Basis weight - Dilution control
When we are talking about conventional headboxes, we find several
shortcomings, which can be solved by the installation of a DGI headbox.
The main thing that produces these shortcomings is the tapered header.
DGI dilution control headbox technology improves quality and productivity
with less than 5% dilution water.
Advantages and benefits
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Basis weight profile control by means of
dilution water, that can be manual or automatic controlled.
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Improvements in paper properties.
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Grade changes are made easily and quickly.
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A ratio of 4:1 is possible
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Control of fibre orientation
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Lower energy costs as the recirculation water is
eliminated.
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Can use furnish of 100% waste, long or short fibres,
or a mixture.
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Product range from ultra light tissue to heavy
board.
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Speed from 15 to 1500 m/min.
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Can be used in fourdriniers, secondary wires, twin
wires, inclined wires, formers, etc.
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Other characteristics are: uniform flow across the
sheet width, pulsation absorption, and uncoupling of mechanical vibrations...
Modular design
The complete system is formed with three elements:
the central distributor, the dilution water system, and the headbox. These three
components are part of a new installation, or used individually for rebuilding
an existing headbox.
The central
distributor
The central distributor is the key element of this
system, and replaces the tapered header.
The pulp goes into the central distributor and exits through several pipes
placed at the same level around the tanks circumference. These pipes connect to
flexible hoses of the same length, feeding to each one of the diffuser sections
on the headbox.
The dilution water
system
The dilution water system for the profile control
avoids the need for spindle adjustment of the top slice lip on the headbox.
On start-up the valves are set to 50%. If one of these valves is closed the
basis weight will increase proportionally in a defined bandwidth of the sheet,
if the valve is opened, the basis weight will decrease.
The headbox
The headbox only has the function of sheet
formation, turbulence generation, and pulp acceleration.
The headbox has a symmetrical structure, which eliminates the thermal
deformation produced by thermal expansion. It also has a rigid top slice lip,
and turbulence generators incorporated into the top and bottom lip. Another
characteristic is the special outlets which stabilise the jet. |
