A distilled water machine is a device that converts raw water (such as tap water or purified water) into high-purity distilled water through a physical process of heating, evaporation, condensation, and cooling. The core principle is to utilize the boiling point difference between water and impurities (salts, organic matter, microorganisms, etc.), separate pure water vapor through evaporation, and then condense it to obtain distilled water with extremely low ion content and no microbial pollution. It is widely used in scenarios such as medicine, laboratory, electronics, etc. that require extremely high water purity. The following provides a detailed explanation of the core structure and its role in water treatment equipment:
1、 The core structure of a distilled water machine
The structure of a distilled water machine is designed around “efficient evaporation sufficient condensation purity guarantee”, mainly consisting of an evaporation system, a condensation system, a heating system, a water replenishment system, a purification auxiliary system, and a control system. The construction details of different types (such as multi effect distilled water machines and tower distilled water machines) may vary slightly, but the core modules are the same:
1. Evaporation system (core steam production unit)
The evaporation system is the core part that heats raw water to boiling point and produces pure water vapor, directly determining the purity and water production of distilled water. It is commonly designed as “multi effect evaporation” (industrial grade) or “single effect evaporation” (laboratory grade).
Multi effect evaporation tank (industrial grade mainstream):
Construction: 3-6 stainless steel evaporation tanks connected in series (made of 316L stainless steel, with mirror polished inner walls), Ra≤0.8μm， Each evaporation tank is called a “one effect” and is equipped with a heating tube bundle (or heating coil) inside the tank to prevent impurities from adhering.
Work logic:
First effect tank: The raw water is heated to boiling point (about 100 ℃, under normal pressure) by an external heat source (such as steam or electric heating), and the generated secondary steam enters the heating tube bundle of the second effect tank;
Second effect tank: Using the secondary steam from the first effect (slightly below 100 ℃) as a heat source, heat the raw water in the tank (due to slightly lower pressure than the first effect, the boiling point of water decreases, achieving “low-temperature evaporation”), and the generated secondary steam then enters the third effect;
Similarly, the secondary steam generated by the final effect tank enters the condensation system, while the “concentrated water” (containing high concentration impurities) that has not evaporated in each effect tank is regularly discharged to avoid scaling and impurities from entering the steam.
Advantages: By utilizing secondary steam cycle heating, the thermal efficiency is increased by 3-6 times compared to single effect, energy consumption is reduced by 60% -80%, and it is suitable for large-scale water production (water production of 0.5-50m ³/h).
Single effect evaporator bottle (laboratory grade):
Construction: A round bottom flask made of glass material (such as quartz glass, high temperature resistant, no leaching), connected to a frosted interface and condenser tube, and heated externally through an electric heating jacket or oil bath.
Advantages: Simple structure, suitable for small batch water production (water production rate 0.1-1L/h), high purity (glass material to avoid metal ion leaching).
2. Condensation system (steam converted into liquid water)
The function of the condensation system is to cool the pure water vapor generated by the evaporation system into liquid distilled water, ensuring sufficient cooling and no impurity pollution.
Core components:
Condenser: It is mostly a 316L stainless steel tubular condenser (industrial grade) or a glass serpentine condenser (laboratory grade), with cooling water pipes inside (for cooling water such as tap water and chilled water).
Condensation logic: Pure water vapor enters from the top of the condenser and flows outside the tube wall. The low-temperature water flow (temperature 20-30 ℃) inside the cooling water pipe transfers heat through the tube wall, causing the vapor to condense into liquid water, which flows down the tube wall and is collected as distilled water.
Gas liquid separator: Some high-end models add a gas liquid separator at the inlet of the condenser to separate small water droplets that may be carried in the steam (which may contain impurities in the original water), further improving the purity of distilled water.
3. Heating system (providing evaporative heat source)
The heating system provides continuous and stable heat to the evaporator tank, which is divided into “steam heating” (industrial grade) and “electric heating” (laboratory grade) according to scale.
Steam heating (industrial grade):
Construction: including steam generator (producing high-pressure steam), steam pipeline (316L stainless steel), and drain valve (discharging condensed water from the heating tube bundle to avoid heat waste).
Advantages: High heating power (suitable for large-scale water production), high thermal efficiency, and lower cost than electric heating.
Electric heating (laboratory grade):
Construction: Electric heating sleeve (with built-in nickel chromium heating wire, temperature control accuracy ± 1 ℃) or electric heating tube (made of 316L stainless steel material, inserted into the evaporator for direct heating).
Advantages: Accurate temperature control, no need for external steam source, suitable for laboratory scenarios.
4. Water replenishment system (stable water supply, ensuring purity)
The water replenishment system needs to continuously replenish qualified raw water (usually pre treated purified water to avoid impurities from entering the evaporation system directly) to the evaporation tank, and control the amount of water replenishment to match the evaporation amount to prevent dry burning of the evaporation tank or excessive concentration of concentrated water.
Core components:
Raw water storage tank: Made of 316L stainless steel, it stores pre treated raw water (such as reverse osmosis water) and is equipped with a liquid level sensor;
Metering pump: corrosion-resistant diaphragm pump (made of PTFE), replenishing water to the evaporation tank according to the set flow rate, with a flow accuracy of ± 2%;
Preprocessing interface: Some models are equipped with a pre filter (0.22 μ m precision filter element) to further filter out fine particles in the raw water, avoiding clogging of the evaporator heating tube bundle.
5. Purification auxiliary system (improving the purity of distilled water)
To meet the stringent purity requirements of industries such as pharmaceuticals and electronics, distilled water machines need to be equipped with purification auxiliary modules to further remove trace impurities that may remain in the steam.
Core components:
Vapor liquid separator: As mentioned earlier, it separates water droplets carried by steam to prevent impurities from entering the raw water;
Ion exchange column (optional): Some high-end models connect a mixed ion exchange column (cation resin+anion resin) in series at the outlet of the condenser to adsorb trace ions (such as metal ions and chloride ions) that may remain in distilled water, increasing the resistivity to 15-18M Ω· cm (ultrapure water grade);
UV sterilizer (essential for pharmaceutical grade): A 254nm wavelength UV lamp tube can kill microorganisms (such as spores) that may remain in distilled water, with a sterilization rate of ≥ 99.99%, in compliance with the “Water for Injection” standard of the Chinese Pharmacopoeia 2025 edition.
6. Control System (Automated Operation and Safety Assurance)
The control system realizes the fully automatic operation, parameter monitoring, and fault protection of the distilled water machine, avoiding the influence of manual operation errors on purity.
Core functions:
Parameter monitoring: Real time display of temperature, pressure, water replenishment, water production, distilled water resistance (or conductivity) of each effect tank through touch screen;
Automatic control: Automatically adjust the water replenishment amount (matching with the water production), heating power (maintaining stable boiling points of each effect tank), and concentrated water discharge frequency (avoiding impurity concentration);
Safety protection: When the liquid level of the evaporator tank is too low (to prevent dry burning), the water resistance rate of distilled water does not meet the standard (to prevent unqualified water production), and the pressure is too high (to prevent tank bursting), it will automatically shut down and sound an alarm.
2、 The role of distilled water machine in water treatment equipment
In the overall water treatment system, the distilled water machine belongs to the “terminal deep purification unit”, usually located after pretreatment (sand filtration, carbon filtration) and primary purification (reverse osmosis, EDI). Its main function is to further upgrade “purified water” to “high-purity distilled water”, meeting the purity requirements that conventional membrane separation technology cannot achieve. Its specific functions can be divided into the following three categories:
1. Produce high-purity water that is free of ions and microorganisms, meeting strict industry standards
Although conventional membrane separation techniques (such as reverse osmosis) can remove over 99% of ions, trace ions (such as silicon and boron) and microorganisms may still remain. Distilled water machines, through the physical process of “evaporation condensation”, can achieve:
Extremely low ion content: The total dissolved solids (TDS) in distilled water is ≤ 1mg/L, and the resistivity is ≥ 10M Ω· cm (multi effect distilled water machine) or ≥ 18M Ω· cm (quartz glass single effect machine), which is much lower than that of reverse osmosis water (TDS ≤ 50mg/L), meeting the requirements of “electronic grade ultrapure water” in the electronics industry (such as semiconductor wafer cleaning, TDS ≤ 0.1mg/L) and “injection water” in the pharmaceutical industry (the Chinese Pharmacopoeia requires resistivity ≥ 15M Ω· cm and microorganisms ≤ 1CFU/100mL).
No microbial contamination: During the evaporation process, a high temperature of 100 ℃ can kill all microorganisms (including spores) in the raw water. After condensation, sterile water can be obtained directly without additional sterilization (laboratory or pharmaceutical grade can be further guaranteed by UV), avoiding the risk of “membrane pore leakage microorganisms” that may exist in membrane separation technology.
2. Remove stubborn impurities that are difficult to handle with membrane separation technology
Some impurities (such as low boiling point organic compounds and volatile silicon compounds) may be removed through reverse osmosis membranes (due to their small molecular weight and easy permeability), but distilled water machines can selectively separate and remove them through “evaporation condensation”:
Low boiling point organic compounds: Although the boiling point of low boiling point organic compounds (such as methanol and ethanol) in raw water is close to that of water, their content can be reduced to ≤ 0.1ppb through “concentrated water discharge” (low boiling point organic compounds are easily retained in concentrated water) and “vapor-liquid separation” (to avoid organic vapor entrainment) in multi effect evaporation, meeting the strict requirements of the pharmaceutical industry for “injection water” for organic compounds.
Volatile silicon compounds: Silicon (such as silicon dioxide) in industrial raw water may scale on the surface of reverse osmosis membranes, and some volatile silicon (such as silicic acid) can pass through reverse osmosis membranes. In the multi effect evaporation tank of the distilled water machine, silicon will be discharged with concentrated water, and the final silicon content in the distilled water is ≤ 0.02mg/L, avoiding the problem of “silicon pollution causing chip short circuits” in the electronics industry.
3. Pure water preparation plan as an “emergency or special scenario”
In scenarios where complex membrane separation systems cannot be built (such as in laboratories or field operations) or where there are extreme requirements for water quality (such as pharmaceutical injection or precision analysis), a distilled water machine is an irreplaceable solution:
Laboratory scenario: A small quartz glass distilled water machine can directly prepare high-purity water for precision instrument analysis such as atomic absorption spectroscopy (AAS) and high performance liquid chromatography (HPLC), avoiding the interference of “metal ions” that may be present in membrane separated water.
Outdoor emergency scenario: The portable electric heating distilled water machine (with a water production rate of 0.5-2L/h) can directly treat river and lake water (with the need to filter suspended solids first) to prepare sterile water for drinking or medical use, without relying on pre-treatment systems.
3、 The core differences between distilled water machines and membrane separation equipment (such as reverse osmosis)
Comparison Dimension Distilled Water Machine Reverse Osmosis Equipment (RO)
Core principle: Heating, evaporation, condensation (physical phase change), membrane selective retention (pressure driven, no phase change)
The effluent purity is extremely high (TDS ≤ 1mg/L, resistivity ≥ 10M Ω· cm) and relatively high (TDS ≤ 50mg/L, resistivity ≤ 0.1M Ω· cm)
High energy consumption (heating water to boiling point, energy consumption of 2000-5000kWh/m ³) and low energy consumption (only requiring a high-pressure pump, energy consumption of 1-5kWh/m ³)
Low to medium water production rate (laboratory grade 0.1-1L/h, industrial grade 0.5-50m ³/h) and high water production rate (industrial grade 1-1000m ³/h)
Applicable scenarios: high-purity requirements (pharmaceutical injection, precision analysis), general purification requirements (industrial circulating water, direct drinking water)
summary
The distilled water machine achieves the conversion of raw water into high-purity distilled water through the core structure of “multi effect evaporation condensation”. Its core value lies in producing ultrapure water that is “ion free, microbial free, and free of stubborn impurities”. It is the “terminal purification guarantee” for harsh scenarios such as medicine, electronics, and laboratories. Although the energy consumption is higher than that of membrane separation equipment, when purity requirements cannot be met through membrane technology, distilled water machines are still an irreplaceable core equipment. Together with pretreatment and membrane separation equipment, they form a complete water treatment system of “stepped purification”.
Post time: Aug-29-2025