The Physical Characteristics of Bio-Oil from Fast Pyrolysis of Rice Straw

Abstract

Rice straw is one of the main renewable energy sources in central and south Taiwan. In this study, bio-oil was produced from rice straw using a bench-scale plant that included a fluidized bed, a char removal system, and an oil collection system using an oil-recycling spray condenser. We investigated the effects of pyrolysis temperature and carrier gas flow rate on the distribution of products and on the properties of the bio-oil obtained. Experiments were conducted at reactor temperatures of 350–500 °C with carrier gas flow rates of 7.5–15 L/min and a feed rate of 1 kg/h. The results indicated that the optimum reaction temperature and carrier gas flow rate for the production of bio-oil were 450 °C and 10 L/min, respectively. The highest percentage of bio-oil in the products in these experiments was 41.3 wt%. The pH value of the bio-oil was ~4.1 and the viscosity was ~9 cSt (at 25 °C), depending on the storage time, temperature, and char content. This study establishes the operating parameters of a biomass fast pyrolysis system and provides some properties of rice straw bio-oil relevant to storage and use.