基于生物质焦油还原的铬渣解毒机理与动力学规律研究

发布时间：2018-05-31 19:00

  本文选题：生物质焦油 + 复合球团　； 参考：《青岛理工大学》2015年硕士论文

【摘要】：铬渣污染是当今对环境威胁最大的难题之一,我国现存铬渣超过6×106t并逐年累加,由于堆存方式缺乏管理、处理技术落后等原因,铬渣析出的Cr(VI)对人类居住地、水源、大气形成了巨大的安全隐患。针对目前铬渣无害化处理技术的优缺点,结合生物质资源储量丰富、易获取和可再生的特点,本研究提出生物质气化副产品—生物质焦油用于铬渣解毒的新途径,将二者混合制成复合球团进行热解还原实验,促进Cr(VI)向Cr(III)的形态转化,实现“以废治废”,并对该焦油热解解毒机理与参数优化匹配展开研究,为后续生物质焦油在铬渣无害化处理领域使的应用提供理论依据和技术支持。首先考察了热解时间,温度,铬渣与焦油当量比,球团粒径,铬渣粒径等若干因素对铬渣中Cr(VI)还原度的影响;然后通过正交实验得出铬渣还原的最佳工况;最后结合实验数据,对还原过程进行了热力学与动力学机理研究,得出结论如下:1.球团粒径对Cr(VI)还原度的影响最为显著,结果表明:直径2.5mm的球团有利于提高还原铬产品的质量,Cr(VI)还原度最高为93.12%;还原度随热解温度增加先提高后降低,温度400℃下铬渣还原度最高;还原度随热解时间的增加先提升后缓慢下降,考虑能耗成本,还原时间以10min为宜;增加生物质焦油的用量能够提高Cr(VI)还原度,但焦油过量会导致球团质量和还原度的下降,球团中铬渣与焦油当量比最佳值为2.29:1;铬渣粒径越小对还原反应越有利。通过正交实验得出,焦油热解还原铬渣的最佳工况为:球团烘干时间40min,热解温度400℃,热解时间10min,铬渣与焦油当量比2.29:1,铬渣粒径为0.074mm,球团粒径为2.5mm。2.生物质焦油还原铬渣的反应属于一级反应,反应的活化能为17298.94J·mol-1。在反应温度573.15K-773.15K范围内,生物质焦油还原铬渣的过程中吉布斯自由焓为极大的负值,反应容易发生;反应平衡常数最大为8.93×10101,表明该反应能够进行的很彻底;铬渣还原以焦油裂解产生的C还原Cr(VI)的固-固反应形式为主。
[Abstract]:The pollution of chromium slag is one of the most dangerous problems to the environment today. The existing chromium slag in our country is more than 6 脳 106 tons and accumulated year by year. Due to the lack of management of storage mode and backward treatment technology, chromium slag precipitated from chromium slag has great influence on human habitation and water resources. The atmosphere poses a huge security hazard. In view of the advantages and disadvantages of the current harmless treatment technology of chromium slag and the characteristics of rich, easy to obtain and renewable biomass resources, a new way of detoxification of chromium residue by biomass gasification by-product, biomass tar, was put forward in this study. The pyrolysis and reduction experiments of the composite pellets were carried out to promote the morphological transformation of CrVI to CrHIII, and to realize "treating waste with waste". The mechanism of pyrolysis and detoxification of the tar was studied, and the optimum matching of parameters was also studied. It provides theoretical basis and technical support for the application of biomass tar in the field of harmless treatment of chromium slag. The effects of several factors, such as pyrolysis time, temperature, the ratio of chromium slag to coke oil equivalent, pellet diameter and chromium slag particle size, on the reduction degree of Cr-VI in chromium slag were investigated, and the optimum condition of chromium slag reduction was obtained by orthogonal experiment. The thermodynamic and kinetic mechanism of the reduction process has been studied. The conclusion is as follows: 1. The effect of pellet diameter on the reduction degree of CrVI was most significant. The results showed that the pellets with diameter 2.5mm were beneficial to the improvement of the quality of Cr products and the reduction degree was 93.12%, and the reduction degree increased first and then decreased with the increase of pyrolysis temperature. The reduction degree of chromium slag was the highest at 400 鈩，

本文编号：1960938