The methane content in the recovered hydrogen is high

Uh... I once came across a Russian publication that discussed the reaction mechanisms behind the presence of methane or methane derivatives as impurities in various chlorosilanes... If hydrogen containing methane enters the reduction furnace, it seems that silicon carbide will be formed. Once silicon carbide impurities are present in the silicon rods, cutting them after ingot formation would damage the cutting machine... Silicon carbide is just too hard...

Hello, Minos, thank you. Does it affect the carbon content and resistivity of polysilicon? Does your company have this kind of phenomenon?

Our company doesn’t seem to be aware of this phenomenon. I haven’t yet checked whether there are carbon impurities in our hydrogen, but since we produce hydrogen through water electrolysis, methane should not be present in it. As for resistivity, I think silicon carbide has no effect on the resistivity of polycrystalline silicon, because once they form an atomic crystal, all electrons are bonded together, and thus no \"donors\" or \"acceptors\" can form...

Silicon carbide has a significant negative impact on the multi-wire cutting of polycrystalline silicon ingots. The mechanism of multi-wire cutting machines involves using steel wires to press silicon carbide coated with PEG in order to cut the silicon ingots; this shows that silicon carbide is extremely hard and can form hard spots within the silicon ingots, which leads to the wires breaking during cutting. Could the methane mentioned by the original poster be caused by substandard activated carbon? confusion

Methane is probably not caused by substandard activated carbon in the adsorption tower... At that temperature, elemental carbon cannot react with hydrogen; it depends on the source of the hydrogen...

It seems strange that such high levels of methane are produced during hydrogen recovery by the original poster; I’m not sure what your process involves. According to our analysis, methane should not be generated at all. If the methane content is too high, not only will silicon carbide be produced, but additional reactions will also occur, resulting in other products that affect product quality; this requires great attention.

Our hydrogen is also produced by electrolyzing water, and the pure hydrogen analysis shows no methane. However, the hydrogen in the exhaust gas from the reduction furnace contains methane after recovery. The following is a description of CDI that I saw on a forum, which mentions the issue of methane in hydrogen. “Regarding CDI’s exhaust gas recovery system, there are a few points that I think deserve attention: 1. The separation efficiency of the HCL-chlorosilane distillation tower has a direct impact on the distillation process. 2. The CH4 content of H2 after adsorption by the adsorption system affects the quality. 3. Absolute stability of the hydrogen compressor system. ” Now we have taken measures such as replacing hydrogen and checking the reduction furnace for oil leakage. Everyone, what is the mechanism behind methane production? I’m a newbie; please help me!

I still don’t understand........ How is it possible for hydrogen to react with activated carbon to produce methane at temperatures in the high 30s degrees? If there is methane in the exhaust gases, then that means your trichlorosilane contains some type of alkane substance... But if that’s the case, then your silicon rods already contain silicon carbide.

If there are no major issues with your system (such as valves on the replaced process pipelines not being degreased or not cleaned properly), then it must be the oil from the reduction furnace causing the problem; it’s impossible for organic substances to originate from elsewhere in the system.

Do you mean that the heat transfer oil has leaked into the equipment and pipes..............? If that’s the case... then the system has security risks... There shouldn’t be such problems... We use water cooling, and if water gets into the system, things will get even worse...