【作者】 黄河洵；

【导师】 陈汉平；

【作者基本信息】 华中科技大学 ， 能源与环境工程， 2012， 博士

【摘要】 随着污水处理厂建设进程的加快,我国市政污泥规模逐年增加,急需减量化和资源化处理。鉴于目前污泥热处理技术存在的效率低、能耗高的不足,本文以基于微波诱导的市政污泥干化和低温热解技术作为研究内容,并针对污泥处理过程中其它关键技术开展了实验和模拟研究。考察了温度、微波破解对市政污泥干燥特性的影响。研究表明：干燥温度越高,污泥干燥的速率就越快。当干燥温度从70℃上升到160℃时,相对应的最大干燥速率从0.005 g·(g·min)-1变化到0.060 g·(g·min)-1。微波诱导污泥相对原始污泥容易干化。在实验条件下,微波诱导污泥干化时间比普通污泥最大可缩短近30%。微波辐射能够大幅度提高市政污泥的扩散系数,在辐射剂量15w/g,60s、90s、180s条件下,相对原始样提高了228%、295%、388%；在20w/g、60s辐射条件下,污泥的有效扩散系数提高了293%。经Fick定律计算得出同等温度条件下,市政污泥的扩散系数比造纸污泥大3个数量级。利用Arrhenius等式对实验数据计算,市政污泥的平均活化能为37kJ/mol。市政污泥的组分和结构与造纸污泥存在较大差异,在相同热力条件下的干化过程,市政污泥比造纸污泥吸热更多,能耗更高。通过最佳拟合度选择,筛选出WeiBull模型相比其他动力学模型能更好地模拟污泥干燥过程。通过对不同污水处理厂的两种污泥开展TG-DSC实验研究,获得污泥热解的温度—失重数据,利用Coats-Redfern积分法计算得到热分解反应的表观活化能、反应级数及频率因子,其中20K/min升温速率下,热解反应的活化能分别为45 kJ/(mol·k)、41 kJ/(mol·k)。采用Malek寻优法在常用的机理函数中找出最慨然函数,证明污泥热解是以三维扩散反应为主的多级反应。利用低剂量微波的诱导作用,了解其在传统热源热解过程中提高产率和节能效果。通过TG-DSC实验,研究微波辐射对污泥热解特性的影响,与污泥—生物质混合热解特性作对比,并利用Coats-Redfern积分法计算出污泥热分解反应的表观活化能、反应级数及频率因子。实验发现在辐射剂量为10、20、25 w/g辐照剂量和10K/min升温速率的条件下,污泥TG实验的失重率分别提高了4.6%、5.7%和11.6%；热解反应的活化能分别降低了19.2、2.6、12.7kJ/(mol·k),平均降低了24%,反应级数略有变化。10K/min升温速率下,添加5%木屑和麦秆提高污泥热解失重率,具有促进作用。通过污泥固定床热解实验,利用红外分析仪、气相色谱-质谱仪等分析手段,定性地分析微波破解对污泥热解反应的促进作用。污泥与微波破解污泥对比实验发现,不同终温下的三态产物产率的变化表明后者热解难度降低,深度得到加强。GC-MS分析发现,污泥热解生物油中多以单环芳香化合物和含氮芳香化合物为主,而后者的热解生物油成分发生了较大改变,含氮芳香化合物含量增加；以400℃终温为例,胺和酮的含量分别提高了152%和118%。实验还发现微波破解污泥在较低终温下气体产率更高,而最大产率没有提高。FTIR光谱对比分析显示,微波作用使热解残渣中烷烃、烯烃、醇、酮有机物含量降低。通过市政污泥粘度测量实验,得到污泥剪切速率与剪切应力关系数据,并且观察到剪切稀化现象；运用分段拟合方法求解出初始屈服应力和临界剪切速率,从而得到全范围污泥流变曲线。在此基础上,建立污泥管流模型并完成计算,计算结果与参考文献中经验公式和实验结果接近。且可知管径、流速以及流动指数对管道流动的影响显著。入口流速不变的条件下,减小流动管径33%,驱动压力增大了152.1%；管径不变条件下,提高入口流速10倍,驱动压力增大了11倍；保持管径和入口流速条件不变,增大流动指数10倍,驱动压力减少了20.2%。通过Aermod、K-ε和K-ω-sst湍流模型对有害气体扩散污染情况的模拟预测。Aermod结果显示最远厂界以外600米范围浓度超过污水厂排放国家一级标准,但是满足二级标准。对比研究发现,相同污染源排放条件下,采用高斯扩散模型为核心的AERMOD模型计算结果比K-ε模型计算浓度值偏大；K-ω-sst模型与K-ε模型计算结果对比,前者的污染物扩散速度更快。更多还原

【Abstract】 With the acceleration of the construction of wastewater treatment plant, the scale of municipal sludge has been increasing year after year. Reduction and resource treatment technologies are need. In view of the deficiency of the current sludge treatment technology on drying efficiency and pyrolysis energy consumption, this paper focused on the drying and low-temperature pyrolysis technology based on microwave inducement. Experimental research and numerical simulation are carried out on the key technology for sludge treatment.Through the municipal sludge drying experiments, the effects of temperature and microwave inducement on the drying characteristics of the sludge are considered. The results show that the higher the drying temperature, the faster the rate of sludge drying. When the drying temperature increases from 70℃to 160℃, the corresponding maximum drying rate changes from 0.005 g·(g·min)-1 to 0.060 g·(g·min)-1. Under the experimental conditions, the time of microwave-induced sludge drying can be reduced by nearly 30% compared with original sludge. The microwave-induced sludge drying is relatively easier than primitive sludge drying. Microwave radiation can significantly improve the diffusion coefficient of municipal sludge. The diffusion coefficient increases by 228%,295%,388% than the original sample under irradiation time 60s,90s,180s with 15 w/g radiation dose; and increases by 293% under irradiation time 60s with 20 w/g radiation dose. Calculated by Fick’s law under the same temperature, the diffusion coefficient of the municipal sludge is three orders of magnitude bigger than that of paper mill sludge. Processing the experimental data with the Arrhenius equations, the average activation energy of the municipal sludge is 37 kJ/mol. There is a big difference of the composition and structure between the municipal sludge and paper mill sludge. Under the same thermal conditions, the drying process of municipal sludge absorbs more heat and consumes more energy than that of paper mill sludge. Through the best fit selection, it is found that the WeiBull model is the best to simulate the sludge drying process compared to other dynamic models.A TG-DSC experiment was designed to observe the pyrolysis characteristics of sludge from two wastewater treatment plant. Coats-Redfern method was used to carry out dynamics calculation concerning pyrolysis of the sludge. When the heating rate is 20K/min, the mean active energy were 45kJ/(mol-k) and 41kJ/(mol·k). Malek optimization method was used to find the most generously function in the mechanism function, and proof of sludge pyrolysis is mainly in accordance with three-dimensional diffusion reaction.In order to understand the effect of low dose microwave radiation on traditional pyrolysis to improve productivity and energy saving effect, TG-DSC experiments were designed to observe the characteristic of sludge treated with various doses of microwave radiation, and compared with the mixture of sludge and biomass pyrolysis characteristics. Coats-Redfern integral method was used to calculate the apparent activation energy, the reaction order and frequency factor of the sludge thermal decomposition reaction. The experiments showed that the reaction depth was improved by the microwave radiation. Microwave-induced sludge samples were treated with the dense of 10 (w/g),20 (w/g) and 25 (w/g) in 10K/min heating rate conditions. And the reductions of mean active energy were 19.2 kJ/(mol·K),2.6 kJ/(mol·K) and 12.7 kJ/(mol·K), an average scale of 24%. On the other hand, the mass-loss rates were increased by a range of 4.6%,5.7% and 11.6%. In lOK/min heating rate conditions, the microwave radiation had slight impact on the reaction rank in the experiments. It was improved that adding 5% of wheat stalk or wood chips could give a boost to the pyrolysis.During the experiments of fixed-bed pyrolysis of sludge, the effect of microwave cracking to the pyrolysis of sludge was analyzed qualitatively through spectrometry and gas chromatography-mass spectrometry analysis and so on. Through comparing the productivity of the tri-state product from the fixed-bed pyrolysis experiments and microwave cracking of the sludge under different ultimate temperature, it was found that the pyrolysis in microwave cracking was easier to proceed and the reaction intensity was strengthened. GC-MS analysis indicated that the bio-oil derived from sludge pyrolysis was dominated by single-ring aromatic compounds and nitrogen-containing aromatic compounds. By contrast, the content of nitrogen-containing aromatic compounds increased in the product of the sludge by microwave cracking. For example, the content of amine and ketone had increased by 152 and 118% respectively. It was also found that the yield of gas was higher under lower final temperature in the pyrolysis of sludge by microwave cracking, but the maximum productivity could not be promoted. The contrast analysis of FTIR spectra indicated that the microwave reduced the contents of organic compounds such as alkanes, olefins, alcohols and ketones in the pyrolysis residue.By measuring the viscosity of municipal sludge, the relationship data of the shear rate and shear stress of sludge were obtained, and the shear-thinning phenomenon was observed. The initial yield stress and critical shear rate were simultaneously solved by piecewise fitting method, and then a full range of sludge flow curve was gained. The results, which numerical simulation of pipe flow sludge through establishing a simplified model, were close to the empirical formula and experimental results of references. And it is found that diameter, flow rate and flow index have significant effects on the pipeline flow. When other conditions remain unchanged, reducing the flow diameter of 33% can lead driving pressure to increase 152.1%, and increasing the flow rate 10 times can lead driving pressure to increase 11 times, as well as increasing the flow index 10 times can lead driving pressure to decrease 20.2%.The Aermod model, K-εmodel and K-ω-sst model were used to simulation and prediction of harmful gas diffusion and pollution. The result of Aermod model showed the most far beyond 600 meters factory boundary concentration exceeded the sewage plant emission standards at the national level, but to meet two criteria. Contrast research discovery, the same source of pollution discharge conditions, calculation using the Gaussian diffusion model as the core of the AERMOD model results than the K-εmodel calculates the value is too large; K-ω-sst model calculation results with the K-εmodel, the former dispersion of pollutants faster.更多还原