**3. Experimental study of PEFB gasification in a lab-scale downdraft gasifier**

As mentioned in section 1.3, there is a large amount of PEFB leftover at the palm oil mills. Gasification is the prominent technology to recover energy from PEFB for heat and power production. Gasification is a thermo-chemical process to convert solid fuel into combustible gases under the sub-stoichiometric condition. The gasifier can be classified into 3 main types by the moving characteristic of bed material: fixed bed, fluidized bed and entrained flow gasifier. Table 6 shows the operating conditions of each gasifier type.


Table 6. Operating condition for each gasifier type (Schaidhauf, 1998).

In this study, a fixed bed downdraft gasifier was chosen as the suitable technology because it has the following advantages (Belgiorno et al., 2003; Knoef, 2005; Laohalidanond, 2008; Obernberger & Thek, 2008):


The experiments about PEFB gasification were carried out in a 10 kg/hr downdraft gasifier in order to identify the behavior of producer gas formation in term of producer gas yield, producer gas composition, heating value of producer gas and cold gas efficiency. Additionally, the temperature profile along the height of gasifier was also investigated.
