Ammonia saturation vapor pressure

Liquid ammonia is stored in a tank at 24°C and a pressure of 1.4 X 106 Pa. A pipe of diameter 0.0945 m breaks off a short distance from the vessel (the tank), allowing the flashing ammonia to escape. The saturation vapor pressure of liquid ammonia at this temperature is 0.968 X 106 Pa, and its density is 603 kg/m3. Determine the mass flow rate through the leak. Equilibrium flashing conditions can be assumed. 

Fig. 4 Saturated vapor pressure of ammonia on the basis of different force fields by Impey and Klein (open diamonds) [108], Kristof et al. (open squares) [246], Eckl et al. (open circles) [97], as well as Zhang and Siepmann (open inverted triangles) [247]. The simulation results are compared with a reference equation of state (solid line) [249]...

Coefficients of the equadon of state and of the equation for transport properties are stored for each substance. Parameters of the critical point and coefficients of equations for calculadon of the ideal-gas functions, the saturated vapor pressure and the melting pressure are kept also. The thermal properties in the single-phase region and on the phase-equilibrium lines can be calculated on the basis of well-known relations with use of these coefficients. The system contains data for 30 reference substances monatomic and diatomic gases, air, water and steam, carbon dioxide, ammonia, paraffin hydrocarbons (up to octane), ethylene (ethene), propylene (propene), benzene and toluene. The system can calculate the thermophysical properties of poorly investigated gases and liquids and of multicomponent mixtures also on the basis of data for reference substances. 

Diversity means using different types of sensors and actuators or different measurement and operating parameters to achieve the same result in a safety system. The objective is to eliminate or minimize the possibilities of common cause failures or systematic errors. The previous diagram shows a typical example where the same limiting condition, in this case pressure in an ammonia storage vessel, can be detected by pressure and by temperature (which determines the saturation vapor pressure of the ammonia). 

If a volatile component is present in the cured propellant, another effect must be considered. In polysulfide formulations a molecule of water is generated each time a polysulfide bond is formed. The vapor pressure of the ammonium perchlorate propellant formulation becomes that of an ammonia-ammonium perchlorate saturated solution. Ammonia and water can be driven from the formulation, and the water condenses on cold surfaces. If the condensate returns to the propellant surface, perchlorate is leached from the surface of the propellant. This perchlorate may later recrystallize on the surface. A surface void of perchlorate is very difficult to ignite, while a perchlorate-rich surface produces the... 

Suppose 3.68 g ammonium chloride reacts in this way at 30°C and a total pressure of 0.9884 atm. At this temperature, the vapor pressure of water is 0.0419 atm. Calculate the volume of ammonia saturated with water vapor that will be produced under these conditions, assuming no leaks or other losses of gas. 

One approach to avoiding intermolecular agglomeration is the additional coordination of the alkaline earth metal ions with neutral ligands [110]. Addition of Lewis bases such as free ligand, tetrahydrofuran, ammonia, or amines to the carrier gas has afforded some improvement in vapor pressure characteristics of the most commonly used strontium and barium MOCVD precursors, Sr(dpm)2 and Ba(dpm)2 [111-119]. These effects may be due to saturation of the Lewis acidic metal centers with the gaseous bases, thereby increasing precursor vapor pressure and stability in a transient fashion. 

Solution We use the NIST WebBook for the properties of ammonia. We will set the evaporator at - 22 °C, 2 °C below the required temperature. The saturation pressure at this temperature is 1.7379 bar. The condenser uses air at 26 °C as the cooling medium. Allowing for a 2 °C temperature difference, the temperature at the exit of condenser must be at least 28 °C. This corresponds to saturation pressure 10.993 bar and sets the compression pressure of the cycle. Thus we have determined the two pressures of the cycle. We set the state at the exit of the condenser to be saturated liquid, and at the exit of the evaporator to be saturated vapor. With reference to Figure 6-12. the states of streams 1 and 3 are fixed (saturated phases at known pressure) and their properties are shown below (also notice that the pressure of all streams are known). 

S-Sj. A hot vapor stream containing 0.4 mole fraction ammonia and 0.6 mole fraction water is to be enriched in a distillation column consisting of enriching section and total condenser. The saturated vapor at 6.8 atm pressure (100 psia) is injected at a rate 100 moles/hour at the bottom of the column. The liquid distillate product withdrawn from the total condenser has a composition 0.9 mole fraction NH3. Part of the distillate is returned as reflux, so that 85% of the NHj charged must be recovered as distillate product. 

Both the GEMC and the grand equilibrium method have been applied to evaluate vapor-liquid equilibrium data for ammonia. Kristdf et al. [246] calculated the vapor pressure and saturated densities using the force field by Impey and Klein [108] and found systematic deviations from experimental data cf. Fig. 3. Therefore, they proposed a new ammonia force field that was optimized to vapor-liquid equilibria [246], achieving a better accuracy. Simulated saturated densities and enthalpies based on this force field agree with the experimental data within 1 and 3%, respectively. However, it shows a mean deviation of 13% from experimental... 

Figures 21.5a and 21.5b show the drying and settling times of water and ammonia droplets versus the droplet radius. The curves have been shown for three combinations of gas temperatures and vapor pressures and for three initial heights. The simultaneous evaporation and settling of droplets have been taken into account in the computation of the curves. Each settling time curve corresponds to one drying time curve, and each intersection point of these curves corresponds to the maximum radius of a totally evaporating droplet. The vapor pressures in Figs. 21.5a and 21.5b correspond to saturation ratios 0.0012 and 0.058 at a gas temperature of 20°C and to a saturation ratio of 0.12 at a gas temperature of 0°C, for both species.

The major difficulty concerning ES for polar compounds is the lack of accurate, comprehensive data or, in most cases, the lack of any data. Steam is probably the only highly polar compound for which there is a large body of data for a variety of properties such as vapor pressure, critical constants, saturation densities, heats of vaporization, single-phase densities in both liquid and vapor, calorimetric. Joule-Thomson, sonic velocities and heat capacity measurements (Z>.8 Recent data (10) and compilation work (11) have Improved the picture for ammonia. There is also a reasonable body of data for methanol but it is not altogether thermodynamically consistent (12). 

The reactor effluent is rapidly quenched with aqueous mother Hquor in specially designed equipment operating at pressures essentially equal to the reactor pressure. This operation yields an off-gas consisting of ammonia and carbon dioxide vapor and a crystalline melamine slurry saturated with ammonia and carbon dioxide. The slurry is concentrated in a cyclone mill. The mother Hquor overflow is returned to the quenching system. The concentrated slurry is redissolved in the mother Hquor of the crystallization system, and the dissolved ammonia is stripped simultaneously. 

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