Thermo‐economic assessment of a bench‐scale pyrolysis unit through a process simulator

Abstract

This article focuses on the holistic appraisal of a pilot‐scale updraft reactor (E1) powered by the processed residue of forest waste (W1) and hog fuel (W2). The detailed analysis of the up‐draft unit includes the availability of energy, economic evaluation, and the determination of the lignocellulose content of the pine waste. The reformed structure of the pine pellet was used for gas, bio‐oil, and char generation. The Aspen HYSYS process simulator was used for simulation purposes and the results were validated with the solution obtained experimentally. For the measurement of the constituent contents of the pine needles, the National Renewable Energy Laboratory (NREL) procedure was adopted. To investigate the similitude of the packed bed reactor, the Soave–Redlich–Kwong model was considered. For comparison of the given prototype, five different reactor types – conversion (R1), equilibrium (R2), Gibbs (R3), continuous stir tank (CST) (R4) and plug flow (R5) – were juxtaposed and their thermodynamic behavior was evaluated. From structural composition, it was noticed that the cellulose and hemicellulose(s) content dropped by 24.95% and 37.37%, respectively, whereas a rise of 23.33% was seen in the acid‐insoluble lignin (AIL) fraction of forest waste after the torrefaction process. Irrespective of the fuel type, the unconsumed fuel percentage was the same for both wood and processed residue pellets for R5. The relative percentage of methane increased by 1% for processed forest residue. The CO2 emission was estimated to be maximum for reactors R3 and R4. The O2 gain was absent in the R2 reactor. Concomitantly, it gained momentum in R1, R3, and R4. The simulated polytropic equations of state for W1 and W2 were PV1.083 = C and PV1.092 = C, respectively. The levelized cost of energy dropped by 12.50% while scaling up a pyrolysis unit.