潔淨室外氣空調箱用化學濾網上之甲苯吸附平衡、動力學及穿透理論模式確效性研究

Adsorption equilibrium, kinetics, and validation of a breakthrough theoretical model on adsorptive chemical filter for toluene removal used in the make-up air unit (MAU) of a cleanroom

薛人瑋(Ren-Wei Shiue)

指導教授 ： 胡石政

國立臺北科技大學/機電學院/機電科技研究所/博士(2010年)

https://doi.org/10.6841/NTUT.2010.00567

摘要

化學濾網廣泛用於半導體製造廠潔淨室，移除空浮分子污染物(airborne molecular contamination, AMC)。潔淨室以活性碳作為化學濾網吸附濾材，是為移除氣狀污染物的實際方法。測試條件維持28 ± 1 ℃、相對溼度40 ± 2% 與面速0.076、0.114 和0.152m/s 決定移除效率與吸附量。甲苯測試氣體濃度設於10、 31、42和70 ppm加速濾材吸附穿透，藉即時(real-time)光離子偵測儀(photoionization detector, PID)測定濃度。本研究的目的為
1) 評估椰子殼活性碳吸附劑負載不織布，由著穿透曲線、內部顆粒擴散特性、線性驅動力(linear driving force, LDF)、空床接觸時間(empty bed contact time, EBCT)與床深使用時間(the bed depth service time, BDST)、質傳區(mass-transfer zone, MTZ)和壓力降決定其性能。動態吸附量計算結果顯示隨面速增加而穿透曲線遞減，內部顆粒擴散效應與可能吸附率視為速率限制機構，其對化學濾網型吸附器結構更深入增進。
2) 為了研究吸附機制，三種簡化模式即偽一級、偽二級動力學模式與內部顆粒擴散模式用來計算動力學數據和速率常數。比較內部顆粒擴散速率常數ki、偽二級速率機構常數k2與偽一級機構速率常數k1，可看出偽一級吸附機構是主要的反應機制。另外由粒狀活性碳吸附過程總速率，顯示吸附程序包含一種以上控制步驟，即外部質傳與內部顆粒擴散機構。
3) 通常Yoon-Nelson模式很符合穿透率低於50%之穿透曲線。無論如何，Yoon-Nelson模式比例常數需由Wheeler-Jonas方程式質傳係數(kv)決定修改。接著假設甲苯濃度和面速模擬操作條件產出一系列穿透曲線，藉由Dubinin-Radushkevich學說方程式解釋對於吸附量證實其確效性。利用更改Yoon-Nelson模式解釋穿透曲線，化學濾網的使用壽命今後足具計算之信賴。

關鍵字

化學濾網 ； 活性碳 ； 吸附學說 ； 穿透曲線 ； 偽一級 ； 偽二級 ； 內部顆粒擴散 ； Yoon-Nelson模式 ； Wheeler- Jonas方程式

並列摘要

Chemical filters are used extensively in the cleanrooms of the semiconductor factories to remove airborne molecular contamination (AMC). Adsorption by activated carbons (AC) as media within the chemical filter is one of the practical methods for removal of gaseous contamination in a cleanroom. The testing conditions were maintained at 28 ± 1 ℃, and relative humidity at 40 ± 2% with face velocities of 0.076, 0.114 and 0.152m/s for removal efficiency and capacity determination. The challenge gas concentrations of toluene were fixed at 10, 31, 42 and 70 ppm to accelerate the breakthrough of media adsorption. The concentrations were measured by a real-time photoionization detector (PID). The objective of this study is
1) To evaluate coconut shell activated carbon adsorbent-loaded nonwoven fabric media performance by determining the breakthrough curves, the intra- particle diffusion characteristics, the linear driving force (LDF), the empty bed contact time (EBCT) and the bed depth service time (BDST), the mass-transfer zone (MTZ), and pressure drop. Results showed that the dynamic adsorption capacity calculated from the breakthrough curves progressively decreased with the increases in the face velocity, suggesting that the effect of intraparticle diffusion and possibly the rate of adsorption as the rate-limiting mechanism were increasingly more profound for a chemical filter-type adsorber configuration.
2) In order to investigate the adsorption mechanisms, three simplified kinetic models, i.e., the pseudo-first-order, second-order kinetic models and intraparticle diffusion model were used to describe the kinetic data and the rate constants were calculated. The rate parameter of intraparticle diffusion (ki), the rate parameter of the pseudo- second- order (k2) and the rate parameter for the pseudo-first-order mechanism (k1) were compared. It was found that the pseudo-first-order adsorption mechanism is predominant and the overall rate of the GAC adsorption process appears to be controlled by more than one step, namely both the external mass transfer and intraparticle diffusion mechanisms.
3) The Yoon-Nelson model generally matched well with the experimental breakthrough curved for breakthrough fraction less than 50%. However, the proportionality constant in the Yoon-Nelson model needed modification through the method from which the mass-transfer coefficient (kv) in the Wheeler-Jonas equation is determined. Subsequently, a series of breakthrough curves for the hypothetical toluene concentrations and face velocities simulating realistic operating conditions was generated, and their validity was verified against the adsorption capacity predicted by the Dubinin-Radushkevich isotherm equation. The useful life of a chemical filter could henceforth be estimated with confidence using the breakthrough curves predicted by the modified Yoon-Nelson model.

並列關鍵字

Chemical filter ； breakthrough curve ； activated carbons ； Yoon-Nelson model ； Wheeler-Jonas equation ； adsorption isotherm ； pseudo-first-order ； pseudo-second-order ； intraparticle diffusion

參考文獻

[2] Muller C. Comparison of Chemical Filters for the Control of Airborne Molecular Contamination. Journal of the IEST 2007; 50(2): 52-73.

[3] Shiue A, Kang YH, Hu SC, Jou GT, Lin CH, Hu MC, Lin SI, Vapor adsorption characteristics of toluene in an activated carbon adsorbent-loaded nonwoven fabric media for chemical filters applied to cleanrooms. Building and Environment Volume 2010; 45(10): 2123-2131.

[4] Shiue A, Den W, Kang YH, Hu SC, Jou GT, Lin CH, Hu MC, Lin SI, Validation and Application of Adsorption Breakthrough Models for the Chemical Filters Used in the make-up air unit (MAU) of a cleanroom. Building and Environment Accepted.

[5] Kang YH, Shiue A, Hu SC, Huang CY, Chen HT. Using phosphoric acid- impregnated activated carbon to improve the efficiency of chemical filters for the removal of airborne molecular contaminants (AMCs) in the make-up air unit (MAU) of a cleanroom Building and Environment 2010; 45(4): 929-935.

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