Draft Tube Mixer Platform for Anaerobic Tank Maintenance
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Solution Overview
Problem
Anaerobic digestion tanks with membrane gasholder covers face limitations in mixing systems, requiring external or internal nozzles that complicate installation and maintenance, and do not allow for easy access or integration of additional instruments, leading to inefficient sludge mixing and stratification.
Innovation Solution
A draft tube mixer is mounted at the top of the tank wall, integrated with a platform that allows for easy access and maintenance, enabling remote monitoring and the installation of additional instruments like sample ports and liquid level sensors, while minimizing the need for tank drainage or side cuts.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a membrane gasholder cover is used for anaerobic digestion tanks, then gas storage and anaerobic condition maintenance are improved, but mixing system installation and maintenance become complicated
Solution Approach 1:
The draft tube mixer is mounted on the tank wall at a height above the tank bottom, transitioning from traditional floor-mounted or external mixing systems. This vertical positioning allows the mixer to operate in a different spatial dimension that does not interfere with the membrane gasholder cover, simplifying both installation and maintenance while maintaining effective sludge mixing throughout the tank volume.
Solution Approach 2:
A platform is introduced as an intermediary structure mounted on the tank wall, serving as a support for the draft tube mixer and providing access points for maintenance personnel. This platform acts as a mediator between the mixing system and the tank environment, enabling easy access to the mixer without requiring tank drainage or membrane cover modification.
2Reliability
If traditional membrane gasholder covers are used, then gas storage is achieved, but access for maintenance and additional instruments is restricted
Solution Approach 1:
The tank wall is segmented to include access openings that provide entry points to the interior space. These openings are positioned at convenient heights and allow maintenance personnel to access the draft tube mixer and other components without compromising the integrity of the membrane gasholder cover or requiring complete tank drainage.
Solution Approach 2:
Maintenance access is provided through vertical positioning of equipment on the tank wall rather than requiring access from the tank bottom or through the membrane cover. This dimensional repositioning allows operators to service the mixing system from the side of the tank, significantly improving ease of operation.
3Productivity
If external or internal nozzle mixers are used with membrane covers, then mixing is achieved, but installation cost and operational complexity increase
Solution Approach 1:
The draft tube mixer design allows for self-contained operation with the motor mounted on the tank wall platform, eliminating the need for complex external drive mechanisms or internal nozzle systems. The mixer serves itself by drawing power from the mounted motor and performing maintenance through accessible openings, reducing overall system complexity and installation cost.
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 simplifies installation and maintenance, enhances mixing efficiency, allows for remote monitoring, and integrates mixing and gas storage efficiently, reducing costs and operational complexity.
Implementation Method 1
In the municipal wastewater treatment field, anaerobic tank covers are needed to close the tank to create an anaerobic condition, and to store the gas generated from the process.
Implementation Method 2
The function of the sludge mixer is to mix and circulate the sludge contents of the digester via a impeller in order to minimize accumulation, distribute heat and keep the solids in suspension in the liquid.
Data Source
AI summary
In a municipal sewage treatment system, a biological process tank, typically an anaerobic digestion process, has a flexible, inflated membrane cover. At least one draft tube mixer is installed on the tank, interrupting the gas supported cover with a platform having a flat base and may have upwardly extending sides that generally follow the contour of the inflated cover. The draft tube is connected to the platform and preferably supported on the floor of the tank. The mixer mechanism can be lifted out of the draft tube without escape of gas from the inflated cover.