1、 The Implementation Principle of "Low Temperature" Evaporation: Starting from the Relationship between Boiling Point and Air Pressure

To understand low-temperature evaporation, it is necessary to first clarify a fundamental physical law: the boiling point of a liquid is not a fixed value, but is positively correlated with the external environmental pressure. The lower the air pressure, the easier it is for liquid molecules to break through the surface tension and vaporize, and the boiling point decreases accordingly. This is the core logic of low-temperature evaporators that can achieve evaporation without high temperature. The specific process can be divided into three key steps.

The first step is to create negative pressure by vacuuming. After the device is started, the vacuum pump will continue to extract air and other gases from the evaporation chamber, creating a stable negative pressure environment inside the chamber. Taking the treatment of industrial wastewater as an example, conventional low-temperature evaporators will reduce the pressure inside the chamber to 1/10 to 1/20 of the standard atmospheric pressure. The specific negative pressure value needs to be adjusted according to the composition of the wastewater, such as salt content and organic matter content.

The second step is a significant decrease in boiling point. In a negative pressure environment, the boiling point of wastewater will significantly decrease. For example, under standard atmospheric pressure, the boiling point of pure water is 100 ℃, while under negative pressure of 0.08MPa, its boiling point can drop to around 45 ℃; If the negative pressure is further reduced to 0.05MPa, the boiling point can even be as low as 32 ℃. This means that wastewater that originally needed to be heated to 100 ℃ for vaporization can now be evaporated by simply heating it to 30-60 ℃, fundamentally achieving "low-temperature" operation.

The third step is' low-grade heat source drive '. Due to the significant decrease in boiling point, the equipment does not need to rely on high-temperature heat sources (such as steam boilers), and only low-grade heat sources are needed to meet the evaporation needs. In practical applications, these heat sources can come from waste heat generated in industrial production (such as equipment cooling water, reactor waste heat), or low-power electric heating tubes, which can reduce energy consumption and adapt to different heat source conditions in different scenarios.

2、 Core component analysis: Vacuum pump determines "low temperature", compressor is responsible for "energy saving"

Many people confuse the roles of vacuum pumps and compressors, but their responsibilities in low-temperature evaporators are completely different, and it is necessary to clearly distinguish their functional positioning and core role.

1. Vacuum pump: the core component for achieving "low temperature"

The vacuum pump is the key to determining whether the equipment can achieve "low-temperature" evaporation. Without it, "low-temperature" cannot be discussed. Its core role is reflected in two aspects.

Creating a negative pressure environment: As mentioned earlier, the vacuum pump continuously extracts air to reduce the pressure inside the evaporation chamber to the target negative pressure value, directly determining the degree of reduction in the boiling point of wastewater. If the power of the vacuum pump is insufficient or the sealing is poor, the pressure inside the chamber cannot be maintained, and the boiling point of the wastewater will rise, resulting in the failure of the "low temperature" effect and even equipment overload.

Maintain stable operation: During the evaporation process, wastewater vaporization produces steam, and the vacuum pump needs to continuously extract this steam (or uncondensed gas) to avoid an increase in pressure inside the chamber and ensure a stable negative pressure environment. Common types of vacuum pumps include water ring vacuum pumps, Roots vacuum pumps, etc. Among them, water ring vacuum pumps are more suitable for treating industrial wastewater containing acid and alkali due to their strong corrosion resistance; Roots vacuum pumps are suitable for scenarios that require higher negative pressure.

2. Compressor: an important component for assisting energy conservation

The compressor does not directly participate in the creation of "low temperature" conditions, but improves equipment energy efficiency and reduces operating costs through heat recovery. Its working logic can be summarized as "recovery heating reuse".

Recycling low-temperature steam: The steam generated by the vaporization of wastewater at low temperatures has a lower temperature (usually the same boiling point as wastewater, about 30-60 ℃), and direct discharge will result in heat waste. At this point, the compressor will suck in these low-temperature vapors and increase their pressure through mechanical compression.

Steam heating and reuse: According to the "ideal gas state equation", when the gas pressure increases, the temperature will rise synchronously. After compression by the compressor, the originally low-temperature steam at 30-60 ℃ can be raised to 80-100 ℃ and converted into high-temperature steam. These high-temperature steam will be introduced into the heating chamber of the evaporator as a heat source to heat the raw water to be treated, achieving heat recycling.

Reduce energy consumption: Through heat recovery, the equipment's demand for external heat sources is significantly reduced, and energy consumption can be reduced by 30% -50% (compared to low-temperature evaporators without compressors). However, it should be noted that the core value of a compressor is "energy saving" rather than "low temperature". Even without a compressor, as long as the vacuum pump works normally, the equipment can still achieve low-temperature evaporation, but the energy consumption will significantly increase.

3、 Summary: Collaborative Logic of Principles and Components

In short, the "low-temperature" effect of a low-temperature evaporator is determined by the principle of "pressure reduction → boiling point reduction", and the vacuum pump is the core component to achieve this principle; The compressor solves the problem of high energy consumption that may accompany low-temperature evaporation through heat recovery. The two work together to ensure the core requirement of "low temperature" while also balancing operational efficiency and cost control. In actual selection, priority should be given to determining the negative pressure capacity of the vacuum pump based on the boiling point requirements of the wastewater, and then selecting whether to configure the compressor and the power of the compressor in combination with the energy consumption budget, in order to ensure that the equipment is suitable for specific application scenarios.