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Modeling and control of multicomponent distillation systems separating highly non-ideal mixturesRueda, Lina María, January 1900 (has links) (PDF)
Thesis (Ph. D.)--University of Texas at Austin, 2005. / Vita. Includes bibliographical references.
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Synthesis of multicomponent azeotropic distillation sequencesLiu, Guilian January 2003 (has links)
A large number of distillation sequences can be generated to separate a multicomponent azeotropic mixture. However, there is no systematic and efficient method for synthesising promising sequences, which also consider recycle connections and flowrates. In this work, a systematic procedure is developed for synthesising economically promising distillation sequences separating multicomponent homogeneous azeotropic mixtures. The procedure uses spherically approximated distillation boundaries, a shortcut column design method, and allows recycle and sequence alternatives to be screened. Both feasibility and design are addressed. Approximation of a distillation boundary as a spherical surface is a simple nonlinear, yet more accurate representation of the actual boundary than a linear approximation. For shortcut column design, azeotropes are treated as pseudocomponents and the relative volatilities of all singular points of the system are characterised, based on the transformation of vapour-liquid equilibrium behaviour in terms of pure components into that in terms of singular points. Once the relative volatilities of singular points are obtained, the classical Fenske-Underwood-Gilliland method can be used to design columns separating azeotropic mixtures. This method is extremely computationally efficient and can be applied to homogeneous azeotropic mixtures with any number of components; the results are useful for initialising rigorous simulations using commercial software and for assessing feasibility of proposed splits. Together with the spherical approximation of distillation boundaries, this shortcut method provides a basis for evaluating distillation sequences with recycles. Analysis of feasibility requirements of splits, component recovery requirements and the effects of recycles on the performance of proposed splits allows rules and procedures for selecting recycles to be proposed. Recycles with compositions of either singular points or mixtures of singular points are identified that are beneficial to the feasibility of sequences and the recovery of components. The principles are applicable to azeotropic mixtures with any number of components; using these procedures, recycle structures can be generated and are much simpler than the superstructures of recycle alternatives. The sequence synthesis procedure of Thong and Jobson (2001c) allows all potentially feasible sequences to be generated. To screen among these sequences, a split feasibility test and a two-step screening procedure are proposed. In the first step, feasibility of splits is tested efficiently and sequences containing either infeasible or sloppy splits are eliminated. In the second step, sequences containing sloppy splits are generated, based on the evaluation of sequences containing only feasible sharp splits. Using this procedure, the number of distillation sequences identified using the procedure of Thong and Jobson (2001c) can be significantly reduced. A systematic methodology is proposed for the synthesis and evaluation of multicomponent homogeneous azeotropic distillation sequences. The methodology is computationally efficient. It is demonstrated through a case study, the synthesis of distillation sequences separating a five-component mixture, in which two homogeneous azeotropes are formed, and for which over 5000 sequences producing pure component products can be generated. Using this methodology, only ten sequences are evaluated to identify three promising sequences. The evaluation of each sequence using the shortcut column design method is extremely efficient compared with that using the boundary value method.
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Modeling and control of multicomponent distillation systems separating highly non-ideal mixturesRueda, Lina María 28 August 2008 (has links)
Not available / text
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Evaluation of entrainers for the dehydration of C2 and C3 alcohols via azeotropic distillationPienaar, Cornelia 03 1900 (has links)
Thesis (MScEng)--Stellenbosch University, 2012. / ENGLISH ABSTRACT: Distillation is the most widely used separation technique in the chemical process industry and typically accounts
for approximately one-third of the total capital cost and more than half of the total energy consumption of a
typical petrochemical-chemical plant. Therefore, the design and optimization of the distillation sequence are of
critical importance to the economics of the entire process. Azeotropic mixtures cannot be separated into their
pure components via normal distillation. Enhanced distillation techniques such as heterogeneous azeotropic
distillation should be considered for these mixtures. Isobaric vapour-liquid-liquid equilibrium (VLLE) data are
highly important for the design and analysis of heterogeneous distillation columns. However, limited VLLE
data are available in literature due to the difficulties involved with measuring such data.
The objective of this work was to systematically evaluate and compare the performance of selected entrainers
(including benzene, DIPE and cyclohexane) for the dehydration of C2 and C3 alcohols. To meet this objective,
phase equilibrium data had to be measured. Isobaric VLLE at standard atmospheric conditions were measured
with a dynamic Guillespie unit equipped with an ultrasonic homogenizer, which prevented liquid-liquid
separation.
Vapour-liquid equilibrium (VLE) and VLLE data were measured for ethanol/water/di-isopropyl ether (DIPE),
n-propanol/water/DIPE and n-propanol/water/isooctane. The VLE data were found to be thermodynamically
consistent according to the L-W (Wisniak 1993) and McDermott-Ellis consistency tests. No thermodynamic
consistency test, specifically for VLLE data, could be found in literature, but the LLE part of the data followed a
regular profile according to the Othmer-Tobias correlation. The binary DIPE/water and isooctane/water
azeotropes, as well as ternary ethanol/DIPE/water and n-propanol/isooctane/water azeotropes, as measured in
this work, agree well with those found in literature.
Regressed parameters for the NRTL, UNIQUAC, and UNIFAC models, generally improved the model
predictions compared with built-in Aspen parameters. This confirmed the importance of having actual measured
VLLE data available for evaluation and improvement of estimations by thermodynamic models. NRTL
predicted the ethanol/DIPE/water and n-propanol/DIPE/water VLLE most accurately. Despite the improved
regressed parameters for n-propanol/isooctane/water predictions, the models are still considered unsuitable for
accurate prediction of the VLLE behaviour of this system. Separation sequences were simulated in Aspen with
built-in and regressed parameters, respectively, to illustrate the significant effect such inaccurate parameters
have on these simulations.
Phase diagram (VLLE data) evaluation of ethanol and isopropanol (IPA) with various entrainers, as found in
literature, indicated that DIPE might be a good entrainer for the dehydration of these alcohols. Benzene and
cyclohexane are generally used as entrainers in industry for these processes. Benzene is however carcinogenic
and therefore an alternative has to be found (United States Department of Labour - Occupational Safety &
Health Administration 2011). Separation sequences were simulated for ethanol dehydration with benzene and
DIPE as entrainers, respectively. Taking cost and safety into account, DIPE can be considered an acceptable
replacement for benzene as entrainer for ethanol dehydration. A separation sequence was also simulated for the dehydration of IPA with DIPE as entrainer and compared to a
simulation with cyclohexane (Arifin, Chien 2007) as entrainer. DIPE was found to be a reasonable alternative
to cyclohexane as entrainer for IPA dehydration. Two other separation sequences were simulated as practical examples where DIPE could be used as entrainer for the recovery of ethanol or n-propanol from aqueous Fischer
Tropsch waste streams.
DIPE is therefore found to be a feasible alternative entrainer to benzene and cyclohexane for the
dehydration of ethanol and IPA via heterogeneous azeotropic distillation, based on pre-liminary cost
considerations, separation ability and safety. Better entrainers than DIPE may exist, but from the data
available in literature and the measurements made in this work DIPE appears to be superior to benzene,
cyclohexane and isooctane. / AFRIKAANSE OPSOMMING: Distillasie is die mees algemeen-gebruikte skeidingstegniek in die chemiese proses-industrie. Dit is tipies
verantwoordelik vir ʼn derde van die totale kapitaalkoste en meer as die helfte van die totale energie verbruik op
ʼn tipiese petrochemiese chemiese aanleg. Daarom is die ontwerp en optimering van ʼn distillasie trein van
kardinale belang vir die winsgewendheid van die proses. Azeotropiese mengsels kan nie slegs deur normale
distillasie in suiwer komponente geskei word nie. Gevorderde distillasie tegnieke soos heterogene azeotropiese
distillasie moet dus oorweeg word vir sulke mengsels. Isobariese damp-vloeistof-vloeistof ewewigsdata is een
van die belangrikste fisiese eienskappe vir die ontwerp van heterogene distillasie kolomme. Die hoeveelheid
damp-vloeistof-vloeistof ewewigsdata wat beskikbaar is in die literatuur is egter baie beperk omdat dit moeilik
is om die data te meet.
In hierdie werk is isobariese damp-vloeistof-vloeistof ewewigsdata met ʼn dinamiese Guillespie eenheid, by
standaard atmosferiese druk gemeet. Die eenheid is toegerus met ʼn ultrasoniese homogeniseerder om
vloeistof-vloeistof skeiding te voorkom. Temperatuur is gemeet met ʼn akkuraatheid van 0.03oC by 0oC. Die
sisteem se druk is konstant gehou op 101.3 kPa met ʼn akkuraatheid van 0.35 % VSU (Vol Skaal Uitset). Die
ewewigsamestellings is met ʼn relatiewe akkuraatheid van 2 % gemeet.
Daar is damp-vloeistof en damp-vloeistof-vloeistof ewewigsdata van etanol/water/di-isopropiel eter (DIPE), npropanol/
water/ DIPE en n-propanol/water/iso-oktaan gemeet. Die damp-vloeistof ewewigsdata is deur die LW
(Wisniak 1993) en McDermott-Ellis termodinamiese konsistensie toetse getoets en konsistent bevind. Geen
termodinamiese konsistensie toets spesifiek vir damp-vloeistof-vloeistof ewewigsdata kon gevind word nie. Die
Othmer-Tobias korrelasie dui egter aan dat die vloeistof-vloeistof ewewig gedeelte van die data ʼn reëlmatige
gang volg. Die binêre DIPE/water en iso-oktaan/water azeotrope en ternêre etanol/DIPE/water en
n-propanol/iso-oktaan/water fase-ewewigte wat in hierdie werk gemeet is, stem ooreen met die wat in die
literatuur te vind is.
Die parameters vir die modelle (NRTL, UNIQUAC en UNIFAC) wat in hierdie werk bestudeer is, is in die
algemeen verbeter deur regressie van die eksperimentele data. Dit dui daarop dat dit belangrik is om
eksperimentele damp-vloeistof-vloeistof ewewigsdata te hê om die voorspellings van termodinamiese modelle
mee te evalueer en te verbeter. Die etanol/water/ DIPE en n-propanol/water/DIPE damp-vloeistof-vloeistof
ewewigsdata is die akkuraatste deur NRTL voorspel. Ten spyte van die verbeteringe wat deur regressie behaal
is met die NRTL en UNIQUAC parameters vir n-propanol/water/isooktaan, word hierdie modelle steeds nie as
gepas vir die voorspelling van hierdie datastel beskou nie.
Skeidingsreekse is gesimuleer met die ingeboude Aspen parameters en regressie parameters, onderskeidelik, om
te illustreer dat onakkurate parameters ʼn beduidende effek op sulke simulasies het.
Die evaluasie van fase diagramme van etanol en IPA met verskeie skeidingsagente, wat in die literatuur te vind
is, dui aan dat DIPE ʼn goeie skeidingsagent kan wees vir die dehidrasie van hierdie alkohole. Skeidingsreekse
vir die dehidrasie van etanol met benseen en DIPE, onderskeidelik, is gesimuleer. Met koste en veiligheid in ag
geneem, is daar gevind dat DIPE ʼn aanvaarbare plaasvervanger vir benseen as skeidingsagent vir etanol
dehidrasie kan wees. Daar is ook ʼn skeidingsreeks vir die dehidrasie van IPA met DIPE as skeidingsagent gesimuleer en met ʼn
simulasie (Arifin, Chien 2007) wat sikloheksaan as skeidingsagent gebruik, vergelyk. Daar is bevind dat DIPE ʼn
redelike alternatief vir sikloheksaan kan wees as skeidingsagent vir IPA dehidrasie. Nog twee skeidingsreekse is gesimuleer om as praktiese voorbeelde te dien van die gebruik van DIPE as skeidingsagent om etanol of
n-propanol vanaf waterige Fischer-Tropsch afvalstrome te herwin.
Daarom is daar bevind dat DIPE ʼn geldige alternatiewe skeidingsagent vir benseen en sikloheksaan is,
gebaseer op koste, skeidingsvermoë en veiligheid. Daar kan beter skeidingsagente as DIPE bestaan, maar
vanuit die data beskikbaar in literatuur en die metings geneem in hierdie werk, is DIPE die beste.
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Measurements of phase equilibrium for systems containing oxygenated compounds.Nala, Mqondisi Edmund. January 2012 (has links)
Accurate and reliable vapour-liquid equilibrium (VLE) and liquid-liquid equilibrium (LLE) data
are the key to a successful design and simulation of most important industrial separation
processes (traditional distillation, extractive and azeotropic distillation). This work focuses on
measurement of new phase equilibrium data for systems comprising of propan-1-ol, water and
diisopropyl ether which are of important use in the petrochemical industry. In addition, an
investigation of phase equilibrium behavior for systems of interest constituted by solvents and
high added-value oxygenated compounds deriving from lignocelluloses biomasses (bio-fuels)
was conducted at the Ecole des Mines de Paris CEP/TEP laboratories (France).Various data
bases such as Science Direct, ACS publications and Dortmund Data Bank (DDB, 2009) were
used to confirm that no literature data is available for these systems.
The VLE data measurements for the system of propan-1ol + water and propan-1ol + diisopropyl
ether (DIPE) ( 333.15, 353.15 and 373.15 K ) were carried out using a dynamic still of Lilwanth
(2011), with a test system (ethanol + cyclohexane at 40 kPa) undertaken prior measurements to
confirm the accuracy of the method and apparatus.The phase equilibrium (VLE and LLE)
behaviours for furan + n-hexane and furan + Methylbenzene, furfural + n-hexane and furan +
water were determined at 101.3 kPa. The atmospheric dynamic ebulliometry was used to
measure VLE systems at 101.3 kPa. A set of LLE data for furfural + n-hexane and furan + water
systems were obtained using a static analytical method, with a newly commissioned LLE
apparatus. Furfural + n-hexane system was compared used as test system, to verify the reliability
of the new equipment. The NRTL model was used to correlate the LLE data, with Cox-
Herington model used to predict the entire LLE curve for furfural+ n-hexane system. The
experimental VLE data were correlated using the combined y − y method. The vapour phase
non idealities were described using the methods from Nothnagel et al. (1973), Hayden and
O’Connell (1975) and the Peng-Robinson (1976) model. The activity coefficients were
correlated using the NRTL model of Renon and Prausnitz (1968) and the modified UNIQUAC
model of Abrams and Prausnitz (1976).
A propan-1-ol dehydration process was simulated using Aspen to illustrate the use and
importance of thermodynamic models in industrial process design and simulation. The model
used in the simulation was validated with measured VLE and literature LLE data. / Thesis (M.Sc.Eng.)-University of KwaZulu-Natal, Durban, 2012.
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Desidratação por destilação azeotrópica da glicerina obtida como subproduto da produção do biodisel. / Dehydration by azeotropic distillation of glycerine obtained as byproduct of biodiesel production.Gutiérrez Oppe, Evelyn Edith 18 March 2008 (has links)
O trabalho visa substituir processos comercialmente usados na indústria para purificação da glicerina obtida a partir de biodiesel. A purificação da glicerina até grau técnico ou P.A. (99,5 % em massa) implica em um grande consumo de energia nos processos de evaporação e destilação, pela necessidade de altos vácuos. Como alternativa, a desidratação da glicerina pode ser realizada por destilação azeotrópica heterogênea usando baixas temperaturas e a pressão atmosférica. O objetivo deste trabalho foi estudar a viabilidade técnica do processo de desidratação da glicerina por meio da destilação azeotrópica com tolueno e comparar o consumo de energia com os processos tradicionais. Para atingir o objetivo, avaliou-se a influencia das variáveis de processo: vazão de alimentação de glicerina (g/s) (X1 codificado), vazão de alimentação do vapor de tolueno (g/s) (X2 codificado), concentração inicial de glicerina (% em massa) (X3 codificado), temperatura de alimentação da glicerina (°C) (X4 codificado), na concentração final de glicerina. A construção do modelo foi feita a partir de um planejamento fatorial composto de segunda ordem, usando glicerina P.A. A concentração final foi estimada mediante o índice de refração e massa específica. Obteve-se o seguinte modelo: 2 1,96X2 13,18X3 6,42X1X3 2,24X2X3 1 %GLI = 79,42 8,88X1 + 4,72X + + + que mostrou que a temperatura de alimentação (X4 codificada) não exerceu influencia na concentração final de glicerina. Observou-se pelo modelo que é preferível utilizar valores máximos de X2.e mínimos de X1. Com estes ensaios foi possível obter uma glicerina 99% pura, porém apresentava um ligeiro cheiro de tolueno, que foi eliminado mediante arraste com ar (stripping). Para verificar o modelo empregou-se glicerina bruta oriunda do biodiesel previamente tratada. O processo prévio consistiu de: acidificação, neutralização, salting out com isopropanol, evaporação do álcool e troca iônica. A glicerina obtida após o processo de troca iônica, aparentemente só água e glicerina com 38,6 % em massa, foi usada para a verificação do modelo. Obteve-se por destilação azeotrópica uma glicerina com 92 % em massa, quando o valor predito pelo modelo foi 99 %. Esta glicerina tratada apresentou um desvio do modelo devido a presença de resíduos de sabões, porém ficou demonstrado a possibilidade de desidratação de glicerina por este processo necessitando apenas de melhorias nas etapas de purificação até a troca iônica. Também, avaliou-se a eficiência da coluna comparando a separação dada pela coluna com a dada por um único estágio de equilíbrio nas mesmas condições de vazão e concentração, concluindo-se que era da ordem de 10 %. Finalmente, este processo consome cerca de 57,72 % de energia em relação aos processos de evaporação e destilação a vácuo tradicionalmente usados. / This study aims to replace commercially processes used in industry for glycerine purification obtained from biodiesel. The purification of glycerine up to technical degree or PA (99.5% by weight) involves a large consumption of energy in the evaporation and distillation processes due to need operate at high vacuum. Alternatively, dehydration of glycerine can be achieved by heterogeneous azeotropic distillation using low temperature and atmospheric pressure. The objective of this work was to study the technical feasibility of the dehydration process of glycerine through azeotropic distillation with toluene and compare the energy consumption with traditional processes. To reach this objective, the influence of process variables: feed flow rate of glycerine (g/s) (X1 coded), feed flow rate of steam toluene (g/s) (X2 coded), initial concentration of glycerine (% by weight) (X3 coded), the temperature of food glycerine (°C) (X4 coded) has been studied in the final concentration of glycerine. The empirical model was built through fitting of data obtained from a factorial second order design, using glycerine PA. The final concentration was estimated by refractive index and density. The fitted model was: 2 1,96X2 13,18X3 6,42X1X3 2,24X2X3 1 %GLI = 79,42 8,88X1 + 4,72X + + + The model appoints that the feed (inlet glycerine solution) temperature (X4 coded) had no influence in the outlet concentration of glycerine. Moreover, it has been observed that is better to use maximum X2.and minimum X1. From these tests were possible to obtain a glycerine 99% purely, but it had a light smell of toluene, which was removed by stripping with air. In order to verify the empirical model, it has been used raw glycerine from biodiesel production. This glycerine was previously treated following the steps: acidification, neutralization, salting out with isopropanol, evaporation of isopropanol and ion exchange. The obtained glycerine after the process of ion exchange, presented 38.6% in weight, apparently only glycerine in water, has been used to check the model. Content of glycerine by this distillation was 92% in weight, when the predict value by the model was 99%. The deviation from the model was due to the presence of soap residues, but it has been demonstrated the possibility of dehydration of glycerine by this process requiring only some improvements in purification steps up to the ion exchange. In addition, it has been estimated the column efficiency by comparison of the separation in both column and single stage at the same flow rate and concentration conditions, concluding that it was 10 %. Finally, this process consumes approximately 57.72% of energy in relation to the processes of evaporation and vacuum distillation traditionally used.
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Desidratação por destilação azeotrópica da glicerina obtida como subproduto da produção do biodisel. / Dehydration by azeotropic distillation of glycerine obtained as byproduct of biodiesel production.Evelyn Edith Gutiérrez Oppe 18 March 2008 (has links)
O trabalho visa substituir processos comercialmente usados na indústria para purificação da glicerina obtida a partir de biodiesel. A purificação da glicerina até grau técnico ou P.A. (99,5 % em massa) implica em um grande consumo de energia nos processos de evaporação e destilação, pela necessidade de altos vácuos. Como alternativa, a desidratação da glicerina pode ser realizada por destilação azeotrópica heterogênea usando baixas temperaturas e a pressão atmosférica. O objetivo deste trabalho foi estudar a viabilidade técnica do processo de desidratação da glicerina por meio da destilação azeotrópica com tolueno e comparar o consumo de energia com os processos tradicionais. Para atingir o objetivo, avaliou-se a influencia das variáveis de processo: vazão de alimentação de glicerina (g/s) (X1 codificado), vazão de alimentação do vapor de tolueno (g/s) (X2 codificado), concentração inicial de glicerina (% em massa) (X3 codificado), temperatura de alimentação da glicerina (°C) (X4 codificado), na concentração final de glicerina. A construção do modelo foi feita a partir de um planejamento fatorial composto de segunda ordem, usando glicerina P.A. A concentração final foi estimada mediante o índice de refração e massa específica. Obteve-se o seguinte modelo: 2 1,96X2 13,18X3 6,42X1X3 2,24X2X3 1 %GLI = 79,42 8,88X1 + 4,72X + + + que mostrou que a temperatura de alimentação (X4 codificada) não exerceu influencia na concentração final de glicerina. Observou-se pelo modelo que é preferível utilizar valores máximos de X2.e mínimos de X1. Com estes ensaios foi possível obter uma glicerina 99% pura, porém apresentava um ligeiro cheiro de tolueno, que foi eliminado mediante arraste com ar (stripping). Para verificar o modelo empregou-se glicerina bruta oriunda do biodiesel previamente tratada. O processo prévio consistiu de: acidificação, neutralização, salting out com isopropanol, evaporação do álcool e troca iônica. A glicerina obtida após o processo de troca iônica, aparentemente só água e glicerina com 38,6 % em massa, foi usada para a verificação do modelo. Obteve-se por destilação azeotrópica uma glicerina com 92 % em massa, quando o valor predito pelo modelo foi 99 %. Esta glicerina tratada apresentou um desvio do modelo devido a presença de resíduos de sabões, porém ficou demonstrado a possibilidade de desidratação de glicerina por este processo necessitando apenas de melhorias nas etapas de purificação até a troca iônica. Também, avaliou-se a eficiência da coluna comparando a separação dada pela coluna com a dada por um único estágio de equilíbrio nas mesmas condições de vazão e concentração, concluindo-se que era da ordem de 10 %. Finalmente, este processo consome cerca de 57,72 % de energia em relação aos processos de evaporação e destilação a vácuo tradicionalmente usados. / This study aims to replace commercially processes used in industry for glycerine purification obtained from biodiesel. The purification of glycerine up to technical degree or PA (99.5% by weight) involves a large consumption of energy in the evaporation and distillation processes due to need operate at high vacuum. Alternatively, dehydration of glycerine can be achieved by heterogeneous azeotropic distillation using low temperature and atmospheric pressure. The objective of this work was to study the technical feasibility of the dehydration process of glycerine through azeotropic distillation with toluene and compare the energy consumption with traditional processes. To reach this objective, the influence of process variables: feed flow rate of glycerine (g/s) (X1 coded), feed flow rate of steam toluene (g/s) (X2 coded), initial concentration of glycerine (% by weight) (X3 coded), the temperature of food glycerine (°C) (X4 coded) has been studied in the final concentration of glycerine. The empirical model was built through fitting of data obtained from a factorial second order design, using glycerine PA. The final concentration was estimated by refractive index and density. The fitted model was: 2 1,96X2 13,18X3 6,42X1X3 2,24X2X3 1 %GLI = 79,42 8,88X1 + 4,72X + + + The model appoints that the feed (inlet glycerine solution) temperature (X4 coded) had no influence in the outlet concentration of glycerine. Moreover, it has been observed that is better to use maximum X2.and minimum X1. From these tests were possible to obtain a glycerine 99% purely, but it had a light smell of toluene, which was removed by stripping with air. In order to verify the empirical model, it has been used raw glycerine from biodiesel production. This glycerine was previously treated following the steps: acidification, neutralization, salting out with isopropanol, evaporation of isopropanol and ion exchange. The obtained glycerine after the process of ion exchange, presented 38.6% in weight, apparently only glycerine in water, has been used to check the model. Content of glycerine by this distillation was 92% in weight, when the predict value by the model was 99%. The deviation from the model was due to the presence of soap residues, but it has been demonstrated the possibility of dehydration of glycerine by this process requiring only some improvements in purification steps up to the ion exchange. In addition, it has been estimated the column efficiency by comparison of the separation in both column and single stage at the same flow rate and concentration conditions, concluding that it was 10 %. Finally, this process consumes approximately 57.72% of energy in relation to the processes of evaporation and vacuum distillation traditionally used.
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The separation of detergent range alkanes and alcohol isomers with supercritical carbon dioxideZamudio, Michelle 04 1900 (has links)
Thesis (PhD)--Stellenbosch University, 2014. / ENGLISH ABSTRACT: Data on the process performance at different operating conditions are required to determine the
feasibility of a separation process. Such data can be experimentally measured, but due to the time and
costs associated with pilot plant scale experiments, the use of predictive process models are often
preferred. The main aim of this project is to establish a working process model in Aspen Plus® that
can be used to predict the separation performance of a supercritical fluid fractionation process aimed
at the separation of mixtures of detergent range alkanes and alcohol isomers where similar boiling
points or low relative volatilities can occur.
Currently, an azeotropic distillation process is employed for the separation of detergent range
alkanes and alcohols. Although this process shows good separation performance, some concerns
regarding the operating conditions are raised: the preferred entrainer, diethylene glycol, is toxic to
humans; very low operating pressures of 0.016 – 0.031 MPa and high temperatures of 473 K are
required; additional processing units and materials are required to remove the entrainer from the
product streams. An alternative process, supercritical fluid fractionation, is proposed in this work
after previous studies have reported that this process have potential for the separation of alkanes and
alcohols. The supercritical fluid fractionation process addresses the concerns of the azeotropic
distillation process in the following ways: a non-toxic solvent, CO2, is used as the separating agent;
mild temperatures of 344 K is proposed, but at the cost of the low operating pressures of the
azeotropic process; and a single process unit and no additional material is required to separate the
solvent from the product streams. A process model was developed in Aspen Plus® to evaluate the separation performance of the
newly proposed supercritical fluid fractionation process and compare it to the current azeotropic
distillation process. The development of the process model included the development of an accurate
thermodynamic model in Aspen Plus®. After thorough evaluation of a number of cubic equations of
state, the RK-ASPEN model was found to be superior in its representation and prediction of phase
transition pressures for multi-component mixtures of detergent range alkanes and alcohols in the
temperature range 318 – 348 K. Phase transition pressures could be predicted with an error of less
than 6 % with the inclusion of regressed polar parameters and binary solute-solvent interaction
parameters for two multi-component mixtures: CO2 + (20 % n-dodecane + 70 % 1-decanol + 10 % 3,7-dimethyl-1-octanol) and CO2 + (25 % n-decane + 25 % 1-decanol + 25 % 3,7-dimethyl-1-octanol
+ 25 % 2,6-dimethyl-2-octanol).
Polar parameters were regressed from pure component vapour pressure data predicted with
correlations available in Aspen Plus®. Binary interaction parameters were regressed from
experimental bubble and dew point data. Binary bubble and dew point data were measured for a
number of systems containing ethane or CO2 and a C10-alkane or C10-alcohol isomer at temperatures
between 308 K and 353 K, and compositions ranging between 0.01 and 0.7 mass fraction solute. A
comparison between the phase equilibrium data measured for these systems revealed that the structure
of the molecule, and not only the molecular weight, influences its solubility in the supercritical
solvent. The phase transition pressures of n-decane, 2-methylnonane, 3-methylnonane and
4-methylnonane did not differ significantly in CO2 or ethane, and these compounds will in all
likelihood not be separated in a supercritical fluid fractionation process. The phase transition
pressures measured for the C10-alcohol isomers decreased in both CO2 and ethane in the following
order: 1-decanol, 3,7-dimethyl-1-octanol, 2-decanol, 2,6-dimethyl-2-octanol and
3,7-dimethyl-3-octanol. The position of the hydroxyl group and the number, length and position of
the side branches, all influence the solubility behaviour and phase transition pressures of the isomeric
alcohols in the supercritical solvent. Since the use of ethane did not show any significant benefits
with regard to selectivity, the use of the less harmful and less expensive solvent, CO2, in further
investigations was justified. The RK-ASPEN thermodynamic model, with the inclusion of the regressed polar and binary
solute-solvent interaction parameters, was implemented in the process model and the separation
performance of the process was simulated at different operating conditions for the CO2 +
(25 % n-decane + 25 % 1-decanol + 25 % 3,7-dimethyl-1-octanol + 25 % 2,6-dimethyl-2-octanol)
mixture. A comparison to experimental pilot plant data revealed that the model cannot be used to
predict the separation performance at low fractionation temperatures (316 K) due to shortcomings in
the thermodynamic model. However, the performance of the process at high fractionation
temperatures (344 K) could be predicted well, with an error of 10 – 36 %. Simulations for the CO2 +
(25 % n-decane + 25 % 1-decanol + 25 % 3,7-dimethyl-1-octanol + 25 % 2,6-dimethyl-2-octanol) and
CO2 + (20 % n-dodecane + 70 % 1-decanol + 10 % 3,7-dimethyl-1-octanol) mixtures showed that the
composition of the feed mixture have a significant effect on the location and size of the operating
window and optimum operating conditions. The optimum operating conditions were defined as the
conditions where an acceptable selectivity ratio and alcohol recovery occurred simultaneously. Since the selectivity ratio and alcohol recovery have opposing optimization approaches, a number of
possible optimum operating conditions exist, based on the product specifications. When an alcohol
and an alkane with similar phase behaviour exist in a mixture, a distinct minimum selectivity ratio
will occur at a point within the extract-to-feed ratio limits of the process. When the alkanes and
alcohols present in a mixture do not have similar or overlapping phase transition pressures, the
minimum selectivity ratio will typically cover a small range of extract-to-feed ratios at the high end
limit of the extract-to-feed ratio range.
To summarize: A process model was established in Aspen Plus® that can be used to determine
the feasibility and separation performance of a supercritical fractionation process for a feed mixture of
detergent range alkane and alcohol isomers. The model was used to prove that an SFF process is a
feasible alternative process to consider for the removal of alkanes from mixtures of detergent range
alcohol isomers, even where overlapping boiling points or low relative volatilities occur. During the
development of the process model, the following significant novel contributions were made:
· New phase equilibrium data were measured for C10-alkane and C10-alcohol isomers in
supercritical ethane, as published in The Journal of Supercritical Fluids 58 (2011) 330 –
342.
· New phase equilibrium data were measured for C10-alkane and C10-alcohol isomers in
supercritical CO2, as published in The Journal of Supercritical Fluids 59 (2011) 14 – 26.
· A thermodynamic model was developed in Aspen Plus® that can accurately predict the
phase transition pressures of binary, ternary and multi-component mixtures of detergent
range alkanes and alcohols in supercritical CO2, as published in The Journal of
Supercritical Fluids 84 (2013) 132 – 145.
· A process model was developed in Aspen Plus® that can be used to predict the separation
performance of a supercritical fluid fractionation process for the separation of mixtures of
detergent range alkanes and alcohols.
· Experimental and simulated results indicated that a supercritical fluid fractionation process
can be implemented successfully to separate an alkane from a mixture of alcohol isomers,
as was shown for two mixtures: CO2 + (25 % n-decane + 25 % 1-decanol + 25 %
3,7-dimethyl-1-octanol + 25 % 2,6-dimethyl-2-octanol) and CO2 + (20 % n-dodecane +
70 % 1-decanol + 10 % 3,7-dimethyl-1-octanol). / AFRIKAANSE OPSOMMING: Data oor die omvang van skeiding by verskillende bedryfstoestande word benodig om die
lewensvatbaarheid van ’n skeidingsproses te bepaal. Sulke data kan eksperimenteel gemeet word,
maar as gevolg van die tyd en kostes geassosieer met eksperimente op loodsaanlegskaal, word die
gebruik van prosesmodelle verkies. Die hoofdoel van hierdie projek is om ’n werkende prosesmodel,
wat daarop gemik is om C8 – C20 alkane en alkohol isomere te skei, in Aspen Plus® tot stand te bring
om die omvang van die skeiding van ’n superkritiese fraksioneringsproses te meet.
Tans word azeotropiese distillasie gebruik vir die skeiding van C8 – C20 alkane en alkoholisomere.
Alhoewel goeie skeiding met hierdie proses bewerkstellig word, is daar sekere eienskappe
van die proses wat aandag vereis: die voorgestelde skeidingsagent, dietileen glikol, is giftig vir mense;
baie lae bedryfsdrukke van 0.016 – 0.031 MPa en hoë temperature van 473 K word benodig;
addisionele proseseenhede en materiaal is nodig om die skeidingsagent van die produkte te verwyder.
Die gebruik van ’n alternatiewe proses - superkritiese fraksionering - word in hierdie werk voorgestel
nadat vorige studies getoon het dat hierdie proses die potensiaal het om alkane en alkohole te skei.
Die superkritiese fraksioneringsproses spreek al die kommerwekkende eienskappe van azeotropiese
distillasie aan soos volg: ’n veilige oplosmiddel, CO2, word as die skeidingsagent gebruik;
gemiddelde temperature van 344 K word voorgestel, maar ten koste van lae bedryfsdrukke; ’n enkele
proseseenheid en geen addisionele materiaal word benodig om die oplosmiddel van die produkte te
skei nie. ’n Prosesmodel is in Aspen Plus® ontwikkel om die omvang van die skeiding wat deur die
voorgestelde superkritiese fraksioneringsproses teweeggebring is, te evalueer en te vergelyk met die
azeotropiese distillasieproses wat tans in gebruik is. Die ontwikkeling van die prosesmodel sluit die
ontwikkeling van ’n akkurate termodinamiese model in Aspen Plus® in. Na deeglike evaluasie van ’n
aantal kubiese toestandsvergelykings is gevind dat die RK-ASPEN-model die faseoorgangsdrukke
van multi-komponentmengsels van C8 – C20 alkane en alkohole die beste voorspel binne die
temperatuurbereik van 318 – 348 K. Faseoorgangsdrukke kon voorspel word met ’n fout van minder
as 6 % met die insluiting van voorafbepaalde polêre parameters en binêre interaksie-parameters vir
twee multi-komponentmengsels: CO2 + (20 % n-dodekaan + 70 % 1-dekanol + 10 % 3,7-dimetiel-1-oktanol) and CO2 + (25 % n-dekaan + 25 % 1-dekanol + 25 %
3,7-dimetiel-1-oktanol + 25 % 2,6-dimetiel-2-oktanol).
Polêre parameters is bepaal met dampdruk data, wat voorspel is met korrelasies in Aspen Plus®.
Binêre interaksieparameters is van eksperimentele faseoorgangsdata bepaal. Binêre faseoorgangsdata
is vir ’n aantal sisteme wat uit etaan of CO2 en ’n C10-alkaan- of C10-alkohol-isomeer bestaan, gemeet
by temperature tussen 308 K en 353 K en samestellings van tussen 0.01 en 0.7 massafraksie van die
opgeloste stof. ’n Vergelyking tussen die gemete fase-ewewigsdata het onthul dat die struktuur van
die molekuul, en nie net die molekulêre massa nie, die oplosbaarheid van die stof in die superkritiese
oplosmiddel beïnvloed. Die faseoorgangsdrukke van n-dekaan, 2-metielnonaan, 3-metielnonaan en
4-metielnonaan het geen skynbare verskille getoon in etaan of CO2 nie en dus sal hierdie stowwe in
alle waarkynlikheid nie met ’n superkritiese fraksioneringsproses geskei kan word nie. Die
faseoorgangsdrukke wat vir die C10-alkohol gemeet is, het in beide etaan en CO2 afgeneem in die
volgende volgorde: 1-dekanol, 3,7-dimetiel-1-oktanol, 2-dekanol, 2,6-dimetiel-2-oktanol en
3,7-dimetiel-3-oktanol. Die posisie van die hidroksielgroep en die aantal, lengte en posisie van die
sytakke beïnvloed die oplosbaarheidsgedrag van die alkohol-isomere in die superkritiese oplosmiddel.
Aangesien die gebruik van etaan nie enige voordele ten opsigte van selektiwiteit inhou nie, is die
gebruik van die minder skadelike en goedkoper oplosmiddel, CO2, vir verdere ondersoeke
geregverdig. Die ontwikkelde termodinamiese model, met die insluiting van die polêre parameters en binêre
interaksieparameters, is in die prosesmodel ingesluit en die omvang van die skeiding van die proses is
gesimuleer by verskillende bedryfstoestande vir die CO2 + (25 % n-dekaan + 25 % 1-dekanol + 25 %
3,7-dimetiel-1-oktanol + 25 % 2,6-dimetiel-2-oktanol) mengsel. ’n Vergelyking tussen die
gesimuleerde data en die eksperimentele loodsaanlegdata het onthul dat die model nie die omvang van
die skeiding kan voorspel by lae fraksioneringstemperature (316 K) nie as gevolg van die
tekortkominge in die termodinamiese model. Die omvang van die skeiding by hoë temperature
(344 K) kon egter goed voorspel word met ’n fout van 10 – 36 %. Simulasies van die CO2 + (25 %
n-dekaan + 25 % 1-dekanol + 25 % 3,7-dimetiel-1-oktanol + 25 % 2,6-dimetiel-2-oktanol) en CO2 +
(20 % n-dodekaan + 70 % 1-dekanol + 10 % 3,7-dimetiel-1-oktanol) mengsels het getoon dat die
samestelling van die voermengsel ’n beduidende effek op die grootte van die bedryfsvenster en
optimum bedryfstoestande het. Die optimum bedryfstoestande word gedefinieer as die toestande waar
’n aanvaarbare selektiwiteitsverhouding en alkoholherwinning terselfdertyd voorkom. Aangesien die
selektiwiteitsverhouding en alkoholherwinning teenstrydige optimeringsbenaderings het, bestaan daar ’n aantal optimum bedryfstoestande gebaseer op die produkspesifikasies. Wanneer ’n alkohol en ’n
alkaan met ooreenstemmende fasegedrag saam in ’n mengsel voorkom, bestaan daar ’n duidelike
minimum selektiwiteitsverhouding by ’n punt binne die ekstrak-tot-voer-verhoudingslimiete van die
proses. Wanneer die alkane en alkohole in ’n mengsel nie ooreenstemmende fasegedrag toon nie, sal
die minimum selektiwiteitsverhouding oor ’n reeks ekstrak-tot-voer-verhoudings voorkom, tipies by
die hoë limiet van die ekstrak-tot-voer-verhoudingsreeks.
Om op te som: ’n Prosesmodel is in Aspen Plus® tot stand gebring wat die lewensvatbaarheid
en omvang van die moontlike skeiding van ’n superkritiese fraksioneringsproses vir voermengsels van
C8 – C20 alkane en alkohol-isomere kan voorspel. Die model is gebruik om te bewys dat ’n
superkritiese proses ’n lewensvatbare alternatiewe proses is om te oorweeg vir die verwydering van
alkane uit mengsels van alkohol-isomere, self waar ooreenstemmende kookpunte of lae relatiewe
vlugtigheid tussen komponente voorkom. Tydens die ontwikkeling van die prosesmodel is die
volgende beduidende nuwe bydraes gemaak:
· Nuwe fase-ewewigsdata is gemeet vir C10-alkaan- en C10-alkohol-isomere in superkritiese
etaan, soos gepubliseer in The Journal of Supercritical Fluids 58 (2011) 330 – 342.
· Nuwe fase-ewewigsdata is gemeet vir C10-alkaan and C10-alkohol isomere in superkritiese
CO2, soos gepubliseer in The Journal of Supercritical Fluids 59 (2011) 14 – 26.
· ’n Termodinamiese model is ontwikkel in Aspen Plus® wat die faseoorgangsdrukke van
binêre, ternêre en multi-komponent mengsels van C8 – C20 alkane en alkohol-isomere in
superkritiese CO2 akkuraat kan voorspel, soos gepubliseer in The Journal of Supercritical
Fluids 84 (2013) 132 – 145.
· ’n Prosesmodel is ontwikkel in Aspen Plus® wat die omvang van die moontlike skeiding
van ’n superkritiese fraksioneringsproses, gemik op die skeiding van mengsels van C8 –
C20 alkane en alkohol-isomere, kan voorspel.
· Eksperimentele en gesimuleerde resultate toon aan dat ’n superkritiese
fraksioneringsproses suksesvol geïmplementeer kan word vir die skeiding van ’n alkaan
vanuit ’n mengsel van alkohol-isomere, soos bewys vir twee mengsels: CO2 + (25 %
n-dekaan + 25 % 1-dekanol + 25 % 3,7-dimetiel-1-oktanol + 25 % 2,6-dimetiel-2-oktanol)
en CO2 + (20 % n-dodekaan + 70 % 1-dekanol + 10 % 3,7-dimetiel-1-oktanol).
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Desenvolvimento de estratégia de desacoplamento no controle de coluna de destilação usando a técnica de separação de sinais. / Decoupling strategy development in the distillation column control using the signals separation technique.CARMO, Shirlene Kelly Santos. 20 April 2018 (has links)
Submitted by Jesiel Ferreira Gomes (jesielgomes@ufcg.edu.br) on 2018-04-20T20:53:07Z
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SHIRLENE KELLY SANTOS CARMO – TESE (PPGEQ) 2015.pdf: 3441674 bytes, checksum: 2a66c0c04d01e56f10189d8b206ebc1c (MD5) / Made available in DSpace on 2018-04-20T20:53:07Z (GMT). No. of bitstreams: 1
SHIRLENE KELLY SANTOS CARMO – TESE (PPGEQ) 2015.pdf: 3441674 bytes, checksum: 2a66c0c04d01e56f10189d8b206ebc1c (MD5)
Previous issue date: 2015-02-06 / Capes / Grande parte das indústrias apresenta complexidade no que diz respeito ao seu modo de operação. A fim de reduzir os problemas relacionados ao forte acoplamento existente nesses processos, a busca pela incorporação de dispositivos de inteligência artificial vem apresentando uma tendência crescente nos últimos anos. Devido à complexidade de operação e controle em processos multivariáveis, o diagnóstico e monitoramento de falhas nos processos tornaram-se cada vez mais difícil, com isso a aplicação destes dispositivos tem alcançado resultados
satisfatórios em relação aos procedimentos executados com operadores humanos. A análise de componentes independentes (ICA) é uma técnica de separação de sinais que se baseia no uso de estatísticas de ordem superior para estimar cada uma das fontes desconhecidas por meio da observação de diversas misturas geradas a partir destas fontes. Embora sejam encontrados trabalhos recentes sobre a utilização do ICA em processos industriais, apenas dois trabalhos até o presente momento, foram aplicados em processos envolvendo colunas de destilação. O presente trabalho tem como objetivo propor uma estratégia de controle a uma coluna de destilação de alta pureza. A estratégia é baseada na técnica de separação de sinais ICA, tornando
as malhas de controle desacopladas e facilitando assim o desempenho do controle. O desempenho do sistema de controle utilizando a técnica apresentou excelentes resultados em relação a uma estrutura convencional sem desacoplamento. As estruturas de controle foram implementadas em ambiente Aspen Plus DynamicsTM e Simulink/ Matlab®. O processo foi estruturado em ambiente Aspen Plus Dynamics™ e os controladores foram implementados no
Simulink. / Much of the industry presents complexity with regard to its mode of operation. In order to reduce the problems related to existing strong engagement in these processes, the search for the incorporation of artificial intelligence devices has shown an increasing trend in recent years. Due to the complexity of operation and control in multivariate processes, the diagnosis and fault monitoring in the processes have become increasingly difficult, thus the application of these devices has achieved satisfactory results in relation to procedures performed with human operators. The independent component analysis (ICA) is a signal separation technique that is based on the use of higher order statistics to estimate each of the unknown source by observing various mixtures generated from these sources. Although found recent work on the use of the ICA in industrial processes, only two studies to date, have been applied in cases involving distillation columns. This paper aims to propose a control strategy to a high purity distillation column. The strategy is based on the ICA signal separation technique, making decoupled control loops, thus facilitating control performance. The performance of the control system using the technique showed excellent results compared to a conventional structure without decoupling. The control structures have been implemented in Aspen Plus Dynamics™ and Simulink / Matlab® environment. The process was structured environment Aspen Plus Dynamics™ and the controls
were implemented in Simulink.
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