14 XERIUM EUROPE
An energy efficient sheet forming process
Oliver Baumann and Stephan Ernst* reveal how newly-developed fabric drainage channels and less friction in the forming process can lead to energy savings and better quality paper
manufacturer. It doesn’t matter what grade of paper is produced, the energy consumption during its production is of increasing importance.
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This article discusses the opportunities for reducing energy use inside the former section and also in other parts of the process by optimising the forming fabric technology. In this respect the efficient
operation is influenced by two major factors, as illustrated in Figure 1. • The drainage resistance of the paper sheet • The total drag of the moving parts in the forming sections. The vacuum level is influenced
by the drainage resistance of the paper sheet. The higher the vacuum applied, the higher its impact on the drive load. The vacuum level depends to a large extent on the sheet forming process. If the sheet structure is open enough after the initial sheet building it is easier to dewater, leading to lower vacuum levels and therefore energy savings in the drives. The total drag of the moving parts is also influenced by friction of the forming fabric running side to the drainage elements. The friction is highly influenced by the yarn material.
September 2013
he efficient operation of a paper making machine is vital to making a profit at any
Figure 1: Theory of friction against the vacuum box To meet this aspect of energy
reduction, Huyck.Wangner, part of the Xerium Group, recently developed and launched two specific product platforms designed to address energy consumption, as shown in Figure 2. Engineered Drainage Channels (EDC) is an innovative warp and weave concept that allows for more efficient drainage of the paper in the formation zone. This new structural concept provides enhanced drainage by providing a more open sheet side surface, thereby enabling reduced drainage velocity. This controlled drainage velocity improves the efficiency of sheet formation during initial
matt building process which leads to improved sheet characteristics and reduced wet-end vacuum requirements. In addition to the EDC fabric
structure, Huyck.Wangner has also introduced a totally new raw material technology, EnerSTAR, which reduces friction of the forming fabrics
Impact of forming fabrics Vacuum Levels: Field results have shown that the initial fibre matt should be open and not too dense. A more dense initial sheet seals the paper and reduces the overall drainage. The flow speed on the paper side of the
wire has a significant impact on the porosity of the initial fibre matt. A higher surface open area provides a lower flow speed and keeps the initial matt more open. In order to provide a more controlled drainage the surface open area on running side needs to be reduced, which is in contrast to conventional wisdom in the industry. Forming fabric performance is mainly defined by its behaviour in the initial fabric drainage section of the paper machine. By thinking out of the box, development engineers shifted the focus from the fabric structure to a specially formed drainage channel, which in conjunction with the paper side topography, paves the way to optimum sheet formation. The optimum initial fibre matt provides: • proper sheet formation, due to mobility of the fibres
• retention of fines and fillers (matt is always finer than the fabric)
Figure 2: EDC and EnerSTAR two unique new technologies
• open structure, to facilitate water removal over the whole former at lower vacuum levels. The precise channel specifications are formed by different ratios between the paper side and running side weft and warp yarns. Also, changing the yarn diameters and/or densities on paper or running side has an influence on the shape of the channel. Application engineers can now build a special channel
Pulp Paper & Logistics
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