Pulp Paper & Logistics
INDUSTRY NEWS 17 XERIUM
derives from the characteristics of the press felts, as new felts have more open structure until they become compressed by multiple nip cycles. Depending on nip load and press felt design this can last for several days. To obtain efficient dewatering at the uhlebox the machine is operating at a reduced speed.
The challenge is to run the paper machine at full speed from start up without uhleboxes. With Booster Technology and QS
Technology Xerium has delivered two press felt concepts to meet this challenge with a variety of energy saving possibilities.
Figure 3
EDC technology and the new running-side material technology EnerSTAR were specifically developed to improve paper making in terms of machine runnability, efficiency and paper quality. Field results have proven these platforms to be beneficial when applied individually. However the combination of EDC together with EnerSTAR, creates benefits up to an even higher potential. Beside the newest forming fabric
technology this article is mainly on potential savings in the press section.
Impact of press felts Dewatering within the press section is a complex interaction between paper, press felt, roll cover, uhlebox vacuum and machine speed. One method of water removal within the press section is uhlebox dewatering. Water is pressed into the void volume of the press felt and transported to the uhlebox where high vacuum levels are applied to remove the water from the press felt. However, the most efficient dewatering on high speed
machines is nip dewatering. High amounts of water can be removed in the press nip from the paper web through the felt into the void volume of the roll cover and finally sprayed out by centrifugal force into the saveall tray. To achieve nip dewatering the press felt needs to be saturated to obtain the efficient
hydraulic forces to accelerate the water flow.
The majority of paper machines
are running with a combination of both. At the start-up of new press felts it is common to run the machine with uhlebox dewatering due to lack of saturation within the press felt structure. This
Booster Technology The Booster Technology focuses on creating the most efficient pore-size and pore-size- distribution within the press felt and can be applied on every design within Xerium’s press felt portfolio. A new standard woven press felt
shows a pore-size-distribution at a major level of 40-50µm; press
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Figure 4 November/December 2014
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