Thickener Segmentation for Slurry Dewatering
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Solution Overview
Problem
In mineral processing, the formation of a thick, fluffy layer of flocculated fine particles, air bubbles, and chemicals on the surface of the liquid in thickeners impairs dewatering performance by reducing capacity and deteriorating overflow quality due to slow settling rates and particle re-entrainment.
Innovation Solution
The process involves splitting the rock slurry into coarse and fine fractions, treating the fine fraction with a flocculant, and optionally treating the coarse fraction, then combining them for sedimentation to prevent the formation of a fluffy layer on the liquid surface, enhancing settling efficiency and clarity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If flocculant is added to increase settling velocity of fine particles, then settling rate is improved, but a thick fluffy layer forms on the liquid surface reducing dewatering capacity
Solution Approach 1:
The patent applies segmentation by dividing the slurry into two separate thickening processes: a first thickener handles coarse particles while a second thickener handles fine particles. This segmentation prevents the formation of a fluffy layer in the first thickener by removing fine particles that would otherwise form the problematic layer, thereby maintaining dewatering capacity while still achieving rapid settling through selective flocculation in the second thickener.
2Loss of time
If flocculant is added to increase settling velocity, then residence time is reduced, but overflow clarity deteriorates due to particle re-entrainment from the fluffy layer
Solution Approach 1:
The patent applies the extraction principle by removing fine particles from the coarse particle slurry before it enters the first thickener. The fine particles are extracted and directed to a second thickener for separate processing. This prevents the formation of the fluffy layer that causes particle re-entrainment, thereby maintaining overflow clarity while still achieving rapid settling through flocculation in the dedicated fine particle thickener.
3Device complexity
If single-stage thickening is used to simplify the process, then device complexity is reduced, but the fluffy layer formation reduces both capacity and overflow quality
Solution Approach 1:
The patent implements segmentation by using two separate thickeners instead of a single thickener. The first thickener is dedicated to coarse particles and the second to fine particles. This segmentation eliminates the fluffy layer formation problem in the first thickener, maintaining high dewatering capacity and overflow quality, while the added complexity is justified by the significant performance improvement.
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 prevents the formation of a fluffy layer on the liquid surface, improving dewatering performance by increasing solids concentration and clarity of the overflow, thereby enhancing the overall dewatering efficiency and reducing flocculant consumption.
Implementation Method 1
agglomeration with flocculant to form relatively large aggregates of fine particles, flocs
Implementation Method 2
Rapid settling of solid particles in a slurry produces a clarified liquid
Implementation Method 3
The mineral particles settle to the bottom of the thickener, and the liquid overflows the top of the thickener
Data Source
AI summary
Some mineral processing plants encounter difficulties in dewatering pulps using clarifier/thickener (C/T) equipment due to a layer of fine particles, air bubbles and chemicals formed at the top of the liquid in the thickener. Such layers are very stable and form a cap on the C/T. The dewatering performance of the C/T then deteriorates under these conditions, and a high percentage of solids is contained in the thickener overflow. A process for removing water from rock slurry containing a wide range of particle sizes in mineral processing operations has been developed. The process includes: (a) classifying the feed slurry into two size fractions, namely a coarse fraction and a fine fraction, (b) treating the fine fraction (and the coarse fraction if required) with a selected flocculant, and (3) thickening the flocculated slurry in sedimentation equipment to separate liquid from solids.