废弃物协同处置过程中重金属行为的热力学模拟

发布时间：2019-01-03 15:19

【摘要】：近年来在我国的经济快速发展,人们消费能力攀升的同时也带来大量消费过后产生的废弃物难以处理的难题,废弃物在焚烧后产生的包含大量有害物质与重金属的飞灰又会带来新的环境问题,针对于飞灰的理化特性,研究表明利用水泥回转窑的高温工况来去除有害物质的同时将大部分重金属固定在熟料中是一种可行有效的处置手段。本文对协同处置过程中重金属As、Cd、Sb、Pb的行为进行热力学模拟,并结合相关文献资料与实验室煅烧条件和实际工业生产监测下重金属物质的流向进行对比,发现流向的不同导致最终固定率存在较大差异。通过热力学模拟与实验室煅烧数据对比,发现两者比较吻合,以上几种重金属的固定率分别约为78%、42%、53%、5%,但与水泥厂现场实验监测数据偏差较大,实际工业生产中90%以上的重金属固留于熟料中,排放进入大气的重金属小于0.01~1%。实际生产中窑灰量占到了生料总量的15%左右,窑灰中包含了大量的高挥发率重金属,如Pb、Cd,利用简化窑灰循环模型模拟窑灰重新入窑的工况,得出结果表明窑灰循环对高挥发率重金属的固定有明显作用,在经历多个循环后,挥发率较高的重金属的固定率逐渐增加并最终趋于稳定。在循环过程的计算中选择4个梯度的不同比例的焚烧飞灰替代率,分别为1%、5%、10%和20%,对窑灰和熟料中重金属浓度的变化进行计算,循环稳定状态下不同的替代率对As在窑灰与熟料中的浓度影响不大,Cd、Sb、Pb的在窑灰与熟料中的变化十分明显。在非稳定状态下设定窑灰循环率为0.4与1,发现重金属在熟料中的固定率呈明显的曲线增加趋势,循环率越高,重金属原本的挥发率越高,达到稳定时经历的循环越多,曲线的趋势也越明显,尤其对Cd与Pb更是如此,表明挥发率高的重金属会附着在窑灰上经过多次循环最终固定在熟料中。
[Abstract]:In recent years, with the rapid economic development of our country, people's consumption power has increased, and at the same time, it has also brought about the difficult problem of disposal of a large amount of waste produced after consumption. After incineration, the fly ash, which contains a lot of harmful substances and heavy metals, will bring new environmental problems, aiming at the physicochemical properties of Yu Fei ash. The study shows that it is a feasible and effective method to remove harmful substances and immobilize most heavy metals in clinker by using the high temperature condition of cement rotary kiln. In this paper, the behavior of heavy metal As,Cd,Sb,Pb in the process of synergistic disposal was simulated by thermodynamics, and the results were compared with the calcination conditions in laboratory and the flow direction of heavy metals under actual industrial production monitoring. It is found that the difference of flow direction leads to great difference in the final fixed rate. Through the comparison between thermodynamic simulation and laboratory calcination data, it is found that the above two kinds of heavy metals are in good agreement with each other. The fixed rates of the above heavy metals are about 78% and 42% and 53% respectively, but there is a big deviation from the field monitoring data of cement plant. More than 90% of the heavy metals in the industrial production remain in the clinker, and the heavy metals discharged into the atmosphere are less than 0.01kW. In actual production, the kiln ash accounts for about 15% of the total raw material, and the kiln ash contains a large number of heavy metals with high volatilization rate. For example, Pb,Cd, uses a simplified kiln ash circulation model to simulate the operating conditions of kiln ash re-entering the kiln. The results show that the kiln ash cycle has an obvious effect on the fixation of heavy metals with high volatilization rate. After several cycles, the fixed rate of heavy metals with higher volatilization rate gradually increases and eventually tends to stabilize. In the calculation of the cycle process, four different proportions of incineration fly ash substitution rates of 1% and 20% were chosen to calculate the change of heavy metal concentration in kiln ash and clinker. The concentration of As in kiln ash and clinker is not affected by different substitution rate under stable cycle condition, but the change of Cd,Sb,Pb in kiln ash and clinker is very obvious. The fixed rate of heavy metals in clinker increased obviously, the higher the cycle rate was, the higher the volatilization rate of heavy metals was, and the more the cycle was achieved, the higher the cycle was when the kiln ash circulation rate was 0.4 and 1, respectively, in the unstable state, the fixed rate of heavy metals in clinker increased obviously. The trend of the curve is more obvious, especially for Cd and Pb, which indicates that heavy metals with high volatilization rate will be attached to kiln ash after many cycles and finally fixed in clinker.
【学位授予单位】：沈阳航空航天大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：X70

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