Steam-Turbine Pump Control for Reverse Osmosis Membrane Protection
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Solution Overview
Problem
Mega-size desalination plants face inefficiencies due to the limited variability of electricity as an energy source, leading to membrane damage and operational challenges from varying raw water conditions, membrane aging, and fluctuating water demand, which conventional electrically driven pumps cannot adequately address.
Innovation Solution
Utilizing steam turbines to power high pressure pumps, allowing for variable speed control between 500 RPM and 5000 RPM, and implementing a slow pressure increase during start-up to prevent membrane damage, replacing the need for pressure release valves.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If electrically driven pumps are used to power reverse osmosis membranes, then the desalination process can be operated, but the limited frequency variability (30-60 Hz) prevents adequate compensation for widely changing conditions
Solution Approach 1:
The patent changes the energy source from electrical motors with limited frequency control (30-60 Hz) to steam turbines with wide speed variability (500-5000 RPM). This parameter change in the prime mover enables the pump system to adapt to widely changing conditions including salinity variations (1000-40000 ppm), temperature changes (1-35°C), and demand fluctuations (>50% variation), thereby resolving the contradiction between adaptability and energy source limitations.
2Productivity
If high pressure is applied quickly to the membrane during start-up, then the process starts faster, but the membrane is damaged due to excessive pressure
Solution Approach 1:
The patent applies dynamic control of the steam turbine driven pump during start-up, gradually increasing the pump rotation speed from 500 RPM to 5000 RPM over time. This dynamic approach allows the membrane to gradually adapt to increasing pressure, preventing damage while achieving operational pressure. The steam turbine's ability to provide wide speed variability enables this controlled ramp-up, resolving the contradiction between fast start-up and membrane protection.
3Adaptability or versatility
If multiple different sized electrically driven pumps are installed to address varying conditions, then the plant can adapt to different water conditions, but additional booster pumps must be installed and removed depending on conditions
Solution Approach 1:
The patent employs a single steam turbine driven pump system that can operate across a wide speed range (500-5000 RPM), making it universally capable of handling all varying conditions including different salinities, temperatures, and demand levels. This eliminates the need for multiple different sized pumps and booster pumps that would need to be installed and removed based on conditions, thereby resolving the contradiction between adaptability and system complexity.
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
Enhances operational flexibility, reduces membrane damage, and improves efficiency by compensating for varying conditions, while also reducing carbon emissions and operational costs.
Implementation Method 1
passing feed water through a high pressure pump driven by at least one steam turbine capable of producing at least 1 MW of energy
Implementation Method 2
the pressurized feed water passing through at least one reverse osmosis membrane to provide a residual brine stream and a product water
Implementation Method 3
passing feed water through a high pressure pump driven by at least one steam turbine
Data Source
AI summary
A large scale water desalination process for producing at least 100,000 m3/day of product water. Feed water is passed through a high pressure pump driven by at least one steam turbine capable of producing at least 1 MW of energy, the pressurized feed water passing through at least one reverse osmosis membrane to provide a residual brine stream and a product water. A start-up step slowly increases pressure in the membrane at a maximum rate of 12 psi (8.3 Newtons/cm2; 0.08 MPa) per second by rotation of the turbine driven high pressure pump at a maximum rate of 30 RPM to slowly increase pressure on the membrane to a predetermined operational pressure and controlling the operational pressure following the start-up step by rotation of the high pressure pump between 500 RPM and 5000 RPM dependent on the pressure applied by the steam turbine.