Goa Petcoke Consultancy Services provides comprehensive consultancy services and solutions in the field of petroleum coke calcination. During the course of working on various assignments, we probed into the fundamental principles of design of the rotary kiln systems for petcoke calcination, resulting into evolution of this paper. The important process criteria in calciner design are retention time, heating up rate and operating drafts. These factors depend on kiln dimensions, slope, heat transfer rate and air injections. To understand this well, we have worked out mass and heat balance across kiln, cooler and incinerator. The mechanical design should consider load factors, thermal expansions and strength of materials at elevated temperatures to ensure mechanical soundness and protection against flexing and distortion of kiln shell. The refractory design should take into account differential thermal expansion coefficients, ability to withstand high temperatures, resistance to spalling, chemical attack, abrasion and good coatability.