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8421583 
Journal Article 
Retrofit and optimization of phosgene recovery system of tolylene diisocyanate unit 
Cheng, HN; Yue, JC; Zheng, SQ 
2006 
No 
Huaxue Gongcheng / Chemical Engineering
ISSN: 1005-9954 
34 
5 
68-71 
Chinese 
The phosgene recovery system of tolylene diisocyanate (TDI) unit was simulated and corresponding factors were analyzed aiming at the problems in the actual operation. A middle-cooler was added to the toluene absorber. The outlet place of the ethyl-chloride and water was identified for the toluene desorber. The feed place of the toluene treatment tower was optimized. In addition, a new hydrochloride tower was added to absorb the HCl in the waster gas. These treatments eliminate the unstable phenomenon of the toluene absorber, increase the recovery of HCl, decrease the ethyl-chloride concentration in whole unit, slow down corrode of towers, decrease the sodium hydroxide needed and make TDI unit more safe and environmental-friendly. 
Optimization; Phosgene recovery; Retrofit