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首页> 外文期刊>Separation and Purification Technology >Photocatalytic air purification: Comparative efficacy and pressure drop of a TiO2-coated thin mesh and a honeycomb monolith at high air velocities using a 0.4 m3 close-loop reactor
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Photocatalytic air purification: Comparative efficacy and pressure drop of a TiO2-coated thin mesh and a honeycomb monolith at high air velocities using a 0.4 m3 close-loop reactor

机译：光催化空气净化：使用0.4 m3闭环反应器，在高风速下，TiO2涂层薄网和蜂窝状整体材料的比较功效和压降

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Photocatalytic purifiers, which are in development for treating gaseous effluents at flow rates generally higher than several tens of m~3 h~(-1), usually employ TiO2 -coated materials either as planar or folded fibrous filters, or as honeycomb monoliths. Our primary objective was to compare the photocatalytic efficacy of two types of these materials using a ca. 0.4 m3 close-loop, air tight, photocatalytic reactor we built at EDF. This loop - through which air can be flowed at rates from 16 to 1800 m~3 h~(-1), i.e. 0.11-12.25 m s~(-1) - includes a paralleliped (560 mm x 295 mm x 200 mm) into which alternate banks of lamps and TiO2 coated-materials (entrance area=408cm2) can be accommodated. The materials tested were (i) an Ahlstrom-supplied, thin, non-woven tissue dried at room temperature after impregnation with both Degussa TiO2 P-25 and colloidal SiO2 used as a binder and (ii) an aluminum honeycomb-shaped material we coated with Degussa TiO2 P-25 and dried at room temperature. U-shaped lamps emitting at 254 nm and having an electrical power of 18 or 35 W were employed. The geometries of the materials and the spatial arrangements of the lamps and materials provided an irradiance of the materials as high and homogeneous as possible according to our modeling [Catal. Today 122 (2007) 66-77]. Methanol was chosen as the test pollutant because it is easily mineralized, which minimized the inhibition of the photocatalytic activity by intermediate products. In the recirculation regime, the initial rates of methanol removal observed for the folded tissue were multiplied by at least four - depending on the numbers of materials and banks of three 35 W lamps - when the honeycomb material was utilized. Several factors can add to cause this high increase in efficacy: distinct shapes and TiO2 supports, differences in photons scattering, and the reduced accessibility of reactants to TiO2 because of SiO2. Regarding energy consumption, the use of two photocatalytic materials sandwiching one bank of three 35 W lamps instead of one material in-between two banks of three lamps led to about the same efficacy. The honeycomb material was also tested with toluene at an initial concentration corresponding to the same amount of carbon as when methanol was the pollutant. The removal rate and CO2 formation rate were lower for toluene than for methanol, which can be easily explained by a lower reactivity with respect to oxidation, a smaller adsorbed amount and a higher competition with the more numerous degradation intermediate products. That comparison illustrates the need of trials for every effluent to be treated. Considerable differences in pressure drop between the two materials clearly demonstrated another interest of using honeycomb shapes, at least for the materials and configurations investigated. Furthermore, a deactivation, together with a yellowing, was noticed at high irradiance for the Ahlstrom tissue, which included cellulose fibers. Folding the material enables one to employ lower irradiances for minimizing this effect, while maintaining the efficacy because of the increase in the material area in the reactor, as well as slightly lowering the pressure drop.
机译：正在开发用于以通常高于几十个m〜3 h〜（-1）的流速处理气态废水的光催化净化器，通常采用TiO2涂覆的材料作为平面或折叠的纤维过滤器，或者作为蜂窝整体材料。我们的主要目的是使用ca来比较两种类型的这些材料的光催化效率。我们在EDF建造的0.4 m3闭环，气密，光催化反应器。该回路可以使空气以16至1800 m〜3 h〜（-1）（即0.11-12.25 ms〜（-1）的速度）流动，其中包括一条平行（560 mm x 295 mm x 200 mm）的管道。可以容纳交替排列的灯和TiO2涂层材料（入口面积= 408cm2）。测试的材料是（i）用Degussa TiO2 P-25和胶态SiO2浸渍后，在室温下干燥的Ahlstrom提供的薄无纺布，在室温下干燥;以及（ii）我们涂覆的铝蜂窝状材料用Degussa TiO2 P-25干燥，并在室温下干燥。使用发射功率为254 nm且功率为18或35 W的U形灯。根据我们的模型，材料的几何形状以及灯具和材料的空间布置为材料提供了尽可能高且均匀的辐照度。今日122（2007）66-77]。选择甲醇作为测试污染物是因为它易于矿化，从而最大程度地减少了中间产物对光催化活性的抑制作用。在再循环方案中，当使用蜂窝材料时，观察到的折叠纸巾的初始甲醇去除率至少要乘以四，这取决于三个35 W灯的材料和堆积数量。可能会导致效率提高的因素有很多：不同的形状和TiO2载体，光子散射的差异以及由于SiO2而使反应物与TiO2的可及性降低。关于能量消耗，使用两种光催化材料将一组三盏35 W的灯夹在中间，而不是将一种材料夹在两组三盏35 W的灯之间，可获得大致相同的功效。蜂窝材料还用甲苯进行了测试，其初始浓度对应于与甲醇为污染物时相同的碳含量。甲苯的去除速率和CO2生成速率低于甲醇，这很容易解释为相对于氧化的较低反应性，较小的吸附量以及与更多降解中间产物的较高竞争。这种比较表明需要对每种要处理的废水进行试验。两种材料之间压降的明显差异清楚地表明了使用蜂窝形状的另一种兴趣，至少对于所研究的材料和构造而言。此外，对于包括纤维素纤维的Ahlstrom组织，在高辐照度下会发现其失活以及变黄。折叠材料使得人们可以使用较低的辐照度来最小化这种影响，同时由于反应器中材料面积的增加以及压力下降的降低而保持了功效。

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