JP2603127B2 - Method for producing high concentration coal / water slurry - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a method for producing a coal / water slurry, and particularly to a method for producing a coal / water slurry having a high concentration and excellent storage stability and transport stability. It is about.

(Prior Art) In recent years, coal has been reviewed as an energy source. However, since coal is a solid unlike oil, there has been a problem that it is difficult to transport and store, and it is difficult to handle various kinds of handling.

In order to remedy such disadvantages of coal, coal is pulverized, dispersed in water to form pulverized coal / water slurry, fluidized, stored and transported, and directly used as fuel for electric power and general industrial boilers Researches have been conducted for use as such (JP-A-58-38791, JP-A-60-1).
No. 8585, JP-A-61-57689, JP-A-62-11669
No. 1).

For coal and water slurries, transport and
Storage stability is required.

This high-concentration coal / water slurry contains
Consisting of 75% by weight, 40 to 25% by weight of water and a small amount of dispersant, the basis of this production technology is the adjustment of the particle size distribution of coal particles and the selection of additives that enable high concentration. .

For this reason, a method of adjusting the particle size based on the optimum particle size distribution formula has been proposed, but the control of the particle size is not always easy, and there is a drawback that a dispersant needs to be formed in order to increase the concentration.

(Object of the Invention) An object of the present invention is to provide a method for producing a coal / water slurry having a high concentration and stability.

(Constitution of the Invention) The present inventors have variously studied the relationship between the particle size distribution of the coal / water slurry and the stability of the slurry in order to solve the above-mentioned disadvantages of the prior art, and have a single peak. The present invention has been found that a coal / water slurry having a wider particle size distribution and sufficient fine powder than a coal / water slurry having a narrow particle size distribution is stable and a higher concentration can be obtained. Reached.

That is, three types of coal fine powder having a relatively small particle size (10 μm,
Pulverized coal having peaks around 20 μm and 40 μm, respectively)
And three kinds of relatively coarse coal powder (80μm, 160μ
m and coarse powder having peaks around 300 μm, respectively, while changing the ratio of each in the range of 10 to 90%, adding water and a dispersing agent (anionic surfactant) to each mixture, and mixing the mixture with a kneader. After measuring the physical properties by adjusting the coal / water slurry by kneading, the logarithmic conversion of the particle diameter of each slurry was performed, and then the value of the coefficient of variation C determined from the average particle diameter and the standard deviation was determined. It has been found that a coal / water slurry having a larger particle size (degree) distribution has preferable physical properties.

In addition, assuming that the average particle diameter is M and the standard deviation is σ after logarithmic conversion of the particle diameter, the coefficient of variation is expressed as C = σ / M.

Also, the measured size (unit: μm) of the i-channel (i-th divided area) in the particle size distribution measurement is Si, and the weight (or volume) occupancy of the i-channel in the particle size distribution measurement is
If Vi (0 ≦ Vi ≦ 1, ΣVi = 1), σ and M are expressed by the following equations, respectively.

σ = (Σ ((log ₁₀ Si−M) ² × Vi)) ^0.5 M = Σ (log ₁₀ Si) × Vi The value of the variation coefficient C is preferably 0.45 or more as described above, but the C value is large. It is more preferable. More preferably 0.
It is 5 or more, and it is considered that the practical range is about 0.7 to 0.8.

If the C value is less than 0.45, the concentration and stability of the slurry will be poor, and the required amount of the dispersant will be large.

The maximum particle size of the coal is 500 μm or less, preferably 300 μm or less, more preferably 200 μm or less. If the diameter is larger than 500 μm, the generation of unburned components becomes large when spray combustion is performed as a coal / water slurry.

The relationship between the C value of the coal / water slurry and the coal concentration, the precipitation rate in the stability test, and the required amount of the dispersant are shown in FIGS.

As can be seen from FIG. 1, when the C value exceeds 0.45, the coal concentration in the coal / water slurry increases as the C value increases, and the coal concentration becomes substantially constant when the C value is 0.5 or more.

As can be seen from FIGS. 2 and 3, the sedimentation rate in the stability test is in a practically acceptable range when the C value exceeds 0.45, and the sedimentation rate is about 10% or less when the C value exceeds 0.5. When the C value exceeds 0.45, the required amount of the dispersant becomes a practically acceptable range, and when the C value exceeds 0.45, only 0.4% (by weight of coal) may be added. Become.

The measuring method in FIGS. 1 to 3 is as follows.

Particle size distribution measurement method Microtrac manufactured by LEEDS & NORTHHRUP
It was measured by Model SRA7995-10.

Coal concentration measurement method in FIG. 1 Measured by a heat drying method according to JIS M8812.

Sedimentation rate measuring method shown in FIG. 2 After applying acceleration in a constant direction for 8 hours using a 20 G centrifugal acceleration tester, the ratio of coal particles separated and settled was measured.

Required amount of additive in Fig. 3 At the coal concentration shown in Fig. 1,
cp.) was measured.

FIG. 4 shows the particle size distributions of the three points of the coal / water slurry indicated by, in FIGS. 1, 2 and 3, respectively. The C value calculated from this particle size distribution is as follows.

: 0.722,: 0.473,: 0.344 Next, a method for producing the coal / water slurry of the present invention will be described.

 In the following description,% indicates% by weight.

The coal slurry of the present invention has a coarse particle powder obtained by pulverizing coal so that a particle content within a range of 500 μm or less and 100 μm or more is about 30% or more, and a particle content of 10 μm or less having a maximum particle diameter of 100 μm or less. % Can be easily produced by mixing and kneading the finely pulverized coal fine particle powder and the coarse particle powder at a ratio of 8/2 to 5/5 (weight ratio) so as to be about% or more.

In this case, at least in the kneading process,
Within the range of 0.3-0.8%, the viscosity of the final coal / water slurry
A sufficient amount of a dispersant and a crosslinkable stabilizer depending on the use of the coal / water slurry are added to achieve a viscosity of 1000 cp or less.

As the dispersant, a nonionic or anionic surfactant usually used in this field is preferable.

Also, as the stabilizer, celluloses such as alkali metal salts of carboxymethylcellulose, xanthan gums and the like which are usually used in this field may be used.

Next, a method for producing a coal / water slurry of the present invention will be described with reference to FIG.

First, coal and water are charged into the pulverizer 1 through the charging port 2 and pulverized to a low concentration of 50% or less in coal concentration and then classified by the classifier 4 to obtain coal having a maximum particle size of 500 μm or less, preferably 200 μm or less. The water slurry is introduced into the dehydrator 5 and dehydrated. The coal concentration of the obtained dewatered cake is 60 or more. On the other hand, the coal / water slurry having a particle size exceeding the maximum particle size in the slurry is recirculated to the pulverizer 1 through the inlet 2 of the pulverizer 1 and further pulverized.

The overcake obtained by dewatering in the dehydrator 5 is then led to the kneader 6, where water having a coal content in the range of 60-80% and 0.3-0.8% (relative to coal). After being mixed and kneaded with the surfactant in an amount, it is withdrawn from the conduit 7 (A), of which about 20% to 50% is led directly to the kneader 10 via the conduit 8, and the remaining about 80% to 50% After the particles having a maximum particle size of 100 μm or less and a particle size of 5 μm or less in the final slurry are further pulverized through a pulverizer 9 so as to have a particle size of 15% or more, preferably 20% or more, the mixture is led to a kneader 10 (B). The mixture is kneaded with the slurry guided directly to the kneader 10 via 8, and the coal / water slurry product is taken out from the conduit 11.

Next, another embodiment of the present invention will be described with reference to FIG.

Coal and water having a coal concentration of 50% or less are introduced into the pulverizer 1 through the inlet 2 and the coal is pulverized at a low concentration without adding additives. A slurry having a diameter of 500 μm, preferably 200 μm or less is guided to a dehydrator 5 to be dehydrated. On the other hand, the slurry having a particle size larger than the maximum particle size of the coal in the slurry guided to the classifier is recirculated to the pulverizer 1 and further pulverized.

The dewatered cake (C) obtained by the dehydrator 5 has a coal concentration of 60%
The mixture is then introduced into the kneading machine 6, where the product slurry and / or water is kneaded with a surfactant having a coal content of 60 to 80% and, if necessary, 0.3 to 0.8% by weight of the coal. It is introduced into the kneader 10 via 7 and 3 '.

Separately from the above, coal and water having a coal concentration of 60 to 80% and a surfactant at a ratio of 0.3 to 0.8% with respect to the coal are introduced through a pulverizer 1 'and an inlet 2'. Is pulverized to a high concentration, and the mixture is guided to a kneader 10 together with a coal slurry withdrawn from a conduit 7 via a conduit 3 ', and the mixture is kneaded so that particles having a particle size of 5 μm or less are 15% or more, preferably 20% or less.
% Of coal / water slurry is obtained.

The dewatered cake obtained by the dehydrator 5 may be directly introduced into the kneader 10 together with additional water and a surfactant.

Using about 0.4% of anionic surfactant with respect to coal, the coal-water slurry (B ') obtained by the pulverizer 1' has a maximum particle size of 100 µm or less and a coal particle content of 10 µm or less in viscosity. % And the slurry concentration is about 68%,
The maximum particle size of the coal in the coal / water slurry (A) obtained from the conduit 7 is set to 200 μm, and the slurry concentration is about 75%.
When the mixture ratio of (A) :( B ′) was adjusted to 30:70 and the C value of the final product, coal / water slurry, was about 0.495.

(Effects of the Invention) According to the present invention, a coal / water slurry having a high concentration and excellent stability can be easily produced by a simple index, and the amount of a dispersant used may be small.

[Brief description of the drawings]

FIGS. 1, 2 and 3 show the relationship between the C value of the coal slurry of the present invention, the coal concentration, the sedimentation rate in the stability test and the required amount of dispersant, respectively, and FIG.
The relationship between the particle diameter (μm) of the coal / water slurry and the integrated weight ratio under the net shown in FIGS. 2, 3 and 3 is shown in FIGS. 5 and 6, and FIG. 5 and FIG. It is a flowchart for demonstrating each different manufacturing method of a slurry. 1,1 ', 9 ... Pulverizer, 2,2' ... Raw material inlet, 4 ... Classifier, 5 ... Dehydrator, 6 ... Kneader, 10 ... Kneader

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Shinichi Tokuda 2609-75, Kamariya-cho, Kanazawa-ku, Yokohama-shi, Kanagawa Prefecture (72) Inventor Osamu Matsumoto 6-1-43-401, Konandai, Konan-ku, Yokohama-shi, Kanagawa Prefecture Document JP-A-62-265392 (JP, A) JP-A-59-157184 (JP, A) JP-A-60-156796 (JP, A)

Claims (6)

(57) [Claims] 1. A dewatered cake containing 60% by weight or more of coal having a particle size range of 500 μm or less obtained by wet-milling and dewatering coal is mixed with water and additives by a kneader to obtain 60 to 80% by weight.
A method for producing a high-concentration coal-water slurry by preparing a slurry (A) containing coal particles of (a), partially pulverizing the mixture with a pulverizer (B), and then mixing with the remainder of the slurry. After the logarithmic conversion of the particle diameter of the high-concentration coal / water slurry, pulverization is performed until the variation coefficient σ / M obtained from the average particle diameter M and the standard deviation σ has a particle diameter distribution of 0.45 or more. Concentration coal / water slurry production method. 2. A 50-80% by weight of the slurry (A) is pulverized with a pulverizer so that the final coal slurry has a coal particle content of 5 μm or less.
The method for producing a high-concentration coal / water slurry according to claim 1, wherein the slurry is finely pulverized so as to be 15% by weight or more. 3. Coal concentration obtained by high-concentration wet pulverization of coal in the presence of an additive;
The following high-concentration coal / water slurry (B ') is mixed with a low-concentration wet-pulverized coal-water slurry dewatered cake (C) having a maximum particle diameter of 500 μm or less obtained by adding no additive to the slurry. In the method for producing a high-concentration coal / water slurry, after logarithmically converting the particle size of the high-concentration coal / water slurry, a variation coefficient σ / M obtained from an average particle size M and a standard deviation σ is used.
A method for producing a high-concentration coal / water slurry, characterized in that the slurry is pulverized to a particle size distribution of 0.45 or more. 4. A product slurry and / or a dewatered cake (C).
Alternatively, water is added and kneaded with a surfactant in a proportion of 60-80% by weight of coal and, if necessary, with a surfactant of 0.3-0.8% by weight based on coal, and then mixed with a high-concentration coal-water slurry (B '). The method for producing a high-concentration coal / water slurry according to claim 3. 5. The mixing ratio between the high-concentration coal / water slurry (B ') and the dewatered cake (C) is 8/2 to 5/5, preferably 7/3 by weight of the respective coals contained therein. A method for producing a high-concentration coal / water slurry according to claim 3 or 4. 6. The method for producing a high-concentration coal / water slurry according to claim 3, wherein the content of coal of 5 μm or less in the final coal slurry is 15% by weight or more.