Photochemical method and device for volatile organic compound pollution control
A method for removing methane and non-methane volatile organic compound concentrations from a gas stream. The method includes exposing the target gas to a halogen gas and a light from a suitable light source having a wavelength sufficient to activate halogen gas to halogen radicals, wherein the halogen radicals react with the VOC in the target gas to provide the target gas with a removed concentration of VOC as well as a device including a reaction chamber for reacting the halogen radicals with the VOC in the target gas.
1 . A method for removing VOC, concentrations in ambient air comprising VOC, the method comprising, exposing the ambient air in a suitable reaction chamber to a halogen radical precursor, and a light from a suitable light source having a wavelength sufficient to activate the halogen radical precursor to halogen radicals, wherein the halogen radicals react with the VOC in the ambient air, wherein the ambient air after reaction in the reaction chamber is transported through a scrubber, and wherein the scrubber is a packed bed having an aqueous phase flowing downward through the packed bed and an air stream flowing up or sideways, to provide the ambient air with a removed concentration of VOC.
2 . The method of claim 1 , wherein the ambient air comprises a greenhouse gas nt.
3 . The method of claim 1 , wherein the ambient air polluted with VOC is ambient polluted air, air in livestock barns, from water treatment plants, from biogas production, from fermentation, other odorous point sources, or fugitive emissions.
4 . The method of claim 1 , wherein the halogen radical precursor is a halogen gas selected from chlorine and bromine gas, where chlorine gas is purchased or produced on site using electrolysis of saltwater or is part of other gases containing chlorine that can be photolyzed.
5 . The method of claim 1 , wherein the wavelength is from 540-180 nm.
6 . The method of claim 1 , wherein the light source is selected from a fluorescent lamp, an LED lamp, an incandescent lamp, a gas discharge lamp, sunlight, or combinations hereof.
7 . The method of claim 1 , wherein the concentrations of VOC in the ambient air are below 4.4%.
8 . The method of claim 7 , wherein the VOC comprises methane, and the methane is in a concentration from 1.8 ppm to 50000 ppm of the ambient air.
9 . The method of claim 1 , wherein the concentrations of VOC in the ambient air are above 4.4%.
10 . The method of claim 1 , wherein the halogen radical precursor is halogen gas wherein the concentration is present in an amount which is at least at the stoichiometric level in relation to the VOC concentration in the gas.
11 . The method of claim 1 , wherein the scrubber decreases or removes halogen acid, unreacted chlorine, formaldehyde, CO, and CO2 from the ambient air.
12 . The method of claim 1 , wherein the suitable reaction chamber is present and has an inlet for receiving the ambient air, a reaction zone wherein the ambient air is reacted with halogen radicals to remove the VOC concentrations, optionally a system to increase the light source pathway, a scrubber wherein the scrubber is a packed bed having an aqueous phase flowing downward through the packed bed and an air stream flowing up or sideways, and an outlet providing the ambient air with the removed concentration of VOC.
13 . The method of claim 1 , wherein gas ozone or liquid ozone, is added into the reaction chamber to convert halogenic acid to volatile and/or photolabile halogen species.
14 . The method of claim 1 , wherein airborne particulate matter of the ambient air that may harm the reaction chamber or destroy halogen gas as the halogen radical precursor in the reaction chamber is removed before being exposed to the halogen gas.
15 . The method of claim 1 , wherein the ambient air is led through a prefilter to remove larger particles from the ambient air before being exposed to halogen gas as the halogen radical precursor in the reaction chamber.
16 . The method of claim 1 , wherein the reaction chamber comprises two compartments, one first reaction compartment and a second compartment, a filter/packed bed separating the first and second compartment, wherein the ambient air after reaction in the first compartment is transported through the filter/packed bed into the second compartment wherein the ambient air with the removed concentration of VOC is exposed to water which reacts with halogenic acid to form halogen that is recycled to the reaction compartment.