Abstract
We developed a photocatalytic solar tower reactor for the elimination of low concentrations of volatile organic compounds (VOCs) typically emitted from small industrial establishments. The photocatalytic system can be installed in a narrow space, as the reactor is cylindrical-shaped. The photocatalytic reactor was placed vertically in the center of a cylindrical scattering mirror, and this vertical reactor was irradiated with scattered sunlight generated by the scattering mirror. About 5 ppm toluene vapor, used as representative VOC, was continuously photodegraded and converted to CO2 almost stoichiometrically under sunny conditions. Toluene removal depended only on the intensity of sunlight. The performance of the solar tower reactor did not decrease with half a year of operation, and the average toluene removal was 36% within this period.
Highlights
Photochemical oxidants, mainly volatile organic compounds (VOCs), are currently a serious global environmental problem, in large cities
To determine the optimum height of the solar tower reactor, the change of the concentration of toluene under a certain amount of UV radiation was measured as a function of the height of the reactor, which was adjusted by changing the number of photocatalyst modules
Two types of photocatalytic units were used: (1) a TiO2-coated ceramic tube optimized for a low pressure drop and low flow rate (1.5 L/min); and (2) a glass tube packed with TiO2-coated silica gel (HQC21) optimized for a high pressure drop and high flow rate (10 L/min)
Summary
Photochemical oxidants, mainly volatile organic compounds (VOCs), are currently a serious global environmental problem, in large cities. In Japan, approximately 10% of VOCs are emitted from automobiles, while the rest are of fixed origin [1,2]. Another major source of VOC emissions (approximately 73%) is solvent from paint and printing industries [2]. Molecules 2014, 19 elimination system is certainly possible at some fixed emission sources, and a few industry groups are undertaking its implementation. Smaller industrial establishments with VOC emissions below the average level in Japan are under no such obligations, self-imposed regulation is recognized. Most establishments cannot install a VOC elimination system, mainly for economic reasons. Small industrial establishments are the main contributors to VOC emissions in Japan; for instance, these are the source of around 70% of VOC emissions in Tokyo [3]
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