| Recovery process of caprolactam from waste water in the caprolactam production was studied in the paper, including liquid liquid equilibria of benzene-water solution containing e -caprolactam, and mass transfer characteristics of experimental pulsed sieve-plate column.The following liquid liquid equilibria were measured in the paper: LC-H2O-C6H6 system at 20 ℃,30℃ and40℃; LC-H2O-SA-C6H6 system at 20℃ and30℃; LC-H2O-SA-C6H6 system at pH value of 2 and 6. The results show that better recovery of caprolactam could be obtained in the following conditions: higher temperature in the range of 20~40℃, higher pH value in the range of 2-6, and addition of (NH4)2SO4 in the water solution containing e -caprolactam.Operation data were also measured in the experimental pulsed sieve-plate column with diameter 0.05m, effective height 0.97m, plate space 0.05m, and sieve-plate hole diameter 0.003m. The results show that maximum sum of two phase flooding velocity is 0.016 m-s-1 , and pulsation intensity is about 0.012 m- s-1. Optimum operation conditions are: two phase apparent velocity being 0.006-0.01 m - s-1, and pulsation intensity about 0.006-0.012 m- s-1. Better LC recovery and smaller apparent height of a transfer unit are obtained when optimum extraction ratio is 4-6.5. Lower LC recovery and larger apparent mass transfer height resulted in when extraction ratio is less than the optimum value. When extraction ratio is larger than the optimum value, LC recovery will increase, but apparent height of a transfer unit varies evenly and operation costing will increase much more obviously.Apparent height of a transfer unit (HTUoxp) of experimental pulsed sieve-plate column in different conditions were measured, and could be correlated as:The above equation gives information for pilot test and scale-up of pulsed sieve-plate column.
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