TABLE OF CONTENTS An important issue that must be assessed in an FBC system is the behavior of the inorganic elements toward bed agglomeration. As previously discussed, the lower bed temperatures are advantageous in that the temperatures can be kept below the ash softening temperatures, especially whenfiring coals. However, because an FBC boiler can fire a wide range of fuels with varying ash chemistries, the interactions of the ash with the bed material can lead to agglomeration, which has a detrimental effect on fluidization. This is especially true with biomass materials where care must be taken in the design of the system (e.g., incorporation of kaolin clay injection systems for agglomeration control) or selection of the feedstocks. This is illustrated in this section, in which the occurrence of inorganic elements in various biomass materials and their effect on combustion behavior in a CFBC system were investigated. This was part of a design for a CFB boiler to be located at Penn State University in which various biomass materials were considered for cofiring with coal [20] [21] [51] [52] [53] [54] [55]
. It has long been recognized that the mode of occurrence of inorganic elements in fossil fuels has a direct bearing on their behavior during combustion [56] [57] [58] [59]. The occurrence of inorganic elements in bio-based fuels is also important. Inorganic species are incorporated in biomass in several ways due to the chemical makeup of the biomass, its origin...
