Tissue Paper Web Heating via Direct Hood Airflow
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Solution Overview
Problem
Current tissue paper manufacturing processes are not energy-efficient in dewatering the tissue paper web, leading to increased energy consumption and potential equipment contamination.
Innovation Solution
A process and machine design that involves passing the tissue paper web through an extended nip between a Yankee drying cylinder and a suction roll, with moist hot air from a Yankee hood being directly supplied to the web to raise its temperature before dewatering, using a system that recirculates and controls the air flow to optimize energy use and reduce heat losses.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If hot air is supplied to the tissue paper web through a fabric (conventional arrangement), then the web can be heated, but the heating efficiency is reduced and equipment contamination increases
Solution Approach 1:
The patent extracts the hot air supply path from the fabric-mediated route and creates a direct path from the hood to the web surface. The hood is positioned to supply hot air directly to the web without it passing through the fabric, eliminating the energy loss associated with fabric filtration and direct contact heating.
Solution Approach 2:
The patent introduces a controlled air flow system as an intermediary between the heat source and the web. By using a hood with controlled air supply, the system mediates the heat transfer process more efficiently than direct fabric contact, allowing precise control over heating while reducing energy loss.
2Productivity
If a suction roll is used to pass the web through an extended nip, then dewatering can be achieved, but energy consumption increases
Solution Approach 1:
The patent changes the physical parameters of the air flow system by heating the air before it reaches the web and controlling the suction parameters of the roll. By optimizing the temperature and flow rate parameters, the system achieves more efficient dewatering with reduced energy consumption compared to conventional ambient temperature systems.
Solution Approach 2:
The patent employs a composite approach combining the suction roll mechanism with a heated air flow system. The combination of mechanical suction and thermal energy creates a synergistic effect that enhances dewatering efficiency while managing overall energy consumption through the coordinated action of these two systems.
3Object-affected harmful factors
If the web is heated at a distance from the press nip (conventional arrangement), then equipment contamination is reduced, but dewatering efficiency decreases
Solution Approach 1:
The patent segments the heating and dewatering functions into distinct zones. The hood provides heating in a separate zone before the web enters the extended nip, allowing the heating function to be performed away from the press nip while maintaining dewatering efficiency through the subsequent mechanical action in the nip zone.
Solution Approach 2:
The patent applies preliminary heating action through the hood before the web enters the extended nip for dewatering. This preliminary heating softens the web structure and prepares it for more effective dewatering in the subsequent nip zone, achieving both contamination reduction and maintained dewatering efficiency.
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
This approach significantly reduces the viscosity of the water in the tissue paper web, enhancing dewatering efficiency and reducing energy consumption while minimizing equipment contamination.
Implementation Method 1
a suction roll having a suction zone
Implementation Method 2
moisture condensates on the tissue paper web
Implementation Method 3
Moist hot air is fed from the first hood and is sucked through the tissue paper web and the felt by the suction roll and the tissue paper web is directly exposed to the first hood such that the moist hot air reaches the tissue paper web without passing through a fabric before reaching the tissue paper web
Implementation Method 4
a Yankee drying cylinder... the tissue paper web contacts the outer surface of the Yankee drying cylinder
Data Source
AI summary
The invention relates to a process and a machine for making a tissue paper web (W) in which the tissue paper web W is passed through an extended nip N formed between an extended nip unit (2) and a Yankee drying cylinder (1) and in which the tissue paper web W is carried on a felt (3) through the extended nip N in such a way that, in the extended nip N, the tissue paper web W contacts the outer surface (4) of the Yankee drying cylinder (1). The web W and the felt (3) are led over a suction roll (5) prior to the extended nip N in such a way that the felt (3) contacts the suction roll (5) and the tissue paper web W is separated from the suction roll (5) by the felt (3). The suction roll (5) has a suction zone (6) over which the felt (3) and the tissue paper web W pass together, and a first hood (7) is arranged opposite the suction roll (5) and partially surrounds the suction roll (5). The first hood (7) has an extension around the suction roll such the first hood (7) covers the entire suction zone (6), and moist hot air is fed from the first hood (7) and sucked through the tissue paper web and the felt (3) by the suction roll (5). The tissue paper web W is directly exposed to the first hood (7) such that the moist hot air reaches the tissue paper web W without passing through a fabric before reaching the tissue paper web W. The Yankee drying cylinder (1) is covered by a second hood (8) which is a Yankee hood which has an air heating and distribution system (9) and hot exhaust air from the second hood (8) is fed through a conduit (10) to the first hood (7) and used to supply the first hood (7) with moist hot air. The moist hot air has a temperature in the range of 130° C.-300° C. and a moisture content of 300 g/kg dry air-1000 g/kg dry air at a rate of 90-130 m3/minute per square meter suction zone area. The moist air is then sucked through the tissue paper web W by the suction roll (5) such that moisture condensates on the tissue paper web W and thereby raises the temperature of the tissue paper web W before the tissue paper web W passes through the extended nip N.