Modelling and &#x2112;<inf>1</inf> adaptive control of temperature in biomass pretreatment

Abstract

Abstract-Biomass steam pretreatment is a key process in converting agricultural wastes to bioethanol. The pretreatment occurs in a large pressurized tank called a thermal reactor. Two key parameters influence the successfulness of the process: the reactor temperature, and the retention time. A particle pump pressurizes untreated biomass from atmospheric to reactor pressure with recycled steam from the reactor. This paper formulates a steam mathematical model both for the thermal reactor and the particle pump, which is then used to design an L1 adaptive output feedback controller for the reactor temperature. As steam is recycled from the reactor to pressurize the particle pump, pressure drops and the reactor temperature is disturbed. The main control challenge is to reject these disturbances and keep a steady temperature.The nonlinear process model embeds mass and energy balances, valve characteristics, and enthalpy-pressure and pressure-temperature dependencies. Nonlinear feed-forward terms are added in the control strategy. The process model, the control strategy, the application of the L1 adaptive controller and its tuning method based on minimizing a cost function represent novelties of this paper.

Dynamic modeling and validation of a biomass hydrothermal pretreatment process—a demonstration scale study

“…The steam layer energy balance together with a temperature controller for the thermal reactor have been formulated in Prunescu et al 26 . The energy balance for the biomass layer has been studied in Prunescu et al 14 and is simplified in this paper by a distributed parameters model on one axis, which is discretized along the reactor, or the z axis: Steam is injected through the bottom of the reactor and gets in direct contact with the biomass.…”