Reasons for unqualified hydrogen quality in dry recovery of polysilicon production
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The polysilicon produced using the Siemens method has an unacceptable level of C and O content after dry recovery; it is too high. What methods can be used to address this issue?
Regarding the oxygen content, it mainly depends on whether tasks such as nitrogen purging and hydrogen displacement were carried out properly before the initial feeding of the material. If done properly, the O content should meet the standards. As for the content of C, it depends first on the previous nitrogen purging and hydrogen displacement processes, and second on the selection of an appropriate adsorbent.
Is a high carbon content indicative of problems with adsorption, and does the filter after adsorption not meet the required standards? O means that the system wasn’t cleaned thoroughly during startup.
The C that is generally detected is likely a gaseous substance existing in forms such as CO and CH4. Increasing the vent volume; if the level still doesn’t drop, it might get problematic
A high carbon content is due to incomplete filtration in the dry recovery system, which fails to meet the standards； If the oxygen content is high, that won’t happen. It’s a closed-loop system; could it be that there’s a leak in your system? But I really can’t figure out how oxygen could be present The previous replacement was of substandard quality.
May I ask the original poster: What method is used to determine the C/O content of the hydrogen gas recovered by dry methods?
If the oxygen level is not up to standard, it’s definitely due to inadequate purging before driving; the amount of fresh hydrogen supplied can be increased, and purging can be carried out while the vehicle is in operation until the standard is met. A high carbon content also allows for an increased supply of fresh hydrogen, which can be used for replacement while the system is in operation. If the results are not satisfactory and the trend continues, it is necessary to analyze as soon as possible whether there is a problem with your system
Activated carbon adsorption, gas chromatography analysis shows the presence of CHO as well as moisture.
If it is an imported adsorbent, then the adsorbent has not been regenerated properly before starting the vehicle. If it is a domestically produced adsorbent, a relatively high C content should be quite normal.
Agree with what was said above; the issue with adsorbents could lead to C,O problems
If the adsorbent is of poor quality, it’s impossible for the C and O levels to be within acceptable limits. If it’s activated carbon, then C levels will definitely be present. By the way, may I ask the original poster what the acceptable standards for C and O levels are for you?
Regarding issue o, I agree with what everyone has said. As for the issue of replacement before driving, there are other possibilities for c as well. If your facility’s reduction furnace uses heat transfer oil for cooling, and there is a leak inside the furnace (not under pressure, that is, the oil pressure is higher than the pressure inside the furnace), the heat transfer oil will vaporize directly due to the high temperature, thereby entering the reduction exhaust gases and ultimately leading to a high C content
If C is high, it could be due to an issue with the quality of the activated carbon, or the activated carbon may have become pulverized; alternatively, there might be a leak in the heat transfer oil used to heat the activated carbon. O-high should be rare; wasn’t the initial replacement thorough enough? It’s unlikely. If the air (containing oxygen) isn’t properly replaced beforehand and the vehicle is driven, that would be extremely risky ； Is it leaking? The possibility is also low; if it could be detected, it would have to be at near-room temperature with water present, in which case it would have hydrolyzed long ago. Let’s all think it over again, work together, and solve the problem.
The exhaust gas recovery systems designed by CDI generally use imported activated carbon. If the oxygen content is too high, it’s definitely because the initial replacement process was not carried out properly. I remember that CDI specifies a value of 0.1V% for this parameter; as for the carbon content, I’m not sure whether the user is referring to activated carbon or something else. If it’s activated carbon, then it’s likely that the filter used for hydrogen recovery is not up to standard – the minimum required specification is 4UM