Thermodynamic simulation of dryer section heat recovery in paper machines

Modern paper machines are equipped with heat recovery systems that are able to recover over 50% of the energy used by the paper machine. The recovered heat is used for the heating of dryer section supply air, process water and machine hall ventilation. Today, the structure of new heat recovery installations is optimised with sophisticated algorithms to match the design point of the paper machine. However, after installation, the real operation point may change over time from the original design point. To study the effect of these changes and to improve the performance of heat recovery, a simulation program was developed based on thermodynamic modelling. In this paper, the simulation program is compared with measurements from three paper machines. Furthermore, practical guidelines are presented for the improvement of dryer section heat recovery based on conclusions from simulated examples.