Wet Classification of Waste Incineration Ashes
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Solution Overview
Problem
Incinerator bottom ash is typically landfilled or recycled as low-grade building material due to high pollutant content, making economic recycling challenging and costly.
Innovation Solution
Implementing a wet classification process that minimizes particle crushing, using an upflow classifier and hydrocyclone to separate ash into pollutant-loaded and low-pollutant fractions, with metal separation and optical inspection to enhance recycling efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If dry classification methods are used to separate ash fractions, then the classification process is simple and cost-effective, but the particle crushing increases pollutant concentration in fine fractions
Solution Approach 1:
The patent applies wet classification using a hydrocyclone (hydraulic separation) to classify ash particles by size. Water is used as the separating medium, and centrifugal forces generated in the hydrocyclone enable efficient separation into coarse and fine fractions. This hydraulic approach reduces particle crushing compared to dry mechanical classification while maintaining classification effectiveness, thereby lowering pollutant concentration in the fine fraction.
2Object-generated harmful factors
If wet classification is used to reduce pollutant concentration in recyclable fraction, then recycling quality improves, but processing complexity and cost increase
Solution Approach 1:
The patent implements a two-stage classification system: first a coarse classification stage followed by a fine classification stage using a hydrocyclone. This segmentation allows the process to handle different particle size ranges separately, optimizing the removal of pollutants from the recyclable coarse fraction while maintaining a relatively simple overall plant configuration.
Solution Approach 2:
Water serves as an intermediary medium in the wet classification process. It facilitates particle separation in the hydrocyclone without requiring direct mechanical contact between particles and classification surfaces, reducing wear and simplifying equipment design while achieving effective pollutant separation.
3Object-generated harmful factors
If fine fraction proportion is increased to capture more pollutants, then pollutant removal efficiency improves, but recyclable material quantity decreases
Solution Approach 1:
The hydrocyclone creates dynamic centrifugal forces that act on particles based on their size, density, and shape. This dynamic separation mechanism allows for continuous adjustment of the separation point by modifying operational parameters (flow rate, pressure), enabling optimization of the boundary between recyclable and landfill fractions to maximize both pollutant removal and recyclable material quantity.
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
Significantly increases the recyclable fraction of incinerator ash while maintaining compliance with legal regulations, allowing for economically viable recycling of a large proportion of the ash.
Implementation Method 1
a hydrocyclone (13) upstream of an upflow classifier (15), in which at least one fine fraction (I) is separated from the ash (A) freed from at least one coarse fraction (III)
Implementation Method 2
an upflow classifier (15), in which at least one fine fraction (I) is separated from the ash (A) freed from at least one coarse fraction (III)
Data Source
Figure 1
AI summary
The invention relates to a method for processing waste incineration ashes, in particular domestic waste incineration ashes, in which the ashes are classified into a plurality of fractions of different grain size distributions in a processing plant separated from the actual waste incineration process. The ashes are classified exclusively using a wet classification process in the processing plant, only wet classification processes that are gentle to the grains being used, and the wet classification process is performed in such a way that all of the ashes are classified into at least one fine fraction loaded with harmful substances and at least one coarse fraction that contains only a small amount of harmful substances or no harmful substances at all.