Jiangsu Shuoyun Petrochemical Equipment Co., Ltd.

I. Overview

   The Rotary Thin Film Evaporator manufactured by our factory is a new high-efficiency evaporator that 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 granular 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 production and application. Over the years, in response to market demands and closely combining customers’ actual production conditions, we select reasonable and proper equipment structures on the premise of meeting customers’ process requirements, guarantee superior and reliable manufacturing quality, continuously improve and perfect tooling equipment, testing methods and product design, and have achieved remarkable results. Our technical level and product quality are in the leading position in China.
II. Structural Features
   The main structure of Z thin film evaporator is shown in Figure 1. Each component is described as follows:
   1. Motor & Reducer
   It is the driving device for rotor rotation. The rotating speed of the rotor depends on the scraper type, material viscosity and inner diameter of 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 evenly distributed on the inner wall of the evaporation cylinder via the distributor installed inside the separation cylinder. The secondary steam evaporated from the evaporation cylinder rises to the separation cylinder. The built-in gas-liquid separator separates liquid droplets or foam entrained by secondary steam, and 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 before the evaporation process is completed.)

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 as a film onto the evaporation surface by 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 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 thin 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 processed and polished by special machine tools, and the connecting flanges at both ends are machined in one setup to ensure the overall concentricity of the equipment. The polished inner wall (mirror polishing if needed) is smooth, less prone to material adhesion and scaling, effectively guaranteeing 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. The rotor is driven by motor and reducer to drive scrapers to perform circular motion. The rotor frame is fabricated from stainless steel and plastic to effectively guarantee 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 achieve thin-film evaporation effect.

   According to material viscosity and other characteristics, the following four types of scrapers are available for selection:

   (1) Sliding Scraper (See Figure 2)
   The sliding scraper is a basic and common scraper type. Scrapers are installed in four scraper guide grooves of the rotor. Under centrifugal force generated by rotor rotation, scrapers are thrown radially toward the inner wall of evaporation cylinder and rotate together with the rotor. Such scraping action makes materials form turbulent film on the evaporation wall, greatly improving the 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 with 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 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, mounted on rotor frame via movable hinges. When the rotor rotates, scrapers are pressed tightly against the inner wall of evaporation cylinder under centrifugal force, sliding on the wall at a certain angle to scrape materials into thin film and prevent wall scaling.
(3) Helical Scraper (See Figure 5)

This scraper is applicable for concentration of materials with poor fluidity, easy scaling and extra-high viscosity. When the rotor rotates, the thrust of helical scraper enables concentrated materials to flow down smoothly.

8. Bottom Head
   Separately designed W-type bottom head equipped with high-temperature resistant self-lubricating bearing, which facilitates material discharging as well as maintenance and repair of the bottom bearing.
   III. Performance Features
   The thin film evaporator has the following unique advantages unmatched by conventional film evaporators:
   1. Minimal pressure loss In rotary scraper thin film evaporator, material flow and secondary steam flow are two independent channels: materials flow downward as forced falling 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, so the pressure loss (also called pressure drop) is extremely small.
   2. Capable of operation under genuine vacuum condition
   Precisely because the resistance of secondary steam from evaporation surface to condenser is minimal, the evaporation surface on the whole inner wall of evaporation cylinder can maintain high vacuum degree (above -750mmHg), nearly equal to the vacuum degree at the outlet of vacuum system. Higher vacuum effectively reduces the boiling point of processed materials.
   3. High heat transfer coefficient and high evaporation intensity
   Lower boiling point of materials increases the temperature difference with heating medium; turbulent liquid film reduces thermal resistance; suppression of coking and scaling on material wall also improves partial heat transfer coefficient of evaporation cylinder wall. The total heat transfer coefficient of high-efficiency rotary 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 processed materials is greatly reduced. Therefore, 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, the scraping end face is provided with diversion grooves (See Figure 6) with an inclined angle usually of 45°. Adjusting the inclined angle can change material residence time. Under scraping by scrapers, materials flow down spirally out of evaporation section. Shortened residence time effectively prevents product decomposition, polymerization or deterioration during evaporation.
   6. Low-grade steam can be utilized
   Steam is a common heating medium. Since material boiling point is reduced, the temperature of heating medium can be lowered while keeping the same Δt. Low-grade steam can be adopted, which benefits comprehensive energy utilization. It is particularly suitable as the final-effect evaporator in multi-effect evaporation system.
7. Strong adaptability and convenient operation
   Unique structural design enables this equipment to handle high-viscosity, granular, heat-sensitive and easy-to-crystallize materials which are difficult for conventional evaporators.
   Rotary thin film evaporator has wide operating flexibility, stable working condition, low maintenance workload and easy repair.
IV. Product Specifications
Note: 1. Evaporation area can be selected from standard specifications ranging from 0.1m² to 40m², and custom design & fabrication can be carried out according to customers' special requirements.
2. Appropriate scraper type can be selected according to different process requirements.
3. Material of main cylinder (material contact part) and jacket can be carbon steel, SUS304, 316L, 356Ti, 310S, titanium, nickel, enamel, etc., according to customer and actual demands.
V. Application Industries & Operation Unit Examples

High-efficiency rotary thin film evaporators have been widely applied 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.

The table below lists main applicable industries and typical materials:
Thin film evaporator can be used for chemical unit operations such as material concentration, degassing, desolventization (solvent recovery) and 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, B)
4. Combined with tube evaporator to form multi-effect evaporator, See Figure (11)
5. Multi-stage distillation combined with short-path distiller, See Figure (12)
VI. Guidelines for Thin Film Evaporator Selection
Evaporator selection shall comprehensively consider various interrelated factors. Generally the following items need to be considered:
1. Determination of evaporation area:
▲ Calculation of evaporation capacity: calculate evaporation capacity (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 margin.
2. Determination of vacuum degree
▲ Vacuum generation consumes energy. There is no need to pursue excessively high vacuum as long as evaporation requirements are satisfied;
▲ Estimate vacuum degree at corresponding evaporation temperature according to material heat sensitivity;

▲ Determine required vacuum degree considering possible leakage and frictional resistance of secondary steam along pipeline.

3. Determination of scraper type and material
▲ Select proper scraper type according to physicochemical properties such as material viscosity, crystallization tendency and foaming, and determine proper material with consideration of evaporation temperature;
4. Determination of heating medium
▲ Select proper heating medium such as steam, hot water or heat transfer oil according to required evaporation temperature and heat consumption.
5. Selection and determination of evaporator material
6. Selection and determination of motor explosion-proof grade
With years of practical application experience, our factory will fully assist customers in proper equipment selection.

Note: Small test machine available. Customers are welcome to send samples for test.