Industrial mercury cell process

Historically, the Japanese chlor-alkali industry started in 1881, when the LeBlanc process was used to produce caustic soda. Osaka Soda and Hodogaya Chemical commercialized the mercury- and diaphragm-cell technologies in 1915. Asahi Glass started the Solvay process soon after. By 1973, 95% of the chlorine was produced by the mercury-cell process and 5% by diaphragm cells. In 1973, mercury pollution issues... 

In 1800, Cruickshank was the first to prepare chlorine electrochemically [38] however, the process was of little significance until the development of a suitable generator by Siemens and of synthetic graphite for anodes by Acheson and Castner in 1892. These two developments made possible the electrolytic production of chlorine, the chlor-alkali process, on an industrial scale. About the same time, both the diaphragm cell process (1885) and the mercury cell process (1892) were introduced. The membrane cell process was developed much mpre recently (1970). Currently, more than 95 % of world chlorine production is obtained by the chlor-alkali process. Since 1970 graphite anodes have been superseded by activated titanium anodes in the diaphragm and mercury cell processes. The newer membrane cell process uses only activated titanium anodes. 

For over a hundred years the chlor-alkali industry has used the mercury cell as one of the three main technologies for the production of chlorine and caustic soda. For historical reasons, this process came to dominate the European industry - while in the United States the asbestos diaphragm cell took the premier position. Over the last two decades developments in membrane cells have brought these to the forefront, and membrane cells of one kind or another now represent the technology of choice worldwide. 

This chapter gives an overview of the chlor-alkali industry in Australia and examines the background to the decision to replace the mercury cell plants. It then describes the new plants, their technical and safety features and the process used to arrive at the selection of the technology supplier. 

An industrial grade, skid-mounted unit (see Fig. 11.2) has been operating successfully at Occidental Chemical s Delaware City mercury cell plant since September 1997. Operating results have met both the expectations of the client and Kvaerner. This chapter discusses the operating experience at OxyChem and the resulting optimised commercial product, the Kvaerner Chemetics Sulphate Removal System or SRS . The acceptance in the market-place has been excellent four systems have been ordered and three are in the process of manufacture, with operations commencing later in 2000. Approximately 50 firm price proposals have been issued in the past two years. Several of these evaluations are in the final stages and will lead to the sale of units in the near future. 

In order to understand how anti-corrosive rubber linings are used in the caustic soda industry it is useful to have a broad understanding of the design, construction and operation of the process, mainly about the cell house where corrosion is severe. A brief description of design, construction and operation of mercury cells in the caustic soda industry is given next [11]. 

Mercury compounds continue to have numerous commercial uses. Besides its use as a preservative, mercury is used in the manufacture of many technical and medical instruments including blood pressure measurement devices, manometers, thermometers, and barometers. Mercury is also used in production of certain types of fluorescent lamps and in the chloralkali industry, where chlorine and caustic soda are produced using brine electrolysis in mercury cells. Metallic mercury is used in the production of precious metals such as gold and silver. As part of the production process, metallic mercury can be used to concentrate gold from... 

In 2000, 45 Mt of CI2 was manufactured by the chloralkali process this represents 95% of the global supply. The main producers are the US, Western Europe and Japan. Whereas the Japanese chloralkali industry operates almost entirely with the membrane cell, the US favours use of the diaphragm cell, and just over half of the Western European industry retains use of the mercury cell. On environmental grounds, the chloralkali industry is being pressured to replace mercury and diaphragm cells by the membrane cell. This is not the only environmental concern facing the industry demand for CI2 has fallen in the pulp and paper industry and in the production of chlorofluorocarbons, the latter being phased out as a result of the Montreal Protocol for the Protection... 

Chlorine gas, CI2, is prepared industrially by the electrolysis of molten NaCl (see Section 19.8) or by the chlor-alkedi process, the electrolysis of a concentrated aqueous NaCl solution (called brine). Chlor denotes chlorine and alkali denotes an alkali metal, such as sodium.) Two of the common cells used in the chlor-alkali process are the mercury cell and the diaphragm cell. In both cells the overall reaction is... 

Hildebrand based his double-cup mercury cathode on the Castner-Kellner process for the industrial production of caustic soda. This process, which has been called the most elegant electrolytic process ever invented," was patented in 1894 by Hamilton Castner, an American analytical chemist. By 1902, Castner had increased its efficiency to 90 percent. The heart of the process was Castner s "rocking" mercury cell. The cell had two chambers through which mercury moved back and forth, continuously removed metallic sodium from the decomposing chamber, thus preventing the recombination of the sodium and chlorine. (24)... 

Three processes, which use different ways for the separation of anolyte and catholyte, are applied in chemical industry (see sections Diaphragm Process Amalgam (Mercury) Process and essay Chlorine and Caustic Technology, Membrane Cell Process ). 

The textile industry uses NaOH in the manufacture of viscose and of cellophane. It was this application which promoted the development of the mercury cell because this process produces the chloride-free rayon quality caustic soda. Cotton and wool can be improved by mercerization, a treatment with NaOH. 

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