Flashing computer-aided

Flash-drum specifications in addition to (T9, T9) and (T9, adiabatic) are also possible but must be applied with care, as discussed by Michelsen [Comp. Chem. Engng., 17,431 (1993)]. Most computer-aided process design and simulation programs permit a wide variety of flash specifications. 

Pressure drop, chart, 102, 103, 111 Computer aided drafting, 17 Condensate, flashing flow, 135-142, 147 Charts, 142, 143 Control valve pressure drop, 90 Calculations, 90-96 Cost estimates, plant, 45-49 Accounting, 48... 

Cavett proposed the following problem as a test problem for computer-aided design. Four flash drums are connected as shown in Fig. P5.ll. The temperature in each flash drum is specified, and equilibrium is assumed to be independent of composition so that vapor-liquid equilibrium constants are truly constant. Is the problem properly specified, or do additional variables have to be given If the latter, what should they be The feed is as follows... 

The computer-aided procedure, unless automated by the program, requires running a series of liquid-liquid equilibrium calculations (the equivalent of vapor-hquid flash calculations) at constant temperature and pressure. The composition is varied around the equilibrium curve, and the transition points from one phase to two, or vice versa, are noted. As many points as needed are obtained this way to generate the entire equilibrium curve. Also, each time an equilibrium calculation is done in the two-phase region, the compositions of the two phases are recorded. Each pair of data points thus obtained defines a tie line. The data obtained at one temperature and pressure generate one triangular diagram. If so desired, the procedure is repeated at other temperatures and pressures to determine the effect of these variables. 

Listed in the paragraphs that follow are the names, symbols, and usual electrical charges for 30 common positive ions, and the names and formulas for 37 common acids that are frequently mentioned in this text. You should memorize these so as to have them at instant recall the use of flash cards or other foreign-language learning aids is recommended (computer-generated drill programs also are helpful). Aside from the direct intrinsic value of these names and formulas, you can reason out from them the names and formulas of almost 50 bases and over 1600 different salts, none of which should be memorized. 

Equations (12.28) through (12.30) are solved by trial and error, by hand, or with the aid of a computer. For example, if P and T are specified, then the iteration must proceed on L/V. When a final temperature is specified, an isothermal flash resulfs. 

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