Resolving biomass gasification wastewater issues
Gasification of biomass holds the promise of producing energy from sustainable sources while at the same time emitting significantly fewer greenhouse gases to the atmosphere. One challenge that must be met concerns the management of the highly contaminated effluent produced during the de-tarring process. The participants in the DE-TAR project investigated the potential of a treatment process involving Supercritical water oxidation (SCWO) and gasification (SCWG). A key contribution was made by the Universita degli Studi di Napoli "Federico II" (UNINA) concerning the modelling of chemical kinetics of SCWO/G. A first-order Arrhenius reaction was used to describe changes in the Total organic carbon (TOC) content of tar water. Isothermal and isobaric plug flow was assumed. Using this approach, the UNINA scientists could obtain the kinetic rate constant for a variety of conditions reproduced in the laboratory. It was then possible to derive the other critical components of the relevant chemical equation. A primary objective of the research was to evaluate the ability of catalysts to reduce TOC content. Additional assumptions regarding activation energy, temperature and mass conservation were made in order to determine the pre-exponential factor. In this way, the relative contributions of catalysts such as active carbon, potash and ammonia were assessed. The knowledge acquired from these experiments was applied during the development of the DE-TAR pilot biomass gasification system.
