INFLUENCE OF MIXING CONDITIONS APPLIED DURING CRYSTALLIZATION PROCESS ON CAKE DEWATERING CHARACTERISTICS
Mechanical cake dewatering is always desired so as to reduce the load on thermal dewatering.Any changes in the up-stream processes such as crystallization can have significant effect on the filtration as well as cake dewatering characteristics.The present study deals with the effect of mixing intensity during salicylic acid crystallization on the air dewatering characteristics in the subsequent pressure filtration.The mixing conditions during crystallization were varied by using three different types of agitators (Anchor impeller,Curved blade turbine and Bar turbine) and also by varying the speed of agitation.The effect of operating pressure and dewatering time on the final moisture content of the cake was also studied.The crystal properties (crystal size and size distribution) were found to vary with the mixing intensity,which further influenced the cake dewatering kinetics as well as the residual moisture content.An anchor impeller being a laminar flow impeller produced crystals with wide size distribution and higher mean particle size,which resulted in cake with high porosity and hence higher moisture content.The high porosity (as well as high cake permeability) causes early air breakthrough that results in ineffective dewatering of cake.Therefore,in this case the residual moisture in cake was found to be higher (27%) even at higher dewatering pressure (1.5 bar gauge) and longer dewatering time (90 sec).Bar turbine creates high turbulence during mixing and it produced crystals with relatively narrow size distribution and lower mean particle size,which gave low porosity cakes.Such cakes could be efficiently dewatered and the final cake moisture content was found to decrease to about 15%,a significant improvement in the filterability of the cake.The dewatering data was modeled according to the correlation between irreducible cake saturation and capillary number for predicting the cake dewatering characteristics (residual moisture as well as dewatering kinetics) and the results were compared with the experimental data.
mixing intensity dewatering kinetics irreducible cake saturation capillary number filterability drying
S.U.Deulgaonkar A.Hakkinen B.N.Thorat
Advanced Drying Laboratory,Department of Chemical Engineering,Institute of Chemical Technology(Forme Department of Chemical Technology,Lappeenranta University of Technology(LUT),Lappeenranta 53851,Finl
国际会议
The 18th International Drying Symposium Conference(第十八届国际干燥学术大会(IDS2012))
厦门
英文
1-9
2012-01-11（万方平台首次上网日期，不代表论文的发表时间）