The photocatalytic degradation characteristics of trichloroethylene (TCE), acetone, and toluene have been determined in an annular flow type, an annulus fluidized bed, a circulating fluidized bed photoreactors.
The effects of trichloroethylene (TCE) gas flow rate, relative humidity, $TiO_2$ film thickness, and UV light intensity on photodegradation of TCE have been determined in an annular flow type photoreactor. Phosgene and dichloroacetyl chloride formation could be controlled as a function of TCE gas flow rate and photodegradation of TCE decreased with increasing relative humidity. The optimum thickness of $TiO_2$ film was found to be approximately 5 ㎛ and the photocatalytic reaction rate of TCE increased with square root of UV light intensity. The decomposition of TCE by photocatalysis increases with decreasing initial TCE concentration and increasing gas-residence time.
The effects of superficial gas velocity $(U_g)$, wavelength and intensity of ultraviolet (UV) light, oxygen and $H_{2}O$ concentration on the photocatalytic degradation of TCE (Trichloroethylene) over $TiO_2/SiO_2$ catalyst have been determined in an annulus fluidized bed photoreactor. The key factor in determining the performance of the annulus fluidized bed photoreactor is found to be an optimum superficial gas velocity $(U_g)$ that provides the optimum UV light transmit through the proper size of bubbles in the photoreactor. The degradation efficiency of TCE increases with light intensity but decreases with wavelength of the UV light and $H_2O$ concentration in the fluidized bed of $TiO_2/silica-gel$ photocatalyst. The optimum concentration of $O_2$ for TCE degradation is found to be approximately 10%.
In addition, the effects of the initial TCE concentration, phase holdup ratio of gas and solid phases $(＼epsilon_g /＼epsilon_s)$, CuO loading on the photodegradation of TCE have been determined in an annulus fluidized bed photoreactor. The TCE photodegradation decreased with increasing the initial TCE concentration. The optimum conditions of the phase holdup ratio $(＼epsilon_g/＼epsilon_s)$ and CuO wt% for the maximum photodegradation of TCE was found to be 2.1 and 1.1 wt%, respectively.
The light transmission increases exponentially with the bed voidage at superficial gas velocity above 1.3 times the minimum fluidizing velocity $(U_{mf})$ in the annulus fluidized bed photoreactor. The effects of gas velocity, annulus gap on solid $(＼epsilon_s)$ and gas phase holdups $(＼epsilon_g)$, UV light transmittance and photocatalytic reduction of TCE (trichloroethylene) over $TiO_2/silica$ gel photocatalyst have been determined in an annulus fluidized bed photoreactor. The optimum TCE reduction efficiency exhibits at $ε_s/＼epsilon_g$ of 0.48, annulus gap of 8 mm and UV light transmittance around 0.20. The most pronounced effects on TCE conversion are found to be gas velocity $(U_g)$ and annular gap in the photoreactor. Therefore, an annulus fluidized bed photoreactor is an effective tool for TCE degradation over $TiO_2/silica$ gel with effcient utilization of photon energy.
The effects of the ratio of $TiO_2/silica$ gel, superficial gas velocity $(U_g)$, solid circulation rate $(G_s)$, solid holdup $(＼epsilon_s)$, initial trichloroethylene (TCE), acetone, toluene concentration, wavelength of UV light, reaction temperature and concentrations of $H_2O$ and $O_2$ on photodegradation of TCE, acetone, toluene over $TiO_2$/silica gel have been determined in a circulating fluidized bed (CFB) photoreactor. The conversion of TCE, acetone, toluene decreases with wavelength of UV light, initial concentration of TCE, acetone, toluene and $H_2O$ concentration in the CFB reactor. The optimum concentration of $O_2$ for TCE, acetone, toluene degradations are found to be approximately 9%, 10%, 7% in the CFB photoreactor, respectively. The CFB photoreactor system is an effective tool for high VOCs degradation and throughput of VOCs with efficient utilization of photon energy.
