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Innovative design and simulation of a castor oil biorefinery
Antonio Espuña, Moisès Graells and Luis Puigjaner (Editors), Proceedings of the 27th European Symposium on Computer Aided Process Engineering – ESCAPE 27 October 1st - 5th, 2017, Barcelona, Spain © 2017 Elsevier B.V. All rights reserved. http://dx.doi.org/10.1016/B978-0-444-63965-3.50187-2
Innovative design and simulation of a castor oil biorefinery Alexandre C. Dimiana, Petrica Iancua*, Valentin Plesua, Alexandra-Elena BonetRuiza,b, Jordi Bonet-Ruizb a
Centre for Technology Transfer in the Process Industries, Department of Chemical and Biochemical Engineering, University POLITEHNICA of Bucharest, 1, Gh. Polizu Street, Bldg. A, Room A056, RO-011061, Bucharest, Romania b University of Barcelona, Department of Chemical Engineering and Analytic Chemistry, Faculty of Chemistry, 1 Martí i Franquès St, ES-08028, Barcelona, Spain [email protected]
Abstract The paper presents computer-aided design of a castor oil biorefinery. Fatty acid methyl ricinoleic ester (FAMRE) is the central building block. The first part deals with the simulation of two innovative technologies based on process intensification for FAMRE manufacturing by transesterification. The first one employs heterogeneous catalysis. Compact and modular reactor design allows customizable reaction time and variable catalyst amount. The second technology makes use of reactive extraction performed in a counter-current mixer-settler device. The principle of removing the constraints of chemical equilibrium is demonstrated by simulation using detailed kinetics. FAMRE is converted to undecylenic methyl ester and heptaldehyde. The paper presents process synthesis and computer simulation based on kinetic modeling of pyrolysis reactor and thermodynamic assessment of separations. The analysis highlights some challenges in using computer simulation when complex functional molecules are involved. Keywords: castor oil, biorefinery, biodiesel, methyl ricinoleic ester, process simulation
1. Introduction The significance of biorefinery concept for computer-aided chemical engineering was highlighted in an early work (Dimian, 2007). Castor oil is a valuable sustainable feedstock, whose remarkable feature is high content in the triglyceride of ricinoleic (12hydroxy-9-octadecenoic) acid, a versatile functional molecule. Methyl ricinoleic ester (FAMRE) plays a key role. This can be obtained by transesterification with methanol and valorized as biodiesel. Much more profitable is the conversion of FAMRE to undecylenic methyl ester and heptaldehyde, used for manufacturing high-value C11 polyamides and various C7 based chemicals, respectively. The paper deals with process synthesis and simulation of the whole biorefinery.
2. Building blocks from castor oil The castor oil composition is about 85 to 90 wt. % ricinoleic acid triglyceride, other fatty acids being linoleic C18:2 (4 to 5%), oleic C18:1 (3 to 4%), C18:0 stearic (1 to 2%), C16:0 palmitic (1 to 2%), linolenic (0.5 to 0.7%), and few amounts of C20+ fatty acids.
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Ricinoleic acid based species are not available in Aspen Plus 9.0 database. Accordingly, properties estimation has been performed for both pure components and mixtures by group contribution methods. Figure 1 presents the chemistry involved in different process design stages (transesterification, pyrolysis, chemical reactions to methyl 10-undecenate and further for obtaining 11- aminoundecenoic acid).
Figure 1. Chemistry of castor oil conversion to biodiesel and chemicals
3. Novel transesterification reactors 3.1. Adaptable residence time device for heterogeneous catalysis Using the heterogeneous catalysis in the transesterification technology is a considerable progress from process intensification viewpoint, since radical simplification of separations: no waste water streams, no distillation of methanol-water solutions, and no costly glycerol purification. Capital and operating expenses may drop by 40–60%. Pure glycerol is obtained directly as high added-value by-product. 1
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Figure 2 Castor oil biodiesel process by heterogeneous catalysis and novel reactor
Figure 2 left-hand presents a novel reactor for transesterification (Dimian, 2016). The device consists of an adiabatic serpentine-type plug flow reactor, assembled as vertical tubular segments filled with solid catalyst. A switching valve system (not shown) is employed for connecting or bypassing the reaction tubes, as well for catalyst change. The set-up makes use of static mixers (STM) and heat transfer elements. Liquid thermal agent
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is used as heat carrier. Saving energy is obtained by means of feed-effluent heat exchangers (FEHE). For achieving the biodiesel specifications, as defined by EN14142, the reaction should take place in two stages with intermediate glycerol separation. Here we present a design with only one-step transesterification stage, in which variable reaction time device is combined with membranes separation. This set-up allows recycling both triglycerides (TAG) and methanol. A remarkable feature of the novel reactor is that the residence time can be adapted to feedstock type and to catalyst activity by varying the number of the active tubes. Employing smaller catalyst particles gives faster reaction rate. Scale-up can be done easily by assembling parallel “reaction boxes”, including building-up of mobile plants. Figure 2 right-hand shows the influence of loss in catalyst activity on conversion after the first and second reactor, as well as on product specifications in term of di-glycerides (DAG) and mono-glycerides (MAG) content. Simulation is performed with rigorous kinetics, adapted from Allain et al. (2016). At least 88% conversion should be obtained in the first stage, to achieve the full specifications after the second stage. When the catalyst activity drops by more than 10% there is the risk of getting off-specs product. Tall column reactors, as employed today in industry, should have significantly oversized inventory to cope with catalyst deactivation. With the above device, only few tubes should be replaced, typically at the front-end, without operation shutdown. 3.2. Reactive extraction The second novel method presented in Figure 3, consists of process intensification by reactive extraction (RE). The principle is proposed by Plesu and co-workers (2015).
Figure 3 Transesterification of castor oil with methanol by reactive extraction
The reaction device consists of mixing/settler vessels with counter-current flows, which may be operated individually, as shown in Figure 3, or put together in a single column. Note that glycerol by-product is used both as separation agent and for shifting the chemical equilibrium. Recycled glycerol is introduced at the top of an extraction column receiving in counter-current the FAME stream from the last decanter. The bottom stream brings back the methanol as reflux in the reaction space. Raw biodiesel leaves the extraction column as top product from, with specifications closed to the commercial fuel, so that only minor washing is necessary. Glycerol leaving decanter 1, separates in a flash
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device to methanol and glycerol streams, both recycled. Make-up methanol and outlet glycerol streams close the material balance. Figure 3 shows the progress for key species, as flowrates of tri-glycerides, di-glycerides, mono-glycerides and FAMRE in logarithmic coordinates. The effect of reactive extraction is compared against the traditional process with intermediate glycerol separation. The feasibility of this approach was proved by simulation with AspenPlus v.9.0. The detailed kinetic model involves three equilibrium reactions (Bambase et al., 2007). Homogeneous NaOH solution catalyst is employed. At 60°C the equilibrium constants are 9.52, 2.71 and 12.85, respectively. The process involves a two-phase liquid system, with reaction taking place in the oil phase. LLE is modelled by UNIQUAC and regression of experimental data (França et al., 2014) combined with estimation by UNIFACDORTMUND. The predictions were found at least qualitatively correct: di-glycerides and FAMRE remain in the oil phase, mono-glycerides are slightly soluble in glycerol phase, while methanol is distributed with preference to glycerol. The reactive oil phase is about 90% from the total volume. The input consists of 5 kmol/h triglycerides, while methanol is added close to stoichiometry. As remarkable feature, by using recycles and counter-current the above device ensures constant flows of methanol and glycerol in both reaction and separation spaces, with important process intensification effects. A series of three CSTRs of 8 m3 at 60°C is used, with decanting at 25°C. The process rate is constraint primarily by the second equilibrium reaction. As seen from Figure 3, due to glycerol extraction from the reactive phase, an enhancement effect of the entire process is obtained. The progress in FAMRE is significant in the first two stages: 77.58% and 96.27%, respectively. The third stage is necessary to fulfil the end-product specifications. The final product got by RE has 99.4% FAMRE, with TAG 1600 ppm, DAG 2000 ppm, MAG 2600 ppm. Without RE, the purity fails to 95.5%, the biodiesel being off-specs.
4. Methyl ricinoleate conversion to chemicals The second part of this work deals with conversion of methyl-ricinoleate ester to aminoricinoleic acid and heptanal. Process synthesis follows the chemistry outlined in Figure1. 4.1. Pyrolysis reaction section The reaction, moderate endothermic, takes place in the presence of steam. Optimal temperature is 550 to 600°C. Kinetic data from Guobin et al. (1996) are regressed as rA=0.664∙exp(-13,400/T)∙pA with pre-exponential factor in m3/(kmol∙s∙Pa). The yield target is 90% in C11 ester. The chemical reactor is designed by kinetic modeling for main reaction, combined with the stoichiometric description for secondary reactions, as: (1) C7H14O → CO + C6H14 with 25% conversion; (2) C6H14 → CH4+C2H4+C3H6 with 90% conversion. The reaction system has the pattern of a heat-integrated design (Dimian et al., 2014). Figure 4 illustrates the flowsheet. The integrated heat exchangers H-1 and FEHE1 are split in two parts connected by duty. The reactor inflow is preheated in (H-1A) by exchange with the outflow. It follows vaporization by dispersion in superheated steam. Then the temperature is raised by passing through FEHE-1A and further through the furnace. Pyrolysis takes place in the tubular reactor R-PYRO, a cylindrical shell filled with metallic Raschig rings. By simulation 18 m3 reactor volume is obtained (with 1.4m diameter and 12m length). The hot outlet stream enters a heat exchanger for heat recovery (steam generator or thermal agent). Then, the hot mixture passes through the other side of FEHE-1B, then further through the heater H-1B, and finally condensed in H-2 for separation.
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Figure 4 Heat integrated reaction system for the cleavage of methyl ricinoleate
Figure 4 illustrates temperatures, vapor fractions and duties. FEHE operates essentially in gas phase with small liquid fractions at inlet and outlet of cold and hot sides, respectively. H-1 is liquid heater with vapor condensation. Finally, H-2 is surface air condenser followed by water cooler, if necessary. Energy saving may be evaluated as follows. Energy injected on the cold side is Q1= 7.66 MW, while energy removed from the hot side is Q2= 6.66 MW. The difference of 1 MW is the energy consumed by reaction. The net energy introduced with superheated steam and furnace is Q in = 5.66 MW. By subtracting the duty of steam generator the effective energy consumed is Qeff=4.56 MW. It follows that the energy saving is 1-4.56/7.66=0.405 or 40.5%. 4.2. Separation of methyl-undecylenoate
Figure 5 Separation of methyl undecylenoate and heptaldehyde
Figure 5 illustrates the simulation. After leaving the reaction section the stream is submitted to separation. The first step is three-phase flash resulting in gas, organic and water streams. Organic phase collects most esters and heptaldehyde, low soluble in water. Waste water is sent to treatment and recycling. The pasteurization column STAB removes gases in top and lights as side stream. It follows the vacuum columns C-1 and C-2, as direct sequence. The first operates at 0.13 bar recovering heptanal, while the second distillates methyl undecenoate at 0.05 bar. Both products can be obtained over 99.5% of purity. The vacuum is determined by the reboiler temperatures, about 200°C in separating heptaldehyde and of 225°C for methyl undecenoate. 4.3. Synthesis of amino-undecanoic acid Figure 6 presents the simulation of the last steps. Firstly, methyl undecenoate ester is hydrolysed to undecylenic acid. Reaction slightly exothermal takes place at 25°C in a CSTR provided with cooling by brine. Residence time of 30 minutes is enough for full conversion. Methanol removal is done in the column STRIPPER in five equilibrium stages and operation under vacuum, to avoid elevated temperature in reboiler.
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Figure 6 Synthesis of 11-aminoundecanoic acid
Water content in bottom should be kept as small as possible. Methanol is recycled to esterification. The bromination consists in the addition of HBr to the terminal double bond, following the anti-Markovnikoff rule. The reaction takes place in toluene solvent in the presence of benzoil peroxide. Since the reaction is highly exothermic, the reactor is provided with efficient refrigeration system, to keep the temperature around 0°C. The selectivity is 95% to Br-C11 product, and 5% to Br-C10 isomer. The simulation had to overcome some difficulties regarding the property estimation of some components properties, as bromo- and amino- derivatives of the undecanoic acids. In addition, some steps have been simplified, as the reactions involving electrolytes and toluene recycle.
5. Conclusions The analysis highlights the remarkable potential of the castor oil as biorefinery resource, but also the challenges in using computer simulation for developing innovative technologies in which complex functional molecules are involved. Two novel process intensification methods for the transesterification of castor oil are presented. The first one makes use of solid catalyst and adaptable reaction time device. The second method based on reactive extraction employs the glycerol by-product to shift the chemical equilibrium and improves separations. Key results are increased productivity, better biodiesel specifications, and more efficient separation scheme. The paper presents also the synthesis and simulation of a process for converting methyl-ricinoleate to high-value chemicals, as heptanal and 11-aminoundecanoic acid.
References F. Allain, J. Portha, E. Girot, E. Falk, A. Dandeu, V. Coupard, 2016, Chem.Eng.J., 283, 833–845 M.E. Bambase, N.J. Nakamura, M. Matsumara, 2007, J. Chem. Techn. Biotechn., 82, 273-280 A.C. Dimian, 2007, Renewable raw materials: chance and challenge for Computer-Aided Process Engineering, Proceedings Escape-17, CACE 24, Elsevier, 309-318 A.C. Dimian, C.S. Bildea, A.A. Kiss, 2014, Integrated Design and Simulation of Chemical Processes, second edition, Elsevier, CACE series, vol. 33 A.C. Dimian, G. Rothenberg, 2016, An effective modular process for biodiesel manufacturing using heterogeneous catalysis, Catal. Sci. Technol., 6, 6097 H. Guobin, L. Zuyu, Y. Suking, Y. Rufeng, 1996, Pyrolysis of methyl ricinoleate, JAOCS, 73 (9), 1109-1112 B. França, F.M. Pinto, F. Pessoa, A.M. Uller, 2009, Liquid-liquid equilibria for castor oil biodiesel + glycerol + alcohol, J. Chem. Eng. Data, 54, 2359–2364 V. Plesu, J.S. Puigcasas, G.B. Surroca, J. Bonet, A.E. Bonet-Ruiz, A.Tuluc, J. Llorens, 2015, Process intensification in biodiesel production with energy reduction by pinch analysis, Energy, 79, 273
Innovative design and simulation of a castor oil biorefinery Alexandre C. Dimiana, Petrica Iancua*, Valentin Plesua, Alexandra-Elena BonetRuiza,b, Jordi Bonet-Ruizb a
Centre for Technology Transfer in the Process Industries, Department of Chemical and Biochemical Engineering, University POLITEHNICA of Bucharest, 1, Gh. Polizu Street, Bldg. A, Room A056, RO-011061, Bucharest, Romania b University of Barcelona, Department of Chemical Engineering and Analytic Chemistry, Faculty of Chemistry, 1 Martí i Franquès St, ES-08028, Barcelona, Spain [email protected]
Abstract The paper presents computer-aided design of a castor oil biorefinery. Fatty acid methyl ricinoleic ester (FAMRE) is the central building block. The first part deals with the simulation of two innovative technologies based on process intensification for FAMRE manufacturing by transesterification. The first one employs heterogeneous catalysis. Compact and modular reactor design allows customizable reaction time and variable catalyst amount. The second technology makes use of reactive extraction performed in a counter-current mixer-settler device. The principle of removing the constraints of chemical equilibrium is demonstrated by simulation using detailed kinetics. FAMRE is converted to undecylenic methyl ester and heptaldehyde. The paper presents process synthesis and computer simulation based on kinetic modeling of pyrolysis reactor and thermodynamic assessment of separations. The analysis highlights some challenges in using computer simulation when complex functional molecules are involved. Keywords: castor oil, biorefinery, biodiesel, methyl ricinoleic ester, process simulation
1. Introduction The significance of biorefinery concept for computer-aided chemical engineering was highlighted in an early work (Dimian, 2007). Castor oil is a valuable sustainable feedstock, whose remarkable feature is high content in the triglyceride of ricinoleic (12hydroxy-9-octadecenoic) acid, a versatile functional molecule. Methyl ricinoleic ester (FAMRE) plays a key role. This can be obtained by transesterification with methanol and valorized as biodiesel. Much more profitable is the conversion of FAMRE to undecylenic methyl ester and heptaldehyde, used for manufacturing high-value C11 polyamides and various C7 based chemicals, respectively. The paper deals with process synthesis and simulation of the whole biorefinery.
2. Building blocks from castor oil The castor oil composition is about 85 to 90 wt. % ricinoleic acid triglyceride, other fatty acids being linoleic C18:2 (4 to 5%), oleic C18:1 (3 to 4%), C18:0 stearic (1 to 2%), C16:0 palmitic (1 to 2%), linolenic (0.5 to 0.7%), and few amounts of C20+ fatty acids.
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Ricinoleic acid based species are not available in Aspen Plus 9.0 database. Accordingly, properties estimation has been performed for both pure components and mixtures by group contribution methods. Figure 1 presents the chemistry involved in different process design stages (transesterification, pyrolysis, chemical reactions to methyl 10-undecenate and further for obtaining 11- aminoundecenoic acid).
Figure 1. Chemistry of castor oil conversion to biodiesel and chemicals
3. Novel transesterification reactors 3.1. Adaptable residence time device for heterogeneous catalysis Using the heterogeneous catalysis in the transesterification technology is a considerable progress from process intensification viewpoint, since radical simplification of separations: no waste water streams, no distillation of methanol-water solutions, and no costly glycerol purification. Capital and operating expenses may drop by 40–60%. Pure glycerol is obtained directly as high added-value by-product. 1
3
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Figure 2 Castor oil biodiesel process by heterogeneous catalysis and novel reactor
Figure 2 left-hand presents a novel reactor for transesterification (Dimian, 2016). The device consists of an adiabatic serpentine-type plug flow reactor, assembled as vertical tubular segments filled with solid catalyst. A switching valve system (not shown) is employed for connecting or bypassing the reaction tubes, as well for catalyst change. The set-up makes use of static mixers (STM) and heat transfer elements. Liquid thermal agent
Innovative design and simulation of a castor oil biorefinery
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is used as heat carrier. Saving energy is obtained by means of feed-effluent heat exchangers (FEHE). For achieving the biodiesel specifications, as defined by EN14142, the reaction should take place in two stages with intermediate glycerol separation. Here we present a design with only one-step transesterification stage, in which variable reaction time device is combined with membranes separation. This set-up allows recycling both triglycerides (TAG) and methanol. A remarkable feature of the novel reactor is that the residence time can be adapted to feedstock type and to catalyst activity by varying the number of the active tubes. Employing smaller catalyst particles gives faster reaction rate. Scale-up can be done easily by assembling parallel “reaction boxes”, including building-up of mobile plants. Figure 2 right-hand shows the influence of loss in catalyst activity on conversion after the first and second reactor, as well as on product specifications in term of di-glycerides (DAG) and mono-glycerides (MAG) content. Simulation is performed with rigorous kinetics, adapted from Allain et al. (2016). At least 88% conversion should be obtained in the first stage, to achieve the full specifications after the second stage. When the catalyst activity drops by more than 10% there is the risk of getting off-specs product. Tall column reactors, as employed today in industry, should have significantly oversized inventory to cope with catalyst deactivation. With the above device, only few tubes should be replaced, typically at the front-end, without operation shutdown. 3.2. Reactive extraction The second novel method presented in Figure 3, consists of process intensification by reactive extraction (RE). The principle is proposed by Plesu and co-workers (2015).
Figure 3 Transesterification of castor oil with methanol by reactive extraction
The reaction device consists of mixing/settler vessels with counter-current flows, which may be operated individually, as shown in Figure 3, or put together in a single column. Note that glycerol by-product is used both as separation agent and for shifting the chemical equilibrium. Recycled glycerol is introduced at the top of an extraction column receiving in counter-current the FAME stream from the last decanter. The bottom stream brings back the methanol as reflux in the reaction space. Raw biodiesel leaves the extraction column as top product from, with specifications closed to the commercial fuel, so that only minor washing is necessary. Glycerol leaving decanter 1, separates in a flash
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device to methanol and glycerol streams, both recycled. Make-up methanol and outlet glycerol streams close the material balance. Figure 3 shows the progress for key species, as flowrates of tri-glycerides, di-glycerides, mono-glycerides and FAMRE in logarithmic coordinates. The effect of reactive extraction is compared against the traditional process with intermediate glycerol separation. The feasibility of this approach was proved by simulation with AspenPlus v.9.0. The detailed kinetic model involves three equilibrium reactions (Bambase et al., 2007). Homogeneous NaOH solution catalyst is employed. At 60°C the equilibrium constants are 9.52, 2.71 and 12.85, respectively. The process involves a two-phase liquid system, with reaction taking place in the oil phase. LLE is modelled by UNIQUAC and regression of experimental data (França et al., 2014) combined with estimation by UNIFACDORTMUND. The predictions were found at least qualitatively correct: di-glycerides and FAMRE remain in the oil phase, mono-glycerides are slightly soluble in glycerol phase, while methanol is distributed with preference to glycerol. The reactive oil phase is about 90% from the total volume. The input consists of 5 kmol/h triglycerides, while methanol is added close to stoichiometry. As remarkable feature, by using recycles and counter-current the above device ensures constant flows of methanol and glycerol in both reaction and separation spaces, with important process intensification effects. A series of three CSTRs of 8 m3 at 60°C is used, with decanting at 25°C. The process rate is constraint primarily by the second equilibrium reaction. As seen from Figure 3, due to glycerol extraction from the reactive phase, an enhancement effect of the entire process is obtained. The progress in FAMRE is significant in the first two stages: 77.58% and 96.27%, respectively. The third stage is necessary to fulfil the end-product specifications. The final product got by RE has 99.4% FAMRE, with TAG 1600 ppm, DAG 2000 ppm, MAG 2600 ppm. Without RE, the purity fails to 95.5%, the biodiesel being off-specs.
4. Methyl ricinoleate conversion to chemicals The second part of this work deals with conversion of methyl-ricinoleate ester to aminoricinoleic acid and heptanal. Process synthesis follows the chemistry outlined in Figure1. 4.1. Pyrolysis reaction section The reaction, moderate endothermic, takes place in the presence of steam. Optimal temperature is 550 to 600°C. Kinetic data from Guobin et al. (1996) are regressed as rA=0.664∙exp(-13,400/T)∙pA with pre-exponential factor in m3/(kmol∙s∙Pa). The yield target is 90% in C11 ester. The chemical reactor is designed by kinetic modeling for main reaction, combined with the stoichiometric description for secondary reactions, as: (1) C7H14O → CO + C6H14 with 25% conversion; (2) C6H14 → CH4+C2H4+C3H6 with 90% conversion. The reaction system has the pattern of a heat-integrated design (Dimian et al., 2014). Figure 4 illustrates the flowsheet. The integrated heat exchangers H-1 and FEHE1 are split in two parts connected by duty. The reactor inflow is preheated in (H-1A) by exchange with the outflow. It follows vaporization by dispersion in superheated steam. Then the temperature is raised by passing through FEHE-1A and further through the furnace. Pyrolysis takes place in the tubular reactor R-PYRO, a cylindrical shell filled with metallic Raschig rings. By simulation 18 m3 reactor volume is obtained (with 1.4m diameter and 12m length). The hot outlet stream enters a heat exchanger for heat recovery (steam generator or thermal agent). Then, the hot mixture passes through the other side of FEHE-1B, then further through the heater H-1B, and finally condensed in H-2 for separation.
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Figure 4 Heat integrated reaction system for the cleavage of methyl ricinoleate
Figure 4 illustrates temperatures, vapor fractions and duties. FEHE operates essentially in gas phase with small liquid fractions at inlet and outlet of cold and hot sides, respectively. H-1 is liquid heater with vapor condensation. Finally, H-2 is surface air condenser followed by water cooler, if necessary. Energy saving may be evaluated as follows. Energy injected on the cold side is Q1= 7.66 MW, while energy removed from the hot side is Q2= 6.66 MW. The difference of 1 MW is the energy consumed by reaction. The net energy introduced with superheated steam and furnace is Q in = 5.66 MW. By subtracting the duty of steam generator the effective energy consumed is Qeff=4.56 MW. It follows that the energy saving is 1-4.56/7.66=0.405 or 40.5%. 4.2. Separation of methyl-undecylenoate
Figure 5 Separation of methyl undecylenoate and heptaldehyde
Figure 5 illustrates the simulation. After leaving the reaction section the stream is submitted to separation. The first step is three-phase flash resulting in gas, organic and water streams. Organic phase collects most esters and heptaldehyde, low soluble in water. Waste water is sent to treatment and recycling. The pasteurization column STAB removes gases in top and lights as side stream. It follows the vacuum columns C-1 and C-2, as direct sequence. The first operates at 0.13 bar recovering heptanal, while the second distillates methyl undecenoate at 0.05 bar. Both products can be obtained over 99.5% of purity. The vacuum is determined by the reboiler temperatures, about 200°C in separating heptaldehyde and of 225°C for methyl undecenoate. 4.3. Synthesis of amino-undecanoic acid Figure 6 presents the simulation of the last steps. Firstly, methyl undecenoate ester is hydrolysed to undecylenic acid. Reaction slightly exothermal takes place at 25°C in a CSTR provided with cooling by brine. Residence time of 30 minutes is enough for full conversion. Methanol removal is done in the column STRIPPER in five equilibrium stages and operation under vacuum, to avoid elevated temperature in reboiler.
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Figure 6 Synthesis of 11-aminoundecanoic acid
Water content in bottom should be kept as small as possible. Methanol is recycled to esterification. The bromination consists in the addition of HBr to the terminal double bond, following the anti-Markovnikoff rule. The reaction takes place in toluene solvent in the presence of benzoil peroxide. Since the reaction is highly exothermic, the reactor is provided with efficient refrigeration system, to keep the temperature around 0°C. The selectivity is 95% to Br-C11 product, and 5% to Br-C10 isomer. The simulation had to overcome some difficulties regarding the property estimation of some components properties, as bromo- and amino- derivatives of the undecanoic acids. In addition, some steps have been simplified, as the reactions involving electrolytes and toluene recycle.
5. Conclusions The analysis highlights the remarkable potential of the castor oil as biorefinery resource, but also the challenges in using computer simulation for developing innovative technologies in which complex functional molecules are involved. Two novel process intensification methods for the transesterification of castor oil are presented. The first one makes use of solid catalyst and adaptable reaction time device. The second method based on reactive extraction employs the glycerol by-product to shift the chemical equilibrium and improves separations. Key results are increased productivity, better biodiesel specifications, and more efficient separation scheme. The paper presents also the synthesis and simulation of a process for converting methyl-ricinoleate to high-value chemicals, as heptanal and 11-aminoundecanoic acid.
References F. Allain, J. Portha, E. Girot, E. Falk, A. Dandeu, V. Coupard, 2016, Chem.Eng.J., 283, 833–845 M.E. Bambase, N.J. Nakamura, M. Matsumara, 2007, J. Chem. Techn. Biotechn., 82, 273-280 A.C. Dimian, 2007, Renewable raw materials: chance and challenge for Computer-Aided Process Engineering, Proceedings Escape-17, CACE 24, Elsevier, 309-318 A.C. Dimian, C.S. Bildea, A.A. Kiss, 2014, Integrated Design and Simulation of Chemical Processes, second edition, Elsevier, CACE series, vol. 33 A.C. Dimian, G. Rothenberg, 2016, An effective modular process for biodiesel manufacturing using heterogeneous catalysis, Catal. Sci. Technol., 6, 6097 H. Guobin, L. Zuyu, Y. Suking, Y. Rufeng, 1996, Pyrolysis of methyl ricinoleate, JAOCS, 73 (9), 1109-1112 B. França, F.M. Pinto, F. Pessoa, A.M. Uller, 2009, Liquid-liquid equilibria for castor oil biodiesel + glycerol + alcohol, J. Chem. Eng. Data, 54, 2359–2364 V. Plesu, J.S. Puigcasas, G.B. Surroca, J. Bonet, A.E. Bonet-Ruiz, A.Tuluc, J. Llorens, 2015, Process intensification in biodiesel production with energy reduction by pinch analysis, Energy, 79, 273