Reverse Osmosis Circulation Pump Switching for Low-Pressure Discharge
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Solution Overview
Problem
Conventional reverse osmosis systems face inefficiencies in discharge at lower pressures and higher flows, energy inefficiency, and issues with membrane fouling and salt precipitation due to complex flow switching, leading to reduced recovery and membrane module degradation.
Innovation Solution
A reverse osmosis system with a forward flow mode and discharge mode, utilizing a circulation pump to circulate concentrate in a forward or reverse direction, and a high-pressure pump to discharge concentrate in parallel, reducing energy consumption and enhancing recovery while minimizing membrane fouling.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional RO systems operate at constant output with complex flow switching, then salt concentration control is achieved, but discharge efficiency at lower pressures and higher flows deteriorates
Solution Approach 1:
The system dynamically switches between forward flow mode and discharge mode, allowing the circulation pump to operate in different configurations. During discharge mode, the pump inlet connects to the concentrate outlet and outlet connects to the concentrate inlet, enabling efficient low-pressure discharge while maintaining salt concentration control during forward flow operation
2Productivity
If high pressure is continuously applied to maintain permeate production, then recovery is improved, but energy consumption increases
Solution Approach 1:
The system employs periodic operation cycles alternating between forward flow mode (where high pressure maintains permeate production and recovery) and discharge mode (where high pressure is reduced or eliminated). This periodic switching allows the system to achieve high recovery during production phases while reducing energy consumption during discharge phases, eliminating the need for continuous high-pressure operation
3Speed
If concentrate is discharged at high pressure, then discharge speed is improved, but energy efficiency deteriorates
Solution Approach 1:
The circulation pump dynamically changes its connection configuration between forward flow mode and discharge mode. During discharge mode, the pump inlet connects to the concentrate outlet and the outlet connects to the concentrate inlet, allowing the pump to drive concentrate discharge at high speed while operating at lower pressure differential, thereby improving energy efficiency compared to high-pressure discharge
4Duration of action of stationary object
If system operates in steady state, then membrane module lifespan is extended, but membrane fouling and salt precipitation increase
Solution Approach 1:
The system periodically switches between forward flow mode and discharge mode, preventing steady-state operation. During discharge mode, the flow reversal and concentration redistribution prevent salt precipitation and fouling accumulation on membranes, while extending membrane lifespan through reduced mechanical stress from pressure cycling
Solution Approach 2:
During discharge mode, the flow direction is effectively reversed compared to forward flow mode, with the circulation pump inlet connected to the concentrate outlet and outlet to the concentrate inlet. This inversion prevents fouling and salt precipitation by disrupting the steady-state concentration gradients that lead to membrane degradation
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 achieves efficient discharge at lower pressures, reduces membrane fouling and salt precipitation, and increases recovery, resulting in higher permeate quality and reduced energy costs.
Implementation Method 1
a circulation pump of the system is connected across the pressure vessel to circulate the concentrate from the second port back to the first port
Implementation Method 2
Reverse osmosis is a process, often used to purify water, that uses one or more semi-permeable membranes to separate permeate molecules, such as water molecules, from other dissolved solids, such as salts. Reverse osmosis applies pressure to overcome osmotic pressure that favors even distribution of salts in solution.
Implementation Method 3
The high pressure pump 22 supplies high pressure feedwater 18 to the pressure vessels 16 to force pure water as permeate 20 through the membranes 15
Implementation Method 4
Each membrane module 13 contains one or more semi-permeable membranes 15... the membranes are configured to permeate water, via reverse osmosis, as a permeate from a concentrate flowing between the first and second ports. The membranes are also configured to block permeation of dissolved solids from concentrate.
Implementation Method 5
In the discharge mode, the circulation pump inlet is connected to the high pressure pump inlet and the circulation pump outlet is connected to the first port, in order to discharge the concentrate out of the second port of the pressure vessel
Data Source
AI summary
A reverse osmosis system includes a pressure vessel comprising first and second ports. Membranes disposed in the pressure vessel, permeate water and block permeation of dissolved solids from concentrate flowing between the first and second ports. A high pressure pump includes an inlet and an outlet. A circulation pump includes an inlet and an outlet and is configured to circulate the concentrate between the first and second ports. A valved circulation apparatus is configured to select between a forward flow mode and a discharge mode of the system. In the forward flow mode, the circulation pump inlet is connected to the second port and the circulation pump outlet is connected to the first port. In the discharge mode, the circulation pump inlet is connected to the high pressure pump inlet and the circulation pump outlet is connected to the first port and production of permeate is prevented.