Regarding the concentration of hyposodium as a by-product of CH3SiCl3 in vapor-phase silica
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RT, our company plans to use CH3SiCl3 instead of SiCl4 for production. However, the current process conditions cannot ensure that the concentration of sodium hypochlorite as a by-product remains above 10%. The carbon dioxide generated during the reaction reacts with the alkali, which not only consumes the alkali but also leads to crystallization in the absorption tower when a high concentration of alkali is used – this issue is most pronounced in winter (in the northern regions). Therefore, we are seeking advice from experts on ways to maintain an appropriate concentration of sodium hypochlorite while avoiding crystallization. Alternatively, we might consider abandoning the use of sodium hypochlorite altogether; we would like guidance on how to deal with such low-concentration levels of this substance
1. Method to prevent crystallization: The pipeline in which a high-concentration alkali solution is added requires steam heating, which is easy to implement. Just check the freezing point of alkali solutions at different concentrations and you’ll understand. 2. Disposal of sodium hypochlorite and treatment of wastewater: This is also a fairly mature treatment process. A low-concentration solution of sodium hypochlorite is introduced into a mixing tank, where it is oxidized and reduced using sodium bisulfite solution; thereafter, the wastewater is neutralized with acids and bases to meet discharge standards. Another approach is to first carry out catalytic oxidation on the sodium hypochlorite-containing wastewater to break down most of the sodium hypochlorite, and then apply the first method to the resulting wastewater. Many manufacturers produce the catalysts used for catalytic oxidation; each manufacturer has slightly different usage conditions, so it is possible to inquire with the catalyst manufacturers. In fact, to go deeper into it, the reason MTS is used instead of STC for calcining silica black is due to the generation of CO2; therefore, the load during MTS production should be reduced, right?
Could you let me know what the range of specific surface area for your fumed silica is?
Our alkali pipeline is equipped with steam tracing, so the alkali delivered through it does not crystallize; however, it causes severe crystallization once it enters the absorption tower
Generally, around 160 and around 210 are produced
Do the pipe ends for adding alkaline solution often get clogged? Since you are preparing a high-concentration hyposodium solution, the concentration of alkali added is too high. Ours is diluted to about 10% and then sent to the alkali scrubber tower to treat the exhaust gases.