Mono Ethylene Glycol Regeneration System Upgrade

Abstract

Objectives/Scope This paper covers the Shwe Offshore Platform (SHP) MEG Regeneration System upgrade works implemented to reduce excessive MEG losses and improve operation of the System. Methods, Procedures, Process The SHP MEG Regeneration System processes MEG used in the topsides for hydrate inhibition in the Low Temperature Separators (LTS) and at the four subsea wells. Since start-up of production in 2013, SHP has suffered from excessive MEG losses and operational difficulties. Later in the field life, MEG injection to subsea wells was discontinued due to contamination with salts from formation water, and Kinetic Hydrate Inhibitor (KHI) injection was introduced. Extensive evaluation of data, laboratory tests and field trials were carried out to investigate the causes of the excessive MEG consumption and operational difficulties. The upgrade of the MEG Regeneration System was finally completed and put in service since May 2018. Results, Observations, Conclusions The followings have been identified as the direct causes for MEG losses and operational difficulties; Poor efficiency of Glycol-Glycol Heat Exchangers (HEXs), causing low operating temperature of the Rich MEG Flash Drum and poor condensate/Rich MEG separation, resulting in MEG losses via Flash Drum condensate outlet.Excessive condensate in the Rich MEG reaching the Reboiler and resulting in contamination of the Lean MEG and downstream section (injection spray bars).Low water loading in the MEG Regeneration System resulting in lack of reflux and MEG losses via Reflux Drum.MEG carryover from LTS to the Export Gas Compressor (EGC) Suction Scrubbers, caused by foaming in the LTSs. In order to resolve the issues above, a number of modifications were implemented. New Glycol-Glycol HEX and a Liquid-Liquid Coalescer Filter were installed to provide better separation of condensate from Rich MEG. Also re-routing of the EGC Suction Scrubbers liquid outlet back to the MEG Regeneration System to recover the carried over MEG. Significant reduction of MEG losses was achieved, in the range of 70%, and overall system performance has improved. The main outcome of such improvement is that the condensate content in Rich MEG has been significantly decreased to below 500ppmV from above 1vol% due to the increase of Rich MEG Operating Temperature in Flash Drum and introduction of the Liquid-Liquid Coalescer Filter. Novel/Additive Information This paper was written to describe the method used for resolving the problems with MEG losses, excessive condensate in the Rich MEG, and MEG carryover. It also explains the data evaluation, preparation, execution, and the results of the MEG Regeneration System Upgrade work.

Regeneration and Reclamation of Mono-Ethylene Glycol (MEG) Used as a Hydrate Inhibitor: A Review

“…The primary culprit for MEG losses in the MRU is the loss during hydrocarbon condensate skimming due to emulsification of MEG and condensate [70]. MEG loss also occurs during the dewatering step in the distillation column.…”

“…MEG loss also occurs during the dewatering step in the distillation column. The sudden changes in the column reflux level and accumulation of the water condensate increase boil-off liquid from the reboiler [21,70]. Consequently, more MEG in the reboiler is vaporised and lost to the reflux drum.…”

“…These results showed that the desalination could cause significant MEG loss from removing the precipitated salt slurry. Conversely, Kim et al (2019) reported operational losses of 1.8 m 3 MEG/month in the reboiler [70]; assuming uninterrupted operation of 24 h in a 30-day month, which amounts to 2.5 kg/h. Kim et al (2019) reported that MEG loss in the operating facility was reduced by up to 75.2% when freshwater was introduced into the distillation column reflux system [70].…”

“…Conversely, Kim et al (2019) reported operational losses of 1.8 m 3 MEG/month in the reboiler [70]; assuming uninterrupted operation of 24 h in a 30-day month, which amounts to 2.5 kg/h. Kim et al (2019) reported that MEG loss in the operating facility was reduced by up to 75.2% when freshwater was introduced into the distillation column reflux system [70]. Another significant factor contributing to MEG loss in the MRU is accumulation of highly soluble salts in the reclaimer.…”