Co-pyrolysis of sludge and kaolin/zeolite in a rotary kiln: Analysis of stabilizing heavy metals

• Adding kaolin/zeolite promotes the formation of stable heavy metals. • The potential ecological risk index of co-pyrolysis biochar is extremely low. • Increasing the pyrolysis temperature reduces the leaching toxicity of heavy metals. • The toxicity of biochar reduces with the increasing content of stable heavy metals. Pyrolysis is a promising technique used for treating of sewage sludge. However, the application of pyrolysis products is limited due to the presence of heavy metals. In this study, sewage sludge mixed with kaolin/zeolite was pyrolyzed in a rotary kiln, aiming to improve the immobilization of heavy metals in pyrolytic carbon. The total concentrations, speciation distributions, leaching toxicities, and potential ecological risk indices of heavy metals in pyrolysis biochar were explored to examine the effects of kaolin/zeolite and pyrolytic temperature on immobilizing heavy metals. Further, mineral composition and surface morphology of biochar were characterized by X-ray diffraction and scanning electron microscopy to reveal the potential mechanism of immobilizing heavy metals. Increasing pyrolysis temperature facilitated the stabilization of heavy metals in pyrolysis biochar. The proportions of stable heavy metals in biochar obtained at 650℃ were 54.50% (Cu), 29.73% (Zn), 79.29% (Cd), 68.17% (Pb) and 86.70% (Cr). Compared to sewage sludge, the potential contamination risk index of pyrolysis biochar obtained at 650℃ was reduced to 17.01, indicating a low ecological risk. The addition of 7% kaolin/zeolite further reduced the risk index of co-pyrolysis biochar prepared at 650℃ to 10.86/15.28. The characterization of biochar revealed that increase in the pyrolysis temperature and incorporation of additives are conducive to the formation of stable heavy metal-inorganics. This study demonstrates that the formation of stable mineral compounds containing heavy metals is the key to stabilizing heavy metals in pyrolysis biochar.     

新型水泥立窑水除尘系统及控制

介绍了一种新型的立窑水除尘系统,该系统采用适用于高温、高湿环境的新型轴流风机,处理用水可循环使用,没有二次污染,除尘效率高,粉尘排放达到标准.同时详细介绍了该系统的控制原理和控制电路的设计.     

水泥窑烟气SNCR脱硝技术喷枪的设计及应用

对脱硝技术喷枪进行了结构设计和试验分析,结果表明,该结构喷枪能够使还原剂的雾化颗粒平均直径在50μm,均匀度在85%以上,雾态氨水喷射可视距离在4 m以上;枪体采用的0Cr18Ni9耐热不锈钢能够抵抗喷枪在分解炉内的高温变形。在日产5 kt的冀东某新型干法水泥生产线烟气SNCR脱硝项目中得到了应用,脱硝效率达70%以上。     

分解炉分级燃烧降氮脱硝技术的研究与应用

低NOx高温燃烧技术与大容积分解炉系统有机结合，具有热效率高、分解炉温度分布均匀、降氮脱硝、NOx排放浓度低等特点。文章介绍了高温分级燃烧技术在水泥窑中的应用，重点分析了分级燃烧、降氮脱硝在分解炉系统中的应用原理，以及推广的价值。     

水泥窑用低氮燃烧器燃烧特性的试验研究

基于水泥生产线NO_x排放机理及控制方法,设计、研发了一种新型水泥窑用低氮燃烧器,并分析了天然气、煤制气及混合气的燃烧特性及其污染物的排放特性。结果表明:在过量空气系数α为1.2、二次风占比β为0.6时,新型低氮燃烧器燃烧天然气的效果较好,NO_x排放量为53 mg/m³,CO排放量为22 mg/m³;在相同燃烧条件下,煤制气燃烧温度及NO_x排放量比天然气高,CO排放量低于天然气;在过量空气系数α为1.2、二次风占比β为0.8时,NO_x排放量为57 mg/m³,CO排放量为6 mg/m³;天然气和煤制气掺烧时,其燃烧特性介于两者之间,且掺烧煤制气可提高天然气的燃烧速率。     

南通市钢丝绳行业污泥处置与利用技术方案研究

通过对南通市钢丝绳行业产生污泥的特征进行分析,在总结了国内外重金属污泥控制技术的基础上,结合南通市实际情况,提出了钢丝绳污泥处置方案,并进行了可行性分析.     

龙岩市水泥厂机立窑除尘设备现状调查

调查了水泥厂机立窑各类除尘设备的现状 ,结果表明 ,干法静电除尘器是目前机立窑烟尘治理的首选除尘器     

孝感华联金属制品厂窑炉烟尘治理

根据麻石水膜除尘器耐酸、耐磨、除尘效率高的特点，将其引用于华联金属制品厂窑炉，效果很好。 介绍了设计思想及设计原理及参数。     

低压脉冲除尘器(长袋式)在水泥机立窑除尘中的应用

介绍了长袋低压脉冲袋式除尘器的工作原理，比较客观详实的分析了在实际除尘过程中的前景及应用除尘效果。实践证明，袋式除尘器在水泥机立窑烟气除尘中适应性强，除尘效率可达99％以上，经济效益显著，是一种较理想的除尘设备．尤其适合在水泥行业中的应用。     

医疗废物典型组分在回转窑内的热解-气化研究

在小型回转窑上对模拟医疗废物的4种典型组分进行了批量热解-气化试验.实验结果表明,热解-气化反应物料的转化率较高（80%～100%）,基本上随热解-气化终温（FPT）的升高而升高.热解-气化反应中物料的热裂解反应在30min以内基本结束.FPT的升高,有利于挥发分的析出、减少残渣量和处置时间.从试验结果来看,第一段初级处理中采用约700℃的回转窑反应温度比较适合实现医疗垃圾的完全热解和气化.