Sintered magnesia is the basic raw material for the manufacturing of refractory products. It is the main component for shaped and unshaped products, mixes and mortars. In 2012 about 6,5 Mio. t of sintered magnesia were produced worldwide. The basis for its production is raw magnesite, which is extracted in open pit and underground mining. The sintered magnesia production is very intensive concerning raw materials an energy costs. This master thesis deals with the optimization of the use of energy in a long rotary kiln for the production of sintered magnesia by burning raw magnesite. In addition to a general overview of refractory materials and magnesia production, the transportation and thermal processes are described. The considered long rotary kiln and its flue gas cleaning system are explained and the provided mass- and energy balances are analysed. The heat losses through the rotary kiln shell are calculated, so that the values from the balance sheet can be verified. Futhermore, opportunities for a better raw material preheating and for optimization of the refractory lining of the rotary kiln are presented.