Membrane Cleaning Flow Control via Energy Recovery Recirculation
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Solution Overview
Problem
Current water treatment installations for seawater desalination using reverse osmosis or nanofiltration require costly high-pressure isolation valves and oversized pipes for cleaning, leading to increased costs and chemical overconsumption due to the high flow rates needed for effective membrane cleaning.
Innovation Solution
The method involves injecting the cleaning solution upstream of the high-pressure pump at a reduced flow rate, with the additional flow rate ensured by recirculation through the energy recovery system, and stopping the high-pressure pump during cleaning, allowing for reduced pipe diameters and the use of a single high-pressure valve.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the cleaning solution flow rate is increased to meet the prescribed Q value for effective membrane cleaning, then the cleaning effectiveness is improved, but the pipe diameter and system size must be increased leading to overconsumption of chemicals and higher costs
Solution Approach 1:
The system dynamically switches between filtration mode and cleaning mode. During cleaning, the high-pressure pump is stopped and the energy recovery system is reconfigured to recirculate cleaning solution, allowing the flow rate to be adjusted to the prescribed Q value without requiring oversized pipes or excessive chemical consumption. The adaptability of the system enables optimal performance for each operating condition.
Solution Approach 2:
The invention changes the operational parameters of the energy recovery system by switching it off during cleaning operations. This parameter change allows the cleaning solution to recirculate through the system without being pressurized by the energy recovery system, enabling effective cleaning at the required flow rate while using appropriately sized pipes and reducing chemical overconsumption.
2Reliability
If two high-pressure isolation valves are installed to prevent leakage from the high-pressure section during cleaning, then the safety and reliability are improved, but the device complexity and cost increase significantly
Solution Approach 1:
The invention extracts the high-pressure pump from the cleaning circuit by stopping it during cleaning operations. This separation removes the source of high pressure from the cleaning system, eliminating the need for multiple high-pressure isolation valves. The cleaning solution is introduced at low pressure upstream of the stopped pump, and the high-pressure section is effectively isolated by the pump's stopped state rather than requiring additional valves.
Solution Approach 2:
The stopped high-pressure pump acts as an intermediary that naturally isolates the high-pressure section from the low-pressure cleaning system. Instead of using active valves to prevent leakage, the system uses the passive state of the stopped pump as a barrier, simplifying the valve configuration while maintaining reliability.
3Stability of the object's composition
If the high-pressure pump operates during cleaning to maintain system pressure, then the pressure stability is improved, but the cleaning solution flow rate cannot reach the prescribed Q value and leakage risk increases
Solution Approach 1:
The system employs periodic action by switching between filtration mode (with high-pressure pump operating) and cleaning mode (with high-pressure pump stopped). This periodic operation allows the system to maintain pressure stability during filtration while achieving adequate cleaning flow rate during cleaning operations. The transition between states is controlled by valves that redirect the cleaning solution through the membrane unit even when the high-pressure pump is off.
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 approach reduces the number of high-pressure valves and pipe sizes, lowering the overall cost and chemical usage while maintaining effective membrane cleaning, thereby optimizing the water treatment installation's efficiency and cost-effectiveness.
Implementation Method 1
at least the additional flow rate of cleaning solution Q-Q1 is ensured by recirculating the solution exiting through the discharge line of the membrane unit and passing through the energy recovery system
Implementation Method 2
at least one high-pressure pump on the inlet line
Implementation Method 3
at least one membrane unit for reverse osmosis or nanofiltration filtration
Implementation Method 4
at least one membrane unit for reverse osmosis or nanofiltration filtration
Data Source
Figure 1
Figure 2~3
AI summary
The invention relates to a method for operating a water treatment plant comprising: at least one membrane unit (M) for filtration by reverse osmosis or nanofiltration, an inlet conduit (1, 1a), at least one outlet conduit (4) for the permeate, and a discharge conduit (5); at least one high-pressure pump (3) on the inlet conduit; an energy recovery system (6); a cleaning solution circuit (16, 17, 18); and a set of valves for controlling the filtration operations and the cleaning operations. According to the invention: the flow rate of cleaning solution passing into the membrane unit must be at least equal to a specified value Q; the cleaning solution is injected upstream of the high-pressure pump (3) at a flow rate Q1 below the specified value Q; at least the flow rate Q-Q1 of cleaning solution is guaranteed by the recirculation of solution leaving the discharge conduit (5) of the membrane unit and passing through the energy recovery system (6); the high-pressure pump (3) is stopped during cleaning.