JPS601289A - Deashing of coal - Google Patents

Abstract

PURPOSE:To prepare a slurry of high quality coal having a high concn. and a low viscosity at a low cost in a simple process, by adding oil to an aqueous slurry of crushed coal for cohesion of carbonaceous components and classifying them by wet process. CONSTITUTION:Coal 1 is cruched in a crusher 2 to a predetermined particle diameter and is fed into a mixing tank 3. Water and oil are fed into the mixing tank from a water tank 4 and an oil tank 5, respectively, to produce a slurry consisting of crushed coal, water and oil. The slurry is fed to a screen 8 for wet classification. Crushed coal remaining on the screen 8 is recovered as high quality coal, while the slurry which passed through the screen 8 is recovered as ash- contg. slurry.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to a coal deashing method for obtaining high-quality coal with a low ash content by removing ash from coal.

[Background of the invention]

A large number of methods have been proposed both domestically and internationally for deashing coal. Among these methods, the heavy liquid separation method that relies on the difference in specific gravity uses carbon tetrachloride as the heavy liquid, which makes waste liquid treatment difficult and may cause pollution.The heavy liquid is also expensive, so it is difficult to remove it. This process has the drawback of increasing the cost of ash charcoal, making it difficult to commercialize it industrially. In addition, in the underwater granulation method, heavy oil is added as a binder to a slurry of pulverized coal and water, and the mixture is stirred to granulate the coal particles to simultaneously perform deashing and dewatering. However, in this process, a large amount of heavy oil is used, accounting for 50% of the weight of coal, which increases the cost of deashing coal. In addition, in order to improve the deashing rate, it is necessary to increase the rotation speed of the stirring blades. However, as a result, there are many problems in putting it into practical use as there is a drawback that the power cost increases.

The flotation method requires additives such as a scavenger, a foaming agent, and a dispersant, and the cost of these additives is high.

Furthermore, when coal water slurry is deashed using the conventional flotation method, the pulp concentration is at most 30%, so the processing cost is low.

The HGMS method using a magnetic field is effective in removing iron-based ash such as nokuillite, but cannot remove other silica and alumina-based ash. In addition to these methods, chemical demineralization methods have also been proposed, but all of them have the disadvantage that the process is complicated.

Furthermore, in addition to deashing methods other than those described above, an oil drop flotation method has been proposed. The oil drop flotation method is a method in which oil having an affinity for the carbonaceous quality in coal is supplied as oil droplets into a slurry consisting of crushed coal and water. Oil droplets have a lower specific gravity than water, so they rise through the slurry, but at this time, lipophilic carbonaceous matter adheres to the oil droplets and floats to the surface, so when they are collected, high-quality charcoal with a low ash content can be obtained.

On the other hand, since ash is hydrophilic, it remains dispersed in the aqueous phase, and by disposing of this as a deashing residue, the carbonaceous and ash can be separated.

Although the oil droplet flotation method has a high separation efficiency of carbonaceous matter and ash, the recovery efficiency of the carbonaceous matter is low, so the disadvantage is that a large amount of oil is used per unit amount of coal processed.

In addition, high-quality coal slurry obtained by the oil drop flotation method contains 20 to 30% oil based on the weight of the coal9, so the carbonaceous components are in an agglomerated state with oil as a binder.

Therefore, even if high-quality coal obtained by the oil drop flotation method is mixed with water to form a water slurry, the carbonaceous components will not be uniformly dispersed in the water phase, making it impossible to form a highly concentrated water slurry. Even if a surfactant is added to forcefully disperse the carbonaceous components into the aqueous phase, the dispersibility is not improved because of the strong binder effect of oil.

[Purpose of the invention]

An object of the present invention is to provide a method for deashing coal, which is low in cost due to the small amount of additive used, and is capable of turning high-quality coal into a high-concentration, low-viscosity slurry through a simple process.

[Summary of the invention]

The present inventors developed a bubble flotation method in order to take advantage of the advantages of the oil drop flotation method described above while improving its drawbacks.

The bubble flotation method is a method in which oil vapor, which is compatible with the carbonaceous content of coal, is supplied to a slurry consisting of crushed coal and water together with an accompanying gas. The supplied oil vapor forms bubbles in the slurry. The oil vapor in the bubbles condenses to form an oil film at the interface with water, and only lipophilic carbonaceous matter adheres to this oil film and floats up together with the bubbles. When this is collected, high-quality charcoal with low ash content can be obtained. .

In the bubble flotation method, the amount of oil used is LO based on the weight of coal.
Since the OP is low, the oil content in the high-quality coal obtained by deashing is also low, and therefore no agglomeration of carbonaceous material is observed.

However, in the bubble flotation method, it is necessary to increase the contact area between the bubbles and the slurry in order to improve the carbon recovery efficiency, and for this purpose, an atomizer is used to make the bubbles finer by the shear force, and the bubbles are made even finer. In order to improve the conversion efficiency, it is necessary to add about 10,001 p of acetic acid, which has the function of lowering the interfacial tension of water, to water. As a result,
In the bubble flotation method, deashing is carried out on the acidic side where the pH of the slurry is around 4, and of course the pH of slurry made of good quality coal is also around 4.
It is on the acidic side.

Here, the zeta potential of coal particles in the aqueous phase and the pH of the slurry
As a result of investigating the relationship between the pH of the slurry and
It was confirmed that the absolute value of the zeta potential increases as the zeta potential increases.

Generally, a force called guandervaarska acts between particles in a dispersion system, and the particles tend to coagulate with each other, but if a repulsive force greater than this cohesive force is applied, dispersibility improves. The zeta potential has the effect of imparting electrostatic repulsion, and therefore, a high zeta potential means improved dispersibility. Since the pH of high-quality charcoal slurry obtained by the bubble flotation method is about 4, there is a problem that it cannot be directly converted into a highly concentrated slurry, and there is also a problem in terms of the cost of acetic acid as an additive.

The present invention is intended to achieve the above-mentioned object without making the pH of high-quality charcoal slurry acidic.

That is, the coal deashing method of this A-Mei involves a coal pulverization step, a water slurry made by mixing the pulverized coal and water, and an oil having a high affinity for carbon content other than ash in the coal added to this slurry. This method is characterized by comprising a step of adding a substance to agglomerate carbon content other than ash in the coal, and a step of wet-classifying the agglomerated carbon content.

The present invention will be explained in more detail below.

In the present invention, in the coal pulverizing process, the coal is
It is desirable to crush the following: If the particle size of the crushed coal is too large, it will be difficult to separate the fine particles contained in the coal.

The additive added to the slurry made by mixing pulverized coal and water is an oil that has an affinity for the carbon content other than the ash content in the coal. As this oil, kerosene is most desirable in view of flocculating action and cost. In addition to kerosene, there are 9 heavy vegetable oils and kerosene.

It is also possible to use cyclohexane, benzene, etc. In the process of wet-classifying the carbon content in which oils are added and aggregated, the most suitable method is a sieve classification method. If the desired high-quality coal (for example, the ash weight ratio in the coal is 10 wt % or less on a dry coal basis) cannot be obtained by the sieve edge, it is desirable to adopt a two-stage sieve edge.

FIG. 2 is a flow diagram showing an example of the present invention employing such two-stage classification.

In FIG. 2, coal 1 is fed to a crusher 2, where it is crushed to a predetermined particle size. The pulverized coal is supplied to the stirring tank 3. Further, water and oil are supplied to the stirring tank 3 from a water tank 4 and an oil tank 5 via a water pump 6 and an oil pump 7, respectively. A slurry consisting of the pulverized coal, water and oil is obtained in the stirring tank 3. This slurry is supplied to a screen (sieve) 8, where it is wet classified.

The crushed material (agglomerate) remaining on screen 8 is good quality coal 1
It is recovered as 0. The slurry that has passed through the screen 8 is supplied to a stirring tank 9. Oil is supplied to this stirring tank 9 from the oil pump 5 via an oil pump 7, and the slurry with the carbon content aggregated by this oil or the screen 8 supplied to Next, the aggregates remaining on the screen 8 are used as high quality coal 1.
The slurry that has passed through the screen 8 is collected as ash slurry 11.

FIG. 3 is a flow diagram showing a method for recovering high-quality coal by dividing pulverized coal having a certain particle size distribution into three particle size ranges in the coal pulverizing process.

At 2 in FIG. 3, coal 12 is supplied to a pulverizer 13 and is pulverized to have a constant particle size distribution M.

The crushed coal is then stirred5. supplied to t714,
In addition, a water tank 15 is connected to the stirring tank 14 via a water pump 16.
Water is supplied to form a slurry. This slurry is supplied to screen 17. By changing the opening of the screen, the coal is divided into coarse coal 18, medium coal 19, and fine coal 20.

The coarse coal 18 is again supplied to the pulverizer 13 and is further pulverized into coal particles with a finer particle size. Medium grain coal 19 usually has a lower ash content weight ratio than raw coal, so it is recovered as is as good quality coal 21.

The fine charcoal 20 is mixed with a pulverized material obtained by re-pulverizing the coarse charcoal 18, and is supplied to the agitator 41724.

Oil is supplied from the oil pump 22 to the stirring tank 24 via the oil pump 23, where the carbon components are aggregated. The slurry containing the aggregate thus obtained is supplied to the screen 25, the crushed material remaining on the screen 25 is recovered as high quality coal 21, and the slurry that has passed through the screen 25 is recovered as an ash slurry.

[Embodiments of the invention]

Example 1 Using Australian W coal, pulverized coal having a particle size distribution as shown in FIG. 4 was produced, and the pulverized coal and water were mixed to form a slurry having a coal weight concentration of IQwt%. kerosene is added to the slurry in an amount of 1ooop based on the weight of coal;
Separately, two slurries containing kerosene added at 1% based on the weight of coal were mixed using a mixer and wet classified using a 37 μm sieve. After drying the crushed material slurry remaining on the sieve after classification, the weight W1 and ash content ratio A of this dry charcoal! I met. Assuming that the coal charging site before deashing is Wo1 and the ash content ratio is Ao, the carbonaceous fraction yield and deashing rate were defined and calculated as shown in the following equation.

The results are shown in FIG. When kerosene is 1ooop, the carbonaceous fraction yield is 75%, the deashing rate is 45%, and the carbonaceous fraction recovery rate is low. However, when 1% of kerosene is added, the recovery rate is 90% and the deashing rate is 55%, improving p-deashing performance.

Here, the recovery rate (7
5%), a two-stage wet classification deashing method shown in FIG. 2 was carried out.

That is, the slurry that passed through a 37 μm sieve was collected, and kerosene was further added thereto in an amount of 1% based on the solid weight of the slurry, followed by stirring with a mixer.

At this time, the outer carbonaceous material coagulates using kerosene as a binder and 37
Since the size is more than μm, the slurry is resized to 37 μm.
When the charcoal was classified using a sieve, high-quality charcoal containing a large amount of non-charcoal material remained on the sieve. This high quality charcoal was collected and its weight and ash content ratio were determined.

Figure 6 shows the overall recovery rate and deashing rate of the first and second stages.

The second stage wet classification deashing method has a recovery rate of 96% and a deashing rate of 55%.
It showed high demineralization performance.

Example 2 Using Australian coal W coal, pulverized coal having a particle size distribution as shown in FIG. 4 was produced, and this was mixed with water to form a slurry having a coal weight concentration of IQwt%. The slurry is 37μ
Figure 7 shows the recovery rate and deashing rate of the crushed slurry remaining on the sieve after wet classification using a sieve of 500 mm. The recovery rate is 65% and the deashing rate is 48%, which is low.

Therefore, in order to improve the deashing performance, a two-stage wet classification deashing method shown in Figure 2 was carried out.

That is, the slurry that passed through the sieve in wet classification was collected, 1% kerosene was added to the solids in the slurry, and then stirred with a mixer. When the slurry was classified again using a 37 μm sieve, high-quality charcoal containing a large amount of non-carbonaceous material remained on the sieve and was collected. Figure 7 shows the overall recovery rate and deashing rate of the first and second stages. The two-stage wet classification deashing method has a recovery rate of 95%.
It showed high demineralization performance with a demineralization rate of 55%.

Example 3 Using W coal from Australia, deashing treatment was performed based on the flow shown in Figure 43. After pulverizing Australian W coal to 5 μm or less, this pulverized coal is mixed with water to make a slurry with a coal concentration of 10 wt%, and this is classified using a 2380 μm and 250 μm sieve to separate particles larger than 2380 μm and 2.
It was divided into three parts: particles in the range of 50 to 2380 μm and particles below 250 μr-'.

When the ash content weight ratio of each of the three pieces of pulverized charcoal was measured, it was 250~
Only the pulverized coal of 380 μm was found to have a lower ash content weight ratio than the raw coal before deashing, so this was recovered as deashed coal. The deashing characteristics at this time were a recovery rate of 45% and a deashing rate of 40%, as shown in FIG. 8 (1).

Next, the pulverized coal of 2380 μm or more was pulverized to 300 μm or less, and then mixed with the previously pulverized coal of 250 μm or less, and this was mixed with water to form a water slurry with a coal concentration of 10 wt%.

This slurry was wet-classified using a 37 μm im[, and the residue on the sieve was collected to determine the overall recovery rate and deashing rate. As shown in FIG. 8 (2), the recovery rate was 80% and the deashing rate was 50%.

Furthermore, kerosene was added to the slurry that passed through a 37 μm sieve in the above classification operation at 1% based on the solid weight in the slurry, and the mixture was stirred with a stirrer and classified using a 37 μm sieve, and the crushed material remaining on the sieve was collected. and its demineralization properties. In Figure 8 (
As shown in 3), high deashing performance was achieved with an overall recovery rate of 95% and a deashing rate of 55%.

〔Effect of the invention〕

As described above, according to the present invention, the amount of oil used is low compared to other deashing methods, so the high-quality coal obtained by the present invention has no agglomeration, and the high-quality coal slurry obtained by the bubble flotation method has no agglomeration. Since the pH is low and it is not acidic, high-quality coal slurry obtained by deashing can be easily converted into a highly concentrated water slurry.

In addition, the deashing operation is simple as it requires only wet classification, and depending on the classification operation, it is only necessary to add inexpensive oil to the slurry of granulated coal, and the amount of oil added to the amount of coal processed is small, so Significant cost reductions can be achieved.

[Brief explanation of the drawing]

Fig. 1 is a diagram showing the influence of slurry pH on slurry viscosity and zeta potential, Fig. 2 is a flow diagram showing one embodiment of the present invention, and Fig. 3 is a flow diagram showing another embodiment of the present invention. Fourth
The figure is a particle size distribution diagram of the pulverized coal used at 0, and Figure 5 is 1.
Figure 6 shows the deashing performance after stage wet classification, Figure 6 shows the deashing performance in Example 1, Figure 7 shows the deashing performance in Example 2, and Figure 8 shows the deashing performance in Example 3. It is a figure which shows the deashing performance for each stage. 1.1.2...Coal, 2,13...Crusher, 3,9
゜14.24... Stirring tank, 4.15... Water tank,
5゜22...Oil tank, 6.16...Water pump, 7
．． 23...Oil pump, 8,17,25...Screen (sieve), 10.21...Good quality coal, 11.26.
...Ash slurry, 18...Coarse granule coal, 19...Medium granule coal, 20...Fine granule coal. Agent Patent Attorney Tatsunokyo Unuma 5 Kuchi 1 Cho 1 Yu Lee hrJ Quantity (F'F Butsuji 1st Dan Ein Z 70 S Prisoner < 1) (Z) '3)

Claims (1)

[Claims] 1. Coal pulverization process, pulverized coal and water are mixed to form a slurry, and oils having a high affinity with carbon content other than ash in the coal are added to this slurry to produce lime. A method for deashing coal, comprising the steps of aggregating carbon content other than ash therein, and wet classifying the agglomerated carbon content. 2. According to claim 1, 2, the step of wet classification is characterized in that the pulverized material remaining on the sieve is recovered as a high-quality charcoal slurry, and the pulverized material slurry that has passed through the sieve is removed as a residue. Coal demineralization method. 3. The coal deashing method according to claim 1, wherein the coal pulverizing step comprises a step of pulverizing the coal to 300 μm or less. 4. The method for deashing coal according to claim 1, wherein the oil is kerosene. 5. In claim 2, oils having a high affinity for carbon other than coal are added to the pulverized slurry that has passed through the sieve, and then wet-classified through the sieve and remaining on the rod. A coal deashing method characterized by recovering pulverized material as a high-quality carbon slurry.