OPTIMIZATION OF PRESSURE-SWING DISTILLATION FOR ANHYDROUS ETHANOL PURIFICATION BY THE SIMULATED ANNEALING ALGORITHM

Battisti, Rodrigo; Claumann, Carlos A.; Marangoni, Cintia; Machado, Ricardo A. F.

doi:10.1590/0104-6632.20190361s20180133

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Process Systems Engineering • Braz. J. Chem. Eng. 36 (1) • Jan-Mar 2019 • https://doi.org/10.1590/0104-6632.20190361s20180133 copy

OPTIMIZATION OF PRESSURE-SWING DISTILLATION FOR ANHYDROUS ETHANOL PURIFICATION BY THE SIMULATED ANNEALING ALGORITHM

Authorship SCIMAGO INSTITUTIONS RANKINGS

ABSTRACT

The present study addresses the novel application of the simulated annealing algorithm (SAA) to optimize the pressure-swing distillation (PSD) process for anhydrous ethanol purification. Three different softwares (Aspen Plus^®, Excel^® and Matlab^®) were integrated to simultaneously optimize seven design and operational variables. The configuration with the best TAC represented a 40.2% saving per year in comparison to the non-optimized PSD. Such reduction was achieved by using the higher acceptance probability and the slower temperature decrement. This saving is mainly related to operational cost reductions, a fact that evidences the viability of using the herein described optimization methodology to improve the PSD design.

Key words:
Optimization; Simulated annealing; Pressure-swing distillation; Anhydrous ethanol

P	β	α	T₀	T_f	Number of evaluations	CPU Time ^a
0.1	0.455	0.95	250,000	0.000001	510	0.32 h
0.25	0.910		500,000	0.000001	526	0.39 h
0.4	2.466		1,500,000	0.000001	547	0.43 h
0.1	0.455	0.97	250,000	0.000001	862	0.59 h
0.25	0.910		500,000	0.000001	887	0.68 h
0.4	2.466		1,500,000	0.000001	921	0.75 h
0.1	0.455	0.99	250,000	0.000001	2,612	1.58 h
0.25	0.910		500,000	0.000001	2,681	1.65 h
0.4	2.466		1,500,000	0.000001	2,785	1.83 h

α = 0.95
	P	0.1		0.25		0.4
	P	TAC ($/year)	Dev.^a	TAC ($/year)	Dev.^a	TAC ($/year)	Dev.^a
Runs	1	1,930,883.6	10.81 ‰	1,943,879.3	17.61 ‰	1,962,323.2	27.27 ‰
	2	1,927,177.6	8.87 ‰	1,932,546.2	11.68 ‰	2,070,604.1	83.95 ‰
	3	2,000,916.0	47.47 ‰	1,969,079.6	30.80 ‰	1,942,502.1	16.89 ‰
	4	2,310,267.4	209.41 ‰	2,038,502.9	67.15 ‰	1,984,675.6	38.97 ‰
	5	2,032,283.8	63.89 ‰	2,021,824.4	58.41 ‰	1,942,483.6	16.88 ‰
α = 0.97
	P	0.1		0.25		0.4
	P	TAC ($/year)	Dev.^a	TAC ($/year)	Dev.^a	TAC ($/year)	Dev.^a
Runs	1	1,911,134.8	0.47 ‰	1,925,995.1	8.25 ‰	1,916,192.9	3.12 ‰
	2	1,928,823.9	9.73 ‰	1,920,250.9	5.24 ‰	1,917,135.6	3.61 ‰
	3	2,075,619.3	86.58 ‰	1,920,222.3	5.23 ‰	1,916,193.6	3.12 ‰
	4	1,915,251.7	2.62 ‰	1,937,206.5	14.12 ‰	1,916,192.6	3.12 ‰
	5	1,915,916.7	2.97 ‰	1,920,222.1	5.23 ‰	1,923,380.9	6.88 ‰
α = 0.99
	P	0.1		0.25		0.4
	P	TAC ($/year)	Dev.^a	TAC ($/year)	Dev.^a	TAC ($/year)	Dev.^a
Runs	1	1,913,690.4	1.81 ‰	1,913,352.8	1.63 ‰	1,910,242.6	0.00 ‰
	2	1,914,901.6	2.44 ‰	1,914,641.4	2.31 ‰	1,910,238.3	0.00 ‰
	3	1,914,108.7	2.03 ‰	1,913,351.0	1.63 ‰	1,910,253.7	0.01 ‰
	4	1,924,727.2	7.58 ‰	1,913,362.2	1.64 ‰	1,910,239.9	0.00 ‰
	5	1,914,667.4	2.32 ‰	1,913,395.9	1.65 ‰	1,910,245.4	0.00 ‰

Items	Non-optimized PSD ^a	Optimized PSD
Low pressure column (LPC)
Feed flow rate (kmol/h)	100	100
Feed composition (ethanol/water)	0.2 / 0.8	0.2 / 0.8
Recycle feed rate (kmol/h)	78.57	78.53
Top composition (ethanol/water)	0.861 / 0.139	0.851 / 0.149
Bottom composition (ethanol/water)	0.005 / 0.995	0.005 / 0.995
Bottoms rate (kmol/h)	80.36	80.32
Distillate rate (kmol/h)	98.21	98.21
Total number of trays (NT1) ^b	28	37
Reflux ratio (RR1)	4.725	2.126
Fresh feed stage (N_F1)	23	23
Recycle feed stage (NR)	13	13
Stage pressure drop (kPa)	0.3	0.3
Condenser duty (kW)	3750.0	3456.1
Reboiler duty (kW)	3320.0	2785.2
High pressure column (HPC)
Feed flow rate (kmol/h)	98.21	98.21
Feed composition (ethanol/water)	0.861 / 0.139	0.851 / 0.149
Top composition (ethanol/water)	0.827 / 0.173	0.815 / 0.185
Bottom composition (ethanol/water)	0.997 / 0.003	0.996 / 0.004
Bottoms rate (kmol/h)	19.64	19.68
Distillate rate (kmol/h)	79.57	78.53
Total number of trays (NT2) ^b	28	40
Reflux ratio (RR₂)	0.435	1.669
Feed stage (N_F2)	14	13
Stage pressure drop (kPa)	0.3	0.3
Condenser duty (kW)	3340.0	1949.6
Reboiler duty (kW)	3010.0	2236.0
Total operating cost ($/year)	2,536,443.7 d	1,406,112.6
Total capital cost ($)	1,983,544.9 d	1,512,377.2
TAC ^c ($/year)	3,197,625.3 d	1,910,238.3

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[1] Corresponding author: Rodrigo Battisti - E-mail: rodrigo.battisti@ifsc.edu.br