INTRODUCTION TO BARBELL HORN ULTRASONIC TECHNOLOGY
Industrial Sonomechanics, LLC (ISM), specializes in high-capacity commercial-scale ultrasonic liquid processors, also called ultrasonic homogenizers, sonochemical reactors and ultrasonic wet milling systems, adapted to many industrial processes. In addition, ISM provides laboratory and bench-scale ultrasonic systems which can be used to study processes before they are scaled up as well as for pilot-scale production. As described below, several unique features of ISM’s patented Barbell Horn Ultrasonic Technology (BHUT) make it possible to directly transfer what can be accomplished in the laboratory to the plant floor, guaranteeing reproducible and predictable results at any scale.
Advantages of High Ultrasonic Amplitudes
Liquids exposed to high-intensity ultrasound undergo ultrasonic cavitation, which produces violently and asymmetrically imploding bubbles and causes micro-jets that create extreme mechanical shear forces. These forces are responsible for the well-known ability of ultrasound to tremendously facilitate many physical and chemical processes. Ultrasonic amplitudes on the order of 100 microns peak-to-peak (below, "microns") are commonly necessary in order to take full advantage of this effect. At low amplitudes (below about 50 microns), the intensity of ultrasonic cavitation is insufficient for many processes, such as nano-crystallization, nano-emulsification, deagglomeration, extraction, as well as many others. In order to produce sufficient cavitation intensity, ultrasonic transducers (converters) are equipped with high-gain acoustic horns (sonotrodes, waveguide radiators, probes), which amplify the vibration amplitudes generated by the transducers and deliver the ultrasonic energy to working liquids.
Converging Horns - Main Limitation of Conventional Ultrasonic Technology
Conventional ultrasonic systems utilize acoustic horns that converge in the output direction. These conventional horns (CH) can only provide high ultrasonic amplitudes when their output tip diameters are small. Conventional horns are appropriate for studying processes on a laboratory scale, but they make it impossible to transfer the processes to an industrial scale. Process scale-up requires switching to horns with larger output tip diameters, able to output the ultrasonic energy into larger volumes of working liquids while still maintaining high amplitudes. If, however, the output tip diameter of a conventional horn is increased, its maximum vibration amplitude necessarily becomes significantly lower.
For example, ultrasonic amplitudes on the order of 100 microns can only be reached by conventional horns when their output tip diameters do not exceed about 20 mm (laboratory scale). Conventional horns with output tip diameters of 40 mm and above (industrial scale) operate at the maximum amplitude of about 25 microns, irrespective of the specified system power. Conventional ultrasonic technology, therefore, does not permit to directly transfer high-amplitude ultrasonic processes from laboratory to industrial scale, which is why numerous successful laboratory studies have never been implemented in industrial production.
Barbell Horns - Scalable High-Amplitude Ultrasound
Barbell horns, developed by ISM, are able to amplify ultrasonic amplitudes while retaining large output tip diameters. This opens up the possibility to directly scale up any high-amplitude ultrasonic process. Barbell horns utilized in our industrial processor, ISP-3000, commonly have output tip diameters of 45 - 50 mm (up to 70 mm in some cases) and produce extremely high ultrasonic amplitudes on the order of 100 microns. Our bench-scale processor, BSP-1200, utilizes Barbell horns with output tip diameters of 32 - 35 mm, which are also able to output ultrasonic amplitudes on the order of 100 microns. Barbell horns make it possible to directly reproduce any laboratory or bench-scale process optimization study in a commercial production environment. Since the scale-up is accomplished without changing any of the optimized parameters, including the amplitude, the process is guaranteed to generate the same results on the plant floor as it does in the laboratory. Since system productivity depends on the size of the active cavitation zone created under a horn, which is proportional to the area of the horn's output surface, productivity rates in Barbell horn-based systems can be orders of magnitude higher than those achieved with conventional ultrasonic devices.
Different Types of Available Babell Horns - Shapes Adapted to Each Application
Barbell horns are available in different shapes and sizes. Besides Full-wave Barbell horns (FBH) shown on this page, Half-wave Barbell Horns (HBH) and Half-wave Barbell Horns with an Opening (HBHO) are available. These devices are shorter and lighter than FBH, but have approximately double the radiating area for the same output tip diameter. Additionally, these horns are designed to work with ISM's reactor chambers (flow cells) in a way that directs all processed liquid through high-intensity cavitation zones, practically eliminating any possibility of bypass. HBH and HBHO devices are, therefore, preferred for the tasks involving high-intensity flow-through ultrasonic processing where uniform exposure to ultrasound is essential, such as for the prodiction of nanocrystals, nanoemulsions and liposimes with narrow particle size distributions.