Pulsating Backwash for Cross-Flow Filter Membrane Cleaning
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Solution Overview
Problem
Existing filter cleaning methods, particularly in cross-flow filtration systems, are inefficient in removing uniform deposits from the filtration membrane, leading to reduced service life and ineffective cleaning, as they often fail to address non-uniform deposit thickness along the flow direction.
Innovation Solution
A method involving pulsating backwashing of the filter membrane, where the permeate is displaced by a gas to create a gas cushion, and the backwash liquid pressure oscillates between minimum and maximum pressures to effectively dislodge and remove deposits, utilizing a cross-flow filter with a filter membrane designed to handle the pressure fluctuations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional backwash method is used to clean the filter membrane, then the cleaning process is simple to operate, but the deposits are not effectively removed and the filter service life is reduced
Solution Approach 1:
The backwash liquid pressure is applied in a pulsating manner, alternating between maximum and minimum pressures periodically. This periodic pressure variation creates strong shear forces that effectively dislodge uniform deposits from the filter membrane surface, significantly extending filter service life from weeks to approximately one year without requiring complex additional equipment
Solution Approach 2:
The backwash liquid pressure parameter is dynamically changed during the cleaning process. The pressure oscillates between a maximum value (sufficient to remove deposits) and a minimum value (allowing permeate displacement by gas), creating optimal conditions for deposit removal while maintaining system simplicity
2Reliability
If the backwash liquid pressure is continuously high to remove deposits, then deposit removal is effective, but energy consumption increases and the filter membrane may be damaged
Solution Approach 1:
Instead of applying continuous high pressure, the system uses periodic pressure pulses during backwash. The pressure is high only during the actual deposit removal phase, then reduced when gas displaces permeate. This periodic application reduces overall energy consumption while maintaining effective deposit removal capability
Solution Approach 2:
The backwash liquid pressure is made dynamic rather than static. The pressure continuously oscillates between maximum and minimum values, adapting to the cleaning needs at different moments. This dynamic pressure application removes deposits effectively when needed while conserving energy during non-cleaning phases
3Device complexity
If permeate is allowed to accumulate on the first side of the filter membrane during backwash, then the backwash fluid path is simplified, but the backwash efficiency is reduced due to the gas cushion requirement
Solution Approach 1:
Before applying backwash liquid, gas is first applied to displace permeate from the first side of the filter membrane and create a gas cushion. This preliminary action prepares the system for effective backwash by ensuring the backwash liquid will contact the deposit layer directly, maximizing cleaning efficiency while maintaining a relatively simple fluid path
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 method significantly extends the service life of ultrafiltration modules from weeks to approximately one year by effectively loosening and removing deposits, enhancing the cleaning process and maintaining filter efficiency.
Implementation Method 1
the gas in contact with the backwash fluid stream has a pressure of > 1 bar
Implementation Method 2
the application of the backwash fluid flow in step B) is such that the pressure of the backwash fluid flow changes more than once between a minimum pressure and a maximum pressure
Data Source
Figure 1~2
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AI summary
The invention relates to a method for cleaning a cross-flow filter (20), comprising the following steps: A) providing a cross-flow filter (20), wherein the cross-flow filter (20) comprises a filter membrane (21) and is configured to draw a permeate flow and the filter membrane (21) comprises a first side facing the permeate flow and a second side that is opposite of the first side and faces the inlet flow, and wherein deposits (1010) to be removed are located at least in part on the second side of the filter membrane (21); and B) applying a backwashing liquid flow through the filter membrane (21). Before applying the backwashing liquid flow in step B), a permeate located on the first side of the filter membrane (21) is displaced by a gas at least in part from the first side of the filter membrane (21), wherein the gas that is in contact with the backwashing liquid flow has a pressure of > 1 bar at least during step B). The backwashing liquid flow in step B) is applied in such a manner that the pressure is pulsating.