高碱松木屑与高氯废物共水热脱碱工艺

Process for Removing Alkalis by Co-hydrothermal Treatment of High Alkaline Pine Sawdust With High Chlorinated Waste

本文以聚氯乙烯(polyvinyl chloride,PVC)和松木屑为原料,开展共水热实验,借助SEM、FTIR和ICP-OES等手段研究了松木屑中碱/碱土金属迁移特性和水热炭燃料性能。元素分析和工业分析的结果表明,温度是影响水热炭性能的最重要因素,其次是水热时间,而木屑粒径几乎无影响。温度为260℃时,碳含量保持在73.75%左右。本文研究范围内,水热条件对碱及碱土金属脱除率无明显影响,所测元素钾(K)、钠(Na)、钙(Ca)、镁(Mg)在水热炭中含量的变化顺序依次为:钙(Ca)>钾(K)>镁(Mg)>钠(Na)。温度由220℃增加至260℃时,钙(Ca)、镁(Mg)、钾(K)、钠(Na)的脱除率分别增加了1.02%、2.77%、4.10%和9.22%。与松木屑水热空白实验对比,添加PVC增强了反应体系的酸性,促进了木屑水热脱除碱/碱土金属。水热温度为260℃时,钙(Ca)、镁(Mg)、钾(K)、钠(Na)的最高脱除率由约26.59%上升到98.59%,93.17%,86.27%和85.84%。水热温度越高,半纤维素、纤维素和木质素分解度越高,生成的气体也越多,生成的水热炭的孔隙结构越发达,为碱金属的逸出提供了良好的通道。本文研究结果可为含氯有机废物和高碱固体燃料协同提质提供参考。

In this work, the PVC(polyvinyl chloride) and pine sawdust were utilized as raw materials to investigate the AAEMs behavior during the co-Hydrothermal treatment(co-HTT). The experimental parameters include the co-HTT temperature(220, 240 and 260℃), the residence time(30, 60 and 90 min), and the particle size of pine sawdust(0.22~0.49, 0.49~0.60, and 0.60~0.90 mm).The SEM and FTIR were adopted to characterize the morphological structures of the hydrochars,and the ICP-OES was used to measure the inorganic content to evaluate the AAEMs’ behavior. The results show that the co-HTT temperature was the most significant factor from the viewpoint of the hydrochar fuel performance, followed by the residence time. The particle size of the pine sawdust has little influence on the properties of hydrochar. At a temperature of 260℃, the carbon content of the hydochars was around 73.75%. In the range studied in this work, the removal efficiencies(RE) of the AAEMs varied little with the co-HTT operating conditions. The RE of Ca, Mg, K, and Na were only increased by 1.02%, 2.77%, 4.10% and 9.22%, respectively, when the temperature was increased from 220 ℃ to 260℃. The variation of AAEMs in these hydrochars followed the order as Ca> K>Mg>Na. The addition of PVC into pine sawdust enhanced the acidity of the reaction system and promoted the removal efficiency(RE) of AAEMs from pine sawdust. At a temperature of 260℃,the highest RE of Ca, Mg, K, and Na was increased from about 26.59% to 98.59%, 93.17%, 86.27%and 85.84%, respectively. Higher temperature promoted the decomposition of cellulose, heminellulose,and lignin, correspondingly improved the generation of gas products, which generated hydrochar with more pore structures providing channels for the escape of alkali metal. As a result, the RE of AAEMs was increased. This work has some referential value for the clean fuel production from organic-chlorinated wastes and high-alkali fuels by co-HTT.