DFI Burner Degreasing for Metal Foil Grain Control
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Solution Overview
Problem
Current methods for degreasing non-steel metal foils or sheets contaminated with lubricants, such as batch chamber furnaces and plasma treatments, face issues of high energy consumption, long processing times, and potential mechanical property alterations, while also requiring costly infrastructure and chemical recycling.
Innovation Solution
A continuous process involving uncoiling and recoiling of the metal foil or sheet, where Direct Flame Impingement (DFI) burners are used to heat the foil or sheet from both sides, controlling temperature to avoid annealing levels, with a fuel/oxidant ratio over stoichiometric, to quickly evaporate and burn off lubricants without affecting mechanical properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of substance
If batch chamber furnace annealing is used to remove lubricants, then lubricant removal is achieved, but processing time becomes very long (up to 100 hours) and energy consumption is high (1300 Kwh per ton coil)
Solution Approach 1:
The patent replaces the traditional thermal diffusion process (mechanical/thermal system) with a plasma oxidation process. Plasma ions chemically oxidize the lubricant on the foil surface, converting it to volatile compounds that are easily removed. This substitution of the fundamental mechanism enables rapid lubricant removal (minutes vs. hours) while maintaining effective degreasing, directly resolving the time consumption contradiction.
Solution Approach 2:
The patent changes the operating parameters from conventional thermal annealing (250-400°C for up to 100 hours) to plasma treatment conditions (lower temperatures with controlled plasma power, gas flow, and exposure time). By adjusting plasma power, gas composition, and treatment duration, the process achieves complete lubricant removal in minutes, resolving both the time and energy consumption issues simultaneously.
2Loss of substance
If batch chamber furnace annealing is used to remove lubricants, then lubricant removal is achieved, but energy consumption becomes very high (1300 Kwh per ton coil)
Solution Approach 1:
The patent replaces the energy-intensive thermal diffusion process with a plasma-based chemical oxidation process. Plasma generation consumes significantly less energy than heating entire coil batches to annealing temperatures for extended periods. The localized plasma treatment efficiently oxidizes lubricants with minimal energy input, directly resolving the high energy consumption contradiction while achieving complete degreasing.
Solution Approach 2:
The patent implements a continuous plasma treatment process where foil passes through the plasma zone continuously, eliminating the batch processing cycles inherent in furnace annealing. This continuous operation maintains constant plasma generation and lubricant oxidation without repeated heating/cooling cycles, significantly reducing overall energy consumption while maintaining effective lubricant removal.
3Loss of substance
If batch chamber furnace annealing is used to remove lubricants, then lubricant removal is achieved, but mechanical properties of the foil may be altered (soft annealing effect)
Solution Approach 1:
The patent changes the temperature parameter from conventional annealing ranges (250-400°C) to lower plasma treatment temperatures. The plasma process effectively removes lubricants at temperatures below the annealing threshold, preventing grain growth and softening. This parameter change resolves the contradiction by achieving complete degreasing while preserving the original mechanical properties and hardness of the foil.
Solution Approach 2:
The patent replaces thermal diffusion-based lubricant removal with plasma oxidation. Since plasma treatment occurs at lower temperatures and involves chemical oxidation rather than thermal soaking, it avoids the soft annealing effect that compromises mechanical strength. This mechanism substitution resolves the contradiction between effective lubricant removal and maintaining mechanical properties.
4Strength
If chemical treatment processes are used to remove lubricants at lower temperatures, then mechanical properties are preserved, but the process requires continuous operation and chemical recycling infrastructure
Solution Approach 1:
The patent replaces chemical treatment processes with plasma treatment. Plasma oxidation uses ionized gas to chemically oxidize and remove lubricants without requiring liquid chemicals, recycling systems, or complex chemical handling infrastructure. This substitution resolves the contradiction by maintaining low-temperature operation (preserving mechanical properties) while eliminating the need for chemical recycling and complex infrastructure.
5Loss of time
If the temperature is increased quickly during annealing, then processing time is reduced, but the coil may crack due to thermal stress
Solution Approach 1:
The patent replaces thermal diffusion-based lubricant removal with plasma oxidation occurring at the foil surface. Since plasma treatment operates at lower temperatures and acts primarily on the surface lubricant layer rather than heating the entire coil mass, rapid temperature increase does not create significant thermal gradients or stress. This mechanism substitution resolves the contradiction by enabling fast processing without compromising coil integrity.
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 method reduces energy consumption, processing time, and maintains mechanical properties by allowing precise control over grain size and lubricant removal, eliminating the need for chemical recycling and high voltage plasma treatments, offering a cost-effective and efficient degreasing process.
Implementation Method 1
the foil or sheet is subjected to DFI burners directed towards the foil or sheet on both sides of the foil or sheet so that the foil or sheet is heated from both sides of the foil or sheet
Implementation Method 2
the lubricant can evaporate and diffuse through the thin air gaps between the layers of foil or sheet in the coil
Implementation Method 3
Ions from the plasma oxidize the lubricant and thereby remove the lubricant
Data Source
Figure 1
AI summary
The invention relates to a process to degrease a metal foil/sheet where the metal foil/sheet is contaminated with a lubricant, where the contaminated foil is coiled. The invention is characterized in, that the foil/sheet coil (1) is first uncoiled and thereafter coiled (2) in a continuous process, in that after having been uncoiled the aluminium foil (6) is subjected to DFI burners (4,5) directed towards the foil (6) on both sides of the foil so that the foil is heated from both sides of the foil, in that the distance from the burners (4, 5) to the foil (6), the fuel/oxidant ratio, the power of the burners (4,5) and the speed of the foil (6) when passing the burners are chosen such that the temperature of the foil (6) is caused not to exceed the annealing temperature of the foil.