Fast pyrolysis of coffee ground in a tilted‐slide reactor and characteristics of biocrude oil

Abstract

Coffee grounds are considered to be a promising biomass resource due to the growth of coffee consumption and their high calorific value. In this study, we produced biocrude oil from coffee grounds in a tilted‐slide reactor, which has been previously used for the fast pyrolysis of woody biomass. Various pyrolysis temperatures were tested and the maximum biocrude oil yield was 59% at the pyrolysis temperature of 550°C with a feeding rate of coffee grounds at 17.7 kg/h. In a multistage condenser, the biocrude oil yields and properties were different in each condenser stage. The higher heating value of the biocrude oil from the primary condenser was 7,157 kcal/kg, which was about 60% higher than that from woody biomass. A phase separation was observed when the biocrude oil was stored at the atmospheric condition, and the biocrude oil viscosity became quite larger than that from woody biomass, which could even impede its flow. The viscosity decreased with increasing temperature and was more sensitive to temperature variations at lower temperatures. Mixing of ethanol also significantly improved viscosity characteristics. © 2017 American Institute of Chemical Engineers Environ Prog, 36: 655–661, 2017