Crack instantaneous

An efficient feed injection system produces extremely small droplets that vaporize quickly. Rapid vaporization minimizes the amount of non-vaporized hydrocarbons that block the active sites. An effective feed nozzle system must instantaneously vaporize and crack asphaltenes and polynuclear aromatics to lower boiling entities. 

In both aqueous and organic environments the crack velocity is related to the instantaneous stress intensity factor, as shown in Fig. 8.53. Three regions may be observed I, II and III. Regions I and III are not always observed and the specific relationship observed depends upon the alloy composition and heat treatment, the environmental composition and the experimental conditions. ... 

Fig. 8.53 Relationship between instantaneous stress intensity factor and crack velocity for a susceptible titanium alloy in 10 n HC1 . Activation energy for Stage 1 = 113 kJ/mol and for...

Whereas ductile materials, such as iron and mild steel, are often considered not to crack when charged with hydrogen and subjected to a tensile stress below the yield stress, the position is different with high-strength ferrous alloys where, depending on the strength of the steel and the hydrogen content, failure may occur well below the yield stress. However, the fracture process is not instantaneous and there is a time delay before cracks are... 

Thns the strain energy release rate is effectively an instantaneous value of Dupre s energy of adhesion, with 6 = 0(0 instead of the equilibrium value. The sign reversal in the left-hand side of Eq. (18) when compared to Eq. (15) is due simply to the fact that we have a closing crack with a spreading liquid. 

Cocaine hydrochloride is a water-soluble salt that can be injected or absorbed by any mucosal membrane (eg, nasal snorting). When heated in an alkaline solution, it is transformed into the free base, "crack cocaine," which can then be smoked. Inhaled crack cocaine is rapidly absorbed in the lungs and penetrates swiftly into the brain, producing an almost instantaneous "rush."... 

Sect. 1.2, the surface of an oxide can change its structure quite easily. For example, cracking catalysts exchange oxygen with water almost instantaneously at higher temperatures [74,75] the interaction of water with such catalysts must therefore be a complex process, involving not only an adsorption in molecular form. 

The increase of thus induces a macroscopic creep under constant stress. Assuming an instantaneous diffusion of the solute within the pore space, the mechanical affinity is Am —psij/el. The strain concentration effect at the crack tip then implies that the dissolution process concentrates at this place and is negligible elsewhere. The rate of crack radius increase a is derived from (22) and gives the evolution f(t) of the damage parameter ... 

Cumene Cracking Reactions on Separated Fractions. Cumene cracking reactions were tested on a gravimetric setup the basic flow diagram for the reactor system is shown in Figure 1. The reactor determines both the activity of the catalyst (cracking of cumene to benzene and propylene) and the instantaneous rate at which coke is deposited on the catalyst (polymerization of the propylene). Conversion of the cumene is adjusted to exclude the amount of cumene disproportionation which yields benzene and diisopropyl benzene. 

Large asphalthenes crack and decompose nearly instantaneously, and metals are deposited on the catalyst surface. 

One method of overcoming this problem is to increase the space time during the experiment by adapting the feed rate, so as to keep the conversion at a constant level. This, however, necessitates an instantaneous effluent analysis, coupled with a control circuit adjusting the inlet flow rates. For the study of the deactivation of a complex reaction mechanism subject to rapid deactivation, such as catalytic cracking on a Y-zcolite catalyst, this would be a... 

Brittle Failure (8). Brittleness is a principal consideration in selecting construction materials for liquid hydrogen service. Brittle fracture can result in the essentially instantaneous release of a vessel s contents, the hazard being a combined one of PV energy release and the possibility of fire and/or explosion. Three conditions must exist for a brittle fracture to occur 1) a stress riser, a crack, notch, or other discontinuity, 2) a section where the actual stress exceeds the yield stress of the material, and 3) a temperature below which failure occurs without appreciable plastic deformation. Metals that are satisfactory for liquid hydrogen service include aluminum, stainless steels, brass, and copper. Carbon steel is not suitable. 

Figure 5. Instantaneous activity versus time on stream for cracking.

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