Energy requirements for production

Interest in catalyzed reduction reactions remains high. The general aim is to develop catalysts for selective reductions under mild conditions. Greater product selectivity has an important impact on energy and resource utilization in terms of reduced process energy requirements for product separation and purification, and in terms of low-value by-products. 

Apart from pure starch polymers (as discussed so far), starch polymers containing petrochemical copolymers are also commercially available. The more of these copolymers is added, the higher the overall energy requirements are (Table 3). Nevertheless, the values are still clearly lower than those for polyethylene (PE), which belongs to the petrochemical polymers with the lowest energy requirements for production. 

Faraday s law states that 96,487 coulombs (1 C = 1 A-s) are required to produce one gram equivalent weight of the electrochemical reaction product. This relationship determines the minimum energy requirement for chlorine and caustic production in terms of kiloampere hours per ton of CI2 or NaOH... 

Recombination reactions are highly exothermic and are inefficient at low pressures because the molecule, as initially formed, contains all of the vibrational energy required for redissociation. Addition of an inert gas increases chemiluminescence by removing excess vibrational energy by coUision (192,193). Thus in the nitrogen afterglow chemiluminescence efficiency increases proportionally with nitrogen pressure at low pressures up to about 33 Pa (0.25 torr) (194). However, inert gas also quenches the excited product and above about 66 Pa (0.5 torr) the two effects offset each other, so that chemiluminescence intensity becomes independent of pressure (192,195). 

Another concentration method involves passing an inert gas such as N2 or CO2 through the reaction medium (12). As the gas passes through, it becomes humidified and carries captured water with it. Most of the energy required for the gas humidification comes from the heat of reaction. An advantage is that expensive drying equipment is not needed. Also, the sulfuric acid mist formed in typical concentrators is minimized. Du Pont uses a similar process in its nitrobenzene production faciUty. 

Table 6. Energy Required for Ammonia Production based on Feedstock Process, GJ/t...

Coal was the primary kiln fuel in 1989 as seen in Table 10. Energy from coal rose from 39 to 84% of the total energy required for cement production between 1972 and 1989. In the same time period, natural gas dropped to 9%, petroleum products to 1% of the total energy consumed. Waste fuels represented 5% of the energy consumed in 1989 cement production. 

Scra.p Copper. The energy required for copper production from scrap is appreciably less than that needed production from ores. If the scrap is of low grade and has to be smelted and refined, the energy consumption is about 45 GJ /1 (43 x 10 Btu/t) of copper (52). Scrap that only requires melting and casting uses about 5 GJ/t (4.7 X 10 Btu/t) of copper. 

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