The impact of ethylene glycol and hydrogen sulphide on the performance of cellulose triacetate membranes in natural gas sweetening

Abstract

In natural gas sweetening, gas dehydration with glycols is typically carried out upstream of membrane separation of carbon dioxide. This means that when process upsets occur, these glycols can reach the membrane unit. In this work, we study the impact of two common glycols (monoethylene glycol and triethylene glycol) on the gas transport performance of CTA. We find that the glycol absorbed into the membrane initially obstructs the permeation of CH 4 and CO 2, due to pore filling or antiplasticisation effects, but the permeability then increases again, indicative of polymer relaxation and a loss of crystallinity in the polymer. The smaller helium molecule is significantly less affected by the presence of the glycols, possibly because its lower solubility within glycol limits its movement through the swollen structure. However, after removing the glycols with a methanol wash, the membrane performance recovers with only a slight residual plasticisation observed. In addition, the permeation of H 2 S, a common contaminant within natural gas streams, was studied across a range of temperatures. At the partial pressures studied (up to 0.75 kPa), H 2 S had very little effect on the membrane performance even in long-term exposure for up to 300 days.

The impact of toluene and xylene on the performance of cellulose triacetate membranes for natural gas sweetening

“…The membrane thickness was measured by a micrometer and was in the range of 65 -75 µm. The membrane density and crystallinity were 1.297 ± 0.003 (g/cm 3 ) and 56 ± 5 (%) respectively [19].…”

“…Dense membrane fabrication followed a typical solvent casting method as described in our previous publications [18,19]. A 1 wt% solution was prepared by dissolving the dried CTA powder into dichloromethane (ChemSupply, Australia).…”

Application of NF Polymeric Membranes for Removal of Multicomponent Heat-Stable Salts (HSS) Ions from Methyl Diethanolamine (MDEA) Solutions

“…Furthermore, it has combustible properties and is widely used in the power generation and petrochemical industries [ 3 ]. In general, natural gas contains methane (75–90%), propane, butane, ethane, heavy hydrocarbons (1–3%), and also impurities such as water vapor, carbon dioxide (CO 2 ), hydrogen sulfide (H 2 S), mercaptans (RSH), carbonyl sulfide (COS), carbon disulfide (CS 2 ), and nitrogen [ 4 , 5 , 6 ]. Some of these impurities are toxic, corrosive, and cause environmental pollution after combustion so their removal from natural gas is extremely important [ 7 , 8 ].…”

Modelling Ion Transport in an Amine Solution Through a Nanofiltration Membrane

“…Thus, these impurities must be removed from the gas to reduce the harmful effects. Alkanol amine solutions including methyl-diethanolamine (MDEA), monoethanolamine (MEA), piperazine (PZ), diethanolamine (DEA) and diisopropanolamine (DIPA) are used in sweetening natural gas and removing impurities (Jaafari et al, 2018;Lu et al, 2017;Najibi and Maleki, 2013;Poormohammadian et al, 2015;Qeshta et al, 2015;Qiu et al, 2014;Rebolledo-Libreros and Trejo, 2004;Santaniello and Golemme, 2018). MDEA is usually used in the concentration range of 40 to 50% for the removal of acid gases in the gas sweetening unit (Keewan et al, 2018;Pal et al, 2015).…”