DE3225784C2 - Process for producing a pulp of coal - Google Patents

Abstract

A pulverized coal of high concentration but low viscosity was prepared by classifying pulverized coal into two or more groups (1, 3) of different particle size ranges, mixing these two or more groups (1, 3) of coals of different particle size ranges in such proportions that the void ratio of 30 or less was found in the mixture, and a medium (2) for forming a pulp was added to this coal mixture, thereby making it possible to reduce the pulp transport cost.

Description

35

The invention relates to a method for producing a Kohietrübe.die is easy to transport.

Techniques for transporting powder in the form of a slurry have long been used as a means of transport of solids in a liquid state that is easy to handle. Turbidity transport is important in the chemical industry and is currently used in various fields. However it is necessary when transporting turbidity, those with a solids concentration of up to about 50, at most 55% by weight taking into account the problems that arise with the wear of the pipes, the pumps and the set other parts of the system to use. F i g. 1 shows viscosities of pulp from coal in FIG Water, the coal was pulverized to particle sizes of up to 62 μm (250 mesh), depending on Concentrations of coal in water, d. H. the weight (g) of the coal in 100 ml of water. One notices that the viscosity of the slurry increases rapidly with an increase in the coal concentration. The viscosity of a The pulp which can practically be transported as a fluid is a maximum of about 1 Pa · s. As in FIG. 1 shows this corresponds to viscosity of 1 Pa · s of the pulp, a coal weight of about 90 g per 100 ml of water or a coal concentration of about 48% (w / w). It was a significant disadvantage of the haze transport that it had to be used Clouds contain large amounts of water or other clouding medium. This disadvantage affects not so much the transport of small amounts of powder, but seriously the transport of fuels such as e.g. B. Coal, in large quantities at a time; for example, this increases fuel transport costs each time Thermal unit value. In particular, there is a separation when transporting fuel cabbage in water the coal from the water taking into account the combustion properties the coal required. So coal concentration was a major problem to increase in a turbidity.

A solution to the above problem in connection with the transport of pulp of fine coal sees propose to regulate the particle size distribution as in the application PCT / US80 / 01419 (international laid-open number WO81 / 01 152, April 30, 1981) is given. While the general, the »cumulative weight percentage of particles under a certain dimension "representing in this patent application given formula was derived under the assumption that coal particles are spherical the charcoal actually not be spherical. Consequently, it is not always true that coal has a particle size distribution which satisfies the formula with the cumulative percentage by weight, a pulp of high coal concentration results.

Another method of regulating the particle size distribution of coal is described in US Pat. No. 3,762,887. This patent specifies the particle size distribution very precisely as 0% by weight over 4.7 mm clear sieve mesh size (4 mesh Tyler standard sieve), 18 to 33% by weight below 0.043 mm clear mesh size, less than 60% by weight between 4.7 and 0.64 mm clear mesh size and the remainder in the particle size range from 0.64 to 0.043 mm clear mesh size fixed. Taking into account the awkwardness and difficulty of making coal with a The process according to this US patent cannot be used in practice for such a precise particle size distribution.

The invention is based on the object of developing a method for producing a carbon drive, which enables the lowering of the viscosity of the pulp to a considerable extent even if the pulp contains a high concentration of coal, thereby reducing the cost of transporting the pulp.

This object is achieved in a method for producing a pulp of coal, in which pulverized coal is used classified into two or more groups of different particle size ranges, these groups in certain proportions mixed and the coal mixture adds a liquid to form the coal pulp according to the invention solved in such a way that one has the two or more groups of coals of different particle size ranges mixed in such ania that there is a void portion of 30% or less results, and by the addition of the liquid a carbon content of the pulp of 55 to 85 wt .-% adjusts.

The upper limit of the maximum particle size is preferably sufficient of the classified coal up to 1 mm in diameter.

The ratio of the minimum particle size of the coal in the pulp to the maximum particle size is expedient up to 0.5.

The cloud medium advantageously contains a surface-active agent or dispersant.

The invention is explained in more detail with reference to the exemplary embodiments illustrated in the drawing; in it shows

1 shows a diagram to illustrate the dependency the pulp viscosity from the coal concentration in the usual coal pulp;

F i g. 2 (a) to (c) a schematic representation for Illustration of the changes in the coal particle

package looks in the usual coal cloud, if the coal concentration is increased;

FIG. 3 is a schematic diagram showing a coal particle package appearance in FIG a pulp of coal which has been subjected to regulation of particle size distribution;

F i g. 4 is a diagram showing the dependence of the void fraction on the mixing fraction of the Coarse-particle coal in coal mixtures which have been subjected to regulation of particle size distribution; and

F i g. 5 is a diagram showing the dependency the pulp viscosity from the mixing proportion of the coarse-particle coal in coal mixtures, the regulation the particle size distribution were subjected.

The inventors considered the following reason for the fact that, according to the prior art, the solids concentration, d. H. the coal concentration, in the pulp, not without a rapid increase in the pulp viscosity can be increased: Coal particles in a turbidity apparently approach the densely packed state under the action of the surface tension of the turbidity medium, when the coal concentration meiir and more increases. During this process, as shown in FIGS. 2 (a) to (c) shows an aggregation of the coal particles 1, since the liquid 2 is removed in the form of water between the coal particles, so that the fluidity of the slurry is reduced and the viscosity of the slurry increases rapidly. The cavity between Coal particles in a tightly packed state are none of the usual coal particles in the case of turbidity Particle size distribution control have been subjected, 30 to 45%.

Therefore, in order to avoid this rapid increase in viscosity, the inventors tried to use small particles of coal 3, as in FIG. 3 is shown between in FIG. 2 to insert coal particles 1 shown to the cavity to reduce, whereby the spaces between the coal particles are filled with water. So it was, she successful in increasing the coal concentration while keeping the pulp viscosity at a low level and have also been successful in reducing the slurry viscosity through additive a surface active agent or dispersing agent for turbidity for the purpose of reducing surface tension of the water and improving the affinity of the coal for the water, whereby the coal particles readily become wettable with the water.

4 shows the dependence of the void fraction the mixing ratio, d. H. on the proportion of coarse particle charcoal, if coarse particle charcoal of one particle size of 1 mm mixed with fine particle carbon with a particle size of 37 to 44 μm in various ratios will. It turns out that. when two groups of coals of different particle sizes interrelate are mixed, the void space with a proportion of the coarse particle coal of about 70 wt .-% Minimum reached.

5 shows the dependence of the pulp viscosity on the proportion of the mixture of the coarse-particle coal when pulp a solids concentration of 55% by weight using the in FIG. 4 shown coal mixtures were manufactured.

The in F i g. 5 and the pulp viscosity shown in F i g. The void fraction shown in Fig. 4 shows the same tendency, which supports the inventors' assumption that the Triibenviskosity is kept low by regulating the particulate size distribution and the Mixes particles so that a state of closely packed particles is obtained. The reason for the fact since "the pulp viscosity becomes minimal at the minimum of the void fraction, it appears to have a lubricating effect to be based on the turbidity medium, as shown in FIG. 3 shows, is evenly distributed between the solid particles, since the void fraction is reduced.

When the pulp produced in this way is highly concentrated and has a low viscosity. the ratio of the finest to the coarsest coal particles (smallest particle size / largest particle size) is preferably made very low, ie up to 0.5. For example, if the largest coal particle size is 10mm. the smallest particle size is preferably up to 5 mm; when the former is 1 mm, the latter is preferably up to 0.5 mm. However, the largest particle size of the coal cannot be freely increased, but is limited mainly because of the settling of coal during the transportation or storage of the pulp, which occurs more and more as the largest particle size increases. From this point of view ΪΛ the largest particle size preferably only up to 1 mm.

Although the above description only applies to the case of mixtures of two different coal groups Particle size ranges are addressed, the cases of mixtures of three or more differ more coal groups essentially, not from the above case, and become more of practical use preferred. As for the turbidity medium, it is, though the above description only covered the cases of water, the replacement of water by other inorganic ones Solvents (e.g. liquid ammonia and liquefied carbon dioxide) and organic solvents (e.g. methanol and kerosene) have the same effect.

The viscosity of the coal pulp can be reduced to a large extent by mixing two or more groups of coals with different particle size ranges are used to form a cavity of 30% or less of the mixture when considering the viscosity with the usual, no such regulation the particle size distribution subject coal compares, so that the pulp transport costs let lower.

The invention will be described in detail with reference to the following Examples presented: In these examples mixtures of three or more groups of coals were used different particle size ranges and a surfactant are used for each slurry sample. However, as already mentioned, the use of mixtures of two groups of coals is also covered different particle size ranges with or without surfactant also in the range the Erfii.vJi-.ng.

55

60

65

example 1

After coal was crushed and classified, groups of coals with particle size ranges were found from 701-589 μm (24-28 mesh), 124-104 μm (115-150 mesh) and less than 38 μm (400 mesh) with = each other in proportions of 60, 28 or 12% by weight mixed. 50 g of the mixture, the volume of which was about 27%. were obtained by stirring well with 22 g Water mixed as "- 0.05% by weight of a nonionic surfactant of the higher alcohol type based on carbon weight. The received Turbidity had a viscosity of about 0.9 Pa · s and a

32 25 784 5 Example 2 JO
Example 3 55
60
65 6th _ Solids concentration of 70% by weight. So could one After crushing and classifying coal, 10 After crushing and classifying coal, Cloud viscosity of about ¹ Ao in comparison with that of the the groups of coals with particle size ranges the groups of coal with particle size ranges In Fig. 1 shown turbidity of the same solids concentration from 701- 589 μm (24-28 mesh), 208-175 μm from 833 - 701 μm (20-24 mesh), 104 ~ 88 μm 35 tration obtained that does not regulate the part (65-80 mesh), 43-38 μm (325-400 mesh) and less (150-170 mesh), 43 - 38 μm (325-400 mesh) and we size distribution and no surface activity ger than 25 μm (600 mesh) together in proportions of 57 niger than 25 μπι (600 mesh) with each other in proportions of ves means contained. or 26 or 11 or 6 wt .-% mixed. 50 g of the Mi- 15 60 or 30 or 8 or 2% by weight mixed. 50 g the schung. whose void ratio was about 27% Mixture, the void fraction of which was about 24%, was mixed by stirring well with 22 g of water, the mixed with 12.5 g of water by stirring well. 40 0.05 wt .-% of an anionic surface-active Mit- the 0.5% by weight of an anionic surfactant tpli Hpc ^ iilfrircänrpntvnc on Wacic Hac l ^ r »h! *» t ** Mi / ir »htc Means based on the weight of coal contained to one contained. The resulting pulp had a viscosity of 20 Turbidity with a solids concentration of 80% by weight about 0.85 Pa · s and a solid content of to produce a viscosity of about 0.9 Pa · s V 70% by weight as in example 1. This could also be a showed. A slurry with a solids con-45 was also obtained ·; Cloud viscosity of about 'Λο compared with that of the concentration of about 85% by adding 20 g of the Turbid are obtained which do not regulate the partial same as the coal mixture prepared above I.
'■ i
■ i
I. Chen size distribution learned. 25th The pulp obtained above produced The pulp obtained From the above two examples it follows. dali showed a viscosity of about 1.2 Pa · s with an off Surfactants apparently the lubricant reaching fluidity. 50 effect of the turbidity medium regardless of the type of For this purpose 2 sheets of drawings promote same.

Claims (5)

Patent claims: 1. Process for the preparation of a pulp, in which pulverized coal is cut into two or more Groups of different particle size ranges classified, these groups mixed in certain proportions and adding a liquid to the coal mixture to form the coal pulp, characterized in that that one has the two or more groups (1,3) of coals of different particle size ranges mixed in such proportions that there is a voids content of 30% or less, and by adding the liquid (2), the pulp has a carbon content of 55 to 85% by weight. 2. The method according to claim 1, characterized in that the upper limit of the maximum particle size of the classified coal is up to 1 mm in diameter. 3. The method according to claim 1 or 2, characterized in that that the ratio of the minimum particle size of the coal in the pulp to the maximum particle size up to 0.5 is enough. 4. The method according to any one of claims 1 to 3, characterized in that the cloud medium (2) contains a surfactant or dispersant. 5. The method according to any one of claims 1 to 4, characterized in that the coal for formation the pulp has three or more groups of coals with different particle size ranges.