Biomass Milling with Conical Barrel and Fan-Like Table Liners
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Solution Overview
Problem
Conventional biomass mills face challenges in efficiently milling woody biomass materials due to their low specific gravity, high fiber content, and compressibility, leading to difficulties in particle size control, increased power consumption, and decreased milling efficiency, as well as issues with biomass-coal mixed combustion systems, where the biomass material is hard to mill and prone to over-milling, resulting in reduced combustion efficiency.
Innovation Solution
A biomass mill design featuring a mill main body with a barrel part of decreased diameter, a material feed pipe for vertical axis feeding, a rotating mill table, a mill roller for pressing force milling, and a ventilation system for air flow conveyance, along with discharge tubes for efficient powder discharge, which allows for controlled air flow and gravitational classification, eliminating the need for mechanical classifiers and reducing the risk of clogging.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a conventional vertical roller mill for coal is used to mill biomass solids, then the existing mill infrastructure can be utilized, but the biomass material cannot be sufficiently milled due to its low specific gravity, high fiber content, and compressibility, resulting in poor particle size control and over-milling
Solution Approach 1:
The patent applies local quality by modifying specific components of the existing mill to suit biomass characteristics. The mill roller is equipped with teeth or protrusions that provide localized mechanical action on biomass particles, while the mill table surface is designed with specific roughness or patterns to enhance grinding efficiency. These localized modifications allow the existing mill infrastructure to effectively mill biomass without requiring complete system replacement.
Solution Approach 2:
The patent implements parameter changes by adjusting operational parameters such as roller pressure, rotation speed, and air flow rates to optimize biomass milling. The air volume and velocity are specifically controlled to prevent over-milling while achieving adequate particle size reduction. These parameter adjustments enable the conventional mill to adapt to biomass's unique properties without structural overhaul.
2Manufacturing precision
If biomass solids are milled by hummer mills or cutter mills, then adequate particle size reduction can be achieved, but a large amount of power is required, decreasing milling efficiency and requiring frequent maintenance
Solution Approach 1:
The patent employs periodic action through the rotating mill roller that repeatedly contacts and grinds biomass particles as they move across the mill table. This continuous cyclic grinding action, combined with the intermittent lifting and dropping of particles by air currents, achieves progressive size reduction without requiring the continuous high-power input of hummer mills. The periodic mechanical impact and grinding actions accumulate to achieve adequate particle size reduction with lower overall power consumption.
3Manufacturing precision
If the air volume is increased to control particle size in conventional mills, then biomass powder can be conveyed, but the A/C ratio becomes 7 or more, requiring bin systems such as bug filters or cyclones that cause clogging and firing issues
Solution Approach 1:
The patent replaces the complex mechanical bin system (bug filters or cyclones) with a simplified pneumatic classification system. By carefully controlling the air flow velocity and direction in the mill chamber, particles are classified and conveyed directly without requiring intermediate mechanical separation devices. This substitution eliminates the clogging and firing issues associated with bin systems while maintaining adequate particle size control through aerodynamic principles rather than mechanical filtration.
4Force
If woody biomass material is compressed between mill roller and mill table, then milling action is applied, but the compressible material does not transfer sufficient pressure, making it hard to mill effectively
Solution Approach 1:
The patent incorporates mechanical vibration or impact elements in the mill roller or mill table to enhance the milling action on compressible biomass material. The vibratory motion prevents the biomass from simply compressing without breaking, instead promoting fracture and size reduction. This vibration adds a dynamic component to the pressing force, making the milling action more effective on materials that tend to deform rather than fracture under static compression.
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 design achieves efficient biomass powder conveyance and classification, reducing power consumption and maintaining combustion efficiency, while simplifying the boiler system and avoiding issues like clogging, thereby enabling stable and efficient biomass-coal mixed combustion.
Implementation Method 1
ventilation means for forming an upward flow from below on the outer peripheral side of the mill table to blow out a carrier gas so as to convey milled biomass powder by a flow of air
Implementation Method 2
mill roller for operating in conjunction with rotation of the mill table so as to mill the biomass material by a pressing force
Implementation Method 3
control the pressing force of a roller and the rotation speed of a table so as to fall within specific ranges to facilitate mutual grinding of biomass chips
Data Source
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AI summary
In order to efficiently discharge crushed biomass powder to the outside, the biomass crushing device body (13) of a biomass crushing device is configured in such a manner that the barrel section (21) at the center of the biomass crushing device body (13) in the vertical axis direction is reduced in diameter, and discharge pipes (22) for discharging the biomass powder (17) are provided in the circumferential direction at the top plate (13a) of the crushing device body (13), the top plate (13a) being located on a line extended from the vertical axis of the barrel section (21) reduced in diameter. In order to efficiently crush a biomass material, the biomass crushing device body (13) is configured in such a manner that the table liner (14b) of a crush table (14) comprises fan-like segments (31a, 31b), with the segments having different thicknesses in the height direction. The biomass crushing device is provided with a roller speed adjustment mechanism (71) which can adjust the rotational speed of a crushing roller (16) so that the peripheral speed of the crushing roller (16) is different from the peripheral speed of the crushing table (14).