Heat loss in ethanol-water distillation column with direct vapour recompression heat pump and its effect on some performance criteria

The economic nature of vapour recompression system has been identified in enhancing reduction in energy consumption and improvement in energy effectiveness of distillation columns. However, the effects of certain parameters have not been taken into consideration in the overall evaluation of such distillation systems. Perhaps this accounts for the low patronage of the system in bio-ethanol distillation which is becoming a competitive motor fuel to petrol and a source of hydrogen for fuel cells. One of such parameters is the column heat loss which has either been assumed to be a certain percent of reboiler heat transfer or negligible. The purpose of this study was to evaluate the heat loss from an ethanol-water vapour recompression distillation column with pressure increase across the compressor (VRCAS) and compare the results obtained and its effect on some parameters in similar system (VRCCS) where the column heat loss has been assumed or neglected. Results from the study show that the heat loss evaluated was higher when compared with that obtained for the column in which the heat loss was assumed to be a certain percent of reboiler heat transfer. The results also showed that increase in heat loss could have significant effect on the total energy consumption, the reboiler heat transfer, the number of trays and energy effectiveness of the column.