Filters regeneration

Fig. 43. Coupled DOC-DPF simulation. Filter regeneration by hydrocarbon injection upstream of the DOC over transient engine operation.

Figure 6.27 Possible metal precursors for making stable doped perovskite catalysts with the general formula AA BB 03, for diesel-soot filter regeneration in situ.

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]).

A combination of platinum and cerium fuel additives with a platinum treated filter results in continuous filter regeneration at the lowest temperature known for fuel additives (595 K). 

Fig. 6 shows the variation in and residual pressure drop during six hours of operation. K is calculated from Eq. 4. Calculated mean specific cake resistance equals 6.5-10 [s ], with a standard deviation of approx. 15%. is defined as the velocity across the exposed filter surface (vy 2 U,). Observed fluctuations in pressure build-up did not result in any increase in the residual pressure drop. The residual pressure drop could be maintained at a constant level. The average filtration efficiency was 0.9983. Filter regeneration was conducted with off-line pulsing (P,a = 2barg and total sand spill of 10 kg). 

Complementary tests were carried out for studying the regeneration process of ceramic sintered filter samples by uncatalysed and catalysed combustion of the accumulated carbon particles. With respect to the uncatalysed case, the presence of catalyst reduces the carbon ignition temperature so favouring spontaneous filter regeneration. However, the catalyst activity appears to be lower than that observed in the reactivity tests. 

Soot emitted from Diesel engines is hazardous for human health since it is made of inhalable particles [1] and contains gases and liquids adsorbed on its smrface, some of which (Polycyclic Aromatic Hydrocarbons) are suspected to be cancerogenic [2]. Virtually, soot-free Diesel exhaust may be obtained combining reduction of soot formation in the combustion chamber with exhaust gas treatment [3]. This latter is generally performed by a ceramic wall-flow filter that collects the carbonaceous particles while the filter regeneration is achieved by post-combustion of collected soot [3, 4]. 

An important step of the above mentioned soot removal process is the filter regeneration that could lead to filter failvu e by melting or breaking when high temperature spots or large temperature gradients occur [5, 6]. These phenomena... 

In this paper results of soot reactivity tests and of catalysed and uncatalysed ceramic filter regeneration experiments are presented. The aim is to investigate the influence of the catalyst features and of the carbon-catalyst contact on the catalyst performances. This is accomplished by comparing the results of combustion tests of mixtures of carbon and catalyst particles, specifically prepared by thorough pounding of the two components in a mortar, with those attainable in a more realistic filter regeneration system. 

Regeneration tests of BS or CB-330 covered filters, impregnated or not with catalyst, were performed by temperature programmed oxidation (TPO) tests in the quartz flow reactor similar to that described above with 35 mm OD. As in the case of the reactivity tests, the carbon oxidation rate and the filter regeneration degree (Xr) were calculated from the concentrations of carbon oxides in the reactor outlet gas. Air flow was 500 Ncm /min. 

Lizarraga L, Souentie S, Boreave A, George C, D Anna B, and Vemoux P. Effect of diesel oxidation catalysts on the diesel particulate filter regeneration process. Enviroru Sci. Technol. 2011 45 10591-10597. 

Haralampous O A, Koltsakis G (2004) Oxygen diffusion modeling in diesel particulate filter regeneration. AlChE Journal 50(9) 2008-2019... 

The DOC provided several functions for the urea SCR and filter system oxidation of HC and CO to meet tailpipe emissions, exotherm generation during cold start and filter regeneration, and NO oxidation for improved, durable SCR performance. Typical curves for HC and CO oxidation for an aged Pt DCXT are shown in Fig. 21.5... 

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