Draft Tube Eductor Backwash for Walnut Shell Filters
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Solution Overview
Problem
Conventional walnut shell filter systems for wastewater treatment are bulky, costly to maintain, and inefficient due to mechanical backwash methods that create dead spots and generate excessive backwash fluid.
Innovation Solution
A compact filter apparatus utilizing a walnut shell filter media with a draft tube and eductor system that induces a roll of the filter media during backwash, using a mixture of gas and fluid to reduce the volume of combustible gas and backwash fluid.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If mechanical mixing and mechanical scrubbing with impellors are used for backwash, then the filter media can be turned and cleaned, but the initial costs and maintenance costs increase due to mechanical seals
Solution Approach 1:
The patent replaces mechanical impellors and seals with a gas sparging system that uses gas bubbles to provide mixing and scrubbing action. Gas is introduced through distributors at the bottom of the vessel, creating upward flow that turns and cleans the filter media without requiring mechanical moving parts or seals.
Solution Approach 2:
The invention uses gas (pneumatic) flow through distributors to achieve backwash functions. Gas bubbles rise through the filter media, providing both mixing action to turn the media and scrubbing action to remove contaminants, eliminating the need for mechanical systems.
2Reliability
If recirculation of the bed with additional pumps is used, then the filter media can be cleaned, but the initial costs and maintenance costs increase and the footprint increases
Solution Approach 1:
The patent extracts and eliminates the recirculation pump system entirely. Instead of pumping media out and back in, the system uses in-situ gas sparging to achieve cleaning directly within the filter vessel, removing the need for external recirculation equipment and associated footprint.
Solution Approach 2:
The filter media is cleaned in-place within the vessel using gas flow generated from the bottom distributors. The system performs self-service cleaning without requiring external pumps or recirculation loops, reducing both footprint and equipment complexity.
3Reliability
If high velocity gas or high velocity water is used for backwash, then the filter media can be turned, but significant amounts of backwash fluid are generated
Solution Approach 1:
The system uses gas (rather than high-velocity liquid water) to provide the backwash action. Gas is introduced through distributors and rises through the filter media, providing turning and cleaning action while generating minimal liquid backwash fluid compared to conventional high-velocity water systems.
Solution Approach 2:
The invention changes the backwash medium from high-velocity liquid to gas flow. This parameter change maintains effective media turning and cleaning while dramatically reducing the volume of liquid backwash fluid that must be handled and disposed of.
4Reliability
If conventional backwash systems are used, then the filter media can be cleaned, but dead spots are created where filter media is not sufficiently turned and oil and suspended solids remain
Solution Approach 1:
The patent uses multiple gas distributors positioned at different locations at the bottom of the vessel to ensure uniform gas flow distribution throughout the filter media bed. This local distribution approach eliminates dead spots by providing cleaning action across all areas of the vessel, including regions that might be missed by single-point injection systems.
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 system effectively reduces greenhouse gas emissions and minimizes maintenance and capital costs by eliminating mechanical equipment, while ensuring thorough cleaning of the filter media without creating dead spots.
Implementation Method 1
an eductor including a fluid inlet, a fluid suction port, and a fluid outlet directed into the draft tube, a first fluid supply coupled to the fluid inlet to deliver a flow of a first fluid... The eductor operates to draw a portion of the gas into the eductor in response to the flow of the first fluid, the first fluid and the gas forming a backwash mixture
Implementation Method 2
a draft tube positioned in the vessel and filled with the filter media... The first fluid and the gas forming a backwash mixture that is discharged into the draft tube via the fluid outlet to induce a roll of the filter media during a backwash process
Data Source
AI summary
A filter apparatus includes a vessel, a filter media positioned in the vessel, a feed inlet positioned in the vessel above the filter media, and a knockout pot coupled to the vessel and arranged to collect a gas discharged from the vessel. The apparatus also includes a draft tube positioned in the vessel and filled with the filter media and an eductor including a fluid inlet, a fluid suction port, and a fluid outlet directed into the draft tube, a first fluid supply coupled to the fluid inlet to deliver a flow of a first fluid, and a conduit arranged to connect the knockout pot to the fluid suction port. The eductor operates to draw a portion of the gas into the eductor in response to the flow of the first fluid, the first fluid and the gas forming a backwash mixture that is discharged into the draft tube via the fluid outlet to induce a roll of the filter media during a backwash process.