JPS59157183A - Coal-water slurry - Google Patents

Abstract

PURPOSE:To provide a coal-water slurry having high coal concentration, low viscosity and high stability, by selecting the weight ratio of each fraction of coal with respect to the particle diameter of the coal particle to fall within a specific range. CONSTITUTION:The objective coal-water slurry is obtained by dispersing coal particles in water in a manner to make the weight ratio of each coal fraction with respect to the diameter to satisfy the formulas I -VI wherein DL represents the maximum diameter of the coal particle. Preferably, the slurry contains coal particles wherein the particle size distribution of coal having diameter of >=1mu is represented by the formula VII [U(D) is the accumulated wt% of the fractions passed through the sieves; DL is 46-420mu; q is 0.25-0.50].

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a coal-water slurry, and particularly to a coal-water slurry having a high coal concentration, low viscosity, and good stability.

Recently, coal has been increasingly used as a substitute for oil, mainly in thermal power plants. However, coal, which is a solid fuel, is difficult to handle and therefore requires high transportation costs, which has a large impact on the price of coal. Therefore,
Techniques are being actively developed to turn coal into a slurry so that it can be handled as a transfer body and L7. One of them is COM (Coal and Oil), which is a mixture of heavy oil and coal.
MixtlLre) is known. However, in COM, the ratio of heavy oil to coal is approximately 1 = 1', so it cannot be said to be a completely oil-free fuel, and the price is not much different from oil, so there are no merits. There weren't many. Furthermore, methacol, which is a mixture of methanol and coal, is expensive and has not yet reached the practical stage.

On the other hand, CWM (Coa) is a mixture of coal and water.
and Water Mixtu, re) is quite practical in terms of price and has been attracting attention recently. However, one of the problems when burning CWM is the moisture in the CWM. Naturally, from the viewpoint of combustion efficiency, the lower the water content in CWM, the better, and when direct combustion is performed, it is said that a water content of 30 inches or less is preferable. However, if the moisture content is low, the viscosity of CWM is high, and pressure loss during transportation via pipelines is also a serious problem.

Furthermore, when CWM is used centrally, its storage becomes a problem. When storing CW B, 4 in a general tank, it has excellent stability (although it needs to be reduced, C'vV M
is composed of coal particles and water, so it is preferable to reduce the particle size in order to suppress sedimentation of the coal particles as much as possible.

However, simply reducing the particle size increases the viscosity and increases the pressure loss as described above.

In order to eliminate these drawbacks, the particle size distribution of coal particles is changed to W'
Attempts have been made to produce CWM with low viscosity and good stability even at high coal concentrations by qM. However, coal particles are not completely spherical;
There are many methods for measuring this, including the method using a sieve, the sedimentation method represented by an antriazene pipette, SEP, and the method of analyzing the shape of the i-photograph and calculating the representative diameter.
The definition of particle size also differs depending on the measurement method. This causes errors when trying to control the particle size distribution, making it difficult to produce CWM with high coal viscosity, low viscosity, and good stability.

The object of the present invention is to eliminate the above-mentioned drawbacks of the prior art, and to achieve 1. The purpose is to provide a coal-water slurry with low viscosity and good stability.

This invention 1 (, jj is coal with coal particles dispersed in water -
In A-class slurry, when the maximum particle size of coal particles is DL, it is determined that the weight ratio of each fraction of coal for the particle size indicated by + is in the following range.
4~DL)=29~50wt%F2 (DL/42
~DL/4) -20~25 uzt %Fs(DT
, /”~DL/4”) “12~15Wtchi” (
DL/ ``'DL/ 4'') =' 6~l Q
wt%Fs (DL/4s-DL/4') = 3
~l2tut%F6(DTJ/45~o)=
In the present invention, the above fractions are typically divided into 6 fractions, but these numbers can be combined or subdivided into 3 to 15 (preferably 5 to 8 fractions) as appropriate.

The present invention will be explained in detail below.

Coal is wet- or dry-pulverized in a mill, and a portion of it is sampled to measure the particle size distribution.When measuring the particle size distribution,
Considering that the amount of fine particles has a large effect on the viscosity and stability of the slurry, the maximum particle size was determined.

When closed, divide it into the following six fractions and sieve them using the closest appropriate sieve (for example, a JIS standard sieve or a millimeter filter with well-controlled particle size) to determine the u The scenery was also determined as I-j.

(1) Ft: Particle size DL / 4 or more, below 1, (2
) Fm: particle size ■/42 or more Db less than /4, (3) F
m: particle size, /, i3 or more, DL less than /42, (4
) F4: Branch diameter DL/4' or more, less than DL/43,
(5) Fs: Particle size DL/4s or more and less than DL/44, (5)'Fa□: Particle size less than DL/45.

The present inventors have determined that the ratio of 17+, F, is moderate <7
) 9. The viscosity and stability were examined by mixing 1 or more coals or coal slurry and adding water as necessary to make the moisture L12. However, if the maximum particle size Dfl is the maximum particle size Dfl, then it is
If the temperature is too small, the slurry viscosity will increase, so it was set to 46μrjL to 420μi·5.

As a result, it was found that when the fraction Fl-F6 was within the following range, the viscosity LL of the coal slurry was low and stable.

Fl: 2'9~5 Q LJt Chi Fm", 20~25 wt Fs: '12~l 5 wt bag F,: 6~10wt% F, = 3~12 wt Chi F6: 2~13 tjJt '14 There is more 1
We selected two types of coal and examined the effect on viscosity by varying the proportion of fractions, and when we converted the proportion of 7-luxions that exhibit relatively low viscosity into a cumulative distribution, we found that there was a certain tendency. . Figure 1 shows A coal (bituminous coal, ash content 9).
．． This is the cumulative particle size distribution for Mizuchi's slurry 1.2.3 of 5th C) when the coal concentration becomes 1,000C,p or less in 70 cycles (however, Dp = 297 μm). (The slurry viscosity is the value obtained when the internal cylinder rotation type viscometer is rotated for 5 minutes at a shearing speed M9 In other words, it was found that there is a relationship expressed by equation (1) between the particle size and the cumulative weight under sieve percentage U (D).

U (D) = (-M-)9X 100...
・・・・・・・・・(1) h ZoC, q: exponent.

Equation (1) is known as the particle μ distribution equation that provides closest packing for continuous particle powders.
Past research has been conducted on the oAndreastrn equation, which is isomorphic to the F t n equation, and for spherical particles, q
=o, it has been confirmed that the filling rate reaches its maximum at 3s to 0°40.

However, the filling rate varies depending on the particle shape, and there is no known example of a systematic relationship between the value of q and the viscosity and stability of the slurry when it is made into a coal-water slurry.

Therefore, the present inventors used the above-mentioned particle size adjustment method to
As a result of changing the ratio of F6 to FJ4B so that the particle size of coal can be approximated by equation (1), and examining the effect of changing the values of m and q on viscosity and stability, the particle size distribution of 1 μIn or more was found. It has been found that the viscosity and stability of the slurry are optimal when

U (D) −(−”−)” L (However, q=0.25~0.50, ■=46~420
μm) There are still 5 to 46wt of particles of 1μm or less, and 0.5wt or more of ultrafine particles of 0.05μm or less, preferably 0.5 to 6.5wt (most preferably 1.0wt). ~4.0
We have found that the stability of the slurry is optimal when φ) is present.

Furthermore, the coal-water solution and laly of the present invention include a dispersant and P.
H regulator can be added, and the amount of dispersant added is 3%.
It has been found that the pH is preferably 0.1 to 1.5, and the pH adjuster is preferably added so that the pH of the slurry is 7 to 9.

In the present invention, preferred dispersants include naphthalene sulfonic acid, orthorin 1112, Hrb+2Pr, 0
zns (n≧2) or HnPnOm (”≧3 >
Table b <;6 Condensed phosphorus 0, tartaric acid, oxalic acid, citric acid, ethylenediaminetetraacetic acid, lignin sulfonic acid, and dirt - At least 11 of the following: salts, quebraco and other tannins, metal salts of carboxymethylcellulose] In addition, as a PHI agent, at least one of hydroxide, potassium hydroxide, calcium hydroxide, barium hydroxide, and sodium carbonate can be used.

A particularly preferable slurry obtained in the present invention has a coal content of 60 to 80 wt%, and has a coal content of 60 to 80 wt%, and a viscosity of 5 minutes after the start of measurement at a shear rate of 995 ec-'' using an internal cylinder rotation type viscometer. The viscosity is 5,000 cp or less.

Hereinafter, the present invention will be explained in more detail with reference to Examples.

Example I For A charcoal (Kase charcoal, ash content 9.5%), the ratio of each fraction was adjusted by the above method, and in equation (1), DL=
For 297 μm and 149 μm, q=0.15.0.2
0.0.25.0.30, 0.35.0.40, 0.4
5. Produce a 2.0 mm coal sample with a particle distribution corresponding to 0.50, . 0.5To of sodium acid per weight of coal
, 'NaOH was added as a pH adjuster at the same time, and the slurry viscosity was measured. The results are shown in FIG. In the figure, A is Db = 297 ttmS13 is DL
= 149μ? Each case of n is shown.

From the results shown in Figure 2, there is no difference in the size of the ratio, and q=0.
It was found that the viscosity was at its minimum between 40 and 0.45. This is larger than 9 = 0.35 to 0.40 in the case of spherical particles in the Adleaztn formula.

Similar studies were conducted for other coal pillars, but q−0,
The viscosity was minimum between 40 and 0.50.

Example 2 Stability of the coal-water slurry prepared in Example 1 was investigated. 50088 graduated cylinder with depth 1
A glass rod with a diameter of 5 mm and a weight of 1,011 mm was inserted into the slurry to a depth of 70 cm, and the change in time until it reached the bottom was measured.

When the penetration time immediately after slurry M production is set to 1, 30 minutes after production.
FIG. 3 shows the relationship between the penetration time and the value of q over the course of days.

As is clear from Fig. 3, the penetration time 1ri q =
It is minimum between 0.25 and 0.35, and it can be seen that this condition has the best stability.

We also considered other coal types by changing the DL, but
From the results of Examples 1 and 2, in which similar results were obtained, it was found that q = 0.25 to 0.50 is preferable in terms of slurry viscosity and stability.

Example 3 Regarding B charcoal (cured charcoal, ash content 13.6%), fruit; monthly 1
Similarly, in equation (1), Dr, = 297μI
A slurry of 70 layers of coal was produced with a particle size distribution corresponding to LL Xq = 0.40. Condensation of sodium naphthalene sulfonate was added to this as a dispersant, and the relationship between its addition amount and slurry viscosity was investigated.
As shown in the figure. Since it was winter, the amount added was the value for the coal foreground, and 0.1 g of NaOH was added per coal as a pH adjuster.

From the results shown in FIG. 4, it can be seen that the slurry viscosity is minimum when the amount of naphthalene sulfonate sodium is added to i 0.5, and even if more than that is added, the above effect will not occur.

Similar cross-cutting was performed for other coal types, but the addition needle was 0.
．． It was found that the viscosity was minimum between 2 and 1.2 inches. Also, when other anionic surfactants are added, the
The minimum viscosity was obtained at a loading of 1.5 inches.

Regarding the example season B coal (Bon blue coal, ash content 13.6%), actual turning
The same slurry as in 3 was produced, and the amount of sodium naphthalene sulfonate as a dispersant was kept constant at 0.5%.
The pH of the slurry was adjusted by changing the addition needle of sodium hydroxide, and the effect of pH on the viscosity of the slurry was examined. The results are shown in FIG.

From the results shown in Figure 5, it can be seen that the slurry viscosity decreases up to pH 8, but hardly changes beyond that. Considering the consumption of sodium hydroxide and the corrosion of the lid and materials, the pH of the slurry should be 7 to 9. is preferred.

The pH of coal varies depending on the oxidation level and surface oxidation level, but the amount of sodium hydroxide added necessary to adjust the pH to 7 to 9 is 0 to 1 per coal weight. .0
It is about 500 yen.

Example 5 Ultrafine particles of coal that had passed through a 0.05 μm Millipore filter were added to the same B coal slurry as in Example 3, and the effect on the stability of the slurry was studied. The results are shown in FIG. However, the penetration time 11 of the vertical axis is the ratio of the penetration time 30 days after production to the penetration time immediately after production, and the amount of ultrafine particles added is the ratio to the total stone weight nil after addition.

From the results shown in Figure 6, it can be seen that the slurry stability is the best when the ultrafine particles are added at 3% (0.05 μm or less particles contribute to the slurry stability. As a result of changing the coal type and placing it on the side, the particle weight of 0.05μm or less, which is effective for improving slurry stability, is approximately 0.5 to 6.5φ.
(preferably 1.0 to 4.0 qL).

As described above, according to the present invention, the particle size distribution of coal particles is
By adjusting the content within a certain range, a high-Q coal-water slurry with low viscosity and good stability can be obtained.

[Brief explanation of the drawing]

Figure 1 shows the cumulative particle size distribution of low viscosity slurry;
The figure shows the relationship between particle size distribution and slurry viscosity, No. 3M shows the relationship between feed diameter distribution and stability, and Figure 4 shows the relationship between the addition of classifier #1 and viscosity. 8! Figure g5 is a diagram showing the relationship between pH and viscosity, and Figure 6 is a diagram showing the relationship between pH and viscosity.
FIG. 3 is a diagram showing the relationship between the amount of one particle added and stability.
・Fig. 1 2 1 q (-) 3 q (-) 2 (Fig. 4

Claims (1)

[Claims] (1) In a coal-water slurry in which coal particles are dispersed in water, if the maximum particle size of coal particles is DL, then the ratio of each of the 7 lactations of coal for the following particle sizes is within the following range. A coal-water slurry characterized by: Fl(DT, /4~Dp)-29~5QwtφF
2 (D1./4"~DL/4), = 20~25w
t attack Fs (DX74"ma DL/4") -12~l
5 wt section F4 (DI, /4'~DL/43) =
6~IQwt Chi F5 (DTj45~DL/4')
= 3~12 wt Chi Fs (D74'~0)-
(2) A coal-water slurry according to claim 1, characterized in that the coal-water slurry contains coal particles having a coal particle size distribution of 1 μm or more substantially represented by the following formula. Iy (D) = (-'-)''
L=46~420/jm%q=0.25~0.
50) (3) In claim 1 or 2, 5 to 46 wt% of coal particles of 1 μm or less are present, and ultrafine particles of 0.05 μm or less are o, s.
A coal-water slurry characterized by the presence of more than wtqb.