Valves adiabatic pressure-reducing

Adiabatic cracking reactor, 10 617-618 Adiabatic decomposition, of hydrogen peroxide, 14 61-62 Adiabatic dehydrogenation, 23 337 Adiabatic dehydrogenation unit, 23 339 Adiabatic evaporation, general separation heuristics for, 22 319 Adiabatic flame temperature, 12 322 Adiabatic flash calculation, 24 681 Adiabatic nitration process, 17 253—255 Adiabatic pressure-reducing valve,... 

In a continuous manufacturing process, chlorodifluo-romethane (CHCIF2), initially at 10 bar arid 420 K, passes through an adiabatic pressure-reducing valve so that its pressure drops to 0.1 bar (this last pressure low enough that CHCIF2 can be considered to be an ideal gas). At these operating conditions, the gas can be represented by a one-term virial equation of state ... 

The following stream comes out of a distillation tower (described in detail in Chapter 6). It is at 138 psia and 197.5°F. If the pressure is reduced (adiabatically) to 51 psia, what will be the vapor fraction and temperature (Hint In Aspen Plus, put a valve before the Flash2 unit, and reduce the pressure with the valve block.)... 

When the pressure of a liquid stream of known composition, flow rate, and temperature (or enthalpy) is reduced adiabatically across a valve as in Fig. l. a, an adiabatic flash calculation can be made to determine the resulting temperature, compositions, and flow rates of the equilibrium liquid and vapor streams for a specified flash drum pressure. In this case, the procedure of Fig. 7.4o is applied in an iterative manner, as in Fig. 7.8, by choosing the flash temperature Tv as the iteration or tear variable whose value is guessed. Then X, y, and L are determined as for an isothermal flash. The guessed value of Tv (equal to TJ is checked by an enthalpy balance obtained by combining (7-15) for Q = 0 with (7-14) to give... 

Entering stage j can be one single- or two-phase feed of molal flow rate JF, with overall composition in mole fractions zq of component i, temperature Tfj, pressure Pp., and corresponding overall molal enthalpy Hp.. Feed pressure is assumed equal to or greater than stage pressure P/. Any excess feed pressure Pp - Pj) is reduced to zero adiabatically across valve F. 

Similarly, from stage j +1 below, interstage vapor of molal flow rate with composition in mole fractions y/j+u enthalpy temperature T +, and pressure Pj+i can enter stage j. Any excess pressure (P,+, - Pj) is reduced to zero adiabatically across valve V. 

Solid carbon dioxide can be manufactured by expanding liquid CO through an adiabatic throttling valve. If CO2 is available for the process as a saturated liquid at 800 psia and the expansion reduces the pressure to 14.7 psia, how many pounds of solid carbon dioxide are produced per pound of liquid CO2 ... 

Throttle valve A throttle valve reduces the pressure of a gas at adiabatic conditions (Q = 0) thus, it is a P-h flash. The resulting temperature is determined by the Joule-Thomson coefficient. 

The flash is operating adiabatically at 20 bar. The bottom of the flash is separated in a shortcut column. In the shortcut column, the condenser and reboiler pressure is 20 bar. The light key component in distillate is HCI and its mole fraction in the bottom is set at 0.001. The heavy key is ethyl chloride and its composition in the distillate is very small in this example it is 0.001. The reflux ratio is 2. The bottom product is mostly pure ethylene chloride. The purge (stream 11) split fraction in the distillate is set at 0.1. The pressure of the recycle stream is reduced to 1 atm using a throttling valve. The exit stream from the valve is heated in a heater to the fresh feed temperature and linked with the fresh feed. The stream conditions and compositions are shown in Figure 9.10. 

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