Revamps 2025 Issue

Troubleshooting a dehydration train

Advanced liquid distributor solutions increase reliability and profitability

Norbis Velazquez and Michael Krela Koch-Glitsch Juan Ruiz Gas Processing Expert

I n the current global energy environment, natural gas is expected to hold a strong position as a reliable fuel in the years to come, and it is considered a bridge fuel towards an era of more sustainable energy sources. 1 Although conditioning of natural gas is a mature field, operators, along with licensors and equipment vendors, keep chasing opportunities to improve processes and opti- mise designs to minimise their environmental footprint, improve energy efficiency, increase reliability, and reduce operational costs. However, in a field where everything seems to have already been said and done, finding such opportunities constitutes a challenge of its own. Natural gas dehydration is one of the ubiquitous pro- cesses that almost any natural gas stream undergoes, as the presence of free water in the gas at pipeline conditions can lead to operational issues, including hydrate formation and corrosion. The degree of dehydration depends on the use and the transit of the gas stream from its source to its destination; the colder the temperature the gas is expected to reach, the more stringent the dehydration specification will be. There are different technologies available to desiccate nat- ural gas streams, and most of them require, to some extent, the use of absorption or distillation processes equipped with mass transfer equipment such as trays, packing, and distributors. Choosing the right process depends on several factors, including the initial water content, process charac- ter, operational nature, economic factors, and the water specification required downstream.2 One such method is water removal by compression and cooling, which aims to decrease water saturation content, first by compressing the

gas and then cooling it to an adequate temperature to gen- erate the desired dehydration level. A plant gas operator in Western Canada, which runs sev- eral midstream assets throughout North America, faces the challenges of conditioning and dehydrating its natural gas production. In its Canadian operation, it operates several proprietary Ifpexol units. This technology allows dehydra- tion and dew point control by using a cold process in the presence of a methanol solution as a single solvent. A methanol-water solution is recovered from the dried gas and recycled back to the two strippers, where a par- tial stream of raw wet gas is used to strip out and recover methanol from the recycled methanol-water mixture. The objective of the stripper is to obtain pure water at the bot- tom and an overhead gas stream loaded with methanol, which serves as an antifreeze agent downstream. The Ifpexol process focuses on the economy generated by a highly integrated dehydration process using a com- pression-cooling approach. In this technology, a methanol closed-loop aqueous solution is recirculated to control hydrate formation in the cold section of the unit. If the methanol losses through the bottom of the strippers are low, the process offers attractive operational costs while being environmentally friendlier than other dehydration technologies, as there are no harmful vent emissions.³ Operating principles The methanol regeneration of the Ifpexol process occurs in the stripping section, where a water-saturated hydrocar- bon gas stream is contacted in counterflow with a methanol solution in a packed stripper tower. The stripping process

Sales gas

Methanol make-up

Cold separator

I fpexol stripper

Methanol solution

C 3 + stabilisation and methanol recovery

Wash water stripper

Gas feed

Wash water + methanol

Compression section

High-purity excess water

Figure 1 Overview of Ifpexol process for dehydration

Revamps 2025