SIMULATION OF EVAPORATION SYSTEM IN PULP AND PAPER PLANT

Abstract

In this thesis, steady state model of sextuple effect backward feed black liquor evaporator including heat recovery by flashing has been developed. Flashing can be either for condensate, or product, or both. The arrangement for condensate flashing can be either series or alternate. All these systems are simulated and compared for the purpose of achieving efficient heat recovery system. A general simulation program, which can handle different types of evaporation systems like backward, forward and mixed feed, with flashing and without flashing, is developed in C++ language. The globally convergent method is used to solve the nonlinear model equations. The program is flexible to handle multiple effect evaporators having number of effects greater than six. The results obtained are compared with those reported by other workers. The results of the simulation agree well with those reported by Kern[13 ], Libby[15] and McDonald [17]. The result from the simulation study shows that an evaporator with series condensate and product flashing arrangement is found to have the best steam economy. An attempt has been made to have alternative modeling tool of evaporator system by Artificial Neural Network (ANN). The ANN model is trained, tested and compared with the data obtained from the conventional method. The comparison between the results of the ANN and simulation model shows an average error of 0.59%. The result of this attempt shows that ANN is capable of modeling the system with very good accuracy.