We operated 2 Girbotol CO2 removal plants for H2 purification for many years with periodic periods of very high corrosion rates until the installation of metal edge filters and carbon towers. Each MEA train consisted of 9 Hxs' with MOC of 316L, both shell and tubes. Installation of the filters immediately helped with the problems of plugging/fouling, but didn't completely eliminate it. The second step was the addition of side stream activated carbon towers, using an SGL carbon. The towers went a long way in mediating the corrosion after several carbon cycles. Initial life of a tower was quite short and required close monitoring even after the initial cleanup period.
I have been unable to find out the specific carbon we used.
I keep thinking it was a Pittsburgh material.
Auto Clean
Our biggest problem was still fouling and corrosion of the exchangers and reboilers.
The carbon towers and filters helped but didn’t completely resolve this problem. We were constantly rebuilding these tube bundles in our shop due complete plugging caused by the close tube spacing and the triangular pitch which precluded any type of blast cleaning.
The layout man in Fab shop and myself solved this problem by sneaking, (midnight plant test) in a tube bundle, reboiler, with 25% less tubes and on a square pitch. The square pitch was for cleaning if necessary. I have looked at some notes where it was deemed that preventing the hold up of the rich MEA went a long way in preventing formation additional deposits and corrosion.
When both plants were decommissioned 3 years later all exchangers were of this design. None of the square pitch bundles were ever pulled for cleaning. The onstream time for the carbon towers and filters also increased.
Hydroblasting
There are hydroblasters and there are real hydroblasters. I can't say how many times that I've caught hydroblasters changing the tips on a lance to take some of pressure off the operator when manually blasting tubes. We had one incident where blaster took out over 100 tubes in 1200 tube bundle. It got to the point that we required mechanical lancing for all tubes. Even then the selection of the tip is still very critical to keep from eroding tubes.
The operating parameters of tube blasting have to determined and watched during the each operation on a specific bundle. I developed a specific list of the operating parameters needed to clean a specific bundle especially the more difficult ones.
