Two-Stage Milling Circuit Optimizing Gap Degree
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Solution Overview
Problem
In two-stage grinding circuits, the complete return of coarse material from the classifier to the first grinding stage reduces the gap degree in the material bed, leading to decreased grinding efficiency and increased energy consumption due to uneven particle size distribution.
Innovation Solution
A partial flow of semolina from the classifier is diverted back to the grinding plate, and coarser material is fed into the second grinding stage, while finer material is sent to the second mill, optimizing the gap degree and efficiency by reducing packing density and distributing grinding force effectively.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the complete return of coarse material from the classifier to the first grinding stage is implemented, then the material bed is maintained continuously, but the gap degree in the material bed decreases leading to decreased grinding efficiency and increased energy consumption
Solution Approach 1:
The coarse material return flow is segmented into two paths: a first portion is returned to the first grinding stage to maintain material bed continuity, while a second portion is fed to the second grinding stage. This segmentation prevents complete recirculation that would reduce gap degree, thereby maintaining grinding efficiency while avoiding excessive energy consumption.
Solution Approach 2:
The invention changes the parameter of material circulation by diverting part of the coarse material to the second grinding stage instead of returning it all to the first stage. This parameter change optimizes the gap degree in the material bed, ensuring effective stress distribution and particle breakage while controlling energy consumption.
2Productivity
If a partial flow of semolina is diverted back to the grinding plate, then the gap degree is optimized and grinding efficiency is enhanced, but the system complexity increases due to additional material flow paths
Solution Approach 1:
The semolina flow is segmented into multiple paths: one path returns to the grinding plate to optimize gap degree, while another path proceeds to the second grinding stage. This segmentation achieves improved comminution efficiency through better stress distribution without requiring complex additional equipment, as it utilizes existing system components.
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 approach enhances the overall comminution efficiency and reduces energy consumption by maintaining a higher gap degree in the material bed, allowing for more effective stress distribution and particle breakage in the vertical roller mill.
Implementation Method 1
a first grinding stage (1) comprising a vertical roller mill (10) with a grinding table (11), at least one grinding roller (12) cooperating with the grinding table (11)
Implementation Method 2
allowing for more effective stress distribution and particle breakage in the vertical roller mill
Implementation Method 3
the crushed material is transported by an air stream to a separator, usually located above the grinding table
Implementation Method 4
a first dynamic classifier (13), wherein the first dynamic classifier (13) comprises a fines outlet (15) for discharging fines
Data Source
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AI summary
The invention relates to a two-stage grinding circuit consisting mainly of a first grinding stage (1), which comprises a vertical roller mill (10) having a grinding disk (11), at least one grinding roller (12) interacting with the grinding disk (11) and a first dynamic separator (13), the first dynamic separator (13) comprising a fine material outlet (15) for discharging fine material (5) and a grit return (16) for returning grits (8) to the grinding disk (11), and a second grinding stage (2), which has a second mill (20), which is formed by a stirred ball mill or a ball mill, the second mill (20) comprising an inlet (21) and an outlet (22). Furthermore, a grit extraction device (18) is provided for extracting part of the grits (8), the grit extraction device being connected to the grit return (16) and being connected to the inlet (21) of the second mill (20).