The ‘low-temperature’ designation for wastewater evaporation equipment refers to the boiling point of water at atmospheric pressure (100°C). The industry-standard core temperature range is 40–60°C Low-temperature" is defined relative to water's boiling point of 100°C at atmospheric pressure. The industry-standard core temperature range is 40–60°C, which can be finely adjusted to 35–40°C for heat-sensitive wastewater (food, pharmaceuticals) and adapted to 60–70°C for high-salinity concentrated water. Throughout the process, temperatures remain significantly below atmospheric boiling points and exhibit stable operation without substantial fluctuations. This constitutes the core distinguishing feature from traditional high-temperature evaporation equipment.

The achievement of this low-temperature evaporation hinges on the dual effects of **‘vacuum-induced boiling point depression’ + ‘low-temperature heat source precision control’**. These form an indispensable closed-loop system, fundamentally altering water's boiling point through physical means before precisely heating it to that point for vaporisation—without excessive overheating. The specific implementation process is as follows:

1. Vacuum Negative Pressure Boiling Point Depression: Establishing the Physical Foundation for Low-Temperature Evaporation

Water's boiling point is directly proportional to external atmospheric pressure; lower pressure yields a lower boiling point, forming the core principle of low-temperature evaporation. The equipment employs a vacuum pump to continuously evacuate the sealed evaporation chamber, expelling air and non-condensable gases. This stabilises the absolute pressure within the chamber at 0.08–0.095 MPa (industry standard vacuum level), directly lowering water's boiling point to the low-temperature range of 40–60°C. The core relationship between pressure and boiling point is as follows:

Absolute pressure 0.095 MPa → Water boiling point ≈ 40°C

Absolute pressure 0.09 MPa → Water boiling point ≈ 45°C

Absolute pressure 0.085 MPa → Water boiling point ≈ 50°C

Absolute pressure 0.08 MPa → Water boiling point ≈ 60°C

The equipment's PLC control cabinet continuously monitors chamber pressure via pressure sensors. Should vacuum levels deviate from setpoints, the vacuum pump automatically activates or deactivates to compensate, ensuring the boiling point remains stable within the target low-temperature range without temperature fluctuations caused by pressure variations.

2. Precise Low-Temperature Heat Source Control: Heating Wastewater to Boiling Point with Zero Overheating Waste

After the boiling point is lowered to the target low-temperature range, the system employs a low-temperature heat source to precisely heat the pre-treated wastewater to its boiling point at the corresponding vacuum level. The wastewater is heated only to its boiling point for vaporisation, eliminating unnecessary overheating. This approach guarantees evaporation efficiency while significantly reducing energy consumption. The predominant heat source is the industry-standard heat pump system (accounting for over 90% of installations). A minority of compact units employ electric heating or thermal oil heating, both achieving low-temperature control:

Heat Pump System (Mainstream Energy-Efficient Model): Utilises refrigerant phase-change cycles (gas → liquid → gas) to supply the evaporation chamber with a low-temperature heat source of 45–65°C, slightly above the wastewater boiling point, ensuring efficient heat exchange. Simultaneously recovers latent heat released during vapour condensation, re-converting it into heat for wastewater heating to achieve thermal circulation. Temperature control precision reaches ±2°C with no overheating throughout the process.

Electric Heating / Thermal Oil Heating (Traditional Models): PT100 temperature sensors continuously monitor wastewater temperature. The PLC temperature control module automatically adjusts heating power based on this data. When wastewater reaches the set boiling point, power is reduced or heating ceases. Should temperatures dip below target, supplementary heating is automatically applied, ensuring wastewater remains within the low-temperature evaporation range at all times.