Burning Behavior of Paper Inhibited by NaHCo3

Flaming limit of paper inhibited by chemical and thermal retardants was in vestigated. The tested retardants were sodium hydrogen carbonate (NaHCO3), sodium carbonate (Na2CO3) and water. With increasing NaHCO3 or Na2CO3, the spreading rate of flaming decreased gradually. At a critical content of 0.25 wt %, stable flaming became impossible. Beyond the critical Na content, slow but stable smoldering combustion was observed. The transition from flaming to smoldering mode in paper burning is based on the surface reaction of carbon activated by sodium and the consumption of decomposed fuels at the surface. Since burning of the premixture at the leading edge is considerably modified by its local stoichiometry, a small reduction of fuel decelerates the gas phase reactions at the leading edge and causes a blowoff of the diffusion flame with increasing the sodium content in paper. Actually, another experiment using a porous plate burner showed that a sufficient amount of O2 for the carbon burn ing in the pyrolysis...