Study On Diesel Exhaust Gas Wet Purification With Attapulgite Clay Absorbent

Based on modern monitoring and analyzing technologies such as combustion analyzer, CO-HC automatic analyzer, Tem, Sem, EDS , GC/MS (gas chromatography/mass spectrometry) and Zetasizer, this thesis investigates the composition, physical and chemical properties of the contaminants in the diesel exhaust gas. The experimental results show that most of the diesel particulates are wad-shaped and chain-shaped and composed mainly of organic compounds or carbon particles covered with organic compounds. The peak value of the diesel particle size distribution is about 40 nm. In the exhaust gas, the PM concentration was 32. 6mg/m³ï½ž143.6mg/m³, NO_x 208 × 10^-6 ～ 568×10^-6(v/v), SO₂ 18 × 10^-6(v/v) and HC about 16 × 10^-6(v/v)..According to the physical and chemical properties of the diesel contaminants, a lot of experiments have been made before attapulgite clay was chosen as the main absorbent. Work has also been made on the rare earth modification of the attapulgite. The experiment used a jet bubble reactor to investigate the effects of the composition and pH value of absorbent solution, liquid level in the reactor, temperature and operating mode on the removal efficiency of the diesel contaminants. The optimal formula of the absorbent solution is as follows: Attapulgite clay 28%, m (Rare earth):m (Attapulgite clay) 6%, NaOH about 1%. Under the optimal experimental condition, the diesel particulates have been removed from the exhaust gas by 71. 3%, NO_x by 90.6%, all other harmful gas such as HC and SO₂ by over 90%. This experimental result was validated in engineering application trials.After experimenting with Tem, Sem, Tg, Master sizer and Infrared spectra, the paper illustrates the crystalline structure of attapulgite and the colloidal properties of the absorbent solution, explores the mechanism of the diesel particulates and other contaminants removal from diesel exhaust gas. The initial result shows that the NO in the exhaust gas was removed through combined absorbent process of catalytic oxidation and alkali neutralization; the diesel particulates and HC were removed by the adsorption on the outer surface of attapulgite clay and colloid particles; the removal of the SO2 and other acid gases is a process of alkali neutralization.