Enhanced Subcritical Water Extraction of Biomass using Hydrodynamic Cavitation

Period of Performance: 06/13/2016 - 03/12/2017


Phase 1 SBIR

Recipient Firm

Dynaflow, Inc.
JESSUP, MD 20794
Firm POC
Principal Investigator


Wet organic wastesuch as biosolids from wastewater treatment plants, manure slurries, and food and beverage production have the potential to be a useful feedstock for the production of biofuels and other bioproducts. Hydrothermal liquefaction using subcritical water can be used to extract the bioproducts from the wet waste without the need for expensive drying processes. However, it is difficult to scale subcritical water extraction processes due to poor mass transfer between the solvent and the biomass particles, degradation of the bioproducts at the high temperatures and pressures required to decrease the permittivity of water, and need for expensive materials, such as Inconel, to construct reactors able to withstand these high temperatures and pressures. One potential method of increasing the extraction efficiency of subcritical water extraction of wet organic waste is the application of hydrodynamic cavitation to the subcritical fluid in order to generate transient local regions of high temperature and pressure where the biomass would be dissolved at relatively low bulk ambient temperatures. HOW THIS PROBLEM IS BEING ADDRESSED: In this proposed Phase I SBIR project, we will investigate the feasibility of using cavitation in the subcritical fluid to break apart solid particles, produce transient high temperatures and pressures that will reduce the permittivity of water and increase mass transfer rates with better mixing. First, cavitation will be applied to reduce the particle sizes of the biosolids and increase the surface area of the particles and the rate of xtraction. Second, the collapse of the bubbles generated during cavitation will create transient regions of high temperature and pressure where the solvent properties of the sub-critical water will be non-polar without the need for higher temperatures in the entire reactor which can degrade the final products. Mass transfer rates will be increased in the fluid due to turbulent mixing. Additionally, if better extraction can be achieved at lower temperatures and pressures in the bulk fluid then cheaper materials of construction could be used to build the reactors. The concept will them be moved to pilot scale systems after addressing R&D issues. WHAT IS TO BE DONE IN PHASE I: The objectives of the project will be to design and construct a subcritical water reactor with specially designed cavitating jets capable of generating cavitation in pressurized water at relatively low pressures and demonstrate the extraction of wet organic waste. Cavitation will be generated in specially designed highly efficient nozzles. During cavitation, bubbles will form in the fluid, expand explosively, then collapse abruptly creating regions of high temperature and pressure within the fluid near the surface of the biomass particles. These nozzles will allow the generation of cavitation in the bulk fluid using relatively low pumping pressures. Thus, using cavitation to enhance subcritical water extraction will be more economical than increasing the temperature and pressure of the entire reactor. The reactor and process design will be helped with numerical simulations of the reactor flow field and of bubble / particle interactions in the wet organic waste. COMMERCIAL APPLICATION AND OTHER BENEFITS: Improving the energy efficiency of subcritical water extraction of biomass with high water content will reduce the production costs for renewable chemicals and fuels produced from wet organic waste. This will reduce the barriers to bringing this technology to commercial scale. The extraction technology developed in this SBIR would also have applications in other fields such as natural product recovery, analytical chemistry equipment, and algae biofuels production. KEYWORDS: subcritical water, biomass, biofuels, organic waste, cavitation