Vapor pressure of ammonia

Diammonium Tetraborate Tetrahydrate. Diammonium tetraborate tetrahydrate, (NH 2 4Dy 4H2O or (NH 2D 2B202 H2O formula wt, 263.37 monoclinic sp gr, 1.58 is readily soluble ia water (Table 9). The pH of solutions of diammonium tetraborate tetrahydrate is 8.8 and iadependent of concentration. The compound is quite unstable and exhibits an appreciable vapor pressure of ammonia. Phase relationships have been outlined and the x-ray crystal stmcture formula is (NH 2P4D5(OH)J 2H20 (124). 

Assume values for Y, (0.012 for example) mol ammo-nia/mol of inert gas and read corresponding vapor pressure of ammonia from Figure 9-75 (curve Y) (=102 mm). This figure was calculated from... 

Read aqua-ammonia vapor pressure curves at wt percent NH3 and corrected temperature (base temperature plus rise) (= 90 + 17.8 = 107.8°F, e.g., or 41.1°C). Read 29.5 mm Hg as vapor pressure of ammonia, Figure 9-76. 

Use data from Table 6.3 to calculate the vapor pressure of ammonia at 235 K. 

Katan, T. Campa, A.B. "Vapor Pressure of Ammonia in Aqueous Potassium Hydroxide Solutions," J. Chem. Eng. Data, 1963,... 

Estimate the volume change of vaporization for ammonia at 20°C. At this temperature the vapor pressure of ammonia is 857 kPa. 

In certain electrolytic media the concentration of salts is so high that the medium could be regarded as consisting of a solvated salt. This is thus the case in the strong solutions (10 M) of many salts in ammonia in which the vapor pressure of ammonia at ambient temperature is less than 1 atm. It also applies to the strong solutions of tetraalkylammonium /7-tolue-nesulfonates in water, used sometimes in organic electrochemistry. 

The operation was countercurrent with the gas entering at the bottom of the vertical tower and the acid passing down in a thin film on the inner wall. The change in acid strength was inappreciable, and the vapor pressure of ammonia over the liquid may be assumed to have been negligible. Calculate the absorption coefficient kg from the data. 

We can use Henry s law to calculate the vapor pressure of ammonia over the surface of solutions of ammonium hydroxide. The Henry s law constant for ammonia is 58 atm/M. Let s assume that we are using 6 M NH4OH ... 

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]...

FIGURE 27.4 The influence of relative humidity on the evaporation of an ammonia droplet. The initial droplet radius is 100 /j.m, the gas temperature is 20°C, and the vapor pressure of ammonia in the gas is negligible. (Source Vesala and Kukkonen, 1992)... 

Because of the G-S process s limitations, alternatives have been developed. The alternative that has been deployed in India and Argentina relies on ammonia-hydrogen exchange. This needs a catalyst and the potassium salt of ammonia, KNH2, dissolved in the ammonia is used. Because of the high vapor pressure of ammonia, the exchange process is carried... 

When a leak occurs in a congested area where atmospheric dissipation is not feasible, the ammonia can be absorbed in water. Its high solubility in water may be used to control the escape of ammonia vapor. Applying a large volume of water from a fog or spray nozzle lessens vaporization, as the vapor pressure of ammonia in water is much less than that of liquid ammonia. Do not neutralize liquid ammonia with acid as the heat generated by the reaction may increase the fumes. 

The problem is that this is not always the case. Also, what happens when you need to break a line for maintenance The vapor pressure of ammonia at... 

Because only free NH3 can be stripped from solution, the pH of the liquid discharge first must be increased to above 11 by the addition of an alkali. This feed then is stripped of ammonia in a countercurrently operated packed column using air. A minimum of 240 CFM of air is required per gpm of liquid feed at 68 F however, in practice 300 to 400 CFM of air per gpm of feed may be used. It must be realized that the air will cool the feed liquid toward the air temperature- Because a reduction of 18°F in the temperature of the water will reduce the vapor pressure of ammonia by about 40%, the use of steam injection to heat the air may be needed to obtain the required ammonia removal in cold climates (below 52°F). 

Figure 4-2. Equilibrium vapor pressure of ammonia over aqueous solutions. From Perry (1941)...

In the Kurabo process, the absorbent solution is maintained at a low pH (3-4) and contains primarily ammonium sulfate. The sulfate is formed from absorbed SO2 by continuously recycling the solution through a separate oxidation step where it is contacted with air. The low pH greatly limits the solubility of SO2 in the liquid, so a large UG ratio is required in the absorber (50-60 gallons per Mscf). However, the low pH suppresses the vapor pressure of ammonia so the formation of an ammonium salt plume at the stack is avoided. A second advantage of this approach is that gypsum rather than calcium sulfite is produced. 

Accidents in which fire and/or explosion of ammonia-air mixtures have been reported to cause the death or injury of personnel are known [77, 78], but are not very frequent. Such accidents have occurred in cold storage warehouses in which ammonia was released in an enclosed space and ignition was caused accidentally. One reason that explosions and lire accidents have not been frequent is that upon release of ammonia from atmospheric or pressurized tanks, rapid evaporation of ammonia cools down the liquid and thereby reduces the vapor pressure of ammonia over the liquid. As noted above, even momentary fatal concentrations of ammonia are much lower than the lower explosion limit in air. Also the fairly high ignition temperature and the low normal flame velocity of an ammonia/air mixture (0.07 to 0.08 m/s) are important [12]. For protection against fire and explosion in ammonia storage or transportation vessels see [13]. 

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