Joost Lauwers

Model based optimisation of a cyclic reactor for the production of hydrogen

Abstract This paper studies the model based optimisation of a cyclically operated tubular reactor, i.e., the Cyclic Water Gas Shift Reactor, for the production of hydrogen. The most important degrees of freedom are first identified based on a sensitivity analysis and are afterwards optimised. The optimisation results show that there exists an optimum. In general, short switching times and quasi symmetric operations are preferred. In addition, deviations from the symmetric operation regime gave rise to a drastic decrease in productivity.

Anaerobic digestion of biomass and waste: Current trends in mathematical modeling

Abstract Although anaerobic digestion is a widely applied technology, the process is not yet fully understood because of its high complexity, and an optimization of the current technology is still needed. The design and control of digester systems is still generally performed by rule-of-thumb since no tools are currently available for an accurate evaluation of performance. The application of mathematical models is a prerequisite to improve digester performance and hence much attention is focused on the development of accurate models. This paper critically reviews the current state of the art about mathematical modeling of anaerobic digestion models. Moreover, the main trends in optimization of the existing models and the development of new models are discussed.

Simulation of the Anaerobic Digestion of Microwave Pre-Treated Waste Activated Sludge with ADM1

Abstract The disposal of sludge originating from municipal waste water treatment is a major issue and represents up to 50% of the operating costs of wastewater treatment plants (WWTP). (Appels et al., 2008) This sludge, a by-product of the treatment processes, however, has the potential to be converted into an energy rich biogas, i.e. a mixture of ca. 65% CH 4 and 35% CO 2 , which can be utilized for the sustainable production of heat and/or electricity. Various pre-treatment methods have been suggested in literature for improving the solids reduction and biogas production rate by enhancing the digestions rate limiting step, i.e. organic matter hydrolysis. They all induce the solubilization of complex particulate matter so this is more rapidly and completely consumed during the anaerobic digestion process. Methods that have been shown to have a positive effect on anaerobic digestion include chemical, mechanical, biological and thermal processes. Microwave disintegration is one of the more recently applied pre-treatment methods. The disintegration is caused by the combination of thermal and athermal effects and may hence provide superior results compared to a heat treatment (Eskicioglu et al., 2007). The application of mathematical models for the optimization of the digestion process is widely acknowledged. Due to the complexity of the microbial process, accurate modelling of anaerobic digestion is, however, a daunting task. A major stride countering this problem was achieved by the development of the Anaerobic Digestion Model no 1 (ADM1) by the corresponding IWA task group (Batstone et al. 2002). This model is ever since, considered to be the state of the art in modelling of anaerobic digestion and has been the platform for further refinements and numerous applications (Batstone et al. 2006). The main aim of this work is to investigate the ability of ADM1 to describe anaerobic digestion of microwave pre-treated sludge. Compared to untreated sludge, the composition and structure of the sludge is changed dramatically due to the treatment. The recorded data and digester performances were compared with the results of a modelling in ADM1 (Batstone et al., 2002). Practically, the ADM1 implementation as described by Rosen & Jeppsson (Rosen and Jeppsson (2005)) is chosen as it effectively completes the mass balance for COD, carbon and nitrogen.