Japanese enginebuilder Daihatsu is in the final stages of validating a new technology that would enable its LNG-burning engines to use LPG as fuel.
The company’s solution involves an onboard gas reformer to convert propane-based LPG into substitute natural gas (SNG), which can be used in the company’s dual-fuel engines. The technology was presented publically for the first time at a regional event held by internal combustion engine council CIMAC in Kobe in October 2018.
LPG is more readily available than LNG but is easier to handle and boasts a similar emissions profile. But the variability of the component gases (mainly propane and butane) makes it difficult to use in engines. Daihatsu’s solution is to follow land-based gas reforming principles: desulphurising LPG, methanising it by steam reformation and then removing carbon dioxide and water to leave SNG that can be burned in engines alongside LNG.
The company studied traditional gas reformer plant before installing a scaled down prototype, which could eventually be put on board a ship, at its factory in Moriyama. There, Daihatsu conducted reformed gas evaluation tests using the factory’s power generator.
At the same time as testing the prototype gas reformer, the company investigated the performance of reformed gas in its lean-burn, dual-fuel engines. This included identifying combustion timings and the speed at which engine load could be ramped up, finding a slightly longer combustion time than for Japan’s City Gas, but a quicker ramp-up to full engine load. A gas composition test identified the ratio at which methane and propane need to be mixed during the reforming process dependent on engine load.
In the final stages of development Daihatsu is now examining the long-term reliability of engines operating on reformed gas well as evaluating the deterioration of the reformer catalyst.