Regenerative falling film technology
With the falling film technology substances from gaseous phases, such as. As air , in liquid deposited are, or gas can be loaded with liquid.
The filtration with regenerative falling film process is based on a wet mechanical and / or wet chemical separation from gaseous phase flows in liquid. In this process, substances are separated from a gas volume flow on a thin film of liquid that trickles down a pipe or hose.
A falling film module consists of several tubes arranged in parallel and in series.
Working principle
The liquid flows in a reactor on pipes or hoses from top to bottom in a liquid film that is as uniform as possible, which represents the reaction surface for the mass transfer. The gas flows horizontally through the reactor. In order to avoid droplet formation and droplet entrainment by the gas volume flow , a low flow rate of the liquid film and good adhesion of the liquid to the hoses are necessary. Then no downstream droplet separator is necessary.
The washing liquid can consist of water, oils or other substances depending on the application. It is circulated and evenly distributed to the hoses through a distribution chamber located above the hoses. Below the filter module, it is collected in a working tank and returned to the distribution chamber. Falling film filters can be operated both independently, in that the used water is taken from the water storage tank, as well as stationary with a permanent connection to a drinking water supply.
The separation efficiency depends on the properties of the substance to be separated, its concentration and the volume flow , the properties of the scrubbing liquid and the construction of the reactor. V. a. the number and arrangement of the tubes in the reactor space is decisive. If the gas volume flow is large or to achieve a higher separation efficiency, several falling film modules are arranged in parallel or in series.
The greatest separation efficiency is achieved with a small hose diameter and a staggered arrangement of the hoses. Many thin tubes result in a relatively large phase interface between gas and liquid. The offset arrangement of the tubes causes constant turbulence and deflection of the gas flow, which is a good prerequisite for very good contact between gas and liquid.
By using different washing solutions, water-soluble and water-insoluble as well as inorganic and organic components can be adsorbed. Substances such as solvents, CO 2 , smoke, fine and coarse dust, as well as bacteria and pollen can be separated.
Possible applications
Regenerative falling film technology can be used in a wide range of applications, including:
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In general, with regenerative falling film technology, pollutants can be separated and both raw materials and heat can be recovered .
The versatility of the possible uses is one of the advantages of regenerative falling film technology. These filters are highly scalable and are relatively flexible with regard to fluctuations in concentration. In operation, they are very powerful and reliable. The size of a falling film reactor is considerably smaller compared to absorption columns. The pressure loss with this technique is relatively low.
Disadvantages are the application limits. The flow rate of the gaseous phase is limited, otherwise liquid will be discharged with the gas volume flow. If the liquid volume flow per tube is too low, no uniform film is formed, which affects the mass transfer surface.
The advantages and disadvantages of filters with regenerative falling film technology are listed below.
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Regeneration
The regeneration of the washing liquid is useful so that it can be circulated. On the one hand, this serves to save liquid, and the separated substance can also be recovered.
The washing liquid can be regenerated by phase separation, stripping or distillation . The phase separation occurs due to differences in density, the lighter component of a two-phase mixture floats, the heavier component sinks to the bottom. During stripping, gas (air) is blown through the washing liquid and discharges the absorbed substances. Stripping is only possible if there is a physical bond between the washing liquid and the absorptive. In the case of chemical bonding, regeneration can be carried out by distillation. The washing liquid is thermally regenerated due to the different boiling points between the absorbent and the absorptive.