DETERMINATION OF THE OPTIMUM GAS EXHAUST TEMPERATURE IN BAGASSE BOILERS

摘要

This paper presents the results of the optimal gas exhaust temperature evaluation in bagasse boilers. Four different options for modifying the construction of an APU 50 boiler, manufactured by Caldema Industrial Equipments Ltda., were considered, as well as different scenarios for bagasse prices and for the commercialisation of the obtained electricity surplus. The boiler's thermal calculations were carried out by using the software SBC-Steam Boilers Calculation. The analysis was implemented based on two approaches: considering the annual incremental cost of boiler operation (approach I) and the commercialisation of the electricity surplus (approach II), the latter using Gate Cycle version 5.51.0r for simulating a sugar mill typical steam cycle and for obtaining the amount of generated electricity. The most important conclusion of this study is that the results obtained by approach II should be given preference. The reason for this is the variability of the bagasse market prices , that are now much lower than the equivalent price of the fuel-oil. The optimal value of the gas exhaust temperature (120-130℃) is much smaller than the value now practised by boiler manufacturers (about 160℃), showing the existence of a potential for increasing the efficiency of bagasse boilers.