Oxidant bleeding

Injection of air or oxygen, called oxidant bleeding, into the fuel stream ahead of the fuel inlet of the fuel cell is a method that has been employed to oxidize the... 

CO from the catalyst surface and to restore the cell performance [77,79-86]. Oxidant bleeding is a promising method in reducing CO contamination due to its simplicity, effectiveness, and economic value. Blending low levels of an oxidant into the anode fuel stream reduces the levels of CO in the fuel by the WGS reaction mechanism and selective oxidation of CO. 

Gottesfeld and Passford [79] reported that the addition of 2 to 5% O2 to a H2 fuel stream resulted in restoration of CO-free cell performance for a fuel cell fed with CO at levels as high as 500 ppm. Murthy et al. [80] also foimd that a 5% air bleed resulted in almost a complete recovery in cell performance for a CO level of 500 ppm at 70°C and atmospheric pressure. However, 5 and 10% air bleed were not sufficient to improve the cell performance in the presence of 3000 ppm CO, and even 15% air bleed resulted in only partial recovery with 3000 ppm CO. As opposed to uninterrupted oxidant bleeding, Chen et al. [81] found that dosing air for 10 s intervals of 10 s yielded similar results (i.e., complete recovery) to that of continuous air bleeding for CO concentrations of 20 ppm and 52.7 ppm in the anode fuel stream. 

Part of the continuously recirculated solution is bled off and sent to the iodine finishing process. Iodine finishing consists of contacting this bleed of concentrated acidic iodide solution with gaseous chlorine, through which iodine is formed by oxidation and precipitated. After iodine precipitation, the resulting acidic mother Hquor, saturated with free iodine, is pumped back to acidify the clarified brine and to recover the remaining iodine. 

If tars are formed (which happened in the trial with mixed PVC waste), it is necessary to apply a partial oxidation to convert these tars into gaseous products. Via a quench, HCl is recovered from the product stream which consists of fuel gas and HCl. After purification the HCl can be used for producing ethylene dichloride (EDC) via oxychlorination. The recovery of CI2 is more then 90%, in general 94%-97%. Inert materials in the feed, such as the chalk and metal stabilisers present in a PVC-formulation, are separated from the flue gas as fly ash or will be set free as a bleed from the circulating sand. 

Hexavalent chromium wastes resulting from rinsewater and the concentrated acid bleed accumulate in the chromium waste sump [T-20], The chromium wastes are then pumped into the chromium treatment module [T-21] for reduction to the trivalent form. This pump is activated only if the oxidation-reduction potential (ORP) and pH are at the proper levels and if the level in the chromium wastewater sump [T-20] is sufficiently high. 

The oxidation-resistant SiC fiber was prepared from polycarbosilane containing Zr(OC4H9)4 by the same process as that used for the aforementioned tita-nia/silica fiber, except that the calcination was performed in Ar atmosphere at 1400 °C. In this case, the polycarbosilane and Zr(OC4H9)4 were effectively converted into SiC-based bulk ceramic and zirconium oxide (cubic zirconia). Before the conversion, bleed-out of the zirconium compound proceeded effectively. AES depth analysis of the fiber surface showed an increase in the concentration of zirconium towards the surface. This construction was confirmed by the TEM image of the cross-section near the fiber surface. This indicates the direct production of a SiC-based fiber covered with a Zr02 surface layer, which... 

Terpenoids are susceptible to a number of alterations mediated by oxidation and reduction reactions. For example, the most abundant molecule in aged Pinus samples is dehydroabietic acid [Structure 7.10], a monoaromatic diterpenoid based on the abietane skeleton which occurs in fresh (bleed) resins only as a minor component. This molecule forms during the oxidative dehydrogenation of abietic acid, which predominates in rosins. Further atmospheric oxidation (autoxidation) leads to 7-oxodehydroabietic acid [Structure 7.11]. This molecule has been identified in many aged coniferous resins such as those used to line transport vessels in the Roman period (Heron and Pollard, 1988 Beck et al., 1989), in thinly spread resins used in paint media (Mills and White, 1994 172-174) and as a component of resin recovered from Egyptian mummy wrappings (Proefke and Rinehart, 1992). 

S adsorption Partial oxidation Low temperature Oz bleeding Autothermal reforming Methanation... 

A bleed stream from the absorption part of the process is dewatered and dried. The crystals of magnesium sulfite and magnesium sulfate are then calcined solid magnesium oxide is returned to the scrubbing process, and sulfur dioxide which is released with the calcination is then converted into a salable product such as sulfuric acid. 

---