Narendra:
You state that the operating manual of one of your Amine (MDEA) suppliers indicates that 260 oF is the maximum temperature that should be applied in the reboiler. However, this is the maximum design temperature for Monoethanolamine (MEA) – not Methyldiethanolamine (MDEA). The boiling point for MEA at atmospheric pressure is 171 oC (339 oF) and that for MDEA is 247 oC (477 oF). MEA decomposes at its boiling point; MDEA does not decompose up to its boiling point (at least not according to Kohl & Riesenfeld).
The problem with this lengthy thread is that Vista has not answered my detailed questions. Furthermore, as Bobby Strain infers, she doesn’t state WHAT the specific problem at hand is with this MDEA stripper. Why bother to “control” (vary) the stripper pressure when 10 to 15 psig are normal, conventional stripper pressures?
I simply fail to recognize what the problem is here. An amine stripper (be it MEA, MDEA, or even DGA) will easily strip out H2S with ease. CO2 is harder to strip out. Nevertheless, an acid gas stripper is a very simple tower with very few trays required to effect a successful regeneration of the amine solution in question. I have designed, built, and operated amine strippers with 6 flat, 5/16” thick trays installed 15” apart. These “trays” had no holes, valves, or even bubble caps – nothing. They had a 15% cut to allow cascading of the solution. They worked very well for years with 85 gpm of solution and a steam bundle in the kettle reboiler. In another application, I used tunnel caps that I fabricated from half-cut pipe. This time I used 10 tunnel cap trays. The results were the same as the first, plain flat tray application – no difference in regenerating the 0.35 mol CO2/mol MEA rich solution to 0.15. I never employed any so-called “reflux” in the strippers that I designed and operated. They all worked exactly as designed and for many years. This all confirms the simplicity of this Unit Operation. If I could do it with nothing more than a slide rule and a pad of paper, then today with all the computers, databases, exotic materials of construction, years of research and improvements you guys ought to have processing plants that far outdo what we did over 50 years ago. Unfortunately, this doesn’t seem to be the case.