Soot combustion Subject

Many different filter designs have been the subject of experimental studies on diesel soot combustion. In the early investigations, structured honeycomb filters made from cordierite, such as those applied for the three-way catalyst for the reduction of spark ignition engine gas emissions, were the focus of the experimental studies [29-39]. The experimental results with these filters were not promising, because the cordierite honeycomb filter did not withstand the thermal stress. Temperature peaks of almost 1200 °C were measured, after which the ceramic structure was partly melted or totally destroyed [29, 40],... 

Luminous Flames Luminosity conventionally refers to soot radiation it is important when combustion occurs under such conditions that the hydrocarbons in the flame are subject to heat in the absence of sufficient air well mixed on a molecular scale. Because soot parti-... 

The subject of chemical reactions under supercritical conditions is well outside the scope of matters of major concern to combustion related considerations. However, a trend to increase the compression ratio of some turbojet engines has raised concerns that the fuel injection line to the combustion chamber could place the fuel in a supercritical state that is the pyrolysis of the fuel in the line could increase the possibility of carbon formations such as soot. The... 

For the measurement of light absorption by airborne carbonaceous particulate (soot), the conventional light absorption techniques fail due, primarily, to the second condition. However, photoacoustic spectroscopy has the necessary sensitivity (.3-6) and is not subject to major interferences from light scattering. For these reasons photoacoustic spectroscopy was first used by Terhune and Anderson, in this laboratory, to study airborne soots produced by a number of combustion processes. ( 4, 5 6)... 

Both diffusional flame calculations and detailed spatial mapping indicate that the nondispersed injection mode produces a vapor cloud that is characterized by diffusionally controlled combustion and bulk heating while subjecting the droplets to near isothermal conditions. The soot produced in this cloud is strongly influenced by bulk diffusion limitations and as such represents a bulk soot formation extreme. It was found that fuel changes had little effect on the overall soot yield due to this diffusion control. Lower gas temperatures and richer conditions were found to favor soot formation under bulk sooting conditions, probably due to a decrease in the oxidation rate of the soot. 

To prevent accumulation of ash and slag in the water circuit, some water is discharged continuously. In a combined chemical and physical treatment sulfides, cyanides and suspended solids (ash) are removed. A concentrated sludge has to be filtered off and disposed of. The run-off water from the filters is stripped of ammonia and after pH-adjustment sent to a biological treatment unit. Uhde [532] has developed an alternative route for soot treatment in which the soot is filtered off and subjected to combustion, and the filtered water is recycled to the quench and scrubbing circuits. Let down water is treated as described above. This soot treatment technique avoids not... 

The raw gas from the partial oxidation contains soot, about 0.8 wt% of the hydrocarbon feed. Soot particles together with ash are removed mainly in the venturi scrubber downstream of the quench. The soot slurry from quench and venturi is sent to the metals ash recovery system (MARS) Figure 58. First the soot slurry is flashed to atmospheric pressure and then filtered, leaving a filter cake with about 80 % residual moisture. The filter cake is subjected to a controlled combustion in a multiple hearth furnace. Under the conditions applied, a metal oxide concentrate containing 75 wt% of vanadium, together with some nickel and iron, is obtained which can be sold to metal reclaimers. The MARS ist practically autothermal as the heat of combustion is sufficient to evaporate the moisture of the filter cake. 

These facts have led to the review and finally the development of an alternative approach and in particular the possibilities of recovering vanadium for metallurgical use. Figure 100 illustrates the principles of the soot ash removal unit. The carbon slurry from the SGP unit is flashed to atmospheric pressure in the slurry tank (a). The slurry is then filtered on an automatic filter (b) to recover a filter cake with about 80% residual moisture and a clear water filtrate. The filter cake is subjected to a controlled oxidation process in a multiple-hearth furnace (c). This type of furnace, which is well established in many industries and specifically in the vanadium industry, allows combustion of the carbon to occur under conditions where the vanadium oxides neither melt nor corrode. This is not an easy task if one considers the problems of burning a high-vanadium fuel oil in a conventional boiler. The product is a vanadium concentrate, which contains about 75% V2O5. Compared to the old naphtha extraction-based recycle system, the new once-through process consists of only two proces-... 

It is obvious that during a fire, we do not find necessarily all the optimum conditions of formation of the PCB found in the laboratory. The temperature varies in time and in space, with variations of many hundred of degrees Celsius between the periphery and the center of the fire. The molecules of PCB are not all subjected to the same combustion temperature. Moreover, it seems that certain molecules of PCB are lacking required to burn and form a molecule of PCDF. The PCB spread on the ground without being degraded as it is proved by the concentrations found in soot. We can deduct without too much risk of error that, during a fire, the quantities of PCDF formed will be much smaller than the maximum value found in optimum laboratory conditions. 

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