Online analysis of exhaust gases from reduction furnaces in the polysilicon industry
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In the polysilicon industry, exhaust gas analysis requires measuring the levels of TCS, DCS, and STC in order to calculate the conversion rate of TCS. I’m not sure what kind of online analyzers are currently used in this industry (are there any good online analyzers included in imported process packages?). Some factories do not conduct such analyses at all, while others need to measure the levels of these components in order to control the temperature and pressure in the reduction furnace. I would be very grateful if the colleagues in instrumentation from various design institutes, as well as experienced users, could share their insights!!!
Regarding the exhaust gas from the reduction furnace, the process package recommends a manual method for handling this gas. This is because of its high corrosivity, and it is necessary to avoid contaminating the reduction furnace; online instruments require zero-point gas and span gas, and in this case H2 can only be used as the zero-point gas. As for the calibration gas, TCS tends to liquefy easily, and manufacturers do not provide such gas. All these factors make it difficult to use online analysis instruments in this application. There are several projects under construction currently, and chromatography is generally the method of choice; however, due to the reasons mentioned above, the valves and columns used in chromatography suffer severe corrosion and damage. When we asked foreigners about this, they outright refused to do it. Their response was that while the system might work well for half a year after using chromatography, it would suffer significant damage after that period, and maintenance would be very costly; therefore, they advised against going ahead with it. But in the distillation section for trichlorosilane, the substance is in liquid state at this point. In this case, we recommend using near-infrared technology, as it allows for the use of plug-in probes that can be inserted into the pipeline; the instrument is then connected to the probe via an optical fiber. The measurement cell is made of highly corrosion-resistant materials, and in the event of corrosion, only the measurement cell needs to be replaced without damaging the instrument. On the other hand, the instrument can be placed in a safe area, eliminating the need for on-site maintenance and thus preventing any harm to personnel. ***Dedicated to the online analysis industry, QQ47076815, 13611128646*********