以Na2S應用於NO2吸收之模廠操作參數研究

Pilot Study for Nitrogen Dioxide Absorption with Sodium Sulfide

林廣泓(Kuang-Hung Lin)

指導教授 ： 陳俊成

淡江大學/工學院/水資源及環境工程學系碩士班/碩士(2006年)

https://doi.org/10.6846/TKU.2006.00747

摘要

由於NOx是產生光化學煙霧的前驅物質又是形成酸雨的主要因素，因此氮氧化物處理技術的研發已成為必要的趨勢。然而，業界目前對NOx的處理方式大多為選擇性觸媒還原法（SCR）及選擇性非觸媒還原法（SNCR）的乾式處理法。對之前的氮氧化物控制技術而言，其處理設備大多是針對單一污染物所設計的，若要同時處理不同之污染物，則需建置另一套系統。故本研究則採用能針對多種污染物的濕式洗滌塔來對NOx進行吸收。
而且過去對Na2S水溶液吸收NO2氣體的相關研究，大多都是在實驗室中以模擬的情況所完成的，欠缺實廠操作上的控制參數與限制條件。所以，本實驗將以模廠規模之設備搭配Na2S溶液對NO2進行一系列的質傳吸收實驗，並針對入口濃度、氣體質量流率、液體質量流率、液氣比(L/G)、Na2S的濃度、pH值、氣體在洗滌塔內停留時間、氣體在洗滌塔內流速等參數尋求最佳的操作條件。之後再配合NO轉化成NO2的研究成果，以提供業界一套完整且符合經濟效益的NOx兩段式處理系統與操作參數。
本研究結果歸納如下：
（1）NO2濃度的改變，並不會對NO2去除效率造成很大的影響，故選
50（ppm）代表之。
（2）氣體質量流率設定在1944.2（kg/m2-hr），液體質量流率為
7320（kg/m2-hr）時，NO2的去除率為80％以上。當氣體質量
流率增加，液體質量流率也應相對的增加，如此一來對NO2的
吸收效果也才能夠提升。
（3）當液氣比逐漸增加，其NO2的去除率亦會顯著的增加。在液氣
比提升為2.51時，所有的pH值之去除率均達至在65%的設計範
圍之內。當Na2S（aq）的濃度為0.002 (M)，而液氣比在2.51
以上時，其吸收效果最為良好，約有80∼90％。若濃度較低者
則需提高液氣比至3.77，才會有不錯的吸收效果產生。
（4）當Na2S（aq）的濃度增加時，所能提供的S(-II)離子較多，可
與NO2進行的吸收反應的量也較多，且氣、液之間的分子碰撞
機會也相對地增加，同時質傳的反應也能夠順利進行，所以會
有較佳的NO2的去除率產生。
（5）pH值控制在鹼性（pH ＝9.0）的狀態下，其NO2的吸收效果較
佳。
（6）當氣體停留時間逐漸地增加，其NO2的去除率亦跟著提升。並
建議氣體停留時間應該要大於4.1秒，塔內氣體流速最好低於
0.45 (m/s)才有比較好的吸收效果。

關鍵字

氮氧化物 ； 洗滌塔 ； 二氧化氮 ； 硫化鈉 ； NO2去除率

並列摘要

Nitrogen oxides is the precursor for photochemical smog and acid deposition, so the research and development of the treatment technology of nitrogen oxide has already become the essential trend. However, treatment ways in NOx at present of the industry are mostly that selective catalytic reduction (SCR) and selective non-catalytic reduction (SNCR) . To before the equipment of NOx control is design to pollutant not single, if will deal with different pollutant at the same time , we will need another system of construction. So this research adopts the scrubber which can absorb of many kinds of pollutant .
It is short of the research of nitrogen dioxide
absorption with sodium sulfide solution in the past, mostly all finish with the situation that is imitated in the laboratory , the operational parameters and limiting conditions to deficient. With current pilot test result to combine with NO conversion, the study can be extend to perform a lower cost, higher NOx removal air pollution control technology for industry. The pilot experiment explores the influence of NO2 concentration,gas mass flow rate, liquid mass flow rate, L/G ratio, Na2S concentration, pH value, gas retention time, gas velocity on NO conversion. The pilot experiment concluded the following findings:
(1) NO2 concentration is not very sensitive to collecting
NO2 .So we can select 50(ppm) to be represented.
(2) The optimal range for scrubber parameters are 1944.2
（kg/m2-hr）gas mass flow rate and 7320（kg/m2-hr）
liquid mass flow rate., collecting rate of NO2 is more
than 80%. As gas mass flow rate increases, the liquid
mass flow rate increases too, and NO2 reductioncan
improve better .
(3) As the L/G ratio increases gradually, NO2 reduction
also increases apparently. When the L/G ratio improves
as 2.51, NO2 reduction of all pH value is reached
within 65% of the design ranges.The Na2S concentration
is 0.002 (M), and the L/G ratio is above 2.51,its
result of absorbing is the best, nearly have 80∼90％.
If the Na2S concentration is too low, we should
improve L/G ratio higher than 3.77 to get the better
NO2 reduction.
(4) When increases the Na2S concentration, there is more
S (- II ) ion that can offer .So we can get the better
NO2 reduction.
(5) pH value is controlled in alkaline condition (pH =9.0)
and we can have the better results of nitrogen
dioxides absorption.
(6) When the gas retention time increases gradually, the
NO2 reduction also improve. It should be greater than
and propose the gas retention time staying 4.1
seconds, and 0.45 m/s of gas velocity

並列關鍵字

nitrogen oxides ； scrubber ； nitrogen dioxide, ； sodium sulfide ； NO2 reduction

參考文獻

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