Studies Of Gas Discharge And Photocatalytic Method Decontaminating Benzene In The Exhaust Gas

This paper tries to combine gas discharge with photocatalytic method for decomposing the harmful air of VOCs jointly. The gas discharge-photocatalytic reactor (GD-PR) consists of a gas discharge reactor (GDR) filled with porcelain beads that are coated nanometer titanium dioxide. Benzene is chosen to use for VOCs and air is used to the background gas in this research. The power supply is the 50 Hz low-frequency alternating current, voltage scope from0to30 kv generally. The experiment shows that the work ability of GD-PR is decided by the strength of gas discharge and the ultraviolet ray which is produced from gas discharge, and the quality and loading condition of the nanometer photocatalyst etc.Study shows that the main factors that affects gas discharge in the GD-PR have tow poles, filler material and size, electric voltage of the poles and the degree of humidity of the reaction gas etc. When the characteristic parameters of GD-PR are given, discharge of the reactor is more strong while the electric voltage of two poles is enhanced. Under a certain condition, inside electrode diameter of the reactor is not the more large, the more good, also not the more smallness, the more good, which exists a reasonable value; at one time, the circle number of outside pole is not the more many, the more good, excessive circle number of outside pole will cause the reactor fever and energy can consume bigly, but the more little of the circle number of outside pole will result in the electric field is not uniformity in the reactor extremely. The relative dielectric constant of filler material has certain influence to the electric field strength of the reactor, which will weaken with the enlargement of relative dielectric constant of filler material and will enhance with the diminishment of filler material diameter. The electric field strength can also be influenced by the relative humidity of test gas, which will become weak with the relative humidity enlargement. The experiment shows that the main factors that affect the reactor efficiency, in addition to the above-mentioned factors that have already mentioned, still have the current velocity and initial concentration of test gas.TiO₂ films are prepared by Sol-Gel method in the experiment and the mix proportion of the raw material making photocatalyst is decided reasonably. The experiment provesthat the photocatalyst can enlarge the relative dielectric constant of filler material and the electric field strength of the gap between filler materials, at the same time, enhance the electrons energy level, the energy utilization, the chemical reaction strength. The benzene decomposition efficiency of GD-PR is increased markedly comparing with the general gas discharge reactor. Still experiments discover that the GD-PR makes CO₂ enhancement in the decomposing benzene gas compared with the general gas discharge reactor. The GD-PR decomposing the low concentration (750 mg/ m³) benzene gas makes the removal efficiency of benzene reach nearly 99% and is the same to the decomposition efficiency, and also reach 90% above in the high concentration (1500 mg/ m³). Through the measurement, the main byproducts in the tail gas are CO₂ and H₂O.The fact explain that the GD-PR compares with the general photocatalytic reactor(PR) having the many characteristics: physical volume small, the decontaminationefficiency high and control easy, etc., with general GDR having more than 10% above fordecomposing benzene in air. Moreover, the photocatalyst can lose active in the long-termusage process, but it is easy to rebirth in this experiment.This research has also analysed the organic byproducts of the tail gas from decomposing benzene in air and the burnt material on the reactor and the filler material with GC-MS and IR, and obtained the many importance results: â‘  Because of the benzene molecule collided by the energetic electrons, the benzene free radical . C₆H₅ is formed easily ,and this is the cause that the benzene derivatives are formed.â‘¡ Because in the system the oxygen O₂ and the steam H₂O can...