Experimental Study On Treatment Of Mother Liquor Of Isoelectric Point Crystallization Of Monosodium Glutamate Production By Freezing Concentration Method

Freeze concentration method is a new type of water treatment method based on physical and chemical phase equilibrium,which treats wastewater and purifies ice crystals and concentrates pollutants.In this paper,the yeast wastewater in monosodium glutamate production was treated by freeze-concentration suspension crystallization.And glutamic acid resource recovery and wastewater purification were realized.The influence of factors such as isoelectric point crystallization process and suspended crystallization effluent water quality on the yield and quality of crystallization were discussed.On this basis,a pilot plant for recovering glutamic acid from isoelectric point resources by freezing concentrated suspension crystallization method was designed.In this paper,monosodium glutamate production wastewater was treated by freeze concentration method,and then glutamic acid was recovered by isoelectric point crystallization method.The effects of ice formation efficiency,crystallization temperature,seed addition amount and seed mesh number on crystallization yield and quality were discussed.The best conditions for the experiment were determined as follows:ice formation rate of 70%,crystal growth temperature of 0℃,3%addition of 150 mesh α-glutamic acid seeds.At this time,the yield and quality of glutamic from the waste liquid using isoelectric point crystallization were the best.13.75 g of glutamic acid can be recovered from per liter of monosodium glutamate production wastewater,and the crystals are basically α-glutamic acid.The freeze-concentration suspension crystallization technology was used to treat the wastewater from monosodium glutamate production,and the experiment was carried out with primary freezing and secondary freezing.The research focus was on the contaminant entrainment of ice crystals.If there are many pollutants in ice crystals,the purity of ice crystals is not high,which leads to the decrease of water quality after ice crystals melting.Therefore,the entrainment of contaminants in ice crystals should be avoided as much as possible.In this paper,the effects of freezing temperature(supercooling),ice formation rate,stirring speed and freezing stages on the purity of ice crystals were studied.The experimental results showed that when the freezing temperature was lower and the degree of subcooling was greater,the pollutants carried by the ice crystals were more and the purity of the ice crystals was lower.And the quality of the ice crystal effluent was poorer with the increase of ice formation efficiency according to the experimental results.The stirring speed affects the entrainment of contaminants during the ice crystal growth process.When the speed was 160 rpm/min,the ice crystal effluent water quality was the best.The final optimal experimental process conditions were that the freezing temperature was-10℃,the ice formation rate was 70%,and the stirring speed was 160 rpm/min.The COD removal rate reached 80.18%after the first-level freezing,and the final COD removal rate improved to 94.32%after the second-level freezing.Through the small-scale experiment of freezing concentration and isoelectric point crystallization of glutamic acid,a set of wastewater treatment equipment for simultaneously treatment of wastewater and recovery of glutamic acid was designed.Through the process of water pre cooling,freeze suspension crystallization,ice crystal growth,ice crystal and concentrate separation,isoelectric point crystallization,ice,concentrate and glutamate separation,the wastewater purification and glutamate recovery were realized at the same time.In the pilot operation stage,designed processing capacity is 0.5 t/d and the COD removal rate of the final discharged water was 61.79%after the suspension freeze concentration,and the recovery rate of isoelectric point crystallization glutamic acid was 51.6%by two-step freeze concentration.The device has strong practicability and convenient operation,and is suitable for large-scale wastewater treatment,which provides an important reference value for the resource utilization of industrial wastewater.