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Preparation of spherical quartz powder by high-frequency plasma melting method

wallpapers Tech 2021-01-15
The high-frequency plasma fusion method is used to prepare spherical quartz powder, with a moderate temperature range, stable control, high output, and high spheroidization rate, so it is a more suitable production method. The principle is similar to that of the flame melting method, and it mainly changes the high temperature heat source into a plasma generator.
 
Thermal plasma is also called local thermodynamic equilibrium plasma. Its main feature is that the local electron temperature (Te), ion temperature (Ti) and gas temperature (Tg) in the plasma are almost the same. Arc plasma, high frequency plasma and induction plasma are all thermal plasmas.
 
The working air is compressed air, and the working air volume is 10m3/h. The input power of the high-frequency plasma generator is 100kW, and it generates 4000℃-7000℃ high temperature gas as the heat source. The silica powder is transported from the top to the arc zone of the plasma reaction furnace through the feeder, and the powder is heated to melt and gasify, After being quenched by a special quencher, then collected by gravity, collected by cyclone (micron level) and bag dust collection (nano-level), within 1s-2s, spherical micron and nano SiO2 powders can be obtained.
 
The main equipment includes plasma generator, powder conveyor, plasma reactor, cooling recovery device, cyclone collector, bag collector.
Powder conveyor
The raw material of silicon powder to be processed into a spherical shape is mixed by gas transportation, and after fluidization, it is continuously and stably transported to the plasma arc area.
 
Plasma generator
It is mainly through the electromagnetic coupling of electric field energy into the discharge medium to generate plasma. When the radio frequency alternating current passes through the matching coil, the oscillating magnetic field generated nearby will be coupled to the partially ionized gas load (the load flows in the discharge cavity) And provide ohmic heating to maintain the plasma. Inductive plasma is particularly suitable for powder spheroidization, because of its large volume and the long residence time of axial powder feeding in the discharge zone.
 
Cooling recovery device
The temperature of the calcined material is above 1000°C. Before the material enters the dust collector, the temperature must be lowered to below 200°C. In order to ensure reliable cooling, the system adopts water cooling and air cooling. The high-temperature spherical silicon powder that has been melted and dispersed is quickly cooled to avoid crystallization.
 
Collection device
The cyclone collector mainly collects the molten spherical silicon powder, and the bag collection mainly collects the gasified nano silicon powder. When it reaches the lower part of the reaction chamber, the high-temperature vapor is quickly cooled and condensed by a large amount of air from 2000℃ to below 120℃, forming spherical silica powder. Under the transportation of plasma gas and chilling gas, the spherical powder is in the bag and cyclone. Collect it and get the finished product.

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