Study On The Volatile Release Behavior Of Aluminum Electrolysis Anode During The Baking Process

The release of volatile during baking process impacts greatly on anode quality and energy saving. It is a main method to make full use of the volatile released during the baking process to save energy. The release behavior of anode volatile is also a important foundation based on which to set baking temperature curve. So there is important value in both theoretical and technical application to carry out basic research on release behavior.This paper studys the pyrolysis character on thermobalance, finds the effect of the heating rate on the pyrolysis character. The result shows volatile release faster as the heating rate increase. Distributed Activation Energy Model(DAEM) analysis method is used to calculate kinetic parameter, which avoids the effect of heating rate. The result shows that the active energy is not consistent, and changes with the temperature changes. It is mainly about 25-60kJ/mol, declining in the stage of semi-coke, and increasing quickly when reaction is about to end.The release curve of hydrogen and methane is measured through fixed bed reactor, finding that their curves are double peak curves. Result of analysis shows that the double peak is resulted from pyrolysis ofβresin andαresin in pitch. Gaussian Muliti-peaks is used to separate them, and then the kinetic parameters are calculated, obtaining the release amount of volatile changing with temperature. Anode weight loss experiments is conduct in tube furnace. Differences between the curves obtained from thermoalblanace and tube furnace are contrasted. Release of tar is get through indirect method. So the tar release curve changing with temperature is obtained.Based on the release curves from experiments, the model of volatile release and transfer is founded coupling heat transfer and mass transfer. The curve that volatile release into flue through flue wall is obtained by simulation. The result shows that volatile released from anode does not enter flue immediately due to the mass and heat transfer. It lags a lot during the process of mass transfer through anode, packing coke and flue wall. For a 32 hours baking furnace, the lag of tar and methane is about 32 hours which is one flame cycle. Lag of hydrogen is less, which is 16 hours. The lag phenomena contribute to the advantage of energy use from volatile.