Airlaid test bench with narrow production width
In the recently completed IGF project 17101 N/1 "Increase of energy efficiency in the short fibre airlaid nonwoven forming process" an airlaid test bench with a process width of 0.5 m has been successfully put into operation at ITA. Due to the modular design of the test bench, it is possible to integrate different, innovative airlaid forming head concepts into the test bench for evaluation. The overall aim is to increase energy efficiency and the homo-geneity of the nonwoven at narrow production widths. The attractiveness of the Airlaid-process increases especially for SMEs, due to lower construction cost of the plant and lesser space requirement. Depending on the fibre forming concept it is thus possible firstly, to produce niche products in the airlaid process at small quantities. Morever, the process provides potential for the processing of production waste such as residual fibres that are previously reclaimed by thermal recycling.
The construction of the entire test bench consists of a variable fibre delivery system, a variable fibre forming system and a suction system. The manually piled up, pre-opened fibres are sucked in by the fibre delivery fan onto a conveyor belt and supplied to a diffuser into the fibre inlet of the fibre forming system. The modular fibre inlet can be variably adapted to the forming process in order to ensure an optimal fibre distribution. Depending on the configuration of the intake and exhaust air volume flow further false air is pulled in via the false air feed.
Forming head concept
The modular design of the fibre forming area with a width of 500 mm and a length of 900 mm is specifically designed to allow integration of different forming head concepts. In the illustration the forming section is shown without a forming head insert. The image illustrates the test bench with an integrated forming head. Because of the transparent design of the housing it is possible to examine the fibre formation process by means of Particle Image Velocimetry (PIV) or high-speed video recordings (HSV). In addition, several measuring points are installed for determination of pressure and velocity of the process air.
Fibre forming system
Below the fibre forming system there is a filter belt, which can be operated at different speeds. The suction box below is designed using Computational Fluid Dynamics (CFD) to ensure a good distribution of the exhausted air over the production width. The housing of the suction box can be opened on one side, in order to integrate different systems of guide plates for investigation purposes and thus to change the trajectory of the fibres. The process air is sucked by an exhaust fan with a maximum airflow of 8,000 m³/h and led into a filter system.
In initial experiments, a forming head was constructed and integrated into the test bench, using oscillating screens for fibre dissolution and distribution on the filter belt. Due to the homogenous distribution of the fibres over the whole production width, the entire process doesn’t show an increase of CV Value in the border regions, as it is often noticed in airlaid processes. The specific air consumption is around 60 % lower compared to the considered benchmark. This airlaid forming principle is characterized by a gentle material processing. Therefore, a possible application is the formation of fragile materials, such as seeds. By cascading several different fibre forming heads a multicomponent nonwoven fabric can be produced.
The IGF-project 17101 N/1 of the Research Association was sponsored by the AiF within the scope of Förderung der industriellen Gemeinschaftsforschung (IGF) from Bundesministerium für Wirtschaft und Energie, following a decision of the Deutschen Bundestag.