| The decompositions of four powdered materials commonly used in the inhibition and quenching of fires and explosions were studied under high heating rate and high temperature conditions using a heated wire grid. The materials studied included Rock Dust/CaCO(,3), Purple K/KHCO(,3), BCD/NaCl, and ABC/NH(,4)H(,2)PO(,4).;The kinetic parameters obtained for Rock Dust/CaCO(,3) and Purple K/KHCO(,3) were incorporated into both static and dynamic models of laminar plane flame propagation. The particle temperatures predicted by the static model (based on an adiabatic flame temperature calculation) were in good agreement with experimental data from the US Bureau of Mines.;The results of the dynamic model indicated that the volatile content of the coal and particle size of both coal and inhibitor have a large effect on flame speed Parameters such as coal dust loading (within a limited range), activation energy of the coal devolatilization or inhibitor decomposition reactions, and enothermic heat of decomposition had little or no effect on flame speed when varied by a much as (+OR-)50%.;The results of the dynamic model also indicated that the difference in the quantities of Rock Dust/CaCO(,3) and Purple K/KHCO(,3) required to quench a stoichiometric coal dust/air flame can be traced to a difference in the rates of decomposition. Purple K/KHCO(,3) achieves its maximum extent of decomposition before the coal has completely devolatilized, and can provide no further heat sink as the coal continues to devolatilize and ignition occurs. Rock Dust/CaCO(,3), on the other hand, only begins to decompose as devolatilization reaches completion, and can therefore act as a heat sink to prevent ignition.;The decomposition reactions of Rock Dust/CaCO(,3) and Purple K/KHCO(,3) were both modeled by equations representing rate control by three-dimensional movement of the phase boundary. BCD/NaCl did not decompose, but melted and, to a limited extent, vaporized. The ABC/NH(,4)H(,2)PO(,4) melted before any decomposition occurred, and it was concluded that the heated grid was not an appropriate apparatus for studying the decomposition of organic liquids. |
