Submitted to: Thermochimica Acta
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: May 24, 2007
Publication Date: July 12, 2007
Citation: Dungan, R.S., Reeves III, J.B. 2007. Pyrolysis of Carbonaceous Foundry Sand Additives: Seacoal and Gilsonite. Thermochimica Acta. 183:213-223.
Interpretive Summary: Carbonaceous additives, such as seacoal (crushed bituminous coal) and gilsonite (a natural asphaltic material), are commonly used in foundry molds to create an atmosphere low in oxygen during casting. An analytical technique known as gas chromatography-mass spectrometry was used to tentatively identify organics generated during the thermal decomposition of seacoal and gilsonite at 500, 750, and 1000oC. The high temperatures were used to simulate the environment within a mold during metal casting. A number of compounds of environmental concern were identified, including substituted benzenes, phenolics and polycyclic aromatic hydrocarbons (PAHs), some of which are known human carcinogens. These organic compounds, and especially PAHs, were generated at each pyrolysis temperature in all foundry sands containing seacoal. In gilsonite-amended sand, however, mainly hydrocarbons were identified at 500 and 750oC and PAHs at 1000oC. While some of the organics will condense in the molding sand, many are volatile and could potentially compromise the safety of foundry workers. Information from this study will be useful to foundries looking to control hydrocarbon emissions during metal casting.
Seacoal and gilsonite are used by the foundry industry as carbonaceous additives in green molding sands. In this study, pyrolysis was used to simulate the heating conditions that the carbonaceous additives would experience during metal casting. Gas chromatography-mass spectrometry was used to tentatively identify major organic products generated during their pyrolysis at 500, 750, and 1000oC. A number of compounds of environmental concern were identified during the pyrolysis of seacoal and gilsonite, including substituted benzenes, phenolics, and polycyclic aromatic hydrocarbons (PAHs). These thermal decomposition products, and especially PAHs, were generated at each pyrolysis temperature in all foundry sands containing seacoal. In gilsonite-amended sand, however, mainly alkanes and alkenes were identified at 500 and 750oC and PAHs at 1000oC. Compared to seacoal, the most intense peaks occurred during the pyrolysis of sand containing gilsonite. The greatest loss of pyrolyzable material also occurred during heating of gilsonite-amended sand from ambient temperature to 1000oC in a thermogravimetric analyzer. The results obtained from this study will be useful to green sand foundries looking to reduce volatile hydrocarbon emissions.