| The electro-membrane processes are novel separation technologies,which have numerous applications in green chemistry and cleaner production.Due to the special charge characteristics of ion exchange membrane,the electro-membrane can achieve the separation and classification of the ions.This thesis focuses on the development of several different types of electro-membrane equipments and their applications.In part one,a novel diffusion dialysis stack,i.e.spiral wound diffusion dialysis(SWDD)membrane module was designed to overcome the drawbacks of low loading density and limited mass transfer efficiency in the conventional plate-and-frame diffusion dialyzer.The configuration of SWDD was optimized and this module was further applied for industrial applications.A large scale production of SWDD was achieved in our lab.In part two,a laboratory-scale bipolar membrane electrodialyzer was developed and applied for the cleaner production of Niacin.The main results are listed as followings.1)A spiral wound diffusion dialysis membrane module was invented and applied for acid recovery process in H2SO4/FeSO4 and HCl/FeCl2 systems.Results indicated that the acid recovery ratio were higher than 85%while the Fe2+ leakage ratio were less than 20%.The acid treatment capacity per square meter membrane in SWDD was much higher than that in the laboratory plate-and-frame diffusion dialyzer.This suggested that the mass transfer efficiency in SWDD is superior to the conventional plate-and-frame diffusion dialyzer.This advantage is more pronounced in HCl/FeCl2 system.2)A geometrical model of SWDD was established based on Archimedes’ spiral.The model was validated with experimental data and the error was less than 1%.The mass transfer in SWDD was discussed and overall mass transfer coefficient equation was developed.3)To optimize the structure in the spiral wound diffusion dialysis stack,two-outlet configuration was invented by abandoning the side outlet.As a consequence,the loading density in the spiral wound stack is higher than that in the plate-and-frame stack,resulting in larger treatment capacity per square meter in the spiral stack.4)SWDD-01 pre-tightening roll machine was designed and developed for the production of 1 m2,5 m2,and 10 11m2 spiral wound diffusion dialysis membraneⅢmodule.The quality standard and control method for SWDD production was established.A long-term stability investigation indicated that this spiral wound stack was stable in 30%sulfuric acid for 6 months.This was no leakage inside the stack.Third part test indicated that acid recovery rate and Al3+ rejection ratio for a 10m2 spiral wound diffusion dialyzer in HCl/AlCl3 solution(Al3+0.995 mol/L,H+2.96 mol/L)were 96.9%and 99.5%,respectively.Meanwhile,the process flow sheet of spiral wound diffusion dialyzer for waste acid recovery was elucidated.5)A laboratory-scale bipolar membrane electrodialyzer was developed for the bipolar membrane experiment.To produce Niacin in an environmental friendly manner,bipolar membrane electrodialysis was used to convert Niacin sodium salt into Niacin.In the electrodialysis apparatus of BP-C-BP configuration,the effects of operating conditions such as current density,feed concentration on the performances of BMED were investigated.The performance of BMED process was evaluated from energy consumption,current efficiency,voltage drop across the stack and product yield.Conversion efficiency can reach more than 73%under economically viable conditions.The highest current efficiency can reach 95%,and the lowest energy consumption for produce 1 kg of Niacin(0.1 mol/L)can reach only 4.1 kWh.The purity of Niacin can be easily improved by a cooling crystallization process and the product purity is up to 99%.Cleaner production of Niacin is achieved using bipolar membranes electrodialysis process. |
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