Abstract:
In the present work, a steady state model of sextuple effect backward feed evaporator system including heat recovery by product and condensate flash has been developed. Flashing can be incorporated for product flash only, alternate condensate flash only, series condensate only or the combination of these. And all these are compared to achieve efficient heat recovery system.
Quasi Newton method is used to solve the nonlinear model equations. Overall Heat Transfer Coefficient (OHTC) is improved using Gudmundson's model for Long Tube Vertical evaporators. In the model, for BPR determination TAPPI correlation has been used. For determining most of the liquor properties Regestad correlations are used.
Results for different flash arrangements are compared and it is concluded that a system with both product and series condensate flash arrangement give the most efficient heat recovery system.
Although the program thus developed is used for multiple effect evaporator system of pulp and paper industry, nevertheless it can also be applied in many other process industries, with suitable modification in calculation method of OHTC.
