How is the performance of Open type headbox?

How is the performance of Open type headbox?
The performance of Open type headboxes can be evaluated from the following aspects:
1、 Structural and design characteristics
Basic structure: An open headbox is generally controlled by the pulp level inside the box to control the speed of the pulp on the web (pulp speed), and is controlled by adjusting the height of the weir plate inside the box. Its structure is relatively simple, mainly including the slurry distribution area, uniform area, and lip plate area.
Design features: The design focus of an open slurry box is on how to evenly distribute the slurry inside the box, and achieve stable and controlled slurry flow by adjusting components such as homogenizing rollers and partitions. When designing, it is necessary to consider factors such as the flow rate, concentration, and fiber length of the pulp to ensure the forming quality of the paper.
2、 Performance performance
Slurry flow stability: An open headbox should ensure smooth slurry flow without large eddies, cross flows, and instantaneous velocity fluctuations. The velocity distribution of the pulp flow over the full width should be consistent to ensure the uniformity of the paper page.
Fiber dispersibility: The fibers in the headbox should be evenly dispersed to avoid sedimentation and flocculation. This helps to improve the strength and uniformity of the paper page.
Consistency of concentration: The concentration of all parts of the online pulp flow should be consistent to ensure uniform quantitative distribution of the paper in the horizontal direction.
Adaptability: Open flow boxes are generally used for low-speed paper machines and have good adaptability to specific types of paper and raw materials. However, with the development of papermaking technology, its applicability may be limited to some extent.
3、 Usage and Maintenance
Easy to operate: Due to the relatively simple structure of the open headbox, its operation and maintenance are relatively simple. Operators can easily adjust and control various parameters of the headbox.
Cleaning and maintenance: The headbox needs to be regularly cleaned and maintained during use to ensure its performance and stability. Open flow boxes may be easier to clean and maintain due to their structural characteristics.
4、 Limitations
Homogenization effect: Compared to some advanced modern headboxes such as air cushion headboxes or multi-layer hydraulic headboxes, the homogenization effect of open headboxes may be poorer. This is mainly limited by its structural design and working principle.
Scope of application: Due to the limited homogenization effect of the open headbox, which is generally used for low-speed paper machines, its applicability may be limited. In high-speed paper machines or situations with high requirements for paper quality, it may be necessary to choose other types of headboxes.
In summary, open flow boxes have certain characteristics in terms of structure and design, performance performance, use and maintenance. However, with the continuous development and progress of papermaking technology, its limitations have gradually become apparent. Therefore, when selecting a headbox, it is necessary to consider the specific production needs and process conditions comprehensively.