Distinguishing respirable quartz in coal fly ash using computer-controlled scanning electron microscopy
- University of Kentucky, Lexington, KY (United States). Consortium for Fossil Fuel Science and Department of Chemical and Materials Engineering
Determination and classification of quartz in coal fly ash (CFA) is a subject of interest because of the adverse health effects caused by inhalation of crystalline silica. Workers with prolonged exposure to this carcinogen can develop respiratory diseases over time. This obviously may include utility plant workers involved in the handling, loading, and hauling of CFA. In this investigation, computer-controlled scanning electron microscopy (CCSEM) and X-ray diffraction (XRD) were used to investigate Si-rich phases in CFA to develop a better approach for the determination of respirable quartz. Three CFA samples from utility boilers and a NIST glass standard CFA sample were investigated. The XRD measurements indicated that the four samples contained from 7.0 to 16.0 wt.% of quartz. The CCSEM measurements utilized both particle size distributions and a particle shape parameter, circularity, to classify the Si-rich phases in these ashes as either crystalline or amorphous (glass). The results indicated that the amount of free, respirable, quartz in these CFA samples ranged from only 0.1-1.0 vol % and showed little correlation with the XRD results for the bulk ash. These results are significant in view of the fact that XRD is the traditional method of measuring crystalline silica in dust collected from workplace atmospheres. The results provide a better understanding of studies that indicate very little evidence of a link between human exposure to CFA and silicosis and lung cancer. 24 refs., 8 figs., 4 tabs.
- OSTI ID:
- 20905841
- Journal Information:
- Environmental Science and Technology, Vol. 41, Issue 10; Other Information: huffman@engr.uky.edu; ISSN 0013-936X
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
QUARTZ
FLY ASH
DUSTS
COAL
X-RAY DIFFRACTION
SILICA
SCANNING ELECTRON MICROSCOPY
BOILERS
FOSSIL-FUEL POWER PLANTS
QUANTITATIVE CHEMICAL ANALYSIS
SHAPE
CHEMICAL COMPOSITION
PARTICLE SIZE
MEASURING METHODS
DISTRIBUTION
OCCUPATIONAL EXPOSURE
INHALATION
PNEUMOCONIOSES
CARCINOMAS