Long silicon powder in the reduction furnace
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The long silicon powder in the reduction furnace – several furnaces produce silicon powder during production. I used to think it was due to an insufficient hydrogen flow rate, but even after increasing the hydrogen ratio to over 3.5, sometimes even higher, the problem persisted. You could say it’s a material issue, but it only occurs in a few units, and that too only in the later stages; it’s due to current or other factors, yet other units under the same conditions are not affected. I would like to ask what the reason is. Could someone help me? Thank you!
Wow, when did you start driving? Don’t even know what atomization is? Silicon powder is primarily formed when the temperature of the exhaust gases is above 550 degrees at later stages; this is also somewhat related to the mixing ratios, but the main factor is the self-decomposition of trichlorosilane. You can search on Baidu for the temperature at which trichlorosilane undergoes self-decomposition.
To be honest, I really don’t know if it’s because of this. Thanks
Reply to 2# ourlive: This person has a good point, but I don’t understand how a tail pipe temperature above 550°C could lead to the formation of silicon powder inside the furnace; it should be the tail pipe itself where silicon powder is formed, right?
Reply to 4# yuanrs: That’s why one needs to take studying seriously – one has to read the characters carefully. I mean the temperature of the exhaust gases is higher than 550 degrees Celsius. Generally, when foreign reduction process packages are imported, there is no exhaust gas heat exchanger, and the inlet temperature is maintained at around 130 degrees Celsius. However, as the power of the silicon rods increases over time, the amount of radiation generated becomes high. The decomposition reaction of trichlorosilane has a characteristic in that once it starts, it cannot be stopped; unless the feed is stopped and fed again, the effect of adjusting the ratio of components is minimal. The methods used to prevent mist formation generally involve reducing the amount of trichlorosilane and lowering the power level.
This post was last edited by yuanrs on 2011-6-24 22:32. Reply 5# ourlive: Thank you for your reply. But then why do, sometimes, several furnaces here suddenly stop operating due to leakage to ground? When they are restarted, there is a thick layer of silicon powder on their bases, and silicon powder appears both in furnaces that have been in use for a long time and those that have been in use for a short time? ((Once silicon powder appears, both units that have been in operation for a long time and those that have been in operation for a short time are unable to avoid it. ）
In the event of leakage, is there any sparking inside the furnace? If black powder appears only around the electrodes, it is likely not silicon powder, but rather carbon powder formed by the decomposition of the tetrafluoro insulation coating due to high temperatures. Silicon powder only deposits on the floor of the reduction furnace when atomization is severe during operation, and the deposition occurs in a uniform thickness.
Increase the feed temperature of trichlorosilane and the return temperature of high-temperature cooling water; pay close attention to the temperature indicated by the infrared micrometer and make adjustments as needed! Could it be uneven air intake? Is the feeding method for the chassis of your furnaces the same as that of other furnaces?