A new software solution with an energy-saving control strategy for dryer sections has been developed by the Siemens Industry Solutions Division to reduce steam consumption in papermaking by decreasing energy needs in the drying process.
Optimised set points are calculated for all parameters relevant to drying and adjusted to the actual process conditions. The Sipaper APC (Advanced Process Control) DrySec system has already been piloted at Rhein Papier’s paper mill in Hürth near Cologne, reducing the main steam requirement by more than three per cent.
This new Siemens syetm is based on a physical process model that takes into account all the parameters relevant to drying. The main focus is on the air requirements, heat recovery, steam and condensate system, together with their mutual interactions and dependencies.
Measured values are used to adapt the model at regular intervals to the current process conditions. Sipaper APC DrySec uses this data to calculate the best possible set points and these values are then transferred to the process control system — air flow in the hood can then be set to minimize the quantity of air supplied. The system also ensures that water evaporating from the paper web is exhausted continuously without condensation.
Calculating parameters
Depending on the type of paper machine, other parameters can also be calculated, such as the heat curve, the heating of the white water and the quantity of steam in the steam box.
In addition, Sipaper APC DrySec can be used as a soft sensor because it also calculates process variables for which no instrumentation is installed. This includes, for example, the moisture content and temperature of the paper web upstream and downstream of each drying cylinder, and the energy consumed in the heat exchanger. This, says Siemens, leads to a better understanding of the plant.
The process model can also be used for diagnostic purposes. For example, it can detect and display the gradual contamination of a heat exchanger, due to scaling and fouling.
Sipaper APC DrySec is one of the modules of the Sipaper solution platform specially developed for the pulp and paper industry. It can be linked to both Siemens and third-party process control systems.
