Reducing Global Warming by Process Integration

Abstract

In an attempt to contribute to the reduction of global warming, the integration of both reaction and separation in a single unit to bring about an improvement in the energy efficiency of the overall process is studied in this chapter. The esterification reaction between acetic acid and ethanol for the production of ethyl acetate (desired product) and water (by-product) is used as the case study. In order to demonstrate the role of the integrated process in global warming reduction, both the conventional system and the integrated one are studied. The conventional system is made up of a reactor (in which the chemical reaction takes place) and a distillation column (in which the desired product is purified) whereas the integrated system consists of a single unit having a single main column divided into three sections (rectification section, reaction section, and stripping section). Comparing the two systems, the results that are obtained from the studies reveal that, for the integrated system, the heat released to the atmosphere from the condenser (that is, the condenser duty) and the one supplied to the reboiler (the reboiler duty) are less than those of the conventional system. These results have actually shown the importance of process integration in reducing global warming and increasing process efficiency. It is therefore suggested to the industrial engineers to always integrate their processes, where possible, in order to contribute their quotas in reducing global warming.

Appendix A

1.1 Calculation of Average Molecular Weight

The average molecular weight of the components is calculated using Eq. (39.A1) shown below:

$$ m{w_{av }}=\sum\limits_{i=1}^m {\left( {{x_i}m{w_i}} \right)} $$

(39.A1)

1.2 Calculation of Average Density

The average density of the components is calculated with the expression shown in Eq. (39.A2) below:

$$ {\rho_{av }}=\sum\limits_{i=1}^m {\left( {\frac{{{x_i}m{w_i}{\rho_i}}}{{m{w_{av }}}}} \right)} $$

(39.A2)

1.3 Calculation of Molar Flow Rate

The molar flow rate of the mixture is calculated using Eq. (39.A3) shown below:

$$ {M}^{\prime}=\frac{{V{\rho_{av }}}}{{m{w_{av }}}} $$

(39.A3)

1.4 Calculation of Heat Transfer Rate

The heat capacity contained in the heat transfer rate equation (Eq. 39.A5) is estimated with the expression given in Eq. (39.A4) while the heat flow rate itself is obtained using Eq. (39.A5):

$$ {C_p}=a+bT+c{T^2}+d{T^3}+e{T^4} $$

(39.A4)

$$ Q={M}^{\prime}\int\nolimits_{{{T_{initial}}}}^{{{T_{final }}}} {{C_p}dT} $$

(39.A5)

The coefficients used for calculating the specific heat capacities are as shown in Table 39.A1 below.

Table 39.A1 Specific heat capacity coefficients of the components [23]