Vaporization of chlorine

Liquid chlorine at 22 C is pumped continuously to the chlorine vaporizer. The vaporization process causes the temperature of the chlorine to drop, lake the heat of vaporization of chlorine to be 290 kj/kg and the heat capacity of chlorine vapor to be 0.48 kJ/(kg C). 

The chosen value of A H (298.15 K) is that reported by Johnson et al. ( ). This investigation has the advantage of being independent of the enthalpy of vaporization of chlorine and any heats of solution in deriving the value of the enthalpy of formation. 

HAZARD RISK Ignites on contact with fluorine, hexalithium disilicide, metal acety-lides and carbides decomposition emits toxic vapors of chlorine gas attacks many metals to form toxic fumes NFPA Code H 3 F 0 R 1. 

A variant of this is the passage of the vapors of chlorinated hydrocarbons mixed with steam over solid alkaline materials, such as lime, yielding alcidiols. 

Nonflammable gas. Chlorine pentafluoride is a highly reactive substance. It reacts explosively with water. Paper, cloth, wood, and other organic matter would burst into flames upon contact with the liquid or vapor of chlorine pentafluoride. Vigorous to violent reaction occurs with metals. Reactions with oxides, sulfides, halides, and carbides of metals are violent. It forms explosive mixtures with hydrogen, carbon monoxide, hydrocarbon gases, ammonia, phosphine, sulfur dioxide, and hydrogen sulfide. It reacts violently with sulfur, phosphorus, silicon compounds, charcoal, and mineral acids. 

The vaporization of chlorine tends to be a small-scale process, usually less than 180 tpd (P9). The unit shown is a steam-heated vertical bayonet exchanger, and the drawing follows Typical Flow Schematic 3 of Pamphlet 9. This pamphlet shows a number of other arrangements, but the gas side is the same in all cases. The following paragraphs describe the functions of these devices. 

The highest relative volatility that we have considered for CI2 is 40. Referring to Eq. (89) and identifying nitrogen trichloride as component A and chlorine as component B, we adopt a corresponding value of = 0.025. The concentration factors for different degrees of vaporization of chlorine are tabulated below. 

FIGURE 9.53. Concentration factors for NCI3 during vaporization of chlorine. 

If a chlorine storage tank is simply diked, a low wall may be sufficient for containment, but the area available for vaporization of chlorine and for transfer of heat to the chlorine from the air and the ground will be relatively very high. Better control of the vaporization process results when the floor under the storage tank is sloped and the liquid is collected into a deeper sump of smaller area. Dike walls should always be vertical or nearly so in order to prevent spillover of chlorine due to wave action or its initial momentum. 

Within a chemical plant and over distances of several kilometers, chlorine can be transported by pipelines, either as gas or liquid [24], [240]. Every precaution should be taken to avoid any vaporization of chlorine in a liquid-phase system or any condensation in a gas-phase system. Wherever liquid chlorine could be trapped between two closed valves or wherever the system could be overpressurized by thermal expansion, an expansion chamber, a relief valve, or a rupture disk should be provided [241], [242]. 

Biofiltration works to degrade a diversity of airborne contaminants, including industrial chemicals like styrene (Arnold et al. 1997), pentane and isobutane mixtures (Barton et al. 1997), toluene (Matteau and Ramsay 1997), chlorinated benzenes (Oh and Bartha 1994), dimethylsulfide (Pol et al. 1994), ethylene (Elsgaard 1998), and other volatile organic compounds (VOCs Leson and Winer 1991). Maintenance of good degrada-tive activity of biofilter microbial communities sometimes requires the addition of nutrients to the bioliltration matrix, since materials like peat or wood chips are generally nutrient poor. Adjustments and careful control of environmental variables such as temperature, pH, and availability of moisture (humidity) also are often required (Arnold et al. 1997 Matteau and Ramsay 1997). Removal rates for contaminants by biofilters can be impressive. For example, removal of vapors of chlorinated compounds (chlorinated benzenes, in one instance) was measured at 300 g of solvent vapor h m of filter volume (Oh and Bartha 1994). 

The reactants dissolve and immediately begin to react to form further dichloroethane. The reaction is essentially complete at a point only two-thirds up the rising leg. As the liquid continues to rise, boiling begins, and finally, the vapor-liquid mixture enters the disengagement drum. A very slight excess of ethylene ensures essentially 100 percent conversion of chlorine. 

In a related process, 1,4-dichlorobutene was produced by direct vapor-phase chlorination of butadiene at 160—250°C. The 1,4-dichlorobutenes reacted with aqueous sodium cyanide in the presence of copper catalysts to produce the isomeric 1,4-dicyanobutenes yields were as high as 95% (58). The by-product NaCl could be recovered for reconversion to Na and CI2 via electrolysis. Adiponitrile was produced by the hydrogenation of the dicyanobutenes over a palladium catalyst in either the vapor phase or the Hquid phase (59,60). The yield in either case was 95% or better. This process is no longer practiced by DuPont in favor of the more economically attractive process described below. 

Chlorine, a member of the halogen family, is a greenish yellow gas having a pungent odor at ambient temperatures and pressures and a density 2.5 times that of air. In Hquid form it is clear amber SoHd chlorine forms pale yellow crystals. The principal properties of chlorine are presented in Table 15 additional details are available (77—79). The temperature dependence of the density of gaseous (Fig. 31) and Hquid (Fig. 32) chlorine, and vapor pressure (Fig. 33) are illustrated. Enthalpy pressure data can be found in ref. 78. The vapor pressure P can be calculated in the temperature (T) range of 172—417 K from the Martin-Shin-Kapoor equation (80) ... 

The iodides of the alkaU metals and those of the heavier alkaline earths are resistant to oxygen on heating, but most others can be roasted to oxide in air and oxygen. The vapors of the most volatile iodides, such as those of aluminum and titanium(II) actually bum in air. The iodides resemble the sulfides in this respect, with the important difference that the iodine is volatilized, not as an oxide, but as the free element, which can be recovered as such. Chlorine and bromine readily displace iodine from the iodides, converting them to the corresponding chlorides and bromides. 

Anhydrous aluminum chloride, AIQ, is manufactured primarily by reaction of chlorine [7782-50-5] vapor with molten aluminum and used mainly as a catalyst in organic chemistry ie, in Friedel-Crafts reactions (qv) and in proprietary steps in the production of titanium dioxine [13463-67-7] Ti02, pigment. Its manufacture by carbochlorination of alumina or clay is less energy-intensive and is the preferred route for a few producers (19). 

Chlorine in the presence of hydrogen chloride in an anhydrous organic solvent yields 2,4,6-trichloroariiline [634-93-5] (36,37). A mixture of aniline vapor and chlorine, diluted with an inert gas, over activated carbon at 400°C yields o-chloroaruline [95-51-2] (38). Aniline when treated with chlorine gas, in an aqueous mixture of sulfuric acid and acetic acid, at 105—115°C gives an 85—95% yield of -chlorarul [118-75-2] (39). 

At equihbrium the vapors are predominantly hydrogen and sihcon tetrachlorides. However, these can be easily removed from the trichlorosilane and recycled. A once-common commercial manufacturing procedure for sihcon tetrachloride was the reaction of chlorine gas with sihcon carbide. 

Titanium tetrachloride is completely miscible with chlorine. The dissolution obeys Henry s law, ie, the mole fraction of chlorine ia a solutioa of titanium tetrachloride is proportional to the chlorine partial pressure ia the vapor phase. The heat of solutioa is 16.7 kJ/mol (3.99 kcal/mol). The appareat maximum solubiUties of chlorine at 15.45 kPa (116 mm Hg) total pressure foUow. 

Thermal Decomposition of GIO2. Chloiine dioxide decomposition in the gas phase is chaiacteiized by a slow induction period followed by a rapid autocatalytic phase that may be explosive if the initial concentration is above a partial pressure of 10.1 kPa (76 mm Hg) (27). Mechanistic investigations indicate that the intermediates formed include the unstable chlorine oxide, CI2O2. The presence of water vapor tends to extend the duration of the induction period, presumably by reaction with this intermediate. When water vapor concentration and temperature are both high, the decomposition of chlorine dioxide can proceed smoothly rather than explosively. Apparently under these conditions, all decomposition takes place in the induction period, and water vapor inhibits the autocatalytic phase altogether. The products of chlorine dioxide decomposition in the gas phase include chlorine, oxygen, HCl, HCIO, and HCIO. The ratios of products formed during decomposition depend on the concentration of water vapor and temperature (27). 

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