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ARGOMENTO: Research status of the deoxidizer for industrial g
Research status of the deoxidizer for industrial g
2 Mesi 2 Settimane fa #10654
Research status of the deoxidizer for industrial gas mixtures
A lot of useful gases in industrial gas mixtures can not be recycled because of their high oxygen concentrations,which easily lead to explosion and bring safety problems to the industrial production.The research on mixed gas deoxidizing catalysts has become more and more important and has bright prospects of application and markets due to the attention to environmental protection,energy saving and emission .Get more news about Oxide Deoxidizing Catalyst,you can vist our website!.
The deoxidization processes,including catalytic deoxidization,chemical adsorption deoxidization and active carbon high temperature deoxidization,and an overview of mixedgas deoxidizers were introduced.The mixed gas deoxidizing catalysts included noble metal deoxidizing catalysts and nonnoble metal deoxidizing catalysts.The nonnoble metal deoxidizing catalysts such as copper based,nickel based,manganese based,molybdenum based and ferrum based deoxidizing catalysts were introduced.The research prospects of mixed gas deoxidizing catalysts in future were outlined.Considering their lower price,the research on nonnoble metal deoxidizing catalysts is superior to those on noble metal deoxidizing catalysts.
Diesel Oxidation Catalysts (DOC) are catalytic converters designed specifically for diesel engines and equipment to reduce Carbon Monoxide (CO), Hydrocarbons (HC) and Particulate Matter (PM) emissions. DOC's are simple, inexpensive, maintenance-free and suitable for all types and applications of diesel engines.
Modern catalytic converters consist of a monolith honeycomb substrate coated with platinum group metal catalyst, packaged in a stainless steel container. The honeycomb structure with many small parallel channels presents a high catalytic contact area to exhaust gasses. As the hot gases contact the catalyst, several exhaust pollutants are converted into harmless substances: carbon dioxide and water.
Diesel exhaust contains sufficient amounts of oxygen, necessary for the above reactions. The concentration of O2 in the exhaust gases from diesel engine varies between 3 and 17%, depending on the engine load. Typical conversion efficiencies for CO and HC in the Nett® diesel oxidation catalyst are given in Figure 2. The catalyst activity increases with temperature. A minimum exhaust temperature of about 200°C is necessary for the catalyst to "light off". At elevated temperatures, conversions depend on the catalyst size and design and can be higher than 90%.
Conversion of diesel particulate matter is an important function of the modern diesel oxidation catalyst. The catalyst exhibits a very high activity in the oxidation of the organic fraction (SOF) of diesel particulates. Conversion of SOF may reach and exceed 80%. At lower temperatures, say 300°C, the total DPM conversion is usually between 30 and 50% (Figure 3). At high temperatures, above 400°C, a counterproductive process may occur in the catalyst. It is the oxidation of sulfur dioxide to sulfur trioxide, which combines with water forming sulfuric acid:
A formation of the sulfate (SO4) particulates occurs, outweighing the benefit of the SOF reduction. Figure 3 shows an example situation, where at 450°C the engine-out and the catalyst total DPM emissions are equal. In reality the generation of sulfates strongly depends on the sulfur content of the fuel as well as on the catalyst formulation. It is possible to decrease DPM emissions with a catalyst even at high temperatures, provided suitable catalyst formulation and good quality fuels of low sulfur contents are used. On the other hand, diesel oxidation catalyst used with high sulfur fuel will increase the total DPM output at higher temperatures. This is why diesel catalysts become more widespread only after the commercial introduction of low sulfur diesel fuel.
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