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面向低浓度排放的含湿油气吸附性能及热效应的研究

作者:完美论文网  来源:www.wmlunwen.com  发布时间:2019/10/8 9:09:45  

摘要:随着中国政府对环保的重视,有机废气的低浓度排放要求日益严格。吸附法处理有机废气具有脱除效果好、回收方便等优点,广泛应用于工业有机废气的处理。然而,有机废气常常含有大量水蒸汽,严重影响到有机废气的吸附处理效果和运行成本。目前,高湿度有机废气的吸附处理及低浓度排放已成为研究难点和热点。此外,吸附剂循环吸附后保持较好的吸附性能是有机废气达到好的处理效果及较低处理成本的关键。吸附剂在处理有机废气的过程中会释放出热量,导致自身升温,影响其吸附效果。

为探究循环次数、湿度、空速对吸附剂吸附性能及吸附热效应的影响,本文选用两种炭基吸附剂AdsFOV-1和AdsFOV-2以及一种疏水硅基吸附剂AdsFOV-3,对正己烷蒸气、水蒸汽和油气进行吸附实验。对三种吸附剂进行表征并分析其结构特点。利用热重仪考察循环吸附次数、吸附温度和吸附质浓度对吸附剂静态吸附以及吸附热的影响。进行自制油气回收实验吸附实验平台填装不同吸附剂的压降测试。利用测试平台考察循环吸附次数、进气湿度、进气浓度以及空速对吸附剂动态穿透吸附量、穿透时间及温升的影响。

(1)吸附剂表征结果表明AdsFOV-1、AdsFOV-2都兼具微孔和中孔结构,AdsFOV-1具有最大的比表面积、微孔孔容比例,AdsFOV-2次之,AdsFOV-3以中孔为主,几乎不含微孔,且比表面积最小。

(2)吸附柱的压降测试表明压降P与吸附剂填充高度H成一次函数关系,与空塔流速U成二次函数关系。AdsFOV-1、AdsFOV-2的压降相近,AdsFOV-3的压降较小。三种吸附剂的压降公式拟合的R2均大于0.94。

(3)在吸附水蒸汽、正己烷蒸气和油气的静态实验中,随着循环吸附次数的增加,各吸附剂的饱和吸附量轻微下降,饱和时间略微提前,吸附热值变化不大。随着吸附温度升高,饱和吸附量下降,饱和时间延后,吸附热值变小。随着吸附质浓度升高,饱和吸附量上升,吸附饱和时间提前,吸附热值变大。

(4)在吸附正己烷蒸气和油气的动态实验中,随着循环次数增加,穿透吸附量会缓慢降低,穿透时间会缓慢提前,温升缓慢降低,45次循环后三者几乎保持不变。随着进气湿度增大,穿透吸附量下降,穿透时间提前,温升变大。随着进气浓度增大,穿透吸附量下降,穿透时间提前,温升增大。随着空速增大,穿透吸附量下降,穿透时间提前,温升增大。在脱附效果较为理想的情况下,炭基吸附剂AdsFOV-1和AdsFOV-2在多次吸附之后仍能保持优良的吸附性能,适宜工业化应用。有机蒸气中水蒸汽含量较高时,吸附剂的吸附性能会受到严重影响,吸附剂的升温情况也会加剧。

在处理时间允许的情况下,降低进气浓度和空速能使吸附剂的吸附效果变好、吸附剂热效应减弱。

With the Chinese government's emphasis onenvironmental protection, the requirements for low-concentration emissions oforganic waste gas is increasingly strict. The organic waste gas treated by theadsorption has the advantages of good removal effect and easy recovery, it iswidely used in the treatment of industrial organic waste gas. However, organicwaste gas often contains a large amount of water vapor, which seriously affectsthe adsorption treatment effect and operating cost. At present, the adsorptiontreatment and low-concentration emissions of high-humidity organic waste gas havebecome a research difficulty and hot spot. In addition, the adsorbent maintaingood adsorption capacity after cycle adsorption is the key of achieving goodtreatment efficiency and low processing cost. The adsorbent will release heatduring the process of adsorbing organic waste gas, causing it to heat up andweaken its adsorption capacity.

In this paper, two carbon-based adsorbentswere marked as AdsFOV-1 and AdsFOV-2, and a hydrophobic silicon-based adsorbentwas marked as AdsFOV-3 were used to carry out adsorption experiments onn-hexane vapor and water vapor and oil vapor. Three adsorbents werecharacterized and their structural characteristics were analyzed. The effect ofcycles of the adsorbent, adsorption temperature and adsorbate concentration onthe static adsorption and adsorption heat were investigated by thethermogravimeter. The pressure drop tests of self-made oil vapor recoveryexperiment adsorption experiment platform filled with different adsorbents werecarried out.The effect of cycles of the adsorbent, the vpor humidity, the vaporconcentration and the gas hourly space velocity on the dynamic breakthroughadsorption capacity, breakthrough time and temperature rise of the adsorbentwere investigated by the self-made organic vapor recovery adsorption testplatform.

(1) The results show that both of AdsFOV-1and AdsFOV-2 have microporous and mesoporous structures, and AdsFOV-1 has alarger specific surface area and a higher micropore volume ratio, whileAdsFOV-3 is all of mesoporous and none of micropores.

(2) In the static experiments of adsorbentsadsorbing n-hexane vapor, water vapor and oil vapor, the saturation adsorptioncapacity decreases slightly, the saturation time shortens slightly, and theadsorption heat value does not change much as increase of the adsorptioncycles. When the adsorption temperature is increased, the saturated adsorptioncapacity and the adsorption heat value are decreased, the saturation time isdelayed. As the adsorbate concentration increases, the saturated adsorptioncapacity increases, the adsorption saturation time shortens, and the adsorptionheat value increases.

(3) The pressure drop of the adsorptioncolumn is in a linear relationship with the height of the adsorbent filling,and is a quadratic function relationship with the gas hourly space velocity ofcolumn. When column was filled with AdsFOV-1 and AdsFOV-2, the pressure drop ofcolumn was similar and larger than the pressure drop when it filled withAdsFOV-3. The R2 of the pressure drop formulas are all greater than 0.94.

(4) In the dynamic experiments ofadsorbents adsorbing n-hexane vapor and oil vapor, the adsorption cyclesincreases, the adsorption breakthrough capacity decreases slowly, thebreakthrough time shortens slowly and the temperature rise decreases slowly,and all of three keep almost unchanged after 45 cycles. As increase of thevapor humidity, the breakthrough adsorption capacity decreases, thebreakthrough time shortens, and the temperature rise increases. As increases ofthe vapor concentration, the breakthrough adsorption capacity decreases, thebreakthrough time advances, and the temperature rise increases. In the case ofgood desorption, the carbon-based adsorbents AdsFOV-1 and AdsFOV-2 can maintainexcellent adsorption capacity after many cycle adsorptions and they aresuitable for industrial

关键词:吸附剂;油气;高湿度;吸附性能;吸附热效应

adsorbent; oil vapor; high humidity;adsorption capacity; adsorption heat effect

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