The ship exhaust gas treatment system (mainly including the two subsystems of denitration and desulfurization) is the key environmental protection equipment for ships required by the International Maritime Organization (IMO) MARPOL Convention. Air pollution caused by emissions.
In view of the increasing awareness of environmental protection and the gradual increase in the approval of ship owners, the market demand for ship exhaust gas treatment systems is huge.
1. Relevant specification requirements
1) In 2016, Tier III came into effect. According to this standard, all ships built after January 1, 2016, with a main engine output power of 130 kW and above, sailing in North America and the US Caribbean Emission Control Area (ECA) , the NOx emission value shall not exceed 3.4 g/kWh. IMO Tier I and Tier II standards are applicable globally, Tier III is limited to emission control areas, and the sea areas outside this area are implemented in accordance with Tier II standards.
2) According to the 2017 IMO meeting, from January 1, 2020, the global 0.5% sulfur limit will be officially implemented.
2. Principle of denitrification system
1) The denitration system adopts the Selective Catalytic Reduction (SCR) method, that is, under the action of the catalyst, the reducing agent reacts with nitrogen oxides in a certain temperature range (280~450℃) to generate harmless nitrogen and water process. In order to ensure the safety of wearing personnel, the reducing agent does not directly use ammonia gas, but adopts the process of spraying urea solution into high-temperature exhaust gas to decompose it to generate ammonia gas, which avoids the danger of ammonia gas storage and use.
The denitration system mainly includes a catalytic reactor, a urea reflection unit, a urea quantitative injection unit, and a distributed control system.
3. Desulfurization system technology
1) In order to meet the increasingly stringent ship sulfur emission standards, ship operators generally use low-sulfur fuel oil, exhaust gas treatment systems or clean energy (LNG dual-fuel engines, etc.) and other solutions. The selection of the specific scheme is generally considered by the shipowner in combination with the economic analysis of the actual ship.
2) The desulfurization system adopts composite wet technology, and various EGC systems (Exhaust Gas Cleaning System) of open, closed, mixed, seawater, magnesium, and sodium methods are used in different waters to meet operating costs and emissions. the optimal combination required.