Experimental Study on Feasibility of H2 and N2 as Hydrate Inhibitors in Natural Gas Pipelines

Abstract

This study applied the temperature search method to investigate the feasibility of pure H2 and N2 gases to inhibit hydrate formation along the subsea natural gas pipeline networks. Hydrates of different mix ratios from CH4 and CO2 were initially formed in a cryogenic sapphire cell to study the component interactions. Each experiment was then repeated by adding either H2 gas or N2 gas to each of the mixes. The component interaction study showed that the risk of hydrates promotion increased with an increase in CH4 content of natural gas. It was discovered that a gas mix of (0.1 CO2 + 0.9 H2) mole fraction did not form hydrate at all pressures up to 20 MPa while that of (0.2 CO2 + 0.8 H2) mole fraction formed at −2 °C at a pressure of 10 MPa. The inability of (0.1 CO2 + 0.9 H2) mole fraction to form hydrate may be due to insufficient CO2 molecules filling the clathrate cage at that particular concentration. Furthermore, all the (CH4 + CO2) mixes formed hydrates and the (0.9 CH4 + 0.1 CO2) mole fraction showed a significant trend at 11 MPa and above. Again, introduction of both N2 and H2 gases to an earlier studied (CH4 + CO2) mix revealed their ability to inhibit formation of hydrate, but H2 showed higher significant effects. This was ascribed to the pressure conditions at which each form hydrate. Conclusively, this study confirmed that the addition of either of the gases will either prolong the formation of hydrate during operation or prevent the agglomeration of formed hydrate. This allows successful transportation of the hydrocarbon which enables the industry to operate at any desired pressure and still control the hydrate formation. Hence, the flow restriction on the operating conditions will be minimized without negative impact on the net profit margin except for the additional initial capital investments resulting from the proposed recommendations from this study.