Steam Quantity Control for Paper Web Moisture
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Solution Overview
Problem
In paper machine drying sections, controlling the moisture content of the paper web is challenging due to the unpredictability of heat input from steam-heated drying cylinders, leading to issues of overdrying or underdrying, as the amount of heat deposited is unknown, and existing methods lack linear control over the moisture evaporation process.
Innovation Solution
A control device with a pilot control system utilizing a neural network adjusts the quantity of steam to regulate the heat input, allowing for precise control of moisture content by determining the actual moisture value and providing correction values, switching to temperature control if the paper web tears, ensuring linear control over water evaporation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If steam pressure control is used to heat drying cylinders, then heating efficiency is improved, but moisture content control precision deteriorates due to unknown heat deposition
Solution Approach 1:
The invention changes the controlled parameter from steam pressure to steam quantity (mass flow rate). By measuring and controlling the actual amount of steam consumed rather than just its pressure, the system can accurately determine heat deposition and thereby precisely control the moisture content of the paper web while maintaining heating efficiency.
2Productivity
If excessive heat energy is input to the paper web, then drying speed is improved, but paper quality deteriorates due to overdrying
Solution Approach 1:
The invention implements a feedback control system where the actual steam quantity is measured and used to adjust the heat input. The control system continuously monitors steam consumption and adjusts the steam supply to match the actual moisture removal needs, preventing both overdrying and underdrying while maintaining optimal drying speed.
3Manufacturing precision
If steam quantity control is implemented, then moisture control precision is improved, but device complexity increases due to additional measurement and control systems
Solution Approach 1:
The invention uses steam quantity (mass flow rate) as an intermediary parameter that directly correlates with heat deposition. By measuring this intermediary parameter instead of directly measuring moisture content or heat flux, the system achieves precise moisture control with relatively simple and reliable measurement technology.
4Device complexity
If temperature control is used instead of heat quantity control, then device complexity is reduced, but moisture content control precision deteriorates due to non-linear relationship
Solution Approach 1:
The invention changes the controlled parameter from temperature to heat quantity (steam mass flow rate). Since heat quantity is directly proportional to the amount of water evaporated, this parameter change creates a linear control relationship that improves moisture content precision while the control system remains manageable in complexity.
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 solution enables reliable control of the paper web's moisture content by accurately adapting heat input to the water evaporation needs, eliminating non-linearities and preventing overdrying or underdrying, while ensuring safe operation by switching to temperature control during paper web breaks.
Implementation Method 1
the water contained in the paper web being evaporated by heat transfer from the drying cylinder to the paper web
Implementation Method 2
the water contained in the paper web being evaporated by heat transfer from the drying cylinder to the paper web
Implementation Method 3
the steam in the drying cylinder largely condenses. As a result, the enthalpy of condensation of the steam is transferred to the drying cylinders
Implementation Method 4
the enthalpy of condensation of the steam is transferred to the drying cylinders
Data Source
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AI summary
The regulating device has a heatable drying cylinder (30), and an operation controller (1) for regulating heat quantity supplied to the drying cylinder to a reference value. A pre-control device (2) predetermines the reference value of the controller, and is adjustable by a device for determining actual moisture value. The pre-control device has a numerical characteristic diagram matrix, a neural network, a linear model and a fuzzy logic. A detection device detects tear of a traverse paper web (33). Independent claims are also included for the following: (1) a dryer section (2) a method for regulating moisture level of a paper web in a dryer section.