零價鐵填充床及流體化床處理二氧化硫之研究

Zero valent iron for sulfur dioxide removal-packed and fluidized column studies

黃揚舜(Yang-Shun Huang)

指導教授 ： 陳孝行

國立臺北科技大學/工程學院/環境規劃與管理研究所/碩士(2005年)

https://doi.org/10.6841/NTUT.2005.00129

摘要

本研究係以實驗室之填充床及流體化床管柱定溫反應實驗，探求零價鐵(zero valent iron, ZVI) 去除空氣污染物二氧化硫(SO2)之可行性研究。經由管柱穿透實驗，在進流率為500 ml/min，進流濃度為400 ppm，鐵粉重量為1.0 g時，求得填充床三種不同反應溫度573 K、623 K、673 K之單位鐵粉填充重量去除SO2量分別為2.9、18.0及75.6 mg - SO2 /1g - Fe，依二種可能反應計量方程式分別計算其單位重量鐵粉去除SO2量分別約為其理論去除量之0.6、3.9及16.5 %或0.6、3.7及15.4 %；而在進流率為250 ml/min，進流濃度為550 ppm，鐵粉重量為0.5 g時，流體化床四種不同反應溫度623 K、673 K、723 K、773 K之單位鐵粉填充重量去除SO2量分別為3.2、9.8、14.0及45.9 mg - SO2 /1g - Fe，依二種可能反應計量方程式計算其單位重量鐵粉去除SO2量分別約為其理論去除量之0.7、2.1、3.1及10.0%或0.7、2.0、2.9及9.4 %。顯示鐵粉去除SO2之反應為表面反應，且鐵粉在填充床比在流體化床反應器有較佳去除效果。
鐵粉去除SO2影響因子實驗結果，單位鐵粉填充重量之SO2去除量隨反應溫度增高及鐵粉量增加而提高，而隨進流率及SO2進流濃度增高而降低；反應溫度太低(573K)及鐵粉量太少(0.25 g)時，短時間內其SO2去除率即急速下降。
空床接觸時間(EBCT)與SO2去除效果間無規律相關性，而單位鐵粉填充重量之SO2去除量隨鐵粉重量/進流率 (W/Q)比及表面積/進流率(S/Q)比增大而增加，且有線性正相關性。使用過鐵粉經XRD試驗結果，其主要反應產物為FeS，Fe2O3或Fe3O4，因此我們可以推測其可能反應式為：
5Fe+2SO2=2FeS+Fe3O4
7Fe+3SO2=3FeS+2Fe2O3

關鍵字

零價鐵 ； 二氧化硫 ； 填充床 ； 流體化床

並列摘要

A novel research was conducted for the chemical reaction between sulfur dioxide (SO2) and zero valent iron (ZVI), and to confirm the feasibility of SO2 removal based on ZVI strong reducing abilities. Four different parameters: temperature(573K, 623K, 673K, 723K and 773 K), influent concentration (380, 650, 900 and 1300 ppm), flowrate(115, 150, 200, 250 ml/min) and ZVI dosages (0.25 g, 0.5, 0.75 g and 1.0 g) were tested in two different types of reactors: packed and fluidized column studies.
For the controlled temperatures of 573 K-773 K, SO2 was completely removed for temperature of 623 K-773 K, but not for 573 K. Exhaustion test was conducted for the four working temperatures and the results indicated, when the temperature was higher, the run time (before breakthrough) was also longer. Since almost complete removal was achieved before breakthrough, SO2 reductions by ZVI (as mg SO2/g ZVI) was used to identify the efficiency of the SO2 for the different operating conditions. In these studies, higher temperature, and more ZVI dosage, can all achieve higher SO2 reduction (as mg SO2/g ZVI), while the SO2 reduction was decreasing with increasing influent concentration and inflow rate.
From fluidized column studies, the empty bed contact time (EBCT) did not show meaningful correlation to the SO2 removal efficiency, since the empty bed volume of ZVI was not linearly proportional to the flowrate as it was expected. The ZVI weight /flowrate (W/Q) or ZVI surface area /flowrate(S/Q), instead of EBCT, is linearly proportional to the SO2 removal efficiency.
XRD (X-Ray Diffraction) was conducted to analyze the crystal structure and oxidation state of the reacted ZVI. Several species were determined from the spectrum: Feo(ZVI) and FeS, Fe3O4 and Fe2O3. ZVI was the most prevalent species: FeS, Fe3O4 and Fe2O3 were less. Apparently, the double bondings between sulfur and oxygen were broken first then the ZVI reacted with sulfur and oxygen, respectively. Therefore, two reactions are proposed based on the XRD analytical results:
5Fe+2SO2=2FeS+Fe3O4 (Equation 1)
7Fe+3SO2=3FeS+2Fe3O4 (Equation 2)
SO2 reductions by ZVI (mg SO2/g ZVI) for various operating conditions were varied from 2.9~75.6 and 3.2~45.9 mg SO2/g ZVI with respect to packed column and fluidized column respectively. Stoichiometrically compared to either Equation 1 or Equation 2, there was only less than 16.5 % ZVI consumed regarding theoretical ZVI usage. Thus, it can be concluded that the heterogeneous reaction was only occurred on the ZVI surface instead of bulk of the ZVI.These ZVI can be reused after regeneration since more than 84% of the ZVI were actually intact.

並列關鍵字

zero valent iron ； sulfur dioxide ； packed column ； fluidized column

參考文獻

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