispersants such as polyoxyethylene alkyl ether sulfates and copolymer salts of acrylic acid and vinyl monomers. However, these known dispersants are still unsatisfactory in terms of fluidity and storage stability, and are not necessarily suitable particularly as dispersants for high-concentration coal-water slurries. Problems to be Solved by the Invention The purpose of the present invention is to provide coal that has fluidity even at high concentrations and that does not cause concentration unevenness even when left.
An object of the present invention is to provide a dispersant useful for easily producing an aqueous slurry. Means for Solving the Problems According to the present invention, the above object is achieved by forming a structure mainly consisting of a structural unit [ ] based on α-olefin and a structural unit [ ] based on maleic anhydride, and having the general formula

[Formula] (However, in the general formula, R represents a hydrocarbon group having 8 to 30 carbon atoms, and n represents an integer of 0 or 1). ] Coal characterized by containing as an active ingredient an alkali metal salt, alkaline earth metal salt or ammonium salt of a modified α-olefin-maleic anhydride copolymer in a molar ratio of 0.005 to 0.2. This is achieved with a dispersant for water slurry. The alkali metal salt, alkaline earth metal salt or ammonium salt (hereinafter referred to as the base of the modified copolymer) of the modified α-olefin-maleic anhydride copolymer (hereinafter sometimes simply referred to as the modified copolymer) ) is the general formula (However, in the general formula, R represents a hydrocarbon group having 8 to 30 carbon atoms, and n represents an integer of 0 or 1.) Polymerize in a solvent to prepare a modified α-olefin-maleic anhydride copolymer containing a small amount of structural units based on the acrylic acid ester monomer in the main chain, and then react the copolymer with a basic compound. It is a hydrophilic, preferably water-soluble, linear polymer obtained by In the above, α-olefin means a linear or branched olefin having a carbon-carbon unsaturated double bond at the α position. Examples of the α-olefin include ethylene, propylene, butene-
1, butene-2, isobutylene, isoprene, pentene-1, pentene-2,2-methyl-1-butene, 2-methyl-2-butene, hexene-1,
2-Methyl-1-pentene, 3-methyl-1-pentene, 4-methyl-1-pentene, 2-ethyl-1-butene, 1,3-pentadiene, 1,4-
hexadiene, 2,3-dimethyl-2-butene,
Diisobutylene etc. having 2 to 12 carbon atoms, preferably 2 to 12 carbon atoms
8 olefins and mixtures thereof are used. Among these, preferred are olefins having 4 carbon atoms and mixtures thereof (eg, return B/B), particularly isobutylene. These α-olefins may be used alone or in combination of two or more. The maleic anhydride may also contain maleic anhydride derivatives such as maleic acid, maleic acid monoalkyl ester, maleic acid dialkyl ester, chloromaleic acid, or citraconic acid. Furthermore, in order to produce the modified α-olefin-maleic anhydride copolymer, an acrylic ester or methacrylic ester represented by the general formula [] is used as the third component. In the general formula, R
represents a hydrocarbon group having 8 to 30 carbon atoms, examples of which include n-octyl, n-nonyl, n-dotecyl, n-hexadecyl, n-octadecyl, n-
Straight chain alkyl groups such as eicosyl and n-docosyl,
Branched alkyl groups such as 2-ethylhexyl and t-dotecyl are mentioned. Among these, linear alkyl groups having 8 to 30 carbon atoms, preferably 10 to 27 carbon atoms, and more preferably 12 to 25 carbon atoms are preferred. Examples of compounds represented by the general formula [] include n-octyl methacrylate, n-dotecyl methacrylate, and t-methacrylate.
-dotecyl, n-hexadecyl methacrylate, n-docosyl methacrylate, 2-ethylhexyl acrylate, and the like. The modified α-olefin-maleic anhydride copolymer used in the form of a basic salt in the present invention is prepared by preparing α-olefin in an organic solvent in the coexistence of an acrylate monomer represented by the general formula [ ]. It can be obtained by radical copolymerization of maleic anhydride and maleic anhydride. In such copolymerization, it is preferable to use a common radical polymerization catalyst, examples of which include:
Examples include azobis compounds such as azobisisobutyronitrile and azobis-1-cyclohexane-1-carbonitrile, and peroxides such as cumene hydroperoxide, dicumyl peroxide, t-butyl hydroperoxide, benzoyl oxide, and perloyl peroxide. It will be done. Examples of organic solvents used during polymerization include ketones such as acetone and methyl ethyl ketone, esters such as methyl acetate, ethyl acetate, and methyl propionate, ethers such as tetrahydrofuran and dioxane, benzene, xylene, toluene, ethylbenzene, n- Examples include alkylbenzenes such as butylbenzene, t-butylbenzene, isopropylbenzene, and p-cymene. Among them, carbon number is 8~
Using 10 alkylbenzenes, especially ethylbenzene, isopropylbenzene, p-cymene,
There are advantages such as a high yield of the copolymer and a molecular weight of the obtained copolymer falling within a preferable range as described below. Addition of polymerization solvent, monomer and polymerization catalyst is
It may be carried out all at once at the beginning of the polymerization, or it may be carried out sequentially. The polymerization temperature may normally be within the range of 0 to 160°C, but
For example, as mentioned above, the polymerization solvent has 8 to 8 carbon atoms.
When using 10 alkylbenzenes, 60~
It is desirable to set the temperature at 150°C, preferably within the range of 80 to 130°C. The polymerization time can be selected as appropriate. Note that a chain transfer agent such as mercaptan may be used to adjust the degree of polymerization of the above copolymer. The α-olefin-maleic anhydride copolymer containing an acrylic ester or methacrylic ester as a third component obtained in this way can be converted into a water-soluble copolymer basic salt by reacting with a basic compound. It is said that The basic compounds are alkali metal compounds, alkaline earth metal salts, ammonia or amines, examples of which include hydroxides, carbonates or organic acid salts of alkali metals and alkaline earth metals, ammonia, amines, etc. used. Preferably used include sodium hydroxide, potassium hydroxide, lithium hydroxide, magnesium hydroxide, calcium hydroxide, sodium carbonate, calcium carbonate, potassium acetate,
Examples include alkali metal compounds or alkaline earth metal compounds such as sodium acetate, or ammonia. The reaction between the modified α-olefin-maleic anhydride copolymer and the basic compound is usually carried out in a solvent, preferably water, at normal pressure, normal temperature, or under heating. The amount of the basic compound used varies depending on the type of basic compound and reaction conditions, but is usually 0.6 to 2 times the molar amount based on the acid anhydride group of the maleic anhydride residue present in the copolymer. , or a surplus amount. As a result, the α-olefin-
The acid anhydride groups in the maleic anhydride copolymer became carboxyl groups, and the carboxyl groups at a ratio of 0.3 to 1.0 to 1 to the total amount of carboxyl groups (hereinafter simply referred to as the degree of neutralization) became salts. A water-soluble copolymer salt is obtained. If the degree of neutralization is too small, a sufficient dispersion effect will not be achieved when used as a dispersant for coal-water slurry. The smaller the coal particles in the coal-water slurry, the better the dispersion stability, but the smaller the coal particles, the higher the pulverization cost. The amount of pulverized coal currently burned in thermal power plants is 200
Since the particle size is 80% of the mesh pass, or about 74 microns, this particle size serves as a guideline for the coal particle size for coal-water slurry. The method of adding the dispersant of the present invention to a coal-water slurry is, for example, in dry pulverization of coal, a method in which a dispersant is added and mixed in advance into water in which coal powder is to be dispersed, and then coal powder is added thereto and mixed; In the pulverization method, a dispersant may be added in advance to the water used for wet pulverization, or may be added and mixed during or after pulverization. The amount of the dispersant of the present invention added to the coal-water slurry varies depending on the type and particle size of the coal, but is preferably 0.01 to 5% by weight based on the coal in the slurry.
By adding 0.05 to 2.0% by weight, an excellent dispersion effect is exhibited. Generally, the fluidity limit of a coal-water slurry is around 50% by weight unless a dispersant is added, but if the dispersant of the present invention is added, it has a large viscosity reducing effect, so when the coal concentration is 70% or more. too,
The slurry has fluidity and can be pumped, and also has excellent stability. The dispersant of the present invention can also be used in combination with surfactants and protective colloids, such as polyoxycetylene alkyl phenyl ether, polyacrylates, polyphosphates, carboxymethyl cellulose, and polyvinyl alcohol. By using the dispersant of the present invention, 70% by weight
It has a low viscosity of 400 to 5000 centipoise at high concentrations, less than 2000 centipoise in preferred cases,
A coal-water slurry can be obtained which has excellent dynamic viscosity characteristics (thixotropy) and fluidity, and which hardly causes concentration unevenness even after being left for a long period of time.
This is because the basic salt of the modified α-olefin-maleic anhydride copolymer used as a dispersant has a group that has an affinity for coal and a group that has an affinity for water. Since they are conveniently arranged in terms of dispersion ability, they exhibit excellent surface activity against coal, and the modified α-olefin-maleic anhydride copolymer or its basic salt itself is rigid. This is expected to be because it exhibits thixotropic properties. EXAMPLES The present invention will be specifically explained below with reference to Examples, but the present invention is not limited thereto in any way. Example 1 Put 326.0 g of ethylbenzene (polymerization solvent) into a No. 1 autoclave equipped with a stirrer, and after purging with nitrogen, add 30.9 g of isobutylene, keep the autoclave internal temperature (polymerization temperature) at 105°C, and add 150 g of methyl isopropyl ketone. Maleic anhydride 46.5g
(isobutylene/maleic anhydride molar ratio 1.1),
10.1 g of n-docosyl methacrylate and 2.05 g of azobisisobutyronitrile (polymerization catalyst) (amount equivalent to 0.025 mol per 1 mol of maleic anhydride)
The sequentially charged solution obtained by dissolving was polymerized over 4 hours while sequentially charging the solution. Thereafter, the polymerization was continued for another hour, and the precipitated polymer was taken out and overdried to prepare a polymer powder. The polymerization rate was 98.5%. The powder has a weight average molecular weight of
9800, containing an average of 3.3 units based on n-docosyl methacrylate per molecule.
It was a maleic anhydride copolymer. 10 parts by weight of the powder was added to an aqueous solution consisting of 5.09 parts by weight of aqueous ammonia with an ammonia concentration of 26.5% by weight and 120 parts by weight of water to prepare an aqueous solution of the ammonium salt of the copolymer. The degree of neutralization of the sodium salt was 0.7, and the concentration of the aqueous solution was 9.65% by weight. Finely ground coal shown in Table 1 was added to an aqueous solution containing the above copolymer at a concentration of 0.5% by weight based on coal at room temperature with stirring, and the coal concentration was adjusted.
Make it 70% by weight and use a high speed stirrer after adding the entire amount.
A coal-water slurry was prepared by stirring at 9000 rpm for 3 minutes.

[Table] This slurry was measured using a BL type viscometer at 25℃.
The slurry viscosity was measured using rotor No. 3 and its fluidity was observed. Furthermore, this slurry was placed in a sample tube with a diameter of 58 mm and a height of 115 mm at 200 c.c.
The slurry was then taken out and examined to see if there was a compacted area at the bottom of the sample tube. As a result, as shown in Table 3, a slurry with good fluidity and good storage stability was obtained. Example 2 10 parts by weight of the copolymer powder prepared in Example 1 and 3.64 parts by weight of sodium hydroxide were added to 120 parts by weight of distilled water, and as in Example 1, the degree of neutralization was 0.7 and the aqueous solution concentration was 10.40 parts by weight. % of the dispersant for coal-water slurry of the present invention was prepared. Next, a coal-water slurry was prepared in the same manner as in Example 1 except for using the above dispersant. The fluidity and stability of the slurry were examined and the results are shown in Table 3. As in Example 1, a slurry with good fluidity and stability was obtained. Examples 3 to 4 Methacrylic acid ester was prepared in the same manner as in Example 1, except that the polymerization temperature was the temperature shown in Table 2, and the sequentially charged solutions were the solutions shown in Table 2. A powder was prepared by copolymerizing isobutylene as a third component and maleic anhydride. The powder had the weight average molecular weight shown in Table 3 and was a copolymer containing the methacrylic acid ester shown in Table 3 as a third component. The copolymers were reacted with ammonia in the amounts shown in Table 2 to prepare aqueous solutions of the copolymers. Next, a coal-water slurry was prepared in the same manner as in Example 1 using the obtained copolymer aqueous solution. The fluidity and stability of the prepared coal-water slurry were investigated. The results are shown in Table 3. Comparative Example 1 Isobutylene-maleic anhydride alternating copolymer was produced in the same manner as Examples 3 and 4 except that methacrylic acid ester was not used, the polymerization temperature was 105°C, and the amount of polymerization catalyst was 2.05 g. A polymer was produced. One end of the molecule of the copolymer had an ethylbenzene residue. After dissolving this copolymer under the dissolution conditions shown in Table 2, the coal-water-
A slurry was prepared. The fluidity and stability of the slurry were examined. The results are shown in Table 3. Comparative Examples 2 to 4 Three types of commercially available dispersants were used as dispersants, namely naphthalene sulfonic acid polymarin condensate sodium salt, polyoxyethylene (oxyethylene group 10
A coal-water slurry was prepared in the same manner as in Example 1 using nonyl phenyl ether and its sodium sulfate. The properties of the slurry are shown in Table 3. The slurry to which the naphthalene sulfonic acid formalin condensate sodium salt was added showed slight fluidity, but the slurries to which the other two types were added had no fluidity.

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[Table] Effects of the invention By using the dispersant for coal-water slurry of the present invention, it has a high concentration and a low viscosity that allows it to be operated as a liquid fuel, and even if left for a long period of time, uneven concentration will occur. A stable coal-water slurry is obtained.

Claims (1)

[Claims] 1 Mainly composed of a structural unit [I] based on α-olefin and a structural unit [] based on maleic anhydride, and in the main chain contains the general formula [formula] (wherein R is a carbon 8 to 30 hydrocarbon groups, n is an integer of 0 or 1) in a molar ratio of 0.005 to 0.2 with respect to the maleic anhydride-based structural unit []. A dispersant for coal-water slurry, which contains as an active ingredient an alkali metal salt, alkaline earth metal salt, or ammonium salt of a modified α-olefin-maleic anhydride copolymer. 2. The dispersant for coal-water slurry according to claim 1, wherein the modified α-olefin-maleic anhydride copolymer has a weight average molecular weight of 1,000 to 20,000. 3. The dispersant for coal-water slurry according to claim 1 or 2, wherein the α-olefin is isobutylene.