Effects of pressure on rapid pyrolysis and resultant char structure of a caking coal

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

OSTI ID:6131087

Lee, C W

An Illinois No. 6 coal was pyrolyzed in both high-pressure and atmospheric-pressure entrained-flow reactors ({approximately}10{sup 4} K/s) at 1189 K, and 0, 100, 309, 530 psig N{sub 2}, with residence times up to 1.7 s. The pyrolysis products were characterized extensively to examine the effects of pressure on physical and chemical structural changes of the coal during pyrolysis. Chars generated at 309 psig are more aromatic than those produced at 100 psig, as indicated by the diffuse reflectance infrared Fourier-transform (DRIFT) spectroscopy results and by their higher C/H ratios. Except at 1.7 s, tars generated at higher pressures are more aromatic as indicated by the Fourier-transform infrared (FTIR) spectroscopy measurements and by their higher C/H ratios. The change in composition of the gaseous pyrolysis products, measured by GC, suggests that more secondary reactions of the volatiles were occurring at 309 psig than at 100 psig, except at 1.7 s when most volatiles have left the particles. Scanning electron microscopy shows that chars generated at different pressures have significantly different surface morphologies. This coal swelled most strongly when pyrolyzed at 100 psig than at other pressures. The observed swelling behavior was caused by the completing combined effects of an improvement in fluidity and resistance to swelling by the applied pressure. This hypothesis is supported by a high-pressure microdilatometry study. The apparent first-order rate constants for devolatilization and for swelling of this coal were calculated. The changes in internal structure of this thermoplastic coal during pyrolysis, determined by CO{sub 2} and N{sub 2} surface areas, and by He density, resulted primarily from the realignment of the carbon layers. Chars generated at 100 psig are the most reactive compared to those generated at other pressures, as shown by thermogravimetric analysis results.

• Research Organization: Pennsylvania State Univ., Middletown, PA (USA)
• OSTI ID: 6131087
• Country of Publication: United States
• Language: English

Related Subjects

01 COAL, LIGNITE, AND PEAT
010409* -- Coal
Lignite
& Peat-- Pyrolysis & Carbonization-- (1987-)
010600 -- Coal
Lignite
& Peat-- Properties & Composition
ACTIVATION ENERGY
AROMATICS
ATMOSPHERIC PRESSURE
BITUMINOUS COAL
BLACK COAL
BROWN COAL
CARBON COMPOUNDS
CARBON DIOXIDE
CARBON OXIDES
CARBONACEOUS MATERIALS
CHALCOGENIDES
CHARS
CHEMICAL ANALYSIS
CHEMICAL PROPERTIES
CHEMICAL REACTION KINETICS
CHEMICAL REACTION YIELD
CHEMICAL REACTIONS
CHROMATOGRAPHY
COAL
COAL GAS
COAL TAR
CRYSTAL STRUCTURE
DECOMPOSITION
DENSITY
DEVOLATILIZATION
ELECTRON MICROSCOPY
ELEMENTS
ENERGY
ENERGY SOURCES
FLUIDS
FOSSIL FUELS
FOURIER TRANSFORMATION
FUELS
GAS CHROMATOGRAPHY
GASES
GRAVIMETRIC ANALYSIS
HELIUM
INFRARED SPECTRA
INTEGRAL TRANSFORMATIONS
KINETICS
LIGNITE
MASS TRANSFER
MATERIALS
MATTER
MICROSCOPY
MICROSTRUCTURE
MORPHOLOGICAL CHANGES
NITROGEN
NONMETALS
ORGANIC COMPOUNDS
OTHER ORGANIC COMPOUNDS
OXIDES
OXYGEN COMPOUNDS
PARTICLE SIZE
PHYSICAL PROPERTIES
PRESSURE DEPENDENCE
PYROLYSIS
PYROLYSIS PRODUCTS
QUANTITATIVE CHEMICAL ANALYSIS
RARE GASES
REACTION KINETICS
SCANNING ELECTRON MICROSCOPY
SEPARATION PROCESSES
SHAPE
SIZE
SPECTRA
SPECTROSCOPY
SUBBITUMINOUS COAL
SURFACE AREA
SURFACE PROPERTIES
SWELLING
TAR
TEMPERATURE DEPENDENCE
THERMAL ANALYSIS
THERMAL GRAVIMETRIC ANALYSIS
THERMOCHEMICAL PROCESSES
TIME DEPENDENCE
TRANSFORMATIONS
VOLATILE MATTER
YIELDS