Molar flowrate fraction

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. 

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. 

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. 

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 ... 

One important physical property assumption is made about heat capacities. The mass heat capacities of all components are assumed to be the same (2kJkg-1 K-1). This means that the product of the mass flowrate and the mass heat capacity is constant for any stream and equal to the sum of the product of the component molar flowrates times the corresponding molar heat capacities. Thus, despite the fact that molar flowrates of individual components vary down the length of the reactor, the term F Ylf=A yjcpj is constant, where F is the total molar flowrate, y - is the mole fraction of component j, and cpj is the molar heat capacity of component j. This relationship is used in the design procedures discussed below to calculate the inlet flowrate from an energy balance around the reactor. 

Both gas absorption and stripping involve at least three components. Usually only one of these components crosses the phase boundary. In the example of ammonia and air, ammonia is the component whose molar flowrate changes by the largest percentage of the inlet value. Although some air will also dissolve in water, and some water will evaporate into the air, the molar flowrates of air and water change by negligible fractions their flows can usually be considered constant. 

The portion of the column that lies below the feed plate is called the stripping section. The function of this section is to obtain a nearly pure bottoms stream, B, of the less volatile component of the feed. As with the rectifying section, we can analyze in terms of a mass balance to obtain an operating line relating the vapor-phase mole fraction to the liquid-phase mole fraction exiting a stage. Again, it is assumed that the molar flowrates B, L and V are constant and that constant molar overflow applies. The overall mass balance around the bottom of the column, then, becomes ... 

Fractional error in the QSSA molar flowrate of C2H4 versus reactor volume.. ... 

Since mass is a more practical property to measure than moles, flowrates are often given as mass flowrates rather than molar flowrates. When this occurs, it is convenient to express concentrations in terms of mass fractions defined similarly to mole fractions. 

In distillation calculations, molar flowrates and compositions are usually employed. Let us assume that the fresh feed flowrate is lOOkmol/h, the feed temperature is 25°C, and the feed pressure is 1.3 atm. These are entered in the middle of the window. The feed composition is 50 mol% IPA and 50 mol% water to represent a typical waste stream from semiconductor industry. The composition can be entered in terms of mole or mass fractions, or it can be entered in terms of component molar or mass flowrates. In our example, we use the dropdown arrow to change to Mole-Frac and enter the appropriate values. Repeat the same procedure to enter the feed-stream data of the entrainer feed (FFl) as can be seen in the flowsheet given in Figure 3.1. 

Figure 6.6 shows a simple two-product distillation column and gives the notation we use for flowrates, compositions, and tray numbering. Feed is introduced on tray Nf, numbering from the bottom. There are Nt trays in the column. The molar feed flowrate is F, its composition is Zj (mole fraction of component j.k and its thermal condition is q (saturated liquid is q = 1, saturated vapor is q — 0). The heat transfer rates are Qr in the reboiler and Qc in the condenser. Distillate product... 

Figure 11.18 Comparison of methane conversion as a function of the molar fraction of oxygen in the total feed in two reactors using porous membranes with a uniform permeability and a decreasing permeability profile at 750 C and a total flowrate of 172 standard cm /min (open circles represent the membrane with a decreasing permeability along its length and open squares represent the membrane with a uniform permeability) (Coronas et al., 1994J...

We desire to use a distillation column to separate an ethanol-water mixture. The column has a total condenser, a partial reboiler, and a saturated liquid reflux. The feed is a saturated liquid of composition 0.10 mole fraction ethanol and a flow rate of 250 mol/hr. A bottoms mole fraction of 0.005 and a distillate mole fraction of 0.75 ethanol is desired. The external reflux ratio is 2.0. Assuming constant molar overflow, find the flowrates, the number of equilibrium stages, optimum feed plate location, and the liquid and vapor compositions leaving the fourth stage from the top of the column. Pressure is 1 atm. 

Run no. Total molar feed flowrate kmol/h.(F Feed mole fraction of o-XyleneXT(f) Feed and bath temperatures Tf- Tc, K... 

This work focuses on the kinetic study of the methane catalytic combustion in a honeycomb monolith wash-coated with Pd/y-AhOa (homemade). The experimental conditions were chosen to adequately represent the operation of a domestic-scale catalytic heater, i.e. relatively high volumetric flowrates and high methane molar fractions (Lopez et al., 2000). From experimental data (obtained at conditions of negligible mass transfer resistances) and using a mathematical model for the laboratory reactor, the intrinsic kinetic parameters are calculated for a power law type rate expression. 

Figs. 1 and 2 show experimental and calculated conversions vs. inlet temperature for different methane inlet molar fractions and inlet flowrates, respectively. Fig. 1 shows that the higher reactant inlet concentration the lower is the outlet conversion. This is the expected... 

Quantity mole flowrate mole fraction molar enthalpy heat flow rate, power... 

Note M denotes material inventory symbols in capital denote stream flowrates (Fig. 5) x denotes component molar fractions for distillation and reactor outlet streams. 

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