Drum Mill Capture Arms for Complete Ore Discharge
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Solution Overview
Problem
The existing output arrangements in rotating drum mills for autogenous or semi-autogenous wet grinding face issues with incomplete discharge of milled ore, leading to reduced milling capacity and increased wear due to recirculation of ore material, which is exacerbated by the need to operate at suboptimal speeds to prevent backflow.
Innovation Solution
The implementation of capture arms within the pulp-lifting chambers, specifically designed as first and second capture arms, which progressively collect and redirect mineral material closer to the central axis, allowing for more controlled discharge and increased milling speed without compromising the filling capacity of the output arrangement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the mill operates at higher speeds closer to critical speeds, then milling capacity is enhanced, but mineral material does not have sufficient time to leave the pulp-lifting chamber and falls back into the pulplifter causing recirculation and wear
Solution Approach 1:
The pulp-lifting chamber is divided into multiple sections along the rotation direction, with each section equipped with its own capture arm. This segmentation allows progressive collection of mineral material at different positions, ensuring complete discharge even at high rotation speeds where material would otherwise fall back into the pulplifter.
Solution Approach 2:
Capture arms are positioned to collect mineral material before the pulp-lifting chamber completes its rotation and before material can fall back into the pulplifter. The first capture arm collects material at an earlier position, and the second capture arm provides backup collection, preventing recirculation before it occurs.
2Reliability
If the mill operates at reduced rotation speed (50-70% of critical speed), then mineral material has sufficient time to leave the pulp-lifting chamber, but milling capacity decreases to unacceptable levels
Solution Approach 1:
By segmenting the discharge function across multiple capture arms positioned at different locations, the system can operate at high speeds while maintaining complete material discharge. Each segment handles a portion of the material flow, collectively achieving 100% discharge efficiency without speed reduction.
Solution Approach 2:
The capture arms act as intermediary structures between the pulp-lifting chamber and the external environment. They intercept mineral material mid-rotation and guide it to the discharge location, enabling complete discharge at high speeds without requiring the mill to slow down.
3Reliability
If capture arms are added to progressively collect and redirect mineral material, then complete discharge is achieved and recirculation is prevented, but device complexity increases
Solution Approach 1:
The capture arms serve multiple functions: they collect mineral material, redirect it toward the discharge location, and prevent recirculation back into the pulplifter. This multi-functionality reduces the need for additional separate components, offsetting the complexity increase with functional consolidation.
Solution Approach 2:
The capture arms are integrated into the existing pulp-lifting chamber structure, with arms extending from the chamber walls. This nested integration minimizes additional structural complexity while achieving the desired material discharge function.
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 solution enables the mill to operate at higher speeds closer to critical speeds, enhancing milling capacity and reducing unnecessary wear by ensuring complete discharge of mineral material, thus maintaining optimal milling efficiency while preventing recirculation.
Implementation Method 1
all mineral material is driven out towards the inner surface of the limiting wall of the pulplifter, located at the outermost radial location and facing in towards the rotation axis, through the influence of centrifugal forces that arise
Implementation Method 2
when promoted to an upper position of the rotation the mineral material falls down towards the material output cone in the centre of the output end wall of the mill
Data Source
AI summary
The invention concerns a method and an arrangement for the output of mineral material from a drum mill having a horizontal rotation axis, a sieving wall at its end wall, material can leave through the sieving openings in to pulp-lifting chambers, limited by the sieving wall, the end wall, a limiting wall, and limiting walls that lead towards an output cone, whereby material in the pulp-lifting chamber is emptied down towards the output cone when the pulp-lifting chamber is an upper part of a revolution. In order to increase the rate of revolution, material that does not reach the material output cone is collected in a material collection pocket which carry the material at a level radially closer to the rotation axis than the inner limiting wall, whereby collected mineral material leaves the material collection pocket during, a subsequent revolution.