How To Prevent Scaling in A Wastewater Evaporator?

Scaling is a common situation in a wastewater evaporator. How we prevent scaling in a wastewater evaporator? Let's discuss in this article.

(1) Pre-filming anti-scaling treatment is performed during the manufacture of evaporator. The use of pre-filming anti-scaling during the manufacture of evaporator can form a protective film on the surface of the evaporator and air cooler pipes, effectively preventing scale crystals from adhering to the copper tube surface, reducing the possibility of evaporator scaling, and extending the evaporator and air cooler structure cycle.

(2) Pre-cooler is installed in evaporator and air cooler to make the evaporation temperature of the evaporator tube surface below 40℃. At the same time, a large water volume and intensive water distributor are used to ensure that the condenser tube surface is always covered with water film without dry spots. The configuration of pre-cooler and the prevention of dry spots are effective in preventing scaling problems of evaporator and air cooler.

(3) A small amount of continuous drainage device is used to control the refining multiples of calcium ions in the cooling circulating water of evaporator and air cooler within a certain limit, which effectively prevents the precipitation of scale. Reducing the calcium ion content of the cooling circulating water of the evaporator, air cooler, and closed cooling tower is a fundamental measure to control scaling problems, and can solve the evaporator anti-scaling and scaling problems from the source.

During the evaporation and vaporization process of concentrated high salt wastewater, secondary steam mist is easily entrained. The salt water carried in the mist is attached to the wire mesh or baffle of the demister, and the crystals are continuously refined to form a scale layer, which causes secondary steam to hit the wall in critical cases.

As the concentration of the circulating concentrated high salt wastewater continues to increase, the calcium sulfate, calcium carbonate, and silicate contained in the wastewater will precipitate and adhere to the cracks of the diffuser of the falling film evaporator, forming scale, causing partial congestion of the diffuser.

The amount of seed control in the circulating concentrated salt wastewater in the evaporator is an important monitoring indicator to prevent the same type of crystal form and low solubility salt from precipitating and adhering to the heat exchange tube (or surface) during the evaporation and crystallization process. Its control limit is narrow, easy to vibrate, and the monitoring and analysis results are delayed. Once the insufficient amount of seed crystals is not found in time for adjustment, scaling may have occurred.