Simulation of the condensation and deposition processes in regenerators of glass furnaces

Abstract

The fouling of regenerators of glass melting furnaces by deposition of flue gas condensates has been studied experimentally with simulated exhaust gases flowing through a cylindrical stack gas tube. The deposition of sodium sulphate and sodium metaborate has been investigated for various furnace conditions. A theoretical model based on thermodynamics and boundary layer transport theories has been developed and applied to determine the nature and deposition rates of the condensates. It has been validated with experiments as well as with practical situations. This model includes the calculation of the composition of the formed dust and of the gaseous phase. The influence of flue gas velocity, temperature distribution and flue gas composition on the fouling of regenerators has been illustrated for soda-lime glass furnaces and sodium borosilicate furnaces. It is shown that sodium sulphate deposition mainly takes place in the sub-top and middle sections of the regenerators. The deposition of sodium sulphate in soda-lime glass furnaces appears to be nearly proportional to the sodium concentration in the flue gas. The chloride and sulphur concentrations influence the deposition behaviour in the sub-top sections, the concentrations of oxygen, water vapor or carbon dioxide hardly influence the fouling in regenerators. In sodium borosilicate furnaces, sodium metaborate and sodium tetraborate formation takes place in the middle sections of the regenerator, sodium sulphate will deposit in the higher sections.