TABLE OF CONTENTS In Chapter 1 we defined gasification as the production of gases with a useable heating value from carbonaceous fuels. The range of potential fuels, from coal and oil to biomass and wastes, would appear to make the task of presenting a theory valid for all these feeds relatively complex.
Nonetheless, the predominant phenomena of pyrolysis or devolatilization followed by gasification of the remaining char are similar for the full range of feedstocks. In developing gasification theory it is therefore permissible to concentrate on the "simple" case of gasification of pure carbon, as most authors do, and discuss the influence of specific feed characteristics separately. In this work we will also be adopting this approach, which can also be used for the partial oxidation of gases such as natural gas.
In the discussion of the theoretical background to any chemical process, it is necessary to examine both the thermodynamics (i.e. the state to which the process will move under specific conditions of pressure and temperature, given sufficient time) and the kinetics (i.e. what route will it take and how fast will it get there).
The gasification process takes place at temperatures in the range 800 C to 1800 C. The exact temperature depends on the characteristics of the feedstock, in particular the softening and melting temperatures of the ash, as is explained in more detail in Chapter 5 (page 93). However, over the whole temperature range described above, the reaction rates are sufficiently high that modeling on the basis of the thermodynamic...
