Agglomeration behavior of lignocellulosic biomasses in fluidized bed gasification: a comprehensive review

Gasification of lignocellulosic biomass in a fluidized bed gasifier is a preferred option for gaseous fuel generation and solid waste management. Erosion, slagging and agglomeration limit the wide adoption of this process. Agglomeration needs serious attention as it leads to defluidization and plant shut down. The present study considers the various aspects of agglomerate formation by the interaction of the inorganic elements (K, Na, Ca) and bed materials. Inexpensive and widely used bed material like silica sand is prone to agglomeration due to the formation of lower-melting alkali silicates. The mechanism involving the formation of agglomerates and ash behavior has been reviewed. K 2 SiO 3 is the commonly formed lower-melting eutectic by the reaction of bed materials and compounds like KCl, K 2 SO 4 and K 2 CO 3 present in the bed. Investigations on various bed materials and their combined effects on bed agglomeration are summarized in this paper. Among the preventive measures, the use of different types of bed materials plays a vital role in the reduction of agglomerate formation, thereby increasing fluidization time. Olivine, dolomite, alumina sand, mullite, etc. are identified as some of the alternatives to the conventional bed materials. The detection of agglomeration using various experimental and online methods is also reviewed. This could further help in the abatement of agglomeration in the reactor without affecting process parameters.