Table 5.

Summary of the sensitivity and optimization results.

setting the molar flow of acetic acid in feed in the range of 0.01–0.08 L/min. In the third case, we have calculated distillate flow rate by varying feed flow rate in the range of 0.01–0.08 L/min to calculate the distillate-to-feed ratio (D/F). Similarly we have also calculated bottom-to-feed ratio (B/F). The result curves are shown in Figures 9 and 10, respectively. A shown in Figure 9, we can observe that the flow rate of methyl acetate is increasing as heat duty is increasing and found the maximum flow rate to be 0.927 lbmol/hr. at heat duty of 6820 Btu/hr. Similarly, we can observe that in Figure 10, the variation in flow rate of acetic acid is observed WRT mole fraction of product methyl acetate. The maximum product fraction is observed as 95.2% at flow rate of 0.0872 cuft/hr. The effect of change in distillate-to-feed Ratio (D/F) and change in bottom-to-feed (B/F) ratio on composition was also observed. It was found that optimized distillate-to-feed (D/F) ratio obtained 0.6275 and optimized bottom-to-feed (B/F) ratio obtained 0.4238 to get maximum product purity.

Figure 8.

Figure 9.

104

Temperature profile of methyl acetate RDC.

Distillation - Modelling, Simulation and Optimization

Sensitivity analysis based on reboiler heat duty.

10. Conclusion

Nomenclature

experimental and simulation studies.

vj stoichiometric coefficient Rn,j reaction rate on nth stage Mn liquid holdup on nth stage

λ heat of reaction

RR reflux ratio

P total pressure

PS

107

ΔHv net heat of vaporization NT total number of stages D distillate flow rate B bottoms flow rate

yn,j vapor composition on nth stage

<sup>j</sup> pure component vapor pressure

Fn feed flow rate on nth stage zn,j feed composition on nth stage

Tn temperature at nth stage

kFn forward reaction rate on nth stage kBn backward reaction rate on nth stage xn,j liquid composition on nth stage Vn flow rate of vapor on nth stage Ln flow rate of liquid on nth stage

This chapter gives details of reactive distillation as effective unit for various synthesis and manufacturing. The detailed case study envisaged to produce methyl acetate using methanol and acetic acid in a pilot plant reactive distillation column. The operating conditions were maintained as feed temperature of 50°C, column pressure of 1 atmosphere, feed rate of 0.03 L/min, and initial reboiler temperature of 70°C. The experiment yielded high purity of methyl acetate. We have succeeded in obtaining 95% purity of methyl acetate. The experimentation was then followed by simulations so as to contrast the results. The Aspen Plus simulation gives methyl acetate purity of 91.1%. This was followed by validation of results using sensitivity and optimization analysis. The optimized value of reflux was obtained as 4.69 and required reboiler duty 2 kW. The sensitivity analysis registered distillation-to-feed (D/F) ratio as 0.6275 and bottom-to-feed (B/F) ratio 0.4235 to obtain maximum product purity. These encouraging results establish a good agreement between

Reactive Distillation: Modeling, Simulation, and Optimization

DOI: http://dx.doi.org/10.5772/intechopen.85433

Figure 11. Sensitivity curve for optimized flow rate and composition.

Figure 12. Sensitivity curve for column temperature based on reflux ratio.

as lower and upper limits, respectively. After the optimization, we obtained 26.99% as the minimum composition of methyl acetate and 2 kW as the required optimized heat duty.

The summary of optimization and sensitivity results obtained from Aspen Plus simulation is included in Table 5. The optimized value of reboiler heat duty obtained was 2 kW, and optimized reflux ratio obtained was 4.69. These values are close to the experimental values which again show good agreement between experimental and simulation studies. The optimized flow rate of methyl acetate obtained using reboiler heat duty as manipulated variable is 0.093 lbmol/hr., and optimized product fraction obtained using standard volumetric flow rate of acetic acid is 0.96. The sensitivity result curve for optimized flow rate and composition of methyl acetate is shown in Figure 11, and sensitivity result curve for variation in column temperature based on reflux flow is shown in Figure 12.
