Air intake velocity of the reduction furnace
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The inlet velocity of the reduction furnace, the type of nozzles, and their distribution have a significant impact on both the flow field and heat field within the furnace. These factors are also related to the stable operation of the furnace as well as its power consumption. According to data from various domestic and international studies, the inlet velocity is said to be between 30–60 m/s (different studies provide varying figures, which may be related to parameters such as the height of the silicon core). Please share your opinions on what you consider to be the optimal range for this velocity.
But doesn’t everyone discuss this issue here?
Who provides 30-60? Please provide your feed rate, inlet area, and inlet pressure as well as the furnace pressure, so that we can discuss this in more detail
Gases are compressible; you’ll understand this if you study fluid dynamics. Velocity is related to the pressure difference between the inside and outside, and blockage pressure must be taken into account when performing calculations. The higher the flow rate, the more turbulent it becomes, which facilitates the renewal of the surface layer in silicon deposition. The number and placement of nozzles, as well as the size of the nozzle holes, are also crucial for production
30-60 m/s are values from numerical simulations in some literature on polysilicon operation. Our inlet area is 0.00271 m², the feed rate is approximately 720 m³/h, and the pressure drop is 700 kPa. What flow rates do you generally use during operation?
Is it 36 pairs or 40 pairs, and the nozzle is 6mm? What is the deposition rate?
It drifts by silently; few people answer such questions these days
The typical nozzle exit velocity is 80 m/s, and the crossbeam velocity should not be less than 2 mm/s
Calculating the gas velocity in a reduction furnace is quite complex; in the past, people themselves weren’t clear about the flow patterns and temperature conditions there, and they just used those as excuses to deceive others. It takes a lot of time to master the Fluent software. The gas velocity will not exceed the speed of sound, which is 340 m/s; if the value you calculate is higher than this figure, then you need to consider it. A high velocity of the gas is not acceptable either; you need to ensure that the gas forms an effective turbulent flow pattern. Those in charge of production should keep the furnace running stably; that’s all that needs to be understood. The manufacturers of reduction furnaces have studied this topic more thoroughly than you do. It takes a lot of time to master this, so you shouldn’t continue working in a company. If you understand fluid dynamics, heat transfer, mass transfer, chemical process simulation, temperature field modeling, and numerical analysis, you will surely be an excellent doctoral graduate. But you do think about this issue carefully.
At present, the flow rate at this nozzle varies from one facility to another; there is still a significant difference between the actual values and those reported in the literature. Previously, the flow rate at the nozzle of the reduction furnace was estimated to be around 167 m/s, with a TCS conversion rate of 10.8% and a deposition rate of 68.47 kg/h. I wonder if anyone here has any experience in this area to share.