Control of a Ternary Extractive Distillation Process with Recycle

Article pubs.acs.org/IECR

Cite This: Ind. Eng. Chem. Res. XXXX, XXX, XXX−XXX

Control of a Ternary Extractive Distillation Process with Recycle Splitting Using a Mixed Entrainer Xia Zhang,† Yongteng Zhao,† Huixin Wang,‡ Bin Qin,† Zhaoyou Zhu,† Nan Zhang,§ and Yinglong Wang*,† †

College of Chemical Engineering, Qingdao University of Science and Technology, Qingdao 266042, China National Registration Center for Chemicals, SINOPEC Research Institute of Safety Engineering, Qingdao 266071, China § Centre for Process Integration, School of Chemical Engineering & Analytical Science, The University of Manchester, P.O. Box 88, Sackville Street, Manchester M60 1QD, U.K. ‡

S Supporting Information *

ABSTRACT: Dynamic control of the ternary extractive distillation process is complex, due to the relatively high number of operating parameters and interactions between multiple azeotropes. In this research, the control structures of the ternary extractive distillation using dimethyl sulfoxide and a mixed solvent of dimethyl sulfoxide and ethylene glycol, as the entrainer, were explored for separating tetrahydrofuran/ ethanol/water. A composition with a ratio of reboiler duty to mole feed flow rate control structure was proposed to obtain good dynamic responses for the ternary extractive distillation process with dimethyl sulfoxide and mixed entrainer. Moreover, control comparisons of the ternary extractive distillation with dimethyl sulfoxide and mixed entrainer demonstrated that the dynamic performances of the extractive distillation with mixed entrainer were better compared with the process using dimethyl sulfoxide. These studies contribute to the development of controllability for ternary extractive distillation processes for separating ternary or multicomponent azeotropic mixtures. produce purity when faced with feed flow rate and feed composition disturbances. The dynamics of the extractive distillation process in binary systems has been widely and deeply investigated in recent years.24−28 Wang et al.29 investigated the dynamic control of an extractive distillation process for the separation of methylal/ methanol and concluded that an improved control scheme with specific reflux flow rate/feed flow rate (R/F) ratio can maintain the desired purity of the products when meeting disturbances. Gil et al.30 developed the control strategy that uses the flow rate of the entrainer makeup to control the feed flow rate of entrainer to the EDC, which achieved good dynamic robustness. Yang et al.31 discussed the separation of benzene and acetonitrile with DMSO (entrainer), and an improved control scheme with a fixed R/F and control structure with dual temperature were explored to obtain good dynamic responses. Luyben32 investigated the dynamic controllability of extractive distillation for separating carbon dioxide/ethane and added a composition controller to hold the ethane impurity in the distillate of the EDC by manipulating

1. INTRODUCTION The separation of azeotropic mixtures is highly important in the chemical and pharmaceutical industries. Special distillation processes, such as extractive distillation,1−6 azeotropic distillation,7−11 and pressure-swing distillation,12−16 have been widely studied for separating binary azeotropes. In the chemical and pharmaceutical industries, however, there are ternary or multicomponent mixtures. Separation of ternary or multicomponent azeotropic mixtures is challenging due to the complexity of the multicomponent system, which has more than one different azeotrope and distillation boundaries. In recent years, studies on the separation of ternary azeotropic mixtures have received increasing attention.17−22 In our previous work,23 the ternary mixture of tetrahydrofuran (THF)/ethanol/water, containing three binary azeotropes, was separated via ternary extractive distillation processes using dimethyl sulfoxide (DMSO), ethylene glycol (EG), and a mixed solvent of DMSO and EG as the entrainer. Mixed entrainer was introduced to reduce energy consumption and the total annual cost (TAC) of the process between two extractive distillation columns (EDCs), with the trade-off being entrainer performance. However, dynamic controllability of the ternary extractive distillation process was not involved in that study. It is of great importance to investigate the dynamic control process, which can ensure stable operation and © XXXX American Chemical Society

Received: September 29, 2017 Revised: November 20, 2017 Accepted: December 16, 2017

A

DOI: 10.1021/acs.iecr.7b04071 Ind. Eng. Chem. Res. XXXX, XXX, XXX−XXX

Article

Industrial & Engineering Chemistry Research

Figure 1. Temperature profiles and temperature difference profiles for ternary extractive distillation with DMSO.

the R/F, which exhibited good controllability. Wang et al.33 studied the trade-off between controllability and economics for an extractive distillation process used in separating binary azeotropes and observed that dynamic controllability could be improved when the entrainer flow rate was increased appropriately with a small increase in TAC. For the separation of a ternary mixture, there are minimal publications on the dynamic controllability of the ternary extractive distillation processes. Luyben34 studied dynamic controllability of the ternary extractive distillation containing an EDC for separating the mixture of benzene/cyclohexane/ toluene that only contained a binary azeotrope. To date, dynamic control of the ternary extractive distillation containing two EDCs with recycle splitting for separating a mixture containing multiple azeotropes has not been explored. This process is more complex because of the relatively high number of operating parameters and interactions between multiple azeotropes. This paper aims to study the control characteristics of the ternary extractive distillation process. In this work, the control structures of the ternary extractive distillation using DMSO and a mixed solvent of DMSO and EG as the entrainer for separating THF/ethanol/water were explored. The feed flow rate and feed composition disturbances were introduced to evaluate the disturbance rejection capability for the proposed control structures. Moreover, a comparison of the dynamic control performance between the ternary extractive distillation processes using the single entrainer DMSO and mixed entrainer was made.

mixed solvent (60 mol % DMSO + 40 mol % EG) as entrainer were obtained based on minimum TAC for all columns. The tray pressure drop was assumed to be 0.0068 atm. The fresh feed flow rate was set at 100 kmol/h with the composition of 30 mol % THF, 30 mol % ethanol, and 40 mol % water. The purities of the three products were set at no less than 99.9 mol %. The dynamic control of the ternary extractive distillation with EG was not explored due to the poor economy. Before exporting to the dynamic process from steady state, the major equipment sizes were the following. According to the commonly used heuristics mentioned by Luyben,35 the sizes of the reflux drum and column sumps were set to provide 10 min of liquid holdup when the vessel is full. Adequate pressure drops were produced by sizing pumps and valves to satisfy changes of flow rate. The slope criterion35,36 was used to select the temperaturesensitive trays. Figure 1 shows the temperature and temperature difference profiles for the ternary extractive distillation with DMSO. In two EDCs, the temperature at entrainer feed has have a rapid rise; fresh feed stages had a rapid fall. However, these locations are not good for temperature control because the fluctuation of feed conditions can easily affect the stability of the control system. There are also rapid changes in temperature near the bottom of the two EDCs. These locations are also not good for temperature control because the composition of the key component is not well inferred. It was apparent that stages 15 and 27 also have steep temperature slopes in the EDC1. For the entrainer recovery column (ERC), the slope profile has two peaks at stages 3 and 11. The temperature-sensitive trays in the rectifying sections are not suggested to be controlled by reboiler duty due to the lag in response.30 Therefore, the temperatures of stage 27 in the EDC1 and stage 11 in the ERC can be controlled by manipulating corresponding reboiler duties. Since the slope of stage 47 is the largest in temperature difference of the profiles for EDC2, stage 47 is selected as the temperature-sensitive tray.

2. PROCESS STUDY AND SELECTION OF TEMPERATURE-SENSITIVE TRAY The commercial software programs Aspen Plus and Aspen Dynamics were used to investigate the steady-state and dynamic processes of the ternary extractive distillation. In our previous work,23 the optimal conditions for the ternary extractive distillation processes using EG, DMSO, and the B


Article


Figure 2. Temperature profiles and temperature difference profiles for ternary extractive distillation with mixed entrainer.

Figure 3. Basic control structure with fixed ratio for ternary extractive distillation with DMSO.

3. DYNAMIC CONTROL OF TWO PROCESSES

Figure 2 shows the temperature and temperature difference profiles for ternary extractive distillation with mixed entrainer. The same criteria were used to select the temperature-sensitive tray for the process with mixed entrainer. It was apparent that stages 17 and 31 have steep temperature slopes in the EDC1; the slope profile has two peaks at stages 3 and 9. The temperatures of stage 31 in the EDC1 and stage 9 in the ERC can be controlled by manipulating corresponding reboiler duties. For the EDC2, stage 35 is selected as the temperaturesensitive tray.

3.1. Dynamic Control of Ternary Extractive Distillation Process with DMSO. 3.1.1. Basic Control Structure. Based on the basic control structure of the binary extractive distillation system,37−39 the basic control structure of the ternary extractive distillation process was proposed. Figure 3 shows the basic control structure for ternary extractive distillation with DMSO. The detailed control loops are listed as follows: 1. The fresh feed flow rate is controlled to guarantee a constant flow. C


Article


Figure 4. Dynamic responses of the basic control structure for the ternary extractive distillation with DMSO: (a) ±20% feed rate disturbance; (b) ±20% feed composition disturbance.

2. The operating pressures are controlled via the manipulation of heat removal rate in corresponding condensers for all columns. 3. The reflux drum levels are held via the manipulation of distillate flow rates for all columns. 4. The sump levels in the two EDCs are controlled through manipulating the bottom flow rate of two EDCs.

5. The sump level of the ERC is controlled via the manipulation of the flow rate of entrainer makeup. 6. The reflux ratios of three columns are fixed. 7. The proportion of total entrainer flow rate and fresh feed flow rate is constant. 8. The proportion of the entrainer flow rate to EDC2 and the bottom flow rate of EDC1 is constant. D


Article


Figure 5. Dual temperature control structure for ternary extractive distillation with DMSO.

ethanol, and 36.6 mol % water, whereas the −20% disturbance consists of 24 mol % THF, 32.6 mol % ethanol, and 43.3 mol % water. As shown in Figure 4b, the system is able to arrive at a new steady state within 3 h after the feed composition disturbances are introduced. The controlled temperatures of two EDCs are brought back to the initial set points, and the temperature of the ERC has a very small fluctuation within a small range. When the +20% feed composition disturbance is introduced, the product purities of THF and ethanol are maintained close to the initial values, while the purity of water has a large deviation from the initial value of 99.90 mol % to 99.15 mol %. When the feed composition is changed from 30/ 30/40 to 24/32.6/43.3 mol % THF/ethanol/water, the purity of THF reduces to 95.24 mol %, which has a large deviation to the desired value of 99.9 mol %. Therefore, the basic control structure cannot efficiently handle the disturbances. 3.1.2. Dual Temperature Control Structure. It is worth noting that the temperatures at stage 15 in the EDC1 and stage 11 in the ERC are also potential temperature control stages. To obtain better dynamic control performance, an improved dual temperature control structure was explored, and the control structure is shown in Figure 5. Two temperature controllers are added to the control structure, in which the temperatures of stage 15 in the EDC1 and stage 3 in the ERC are controlled by the corresponding reflux ratio. The other control loops are the same control strategy mentioned in the basic control structure. The tuning parameters of dual temperature control structure for the ternary extractive distillation with DMSO are summarized in Table S2. Figure 6a gives the dynamic responses of the dual temperature control structure for ternary extractive distillation with DMSO after introducing the ±20% feed rate disturbance. The purities of the three products come very close to the initial values, and the controlled temperatures are also maintained at set points. It is apparent that dual temperature control structure has better control performance than the basic control structure, when faced with the same flow rate disturbances.

9. The temperature of recycled entrainer is maintained at 50 °C through manipulating the heat removal rate of the cooler. 10. The temperatures of the suitable temperature-sensitive tray in all columns are controlled via the manipulation of the corresponding reboiler duties. Conventional proportional−integral (PI) controllers were used for all controllers, except the liquid level controllers. All level control loops were achieved by proportional controllers with a gain (KC) of 2 and an integral time (τI) of 9999 min. The PI settings of the feed flow controller were at KC = 0.5 and τI = 0.3 min. The PI settings were KC = 20 and τI = 12 min for the pressure controllers. The dead time of 1 min was used for all temperature control loops. Relay-feedback tests were implemented on the temperature controllers to obtain the ultimate gain (KU) and periods (PU). The KC and τI were calculated using the Tyreus−Luyben rule. The tuning parameters of the basic control structure for the ternary extractive distillation with DMSO are listed in Table S1. The disturbance rejection capability of the proposed control structures was evaluated by introducing a ±20% feed flow rate and composition disturbances. All disturbances were added at 0.5 h, and the termination time was 8 h. Figure 4a shows the dynamic responses of the basic control structure for the ternary extractive distillation with DMSO after introducing the ±20% feed rate disturbance. The system can arrive at a new steady state within 3 h, and all controlled temperatures can also return to the initial value. The purities of the three products come very close to the initial values when they encounter a −20% feed rate disturbance. When disturbances of 20% increase the feed flow rate, the purities of THF and water are 99.83 and 99.86 mol %, respectively, having a large deviation to their desired values when the new steady state arrives. Figure 4b shows the dynamic responses of the basic control structure for the ternary extractive distillation with DMSO after introducing the ±20% feed composition disturbance. The composition mole fraction for the +20% feed composition disturbance for THF consists of 36 mol % THF, 27.4 mol % E


Article


Figure 6. Dynamic responses of the dual temperature control structure for the ternary extractive distillation with DMSO: (a) ±20% feed rate disturbance; (b) ±20% feed composition disturbance.

brought back to the set points, and the temperature of the ERC has a very small fluctuation within a small range. After introducing a +20% feed composition disturbance, the purity of water is held quite close to the initial value, while the product purities of THF and ethanol have large deviations from the initial values. Therefore, a more efficient control structure should be further explored.

However, all controlled temperatures and product purities have large transient deviations from the set points when the feed flow rate disturbances are introduced. Figure 6b gives the dynamic responses of the dual temperature control structure for ternary extractive distillation with DMSO after introducing the ±20% feed composition disturbance. The controlled temperatures of two EDCs are F


Article


Figure 7. Composition with QR/F control structure for ternary extractive distillation with DMSO.

EDC1, the variation is smaller than 5 °C in EDC2, and the variation is less than 3 °C in the ERC. Overall, the composition with the QR/F control structure shows a good disturbance rejection capability. 3.2. Dynamic Control of the Ternary Extractive Distillation Process with a Mixed Entrainer. 3.2.1. Basic Control Structure. The proposed basic control structure was also used for the ternary extractive distillation process with a mixed entrainer. The tuning parameters of the basic control structure for ternary extractive distillation with a mixed entrainer are listed in Table S4. Figure 9a shows the dynamic responses of the basic control structure for the ternary extractive distillation with a mixed entrainer after introducing the ±20% feed rate disturbance. The system can arrive at a new steady state in 3 h, and all controlled temperatures return to the initial value. The purities of the three products come very close to the initial values; however, the product purities of THF and water have large transient deviations relative to the initial values when the feed flow rate increases. The three controlled temperatures have large transient deviations relative to the initial values as well. Figure 9b shows the dynamic responses of the basic control structure for the ternary extractive distillation with a mixed entrainer after introducing the ±20% feed composition disturbance. When the feed composition is changed to 36/ 27.4/36.6 mol % THF/ethanol/water, the product purities of THF and ethanol are held close to the specified values, while the purity of water has a large deviation from the initial value of 99.93 mol % to 99.65 mol %. When the feed composition is changed to 24/32.6/43.3 mol % THF/ethanol/water, the purities of THF and ethanol are 96.39 and 99.81 mol %, respectively, having a large deviation to their specified purity of 99.9 mol % when arriving at the new steady state. Therefore, the basic control structure cannot efficiently handle the disturbances for the ternary extractive distillation with a mixed entrainer. 3.2.2. Composition with the QR/F Control Structure. To obtain better dynamic control performance for the ternary

3.1.3. Composition with QR/F Control Structure. The dual temperature control structure was adjusted to obtain better dynamic control performance. The composition with the ratio of reboiler duty to mole feed flow rate (QR/F) control structure is shown in Figure 7. The temperature control loop of the stage with a reflux ratio in EDC1 is deleted, and the product purity of THF is controlled by the reflux ratio. The product purity of ethanol is controlled by the reflux ratio in EDC2. To solve the large transient deviations (Figure 6a), the feed-forward control structure is added, in which the direct control duty of the reboiler is replaced by controlling the QR/ F. The composition control loop usually entails using a larger dead time (3 min) than a temperature control loop uses. The tuning parameters of the composition with the QR/F control structure are shown in Table S3. Figure 8a gives the dynamic responses of the composition with the QR/F control structure for the ternary extractive distillation with DMSO after introducing the ±20% feed rate disturbance. All product purities are maintained quite close to the initial values after the system arrives at a new steady state and have small transient deviations from the initial values. The controlled temperatures of two EDCs are brought back to the initial set points, and the temperature of the ERC has a very small fluctuation within a small range; however, this phenomenon does not affect the purity of the product. The variations of controlled temperatures are not more than 5 °C in EDC1 and EDC2, and the variation is less than 3 °C in the ERC. These results of dynamic responses show that the composition with the QR/F control structure can effectively handle a ±20% feed rate disturbance. Figure 8b gives the dynamic responses for the composition with the QR/F control structure after introducing the ±20% feed composition disturbance. Three product purities are maintained very close to their specified values, with only small transient deviations from the initial values. The temperature control loop of the ERC has a very small fluctuation within a small range and does not affect the product purity. The variation of controlled temperatures is not more than 7 °C in G


Article


Figure 8. Dynamic responses of the composition with QR/F control structure for the ternary extractive distillation with DMSO: (a) ±20% feed rate disturbance; (b) ±20% feed composition disturbance.

extractive distillation process with a mixed entrainer, the improved composition with the QR/F control structure was also explored; tuning parameters are shown in Table S5. Figure 10a gives the dynamic responses for the composition with the QR/F control structure after introducing the ±20% feed rate disturbance. All product purities have small transient deviations from the initial values and are maintained close to

the initial values after the system arrives at a new steady state. The controlled temperatures are brought back to the initial set points with only small deviations. The variation of controlled temperatures are not more than 3 °C in EDC1 and the ERC, and the variation is less than 3 °C in EDC2. Figure 10b gives the dynamic responses for the composition with the QR/F control structure after introducing the ±20% H


Article


Figure 9. Dynamic responses of the basic control structure for the ternary extractive distillation with mixed entrainer: (a) ±20% feed rate disturbance; (b) ±20% feed composition disturbance.

and EDC2, and the variation is less than 3 °C in the ERC. Overall, the composition with the QR/F control structure shows a good disturbance rejection capability.

feed composition disturbance. Three product purities are maintained very close to their specified values with only small transient deviations from the initial values. The controlled temperatures are also brought back to the initial set points with only small deviations. The temperature control loop of the ERC has a very small fluctuation within a small range, and does not affect the purity of the product. The variations of controlled temperatures are not more than 5 °C in EDC1

4. COMPARISONS AND DISCUSSION The dynamic performances of the ternary extractive distillation process with DMSO and a mixed entrainer were compared in this section. Figure 11 provides the comparison of the dynamic I


Article


Figure 10. Dynamic responses of the basic control structure for the ternary extractive distillation with mixed entrainer: (a) ±20% feed rate disturbance; (b) ±20% feed composition disturbance.

disturbances and purities of the products can be held at acceptable values in 3 h after several oscillations. As seen from Figure 11a, the extractive distillation process with DMSO has larger transient deviations relative to the

performance between the ternary extractive distillation with DMSO and a mixed entrainer using a composition with the QR/F control structure for the same disturbances. It can be observed that the two processes can efficiently handle the J


Article


Figure 11. Comparisons of dynamic performance between ternary extractive distillation with DMSO and mixed entrainer for (a) feed flow rate disturbances and (b) feed composition disturbance.

purities of ethanol and water when it encounters a −20% feed flow rate disturbance. Although the extractive distillation process with DMSO has larger transient deviations, relative to the initial value when maintaining the THF product purity and compared with the process of the mixed entrainer, the difference is relatively small. This results from the decrease lag in the entrainer, resulting in the amount of entrainer to be

initial values when maintaining the product purities of THF, ethanol, and water when it encounters +20% feed flow rate disturbances. In this study, the excellent separation performance of the mixed entrainer can offset partial transient deviations of the product purities caused by the delay of the increase in entrainer, when the feed flow rate increases. There are similar transient deviations in maintaining the product K



■

enough for the process with DMSO and mixed entrainer; when the feed flow rate decreases, the differences in dynamic response are relatively small for two processes. As shown in Figure 11b, there are similar transient deviations when maintaining the product purities of ethanol and water when it encounters ±20% feed composition disturbances. Although the extractive distillation process with DMSO has larger transient deviations, relative to the initial value when maintaining the THF product purity and compared with the process of the mixed entrainer, the difference is relatively small Therefore, the mixed entrainer has little effect on the dynamic performance when feed composition disturbances occur, since the total amount of entrainer does not change, adequate when feed composition disturbances occur, and the response of other manipulated variables are similar for the two processes. Overall, the ternary extractive distillation process with a mixed entrainer showed better dynamic behavior when compared with the ternary extractive distillation process using DMSO.

Article

ASSOCIATED CONTENT

S Supporting Information *

The Supporting Information is available free of charge on the ACS Publications website at DOI: 10.1021/acs.iecr.7b04071.

■

Detailed tuning parameters of all control structures (PDF)

AUTHOR INFORMATION

Corresponding Author

*E-mail: [email protected]. ORCID

Yinglong Wang: 0000-0002-3043-0891 Notes

The authors declare no competing financial interest.

■

ACKNOWLEDGMENTS This work is supported by the National Natural Science Foundation of China (No. 21776145), National Natural Science Foundation of China (No. 21676152), and Key Research Project of Shandong Province (No. 2016GSF116004).

5. CONCLUSIONS The control structures of the ternary extractive distillation using dimethyl sulfoxide and a mixed solvent of dimethyl sulfoxide and ethylene glycol, as the entrainer for separating THF/ethanol/water, were investigated. The ±20% feed flow rate disturbances and ±20% feed composition disturbances were introduced to evaluate the disturbance rejection capability of the proposed control structures. The improved composition with the ratio of reboiler duty to mole feed flow rate control structure showed good dynamic behavior for the ternary extractive distillation processes with dimethyl sulfoxide and the mixed entrainer after the disturbances were introduced. Moreover, the dynamic performances of the ternary extractive distillation with dimethyl sulfoxide and the mixed entrainer were compared. The extractive distillation process with a mixed entrainer reduces transient deviations relative to the initial values, keeping all product purities when it encounters +20% feed flow rate disturbances, and the mixed entrainer has little effect on the dynamic performance when −20% feed flow rate and ±20% feed composition disturbances occur. In this study, the transient deviation, which is caused by an increase lag in entrainer, can be partially offset due to the excellent separation performance of the mixed entrainer when feed flow rate disturbances occur. The result shows that the dynamic performances of the extractive distillation process with a mixed entrainer were better compared with the extractive distillation process with dimethyl sulfoxide. In addition, the economics of the extractive distillation process with a mixed entrainer for separating THF/ethanol/ water was demonstrated in our previous work. There is typically a trade-off between process economics and controllability in the engineering design. This research shows that there is no conflict between the economics and dynamic controllability. The economics and dynamic performance are both enhanced by introducing a mixed entrainer, although two components were introduced to the ternary extractive distillation process. More systems are needed to study this process, and the reasons in which to study this process should also be further explored.

■

REFERENCES

(1) Li, L.; Guo, L.; Tu, Y.; Yu, N.; Sun, L.; Tian, Y.; Li, Q. Comparison of different extractive distillation processes for 2methoxyethanol/toluene separation: Design and control. Comput. Chem. Eng. 2017, 99, 117−134. (2) Patraşcu, I.; Bildea, C. S.; Kiss, A. A. Dynamics and control of a heat pump assisted extractive dividing-wall column for bioethanol dehydration. Chem. Eng. Res. Des. 2017, 119, 66−74. (3) Wang, Y.; Cui, P.; Ma, Y.; Zhang, Z. Extractive distillation and pressure-swing distillation for THF/ethanol separation. J. Chem. Technol. Biotechnol. 2015, 90 (8), 1463−1472. (4) Tututi-Avila, S.; Medina-Herrera, N.; Hahn, J.; JiménezGutiérrez, A. Design of an energy-efficient side-stream extractive distillation system. Comput. Chem. Eng. 2017, 102, 17−25. (5) Han, J.; Lei, Z.; Dong, Y.; Dai, C.; Chen, B. Process intensification on the separation of benzene and thiophene by extractive distillation. AIChE J. 2015, 61 (12), 4470−4480. (6) Benyounes, H.; Shen, W.; Gerbaud, V. Entropy Flow and Energy Efficiency Analysis of Extractive Distillation with a Heavy Entrainer. Ind. Eng. Chem. Res. 2014, 53 (12), 4778−4791. (7) Franke, M. B. MINLP optimization of a heterogeneous azeotropic distillation process: Separation of ethanol and water with cyclohexane as an entrainer. Comput. Chem. Eng. 2016, 89, 204−221. (8) Tabari, A.; Ahmad, A. A semicontinuous approach for heterogeneous azeotropic distillation processes. Comput. Chem. Eng. 2015, 73, 183−190. (9) Kiss, A. A.; Suszwalak, D. J. P. C. Enhanced bioethanol dehydration by extractive and azeotropic distillation in dividing-wall columns. Sep. Purif. Technol. 2012, 86, 70−78. (10) Wang, S.-J.; Huang, K. Design and control of acetic acid dehydration system via heterogeneous azeotropic distillation using pxylene as an entrainer. Chem. Eng. Process. 2012, 60, 65−76. (11) Janakey Devi, V. K. P.; Sai, P. S. T.; Balakrishnan, A. R. Heterogeneous azeotropic distillation for the separation of n-propanol + water mixture using n-propyl acetate as entrainer. Fluid Phase Equilib. 2017, 447, 1−11. (12) Li, R.; Ye, Q.; Suo, X.; Dai, X.; Yu, H. Heat-Integrated PressureSwing Distillation Process for Separation of a Maximum-Boiling Azeotrope Ethylenediamine/Water. Chem. Eng. Res. Des. 2016, 105, 1−15. (13) Cao, Y.; Hu, J.; Jia, H.; Bu, G.; Zhu, Z.; Wang, Y. Comparison of pressure-swing distillation and extractive distillation with variedL


Article

Industrial & Engineering Chemistry Research diameter column in economics and dynamic control. J. Process Control 2017, 49, 9−25. (14) Wang, Y.; Zhang, Z.; Xu, D.; Liu, W.; Zhu, Z. Design and control of pressure-swing distillation for azeotropes with different types of boiling behavior at different pressures. J. Process Control 2016, 42, 59−76. (15) Liang, S.; Cao, Y.; Liu, X.; Li, X.; Zhao, Y.; Wang, Y.; Wang, Y. Insight into pressure-swing distillation from azeotropic phenomenon to dynamic control. Chem. Eng. Res. Des. 2017, 117, 318−335. (16) Zhu, Z.; Wang, L.; Ma, Y.; Wang, W.; Wang, Y. Separating an azeotropic mixture of toluene and ethanol via heat integration pressure swing distillation. Comput. Chem. Eng. 2015, 76, 137−149. (17) Luyben, W. L. Control of a triple-column pressure-swing distillation process. Sep. Purif. Technol. 2017, 174, 232−244. (18) Zhao, L.; Lyu, X.; Wang, W.; Shan, J.; Qiu, T. Comparison of heterogeneous azeotropic distillation and extractive distillation methods for ternary azeotrope ethanol/toluene/water separation. Comput. Chem. Eng. 2017, 100, 27−37. (19) Zhu, Z.; Xu, D.; Liu, X.; Zhang, Z.; Wang, Y. Separation of acetonitrile/methanol/benzene ternary azeotrope via triple column pressure-swing distillation. Sep. Purif. Technol. 2016, 169, 66−77. (20) Zhu, Z.; Xu, D.; Jia, H.; Zhao, Y.; Wang, Y. Heat Integration and Control of a Triple-Column Pressure-Swing Distillation Process. Ind. Eng. Chem. Res. 2017, 56 (8), 2150−2167. (21) Modla, G.; Lang, P.; Denes, F. Feasibility of separation of ternary mixtures by pressure swing batch distillation. Chem. Eng. Sci. 2010, 65 (2), 870−881. (22) Raeva, V. M.; Sazonova, A. Y. Separation of ternary mixtures by extractive distillation with 1,2-ethandiol and glycerol. Chem. Eng. Res. Des. 2015, 99, 125−131. (23) Zhao, Y.; Zhao, T.; Jia, H.; Li, X.; Zhu, Z.; Wang, Y. Optimization of the composition of mixed entrainer for economic extractive distillation process in view of the separation of tetrahydrofuran/ethanol/water ternary azeotrope. J. Chem. Technol. Biotechnol. 2017, 92 (9), 2433−2444. (24) Sun, L.; Wang, Q.; Li, L.; Zhai, J.; Liu, Y. Design and Control of Extractive Dividing Wall Column for Separating Benzene/Cyclohexane Mixtures. Ind. Eng. Chem. Res. 2014, 53 (19), 8120−8131. (25) Luyben, W. L. Control comparison of conventional extractive distillation with a new split-feed configuration. Chem. Eng. Process. 2016, 107, 29−41. (26) Luo, H.; Liang, K.; Li, W.; Li, Y.; Xia, M.; Xu, C. Comparison of Pressure-Swing Distillation and Extractive Distillation Methods for Isopropyl Alcohol/Diisopropyl Ether Separation. Ind. Eng. Chem. Res. 2014, 53 (39), 15167−15182. (27) Qin, J.; Ye, Q.; Xiong, X.; Li, N. Control of Benzene− Cyclohexane Separation System via Extractive Distillation Using Sulfolane as Entrainer. Ind. Eng. Chem. Res. 2013, 52 (31), 10754− 10766. (28) Tututi-Avila, S.; Jiménez-Gutiérrez, A.; Hahn, J. Control analysis of an extractive dividing-wall column used for ethanol dehydration. Chem. Eng. Process. 2014, 82, 88−100. (29) Wang, Q.; Yu, B.; Xu, C. Design and Control of Distillation System for Methylal/Methanol Separation. Part 1: Extractive Distillation Using DMF as an Entrainer. Ind. Eng. Chem. Res. 2012, 51 (3), 1281−1292. (30) Gil, I. D.; Gómez, J. M.; Rodríguez, G. Control of an extractive distillation process to dehydrate ethanol using glycerol as entrainer. Comput. Chem. Eng. 2012, 39, 129−142. (31) Yang, S.; Wang, Y.; Bai, G.; Zhu, Y. Design and Control of an Extractive Distillation System for Benzene/Acetonitrile Separation Using Dimethyl Sulfoxide as an Entrainer. Ind. Eng. Chem. Res. 2013, 52 (36), 13102−13112. (32) Luyben, W. L. Control of an Extractive Distillation System for the Separation of CO2and Ethane in Enhanced Oil Recovery Processes. Ind. Eng. Chem. Res. 2013, 52 (31), 10780−10787. (33) Wang, Y.; Liang, S.; Bu, G.; Liu, W.; Zhang, Z.; Zhu, Z. Effect of Solvent Flow Rates on Controllability of Extractive Distillation for

Separating Binary Azeotropic Mixture. Ind. Eng. Chem. Res. 2015, 54 (51), 12908−12919. (34) Luyben, W. L. Control comparison of conventional and thermally coupled ternary extractive distillation processes. Chem. Eng. Res. Des. 2016, 106, 253−262. (35) Luyben, W. L. Distillation Design and Control Using Aspen Simulation; John Wiley & Sons: 2013. (36) Luyben, W. L. Evaluation of criteria for selecting temperature control trays in distillation columns. J. Process Control 2006, 16 (2), 115−134. (37) Luyben, W. L. Plantwide control of an isopropyl alcohol dehydration process. AIChE J. 2006, 52 (6), 2290−2296. (38) Luyben, W. L. Comparison of Extractive Distillation and Pressure-Swing Distillation forAcetone-Methanol Separation. Ind. Eng. Chem. Res. 2008, 47, 2696−2707. (39) Arifin, S.; Chien, I.-L. Design and control of an isopropyl alcohol dehydration process via extractive distillation using dimethyl sulfoxide as an entrainer. Ind. Eng. Chem. Res. 2008, 47, 790−803.

M


Control of a Ternary Extractive Distillation Process with Recycle

Recommend Documents