«A Conquest of Tornado» — so could be called a story of development of a unique air-vortex milling machine and the technology for grinding of any materials up to the nano-particle size.
Several such a tornado vortexes are enclosed in the working chamber and directed through resonators to icrease their destructive power. Between vortexes (red coored in the picture) there are some zones of a pressure gradience (dark areas) being formed. These zone of depression are almost a vacuum. A structure lattice of any material which repeatedly traversing through such zones of the highest pressure and vacuum in the working chamber is literally broken, called crushed. The technology sence is, a controlled grinding of materials from super-hard to ceramics, polymers and biomass, which found practical applications in a variety of ways- from the grinding up or dressing of ores, to the creation of composites or functionalization and nano-structuring of materials.
Application areas of «TORNADO» technology:
- Powder metallurgy
- Additive, laser and plasma technology
- Mining, ore-dressing
- Engineering Materials
- Building technologies
- Medical and cosmetic industry
- Processing of technogenic and secondary resources
Our production factory can be visited in Prague (Czech Republic).
General description of a typical TORNADO installation as a model
The resonant vortex TORNADO installation is a gas-dynamic mill in which the technology of cascaded adiabatic resonance impact grinding is implemented, impact velocities of which are close to a breakdown threshold. The installation is designed in a way so that any particle of the input material gets literally torn by the repeated crossing of the differential pressure zones in the intervortex vacuum chamber, which produces ultrahigh gradient (pressure drops) at the interface (up to hundreds of thousands atmospheres). When the material is injected into such area of pressure differential, a rupture of the material’s structure and clusters occurs. Such mechanism can be compared to the mechanism of material’s sample destruction, which is done in order to determine its strength characteristics at tensile test plants. That is, the grinding occurs not due to the friction or any other mechanic force, but by “air” and resonances, which provide a high and efficient performance, great flow rate of raw material as well as inexpensive exploitation (no rubbing parts) with low power consumption.
- As an energy carrier (fuel) may be used:
- pressurized air (compressor or a turbine);
- any inert gas supplied under pressure such as argon;
- high-pressure steam (superheated steam);
- Energy gas generated by a free piston engines;
- Supercritical media (fluids), (CO2) for instance;
A new technology is being used inside the resonance vortex mills, a non-contact material grinding, where the grinding processes are performed by means of an air vortex, artificially produced in an enclosed space within the processing chamber.
The equipment is based on the resonance vortex grinding technology, which allows the grinding of any material, from wheat grain to diamonds. The phenomenon of crushing materials of any hardness is possible due to the occurring of pressure gradient zones in the vortex mill that have a of up to hundreds of thousands of atm’s, the generation of multi-stage resonance, and the impact of particles. These effects are similar to those that develop in the air of a tornado column created by nature.
The second (resonance) grinding mechanism is related to the generation of undulating vibrations with a frequency range from sonic to hypersonic (100 MHz and higher). In such a wide spectrum of vibrations for grinded material particles of any size, a frequency is found equal to the resonance frequency of a particle. This mechanism is able to carry out grinding to ultra-fine pieces, measured in hundredths and thousandths of microns (0.01-0.001 microns).
The third (impact) material grinding mechanism is mutual particle impact. At resonance vortex mills, particle impact brings an insignificant contribution to the process of material breakdown. At the currently widespread torsion (blast) mills (Japanese production, for example), this mechanism is essential, however their performance and capabilities are inferior compared to the “Tornado”.
Comparison with jet mills
By the principle of functioning, jet mills are not analogous to gasdynamic vortex mills, and have a specific energy consumption of 20-70 kW*h/t of grinded material, which is comparable to the figure (according to manufacturer) of Tornado -30-75 kWh/t for the same fineness of grind. However, it must be noted that the cost – 75 kW/h, indicated in the catalogue, is estimated in accordance with the power of the compressor Keiser (Germany) the performance of which is 11-13 cubic meters/min at a pressure of 9-11 bar (modes). In reality, such capacity is enough to sustain 2 Tornado installations with a 350 mm processing chamber, since the actual consumption is 6 cubic meters/min for 1 cell at a pressure of 6 bar. Thus, at the capacity of a given compressor, 2 Tornado installations can function simultaneously or even 4 if in rotation. In addition to all – 75 kW*h is the maximum mode of air discharge at receivers (2 in Prague), which allows low-cost mode functioning synchronously with the dispenser when the Compressor supplies the receivers in isolation and spends only 15-25 kWh. The performance of jet mills varies from 50 kg/h to 1.5 t/h. The performance of the gas-dynamic Tornado jet mill varies from 100 kg/h (diamonds) to 3 t/h (biomass) in the working chamber of 350 mm. The performance of steam mills operating on coal and cement is excepted. Their performance may reach up to 10 t/h or more, but they are not suitable for producing ultrafine dry grinding.
The Tornado installations are scalable, all the data provided at the presentations and on the website is applicable to a typical installation with the processing chamber of 350 mm, if necessary, the processing chamber can be increased to 750 mm or 1000 mm, which dramatically increases the air consumption. For instance, the 750 mm chamber requires 35-40 cubic meters/min, which must be determined by the specifics of the material and the need. In many cases, it is cheaper to install one Tornado installation and equip it with 2-3-4 processing chambers under one type of Keiser compressor for homogeneous material, or if required (grinding rocks, for instance) to produce a two or three-stage setup, where each chamber with resonances would fulfil its tasks.
If for torsion (blast) mills, the use of compressed air at pressures of 0.7-1.4 MPa is common, then in a vortex “Tornado”mill the same effect is achieved with 0.2-0.6 MPa, which significantly reduces the costs and allows to obtain a very fine powder that cannot be obtained by any other method. Due to adiabatic expansion there is a decrease in the temperature of the functioning medium within the processing chamber of the Tornado, which allows the prevention of local heating and thermal degradation of the grinded material. The grinding chamber of a Tornado does not contain any rotating or moving parts, which significantly increases its service life, simplifies its construction, facilitates maintenance and its cleaning when replacing the input material that is grinded, which helps in avoiding impurities of the finished product.
The constructive solutions applied in the creation of the equipment provide a significant reduction in electricity cost for powder production, as in comparison with vaguely similar analogies.
The “Tornado” installations have different modifications for different types or groups of materials, as well as various performances. They are equipped with an ICS and a spare processing chamber with a set of resonators for various purposes.
Table 1. Characteristics and the typical “Tornado” installations with a 350mm processing chamber.
* Note: The performance calculations are based on the parameters of the air compressor made by the firm Keyser (Germany): 9-12 m cube/min, 9 bar, class 2/2 air, dew point – 40°C. If a higher performance is required, an individual installation project must be completed on the basis of task terms. In case of additional questions on design, contact the technical Department of the company TORtec ltd.: email@example.com