Development of a High-Pressure Bubbling Sampler for Trace Element Quantification in Natural Gas

Abstract

A high-pressure bubbling sampler has been developed to trap and preconcentrate metals and metalloids from natural gas. This high-pressure sampler was designed to work at pressures up to 100 bar and be directly plugged into distribution and transportation networks. It consists of three vials in series, which contain 50 mL of metal trapping solution and the gas flows at the network pressure with a flow rate up to 40 L/min. The trapping solutions for mercury and other metals are permanganate/ sulfuric acid or nitric acid/hydrogen peroxide according to standards EN 13211 and EN 14385. The sampler design, development, and validation steps are presented in this work. First, the trapping vials were tested in the laboratory, where argon gas was spiked with mercury at two different pressures that represented the distribution and transportation networks. The results show that more than 96% of the metal was trapped from the gas phase into the solution for both tested pressures. Moreover, more than 90% of the trapped metal was found in the first vial, which shows the good efficiency of the traps. Finally, the highpressure bubbling sampler was tested in three field campaigns of natural gas sampling from a transportation network at 60 bar. Each sampling was performed for 5 days with a flow rate of 20 L/min, which makes a total volume of 140 Nm 3 of sampled gas. The gas flowed through three vials of 50 mL, which makes a final preconcentration factor of 3 × 10 6 . The trapping solutions were analyzed for trace metal concentrations using inductively coupled plasma mass spectrometry. The concentrations were 10 −1 ng/ Nm 3 for barium, from 10 −1 to 5 ng/Nm 3 for tin, from 0.9 to 10 ng/Nm 3 for arsenic and copper, and from 1 to 10 1 ng/Nm 3 for aluminum, selenium, and zinc. The efficiency of the traps and the low measured concentrations make this high-pressure bubbling sampler a useful tool for trace element analyses in natural gas.

Arsenic release to the environment from hydrocarbon production, storage, transportation, use and waste management

“…There are several approaches for separation, which often include use of solvents, hot water extractions (Jacobs and Filby, 1983) or acid digestions (Bicalho et al, 2017). Extracting volatile As species from natural gas is particularly challenging (Puri and Irgolic, 1989;Delgado-Morales et al, 1994b;Krupp et al, 2007;Xu et al, 2015;Cachia et al, 2017). Extraction methods include use of adsorption tubes or solutions (silver nitrate or nitric acid) to take up the volatile species such as trimethylarsine (TMA) from natural gas prior to analysis.…”

“…Most papers on methods focus on analyzing As in specific hydrocarbon sources, such as crude oil (Puri and Irgolic, 1989;Hardaway et al, 2004;Sánchez et al, 2013), oil sands (Bicalho et al, 2017), gasoline, diesel and naphtha (Brandão et al, 2006), and natural gas (Irgolic et al, 1991;Delgado-Morales et al, 1994b;Krupp et al, 2007;Xu et al, 2015;Cachia et al, 2017;Freije-Carrelo et al, 2017). As there are dozens of papers on analysis of As species in different hydrocarbon products, the reader is directed to these papers in addition to reviews (e. g., Nadkarni, 1991;Cassella et al, 2002;Sánchez et al, 2013) for more information.…”

“…Although there are microbially mediated processes that generate TMA, Puri and Irgolic (1989) suggest that the majority of TMA in natural gas is a product of diagenetic reactions and not from modern microbial activity. Although As measurements in natural gas have been reported in a few studies (Irgolic et al, 1991;Krupp et al, 2007;Cachia et al, 2017), the sampling strategies, phases sampled and measurement units are significantly different, making concentrations difficult to summarize and compare.…”

Novel field-portable high-pressure adsorbent tube sampler prototype for the direct in situ preconcentration of trace compounds in gases at their working pressures: application to biomethane

“…To the authors' knowledge, biomethane has only been in situ sampled directly on the pipelines at the grid pressure (40 bar a ) by Cachia et al 22 using a high-pressure acid bubbling impinger for the direct preconcentration of metallic TC in gas samples. 31 So far, other reported determinations of TC in high-pressure gases (typically natural gas) have always been carried out by depressurization of the gas and preconcentration at atmospheric pressure: the gas is either depressurized in situ from the pipe aer what the sampling system is installed at atmospheric pressure, 32 or it is sampled at its grid pressure in surface-treated high-pressure stainless-steel cylinders subsequently transported to the lab for depressurization and preconcentration. 29,[33][34][35][36] Depressurization is detrimental to the preconcentration of TC since, assuming the ideal gas law PV ¼ nRT, a dilution factor equal to the ratio of the high pressure to the pressure aer depressurization leads to a concentration decrease of the TC, implying larger gas volumes have to sampled at atmospheric pressure than at high pressure to trap a given amount of TC.…”

Solid Particles in Natural Gas from a Transportation Network: A Chemical Composition Study

“…These specifications ensure high quality gas for combustion but are also essential to prevent damage to facilities and protect consumer health. However, studies have revealed the presence of arsenic compounds, mercury and other metals/metalloids in natural gas from different origins at very low concentrations ranging from 10 −1 to 10 3 µg/m 3 [6][7][8][9][10][11]. These elements have well-known risks and potentially can cause industrial damage, such as through corrosion or catalytic poisoning.…”