10th International Aerosol Conference September 2 - September 7, 2018 America's Center Convention Complex St. Louis, Missouri, USA
Abstract View
Collection Characteristic of Diesel Nano-Particles in an Electrostatic Precipitator: Experiment Using Residual Fuel Oil and Light Fuel Oil
HIDETOSHI SAWANO, Akinori Zukeran, Yasumoto Koji, Kanagawa Institute of Technology
Abstract Number: 194 Working Group: Combustion
Abstract Diesel engines have been extensively used as a generator, an automobile or an agrimotor due to low CO2 emission. However, their exhaust gases contain air pollutants, such as NOx and particulate matter (PM). It is known that nano-particles are included in PM. SOx is also included in exhaust gas, when residual fuel oil is used.
The purpose of this study is to remove PM using an electrostatic precipitator (ESP). In particular, the relationship between nano-particle collection efficiency and the particle diameter was investigated for emission gas from diesel engine with residual fuel oil and light fuel oil.
The experimental system consisted of a diesel engine (displacement 400cc) and an ESP, and residual fuel oil (ENEOS LSA heavy oil (01)) or light fuel oil (ENEOS gas oil) were used for the diesel engine. The ESP has a needle-to-cylinder electrode structure with a metal cylinder with an inner diameter of 58 mm and a stainless steel needle electrode with a diameter of 1.6 mm (tip angle 14 °, curvature radius 22 μm). The voltage applied to the needle electrode was DC-16 kV.
A portion of the gas was drawn at the gas temperature of 160℃ and 10-hold diluted by the diluter at the same temperature of the gas. After cooling to the room temperature, the particle concentration was measured using a scanning mobility particle sizer (SMPS, TSI, Model 3936). SMPS can measure the particle concentration for the particle diameter between 5.9 and 250 nm. The collection efficiency η was calculated by equation (1): （1-（N/N0））×100% (1) where, N is particle density after applying the voltage, and N0 is particle density before applying the voltage.
When residual fuel oil was used for a diesel engine, the particle size distribution at the voltage of 0 kV had a peak of approximately 6.0 × 106 parts/cm3at the particle size of 57 nm. At the voltage of -16 kV, the particle concentration at 57 nm decreased to approximately 2.2 × 105 part / cm3. The collection efficiency was greater than 95%. This is due to electrostatic precipitation effect. However, the concentration for the particle size less than approximately 20 nm increased at the voltage of -16 kV in comparison with that at 0 kV. Thus, the experiment using the light fuel oil was carried out in order to investigate this cause. As a result, the particle size distribution at the voltage of 0 kV had a peak of approximately 6.6 × 106 parts / cm3 at the particle diameter of 71 nm. At a voltage of -16 kV, the particle concentration at 71 nm decreased to 0.8 × 106 parts / cm3 due to the electrostatic precipitation effect. However, particle concentration for the particle diameter less than 20 nm did not increase.
It is known that fine particles are generated by ion-induced nucleation when corona discharge is generated in the gas included SO2. Analysis of the components in the exhaust gas revealed that the SO2 concentration in the exhaust gas using residual fuel oil was 37 ppm, although it was 2 ppm in the case of light fuel oil. Therefore, the increase the concentration for particles diameter less than 20 nm in the exhaust gas using residual fuel oil was due to ion-induced nucleation.
However, the total number collection efficiency in the exhaust gas using the residual fuel oil was 87%, and the ion-induced nucleation did not influent on the total collection efficiency. It is also known that the collection efficiency of fine particles can be improved by increasing the collection electrode length.