Explosions with Liquid Refrigerants

Several studies have been carried out in which liquid refrigerants were contacted with either water or oils. In view of the similarity of such 

Five refrigerants have been studied. Some property values are shown in Table XVI. 

Fauske (1973) showed that drops of R-11 could be injected into warm water (—343 K) with little boiling. The drops, being more dense than water, fell to the bottom of the vessel. No explosions were noted. Also, for R-11 and (R-21), Chukanov and Skripov (1971) measured the super-heat-limit temperatures (see Table XVI). 

Several investigators studied R-12. Holt and Muenker (1972) and Rausch and Levine (1973) made simple spills of this cryogen into water. The highest water temperature used by both teams was —342 K and weak explosions were noted. From Table XVI, it can be seen that this water temperature was barely within the range of the superheat-limit temperature, so no or only minor explosions might have been expected. Henry et al. (1974) spilled R-12 on top of a hot mineral oil. For oil temperatures less than about 409 K, there was little interaction except rapid boiling. Above 409 K, explosions resulted. Henry et al. state that this oil temperature would lead to an interface temperature [see Eq. (1)] close to the expected homogeneous nucleation temperature (—345 K) so that the explosions were to be expected. 

Rausch and Levine (1973) spilled R-114 on hot ethylene glycol. Explosions were reported if the glycol temperature exceeded about 386 K. They estimated the interface temperature between the R-114 and glycol to be about 354 K. Thus, explosions were noted when the bulk glycol temperature exceeded the expected homogeneous nucleation temperature, T i, even though the interface temperatures were less than T.  

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Liquid air. Do not refrigerate a trap with liquid nitrogen until the system pressure is reduced below a few Torr. (Liquid air boils at higher temperature than liquid nitrogen and can easily be condensed at 77 K.) Liquid air present in a trap may react explosively with any organic substances that condense there. The liquid air can also produce excess pressure and likely damage to the vacuum system should the trap warm without venting this is a common mishap with vacuum systems. 

Ammonia, when released is a toxic gas with little flammability. It is imported by sea into the 14,(XX) tonnes capacity tank at Shell UK Oil where the refrigeration maintains the temperature below the boiling point of the gas (33° C). Three ways were identified whereby several hundred tonnes of liquid ammonia could be released into the river to vaporize and disperse. The worst accident would have an accompanying explosion or fire on an ammonia carrier berthed at the unloading jetty. Next in order of severity is a ship collision and spillage into the river near the unloading jetty. The consequences of a collision between ships occurring within the area but not near the jetty were also calculated. 

Most of us are familiar with the hquid form of ammonia known as ammonium hydroxide (NH OH), a colorless liquid that, with its strong odor, is irritating to the eyes and potentially harmful to the moist mouth and nose, throat, and lungs if its vapors are breathed. Weak solutions of NH OH are ingredients in household cleaning ammonia. Concentrated ammonium hydroxide has many industrial uses, including the manufacture of rayon, fertilizers, refrigerants, rubber, pharmaceuticals, soaps lubricants, inks, explosives, and household cleaners. 

Nitrogen In the production of ammonia by the Haber process (see p. 176) the ammonia is then used to make nitric acid, which is used in the manufacture of dyes, explosives and fertilisers In liquid form, as a refrigerant As an inert atmosphere for some processes and chemical reactions, because of its unreactive nature for example, empty oil tankers are filled with nitrogen to prevent fires In food packaging to keep the food fresh, for example in crisp packets where it also prevents the crisps being crushed (Figure 11.10)... 

Khattak, M. A., Engineering Horizons (Pakistan), 1991, (Aug.), 33 Chlorine reacts with ammonia and compounds to form the treacherously explosive nitrogen trichloride. A change was made to ammonia as refrigerant in the production of liquid chlorine some months later minor explosions when transferring the chlorine... 

Flammable Liquid, Corrosive, Poison SAFETY PROFILE A poison by skin contact and ingestion. Moderately toxic by inhalation. Ingestion of even small amounts can be fatal. A skin and severe eye irritant. Inhalation of a small amount can cause immediate lachrymation, coughing, choking, and respiratory distress. Death may result from pulmonar) edema which may not appear for several hours after exposure. A dangerous fire and moderate explosion hazard when exposed to heat, spark, or flame. Self-reactive. Iron salts may catalyze a potentially explosive thermal decomposition. Incompatible with water, iron, metal salts, acids, alkalies, amines, alcohols. Stable under refrigeration below 20°, but one reference (1973) reports that it has exploded while stored in a refrigerator. Present-day formulations appear to be more stable. Temperatures above 20° can cause decomposition. When heated to decomposition it emits acrid smoke and fumes. 

Liquid air is potentially dangerous and is now rarely used. Liquid oxygen should never be used as a refrigerant, it can cause an explosion when in contact with some organic substances. Should LN be poured into a dewar flask which contains water, no matter what its source, then the ice which forms will break the dewar. All dewars must be dried out before adding LN. 

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