Title : Heat Transfer Fluid (HTF) degradation in a LNG Plant: A case study highlighting findings and mitigations
Abstract:
Heat transfer fluid (HTF) is one of the important utilities in any chemical/LNG/Gas processing plant. HTF gets heated in fired equipment’s and passes through number of reboilers to provide required heat duty. However, in number of cases, it is difficult to maintain the quality of HTF over a period of time, specifically in terms of flash-point. This paper narrates a case study, where flash-point of HTF dropped from >2000C to <400C and the investigation was conducted to understand the root causes. Inability to maintain the HTF quality specifically in terms of flash point has a potential to cause process safety incident. There are number of factors that could have led to degradation of HTF fluid which includes thermal degradation, oxidation, ageing, contamination (due to solids, acids, low-boilers, high boilers or water) and lack of quality control. However, detailed HTF analysis followed by investigation on this topic inferred that there were two major causes for this significant degradation: thermal degradation and contamination due to solids ingress. Thermal degradation of HTF was caused because of over-firing of the furnaces, mal functioning of trim coolers and flame impingement due to fallen refractory and burner misalignment, whereas solids ingress was caused due to under- ground piping corrosion, clogged HTF pump strainers & seal failures and deposits/debris/corrosion products found in reboilers. All the above factors were heightened/went un-noticed because of lack of quality control on HTF analysis. Based on the identified causes of HTF degradation, mitigation strategies were defined in terms of HTF quality control, preventative maintenance regime on trim coolers, reduced alarm point on furnaces, follow-dry-out procedure for furnace refractories etc. to avoid such incident in the future.
