This book is an engineering application on energy saving and sustainable use of resources. Using available industrial water for cooling and reducing energy losses due to fouling problems by using quality water for cooling air compressors in a power plant with cooling exchangers, minimising energy cost increases and improving compressor efficiency. The second application deals with combustion processes for an altitude of 3800 m.a.s.l., in which the residual oil N°6, requires to be preheated for better atomisation and efficient combustion, resulting in an economical operation; and that due to the effect of altitude, the volume or flow of supply air for combustion is affected. It is important that the flue gas outlet temperature is on average 365°C, to avoid that at 150°C the acid dew point of flue gases with sulphur content appears, causing corrosion damage by condensation of SO2.