Removal of Char Particles by Microfiltration Process to Improve the Stability of Bio-Oils

Char particles are believe to play a significant role in decreasing the stability of bio-oils. While cyclone and hot gas filtration can remove char particles greater than 10 micron size, the main challenge is to remove char particles in the region from 10-0.1 micron size and produce bio-oil that has very low overall char content. Microfiltration has previously been widely applied for removal of solid particles from liquid streams; however this technology has not yet been applied to a highly viscous stream such as bio-oils.

This study focused on the development of microfiltration technology for the removal of char particles. Our aim was to reduce the overall char content in the bio-oil to less than 0.01 weight percent. An experimental rig was built which was able to run bio-oil through ceramic microporous membranes at elevated temperatures. Commercially available Membralox membranes with pores sizes ranging from 0.1-0.5 micron were evaluated in terms of their ability to remove char particles. The char particles in pre-filtered and filtered bio-oil were characterized by dynamic light scattering method. An analysis of the fouling mechanism and regeneration of the membranes by back flushing and chemical treatment was also carried out.