A Study on the Effects of Reactor Size and Mixing Conditions during Hydrothermal Liquefaction of Waste Water Algae

Hydrothermal liquefaction (HTL) is a process that converts biomass into a biocrude oil. High temperatures and pressures are required to achieve the subcritical stage creating a highly reactive environment.  This highly reactive environment of subcritical water produces a higher biocrude yield because it breaks down carbohydrates, proteins, and lipids to produce the biocrude oil. A large advantage of the HTL process is it eliminates the high energy and thus costly step of dewatering in certain biomasses such as algae. The products of HTL using waste water algae are an aqueous product, a solid product, and biocrude oil. For results to be comparable the effect of reactor conditions such as reactor size and mixing need to be studied. The techniques used for this analysis include GC-MS, simulated distillation based on thermogravimetric analysis, and CHN-O analysis on the biocrude oil produced from HTL of waste water algae. HTL reactions preformed on waste water algae in a 30 mL, 75 mL, and 450 mL reactors at 350 °C were analyzed and different biocrude oil composition was found using a GC-MS profile. Reactions preformed in a 450 mL reactor at 0 rpm, 50 rpm, and 100 rpm and the biocrude produced where compared and subtle differences where observed in the simulated distillation profile. This study shows that reaction conditions such as mixing rate and reactor size effect the biocrude product of HTL to some extent with reactor size having a greater impact. The effects of this have profound effects on scale up applications and understanding fundamentally what is happening.