Closed Loop Membrane Filtration with Periodic Deconcentration
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Solution Overview
Problem
Current membrane filtration systems face inefficiencies in handling high-solid concentration feed waters and producing concentrated waste streams, particularly in applications like oily wastewater or bioreactor sludge treatment, due to limitations in pressure management and flux control.
Innovation Solution
A cross-flow membrane filtration system and process that uses tubular or flat sheet membranes without feed channel spacers, employing a closed loop configuration with a recirculation pump and permeate pump to maintain constant flow and flux, and includes concentration and deconcentration steps to manage solid concentration and flux, while minimizing pressure and energy consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If conventional membrane filtration systems are used to handle high-solid concentration feed waters, then filtration can be performed, but pressure management and flux control become inefficient and energy consumption increases
Solution Approach 1:
The system implements periodic alternating of concentration and deconcentration steps. During concentration steps, feed water is filtered to concentrate solids in the loop. During deconcentration steps, a portion of concentrated retentate is removed and replaced with feed water to reduce solids concentration. This periodic action prevents excessive pressure buildup and maintains efficient flux throughout operation, resolving the contradiction between filtration efficiency and energy consumption.
2Quantity of substance
If continuous concentration is performed without deconcentration steps, then solid concentration increases, but pressure and energy consumption increase excessively
Solution Approach 1:
The system alternates between concentration steps (where solids are concentrated in the loop) and deconcentration steps (where concentrated retentate is partially removed and replaced with feed water). This periodic deconcentration prevents excessive pressure buildup that would occur with continuous concentration, while still achieving the desired solid concentration over time.
Solution Approach 2:
During deconcentration steps, a portion of the highly concentrated retentate is discarded from the loop and replaced with lower-concentration feed water. This discarding of excess concentrate prevents the system pressure from rising excessively while maintaining productive filtration during concentration steps.
3Reliability
If feed channel spacers are used in membrane modules, then membrane support is provided, but device complexity and potential fouling increase
Solution Approach 1:
The system removes feed channel spacers from the membrane module design. Instead of using spacers to maintain feed channels and support membranes, the system uses a spacerless configuration where the membrane itself and the module housing define the flow channels. This extraction of the spacer component simplifies the device structure, reduces potential fouling sites, and lowers device complexity while maintaining reliable membrane support.
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 increases solid concentration in the loop, reduces waste volume, and maintains efficient membrane performance by controlling flux and pressure, producing a highly concentrated waste stream with reduced energy consumption and fouling.
Implementation Method 1
The system employs a cross-flow membrane filtration process using tubular or flat sheet membranes
Implementation Method 2
The process operates with pressurized water on the feed side of the membranes, optionally combined with suction on the permeate side of the membranes
Implementation Method 3
The membranes are preferably in the form of tubular or flat sheet membranes and suited for ultrafiltration or microfiltration
Implementation Method 4
The membranes are preferably in the form of tubular or flat sheet membranes and suited for ultrafiltration or microfiltration
Implementation Method 5
feed water flows by gravity from the feed tank
Data Source
AI summary
In a membrane filtration system and process, retentate exiting a filtration element is maintained inside a loop and redirected back to the inlet of a pump. The pump may produce a generally constant velocity in the loop. Water is concentrated inside the loop until discharged in batches. Feed water enters the loop automatically. The flux through the filtration element is maintained by a controlled valve or pump in communication with a permeate outlet. A filtration element has one or more rigid inserts in a housing. The inserts are covered with membranes. The element is configured to provide open feed channels beside the inserts. The membranes and inserts are potted at an edge, which may be their only attachment to the housing. Permeate flows between the membrane and the insert to the potted edge. The filtration element may be used in the system and process described herein or in others.