Modeling of Thermochemical Conversion of Glycerol: Pyrolysis and H_2O and CO_2 Gasification

摘要

Glycerol is the byproduct of biodiesel production. Biodiesel has been considered a strong alternative candidate to petro diesel. Stoichiometrically, one mole of glycerol is generated during the conversion of one mole of triglyceride feedstock or per three produced moles of biodiesel. This an equivalent to 10-15% byproduct volume/mass. The biodiesel production has observed a huge jump in production, being preserved as a renewable, sustainable and near CO2 neutral source. This is driven by advances in technology of 1st generation biomass lipid harvesting and advancement of 3rd generation breeding and maximizing algae lipids and their extraction. Therefore, a sound solution for velarizing the glycerol byproduct is becoming a necessity before it is viewed as waste burden. Currently, the glycerol market is saturated and substantial production can lead to an economic imbalance. Therefore, satisfying the energy needs following thermochemical conversion of glycerol into clean syngas fuel is a more favorable and dual solution to the problem, i.e. reducing process waste and generating clean fuel. In this work, the process metrics in using Glycerol as feedstock for the production of syngas fuel is evaluated under pyrolysis then gasification under steam (H2O(g)) and CO2 moderators. Process metrics are assessed using the syngas mole fractions and their normalized value termed as the cold gasification efficiency. The analysis followed equilibrium modeling based on Gibbs Energy Minimization and under sweeping reaction temperatures. The model is validated against experimental literature. Result of glycerol pyrolysis achieved a maximum of 83% at 0.43 CO and 0.57 H-2 mole fraction. Glycerol gasification under steam moderator resulted in a slightly higher efficiency of 84% and 0.20 CO and 0.55 H-2 mole fractions, while under CO2 moderator resulted in a lower efficiency of 80% and 0.40 CO and 0.30 H-2 mole fractions. This emphasizes the technical feasibility of thermochemical conversion of glycerol into clean syngas and closes the loop of biodiesel production towards zero byproduct process.