Energy reduction in the manufacture of pre-baked carbon containing

Abstract

Carbon containing electrodes are made with a considerable reduction of energy over conventional methods for use in the aluminum industry and the like that have the strength, density and control of dimensional shape necessary for an electrode withstanding the considerable thermal, electromagnetic and chemical forces encountered in the electrolytic production of metals such as aluminum. Thus, the manufacturing process forms the green electrode materials of carbon powder or a carbon-alumina, etc. mixture and mixed with a binder comprising a liquid thermo-setting resin which is pre-cured under pressure to form a hardened stable electrode form that does not droop during coking or require support. Savings of energy here results by eliminating a heat cure step and in a reduced coking volume and time for such electrodes. Preferably the coking takes place in a tunnel kiln to further reduce energy by heating substantially only the electrodes. Coking times for such electrodes are further significantly reduced from the usual 2 days coking cycle with several days of controlled warmup getting the furnace to the maximum temperature and may be only a few hours particularly when indented slots or holes are provided in the green electrodes to minimize path lengths for escape of volatiles during coking. This permits a much faster warmup cycle and a much shorter overall coking period to save additional significant amounts of energy. Thus both faster heating rates to achieve maximum coking temperatures and shortened coking times required at peak heats are afforded by this invention. Further energy saving improvement is afforded by use of metallic or graphite heat conductors positioned in the holes or slots during coking.