JPS62158792A - Production of highly concentrated coal-water slurry - Google Patents

Abstract

PURPOSE:To produce the titled slurry at low cost without adversely affecting the properties of high concentration and low viscosity despite decreased dispersant usage, adding water, a dispersant, a radial polymerization reaction retarder, etc., to coal and grinding the coal. CONSTITUTION:Added to coal are water and a dispersant (e.g., anionic dispersant), and further at least one member selected from a radical polymerization retarder (e.g., hydroquinone), a radical polymerization inhibitor (e.g., naphthoquinone) and an antioxidant (e.g., 2,4,6-trimethylphenol). The coal is ground in the above-added materials to produce a highly concentrated coal-water slurry. According to this process, the usage of a dispersant can be decreased in the manufacture of a coal-water slurry having a high fluidity. That is, while the dispersant usage ranges from 0.5-1.0% in the past,the usage can be decreased to 0.1-0.2% according to the present process. Thus it is possible to produce a slurry as desired in an economical manner.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to a method for producing a highly concentrated coal-water slurry, and particularly to an economical method for producing the same by reducing the amount of dispersant added in the production.

[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, the above-mentioned slurry transportation technology has been applied to the transportation of 1 coal, and it is safe without problems such as spontaneous ignition of 1 coal or dust scattering, and can be transported via pipes, making it easy to handle and improving transportation efficiency. The development of manufacturing technology for coal-water slurry that can improve the performance of coal-water slurry is actively being carried out.

In the coal-water slurry, the coal transport efficiency can be improved by increasing the coal content as much as possible, and by reducing the water content, the coal-water slurry can be directly combusted without dehydration in the transport machine. Since it has become possible to do so, 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, but in a coal-water slurry, the coal concentration is kept as high 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 increase the dispersibility of the coal particles. A method of lowering the viscosity is known (Japanese Patent Publication No. 56-501568), and there are many methods of producing a highly concentrated and low viscosity coal-water slurry in addition to the above-mentioned publicly known methods. It is based on two basic principles:

The method for producing coal water slurry according to these known examples is (1
) A method in which coal, water, and a dispersant are mixed in predetermined amounts in a wet powder frame using a tube mill to directly produce a highly concentrated coal-water slurry; (2) Coal is powdered into several types of particle sizes and then (3) A tube mill with a low coal concentration in the coexistence of water and a dispersant. There are products that are produced by making the slurry into a wet powder frame and then dehydrating and concentrating the resulting slurry to increase the concentration. Even if any of these methods is used, the coal production degree is 70% by weight or more, and the viscosity is about 1y500 c.
A highly fluid coal-water slurry can be obtained below p.

As described above, the technology for producing a highly concentrated and low viscosity coal-water slurry appears to have been established. However, the main purpose of using coal is to burn it and use it as a cheap fuel, and as mentioned above, it can be made into a fluid to improve safety and operability in transporting and handling coal, and it can also be used to make slurry with high concentration and low concentration. Although it is effective to improve the transport efficiency by making it viscous.

The coal powder frame power and the amount of dispersant required to satisfy the above two basic principles for producing coal-water slurry are real, and with conventional technology alone, coal-water slurry is not necessarily economical. It is hard to say that it has been established as a form of coal utilization.Incidentally, the power cost for the coal powder frame necessary to satisfy the first basic principle varies somewhat depending on the type of coal, but currently it is about 0.2 yen/ 1,0OOKcal, and the cost of the dispersant required to satisfy the second basic principle is currently approximately 0.5 yen/1,000 Kcal, and the total cost of both is approximately 0.7 yen/71,000 cal. 0The price of coal is currently about 2 yen/1,000Kcal,
The powder frame power and dispersant alone in the production of coal-water slurry add about 35% to the cost. In the prior art as already mentioned, the amount of dispersant required to produce the target high concentration, low viscosity coal water slurry is 0.01 to 5.0% by weight based on dry coal. However, according to experiments, the amount of dispersant required to produce, for example, a coal-water coal slurry with a coal concentration of 70 deuterium and a viscosity of L500 c p by a known method is about 1% by weight, and if the amount is reduced below this amount, The viscosity increased dramatically, and it was confirmed that a fluid slurry could not be obtained. As described above, the technical issue of reducing the manufacturing cost of coal-water slurry has not yet been solved.

[Purpose of the invention]

affection In view of the above circumstances, the object of the present invention is to provide high concentration.

It is an object of the present invention 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 low viscosity properties.

[Summary of the invention]

The method for producing a highly concentrated coal-water slurry according to the present invention involves adding water and a dispersant to coal, and further adding at least one of a radical polymerization reaction suppressor, inhibitor, or antioxidant. After that, the coal to which water and the above-mentioned substances have been added is powdered.

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

As a result, as mentioned above, it is difficult to reduce production costs as long as production is carried out using conventional methods, and in particular, as mentioned above, the amount of dispersant added is approximately 1 weight per dry coal. It became clear that it was not possible to reduce it below %.

Considering the specific surface area of coal and the adsorption characteristics of the dispersant to coal, the addition amount of about 1% by weight is a very large amount.
8 The present inventors found that the amount was several tens of times more than that required to form a monomolecular layer on the surface of coal.

We conducted repeated research in the belief that by investigating the cause of the need for such a large amount of dispersant, we would be able to obtain suggestions on how to reduce the amount of dispersant used. Hereinafter, the progress that led to the present invention will be explained.

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, as mentioned above, the dispersant was added to disperse the coal particles. We need to improve our sexuality. 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 in its pores, but when it is immersed in water in the coexistence of a dispersant, as in the production of coal-water slurry, it dissolves in water at the same time as it absorbs water. It is thought that the dispersant contained in the coal is also absorbed into the coal and adsorbed on its walls.

It is thought that the total surface area of the pores developed inside the particles is considerably larger than the outer surface area of the particles, and therefore it is thought that most of the dispersant is adsorbed on the pore walls 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 dispersing agent for several types of coal with different pore distributions (
When we investigated the properties of adsorption of anionic substances (containing naphthalene rings), we obtained the results shown in Figure 1.We found that the equilibrium adsorption amount of dispersants on various types of coal is proportional to the specific surface area of the coal. It shows. 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 2 shows the adsorption isogen of one of the coal types, and it can be seen that the dispersant has a Freundlich-type adsorption to the coal, and when the concentration in the liquid increases to a certain extent, the amount of adsorption reaches saturation. Even if a dispersant is added above this saturated adsorption point.

It is not adsorbed by coal, and its concentration in the liquid only increases. Here, the points indicated by black circles in Figure 1 indicate the points when 0.5% by weight of the dispersant was added to the coal in the coal-water slurry with a concentration of 70%.

As can be seen 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. This indicates that there is another reason why a large amount of dispersant is required.

In order to investigate the cause of this, the inventors prepared and investigated various coal water slurries. In the process of this study, we discovered the following new fact, which will be explained using an example.

First, coal-water rallies with various particle size distributions were prepared for investigation. As previously mentioned, the coal was mixed with water and a dispersant, and the mixture was packed into a tube mill and milled to form a slurry. The tube mill was filled with coal that had been pulverized in advance to a maximum particle size of about 50 μm as shown in FIG. 3a. Furthermore, an anionic dispersant was added in an amount of 0.3% by weight based on the dry coal. Powder frame for 30 minutes.

The particle size distribution of coal in the slurry produced after 60 minutes and 120 minutes is shown in Figure 3, c and d.

When the powder time is 30 minutes, the coal particles in the slurry are considerably smaller than the raw coal. It can be seen that the powder frame is further reduced when the powder frame time is 60 minutes.

However, even if the powder frame time 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 shown in FIG. 3C is at the limit of the powder frame 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, those in Figure 3 were 1.33 rrr/g, c was 1.51 rrr/g, and d was 1.58 i/g. Ta.

As described above, it was found that the particle size distribution and outer surface area of coal in a slurry prepared using coal that had been pulverized in advance did not change significantly even if the pulverization time was changed. However, as discussed below, the flow characteristics of these slurries were found to vary widely. Figure 4 a, b,
Q is the wet powder frame time by tube mill of 30 and 6, respectively.
The flow curve of the slurry at 0°120 minutes is shown. Figure 5 shows the shear rate of each slurry at 18g-1.
The apparent viscosity at is plotted against the powder window time. It was found that as the powder time in the wet tube mill increases, the flow characteristics of the slurry change from dilatant and thixotropic to pseudoplastic and rheopexic, and at the same time, the apparent viscosity increases significantly.

The above flow characteristic test results can be interpreted as follows from the knowledge of colloid chemistry accumulated up to now.

The flow characteristics of the slurry as targeted by the present invention are as follows:
It is greatly affected by the state of dispersion and agglomeration of the particles present within it. Generally, in slurries with well-dispersed particles,
Slurries that exhibit dilatant and thixotropic flow characteristics and a large degree of agglomeration per particle exhibit coagulation-plastic and rheopexic properties.From this, the slurry produced as described above has coal particles when the powder time is 30 minutes. were well dispersed, suggesting that as the powder window time increased to 60 and 120 minutes, the cohesiveness of the coal particles increased for some reason. As already mentioned, the outer surface area of the coal particles does not change significantly with the above-mentioned powder time, and the amount of the dispersant added is 0.5% by weight based on the dry coal, which increases the adsorption capacity predicted from the specific surface area of the coal. It exists in large excess. Therefore, it is clear that the reason why the cohesiveness of the coal particles becomes higher as the powder frame time becomes longer is not because the amount of dispersant is insufficient.

The present inventors have determined that the slurry is
The reason for the change in properties and the increased viscosity of the slurry as it was kept in the powder frame for a long time was thought to be that the dispersant changed in quality in the powder frame due to a chemical reaction and the dispersion effect decreased. When a new surface of coal is generated during the powder frame process, molecules near the surface are cleaved and highly reactive radicals are generated. The dispersant used in the slurry is a high molecular weight polymer that reacts with the radicals generated on the new surface of the coal.
It is thought that the dispersant molecules further reacted and changed into a substance with no dispersing effect. This is commonly known as a mechanochemical reaction. if.

If the above-mentioned reaction occurs in the powder frame and the dispersant changes in quality, it is possible to prevent such dispersion by deactivating the radicals formed on the new surface of the coal by some method before reacting with the dispersant. It is believed that this prevents deterioration of the agent, keeps the coal particles in the slurry in a highly dispersed state with a small amount of addition, and makes it possible to produce a low-viscosity slurry. This means that the amount of dispersant required to reduce the viscosity of a 1-coal-water slurry can be reduced and an economical slurry can be produced.

[Embodiments of the invention]

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

<Example 1> Dry powdered charcoal having the particle size distribution shown in Figure 3a was wet-processed for 2 hours using a ball mill with water added as a dispersant (anionic) and hydroquinone as a radical polymerization inhibitor. I made a powder frame. The table below summarizes the amount of dispersant and hydroquinone added during the powder frame.

All tests involved mixing coal and water such that the coal concentration in the slurry was 63%. All of the prepared slurries exhibited very good fluidity, and when their flow properties were measured, all of the slurries showed the flow curve shown in Figure 4a. Figure 4G
As mentioned above, the slurry with the fluidity characteristics shown in Figure 1 was made into a powder frame with the addition of 0.5% dispersant and no radical inhibitor; Although the amount was small, the coal particles were very well dispersed, proving that the inventors' idea previously described was correct. What should be noted here is that a slurry with high fluidity can be obtained even if the amount of dispersant is 0.2%, and that the amount of hydroquinone is only 0.2% compared to dry coal.
Even at 0.03%, it shows a very high effect.

<Example 2> A test was conducted under exactly the same conditions as in Example 1 using naphthoquinone, which is an inhibitor of radical polymerization reaction, as a radical inhibitor, and the same results as in Example 1 were obtained.

<Example 3> Antioxidant 2゜4.6 under exactly the same conditions as Example 1
- A test using trimethylphenol was conducted, Example 1
obtained similar results.

In addition, P-
Pesozoquinone, diphenylamine, N-phenyl-N'
-isopropyl-P-phenylenediamine, 6-ethoxy-2.2.4-trimethyl-1,2-dihydroquinoline, nitrobenzene, etc. are effective.

In addition, as an inhibitor of radical polymerization reaction, 2,
4-dinitrochlorobenzene, 2,2-diphenyl-1
- Picrylhydrosyl, glylated hydroxyanisole,
α-Naphthylamine, N-nitrosophenylhydroxyamine, etc. are effective.

Furthermore, as an antioxidant, 2,4-dimethyl-6
Effective examples include -tsrt-butylphenol, 2-tert-butyl-4-n-butylphenol, phenyl-β-naphthylamine, phenoazine, N-methyl-N-nitrosoaniline, and 2-tert-butylhydroquinone.

〔Effect of the invention〕

According to the present invention, the amount of dispersant added is effective in reducing the amount of dispersant in the manufacturing process of highly fluid coal-water slurry. The amount of dispersant added varies depending on the properties of the coal used in the slurry, but is usually 0.5 to 1. .0% is added. The added amount of the drug according to the present invention is 0.01% to 0.1%, and the amount of the dispersant is 0.1% to 0.2%.
can be reduced to Therefore, the cost for additives varies depending on the unit price of each additive, but by applying the present invention,
It is possible to reduce it to 1/2.

[Brief explanation of drawings]

Claims (1)

[Claims] 1. Water and a dispersant are added to coal, and at least one substance selected from a radical polymerization reaction suppressor, inhibitor, or antioxidant is added, and then, A method for producing a highly concentrated coal-water slurry, which comprises powdering coal to which these water and the above-mentioned substances have been added. 2. As an inhibitor of radical polymerization reaction, hydroquinone, P-benzoquinone, diphenylamine, N-phenyl-N'-isopropyl-P-phenylenediamine, 6-
The method for producing a highly concentrated coal-water slurry according to claim 1, characterized in that at least one of ethoxy-2,2,4-trimethyl-1,2-dihydroquinoline and nitrobenzene is used. 3. Naphthoquinone as an inhibitor of radical polymerization reaction,
A patent characterized in that at least one of 2,4-dinitrochlorobenzene, 2,2-diphenyl-1-picrylhydrosyl, glylated hydroxyanisole, α-naphthylamine, and N-nitrosophenylhydroxyamine is used A method for producing a highly concentrated coal-water slurry according to claim 1. 4. As an antioxidant, 2,4,6-trimethylphenol, 2,4-dimethyl-6-tert-butylphenol, 2-tert-butyl-4-n-butylphenol, phenyl-β-naphthylamine, phenoazine, N-
The method for producing a highly concentrated coal-water slurry according to claim 1, characterized in that at least one of methyl-N-nitrosoaniline and 2-tert-butylhydroquinone is used.