摘要
针对目前有机污染土壤直接热脱附装备在处理高含水率土壤时存在的高能耗问题,提出利用系统余热对土壤进行预干燥的方法以降低土壤含水率.以多环芳烃污染土壤为对象,采用非等温干燥特性测试、污染物析出测试以及转筒式干化机干燥特性实验,对土壤干燥过程与污染物析出特性进行研究.结果表明:(1)土壤非等温干燥过程分为升速和降速干燥两个阶段,处于升速阶段时土壤的干燥效果较好.通过实验获得了5、10、15和20℃/min升温速率下的临界温度,发现升温速率为5℃/min时,临界温度和土壤含水率均为最低,分别为66.7℃和2.57%,即低升温速率时土壤的干燥效果最好,但干化时间较长,影响土壤处理量.(2)干化机转速显著影响土壤停留时间,转速越高,停留时间越短,土壤处理量越大.干化机转速为1、2和3 r/min时,土壤出口温度分别为107.7、103.9和101.9℃,均超过临界温度,由于干化机筒内扬料板的强扰动作用,3种转速下土壤出口含水率均较低,与非等温干燥测试结果吻合较好.(3)土壤初始含水率为12.10%、16.05%和24.03%时,出口土壤含水率分别为0.23%、0.27%和0.22%,干化机能满足宽范围初始含水率土壤的干燥效果.(4)由于多环芳烃污染物沸点较高,土壤干燥过程中不易析出此类污染物.(5)经传热计算,对于初始含水率为12.10%~24.03%的土壤,其干化机体积传热系数为89~98 W/(m^(3)·℃).研究显示,使用转筒式干化机干燥多环芳烃污染土壤,可以大幅降低土壤的含水率,减少热脱附能耗,同时,干燥过程不易析出污染物.上述研究结果可为转筒式干化机在污染土壤干燥领域中的应用提供理论和设计指导.
In order to solve the problem of high energy consumption in direct thermal desorption treatment of organic contaminated soil with high moisture content,this study proposes utilizing the waste heat of the treatment process for soil pre-drying to reduce moisture content.This research focuses on soil contaminated with polycyclic aromatic hydrocarbons(PAHs)and employs non-isothermal drying characteristic tests,pollutant precipitation tests,and rotary drum dryer drying characteristic experiments to investigate the soil drying process and pollutant precipitation characteristics.The results reveal that:(1)The non-isothermal drying process includes two stages:acceleration and deceleration drying.The critical temperatures were obtained under heating rates of 5,10,15 and 20℃/min.At a heating rate of 5℃/min,the critical temperature and soil moisture content were the lowest,at 66.7℃ and 2.57%,respectively.This suggests that the optimal soil drying is achieved at low heating rates.However,this increases the drying time,(2)Consequently affecting the soil treatment capacity.The rotation speed of the dryer significantly influences soil retention time.As rotation speed increases,retention time decreases,resulting in larger soil treatment capacities.At rotation speeds of 1,2 and 3 r/min,the outlet temperatures of the soil are 107.7,103.9 and 101.9℃,respectively,all surpassing the critical temperature.Due to the strong disturbance caused by the lifting plates within the dryer drum,the outlet moisture content of the soil remains relatively low across all three rotation speeds,aligning well with nonisothermal drying test results.(3)When initial soil moisture content is 12.10%,16.05% and 24.03%,the outlet soil moisture content is 0.23%,0.27% and 0.22%,respectively,indicating that the dryer can achieve satisfactory drying results over a wide range of initial moisture content.(4)Due to the high boiling points of PAH pollutants,they are not easily precipitated during the soil drying process.(5)According to the heat transfer calculation,when the initial soil moisture content ranges from 12.10% to 24.03%,the volumetric heat transfer coefficient of the dryer is between 89 and 98 W/(m^(3)·℃).This study demonstrates that utilizing a rotary drum dryer to dry PAHcontaminated soil can significantly reduce soil moisture content,decrease thermal desorption energy consumption,and the drying process is not easy to precipitate pollutants.These findings can provide theoretical and design guidance for the application of rotary drum dryers in contaminated soil drying.
作者
周志毅
柴瑞
黄震威
吴昊
王进卿
毛伟洋
詹明秀
徐旭
池作和
焦文涛
ZHOU Zhiyi;CHAI Rui;HUANG Zhenwei;WU Hao;WANG Jinqing;MAO Weiyang;ZHAN Mingxiu;XU Xu;CHI Zuohe;JIAO Wentao(School of Metrology and Measurement Engineering,China Jiliang University,Hangzhou 310018,China;State Key Laboratory of Urban and Regional Research,Research Center for Eco-Environmental Sciences,Chinese Academy of Sciences,Beijing 100085,China)
出处
《环境科学研究》
CAS
CSCD
北大核心
2023年第8期1577-1585,共9页
Research of Environmental Sciences
基金
河北省省级科技计划项目(No.21283802Z)
国家重点研发计划项目(No.2018YFC1802102)。
关键词
多环芳烃
有机污染土壤
干燥
转筒干化机
体积传热系数
污染物析出
polycyclic aromatic hydrocarbons
organic contaminated soil
drying
rotary drum dryer
volumetric heat transfer
contaminant release
