Session: 14-02-02: Reliability and Risk in Energy Systems

Paper Number: 111150

111150 - Challenges of Purging Air With Natural Gas and Hydrogen Blends in Pipe Segments 

The aspiration for blending hydrogen (H₂) into natural gas (NG) in gas transmission systems is high and is happening globally. However, several design and operational aspects need to be developed to ensure safe and reliable delivery of these blends to the end users. One of these aspects is the development of effective purging procedure of air with NG+H₂ blends during commissioning of a pipe section.  The present research examines various aspects the purging procedures and attempts to address salient parameters and conditions when NG+H₂ blend are the purging gas in relation to the current practices described in AGA Purging Principles and Practice, 2001. Three principal aspects were investigated, namely: 1) The stratification velocities of the air and gas wave fronts for different NG+H₂ blend ratios, and the applicable multiplication factor for effective purge velocities, 2) The interfacial turbulent diffusivity coefficients between air and NG+H₂ blends that determine the extent of the mixing spread as purging progresses, and 3) Evaluate the applicability of the minimum stratification velocity to smaller pipe sizes ≤ NPS 4 where AGA Purging Principles and Practices exhibit a clear inflection behavior pointing to the need for a much higher purge velocity. The present investigation found that the stratification velocity of the air wave is higher than that of the NG+H₂ wave, and both deviate from the classical value corresponding to Fr # = 0.707 assumed in AGA Purging Principles and Practices. It was also found that the inflection shape of the minimum velocity curves in AGA Purging Principles and Practices was not necessary, and that the same procedure applied to large pipe sizes could still be applied to pipe sizes ≤ NPS 4.  Initial results of the diffusivity coefficients show upward deviation from that currently in use in the gas transmission industry. Recommendations for future work are suggested  before the above findings are implements in standards, purge Tables and purging tools particularly to look into the turbulent diffusivity coefficient for a wider range of Reynolds number, in addition to detail analysis of the dual interface mixing if nitrogen buffer is required according to ASME B31.12 code. This is important to accurately quantify the nitrogen buffer volume and interface mixing volumes that would be vented at the outlet end or the pipe section under purging.  The ultimate goal of this work is to be able to model the principal parameters to safely purge pipelines and facilities and perform a thorough safe gas handling operations.

Presenting Author: Kamal Botros Nova Husky Res Corp

Presenting Author Biography: Kamal K. Botros is a Research Fellow of Fluid Dynamics with NOVA Chemicals. Over the past 40 years he has worked on various fluid flow and equipment dynamic problems related to pipelines, oil and gas processing, as well olefins and polyolefins manufacturing plants. Fluid flow problems included unsteady, transient, oscillatory flows, flow induced instabilities in compressor and pump stations, and process plants. He has led several fluid and environmental research programs of significant industrial applications, published over 220 papers in refereed journals and conference proceedings, has been an invited speaker, delivered international seminars on related topics. Current aspiration of Dr. Botros is to make the P/L the leader in ESG, and in achieving the goal of net zero emission well before 2050 through solving technological challenges in CNG, RNG, LNG, green and blue hydrogen, alternative energy and renewable energy. Dr. Botros has six patents and two textbooks on pipeline pumping and compression systems credited to him. Dr. Botros has a Ph.D. in Mechanical Engineering from the University of Calgary and is a registered professional engineer in Alberta, Canada.

Authors:

Kamal K. Botros Nova Husky Res Corp
Colin Hill Think Solutions
Paul Ziade Think Solutions
Craig Johansen Think Solutions
Greg Van Boven TC Energy