Overview of Scraper Evaporator

The scraper evaporator is a new type of evaporator with strong adaptability. It is suitable for high-viscosity, heat-sensitive, easy-to-crystallize and easy-to-foul materials. It mainly consists of a heating jacket and scrapers. Heating steam passes through the jacket. The scrapers are mounted on a rotating shaft, maintaining a tiny clearance of usually 0.5~1.5 mm from the inner wall of the heating jacket.After preheating, the feed liquid is fed tangentially from the upper part of the evaporator. Under gravity and the action of rotating scrapers, the liquid spreads on the inner wall to form a downward-flowing thin film, which is continuously evaporated and concentrated as it descends. The concentrated liquid is discharged from the bottom, while secondary vapor escapes from the top. In some applications, this evaporator can dry the solution completely, and solid products can be obtained directly at the bottom.

Working Principle of Scraper Evaporator

The shell of the scraper evaporator is equipped with a heating steam jacket, inside which rotating blades (scrapers) are installed. There are two types of scrapers: fixed type and rotor type. The fixed scraper maintains a clearance of 0.5~1.5 mm from the inner wall of the shell, while the clearance of the rotor-type scraper from the vessel wall varies with the rotor speed.

The feed liquid is fed tangentially from the upper part of the scraper evaporator (it can also be fed onto the coaxial distributor disc). Under the combined action of gravity, centrifugal force and scraping of rotating scrapers, the solution forms a downward-spiraling thin film on the inner wall of the vessel and is evaporated and concentrated during this process. The concentrated liquid is discharged from the bottom. This evaporator is a single-pass evaporator that forms a liquid film by external power.

Features of Scraper Evaporator

High efficiency and large capacity. The evaporation capacity for water, organic solvents and other solutions reaches 100–300 kg/h·m.

The residence time of processed materials on the evaporation surface is short, about 10 seconds, with no coking or scaling.

It enables low-temperature evaporation under vacuum conditions.

Suitable for continuous production, featuring wide operating flexibility, simple structure, easy maintenance and automatic control.

Adjusting the inclination angle of grooves on the outer side of scrapers can change the material residence time inside the evaporator to meet evaporation requirements of materials with different viscosities.

All parts and equipment in contact with feed liquid are made of stainless steel to avoid contamination of the feed liquid.

A quick-opening cover plate is installed on the top for convenient cleaning of heating tubes. Lamp ports and sight glasses are arranged on both sides of the top for observation during operation.

Application Scope of Scraper Evaporator

Scraper evaporators are widely used in petroleum, chemical, pharmaceutical and other industries. They are especially suitable for high-viscosity, easy-to-crystallize, easy-to-foul and heat-sensitive materials.