Grinding Apparatus with Offset Axis and Sinusoidal Excitation
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Solution Overview
Problem
Conventional grinding processes, such as tumbling mills and high pressure grinding rolls, are energy inefficient and limited in their ability to handle varying moisture content and particle sizes, necessitating the development of a more efficient grinding apparatus.
Innovation Solution
A grinding apparatus featuring a rotatable receptacle and grinding element with an offset axis, forming an annular grinding chamber, which uses centrifugal force and sinusoidal excitation to compress and comminute particles, allowing for adjustable gap sizes and optional use of grinding media, enhancing energy efficiency and size reduction capabilities.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If tumbling mills are used for grinding, then particle size reduction is achieved, but energy efficiency deteriorates (0.1% to 2% energy efficiency)
Solution Approach 1:
The invention employs dynamic motion of the grinding element within the receptacle, creating varying compression forces and particle trajectories. The grinding element moves in a complex path that alternates between compression zones and release zones, dynamically engaging particles throughout the grinding chamber rather than static or simple rotational motion.
Solution Approach 2:
The grinding process utilizes mechanical vibration through the reciprocating motion of the grinding element, which creates vibratory forces that enhance particle comminution. The vibration generates micro-impact events and prevents particle bridging, improving energy transfer efficiency to the particles being ground.
2Use of energy by moving object
If high pressure grinding rolls are used, then energy efficiency improves (10% to 50% more efficient than tumbling mills), but moisture content capability deteriorates (limited to maximum 10% moisture)
Solution Approach 1:
The invention introduces a fluid injection system that delivers process fluid (water or other liquids) directly into the grinding chamber during operation. This hydraulic/pneumatic approach allows the addition of moisture to control dust, adjust particle flow characteristics, and enable processing of higher moisture feed materials without limiting the energy efficiency benefits of compression grinding.
3Productivity
If tumbling mills rotate large cylindrical chambers, then grinding capacity is achieved, but energy loss increases (most input energy dissipated as heat and noise)
Solution Approach 1:
The invention segments the grinding action into discrete compression and release zones within the receptacle, rather than continuous tumbling motion. The grinding element creates localized compression zones where particles are intensively comminuted, followed by release zones where particles are redistributed. This segmentation concentrates energy input into productive compression events rather than continuous rotational kinetic energy that dissipates as heat.
Solution Approach 2:
The invention replaces the traditional mechanical rotation of large cylindrical chambers with a more efficient mechanical system using a reciprocating or oscillating grinding element within a stationary or slowly rotating receptacle. This substitution eliminates the need to continuously rotate massive chambers, reducing energy losses to heat and noise while maintaining grinding capacity through focused compression actions.
4Productivity
If high pressure grinding rolls compress material bed, then micro-cracking benefits further comminution, but device complexity increases (contra rotating rollers system)
Solution Approach 1:
The invention extracts the essential compression function from the complex contra-rotating roller system and implements it through a single grinding element that reciprocates or oscillates within the receptacle. This extraction maintains the beneficial micro-cracking effect of compression while eliminating the mechanical complexity of multiple synchronized rotating rollers, drive systems, and alignment mechanisms.
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 apparatus achieves energy efficiencies comparable to high pressure grinding rolls while handling larger particle sizes and varying moisture levels, combining the benefits of compression and attrition to produce a narrower size distribution of discharge particles.
Implementation Method 1
High pressure grinding rolls, which compress a material bed of feed material particles between contra rotating rollers
Implementation Method 2
which uses centrifugal force and sinusoidal excitation to compress and comminute particles
Implementation Method 3
grinding element with an offset axis, forming an annular grinding chamber, which uses centrifugal force and sinusoidal excitation to compress and comminute particles
Implementation Method 4
This limitation is caused by sliding friction on the rollers, whilst they draw feed material into the compression zone formed in the material bed
Data Source
AI summary
A grinding apparatus includes a receptacle, a grinding element and a drive means. The receptacle has a receptacle inner wall defining a receptacle cavity. The receptacle inner wall is in the general form of a surface of a revolution extending about a central vertically extending receptacle axis. The receptacle is rotatable about the receptacle axis. The grinding element has a grinding element outer wall in the general form of a surface of revolution extending about a central vertically extending grinding element axis.