颗粒特性对超重力湿法除尘性能的影响

工业锅炉粉尘成分复杂,颗粒物性差别很大,若采用常规除尘器,无法达到高效脱除。超重力旋转填料床是一种新型的除尘设备,能耗低,除尘效率较高。为探究粉尘颗粒物性对超重力湿法除尘性能的影响,选取吹风气锅炉粉尘和生物质锅炉粉尘两种工业锅炉粉尘,以错流旋转填料床为除尘设备,进行了除尘实验。实验分别测定了粉尘颗粒的粒径、有效密度和润湿性,并采用单因素实验方法,考察了粉尘脱除效率随超重力因子、气量和液量的变化规律。研究结果表明:从粉尘物性角度分析,两种粉尘差异较大,吹风气锅炉粉尘更适用于湿法除尘技术,相应的,在相同的操作条件下,吹风气锅炉粉尘的脱除效率高于生物质锅炉粉尘。但在各自的最适宜操作条件下,两者的脱除效率分别可达91.48%、90.23%。可见,超重力湿法除尘技术受粉尘颗粒特性的影响较小,能够高效脱除工业锅炉粉尘,应用前景广阔。     

超重力液相沉淀法制备纳米铁酸钴

针对磁力搅拌器制备纳米材料时存在粒径分布宽、分散不均匀的问题,采用撞击流-旋转填料床结合化学共沉淀法,以Fe（NO₃）₃·9H₂O、Co（NO₃）₂·6H₂O、NaOH为原料制备CoFe₂O₄纳米颗粒。研究了转速、液体流量、NaOH浓度以及晶化时间对CoFe₂O₄纳米颗粒粒径的影响;并与磁力搅拌器制备的CoFe₂O₄纳米颗粒在磁性能方面进行了对比。采用X射线衍射仪（XRD）、傅里叶红外光谱仪（FTIR）、透射电镜（TEM）、纳米粒度仪及振动样品磁强计（VSM）对产物的粒径形貌及磁性能进行表征。结果表明：CoFe₂O₄纳米颗粒的粒径随转速、液体流量和NaOH浓度的增加而减小,但随晶化时间的增加而增大。最佳工艺条件为：转速900r/min,液体流量60L/h,NaOH浓度3mol/L,晶化时间6h。此条件下制备的CoFe₂O₄纳米颗粒的粒径约为20nm,饱和磁化强度为75.43emu/g,较磁力搅拌器提高40%。     

液体初始分散对错流旋转填料床传质性能的影响

为提高错流床传质性能,从液体初始分散的角度出发,设计了四种不同结构的中心管式液体分布器,喷液孔数量分别为4,6,8,10.以NaOH-CO_2为实验体系,测定了不同超重力因子、液量和气量下的有效传质比表面积a_e和液相体积传质系数k_la_e.结果表明:随各操作参数的增大,a_e和k_la_e先增大后减小.超重力因子、液量增大,喷液孔数目为6时传质最好;不同气量下,传质性能在喷液孔数目为8时最佳,但下降趋势明显,6孔的传质稳定.本实验中液体分布器最合适喷液孔数目为6.经数据回归得出a_e和k_la_e的关联式,平均误差均小于15%.     

Comparison of mass transfer characteristics between countercurrent-flow and crosscurrent-flow rotating packed bed

Rotating packed bed (RPB), mainly including countercurrent-flow RPB (Counter-RPB) and crosscurrent-flow RPB (Cross-RPB) classified from the perspective of gas-liquid contact style, is a novel process intensification device. A significant measure standard to evaluate performance of RPB is mass transfer effect. In order to contrast the mass transfer characteristics of Counter-RPB and Cross-RPB that with the same size, liquid volumetric mass transfer coefficient (klae) and effective interfacial area (ae) were measured under identical operation conditions. Meanwhile, comparison of comprehensive mass transfer performance was conducted with ΔP (pressure drop)/klae as the standard. Experimental results indicated that klae and ae increased with increase of liquid spray density q, gas velocity u and high gravity factor β. Furthermore, compared with Cross-RPB, Counter-RPB has higher liquid volumetric mass transfer coefficient and slightly larger effective interfacial area. The experimental results of comprehensive mass transfer performance showed that the Counter-RPB had higher ΔP/klae than the Cross-RPB with changes of liquid spray density and high gravity factor, and there exists a turning point at 0.71 m/s accompanied by a variation with gas velocity. Moreover, the relative error of experimental values to calculated values calculated by the correlative expressions of klae was less than 5%. In conclusion, the mass transfer characteristics of RPB are deeply impacted by the manner in which the flows are established and Cross-RPB would have a great potential for industrial scale-up applications.