Flash distillation fraction vaporized

A solution containing 12 wt % of dissolved nonvolatile solid is fed to a flash distillation unit. The molecular weight of the solid is 123.0. The effective vapor pressure of the solution is equal to the mole fraction of water,... 

The stream defined below is heated to 100°C to be partially vaporized in a flash drum before entering a distillation column. The fraction vaporized is controlled by the flash drum pressure. Calculate the required pressure at 100°C to have 20% mole vaporization, assuming Raoult s law applies. What are the products flow rates and compositions The constants for the Antoine Equation 2.19 are given for each component, with the pressure in kPa and the temperature in K. 

Example 18.1. A mixture of 50 mole percent benzene and 50 mole percent toluene is subjected to flash distillation at a separator pressure of 1 atm. The vapor-liquid equilibrium curve and boiling-point diagram are shown in Figs. 18.2 and 18.3. Plot the following quantities, all as functions of f, the fractional vaporization (n) the temperature in the separator, b) the composition of the liquid leaving the separator, and (c) the composition of the vapor leaving the separator. 

In the table the second, third, and fourth problems each result from a permutation of the known and unknown quantities that occur in the bubble-T calculation. We refer to these as P-problems, because each problem is well-posed when values are specified for P independent intensive properties, where the value of T is given by the phase rule (9.1.14). However, the flash problem in Table 11.1 differs from the others in that it is an P -problem it is well-posed when values are specified for T independent intensive properties, with the value of T given by (9.1.12). Flash calculations pertain to separations by flash distillation in which a known amount N of one-phase fluid, having known composition z, is fed to a flash chamber. When T and P of the chamber are properly set, the feed partially flashes, producing a vapor phase of composition xP in equilibrium with a liquid of composition x ). The problem is to determine these compositions, as well as the fraction of feed that flashes NP/N. Unlike the other problems in Table 11.1, the flash problem involves the relative amounts in the phases and therefore a solution procedure must invoke not only the equilibrium conditions (11.1.1) but also material balances. 

C9. For a vapor-liquid-liquid flash distillation, derive Eqs. (2-62) and (2-63) and the equations that allow calculation of all the mole fractions once V/F and i/F are known. 

D26. We are feeding 100 kmol/h of a 45 mol% propane, 55 mol% n-pentane feed to a flash distillation system. We measure the outlet vapor and liquid mole fractions leaving the flash drum, which is an equilibrium stage, and obtain, ypropane = 0.8, Xp pane = 0.2162. 

F3. (Long Problem ) We wish to flash distill a mixture that is 0.517 mole fraction propane, 0.091 mole fraction n-pentane, and 0.392 mole fraction n-octane. The feed rate is 100 kmol/h. The feed to the flash drum is at 95°C. The flash drum will operate at 250 kPa. Find the drum tenperature, the value of V/F, and the mole fractions of each conponent in the liquid and vapor products. Converge AT,]j to < 0.20°C. 

F4. We wish to do a flash distillation of 10 kmol/h of a feed that is 25 mol% water and and 75 mol% n-propanol. The flash chamber is at 1.0 atm and is adiabatic. We vaporize 40% of the feed in the flash chamber. Find the flow rates of the liquid and the vapor and the mole fraction of water in the liquid and vapor products. 

It is interesting to conpare the sinple batch distillation result to a flash distillation of the same feed producing y = 0.892 mole fraction methanol. This flash distillation problem was solved previously as Problem 2.D1. The results were x = 0.756 (conpare to = 0.65), V = 16.18 (conpare to D otai = 31.06), and L = 33.82 (conpare to Wfjnai = 18.94). The sinple batch distillation gives a greater separation with more distillate product because the bottoms product is an average of liquids in equilibrium with vapor in the entire range from y = 0.915 (in equilibrium with x = z = 0.8) to y = 0.845 (in equilibrium with x = = 0.65), while for the flash distillation the liquid is always in equilibrium... 

Flash distillation of multicomponent mixture. For flash distillation, the process flow diagram is shown in Fig. 11.3-1. Defining/= VjF as the fraction of the feed vaporized... 

In manufacturing ethylene from reduced crude oil or residues, the feed is heated and sent to a flash or evaporator chamber to vaporize a gas-oil or distillate fraction, as practiced in the early Gyro Vapor Phase cracking process for the production of ethylene. Steam is used to assist in the vaporization and to reduce the partial pressure in the reaction zone as... 

It is possible to calculate the properties of wider cuts given the characteristics of the smaller fractions when these properties are additive in volume, weight or moles. Only the specific gravity, vapor pressure, sulfur content, and aromatics content give this advantage. All others, such as viscosity, flash point, pour point, need to be measured. In this case it is preferable to proceed with a TBP distillation of the wider cuts that correspond with those in an actual refinery whose properties have been measured. 

To obtain a low flash zone pressure, the number of plates in the upper section of the vacuum pipe still is reduced to the minimum necessary to provide adequate heat transfer for condensing the distillate with the pumparound streams. A section of plates is included just above the flash zone. Here the vapors rising from the flash zone are contacted with reflux from the product drawoff plate. This part of the tower, called the wash section, serves to remove droplets of pitch entrained in the flash zone and also provides a moderate amount of fractionation. The flash zone operates at an absolute pressure of 60-90 mm Hg. 

Xenon is recovered from air by liquefaction and fractional distillation. Usually it is obtained as a by-product of making other noble gases. It is collected in the liquid oxygen fraction along with krypton, acetylene, and other hydrocarbons that may be present in air. The xenon fraction is flash vaporized. Hydrocarbons present are separated by burning over a catalyst. Xenon is absorbed on silica gel at low temperatures. Finally, it is separated from krypton by selective absorption and desorption from charcoal. 

The ASTM distillation flash char test provides a good indication of both esters and heavy polymers in the reactor effluent. The addition of water dispersible filming amine corrosion inhibitors into the fractionator overhead vapor lines and the addition of mono- and triethanol amines into the feed line of the fractionators has aided in many cases. 

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