Proper ventilation is essential for the operation of an EDI water treatment system. It is not only related to equipment performance and service life, but also to explosion prevention and personnel safety. The necessity of ventilation mainly comes from the following three aspects.
Removing Electrolysis Byproduct Gases to Prevent Hydrogen Accumulation and Explosion
The core principle of an EDI water treatment system is that, under a DC electric field, ions in the water migrate through ion exchange resins and ion exchange membranes into the concentrate chamber. At the same time, water electrolysis reactions occur. Oxygen is generated at the anode, while hydrogen is generated at the cathode.
2H₂O → 2H₂↑ + O₂↑
Hydrogen is an extremely flammable and explosive gas. Its explosion limit in air is 4.0%–75.6% by volume. According to occupational exposure standards and ventilation design regulations, the concentration of combustible gases must remain far below the lower explosive limit. In practice, the hydrogen concentration is typically required to stay below 25% of the lower explosive limit, meaning the hydrogen concentration should be controlled below 1%.
For example, in a medium-sized EDI water treatment system with a product water flow rate of 10 m³/h, the total operating current is often around 100A when multiple modules are connected in parallel. Based on Faraday’s law, the hydrogen generation rate can be calculated as follows:
- Theoretical hydrogen production per ampere-hour: 0.418 L (standard condition)
- Hydrogen generated at 100A per hour:
100×0.418=41.8 L/h100 \times 0.418 = 41.8\,L/h100×0.418=41.8L/h
If 41.8 L of hydrogen enters an enclosed or poorly ventilated equipment room with a volume of 200 m³, the hydrogen concentration could theoretically reach 1% in only about 4.6 hours under complete mixing conditions.
In actual operation, uneven gas distribution may cause localized hydrogen concentrations to exceed safe levels even faster. Once exposed to sparks or static electricity, the consequences can be extremely serious. Therefore, forced ventilation is necessary to continuously dilute and discharge hydrogen gas, ensuring the concentration remains far below safety limits.
Removing Heat and Maintaining Proper Operating Temperature
During operation, nearly all electrical energy in an EDI water treatment system is converted into heat, causing the water temperature to continuously rise. The inlet water temperature is usually between 15–25°C, while the concentrate circulation piping and electrode water discharge temperature may increase to 30–40°C after EDI treatment.
For a typical 10 m³/h EDI water treatment system, the DC power supply generally consumes around 2–5 kW. Combined with the heat generated by the concentrate circulation pump, the total heat load can reach 3–6 kW. If this heat is not dissipated promptly, the equipment room temperature can rise rapidly.
The recommended inlet water temperature for EDI modules is generally 5–35°C, with an absolute maximum of 40°C. Long-term operation at elevated temperatures may lead to:
- Thermal damage to ion exchange membranes and resins, reducing desalination performance;
- Accelerated aging of sealing materials, resulting in leakage;
- Increased scaling tendency inside the modules.
When the room temperature exceeds 40°C, the risk of module damage increases significantly. Proper ventilation introduces cooler outside air and removes heat released from equipment and piping surfaces, helping maintain the ambient temperature within the ideal range of 5–30°C.