Steam continued equilibria

Liquid is heated in a vessel by means of steam which is supplied to an internal coil in the vessel. When the vessel contains 1000 kg of liquid it takes half an hour to heat the contents from 293 to 368 K if the coil is supplied with steam at 373 K. The process is modified so that liquid at 293 K is continuously fed to the vessel at the rate of 0.28 kg/s. The total contents of the vessel are always being maintained at 1000 kg. What is the equilibrium temperature which the contents of the vessel will reach, if heat losses to the surroundings are neglected and the overall heat transfer coefficient remains constant ... 

This reaction also plays a role in the degradation of polysulfides. A back-biting mechanism as shown in equation 6 results in formation of the cyclic disulfide (5). Steam distillation of polysulfides results in continuous gradual collection of (5). There is an equilibrium between the linear polysulfide polymer and the cyclic disulfide. Although the linear polymer is favored and only small amounts of the cyclic compound are normally present, conditions such as steam distillation, which remove (5), drive the equilibrium process toward depolymerization. 

Hydrolysis by Steam. High pressure steam, 4.5—5.0 MPa (650—725 psi), at 250°C in the absence of a catalyst hydrolyzes oils and fats to the fatty acids and glycerol (20). The reaction is commonly carried out continuously in a countercurrent method. The glycerol produced during the reaction is continuously extracted from the equilibrium mixture with water. A yield of 98% can be achieved. Currently, the preferred method to produce soaps is steam hydrolysis of fats followed by alkali neutralization of the fatty acids. 

As mentioned earlier, the state of a pure homogeneous fluid is fixed whenever two intensive thermodynamic properties are set at definite values. However, for more complex systems this number is not necessarily two. For example, a mixture of steam and liquid water in equilibrium at 101.33 kPa can exist only at 100°C. It is impossible to change the temperature without also changing the pressure if vapor and liquid are to continue to exist in equilibrium one cannot exercise independent control over these two variables for this system. The number of... 

Carbon monoxide at 25°C and steam at 150°C are fed to a continuous water-gas shift reactor. The product gas, which contains 40.0mole% H , 40.0% CO2, and the balance H20(v). emerges at 500°C at a rate of 2.50 SCMH (standard cubic meters per hour) and goes to a condenser. The gas and liquid streams leaving the condenser are in equilibrium at 15 C and 1 atm. The liquid may be taken to be pure water (no dissolved gases). 

As Fig. 4.6 shows, saturated steam at a temperature s is condensing on a vertical wall whose temperature 0 is constant and lower than the saturation temperature. A continuous condensate film develops which flows downwards under the influence of gravity, and has a thickness 5 x) that constantly increases. The velocity profile w(y), with w for wx, is obtained from a force balance. Under the assumption of steady flow, the force exerted by the shear stress are in equilibrium with the force of gravity, corresponding to the sketch on the right hand side of Fig. 4.6... 

Da as would be expected. Conversion in an ordinary reactor reaches a certain maximum due to the establishment of the chemical equilibrium. In a membrane reactor conversion keeps increasing as a result of continuous hydrogen permeation. This is an important aspect of the membrane reactor, because the steam excess can be reduced which leads to a favourable economy of the process. 

An open kettle contains 50 kmol of a dilute aqueous solution of methanol (2 mol% of methanol), at the bubble point, into which steam is continuously sparged. The entering steam agitates the kettle contents so that they are always of uniform composition, and the vapor produced, always in equilibrium with the liquid, is led away. Operation is adiabatic. For the concentrations encountered it may be assumed that the enthalpy of the steam and evolved vapor are the same, the enthalpy of of the liquid in the kettle is essentially constant, and the relative volatility is constant at 7.6. 

One hundred kilogram/moles per hour of a saturated liquid mixture of 12mole% ethyl alcohol in water is distilled continuously by direct steam at I atm. Steam is introduced directly to the bottom plate. The distillate required is 85 mole% alcohol, representing 90% recovery of the alcohol in the feed. The reflux is saturated liquid with L/D = 3. Feed is on the optimum stage. Vapor-liquid equilibrium data are given in Problem 8.30. Calculate ... 

A saturated liquid mixture of 69.4mole% benzene in toluene is to be continuously distilled at atmospheric pressure to produce a distillate containing 90mole% benzene, with a yield of 25 moles distillate per 100 moles of feed. The feed is sent to a steam-heated still (reboiler), where residue is to be withdrawn continuously. The vapors from the still pass directly to a partial condenser. From a liquid separator following the condenser, reflux is returned to the still. Vapors from the separator, which are in equilibrium with the liquid reflux, are sent to a total condenser and are continuously withdrawn as distillate. At equilibrium the mole... 

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