The Rototherm-E is Artisan’s most common evaporator design and belongs to the Thin-Film or Wiped-Film class of Evaporators. Artisan Industries has been designing and manufacturing these evaporators since the 1960’s. They installed more than 500 units worldwide.
The Rototherm-E is designed for applications where both the product feed entering the evaporator and the concentrated product exiting the evaporator are pumpable fluids (either liquids, pastes or sludges).
The Rototherm-E has many advantages over other kinds of finishers (as e.g. falling film finishers):
Short product residence time
The exposure of the product to a heated surface is very short (typically 1-5 minutes). Hence there is a reduced chance of product quality degradation.
Low Production Losses
The horizontal design assures that no dry spots will be created. As a result no fouling will occur on the heated surfaces. Consequently production losses are close to zero.
The residence time of the product inside the evaporator is very short. As a result the start-up (and the shut-down) of an operation is very quick.
High Turn-Down Ratio
The evaporation process is virtually independent of gravity. Consequently the feed-flow has little impact on the operation.
Highly Viscous Products
The design of the Rototherm-E allows handling of highly viscous materials (up to 4 million cP ). As such very high product concentration can be obtained.
High Heat Flux
The evaporation principle uses a large temperature difference over the heated surface. As such, a Rototherm requires only a relative small heat transfer area.
The Rototherm®-E is easy to maintain. It has few moving parts installed. The bearings are on the outside the product flow area.
Some Applications for the Rototherm-E
To carry out an equilibrium reaction, while simultaneously concentrating the product and discharging a solid or a slurry, all in a single step. Equilibrium reactions, such as saponification and esterification are typically carried out in batch reactors, taking 24 to 30 hours to reach the desired conversion. Furthermore, it has been demonstrated that rapid removal of reaction by-products, such as water in esterification reactions, significantly reduces reaction time. However, both heat and mass transfer rates are limited in batch reactors. Consequently, as the reaction proceeds toward completion, the water removal rate drops dramatically, inhibiting the reaction rate and wasting valuable reactor time.
Use an Artisan two-zone Rototherm-E to carry out continuous equilibrium reactions. A co-current design, along with a two-zone process section, permits reaction, concentration, and a heavy slurry or solid discharge in a single step. This mechanically-agitated thin-film processor provides a unique combination of efficient heat and mass transfer capability, short residence time, and mechanical integrity to perform continuous reactions of highly viscous, foaming, fouling and solids-containing products. The rapid evaporation of reaction by-product(s) enables near complete conversion of most saponification and esterification reactions in minutes, yielding superior products, while minimizing energy consumption.
While concentrating a soap product all of the following are done in a single step:
- Single stage saponification of isostearic acid with sodium hydroxide, forming a stoichiometric soap.
- Steam stripping the “un-saps” from the soap.
- Discharging a paste-purified soap with an acid value of 195, and an un-sap value < 1.