A Vertical Combined Feed / Effluent Exchanger (VCFE or Texas Tower) at a large refinery in Asia was suffering from a significant performance drop caused by tube bore blockages. This was compounded by the implementation of traditional fouling removal methods including chemicals which were unable to access the worst of the fouling, resulting in very little improvement. Using chemicals to remove fouling from the external tube surface (shell side) of a texas tower is even riskier as chemicals cannot react with force to flush deposits away from the baffle plates, causing deposits to remain and worsening having absorbed moisture. These swollen deposits cause even more of a problem between the tubes.
Previous attempts to remove fouling had been unsuccessful due to the limitations of traditional water jetting systems unable to unblock the 25m long tubes as they create dangerous hydraulic back pressure with slow retro firing jetting nozzles i.e., it takes 20 minutes to several hours per tube so it takes up to 50 shifts to complete and will go back online with many blockages remaining and continuing the under scale corrosive action.
As Tube Tech worked during a critical path, there was a limited time frame in which to complete the fouling removal. With typical VCFE downtime costs ranging from $100k to $500k per day, overrunning the shutdown deadline was to be avoided.
Shell Global Solutions challenged Tube Tech to develop a technology to remove the unknown deposits via limited access, and requested tube wall integrity results.
Dimensions: VCFE 3200 tubes x 11.66mm i.d. x 25m long vertical tubes.
Fouling: Salts, Iron oxides / sulphates, Hydrocarbon Coke Scale, gummy polycyclic aromatics.
Access: Restricted 18″ man way nozzle using BA suits due to the potential presence of polycyclic aromatics.
Time limit: 7 shifts.
New accelerator jets.
Super high-pressure pumps 55,000psi capability.
Remote drilling unit.
“We have cleaned many VCFEs all over the world and can honestly say that this was the most fouled VCFE (Texas Tower) we have ever worked on. We are pleased that the client was satisfied with the inspection results that we provided.”