A twin-wire model gap former: design and evaluation methods
2006 (English)In: Nordic Pulp & Paper Research Journal, ISSN 0283-2631, Vol. 21, no 1, 54-58 p.Article in journal (Refereed) Published
A one-sided model twin wire gap former, the KTH-former has been developed. The former consists of headbox with transparent gables, forming unit, including a forming roll with a transparent surface and outer forming wire and a reservoir system for water/fibre suspension handling. To allow the study of blade forming, a blade can be introduced against the outer wire to generate a pressure pulse.
Two measurement techniques have been utilized to study the flow mechanisms of fibre suspension flow in the forming zone;
A pressure sensor has been used to study the dewatering pressure along the forming zone.
A high speed video system was used to visually study the suspension flow.
The study was made with pulp fibres. Fibre floes were introduced in the center of the headbox at the beginning of the linear nozzle contraction, by an introduction tube with an inner diameter of 10 mm. The acceleration in the nozzle contraction was used to separate the fibre floes in the Suspension making them move individually, thus making the visualisations easier. To avoid the problem of floc break-down at nozzle exit when using a conventional linear nozzle with parrot's beak outlet, two Curved contraction blocs were inserted, giving a more constant acceleration profile, letting the floes keep their integrity in the emerging jet.
The high speed video system had two main arrangements, for the Study of floc behaviour in the forming zone. A mirror installed on the machine structure visualised a certain area of the forming zone. Alternatively, a mirror fastened to the back plate of the forming roll followed a specific area of the wire (and roll), making it possible to follow the floes through the entire forming zone. It is then possible to detect any relative motion between floes and wire.
Place, publisher, year, edition, pages
2006. Vol. 21, no 1, 54-58 p.
Blade forming, Experimental studies, Fibre flocs, Roll forming, Twin-wire forming, Dewatering, Flocculation, Reservoirs (water), Video cameras, Blade forming, Experimental studies, Fibre flocs, Twin-wire forming, Fibers, Blade, Drainage, Fibers, Flocculation, Forming Rolls, Gap Formers, Twin Wire Machines
Paper, Pulp and Fiber Technology
IdentifiersURN: urn:nbn:se:kth:diva-5218ISI: 000236358800009ScopusID: 2-s2.0-33645656027OAI: oai:DiVA.org:kth-5218DiVA: diva2:8036
QC 20100901. Tidigare titel: The KTH-Former, a model gap former: design and evaluation methods. Titel ändrad samt uppdaterad från Manuskript till Artikel i tidskrift 20100901.2005-05-312005-05-312010-09-01Bibliographically approved