Reduction of gaseous boron compounds in the waste gas of glass melting furnaces

For boron containing glasses, you have to consider a gaseous fraction in the exhaust gas besides the particulate boron compounds. Within the framework of a research project finished in the year 2005 investigations into the emission of particulate and gaseous boron compounds were carried out on 18 glass melting furnaces with boron containing batch. The plants are different with regard to the molten glasses, furnace type, type of firing as well as downstream emission control technologies. The precipitation of particulate boron compounds is unproblematic. The precipitation of gaseous boron compounds is clearly more difficult and further measures have to be taken in respect of the effective precipitation. In a current follow up project, especially the reduction potential of gaseous boron compounds is investigated through the installation of a high temperature sorption stage (injection of fine-ground glass raw materials into the exhaust gas flow behind the superstructure at exhaust gas temperatures of 1400 degrees C) and/or the injection of alkaline solutions into the waste gas at lower temperatures. Investigations in the exhaust gas of E-glass melters were carried out successfully. Reduction rates of more than 95 % could be proved for gaseous boron compounds. The activities are supported by thermo-chemical calculations in the run up and during the measurements.