Jiangsu Shuoyun Petrochemical Equipment Co., Ltd.

Products

Z series high-efficiency rotating thin film evaporator

1. Overview
The Z-series Rotating Scraper Thin Film Evaporator manufactured by our factory is a new high-efficiency evaporator which forms forced film by rotating scrapers and performs falling-film evaporation under vacuum conditions. It features high heat transfer coefficient, high evaporation intensity, short residence time and wide operating flexibility. It is especially suitable for evaporation concentration, degassing, desolventization and distillation purification of heat-sensitive materials, high-viscosity materials and easy-to-crystallize particulate materials.

Therefore, it is widely used in chemical, petrochemical, pharmaceutical, pesticide, daily chemical, food, fine chemical and other industries.
Our factory has been manufacturing this type of equipment for more than ten years and has accumulated rich experience in fabrication and application. Over the years, in response to market demands and closely combining customers’ actual production conditions, we select reasonable and suitable equipment structures on the premise of meeting customers’ process requirements, with superior and reliable manufacturing quality. Continuous improvements have been made in tooling equipment, testing methods and product design, achieving remarkable results. Our technical level and product quality rank among the leading level in China.
2. Structural Features
The main structure of Z-series thin film evaporator is shown in Figure 1. Each component is described as follows:
1. Motor & Reducer
It serves as the driving unit for rotor rotation. The rotating speed of the rotor depends on the scraper type, material viscosity and inner diameter of the evaporation cylinder. Selecting a proper linear speed of the scraper is one of the important parameters to ensure stable and reliable operation of the evaporator and satisfactory evaporation performance.
2. Separation Cylinder
Materials enter the evaporator tangentially through the inlet at the lower end of the separation cylinder, and are continuously and uniformly distributed onto the inner wall of the evaporation cylinder by the distributor installed inside the separation cylinder. The secondary steam evaporated from the evaporation cylinder rises into the separation cylinder, where an internal gas-liquid separator separates liquid droplets or foam entrained by secondary steam. The secondary steam is led out of the evaporator from the outlet at the top.
Reasonable design of the separation cylinder based on resistance calculation inside the evaporator is one of the key factors to avoid material "short-circuit". (The so-called "short-circuit" means that materials leave the evaporator from the secondary steam outlet immediately after entering the evaporator without completing the evaporation process.)
3. Distributor

The distributor is mounted on the rotor. With reasonable design, materials entering the evaporator in tangential direction are continuously and uniformly splashed and distributed onto the evaporation surface in the form of film via the rotating distributor.
4. Gas-Liquid Separator
The rotary vane gas-liquid separator is installed above the separation cylinder. It captures liquid droplets or foam entrained by the rising secondary steam and makes them fall back to the evaporation surface.
5. Evaporation Cylinder
Also known as heating cylinder. It is the evaporation surface where materials forced into film by rotating scrapers exchange heat with the heating medium in the jacket. The inner diameter and length of the evaporation cylinder are determined by evaporation area and appropriate length-diameter ratio.
The inner wall of the heating cylinder is machined and polished by special machine tools, and the connecting flanges at both ends are processed in one setup to guarantee the overall concentricity of the equipment. The polished (mirror polishing when necessary) cylinder inner wall is smooth and clean, less prone to material adhesion and scaling, effectively ensuring the high heat transfer coefficient of the equipment.
5.1 If steam is used as heating medium, the heating cylinder generally adopts jacket structure.
5.2 If heat transfer oil or high-pressure steam is used as heating medium, the heating cylinder generally adopts half-pipe structure.
6. Rotor
The rotor installed inside the evaporator cylinder consists of rotating shaft and rotor frame. Driven by the motor and reducer, the rotor drives scrapers to perform circular motion. The rotor frame is fabricated from stainless steel or plastic, which effectively guarantees its strength, geometric dimension and stability.
7. Scraper
With the movement of scrapers, materials are continuously scraped into thin film on the evaporation surface to realize thin-film evaporation.
Four types of scrapers are available for selection according to material viscosity and other properties:
(1) Sliding Scraper (See Figure 2)
Sliding scraper is the most basic and common scraper type. Scrapers are fitted in four scraper guide grooves of the rotor.

Under the centrifugal force generated by rotor rotation, scrapers are thrown radially toward the inner wall of evaporation cylinder and rotate together with the rotor. This scraping action makes materials form turbulent liquid film on the evaporation wall, greatly increasing heat transfer coefficient. Meanwhile, continuous scraping effectively suppresses overheating, dry wall and scaling of materials.
Normally, scrapers are made of filled PTFE, suitable for working temperature below 150℃; carbon fiber material shall be adopted when evaporation temperature exceeds 150℃. Liquid guide grooves at a certain angle are machined on the end face of scrapers.
(2) Fixed Scraper (See Figure 3)
Fixed scrapers are all made of metal and rigidly connected to the rotor. The scraper length matches the evaporation cylinder. The clearance between rotating scraper and cylinder inner wall is only 1-2mm, requiring high machining and installation precision. It is suitable for evaporation concentration, desolventization or purification of extra-high viscosity and foaming-prone materials.
(3) Hinged Scraper (See Figure 4)
This type of scraper is suitable for materials easy to scale on heating surface. Scrapers are usually non-metallic parts and mounted on rotor frame via movable hinges. When the rotor rotates, scrapers are pressed tightly against cylinder inner wall by centrifugal force and slide on the wall at a certain angle to scrape materials into thin film and prevent wall scaling.
(3) Spiral Scraper (See Figure 5)
This scraper is suitable for concentration of materials with poor fluidity, easy scaling and extra-high viscosity. When the rotor rotates, the thrust of spiral scraper enables concentrated materials to flow down smoothly.

8. Bottom Head
Separately designed W-type bottom head equipped with high-temperature self-lubricating bearing, which facilitates material discharging as well as maintenance and repair of the bottom bearing.
3. Performance Features
The thin film evaporator possesses the following unique advantages incomparable with conventional film evaporators:
1. Extremely low pressure loss In rotating scraper thin film evaporator, material flow and secondary steam flow are two independent channels: materials flow downward as falling film (forced film) along the inner wall of evaporation cylinder; while secondary steam evaporated from evaporation surface leaves the evaporator almost unobstructed through the central space of cylinder. Therefore, pressure loss (also called pressure drop) is extremely low.
2. Operation under genuine vacuum condition
Precisely because the resistance of secondary steam from evaporation surface to condenser is minimal, a high vacuum degree (above -750 mmHg) can be maintained on the evaporation surface of the entire cylinder inner wall, nearly equal to the vacuum degree at the outlet of vacuum system. The increased vacuum degree effectively reduces the boiling point of treated materials.
3. High heat transfer coefficient and high evaporation intensity
The decreased boiling point of materials enlarges the temperature difference with heating medium; turbulent liquid film reduces thermal resistance; similarly, suppression of coking and scaling on material wall improves heat transfer coefficient of cylinder wall. The total heat transfer coefficient of high-efficiency rotating thin film evaporator can reach up to 8000 kJ/h·㎡·℃, so it features high evaporation intensity.
4. Low-temperature Evaporation
Since high vacuum can be maintained inside evaporation cylinder, the boiling point of treated materials is greatly reduced, so it is especially suitable for low-temperature evaporation of heat-sensitive materials.
5. Short Residence Time
The residence time of materials inside evaporator is very short, less than about 10 seconds. For common movable scrapers, diversion grooves are machined on the scraping end face (See Figure 6) with an inclined angle normally at 45°. Adjusting the inclined angle can change material residence time. Under scraping action, materials flow downward spirally and leave the evaporation section. Shortened residence time effectively prevents decomposition, polymerization or deterioration of products during evaporation.
6. Low-grade Steam Utilization
Steam is a common heating medium. Due to reduced boiling point of materials, the temperature of heating medium can be lowered under the same Δt, so low-grade steam can be used to realize comprehensive energy utilization. It is especially suitable as the last-effect evaporator in multi-effect evaporation system.

7. Strong Adaptability & Easy Operation
Unique structural design enables this equipment to handle high-viscosity, particulate, heat-sensitive and easy-to-crystallize materials which are difficult for conventional evaporators.
The rotating thin film evaporator has wide operating flexibility, stable running condition, low maintenance workload and convenient repair.
4. Product Specifications

Note: 1. Evaporation area is available from 0.1m² to 40m² according to above standard specifications, and custom design & fabrication can be provided upon customers’ special requirements.
2. Suitable scraper type can be selected according to different process requirements.
3. Materials for main cylinder (parts in contact with materials) and jacket can be carbon steel, SUS304, 316L, 316Ti, 310S, titanium alloy, nickel alloy, enamel, etc., based on customer demands and practical conditions.
5. Application Industries & Operation Unit Examples
High-efficiency rotating thin film evaporator has been widely used in Chinese & Western medicine, pesticide, light industry, daily chemical, biochemical, fine chemical, petrochemical and other fields with good results. See the table below for reference.

Table: Main Application Industries & Typical Materials
Thin film evaporator can be used for chemical unit operations such as material concentration, degassing, desolventization (solvent recovery), purification. The following processes are for reference:
1. Material Concentration (water evaporation) See Figure 8
2. Desolventization or Purification See Figure 9
3. Used as reboiler of rectification column, See Figure 10A, 10B
4. Combined with tube evaporator to form multi-effect evaporator, See Figure 11
5. Multi-stage distillation together with short-path distiller, See Figure 12

6. Guidelines for Thin Film Evaporator Selection
Evaporator selection shall comprehensively consider interrelated factors, generally including:
1. Determination of Evaporation Area:
▲ Calculate evaporation capacity: compute evaporation rate (kg/h) per unit time according to throughput and inlet/outlet concentration;
▲ Estimate evaporation intensity of evaporator based on material viscosity, concentration, evaporation temperature, etc.;
▲ Calculate required evaporation area with certain safety margin.
2. Determination of Vacuum Degree
▲ Vacuum is obtained at the cost of energy consumption. Excessively high vacuum is unnecessary as long as evaporation requirements are satisfied;
▲ Estimate vacuum degree required at evaporation temperature according to material heat sensitivity;
▲ Determine required vacuum degree by considering possible leakage and frictional resistance of secondary steam along pipeline;
3. Determination of Scraper Type & Material
▲ Select suitable scraper type according to physical and chemical properties such as material viscosity, crystallization tendency and foaming property, and confirm material grade by evaporation temperature;
4. Determination of Heating Medium
▲ Select proper heating medium (steam, hot water, heat transfer oil, etc.) according to required evaporation temperature and heat consumption.
5. Selection of evaporator material
6. Selection & confirmation of motor explosion-proof grade
Our factory, with years of practical application experience, will fully assist customers in proper equipment selection.

Note: Small test machine available. Customers are welcome for material test.