13-07: Terrabon fermentation model

The MixAlco process being commercialized by Terrabon, Inc. uses mixed-acid fermentation to convert biomass into carboxylic acids (e.g., acetic acid), which are then processed chemically downstream into hydrocarbon fuel. Mixed-acid fermentations can be performed in stages via co-current or counter-current operation.  The feedstock, loading rates, substrate concentration, and environmental parameters (e.g., pH, temperature, nutrient levels) all influence performance. Experimentally optimizing all controllable parameters has been the subject of over a decade’s research and is an ongoing effort.  To accelerate optimization and understanding of mixed-acid fermentations, a model is needed.

 Continuum Particle Distribution Modeling (CPDM), first developed in 1996, is an empirical approach used to model complex reactions such as mixed-acid fermentations. For a given substrate system (e.g., paper and chicken manure) an array of batch fermentations are run at different initial substrate concentrations but all having the same environmental conditions.  Acid concentration, conversion, and specific reaction rate data are measured with time.  From these data a five-constant non-linear specific reaction rate equation is regressed.  Mathematically, this rate equation is the embodiment of CPDM theory.  All other equations describe the physics involved.

 Until recently, the fermentation model over simplified the physics, only provided steady-state information, and predictions were less reliable.  Terrabon has developed a new more sophisticated model that is still based on CPDM theories but much more accurately describes the fermentation physics.  The model also provides transient data thus allowing unsteady-state simulation.  This presentation will give and introduction providing conceptual details, simulation capabilities, and validating results.