Plug removal, mechanism

To incorporate mixing by the dispersed plug flow mechanism into the model for the bubble column, we can make use of the equations developed in Chapter 2 for dispersed plug flow accompanied by a first-order chemical reaction. In the case of the very fast gas-liquid reaction, the reactant A is transferred and thus removed from the gas phase at a rate which is proportional to the concentration of A in the gas, i.e. as in a homogeneous first-order reaction. Applied to the two-phase bubble column for steady-state conditions, equation 2.38 becomes ... 

The plugs have caused no problems during initial 2 or 3 years of operation. On the basis of the feedback from BN350 and taking into account the experience gained at the BN600 reactor from the monitoring of the protective liquid and hydraulic seal eutectic the former was decided to be periodically replaced and cleaned to remove mechanical impurities. 

Dezincification is readily apparent, since the yellow colour of the brass is replaced by the characteristic red of copper, which may take the form of small plugs or of layers that in some cases can extend over the whole of the surface (Fig. 1.60). In plug-type dezincification a mechanically weak, porous residue of copper is produced, which may remain in situ or become removed by the pressure of water, leading to a perforation. In the layer type the transformation of the alloy into a mechanically weak layer of copper results in loss of strength, and failure may occur by splitting when the metal is subjected to water pressure or to external stress. 

Although the FTS is considered a carbon in-sensitive reaction,30 deactivation of the cobalt active phase by carbon deposition during FTS has been widely postulated.31-38 This mechanism, however, is hard to prove during realistic synthesis conditions due to the presence of heavy hydrocarbon wax product and the potential spillover and buildup of inert carbon on the catalyst support. Also, studies on supported cobalt catalysts have been conducted that suggest deactivation by pore plugging of narrow catalyst pores by the heavy (> 40) wax product.39,40 Very often, regeneration treatments that remove these carbonaceous phases from the catalyst result in reactivation of the catalyst.32 Many of the companies with experience in cobalt-based FTS research report that these catalysts are negatively influenced by carbon (Table 4.1). 

Deep cavity projectiles contain an aluminum fuze well liner (some rounds on hand may have a cardboard liner), that also serves as a support for the HE filler. This liner is not to be removed. Insertion of a supplementary charge into the fuze cavity adapts the projectile for mechanical-type point fuzes and boosters. When deep-cavity projectiles are assembled with any authorized fuze, the data are the same as for the normal-cavity projectiles so fuzed. Deep-cavity projectiles may be shipped with closing plug (with or without supplementary charge) or with supplementary charge and mechanical-type fuze (Ref 40b, pp 9-10)... 

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