Application of Seawater Electrochlorination Systems in US Power Plants

Approximately 75% of coastal power plants in the United States rely on seawater as a source of circulating cooling water. However, issues such as microbial corrosion and biological slime blockage caused by seawater have long plagued the safe operation and energy efficiency improvement of these power plants. Seawater electrochlorination systems, based on the core principle of "on-site chlorine production via seawater electrolysis," replace the traditional liquid chlorine transportation and storage model. They not only address the safety pain points of disinfection in power plants but also, through technological iterations, adapt to the high-load, high-compliance, and high-stability operational requirements of power plants. This article will analyze the practical pathways and value of seawater electrochlorination systems in U.S. power plants from four dimensions: application scenarios in power plants, technical adaptation solutions, typical cases, and future trends.

1. Core Drivers for Power Plant Application: From "Safety Pain Points" to "Compliance Mandates"

The adoption of seawater electrochlorination systems by U.S. power plants is essentially an inevitable outcome of addressing three core contradictions:

1.1 Safety Risks and Efficiency Bottlenecks of Traditional Disinfection Methods

When coastal power plants traditionally used liquid chlorine for disinfection, they faced dual risks: First,transportation and storage risks—liquid chlorine is classified as a "highly toxic hazardous substance" by the U.S. Department of Transportation (DOT). In 2019, a liquid chlorine transportation leak at a power plant in Florida led to the evacuation of a 3-kilometer area around the plant, resulting in direct losses exceeding $5 million. Second,dosing efficiency shortcomings—liquid chlorine easily reacts with organic matter in seawater to form trihalomethanes (THMs), and its concentration decays by 15%-20% per month, requiring frequent replenishment. This causes fluctuations of ±0.3ppm in residual chlorine in circulating water, an annual average increase of 2.2℃ in condenser end difference, and a 1.1% rise in unit heat rate.

1.2 Stringent Constraints of Environmental Regulations

The U.S. Clean Water Act (CWA) and the Environmental Protection Agency (EPA) have continuously tightened controls on power plant effluents: The "Power Plant Cooling Water Rule" enacted in 2020 requires residual chlorine in circulating water discharge to be ≤0.1ppm, and limits for disinfection by-products (THMs, HAA5) to be reduced to 80ppb and 60ppb, respectively. Regions with strict environmental protections, such as California, have even imposed "zero liquid chlorine discharge" requirements. Traditional liquid chlorine dosing systems, which struggle with precise dosage control and excessive by-products, are gradually being phased out of coastal power plants.

1.3 Adaptation Needs for Special Operating Conditions in Power Plants

The "high-load, long-cycle, emergency redundancy" characteristics of power plant operations impose special requirements on disinfection systems: The daily flow rate of circulating cooling water systems can reach 100,000-150,000 m³/h, demanding high-flow dosing capabilities from disinfection systems; emergency cooling systems in nuclear power plants must initiate disinfection within 10 seconds as required by the Nuclear Regulatory Commission (NRC); and during unit start-up/shutdown and load fluctuations, disinfection systems must dynamically adapt to changes in water quality. These needs perfectly align with the advantages of seawater electrochlorination, such as "on-demand chlorine production, rapid response, and intelligent adjustment."

2. Three Core Application Scenarios: Targeted Solutions to Water Treatment Pain Points in Power Plants

The application of seawater electrochlorination systems in U.S. power plants focuses on three core scenarios—circulating cooling, emergency safety, and water quality pretreatment—and has developed mature technical adaptation solutions.

2.1 Circulating Cooling Water Systems: Breaking the "Biological Slime-Energy Loss" Vicious Cycle

Circulating cooling water represents the largest application scenario for seawater electrochlorination in U.S. coastal power plants. Seawater is rich in algae and bacteria (e.g., iron bacteria, sulfate-reducing bacteria). If disinfection is delayed, biological slime forms on the surface of condenser copper tubes, reducing heat transfer efficiency—each 1mm of slime increases the condenser end difference by 3℃ and decreases unit power generation efficiency by 0.8%.

Typical Case: 600MW Coal-Fired Power Plant in Charleston, South Carolina

This plant has three units with a circulating water flow rate of 120,000 m³/h. Before 2021, when using liquid chlorine for disinfection, high sand content in seawater (suspended solids ≤50ppm) caused blockages in liquid chlorine dosing pipelines 2-3 times per month. The condenser end difference rose from the design value of 1.8℃ to 4.3℃, with annual maintenance costs exceeding $300,000. After introducing the De Nora SANILEC® SC-240 seawater electrochlorination system in 2021, three major optimizations were achieved:

1. Anti-Clogging Design: Four electrolyzers with a chlorine production capacity of 240kg/h each were configured, adopting an "N-type turbulent flow channel + 50μm self-cleaning filtration" design. This system can withstand seawater suspended solids ≤15ppm, reducing blockage frequency to once per year;
2. Precise Dosing: Linked with ultrasonic flowmeters (accuracy ±0.5%) via PLC, the dosing amount is dynamically adjusted based on circulating water flow rates (continuous dosing at 0.5ppm, shock dosing at 2ppm), narrowing residual chlorine fluctuations from ±0.3ppm to ±0.1ppm;
3. Energy Efficiency Improvement: The DSA® ruthenium-iridium coated electrodes have a service life of 8 years, with power consumption ≤4.2kWh/kg Cl₂. The condenser end difference was stabilized at 1.9℃, reducing the unit heat rate by 0.7% and saving $1.8 million annually in coal costs.

Similar practices are common in gas-fired power plants: After adopting the Evoqua OSEC® B-Pak system at the 9F-class gas-fired power plant in Corpus Christi, Texas, the condenser chemical cleaning cycle was extended from 6 months to 24 months, reducing annual acid cleaning costs by $120,000.

2.2 Emergency Cooling Systems in Nuclear Power Plants: Meeting "Second-Level Response-Seismic and Radiation Resistance" Safety Standards

As a key component of the U.S. base-load power supply, nuclear power plants have far stricter requirements for "safety, redundancy, and rapidity" of disinfection in their emergency cooling systems compared to conventional power plants. The NRC 10CFR50.46 standard explicitly mandates that emergency cooling systems must initiate disinfection within 10 seconds after reactor shutdown to prevent microbial growth and blockage in containment spray pipelines, while also withstanding extreme conditions such as earthquakes and radiation.

Typical Case: Turkey Point Nuclear Power Plant, Florida

This plant originally used a reserve-based sodium hypochlorite dosing system, but transportation restrictions for chemicals in radioactive areas resulted in a response time exceeding 15 seconds. Additionally, stored sodium hypochlorite easily reacted with metal pipelines in the radiation environment to form corrosion products. After upgrading to the Milestone Chlorination pulsed seawater electrochlorination system in 2022, key breakthroughs were achieved:

1. Second-Level Emergency Response: Three sets of electrolyzers (2 in use, 1 standby) with a chlorine production capacity of 1000g/h each adopted pulsed electrolysis technology (500Hz frequency). The sodium hypochlorite generation rate was 30% faster than traditional DC electrolysis, enabling the system to increase the sodium hypochlorite concentration in cooling water to 2ppm within 7.2 seconds in emergency situations;
2. Extreme Condition Adaptation: The electrolyzer shell was made of 316L stainless steel + lead shielding, with a radiation dose ≤0.5mSv/h. The electrode cables could withstand a radiation dose of 10⁶Gy and passed the ASME BPVC III Seismic Category I certification (displacement <0.2mm under 0.3g acceleration);
3. Safety Redundancy Design: Equipped with a dual-circuit power supply (main power + emergency diesel generator), the system resumed operation within 10 seconds after a power outage. The hydrogen exhaust pipeline had a flow rate ≥10m/s to avoid gas accumulation risks in radioactive areas.

Currently, this system has passed the annual NRC review, reducing spare parts inventory costs by 50% and becoming a benchmark solution for emergency disinfection in U.S. nuclear power plants.

2.3 Boiler Feedwater Pretreatment: Ensuring Safe Operation of "Desalinated Water-Membrane Systems"

Due to freshwater shortages, coastal power plants in western the United States (e.g., California, Washington State) often use desalinated seawater as boiler feedwater. Reverse osmosis (RO) membranes in seawater desalination are extremely sensitive to microbial contamination—microbial growth on the membrane surface can reduce membrane flux by over 20%, with replacement costs exceeding $200,000 per set. Seawater electrochlorination systems, through pretreatment disinfection, have become a key link in protecting RO membranes.

Typical Case: 300MW Gas-Fired Power Plant, San Diego, California

This plant adopted an "ultrafiltration + RO" seawater desalination process (daily water production 20,000 m³). When originally using sodium hypochlorite solution dosing, concentration decay (from 15% to 8%) caused fluctuations of ±0.2ppm in residual chlorine at the RO inlet, requiring membrane module replacement twice a year. After introducing the Pepcon Systems ChlorMaster® BP III bipolar seawater electrochlorination system in 2023:

1. Membrane Protection Optimization: Integrated with online ORP sensors (accuracy ±2mV), the residual chlorine at the RO inlet was stabilized at 0.8±0.1ppm. The microbial contamination rate decreased from 15% to 2%, extending the membrane module service life from 6 months to 18 months;
2. Anti-Pollution Design: To address high-organic-matter seawater (TOC ≤5mg/L) in California coastal waters, a "pre-oxidation unit" was added. Trace sodium hypochlorite was used to oxidize organic matter into small-molecule substances, preventing adsorption on the membrane surface;
3. Energy Efficiency Improvement: The bipolar electrode current efficiency increased from 60% to 75%, reducing disinfection energy consumption per ton of water from 0.3kWh to 0.22kWh and saving $120,000 annually in electricity costs.

3. Power Plant-Specific Technological Innovations: From "General Solutions" to "Customized Adaptation"

U.S. suppliers have optimized seawater electrochlorination systems through multiple technical dimensions to address the special operating conditions of power plants, with core breakthroughs focusing on three directions:

3.1 Electrode Materials: Adapting to High-Load Operation in Power Plants

Disinfection of circulating water in power plants requires long-term full-load operation of electrolysis systems (annual operating time exceeding 8,000 hours), making electrode service life a critical factor. De Nora's upgraded DSA®-XT electrodes, optimized with a ruthenium-iridium-palladium ternary coating, extended their service life from 5 years to 8 years, while improving corrosion resistance by 40% in high-salinity seawater (Cl⁻ concentration 20,000ppm) in power plants. Emerson's developed boron-doped diamond (BDD) electrodes can withstand pH fluctuations (6-9) in power plant circulating water, with electrolysis efficiency 15% higher than traditional electrodes, and have been applied in multiple gas-fired power plants in Florida.

3.2 Intelligent Control: In-Depth Integration with Power Plant DCS Systems

Mainstream U.S. power plants have achieved linked control between seawater electrochlorination systems and Distributed Control Systems (DCS): De Nora's ClorTec® system connects to the power plant DCS via the OPC UA protocol, collecting real-time data such as circulating water flow rate, condenser end difference, and residual chlorine value. When the end difference exceeds 2℃, it automatically increases the sodium hypochlorite dosing amount by 0.2ppm, realizing closed-loop "disinfection-energy efficiency" regulation; Evoqua's OSEC® system introduces "digital twin" technology, predicting the remaining service life of electrodes based on historical operating data (current, voltage, electrode temperature) with an error ≤5%, avoiding unplanned downtime. After application in a coal-fired power plant in Texas, unplanned downtime was reduced by 90%.

3.3 Adaptation to Complex Marine Environments: Addressing Diverse Water Intake Conditions of Power Plants

Significant differences in water quality exist between the U.S. East Coast, West Coast, and Gulf of Mexico. Suppliers have launched customized solutions exclusively for power plants:

• Alaska Low-Temperature Coastal Waters: Xylem developed a "low-temperature electrolyzer" for local power plants, maintaining seawater temperature at 15℃ through a built-in heating module to avoid electrolysis efficiency degradation caused by low temperatures (electrolysis efficiency decreases by 12% for every 10℃ drop in seawater temperature);
• Gulf of Mexico High-Sulfur Seawater: Milestone designed a "sulfur removal unit" for power plants in Louisiana, using trace sodium hypochlorite to oxidize sulfides (≤5ppm) into sulfates, preventing the formation of copper sulfide through reactions with electrodes and avoiding electrode failure;
• Hawaiian Island Power Plants: Process Solutions launched a "containerized integrated system" that integrates salt dissolution, electrolysis, and dosing modules, covering an area of only 3m². This adapts to the limited space of island power plants, shortening the installation cycle from 15 days to 5 days.

4. Challenges and Future Trends: From "Disinfection Tool" to "Energy Synergy Carrier"

4.1 Current Core Challenges

Despite the widespread application of seawater electrochlorination systems in U.S. power plants, two major bottlenecks remain:

• High Initial Investment: The initial investment for a system with a chlorine production capacity of 100kg/h is approximately $2 million, three times that of traditional liquid chlorine dosing systems. Some small and medium-sized power plants rely on the U.S. Department of Energy's "Coastal Power Plant Energy Efficiency Subsidy" (covering 30% of the investment);
• High-Salinity Corrosion: Long-term exposure of power plant circulating water pipelines to high-salinity seawater results in a corrosion rate of 0.2mm/year. This requires the use of Super Duplex stainless steel (UNS S32750) or Hastelloy C-276, increasing pipeline replacement costs. A power plant calculation showed that corrosion protection costs account for 25% of the system's life-cycle costs.

4.2 Three Future Development Trends

As U.S. power plants transition toward "cleaner and low-carbon" operations, seawater electrochlorination systems are evolving from "disinfection tools" to "energy synergy carriers":

• Coupling with Renewable Energy: California has piloted a "photovoltaic-electrochlorination" combined system, where power plants use surplus daytime photovoltaic power to electrolyze seawater. This reduces the disinfection energy cost from \(0.15/ton to \)0.08/ton, with plans to promote it to 20 coastal power plants by 2030;
• Synergistic Hydrogen Production: De Nora developed a "dual-function electrolyzer" for a power plant in Florida. While generating sodium hypochlorite, the cathode produces hydrogen with a purity ≥99.9%, with an annual output of 120 tons. This hydrogen can be used as fuel for power plant gas turbines, achieving a "win-win" of "disinfection-energy recovery";
• Carbon Footprint Optimization: Through Life Cycle Assessment (LCA), the carbon emissions of seawater electrochlorination systems are only 1/3 of those of traditional liquid chlorine dosing. In the future, they will be incorporated into the carbon emission accounting system of the U.S. "Clean Power Plan" to further promote their application in power plants.

5. Conclusion

The application of seawater electrochlorination systems in U.S. power plants is not merely a replacement of disinfection technology but a microcosm of the coordinated upgrading of "safety-environmental protection-energy efficiency" in power plants. From biological slime control in circulating cooling water to second-level response in nuclear power emergencies, and from membrane protection in desalinated water pretreatment, this system has addressed the core pain points of traditional disinfection methods through technological iterations tailored to power plant operating conditions. Chlory has long been committed to the development and application of seawater electrochlorination technology. In the future, with breakthroughs in innovative directions such as in-depth coupling with renewable energy and synergistic hydrogen production, seawater electrochlorination systems will no longer be just "auxiliary equipment" for water treatment in power plants, but will become a "key carrier" for U.S. power plants to achieve low-carbon transformation and improve comprehensive energy utilization efficiency, setting an important reference model for the sustainable operation of coastal power plants worldwide.

The seawater electrochlorination systems developed by Chlory have been successfully applied in power plants, municipal water treatment plants, and sewage treatment plants in the Middle East, Southeast Asia, Africa, and other regions, earning wide acclaim from end customers for their stable and efficient performance. In the future, Chlory will strategically focus on the United States, Canada, and other American countries, continuously deepen market penetration, and provide customized solutions for local power plants and water plants with leading technology and high-quality services.