Chloride Analysis in HC Gases

The water vapor is the main source of the chloride ion in natural gas and its concentration depends on the concentration of the chloride ions in the reservoir water phase. The vapor cause operational problems such as hydrate formation, corrosion, high pressure drop, and consequently slugging flow and reduction in gas transmission efficiency.

 There is no standard method to analyze the chloride ions in gas stream. Since the source of the chloride in the gas is that the dissolved water, therefore we extract such water and analyze the chloride in such extracted water by ion chromatograph.

Method of extraction.

1. Wash the cylinder carefully with a proper solvent followed by deionized water and then dry it.

2. Evacuate the cylinder by connecting them to the vacuum pump.

3.  Place Deionized water was in beaker of 500 ml and inserted the bottom cylinder valve into such water and opened it to suck a sufficient amount of this water and then closed the valve.

4. The cylinder was checked for 15 minutes.

5.  Analyze the water in the cylinder by ion chromatograph to measure any amount of chloride ions in the used water.

6. Repeat steps 3, 4 and 5 until the chloride ions in water were nil or were as low as possible.

7. Insert 100 ml of deionized water in the cylinder (as in step 3) and it allows to settle down.

8.  Connect the upper cylinder valve to the suction pump to evacuate the air inside the cylinder to facilitate the entrance of the gas volume into the cylinder.

9.  Put 300 cc volume of gas sample on the gas meter and connect it the upper valve of the cylinder and opened it to suck such volume of gas and closed the valve. The gas water mixture was checked for 1/4 hr.

10. The water was discharged from the cylinder into a bottle and analyzed by ion chromatography to measure the chloride ion concentration.

Water Samples

The anions in water sample will be determined experimentally according to ASTM: D-4327 using the same method conditions used in the analysis of the water extracted from gas samples.

Each water sample was filtered using Whatman No.42 filter paper and diluted with deionized water prior analysis. Aliquots of the water samples were diluted with measured volume to be within the measuring range, and 10 microliter of the solution was injected into the column.

Conclusion

 The accuracy of the method for measuring the chloride contents in gas samples depends mainly on the method of water extraction from gas sample.

  Ion chromatography is a good analytical tool for accurate quantitative determination of chloride content in the gas production process.