Jet Mill Operation With Steam and Additives Against Reagglomeration
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Solution Overview
Problem
Jet mills face inefficiencies due to reagglomeration of fine particles below 2 µm, leading to increased energy consumption as air classifiers mistakenly treat these agglomerates as coarse particles, requiring additional grinding.
Innovation Solution
Incorporating superheated steam or technical gases like helium or hydrogen as operating media, and adding surface-active additives such as stearic acid or silanes to stabilize fine particles during milling, ensuring they are mixed with the material before or within the grinding chamber.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional air classification is used to separate fine particles, then coarse particles can be rejected, but fine particles below 2 µm are mistakenly treated as coarse and subjected to additional grinding, increasing energy consumption
Solution Approach 1:
The patent changes the physical-chemical parameters of the operating medium from conventional air to superheated steam or technical gases with specific properties (inlet temperature ≥50°C, dry after passing through the mill). This parameter change allows the medium to differentiate between fine particles and agglomerates based on their interaction with the steam/gas, enabling fine particles to be carried through while agglomerates are rejected, thus resolving the energy consumption issue without sacrificing separation accuracy
Solution Approach 2:
The patent introduces surface-active additives (such as stearic acid, silanes, or condensates of naphthalenesulfonic acid) as intermediaries that adsorb onto particle surfaces. These additives modify the surface properties of particles, causing fine particles to interact differently with the operating medium compared to agglomerates. This intermediary substance enables the air classifier to correctly distinguish between fine particles and coarse agglomerates, preventing unnecessary re-grinding of fine particles
2Manufacturing precision
If fine particles are produced below 2 µm, then ultrafine particle production is achieved, but reagglomeration occurs due to surface-acting forces having disproportionately large effects
Solution Approach 1:
Surface-active additives serve as intermediary substances that adsorb onto the surfaces of ultrafine particles. These additives create a protective layer that reduces the influence of surface-acting forces (van der Waals forces, electrostatic forces) that cause reagglomeration. By introducing this intermediary layer, the patent stabilizes ultrafine particles and prevents them from re-agglomerating while maintaining their fine particle status
Solution Approach 2:
The use of superheated steam or technical gases (He, H2) creates an inert atmospheric environment that reduces particle-particle interactions. The specific properties of these gases (temperature, dryness) create conditions where surface-acting forces are minimized, preventing reagglomeration of ultrafine particles while allowing them to be produced and transported effectively
3Stability of the object's composition
If surface-active additives are added to stabilize fine particles, then reagglomeration is prevented, but additive cost and process complexity increase
Solution Approach 1:
The patent employs surface-active additives with self-adsorbing properties that automatically stabilize particle surfaces upon contact. The additives (such as stearic acid, silanes, or condensates of naphthalenesulfonic acid) have inherent affinity for particle surfaces and self-organize to form protective layers without requiring complex application systems. This self-service mechanism simplifies the overall process despite the addition of chemical substances
Solution Approach 2:
The patent specifies precise parameter ranges for additive concentration (0.1% to 4% of mass throughput) and operating medium conditions (inlet temperature ≥50°C, dry after passing through the mill). By optimizing these parameters, the patent achieves effective particle stabilization with minimal additive quantities, reducing both cost and process complexity while maintaining high particle stability
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
Reduces energy consumption by up to a factor of 3.3 while producing finer particles, effectively preventing reagglomeration and optimizing the milling process.
Implementation Method 1
particles are fed into a grinding chamber of the jet mill as material to be ground and are ground there into fine particles by using superheated steam, which can also be referred to as process or grinding steam, or technical gases (He, H2), which can also be referred to as process or grinding gases, as operating media
Implementation Method 2
at least one surface-active additive is added to the material to be ground in order to stabilize the fine particles produced
Implementation Method 3
at least one surface-active additive for stabilizing the fine particles produced: Stearic acid for hydrophobic stabilization, or diols, polyols or other long-chain alcohols for hydrophilic stabilization
Implementation Method 4
jet mills face inefficiencies due to reagglomeration of fine particles below 2 µm, leading to increased energy consumption as air classifiers mistakenly treat these agglomerates as coarse particles
Data Source
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AI summary
The method involves supplying particles as grinding stock in a grinding chamber (5) of the jet mill (1). The grinding stock is grinded to fine particles by grinding as superheated water vapor or technical gas is used as operating fluid. The surface active additive is supplied to the grinding stock for stabilizing the generated fine particles. The additive is mixed with the grinding stock before grinding. The additive is directly introduced in the grinding chamber. The operating fluid contains hydrogen or helium as technical gas. An independent claim is included for a jet mill with an operating fluid supply unit.