Preparation and regeneration performance of modified semi-carbon for flue gas SO2 adsorbent
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摘要: 利用活性炭(焦)等吸附劑將煙氣中的污染物分離出來是一種有效的煙氣治理與資源化方式。蘭炭作為一種廉價半焦碳素材料,是一種有潛力代替現有商用活性焦的多孔材料。本文采用陜西蘭炭作為研究對象,研究炭化時間、炭化溫度、黏結劑添加量等改性工藝對所制備的吸附劑性能的影響,考察了微觀形貌變化,利用X射線光電子能譜(XPS)探究在吸附解吸過程中的表面官能團的變化。結果表明,炭化溫度對耐磨強度、耐壓強度指標影響顯著,炭化時間對飽和脫硫值和穿透脫硫值影響顯著;在煤焦油添加比例50%,700 ℃炭化20 min,900 ℃活化60 min條件下制得改性蘭炭參數為:耐磨強度95.81%,抗壓強度536.1 N·cm?1,每克蘭炭飽和脫硫值45.71 mg,每克蘭炭穿透脫硫值23.45 mg;經歷多次吸脫附過程第一次失活時,表面被大面積刻蝕,孔隙與小顆粒增多。蘭炭吸附劑失活后可以通過二次活化的方式提高其吸附性能,但衰減速度比新改性蘭炭要快。二次失活后,在酸蝕刻、水蒸氣擴孔等共同作用下致使骨架結構過度燒蝕而坍塌;改性蘭炭表面含氧基團的量和構成比例會影響吸附性能。含氧與含碳基團的比值與吸附性能相對應,含氧基團比例越高,吸附性能越差。二次活化再生改變了各含氧基團所占比例,令C=O顯著下降,O?C=O顯著增加,C?O變化不大。O?C=O官能團盡管含氧,但可能對吸附抑制作用不顯著。本研究將為工業煙氣治理提供一種新型吸附劑的制備方法,同時也為蘭炭表面改性以及二氧化硫吸附解吸機制的研究提供參考。Abstract: The use of adsorbents such as activated coke to separate pollutants from flue gas is an effective flue gas treatment method. As a cheap carbon material, semi-carbon is a potential porous alternative material to the existing commercial activated coke. In this work, the effects of the carbonization time, carbonization temperature, and binder addition on the properties of prepared adsorbents from Shanxi semi-coke were studied. The microstructure changes were investigated, and the changes in the surface functional groups in the adsorption and desorption process were explored via X-ray photoelectron spectroscopy (XPS). The results show that the carbonization temperature has a significant effect on the wear resistance and compressive strength index, and the carbonization time has a significant effect on the saturated desulfurization value and the breakthrough desulfurization value. In addition, under the conditions of 50% coal tar addition ratio, 700 ℃ carbonization for 20 min, and 900 ℃ activation for 60 min, the modified semi-coke parameters were as follows: abrasion resistance 95.81%, compressive strength 536.1 N·cm?1, saturated desulfurization value per g of semi-carbon is 45.71 mg, and breakthrough desulfurization value per g of semi-carbon is 23.45 mg. When the first failure occurred in the adsorbents after 10 thermal regeneration processes, the activated carbon surface was etched over a large area with severe changes in the surface morphology under the above conditions. Some large granular activated carbons were etched and pulverized into small particles. The activated carbon surface structure was also etched out of pores, which may be caused by the C consumption resulting from the interaction of C and H2SO4. The results also show that the secondary activation could increase the adsorption capacity in a short time, but the activated carbon performance degradation is also significant. The amount and composition ratio of the oxygen-containing groups on the surface of the modified semi-coke affected the adsorption performance. The ratio of oxygen to carbon groups corresponded to the adsorption performance: the higher the proportion of oxygen-containing groups, the worse the adsorption performance. The proportion of oxygen-containing groups was changed by the second activation regeneration, and C=O decreased significantly, O?C=O increased significantly, while C?O changed slightly. Although the O?C=O functional group contains oxygen, it may not significantly inhibit adsorption. This study provides a new adsorbent-preparation method for industrial flue gas treatment and also provides a reference for the research on the surface modification of semi-coke and the adsorption and desorption mechanisms of sulfur dioxide.
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Key words:
- semi-coke /
- adsorbents /
- flue gas purification /
- regeneration /
- activation
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圖 3 吸附脫附前后、二次活化及吸附脫附后掃描電鏡圖。(a)新鮮改性蘭炭(LAC);(b)一次失活蘭炭(LAC-10);(c)二次活化后蘭炭(LAC-ZHH);(d)二次失活蘭炭(LAC-ZHH-5)
Figure 3. SEM micrographs of semi-coke in different cycles: (a) fresh modified semi-coke (LAC); (b) once deactivated semi-coke (LAC-10); (c) secondary activated semi-coke (LAC-ZHH); (d) secondary deactivated semi-coke (LAC-ZHH-5)
圖 5 改性蘭炭再生前后X射線光電子能譜圖。(a)新鮮改性蘭炭(LAC);(b)一次失活蘭炭(LAC-10);(c)二次活化后蘭炭(LAC-ZHH);(d)二次失活蘭炭(LAC-ZHH-5)
Figure 5. XPS spectra of semi-coke in different cycles: (a) fresh modified semi-coke (LAC); (b) primary deactivated semi-coke (LAC-10); (c) secondary activated semi-coke (LAC-ZHH); (d) secondary deactivation of semi-coke (LAC-ZHH-5)
表 1 蘭炭原料特性分析結果
Table 1. Analysis results of raw material characteristics of semi-coke
Samples Moisture /% Ash /% Volatile matter and fixed carbon in ash Pore size/nm Specific surface area/(m2·g?1) Specific pore volume/(cm3·g?1) Volatile matter /% Fixed carbon /% semi-coke 8.76 11.73 10.49 89.51 2.367 307.983 0.1710 表 2 正交實驗結果
Table 2. Results of three-factor orthogonal experiment
Number Coal tar
ratio /%Carbonization
time /minCarbonization
temperature /℃Wear-resisting /
%Compressive strength /
(N·cm?1)Saturated desulfurization value per g semi-coke /mg Penetration desulfurization value per g semi-coke /mg 1 30 30 650 94.72 416.9 8.33 4.94 2 20 30 750 95.40 393.3 8.14 4.72 3 40 30 700 94.55 301.0 19.96 9.10 4 30 20 750 96.13 354.1 10.69 5.83 5 20 20 700 96.89 322.5 9.05 5.03 6 40 20 650 95.41 483.7 17.98 8.21 7 30 10 700 96.09 686.1 23.85 9.73 8 20 10 650 95.55 530.7 9.57 5.68 9 40 10 750 96.03 431.2 9.26 5.27 表 3 活化溫度和時間對活化性能的影響
Table 3. Effect of temperature and activation time on activation property
Influence factor Index Wear-resisting/% Compressive strength/
(N·cm?1)Saturated desulfurization value per g semi-coke /mg Penetration desulfurization value per g semi-coke /mg Activation temperature 860 ℃ 95.85 436.8 45.98 20.33 880 ℃ 96.19 370.7 34.50 18.71 900 ℃ 95.81 536.1 45.71 23.45 920 ℃ 95.35 355.0 44.68 19.35 Activation time 20 min 94.69 480.4 32.74 14.07 40 min 94.63 546.6 27.93 12.83 60 min 95.70 548.3 34.71 16.45 80 min 94.78 412.0 22.84 10.82 259luxu-164 -
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