Cryogenic Grinding Apparatus with Wind Classifier and Gas Recycling
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Cryogenic grinding processes face challenges in achieving fine material separation due to fluctuations in pressure, density, and flow rate in the mill-output volumetric flow, which hinder the operation of wind classifiers, and require heating the ground material for screening, leading to energy inefficiency and limitations in achieving desired fineness.
Innovation Solution
A cryogenic grinding apparatus and process that includes a low-temperature embrittling device, a mill, a separating device with a wind classifier, and a directing device to manage the mill-output volumetric flow, allowing for the separation of fine material by feeding a controlled gas fraction into the classifier-input flow, maintaining a consistent low-temperature atmosphere, and recycling excess gas to reduce energy consumption and prevent reagglomeration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If wind classifier is used to separate fine material from heterogeneous mixture, then separation precision is improved, but the device complexity increases and the operation becomes difficult due to pressure fluctuations in mill-output volumetric flow
Solution Approach 1:
A buffer chamber is introduced as an intermediary component between the mill and the wind classifier. This buffer chamber receives the mill-output volumetric flow and provides a stabilized gas stream to the wind classifier, decoupling the pressure fluctuations from the classifier operation and enabling precise separation
Solution Approach 2:
The ground material is extracted from the mill-output volumetric flow before being fed to the wind classifier. This separation allows the classifier to receive only the necessary material stream while the excess gas is discharged, simplifying the classifier operation and improving separation precision
2Ease of operation
If ground material is heated to allow screening, then ease of operation is improved, but energy consumption increases
Solution Approach 1:
Instead of heating the ground material to enable separation, the invention inverts the approach by maintaining the material in a cold state and using a wind classifier that operates effectively at low temperatures. This eliminates the need for heating while achieving the same separation objective, significantly reducing energy consumption
3Manufacturing precision
If screen deck is used to obtain fine fraction, then separation precision is improved, but the achievable separation cut is limited because screen deck becomes clogged with finer mesh widths
Solution Approach 1:
The mechanical screen deck system is replaced with a wind classifier that uses aerodynamic forces for separation. This substitution eliminates the clogging problem inherent in screen decks, as the classifier wheel design prevents fine particles from blocking the separation mechanism, thereby extending the achievable separation cut to much finer mesh widths
4Productivity
If compressed air is used to blow ground material to classifier, then productivity is improved, but temperature control is compromised and energy consumption increases
Solution Approach 1:
The invention changes the parameter of the gas stream from warm compressed air to cold mill-output gas. By utilizing the existing cold gas from the mill output, the system maintains temperature control while still achieving the necessary productivity for transporting ground material to the classifier, eliminating the need for additional heating and energy input
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
The solution enables the production of finer powdered materials, such as powdered rubber with particle sizes below 100 microns, while maintaining a cold classification environment, preventing reagglomeration and clogging, and optimizing energy use by recycling gases, thus improving the efficiency and consistency of the fine-material end product.
Implementation Method 1
the coarse material to be ground is fed to a low-temperature embrittling device, for example in the form of a cooling screw, in which the coarse material is cooled down with a gas supplied in a liquid state, for example liquid nitrogen, and embrittled
Implementation Method 2
Particles of the material to be classified are entrained by an upwardly directed air stream in the classifier chamber or, if the particles are too heavy, the particles are not entrained
Implementation Method 3
grinding the embrittled material to be ground in an atmosphere containing the supplied liquid low-temperature gas
Data Source
AI summary
A cryogenic grinding apparatus is provided. The apparatus includes a material charge, a low-temperature embrittling device for embrittling the charged ground material by supplying liquid low-temperature gas, a mill for grinding the low-temperature embrittled ground material in an atmosphere containing the low-temperature gas, and a separating device. The separating device has a wind classifier, a removal device to remove the ground material from the mill-output volumetric flow, and a directing device to feed the removed ground material into a classifier-input volumetric flow and to discharge excess mill-output gas of the mill-output volumetric flow. In addition, a cryogenic grinding process is provided in which the ground material is removed from the volumetric flow, excess grinding gas is discharged, removed ground material is feed into a classifier-input volumetric flow of a wind classifier and a classifier-input volumetric flow is classified for separating off a classifier-output volumetric flow containing the fine material.