To cite this version:Leena Sivill, Pekka Ahtila. Energy efficiency improvement of dryer section heat recovery systems in paper machines -A case study. Applied Thermal Engineering, Elsevier, 2009, 29 (17-18) This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
ACCEPTED MANUSCRIPTEnergy efficiency improvement of dryer section heat recovery systems in paper machines -A case study
AbstractModern paper machines are equipped with heat recovery systems that transfer heat from the humid exhaust air of the paper machine's dryer section to different process streams. As a result of process changes, the heat recovery systems may operate in conditions far from the original design point, creating a significant potential for energy efficiency improvement. In this paper we demonstrate this potential with a case study of three operating paper machines. Both operational and structural improvement opportunities are examined. Since the existing retrofit methodologies for heat exchanger networks can not be applied to cases with condensing air, we use thermodynamic simulation models presented earlier to assess the effects of possible changes on the existing heat recovery systems. In order to reduce the required processing time of the simulation models, only a limited number of pre-screened retrofit designs are considered. The pre-screening is carried out on the basis of guidelines presented earlier.The analysis in the case mill revealed savings of 110 GWh/a in process heat with profitable investments. According to the follow-up study, the investments carried out have resulted in 12 % lower fuel use and 24 % lower CO 2 emissions. The results imply that all operating paper machines should be similarly examined.