燃煤鍋爐中高反應性二氧化硫吸收劑之製備

Preparation of high-reactivity absorbent for sulfur dioxide produced in a coal-fired boiler

吳奇穎(Chi-Ying Wu)

指導教授 ： 施信民

國立臺灣大學/工學院/化學工程學研究所/碩士(2004年)

https://doi.org/10.6342/NTU.2004.00548

摘要

因石油之儲量已低，燃煤發電廠已在近年來有增加的趨勢。燃煤產生的二氧化硫會造成空氣污染，進而形成酸雨，危害生態環境。減低二氧化硫之排放量遂成為環境保護之重要研究課題。目前廣受重視的方法是將含鈣之吸收劑注入燃燒爐或煙道中，與二氧化硫作用形成硫酸鈣，以降低廢氣中二氧化硫之含量。此法簡便，但卻因吸收劑之利用率太低而遭到其它程序之挑戰。吸收劑的反應性與其粒徑、結構性質以及燒結現象有關。近年來製備高反應性吸收劑成為重要的研究課題。
本研究在氫氧化鈣水溶液通入二氧化碳以產生高比表面積的多孔性碳酸鈣。實驗探討多種操作變數對產物結構性質的影響，包括Ca(OH)2濃度、CO2流量、添加劑種類及用量等。碳酸鈣對SO2之反應性則以一微分固定床測量之。
碳酸鈣比表面積隨著Ca(OH)2濃度與CO2流量增加而增加，但是Ca(OH)2濃度超過2.72 wt%、CO2流量超過2.0L/min以上則無明顯的變化，比表面積達25.7m2/g。添加介面活性劑Dispex N40(4.0vol%)與Dispex A40(6.0vol%)可提升碳酸鈣的比表面積至70~80 m2/g，添加FeCl3些為降低比表面積。
在低溫反應條件(60oC、70%RH)下，含有介面活性劑碳酸鈣的反應性較低；在900 oC高溫下，其反應性很高，但在950 oC下則因其較易燒結而導致其反應性較低，但若縮短其燒結時間，則反應性較未添加者高。

關鍵字

二氧化硫 ； 碳酸鈣 ； 氫氧化鈣 ； 反應動力學 ； 污染防治

並列摘要

The number of coal-fired power plants is increasing due to the decreasing reserve of oil. Sulfur dioxide generated by burning coal has resulted in the air pollution and acid rain problems. The reduction of SO2 emission is important to the environmental protection. One way to achieve the goal is by injection of Ca-containing sorbent into the furnace or the duct to react with SO2 to form CaSO4. This technique is simple and easy to use. However, it is challenged by other processes due to its low sorbent utilization. The sorbent reactivity is related to the particle size and the structural properties of the sorbent, as well as the sintering of CaO.
High surface area CaCO3 particles were produced by bubbling CO2 through Ca(OH)2 solution in this study. Effects of several operating variables, including Ca(OH)2 concentration, CO2 flow rate, type and amount of additive, were investigated. The reactivity of CaCO3 toward SO2 was tested in a differential fixed-bed reactor.
The specific surface area of CaCO3 increased with increasing Ca(OH)2 concentration and CO2 flow rate until 2.72wt% Ca(OH)2 and 2.0L/min of CO2,reaching 25.7m2/g. The surface area could be increased to 70~80 m2/g by adding Dispex N40(4.0vol%) and Dispex A40(6.0vol%),but it was slightly reduced by adding FeCl3.
CaCO3 samples prepared with surfactants added were less reactive toward SO2 than those without under the conditions of 60oC and 70%RH due to lower water adsorption capacity; however, they were more reactive at high temperatures( 900 oC) if the calcinations time was minimized to prevent the excessive sintering of CaO.

並列關鍵字

reaction kinetics ； calcium carbonate ； sulfur dioxide ； calcium hydroxide ； pollution control

參考文獻

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