Test Driving Equipment: The Value of Paper Drying Simulations
Production rates are impacted by every section of a paper machine and the dryer section is no exception. Making sure your machine has adequate drying capacity and it is not "dryer limited" is key to achieving desired machine speeds. This can be very challenging when your machine runs several different grades. Each grade requires different system settings and potentially different drainage equipment to optimize its speed and quality.
Dryer testing in a controlled laboratory can allow any mill to determine the best settings and equipment for each grade to achieve uniformity and desired speed. With this information and what production tonnage needs to be produced for each grade per month, intelligent decisions can be made about how to optimize value generated by the machine.
Equipment to maximize heat transfer and provide the best thermal profile for high production grades at the determined machine speed can be assessed. Using the same equipment, conditions for the other grades can be run to determine what ideal settings for their speeds will lead to energy savings and higher quality product. This knowledge can also guide decisions in the cases where a compromise needs to be made in equipment type and potentially save money.
Typically, mills want to know the best they can achieve with their current equipment for the grades they produce. It is important for them to understand and quantify the value modern equipment can provide. The type of equipment selected is important, but equally important is how the equipment is set-up at installation.
How equipment is set-up will have significant impact on performance. Changing syphon clearance can impact heat transfer, but also drive loads if condensate behavior transitions from rimming to cascading. In some cases, off-setting stationary syphon pick-ups can improve drainage, heat transfer, and steam use. Dryer bar count and spacing can also be used to increase heat transfer or to "tune" a dryer to address edge effects on the paper quality. These are things you can not easily change, but understanding how they impact the value across the grade range gives you the information to make the right decisions.