THERMODYNAMIC CALCULATIONS USING THE WATER TO COMBUSTIBLES RATIO

A METHOD is presented that uses the water to combustibles ratio (W/C) introduced by Frew and James to predict more accurately the thermodynamic outcomes from the use of bagasse as a fuel. Key features of the model presented include: mass balance equations; constant pressure specific heat equations of flue gas components; equations for the change in enthalpy of flue gas components between a gas temperature T and an ambient temperature To and in combustion air between To and a preheated air temperature Ta; estimation of enthalpy losses in exhaust flue gas; spreadsheet modelling; discussion of ‘minor losses’; sugar cane technology applications: prediction of steam and power production capacity; calculation of adiabatic combustion temperature; estimation of furnace combustion temperature; implications for boiler process control; and design of dehydration plants. It is suggested that the model is more accurate than methods generally used in the industry, based as it is on more detailed empirical specific heat equations for flue gas component gases and on a more precise application of different latent heat values (i) for water formed by combustion, and (ii) for water present in the fuel.