城市污泥热解焦炭结构演化与其应用性能的关系研究

At present, Xinjiang has entried a accelerating period of the urbanization．With the rapid increase of sewage treatment plants，the disposal and the enviromental impact of municipal sludge have been paid more and more attention．Application of sewage sludge has become an important way for sludge dissposal because of its lower cost and higher efficiency．But heavy metals are the kev factor that affects the application of sewage sludge．Recently,pyrolytic technique has been applied to treatment of sewage sludge due to its less secondary pollution.Based on our early stage research work about preparation of chars from cotton stalk with microwave radiation, the pyrolysis of sewage sludge and the application of the chars would be researched.Accroding to researching on the pyrolysis process of sludge and the characters of the chars, we will analyze the influential degree of factors (pyrolysis conditions, material characteristics and activation conditions) on the surface structure formation and remove,inversion and solidification of heavy metal in the sludge,make clear the similarities and differences of structure formation and heavy metal solidification regulation between the tradition and the microwave heating process, the disclose the affection of microwave heating on the structure formation regulation,heavy metal solidification, energy and material consumptions. Based on these studies, varied structural characteristic chars would apply in pollutants adsorption and soil amelioration to reveal quantitative relationship between surface structure characters and usage capacities. At the same time the heavy metal content was analyzed to evaluate the safety of the chars. And a sludge treatment method of energy conservation and consume reduction will be found while keeping or increasing usage capacity. Though the project is performance,the practical needs of Xinjiang would be considered, special purpose adsorbents from sludge will be developed, and the problems of soil compaction in Xinjiang are expected to be partly solved.

随着新疆城镇化建设的加速，城市污水污泥排放量逐年增加，但因其中含有较多的重金属离子，使得污泥资源化困难。目前，热解技术因二次污染少的特点正逐渐应用于污泥处理领域。本项目在前期利用微波加热制备棉秆基生物焦炭的基础上，研究污泥热解过程及热解焦炭应用领域的科学问题。通过对热解过程以及污泥焦炭特性的研究，明确热解条件、原料特性、活化条件等因素对污泥焦炭表面结构形成以及污泥中重金属的迁移、转化、固化的影响，阐明两类加热方式（微波加热、电炉加热）下，污泥热解焦炭表面结构形成规及重金属固化规律的差异性，揭示微波加热对焦炭表面结构形成、重金属固化以及热解能耗的影响，分析炭表面结构与其吸附容量、土壤改良特性、重金属固化及溶出率间的内在联系，在保证焦炭环境安全性的前提下，建立节能、降耗的污泥处理方法，为开发环境友好型污泥焦炭材料奠定基础。此外，本项目的完成可为部分解决新疆土壤板结问题，提高土地的利用奠定基础。

我国污水污泥年产量大，且其中含有大量有毒有害物质，若处理处置不当将带来环境问题。因此，以污水污泥为原料，采用微波加热、电炉加热对其进行热解，研究热解条件与焦炭产率及其表面结构间的相互关系，对比分析微波与传统热解的特点，确立能耗较低、焦炭性能优良的污水污泥热解处理工艺。在此基础上，探索添加碳素调整剂对污泥焦炭结构形成的影响，考察重金属离子在污泥热解过程中转化、转移以及固化规律。最后，探讨焦炭中的重金属在水以及土壤中的溶出特性，分析焦炭应用的环境安全性。得出主要结论如下：1）热解条件会影响污泥炭的比表面积、总孔容、平均孔径、表面官能团的种类及数目，但各因素对于各参数的影响顺序各不相同，且随因素水平的改变，各参数呈现出不同的变化趋势。2）微波热解是较电炉热解更具有经济优势的热解方式，其费用为电炉热解费用的38.2%-42.5%。3）碳素调整剂的添加可以影响污泥炭的孔结构及表面结构，棉秆添加可以显著提高污泥炭的比表面积以及表面官能团的种类和数量。4）在化学活化条件下，污泥与棉秆共热解会增加炭中部分重金属的总量以及浸出量，但基于综合污染指数法分析，所有污泥-棉秆炭均属于安全型材料。5）利用磷酸活化和氢氧化钾活化法，棉秆与污泥共热解可制备符合国家木质净水用活性炭一级品标准的吸附剂，磷酸活化最优制备工艺条件为污泥含量70 %，磷酸浓度40 %，微波功率280 W，辐照时间12 min，装填量120 g；氢氧化钾活化最优制备工艺条件为污泥质量分数30 %，微波功率280 W，辐照时间24 min，KOH浓度50 %，装填量150 g。6）污泥-棉秆炭作为土壤改良剂，它的施加会促进种子的萌发以及增加土壤的持水能力、土壤淋溶液的电导率和N的含量，同时增大第二次土壤淋溶液中K与Na的含量。