Purification technology and equipment for multi-pollutants of ship exhaust based on EGC in-situ O3/NaClO

Maritime transportation undertakes more than 90% of my country’s international trade transportation volume, and 90% of commercial ships use heavy fuel oil, which emits a large amount of NOx (~20g/kW•h), SOx (~22g/kW•h), PM (~0.8g/ kW•h), contributing rates to the concentration of NOx, SO2, and PM10 in the ambient air of coastal areas, especially port cities, are as high as 10%~30%, 15%~50%, and 5%~37%, ocean-going vessels have become the primary atmosphere reason of pollution.

The International Maritime Organization (IMO) announced the amendment to “the International Convention for the Prevention of Pollution from Ships” (implemented on January 1st, 2020) based on the resolution MEPC.277(70) on October 28th, 2016, it is urgent to reduce the emission of air pollutants from ships.

In my country's latest ship air pollutant control policy (Issued by the Maritime Safety Administration of the Ministry of Communications [2018] No.168), marine fuel oil is more stringent than IMO requirements.

In the future, green emission commercial ships will present three mainstream response measures, that is, use low-sulfur ship combustion, or install tail gas purification measures to use high-sulfur ship combustion, or use alternative fuels (such as liquefied LNG).

In view of the large price difference between low-sulfur ship fuel and high-sulfur ship fuel and the use of alternative clean fuels requires a comprehensive power system retrofit, the installation of exhaust gas purification measures has become the most competitive development direction of ship exhaust gas purification.

At present, in terms of ship exhaust gas aftertreatment technology, single pollutant control technology is mostly used internationally, such as particle trap (DPF) to control PM, selective catalytic reduction (SCR) to control NOx, and wet seawater scrubbing technology (EGC) Control SO2, but the above-mentioned technical combination has problems such as complex system, large number of equipment, large area, difficult layout, high investment operation cost, etc.

Therefore, combined with the development trend of domestic and foreign ship exhaust gas treatment technology, it is inevitable to realize the removal of multiple flue gas pollutants in the limited space of ships. The EGC-based multi-pollutant collaborative control technology developed by our company focuses on the three footholds of light weight, high performance and stability of denitrification, sulfur removal and dust removal equipment, to meet the development needs of green shipping.

Technical features:

1) O3/NaClO is prepared by in-situ air and seawater, no need to store desulfurizer and denitrification reducing agent on board, and the operation is safe and reliable.

2) O3/NaClO synergistic oxidation of NO, electrolyte\seawater combined with ex-situ stepwise absorption of NOx/SOx, low emission index for comprehensive deep purification of flue gas with multiple pollutants.

3) Flexibly adapt to the free switching working mode of the ship's power grid load, and the system integration, reliability, flexibility, economy, and environmental friendliness are significantly improved.

4) Multi-purpose and multi-productive coupling, can simultaneously provide marine protective gas and ship ballast water treatment agent, low comprehensive demand for electric power, and great economic competitive advantage.