Process Downs

Energy Requirements. The energy requirements of several sodium manufacturiag processes are compared ia Table 7 (76). The data contain some ambiguities because of the allocation of energy to the coproduction of chlorine. An iadependent calculation shows a somewhat lower energy consumption for the Downs process (92). 

Because of the melt-elasticity effects of the material, it does not draw down in a simple proportional manner thus, the draw-down process is a source of errors in the profile. Errors are significantly reduced in a balanced situation such as circular extrudate. These errors must be corrected by modifying the die and takeoff equipment. 

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) ... 

FIGURE 12.15 In the Downs process, molten sodium chloride is electrolyzed with a graphite anode (at which the Cl ions are oxidized to chlorine) and a steel cathode (at which the Na4 ions are reduced to sodium). The sodium and chlorine are kept apart by the hoods surrounding the electrodes. Calcium chloride is present to lower the melting point of sodium chloride to an economical temperature. 

The alkali metals are the most violently reactive of all the metals. They are too easily oxidized to be found in the free state in nature and cannot be extracted from their compounds by ordinary chemical reducing agents. The pure metals are obtained by electrolysis of their molten salts, as in the electrolytic Downs process (Section 12.13) or, in the case of potassium, by exposing molten potassium chloride to sodium vapor ... 

Sodium metal is produced from the electrolysis of molten sodium chloride in the Downs process (Section 12.13). Determine (a) the standard Gibbs free energy of the reaction... 

Figure 1.3 Today s bottom-up (equipment dominance) and sketch of future top-down (process dominance) approaches in process development.

OS 12] [reactor given in [84]] [P 11] In [84], the scale-down from a 250 ml batch reactor to a 10 ml batch reactor is described. The validity of applying a pseudo-second-order kinetic model for the scaled-down processing was confirmed (Figure 4.41). 

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 ... 

If you want to scale up or scale down process equipment using one of the parameters in Table B.2, a typical rule of thumb is the following relation... 

To study this buy-down process for hydrogen and fuel-cell vehicles, the Simplified Transition Model (STM) was used to aggregate costs over the entire fleet, based on the fuel-cell vehicle and hydrogen infrastructure costs previously described ... 

Since the cross section for nonrelativistic Coulomb scattering is the same in classical and quantum mechanics, equation (2) must contain much of the essential physics in the slowing-down process. However, it also contains an undetermined minimum energy transfer rmin which is nominally zero and hence leads to an infinite stopping force. 

At the beginning of a pump down process, the gas ballast pump should always be operated with the gas ballast valve open. In almost all cases a thin layer of water will be present on the wall of a vessel, which only evaporates gradually. In order to attain low ultimate pressures the gas ballast valve should only be closed after the vapor has been pumped out. LEYBOLD pumps generally offer a water vapor tolerance of between 33 and 66 mbar. Two-stage pumps may offer other levels of water vapor tolerance corresponding to the compression ratio between their stages -provided they have pumping chamber of different sizes. 

For purification, scale-up considerations are important even in the earliest phases of development. It is important to avoid the use of purification techniques of limited scale-up potential even for early clinical production because thorough justification of process changes and demonstration of biochemical comparability are necessary prior to product licensure. For successful scale-up, it is important to understand the critical parameters affecting the performance of each purification step at each scale. Conversely, it is important to verify that the scaled-down process is an accurate representation of the scaled-up process, so that process validation studies, such as viral clearance and column lifetime studies, can be performed at the laboratory scale. 

Complexity of the regulatory process and its requirements (which can slow down process changes)... 

Development projects should change from top-down processes towards bottom-up processes (see Extension method is top down). 

Sodium chloride is plentiful as rock salt, but the solid does not conduct electricity, because the ions are locked into place. Sodium chloride must be molten for electrolysis to occur. The electrodes in the cell are made of inert materials like carbon, and the cell is designed to keep the sodium and chlorine produced by the electrolysis out of contact with each other and away from air. In a modification of the Downs process, the electrolyte is an aqueous solution of sodium chloride. The products of this chloralkali process are chlorine and aqueous sodium hydroxide. 

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