Prediction of Conditions for Hydrate Formation in Natural Gases

Charts for predicting the pressure to which natural gases may be expandedwithout hydrate formation have been prepared for gases of even gravity.Pressure-temperature curves for hydrate formation were established for gaseshaving gravities from 0.6 to 1.0. These curves and the thermal behavior of thegases during free and adiabatic expansion were used to prepare the charts forestimating the permissible expansion of natural gases without hydrateformation. The problem was solved by L. F. Albright, W. 'T. Boyd; J. J. McKetta, G.Martin, F. Poettman, and A. P. Snyder, who are first year graduate students inthe department of Chemical and Metallurgical Engineering at the University ofMichigan. This paper is essentially a summary of their results. Prediction of Conditions for Hydrate Formation in Natural Gases Each natural gas under a given pressure will form solid hydrates at acorresponding temperature provided sufficient water is present. The temperatureof natural gases below about 5000 lb. per sq. in. decreases when the gases areexpanded freely. This decrease in temperature may cause the expanding gas toenter the region of temperature and pressure at which hydrates will form. Thefinal pressure to which a natural gas may be expanded without hydrate formationdepends upon the initial temperature and pressure and the gascomposition. This paper presents charts that give the final pressures to which gases ofgravity 0.6 to 1.0 at given initial temperatures and pressures may be expandedwithout formation of hydrate. Hydrate-Forming Temperatures and Pressures as a Function of Gas Gravity Experimental data of pressure versus temperature, at which solid hydrate willform, provided sufficient water is present, are available for a series ofgases. A method of predicting the pressure-temperature curve for a given gascomposition has been reported. The solution to this problem requires that thesecurves relating pressure to temperature be established for gases of givengravities. T.P. 1748