Vents emitted in the Ullage system of a solar power plant contain benzine and other contaminants, which may include phenol, toluene and xylene. Given the danger of these contaminants, especially benzine, the law establishes very strict emission limits that enforce the treatment of the vents before their release into the atmosphere.
The Ullage system’s function is to recuperate the thermal oil and to do this, it evaporates it, giving rise to vapors that contain the above-mentioned contaminants.
The most appropriate air treatment technology for such cases is activated carbon filters.
A real example of a plant applied by Condorchem Envitech in a solar power plant, consists of an adsorption unit with two separate contact and serial chambers.
The air arrives at the adsorption unit and crosses the activated carbon bed where the contaminants are retained and the clean air goes out, complying with the legal limits for emissions.
The adsorption unit must be installed so that it is easy to extract and reinsert activated carbon. It is therefore important to mention that the adsorption of volatile substances over time involves the saturation of the carbon bed, which is why periodically, and depending on the quantity of Volatile Organic Compounds contained in the processed air, the carbon must be replaced.
To determine when the carbon must be replaced, the total bed mass is measured via 4 load cells per filter. At the outlet of the filtration unit, a gas flow meter is installed to continuously read and record the precise, average and accumulated flow emitted.
Once the bed of the first chamber is saturated, and after replacing it, the adsorption unit has the possibility of sending the contaminated flow initially to the second chamber and immediately afterward to the first, and vice versa. This is made possible thanks to the installation of the 4 manual valves.
It is also important that the adsorption unit has a safety valve, which if necessary, activates to prevent excessive pressure of the system.