Fiber Bed Mist Eliminator Re-entrainment Control Device
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Solution Overview
Problem
Re-entrainment of collected liquid from the downstream surface of fiber bed mist eliminators leads to fouling, corrosion, and difficulty in achieving emission requirements due to gas phase drag causing bubbling and fragmentation of the draining liquid, resulting in re-entrainment of droplets into the gas stream.
Innovation Solution
A re-entrainment control device is placed downstream of the fiber bed, redirecting the gas stream's flow path to separate aerosols and soluble solids from the gas stream using inertial forces, with a baffle configuration that changes the direction of the gas stream, preventing re-entrainment by ensuring larger particles and liquids impact the device surfaces.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the gas stream passes directly through the fiber bed without flow direction change, then the structure is simple, but re-entrainment of liquid droplets occurs due to gas phase drag causing bubbling and fragmentation
Solution Approach 1:
The downstream space is segmented into multiple flow channels by baffles, dividing the gas stream into separate paths. This segmentation allows the gas to change direction multiple times while passing through the re-entrainment control device, enhancing droplet separation through inertial forces without requiring a complex overall structure
Solution Approach 2:
Baffles serve as intermediary elements between the fiber bed and the gas stream outlet. These baffles redirect the gas flow and provide surfaces for droplet impaction, acting as a mediator that enhances separation efficiency without requiring direct modification of the fiber bed structure
2Reliability
If a re-entrainment control device is added to redirect gas flow, then re-entrainment is reduced by 91.7%, but the device complexity increases
Solution Approach 1:
Instead of trying to prevent droplet formation at the fiber bed surface, the invention inverts the approach by allowing droplets to form and then using flow redirection to separate them. The baffles redirect the gas stream in the opposite direction of droplet movement, causing droplets to impact the baffles and be removed from the gas phase
Solution Approach 2:
The re-entrainment control device introduces a new spatial dimension for separation by adding vertical baffles that extend into the gas stream. This creates additional separation surfaces in the vertical dimension, enhancing droplet capture without increasing the horizontal footprint of the device
3Reliability
If the fiber bed thickness is increased to improve separation efficiency, then aerosol removal improves, but pressure drop and energy consumption increase
Solution Approach 1:
The re-entrainment control device performs preliminary separation of droplets before they can be carried out with the gas stream. By redirecting the gas flow and causing droplets to impact baffles upstream, the device prevents re-entrainment from occurring in the first place, maintaining high separation efficiency without requiring additional fiber bed thickness
Solution Approach 2:
The invention replaces the mechanical approach of increasing fiber bed thickness with a fluid dynamic approach using flow redirection and inertial separation. Instead of relying on more fibers to capture droplets, the system uses baffles to redirect gas flow and exploit the inertia of droplets to separate them from the gas stream
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
The re-entrainment control device effectively reduces re-entrainment by 91.7% for particles ranging from 0.2 to 10 μm, with significant improvements for larger particles, enhancing the separation efficiency and preventing re-entrainment-induced fouling and corrosion.
Implementation Method 1
redirecting the gas stream's flow path to separate aerosols and soluble solids from the gas stream using inertial forces
Implementation Method 2
The fibers in the fiber bed capture the aerosol in the gas by the mechanisms of impaction, interception, and Brownian diffusion
Implementation Method 3
The fibers in the fiber bed capture the aerosol in the gas by the mechanisms of impaction, interception, and Brownian diffusion
Implementation Method 4
The moving gas urges the droplets to move toward the downstream face of the fiber bed where the captured liquid exits the fiber bed and drains downward under the force of gravity
Implementation Method 5
Re-entrainment in fiber bed separators can arise from two mechanisms. As the liquid drains down through the fiber bed and/or the downstream surface thereof, the moving gas stream can cause some of the draining liquid to break or bubble out of the descending liquid stream and become re-entrained in the gas stream as droplets
Data Source
AI summary
A fiber bed assembly used to remove aerosols and/or wetted soluble solids from a moving gas stream includes a fiber bed support and a fiber bed supported by the fiber bed support so that the gas stream passes through the fiber bed moving from an upstream space to a downstream space with respect to the fiber bed. A re-entrainment control device is located within a downstream space defined by the fiber bed so that at least a portion of the gas stream passes through the re-entrainment control device. The re-entrainment control device is shaped to change the direction of the average flow path of the gas stream as the gas stream passes through the re-entrainment control device so as to cause aerosols and/or wettable solids contained therein to be separated from the gas stream by inertial force. A re-entrainment control device and method of use are also disclosed.