Applications soots

Using 2eohte catalysts, the NO reduction takes place inside a molecular sieve ceramic body rather than on the surface of a metallic catalyst (see Molecularsieves). This difference is reported to reduce the effect of particulates, soot, SO2/SO2 conversions, heavy metals, etc, which poison, plug, and mask metal catalysts. ZeoHtes have been in use in Europe since the mid-1980s and there are approximately 100 installations on stream. Process applications range from use of natural gas to coal as fuel. Typically, nitrogen oxide levels are reduced 80 to 90% (37). 

Opacity reduction is the control of fine particulate matter less than 1 ixm). It can be accomplished through the application of the systems and devices discussed for control of particulate matter and by use of combustion control systems to reduce smoke and aerosol emission. In addition, operational practices such as continuous soot blowing and computerized fuel and air systems should be considered. 

The flame maps shown in Figure 8.3.12 indicate reduction of peak temperatures with the increase in the EGR content, and this translates into tangible decrease in engine-out NO,.. While using EGR is a very effective way of reducing its percentage and thus magnitude of NO t reduction in a practical application is limited by the increased soot formation. 

The small particles are reported to be very harmful for human health [98]. To remove particulate emissions from diesel engines, diesel particulate filters (DPF) are used. Filter systems can be metallic and ceramic with a large number of parallel channels. In applications to passenger cars, only ceramic filters are used. The channels in the filter are alternatively open and closed. Consequently, the exhaust gas is forced to flow through the porous walls of the honeycomb structure. The solid particles are deposited in the pores. Depending on the porosity of the filter material, these filters can attain filtration efficiencies up to 97%. The soot deposits in the particulate filter induce a steady rise in flow resistance. For this reason, the particulate filter must be regenerated at certain intervals, which can be achieved in the passive or active process [46]. 

Several researchers have focused their attention on the application of oxide materials to lower the oxidation temperature of soot particulates. It was reported that active soot oxidation catalysts are PbO, C03O4, V2O5, M0O3, CuO, and perovskite type oxides[3]. 

Under the EuroIV regulation (2005), the Diesel Particle Filter (DPF) emerged and is necessary for the heavily loaded applications. Renault plans to make a CSF offer for all the diesel product range. This system enables to treat nearly 100% of the particle matter (PM, soot). When loaded, the DPF requires a regeneration phase to bum the accumulated soot. This regeneration is mandatory to keep not only the engine performance and reliability, but also the DPF reliability itself. 

Overall, EGR and combustion/injection systems constitute the key factors to comply with the EuroIV standards (applied in January, 2005). The EuroIV step exhibits EuroIII NO and soot particles limits divided by 2. Besides, vehicle s weight is always increasing due to the introduction of new safety systems and equipment. Therefore, pollutants emissions increase and a supplementary effort to reach the normative threshold is to be made. To comply with this target, some evolutions have been introduced, as for example multi-injection or water-cooling of the EGR system. The NO,/particle compromise adjustment remains possible for most of the applications without any after-treatment system like the Diesel particle filter (DPF). 

With a limit of soot particles emissions proposed at 5mg/km, the DPF has to be installed in the exhaust line and becomes mandatory for EuroV (the date of application for EuroV is unknown, of course, but foreseen in the middle of 2009). 

High temperature The high-temperature off-gases from combustion-based sources of inerts typically must be quenched before use. Water scrubbing, in addition to reducing the temperature, can remove soot and sulfur compounds (which could react with moisture to form corrosive acids) present in the off-gas. The humidity of the resultant gas stream may make it unsuitable for inerting applications where moisture cannot De tolerated. 

Carbon black (soot). It is obtained by the incomplete combustion of natural gas or liquid hydrocarbons. The particle size of carbon black is very small its applications are mainly in rubber industry (to strengthen and reinforce rubber) and also as a pigment in the preparation of inks, etc. 

This approach, however, requires the absence of ill-defined carbon deposits originating from defect-induced soot formation on the surface of nanocarbons during their synthesis. Pyrolytic structures often counteract the control over activity and selectivity in catalytic applications of well-defined nanocarbons by offering an abundance of highly reactive sites, however, in maximum structural diversity. Although some nanocarbons are equipped with a superior oxidation stability over disordered carbons [25], such amorphous structures can further induce the combustion of the well-ordered sp2 domains by creating local hotspots. Thermal or mild oxidative treatment,... 

Several units with a PM collection device located upstream of the SCR have seen increased pressure drop from fine particulates accumulating on the catalyst bed. Soot blowers have been partially successful in this application. When the SCR is applied to a CO boiler with limited pressure drop, the SCR has typically been located upstream of PM removal to avoid this problem. Some refiners have chosen to install a spare SCR reactor to provide redundancy due to pressure drop concerns. Others have used a bypass where local regulations allow. 

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