Resid conversion definition

GL 18] ]R 6a]]P 17/Using the same experimental conditions and catalysts with the same geometric surface area, the performance of micro-channel processing was compared with that of a fixed-bed reactor composed of short wires [17]. The conversion was 89% in the case of the fixed bed the micro channels gave a 58% yield. One possible explanation for this is phase separation, i.e. that some micro channels were filled with liquids only, and some with gas. This is unlikely to occur in a fixed bed. Another explanation is the difference in residence time between the two types of reactors, as the fixed bed had voids three times larger than the micro channel volume. It could not definitively be decided which of these explanations is correct. 

Each flow pattern of fluid through a vessel has associated with it a definite clearly defined residence time distribution (RTD), or exit age distribution function E. The converse is not true, however. Each RTD does not define a specific flow pattern hence, a number of flow patterns—some with earlier mixing, others with later mixing of fluids—may be able to give the same RTD. 

The polymerization time in continuous processes depends on the time the reactants spend in the reactor. The contents of a batch reactor will all have the same residence time, since they are introduced and removed from the vessel at the same times. The continuous flow tubular reactor has the next narrowest residence time distribution, if flow in the reactor is truly plug-like (i.e., not laminar). These two reactors are best adapted for achieving high conversions, while a CSTR cannot provide high conversion, by definition of its operation. The residence time distribution of the CSTR contents is broader than those of the former types. A cascade of CSTR s will approach the behavior of a plug flow continuous reactor. 

The average conversion can be calculated from Eq. (14-26), but first it is necessary to evaluate x,- for each fraction of the particles. To, do this we must obtain the residence time for each fraction from the given distribution. From the definition of 9,... 

At steady state, the concentrations within the reactor will not change, meaning that the accumulation term equals zero. By using the definition of x (Eq. (5)), the residence time x necessary to reach the desired conversion x can be calculated (Eq. (60)) ... 

The term "space velocity" has established itself as a measure for the exhaust gas flow referred to the catalyst volume. By this definition it is an indication for the residence time of exhaust gas molecules within the catalyst. As mentioned before the inverse residence time plotted versus the selectivity of the reactants gives a tool for the identification of reaction paths. Therefore, the conversion efficiency over the catalyst was measured at 225°C by varying the space velocity (test 5, Table From these data the selectivities S(N2), S(N02) and S(N20) were calculated by using the equations given in chapter 2 and plotted in Fieure 7. 

At high-mass-transfer Peclet numbers, sketch the relation between average residence time divided by the chemical reaction time constant (i.e., r/co) for a packed catalytic tubular reactor versus the intrapeUet Damkohler number Aa, intrapeiiet for zeroth-, first-, and second-order irreversible chemical kinetics within spherical catalytic pellets. The characteristic length L in the definition of Aa, intrapeiiet is the sphere radius R. The overall objective is to achieve the same conversion in the exit stream for all three kinetic rate laws. Put all three curves on the same set of axes and identify quantitative values for the intrapeiiet Damkohler number on the horizontal axis. 

The principle of stationary (or instationary) is also applied to the atmospheric budget of trace species, regarding F+ the source term (emission Q) and F the total removal term R (deposition and chemical conversion). With the definition of the residence time (see Chapter 4.5 for more details) it follows from Eq. (4.96) that ... 

As with residence time, the correlating definition of hydrocarbon partial pressure must consider the partial pressure history in the coil. For a given feedstock cracked at a fixed conversion and gas outlet pressure in a pyrolysis coil of a given configuration, the average hydrocarbon partial pressure, PhCA determined by ... 

Tan et al. (1991) extended the temperature range studied by Fairburn et al. (1990) to 1000 °C. They showed the importance of the Temperature Rise Time (TRT) on the n-hexadecane conversion at these high temperatures (Figure 9), reporting conversions of 8% and 10%, corresponding to TRTs of 100 and 125 ms, at 900°C and 1000°C, respectively. Based on these results, they defined the Effective Residence Time (ERT) in the microreactor as the time period at which the exact Curie Point Temperature would yield the same conversion as the actual reaction for the Total reaction Time (TT). According to this definition... 

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