A Study on the Temperature and Residence Time Needed to Resolve Asbestos Using a Simulated Cement-Burning Kiln

Research was conducted on how to change asbestos into a non-asbestos substance and/or into cement through a burning process in a cement rotary kiln. Urgent research is necessary for resolving the problem of how to deal with asbestos remnants found in waste from construction materials. As our research method, we tested and verified temperature and time conditions regarding how asbestos fiber remnants which may be dispersed into the vertical updraft of a suspension preheater when thrown into the kiln from the lower inlet, could be changed into a non-asbestos substance. Experimental fluidized-bed kiln equipment that imitates a suspension preheater was used. The density of asbestos in exhaust gas, with 0.8 seconds of residence time in a furnace of 900°C, became 30-80 f/L, when asbestos-containing waste from construction materials was thrown into the furnace at a fixed rate. With the same residence time as above and a furnace temperature of 950°C, it decreased to 15-33 f/L and almost became quantitative lower limit with an in-furnace temperature of 1, 000°C or more. In cases where Chrysotile, Crocidolite and/or Amosite were instantly heated up in an electric furnace, Chrysotile began changing into a non-asbestos substance at 700°C upward, and a portion of Crocidolite and Amosite began changing into a non-asbestos substance at 950°C and higher.