The application range of this business encompasses all industrial workings that generates polluting fumes in the chemical, pharmaceutical, mechanical, galvanic, leather and paper industries, among the others.
Moreover, for civil applications, ecological plants are typically installed to scrub foul-smelling compounds that develops inside water treatment plants.
In a scrubbing colomn, gases that are sucked in by the fan then pass through one or more layers of filling bodies, which are sprayed in counter-current by the scrubbing liquid. Finally, a demister retains all particles that are drawn by the gas flow.
This specific type of plant is used where the pollutant results to be a soluble compound; the gas/liquid exchange phase takes place in the scrubbing column and then all the polluting compounds, now retained by the scrubbing liquid, are neutralized through a chemical reaction. Such reaction could also frequently generate products that can be reused in the initial production cycle of the same plant.
Several types of scrubbing columns are designed, each one with characteristics that are suitable to treat a specific gas flow to be scrubbed:
- parallel flow scrub: when gas and liquid flows in the same direction
- counter-current scrub: when gas and liquid flows in opposite directions
- cross-current scrub: when gas and liquid flows with a relative 90° angle
- Venturi scrub system: when gas and liquid flows are compressed and thereby accelerated
- turbulence-scrubber system: when gas and liquid are mixed under turbulent flow conditions
- separator: droplets elimination
The first three types are mostly used for highly soluble pollutants, which can chemically react with the scrubbing liquid.
The next two are used to scrub dust and particles of several sizes. The last one eliminate only droplets.
Considering all these classes, the type and size of the scrubbing column is then established considering various parameters, such as: the required type of pollutant, its concentration and the requested performance. Particular focus is maintained on the selection and sizing of the filling vessels. Finally the gas/scrubbing liquid ratio determines the required characteristics of the pump (flow mass rate) and the consequent sizing of the recirculation tank.
Several types of filling methods are also available: from loose filling bodies that are carried out in various forms and sizes to structured filling with diversified passage sections. The combination of all these parameters enables the designer to safely tackle several environmental issues, designing plants always within the set-limits of the most up-to-date antipollution regulations.
The most commonly used building materials are anti-acid thermoplastics, like Polypropylene PP, Self-Extinguishing Polypropylene PPS, Polyethylene PE and PVC both with or without external FRP reinforcing.
In case of installations in hazardous ATEX classified areas, self-extinguishing materials as PPS and anti-static materials, like PPS EL, are used.
The presence of thermoplastic materials limits the operating temperature, which must be lower than 100°C.
These kind of plants can be run either manually or fully automatically by adding the appropriate control instrumentation.
