Exergy Efficiency of Bulgarian Lignite fired Steam Boiler P-62 at various Load and Fuel Quality

The article is presented a study of exergy and energy efficiency of steam boiler Ep 670/140 also referred as P-62 that burns low-quality Bulgarian lignite. Both efficiencies were determined in design modes of the boiler: on two loads - 70 % and 100 % and using on each load three different qualities of fuel in terms of its lower heating value - deteriorated 5525 kJ/kg (1320 kcal/kg), guaranteed 5945 kJ/kg (1420 kcal/kg) and improved 6700 kJ/kg (1600 kcal/kg). Due to the specific design features of the boiler - "T" shape design and numerous heat transfer surfaces the "fuel-product efficiency" method for calculation is used. The obtained results show that exergy efficiency in whole range of load and lignite quality change is low - between 31