为改善脱水、降低能耗、延长压榨毛布使用寿命优化压区系统的措施

Improving dewatering, energy usage, and press fabric life by optimizing the nip system

新式多层有接缝高定量压榨毛布的使用,以及纸机车速不断提高,导致了出压榨总干度不够,无法实现压榨干度最大化。压区脱水可以提高出压榨的干度、降低真空度而且延长压榨毛布的使用寿命。压区脱水要有一些为整个压区系统工作所必须的部件。造纸厂通过收集和监控与纸机性能相对应的数据,就有机会优化系统,以便在许多方面对性能进行改善。

Press fabric suppliers for years have promoted increased void volume, heavier press fabric design and the need for improved vacuum levels in the press section. Today most mills lack adequate vacuum to dewater press fabric designs that can be as heavy as 2100 g/m2. Vacuum systems were originally designed to dewater compress- ible endless designs with weights between 1300 and 1500 g/m2. Eight to 12 CFM was all that was required to dewater these designs effectively. Today’s modern multiple layer seam press fabric designs require between 18 and 20 CFM to dewater effectively, relying strictly on vacuum box dewatering. This has led to inefficiencies in total dryness leaving the press and most presses are operating with press fabric designs that are too heavy for the application. The other overriding factor is speed. As machines are pushed to the upper limits, the effectiveness of traditional vacuum box dewatering is reduced, therefore press solids are not maximized at increased running speeds. Nip dewatering can lead to improved press solids, a reduction in vacuum and im- proved press fabric life. Many modern machines have proven that controlled nip dewa- tering versus strictly vacuum dewatering is a very efficient way to improve press performance. Nip dewatering has some necessary components that must be present in order for the total nip system to work. Doctor blades, saveall pans, moisture monitoring equipment, and proper press fabric designs need to be in place to effectively nip dewater. This equipment allows for proper control of the nip system. One must be able to control vacuum so that the split between nip and vacuum box is optimized. In order to do this, one must catch the water being discharged in the nip and what is removed at the suc- tion box. These levels must be measured over fabric life in order to maintain the proper splits. Once this data is collected and monitored versus machine performance, the papermaker will see opportunity to optimize the system for improved performance in many areas and realize the true benefits of nip dewatering.