Hydrogen blending with natural gas for combustion efficiency improvement toward decarbonisation of power plants

Abstract

The 12th Malaysia Plan highlighted Malaysia’s commitment to reduce Greenhouse Gas (GHG) emissions by 45% based on Gross Domestic Product (GDP) in 2030 and reach net zero by 2050. To achieve this target, Malaysia has to decarbonise the energy sector as it is the primary emission source, contributing up to 75% of GHG emissions in Malaysia. Hydrogen fuel is getting much attention globally, and it has been said that it can be a new renewable energy source to replace fossil fuels. Hydrogen combustion is clean and only produces water and energy. However, several studies have identified that hydrogen combustion could produce NO_x, which is more harmful to the environment than CO₂. Studies on hydrogen application in the energy sector in Malaysia are limited, and the implementation of total hydrogen fuel in power plants may not happen shortly. Hence, a fundamental study was proposed on co-firing hydrogen and natural gas fuel. This study aimed to examine co-firing characteristics such as temperature, pressure, and air-to-fuel ratio on GHG emission and energy release to find the optimum natural gas-to-hydrogen ratio. The model was developed using Aspen Plus, and hydrogen-natural gas blend percentages varied from 0% to 30%. The findings showed that increased operating temperature led to higher NO_x formation, while varying pressures did not impact the CO₂ and NO_x formation. The pure natural gas combustion system was more sensitive towards air-to-fuel ratio changes, and an increase in air-to-fuel ratio to 1.5 led to 160% higher NO_x formation due to an increase in nitrogen content. The combustion of the hydrogen blend led to lower CO₂ formation but higher NO_x formation. Lastly, the energy released by the hydrogen blending system was lower due to the formation of water that absorbed the heat released by the combustion.