JPS62187793A - Production of highly concentrated deashed coal slurry - Google Patents

Abstract

PURPOSE:To obtain the titled slurry having a high degree of deashing and a desired particle diameter distribution, by mixing a first froth obtd. by making use of a first floating machine with a third froth obtd. by grinding a second froth and recovering the third froth by making use of a second floating machine and kneading the mixture after addition of a dispersant. CONSTITUTION:Raw coal 11 which has been ground so as to have a max. particle diameter of 3mm or less is fed together with water into a wet mill 12, where it is pulverized so as to have a particle diameter of 300mum or less. Water is added to the pulverization product to prepare a raw coal slurry 13 having a concn. of 2-15wt%. The raw coal slurry is fed into a first floating machine 14. A given amt. of a floating agent is added to the slurry, and a first froth 16 in an amt. corresponding to 50-70wt% of the fed coal and contg. low-ash coal having a relatively small particle diameter is recovered therefrom. The floating agent is further added to the residual slurry to obtain a second froth 17 contg. medium-ash coal having a relatively large particle diameter. The second froth is optionally pre-dehydrated and fed into a wet mill 18, where it is pulverized so as to have a particle diameter of 30-50mum. The pulverization product is then fed into a second floating machine 14', where it is deashed again in the presence of a floating agent to obtain a third forth 16' composed of a low-ash coal slurry. The third froth is concentrated together with the first froth 16 by means of a dehydrator 19 to have a water content of 25-35%. The dehydration product is kneaded with a dispersant by means of a kneader 20 to obtain the titled slurry 21.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a method for producing a demineralized high-concentration coal slurry, and more specifically, it involves pumping, shipping, storage, etc. in the same manner as petroleum. The present invention relates to a method for producing a deashed highly concentrated coal slurry that can be directly supplied to a boiler and combusted.

[Conventional technology] As a method for producing demineralized high-concentration coal slurry.

For example, as seen in Japanese Unexamined Patent Publication No. 58-80388.

The most common method is to finely pulverize raw coal (raw coal) and subject it to flotation and deashing, but there is also the method of
As proposed in Publication No. 91, a method for producing highly concentrated deashed coal slurry is also known, which takes advantage of the high specific gravity of coal with a high ash content and combines the specific gravity separation of raw coal with flotation deashing. It is being

[Problems to be solved by the invention] Among the conventional methods described above, in the method of finely pulverizing raw coal and flotation deashing, the deashing performance depends on the pulverized particle size.
In order to improve deashing performance, all of the raw coal must be finely pulverized, which is disadvantageous. On the other hand, a method that combines specific gravity separation and flotation deashing has the advantage of being able to produce coal slurry with high deashing properties, in other words, with a low ash content, without having to finely pulverize all of the raw coal. However, this method is not always successful because the device configuration becomes complicated.

[Means for Solving the Problems] The inventors of the present invention have endeavored to solve the above-mentioned problems, and as a result of repeated research into a new method for producing deashed high-concentration coal slurry, they have discovered the following. I gained new knowledge. That is, (1) When coal that has been pulverized to about 300 μm or less is deashed by flotation, coal with relatively small particle size and low ash content (low ash coal) can be recovered as floss in the first half of flotation. , the grain size is relatively coarse in the later stages of flotation;
Floss containing coal with a slightly higher ash content (medium ash coal) can be separated from the tail consisting of high ash coal.

(2) If the medium ash coal is pulverized to about 40 μm or less and deashed again by flotation, coal with a low ash content can be recovered as froth.

(3) By mixing the low ash coal froth obtained in (1) and (2) above at a ratio of about 6:4, a coal slurry with good fluidity can be obtained.

Based on these new findings, the present invention utilizes the difference in flotation properties depending on the ash content of coal to improve deashing performance and adjust particle size distribution, while achieving deashing with good properties. A method for producing highly concentrated coal slurry is proposed,
The method includes (a) 30% coal slurry for producing a deashed high-concentration coal slurry by crushing raw coal and flotation deashing treatment.
The raw coal slurry pulverized to 0μl or less is supplied to the first flotation and deashing step, and the first froth containing low ash coal with relatively small particle size is recovered first, and then medium ash coal with relatively large particle size is recovered. separating a second froth comprising: from a tail consisting of high ash coal; (b) a second froth obtained from the first flotation-deashing step;

After pulverizing this so that the medium ash content coal contained in it is 50 μm or less, it is supplied to a second flotation deashing step to recover a third froth with a relatively low ash content; (c) the first froth and The third floss is mixed, dehydrated, and then a dispersant is added thereto and kneaded.

[For production] The present invention will be described in detail with reference to the accompanying drawings.

Raw coal that has been crushed to a maximum particle size of 3Il+I11 or less is usually
Line 11 feeds the raw coal to a wet mill 12 where it is ground to a particle size range below 300 μm, preferably below 200 μm, and is refilled with water to a solids concentration of 2.
A raw coal slurry of ~15% by weight, preferably 3-10% by weight, is sent from line 13 to a first flotation machine 14 .

In the 14th sorter 14, a flotation agent commonly used for flotation of coal, such as kerosene, light oil, MIBC, etc., is added, and this makes it possible to obtain coal with relatively small particle size and low ash content, that is, low ash coal. The slurry can be collected in line 16 as a first froth. In this case, the amount of the :4 selection agent added is adjusted so that about 50 to 70% by weight of the coal supplied to the first flotation machine 14 is recovered in the line 16 as the first froth.

A flotation agent is added again to the residual slurry from which the first froth containing low ash coal has been separated, and a slurry of coal (medium ash coal) with larger particle size and higher ash content than the low ash coal is produced. The second froth is taken out to line 17, and the remaining high ash coal is discharged to line 15 as a tail. In addition,
If it is a national policy to collect the first and second floss using the same flotation machine, it is of course possible to use two flotation machines in series.

The medium ash coal froth recovered in the line 17 in the latter half of the first flotation machine 14 is fed to the wet mill 18 after preliminary dewatering if necessary.
Here, the medium ash coal is pulverized to a particle size range of 30 to 50 μm, and then subjected to deashing treatment again in the second flotation machine 14' in the presence of a suitable flotation agent. In other words, when the medium ash coal, which was relatively coarse particles, is pulverized into a particle size range of 30 to 50 μm, separation of the coal content and ash content is promoted. The ash treatment allows a slurry of low ash coal to be obtained in line 16' as a froth. The remaining high ash coal is used as a tail line 15.
' is discharged.

The low ash coal slurry taken out from the first flotation machine and the second flotation machine into lines 16 and ]6', respectively, is mixed and supplied to the dehydrator 19, where it is concentrated to a moisture content of 25 to 35%. After that, it is kneaded with a dispersant in a kneader 20, and thus a deashed high concentration coal slurry can be obtained in a line 21. Conventionally known dispersants can be used as the dispersant when obtaining the deashed highly concentrated coal slurry.1 For example, anionic surfactants such as higher alcohol sulfate ester salts, nonionic surfactants such as polyoxyalkyl ethers, etc. is available.

[Example] Example Raw coal with an ash content of 14.4% was wet-pulverized at a coal concentration of 40 wt% to prepare a raw coal slurry with a maximum particle size of 200 μm. After diluting this slurry with water to a coal concentration of 8%, It was fed to the first flotation machine. A mixture of light oil and MIBC in a ratio of 2:1 was used as a flotation agent at a rate of 700 g per ton of coal, and the first froth of low ash coal was recovered. Next, add the same flotation agent as above to the remaining coal slurry at a rate of 1/ton of coal.
The flotation was continued by adding at a rate of 400 g to separate the second froth of medium ash coal and the tail of high ash coal.

In the first flotation step, low ash coal (ash content = 9.3'%) corresponding to 65.3% of the raw coal was used as the first flotation.

Medium ash coal (ash content = 16.5
%) were collected as the second floss, and the remaining 4.8%
The high ash content coal (ash content = 72.2%) was discarded as tail.

The second floss obtained in the first flotation step has a maximum particle size of 50 μI.
After wet pulverization as it is, the coal concentration is 8wt.
% and supplied to a second flotation machine, and second flotation was carried out by adding the flotation agent described above at a rate of 2400 g per ton of coal. Through this second flotation, medium ash coal, which accounts for 29.9% of the raw coal, is converted into coal with relatively low ash content (ash content = 10
．． 2%) and a third floss containing high ash content (ash content =
It was separated into a tail containing 73.9%). The amount of coal recovered as the third floss was equivalent to 26.9% of the raw coal.Next, the above-mentioned first floss and third floss were mixed and vacuum dehydrated to reduce the water content to 28%. Got the cake. The amount of coal contained in this cake corresponded to 92.2% of the raw coal, and the ash content was 9.6%.

When this dehydrated cake was mixed with an anionic surfactant equivalent to 1% of the weight of dry coal and a small amount of water, a highly concentrated deashed coal slurry with a coal concentration of 67.4w/1i% and a viscosity of 1750 cp was obtained. I was able to manufacture l.

Comparative Example In the same first flotation step as in the example, the same raw coal was treated under the same conditions to obtain deashed coal with a 1-coal recovery rate of 92.0%. The ash content of this deashed coal was 11.0%. When a coal slurry was produced using this deashed coal in the same manner as in the example, the maximum coal concentration was 64.9% by weight and the viscosity was 1600%.
cp was the limit.6 [Effects of the Invention] The method of the present invention first recovers low ash coal from raw coal in the first flotation deashing step, and then recovers the medium ash coal recovered in the latter half of the first step. Since it is further finely pulverized and subjected to the second flotation and deashing step, the overall degree of deashing can be improved. Furthermore, in the method of the present invention, the low ash coal obtained in the first step and the
Since the particle size of the low ash coal obtained in the process is different, the particle size distribution in the high concentration coal slurry can be arbitrarily adjusted by appropriately adjusting the mixing ratio of the two.

[Brief explanation of drawings]

FIG. 1 is a flow sheet showing one embodiment of the method of the present invention.

Claims (1)

[Scope of Claims] 1. In a method for producing a highly concentrated deashed coal slurry by subjecting raw coal to flotation and deashing treatment, (a) raw coal slurry pulverized to 300 μm or less is first
A first froth containing low ash coal having a relatively small particle size is first recovered by being fed to a flotation deashing process, and then a second floss containing medium ash coal having a relatively large particle size is recovered as a tail consisting of high ash coal. (b) The second floss obtained in the first flotation deashing step is crushed so that the medium ash content contained therein is 50 μm or less, and then supplied to the second flotation deashing step. (c) mixing the first and third froths, and after dehydration, adding a dispersant to the mixture and kneading it. Method for producing concentrated coal slurry. 2. The amount of coal recovered as the first floss in the first flotation and deashing process is 50 to 70w of the amount of raw coal supplied to this process.
The method according to claim 1, wherein t%.