JPS62116690A - Production of coal-water slurry - Google Patents

Abstract

PURPOSE:To produce at low cost a coal-water slurry of high concn. and low viscosity, by adding water and a dispersant to a coal pulverized so as to have a predetermined particle size distribution and then agitating so as to maintain the particle size distribution before addition of the dispersant, thereby minimizing the use of the dispersant. CONSTITUTION:Coal is pulverized in a mill 1 for about 30min, and caused to pass through a classifying device 2 so as to obtain a coal having a particle size distribution with a maximum particle size of about 50mum. The coal, together with water, is introduced in a wet mill 3, in which the coal is wet pulverized. The resulting coal is fed into a mixer 4, and a dispersant comprised of at lest one compd. selected from among org. anionic surfactants, nonionic surfactants and inorg. ionic compds. is added in an amt. of 0.01-5.0wt% based on the dry weight of the coal. Alternatively, coal is processed through the mill 1 and the classifying device 2 and fed into the mixer 4, in substantially the same manner as described above. The above-mentioned dispersant is added in the above-mentioned amt. to obtain a slurry. After addition of the dispersant, mixing under agitation is conducted while maintaining the coal particle size distribution before addition of the dispersant without pulverizing coal to a coal-water slurry.

Description

[Detailed description of the invention] [Field of application of the invention] The present invention relates to a method for producing a coal-water slurry, and more particularly.

The present invention relates to an economical manufacturing method that reduces the amount of dispersant added in the manufacturing process.

[Background of the invention]

Powder slurry transportation technology has been studied for a long time as a method for transporting solid powder in a fluid state that is easy to handle. In recent years, this slurry transportation technology has been applied to the transportation of coal, and it is safe without problems such as spontaneous combustion or dust scattering, and can be transported through pipes, making it easy to handle.

BACKGROUND ART The development of manufacturing technology for coal-water slurry that can improve transportation efficiency is being actively conducted.

The coal-water slurry can improve the transport efficiency of coal by increasing the coal content as much as possible (by increasing the coal content as much as possible), and by reducing the moisture content.

Since it is possible to directly burn the coal-water slurry without dehydration after transporting it, a high concentration technology has been developed to increase the coal concentration in the coal-water slurry. It is a well-known fact that increasing the solids concentration in a slurry increases its viscosity.In the case of coal-water slurry, the coal concentration should be kept as low as possible while keeping the viscosity low enough to allow pipe transportation. Firstly, the particle size distribution of the coal particles in the coal-water slurry is adjusted to increase the concentration, and secondly, a dispersant is further added to improve the dispersibility of the coal particles. A method of lowering the viscosity by increasing the concentration is known (Japanese Patent Publication No. 501568/1983).

Many methods for producing coal-water slurry with high concentration and low viscosity have been disclosed in addition to this known example, but all of them are based on the above two basic principles.

The method for producing coal water slurry according to these known examples includes (1)
A method in which coal, water, and a dispersant are mixed in predetermined amounts and then wet-pulverized in a tube mill to directly produce a high-concentration coal-water slurry. After wet grinding, the resulting slurry is dehydrated and concentrated to make it highly concentrated. By any of these methods, a highly fluid coal-water slurry having a coal concentration on a 70-weight plate and a viscosity of about 1.500 cp or less can be obtained.

In this way, the technology for producing a highly concentrated and low viscosity coal-water slurry appears to have been established. However, by improving the safety and operability of transporting and handling fluidized coal, and by making the slurry highly concentrated and low in viscosity.

Improving its transportation efficiency is effective, but the amount of coal crushing power and dispersant required to satisfy the two basic principles for producing coal-water slurry is enormous; ° It cannot be said that coal-water slurry has necessarily been established as an economical form of coal utilization using only conventional technology. By the way, the coal crushing power cost required to satisfy the first basic principle varies somewhat depending on the type of coal, but at present it is approximately 0.2 yen/1.000 K cal, which is the basic cost of p, g2o. Currently, the cost of the dispersant required to satisfy imt is approximately 0.5 yen/1.000 Kcal, and when both are combined, the cost is 0.7 yen/1.000 Kcal. Since the price of coal is currently about 2 yen/1.000 Kcal, the cost will increase by about 35% just for the crushing power and dispersant in producing one coal-water slurry. In conventional technology, the amount of dispersant required to produce the target high concentration, low viscosity coal water slurry is said to be 0.01 to 5.0% by weight of dry coal, but in experiments According to known methods.

For example, the amount of dispersant required to produce a coal-water slurry with a coal grade of 70 weight and a viscosity of 1.500 cp is approximately 1 weight. It was confirmed that a certain slurry cannot be achieved. As described above, the technical issue of reducing manufacturing costs for single-coal-water slurries has not yet been resolved.

[Purpose of the invention]

An object of the present invention is to provide a method for producing a coal water slurry that reduces the amount of dispersant required for producing the coal water slurry without impairing its properties of high concentration and low viscosity.

[Summary of the invention]

The present invention is a method for producing a coal-water slurry consisting of pulverized coal, water, and a dispersant. The coal in this slurry is not crushed after the addition of the dispersant, but is characterized in that it has the same particle size distribution as before the addition of the dispersant.

The inventors of the present invention have conducted intensive research on a method for producing a coal-water slurry at low cost by reducing its high concentration and viscosity technology, dispersant, and crushing power.

As a result, as mentioned above, it is difficult to reduce production costs when manufacturing using conventional methods, and as mentioned above, the amount of dispersant added is about 1% per dry coal.
It became clear that it was impossible to reduce the weight below the weight factor.

Considering the surface area of coal and the adsorption focus of the dispersant on coal, the addition amount of about 1% by weight is a very large amount.
The amount is several tens of times higher than that required to form a monomolecular layer on the surface of coal. The inventors have conducted repeated research in the belief that by investigating the reason why such a large amount of dispersant is required, suggestions regarding methods for reducing the amount of dispersant can be obtained.

The inventors first investigated the adsorption properties of the dispersant to coal. In order to make the coal water slurry highly concentrated and low in viscosity, it is necessary to add a dispersant to improve the dispersibility of coal particles. However, current knowledge of colloid chemistry indicates that it is sufficient to disperse the particles if the dispersant is adsorbed only on the outer surface of the particles. However, coal is a porous substance, and many pores are formed inside the particles. As is well known, coal absorbs water within its pores.

When coal is immersed in water in the coexistence of a dispersant, as in the production of coal-water slurry, it is thought that the dispersant dissolved in the water is absorbed into the coal at the same time as the water is absorbed, and is adsorbed on its wall surface. The total surface area of the pores developed inside the particles is considered to be considerably larger than the outer surface area of the particles, and therefore it is considered that most of the dispersant is adsorbed on the walls of the molecular fi pores and exists inside the particles.

If this is true, judging from the knowledge of colloid chemistry mentioned above, most of the dispersants (those adsorbed on the pore walls)
This means that the particles are not effectively dispersed. The inventors developed a dispersant for several types of coal with different pore distributions (
When we investigated custom-made adsorption of anionic products (having naphthalene rings), we obtained the results shown in Figure 2. It has been shown that the equilibrium adsorption amount of dispersant onto various types of coal is proportional to the specific surface area of the coal. This result shows that the above assumption is correct and that a large amount of dispersant is adsorbed on the inner walls of the pores.

Figure 3 shows the adsorption isotherm of one of the coal types, and it can be seen that one dispersant causes Freundlitz type adsorption to coal, and when the concentration in the liquid increases to a certain extent, the amount of adsorption reaches saturation.

Even if the dispersant is added above this saturated adsorption point, it will not be adsorbed by the coal and the concentration in the liquid will only increase. Here, the points indicated by black circles in the figure are! The points are shown when 0.5% by weight of a dispersant is added to 1 coal in a coal-water slurry with an I degree of 70%. As is clear from this result, the amount of dispersant added to a normal coal-water slurry is much larger than the saturated adsorption amount on the entire surface of the coal, including the pore walls, as described above for one coal-water slurry. The need for a large amount of dispersant indicates another cause.

In order to investigate the cause of this, the inventors prepared and investigated various coal water slurries. In the process of this investigation, we discovered the following new facts.

First, coal-water slurries with various particle size distributions were prepared for investigation. As described above, one coal was mixed with water and a dispersant, and the mixture was filled into a tube mill and pulverized to prepare a slurry. The coal filled in the tube mill was previously pulverized to a maximum particle size of about 50 μm, as shown in FIG. 4a. In addition, as a dispersant, an anionic dispersant was added at 0.3 parts per dry coal. Grind 30
The particle size distribution of coal in the slurry produced when the heating was carried out for 1, 60 minutes, and 120 minutes is shown in FIG. 4, c, and d. When the grinding time was 30 minutes, the coal particles in the slurry were much smaller than the raw coal. In addition, when the grinding time is 60 minutes,
It can be seen that it is finely pulverized.

However, even if the grinding time e is increased to 120 minutes, there is not much difference from the case of 60 minutes, and it is considered that the particle size distribution of C in FIG. 4 is at the grinding limit of the tube mill used in this test. Calculating the outer surface area of the coal particles in each slurry from these particle size distributions, the one in b in Figure 3 is 1.33i/g, and the one in c is 1.
．． 51yd/g, d is 1, 58 rr? /g.

Thus, it was found that the particle size distribution and outer surface area of coal in a slurry prepared using previously pulverized coal did not change significantly even if the pulverization time was changed. However, as discussed below, the flow customization of these slurries has been found to vary widely. a, b, c in Figure 5 are
Wet grinding time by tube mill is 30, 60, 1, respectively.
The flow curve of the slurry for 20 minutes is shown. Figure 6 shows the apparent viscosity of each slurry at a shear rate of 188'' plotted against the grinding time.The longer the grinding time with the wet tube mill, the more the custom slurry flow changes from giratant and thixotropic curves to pseudoplastic. At the same time, the apparent viscosity was found to increase significantly.

The results of this custom flow test can be interpreted as follows based on the knowledge of colloid chemistry that has been accumulated to date. In other words, customizing the flow of slurry, which is the object of the present invention, is greatly influenced by the state of dispersion and agglomeration of the particles present therein. In general, slurries with well-dispersed particles exhibit dilatant and chikuntropic flow customization, while slurries with large particle cohesion exhibit pseudoplastic and rheopectic flow characteristics. From this, it can be seen that in the slurry produced as described above, coal particles are well dispersed when the grinding time is 30 minutes, but as the grinding time increases to 60, 120 minutes, the coal particles are agglomerated due to some reason. It is suggested that the beatings increased. As already mentioned, the outer surface area of one coal particle does not change significantly with the above-mentioned pulverization time, and the adsorption capacity predicted from the specific surface area of the coal is that the added dispersant is 0.5% by weight based on the dry coal. It exists in large excess. Therefore, it is clear that the reason why the cohesiveness of the coal particles becomes higher as the grinding time becomes longer is not because the amount of dispersant is insufficient.

The present inventors discovered that, as mentioned above, the properties of cisurari change depending on the grinding time, and as the grinding time increases.

The reason for the high viscosity of the slurry was thought to be that the dispersant 1 was altered by a chemical reaction during grinding, resulting in a decrease in the dispersion effect. During the pulverization process, a new surface of coal is generated, and molecules near the first surface are cut off, producing highly reactive radicals.

The dispersant used in the slurry is a high molecular weight polymer.

It is thought that the dispersant molecules reacted with the radicals generated on the newly formed surface of the coal, caused further reactions, and turned into a substance with no dispersing effect. This is commonly known as a mechanochemical reaction. If such a reaction occurs during grinding and the quality of the dispersant changes, then measures should be taken to prevent this change in order to reduce the amount of the dispersant added. . The radicals generated on the new surface have extremely high reactivity, so even in the absence of a reactive substance such as a dispersant, they react with oxygen etc. dissolved in the medium and turn into stable substances. It is thought that then. Based on the above considerations, 0 coal was pulverized in the absence of a dispersant and left until the highly reactive radicals on the newly formed surface changed to stable ones, that is, 1
By adding a dispersant after the coal surface is ray-sung and preventing the formation of a new surface of the coal, 1.
It is believed that deterioration of the dispersant is prevented, and therefore sufficient fluidity can be given to the slurry by adding a small amount.

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

[Embodiments of the invention]

<Example 1> The coal is finely ground to 37μm or less using a dry process in advance.

Wet milling was carried out in the presence and absence of a dispersant. Hereinafter, the slurry prepared by pulverization in the presence of dispersant A1 and the slurry prepared by pulverization in the absence of dispersant A1 will be referred to as B. Slurry A has a coal concentration of 5
Water was added to give a dispersant of 7.5 wt%, 5 wt% of an anionic naphthalene sulfonic acid dispersant was added to the dry coal, and the mixture was ground in a ball mill for 1 hour. Slurry B has a coal concentration of 56.3wt.
%, but without adding a dispersant, it was prepared by milling in a ball mill for 3 hours. The particle size distribution of coal in the slurry was the same in both cases.

The flow curves of these two slurries are shown in FIG.

However, after wet pulverizing slurry BK, the same dispersant used in preparing slurry Oita was added to dry coal.
0.5 wt% was added. Slurry A has a large yield value and exhibits pseudoplastic fluidity, whereas slurry B does not have a yield value and exhibits giratant properties.

The relationship between the customization of slurry flow and the dispersibility of solid particles in the slurry has been known for a long time, and from the results shown in Figure 7, the dispersibility of particles in slurry A is poor and one particle aggregates. It forms aggregates.

On the contrary, it can be seen that the particles in Sura'JB are very well dispersed. Here, the only difference between slurries A and B is whether the dispersant was added and pulverized or whether it was added after pulverization. From the results of this example.

If a dispersant coexists during coal pulverization, the effect of the dispersant becomes smaller. In other words, it became clear that the dispersant had been altered and deteriorated.

<Example 2> A slurry was prepared using the same coal as in Example 1, and the influence of the amount of dispersant added was studied. In this example, the particle size is 3rt.
! Coal that had been roughly pulverized to less than R was wet-pulverized in a ball mill with water added to a concentration of 58.1 wt% to prepare a slurry. Slurry C was wet-pulverized after adding a predetermined amount of dispersant.

In addition, slurry 1) D was prepared by pulverizing without adding a dispersant and then adding a dispersant later. The maximum particle size of coal particles in Sura IJ C and D is approximately 300μ.
Both had the same particle size distribution. What is the coal concentration in the slurry used for viscosity measurement?

Both slurries C and D were bound at 58.1 wt%. The same dispersant as in Example 1 was used. FIG. 8 shows the relationship between the amount of dispersant added and the viscosity of the slurry. The slurry viscosity of IJC prepared by adding a dispersant and pulverization decreases as the amount of dispersant increases, and becomes a nearly constant value when the amount of addition is Q, 8wt96 or more. On the other hand, slug I to which dispersant was added after crushing
In JD, the slurry viscosity is approximately constant when the amount added is 0.1 wt% or more. This means that in Slurry D, approximately Q, 1 wt% of dispersant is sufficient to disperse the coal particles, while Slurry C requires approximately 0,8 wt%. That is, in sura IJC, it is approximately 0.
This indicates that the 7wt1 additive has deteriorated and deteriorated.

This confirms that the thinking of the present inventors, which has already been stated, is correct. From these results, it is clear that the amount of dispersant added can be greatly reduced by preparing the cis slurry according to the method of the present invention.

<Example 3> Using the same coal as in Example 2, slurry E,
F was prepared. Slurry E was prepared by adding 0.2 wt % of a dispersant and wet milling using a ball mill. Slurry F is wet-pulverized without adding a dispersant, and then the dispersant is added to the slurry IJ.
It was prepared by adding the same amount as E.

The same dispersant as in Example 1 was used. Sura! J
Figure 9 shows the relationship between the viscosity of E and F and the coal concentration. As is clear from Figure 9, for example, the viscosity is 1000m100O
, slurry F has a coal concentration of about 5w compared to slurry E.
t% can be increased.

In this way, according to the present invention, 1 dispersant is added after 1 coal is crushed in advance and adjusted to a predetermined particle size, and 1 dispersant is added by not increasing the outer surface area of the coal particles thereafter. or increase the concentration of slurry.

As is well known, a highly concentrated coal-water slurry does not exhibit fluidity without a dispersant. Currently, a method is used in which two coals, water, and a dispersant are mixed in predetermined amounts and wet-pulverized using a tube mill to directly produce a highly concentrated coal-water slurry, but in this method, the method of the present invention is applied. It is not possible.

This is because, as mentioned above, when high-concentration wet milling is performed without adding a dispersant, the slurry shows no fluidity at all, and therefore the slurry is not inserted into the tube mill, making continuous operation of the mill impossible. This is because it will not be possible. In addition, if there is no fluidity, pulverization using a tube mill will not be possible. Therefore.

When this method is applied, the slurry in the mill must be diluted to exhibit fluidity even in the absence of a dispersant, pulverized at a low concentration, concentrated, and then a dispersant added. benefits are reduced. The method of the present invention can be most efficiently applied to the process shown in FIG. After the coal is dry coarsely pulverized in the mill 1, it is passed through the dispersion machine 2.
The coarse particles are classified by tube mill 3 according to the predetermined particle size.
where water is added and wet-pulverized to form a fine slurry. Here, low-concentration pulverization is performed without adding a dispersant. The prepared fine particle slurry is mixed with the previously separated dry pulverized particles in a mixer 4. At this point, a dispersant is added for the first time, creating a highly concentrated coal-water slurry. By doing so, it is possible to economically prepare a highly concentrated coal-water slurry by the method of the present invention without performing operations such as dehydration and concentration.

〔Effect of the invention〕

According to the present invention, since there is no deterioration in quality of the dispersant during slurry preparation, it is possible to reduce the amount of the dispersant added and improve the economical acidity of the coal-water slurry.

[Brief explanation of drawings]

FIG. 1 is a system diagram showing the manufacturing process of an embodiment of the present invention, FIG. 2 is a diagram showing the specific surface area of coal and the adsorption amount of dispersant,
Figure 3 is a diagram showing crosstalk such as adsorption of coal/dispersant, Figure 4
The figure shows the particle size distribution of the tested coal and the coal in the slurry, and Figure 5 shows the flow curve of the slurry produced in the test.
Figure 6 shows the relationship between slurry viscosity and grinding time, Figure 7
8 is a graph showing the results of Example 1, FIG. 8 is a graph showing the results of Example 2, and FIG. 9 is a graph showing the results of Example 3. 1... Mill, 2... Classifier, 3... Wet mill, 4
...Mixer.

Claims (1)

[Claims] 1. A method for producing a coal-water slurry consisting of pulverized coal, water, and a dispersant, including adding the dispersant to a mixture of the coal and the water that have been pulverized in advance to a predetermined particle size distribution. Alternatively, the water and the dispersant are added to the pulverized coal and stirred to form a slurry, and after the addition of the dispersant, the coal in the slurry is not pulverized and is the same as before the addition of the dispersant. A method for preparing a coal-water slurry characterized by having a particle size distribution of 2. In claim 1, at least one compound selected from an organic anionic surfactant, a nonionic surfactant, and an inorganic ionic compound is used as the dispersant in an amount of 0.0% per dry weight of coal. 01
A method for preparing a coal water slurry characterized by using ~5.0 weight.