Page 20 - Modeling of Chemical Kinetics and Reactor Design

to the vapor pressure at ambient temperature. Table 2 shows the raw
materials requirements, yield, and properties of ammonia.
Transportation is by railroad tank vehicle, by tank truck, or by
pipeline. In this case, transportation at ambient temperature is the best
choice. The choice of storing ammonia at an ambient temperature
liquid or partially refrigerated liquid or an ambient pressure liquid
depends mostly on economic factors. One of the factors that deter-
mines the storage method is the quantity of ammonia to be stored.
Ammonia is toxic and flammable, although the lower flammable
limit is quite high and fires in ammonia facilities are rare. However,
spillage from storage vessel or transfer piping must be considered and
adequate precautions taken to minimize its effect. Storage tanks must
have adequate vents so the pressure cannot rise above safe levels, and
are diked to prevent the spread of liquid in case of a spill. For ambient
pressure storage, the vents must be large in area and operate at
pressures only slightly above ambient pressure. Alternatively, for
ambient temperature, the vents are smaller, but operate at much higher
pressure. At ambient temperature, ammonia in common with other
liquified gases must have sufficient ullage space in the tank to allow
for expansion when the temperature rises. Otherwise, liquid loaded into

Table 2
Raw materials requirements and yield
Raw materials required per ton of ammonia:
Natural gas: 810 m 3 Yield: 85%
Properties: Colorless liquid or gas with a very pungent odor. Soluble in water,
ethyl alcohol, and ether.
Molecular weight: 17.03 Vapor density (air = 1): 0.597
Density at 20°C (gas): 0.771
Melting point: –77.7°C Boiling point: –33.4°C
Autoignition temperature: 651°C
Critical temperature, T : 132.4°C
C
Critical pressure, P : 111.3°C
C
3
Critical volume, V : 72.4 cm /gmol
C
Critical compressibility factor Z: 0.243
xx