Hazardous air pollutant formation from pyrolysis of typical Chinese casting materials

Analytical pyrolysis was conducted to evaluate the major hazardous air pollutant (HAP) emissions from pyrolysis of bituminous coal and a furan binder, which are the two most commonly used casting materials for making green sand and furan no-bake molds in Chinese foundries. These two materials were flash pyrolyzed in a Curie-point pyrolyzer at 920 °C and slowly pyrolyzed in a thermogravimetric analyzer (TGA) from ambient temperature to 1000 °C with a heating rate of 30 °C/min. The emissions from Curie-point and TGA pyrolysis were analyzed with gas chromatography-mass spectrometer/flame ionization detector. Thirteen HAP species were identified and quantified in the pyrolysis emissions of the two materials. The prominent HAP emissions were cresols, benzene, toluene, phenol, and naphthalene for the bituminous coal, whereas they were m,p,o-xylenes for the furan binder. Xylenesulfonic acid, the acidic catalyst in furan binder, was found to be the major source of xylene emissions. Thermogravimetry-mass spectrometer monitored the evolution of HAP emissions during TGA pyrolysis. For both of the casting materials, most of the emissions were released in the temperature range of 350-700 °C.