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.

Co-digestion of water hyacinth, municipal solid waste and cow dung: A methane optimised biogas–liquid petroleum gas hybrid system

“…1. WI for LPG is around 85 MJ/m 3 and that of methane from biogas is 36 MJ/m 3 [29]. This shows that LPG and methane from biogas cannot be directly interchanged.…”

Optimization of domestic biogas stove burner for efficient energy utilization

“…The challenge arises that Liquefied Petroleum Gas (LPG) burner does not work directly on biogas . The Wobbe index for LPG is considered to be twice for that of biogas which means these burners are not interchangeable gases (Suwansri et al, 2015).…”

“…Vital parameters to be observed for combustion of biogas are flame speed, ignition temperature, gas pressure as well as the rate of mixing gas and air. The steadiness of biogas flame in reference burners was studied by Suwansri et al (2015). However, the biogas used 70% methane including varying the primary airflow.…”

“…These stoves are poorly designed especially in areas such as an injector diameter and throat diameter. To use biogas as an alternative for liquefied petroleum gas (LPG) in domestic applications, rectifications are required for the burner stoves while considering health, economic, and environmental issues (Suwansri et al, 2015). The available biogas burners have not only poor quality and low energy output, but their designs have also been reported that they do not follow the burner theory sufficiently .…”