A microscopic and kinetic study of coal particle devolatilization in a laser beam.
Hertzberg M; Ng DL
Publ in "Fund of Physical Chem of Pulverized Coal Comp " Adv Sci Inst Ser E (137), 1987; :1-22
This paper describes a new experimental method to determine the effect of morphological changes on coal particles when exposed to laser heating. Using direct weight loss measurements for single particles or small arrays of particles, this technique permits devolatilization data to be correlated directly with scanning electron microscopy. For coal particles exposed to the laser flux in an air environment, essentially the same devolatilization process is observed initially; however, when devolatilization is complete, it is followed by a heterogeneous char oxidation process that occurs on a much the reaction mechanism for devolatilization involves the simple, inward progression of a laminar pyrolysis-devolatilization wave from the exposed surface. Simple thermodynamic transport constraints require that the pyrolysis wave velocity be determined by the sum of the absorbing heat flux necessary to raise each element of the solid to its devolatilization temperature (500 degrees to 600 degrees c), plus the flux required to supply the heat of devolatilization. The reaction rate for a particle is then simply controlled by the time required for that devolatilization wave to traverse through it, and that time is predicted to be directly proportional to the particle diameter and inversely proportional to the absorbed flux.
Coal mining; Coal processing; Morphology; Lasers; Heat; Coal; Particulates; Weight factors; Weight measurement; Scanning electron microscopy; Scanning techniques
Publ. in "Fund. of Physical Chem. of Pulverized Coal Comp." Adv. Sci. Inst., Ser. E, No. 137