Reaction of Charcoal Particles with Carbon Dioxide and Water at Temperatures up to 2,800° K

Abstract

BOTH carbon dioxide and water vapour are present in appreciable concentrations in any coal combustor. The rates of reaction of these species with carbon or charcoal particles in the size range of pulverized fuel (less than 100µ diameter) are unknown at temperatures greater than about 1,500° K. Extrapolation from the results of lower temperatures1 suggests that surface reactions with both carbon dioxide and water would be very fast and that the overall reaction rate would be controlled by bulk gas diffusion at the higher temperatures; but, because extrapolation over such a wide range of conditions may well be misleading, some experiments have been conducted in which particles of charcoal (35µ diameter) have been reacted with carbon dioxide or water vapour (1–10 per cent in argon at a total pressure of 1 atm.) at temperatures up to 2,800° K. The charcoal was a commercial sample prepared from coal by steam activation. In contrast to previous high temperature investigations3–6 which have been carried out under anisothermal conditions (hot solid with gas at lower temperature), the reaction rates have been measured under isothermal conditions (gas and particles at the same temperature) by introducing the hot particles into a gas stream, preheated by an inductively coupled plasma torch2, flowing through a furnace tube heated to the same temperature. The reaction rates are calculated both directly from the weight loss of the particles and indirectly from the quantity of carbon oxides produced.