Process Safety and Environmental Protection 9 0 ( 2 0 1 2 ) 108–120

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Large scale high pressure jet fires involving natural gas and natural gas/hydrogen mixtures
Barbara Joan Lowesmith ∗ , Geoffrey Hankinson
Loughborough University, Loughborough, UK

a b s t r a c t
A series of six large scale high pressure jet fires were conducted using natural gas and natural gas/hydrogen mixtures. Three tests involved natural gas and three involved a mixture of natural gas and hydrogen containing approximately 24% by volume hydrogen. For each fuel, the three tests involved horizontal releases from 20, 35 and 50 mm diameter holes at a gauge pressure of approximately 60 bar. During the experiments, the flame length and the incident radiation field produced around the fire were measured. The fires also engulfed a 1 m diameter horizontal pipe placed across the flow direction and about halfway along the flame. This pipe was instrumented to measure the heat fluxes to the pipe. The data obtained is compared with previous data obtained for various hydrocarbons at large scale. © 2011 The Institution of Chemical Engineers. Published by Elsevier B.V. All rights reserved. Keywords: Jet fires; Large scale experiments; Natural gas/hydrogen mixtures; Heat loads

1.

Background

Hydrogen is seen as an important energy carrier for the future which offers carbon free emissions at the point of use. However, transition to the hydrogen economy is likely to be lengthy and will take considerable investment with major changes to the technologies required for the manufacture, transport and use of hydrogen. In order to facilitate the transition to the hydrogen economy, the EC funded project Naturalhy (NATURALHY, 2010) has studied the potential for the existing natural gas pipeline networks to transport hydrogen from manufacturing sites to hydrogen users. The hydrogen, introduced into the pipeline network, would mix with the natural gas. The end-user may then extract the hydrogen for use in fuel cell applications or burn the gas mixture directly within existing gas-fired appliances, thereby reducing carbon emissions compared to natural gas. Using the existing pipeline network to convey hydrogen in this way would enable hydrogen production and hydrogen fuelled applications to become established prior to the development of a dedicated hydrogen transportation system, which would require considerable capital investment and time for construction. However, the existing gas pipeline networks are designed, constructed and operated based on the premise that natural gas is the material to be conveyed. Hydrogen has different

chemical and physical properties which may adversely affect the integrity or durability of the pipeline network, or which may increase the risk presented to the public. For these reasons, the Naturalhy project (www.naturalhy.net) has assessed the feasibility and impact of introducing hydrogen into a natural gas pipeline system. Determining any change in risk to the public was a major part of this project. As part of the safety related work, the characteristics and consequences of fires following a release of methane/hydrogen from high pressure transmission pipelines or above ground high pressure pipework have been studied by the conduct of large scale experiments and the development of associated mathematical models. In this paper, a programme of large scale high pressure jet fires is reported. The key objective of the work was to provide experimental data on the characteristics of fires which will assist in the development and validation of mathematical models which can be used to predict fire hazards.

2.

Introduction

Failure of fittings or small bore pipework, or mechanical tool impact on pipework or vessels of the high pressure gas infrastructure could give rise to a jet fire. These fires can persist