Converting LPG Stoves To Use Biomethane

ABSTRACT

This article presents a study on using portable biomethane for domestic cooking in Thailand in domestic stoves. Thailand presently uses approximately 20,000 tonnes of LPG every day. It is estimated that Thailand has the potential to produce the equivalent of 3,000 tonnes of LPG equivalent energy from compressed biomethane gas (CBG) per day. This assumes full conversion of all agricultural, industrial and municipal wastes into CBG. Since CBG is a form of renewable energy, the use of it for domestic cooking purposes will help to reduce Thailand's dependence on imported energy and have a positive impact on the environment. The difficulty arises when a cylinder of biomethane, which is processed biogas comprising of at least 85% methane, is used instead of LPG, which is comprised of propane and butane, in a cooking stove. The Wobbe index for LPG is approximately double that of biomethane indicating that they are not interchangeable gases. The density of LPG is also 2 - 3 times that of biomethane which results in incompatible calorific or heating values and flow rates, assuming constant pressure, in domestic stoves. Without modification to the stove or the supply conditions the biomethane will not properly combust. Two domestic stoves types were selected and modified to allow biomethane to be used. An experiment was setup to measure the fuel flow rates, pressure and combustion efficiency in these modified stoves. The results of these experiments point to an optimal design modifications for converting an LPG to a biomethane stove.

Keywords::

• Biomethane
• LPG
• Domestic Stove
• Porous Burner
• Vertical Burner
• Wobbe Index

Acknowledgments

The authors would like to express their thanks to the Energy Policy and Planning office of Thailand (EPPO) and the Center of Excellence for Renewable Energy at Chiang Mai University for supporting this research.

Notes

* The International Standard Metric Conditions for natural gas and similar fluids are 288.15 K (15.00 °C; 59.00 °F) and 101.325 kPa. Natural gas — Standard reference conditions (ISO 13443). Geneva, Switzerland: International Organization for Standardization. 1996.

Additional information

Notes on contributors

S. Suwansri

Mr. Suriyun Suwansri obtained his Master's degree from Chiang Mai University, specializing in the field of design and development of domestic burners. He now works as a research engineer in burner development at the Lucky Flame Company which develops and produces stoves for the market in Thailand. His research focuses on thermal efficiency and emissions characteristics of these burners.

J.C. Moran

Dr. James Moran, the corresponding author, received his Ph.D. degree in Mechanical Engineering from the Massachusetts Institute of Technology in 2001. He is currently an Assistant Professor at the Department of Mechanical Engineering in Chiang Mai University, Thailand. His research interests include low friction surfaces, meso scale combustion, sustainability and sources of bioenergy. Email: [email protected]

P. Aggarangsi

Dr. Pruk Aggarangsi is an assistant professor in mechanical engineering at Chiang Mai University where he moved after receiving his doctorate from Carnegie Mellon University. He is also the deputy director of the Energy Research and Development Institute-Nakorping which is well known for decades of biogas developments in Thailand and South-East Asia. Dr. Pruk specializes in the fields of anaerobic digestion technology, design and development of biogas system in tropical areas as well as mathematical modeling in many engineering applications. E-mail: [email protected]

N. Tippayawong

Dr. Nakorn Tippayawong received his B.Eng. degree in Mechanical Engineering and Ph.D. degree in Internal Combustion Engines from Imperial College London, UK in 1996 and 2000, respectively. He is currently an Associate Professor at Chiang Mai University, Department of Mechanical Engineering. His research interests include biomass utilization, energy efficiency improvement, and aerosol analysis. So far, he has published more than 100 papers in peer reviewed international journals.

P. Rerkkriangkrai

Dr. Prasert Rerkkriangkrai received his B.Eng. (Mechanical Engineering) from Chiang Mai University, Thailand, and M.Eng. (Energy Technology) from the Asian Institute of Technology in 1986 and 1988, respectively. He is currently an Associate Professor at Chiang Mai University in the Department of Mechanical Engineering. He is also the Director of the Energy Research and Development Institute - Nakornping, Chiang Mai which for decades has developed biogas projects throughout Thailand and South-East Asia.