- Library Home /
- Search Collections /
- Open Collections /
- Browse Collections /
- UBC Theses and Dissertations /
- Flocculation, hydrophobic agglomeration and filtration...
Open Collections
UBC Theses and Dissertations
UBC Theses and Dissertations
Flocculation, hydrophobic agglomeration and filtration of ultrafine coal Yu, Zhimin
Abstract
In coal preparation plant circuits, fine coal particles are aggregated either by oil agglomeration or by flocculation. In a new hydrophobic agglomeration process, recently developed hydrophobic latices are utilized. While the selectivity of such aggregation processes determines the beneficiation results, the degree of aggregation has a strong effect on fine coal filtration. The aim of this research was to study the fundamentals and analyze the common grounds for these processes, including the potential effect of the coal surface properties. The selective flocculation tests, in which three types of coal, which differed widely in surface wettability, and three additives (hydrophobic latices, a semihydrophobic flocculant and a typical hydrophilic polyelectrolyte) were utilized, showed that coal wettability plays a very important role in selective flocculation. The abstraction of a hydrophobic latex on coal and silica revealed that the latex had a much higher affinity towards hydrophobic coal than to hydrophilic mineral matter. As a result, the UBC-1 hydrophobic latex flocculated only hydrophobic coal particles while the polyeletrolyte (PAM) flocculated all the tested coal samples and minerals, showing no selectivity in the fine coal beneficiation. The oil agglomeration was tested using kerosene emulsified with various surfactants (e.g. cationic, anionic and non-ionic). Surfactants enhance not only oil emulsification, hence reducing oil consumption (down to 0.25-0.5%), but also entirely change the electrokinetic properties of the droplets and affect the interaction energy between oil droplets and coal particles. Consequently, the results found in the course of the experimental work strongly indicate that even oxidized coals can be agglomerated if cationic surfactants are used to emulsify the oil. Oil agglomeration of the Ford-4 ultrafine coal showed that even at extremely low oil consumption (0.25 to 0.5%), a clean coal product with an ash content around 5% at over 99.9% coal recovery could be obtained in a one-stage separation by screening the agglomerated product. If a conventional oil agglomeration process is used instead, oil consumption as high as 30% is needed to obtain comparable results. In the tests on filtration and dewatering of ultrafine and fine coals, the effect of chemical additives and coal surface properties was investigated. The tests revealed very significant differences in the filtration of ultrafine (-45 um) and fine (-500 um) coals. The moisture contents in the filter cakes in the tests with ultrafine coal were around 40% (irrespective of the coal surface properties), while for the fine coal the moisture content fluctuated around 18% (Ford-4) and 30% (Ford-13). The results revealed that the hydrophobic latex and the emulsified oils could not only successfully beneficiate the ultrafine coal but also significantly increase filtration rate and/or reduce moisture content of the filter cake. Among the chemicals tested, the emulsified oils were found to be the most promising not only for the beneficiation but also for filtration and dewatering processes. Surfactants were found to only slightly affect the filtration of fine coal. However, they can influence filtration very profoundly if utilized to emulsify the oil which is used to agglomerate coal prior to its filtration.
Item Metadata
Title |
Flocculation, hydrophobic agglomeration and filtration of ultrafine coal
|
Creator | |
Publisher |
University of British Columbia
|
Date Issued |
1999
|
Description |
In coal preparation plant circuits, fine coal particles are aggregated either by oil
agglomeration or by flocculation. In a new hydrophobic agglomeration process, recently
developed hydrophobic latices are utilized. While the selectivity of such aggregation
processes determines the beneficiation results, the degree of aggregation has a strong
effect on fine coal filtration. The aim of this research was to study the fundamentals and
analyze the common grounds for these processes, including the potential effect of the coal
surface properties.
The selective flocculation tests, in which three types of coal, which differed
widely in surface wettability, and three additives (hydrophobic latices, a semihydrophobic
flocculant and a typical hydrophilic polyelectrolyte) were utilized, showed
that coal wettability plays a very important role in selective flocculation. The abstraction
of a hydrophobic latex on coal and silica revealed that the latex had a much higher
affinity towards hydrophobic coal than to hydrophilic mineral matter. As a result, the
UBC-1 hydrophobic latex flocculated only hydrophobic coal particles while the
polyeletrolyte (PAM) flocculated all the tested coal samples and minerals, showing no
selectivity in the fine coal beneficiation.
The oil agglomeration was tested using kerosene emulsified with various
surfactants (e.g. cationic, anionic and non-ionic). Surfactants enhance not only oil
emulsification, hence reducing oil consumption (down to 0.25-0.5%), but also entirely
change the electrokinetic properties of the droplets and affect the interaction energy
between oil droplets and coal particles. Consequently, the results found in the course of
the experimental work strongly indicate that even oxidized coals can be agglomerated if
cationic surfactants are used to emulsify the oil. Oil agglomeration of the Ford-4 ultrafine
coal showed that even at extremely low oil consumption (0.25 to 0.5%), a clean coal
product with an ash content around 5% at over 99.9% coal recovery could be obtained in
a one-stage separation by screening the agglomerated product. If a conventional oil
agglomeration process is used instead, oil consumption as high as 30% is needed to
obtain comparable results.
In the tests on filtration and dewatering of ultrafine and fine coals, the effect of
chemical additives and coal surface properties was investigated. The tests revealed very
significant differences in the filtration of ultrafine (-45 um) and fine (-500 um) coals. The
moisture contents in the filter cakes in the tests with ultrafine coal were around 40%
(irrespective of the coal surface properties), while for the fine coal the moisture content
fluctuated around 18% (Ford-4) and 30% (Ford-13). The results revealed that the
hydrophobic latex and the emulsified oils could not only successfully beneficiate the
ultrafine coal but also significantly increase filtration rate and/or reduce moisture content
of the filter cake. Among the chemicals tested, the emulsified oils were found to be the
most promising not only for the beneficiation but also for filtration and dewatering
processes. Surfactants were found to only slightly affect the filtration of fine coal.
However, they can influence filtration very profoundly if utilized to emulsify the oil
which is used to agglomerate coal prior to its filtration.
|
Extent |
11123161 bytes
|
Genre | |
Type | |
File Format |
application/pdf
|
Language |
eng
|
Date Available |
2009-07-02
|
Provider |
Vancouver : University of British Columbia Library
|
Rights |
For non-commercial purposes only, such as research, private study and education. Additional conditions apply, see Terms of Use https://open.library.ubc.ca/terms_of_use.
|
DOI |
10.14288/1.0081091
|
URI | |
Degree | |
Program | |
Affiliation | |
Degree Grantor |
University of British Columbia
|
Graduation Date |
1999-05
|
Campus | |
Scholarly Level |
Graduate
|
Aggregated Source Repository |
DSpace
|
Item Media
Item Citations and Data
Rights
For non-commercial purposes only, such as research, private study and education. Additional conditions apply, see Terms of Use https://open.library.ubc.ca/terms_of_use.