Industrial processes Downs process

K.18 The industrial production of sodium metal and chlorine gas makes use of the Downs process, in which molten sodium chloride is electrolyzed (Chapter 12). Write a balanced equation for the production of the two elements from molten sodium chloride. Which element is produced by oxidation and which by reduction ... 

We have already described the refining of copper and the electrolytic extraction of aluminum, magnesium, and fluorine. Another important industrial application of electrolysis is the production of sodium metal by the Downs process, the electrolysis of molten rock salt (Fig. 12.15) ... 

It is clear from this discussion that the dose requirement and unit cost will be lower if the material has a higher molar mass M and the reaction has a high G value. Thus, the best candidates will be a polymeric material and a chain reaction. Quite often, a free-radical irradiation is used. The radiation source of choice is usually a 60Co - y facility, although electron beam irradiation is also used. Since most radiation-chemical reactions used in industry can also be brought about by other conventional means such as thermal, or photochemical processes, the processing cost must be below 10irradiation cost one has to include the cost of operation, maintenance, and the like. (Danno, 1960). 

Although proteins can be expressed in many heterologous production systems, including bacteria such as Proteus mirabilis [1], fungi such as Pichia pastoris [2, 3] and Aspergillus awamori [4] and insect cells [5, 6], the pharmaceutical industry has narrowed down process development to a small number of platform technologies ... 

Industrially, the silver is recovered from either the wash water, or the bleach fix separately or from a mixture of the two using electrolysis employing a stainless steel cathode cylinder and an anode of stainless steel mesh. A typical wash solution composition contains silver (4 g L ), sodium thiosulphate (220 g L ), sodium bisulphite (22 g L ) and sodium ferric EDTA (4 g L ). At Coventry we have used a scaled down version of the industrial process employing 250 mL samples [46]. Electrolysis experiments were performed at ambient temperature with both wash and bleach fix solutions and in which the potential applied to the cathode and the speed of rotation of the cathode were varied. The sonic energy (30 W) was supplied by a 38 kHz bath. The results are given in Tab. 6.9. The table shows that the recovery of silver on sonication of the wash or bleach fix solutions is much improved especially if the electrode is rotated while ultrasound is applied. Yields with bleach fix (which contains ferric ions) are less since Fe and Ag compete for discharge (Eqs. 6.13 and 6.14). 

This process has evolved considerably from the start of the Iron Age, when our amateur engineer ancestors developed batch processes, through the continuous processes that fueled the Industrial Revolution, down to the twentieth century, where specialty steels are the desired products. As might be expected, these processes evolved primarily by trial-and-error methods, because no detailed analysis of reactor flows and reactions are productive or even possible. 

In order that chemists might have an opportunity to study the new substance, Courtois generously presented some of it to the pharmaceutical firm of Vallee and Baget (13). He was unable to prepare it fast enough to supply the demand, however and could sell only small amounts of it, at a price of 600 francs per kilogram. In 1824 M. Tissier the elder perfected an industrial process which in a few months brought the price of iodine down to 200 francs per kilogram. 

These filters are useful for retrofitting to existing cooling water systems that may be required to operate with a deteriorating water quality, and they usually present minimal installation problems. For most applications, however, they are installed in-line, and this can present installation problems in larger industrial process cooling systems that cannot be shut down. 

Foams, or more generally the formation of bubbles, can also be a nuisance. For example, the mixing of two liquids in an industrial process can be significantly slowed down by the development of foam. In the glass industry, the release of gas from the melt can lead to the formation of bubbles in the final glass. 

Feed/effluent heat exchangers are used in many industrial processes to warm up the fluid before the reactor and to cool it down after treatment at high temperature. The conventional design of such heat exchangers is based on shell-and-tube units. But to increase the thermal effectiveness of the heat exchangers, the required heat length becomes very important, and high pressure drop will occur. 

There are few examples of industrial processes with pure gas-phase reactions. The most common and oldest example is combustion. Although termed homogeneous, most gas-phase reactions take place in contact with solids, either the vessel wall or particles as heat carriers. With inert solids, the only complication is with heat transfer. Several of these reactions are listed in Table 19-1. Whenever possible, liquefaction of gas-phase systems is considered to take advantage of the higher rates of liquid reactions, to utilize liquid homogeneous catalysts, or to keep equipment size down. 

The publication of an actual industrial plant-wide control problem, the Tennessee Eastman challenge process (Downs and Vogel 1993) generated several... 

Downs, J. J. and Vogel, E. F. (1993). A plant-wide industrial process control problem. Comput. Chem. Eng., 17, 245-255. 

The CVI method can also be used to repair ceramic membranes in situ in industrial processes. In this case the defects formed in the membranes in the reactor or separation unit are repaired by controlled CVI during a shut-down. This has the advantage that the membranes in the unit need not to be replaced, which in most cases would mean the replacement of the complete unit. A second advantage is that repairing the membranes is probably less time-consuming than complete replacement. 

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