Fluidized Bed Classifier for Granule Size Segregation
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Solution Overview
Problem
Conventional fluidized bed spray granulation processes often result in granules outside the desired size range, necessitating costly and inefficient recycling, which increases investment and operating costs due to the need for handling, processing, and temperature control issues.
Innovation Solution
Incorporating a classifier with heat exchanger tubes in the granulation zone to segregate granules by size and recirculate undersize granules internally for further enlargement, reducing external recycling and improving temperature homogeneity, thereby enhancing production rate and quality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If fluidised bed spray granulation is used to produce granules, then homogeneous evenly shaped granules can be formed, but granules with sizes outside the desired range are produced requiring recycling
Solution Approach 1:
The granulation process is segmented into distinct zones: a fluidisation zone for temperature control and a granulation zone for particle formation. The classifier divides the bed into different height zones, creating separate functional regions that improve both granule quality and reduce recycling needs by optimizing conditions in each segment.
Solution Approach 2:
Different zones within the fluidised bed are given different local conditions - the fluidisation zone maintains specific temperature characteristics while the granulation zone provides conditions optimal for granule formation. This local differentiation allows simultaneous optimization of temperature control and granulation efficiency, reducing the need for recycling.
2Loss of substance
If recycling of undersize and oversize granules is implemented, then material can be reused, but investment costs and operating costs increase due to handling and processing requirements
Solution Approach 1:
The classifier extracts and removes oversize granules from the fluidised bed before they can cause problems downstream. By taking out oversized particles at the source, the system prevents the need for complex external recycling loops and crushing equipment, while still allowing undersize granules to be processed efficiently.
Solution Approach 2:
The classifier acts as an intermediary device between the granulation process and the product output. It mediates by sorting granules in-situ within the fluidised bed, enabling selective removal of oversize particles without requiring external handling systems, thereby reducing equipment complexity while maintaining material utilization.
3Stability of the object's composition
If external recycling is used to maintain system balance, then heat and water balance can be maintained, but operating costs increase due to electricity consumption for handling equipment and heat consumption for reheating
Solution Approach 1:
The classifier combines the functions of granule classification and in-bed recycling into a single integrated component within the fluidised bed. This merging eliminates the need for separate external recycling equipment and associated energy consumption, while maintaining system balance through internal circulation of undersize granules.
Solution Approach 2:
The fluidised bed system with classifier provides self-service by automatically classifying and recirculating undersize granules within the bed itself. This self-contained approach maintains heat and water balance internally without requiring external handling equipment or additional heating systems, thereby reducing energy consumption while preserving system stability.
4Temperature
If classifier with heat exchanger tubes is installed in the granulation zone, then temperature homogeneity is improved and external recycling is reduced, but device complexity increases
Solution Approach 1:
The classifier structure serves multiple functions simultaneously: it acts as a granule classifier to separate sizes, provides heat exchange surfaces for temperature control, and creates the fluidisation-granulation zone division. This multi-functionality reduces the need for separate temperature control equipment, offsetting the added complexity of the classifier structure itself.
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 reduces external recycling by approximately one-third, decreases operational costs, and achieves a more homogeneous temperature profile, leading to increased productivity and improved granule quality by minimizing the need for external recycle equipment and optimizing heat transfer.
Implementation Method 1
heat is exchanged from the granulation zone in the classifier (3a, 21) by use of heat exchanger tubes (20) extending in a distance from each other across the horizontally oriented cross-sectional area of the classifier (3a, 21)
Implementation Method 2
forming a granulation zone (3, 13) in the fluidised bed where contacted/coated seed particles are dried, shaped and cooled to form granules
Data Source
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AI summary
This invention relates to a method and device for processing of granules of solidified salts, by forming at least one injection zone in a fluidised bed where a feed stream of seed particles is contacted/coated by the liquid product by simultaneous injection of a feed stream of the seed particles and a feed stream of the liquid product to be sprayed, forming at least one granulation zone in the fluidised bed where contacted/coated seed particles may be dried and/or shaped and/or cooled to form granules, extracting granules from the at least one granulation zone(s) and sorting the extracted granules into three fractions; undersize granules with too small diameters compared to the desired size range, on-size granules with diameters within the desired size range, and oversize granules with too large diameters compared to the desired size range, passing the fraction of on-size granules to post-processing treatment for forming the product granules, removing the oversize, typically by reducing the size of at least a fraction of the oversize granules and admixing them with the fraction of undersize granules, and passing the fraction of undersize granules into the feed stream of seed particles, wherein the granules are made to pass through at least one classifier placed in the at least one granulation zone(s) of the fluidised bed, which segregates the granules according to their size and which passes at least a part of the segregated undersize granules back into the injection zone(s) for further enlargement. The invention also relates to a granulator for performing the inventive method.