Development of a High-Pressure Bubbling Sampler for Trace Element Quantification in Natural Gas.
Résumé
A high-pressure bubbling sampler has been developed to trap and preconc. 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 soln. and the gas flows at the network pressure with a flow rate up to 40 L/min. The trapping solns. for mercury and other metals are permanganate/sulfuric acid or nitric acid/hydrogen peroxide according to stds. 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 lab., 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 soln. 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 high-pressure 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 vol. of 140 Nm3 of sampled gas. The gas flowed through three vials of 50 mL, which makes a final preconcn. factor of 3 × 106. The trapping solns. were analyzed for trace metal concns. using inductively coupled plasma mass spectrometry. The concns. were 10-1 ng/Nm3 for barium, from 10-1 to 5 ng/Nm3 for tin, from 0.9 to 10 ng/Nm3 for arsenic and copper, and from 1 to 101 ng/Nm3 for aluminum, selenium, and zinc. The efficiency of the traps and the low measured concns. make this high-pressure bubbling sampler a useful tool for trace element analyses in natural gas.