It is quite often the case that companies are interested in the benefits that ultrasound provides, but do not have the technical experience and/or equipment to test the efficacy of ultrasound on a unique process or substrate. ISM is capable of providing testing and results dissemination services in addition to advising its clients on the process improvement. After the initial feasibility assessment is done, many clients ask us to optimize their ultrasonic process and estimate the potential commercial-scale production rate. This is commonly a three-phase procedure:
Phase 1. Laboratory-scale studies aimed at testing the feasibility of the process and optimizing the formulation (ratio of components) are conducted first. These experimnets are commonly carried out in the batch mode utilizing a conventional ultrasonic horn (CH) with the output tip diameter of about 12 mm. Sample volumes are 30 - 50 ml and the electric power consumption is under 200 W. Typical results are presented in the figure on the left. In this case, the process for producing a 10 % soybean oil-in-water nanoemulsion concentrate was studied. The figure shows the dependence of the mean droplet size (MDS) of the oil phase on the hydrophilic-lipophilic balance (HLB) of surfactants. In this example, the optimal HLB was about 12.5.
In addition, the effect of ultrasonic amplitude can be studied during this phase. These experiments are also commonly conducted in the batch mode using the same horn type and sample volumes. Typical results are presented in the figure on the left, showing the MDS of the oil phase in the nanoemulsion as a function of the ultrasonic amplitude. In this example, the optimal ultrasonic amplitude value was 90 microns. The studies in Phase 1 are commonly carried out with the LSP-500 or BSP-1200 processor.
Phase 2. Bench-scale pilot experiments are carried out next in order to optimize such ultrasonic processing conditions as the processing rate, back pressure, temperature, etc. These experiments are commonly conducted in the flow-through mode, utilizing a Half-Wave Barbell Horn (HBH) with the output tip diameter of about 32 mm, in combination with a bench-scale flow-through reactor chamber (flow cell). The ultrasonic amplitude during this phase must be maintained at the optimal value found in Phase 1 (in the provided example, 90 microns). Processed sample volumes are on the order of 1 - 2 L and the electric power consumption is approximately 900 - 1200 W. Typical results obtained at the end of this step are presented in the figure on the left, showing the dependence of the MDS on the processing rate. The studies in Phase 2 are commonly carried out with the BSP-1200 processor.
Phase 3. The results obtained during Phase 2 can be used to theoretically predict the scale-up factor that will be achieved when the process is transferred to the plant floor, as explained elsewhere. However, it is sometimes necessary to run a full-scale study to ensure that this prediction is accurate. The verification is done by further increasing the diameter of the HBH horn and the size of the reactor chamber. The ultrasonic amplitude during this phase must be maintained at the optimal value found in Phase 1 and utilized in Phase 2 (in the provided example, 90 microns). During this phase, the productivity scale-up factor is approximately 30 - 40 compared to Phase 1 laboratory experiments and 3 - 4 compared to Phase 2 pilot studies. Processed sample volumes are anywhere from 5 to 100 L and the electric power consumption is approximately 2000 - 3000 W. The goal is to determine the exact scale-up factor and ensure that the quality of the product remains unchanged. The studies in Phase 3 are commonly carried out with the ISP-3000 processor. A photo of the set-up used for the exemplified process is provided on the left.