Effectiveness of Thermoplastic Powder to Retard Self-Heating and Spontaneous Combustion of Coal

To meet the specific requirements for storage and transportation of coal, the use of thermoplastic powder (TP) is proposed for retarding or suppressing self-heating and spontaneous combustion of coal. Thermal behavior analysis of the materials by differential scanning calorimetry and thermal station showed that some of the heat generated during self-heating of coal was removed as TP fused at 39 degrees C. The fused TP blocked pores and cracks in the coal, preventing heat and mass transfer between coal and oxygen. Thermogravimetric and mass spectrometer apparatus determined weight loss and evolved H-2, H2O, CH4, CO, CO2, and O-2. Absorbed oxygen increased by 0.6 wt% between 175 degrees C and 272 degrees C in coal, but TP/coal powder (TCP) showed no weight increase. Since TP prevented most of the moisture loss in the coal, the weight loss rate of TCP was significantly less than that of coal up to a temperature of 325 degrees C. Mass spectrometry analysis showed that consumed O-2 produced H-2, CH4, CO, CO2, and H2O at temperatures below 400 degrees C in coal, and above 400 degrees C in TCP. In these experiments, TP retarded or in some cases prevented self-heating of coal at low temperatures, and also retarded coal pyrolysis without affecting the use of the coal.