The Electro-Thermal Fluidized Bed (ETFB) is one among the variety of available purification technologies that can provide growing demand of the global market for high quality carbon materials like graphitized natural or synthetic graphite including battery grades, petroleum coke and even conductive carbon black. However, there are some distinctive features that put the ETFB technology forward and thus merit to be mentioned.
(Notice: The description of the ETFB basics itself requires a separate narration. If interested, please follow the link https://youtu.be/ujR1Ztve3wo and see a short video in advance to get briefed on what the ETFB is).
So what are the key advantages of ETFB? In fact, there are only two but quite powerful. They are the direct resistive heating and highly intense mixing of material.
The direct resistive heating occurs due to the electric current passing through a fluidized bed of conductive carbon material, between two submerged electrodes. To be more precise, in a fluidized bed formed by certain amount of feedstock material, semi-product and final product, only the last two are most likely to be heated electrically, because of their purity, improved crystallinity and quantity. The incoming feedstock is heated up to operating temperatures mainly by thermal radiation from the fluidized bed core. The duration of heating is nearly 1-2 seconds.
The positive effect of the direct heating is that it is possible to reduce drastically the furnace’s inside operating space approximately to 10-20 cubic feet in size. That provides direct concentration of huge amount of energy in a relatively small volume and creates favorable conditions for ultra-high temperatures of 2800-3200°C, quite enough to reach 99.99% graphite grade and even higher.
However, the direct heating would not be so beneficial without the highly intense mixing of material in the fluidized bed.
The nature of the electric current is it passes through 3D-objects in random directions, especially if we talk about unstable bulk material systems like fluidized beds. In a ETFB it is highly likely to have a number of shot-lived changing streamers which release energy locally. At the same time the mixing process tends to level such heterogeneity. It stabilizes the thermal regime almost instantly and makes the fluidized bed homogeneous.
Another side-effect provided by mixing is that vaporized impurities can be easily moved out from the particles’ surface via the inert gas agent. This feature matters, because it prevents graphite from secondary contamination.
Therefore, the direct resistive heating and highly intense mixing of material in a fluidized bed are closely tied physical processes which secure required temperature mode, uniformity, fast treatment and, finally, excellent product grade. The mentioned above particularities in turn ensure high productivity rate in range of 100-1000 kg/h and, what is not less important, at continues mode.
So that are main reasons why the ETFB technology attracts some manufactures and should be paid attention to.
All the best and have a nice day wherever you are.
February 02, 2019
by Serhii Fedorov
Thermal & Material Engineering Center –
Graphite Purification Technologies
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