Method in the regulation of a multi-layer headbox and a multi-layer headbox
AssigneeValmet Paper Machinery Inc.
InventorsJyrki Huovila, Petri Nyberg, Michael Odell
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Abstract
A method and device for the regulation of a pulp suspension flow in a multi-layer headbox and a multi-layer headbox for a paper machine/board machine. For the formation of different layers in the web, at least two pulp suspensions having different pulp concepts flow through the multi-layer headbox. The flow of a pulp suspension that forms one of the layers in the web is regulated by regulating the component flows that constitute this flow and regulating the concentration of the component flows independently from one another. In this manner, i.e., by regulating only this the particular layer, the total flow of the pulp suspension leaving the headbox is regulated.
Claims20
A method for regulating a total pulp flow from a headbox, comprising the steps of:
- passing at least a first, second and third component flow having certain pulp properties from said headbox to form a first, second and third layer of a web, respectively, said second component flow being situated intermediate of said first and third component flows, and
- regulating the pulp properties of said second component flow in a direction transverse to the direction of said second component flow to provide different pulp properties at different locations in the transverse direction of said second component flow without regulating the pulp properties of said first and third component flows in a direction transverse to the direction of said first and third component flows, respectively, the pulp properties of said second component flow being regulated by
- forming said second component flow from a plurality of component subflows arranged in the transverse direction of said headbox,
- regulating the rate of at least one of said component subflows, and
- regulating the concentration of said at least one of said component subflows independently from the regulation of the rate of said at least one of said component subflows,
- whereby the pulp properties of the total headbox pulp flow is regulated.
In a multi-layer headbox for forming a total pulp flow, said headbox including an inlet header, distributor pipes, a turbulence generator and a discharge duct, means for passing a first pulp suspension component flow from said inlet header into said distributor pipes, through said distributor pipes into said turbulence generator and further into said discharge duct, said first pulp suspension component flow being discharged from said discharge duct and forming a first layer of a web, means for passing a second pulp suspension component flow into said turbulence generator and then into said discharge duct to combine with said first pulp suspension component flow, said second pulp suspension component flow being discharged from said discharge duct and forming a second layer of the web, and means for passing a third pulp suspension component flow from said inlet header into said distributor pipes, through said distributor pipes into said turbulence generator and further into said discharge duct to combine with said first and second pulp suspension component flows, said third pulp suspension component flow being discharged from said discharge duct and forming a third layer of the web, said second pulp suspension component flow being situated intermediate of said first and third pulp suspension component flow, the improvement comprising;
- means for introducing a plurality of adjacent second component subflows at different points in a transverse direction of said second pulp suspension component flow to form said second pulp suspension component flow, said introducing means comprising a first and second medium source for providing first and second subcomponent flows, respectively, for each of said adjacent second component subflows, and
- regulating means for providing different pulp properties of said second pulp suspension component flow at said points by independently regulating the rate and concentration of each of said plurality of adjacent second component subflows such that the total headbox pulp flow is regulatable by means of the regulation of said second pulp suspension component flow without regulating said first and third suspension component flows, respectively, said regulating means comprising a mixer unit for combining respective ones of said first and second subcomponent flows, such that for a constant second component subflow, said first subcomponent flow is increased and said second subcomponent flow is reduced by a corresponding amount.
Dependencies are inferred from the claim text.