A falling film evaporator is a type of heat exchanger that uses a shell and tube design to evaporate heat-sensitive liquids. The feed is pumped into the evaporator from the top. It’s then uniformly dispersed throughout the heating tubes of the device. While partially evaporated, the liquid flows through tubes, forming a thin layer on the tube walls. To guarantee a high heat exchanger coefficient, the heat is given through the heating medium (usually steam). Under the influence of gravity, the liquid and vapour move downhill. The vapour flow in the co-current direction aids the liquid’s downward descent. At the bottom of the falling film evaporators unit, the concentrated product and its vapour are separated from one another.
The design of Alaqua’s falling film evaporators takes into account two important considerations:
- To reduce the feed’s residence time, maximise heat transmission in the shortest period possible.
- The homogeneous distribution of heat ensures that no clumps or fouling occur on the inner side of the walls during the feed transfer.
High and efficient heat transmission is ensured by a standard technique used during material selection that considers the feed qualities. The distributor head that feeds into the tubes is intended to guarantee uniform wetting of the tube surfaces, preventing crusting, which is the source of many of the major maintenance issues with falling film evaporators.
How Falling Film Evaporator Works?
A falling film evaporator (FFE) is a form of vertically oriented shell and tube (S&T) heat exchanger used to separate two or more liquids with different boiling points.
Two compartments are included in a shell and tube heat exchanger. Its most fundamental function is to put a heating or cooling fluid, referred to as the media, into indirect but close contact with a product fluid, referred to as the process fluid. Between the media and the process fluids, energy is exchanged as heat through a shell and tube heat exchanger. When an S&T heat exchanger is used to evaporate a component of a process fluid, the media is hotter than the process fluid, and energy is transferred from the media into the process liquid.
The heating medium is cycled through the shell side of the S&T heat exchanger in the case of the falling film evaporators in particular. The evaporator’s tube side receives the process fluid. A portion of the product is vaporised, and energy is transmitted from the heating medium into the product.
The process liquid is poured into the top of the falling film evaporators and is uniformly distributed throughout the heat exchanger’s heating tubes. The liquid must be equally dispersed to flow down the inside walls of each tube. The term “falling film” refers to the liquid film that descends down the tubes and is the source of the heat exchanger’s name.
Why Falling Film Evaporators?
A falling film evaporator is a form of heat exchanger that is very efficient and effective. Indeed, due to the outstanding thermal performance of a well-designed FFE, many firms across most key sectors have been gradually upgrading their equipment from outdated rising film evaporators, calandria type evaporators, or forced circulation style evaporators to falling film evaporators.
The development and maintenance of a very thin film of rapidly descending liquid laminated to the internal surface of the evaporation tubes allow falling film evaporators to attain their excellent thermal performance. The contact between the process liquid and the heating medium is maximised by an equally dispersed liquid layer, allowing for the fastest energy transfer from the media to the process fluid. This entails quicker evaporation rates and the capacity to employ a cooler heating medium, both of which are advantageous for treating thermally degraded materials.
To attain this high degree of performance, the descending liquid must be evenly dispersed throughout all of the tubes, equally disseminated around the circumference of each tube, thoroughly laminated to the inside surface of each tube, and travel down each tube at the optimal velocity. Tubes that haven’t been adequately wetted can cause thermally labile products to degrade, are the leading source of fouling evaporators services, and have poor thermal performance.
Falling Film Evaporator Applications
- Pharmaceuticals
- Food and Beverages
- Dairy Industry
- Papers
- Chemical Industry
- For products with low fouling property
Alaqua optimizes its flow lamination technology for each FFE it designs and builds. When designing the flow lamination system, Alaqua acknowledges that various applications may have a unique mix of variables, such as solids content, extract content, desired (per cent) reduction in the solvent, and vapour velocity, which must be taken into account. The result is a small FFE with high throughput, little fouling, and consistent, regulated evaporation temperatures.
Various interpretations of falling film evaporators are quickly gaining favour, particularly in the hemp business. The performance and dependability of an FFE are highly dependent on the designer’s real technical skills. Alaqua takes pleasure in offering high-performance equipment and equipment services that have been meticulously developed, produced, and are field-tested. Contact us today to know more about our processing equipment and its services!
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