Use of Elemental Chlorine

In 1990 about 10% of the world s chlorine production (ca. 3.4 million tonnes) was used for pulp and paper [329]. As a consequence of the change-over to chlorine free bleaching processes, the use of elemental chlorine was drastically reduced to 2.95 million tonnes in 1994, and is anticipated to be 1.9 million tonnes in 2000) [319]. In 1983 in the United States 13 % of the chlorine production was used for pulp and paper, 1994 9%, 2000 6%, 2010 0% (estimated). In areas like Canada or Western Europe, the reduction was even more drastic 1998, in Western Europe 18 000 tonnes of chlorine went into this production, accounting for only 0.2 % of the production [330],... 

Its use as water disinfectant is discribed in chapter 14.1 (Use of elemental chlorine). 

The production and use of certain industrial chemicals such as carbon tetrachloride, CFCs, chlorinated biphenyls and the use of elemental chlorine in the pulp and paper industry has been severely curtailed. 

Thus, for the initial chlorination of the ore, ferric chloride can very well be used instead of elemental chlorine. From ferric chloride vapor chlorine can be regenerated by the reaction... 

ECF [Elemental chlorine free] A generic term for pulp-bleaching processes which use chlorine dioxide and other oxidants in place of elemental chlorine. See also TCF. 

In practice, only about 10% of the elements on the periodic chart are adaptable to chemical rocket propellants. Propellants have made little use of elements other than hydrogen, carbon, nitrogen, oxygen, chlorine, fluorine, aluminum, boron, and beryllium. 

The halogenation of a wide variety of aromatic compounds proceeds readily in the presence of ferric chloride, aluminum chloride, and related Friedel-Crafts catalysts. Halogenating agents generally used are elemental chlorine, bromine, or iodine and interhalogen compounds (such as iodine monochloride, bromine monochloride, etc.). These reactions were reviewed554 and are outside the scope of the present discussion. 

The most useful compounds of this type are (dichloroiodo)arenes. The method of choice for their preparation remains the old, direct combination of elemental chlorine with the corresponding iodide, as originally applied by Willgerodt. The usual procedure for iodoarenes is to dissolve them in a suitable solvent (preferably chloroform or dichloromethane) and pass chlorine at 0°C (Scheme 2) [5]. 

On the basis of reactions (1), (6), and (7) we can see that chlorate can be produced in an undivided cell in a consecutive process consisting of an electrochemical, a chemical, and another electrochemical process, needing nine electrons to generate a chlorate anion. But there is a better pathway, using the hydrolysis of elemental chlorine in water, depending on the pH-value... 

Instead of elemental chlorine, sulfuryl chloride or carbon tetrachloride can also be used as chlorinating agent (Steinberg, 1950 Fiszer and Michalski, 1952 Schrader, 1964). 

Problem Nuclear engineers use chlorine trifluoride in the processing of uranium fuel for power plants. This extremely reactive substance is formed as a gas in special metal containers by the reaction of elemental chlorine and fluorine. 

Chlorine fluoride is a versatile and very useful reagent. Preparation from the elements is well established, but since the reaction involves the use of elemental fluorine and either Monel or nickel reactors, it is a procedure not readily accessible to many laboratories. In addition, the reaction is exothermic. Two procedures that are excellent lower temperature routes to chlorine fluoride are described below. 

A number of elements are naturally toxic. These include arsenic mercury heavy metals, such as lead and cadmium and the halogens fluorine, chlorine, bromine and iodine. Fluorine and chlorine are covered in Chapter 4 in the Poison Gas section. It is important to note the uses of elements, because they give an indication where these materials may be found in storage and manufacturing. 

Most organic compounds are oxidized with the dichromate reflux method under standard procedure, but ammonia and organic nitrogen are not oxidized by dichromate in the absence of significant concentration of elemental chlorine. Flence, the dichromate reflux method is preferred over procedures using other oxidants because of its superior oxidation ability. There are, however, several potential sources of limitation in the test including the following ... 

The other options include enhanced recovery of elemental chlorine and its conversion to another product. We might include, under enhanced recovery, the addition of higher-severity stages to a liquefaction plant. While this is more correctly a reduction in the amount of chlorine present in the tail gas rather than its recovery, it is a viable retrofit technique and one that has been used to replace some of the older recovery plants. A unit quantity of refrigeration becomes more expensive, hydrate accumulation may be more troublesome, and some of the problems of deep liquefaction are exacerbated. TTiese are the normal effects of extending the process, and they add nothing new to the technical discussion on liquefaction. 

Production of HCl uses chlorine that otherwise could be recovered (at a cost) and so detracts from its net production. Where there is a reliable outlet for caustic, however, the best approach may be to increase electrolytic capacity, use HCl liberally in its in-plant applications, and reduce somewhat the severity of liquefaction. This improves the quality of the cell gas and allows more chlorine to appear in the tail gas, which is the raw material for HCl production. Both these changes reduce energy consumption in the liquefaction process. The gross production of elemental chlorine is preserved, all the benefits of acidification are obtained, and more caustic is available for use or sale. 

Safety. Because of the presence of active chlorine and the possibility of evolution of elemental chlorine, hypochlorite solutions are highly corrosive and toxic. No one should be allowed to handle these substances without thorough training. Plant systems should be carefully designed, using the proper materials of construction (Section 15.3.2.3), and in particular should rigidly exclude the possibility of accidental contact with excess acid. 

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