Spontaneous Ignition of Pressurized Releases of Hydrogen and Natural Gas Into Air

Abstract

This paper demonstrates the ''spontaneous ignition'' (autoignition=inflammation and sustained diffusive combustion) from sudden compressed hydrogen releases that is not well documented in the present literature, for which little fundamental explanation, discussion or research foundation exists, and which is apparently not encompassed in recent formulations of safety codes and standards for piping, storage, and use of high pressure compressed gas systems handling hydrogen. Accidental or intended, rapid failure of a pressure boundary separating sufficiently compressed hydrogen from air can result in multi-dimensional transient flows involving shock formation, reflection, and interactions such that reactant mixtures are rapidly formed and achieve chemical ignition, inflammation, and transition to turbulent jet diffusive combustion, fed by the continuing discharge of hydrogen. Both experiments and simple transient shock theory along with chemical kinetic ignition calculations are used to support interpretation of observations and qualitatively identify controlling gas properties and geometrical parameters. Although the phenomenon is demonstrated for pressurized hydrogen burst disk failures with different internal flow geometries, similar phenomena apparently do not necessarily occur for sudden boundary failures potential for producing ignition and continuing combustion. Much more experimental and computational work is required to quantitatively determine the envelope of parameter combinations that mitigate or enhance spontaneous ignition characteristics of compressed hydrogen as a result of sudden release, particularly if hydrogen is to become a major energy carrier interfaced with consumer use. Similar considerations for compressed methane, for mixtures of light hydrocarbons and methane (simulating natural gas), and for larger carbon number hydrocarbons show similar autoignition phenomena may occur with highly compressed methane or natural gas, but are unlikely with higher carbon number cases, unless the compressed source and=or surrounding air is sufficiently pre-heated above ambient temperature. Spontaneous ignition of compressed hydrocarbon gases is also generally less likely, given the much lower turbulent blow-off velocity of hydrocarbons in comparison to that for hydrogen.

Pressure limit of hydrogen spontaneous ignition in a T-shaped channel

“…Dryer et al [8] reported that spontaneous ignition events are statistically distributed in a narrow pressure range of 2.04e2.21 MPa, with zero probability for membrane failure pressures less than 2.04 MPa and certain ignition for failure pressures above 2.21 MPa at their experimental set up. In addition to identifying a minimum pressure below which no spontaneous ignition can be observed, it is found that reducing the length of the 1.27 cm (1/2 00 ) NPT pipe nipple to 3.81 cm (1.5 00 ) led to no spontaneous ignition at all failure pressures even up to 5.66 MPa.…”

“…H owever, spontaneous ignition was observed in experiments that included pipes located downstream of a rupture disk. Such experiments were performed by different groups including Dryer et al [8], Mogi et al [9], Golub et al [10], Pinto et al [11], etc.…”

Gas Safety for TFT-LCD Manufacturing

“…Although hydrogen is not pyrophoric like silane or phosphine, hydrogen release from a tube or a crack under high pressure may lead to spontaneous ignition. This is attributed to the low ignition energy, high blow-off velocity and the adiabatic compression from the shock wave of the release (Dryer et al, 2007) Gaseous hydrogen may be supplied in cylinders or in tubes that are designed and manufactured according to applicable codes and specifications for the pressures and temperatures involved. The pressure rating and internal volume of a container determines the quantity of hydrogen it can hold.…”

Ignition of Hydrogen Suddenly Leaked from a High Pressure Tank

“…They fill up a tube by high pressure hydrogen directly to break a cupper plate and to release it into atmosphere. Recently Dryer et al 3 performed several experiments with high pressure hydrogen jets spouting to atmosphere by using compressed hydrogen bottles and burst disks to get auto ignition and diffusion flame. Liu et al 4 studied numerically the high pressure hydrogen jet spouted into atmosphere using a direct numerical simulation method with a full hydrogen chemistry.…”