CN114486632A - Coal slurry particle analysis method based on fractal theory - Google Patents

Coal slurry particle analysis method based on fractal theory Download PDF

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CN114486632A
CN114486632A CN202111554335.4A CN202111554335A CN114486632A CN 114486632 A CN114486632 A CN 114486632A CN 202111554335 A CN202111554335 A CN 202111554335A CN 114486632 A CN114486632 A CN 114486632A
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coal
coal slurry
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particle size
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白伦
常乐
路云
黄孟
王珂
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Wuhan Design and Research Institute of China Coal Technology and Engineering Group
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Abstract

The invention provides a coal slurry particle analysis method based on a fractal theory, which comprises the following steps: (1) performing a screening test on a coal sample prepared by single-stage grinding or multi-stage grinding, analyzing the particle size distribution condition of the coal sample, and (2) determining the maximum particle size d of the coal slurry conveyed by the pipemaxAnd carrying out coal powder proportioning according to the maximum particle size, wherein the fractal dimension of the initially proportioned coal powder is H0And (3) preparing the coal sample into a plurality of different coal slurries, obtaining the change of the viscosity of the coal slurry along with the fractal dimension, and obtaining the change of the viscosity of the coal slurry along with the weight concentration. The invention can quantify the size grading, further analyze the relation between the size grading and the viscosity of the coal slurry, and provide a theoretical basis for the safe and economic operation of the coal slurry pipeline system.

Description

Coal slurry particle analysis method based on fractal theory
Technical Field
The invention relates to the technical field of new materials, in particular to a coal slurry particle analysis method based on a fractal theory.
Background
Under the environment of green and low-carbon economic development, the pipeline transportation of coal slurry to the end user with high efficiency, low cost and no pollution is an important development direction, but has higher risk, for example, in the early stage of the operation of the pipeline of Heimasa in America, pipeline blockage caused by unreasonable material granularity and composition occurs. Therefore, the method has important significance for ensuring the safe and economic operation of the coal slurry pipeline system and researching and analyzing the particle size composition and distribution of the coal slurry.
In the traditional method for analyzing the particle size composition of the coal slurry, parameters such as average particle size, median particle size, sorting coefficient, skewness, kurtosis and the like are mainly used, and a formula is not established for quantifying the correlation relationship between the rheological property of the coal slurry and the particle size distribution and concentration of the coal slurry.
Disclosure of Invention
Aiming at the defects of the prior art, the invention provides a coal slurry particle analysis method based on a fractal theory, which scientifically shows the particle size distribution condition in coal slurry and provides a theoretical basis for optimizing the coal slurry preparation process and improving the coal slurry conveying safety.
The technical scheme provided by the invention is as follows: a coal slurry particle analysis method based on a fractal theory comprises the following steps:
(1) through grinding, screening, weighing, carry out the screening test to the coal sample, screen out eight size fractions, 0 ~ 0.045mm, 0.045 ~ 0.075mm, 0.075 ~ 0.15mm, 0.15 ~ 0.3mm, 0.3 ~ 0.425mm, 0.425 ~ 0.83mm, 0.83 ~ 1.4mm, 1.4 ~ 2.8mm, obtain coal sample granularity range A1-A8Mass and mass fraction w of1-w8，
(2) Determining the maximum particle size d of the coal slurry transported in a pipemaxAnd coal powder is proportioned according to the maximum particle size, and the fractal dimension of the initially proportioned coal powder is H0；
(3) Mixing the prepared coal powder with water, and fully stirring to obtain the coal powder with the mass concentration of Cw0Measuring the viscosity of the coal slurry;
(4) in fractal dimension H0Mass concentration of Cw0Adding coal powder and water into coal slurry with mass M to change fractal dimension into HiMeasuring the viscosity of the coal slurry while the mass concentration is kept unchanged, and fitting the change relation of the viscosity of the coal slurry along with the fractal dimension through regression analysis;
(5) in the fractal dimension of coal dust of H0Mass concentration of Cw0Coal slurry with mass M is added with coal powder and water, so that fractal dimension is kept unchanged, and mass concentration is changed into CwiMeasuring the viscosity of the coal slurry and dividing by regressionAnalyzing the change relation of the viscosity of the fitted coal slurry along with the mass concentration.
Further, the mass concentration range of the coal slurry prepared in the step (3) is 45-65%, and the viscosity of the coal slurry is measured by a capillary viscometer.
Further, in the step (2), the cumulative mass fraction W (d < d) is calculatedi) And the initial match fractal dimension H0Satisfy the following requirements
Figure BDA0003418099440000023
Size range of coal slurry (d)i-1，di) Mass fraction w ofiSatisfy the requirement of
Figure BDA0003418099440000024
Size range of coal slurry (d)i-1，di) Mass m of pulverized coaliIs composed of
mi＝MCwwi
Wherein M is the mass of the coal slurry to be prepared.
Further, the mass Δ m of water to be added when preparing the coal slurry in the step (4)wAnd particle size range AiMass of coal powder added internallyiCalculated by the following procedure;
particle size range (d) contained in fresh coal slurryi-1，di) Mass m 'of pulverized coal'iM 'should be satisfied'i＝M′Cw0w′i
m′i≥max{mi}
W 'of'iIs the particle size range (d) of the newly prepared coal slurryi-1，di) The mass fraction of (3) is calculated according to the formula in the step (2);
the total mass M' of the newly prepared coal slurry meets the requirement
Figure BDA0003418099440000031
When the equal signs are established, the added water and the coal powder have the minimum mass respectively
Δmw＝(M′-M)(1-Cw0)
Δmi＝(M′Cw0w′i-MCw0wi)。
Further, the mass delta m of water to be added when the coal slurry is prepared in the step (5)wAnd particle size range AiMass of coal powder added internallyiCalculated by the following procedure;
if Cwi＜CwThe total mass M' of the newly prepared coal slurry meets the requirement
Figure BDA0003418099440000032
The mass of water to be added is
Figure BDA0003418099440000033
If Cwi＞CwThe total mass M' of the newly prepared coal slurry meets the requirement
Figure BDA0003418099440000041
Particle size range AiMass of coal powder added internallyiIs composed of
Figure BDA0003418099440000042
The invention has the beneficial effects that:
(1) the invention provides a method for quantizing the particle size distribution of coal slurry by using fractal dimension, which can realize that a single quantization index only manages and describes the particle size distribution of the coal slurry;
(2) the invention provides a method for researching the particle size distribution, the weight concentration and the viscosity of coal slurry by taking the fractal dimension as a variable, and provides a scientific adjustment method for the fractal dimension and the concentration of the coal slurry, so that the safety of coal slurry conveying is ensured;
(3) the invention obtains the relationship between the fractal dimension and the concentration and the viscosity of the coal slurry transported by the pipe, can provide reference for the preparation of the coal slurry, and preferably selects the coal slurry with low viscosity and coarse granularity as the optimal slurry for transporting.
Drawings
FIG. 1 is a coal slurry particle size distribution diagram for a pipeline coal transportation test;
FIG. 2 is a regression plot of slurry viscosity versus fractal dimension;
FIG. 3 is a regression plot of slurry viscosity versus mass concentration.
Detailed Description
The invention is further described with reference to the following figures and specific embodiments.
A coal slurry particle analysis method based on a fractal theory is characterized by comprising the following steps:
(1) grinding and sieving to obtain the coal powder with a granularity range A1-A8: (iii) a mass of < 0.045, 0.045-0.075, 0.075-0.15, 0.15-0.3, 0.3-0.425, 0.425-0.83, 0.83-1.4, 1.4-2.8 (mm);
(2) determining the maximum particle size d of the coal slurry transported in a pipemaxAnd coal powder is proportioned according to the maximum particle size, and the fractal dimension of the initially proportioned coal powder is H0；
First, for the cumulative mass fraction W (d < d)i) And initial ratio fractal dimension H0Satisfy the following requirements
Figure BDA0003418099440000051
Thus, the particle size range (d) of the coal slurryi-1，di) Mass fraction w ofiShould satisfy
Figure BDA0003418099440000052
Size range of coal slurry (d)i-1，di) Mass m of pulverized coaliIs composed of
mi＝MCwwi
In the formula, M is the mass of coal slurry to be prepared;
(3) mixing the prepared coal powder with water, and fully stirring to obtain the coal powder with the mass concentration of Cw0The mass concentration range of the slurry is 45-65%, and the viscosity of the coal slurry is measured by using a capillary viscometer;
(4) in fractal dimension H0Mass concentration of Cw0Adding coal powder and water into coal slurry with mass M to change fractal dimension into HiWhile the mass concentration remains unchanged. Mass delta m of water to be added when preparing coal slurrywAnd particle size range AiMass of coal powder added internallyiCan be calculated by the following procedure;
particle size range (d) contained in fresh coal slurryi-1，di) Mass m 'of pulverized coal'iShould satisfy m'i＝M′Cw0w′i
m′i≥max{mi}
W 'of'iIs the particle size range (d) of the newly prepared coal slurryi-1，di) The mass fraction of (2).
The total mass M' of the newly prepared coal slurry meets the requirement
Figure BDA0003418099440000061
When the equal sign is established, the mass of the added water and the added coal powder is the minimum, respectively
Δmw＝(M′-M)(1-Cw0)
Δmi＝(M′Cw0w′i-MCw0wi)
(5) Measuring the viscosity of the coal slurry, and calculating the mass concentration C when the coal slurry meets a certain specific mass concentrationw0Fractal dimension H of time, coal powderiViscosity mu of coal slurryi(or stiffness coefficient);
(6) in the fractal dimension of coal dust of H0Mass concentration of Cw0Coal slurry with mass M is added with coal powder and water, so that fractal dimension is kept unchanged, and mass concentration is changed into Cwi. The mass delta m of water to be added when preparing coal slurrywAnd particle size range AiMass of coal powder added internallyiCan be calculated by the following procedure.
If Cwi＜CwThe total mass M' of the newly prepared coal slurry meets the requirement
Figure BDA0003418099440000062
The mass of water to be added is
Figure BDA0003418099440000063
If Cwi＞CwThe total mass M' of the newly prepared coal slurry meets the requirement
Figure BDA0003418099440000064
Particle size range A with unchanged fractal dimensioniMass fraction w ofiNor will it change. Particle size range AiMass of coal powder added internallyiIs composed of
Figure BDA0003418099440000065
(7) Measuring the viscosity of coal slurry, and calculating the fractal dimension H of coal powder0In weight percent, concentration CwiAnd viscosity mui(or stiffness coefficient).
Example 1:
example data using coal slurry data from a certain pipeline coal transportation test measurement, the maximum particle size was 2.4mm, the particle size distribution diagram is shown in fig. 1, and a total of 12 groups of coal slurries of different coal dust fractal dimensions were prepared.
Serial number 1 2 3 4
Fractal dimension 2.4894 2.4611 2.5795 2.5152
Serial number 5 6 7 8
Fractal dimension 2.5681 2.5332 2.5513 2.5517
Serial number 9 10 11 12
Fractal dimension 2.5436 2.528 2.5007 2.5351
The relationship between the slurry viscosity and the fractal dimension at a slurry concentration of 53% is shown in fig. 2, and the relationship obtained by fitting is-200.35H + 645.76.
When the coal powder fractal dimension is 2.5152, the relationship between the viscosity and the weight concentration of the coal slurry is shown in figure 3, and the fitted relation is that mu is-14.459Cw+638.4。
The relation between the viscosity and the fractal dimension of a plurality of groups of coal slurry can be obtained within the range of 45-65% of the mass concentration of the coal slurry, the relation between the viscosity and the mass concentration of a plurality of groups of coal slurry can be obtained within the range of proper fractal dimension, and data reference can be provided for the coal slurry with low viscosity and coarse granularity which is preferably selected.
The foregoing shows and describes the basic principles and principal features of the invention, together with the advantages thereof. It will be understood by those skilled in the art that the present invention is not limited to the embodiments described above, which are described in the specification and illustrated only for the purpose of illustrating the structural relationship and principles of the present invention, but that various changes and modifications may be made without departing from the spirit and scope of the invention as defined in the appended claims. The scope of the invention is defined by the appended claims and equivalents thereof.

Claims (5)

1. A coal slurry particle analysis method based on a fractal theory is characterized by comprising the following steps:
(1) through grinding, screening and weighing, a coal sample is subjected to a screening test to screen eight size fractions of 0-0.045 mm, 0.045-0.075 mm, 0.075-0.15 mm, 0.15-0.3 mm, 0.3-0.425 mm and 0.425-0.83 mm,0.83-1.4 mm and 1.4-2.8 mm, and obtaining the granularity range A of the coal sample1-A8Mass and mass fraction w of1-w8；
(2) Determining the maximum particle size d of the coal slurry transported in a pipemaxAnd carrying out coal powder proportioning according to the maximum particle size, wherein the fractal dimension of the initially proportioned coal powder is H0；
(3) Mixing the prepared coal powder with water, and fully stirring to obtain the coal powder with the mass concentration of Cw0Measuring the viscosity of the coal slurry;
(4) in fractal dimension H0Mass concentration of Cw0Adding coal powder and water into coal slurry with mass M to change fractal dimension into HiMeasuring the viscosity of the coal slurry while the mass concentration is kept unchanged, and fitting the change relation of the viscosity of the coal slurry along with the fractal dimension through regression analysis;
(5) in the fractal dimension of coal dust of H0Mass concentration of Cw0Coal slurry with mass M is added with coal powder and water, so that fractal dimension is kept unchanged, and mass concentration is changed into CwiAnd measuring the viscosity of the coal slurry, and fitting the change relation of the viscosity of the coal slurry along with the mass concentration through regression analysis.
2. The fractal theory-based coal slurry particle analysis method according to claim 1, wherein: the mass concentration range of the coal slurry prepared in the step (3) is 45-65%, and the viscosity of the coal slurry is measured by adopting a capillary viscometer.
3. The coal slurry particle analysis method based on the fractal theory as claimed in claim 1, wherein: for the cumulative mass fraction W (d < d) in the step (2)i) And initial ratio fractal dimension H0Satisfy the following requirements
Figure FDA0003418099430000021
Size range of coal slurry (d)i-1,di) Mass fraction w ofiSatisfy the requirement of
Figure FDA0003418099430000022
Size range of coal slurry (d)i-1,di) Mass m of pulverized coaliIs mi＝MCwwi
Wherein M is the mass of the coal slurry to be prepared.
4. The fractal theory-based coal slurry particle analysis method according to claim 3, wherein: the mass delta m of water to be added when the coal slurry is prepared in the step (4)wAnd particle size range AiMass of coal powder added internallyiCalculated by the following procedure;
particle size range (d) contained in fresh coal slurryi-1,di) Pulverized coal mass m'iShould satisfy
mi′＝M′Cw0w′i
m′i≥max{mi}
W 'of'iIs the particle size range (d) of the newly prepared coal slurryi-1,di) The mass fraction of (3) is calculated according to the formula in the step (2);
the total mass M' of the newly prepared coal slurry meets the requirement
Figure FDA0003418099430000023
When the equal sign is established, the mass of the added water and the added coal powder is the minimum, respectively
Δmw＝(M′-M)(1-Cw0)
Δmi＝(M′Cw0w′i-MCw0wi)。
5. The fractal theory-based coal slurry particle analysis method according to claim 3, wherein: the mass delta m of water to be added when the coal slurry is prepared in the step (5)wAnd particle size range AiMass of coal powder added internallyiCalculated by the following procedure;
if Cwi＜CwThe total mass M' of the newly prepared coal slurry meets the requirement
Figure FDA0003418099430000031
The mass of water to be added is
Figure FDA0003418099430000032
If Cwi＞CwThe total mass M' of the newly prepared coal slurry meets the requirement
Figure FDA0003418099430000033
Particle size range AiMass of coal powder added internallyiIs composed of
Figure FDA0003418099430000034
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