煤化学---英语课件chapter-9-thermal-pyrolysis-of-coal.pptVIP

08-06-06 Chapter 9 Thermal decomposition of coal Products from coal pyrolysis Combustible Gases: hydrogen, methane, and carbon monoxide as well as lesser amounts of hydrocarbons Tarry products: small molecular volatile matters such as hydrocarbons, aromatics and their derivatives Coke: char residue which consists of carbon and mineral matter Ⅱ Thermal decomposition process 　A. Pyrolysis B. Carbonization C. Flash Pyrolysis and Hydropyrolysis A. Pyrolysis Summary The Chemistry of Coal and Technology By Ding Ming-jie Department of Chemical Engineering In August 2009 ⅠGENERAL CONCEPTS The thermal decomposition of coal has been the subject of many investigations and, not surprisingly, several forms of terminology have come into common usage. Thus, the terms thermal decomposition, pyrolysis, and carbonization often may be used interchangeably, but it is more usual to apply the term pyrolysis to a process which involves widespread thermal decomposition of coal (with the ensuing production of a char or carbonized residue) whereas the term carbonization is more correctly applied to the process for the production of char or coke when the coal is heated at temperature in excess of ～500℃（～930°F）. The ancillary terms volatilization and distillation are also used from time to time but more correctly refer to the formation and removal of volatile products (gases and liquids) during the thermal decomposition process . Coal undergoes a large variety of physical and chemical changes when heated to a temperature at which thermal decomposition occurs. However, some changes may be noted before the onset of thermal decomposition proper (i.e., carbon –carbon bond scission and the like), and may manifest themselves as the formation of low molecular weight species. For example, while the temperature of thermal decomposition proper is generally recognized to be approximately 350℃(660°F；the so –called cracking temperature ), water will appear as a product of he