Energy efficiency chemical factor

Many older processes (developed before the 1970s oil price crisis) were less energy efficient than those developed more recently. This should be apparent by consideration of the energy conservation features included in new plants, and the subsequent increase in complexity of the associated P ID. Energy conservation is discussed in Section 8.2.1. The selection of a process route for production of a chemical will depend upon the following factors/considerations ... 

E energy enhancement factor in chemisorption eq. (14.50) activation energy in chemical reactions efficiency factor of the absorption process (Section 10.3.2)... 

The efficiency to convert solar energy into chemical energy (H2) will be the main determining factor of hydrogen production costs using photocatalyst technology. As mentioned in the previous section, the thermodynamic... 

Here Xe is the coefficient of anharmonicity and B is the normalizing factor. Comparison of the parabolic-exponential Treanor distribution with the linear-exponential Boltzmann distribution is illustrated in Fig. 3-3. A population of highly vibrationally excited levels at TV > To can be many orders of magnitude higher than that predicted by the Boltzmaim distribution even at vibrational temperature. The Treanor distribntion resnlts in very high rates and energy efficiencies of chemical reactions stimulated by vibrational excitation in plasma. 

This mechanism can provide the highest energy efficiency of endothermic plasma-chemical reactions in non-equilibrium conditions because of the following four factors ... 

Mechanisms of stimulation of plasma-chemical reactions by electronic excitation were discussed in Section 2.5.5. No one of the four kinetic factors mentioned in Section 3.6.2 can be apphed in this case therefore, energy efficiency is relatively low, usually below 20-30%. Plasma-chemical processes through electronic excitation can be energy effective if they initiate chain reactiorrs. Such a situation takes place, for example, in NO synthesis, where the Zeldovich mechanism can be effectively initiated by dissociation of molecular oxygen through electronic excitation (see Section 6.1.2). 

Components of Total Energy Efficiency Excitation, Relaxation, and Chemical Factors... 

The total energy efficiency of ary non-equilibrium plasma-chemical process can be subdivided into three main components an excitation factor (jjex), a relaxation factor (jjrei), and a chemical factor ( chem) ... 

The chemical factor restricts energy efficiency mostly because the activation energy often exceeds the reaction enthalpy > A/f.Forexample,intheplasma-chemical process of NO synthesis, proceeding by the Zeldovich mechanism (see Section 6.3.5), the second reaction is significantly exothermic. This results in a relatively low value of the chemical factor ) chem 50%. 

A simplified set of chemical reactions nnmerically describing neutral chemistry of the CO2 plasma dissociation is presented in Table 5-1. Elementary chemical reactions are accompanied in the table by corresponding aetivation energies, pre-exponential factors (given in cm /s forbimolecular reactions, cm /s for three-body processes), and efficiencies a of vibrational energy in overcoming the aetivation energy barrier. 

The energy efficiency of the plasma-chemical processes is usually divided into three factors excitation factor relaxation factor ()]rei), and chemical factor ()]chem)- The most... 

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