Fluidized Bed Dryer Level Reduction to Prevent Powder Plugging
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Solution Overview
Problem
Fluidized bed drying methods face challenges such as non-fluidizable wet cakes plugging openings, leading to heating inefficiencies and frequent system stoppages, especially when drying powders with low molecular weight polyolefins, requiring extensive cleaning and maintenance.
Innovation Solution
A continuous method for preparing dried powder in a fluidized bed dryer involves periodically lowering the fluidized bed height to remove lumps and agglomerates, using a closable discharge opening and a separate lump outlet, with controlled bed height maintenance within a predetermined range.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If fluidized bed drying is used to increase drying speed, then drying efficiency is improved, but plugging of openings occurs leading to system stoppages
Solution Approach 1:
The invention extracts and removes lumps and agglomerates from the fluidized bed using a dedicated removal system with a screw conveyor and discharge opening, preventing them from plugging the drying system openings and maintaining continuous operation
Solution Approach 2:
The invention implements a feedback mechanism where the level of material in the fluidized bed is continuously monitored and the discharge opening is controlled to maintain the optimal bed level, preventing lump accumulation that would cause plugging
2Productivity
If wet cake is processed in fluidized bed dryer, then drying capacity is increased, but non-fluidizable portions plug openings requiring cleaning
Solution Approach 1:
The invention extracts problematic lumps and agglomerates from the wet cake mixture before they can cause plugging, using a screw conveyor system that continuously removes these materials from the fluidized bed
Solution Approach 2:
The invention performs preliminary removal of lumps through the screw conveyor and discharge opening before they can accumulate and block the drying system, preventing the need for subsequent cleaning operations
3Use of energy by moving object
If heating elements are covered by non-fluidized portions, then heating efficiency decreases, but increasing temperature to compensate causes thermal blocking
Solution Approach 1:
The invention removes lumps and agglomerates that would otherwise cover heating elements and reduce heating efficiency, preventing thermal blocking by extracting these materials before they can accumulate on heated surfaces
Solution Approach 2:
The invention converts the potentially harmful effect of lumps (which would cause thermal blocking) into a benefit by using the lump removal mechanism to actively prevent thermal blocking, turning a problem into a solution
4Reliability
If lump outlet is continuously open to remove agglomerates, then lump accumulation is prevented, but dried powder is lost
Solution Approach 1:
The invention uses periodic rather than continuous operation of the lump outlet, opening it only when lumps need to be removed and closing it during normal operation to prevent dried powder loss while still maintaining effective lump removal
Solution Approach 2:
The invention makes the lump outlet dynamic rather than static, controlling its opening and closing based on the actual need for lump removal, optimizing both lump removal effectiveness and powder retention
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 dryer performance degradation, minimizes shutdowns, and increases throughput by preventing lump accumulation, thus maintaining consistent heating efficiency and reducing cleaning cycles.
Implementation Method 1
Fluidized bed drying has gained dominance in the field of powder drying due to an increased drying speed. In particular, fluidized bed drying provides controlled and uniform drying conditions.
Implementation Method 2
a wet cake or slurry may not be readily fluidizable... portions of the cake may plug openings or apertures in grids
Data Source
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AI summary
A method for the preparation of a dried powder in a fluidized bed dryer is disclosed. The method is characterized by periodically carrying out a level decrease in which the height of the fluidized bed within the fluidized bed dryer is reduced to a basic height which is from 30% to less than 95%, preferably from 50% to 75% of the setpoint height. It has been surprisingly found that by periodically carrying out the level decrease, plugging and a reduction of heat transfer over time may be mitigated or even avoided.