Liquid Nitrogen Bath Cooling for Uniform Cryogenic Milling
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Solution Overview
Problem
Existing methods for grinding temperature-sensitive and difficult-to-grind materials result in uneven cooling and thermal strain on the mill, leading to poor particle distribution and reduced material quality.
Innovation Solution
A method involving a liquid nitrogen bath with mechanical vibrations to transport fragmented material to a mill, ensuring uniform cooling below -150°C without direct application of liquid nitrogen to the mill, using a chute for direct material transfer and controlling transport speed through adjustments in frequency, amplitude, and inclination.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If liquid nitrogen is applied directly to the mill during grinding, then cooling effect is achieved, but thermal strain on the mill and uneven cooling occur
Solution Approach 1:
The fragmented material is cooled in a liquid nitrogen bath before entering the mill, rather than applying liquid nitrogen directly to the mill during grinding. This preliminary cooling action achieves the desired temperature reduction while avoiding thermal strain on the mill equipment.
Solution Approach 2:
The liquid nitrogen bath serves as an intermediary medium between the fragmented material and the mill. The material is cooled in the bath and then transferred to the mill, preventing direct contact between liquid nitrogen and the mill, thereby eliminating thermal strain while maintaining cooling effectiveness.
2Temperature
If liquid nitrogen is applied during milling, then cooling is achieved, but uneven particle distribution results
Solution Approach 1:
Cooling is performed before milling in a liquid nitrogen bath, ensuring uniform temperature distribution throughout the material. This preliminary cooling prevents the uneven particle distribution that would result from applying liquid nitrogen directly during the milling process.
Solution Approach 2:
The liquid nitrogen bath provides homogeneous cooling to all fragmented material particles before they enter the mill. This uniform pre-cooling ensures consistent material properties throughout the batch, leading to even particle distribution in the final milled product.
3Ease of manufacture
If conventional grinding is used on temperature-sensitive materials, then grinding is simple, but material quality decreases due to temperature increase
Solution Approach 1:
The fragmented material is pre-cooled in a liquid nitrogen bath before grinding to maintain its temperature-sensitive properties throughout the grinding process. This preliminary cooling action preserves material quality while keeping the grinding process itself simple and straightforward.
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
Achieves uniform cooling and grinding of temperature-sensitive materials to -150°C or lower, maintaining material quality and reducing thermal stress on the mill, enabling consistent particle distribution for added manufacturing processes.
Implementation Method 1
providing an amount of the fragmented material at a material inlet to a liquid bath of liquid nitrogen
Implementation Method 2
transporting the fragmented material from the material inlet to a material outlet of the liquid bath
Implementation Method 3
transporting the fragmented material from the material inlet to a material outlet of the liquid bath by exciting mechanical vibrations in the liquid bath
Implementation Method 4
grinding the fragmented material in the mill to a grinded material
Data Source
Figure 1
Figure 2
AI summary
According to the present invention fragmented material 2, e.g. made from a material comprising Polyamides, is passing through a liquid bath 6 filled with liquid nitrogen 7 to cool the fragmented material 2 before entering a mill 10 for grinding the fragmented material 2. The fragmented material 2 is moved through the liquid bath 6 by exciting mechanical vibrations in the liquid bath 6 e.g. by a vibrational motor 28 coupled to the liquid bath 6 and/or an ultrasonic resonator 26 attached o the liquid bath 6. The invention allows to grind even materials being difficult to grind by reaching a temperature of -150°C and less before entering the mill 10 while avoiding a direct cooling e.g. by introducing liquid nitrogen directly into the mill 10.