Solids Displacement Elements in Bayer Process Thickeners
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
The Bayer process experiences 'rat-holing' and build-up of settled solids in thickeners due to high viscosity, leading to reduced operational volume, inconsistent precipitate content, and frequent shutdowns, which negatively affects subsequent processing steps.
Innovation Solution
The introduction of solids displacement elements within the thickener vessel directs settled solids back into the flow path of the slurry, preventing build-up and maintaining a consistent solids content by engaging and re-entraining solids near the side walls and base into the slurry flow, thereby increasing the solids content of the extracted slurry.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If thickening is performed to separate coarse precipitates from fine precipitates, then precipitate separation is improved, but rat-holing and solids build-up occur reducing operational volume
Solution Approach 1:
The thickener is divided into multiple zones with different functions: a classification zone for separating coarse and fine precipitates, and a thickening zone for concentrating slurry. The underflow is further segmented into multiple outlets positioned at different locations to prevent localized solids build-up and rat-holing while maintaining effective separation performance
Solution Approach 2:
A solids displacement element is introduced as an intermediary component between the settled solids and the slurry flow path. This element actively redirects settled solids back into the slurry flow, preventing harmful build-up on vessel walls and floors while maintaining the precipitate separation function
2Productivity
If slurry is removed by pumping from the bottom of the thickener, then slurry extraction is achieved, but preferential flow paths form causing solids build-up
Solution Approach 1:
Solids displacement elements are positioned in advance within the thickener to intercept and redirect settled solids before they can form stable build-ups. This preliminary action prevents the formation of rat-holes and maintains uniform slurry composition throughout the extraction process
Solution Approach 2:
The system uses the existing slurry flow itself to transport and redistribute solids. The solids displacement elements leverage the natural slurry movement to continuously circulate solids back into the flow path, eliminating the need for additional mechanical agitation or cleaning mechanisms
3Loss of time
If settled precipitate reduces operational volume, then residence time decreases, but precipitate content in extracted slurry becomes lower than desired
Solution Approach 1:
The solids displacement element acts as an intermediary that transfers settled solids back into the slurry flow path. This maintains both the operational volume and residence time while ensuring consistent precipitate content in the extracted slurry by continuously replenishing solids in the flow
4Reliability
If thickeners are shut down every two months to clean settled precipitate, then operational continuity is disrupted, but precipitate content consistency is maintained
Solution Approach 1:
The solids displacement elements operate continuously to prevent solids build-up and rat-holing throughout the thickening process. This continuous action eliminates the need for periodic shutdowns for cleaning, maintaining both operational continuity and precipitate content consistency simultaneously
Solution Approach 2:
The system performs self-maintenance by continuously redirecting settled solids back into circulation. The solids displacement elements automatically prevent the formation of problematic build-ups, eliminating the need for external intervention and shutdowns for cleaning
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 solution reduces the formation of 'rat-holes', maintains a higher solids content in the slurry, and extends the campaign life of the thickener vessel beyond two months, ensuring consistent precipitate content and improved processing efficiency.
Implementation Method 1
a vessel having a base and a side wall that define an internal volume for containing the process liquor and for allowing gravity settling of the solids in the liquor
Implementation Method 2
solids displacement elements disposed within the internal volume, for directing settled solids and/or settling solids in the vicinity of the side wall or of the base toward a flow path of the slurry
Data Source
Figure 1
Figure 2
Figure 3A~3B
AI summary
An apparatus for refining a process liquor that includes solids, which apparatus includes a vessel having a base and a side wall that define an internal volume for containing the process liquor and for allowing gravity settling of the solids in the liquor, whereby to produce a refined liquor toward a top of the internal volume and a slurry toward a bottom of the internal volume, the apparatus further includes solids displacement elements disposed within the internal volume for directing settled solids and/or settling solids in the vicinity of the side wall or of the base toward a flow path of the slurry being extracted from the slurry outlet. A processing plant including the above refining apparatus and a method for refining a process liquor.