Seawater desalination for ships and islands

The demand for fresh water on ships and islands has core requirements such as "emergency, mobility, and low energy consumption." Desalination equipment must be specifically adapted to harsh working conditions and limited space. Its equipment features and filtration principles are centered around "efficient water production, stable operation, and adaptability to extreme environments," as follows:

Equipment core features

The special scenarios of ships (turbulence during navigation, narrow space, limited energy) and islands (windy, high salt fog, poor maintenance conditions) determine that this type of equipment must have the following differentiated features：
1. Shock resistance and high stability for extreme operating conditions

Anti-turbulence/vibration design: Ships are subject to rolling and pitching (up to ±30°) during navigation. Core components within the equipment (such as membrane modules, pump bodies, and piping) utilize anti-vibration mounting structures (such as elastic shock-absorbing brackets) to prevent seal failure or component damage caused by shaking. For island equipment, typhoon and corrosion resistance are essential. Casings are typically constructed of 316L stainless steel or fiberglass reinforced plastic (FRP) to withstand high salt spray environments (salt spray concentrations exceeding 50mg/m³).

Wide operating adaptability: The salinity of incoming seawater (ships may pass through different sea areas with a salinity of 30-35‰; islands near the coast may be affected by rivers, with large fluctuations in salinity) and temperature (-5°C to 40°C) vary greatly. The equipment is equipped with automatic adjustment systems (such as inlet flow valves and temperature compensation modules) to ensure the stability of the produced water quality (in compliance with the "Sanitary Standard for Drinking Water" GB 5749-2022, with a salt content of ≤500mg/L).

2. Compact and modular design saves space.

Small size and light weight: Due to limited space in ship engine rooms and decks, equipment often adopts a vertically stacked or integrated cabinet design. For example, a 5 m³/d reverse osmosis system can occupy less than 1.5 m² and weigh ≤ 500 kg. Island-mounted equipment supports modular assembly (e.g., a single 10 m³/d module can be combined up to 100 m³/d as needed), facilitating transportation and on-site installation without requiring large-scale civil engineering.

High degree of integration: The pretreatment, desalination mainframe, post-treatment, and control systems are integrated into a single unit, reducing external piping connections (e.g., pretreatment filter elements, dosing equipment, and reverse osmosis membrane housings are integrated into the same cabinet), minimizing leakage risks and simplifying operation.

3. Low Energy Consumption and Multi-Energy Compatibility Reduce Operating Costs

Low-energy design: Core desalination technologies (such as reverse osmosis) utilize energy recovery devices (such as PX energy recovery units) to recover approximately 50-60% of the high-pressure energy (approximately 50-60%) of the concentrated seawater discharged back to the water inlet, reducing unit water production energy consumption from the traditional 4-5 kWh/m³ to 2-3 kWh/m³. This adapts to the limited power supply of ship generators or island photovoltaic/wind power generation.Multi-Energy Compatibility: Some equipment supports hybrid power supply (mains power + photovoltaic + diesel generator) and is equipped with energy storage modules to address unstable island power supply issues. Shipboard equipment can be directly connected to the ship's power grid (AC 380V/50Hz or AC 440V/60Hz) without the need for additional modification.

Core filtering principles

The seawater desalination equipment for ships and islands uses reverse osmosis (RO) as its core technology. It needs to go through three stages of filtration: pre-treatment → core desalination → post-treatment to ensure that the seawater meets the freshwater standard after removing impurities and salt. The specific process and principle are as follows:

1. Pretreatment: Removes large particles, colloids, and microorganisms, protecting the reverse osmosis membrane.

2. Core desalination: Reverse osmosis (RO) removes over 99% of salt and small molecule impurities.

3. Post-treatment: Improves the taste and safety of fresh water, meeting end-use requirements.