Flowbox (Headbox)
The flowbox is the core component of the paper machine. It achieves uniform distribution and precise jetting of the stock through the synergistic action of three main parts: the distributor, the slice chamber, and the slice.
Its structure includes components such as turbulence generators and dilution water devices, which can adjust stock flow velocity, pressure, and fiber dispersion, directly affecting the basis weight distribution and strength properties of the paper .
It is mainly divided into three types: open, air-cushion, and hydraulic, with a design speed range of 1200-1500 m/min and an approach flow consistency range of 0.4%-1.0%.
The flowbox consists of three core components:
Distributor:Uses a cylindrical structure to eliminate pressure differences, equipped with dilution water devices for automatic cross-direction basis weight control, and flexible branch pipes to attenuate stock flow pulsations.
Slice Chamber:Contains an equilibrium chamber to mix stock flows and eliminate pressure pulsations, equipped with a thermal compensation system to balance temperature-induced deformation.
Slice:Features 61 micro-adjusters spaced 102mm apart; edge flow channels allow for adjustment of fiber orientation; the slice opening width reaches 6180mm.
The turbulence generator employs a combination of fixed and movable sections. By adjusting the flow channel cross-sectional area, it controls turbulence intensity, maintaining an effective turbulence level within a flow velocity range of 300-800 m/min.
Main Types
Open Flowbox:Suitable for medium- and low-speed paper machines, uses a tapered header distributor structure, with manual adjustment range of 0-100mm.
Air-Cushion Flowbox:Equipped with an air cushion to stabilize the liquid level, compatible with cylindrical distributors, improving basis weight fluctuation by over 40%.
Hydraulic Flowbox:Employs a spiral perforated roll and integrates a step diffuser for efficient flow rectification.
Multi-Layer Former:Produces multi-layer composite sheets through stratified stock distribution technology.
Design Parameters and Technological Innovations
As of 2022, mainstream technical parameters include:
Approach flow rate range: 1000-1800 L/s
Number of slice lip micro-adjusters: 61
Jet consistency: 0.4%-1.0%
Technological innovations are reflected in:
Movable turbulence generators enabling adaptive flow rate control.
Cylindrical distributors replacing traditional tapered headers, eliminating hydrodynamic defects.
Thermal compensation systems using hot water circulation to compensate for temperature-induced deformation of the slice beam.
Integrated Systems and Production Process
Forms an integrated system with dewatering elements:
Forming board controls initial dewatering rate and eliminates fiber flocculation.
Deflectors (or doctor blades) and vacuum boxes work together to create vacuum suction for dewatering.
Vacuum couch roll increases wet web dryness to 16-22%.
Within the production process:
- Stock forms micro-turbulence through the step diffuser.
- Stock speed and wire speed matching accuracy reaches ±0.05 m/s.
- Full-automatic cross-direction control is achieved through the QCS (Quality Control System).