1000 W Processor with Water-Cooled Transducer
SYSTEM DESCRIPTION
Industrial Sonomechanics (ISM)’ 1000 W (output power) bench-top water-cooled ultrasonic system is a "special request" unit, designed for batch and flow-through process investigations and semi-industrial scale production. The system operates at the frequency of approximately 22 kHz. FBH-type Barbell horns used in this system have output tip diameters up to 35 mm and can provide stable operation at output amplitudes up to 75 microns in aqueous loads at a normal pressure, corresponding to acoustic power intensities up to 50 W/cm2. This gives investigators a wide range of possible experimental conditions to determine optimal parameters for even the most challenging ultrasonic processes. When optimal process conditions are established, the same system can be used for production on a semi-industrial scale. The system is based on a water-cooled magnetostrictive transducer, which offers several advantages, as described below.
System Schematic
1000 W flow-through ultrasonic reactor system in its most common configuration is illustrated on the left. Ultrasonic generator, controlled form the front panel interface or (optional) from a computer running Generator Control software, excites vibrations in the magnetostrictive transducer, which are subsequently amplified by the Full-wave Barbell horn. The horn delivers the ultrasonic energy to the liquid, flowing through the reactor chamber. The reactor chamber may include a cooling/heating jacket. The working liquid inlet and outlet valves may be designed to enable adjustable, pressurized (if needed) flow through the ultrasonic reactor chamber (optional). The system can be designed to operate under static pressures of up to 3 atmospheres.
The processor can be configured for the use in hazardous environments, such as chemical factories or refineries, by incorporating the following protective features into its magnetostrictive transducer and ultrasonic generator:
- The transducer can be built without any high-power cable connections. In this configuration, the Teflon-insulated wire wound around its magnetostrictive element continues uninterrupted from the unit all the way to the generator, thereby eliminating any possibility of creating a spark inside a failed connector. In addition, since the magnetostrictive transducer is water-cooled, any possibility of introducing a hazardous gas into its internal area is eliminated.
- Two methods of protection may be employed for the ultrasonic generator: a) since the generator can be fully monitored and controlled by a computer, it may be kept out of the hazardous area altogether; b) the generator may be designed to be water-cooled, which means that it will not depend on the external air for heat removal. The generator’s enclosure can, therefore, be sealed and/or pressurized with an inert gas, eliminating the possibility of introducing external air (possibly with hazardous gasses) into its internal area.
Maximum flow rate through the processor is approximately 2,500 liter/h (11 gpm). The system design corresponds to the International Patent Application PCT/US2008/068697, "High capacity ultrasonic reactor system". The incorporated Barbell horn design corresponds to the US Patent 7,156,201, "Ultrasonic rod waveguide-radiator".
Assemblies for Flow-through and Batch Processes
Photographs are presented of: 1 - 2000 W ultrasonic generator, 2 - magnetostrictive transducer (maximum output power - 1000 W) assembled with Full-wave Barbell horn and reactor chamber (for flow-through process studies and semi-industrial scale production), 3 - magnetostrictive transducer assembled with Full-wave Barbell horn (for batch experiments).
Besides Full-wave Barbell horns (FBH) of the type shown on the left, specialized Half-wave Barbell horns (HBH) and Half-wave Barbell horns with an Opening (HBHO) are available. These horns are shorter and lighter than Full-wave Barbell horns and have shapes that, when incorporated into appropriately designed reactor chambers, ensure that no working liquid bypasses the active cavitation zone. These horns are frequently preferred for the tasks involving high-intensity flow-through ultrasonic processing, such as dispersion and deagglomeration of solid particles, nanoemulsification and the production micronized waxes, where uniform exposure to ultrasound and the resulting narrow particle size distributions are essential.
Examples of Available Horns and Reactor Chambers
Photographs of several types of horns and reactor chambers are presented. 1 – Full-wave Barbell horn with an upper-node attachment flange (works with reactor chamber 5; also used for medium-size batch studies), 2 – Full-wave Barbell horn with a lower-node attachment flange (works with reactor chamber 6; also used for medium-size batch studies), 3 – Half-wave Barbell horn (works with reactor chamber 6; also used for medium-size batch studies), 4 – Conventional converging horn (works with reactor chamber 6; also used for small-size batch studies), 5 - long reactor chamber (works with Full-wave Barbell horn 1), 6 - short reactor chamber (works with Barbell horns 2 and 3 as well as with horn 4).
Common Setup Example 1
A common setup of the 1000 W ultrasonic system is shown, where: 1 - ultrasonic generator; 2 – computer running Generator Control software, 3 - magnetostrictive transducer; 4 - Full-wave Barbell horn; 5 – flow-through reactor chamber; 6 – pump; 7 - pipeline; 8 – tank for supplying additional components; 9 – valve; 10 – main liquid supply tank. This setup may be used for such processes as biodiesel production, nano-emulsification, oil extraction, solid particle dispersing, etc. The product may be collected from the product output line or re-circulated into the main liquid supply tank, 10.
Common Setup Example 2
Medium batch (150 - 2000 ml) studies and processes may be carried out using this setup. The flow-through reactor chamber is replaced by a beaker. Ultrasonic generator, 1, excites vibrations in the magnetostrictive transducer, 2, which are subsequently amplified using the Full-wave Barbell horn, 3, and delivered to the working liquid contained in the beaker, 4. If desired, the ultrasonic generator may be programmed and the data may be recorded by a computer, 5, running Generator Control software. The working liquid inside the beaker may be cooled by using an ice bath. Using narrow (about 50 – 60 mm in diameter) 500 ml beakers and liquid batch volumes of 150 - 250 ml is recommended for best performance.
CHALLENGING PROCESS SETUP EXAMPLES
The following two examples illustrate setup arrangements that can be used for especially challenging processes, such as the production of translucent nanoemulsions with dispersed phase droplet diameters below 100 nanometers. These processes frequently require longer ultrasound exposure times, which may be achieved by reducing liquid flow rates through the reactor, passing the liquid several times through the system (Example 3) or utilizing several in-series reactors (Example 4).
Common Setup Example 3
Schematic is illustrated of a setup appropriate for challenging processes, such as the production of translucent nanoemulsions in which the dispersed phase droplet sizes must be below 100 nanometers. Coarse pre-emulsion (premix) is initially supplied through the "premix supply" line into vessel, 6. Ultrasonic generator, 1, controlled by computer, 2, excites mechanical vibrations in magnetostrictive transducer, 3, which are amplified by Full-wave Barbell horn, 4. Pass 1: liquid is drawn from the bottom of vessel, 6, through valve, 7, by pump, 8, which then pushes it into reactor, 5, through valve, 9. From there it is deposited into vessel, 11, through valve, 10. Pass 2: liquid is drawn from the bottom of vessel, 11, through valve, 7, by pump, 8, which then pushes it into reactor, 5, through valve, 9. From there it is deposited into vessel, 6, through valve, 10. The process repeats itself for as many passes as needed, and when it is finished, the resulting product comes out through valve, 7, pump, 8, and valve, 9, out of "product exit" line. Nitrogen gas, 12, maintains inert atmosphere and provides the necessary static pressure.
Common Setup Example 4
Diagram of a translucent nanoemulsion production process is shown in this example, which utilizes a multiple series ultrasonic reactor setup. Oil and aqueous phases are brought together in appropriate proportions and are sequentially pumped through multiple ultrasonic reactors, each incorporating a magnetostrictive transducer and a Full-wave Barbell horn.