Vertical Roller Mill Attrition for Concrete Recycling Purity

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Solution Overview

Problem

Existing methods, such as roller mills, are ineffective in separating and recovering gravel and sand from broken concrete due to the lack of ductile components, leading to inferior concrete quality when used for recycling, as all components are crushed under pressure, preventing the desired degree of purity and separation.

Innovation Solution

A method utilizing a vertical roller mill with an extremely low contact pressure and a grinding bed design that promotes in-bed attrition, allowing components without ductile properties to be separated through mutual attrition and friction, rather than direct crushing, ensuring the separation of components like gravel and sand from cement stone without degrading them.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Strength

If traditional roller mills with high contact pressure are used to crush broken concrete, then comminution of the material is achieved, but all components including gravel and sand are crushed, preventing separation and reducing concrete quality

Engineering Contradiction:

Improveconcrete qualityVSAvoidseparation purity

Core Design Contradiction:

StrengthVSManufacturing precision

Solution Approach 1:

The patent changes the operating parameters of the roller mill by reducing contact pressure to extremely low levels (15-140 kN/m²) and increasing grinding bed height to 50-200 mm, transforming the mill from a comminution device into an attrition device that separates components without crushing them

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

Instead of using high pressure to crush and then separate components, the patent inverts the approach by using low pressure attrition where components separate through mutual friction and abrasion in the grinding bed, preserving the integrity of gravel and sand particles

Inventive Principle:

Principle #13The other way round (Inversion)

2Productivity

If high contact pressure is applied in roller mills, then comminution efficiency is improved, but separation of components without ductile properties becomes impossible as all materials are crushed

Engineering Contradiction:

Improvecomminution efficiencyVSAvoidseparation effectiveness

Core Design Contradiction:

ProductivityVSReliability

Solution Approach 1:

The patent fundamentally changes the pressure parameter from high (traditional comminution) to extremely low (15-140 kN/m²), and changes the grinding bed height parameter to 50-200 mm, enabling attrition-based separation that works for all materials regardless of ductility

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent replaces the traditional mechanical crushing mechanism with an attrition mechanism based on particle-particle friction and abrasion in the grinding bed, eliminating the need for ductile components and enabling separation of brittle materials

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

3Productivity

If broken concrete is processed to recover gravel and sand, then recycling rate is improved, but cement stone contamination reduces the strength and quality of recovered materials

Engineering Contradiction:

Improverecycling rateVSAvoidpurity of recovered components

Core Design Contradiction:

ProductivityVSManufacturing precision

Solution Approach 1:

The patent uses a circulating grinding bed where material continuously undergoes attrition, and incorporates classification devices that continuously separate cleaned gravel and sand from cement stone, enabling high-purity recovery that allows unrestricted use in concrete production

Inventive Principle:

Principle #20Continuity of useful action

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 enables the efficient separation and cleaning of gravel and sand from cement paste, achieving high purity levels, allowing for their effective reuse in concrete production, significantly increasing the recycling rate beyond previous limitations.

Implementation Method 1

the material is separated into the first and second components by means of grinding rollers in the grinding bed by shear stress and abrasion of the particles of the components

Methodology Applied

Scientific EffectShear stress: Shear Stress

Implementation Method 2

the material is separated into the first and second components by means of grinding rollers in the grinding bed by shear stress and abrasion of the particles of the components

Methodology Applied

Scientific EffectAbrasion: Abrasion

Implementation Method 3

the grinding bed has a minimum height which is greater than the diameter of the particles of one of the two components

Methodology Applied

Scientific EffectFriction: Friction

Data Source

PatentEP2903744B1Method and device for preparing and separating a material from a combined multicomponent system

Publication Date: 2017.02.22 LOESCHE GMBH

AI summary

The invention relates to a method for preparing and separating a material from a combined multicomponent system. The material is fed to a roller mill as feedstock. An in-bed attrition is carried out in a grinding bed by means of grinding rollers in the roller mill, said material being attrited by shearing stresses and abrasion. In the process, the roller mill is operated such that the grinding bed has a minimum height which is greater than the diameter of one of the particles of one of the two components, and the pressure force of the rollers is selected so as to achieve a surface pressure ranging from 50 kN/m2 to 140 kN/m2 relative to the perpendicularly projected surface of the central roller diameter. The invention further relates to a vertical roller mill which is developed in order to carry out the method according to the invention.