I. 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-called��short circuit��means 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
The sliding scraper is the most basic and common scraper form.
The scraper is installed inside the four scraper guide grooves of
rotor. Under the effect of centrifugal force due to rotor
rotation, it is radially thrown to the inner wall of the
evaporating cylinder, and make circular motion together with the
rotor. This scraping of the scraper makes the materials under the
status of membranous turbulence on the evaporating wall and
greatly enhances heat transfer coefficient. In addition, the
continuous scraping can effectively avoid the occurrence of
overheating, dry wall, scaling, etc.
Generally, the scraper adopts filled PTFE. It is suitable for a
working temperature of lower than **0��.When the evaporating
temperature is higher than **0��, carbon fiber shall be
adopted. The end machining of the scraper is provided with liquid
guide groove of certain angle.
(2) Fixed scraper
The fixed scraper is made of metal materials. It is rigidly
connected with the rotor. The length of the scraper is the same
as that of the evaporating cylinder. The interval between the
rotary scraper and the inner wall of evaporating cylinder is only
**2mm. Higher machining and installation precision is required.
It is suitable for evaporation, concentration, precipitation and
purification of materials of high viscosity and those easy to
produce bubbles.
(3) Hinge scraper
The scraper is suitable for materials that easily form scaling on
the heating surface. The scraper is generally made of metal
parts. The scraper is installed on the rotation bracket by
adopting the flexible hinge. When the rotor turns, under the
effect of centrifugal force, the scraper is tightly pressed at
the inner wall of evaporating cylinder, and slides at certain
angle (with the wall) to scrape the materials into films, and
scaling on the wall is avoided.
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.
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II. Performance features
The film evaporator is provided with the following unique
features, which are incomparable with other conventional film
evaporators:
1.   Very low pressure loss
2.   Operation under vacuum can be realized in a
real sense
3.   High heat transfer coefficient and high
evaporation intensity
4.   Low temperature evaporation
5.   Short flow passing time
6.   Low grade steam can be utilized
7.   Strong adaptability and convenient operation
8.   Jacket pressure: normally designed according
to 0.4Mpa steam, or designed according to user requirements. When
heat transfer oil is adopted, other design can also be made.
9.   Vacuum degree inside evaporating cylinder:
normally designed according to *0.*9Mpa (about ***0mmHg), or
*0.**5Mpa (about ***0mmHg) and *0.***6Mpa (about ***0mmHg) can
also be designed according to user requirements.
*0. Materials of main cylinder (parts that contact
materials) and jacket: carbon steel, SUS**4, **6L, **6Ti, **0S,
titanium, nickel, etc. can be adopted according to actual
conditions and user requirements.
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