Pinch analysis of the Norske Skog Skogn TMP mill

Examensarbete för masterexamen

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Type: Examensarbete för masterexamen
Master Thesis
Title: Pinch analysis of the Norske Skog Skogn TMP mill
Authors: Festin, Moa
Mora, Valeria
Abstract: Energy conservation measures can bring important environmental and economical benefits to the most energy-intensive industry sectors such as the pulp and paper industry. The measures include among others investing in more energy efficient process equipment and improving process integration. A tool that has successfully been used in pulp and paper mills to improve process integration and achieve steam savings is pinch analysis. In this master’s thesis, a pinch analysis of one part of a thermo-mechanical pulp (TMP) mill, Norske Skog Skogn, is presented. The study aimed at improving the process integration and to decrease the steam demand of the mill. Additionally, the effect of decreasing the electricity consumption was studied for two different scenarios: when certain amount of the electricity-intensive mechanical pulp is replaced with recycled paper and fillers and/or when implementing more energy efficient refining. The results showed that investing in measures that decrease the electricity consumption of the mill can lead to an insufficient production of internal steam and consequently to an increased demand of external steam to cover the deficit. Another way to cover the deficit of steam is to decrease the steam demand of the process by improving process integration. Pinch analysis was used to identify the major sources of inefficient heat exchange i.e. pinch violations in the system and to propose three retrofits that improve the heat exchanger network. Apart from these three retrofits focusing on the heat exchanger network, two additional retrofits, not connected to the heat exchanger network, were also investigated. These were preheating of certain streams and the integration of a heat pump. The major source of pinch violations is the paper machine heat recovery system, the cooling system and the district heating system. In the proposed retrofits the total clean steam consumption is decreased by improved process integration. In the first retrofit 1.1 MW of clean steam (4 % of the total clean steam consumption) are recovered by solving pinch violations mainly associated with the district heating system. In the second and third retrofits 2.2-2.8 MW (8 %-11 %) respectively of savings are achieved by modifying the paper machine heat recovery system and the district heating system. By investing in a reboiler with higher capacity and preheating certain streams it is possible to save 4.6 MW (18 %) clean steam. Finally, by integrating a heat pump it is possible to reduce the clean steam consumption by 3.5 MW (13 %). The combination of the previous retrofits makes it possible to reduce the total clean steam consumption by 8.9MW (34 %).
Keywords: Kemiska processer;Chemical Process Engineering
Issue Date: 2009
Publisher: Chalmers tekniska högskola / Institutionen för energi och miljö
Chalmers University of Technology / Department of Energy and Environment
Collection:Examensarbeten för masterexamen // Master Theses

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