Artisan Industries designs and manufacturers high-end evaporators under the brand name Rototherm ®. Artisan provides world-wide sales support, but concentrates mainly on the US market. TEC Square provides support for these evaporators in Europe and Asia. We have installed and commissioned several units in the Far East and we provide support with regards to operational conditions in the food industry.
Advantages of the Rototherm®
- A fully–wetted process wall at all evaporation- and feed rates guarantees less fouling. As a result these units have less product loss.
- The thin film is unaffected by gravity. For that reason the unit provides enormous flexibility with regards to the feed rate. And as a result, the turn-down ratio is very high.
- The evaporator has a high heat flux, as the product film is more uniform.
- The evaporator requires considerably less cleaning. First of all the product walls are fully-wetted at all times. Secondly the 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. As a matter of fact, the only serviceable parts are readily accessible external bearings and double mechanical seals.
- The design is horizontal. As a result the internal bearings and seals are never in contact with the product.
- The installation is easy as Artisan delivers the unit skid-mounted.
Rototherm® – several executions exist
- Rototherm-E: The unit works as an evaporator or finisher. As such, the aim of the Rototherm is to create a concentrated liquid end-product.
- Rototherm-P: The unit works as an evaporator, but the product can actually go to a full dry stage as well. As a result, the Rototherm makes a powder from a liquid feed. However, it is important to realise that not all products can go to a powder. Pilot plant tests will need to be done.
- Rototherm-D: Designed to post-dry solid streams of material.
A Rototherm can range in size from 1 sqft (about 11 dm2) to 200 sqft (about 23 m2) of heated surface.
The biggest unit can evaporate up to 2,000 kilograms of water/solvent per hour.
Rototherm® – Design features
The Rototherm® units have 2 executions: co-current and counter-current liquid/vapour flow.
Co-Current
The liquid and resulting vapour travel in the same direction. As a result this method is recommended, when the unit works as an evaporator or finisher. On the other hand it is also a better solution for high-viscosity applications. Lastly, we use this design, when we aim to minimise liquid entrainment into the vapour ducting.
Counter-Current
The liquid and resulting vapour travel in opposite directions. As a result we prefer this design when we have the objective to get to high product concentrations.
Rototherm® – Principle of operation
The Rototherm’s 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. Accordingly the product film thickness is virtually independent of the feed rate or evaporation rate. And as a result there are no dry spots on the heated cylinder wall. The process wall remains fully-wetted at every evaporation rate.
The evaporator creates, due to its high rotor speed a very turbulent product film. Subsequently this makes it possible to work with very high temperature differences over the cylinder wall. And as a result the evaporation area of a Rototherm is relatively small. Fresh product “pushes” the film continuously towards the bottoms discharge nozzle. This in return means that the product gets more concentrated as it moves through the evaporator. Moreover, as the film is very thin, the product residence time inside the Rototherm is generally only a few seconds. This again minimizes degradation of heat-sensitive materials.
A Rototherm is an ideal evaporator for quality applications. Firstly the unit works with very short residence times. And secondly it can work at very low evaporation temperatures as well.
Lastly a Rototherm allows for up to 99% evaporation in a single pass. As a result, a Rototherm can sometimes concentrate a liquid solution directly to a dry powder.
For more information please consult the Artisan Industries website.
