Flow rate fractional properties

The desire to save energy calls for low pressure drop over the catalyst layers because they account for a significant part of the total pressure drop through the sulphuric acid plant. According to simple correlations such as the Ergun equation [12], the pressure drop over a catalyst bed per bed length at a given flow rate and properties of the gas only depends on the bed void fraction e and a characteristic pellet diameter... 

The Sherwood number can be determined from the solution of the nondimensional problem by evaluating the nondimensional mass-fraction gradients at the channel wall and the mean mass fraction, both of which vary along the channel wall. With the Sherwood number, as well as specific values of the mass flow rate, fluid properties, and the channel geometry, the mass transfer coefficient hk can be determined. This mass-transfer coefficient could be used to predict, for example, the variation in the mean mass fraction along the length of some particular channel flow. 

The capital cost of a reactor is a function of the number of stages, their complexity and operating conditions, and of the flow rate and properties of the reactant stream. This cost has to be financed and repaid over a certain period of years from the profit of the plant. Experience gives some idea of the kind of maintenance that is needed with various kinds of reactors and what fraction of the year they are liable to be out of production. All these factors must be considered, together with the estimated useful life of the plant and current economic predictions, in order to arrive at a number C, the combined cost per unit time of these charges. 

Usually, packed columns are designed based on either of two criteria a fractional approach to flooding gas velocity or a maximum allowable gas-pressure drop. For given fluid flow rates and properties, and a given packing material, equation (4.8) is used to compute the superficial gas velocity at flooding, vGF. Then, according to the... 

Engineering factors include (a) contaminant characteristics such as physical and chemical properties - concentration, particulate shape, size distribution, chemical reactivity, corrosivity, abrasiveness, and toxicity (b) gas stream characteristics such as volume flow rate, dust loading, temperature, pressure, humidity, composition, viscosity, density, reactivity, combustibility, corrosivity, and toxicity and (c) design and performance characteristics of the control system such as pressure drop, reliability, dependability, compliance with utility and maintenance requirements, and temperature limitations, as well as size, weight, and fractional efficiency curves for particulates and mass transfer or contaminant destruction capability for gases or vapors. 

Following the steps for formulation of a CFD model introduced earlier, we begin by determining the set of state variables needed to describe the flow. Because the density is constant and we are only interested in the mixing properties of the flow, we can replace the chemical species and temperature by a single inert scalar field (x, t), known as the mixture fraction (Fox, 2003). If we take = 0 everywhere in the reactor at time t — 0 and set / = 1 in the first inlet stream, then the value of (x, t) tells us what fraction of the fluid located at point x at time t originated at the first inlet stream. If we denote the inlet volumetric flow rates by qi and q2, respectively, for the two inlets, at steady state the volume-average mixture fraction in the reactor will be... 

The input requirements for post-flashover types of models can be quite broad. Besides the compartment and vent dimensions, detailed fuel combustion characteristics are often needed. The fuel characteristics include the fraction of carbon, hydrogen, nitrogen, and oxygen that make up the fuel, the burning efficiency, and the quantity of fuel available for burning. Mechanical ventilation flow rates and the material properties of the compartment boundaries may be necessary. Some models can account for the heat transfer through the boundaries in detail, and may even allow the user to supply time-dependent material properties. An example of a post-flashover fire model is COMPF (Babrauskas, 1979). 

Compressed into a 6-inch (ID = 5.761 inches) pipeline at 1000 psia is 2.4 MMscfd of the separator gas of page 9 of Table 10-1. Assume the temperature is 100°F. Calculate the actual volumetric flow rate in cubic feet per day, the mass flow rate in pounds per hour, and the superficial gas velocity (average linear velocity) in feet per second. Assume the heptanes plus fraction has the properties of n-heptane. 

Figure 3.14. The lower ends of fractionators, (a) Kettle reboiler. The heat source may be on TC of either of the two locations shown or on flow control, or on difference of pressure between key locations in the tower. Because of the built-in weir, no LC is needed. Less head room is needed than with the thermosiphon reboiler, (b) Thermosiphon reboiler. Compared with the kettle, the heat transfer coefficient is greater, the shorter residence time may prevent overheating of thermally sensitive materials, surface fouling will be less, and the smaller holdup of hot liquid is a safety precaution, (c) Forced circulation reboiler. High rate of heat transfer and a short residence time which is desirable with thermally sensitive materials are achieved, (d) Rate of supply of heat transfer medium is controlled by the difference in pressure between two key locations in the tower, (e) With the control valve in the condensate line, the rate of heat transfer is controlled by the amount of unflooded heat transfer surface present at any time, (f) Withdrawal on TC ensures that the product has the correct boiling point and presumably the correct composition. The LC on the steam supply ensures that the specified heat input is being maintained, (g) Cascade control The set point of the FC on the steam supply is adjusted by the TC to ensure constant temperature in the column, (h) Steam flow rate is controlled to ensure specified composition of the PF effluent. The composition may be measured directly or indirectly by measurement of some physical property such as vapor pressure, (i) The three-way valve in the hot oil heating supply prevents buildup of excessive pressure in case the flow to the reboiier is throttled substantially, (j) The three-way valve of case (i) is replaced by a two-way valve and a differential pressure controller. This method is more expensive but avoids use of the possibly troublesome three-way valve.

Run the Vessize program, clicking on the Run Start button. (See Fig. 4.5.) Please note the input data and the output answers. This program sizes the vessel, based on the gas volume rate. You pick a vessel diameter and also input the fraction of the cross-section area you want the vessel to have. With the physical property data and flow rates input as shown, the program calculates a vessel length required to make the average liquid droplet size separation. 

Example 5.2 Assume that a typical hydrocarbon naphtha liquid from a fractionation tower-side cut stream is to be cooled to 150°F. The naphtha stream enters the air cooler at 250°F at a flow rate of 273,000 lb/h. The physical tube-side properties at the average temperature of 200°F are ... 

The next text box to be made is named txtMHR. Please refer again to Fig. 9.12. This name stands for component mol/h flow rates summary. This text box will be a near duplicate of the previous one, replacing the mole fractions with molar rates. Therefore, make a similar text box, sizing it wider as shown on your screen. Make the following inputs to the respective text box Properties menu ... 

Note that, from steady-state considerations, in order to remove an appreciable amount of impurity from the recycle loop via the purge stream (whose flow rate is small), the mole fraction of the impurity in the vapor phase in the condenser, 2/i, has to be 0(1). This implies that O(e) moles of impurity enter and leave the system through the feed and purge streams. Note also that our assumption concerning the mass-transfer properties of the component I implies that a negligible amount of impurity leaves the recycle loop through condensation, exiting the process with the liquid stream from the bottom of the condenser. 

Three different zeolites (USY-zeolite, H-ZSM-5 and H-mordenite) were investigated in a computer controlled experimental equipment under supercritical conditions using the disproportionation of ethylbenzene as test reaction and butane or pentane as an inert gas. Experiments were carried out at a pressure of 50 bar, a flow rate of 450 ml/min (at standard temperature and pressure), a range of temperatures (573 - 673 K) and 0.8 as molar fraction of ethylbenzene (EB) in the feed. The results showed that an extraction of coke deposited on the catalysts strongly depends on the physico-chemical properties of the catalysts. Coke deposited on Lewis centres can be more easily dissolved by supercritical fluid than that on Brnsted centres. 

Table 1. Relationship between X and the physical solute properties using different FFF techniques [27,109] with R=gas constant, p=solvent density, ps=solute density, co2r=centrifugal acceleration, V0=volume of the fractionation channel, Vc=cross-flow rate, E=electrical field strength, dT/dx=temperature gradient, M=molecular mass, dH=hydrodynamic diameter, DT=thermal diffusion coefficient, pe=electrophoretic mobility, %M=molar magnetic susceptibility, Hm=intensity of magnetic field, AHm=gradient of the intensity of the magnetic field, Ap = total increment of the chemical potential across the channel...

The objective in analyzing these units is to calculate the temperature, the conqjosition, and the flow rates of the vapor and hquid exit streams, given the properties of the entering streams. First, write the mole balances. For two components, we write two component balances and a mole fraction summation for each unknown stream as given by Equations 3.3.1 to 3.3.4 in Table 3.3.1. There are two phases in equilibriiun leaving the valve, condenser and vaporizer, although the phases have not, as yet, been separated. A phase separator will separate the phases. For a vaporizer, both component and phase separation occur in the same process unit. As stated before, the first numerical subscript is the line number and the second the component number. We also identify the phases by an additional subscript, V for vapor and L for liquid. Because we are assuming equilibrium between the vapor and liquid for each component downstream of the valve, we can... 

This obvious relationship is used in Table 5.11 to obtain mass-fraction averages of thermodynamic properties of steam-condensate mixtures. The macroscopic energy balance, is used to obtain the steam flow rate. Like compressors, the kinetic and potential energy terms are not significant, and the expansion is assumed to be adiabatic. 

In this table, A, B, and C are Antoine equation constants, al, av, and bv are the coefficients of the given heat capacity formulas Tbp(°C) and DHv(kJ/mol) (A v) are the normal boiling point and heat of vaporization, xF(mol pentane/mol) is the mole fraction of pentane in the feed. TfCC) is the feed temperature, P(mm Hg) is the system pressure. HAF (Haf) and HBF (Hbf) are the specific enthalpies of pentane and hexane in the feed stream, pA is the vapor pressure of n-pentane (to be determined using the Antoine equation), x and nL x and l) are the mole fraction of pentane in the liquid product stream and the molar flow rate of that stream, respectively, y and nV are the corresponding properties of the vapor product stream. HAL is the specific enthalpy of pentane in the liquid product stream, and DH (A//) is the expression given in Equation 5 for the change in total enthalpy from inlet to outlet. 

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