The development of energy-efficient designs direct heating the Castner furnace for graphitization electrode products
Energy-saving constructions and regulations of the Castner furnaces operation were developed for graphitization of large-sized electrode workbenches, which have no other analogue in Ukraine and reach energy expenses decrease by 20–25 %. Thermal and electrical furnace state was experimentally investigated during graphitization of electrode workbenches with different expansion blocks. It was found out that gasification process of carbon material by water vapor occurs in operation area during graphitization process in the Castner furnace. It leads to decrease of heating velocity of electrode workbenches by 10–20 %. Physical and general mathematical models of graphitization process of electrode workbenches in the Castner directly heated furnaces were designed, taking into account transferring mechanisms of damp and water vapor, thermal effects of chemical gasification reactions of carbon containing furnace materials, hydrogen and carbonic oxide conversion in heat-insulating material, hydrostatic pressure in granular heat-insulating layer. Numerical model of thermal-electrical and mechanical state of the Castner graphitization furnace was developed, taking into account non-linear dependence of thermal and electrical properties of carbon materials on temperature and pressure. This dependence was verified by data of physical experiment. The influence on thermal and electrical state of graphitization furnace was defined for different parameters of technological regulations and equipment: electrical energy introduction mode; bleeder stacks location scheme; the form of electric-contact blocks; physical properties of heat-insulating furnace feed. Technical solution for temperature drop in end workbenches was found. It was determined that the usage of expansion blocks is the most efficient method. The blocks must be in the form of hollow graphite cylinders filled with high-resistance heat insulating granular material. The recommendations for implementation of energy-saving technological regulations of graphitization process and technical solutions for improvement of furnace construction were developed.