Double Nip Press for Fibrous Web Dewatering
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Solution Overview
Problem
Conventional dewatering devices for fibrous webs experience overload and reduced dewatering performance at high production speeds due to the felt being overloaded in the 'lump breaker' press.
Innovation Solution
A double nip configuration in the first press, with a wire roll and two couch rolls forming nips, where the wire roll is wrapped by a wire conveyor and the couch rolls are wrapped by a common felt, and a tubular suction device dries the felt between nips, with optional heating by a steam blower box to modify water viscosity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a single nip press configuration is used, then the device complexity is low, but the dewatering performance deteriorates at high production speeds due to felt overload
Solution Approach 1:
The single press nip is segmented into two separate nips by introducing a second couch roll. The first nip is formed between the wire roll and first couch roll, while the second nip is formed between the wire roll and second couch roll. This segmentation allows the felt to be used in two separate pressing actions rather than being overloaded in a single action, thereby maintaining dewatering performance at high production speeds.
Solution Approach 2:
The pressing action is extended from one dimension (single nip) to two dimensions (double nip configuration). By adding another couch roll and creating a second pressing point, the system utilizes an additional spatial dimension to perform dewatering, effectively distributing the moisture removal task across two separate pressing zones rather than concentrating it in one location.
2Productivity
If the felt is used continuously without drying, then the device complexity is low, but the dewatering efficiency decreases due to felt saturation
Solution Approach 1:
The felt is dried between the two nips using a suction device, performing a preliminary drying action before the felt enters the second nip. This preliminary action removes excess moisture from the felt, preventing it from becoming saturated during the second pressing operation and maintaining consistent dewatering efficiency throughout the process.
Solution Approach 2:
A suction device is introduced as an intermediary element between the two nips to manage the felt's moisture content. This intermediary component actively removes moisture from the felt during the transition between pressing actions, preventing the felt from carrying over excessive moisture that would reduce dewatering efficiency in the second nip.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
Enhances dewatering performance at high production rates by effectively managing moisture absorption and discharge through the double nip system, improving web dewatering efficiency.
Implementation Method 1
the felt is dewatered between the first and the second nip by way of a tubular suction device
Implementation Method 2
the fibrous web is heated between the first and the second nip of the first press by a steam blower box
Data Source
AI summary
A method for dewatering a fibrous material web, wherein fibrous material is applied via a headbox on at least one wire and is subsequently dewatered in order to form a fibrous material web. Following the wire section, the resulting fibrous material web is dewatered by several presses, wherein the first press through which the fibrous material web is guided following the headbox is equipped with a double nip. The first press is formed by a wire roll and two couch rolls which are each pressed against the wire roll for forming a nip. Also disclosed is a corresponding device for carrying out the method.