JPH0154399B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Application Field] The present invention is to efficiently granulate the coal particles in the coal/water slurry into pellets after adjusting the pH of the coal/water slurry to produce granulated coal with improved properties. This invention relates to a method for granulating coal to be recovered. [Conventional technology] In recent years, due to the instability of oil supply, the development of technology to effectively utilize coal has been progressing. In order to reduce the cost of transporting coal, it is effective to transport coal as a slurry, and therefore there is a current demand for the development of a method for efficiently recovering coal particles transported as a slurry. Conventionally, a method of transporting slurry of coal directly from a coal-producing area has been carried out in the United States and the Soviet Union, and has been reported in the literature. Furthermore, in a conventional method, JP-A-53-70076 discloses a method in which fine coal powder is agglomerated from a coal slurry and, if ash is present, the ash is removed at the same time. A method is described in which an aqueous emulsion is added, the mixture is stirred, and the agglomerates formed are removed. Furthermore, JP-A No. 56-67395 states, ``Belmont coal is dispersed in water at room temperature and stirred to obtain a coal-water slurry, a predetermined amount of granulating agent is added to this mixture, and further carbon Add heavy oil and granulate it.
The technology is described in Japanese Patent Application Laid-open No. 159292/1982, which states, ``Pleasol coal is dispersed in water at room temperature and stirred to obtain a coal-water slurry, and this mixture is granulated in a predetermined amount. A technology is described in which a curing agent is added, further C heavy oil is added, and the mixture is granulated. [Problems to be Solved by the Invention] In the conventional method described above, separation of coal particles and water after slurry transport is performed using a centrifugal separator, and although it consumes a large amount of energy, it is difficult to separate water from coal particles after dewatering. There are disadvantages such as high water content (approximately 25 to 39%). Furthermore, in the method described in JP-A-53-70076, since an aqueous emulsion of oil fraction is added,
Surfactants are used to emulsify the oil fraction, which weakens the modification effect on the surface of coal particles. In addition, JP-A No. 56-67395 and JP-A-56
- Publication No. 159292 states, “PH of coal/water slurry
There is no mention of the technical idea of ``adjusting it to 6.5 to 10''. When coal is pulverized and slurried in water,
Generally, the PH value indicates a value around PH6.0. Furthermore, when coal is transported or stored, its surface may become oxidized and exhibit strong acidity. for example,
Blairsall charcoal can have a pH of 4.0 to 3.0. Therefore, in order to fully utilize the performance of the granulation accelerator, it is necessary to adjust the pH. The present invention was made in view of the above points, and has low power consumption and high dewatering efficiency (approximately 20 to 25% moisture in coal after dewatering), improves the properties of granulated coal, and The object of the present invention is to provide a method for granulating coal that can partially separate and remove the ash contained therein. [Means and effects for solving the problem] In order to achieve the above object, the coal granulation method of the present invention adjusts the coal/water slurry to pH 6.5 to 10, as shown in Fig. 1. After that, add heavy oil and a granulation accelerator, or add heavy oil and a granulation accelerator to the coal/water slurry and adjust the pH to 6.5 to 10, and then stir and mix this coal/water slurry in the stirring mixing tank 1. After forming mixed pellets of coal particles and heavy oil, the solid-liquid separator 7 separates the mixed pellets from water to recover the coal particles in the coal/water slurry. In the present invention, surfactants used as granulation accelerators include anionic, cationic, and nonionic surfactants. Anionic and cationic surfactants dissolve in water and exhibit ionicity, so they depend on the PH value of the slurry. It affects the action and effectiveness. That is, in alkaline conditions, anionic compounds promote the dissociation of sulfonic acid groups and carboxylic acid groups that exhibit surface activity, and exhibit sufficient surface activity, but in acidic conditions, dissociation is suppressed and the surface activity cannot be sufficiently exhibited. In addition, the cationic type promotes the dissociation of amine groups exhibiting surface activity in acidic conditions and exhibits sufficient surface activity, but in alkaline conditions, dissociation is suppressed and the surface activity cannot be sufficiently exhibited. Furthermore, when determining the pH value, corrosion issues must be taken into account in addition to surface activity. In other words, acidic conditions corrode mechanical equipment, which limits the pH value. Furthermore, at a pH of less than 6.5, the dissolution of the ash component contained in the coal is promoted, the function of the granulation accelerator is reduced, and the granulation rate is reduced. On the other hand, if the pH exceeds 10, saponification of the heavy oil is promoted and the surface tension of the solution decreases, causing a foaming phenomenon. Therefore, the coal and heavy oil are not sufficiently mixed, and the granulation rate is reduced. Considering these points, the applicable pH value is PH6.5 to 10 for nonionic and anionic surfactants, and PH6.5 for cationic surfactants.
-8 is the applicable range. Furthermore, for pH adjustment, basic substances such as alkali metal and alkaline earth metal hydroxides and ammonia, and acidic substances such as hydrochloric acid and sulfuric acid are used. Hereinafter, the configuration of the present invention will be explained based on the drawings. FIG. 1 shows an example of an apparatus for carrying out the method of the invention. 1 is a stirring mixing tank equipped with stirring blades 2, and a coal/water slurry supply pipe 3, a heavy oil supply pipe 4, a granulation accelerator supply pipe 5, and a mixed pellet/water extraction pipe 6 are connected to this stirring mixing tank 1. This mixed pellet/water extraction pipe 6 is connected to a solid-liquid separator 7 of a simple structure such as a vibrating screen. 8 is a mixed pellet extraction line, and 9 is a waste water extraction pipe. In the apparatus configured as described above, coal/water slurry, heavy oil, and granulation accelerator are supplied into the stirring mixing tank 1, and after stirring and mixing to form mixed pellets of coal particles and heavy oil, A solid-liquid separator 7 such as a sieve separates the mixed pellets from water. The separated mixed pellets are either transported again or burned in a boiler. When supplying coal/water slurry, heavy oil, and a granulation accelerator into the stirring mixing tank 1, instead of feeding each directly to the stirring mixing tank 1 separately as shown in Fig. 1, the granulation accelerator can be added to the coal in advance. - May be added to water slurry. usually,
The concentration of coal in coal/water slurry transported from coal producing areas is often 40 to 50% by weight, especially 43 to 47% by weight on a dry basis, and the present invention is capable of processing coal/water slurries with these concentrations. suitable for. The heavy oil used in the present invention must have a viscosity necessary as a binder during granulation and must be relatively inexpensive. In this sense, C heavy oil, B heavy oil, atmospheric distillation column bottom oil, etc. are suitable. The amount of heavy oil added is 6 to 20% by weight, preferably 10 to 15% by weight of the coal on a dry basis. Furthermore, the granulation accelerator used in the present invention is
Anionic, nonionic, and cationic surfactants are used alone or in combination, and are appropriately selected depending on the type of coal. Specifically, anionic surfactants include alkylbenzene sulfonates, alkyl sulfate ester salts, polyoxyethylene alkyl (alkylphenol) sulfate ester salts, alkyl phosphate ester salts, dialkyl sulfosuccinate ester salts, acrylic acid and/or and maleic anhydride copolymers, polycyclic aromatic sulfonates, or formalin compounds, etc. As cationic surfactants, alkyl amine salts, quaternary amine salts, etc. are used, and nonionic surfactants Polyoxyalkyl ethers, polyoxyethylene alkyl phenol ethers, oxyethylene/oxypropylene block polymers, polyoxyethylene alkyl amines, sorbitan fatty acid esters, polyoxyethylene sorbitan fatty acid esters, etc. are used as amphoteric surfactants. For example, alkyl betaines are used, and 1,2,3 monoamines,
Amine compounds such as diamines are used. In addition, the amount of granulation accelerator added is 0.01 of coal on a dry basis.
-5.0% by weight, preferably 0.05-2.0% by weight. It is thought that granulation in the present invention is carried out by the following process. First, the heavy oil and granulation accelerator added to the coal/water slurry are dispersed, and the granulation accelerator adsorbs onto the surface of the coal particles to modify the surface of the coal particles.Then, the heavy oil adheres to the surface of the coal particles. An oil film is formed, and then the coal particles adsorbed with heavy oil and granulation accelerator collide and come into contact with each other, coagulate and combine with oil as a binder, form and grow flocs, and are further compacted to form pellets. Figure 2 shows the power consumption and oil concentration in the liquid phase (n-hexane extract/) when the inventors performed the above granulation in a batch manner using the apparatus shown in Figure 1. It shows the change over time. The granulation conditions were as follows: Ca(OH) ₂ was added to a 41% water slurry of Blairsall coal with a particle size of 1 mm or less (weight of coal particles: 450 g).
After adjusting the pH to 8.5, an anionic surfactant as a granulation accelerator was added to this coal/water slurry in an amount of 01% by weight based on the coal (dry base), and Middle Eastern C heavy oil (viscosity at 50°C, 137.3 centistokes,
Specific gravity (15/4℃) 0.9515) was added at 12% by weight of coal (dry base), and the rotation speed of the stirring blade was 350 rpm.
The mixture was stirred and mixed for 60 minutes. As shown in Figure 2, in the first half, 20 minutes after adding heavy oil, power consumption is small, and the concentration of oil in the liquid phase decreases rapidly, indicating that oil is adsorbed on the surface of coal particles. I understand. It can be seen that in the second half, that is, approximately 20 minutes after the addition of heavy oil, the power consumption increases, and during this period, granulation occurs and pellets are formed. Furthermore, Figure 4 shows the change over time in the oil concentration (n-hexane extract/) in the liquid phase depending on the PH value when the above-mentioned granulation was carried out batchwise using the apparatus shown in Figure 1. It is something. The granulation conditions were adjusted to PH5, PH8.5, and PH12 by adding Ca(OH) ₂ to a 41% by weight water slurry of Blairsall coal with a particle size of 1 mm or less (coal particle weight: 450 g). Other conditions are the same as in the case of FIG. From FIG. 4, it can be seen that the oil concentration in the liquid phase is the lowest at PH8.5, and the oil concentration in the liquid phase is high at PH5 and PH12. [Example] Next, Examples and Comparative Examples of the present invention will be shown. Example 1 A 44% by weight water slurry of Blairsall coal with a particle size of 1 mm or less has a _pH of 5.5.
0.3% by weight, or 132g, was added to adjust the pH to 8.5. To this coal/water slurry, sodium dioctyl sulfosuccinate, an anionic surfactant, was added as a granulation accelerator in an amount of 0.1% by weight based on Blairsol coal.
That is, 44g was added, and Middle Eastern C heavy oil (50℃
viscosity of 137.3 centistokes and specific gravity (15/4℃) of 0.9515) was added at 12% by weight of Blairsall coal, i.e. 5280g, and the rotation speed of the stirring blade was increased.
After stirring and mixing at 300 rpm for 40 minutes, the mixture was passed through a 16-mesh vibrating sieve to separate water and the mixed pellets. As a result, mixed pellets with a total moisture content of 20.0% by weight, an oil content of 8.0% by weight (dry base), and an average particle size of 1 mm were obtained. Example 2 A 41% by weight water slurry of Blairsall coal with a particle size of 1 mm or less has a pH of 5.8, so dioctyl sulfosuccinic acid, an anionic surfactant, was added to this coal/water slurry as a granulation accelerator. Sodium to coal ratio is 0.001 (weight ratio), Ca (OH) ₂ to coal ratio is 0.004 (weight ratio), Middle East C heavy oil (viscosity 137.3 centistokes at 50℃, specific gravity (15/4℃)
0.9515) was added to coal by 0.12 (weight ratio), and the PH was
7.0 and stirred and mixed for 60 minutes at a stirring blade rotation speed of 300 rpm, and then drained with a 16-mesh vibrating sieve to obtain mixed pellets. The properties of the mixed pellets (granulated coal) and Blairsol pulverized coal as raw material were as shown in Table 1.

【table】

[Table] The calorific value of granulated coal is the value measured using an air-dried sample. As is clear from Table 1, the ash content of the granulated coal is significantly reduced by granulating it by the method of the present invention. This is thought to be due to the fact that oil easily adheres to coal and is difficult to adhere to ash. Note that the total (accumulation) of the raw material Blairsall pulverized coal used in this example and the obtained granulated coal
The particle size distribution is shown in Figure 3. Next, a comparative example for Example 2 will be shown. Comparative Example 1 A 41% water slurry of Blairsall coal with a particle size of 1 mm or less has a pH of 5.8, but sodium dioctyl sulfosuccinate, an anionic surfactant, is added as a granulation accelerator at a ratio of 0.001 (by weight) to the coal. ), Middle Eastern C
Heavy oil (viscosity 137.3 centistokes at 50°C,
Specific gravity (15/4°C) 0.9515) was added to the coal at a ratio of 0.12 (weight ratio), and after stirring and mixing for 60 minutes at a stirring blade rotation speed of 300 rpm, water was drained using a 16-mesh vibrating sieve to obtain mixed pellets. . The properties of this mixture, pellets (granulated coal), and Blairsol pulverized coal as raw material were as shown in Table 2.

【table】

〔Effect of the invention〕

As explained above, according to the method of the present invention,
Not only can the coal particles contained in the coal/water slurry be recovered with a simple process, low power consumption, and high dewatering efficiency, but the properties of granulated coal can be improved, and the ash content contained in the coal can be recovered. Also part of is separated,
It has the effect of being able to be removed.

[Brief explanation of drawings]

Figure 1 is an explanatory diagram showing an example of an apparatus for carrying out the method of the present invention, and Figure 2 is a diagram showing changes over time in stirring power and changes in oil concentration in the liquid phase over time when the method according to the present invention is carried out batchwise. Figure 3 is a curve diagram showing the particle size distribution of raw Blairsall pulverized coal and granulated coal when Blairsall pulverized coal is used as a raw material and granulated by the method of the present invention, and Figure 4 is a curve diagram showing the particle size distribution of Blairsole pulverized coal and granulated coal. FIG. 2 is a curve diagram showing changes over time in oil concentration in a liquid phase. 1... Stirring mixing tank, 2... Stirring blade, 3... Coal/water slurry supply pipe, 4... Heavy oil supply pipe, 5... Granulation accelerator supply pipe, 6... Mixed pellet/water extraction pipe, 7... Solid-liquid separator , 8... Mixed pellet extraction line, 9... Waste water extraction pipe.

Claims (1)

[Claims] 1. After adjusting the coal/water slurry to pH 6.5 to 10,
Add heavy oil and granulation accelerator or add coal/
PH while adding heavy oil and granulation accelerator to water slurry
6.5 to 10, this coal/water slurry is stirred and mixed in the stirring mixing tank 1 to form mixed pellets of coal particles and heavy oil, and then the mixed pellets and water are separated by the solid-liquid separator 7. A method for granulating coal, characterized by recovering coal particles in a coal/water slurry. 2. The coal granulation method according to claim 1, which uses a cationic surfactant as a granulation accelerator and adjusts the coal/water slurry to pH 6.5 to 8. 3 Concentration of coal/water slurry is 40 on dry basis
The method for granulating coal according to claim 1 or 2, wherein the amount is 50% by weight. 4 The amount of heavy oil added is 6 to 20 that of coal on a dry basis.
The method for granulating coal according to claim 1 or 2, wherein the coal granulation method is % by weight. 5 The amount of granulation accelerator added is
The method for granulating coal according to claim 1 or 2, wherein the content is 0.01 to 5.0% by weight.