Research and Discussion on Membrane Contamination during Membrane Filtration of Glutamic Acid Fermentation Solution and Countermeasures XU Zhao-hui, WANG Huan-zhang, LI Bi-wen, XING Wei-hong, XU Nan-ping, WANG Huai-lin, Guangdong Zhaoqing Xinghu Co., Ltd. 526061) Institute of Membrane Science and Technology, Sakai University of Chemical Technology, 10009) 510009 has a good application prospect, but the pollution of ceramic membrane is a key problem that must be solved. The site of the process to extract glutamic acid. Because the bacteria in fermentation broth have negative effects on isoelectric crystallization, separation and concentration processes, sterilization of fermentation broth is of great significance. On the one hand, sterilizing the fermentation broth can increase the yield and quality of glutamic acid; on the other hand, it can greatly reduce the load on the ion exchange process; reduce the amount of washing water, and even can not wash; reduce the amount of waste water discharge by more than half, is a Meaningful pollution control measures in the production process. Fermentation liquid, etc. Electro-crystallization separation of crude products glutamic acid high flow elution ion exchange and other mother liquor extraction process of glutamic acid from the fermentation broth Ceramic micro-filtration membrane has good filtration and separation performance and resistance to cleaning and other characteristics fully consistent with the fermentation Liquid sterilization requirements, the solution to the problem of membrane fouling is of great significance to the promotion and application of this technology. This article uses the 0.2! g of 19-channel zirconia ceramic membranes. 2 Filtration Operation and Membrane Contamination Effect of Operating Pressure on Membrane Contamination It can be seen that the pressure is at a constant surface flow rate and operating temperature. In the range of l.2 MPa, the effect on the flux is small, and when the surface velocity is low, the high pressure causes the flux of the membrane to become smaller. This is mainly because the gel layer formed on the membrane surface by the bacteria and residual sugar in the fermentation broth has compressibility, and the gel layer formed at high pressure has a large filtration resistance due to its large filtration resistance and increased The possibility of membrane fouling. In the experiment, we found that when the high pressure operation is switched to low pressure operation, the flux does not recover, but when the low pressure operation is performed first and then the high pressure operation is performed, the reproducibility of the experiment is good, which strongly suggests that the high pressure operation will significantly increase the membrane Pollution. In addition, theoretically speaking, research and discussion on the microfiltration process of the gel layer resistance control, the influence of the compactness of the gel layer on the flux is greater than the increase of the pressure so that the driving force increases the impact on the flux. 2.2 Effect of surface flow velocity We fixed the pressure at 0.1 MP and examined the effect of membrane surface velocity on the flux. It can be seen that the relationship between the flow rate of the film surface and the surface flow rate is linear between 0.5 ms. This is mainly because the surface flow rate directly affects the thickness of the laminar bottom layer, that is, the thickness of the gel layer, and is relatively high. Membrane flow rate can reduce the chance of contaminants deposited on the membrane surface to reduce the occurrence of membrane fouling and thus have a decisive influence on the filtration process. 3 Membrane fouling and cleaning 3.1 Membrane fouling level Table 2 Recovery of flux under several membrane washing operations Membrane washing operation New membrane water flux After washing, the flux recovery rate of the whole process is closed during the latter half of the permeate. Through the whole process of liquid through the open liquid through the liquid membrane 2 is the same membrane tube, under the same conditions after filtering pollution, after taking three operators to clean the flux recovery rate compared, we can see the three modes of operation The difference in volume recovery rate is very small, so it can be concluded that when the fermentation broth is filtered, the major part of the membrane fouling is that there are few contaminants entering the membrane on the membrane surface. Based on this conclusion, closing the permeate outlet at the time of cleaning can not only save the backflow operation of the permeate, but also prevent other pollutants from entering the membrane pores during cleaning to form secondary pollution. 3.2 Cleaning Effect and Membrane Contamination Membrane flux recovery after membrane cleaning has a significant impact on the membrane fouling process. For this reason, we compared the filtration process of several ceramic membranes with different recovery rates. It can be clearly seen that the flux recovery High-rate membrane tubes have a significantly higher filtration flux throughout the entire process. The reason for this is simple: when filtering, pores with smaller pore diameters are less likely to clog, but the opposite is true when cleaning. The smaller pores are less likely to be washed. 4 Measures to reduce membrane fouling Through the above experiments and analysis, the causes of membrane fouling and flux decline have been clearly understood. Based on this, the following measures have been taken to reduce membrane fouling: enhanced membrane washing process; appropriate temperature control to reduce the effect of viscosity, maintain a moderate diffusion effect; add filter aids to destroy the gel layer and increase filter cake porosity to reduce the filter Cake compaction; optimize operating conditions to increase membrane surface flow rate to reduce transmembrane pressure difference. The adoption of these measures has achieved the expected results, and the above analysis has also been verified on the other hand. The curve 2 in the curve is the filtration characteristic curve of the stable operation experiment after adopting these measures, the average flux has reached 80L/m2h or more, and it can fully meet the requirements of production on the operation, investment cost and glutamic acid recovery rate. 5 Conclusions The composition and physicochemical properties of the fermentation broth are the root causes of the contamination of the ceramic membrane. The operation process and the membrane washing process have an important influence on the membrane fouling; after the cause of the membrane fouling is clearly identified, measures are taken to reduce the membrane fouling. Can meet the production requirements of ceramic membrane filtration fermentation broth.
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