Waste Mill With Chain Rotors for RDF Production
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Solution Overview
Problem
Existing waste grinding technologies face inefficiencies, including high energy consumption, complex structures, and temperature issues due to the presence of non-grindable materials, which affect the operation and output quality of refuse-derived fuel (RDF).
Innovation Solution
A mill with two rotors and a unique grinding chamber design, featuring chains that impart high centrifugal acceleration and impact forces to efficiently break down waste, combined with a simple structure and automatic removal mechanisms for non-grindable bodies, and a vacuum system for efficient waste expulsion and bacterial reduction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a counter-rotating blade mill is used for grinding waste, then the grinding function is provided, but the operation is easily affected or prevented by non-grindable bodies such as mineral or metallic bodies
Solution Approach 1:
The patent removes non-grindable bodies from the waste stream before the grinding stage using magnetic separators and other removal devices. This extraction of harmful elements prevents them from interfering with the grinding operation, thereby maintaining both ease of operation and reliability simultaneously.
2Productivity
If traditional grinding apparatus are used to process municipal solid waste, then waste grinding is achieved, but the energy consumption exceeds 250 kW per tonne of waste processed
Solution Approach 1:
The patent divides the waste processing into distinct stages: removal of non-grindable bodies, grinding of remaining material, and separation of ground product. This segmentation allows each stage to be optimized independently, reducing overall energy consumption while maintaining productivity.
Solution Approach 2:
The patent changes the operational parameters by removing problematic materials before grinding, which allows the grinding apparatus to operate more efficiently at lower energy consumption levels while maintaining the required grinding capacity.
3Productivity
If non-grindable bodies are present in the waste stream, then the grinding process continues, but local temperature increases to hundreds of degrees Celsius causing softening of polymer fractions and blockage of output grilles
Solution Approach 1:
The patent extracts and removes non-grindable bodies before the grinding stage, eliminating the source of excessive friction and heat generation. This prevents local temperature rise that would otherwise cause polymer softening and grille blockage, while maintaining continuous processing capability.
4Productivity
If the RDF particle size is reduced from 25-30 mm to 5-10 mm for direct fuelling, then the combustion efficiency is improved, but the energy consumption increases further
Solution Approach 1:
The patent segments the processing into removal of non-grindable materials and grinding of combustible materials. By removing the non-grindable fraction first, the grinding apparatus can more efficiently reduce the particle size of the remaining combustible material to the optimal 5-10 mm size for direct combustion, improving combustion efficiency without excessive energy consumption.
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 mill achieves high energy efficiency, reduces bacterial content by 90%, and produces RDF with a fine particle size suitable for direct combustion, replacing coal dust, while maintaining a stable temperature and preventing output grille blockages.
Implementation Method 1
The chains (34) are designed to rotate with high speed, so as to impart high centrifugal acceleration and/or impact forces to the waste (R)
Implementation Method 2
The chains (34) are designed to rotate with high speed, so as to impart high centrifugal acceleration and/or impact forces to the waste (R)
Implementation Method 3
a vacuum system for efficient waste expulsion and bacterial reduction
Data Source
AI summary
The present invention relates to a mill 20 for grinding rubbish R. The mill 22 comprises at least one grinding chamber 24 defined by a side wall 26 and a floor 26. The mill also comprises at least two rotors 301 and 302 rotatable about respective substantially vertical axes X1 and X2. Each of the rotors 30 comprises a hub 32 and a plurality of chains 34 connected to the hub 32 and designed to sweep over part of the grinding chamber 22 during rotation of the rotor 30.