Acid Gas Scrubbing in Solar Factories: Capturing HCl, HF and Chlorine

… more less Acid gas scrubbing in solar factories catches the corrosive gases that come out of many process steps. Trichlorosilane plants vent HCl. Phosphorus diffusion furnaces release chlorine and traces of POCl3. Etch benches give off HF, and nitric acid etching gives off nitrogen oxides (NOx). All of these harm lungs, plants and metal. Most are pulled into a wet scrubber. This is a tall tower where exhaust rises through packing while water or a base runs down. HCl and HF dissolve in water very easily. A base such as sodium hydroxide (NaOH) then neutralises them: HCl + NaOH -> NaCl + H2O. Chlorine needs the base to be captured well. NOx is harder, because it does not dissolve easily, so plants may add extra steps. A working scrubber removes nearly all of the acid gas. But the acid does not vanish. It moves into the scrubber water, which becomes salty and full of fluoride and must be treated before release. When scrubbers are skipped or fail, nearby crops and people can be harmed. The trade-off is cost: scrubbing uses power, chemicals and water. After this Concept you can trace an acid gas from a process step to the scrubber and on to the wastewater it creates.