Modeling of heat transfer and kinetics of lignocellulosic biomass undergoing pyrolysis in an auger feeder

Abstract

Abstract A well-studied method of producing biofuels from biomass is pyrolysis, or thermal decomposition in the absence of oxygen. Bio-oil yield is maximized by fast heating rates, short vapor residence times, and temperatures at or above 500 °C. A typical feeding mechanism for pyrolysis reactors is a lock hopper followed by a horizontal auger feeder. These auger feeders sometimes experience material deposition on the auger screw. In this work, we developed one-dimensional simulations of heat transfer throughout the auger feeder to investigate whether heat transfer from the reactor could be responsible for causing reactions and changing the material properties of the biomass, resulting in plugging of the auger feeder. One-dimensional temperature profiles were obtained from the model with the shooting method. The overall heat transfer parameters were used as fitting parameters in the simulation to achieve cooling loop temperatures that were in reasonable agreement with the experimental temperature data. Using the model, key parameters were determined that could be used to decrease the temperature of the biomass in the auger feeder. The temperature profiles were used with a 32 reaction pyrolysis kinetics model to determine the amount of pyrolysis intermediates and products present in the auger feeder. By changing operating parameters, the activity of pyrolysis reactions in the auger feeder can be decreased. This model can be used by operators to understand the effect of changing operating parameters, to inform auger feeder design, and to improve auger feeder performance.