Molar flowrate

The term V/F for flow reactors is used to evaluate the size of the reactor required to achieve the conversion of a reactant feed rate F. It is the numher of reactor volumes of feed at specified conditions that can he treated in unit time, where F is the molar flowrate (uC q) and V is the volume of the reactor. 

For the minimum volume in a CFSTR under adiabatie eondition, Equation 6-192 requires only that the operating temperature within the reaetor be T p. In this ease, there is nothing about the mode of operation, sueh as the feed temperature Tg or heat transfer, either within the reaetor or upstream of it. However, if the CFSTR is operated adiabatieally for speeified eonversion (X ) and molar flowrate (F q = uC o) without internal heat transfer, Tq must be adjusted to a value obtained from the energy balanee as determined by... 

Figure 9.26. Steady-state effect of applied current on the increase in the consumption rates of H2 (A) and 02 (A) rg = r°2 =Tq = 0.7xl0 7mol/s total molar flowrate fm=17xl0 5 mol/s.35 Reproduced by permission of The Electrochemical Society.

Figure 9.28. Effect of P02 on the rate of O consumption (u.) and corresponding catalyst potential ( ), U°ile, under open-circuit conditions and on the rate of O consumption (A) and corresponding A0 value under closed-circuit conditions at fixed catalyst potential Urhe-1.05 V total molar flowrate fm=l.7 l0 4 mol/s.35 Reproduced by permission of The Electrochemical Society.

Assuming the molar flowrate of gas remains constant, the amount of NO to be removed... 

The ratio of molar flowrates of the vapor and liquid phases is thus given by the ratio of the opposite line segments. This is known as the Lever Rule, after the analogy with a lever and fulcrum7. 

Fj, Vj, Lj = feed, vapor and liquid molar flowrates for Stage j... 

Equation 9.34 can also be written in terms of the molar flowrates of the products ... 

Equations 10.4 to 10.6 and 10.8 to 10.10 can be written in terms of mole fractions and molar flowrates. Alternatively, mass fractions and mass flowrates can be used instead, as long as a consistent set of units is used. 

The flux, and hence the permeance and permeability, can be defined on the basis of volume, mass or molar flowrates. The accurate prediction of permeabilities is generally not possible and experimental values must be used. Permeability generally increases with increasing temperature. Taking a ratio of two permeabilities defines an ideal separation factor or selectivity awhich is defined as ... 

If a material balance is to be solved, then the convergence variables can be taken to be the component molar flowrates. When a material and energy balance is to be solved, the additional convergence variables are usually taken to be pressure and enthalpy. 

Air containing ammonia is contacted with fresh water in a two-stage countercurrent bubble-plate absorber. Ln and V are the molar flowrates of liquid and gas respectively leaving the nth plate. xn and yn are the mole fractions of NH3 in liquid and gas respectively leaving the nth plate. // is the molar holdup of liquid on the nth plate. Plates are numbered up the column. 

A. Assuming (a) temperature and total pressure throughout the column to be constant, (b) no change in molar flowrates due to gas absorption, (c) plate efficiencies to be 100 per cent, (d) the equilibrium relation to be given by yn = mx + b, (e) the holdup of liquid on each plate to be constant and equal to H, and (f) the holdup of gas between plates to be negligible, show that the variations of the liquid compositions on each plate are given by ... 

The changes in the molar flowrate of A with distance Z at steady-state conditions are thus... 

The procedure developed by Joris and Kalitventzeff (1987) aims to classify the variables and measurements involved in any type of plant model. The system of equations that represents plant operation involves state variables (temperature, pressure, partial molar flowrates of components, extents of reactions), measurements, and link variables (those that relate certain measurements to state variables). This system is made up of material and energy balances, liquid-vapor equilibrium relationships, pressure equality equations, link equations, etc. 

Gm is the molar flowrate of gas, W is the mass of solids in the bed, F is the number of moles of vapour adsorbed on unit mass of solid, and y0, y is the mole fraction of vapour in the inlet and outlet stream respectively. 

G Molar flowrate of vapour per unit time and unit cross-section kmol/m2s NL 2T 1... 

Gno Molar flowrate of nitrogen monoxide before oxidation. 

G N204 Molar flowrate of nitrogen tetroxide before oxidation. 

Ggss Molar flowrate of total absorption-gas stream. hap Height of apron beneath tray downcomer. 

The same kinetic case considered in the previous section is used in the reactor. The reactor effluent F (with composition z) is fed to a stripping column that sends the lighter component A out the top as a recycle stream and the heavier component B out the bottom as the final product stream. A stripping column is used, as opposed to a full column with reflux, because previous studies have shown that a stripper is the optimum economic design. Since the overhead is not a product stream, it does not have to have a high purity. The vapor going overhead is condensed and pumped back to the reactor at a molar flowrate D and composition xD. The liquid rate in the stripper is F and the vapor rate is D. 

Molar concentrations are converted into mole fractions, and volumetric flowrates are converted to molar flowrates for the tray-to-tray calculations in the column. The fresh feedstream F0 is 0.03506 kmol/s with a composition zo = 1 mole fraction A. Since the reaction is equimolar (one mole of A produces one mole of B), the molar flowrate of the bottoms from the column P is equal to the fresh feed flowrate F(). The overall conversion is set at 98%, so the concentration of reactant in the column bottoms (the product stream P) is xP = 0.02 mole fraction A. 

The dynamic model of the column consists of two ordinary differential equations per tray if equimolal overflow, constant tray holdup, and instantaneous liquid hydraulics are assumed. Molar flowrates and concentrations in mole fractions are used. The liquid holdup on each tray is 0.4 kmol ... 

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