Optimized process control is important for the entire papermaking process. The goal is to achieve the required product quality while at the same time minimizing the costs of raw materials, additives and energy. Utilizing steam to dry the paper, accounts for a large portion of the energy costs in the paper industry. Siemens has developed the Sipaper APC DrySec software solution to reduce the steam consumption. It 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. The 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. Depending on the type of paper machine, other parameters can be calculated, such as the heat curve, the heating of the white water and the quantity of steam in the steam box.
Sipaper APC DrySec can, in addition, 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 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. The Siemens solution for an energy-saving operation mode for dryer sections has already been implemented in the papermaking process at Rhein Papier paper mill. Siemens supplied the electrical equipment in July 2001, when the mill was built. Rhein Papier GmbH produces newsprint and is an alliance partner of the Myllykoski Group.