The drying section stands out as the most significant consumer of thermal energy within the paper machine; through processes like heat transfer, evaporation, water removal, hoods and hot cylinders, the slurry pulp transforms into paper with approximately 90% to 95% solid content.
Given this, optimizing the operation of the dryer section in terms of both heat transfer and water removal becomes crucial. The good news is that energy efficiency can be enhanced with relatively modest investments: improving doctoring can help increasing cylinder drying capacity and runnability. At the same time, it can lead to better paper quality and improved production efficiency, with consequent reduced power consumption and operating costs.
To start from scratch, Oradoc meticulously evaluates critical positions within the drying section, specifically, the section’s beginning and end; in some cases, doctoring systems are also responsible for detaching the paper from the last drying cylinder and directing it either to the pulper tank or to the pope or size press. When poor performance coincides with severe wear conditions, a complete overhaul of the doctors is often the wisest choice, as this safeguards optimal cleaning performance, even at higher machine speeds. In response to a request to enhance the paper machine’s performance in the drying area, Oradoc proposed its well-known OraClean, the rigid doctoring system that ensures correct and uniform cleaning of the dryer cylinder, while its simple design guarantees easy maintenance and blade replacement. The supply usually includes doctor backs, supports, bearings, and an electro-mechanical or pneumatic oscillation system, that is all components that can be configured according to customer specifications, offering options for manual execution or via pneumatic cylinders.
Oradoc – Boosting Performances
But what features should an effective drying doctor have? The rigid back of the OraClean system has a simple geometry with minimal volume, ensuring the correct working load on the dryer cylinder for maximum cleanliness. Additionally, the electro-mechanical or pneumatic oscillation enhances cleaning efficiency on the cylinder, allowing proper operation even at high production speeds. To optimize performance at both the beginning and end of the drying battery, Oradoc recommends adopting the complete OraFlex flexible blade holder. In this specific section of the drying area, flexibility proves most effective. The OraFlex blade holder includes special high-temperature pressure tubes, ensuring an even load across the drying cylinder surface during work. Moreover, it facilitates easier blade replacement during rest phases. The rigid doctor back, equipped with torque arms, maintains the correct working position and ensures stability in case of paper breaks. Meanwhile, the electro-mechanical or pneumatic oscillation further enhances cleaning efficiency on the cylinder, guaranteeing proper operation even at the highest production speeds.
Another often underestimated aspect that can significantly impact the drying process is a device designed to prevent paper dust and trims from causing issues. Our brand-new dust removal system can be installed on both flexible and rigid blade holders, regardless of format. It includes a suction box directly attached to the crossbeam and a suction nozzle on the blade holder: this setup allows to concentrate suction precisely where needed – close to the blade – thanks to an adjustable front part. The implementation of the dust removal system has no adverse impact on the blade holder’s flexibility, but it rather ensures high efficiency by specifically addressing air leakages.
This system can be equipped with either an electromechanical or pneumatic oscillation system, which is particularly favored in paper mills operating under high-temperature conditions.
While flexible hoses are generally preferred for high temperatures, the system can accommodate various hose types suitable for different installations. Its compact and open structure minimizes maintenance issues and product non-compliance concerns, facilitating easier dust removal and preventing contamination. Consequently, this design contributes to overall product quality. Furthermore, all drying area doctors can be outfitted with either the OraThread or OraShoot systems. These systems enable seamless threading of the tail from one roll to another without relying on ropes the most hazardous elements in paper machines.
Additionally, air blows can be integrated into both OraClean rigid doctors and OraFlex flexible doctors. These enhancements offer substantial benefits, including improved machine operator safety and greater efficiency in terms of time and energy savings, finally automating the operation.
