Clouds ammonia

An early morning explosion, Dec. 13, 1994, killed four employees and injured 18 at Terra Industries Port Neal, Iowa, nitrogen fertilizer plant, 16 miles south of Sioux City, The blast leveled half the facility and forced evacuation of more than 2,500 people from nearby towns with an ammonia cloud released from a ruptured storage tank. Road and air traffic were diverted. Some were injured by falling debris and others by the impact of the explosion. Many suffered from ammonia inhalation. 

The most obvious visual features of Jupiter are a number of dark and bright hands that are generally known as belts and zones. These bands are caused by ammonia clouds that blow parallel to the planet s equator. Between 15° north latitude and 15° south latitude, the clouds blow in the same direction as the planet s rotation, west to east, at speeds of about 100 meters/second (200 mph). Between latitudes 15° and 45° north and south, they tend to blow in the opposite direction, from east to west, at about half the speed of the equatorial winds. At latitudes higher than 45°, the winds appear to be largely absent, and the banded appearance on this part of the planet s face disappears. 

Description of Experiments The Desert Tortoise Series of ammonia spill experiments was performed by LLNL at the Frenchman Flat area of the Nevada Test Site during the summer of 1983. There were four experiments for the study of the size, shape, and temperature of the ammonia clouds, as well as the extent of the hazardous concentrations downwind. In order to simulate simple cases, which later could be modeled, the tests were performed at constant pressure and on the dry lakebed, which provided a relatively flat and smooth surface. 

Most of the heavier-than-air cloud field experiments have focused on the dispersion of gaseous clouds. However, some experiments have been conducted with two-phase effects, e.g., the Desert Tortoise, Eagle, Goldfish series (Koopman et al., 1989) and FLADIS field experiments (Nielsen et al., 1997). In particular, the Desert Tortoise series was designed to study the dispersion of two-phase ammonia clouds. It was reported that two-phase effects had a dominating influence on the temperature and spreading behavior of the cloud and the extent of the heavy cloud dispersion regime (Koopman et al., 1986). Recently, available field data sets have been reviewed within the SMEDIS (Scientific Model Evaluation of Dense Gas Dispersion Models) project (Daish et al., 1998 Carissimo et al., 1999). 

We have illustrated the model predictions by evaluating two-phase ammonia clouds released in dry and moist air. The numerical test cases are identical to those in Kukkonen et al. (1993), which presents a comparison of the model AERCLOUD and the thermodynamical submodel of the heavy cloud dispersion program DRIFT (Webber et al., 1992). DRIFT embodies the homogeneous equilibrium model, while AERCLOUD allows also for thermodynamic nonequilibrium effects. Both models will cope with ammonia interactions with moist air as well as with the simpler dry air problem. 

Selection of Cases. We have made predictions for instantaneous releases of a pure ammonia cloud into both dry and humid air. A summary of the initial and ambient conditions for the cases chosen is shown in Table 27.1. The ambient temperature was taken to be 15°C, the Pasquill class was D, the average wind velocity at a height of 10 m was 2 m/s, and the roughness length was 6 mm. 

Driving through a dense ammonia cloud is very risky and should not be attempted. 

Consequence A measure of the expected effects of an incident outcome case (e.g., an ammonia cloud fiom a 10 Ib/s leak under Stability Class D weather conditions, and a 1.4-mph wind traveling in a northerly direction will injure 50 people)... 

Risk analysis The development of a quantitative estimate of risk based on engineering evaluation and mathematical techniques for combining estimates of incident consequences and frequencies (e.g., an ammonia cloud from a 10 Ib/s leak might extend 2000 ft downwind and injure 50 people. For this example, using the data presented above for likelihood, the frequency of injuring 50 people is given aslxlff x0.1x0.1 = lx 10" events per year)... 

At atmospheric temperature and pressure, ammonia is a colorless gas with a sharp and pungent odor. Ammonia also exists as a colorless liquid. Its vapor pressure at — 33.6 °C is 1 atm, at + 4.7 °C it is 5 atm, at 20 °C it is 8 atm, and at 25.7 °C it is 10 atm. At 50.1 °C, the vapor pressure is 20 atm. Ammonia vapor at the boiling point of — 33 °C will have a vapor density of approximately 70% of the density of ambient air. However, ammonia and air can, under certain conditions, form mixtures that are denser than ambient air [1], as a result of the mixture being at a lower temperature caused by the evaporation of cold ammonia. An ammonia cloud formed by an accidental release of ammonia may contain a mist of liquid ammonia and its density may be greater than that of air. For the density of an ammonia cloud containing liquid ammonia as it is diluted with dry air, see [2]. 

In the Pensacola accident, 50% of the contents of one ammonia rail car were released within 10 minutes, while the contents of another ammonia rail car were slowly vaporized over 12 hours. A lethal cloud engulfed a populated area within minutes, and before the residents could be evacuated. They were later escorted on foot for distances from 60 to 300 m through the ammonia cloud, until out of the affected area. One of the lessons learned in this accident and also in the Crete, Nebraska accident, in which 3 anhydrous ammonia tank cars were struck by a passing train and one tank ruptured, is that people who stay in their homes... 

Oxidation of sulfur dioxide in aqueous solution, as in clouds, can be catalyzed synergistically by iron and manganese (225). Ammonia can be used to scmb sulfur dioxide from gas streams in the presence of air. The product is largely ammonium sulfate formed by oxidation in the absence of any catalyst (226). The oxidation of SO2 catalyzed by nitrogen oxides was important in the eady processes for manufacture of sulfuric acid (qv). Sulfur dioxide reacts with chlorine or bromine forming sulfuryl chloride or bromide [507-16 ]. 

Dutch State Mines (Stamicarbon). Vapor-phase, catalytic hydrogenation of phenol to cyclohexanone over palladium on alumina, Hcensed by Stamicarbon, the engineering subsidiary of DSM, gives a 95% yield at high conversion plus an additional 3% by dehydrogenation of coproduct cyclohexanol over a copper catalyst. Cyclohexane oxidation, an alternative route to cyclohexanone, is used in the United States and in Asia by DSM. A cyclohexane vapor-cloud explosion occurred in 1975 at a co-owned DSM plant in Flixborough, UK (12) the plant was rebuilt but later closed. In addition to the conventional Raschig process for hydroxylamine, DSM has developed a hydroxylamine phosphate—oxime (HPO) process for cyclohexanone oxime no by-product ammonium sulfate is produced. Catalytic ammonia oxidation is followed by absorption of NO in a buffered aqueous phosphoric acid... 

Evaporation of a relatively-small volume of liquid in an enclosed space can produce a flatmuable or toxic vapour hazard. Leakage, or spillage, of a chemical maintained as a liquid above its atmospheric boiling point by pressure (e.g. liquefied petroleum gases) or as a liquid by refrigeration (e.g. ammonia) can result in a sizeable vapour cloud. 

Lethal range for releases of toxic or explosive materials such as an ammonia spilt on water or land, or explosion or conflagration from a cloud of methane or liquefied petroleum gas... 

A more serious incident occurred at a plant in which ethylene oxide and aqueous ammonia were reacted to produce ethanolamine. Some ammonia got back into the ethylene oxide storage tank, past several check valves in series and a positive pump. It got past the pump through the relief valve, which discharged into the pump suction line. The ammonia reacted with 30 m of ethylene oxide in the storage tank. There w as a violent rupture of the tank, followed by an explosion of the vapor cloud, which caused damage and destruction over a wide area [4],... 

The giant planets possess low surface temperatures and have atmospheres that extend several thousand miles. The markings on Jupiter, the largest planet, consist of cloud formations composed of methane containing a small amount of ammonia. The atmosphere of Jupiter absorbs the extreme red and infrared portions of the spectrum. These absorptions correspond to the absorption spectra of ammonia and methane, suggesting the presence of these gases in Jupiter s... 

When Explosive D is ignited in an unconfined state, it burns slowly, emitting dense black smoke without detonation. When confined and heated to its ignition temp, it will expld. When detonated completely, it emits a dense cloud of black smoke with a sooty deposit and an odor of ammonia. 

As mentioned after Equation (10), the equilibrium constant may be expressed when the reactants are in several phases. As an example, the equilibrium between ammonia in a large cloud droplet and in the gas phase, NH3(aq) and NH3(g), is described by the equilibrium constant expression... 

Perhaps because the unpolluted atmosphere can appear to be perfectly free of turbidity, it is not immediately obvious that it is a mixture of solid, gaseous, and liquid phases - even in the absence of clouds. Particles in the aerosol state constitute only a miniscule portion of the mass of the atmosphere - perhaps 10 or 10 ° in im-polluted cases. However, the condensed phases are important intermediates in the cycles of numerous elements, notably ammonia-N, suT... 

All of these species are very soluble in a rain or cloud drop and are an important source of atmospheric aerosols. For ammonia and ammonium, the condensed phases (I and s) represent approximately two-thirds of the total atmospheric burden, whereas for nitric acid and nitrates, about two-thirds is in the gas phase (Soderlund and Svensson, 1976). 

Escapes or spillages of liquefied petroleum gas, or chlorine or ammonia, rapidly generate a vapour cloud. 

Twenty tons of ethylene oxide were contaminated by ammonia accidentally. The tank broke open releasing a fume cloud , which gives rise to a devastating explosion. Again, it is rather difficult to interpret this accident. Indeed, it could be a violent polymerisation, which was the result of the catalytic effect of ammonia or a very exothermic reaction ... 

The above examples should suffice to show how ion-molecule, dissociative recombination, and neutral-neutral reactions combine to form a variety of small species. Once neutral species are produced, they are destroyed by ion-molecule and neutral-neutral reactions. Stable species such as water and ammonia are depleted only via ion-molecule reactions. The dominant reactive ions in model calculations are the species HCO+, H3, H30+, He+, C+, and H+ many of then-reactions have been studied in the laboratory.41 Radicals such as OH can also be depleted via neutral-neutral reactions with atoms (see reactions 13, 15, 16) and, according to recent measurements, by selected reactions with stable species as well.18 Another loss mechanism in interstellar clouds is adsorption onto dust particles. Still another is photodestruction caused by ultraviolet photons produced when secondary electrons from cosmic ray-induced ionization excite H2, which subsequently fluoresces.42... 

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