Diesel Generator Set Exhaust Purification
Diesel generator sets, as the current mainstream preferred choice for emergency power sources, have been widely adopted. With the gradual increase in national environmental protection standards for emissions, the installation of exhaust gas purification systems in the exhaust smoke systems of diesel generator sets has become an inevitable requirement.
- Emission Requirements for Diesel Engines
The emissions from the diesel engines of generator sets should be lower than the limits stipulated by the Chinese National Standard GB. When the average effective pressure of the diesel engine is greater than 300 kPa and the fuel consumption rate is 226–238 g/(kW·h), the specific emission limits for CO and NOx are 10 g/(kW·h) and 21 g/(kW·h), respectively. Typical emission values for diesel engines are shown in Table 1.
Table 1 Diesel Engine Emission Standards (For Reference)
Component Emission Value (g/(kW·h)) Treatment Method
NOx 8.2–20 Water washing, SCR reduction
CO 3 DOC catalytic oxidation
PM (Particulates) 0.4–0.7 DOC+DPF interception regeneration, interception
SO₂ 0.7–10 Use of fuel compliant with national standards
Noise
(1) The specific emission values for a particular model of diesel generator set should be provided by the generator manufacturer.
(2) Whenever possible, choose diesel engines with low emissions. If the engine’s emissions exceed the limits set by the national standard, external purification treatment is necessary.
Treatment Solutions
I. Water Washing and Spraying Method
The water washing filtration method can simultaneously filter PM particulates and NOx but cannot remove CO and CH.
NOx (nitrogen oxides) is a general term for a group of compounds, primarily including NO, NO₂, etc.
NO₂ is soluble in water and undergoes a chemical reaction with it to form nitric acid (HNO₃). The wastewater requires further treatment before it can be discharged directly (note the requirements for visible water vapor emissions).
II. Metal Felt Filtration Method (Intercepts PM Only)
This method uses filtration material made from 316L alloy metal wire felt. Based on the characteristics of internal combustion engine exhaust, a modular and customized design is adopted, utilizing a DPF filtration substrate designed with professional fluid dynamics (allowing exhaust gas to pass through the filter element 360 degrees). The diesel particulate filter (DPF) must consist of multiple sets of DPF filtration substrates connected in parallel to facilitate later maintenance. It also features noise reduction functionality. The particulate capture cross-sectional area is large, the initial back pressure is small, and the back pressure increases slowly, while the soot treatment efficiency needs to achieve a 90%–98% interception rate. The units are designed for easy disassembly and flexible removal for water washing and regeneration, ensuring convenient and quick maintenance. The equipment must be equipped with a safety bypass that automatically opens upon high back pressure alarm caused by blockage, ensuring safe operation.
III. Oxidation Reduction: DOC + DPF + SCR + ASC
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The design of catalytic oxidation reduction equipment should match the unit’s parameters, emission requirements, and installation attributes to determine the layout and quantity of catalysts used. Different projects have varying local acceptance requirements.