Sodium hypochlorite generator

　　The principle of bactericidal and disinfecting action of sodium hypochlorite

　　The primary mechanism of sodium hypochlorite disinfection involves its hydrolysis to generate hypochlorous acid, which further decomposes to produce nascent oxygen [O]. The highly oxidizing power of nascent oxygen denatures proteins and other biomolecules on bacterial cells and viral envelopes, thereby inactivating pathogenic microorganisms. Furthermore, during the process of killing bacteria and viruses, hypochlorous acid not only acts on cell walls and viral capsids but, owing to its small molecular size and lack of charge, can also penetrate microbial (viral) cells, where it reacts oxidatively with cellular proteins, nucleic acids, enzymes, and other organic macromolecules, leading to the death of pathogenic microorganisms. Additionally, the chloride ions released by hypochlorous acid can significantly alter the osmotic pressure of bacterial and viral cells, causing them to lose viability and die.

　　Overview of the Principle of Sodium Hypochlorite Generators

　　The main electrolytic reaction process of a sodium hypochlorite generator can be represented by the following equation:

　　NaCl + H₂O = NaClO + H₂↑

　　Electrode reactions: Anode: 2Cl⁻ - 2e⁻ → Cl₂; Cathode: 2H⁺ + 2e⁻ → H₂

　　Solution reaction: 2NaOH + Cl2 → NaCl + NaClO + H2O

　　The electrolysis process in an electrolytic sodium hypochlorite generator is an electrochemical reaction that uses only salt and water as raw materials, producing a highly pure sodium hypochlorite solution. Although the underlying chemical principle is straightforward, numerous technical parameters influence its economic performance. Therefore, the design of the electrolytic electrodes must account for a wide range of factors, with particular emphasis on compact and rational construction, energy efficiency, ease of operation and maintenance, high operational reliability, and long equipment life. Sodium hypochlorite solutions can be dosed with precision, ensuring safe handling, convenient use, and easy storage; they are non‑toxic to the environment, pose no risk of gas release or leakage, and can be dosed under any operating conditions.

　　System Process Overview

　　The system automatically dissolves salt granules to produce saturated brine, which is then filtered to a precision of 5 µm, effectively removing any entrained impurities and thereby extending the service life of the electrodes. The filtered saturated brine is subsequently diluted with water to yield a 3.0% saline solution suitable for electrolysis. The generator’s main unit employs the latest high‑frequency constant‑current, voltage‑regulated electronic switching power supply technology as its power source, and utilizes pure titanium electrodes coated with a specialized surface material for electrolysis. All tanks and components are fabricated from food‑grade PE and food‑grade CPVC, enabling convenient, safe, and stable production of high‑purity, food‑grade sodium hypochlorite disinfectant solutions.

　　Performance Characteristics of Sodium Hypochlorite Generators

　　◎ Automatic brine tank: Solid salt is added according to a specified ratio. Once the initial dissolution cycle completes (automatically), additional solid salt is introduced, maintaining a mixture of salt and water. This ensures that undissolved salt remains in the tank at all times, keeping the solution in a saturated, moist‑salt state. Simply maintain the salt level between its maximum and minimum positions.

　　◎ Salt‑dissolving filter: Removes particulate impurities from the saturated brine solution after industrial salt has been dissolved, ensuring that these contaminants do not enter the sodium hypochlorite generator system, thereby maintaining the purity of the sodium hypochlorite solution and preventing any contamination of drinking water.

　　◎ Post‑filtration Saturated Brine Tank: The control system continuously monitors the liquid level switch in the saturated brine tank. When the level drops below the refill threshold, the system automatically starts the brine‑dissolving pump and opens the corresponding electric valve to perform brine dissolution and filtration for replenishment, continuing until the high‑level switch closes and the brine tank is fully filled; the filtration process then automatically starts and stops.

　　◎ Automatic Dilute Salt Solution Mixing Unit and Dilute Salt Tank: The automatic dilute salt solution mixer employs high‑low level proportional control. The control system automatically starts and stops the mixer based on the liquid levels in both the dilute salt tank and the brine dissolving tank, eliminating the need for manual intervention. When the dilute salt tank level drops below the make‑up water level, the system automatically opens the electric mixing valve to prepare the dilute salt solution until the tank is full. It is essential to ensure that the municipal water pressure is ≥0.25 MPa; otherwise, the dilute salt solution preparation will not function properly.

　　◎ Dilute brine metering pump: This system employs a single dilute brine metering pump to deliver a precisely measured flow of dilute brine to the electrolytic cell. When the liquid level in the dilute brine tank drops below the low-level control setpoint, indicating that the tank is running low on brine, the system automatically shuts down the metering pump and resumes automatic operation once the level has recovered.

　　◎ Sodium hypochlorite generator host: integrates the electrolytic cell, power supply, metering pump, control system, and other components into a single unit.

　　The electrolyzer utilizes the current supplied by the electrolysis power source to induce ionization of the dilute brine solution between its anode and cathode, thereby generating a sodium hypochlorite solution. A metering pump is employed to feed the dilute brine into the electrolyzer. The electrolyzer maintains a consistently low operating temperature, which ensures high electrolysis efficiency.

　　The electrode plate uses titanium as the substrate, with the anode surface coated with ruthenium–iridium metal oxide particles having a particle size of 20 nanometers. The coating thickness is 20 micrometers and is applied in 23 layers, ensuring both high current efficiency and long service life.

　　Electrolysis power supply: Utilizes a professionally engineered regulated switching power supply with a conversion efficiency exceeding 92%, low heat generation, and stable operation. The power supply incorporates built-in protections against input over‑voltage/under‑voltage, output over‑voltage/over‑current/short circuit, and overheating, ensuring high reliability and absolute safety during operation.

　　Control System: The system employs a PLC-based control system that directly monitors the safe and reliable operation of the entire generator unit, as well as its self‑diagnostic, alarm‑triggering, and automatic shutdown functions in the event of a fault. A color touchscreen provides real-time display of the operational status of each subsystem—such as the brine‑dissolving unit, the dilution‑and‑mixing unit, the electrolysis unit, the dosing unit, and the acid‑cleaning unit—while also enabling parameter adjustment and configuration. The system acquires sensor signals from each unit and, according to predefined logic, controls the start-up and shut-down of individual units via electrically actuated valves. All system parameters can be transmitted remotely through communication modules. The entire sodium hypochlorite generation system operates automatically, thereby mitigating equipment malfunctions caused by human error.

　　◎ Sodium Hypochlorite Storage Tank: The storage tank is used to hold all the sodium hypochlorite solution produced by the generator. It is equipped with high-level, make-up water, and low-level controls. When the liquid level reaches the high‑level setpoint, the tank is considered full; the generator automatically shuts down, and the “full‑tank” indicator light illuminates. As the solution is gradually consumed, once the level drops to the mid‑level setpoint, the generator restarts, and the “full‑tank” light turns off. If the liquid level falls below the low‑level control point, it indicates that very little sodium hypochlorite remains in the storage tank; the system will then suspend automatic chlorine dosing until the level rises above the low‑level control point.

　　◎ Hydrogen‑venting system: During electrolysis, the generator produces a small amount of hydrogen as a byproduct. Hydrogen is highly flammable and explosive, and national standards require that its concentration in the surrounding space remain below 3%. To ensure safer and more reliable operation, this system is designed to maintain hydrogen concentrations below 1%—achieving zero residual hydrogen and zero residual chlorine—and to continuously and forcibly dilute and vent hydrogen in real time. The system employs a two‑stage venting process to guarantee thorough and safe hydrogen discharge. The mixed stream of sodium hypochlorite and hydrogen flows through the outlet pipeline, where it first undergoes primary vapor–liquid separation (since hydrogen is lighter than the liquid). The liquid then enters a storage tank, where another vapor–liquid separation takes place before entry. Simultaneously, a high‑capacity exhaust fan injects air into the tank; due to the high pressure of the injected air, any residual hydrogen and trace amounts of chlorine released from the decomposition of the sodium hypochlorite solution are inevitably expelled through the hydrogen‑venting line. As a result, only air remains in the storage tank, while the trace chlorine and hydrogen are diluted and forcefully vented into the atmosphere for safe release.

　　◎ Automatic sodium hypochlorite dosing and disinfection pump: A complete closed-loop dosing control system comprising a variable-frequency dosing pump, an online residual chlorine monitor, and a control center. The residual chlorine monitor continuously measures the residual chlorine level in the sample water and converts the measurement into a 4–20 mA signal, which is transmitted to the PLC in the control center. After processing this data, the control center outputs a corresponding 4–20 mA signal to the variable-frequency drive, thereby regulating the flow rate of the dosing pump and maintaining a stable residual chlorine level throughout the distribution network, achieving closed-loop, reliable, stable, and safe variable-frequency dosing, monitoring, and control.