A Detailed Guide to Falling Film Evaporators

Are you familiar with the concept of falling film evaporators (FFEs)? These heat exchangers are used in a variety of industries, such as the hemp and agriculture industries.

FFEs are ideal for ethanol recovery and botanical oil separation. Their separation efficiency ranges between ninety and ninety-five percent.

We hope the following guide to falling film evaporators helps you understand the concept.

What are they?

Falling film evaporators are vertical shell and tube heat exchangers used for the separation of at least two substances with different temperatures of boiling. These heat exchangers consist of two compartments. Their role is to bring the media, referring to a cooling or heating fluid, into indirect yet close contact with the process fluid, also named the product fluid.

Moreover, the transfer of energy is quick and efficient across the falling film evaporator, more precisely between the process and media fluids. When the heat exchanger is used to evaporate a process fluid component, the media fluid is hotter than the process fluid.

Heat travels through the shell compartment, whereas the process fluid travels through the tube. Consequently, energy undergoes a transfer from the media in charge of heating to the product, which allows a portion of it to get vaporized.

Furthermore, the process fluid gets pumped to the top of the FFE and becomes evenly distributed across every heating tube. Unless the fluid is evenly distributed, it wouldn’t be able to flow down the interior walls of every tube. The film of fluid that flows down the tubes is called the falling film. Click here to gain a better understanding of a falling film evaporator.

How does an FFE work?

FFEs are among the most effective technologies for a rapid recovery of solvent in the extraction process, during which sensitive compounds are protected from heat degradation. As mentioned previously, the solvent is dispersed equally throughout all tubes while clinging evenly to the interior surface. Afterward, hot steam or water is circulated through the shell side.

There is a conduction of heat through the tube walls from the hot steam or water into the process liquid, which results in evaporation. The steam travels downwards, accompanied by the remaining fluid solution. The liquid gets collected at the bottom of the system, whereas the vapor travels through a condenser.

Features

Falling film evaporators have specific features that make them attractive, such as high product quality, high energy efficiency, automation, simple process control, and flexible operation. The high product quality of these heat exchangers results from gentle evaporation and incredibly short residence times. Energy efficiency is high because of the use of mechanical and thermal vapor recompressor, relying on the lowest difference between theoretical temperatures.

The process is automated and controlled easily, as FFEs react rapidly to energy supply changes, concentrations, vacuum, etc. Additionally, the operation is considered flexible owing to the fast startup and smooth switchover from operation to the process of cleaning.

Why choose FFEs?

Falling film evaporators are used by a myriad of factories in different industries, which have decided to update their equipment. FFEs have been gradually replacing calandria evaporators and rising film evaporators owing to their impeccable thermal performance and design. For years, these heat exchangers have been used in the seawater desalination and agriculture industry. The following link, https://www.wired.com/story/desalination-is-booming-but-what-about-all-that-toxic-brine/, explains why desalination is booming.

Nowadays, they are largely used in the hemp industry. The majority of cannabis extraction methods impose a solvent requirement, such as ethanol. In order for the final product to be created, technicians must come up with a way to filter the solvent out from the biomass. An effective method of achieving such separation is through falling film evaporation.

FFEs rely on a combination of gravity and evaporation to remove the solvent from cannabinoids and terpenes. The first step is for the solvent and cannabis to be added to the first chamber of the evaporator, called the pre-warmer. The temperature of the solvent is close to reaching its point of boiling. Then, the solvent is moved to the evaporator’s top and starts sliding down the heated tubes owing to gravity.

Since alcohol has a lower boiling point than the extract rich in cannabinoids, it evaporates while the mixture is moving downwards. In contrast, cannabis oil keeps on flowing down towards the container. The evaporator walls should be sufficiently coated for the oil to flow down without any obstructions.

The entire process is conducted under a vacuum, which decreases the temperature necessary for alcohol to evaporate. Low temperature provides protection to thermally-liable ingredients like terpenes and THC. This process is cost-effective in comparison with other methods, as ethanol vapor can be recycled and used again.