Hypochlorites production

Cells for the hypochlorite production do not principally require a separator, since cathodically generated hydroxide... 

Emission of Chlorine Dioxide in a Hypochlorite Production Unit in the Steady State and at Peak Load... 

In the electrolysis plant of Akzo Nobel in Rotterdam a hypochlorite production unit is in operation. This unit has two functions handling chlorine-containing waste gases from the plant and production of hypochlorite. The reaction is carried out in a two-step apparatus in which a liquid jet-loop reactor and a packed column are in series. In this way chlorine is converted to hypochlorite and emissions of chlorine to the atmosphere are avoided. 

In the first step the chlorine from the tail gas and chlorine feed reacts with the caustic in the jet-loop reactor. The advantage of the jet-loop reactor is that it also acts as a suction device for the gas stream. The residence time of the liquid in step one is dependent on the capacity of the hypochlorite production and liquid level in the tank and varies between 1 and 4 h. A heat exchanger in the loop controls the temperatures in steps one and two. The amount of caustic in the feed-tank of step two is the back-up for failure of chlorine liquefaction. 

Yang CH. Hypochlorite production on Ru-Sn binary oxide electrode and its... 

Cheng, C.Y. and Kelsall, G.H. (2007) Models of hypochlorite production in electrochemical reactors with plate and porous electrode. J. Appl. Electrochem. 37, 1203-1217. 

Kraft, A., Stadelmann, M., Blaschke, M., Kreysig, D., Sandt, B. and Schroeder, F. (1999a) Electrochemical water disinfection, part I Hypochlorite production from very dilute chloride solutions. J. Appl. Electrochem. 29, 861-868. 

Calcium hypochlorite Production and consumption of calcium hypochlorite in the most important regions in 1994 are given in Table 1.7-20. The chlorine equivalents are the quantities of chlorine which correspond to the oxidation capacity of the quantities of hypochlorite. 

HTH [Olin]. TM for a high-test calcium hypochlorite product commercially available as a stable, water-soluble material in both granular and tablet form, containing a minimum of 70% available chlorine as calcium hypochlorite. 

Caution. Extreme care should be exercised in handling chlorine monofluoride, carbonyl fluoride, and the hypochlorite products because of their very high reactivities and hazardous properties. Safety shielding and leather gloves... 

Kraft A, Blaschke M, Kreysig D, Sandt B, Schroder F, Rennau J. (1999b). Electrochemical water disinfection. Part II Hypochlorite production from potable water, chlorine consumption and the problem of calcareous deposits. Journal of Applied Electrochemistry 29 895-902. 

Most hypochlorite production is in the form of the sodium compound, which will be the focus of our discussion. There will also be a short note on calcium hypochlorite (Section 15.3.4). Figure 15.14 shows a typical flowsheet for production of NaOCl solution [55]. We note here that the compound is more properly designated NaQO. Industry practice, however, favors the form NaOCl. 

TABLE 16.6. Example of Hazop Output— Hypochlorite Production... 

In a mercury cell, the brine is removed before sodium hydroxide is formed, thus the resulting solution typically contains <50 mg kg of sodium chloride and even lower concentrations of other salts. The amount of water added to the decomposer is usually adjusted to make 50% sodium hydroxide, or rarely 73% sodium hydroxide. These solutions are simply cooled and filtered without the need for evaporation. This avoids contamination by nickel and other metals, which occurs during the concentration of sodium hydroxide from diaphragm cells. Because rayon production requires low concentrations of metals and salt, mercury cell sodium hydroxide is also called rayon grade. However, mercury cell sodium hydroxide typically contains 10-50 pg kg of mercury. Some of this mercury ends up in hypochlorite products, although the concentration is reduced by dilution and processing operations such as filtration. 

Figure 24.1 shows the instantaneous disproportionation rate as a function of pH and temperature. During hypochlorite production, adequate agitation and an excess of hydroxide is usually maintained to prevent localized areas of low pH where hypochlorite rapidly disproportionates. The figure also shows how adequate cooling limits decomposition by disproportionation. 

The first reaction predominates if the product contains a large amount of water (-18%). This reaction is analogous to the disproportionation of aqueous hypochlorite. However, disproportionation is much slower in solid calcium hypochlorite than in solution. Under dry conditions, the second reaction predominates. It is catalyzed by transition metals including iron and manganese. It may occur explosively 150°C. Thus, calcium hypochlorite products usually contain some water or an additive such as magnesium sulfate heptahydrate. The third reaction is the reverse of chlorination. The fourth reaction is due to the adsorption of carbon dioxide from air or the release of carbon dioxide from carbonate salt impurities. It is accelerated by water and temperature. The first reaction accounts for -70%, and the second reaction -30%, of the decomposition of solid calcium hypochlorite made in the United States and stored in sealed containers at 25°C. ... 

New inorganic hypochlorite bleaching agents are unlikely to be developed. The relative economics and use patterns of hypochlorites for water treatment, cleaning, and disinfection are also unlikely to change. However, the use of hypochlorites as a safer alternative to transportation and storage of chlorine may increase. In the United States, this may also cause closer affiliation of hypochlorite production with chlorine sources. The competition with point-of-use electrolytic generators will also increase as these become cheaper and more prevalent. 

In-situ hypochlorite production data Comparison of ESP performance at test plant Mass balance for a caustic scrubber... 

Fig. 7.12 Cells for hypochlorite production. Four units each producing 160 kgh" at a nuclear power plant at Paluel, France. The installation provides sterilization of the seawater coolant. (Courtesy Krebs.)...

Fig. 23.3 [12] shows differences among various electrode materials for hypochlorite production in chloride solutions. Hypochlorite production is much more efficient with the use of the BDD electrode than with the use of the DSA (dimensionally stable anode) or the platinum electrode. Figure 23.4 shows anodic polarization curves for BDD and platinum electrodes in sodium chloride and sodium sulfate solutions. Concerning the platinum... 

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