Chemical industries, specifically the production of acids and fertilizers involves the consumption of high amounts of fossil energy from various sources, that generate tremendous toxic pollutants causing significant energy and environmental costs per total production. In this work, a case study of a triple-super-phosphate plant of ‘Mdhilla’ in the southwestern region of Tunisia is presented. Heat and mass balances were developed for the rotary kiln dryer in this plant. Exergetic analysis was also conducted to improve the production process performance level. The heat losses to the environment by radiation and natural convection were found to be less than 3%. However, the hot exhaust air heat losses were as high as 77% of the total input energy. To reduce this important waste heat, two practical solutions were proposed in this study: heat recovery from the rotary kiln dryer to preheat the combustion air and thus reduce the fuel consumption and secondly, the substitution of heavy fuel by natural gas to reduce the cost and hence, limit pollutants emissions. The presented results revealed pertinence of both solutions that give 40.36% energy saving and 31.68% reduction in CO₂ emissions.