Heavy oil-water emulsion for bivalent dual-fuel engines

Marine diesel engines are highly efficient power engines. The relatively low engine speed and high combustion temperatures in the stoichiometric combustion zones lead to high nitrogen oxide formation. In addition, unburned hydrocarbons, carbon monoxide, sulfur dioxide, and particulate matter are also emitted. In recent years, developments in marine diesel engines have been shaped by the need to comply with increasingly stringent emissions regulations while maintaining efficiency. Key to this are the regulations for nitrogen oxide and sulfur oxide emissions set by the International Maritime Organization (IMO). With the introduction of the IMO Tier III emissions standard in 2016 in the so-called Emission Control Areas (ECAs), nitrogen oxide emissions will be drastically reduced once again. This offers the advantage of eliminating the need for costly measures, such as exhaust gas aftertreatment and, in some cases, additional operating fluids.

As part of the research project, the influence of a fuel-water emulsion, intake manifold water injection, and direct water injection on the combustion process in dual-fuel operation was investigated. In this study, the water content and the energy content of the ignition jet were varied, and high-viscosity heavy fuel oil was used as the ignition oil in addition to diesel fuel. Due to the enthalpy of vaporization of the injected water, it is possible to lower the combustion temperatures and thus reduce nitrogen oxide emissions while simultaneously improving other parameters, such as the filter soot index, the effective efficiency, and combustion stability. This operating strategy makes it possible to fall below the IMO Tier III nitrogen oxide limit currently in effect in emission control areas while simultaneously achieving good results for other combustion-related parameters.

This means that the process investigated in the research project is in direct competition with exhaust aftertreatment technology using SCR catalysts. However, from a business perspective, a key advantage is that there is no need to procure an aqueous urea solution as a reducing agent, and the process under investigation requires less space. The operating strategy is aimed at operators of medium-speed marine engines who are seeking solutions to comply with applicable emission limits both within and outside emission control areas under highly fluctuating operating conditions.