Traps particulate

These catalysts contained promoters to minimise SO2 oxidation. Second-generation systems are based on a combined oxidation catalyst and particulate trap to remove HC and CO, and to alleviate particulate emissions on a continuous basis. The next phase will be the development of advanced catalysts for NO removal under oxidising conditions. Low or 2ero sulfur diesel fuel will be an advantage in overall system development. 

The second is a neat idea coming from Johnson Ma tthey. They invented the so-called continuously regenerating trap (CRT) consisting of a monolithic preoxidizer and a particulate trap, see Figure 9.3 [24]. The first monolith (containing Pt) oxidizes hydrocarbons and CO to CO2 and NO into NO2, which is very reactive... 

Hawker, P., Myers, N., Huthwohl, G., Vogel, H., Bates, B., Magnusson, L., and Bronneberg, P. Experience with a new particulate trap technology in Europe. SAE Paper No 970182, (1997). 

Konstandopoulos, A. G., and Kostoglou, M. Periodically reversed flow regeneration of diesel particulate traps. SAE Technical Paper No. 1999-01-0469 (1999b). 

Konstandopoulos, A. G., Vlachos, N., Stavropoulos, I., Skopa, S., Schumacher, U., and Woiki, D. Study of a sintered metal diesel particulate trap. SAE Technical Paper Offer No. 05FL-106, (submitted) (2005). 

As in the case of the slag tank, there was no way to measure quantitatively the precipitator residue flow rate. These residues are slurried with water and flushed continuously into the ash pond. However, for all of the elements except selenium, the precipitator was extremely efficient (>95%) as calculated from the inlet and outlet fly ash concentrations using Equation 6. The reason that selenium fails to be scavenged effectively is not known and certainly warrants investigation. One possibility is that part of the selenium is in a volatile state but is readily adsorbed on particulates trapped by the alundum thimbles. 

Other investigations were conducted at school bus stops to appraise the exposure on pupils. It was found that short (2-6 s) but very high EC mass concentrations of about several hundred gg/m3 occurred (Figure 38). This underlines the need for comprehensive equipping of buses with particulate traps. 

Figure 13.1 Schematic diagram showing various components of a CVD system (1 reactor 2 heating element 3 reaction tube 4 water-cooled end flanges 5 power controller 6 pressure indicator 7 temperature sensor 8,10,11. -precursor gas tanks, 9 metal halide (liquid) vaporizer 12 particulate trap 13 gas scrubber 14 flow meter 15 flow meter valves 16 gas tank regulators 17 substrate support 18 substrates).

As an example of the performance of such a diesel particulate trap, a spontaneous filter regeneration is shown in Fig. 15.3. 

Fig. 15.3. P ressure drop over an experimental diesel particulate trap versus time, showing a spontaneous filter regeneration event (from Ref. [18]).

Many working groups have modeled the performance of diesel particulate traps during the past few decades. Concentrated parameter models (CSTR assumption) have been applied for the evaluation of formal kinetic models and model parameters. The formal kinetic parameters lump the heat and mass transfer effects with the reaction kinetics of the complicated reaction network of diesel soot combustion. Those models and model parameters were used for the characterization of the performance of different filter geometries and filter materials, as well as of the performance of a variety of catalytically active coatings and fuel additives [58],... 

Regeneration curves for different diesel particulate trap geometries and materials are shown in Fig. 15.6. 

Fig. 15.5. Typical pressure drop and concentration-time curves of a diesel particulate trap in a closed gas-loop experiment with constant heating rate for the characterization of catalyst or filter performance for the combustion of diesel soot. Sintered SiC ceramic filter, without catalyst coating or fuel additive (from Ref. [46]).

Most commonly, distributed parameter models are applied to describe the performance of diesel particulate traps, which are a part of the diesel engine exhaust system. Those models are one- or two-dimensional, non-isothermal plug-flow reactor models with constant convection terms, but without diffusion/dispersion terms. 

Some mathematical models have been developed to predict the behavior of the pressure drop over the diesel particulate trap with time during the loading/regenera-tion cycles [62, 67-69], to calculate the effect of filter-medium properties on filter performance of fibrous filters [70] or to describe the flow and filtration process [71] and the regeneration process [72-75]. An illustrative example for the performance of such a pressure drop model is provided in Fig. 15.7. 

Fig. 15.7. Modeling and experimental results of the pressure drop of a catalytic diesel particulate trap (from Ref. [68]).

Particulate traps that physically block the passage of large pieces (>2 microns) of materials from getting into mechanical pump. 

Particulate traps are simply physical barriers, or screens, that catch particulate matter just as the screens in clothes dryers catch lint. If your processes create particulate matter, it is very important to prevent it from getting into a mechanical pump of any kind. These traps can slow the pumping speed to some degree, but that is a small price to pay to prevent damage to the pump. Only particulate traps can stop particulate matter no other trap can do so in an effective manner and should not be expected to perform this function. 

Coaxial Traps Molecular Sieve Particulate Traps ... 

Sulfur Toxic, NOx Inhibits exhaust catalysts, 02 sensors, NOx adsorbers, particulate traps... 

NOx emissions can be curtailed by equipping vehicles with modem catalytic converter technology. However, sulfur oxides in the exhaust reduce the efficiency of NOx conversion. Sulfur oxides also impede diesel particulate traps. Both SOx and NOx contribute to acid rain, causing other adverse environmental consequences. 

The typical regeneration took 10 minutes, although shorter durations also met ERA specifications for an acceptable particulate level. The key advantages of shorter regeneration are significant fuel savings and minimal thermal fatigue of the ceramic filter, both of which arc critical to the viability of a wall-flow particulate trap system. The soot filter... 

Lichens are adapted to accumulate all the elements necessary for their life from the atmosphere. They have no root system and absorb very little from the substrate on which they grow. Atmospheric materials, including trace metals and radionuclides, can be concentrated by particulate entrapment, ion exchange, electrolytic sorption and processes mediated by metabolic energy (Crete et al., 1992). Passive particulate trapping is, however, thought to be the dominant uptake mechanism. This is also true for mosses which absorb nutrients directly through leaf and stem surfaces. 

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