Techno-economic analysis of integrated torrefaction and pelletization systems to produce torrefied wood pellets

Abstract

We investigated the techno-economic analysis of two integrated torrefaction and pelletization systems: (1) Torrefaction befOre Pelletization and (2) Torrefaction After Pelletization configurations to produce torrefied wood pellets. The detailed mass and energy balances and operating parameters were obtained from the process simulation model developed with the base case plant capacity of 100,000 Mg yr−1 using natural gas as an auxiliary fuel source. A discounted cash flow analysis was conducted for both configurations to estimate the capital expenditure, operating expenses, production cost, and the minimum selling price of torrefied pellets. The minimum selling price of torrefied pellets at the plant gate was $207 Mg−1 ($8.5 GJ−1) for the Torrefaction before Pelletization and $197 Mg−1 ($8.1 GJ−1) for the Torrefaction After Pelletization configurations. An increase in the plant capacity of up to 200,000 Mg yr−1 for both configurations decreased the minimum selling price by 10%. The sensitivity analysis of various operational and financial parameters demonstrated that the feedstock cost and torrefaction product yield were the most sensitive parameters influencing the minimum selling price of torrefied pellets. Future opportunities exist to reduce the minimum selling price of torrefied pellets to become competitive to conventional wood pellets and coal.