The filtration of gaseous material streams for separating liquid fractions that are present in droplet or mist form may be realized in different ways. Depending on the requirements and the framework, there are used various techniques for this purpose.
Known filtration systems are based, e.g., on the principle of centrifugal force for separating droplets having a higher mass than the gas stream. Another known filtration system is based on the principle of electrostatic interaction with particles in material streams. These are so-called electrostatic precipitators.
Filtration systems according to the type, as initially described, are mostly based on filter layers on the basis of fibre material filtration media. Due to their high effectiveness regarding the separation of solid or liquid particles from gaseous material streams or of solid particles from liquid material streams, at simultaneously relatively low system costs, such filtration systems are most common. Two different concepts, hence, are most commonly used. In the so-called surface filters very densely packed filter materials or filter layers having very small pores are inserted, wherein the filter layers are embodied having relatively thin layers in order to prevent too high pressure losses. On the other hand, there are so-called depth filter systems, wherein relatively loosely packed fibre materials are used in correspondingly thick filter layers.
Surface filters and depth filters are known in various embodiments and most commonly used in technical applications. There are, however, known some problems for which there has not been found a solution so far. One big problem is that in the separation of liquid fractions that are present in droplet form from gaseous material streams these droplets will coagulate in the filter layer—in particular in a fibre fabric of the filtration medium—into coherent liquid sectors and fill in the cavities in the filter layers. In this way, these sectors will become impassable for the gas stream. Currently, this problem is solved by correspondingly high filter volumes being situated upstream, which will lead to correspondingly high costs or unacceptably high dimensions for the filter housings, respectively. Successful approaches for discharging the liquid from the filtration medium or the filter insert, respectively, have not been known so far. Discharging the liquids from the filter insert is in particular difficult if the filter layers are very densely packed as well as if the liquid has a relatively high viscosity.