I. Summary
The rotary scraper type film evaporator is a kind of new high-efficiency evaporator that carries out falling film evaporation under vacuum through forced film forming by rotary scraper. With such features as high heat transfer coefficient, high evaporation intensity, short flow passing time and high operating elasticity, it is especially suitable for evaporation, concentration, degassing, precipitation, distillation and purification of heat sensitive materials, materials of high viscosity, materials easy to crystallize and materials containing granules. It is widely applied in chemical industry, petrochemical industry, medicine, fertilizer, daily chemicals, food, fine chemical industry, etc.
II. Structural features
1. Motor and speed reducer.
It is the driving unit for rotor rotation. The rotating speed of rotor depends on the form of scraper, material viscosity and inside diameter of evaporating cylinder. The selection of a suitable linear speed of the scraper is an important parameter to guarantee stable and reliable operation of the evaporator and satisfactory evaporating effect.
2. Separating barrel
The materials enter the evaporator through the inlet at the bottom of the separating barrel, and are continuously and evenly distributed on the evaporating cylinder by the material spreader installed inside the separating barrel. The secondary steam evaporated from the evaporating cylinder rises to the separating barrel. After passing through the gas-liquid separator inside it, the liquid drops or bubbles that may be carried by the secondary steam are separated, and the secondary steam will be discharged out of the evaporator from the outlet at the top.
The reasonable design of the separating barrel based on the calculation of resistance inside the evaporator is one of the key factors that avoid short circuit of materials. (The so-calledshortcircuitmeans that the materials leave the evaporator at the secondary steam outlet before the evaporation process is completed).
3. Material spreader
The material spreader is installed on the rotor. Through reasonable design, the materials entering the evaporator from the tangent direction are continuously and evenly spread on the evaporating surface by the rotary material spreader.
4. Gas-liquid separator
The rotary vane type gas-liquid separator is installed at the top of the separating barrel. It is used to collect liquid drops or bubbles that may be carried by the rising secondary steam and make them drop back onto the evaporating surface.
5. Evaporating cylinder
It is also called heating cylinder. It is the evaporating surface where the materials that are subject to forced film forming by rotary scraper and the heating media inside the jacket carry out heat exchange. The inside diameter and length of the evaporating cylinder are determined by the evaporating area and appropriate length-diameter ratio.
6. Rotor
The rotor installed inside the evaporating cylinder is composed of rotary shaft and rotary bracket. Driven by motor and reducer, the rotor drives the scraper to make circular motion. The rotary bracket is made of stainless steel precision castings, so that its strength, geometrical dimensions, stability, etc. are effectively guaranteed.
7. Scraper
Due to the movement of the scraper, the materials are constantly scraped into films on the evaporating surface,so as to achieve the effect of film evaporation.According to material viscosity, the following three kinds of scraper forms are available for selection:
(1) Sliding scraper
(2) Fixed scraper
(3) Hinge scraper
8. Bottom head
The individually designed W model bottom head is provided with the high temperature resistant self-lubricating bearing, which not only facilitates material discharging, but also makes maintenance and servicing of bottom bearing convenient.

LG 0.8 LG 1.5 LG 2.5 LG 4 LG 6 LG 10
Heat exchange area  ( m2 ) 0.8 1.5 2.5 4 6 10
Vapor pressure (MPa) 0.3 0.3 0.3 0.3 0.3 0.3
degree of vacuum (KP) 70 70 70 70 70 70
Evaporation capacity
160 300 500 800 1200 2000
Steam consumption (kg/h) 168 315 525 840 1260 2100
Motor power
1.1 1.5 2.2 4 5.5 11
Agitation speed (rpm) 300 300 280 134 134 88
Height of equipment (mm)
2500 3295 4100 5180 5800 7800