For silicon containing wastes
Incineration of Si-containing wastes is much more complex compared to the previous processes and bears the risk of clogging the system. Basically the Si part of the silanes will be oxidised to SiO2. However depending on the conditions in the combustion process, the SiO2 can either be formed in particle solid stage or in case of not appropriate conditions, sticky SiO2 material will be generated by combustion. In order to avoid the forming of this sticky material, the temperature in the combustion chamber has to be kept below a critical limit. By this measure, just SiO2 in particle form is created. In order to avoid the agglomeration of the SiO2 particles on the refractory lining of the incinerator, special attention to be paid to the flow pattern in the combustion stage. The gaseous and/or liquid waste streams will be fed from top into the vertical arranged combustion chamber via special designed nozzle arrangements. At defined operating conditions, the organic parts will react with the combustion air to CO2 and H2O, the silicon will be oxidised to SiO2. In case the silanes are present as chlorosilanes, HCl and Cl2 will be formed acc. to the deacon equilibrium.
After the combustion stage, the fluegas will be quenched to a temperature suitable for a baghouse filter application either by liquid / air injection or if possible by using a steam boiler.
The SiO2 formed in the combustion process will be precipitated in a baghouse filter before the fluegas will be either released to the atmosphere or, if chlorosilanes have been disposed, HCl will be recovered in a HCl recovery stage.
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