Production of town gas from natural gas in Hong Kong for a reduction in cost and greenhouse gas emissions

Abstract

Hong Kong has a well-established piped town gas network, with 27.7 billion MJ of gas sales in 2021. The feedstock for town gas production was converted from naphtha to a mixed feedstock of 40% naphtha and 60% natural gas (NG) in 2006, resulting in a 21% decrease in greenhouse gas (GHG) emissions and 1.58 billion HKD/year of cost savings. Increasing the proportion of the NG feedstock would potentially lead to more benefits. However, there may be difficulties in meeting the stringent combustion characteristics of town gas and the existing plant capacity may be reduced. Four processes for the production of town gas from NG are proposed in this work. The feasibility of each process was verified via simulation with Aspen Plus V14. A techno-economic evaluation showed that 296 million HKD/year of cost savings and 172224 t CO2-eq/year of GHG emission reduction could be achieved by using the proposed processes to produce town gas from NG. The reformer duties in the new processes were up to 16.6% lower compared to the existing process. There would not be any reduction in plant capacity associated with a limitation in heat transfer area, which is a common bottleneck.