Troubleshooting a Furnace Emissions Problem

摘要

Troubleshooting a Furnace Emissions ProblemThe ethylene plant at Dupont's Sabine River Works (Orange, TX) has 10 crackingheaters. Nine are original to when the plant was built in the mid-late 1960's. Anew heater was added in the late 1990's; problems with this heater are thesubject of this paper.All of the cracking heaters use CEMS (Continuous Emissions Monitoring System)analyzers to monitor CO and NO_x emissions, according to the EPA's 40 CFRMethod 19 Of Appendix A. Basically, this method uses the firing rate and fuelcomposition to calculate the flue gas flow rate, along with the measuredemission concentrations to calculate the hourly emission rates.Starting in mid-2011 and through most of 2012, the heater had CO problemseven when the heater was at full operating rates. The problem graduallybecame worse and a detailed investigation was begun into the root cause of theproblem.Eventually, it was determined that the cause of the problem was leaking mixedfeed preheat tubes in the convection section. The root cause of the leaks waspolythionic acid stress corrosion cracking, due to inadequate metallurgy.