Improved Dryer Drainage with Managed Differential Pressure Control

摘要

Paper dryers have traditionally been controlled by two methods; differential pressure control or blowthrough flow control. Both of these methods provide adequate performance when properly applied; however each method has limitations and neither provides optimal dryer drainage or energy efficiency. Steam is vented and potentially wasted under many operating conditions, excessive high-pressure motive steam is used in thermocompressor systems and unnecessary equipment and line erosion occurs. A new concept in dryer drainage control called managed differential pressure control combines the advantages of both traditional methods. This strategy automatically adjusts the differential pressure varying machine speeds, dryer pressures, and condensing load without the need for operator intervention. Siphon characteristics are used to determine the differential pressure required to maintain optimum blowthrough flow rates with the sheet on and off of the dryers. Significant cost reduction can be achieved in steam consumption, equipment and piping replacement/repair, at a lower overall cost of ownership than conventional control methods.