JPH0113517B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a thinner for coal-water slurries.
More particularly, it relates to a thinning agent for dispersing pulverized coal in water to provide a highly concentrated coal-water slurry that can be pumped. In recent years, due to the depletion of petroleum resources, the use of coal has been reconsidered, and various methods of its use are being considered. However, unlike oil, coal is a solid and cannot be transported by pump. For this reason, various methods are being considered for pulverizing coal and dispersing it in water to form a water slurry. However, with current technology, this method
As the coal concentration increases, it becomes significantly thicker and loses its fluidity, making pumping difficult.
On the other hand, lowering the coal concentration reduces transportation efficiency and requires a dehydration process before combustion, which is not practical as it increases costs. JP-A No. 54-33803 describes adding a polymeric surfactant to a fine ore slurry, but it only specifically exemplifies polyacrylamide and polyethyleneimine, and It is intended for fine ore slurry. The present inventors have conducted intensive research on a thinning agent for coal-water slurry that can fluidize highly concentrated coal-water slurry and enable pumping.
A thinning agent has been successfully developed that significantly reduces the viscosity of a coal-water slurry and thus provides a coal-water slurry that is pumpable even at high coal concentrations. By using the thinner of the present invention, coal can be fluidized with a small amount of water, which not only makes it possible to transport it by pump, but also allows it to be burned in a boiler as it is.
The dehydration step before combustion can also be omitted. By using the thinning agent of the present invention, handling of coal becomes extremely simple, and its applications are greatly expanded. The coal used in the coal-water slurry is anthracite;
Any coal may be used, such as bituminous coal, sub-bituminous coal, brown coal, or cleaned versions thereof. Furthermore, the particle size of the coal in the water slurry may be any particle size as long as it is powder, but since the pulverized coal currently burned in thermal power plants is 70% or more of 200 mesh pass, this particle size is suitable for pulverized coal. This is a guideline for the particle size of However, the thinner of the present invention is not affected by particle size and exhibits excellent effects on coal powder of any particle size. In addition, the cleaned coal contains more inorganic substances than in the coal.
For example, ash and sulfur have been removed. Methods for cleaning coal include, for example, heavy liquid separation method, oil agglomeration method (hereinafter referred to as OA method), and coal flotation method. However, methods other than these may also be used and are not particularly limited. Regarding the OA method, coal is pulverized dry or wet, then a water slurry is prepared, and an appropriate amount of oil is added, or coal is coated with oil in advance, a water slurry is prepared, and the water slurry is stirred. Utilizing the difference in wettability of the organic and inorganic components of coal to oil and water, the organic components of coal are coagulated using oil that selectively wets the organic components of coal as a binder. On the other hand, since inorganic substances have a weak affinity with oil and float in water, this method can remove inorganic substances at the same time by separating the water from coagulated coal. The coal concentration in the coal-water slurry of the OA method is usually 10-65%. The oil used in the OA method is generally crude oil or various fractions obtained from crude oil, such as kerosene, light oil, A heavy oil, B heavy oil, C heavy oil, etc., tar or shale oil, ethylene cracked residual oil, or various blended oils. The oils used are mineral oils such as lubricating oils and cleaning oils. Water-insoluble oils such as benzene, toluene, xylene, and animal and vegetable oils may also be used, but heavy oils such as C heavy oil and tar residue oil are particularly preferred because they are inexpensive. This oil is generally sufficient in an amount of 20% or less of the coal in the coal-water slurry to be treated for mineral removal. The flotation coal washing method is an existing coal washing method in which a very small amount of oil is added to a pulverized coal-water slurry and stirred to create froth. This method also
Similar to the OA method, the organic components of the coal adhere to the froth oil film, but the inorganic components float in the water and can be separated from the organic components of the coal. The oils used in the flotation method are turpine oil, tar, A heavy oil, C heavy oil, light oil, and kerosene. Generally, several tens of percent or more of inorganic substances are removed from coal by the above method. If coal cleaned in this way is used, the effect of the additive of the present invention is significantly superior to coal that has not been cleaned, and a coal-water slurry with several points higher concentration can be obtained. Furthermore, when cleaned coal is used, in addition to this effect, boiler corrosion during combustion is suppressed, and the burden on ash removal equipment and desulfurization equipment is reduced, among other great benefits. The thinner for coal-water slurries of the present invention contains as an essential component carboxymethyl cellulose or a salt thereof, which has a viscosity of 2% aqueous solution at 25° C. of 10,000 cp or less, preferably 2,000 cp or less. Carboxymethylcellulose is represented by the general structural formula below, taking as an example a typical case with a degree of etherification of 1.0. In the formula, M is hydrogen or a salt-forming cation, n
means the degree of polymerization. The degree of etherification of carboxymethylcellulose or its salt used in the present invention is in the range of 0.3 to 3.0,
Any material may be used as long as it is water-soluble or water-dispersible. Examples of salts that can be used include alkali metal salts such as sodium and potassium salts, ammonium salts, amine salts, and salts in which a portion of these salts is substituted with an alkaline earth metal such as calcium. As is well known, carboxymethyl cellulose and its salts can be produced by a water-based method using only water as a reaction medium, a solvent method using an organic solvent and water, or a method in which pulp is mixed with sodium hydroxide and monochloroacetic acid or its alkali salt. It can be obtained by etherification. The thinning agent of the present invention is effective only with carboxymethyl cellulose or its salts whose viscosity in a 2% aqueous solution is 10,000 cp or less, preferably 2,000 cp or less at 25°C, and in order to obtain a product having these viscosities, suitable raw materials are required. In addition to selecting the pulp, viscosity can be easily adjusted by oxidative decomposition using peroxides, hypohalites, periodates, nitrogen dioxide, other oxidizing agents, and ultraviolet rays, or by enzymatic decomposition during or after the manufacturing process. can do. It is thought that coal particles are adsorbed on the surface of coal particles with their charged carboxyl groups facing the water side, and the coal particles are dispersed due to the repulsion of the charges, improving fluidity and causing a significant decrease in viscosity. Carboxymethyl cellulose is a polymer electrolyte with many dissociative groups along its chain, and because it dissociates in aqueous solution to produce polymer ions, its physical properties strongly affect the average degree of polymerization, that is, the viscosity of the aqueous solution. receive. Only 2% aqueous solutions with a viscosity of 10,000 cp or less, preferably 2,000 cp or less at 25°C are effective; if it exceeds 10,000 cp, flocculation occurs and the viscosity of the slurry increases significantly, making it difficult to obtain a fluid slurry. Can not. Such a thinner of the present invention is used in an amount of 0.01 to 5.0% by weight, preferably 0.03 to 2.0% by weight of carboxymethylcellulose or its salt based on the coal-water slurry.
Excellent effects can be achieved by adding % by weight. The fluidity limit of a coal-water slurry differs depending on the type and particle size of the coal, but generally, if a thinner is not added, fluidity will be lost at a coal concentration of around 50%, but with the thinner of the present invention, When added, the viscosity decreases significantly, so it has fluidity even when the coal concentration is 61% or more, especially 70% or more. If cleaner coal is used, the coal concentration will increase by several points, typically 3 to 10 points. The thinner of the present invention can also be used in combination with other surfactants. Regarding the method of producing a coal-water slurry and the method of adding a thinner, there are two methods: dry-pulverizing coal in advance and then mixing it into an aqueous solution of a thinner;
There are methods that add a thinner after making a water slurry, methods that add coal, water, and a thinner to a mill, and mix while grinding the coal. Any method can be used, such as a method of mixing using coal. The thinner of the present invention has an excellent effect of stably dispersing coal in water, and does not cause water separation even when left standing for a long period of time, for example, one month, and maintains a homogeneous coal-water slurry. There is. Thus, the thinner of the present invention can be used in an amount of 0.01 to 5.0% by weight, preferably 0.03 to 5.0% by weight, based on the coal-water slurry.
By adding only 2.0% by weight, the viscosity of the coal-water slurry can be significantly reduced and a highly concentrated coal-water slurry can be produced that can be pumped. Examples are shown below. In the examples, percentages are by weight. Example 1 Coal pulverized to 80% pass of 200 mesh is added to an aqueous solution containing a predetermined amount of a thinning agent while stirring at room temperature to prepare a coal-water slurry of a predetermined concentration. The viscosity of this slurry was measured at 25℃,
Also observe fluidity. Add this slurry to 1
After allowing it to stand for several months, measure the state of water separation. The test results are shown in Table 1. As shown in Table 1, when the thinner of the present invention is added, the viscosity of coal is 72 to 77.
%, the viscosity is 1000 to 3000 cp, and the fluidity is extremely good. To this, general anionic surfactants or CMC other than the present invention may be added,
If no thinner is added, the viscosity will be over 20,000 cp at a coal concentration of 50%, and it will not flow at all.

【table】

[Table] Example 2 A coal-water slurry of a predetermined concentration is prepared in the same manner as in Example 1 using cleaned coal. The coal particle size is 80% pass of 200 mesh. The viscosity of this slurry is measured at 25°C and the fluidity is also observed. After this slurry was allowed to stand for one month, the state of water separation was measured. The test results are shown in Table 2. As shown in Table 2, when the thinner of the present invention is added to a coal-water slurry, the viscosity is 1000 to 3000 cp even at a coal concentration of 76 to 80%, resulting in extremely good fluidity. On the other hand, adding a thinner other than the present invention,
If no thinner is added, the viscosity will be over 20,000 cp at a coal concentration of 80%, and there will be no flow at all.

【table】

【table】

Claims (1)

[Claims] 1. In order to reduce the viscosity of the coal-water slurry and improve its fluidity, carboxymethyl cellulose or its salt, whose viscosity in a 2% aqueous solution is 10,000 cp or less, preferably 2,000 cp or less at 25°C, is an essential component. A thinning agent for coal-water slurry, characterized in that it is added as a thinner. 2. The thinning agent for coal-water slurry according to claim 1, for use in a coal-water slurry having a coal concentration of 61% or higher, preferably higher than 70%. 3. The thinner for coal-water slurry according to claim 1 or 2, wherein the coal is cleaned coal.