Liquid Air Separator for Membrane Bioreactor Splash Control
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Solution Overview
Problem
In flat plate membrane bioreactors, the deposition of the air and liquid stream above the water surface during diffuser cleaning causes undesirable splash and spray, which can inhibit the venturi action required for efficient cleaning of submerged membrane units.
Innovation Solution
A multistage immersion type membrane separator with a liquid air separator device that separates air and water using a cylindrical outlet tube and inlet pipe configuration, where the mixed flow enters tangentially, causing the liquid to be forced to the wall and the air to accumulate inside, reducing splashing and spray by separating the streams effectively.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the automated diffuser cleaning valve is opened to flush diffusers with mixed liquor, then the diffusers are cleaned effectively, but the deposition of air and liquid stream above the water surface causes undesirable splash and spray
Solution Approach 1:
The outlet is segmented into separate air and liquid discharge paths. The air outlet tube discharges air at a higher location while the liquid outlet discharges liquid at a lower location, separating the mixed stream into distinct components to eliminate splash and spray while maintaining cleaning effectiveness
Solution Approach 2:
A separation chamber acts as an intermediary between the mixed liquor inlet and the final discharge points. This chamber allows the air-liquid mixture to separate by density before being discharged through dedicated outlets, preventing direct deposition of mixed stream above the water surface
2Object-generated harmful factors
If a liquid air separator is introduced to separate air and water streams, then splash and spray are eliminated, but backpressure may inhibit the venturi action of the diffuser cleaning operation
Solution Approach 1:
The separator utilizes pneumatic-hydraulic separation where air and liquid phases are separated based on density differences and flow dynamics. The design maintains pressure balance by providing separate discharge paths that do not create backpressure on the venturi action, allowing effective cleaning without splash
Solution Approach 2:
The separator introduces a vertical dimension to the discharge system with the air outlet positioned at a higher elevation than the liquid outlet. This dimensional separation allows air to escape vertically without interfering with liquid discharge, eliminating splash while maintaining flow efficiency
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 liquid air separator eliminates undesirable splashing and spray, ensuring equal air scouring and maintaining the venturi action necessary for diffuser cleaning, while imposing minimal head loss to prevent backpressure and maintain efficient operation.
Implementation Method 1
The mixed flow separates as the liquid has a higher density than the air
Implementation Method 2
The cylindrical body promotes a swirling action in the device to separate the air and water
Implementation Method 3
air flows through the diffusers creating a venturi action, which pulls in the liquid mixed liquor through the diffusers
Data Source
AI summary
A multistage immersion type membrane separator includes a liquid air separator, the liquid air separator including an outlet tube, an inlet tube, and a skirt. The outlet tube is cylindrical and has a outlet tube diameter, and the inlet pipe has an inlet pipe diameter of less than the outlet tube diameter. The inlet pipe is attached to and in communication with the outlet tube so that a mixed flow of air and liquid passing through the inlet tube is introduced into the outlet tube and flows circumferentially around the inside of the outlet tube. The inlet pipe is attached to the cylindrical outlet tube so that the inlet pipe is perpendicular to the outlet tube. The outlet tube has two ends, one end being closed and the other end being open. The skirt is attached to the outlet tube and is concentric with the outlet tube. The skirt is attached to the closed end of the outlet tube, and extends to just past the point of attachment of the inlet tube to the outlet tube. The skirt also has two open ends, and one open end penetrates through the closed end of the outlet tube.