“Falling film” photoreactor

The efficient irradiation of liquids with low UV optical transmission poses a complex challenge in certain photochemical processes. If there is a lack of penetration in the liquid, photons are entirely absorbed by the outermost layer of the volume, meaning the reactor’s full optical path is not utilized, leading to an inefficient reaction process. Furthermore, in the specific case of photolysis or photochemically initiated reactions where intermediate radicals are formed, large quantities of macromolecular by-products can deposit on the surface of the immersion lamp. These deposits, often caused by photochemical or thermal polymerization, end up absorbing a significant portion of the UV radiation and can cause conventional photochemical reactors to overheat.

The “Falling Film” photoreactor by UV-Consulting provides an effective solution to these problems, allowing for the homogeneous irradiation of liquids with low UV transmittance through the use of a thin layer with high turbulence. Deposits on the irradiation system are avoided since the liquid never comes into contact with it, ensuring proper operation throughout the entire trial.

With this reactor, the turbulence required for material mixing in the boundary layer is guaranteed with a Reynolds number greater than 400, without requiring high flow rates. The specific design of the discharge edge prevents the breakdown of the formed film.

Compared to an annular thin-film reactor, its advantages are clear: in an annular reactor, residence time is severely limited due to the high flow required to achieve necessary turbulence, whereas in the “Falling Film” reactor, this time increases considerably, resulting in improved reaction efficiency.

Regarding its geometric design, it is engineered so that the irradiated liquid area—in relation to the source intensity and distance—is optimal for a wide range of photochemical reactions. Additionally, its double-chamber design ensures that any radiation not absorbed by the liquid curtain is captured within the reactive medium.