A Comparison Between Vertical and Horizontal Thin Film Thermal Processing

A Comparison Between Vertical and Horizontal Thin Film Thermal Processing 

The process of “evaporation and drying” is one of the most important operations in process technology and Artisan Industries has over 85 years of experience in manufacturing and application of thin film evaporators in solving customers’ separation requirements.

Overview

Thin film evaporators are designed in vertical and horizontal orientation. They are both perfectly adapted to a multitude of separation tasks in distillation, concentration, de-gassing, drying stripping, solvent recovery, purifying, and reacting. 

Characteristics of both compared to other evaporator types include: 

• Dependable .and continuous processing of viscous, fouling and soiled liquids
• Temperature sensitive products experience a gentle treatment in the evaporator, due to the short residence time and the narrow residence time range 
• High heat flux allows for a high evaporation rate in a single pass
• Low hold-up with minimal losses in case of product changes
• Easy to regulate and to adjust

These advantages expound why thin film evaporators are the best choice for a wide range of applications, especially for the treatment of mixtures that are difficult to process.

Artisan’s Rototherm® Vertical Thin-Film Processor Handles High-Viscosity Solids

The Rototherm® V is a mechanically aided, continuous vertical processor designed for concentration, evaporation and stripping applications in the food, chemical, oleo chemical, pharmaceutical, and polymer industries.

The processor handles high-viscosity, heat-sensitive, and solids-containing materials.

Advantages:

• Minimal to no degradation of heat sensitive materials
• Up to 90% evaporation in a single pass
• Operating pressure to as low as 1 mm Hg absolute
• Co-current or counter-current operation
• Integral mist eliminator
• Overhung or double-ended design for heavy duty service
• Robust construction for unparalleled service life
• Easy installation and maintenance
• Small footprint

Operation:

The spinning rotor distributes the product as a turbulent thin-film inside the jacketed process wall, maximizing heat transfer 

performance. The film is constantly renewed by the incoming feed as the concentrated material falls towards the outlet at the bottom. 

As the residence time is generally measured in seconds, the degradation of heat sensitive materials in minimized or eliminated.

The integrated mist eliminator minimizes product carry-over into the vapor stream, without the need for an external entrainment separator.

Artisan’s Rototherm® Horizontal Thin-Film Evaporator with Optional Twin Screw Extruder Outlet is designed for applications that involve processing viscous liquids or polymers, performing solvent reduction, mixing, and/or reacting.  

The mechanically agitated thin-film, short-residence-time process technology with the Rototherm® can process materials with viscosities up to 2 million centipoise.

Advantages:

• A fully–wetted process wall at all evaporation- and feed rates guarantees less fouling. These units have less product loss as a result.
• The thin film is unaffected by gravity. This provides enormous flexibility with regards to the feed rate. As a result, the turn-down ratio is very high.
• The evaporator has a higher heat flux due to a more uniform film.
• The evaporator requires considerably less cleaning as product walls are fully-wetted and product is never stationary on the wall. As a result, the system gives higher run times and less product losses.
• Maintenance on an evaporator is rather simple. The only serviceable parts are readily accessible external bearings and double mechanical seals.
• The design is horizontal. The internal bearings and seals are never in contact with the product.
• The installation is easy. Artisan delivers the unit skid-mounted.

Operation:

The Rototherm® uses a combination of very small production gaps and high speed mixing in an innovative way. A high-speed rotor creates centrifugal force on the product. This keeps the product feed against the heated cylinder wall at all times. This is virtually independent of the feed rate or evaporation rate. As a result, there are no dry spots on the heated cylinder wall. The evaporator creates, due to its high rotor speed, a very turbulent product film, which makes it possible to work with very high temperature differences over the cylinder wall. This in turn minimizes the evaporation area. Fresh product “pushes” the film continuously towards the bottoms discharge nozzle. This again means that the product gets more concentrated as it moves through the evaporator. As the film is very thin, the product residence time is measured inside, generally in seconds. This again minimizes degradation of heat-sensitive materials. A Rototherm® allows for up to 99% evaporation in a single pass. As a consequence, it can concentrate certain liquid solutions directly to a dry powder in a single pass. Dry spots do not exist inside a Rototherm®. The process wall remains fully-wetted at all evaporation rates and are ideal evaporators.

This is possible, as the units work with very short residence times, while at the same time it can work with low evaporation temperatures as well. The Rototherm® can range in size from 1/2 sq.ft. (about 0.5 dm2) to 250 sq.ft. (about 23 m2) of heated surface.