To measure organics in a fluid sample, one either has to bring the sample in the form of a colloid to the instrument, or extract the organics from the sample and bring the liquid extract to the instrument. The disclosed technique enables both extraction and transport of the fines or the organics.
The solution is to use piezoelectric transducers to excite ultrasonically the fluid/fines mix. There are two excitation regimes. The first is where the ultrasound helps to levitate the particulate sample in the slurry/colloid. The particle levitation force depends on the relative densities and compressibility of the particulate and fluid, and on the kinetic and potential energy densities associated with the velocity and pressure fields. The second regime is driven at high power in resonance where the solid/fines region is part of an acoustic resonance chamber and has the highest loss. In this regime, acoustic energy is pumped into the solution/fines mix and rapidly heats the sample.
Across the thickness of the sample volume, the power dissipated increases to a maximum at the middle of the resonance at the fundamental, and at the nodal planes at higher harmonics. The system is a chamber that has a least one piezoelectric plate driven in the thickness mode. The bottom base could also be a piezoelectric, and they could be driven simultaneously and in phase to produce larger pressures in the chamber. The flow is in a direction perpendicular to the direction of the extensional wave of the acoustic pressure. The various frequencies and amplitudes of the voltage applied to the piezoelectric can be tuned to either elevate or fluidize particulate in the solution, or the piezoelectric plate can be driven at higher powers and in resonance to heat the solution and suspended particulates.
The novelty of this technical disclosure is the use of an acoustic resonant chamber to excite a fluid-solid fines mixture in different frequency regimes to accomplish a variety of sample processing tasks. Driving the acoustic resonant chamber at lower frequencies can create circulation patterns in the fluid and mixes the liquid and fines, while driving the chamber at higher frequencies can agitate the fluid and powder. At the fundamental resonance of the chamber, the fluid/fines mixture has the most acoustic attenuation. The dissipated energy is thereby distributed primarily in the fluid/fines system rather than in the other components of the chamber; that is, one can selectively heat only the fluid/fines and bring it to elevated temperatures to allow for sub-critical water extraction.