Formation mechanism of NOx precursor during organic waste pyrolysis coupled with hydrothermal pretreatment
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摘要: 以城市污泥(SS)、中药药渣(HTW)和硅藻(DT)为对象,在水平管式反应器上对比研究了水热处理前后样品在热解过程中NOx前驱物的生成特征,并结合热重(TGA)和X射线光电子能谱(XPS)表征分析了该耦合过程对NOx前驱物的影响机制。结果表明,在240 ℃下进行水热预处理能直接或间接地影响样品燃料N在不同热解阶段时的转化路径,从而在整体层面上降低NOx前驱物的释放量,例如当热解温度为900 ℃时,源于水热焦燃料N的NOx前驱物为55.0%(SS240)、48.1%(HTW240)和51.2%(DT240),比未经处理样品的NOx前驱物释放量分别少9.5%(SS)、6.0%(HTW)和15.4%(DT),但若以原料燃料N为基准,源于水热焦的NOx前驱物则比未经处理样品的NOx前驱物释放量分别少90.1%(SS)、41.9%(HTW)和59.8%(DT),并且对NH3的抑制效果高于HCN。进一步根据热失重曲线及其半焦N官能团的演变规律可以推测,水热预处理对NOx前驱物的两条影响机制,即含N官能团的脱除(对于初次反应的NH3释放)与含N官能团的稳定化(对于二次反应的HCN释放),可为废弃物的清洁利用提供理论参考。Abstract: Taking the high moisture-containing sewage sludge (SS), herbal tea waste (HTW) and diatom (DT) as the feedstock, the characteristics of NOx precursors during pyrolysis with or without hydrothermal pretreatment in a horizontal tubular reactor were compared. The formation mechanism of NOx precursors in pyrolysis coupled with hydrothermal pretreatment was also investigated by means of TGA and XPS techniques. The results show that the hydrothermal pretreatment can affect the formation pathways related to NOx precursors at different pyrolysis stages and reduce the release amount of NOx precursor on the whole level. For example, when the pyrolysis temperature is 900 ℃, the NOx precursor yield derived from the hydrothermal treated coke is 55.0% for SS240, 48.1% for HTW240 and 51.2% for DT240, which is 9.5%, 6.0% and 15.4% less than that for SS, HTW and DT untreated sample, respectively. But if calculating based on the amount of N content in feedstock, the released NOx precursor from the hydrothermal treated coke is 90.1%, 41.9% and 59.8% less than that for SS, HTW and DT untreated sample, respectively. The inhibition effect on NH3 formation is higher than that on HCN formation. Meanwhile, two influencing pathways caused by hydrothermal pretreatment were further elaborated, i.e., the removal of N functionalities that leads to a decrease in NH3 on the primary reaction and the stabilization of N functionalities that leads to a decrease in HCN on the secondary reaction.
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Key words:
- organic wastes /
- hydrothermal pretreatment /
- pyrolysis /
- NOx precursor /
- regulatory mechanism
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表 1 原料与水热焦的基本特性
Table 1 Properties of feedstock and the corresponding hydrochar
Sewage sludge Herbal tea waste Diatom SSraw SS240 HTWraw HTW240 DTraw DT240 Yield w/% - 70.27 - 53.95 - 45.77 Ultimate analysis w/% Carbon 21.57 12.65 45.08 53.18 31.92 26.27 Hydrogen 3.67 1.82 6.07 5.46 4.45 2.80 Oxygen 14.22 7.07 32.48 12.71 22.04 15.10 Nitrogen 3.43 1.16 2.72 1.79 5.22 2.74 Sulfur 0.51 0.31 0.26 0.12 1.14 0.22 Proximate analysis w/% Volatile matters 36.57 19.51 69.24 44.69 52.39 23.68 Ash 56.60 76.99 13.39 26.74 35.23 52.87 Fixed carbon 6.83 3.50 17.37 28.57 12.38 23.45 Coalification degree Atomic ratio of O/C 0.49 0.42 0.54 0.18 0.52 0.43 Atomic ratio of H/C 2.04 1.72 1.62 1.23 1.67 1.28 Fuel properties QHHV/(MJ·kg-1) 9.67 8.25 19.37 22.11 13.67 14.44 Energy density ratio 1 0.85 1 1.14 1 1.06 ERE/% - 59.91 - 61.57 - 48.33 note: HHV, higher heating value; ERE, energy recover efficiency 表 2 快速热解中挥发分的组分分析
Table 2 Volatile compositions of sample during fast pyrolysis at 800 ℃
Sewage sludge Herbal tea waste Diatom SSraw SS240 HTWraw HTW240 DTraw DT240 Organic acids /% 5.3 4.4 7.5 4.1 20.1 16.6 Aldehydes & ketones /% 3.1 1.3 16.6 10.9 2.3 1.5 Benzene & phenols /% 47.1 65.4 53.6 69.3 33.7 46.8 Furfuran derivations /% 8.1 0.0 7.1 3.3 1.0 0.0 N-related compounds /% 36.4 28.9 15.2 12.4 42.9 35.1 note: the fast pyrolysis is carried out with 104 K/min and argon atmosphere -
[1] REN Q Q, ZHAO C S. Evolution of fuel-N in gas phase during biomass pyrolysis[J]. Renewable Sustainble Energy Rev, 2015, 50:408-418. doi: 10.1016/j.rser.2015.05.043 [2] MLADENOVIĆ M, PAPRIKA M, MARINKOVIĆ A. Denitrification techniques for biomass combustion[J]. Renewable Sustainble Energy Rev, 2018, 82:3350-3364. doi: 10.1016/j.rser.2017.10.054 [3] LI J J, YANG H R, WU Y X, LV J F, YUE G X. Effects of the updated national emission regulation in china on circulating fluidized bed boilers and the solutions to meet them[J]. Environ Sci Technol, 2013, 47(12):6681-6687. doi: 10.1021/es4001888 [4] ZHAN Z, ZHUANG X Z, SONG Y P, CHANG G Z, WANG Z K, YIN X L, WANG X M, WU C Z. Formation and regulatory mechanisms of N-containing gaseous pollutants during stage-pyrolysis of agricultural biowastes[J]. J Clean Prod, 2019, 236:117706. doi: 10.1016/j.jclepro.2019.117706 [5] 詹昊, 张晓鸿, 阴秀丽, 吴创之.生物质热化学转化过程含N污染物形成研究[J].化学进展, 2016, 28(12):1880-1890. doi: 10.7536/PC160438ZHAO Hao, ZHANG Xiao-hong, YIN Xiu-li, WU Chuang-zhi. Formation of nitrogenous pollutants during biomass thermo-chemical conversion[J]. Prog Chem, 2016, 28(12):1880-1890. doi: 10.7536/PC160438 [6] CHEN H F, NAMIOKA T, YOSHIKAWA K. Characteristics of tar, NOx precursors and their absorption performance with different scrubbing solvents during the pyrolysis of sewage sludge[J]. Appl Energy, 2011, 88(12):5032-5041. doi: 10.1016/j.apenergy.2011.07.007 [7] LIU T T, GUO Y C, PENG N N, LANG Q Q, XIA Y, GAI C, LIU Z G. Nitrogen transformation among char, tar and gas during pyrolysis of sewage sludge and corresponding hydrochar[J]. J Anal Appl Pyrolsis, 2017, 126:298-306. doi: 10.1016/j.jaap.2017.05.017 [8] FENG Y H, YU T C, CHEN D Z, XU G L, WAN L, ZHANG Q, HU Y Y. Effect of hydrothermal treatment on the steam gasification behavior of sewage sludge:Reactivity and nitrogen emission[J]. Energy Fuels, 2018, 32(1):581-587. doi: 10.1021/acs.energyfuels.7b03304 [9] ZHAN H, ZHUANG X Z, SONG Y P, HUANG Y Q, LIU H C, YIN X L, WU C Z. Evolution of nitrogen functionalities in relation to NOx precursors during low-temperature pyrolysis of biowastes[J]. Fuel, 2018, 218:325-334. doi: 10.1016/j.fuel.2018.01.049 [10] CHEN H F, ZHAO P T, WANG Y, XU G W, KUNIO Y. NO Emission control during the decoupling combustion of industrial biomass wastes with a high nitrogen content[J]. Energy Fuels, 2013, 27(6):3186-3193. doi: 10.1021/ef301994q [11] ZHAN H, ZHUANG X Z, SONG Y P, YIN X L, CAO J J, SHEN Z X, WU C Z. Step pyrolysis of N-rich industrial biowastes:Regulatory mechanism of NOx precursor formation via exploring decisive reaction pathways[J]. Chem Eng J, 2018, 344:320-331. doi: 10.1016/j.cej.2018.03.099 [12] 庄修政, 黄艳琴, 阴秀丽, 吴创之.污泥水热处理制备清洁燃料的研究进展[J].化工进展, 2018, 37(1):311-318. http://d.old.wanfangdata.com.cn/Periodical/hgjz201801040ZHUANG Xiu-zheng, HUANG Yan-qin, YIN Xiu-li, WU Chuang-zhi. Research on clean solid fuel derived from sludge employing hydrothermal treatment[J]. Chem Ind Eng Prog, 2018, 37(1):311-318. http://d.old.wanfangdata.com.cn/Periodical/hgjz201801040 [13] ZHAO P T, CHEN H F, GE S F, YOSHIKAWA K. Effect of the hydrothermal pretreatment for the reduction of NO emission from sewage sludge combustion[J]. Appl Energy, 2013, 111:199-205. doi: 10.1016/j.apenergy.2013.05.029 [14] MA D C, ZHANG G Y, AREEPRASERT C, LINA G, YOSHIKAWA K. NO emission characteristics of hydrothermally pretreated antibiotic mycelial dreg combustionin a drop tube reactor[J]. Energy Procedia, 2014, 61:743-746. doi: 10.1016/j.egypro.2014.11.956 [15] MA D C, ZHANG G Y, AREEPRASERT C, LI C X, SHEN Y F, YOSHIKAWA K, XU G W. Characterization of NO emission in combustion of hydrothermally treated antibiotic mycelial residue[J]. Chem Eng J, 2016, 284:708-715. doi: 10.1016/j.cej.2015.08.149 [16] LIU Z, QUEK A, PARSHETTI G, JAIN A, SRINIVASAN M P, HOEKMAN S K, BALASUBRAMANIAN R. A study of nitrogen conversion and polycyclic aromatic hydrocarbon (PAH) emissions during hydrochar-lignite co-pyrolysis[J]. Appl Energy, 2013, 108:74-81. doi: 10.1016/j.apenergy.2013.03.012 [17] ZHAN H, ZHUANG X Z, SONG Y P, YIN X L, WU C Z. Insights into the evolution of fuel-N to NOx precursors during pyrolysis of N-rich nonlignocellulosic biomass[J]. Appl Energy, 2018, 219:20-33. doi: 10.1016/j.apenergy.2018.03.015 [18] 詹昊, 阴秀丽, 黄艳琴, 张晓鸿, 袁洪友, 谢建军, 吴创之.药渣热解过程NOx前驱物生成特征及规律研究[J].燃料化学学报, 2017, 45(3):279-288. doi: 10.3969/j.issn.0253-2409.2017.03.004ZHAN Hao, YIN Xiu-li, HUANG Yan-qin, ZHANG Xiao-hong, YUAN Hong-you, XIE Jian-jun, WU Chuang-zhi. Characteristics of NOx precursors and their formation mechanism during pyrolysis of herb residues[J]. J Fuel Chem Technol, 2017, 45(3):279-288. doi: 10.3969/j.issn.0253-2409.2017.03.004 [19] 詹昊, 林均衡, 黄艳琴, 阴秀丽, 刘华财, 袁洪友, 吴创之.抗生素菌渣热解N官能团变化特征及其与NOx前驱物关系研究[J].燃料化学学报, 2017, 45(10):1219-1229. doi: 10.3969/j.issn.0253-2409.2017.10.009ZHAN Hao, LIN Jun-heng, HUANG Yan-qin, YIN Xiu-li, LIU Hua-cai, YUAN Hong-you, WU Chuang-zhi. Evolution of nitrogen functionalities and their relation to NOx precursors during pyrolysis of antibiotic mycelia wastes[J]. J Fuel Chem Technol, 2017, 45(10):1219-1229. doi: 10.3969/j.issn.0253-2409.2017.10.009 [20] 庄修政, 詹昊, 黄艳琴, 宋艳培, 阴秀丽, 吴创之.两类药渣的水热提质效果及其燃烧特性研究[J].燃料化学学报, 2018, 46(8):940-949. doi: 10.3969/j.issn.0253-2409.2018.08.006ZHUANG Xiu-zheng, ZHAN Hao, HUANG Yan-qin, SONG Yan-pei, YIN Xiu-li, WU Chuang-zhi. Influence of hydrothermal upgrading on the fuel characteristics and combustion behavior of herb wastes[J]. J Fuel Chem Technol, 2018, 46(8):940-949. doi: 10.3969/j.issn.0253-2409.2018.08.006 [21] 张光义, 马大朝, 彭翠娜, 许光文.水热处理抗生素菌渣制备固体生物燃料[J].化工学报, 2013, 64(10):3741-3749. http://d.old.wanfangdata.com.cn/Periodical/hgxb201310035ZHANG Guang-yi, MA Da-zhao, PENG Cui-na, XU Guang-wen. Hydrothermal treatment of antibiotic mecelial dregs for solid bio-fuel preperation[J]. Chem Ind Eng Prog, 2013, 64(10):3741-3749. http://d.old.wanfangdata.com.cn/Periodical/hgxb201310035 [22] ZHUANG X Z, HUANG Y Q, SONG Y P, ZHAN H, YIN X L, WU C Z. The transformation pathways of nitrogen in sewage sludge during hydrothermal treatment[J]. Bioresour Technol, 2017, 245:463-470. doi: 10.1016/j.biortech.2017.08.195 [23] ZHUANG X Z, ZHAN H, SONG Y P, HE C, HUANG Y Q, YIN X L, WU C Z. Insights into the evolution of chemical structures in lignocellulose and non-lignocellulose biowastes during hydrothermal carbonization (HTC)[J]. Fuel, 2019, 236:960-974. doi: 10.1016/j.fuel.2018.09.019 [24] MA D C, ZHANG G Y, ZHAO P T, AREEPRASERT C, SHEN Y F, YOSHIKAWA K, XU G W. Hydrothermal treatment of antibiotic mycelial dreg:More understanding from fuel characteristics[J]. Chem Eng J, 2015, 273:147-155. doi: 10.1016/j.cej.2015.01.041 [25] WU K, GAO Y, ZHU G K, ZHU J J, YUAN Q X, CHEN Y Q, CAI M Z, FENG L. Characterization of dairy manure hydrochar and aqueous phase products generated by hydrothermal carbonization at different temperatures[J]. J Anal Appl Pyrolysis, 2017, 127:335-342. doi: 10.1016/j.jaap.2017.07.017 [26] YAO Z L, MA X Q. A new approach to transforming PVC waste into energy via combined hydrothermal carbonization and fast pyrolysis[J]. Energy, 2017, 141:1156-1165. doi: 10.1016/j.energy.2017.10.008 [27] TIAN K, LIU W J, QIAN T T, JIANG H, YU H Q. Investigation on the evolution of N-containing organic compounds during pyrolysis of sewage sludge[J]. Environ Sci Technol, 2014, 48(18):10888-10896. doi: 10.1021/es5022137 [28] LI J, WANG Z Y, YANG X, HU L, LIU Y W, WANG C X. Evaluate the pyrolysis pathway of glycine and glycylglycine by TG-FTIR[J]. J Anal Appl Pyrolysis, 2007, 80(1):247-253. doi: 10.1016/j.jaap.2007.03.001