Double-Acting Piston RO Assembly for Low-Downtime Batch Desalination
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Solution Overview
Problem
Existing reverse osmosis desalination systems face high energy consumption and downtime issues, particularly in batch processes, due to brine mixing and the need for recharging the system after each cycle.
Innovation Solution
A high-pressure, variable-volume piston-like tank is used in a quasi-batch RO system, allowing alternating use of tank sides for feed and brine, reducing downtime and energy losses by eliminating the need for tank emptying and minimizing brine mixing, combined with a Stirling engine for power and a closed-loop counter-flow process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If batch reverse osmosis process is used, then energy consumption is reduced compared to continuous process, but downtime between cycles increases due to tank emptying and recharging requirements
Solution Approach 1:
The high-pressure tank is divided into two distinct sides (first side and second side) that can be independently filled and emptied. This segmentation allows one side to be in production mode while the other is being recharged or emptied, eliminating the need to shut down the entire system for tank maintenance or recharging.
Solution Approach 2:
The dual-sided tank design enables continuous operation by allowing the RO system to switch between two sides. While one side is producing permeate, the other side can be emptied or recharged, ensuring that the useful action of desalination continues without interruption or downtime.
2Ease of operation
If conventional single-stage continuous RO is used, then system operation is simple, but energy consumption is high due to constant pressurization of entire feed stream
Solution Approach 1:
The system employs periodic batch operation where feed is introduced into the high-pressure tank, pressurized, and processed in cycles. This periodic action allows the system to concentrate brine over time and recover energy, reducing overall energy consumption compared to continuous pressurization while maintaining operational simplicity through automated cycling.
Solution Approach 2:
The system recovers energy by utilizing the high-pressure brine produced during each batch cycle. Instead of discarding the pressurized brine, it is redirected to pre-pressurize the feed for the next cycle, thereby recovering the energy invested in pressurization and reducing the energy required for the subsequent batch.
3Duration of action of moving object
If brine is recirculated back to feed side in batch RO, then process is extended in time, but brine mixing with fresh feed occurs causing inefficiency
Solution Approach 1:
The high-pressure tank is segmented into two separate sides with dedicated inlet and outlet ports. This physical segmentation prevents brine from mixing with fresh feed by keeping them in separate compartments, allowing the process to extend over time without compromising desalination efficiency.
Solution Approach 2:
The system extracts and removes brine from the high-pressure tank through dedicated outlet ports before it can mix with fresh feed. By taking out the concentrated brine stream separately and directing it to appropriate discharge or recovery systems, the inefficiency of mixing is eliminated while maintaining extended process duration.
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 significantly reduced energy consumption (below 2 kWh/m3 for seawater) and downtime (around 2% of cycle time) compared to conventional systems, with improved efficiency and reduced entropy generation.
Implementation Method 1
at least one reverse osmosis module operationally connected in the system, the at least one reverse osmosis module having an inlet operably connected to the second valve outlet and having a brine outlet and a desalinated water outlet
Implementation Method 2
the exerted hydraulic pressure follows the osmotic pressure of the brine over time leading to significant energy savings
Data Source
AI summary
An assembly for reverse osmotically desalinating water, including a source containing feed water to be desalinated, a high-pressure tank having a first portion and a second portion and a movable piston wall operationally connected therebetween, a first portion inlet operationally connected to the first portion and a second portion inlet operationally connected to the second portion, a first portion outlet operationally connected to the first portion and a second portion outlet operationally connected to the second portion, a first valve having a first first valve inlet, a second first valve inlet, a first first valve outlet in fluidic communication with the first portion inlet and a second first valve outlet in fluidic communication with the second portion inlet, a high-pressure pump operationally connected to the source and to the first first valve inlet, a second valve having a first second valve inlet in fluidic communication with the first portion outlet and a second second valve inlet in fluidic communication with the second portion outlet and a second valve outlet, at least one reverse osmosis module having at least one reverse osmosis module inlet connected in fluidic communication with the second valve outlet, at least one brine outlet and at least one desalinated water outlet, a circulation pump having a circulation pump inlet port connected in fluidic communication with the brine outlet and a circulation pump outlet connected in fluidic communication with the second first valve inlet, and an electronic controller operationally connected to the first valve, to the second valve, to the high-pressure pump and to the circulation pump.