To achieve these, the main tasks that a headbox must perform are:
- Ensure a uniform distribution of the fibrous suspension over the entire width of the machine, so that the same amount of stock always flows in each point of the forming wire;
- Ensuring that the fibrous jet lands on the forming wire in a specific area, with the right angle and with a defined speed differential with respect to the forming wire itself;
- Avoid the formation of directional currents in the liquid mass, to prevent the generation of inhomogeneity between the various areas in a transverse direction with respect to the machine direction;
- Avoid the formation of fiber flocs by means of a controlled microturbulence.
Having said that, let’s analyze how the quality of the headbox can affect energy consumption.
Headbox and energy consumption
As regards the sheet formation, it is important to emphasize the relationship between the density of the stock and the formation itself. In case of high density of fibers in suspension, i.e. in the presence of a poorly diluted stock, the fibers are very close together and tend to aggregate forming flocs, thus negatively affecting the quality of the sheet formation. To avoid this inconvenience, the conventional solution is to increase the dilution of the stock entering the headbox, in order to decrease the density of the fibers and thus keep them separate from each other. This option, however, involves an increase in the flow that the fan pump must supply and this, correspondingly, leads to a higher energy consumption, since the pumping power is directly proportional to the flow. Luckily, there is an alternative solution: equip yourself with a headbox capable of developing microturbulence such as to avoid, or at least limit, the formation of flocs within the feed flow.
The A.Celli hydraulic headbox has been designed precisely for this purpose: to obtain excellent sheet formation at high concentrations and, at the same time, reduce the energy consumption of the production process.
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