The advantages of fast fast pyrolysis of biomass materials include availability and simplicity, and it has been studied by numerous authors using various kinds of reactors like bubbling fluidized beds (BFBs), circulating fluidized beds (CFBs), and fixed beds (FBs). In this work, several experiments were carried out to evaluate the qualities of product gas composition in a circulating fluidized bed (CFB). The data obtained showed that an increase in the pyrolysis temperature leads to an increase in the gas caloric value. The experimental runs also showed that the particle size plays a minor role in the quality of the product gas composition; smaller particle size is favorable for higher HHV and lower CO2 production