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Energy efficiency, Runnability and Cleanliness as Key Factors for PM Drying Section Productivity

Esa Virtanen, Timo Haverinen, Suvi Mynttinen, EV Group Oy, Riikka Gerlander, Novide Oy

Oversupply in several paper grades, increasing energy costs as well as paper industry structural change in many markets force paper producers to seek utmost cost-efficiency in production. Production unit closures have been the reality during the recent years, while the remaining units seek machinery optimization to ensure the best possible profitability.

Energy efficiency and runnability optimization constitute a remarkable, yet often untapped potential to improve PM productivity and paper quality in many production units. Reduction of energy costs and drying section runnability improvement seldom require large scale investments. Already minor up-dates, section rebuilds or production adjustments clearly improve the drying section performance. However, drying section productivity optimization always requires a deep understanding on how drying efficiency, runnability and cleanliness of fabrics and cylinders affect each other and the entire drying section performance.

Energy Constitutes Major Part of Drying Section Production Costs

Energy costs constitute 12-14% of total production costs in European countries. In future the energy costs will significantly increase. Drying is the main energy consumer in paper machine: for example the steam consumption of a SC production line causes 53% of the energy costs (VTT Energy). Because no other part of the process consumes as much energy as drying, it is evident that even minor energy savings in drying steam consumption generate remarkable production cost savings

Figure 2
Picture 2. Total energy consumption of SC-paper line (VTT Energy)

Pocket Ventilation, Heat Recovery and Cleanliness Decrease Energy Costs

Moisture profile problems in drying section always indicate decrease of drying efficiency. Already the correction of moisture profile allows significant savings in steam and energy consumption. Moisture profile optimization / correction requires precise information on moisture profile problems' and peaks' origins and reasons. A complete professional survey with measurements performed at different drying section positions enables relevant information for the profile correction. It is normally possible to adjust the process immediately after the survey to even the moisture profile. In addition, a professional survey defines necessary further action for profile correction. Typically moisture peaks originate in moist cylinder pockets without adequate ventilation.

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