Stream properties

The essential differences between sequential-modular and equation-oriented simulators are ia the stmcture of the computer programs (5) and ia the computer time that is required ia getting the solution to a problem. In sequential-modular simulators, at the top level, the executive program accepts iaput data, determines the dow-sheet topology, and derives and controls the calculation sequence for the unit operations ia the dow sheet. The executive then passes control to the unit operations level for the execution of each module. Here, specialized procedures for the unit operations Hbrary calculate mass and energy balances for a particular unit. FiaaHy, the executive and the unit operations level make frequent calls to the physical properties Hbrary level for the routine tasks, enthalpy calculations, and calculations of phase equiHbria and other stream properties. The bottom layer is usually transparent to the user, although it may take 60 to 80% of the calculation efforts. 

Treatment Technology Feed Stream Properties Output Stream Characteristics... 

Membranes will also remove some of the water vapor. Depending upon the stream properties, a membrane designed to treat CO2 to pipeline specifications may also reduce water vapor to less than 7 Ib/MMscf. Often, however, it is necessary to dehydrate the gas downstream of the membrane to attain final pipeline water vapor requirements. 

Isolation A means of preventing certain stream properties (deflagration, mass flow, ignition capability) from being conveyed past a predefined point. 

If the tank is well-mixed, the concentrations and density of the tank contents are uniform throughout. This means that the outlet stream properties are identical with the tank properties, in this case concentration Ca and density p. The balance region can therefore be taken around the whole tank (Fig. 1.5). 

Tn proportionality constant introduced out refers to outlet stream property... 

A schematic representation of this reactor model is shown in Figure 22.2. Particles of solid reactant B are in BMF, and fluid reactant A is uniform in composition, regardless of its flow pattern. The solid product, consisting of reacted and/or partially reacted particles of B, leaves in only one exit stream as indicated. That is, we assume that no solid particles leave in the exit fluid stream (no elutriation or entrainment of solid). This assumption, together with the assumption, as in the SCM, that particle size does not change with reaction, has an important implication for any particle-size distribution, represented by P(R). The implication is that P(R) must be the same for both the solid feed and the solid exit stream, since there is no accumulation in the vessel in continuous operation. Furthermore, in BMF, the exit-stream properties are the same as those in the vessel Thus, P(R) is the same throughout the system ... 

Table 9-6 Stream Properties for the Natural Gas Fueled Pressurized PAFC...

Table 9-19 Stream Properties for the 500 MW Class Coal Gas Fueled Cascaded SOFC... 

Perfect mixing flow This flow assumes that the vessel contents are completely homogeneous, and no difference exists between the various portions of the vessel, and the outlet stream properties are identical to the vessel fluid properties. 

Steps 1, 2, 3 and 4 This is a steady state problem. The system is open. No reaction occurs. The stream properties are placed in the figure... 

Finally, we can solve the equations listed in Table 3.2.2 simultaneously using POLYMATH [19] or some other suitable mathematical software. The solution procedure used in POLYMATH is the bounded Newton-Raphson method described by Shacham and Shacham [20]. Table 3.2.5 lists the stream properties, which include the solution to the equations and specified temperatures and pressures at each line. The difference in the water flow rates into and out of the cooling tower is the water evaporated. Thus, to cool 164,700 Ibmol/h (74,700 kg mol/h) water requires evaporating 5,200 Ibmol/h (2,360 kg mol/h) of water. The evaporated water, along with water lost because of leaks, blowdown, and drift are a cost of operation. 

Table 3.2.5 Stream Properties - Cooling-Tower Analysis... 

Table 3.4.4 Stream Properties - Formaldehyde-Synthesis Reactor... 

Table 3.5.8 Summary of Stream Properties—Methanol Synthesis Process... 

For a process system that involves a single condensable component, a vapor-liquid phase change, and specified or requested values of feed or product stream properties (temperature, pressure, dew point, relative saturation or humidity, degrees of superheat, etc.), draw and label the flowchart, carry out the degree-of-freedom analysis, and perform the required calculations. 

These relations can be rewritten for internal flow by using bulk mean properties instead of free stream properties. After some simple mathematical manipulations, the three relations above can be rearranged as... 

Reactor plus Separator To avoid calculating the reactor output stream properties, we will make the system the reactor plus the separator. First we need to calculate the pounds of water consumed in the reaetion per pound of sucrose consumed in the reaction. 

Frequently process plants contain recycle streams and control loops, and the solution for the stream properties requires iterative calculations. Thus efficient numerical methods for convergence must be used. In addition, appropriate physical properties and thermodynamic data have to be retrieved fi om a data base. Finally, a master program must exist that links all the building blocks, physical property data, thermodynamic calculations, subroutines, and numerical subroutines, and that also supervises the information flow. You will find that optimization and economic anafy-sis are really the ultimate goal in the use of flowsheet codes. 

Stream properties required for solving material and energy balance equations... 

In using a flowsheet simulator, one of the most important decisions is the choice of thermodynamics package. The choice of thermodynamics options affects the accuracy of the material and energy balances. Appropriate choices depend on the compounds in the system, temperature, pressure, and the availability of parameters. Equations of state and activity models are used to calculate stream properties number of phases, phase composition, PVT relationships, enthalpy, and entropy. 

Same product stream property requirements as in case 4 however, the feed gas contains 30% C02 at 65 psia... 

FIGURE 6.7 Effects of viscosity changes across a laminar liquid boundary layer on surface shear and heat flux—reference shear from Blasius solution with free-stream properties, reference heat flux from Pohlhausen solution with wall properties [7]. 

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