Current Status and Development Trends of Marine Methanol Engine Technology

As a marine fuel, methanol has certain prominent advantages. Compared with alternative fuels such as liquefied natural gas (LNG), methanol is in a liquid state at room temperature, which simplifies the design and construction of ship fuel tanks and offers significant cost advantages. It contains no sulfur. When a dual-fuel engine is in operation, only a small amount of sulfides is produced by the ignition of diesel, so it can easily meet the IMO's emission reduction requirements for sulfur oxides (SOx) and avoid the additional cost of SOx post-treatment. 

In terms of nitrogen oxide (NOx) emission control, methanol performs excellently. Taking the FARIZON engine as an example, its pre-treatment layer is equipped with a methanol fuel pre-desulfurization device, which can efficiently remove most sulfides; the combustion optimization layer adopts adaptive swirl ratio control, greatly reducing particulate matter emissions to an extremely low level; the post-treatment layer uses a compact SCR (Selective Catalytic Reduction) system, significantly reducing ammonia slip, resulting in a remarkable emission reduction effect that meets the IMO Tier Ⅱ standard. Moreover, methanol contains 50% oxygen atoms, with a fast combustion speed and high combustion quality, which can effectively reduce pollutant emissions. 

In terms of industrial supporting facilities, as an important chemical raw material, China has built a complete system for methanol production, storage, transportation and refueling, with sufficient production capacity; methanol supporting facilities in regions with developed international shipping are also relatively complete. With the development of renewable energy, the industrial scale of bio-methanol and renewable synthetic methanol is expanding, further highlighting its potential as a carbon-neutral fuel for ships.

The research on marine methanol engines can be divided into three stages. The first is the low-pressure port injection methanol combustion technology, which is the early exploration stage. The methanol substitution rate is about 40%, and combustion problems are prone to occur under medium and high load conditions, making it unsuitable for high-power marine engines. The second is the high-pressure in-cylinder direct injection technology for pure methanol fuel, which is the theoretical attempt stage. Due to the low cetane number of methanol, the intake air temperature needs to be increased to 155℃ to achieve stable operation, leading to high application difficulty. The third is the high-pressure in-cylinder direct injection methanol-diesel pilot ignition technology, which is the mainstream development direction. Both MAN and Wartsila have adopted this route, which can solve the problems of port injection. The research on our FARIZON marine methanol engine is based on this technology, which can achieve a relatively high methanol substitution rate.

Against the background of the low-carbon transformation of the maritime industry, methanol port injection pure fuel technology is difficult to adapt to high-power ships, and dual-combustion technology has limited applications due to its low substitution rate. In contrast, the dual-fuel engine with in-cylinder dual direct injection of methanol and diesel has become the industry-recognized core development trend in the future, relying on its prominent advantages of high fuel flexibility and high methanol substitution rate. This technical route not only meets the urgent need for carbon neutrality in the global maritime industry, but also is an important direction for FARIZON marine engines to focus on the green shipping track and plan for future development. With the continuous improvement of supporting facilities for green methanol production, storage and refueling, as well as the continuous innovation of core engine technologies, this technology will further release its potential and provide solid support for the maritime industry to move towards the goal of carbon neutrality.