Can Well-Configured Hot Vapor Bypass Condenser Controls Become Unstable?

 Can Well-Configured Hot Vapor Bypass Condenser Controls Become Unstable?

Henry Z. Kister, Fluor Corp., Aliso Viejo, CA and

Daryl W. Hanson, Valero Energy, San Antonio, TX

 Our survey of tower failures identified the hot vapor bypass as the most troublesome pressure and condenser control method in distillation. About one third of the pressure and condenser control malfunction case histories reported in the literature were problems with hot vapor bypasses, most in refineries. Most of the problems are due to poor configuration of hot vapor bypass piping, which evolves from poor understanding of its principles. These principles have been in the literature for more than 60 years, described by excellent papers by Whistler and Hollander, and later by the classic article by Chin and in some texts. When configured correctly, the experience is that hot vapor bypasses are usually non-troublesome. Cures have been to revert to the correct configurations as recommended by the literature references.

Recently, we encountered some situations that even though the hot vapor bypass schemes used correct configurations, problems were experienced. To gain better understanding we applied field measurements and testing as well as hydraulic analysis which led to successful solutions. This paper describes our experiences, findings, and the lessons learnt for troubleshooting and design of hot vapor bypass schemes.