Vertical Roller Mill Fixed Separator Coating
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Solution Overview
Problem
The fixed separator in vertical roller mills suffers from poor coarse particle size separation efficiency, leading to an increase in unburnt combustibles in coal-fired boilers due to the mixing of coarse particles with fine powder, which is exacerbated by the high repulsive force of iron blades causing coarse particles to rebound and stall, rather than being separated effectively.
Innovation Solution
The implementation of a fixed cyclone separator with a surface layer having a higher coefficient of rebound than iron on the inner cylinder, inclined surfaces on the outer cylinder, an inverted conical reflector, or a low-repulsive surface on the fixed blades to manage the trajectory and centrifugal force of coarse particles, preventing stalling and ensuring they drop back onto the mill table for re-pulverization.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a fixed separator with iron blades is used, then the structure is simple and maintenance is easy, but coarse particle separation accuracy deteriorates due to high repulsive force causing particle stalling
Solution Approach 1:
The patent changes the surface property parameter of the inner cylinder by forming a low-repulsive surface layer with a coefficient of rebound lower than iron plates. This parameter change reduces the repulsive force on coarse particles, preventing stalling and improving separation accuracy while maintaining the simple fixed separator structure.
Solution Approach 2:
The patent applies a composite material solution by forming a surface layer on the inner cylinder that has different rebound properties than the base iron plate material. This composite structure (inner cylinder + surface layer) achieves lower repulsion and better particle separation while keeping the overall structure simple and maintenance-free.
2Measurement precision
If the inclination angle of fixed blades is increased to adjust fineness, then separation performance improves, but coarse particles stall more due to increased repulsive force
Solution Approach 1:
The patent converts the harmful repulsive force that causes stalling into a beneficial low-repulsion effect. By forming a surface layer with lower rebound coefficient, the previously harmful high repulsion from iron blades is transformed into a beneficial low-repulsion surface that guides particles smoothly without stalling, while still maintaining the inclination angle needed for fineness separation.
Solution Approach 2:
The patent changes the surface rebound parameter of the inner cylinder to reduce repulsive force. This parameter change allows the fixed blades to maintain their inclination angle for fineness adjustment without causing excessive particle stalling, as the low-repulsive surface layer mitigates the harmful rebound effect.
3Productivity
If coarse particles are allowed to pass through, then productivity increases, but unburnt combustibles in ash increase
Solution Approach 1:
The patent changes the surface rebound parameter of the separation zone to optimize particle trajectory. The low-repulsive surface layer ensures coarse particles are properly directed to the outer wall and removed, preventing them from contaminating the fine powder product. This maintains high separation efficiency and reduces unburnt combustibles while preserving productivity.
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
This configuration reduces the proportion of coarse particles in the product pulverized coal, enhancing separation efficiency and reducing unburnt combustibles in ash, while maintaining a low-cost and easily maintainable separator design suitable for low-grade coal.
Implementation Method 1
Particles of pulverized coal in the solid-gas two-phase flow having passed between adjacent ones of the fixed blades 23 through the fixed blade inlet window 22 are centrifugally separated into coarse particles and fine powder by a swirl flow
Implementation Method 2
gravitational separation is performed, in which coarse particles having a large particle size drop down due to the force of gravity and return onto the mill table 12
Data Source
AI summary
A vertical roller mill provided with a cyclone-type fixed separator that separates fine powder and allows the separated powder to flow out to the outside, the cyclone-type fixed separator being provided inside a housing, wherein the fixed separator is configured so that a solid-gas two-phase flow is introduced from a fixed blade inlet window opening on a cone into the inside and the solid-gas two-phase flow is swirled using a fixed blade attached in the inside vicinity of the fixed blade inlet window, whereby the fine powder flows out to the outside from a pulverized coal outlet in an upper portion of the vertical roller mill through the lower end side of an inner cylinder provided inside the cone, a surface layer in which the rebound coefficient of collided particles is higher than in an iron plate surface being formed in the outer surface of the inner cylinder.