In the industrial process of ferronickel production from lateritic minerals, the influence of design factors, constructive and dimensional aspects on the heat transfer and energy performance of the equipment have been little addressed. The literature focuses on cement kilns or iron and steel production applications. This work compares the influence of the approaches considered in the early phases of the design process on heat transfer and energy performance for two ferronickel rotary kilns. For this purpose, a retrospective analysis was realized identifying requirements, operating principles, and approaches applied in the definition of specification and conceptual design. This analysis was carried out, taking into account one operation year data of two rotary calcining kilns of 185 meters and 135 meters in length, both of 6 meters in diameter and similar feeding rate between 170,000 and 180000 kilograms per hour. The analysis showed that kiln 1 had a functional approach in the early phases of the design process, while kiln 2 additionally has an environmental and energy approach, which allowed to improve the heat transfer and energy performance. This was verified with software based on the AHP method. The software results showed that counter-current and cross-flow rotary kiln 2 is a better conceptual design alternative for environmental and energy requirements than counter-current rotary kiln 1.