JPH0469677B2 - - Google Patents

Description

[Detailed description of the invention]

A. Industrial Application Field The present invention relates to a dispersion stabilizer for a water slurry system of fine coal powder. In recent years, due to concerns about crude oil supply, efforts have been made to reduce dependence on crude oil as an energy source, and one of these efforts is to reconsider coal, which has large reserves and is widely available around the world, and various ways of using it 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. As a method to improve this problem, it has been proposed to handle coal in the form of a slurry.
Coal-Mixture) and slurry made by dispersing coal powder in water (Coal-Water-Mixture) have been developed, but among these, coal-water slurry is the most effective in terms of complete oil-free use and safety. It is seen as promising. B. Conventional technology By slurrying coal powder with water, the slurry can be transported, stored, and burned as a liquid fuel, making it easier to operate and control the combustion system, and making it a stable fuel that requires no measures against ignition or dust. However, because the coal is diluted with water, the calorific value as a fuel decreases and transportation costs inevitably increase, and the slurry must be as concentrated as possible. is required. Various attempts have been made to increase the coal concentration and maintain fluidity in water slurry by adjusting the particle size distribution of coal powder and using appropriate dispersion stabilizers. Examples of dispersion stabilizers include formalin condensates of naphthalene sulfonates, lignin sulfonates, polyoxyethylene alkyl phenyl ethers, polyacrylates, polyoxyethylene alkyl ether sulfates, and copolymers of acrylic acid and vinyl monomers. Dispersion stabilizers such as salts are used, but at least 70%
Shows sufficient fluidity even at high concentrations by weight%,
Moreover, from the viewpoint of a coal-water slurry with excellent storage stability, it has not always been possible to obtain a satisfactory coal-water slurry. C. Problems to be Solved by the Invention As described above, the present invention provides a dispersion stabilizer capable of providing a coal-water slurry with excellent fluidity and storage stability at a high concentration, that is, at least 70% by weight or more of coal concentration. It is something. D. Means for Solving the Problems As a result of intensive study by the present inventors on a coal-water slurry with high concentration and excellent fluidity and storage stability, the general formula P ¹ (-S-P ² ) _o [n A dispersion stabilizer for coal-water slurry systems, characterized in that it contains a block copolymer represented by 1 or 2 as an active ingredient. [However, P ¹ represents a hydrophobic polymer, and P ² represents an acrylic polymer. A polymer consisting of acid or methacrylic acid, or its alkali metal salt, alkaline earth metal salt, or ammonium salt, and has a degree of polymerization of 10 or more and 3,500 or less. ] The present invention has been completed by discovering that the above object can be achieved by using the following. The block copolymer represented by the general formula P ¹ (-S-P ² ) _o [n is 1 or 2] used in the present invention is a hydrophobic polymer P ¹ and acrylic acid or methacrylic acid, or both. It is a block copolymer consisting of a polymer ^P2 having a polymerization degree of 10 or more and 3500 or less. Here, the hydrophobic polymer P ¹ means a polymer that is insoluble in water, and examples of P ¹ include polystyrene, polymethyl methacrylate, polybutene, polyvinyl acetate, polyvinyl chloride, and polyversatate vinyl. Examples include water-insoluble vinyl polymers and vinyl copolymers such as exemplified by water-insoluble vinyl polymers and vinyl copolymers, water-insoluble polyoxyalkylenes such as polyoxypropylene and polyoxytetramethylene, and polymers such as polyamide and polyester. . Particularly preferred are polystyrene, polymethyl methacrylate, polyoxypropylene, polyoxytetramethylene or vinyl polyversatate. The degree of polymerization of P ¹ is 2 or more and 500 or less, preferably 2 or more and 200 or less, and more preferably 2 or more and 100 or less. P ² represents a polymer consisting of acrylic acid or methacrylic acid, or its alkali metal salt, alkaline earth metal salt, or ammonium salt, but it also includes cases where P ² consists of two or more of these constituent units. It will be done. Furthermore, the general formula P ¹ (-S-P ² ) _o [n
As long as the polymer represented by 1 or 2 is water-soluble or water-dispersible, there is no problem with P ² containing other structural units than those mentioned above. However, if the amount of other constituent units is too large,
Since the hydrophilicity of P ² becomes low and it becomes impossible to obtain the desired dispersion stability, or it becomes difficult to obtain the desired degree of polymerization of P ² , the content of other structural units is preferably 50%. It is less than mol %, more preferably 20 mol % or less. Examples of these structural units include acids such as maleic acid, fumaric acid, crotonic acid, and itaconic acid, and their salts, acid anhydrides such as maleic anhydride, methyl (meth)acrylate, and (meth)acrylic acid. Examples include (meth)acrylic acid esters such as ethyl, (meth)acrylamide and its derivatives, α-olefins such as ethylene, propylene, and isobutene, styrene, acrylonitrile, vinylpyrrolidone, vinyl chloride, and vinyl fluoride. In addition, the degree of polymerization of ^P2 is 10 to 3500, preferably 10
~500. The block copolymer represented by the general formula P ¹ (-S-P ² ) _o of the present invention has a wide range of water solubility from water-solubility to water-dispersibility. Of course, water-dispersible ones can also be suitably used in the present invention. General formula of the present invention P ¹ (-S-P ² ) _o [n is 1 or 2]
The effect of the block copolymer represented by P1 ^{and P2} as a dispersion stabilizer for coal-water slurry systems varies depending on the chemical composition, molecular weight, etc. of the polymers ^P1 and ^P2 that make up the block copolymer. The unit number ratio (polymerization degree ratio) of the vinyl monomers constituting P ₁ and P ₂ is preferably 0.001≦P ¹ /P ² ≦2, more preferably 0.001≦P ¹ /P ² ≦1. Particularly effective are those that have it. There are no particular restrictions on the method for producing the block copolymer of the present invention, but monomers mainly composed of acrylic acid and methacrylic acid are polymerized in the presence of a hydrophobic polymer having a thiol group at the end. Most preferred is a method in which the polymer is dissolved in water or an aqueous alkaline solution. The amount of the dispersion stabilizer of the present invention added to the coal-water slurry system varies depending on the type of coal, particle size (distribution), etc., but is 0.01 to 5.0% by weight based on the coal in the slurry.
Preferably it is 0.05 to 2.0% by weight. If the amount is less than 0.01% by weight, the dispersion itself will be insufficient, while if it is added more than 5.0% by weight, no increase in effectiveness will be observed, and rather aggregation and sedimentation will tend to occur. There are no particular restrictions on the method of adding the dispersion stabilizer to the coal-water slurry system; for example, in the case of dry-pulverized coal, the dispersant is added and mixed in advance into water in which the coal powder is to be dispersed, and then the coal powder is added thereto. When the mixing method is wet pulverization, it can be added at the time of pulverization, or during or after pulverization. The dispersion stabilizer of the present invention is not particularly limited by the type of coal, and may be any subbituminous coal, bituminous coal, anthracite coal, etc. Also, the particle size (distribution) of coal powder certainly affects the viscosity and stability of the slurry, but 200 mesh pass is at least 50% by weight, preferably 70% by weight.
If the above conditions are met, the prepared coal-water slurry can be used without causing any trouble during pipeline transportation, burner combustion, etc. It goes without saying that the dispersion stabilizer of the present invention may be used in combination with other surfactants, wetting agents, and polymers that act as protective colloids, such as ordinary polyvinyl alcohol polymers and cellulose derivatives such as carboxymethyl cellulose. E Action and Effect of the Invention General formula of the present invention P ¹ (-S-P ² ) _o [n is 1 or 2]
Although the mechanism by which the dispersion stabilizer containing the block copolymer represented by P as an active ingredient acts extremely effectively is not clear, the block copolymer exhibits surface activity and the hydrophobic polymer ^P1 portion This seems to be due to the increased adsorption power to the powder surface. EXAMPLES The present invention will be specifically explained below with reference to Examples, but the present invention is not limited thereto. In the following, "parts" and "%" mean "parts by weight" and "% by weight" unless otherwise specified. (A) Synthesis example of a polymer having a thiol group at the end 300 parts of methyl methacrylate was charged into a polymerization vessel, heated to 80°C under a nitrogen atmosphere, and then 40 parts of thioacetic acid and 0.3 parts of azobisisobutyronitrile were added. was added and polymerization was carried out for 6 hours. After cooling to room temperature, the polymerization solution was poured into n-hexane to obtain polymethyl methacrylate, which was purified by reprecipitation once in an acetone-n-hexane system and twice in an acetone-water system, and thioacetic acid was added to the end. Polymethyl methacrylate having ester groups was obtained. Next, 180 parts of polymethyl methacrylate having a thioacetate group at the end was mixed with 250 parts of methanol and 100 parts of acetone.
Dissolved in a mixed solvent of 10% at 40℃ under nitrogen flow
10 parts of a methanol solution of NaOH was added and stirred for 2 hours. Next, it was poured into 5,000 parts of distilled water containing 30 parts of 1N sulfuric acid to obtain polymethyl methacrylate having a thiol group at the end. This polymer was determined by iodometric titration to contain 4.55×10 ⁻⁴ eq/g of thiol groups at the ends. (B) Synthesis example of block copolymer 700 parts of acrylic acid and 700 parts of tetrahydrofuran were placed in a polymerization vessel, heated to 60°C under a nitrogen atmosphere, and then polymethyl methacrylate (PMMA) 213 having a thiol group at the end was added. 1.4 parts of azobisisobrothyronitrile were added to initiate polymerization. The polymerization was stopped by cooling after 6 hours.
The polymerization rate of acrylic acid at this time was 98%.
After drying this solution, it was pulverized to obtain a powder. In addition, a portion of this solution was poured into a large amount of toluene to obtain a polymer, which was thoroughly washed with toluene, and after drying, ^{the 1} H-NMR spectrum was measured.
The number average degree of polymerization of the polyacrylic acid portion of the block copolymer was found to be 100 from the signal intensity ratio of methine protons derived from acrylic acid and protons of methoxy groups derived from PMMA. Add and dissolve 1091 parts of water and 43 parts of sodium hydroxide to 100 parts of the polymer powder, and dissolve 10 parts of the block copolymer of PMMA and sodium polyacrylate.
% aqueous solution was obtained. This is used as a 10% aqueous solution of polymer [A]. Block copolymer [B] ~
An aqueous solution of [F] was prepared. Details are shown in Table 1. Examples 1 to 6 and Comparative Examples 1 to 5 (C) Coal-water slurry preparation method and evaluation method Pre-dried Australian coal was dry-pulverized in a ball mill, and 200 mesh pass was 80% by weight.
of coal powder was obtained. Dilute the 10% aqueous solution of the polymer to make an aqueous solution containing a predetermined amount of dispersion stabilizer, mix this with a predetermined amount of coal powder to give a coal concentration of 70%, and mix with a homomixer at 5000 rpm.
The mixture was stirred for 10 minutes to prepare a coal-water slurry. The viscosity of the obtained slurry was measured at 25°C using a BL type viscometer to evaluate the fluidity. Also,
The slurry was allowed to stand at room temperature for one month, and the state of the upper and lower parts was observed to evaluate the storage stability of the slurry. The results are shown in Table 2. From Table 2, coal using the dispersion stabilizer of the present invention -
The water slurry system has low viscosity and excellent fluidity.
It is also clear that it has excellent storage stability.

[Table] *2: Degree of neutralization represents the molar ratio of the basic substance used to the carboxyl groups in the polymer.

【table】

Claims (1)

[Claims] 1. A coal-water slurry system characterized by containing a block copolymer represented by the general formula P ¹ (-S/P ² ) _o [n is 1 or 2] as an active ingredient. dispersion stabilizer. [However, P ¹ represents a hydrophobic polymer, and P ² represents a polymer consisting of acrylic acid or methacrylic acid, or its alkali metal salt, alkaline earth metal salt, or ammonium salt, with a degree of polymerization of 10 or more.
Represents a polymer of 3500 or less. ] 2. The coal-water slurry according to claim 1, wherein P ¹ is at least one selected from polystyrene, polymethyl methacrylate, polyoxypropylene, polyoxytetramethylene, or vinyl polyversatate. Dispersion stabilizer for systems. 3. The dispersion stabilizer for a coal-water slurry system according to claim 1, wherein the degree of polymerization of ^P1 is 2 or more and 500 or less. 4. The dispersion stabilizer for a coal-water slurry system according to claim 1, wherein the degree of polymerization of ^P2 is 10 or more and 500 or less.