Atmospheric evaporators for wastewater treatment

Our atmospheric evaporators and distillation systems ENVIDEST EA are designed to provide a low investment system to minimize liquid waste when it is not possible to reuse or discharge the water due to the absence of a point of discharge. In this case, water vapor is not condensed and it is released into the atmosphere.

Atmospheric evaporators are equipment used in wastewater treatment. The process relies on the application of heat to convert water into vapor and remove it from the system by releasing it into the atmosphere, leaving behind only solids and other residues that can be subsequently managed in a more straightforward and cost-effective manner.

The range of atmospheric evaporators comprises devices with a production capacity from 35 to 1,500 L/h. These evaporators can be heated by biogas, natural gas, propane, steam, kerosene, residual oil or electricity.

Atmospheric evaporators are mainly used in the concentration of:

• Recovery of high value chemical products used during surface treatment processes, metallic coatings and aluminum anodizing.
• Reduction of photographic liquid waste.
• Concentration of saline solutions (rejection, decalcification, reverse osmosis).
• Residual food brines (pickles, olives, etc.).
• Concentration of landfill leachates.

Volatile substances can cause air emissions issues when these react with the water vapor. This point must be considered before installing an atmospheric evaporator to make sure that hazardous emissions are not being released to the atmosphere.

The operating cost can sometimes be high due to the amount of energy needed to run the system. In some cases, when cheap or spare thermal energy is available (biogas, hot water, etc.) it is a good solution to use it to make the evaporator more efficient.

Once the wastewater is introduced into the evaporator, it is heated using either steam or residual heat from other industrial processes. The heat is transferred to the liquid through heat exchangers or coils. As the liquid is heated, the water present in it starts to evaporate.

With the increase in temperature, the water undergoes evaporation, transitioning from a liquid state to a gaseous state. Non-volatile or unwanted components remain as solids or liquid concentrates.

The water vapor generated during evaporation is directed towards a separation device such as a vapor separator or ventilation system. Here, the water vapor is released into the atmosphere, while the solids or liquid concentrates remain in the evaporator.

The concentrated liquid, with a reduced amount of water, is collected at a specific outlet of the evaporator. This concentrate can be extracted from the evaporator for further treatment or disposal.

Atmospheric evaporators are efficient equipment for concentrating dissolved or suspended substances in water and for recovering valuable products present in the wastewater effluent. Additionally, they reduce the total volume of the effluent, facilitating its subsequent treatment or disposal.

Evaporators can help reduce the amount of water used in industrial processes by recycling and reusing treated water.

Pressure of operation

Atmospheric evaporators operate at atmospheric pressure, meaning they operate at the pressure of the surrounding environment. A vacuum is not created in the equipment, and the evaporation process relies on the supply of heat to raise the temperature of the water and convert it into vapor.

On the other hand, vacuum evaporators operate at pressures lower than atmospheric pressure, meaning a vacuum is created in the equipment. The decrease in pressure lowers the boiling point of water, allowing for evaporation at lower temperatures.

Evaporation Temperature

In atmospheric evaporators, the evaporation temperature is relatively high, typically above 70 °C.

The evaporation temperature is lower in vacuum evaporators due to the reduced pressure. It can be in the range of 30-50 °C, leading to significant energy savings compared to atmospheric evaporators.

Energy Efficiency

Due to the higher operating temperatures, atmospheric evaporators may require a higher amount of thermal energy to achieve the desired evaporation. However, this energy can be provided by residual heat sources or available steam in industrial processes.

By operating at lower temperatures, vacuum evaporators require less thermal energy to achieve evaporation, resulting in lower energy consumption and operational costs.

Concentration Capacity

Atmospheric evaporators are capable of handling wastewater with moderate concentrations of contaminants, as the high operating temperatures limit the degree of concentration that can be achieved.

Vacuum evaporators achieve higher concentration of contaminants as they operate at lower temperatures. This can be beneficial in cases where a significant reduction in the volume of the effluent is required.