MODELING OF HYDROTHERMAL LiQUEFACTION PROCESS FOR ENERGY REQUIREMENTS AND YIELD OF DIFFERENT PRODUCTS

Abstract

Hydrothermal liquefaction (HTL) is one of the ways to produce biofuel from biomass. However, it was observed that there was a chance to develop improved energy consumption estimation for HTL process. Therefore, this study was undertaken to develop energy requirement calculation for HTL process which used algal biomass as the feed. Besides, direct energy requirement for HTL reactor (1.3 MJ/kg feed), this study also estimated the energy required for concentrating biornass, and separation of oil fraction from aqueous phase (0.02 Mi/L feed). The algal productivity through algal raceway pond is also calculated for Chennai by using available data. Results show that about 20g/m2/day of algal biomass can be grown in raceway pond in India. The optimum algal solid content range, that should give maximum yield with reasonable energy requirements, was determined. The maximum range of algal solid content that would give lower energy requirement in hydrothermal liquefaction without reducing the yield comes out to be approx. 25-30%. After estimating the energy requirement for HTL reactor, a model was developed which could predict the biocrude production taking into account solid content in the feed, and carbohydrate, lipid and protein content in the algal biomass. The model was used to predict successfully the biocrude production estimated in laboratory studies of three different algal species namely C. protothecoides, Scenedesmus sp., and C. pyrenoidosa sp. Further, first order rate constants for the reactions that took place in the HTL at high temperature and pressure, for the conversion of algal biomass content to various HTL products were estimated. However, estimated rate constant does not follow any trend for different feedstock used in the modeling study