Coal-flotation chemistry

Thesis/Dissertation · Sun Jan 01 04:00:00 EST 1989

OSTI ID:6764185

Jin, R

The hydrophobic character of coals of different rank, ranging from lignite to anthracite, was evaluated by contact angle, bubble attachment time, reagentless Hallimond tube flotation response, and the heat of immersion. Using DRIFT- and ATR-FTIR, and XPS spectroscopic techniques, it was shown that coal hydrophobicity depends on the chemical characteristics of the coal surface. Coal hydrophobicity and its rank-dependence can be described by an FTIR spectroscopic criterion - the hydrophilicity index - which contrasts the relative abundance of surface hydrophilic groups OH and COOM with the relative abundance of surface hydrophobic groups ArH and RH. Coal hydrophobicity can also be evaluated by an XPS hydrophobicity index which is the carbon to oxygen ratio in the surface layer of about 20 {angstrom}. As compared to conventional flotation, carbon dioxide flotation increased yield/rate and concomitantly improve ash/sulfur rejection for coals of different rank. Thermal pretreatment also improved flotation performance. The success of carbon dioxide flotation is attributed to the high specific affinity of coal for CO{sub 2} which results in the displacement of pore and hydration water by CO{sub 2} and leads to microbubble formation at the coal surface. The CO{sub 2} adsorption capacity of coal was much larger than that of mineral matter, such as pyrite. The specific affinity of CO{sub 2} for coal was confirmed by relatively large exothermic heats of adsorption of CO{sub 2} at coal surfaces. Increased hydrophobicity by thermal pretreatment is attributed to the removal of pore and hydration water from coal, the diffusion of volatile matter to the coal surface, and the reorientation of surface functional groups.

• Research Organization: Utah Univ., Salt Lake City, UT (USA)
• OSTI ID: 6764185
• Country of Publication: United States
• Language: English

Related Subjects

01 COAL, LIGNITE, AND PEAT
010300* -- Coal
Lignite
& Peat-- Preparation-- (1987-)
010600 -- Coal
Lignite
& Peat-- Properties & Composition
ADSORPTION
ADSORPTION HEAT
ANTHRACITE
BITUMINOUS COAL
BLACK COAL
BROWN COAL
CARBON COMPOUNDS
CARBON DIOXIDE
CARBON OXIDES
CARBONACEOUS MATERIALS
CHALCOGENIDES
CHEMICAL REACTIONS
COAL
COAL PREPARATION
COAL RANK
DEASHING
DESULFURIZATION
ELECTRON SPECTROSCOPY
ENERGY SOURCES
ENTHALPY
FLOTATION
FOSSIL FUELS
FOURIER TRANSFORMATION
FUELS
HEAT TREATMENTS
INFRARED SPECTRA
INTEGRAL TRANSFORMATIONS
IRON COMPOUNDS
IRON SULFIDES
LIGNITE
MATERIALS
MINERALS
OXIDES
OXYGEN COMPOUNDS
PHOTOELECTRON SPECTROSCOPY
PHYSICAL PROPERTIES
PYRITE
SEPARATION PROCESSES
SORPTION
SORPTIVE PROPERTIES
SPECTRA
SPECTROSCOPY
SUBBITUMINOUS COAL
SULFIDE MINERALS
SULFIDES
SULFUR COMPOUNDS
SURFACE PROPERTIES
THERMODYNAMIC PROPERTIES
TRANSFORMATIONS
TRANSITION ELEMENT COMPOUNDS
WETTABILITY
X-RAY SPECTROSCOPY