The role of pore structure on char reactivity

Technical Report · Mon Jun 01 04:00:00 EDT 1992

DOI:https://doi.org/10.2172/7095351· OSTI ID:7095351

Sarofim, A F

The Wyoming lignite raw coal was size classified to 38--45 [mu]m, first by air-classification to remove the fine panicles, and then by sieving with a standard Ro-tap sieving machine. The size-classified Wyoming lignite was then pyrolyzed in a laboratory-scale laminar flow furnace at 1650K, 100% N[sub 2]. About one gram of pyrolyzed char was collected with Millipore membrane filters (teflon/polyethylene). The char sample thus collected was carefully poured into an cylindrical mold filled with epoxy resin and thoroughly mixed with epoxy resin. In order to remove the air bubbles trapped during mixing in the mixture, the sample-filled mold was placed in a dessicator connected to a vacuum pump. By periodically evacuating the dessicator, trapped air bubbles could be removed. The mold with the char sample and epoxy resin was placed in a cool area for 24 hours until it hardened. One end of the hardened cylindrical plug was carefully polished with alumina paste so that char particles embedded could also be cross-sectioned. The polished end of the sample plug thus prepared was observed under a Wetzlar optical microscope with a built-in camera. Pictures of fifty cross-sections of char particles were taken. The magnification was in the range of [times] l00 and [times] 650. Figure 1 shows cross-sections of char particles shown in black and white images. (The carbonaceous matrix is shown in black). Characterization of the pore structure of the char was carried out by digital image processing on cross-sections of the char particles. Pictures of cross-sections were scanned in, digitized in 600 [times] 5l2-pixel, 256-grayscale images using an Apple Scanner. Grayscale images were first converted to binary black-and-white images by setting a grayscale threshold that gives the best images of pores and char. Editing, i.e., sharpening and noise reduction, was performed to the binary images using Image v 1.17, a public domain program.

• Research Organization: Massachusetts Inst. of Tech., Cambridge, MA (United States). Dept. of Chemical Engineering
• Sponsoring Organization: DOE; USDOE, Washington, DC (United States)
• DOE Contract Number: FG22-91PC91294
• OSTI ID: 7095351
• Report Number(s): DOE/PC/91294-T3; ON: DE93009672
• Country of Publication: United States
• Language: English

Related Subjects

01 COAL, LIGNITE, AND PEAT
014000* -- Coal
Lignite
& Peat-- Combustion
CARBONACEOUS MATERIALS
CHARS
CHEMICAL REACTION KINETICS
CHEMICAL REACTIONS
CLASSIFICATION
COAL
CRYSTAL STRUCTURE
DECOMPOSITION
DOCUMENT TYPES
ENERGY SOURCES
FOSSIL FUELS
FUELS
KINETICS
MATERIALS
MICROSCOPY
MICROSTRUCTURE
OPTICAL MICROSCOPY
PARTICLE SIZE
POROSITY
PROGRESS REPORT
PYROLYSIS
PYROLYSIS PRODUCTS
REACTION KINETICS
SAMPLE PREPARATION
SIZE
THERMOCHEMICAL PROCESSES