Numerical Investigation of the Effects of Reactor Pressure on Biomass Pyrolysis in Thermally Thin Regime

Abstract

Effects of reactor pressure [vacuum (0.0001, 0.01 atm), atmospheric (1 atm) and pressurized (10, 100 atm) regions] on primary tar production rate, primary tar intra-particle secondary reactions, and tar and gas release rates during  pyrolysis in thermally thin regime at a heating rate of 30 K/s and final reactor temperature of 973 K have been numerically investigated. Wood cylinder (  was modeled as a two –dimensional porous solid. Transport equations, chemical kinetic models, pressure and energy conservation equations were coupled and used to simulate the pyrolysis process. Solid mass conservation equations were solved by first-order Euler Implicit Method. Finite volume method was used to discretize the mass conservation equation for argon, primary tar, gas and secondary tar, energy conservation equation and pressure equation. Findings showed that pressure increase, either from vacuum to atmospheric or from atmospheric to pressurized region, has no significant effect on the primary decomposition reactions of the sample. Pressure increase within vacuum region (0.0001 to 0.01 atm) and within pressurized region (10 to 100 atm) has no significant effect on primary tar intra-particle secondary reactions, and tar and gas release rates. However, pressure increase from vacuum to atmospheric and from atmospheric to pressurized region increased primary tar residence time within the pyrolyzing solid thereby enhancing intra-particle secondary reactions.

Keywords: Biomass, pyrolysis, pressure effect, intra-particle secondary reactions, thermally thin regime