Heat-Sensitive Feedstock Comminution Without Cryogenic Cooling
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Solution Overview
Problem
Conventional methods for comminuting heat-sensitive feedstock, such as thermoplastics and elastomers, face challenges in preventing thermal damage and achieving fine grinding without cooling below freezing temperatures, leading to inefficient operation and costly coolant usage, as well as undesirable particle properties.
Innovation Solution
A method that combines continuous cooling via self-generated air with dynamic supplementation of coolant, such as water, and controlled metering of feedstock to manage heat input, along with suction-based transport to prevent agglomeration and enhance bonding properties, allowing for fine grinding at temperatures above 0°C without cryogenic cooling.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the production output is increased to achieve maximum machine output, then productivity is improved, but thermal damage to heat-sensitive feedstock occurs
Solution Approach 1:
The patent converts the harmful heat generated during comminution into a beneficial cooling mechanism by introducing a small amount of moisture (1-10 g per kg feedstock) that absorbs heat through evaporation. The self-generated airflow, which would otherwise merely transport material, is utilized to remove the evaporated moisture and carry away heat, thus transforming the harmful thermal effect into a beneficial cooling process that enables high-speed comminution of heat-sensitive materials without thermal damage.
Solution Approach 2:
The patent changes the physical state parameters of the feedstock by introducing controlled moisture content (1-10 g per kg) and controlling the temperature through evaporative cooling. This parameter change allows the material to withstand the mechanical stresses of fine grinding without softening or melting, enabling operation at maximum productivity while preventing thermal damage.
2Object-affected harmful factors
If cryogenic cooling is used to prevent thermal damage, then thermal damage is prevented, but cost increases due to coolant consumption
Solution Approach 1:
The patent replaces expensive cryogenic coolants with inexpensive water or moisture, which is introduced in small amounts (1-10 g per kg feedstock). This cheap substance serves as a disposable cooling medium that evaporates to absorb heat, then is removed by the self-generated airflow. The approach eliminates the need for costly liquid nitrogen or other cryogenic agents while effectively preventing thermal damage.
Solution Approach 2:
Instead of using expensive cryogenic coolants, the patent utilizes the evaporative cooling effect of small amounts of moisture, converting a simple phase change process into an effective and economical cooling mechanism that prevents thermal damage without the high costs associated with cryogenic materials.
3Ease of manufacture
If cryogenic cooling is used to embrittle feedstock for comminution, then comminution is enabled, but particle shape becomes cubic with smooth surface which is disadvantageous for bonding
Solution Approach 1:
The patent changes the temperature parameter from cryogenic levels to near-ambient temperatures by using evaporative cooling with moisture. This parameter change prevents the feedstock from becoming overly embrittled, allowing particles to maintain their natural irregular shapes and rough surfaces during comminution. The result is improved bonding properties while still enabling effective comminution of heat-sensitive materials.
4Temperature
If self-generated air flow is increased to remove heat, then cooling effect is improved, but residence time decreases and fineness of end product is reduced
Solution Approach 1:
The patent changes the cooling mechanism from relying on high airflow rates to utilizing evaporative cooling with small amounts of moisture (1-10 g per kg feedstock). This parameter change allows the self-generated air flow to maintain optimal residence time for fine grinding while still achieving effective heat removal through the phase change of the introduced moisture, thus simultaneously achieving both cooling and fine particle size.
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
Enables efficient fine grinding of heat-sensitive materials to particle sizes below 500 μm without cryogenic coolants, reducing costs and improving bonding properties of the comminuted particles, while maintaining machine efficiency and preventing thermal damage.
Implementation Method 1
In comminuting devices through which air flows, the feedstock is cooled by the airflow necessary for transporting of the feedstock within the device. This so-called self-generated air can be produced by the device itself
Implementation Method 2
10. The comminution or fine grinding is carried out with the introduction of small amounts of moisture into the material stream
Data Source
AI summary
A method for comminuting heat-sensitive feedstock, particularly thermoplastics, rubber, caoutchouc, and elastomers, to a particle size of less than 500 μm, preferably less than 425 μm. Process steps are provided to achieve an economic material processing without the use of cryogenic comminution. First, a precomminution of the feedstock to a size smaller than 4 mm is performed in a rotating comminuting device through which a first process gas PG1 flows. Then, a fine grinding is performed of the precomminuted feedstock to a size smaller than 500 μm, preferably smaller than 425 μm, in a rotating fine grinding device through which a second process gas PG2 flows. Whereby the temperature of the precomminuted feedstock in the outlet of the fine grinding is regulated in a second control circuit by adding water to the precomminuted feedstock before and/or during and/or after the fine grinding.