A temperature control system for batch pretreatments of lignocellulosic biomass: proposal, implementation and evaluation

Accurate temperature tracking for fast heating/cooling and regulation during the batch pretreatment of lignocellulosic biomass (LCB) is required to guarantee high product yield and quality repeatability. However, yield discrepancies are frequently found in the pretreatment literature in which temperature trajectory or heating sources details are seldom reported. Innacurate temperature control may be one of the reasons for these discrepancies. This paper proposes a tracking-regulation-tracking temperature control system for batch pretreatments of LCB heated by an electrical jacket heater. The accuracy of the control system in tracking the temperature set-point trajectory is measured with the weighted integral of the absolute error \({\overline{IAE}}\). The controlled process performance was measured with the percentage difference between the experimental lignin recovery percentage and the value calculated with a steady-state mathematical model using the average temperature of the isothermal reaction period. The system was tested in an ethyl lactate-based 190 \(^\circ \)C, 1 L batch organosolv pretreatment with a maximum heating rate of 8.6\(^\circ \)C/min and a mean cooling rate of -2.4 \(^\circ \)C/min. The process performance was 2.8% for an \({\overline{IAE}}\) of 1044 \(^\circ \)C/min thus confirming the efficacy of the proposed control system.